The X Keyboard Extension:

Library Specification

Amber J. Benson

Gary Aitken

Erik Fortune

Silicon Graphics, Inc

Donna Converse

X Consortium, Inc

George Sachs

Hewlett-Packard Company

Will Walker

Digital Equipment Corporation

X Version 11, Release 7.7

Copyright © 1995, 1996 X Consortium Inc., Silicon Graphics Inc.,
Hewlett-Packard Company, Digital Equipment Corporation

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Table of Contents

Acknowledgement
1. Overview

    Core X Protocol Support for Keyboards
    Xkb Keyboard Extension Support for Keyboards
    Xkb Extension Components

        Groups and Shift Levels
        Radio Groups

    Client Types
    Compatibility With the Core Protocol
    Additional Protocol Errors
    Extension Library Functions

        Error Indications

2. Initialization and General Programming Information

    Extension Header Files
    Extension Name
    Determining Library Compatibility
    Initializing the Keyboard Extension
    Disabling the Keyboard Extension
    Protocol Errors
    Display and Device Specifications in Function Calls

3. Data Structures

    Allocating Xkb Data Structures
    Adding Data and Editing Data Structures
    Making Changes to the Server’s Keyboard Description
    Tracking Keyboard Changes in the Server
    Freeing Data Structures

4. Xkb Events

    Xkb Event Types
    Xkb Event Data Structures
    Selecting Xkb Events

        Event Masks

    Unified Xkb Event Type

5. Keyboard State

    Keyboard State Description
    Changing the Keyboard State

        Changing Modifiers
        Changing Groups

    Determining Keyboard State
    Tracking Keyboard State

6. Complete Keyboard Description

    The XkbDescRec Structure
    Obtaining a Keyboard Description from the Server
    Tracking Changes to the Keyboard Description in the Server
    Allocating and Freeing a Keyboard Description

7. Virtual Modifiers

    Virtual Modifier Names and Masks
    Modifier Definitions
    Binding Virtual Modifiers to Real Modifiers
    Virtual Modifier Key Mapping

        Inactive Modifier Sets

    Conventions
    Example

8. Indicators

    Indicator Names
    Indicator Data Structures

        XkbIndicatorRec
        XkbIndicatorMapRec

    Getting Information About Indicators

        Getting Indicator State
        Getting Indicator Information by Index
        Getting Indicator Information by Name

    Changing Indicator Maps and State

        Effects of Explicit Changes on Indicators
        Changing Indicator Maps by Index
        Changing Indicator Maps by Name

    Tracking Changes to Indicator State or Map
    Allocating and Freeing Indicator Maps

9. Bells

    Bell Names
    Audible Bells
    Bell Functions

        Generating Named Bells
        Generating Named Bell Events
        Forcing a Server-Generated Bell

    Detecting Bells

10. Keyboard Controls

    Controls that Enable and Disable Other Controls

        The EnabledControls Control
        The AutoReset Control

    Control for Bell Behavior

        The AudibleBell Control

    Controls for Repeat Key Behavior

        The PerKeyRepeat Control
        The RepeatKeys Control
        The DetectableAutorepeat Control

    Controls for Keyboard Overlays (Overlay1 and Overlay2 Controls)
    Controls for Using the Mouse from the Keyboard

        The MouseKeys Control
        The MouseKeysAccel Control

    Controls for Better Keyboard Access by Physically Impaired Persons

        The AccessXKeys Control
        The AccessXTimeout Control
        The AccessXFeedback Control
        AccessXNotify Events
        StickyKeys, RepeatKeys, and MouseKeys Events
        The SlowKeys Control
        The BounceKeys Control
        The StickyKeys Control

    Controls for General Keyboard Mapping

        The GroupsWrap Control
        The IgnoreLockMods Control
        The IgnoreGroupLock Control
        The InternalMods Control

    The XkbControlsRec Structure

         

    Querying Controls
    Changing Controls

        The XkbControlsChangesRec Structure

    Tracking Changes to Keyboard Controls
    Allocating and Freeing an XkbControlsRec
    The Miscellaneous Per-client Controls

11. X Library Controls

    Controls Affecting Keycode-to-String Translation

        ForceLatin1Lookup
        ConsumeLookupMods
        AlwaysConsumeShiftAndLock

    Controls Affecting Compose Processing

        ConsumeKeysOnComposeFail
        ComposeLED
        BeepOnComposeFail

    Controls Effecting Event Delivery

        IgnoreNewKeyboards

    Manipulating the Library Controls

        Determining Which Library Controls are Implemented
        Determining the State of the Library Controls
        Changing the State of the Library Controls

12. Interpreting Key Events

    Effects of Xkb on the Core X Library

        Effects of Xkb on Event State
        Effects of Xkb on MappingNotify Events
        X Library Functions Affected by Xkb

    Xkb Event and Keymap Functions

13. Keyboard Geometry

    Shapes and Outlines
    Sections
    Rows and Keys
    Doodads
    Overlay Rows and Overlay Keys
    Drawing a Keyboard Representation
    Geometry Data Structures

        DoodadRec Structures

    Getting Keyboard Geometry From the Server
    Using Keyboard Geometry
    Adding Elements to a Keyboard Geometry
    Allocating and Freeing Geometry Components

14. Xkb Keyboard Mapping

    Notation and Terminology

        Core Implementation
        Xkb Implementation

    Getting Map Components from the Server
    Changing Map Components in the Server

        The XkbMapChangesRec Structure

    Tracking Changes to Map Components
    Allocating and Freeing Client and Server Maps

        Allocating an Empty Client Map
        Freeing a Client Map
        Allocating an Empty Server Map
        Freeing a Server Map

15. Xkb Client Keyboard Mapping

    The XkbClientMapRec Structure
    Key Types

        The Canonical Key Types
        Getting Key Types from the Server
        Changing the Number of Levels in a Key Type
        Copying Key Types

    Key Symbol Map

        Per-Key Key Type Indices
        Per-Key Group Information
        Key Width
        Offset in to the Symbol Map
        Getting the Symbol Map for Keys from the Server
        Changing the Number of Groups and Types Bound to a Key
        Changing the Number of Symbols Bound to a Key

    The Per-Key Modifier Map

        Getting the Per-Key Modifier Map from the Server

16. Xkb Server Keyboard Mapping

    Key Actions

        The XkbAction Structure
        The XkbAnyAction Structure
        Actions for Changing Modifiers’ State
        Actions for Changing Group State
        Actions for Moving the Pointer
        Actions for Simulating Pointer Button Press and Release
        Actions for Changing the Pointer Button Simulated
        Actions for Locking Modifiers and Group
        Actions for Changing the Active Screen
        Actions for Changing Boolean Controls State
        Actions for Generating Messages
        Actions for Generating a Different Keycode
        Actions for Generating DeviceButtonPress and DeviceButtonRelease
        Actions for Simulating Events from Device Valuators
        Obtaining Key Actions for Keys from the Server
        Changing the Number of Actions Bound to a Key

    Key Behavior

        Radio Groups
        The XkbBehavior Structure
        Obtaining Key Behaviors for Keys from the Server

    Explicit Components—Avoiding Automatic Remapping by the Server

        Obtaining Explicit Components for Keys from the Server

    Virtual Modifier Mapping

        Obtaining Virtual Modifier Bindings from the Server
        Obtaining Per-Key Virtual Modifier Mappings from the Server

17. The Xkb Compatibility Map

    The XkbCompatMap Structure

        Xkb State to Core Protocol State Transformation
        Core Keyboard Mapping to Xkb Keyboard Mapping Transformation
        Xkb Keyboard Mapping to Core Keyboard Mapping Transformations

    Getting Compatibility Map Components From the Server
    Using the Compatibility Map
    Changing the Server’s Compatibility Map
    Tracking Changes to the Compatibility Map
    Allocating and Freeing the Compatibility Map

18. Symbolic Names

    The XkbNamesRec Structure
    Symbolic Names Masks
    Getting Symbolic Names From the Server
    Changing Symbolic Names on the Server

         

    Tracking Name Changes
    Allocating and Freeing Symbolic Names

19. Replacing a Keyboard “On the Fly”
20. Server Database of Keyboard Components

    Component Names
    Listing the Known Keyboard Components
    Component Hints
    Building a Keyboard Description Using the Server Database

21. Attaching Xkb Actions to X Input Extension Devices

    XkbDeviceInfoRec
    Querying Xkb Features for Non-KeyClass Input Extension Devices
    Allocating, Initializing, and Freeing the XkbDeviceInfoRec Structure
    Setting Xkb Features for Non-KeyClass Input Extension Devices
    XkbExtensionDeviceNotify Event
    Tracking Changes to Extension Devices

22. Debugging Aids
Glossary
Index

List of Figures

1.1. Overall Xkb Structure
5.1. Xkb State
10.1. MouseKeys Acceleration
13.1. Rotated Keyboard Sections
13.2. Keyboard with Four Sections
13.3. Rows in a Section
13.4. Xkb Geometry Data Structures
13.5. Xkb Geometry Data Structures (Doodads)
13.6. Xkb Geometry Data Structures (Overlays)
13.7. Key Surface, Shape Outlines, and Bounding Box
14.1. Shift Levels and Groups
15.1. Xkb Client Map
16.1. Server Map Relationships
16.2. Virtual Modifier Relationships
17.1. Server Interaction with Types of Clients
17.2. Server Derivation of State and Keyboard Mapping Components
17.3. Xkb Compatibility Data Structures
20.1. Building a New Keyboard Description from the Server Database

List of Tables

1.1. Function Error Returns Due to Extension Problems
2.1. Xkb Protocol Errors
2.2. BadKeyboard Protocol Error resource_id Values
4.1. Xkb Event Types
4.2. XkbSelectEvents Mask Constants
5.1. Real Modifier Masks
5.2. Symbolic Group Names
5.3. XkbStateNotify Event Detail Masks
6.1. XkbDescRec Component References
6.2. Mask Bits for XkbDescRec
8.1. XkbIndicatorMapRec flags Field
8.2. XkbIndicatorMapRec which_groups and groups, Keyboard Drives Indicator
8.3. XkbIndicatorMapRec which_groups and groups, Indicator Drives Keyboard
8.4. XkbIndicatorMapRec which_mods and mods, Keyboard Drives Indicator
8.5. XkbIndicatorMapRec which_mods and mods, Indicator Drives Keyboard
9.1. Predefined Bells
9.2. Bell Sounding and Bell Event Generating
10.1. Xkb Keyboard Controls
10.2. MouseKeysAccel Fields
10.3. AccessXFeedback Masks
10.4. AccessXNotify Events
10.5. AccessXNotify Event Details
10.6. Xkb Controls
10.7. Controls Mask Bits
10.8. GroupsWrap options (groups_wrap field)
10.9. Access X Enable/Disable Bits (ax_options field)
11.1. Library Control Masks
13.1. Doodad Types
14.1. Xkb Mapping Component Masks and Convenience Functions
14.2. XkbMapChangesRec Masks
14.3. XkbAllocClientMap Masks
14.4. XkbAllocServerMap Masks
15.1. Example Key Type
15.2. group_info Range Normalization
15.3. Group Index Constants
16.1. Action Types
16.2. Modifier Action Types
16.3. Modifier Action Flags
16.4. Group Action Types
16.5. Group Action Flags
16.6. Pointer Action Types
16.7. Pointer Button Action Types
16.8. Pointer Button Action Flags
16.9. Pointer Default Flags
16.10. ISO Action Flags when XkbSA_ISODfltIsGroup is Set
16.11. ISO Action Flags when XkbSA_ISODfltIsGroup is Not Set
16.12. ISO Action Affect Field Values
16.13. Switch Screen Action Flags
16.14. Controls Action Types
16.15. Control Action Flags
16.16. Message Action Flags
16.17. Device Button Action Types
16.18. Device Button Action Flags
16.19. Device Valuator v<n>_what High Bits Values
16.20. Key Behaviors
16.21. Explicit Component Masks
17.1. Symbol Interpretation Match Criteria
17.2. Compatibility Map Component Masks
18.1. Symbolic Names Masks
18.2. XkbNameChanges Fields
19.1. XkbNewKeyboardNotifyEvent Details
20.1. Server Database Keyboard Components
20.2. XkbComponentNameRec Flags Bits
20.3. Want and Need Mask Bits and Required Names Components
20.4. XkbDescRec Components Returned for Values of Want & Needs
21.1. XkbDeviceInfoRec Mask Bits
22.1. Debug Control Masks

Acknowledgement

This document is the result of a great deal of hard work by a great many
people. Without Erik Fortune’s work as Architect of the X Keyboard Extension
and the longtime support of Silicon Graphics Inc. there would not be a keyboard
extension.

We gratefully thank Will Walker and George Sachs for their help and expertise
in providing some of the content for this document, and Digital Equipment
Corporation and Hewlett-Packard for allowing them to participate in this
project, and we are deeply indebted to IBM for providing the funding to
complete this library specification.

Most of all, we thank Gary Aitken and Amber J. Benson for their long hours and
late nights as ultimate authors of this specification, and for serving as
authors, document editors, and XKB protocol and implementation reviewers. Their
commitment to accuracy and completeness, their attention to detail, their keen
insight, and their good natures when working under tremendous pressure are in
some measure responsible not only for the quality of this document, but for the
quality of the Keyboard extension itself.


Matt Landau
Manager, X Window System
X Consortium Inc.

X Version 11, Release 7 addendum

This document is made available to you in modern formats such as HTML and PDF
thanks to the efforts of Matt Dew, who converted the original troff sources to
DocBook/XML and edited them into shape; Fernando Carrijo, who converted the
images to SVG format; Gaetan Nadon, who set up the formatting machinery in the
libX11 builds and performed further editing of the DocBook markup; and Alan
Coopersmith, who converted the DocBook tags to semantic markup and cleaned up
other formatting issues.

Chapter 1. Overview

Table of Contents

Core X Protocol Support for Keyboards
Xkb Keyboard Extension Support for Keyboards
Xkb Extension Components

    Groups and Shift Levels
    Radio Groups

Client Types
Compatibility With the Core Protocol
Additional Protocol Errors
Extension Library Functions

    Error Indications

The X Keyboard Extension provides capabilities that are lacking or are
cumbersome in the core X protocol.

Core X Protocol Support for Keyboards

The core X protocol specifies the ways that the Shift, Control, and Lock
modifiers and the modifiers bound to the Mode_switch or Num_Lock keysyms
interact to generate keysyms and characters. The core protocol also allows
users to specify that a key affects one or more modifiers. This behavior is
simple and fairly flexible, but it has a number of limitations that make it
difficult or impossible to properly support many common varieties of keyboard
behavior. The limitations of core protocol support for keyboards include:

  • Use of a single, uniform, four-symbol mapping for all keyboard keys makes
    it difficult to properly support keyboard overlays, PC-style break keys, or
    keyboards that comply with ISO9995, or a host of other national and
    international standards.

  • A second keyboard group may be specified using a modifier, but this has
    side effects that wreak havoc with client grabs and X toolkit translations.
    Furthermore, this approach limits the number of keyboard groups to two.

  • Poorly specified locking key behavior requires X servers to look for a few 
    “magic” keysyms to determine that keys should lock when pressed. This leads
    to incompatibilities between X servers with no way for clients to detect
    implementation differences.

  • Poorly specified capitalization and control behavior requires modifications
    to X library source code to support new character sets or locales and can
    lead to incompatibilities between system wide and X library capitalization
    behavior.

  • Limited interactions between modifiers specified by the core protocol make
    many common keyboard behaviors difficult or impossible to implement. For
    example, there is no reliable way to indicate whether or not the shift
    modifier should “cancel” the lock modifier.

  • The lack of any explicit descriptions for indicators, most modifiers, and
    other aspects of the keyboard appearance requires clients that wish to
    clearly describe the keyboard to a user to resort to a mish-mash of prior
    knowledge and heuristics.

Xkb Keyboard Extension Support for Keyboards

The X Keyboard Extension makes it possible to clearly and explicitly specify
most aspects of keyboard behavior on a per-key basis. It adds the notion of a
keyboard group to the global keyboard state and provides mechanisms to more
closely track the logical and physical state of the keyboard. For
keyboard-control clients, Xkb provides descriptions and symbolic names for many
aspects of keyboard appearance and behavior.

In addition, the X Keyboard Extension includes additional keyboard controls
designed to make keyboards more accessible to people with movement impairments.

Xkb Extension Components

The Xkb extension is composed of two parts: a server extension, and a
client-side X library extension. These consist of a loadable module that may be
activated when an X server is started and a modified version of Xlib. Both
server and Xlib versions must be at least X11 R6.

Figure 1.1 shows the overall structure of the Xkb extension:

Figure 1.1. Overall Xkb Structure


The server portion of the Xkb extension encompasses a database of named
keyboard components, in unspecified format, that may be used to configure a
keyboard. Internally, the server maintains a keyboard description that includes
the keyboard state and configuration (mapping). By “keyboard” we mean the
logical keyboard device, which includes not only the physical keys, but also
potentially a set of up to 32 indicators (usually LEDs) and bells.

The keyboard description is a composite of several different data structures,
each of which may be manipulated separately. When manipulating the server
components, the design allows partial components to be transmitted between the
server and a client. The individual components are shown in Figure 1.1.

Client Map    The key mapping information needed to convert arbitrary keycodes
              to symbols.

Server Map    The key mapping information categorizing keys by functionality
              (which keys are modifiers, how keys behave, and so on).

              Client configurable quantities effecting how the keyboard
Controls      behaves, such as repeat behavior and modifications for people
              with movement impairments.

Indicators    The mapping of behavior to indicators.

Geometry      A complete description of the physical keyboard layout,
              sufficient to draw a representation of the keyboard.

Names         A mapping of names to various aspects of the keyboard such as
              individual virtual modifiers, indicators, and bells.

Compatibility The definition of how to map core protocol keyboard state to Xkb
Map           keyboard state.

A client application interrogates and manipulates the keyboard by reading and
writing portions of the server description for the keyboard. In a typical
sequence a client would fetch the current information it is interested in,
modify it, and write it back. If a client wishes to track some portion of the
keyboard state, it typically maintains a local copy of the portion of the
server keyboard description dealing with the items of interest and updates this
local copy from events describing state transitions that are sent by the
server.

A client may request the server to reconfigure the keyboard either by sending
explicit reconfiguration instructions to it, or by telling it to load a new
configuration from its database of named components. Partial reconfiguration
and incremental reconfiguration are both supported.

Groups and Shift Levels

The graphic characters or control functions that may be accessed by one key are
logically arranged in groups and levels. See section 14.1 for a complete
description of groups and levels.

Radio Groups

A radio group is a set of keys whose behavior simulates a set of radio buttons.
Once a key in a radio group is pressed, it stays logically depressed until
another key in the group is pressed, at which point the previously depressed
key is logically released. Consequently, at most one key in a radio group can
be logically depressed at one time. A radio group is defined by a radio group
index, an optional name, and by assigning each key in the radio group 
XkbKB_RadioGroup behavior and the radio group index.

Client Types

This specification differentiates between three different classes of client
applications:

  • Xkb-aware applications

    These applications make specific use of Xkb functionality and APIs not
    present in the core protocol.

  • Xkb-capable applications

    These applications make no use of Xkb extended functionality and
    Application Programming Interfaces (APIs) directly. However, they are
    linked with a version of Xlib that includes Xkb and indirectly benefit from
    some of Xkb’s features.

  • Xkb-unaware applications

    These applications make no use of Xkb extended functionality or APIs and
    require Xkb’s functionality to be mapped to core Xlib functionality to
    operate properly.

Compatibility With the Core Protocol

Because the Xkb extension allows a keyboard to be configured in ways not
foreseen by the core protocol, and because Xkb-unaware clients are allowed to
connect to a server using the Xkb extension, there must be a means of
converting between the Xkb domain and the core protocol. The Xkb server
extension maintains a compatibility map as part of its keyboard description;
this map controls the conversion of Xkb generated events to core protocol
events and the results of core protocol requests to appropriate Xkb state and
configuration.

Additional Protocol Errors

The Xkb extension adds a single protocol error, BadKeyboard, to the core
protocol error set. See section 2.6 for a discussion of the BadKeyboard
protocol error.

Extension Library Functions

The X Keyboard Extension replaces the core protocol definition of a keyboard
with a more comprehensive one. The X Keyboard Extension library interfaces are
included in Xlib.^[1]

Xlib detects the presence of the X Keyboard server extension and uses Xkb
protocol to replace some standard X library functions related to the keyboard.
If an application uses only standard X library functions to examine the
keyboard or process key events, it should not need to be modified when linked
with an X library containing the X keyboard extension. All of the
keyboard-related X library functions have been modified to automatically use
Xkb protocol when the server extension is present.

The Xkb extension adds library interfaces to allow a client application to
directly manipulate the new capabilities.

Error Indications

Xkb functions that communicate with the X server check to be sure the Xkb
extension has been properly initialized prior to doing any other operations. If
the extension has not been properly initialized or the application, library,
and server versions are incompatible, these functions return an error
indication as shown in Table 1.1. Because of this test, BadAccess and BadMatch
(due to incompatible versions) protocol errors should normally not be
generated.

Table 1.1. Function Error Returns Due to Extension Problems

┌──────────────────────┬────────────┐
│Functions return type │Return value│
├──────────────────────┼────────────┤
│pointer to a structure│NULL        │
├──────────────────────┼────────────┤
│Bool                  │False       │
├──────────────────────┼────────────┤
│Status                │BadAccess   │
└──────────────────────┴────────────┘


Many Xkb functions do not actually communicate with the X server; they only
require processing in the client-side portion of the library. Furthermore, some
applications may never actually need to communicate with the server; they
simply use the Xkb library capabilities. The functions that do not communicate
with the server return either a pointer to a structure, a Bool, or a Status.
These functions check that the application has queried the Xkb library version
and return the values shown in Table 1.1 if it has not.


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^[1] X11R6.1 is the first release by the X Consortium, Inc., that includes the
X Keyboard Extension in Xlib. X11R6 included work in progress on this extension
as nonstandard additions to the library.

Chapter 2. Initialization and General Programming Information

Table of Contents

Extension Header Files
Extension Name
Determining Library Compatibility
Initializing the Keyboard Extension
Disabling the Keyboard Extension
Protocol Errors
Display and Device Specifications in Function Calls

Extension Header Files

The following include files are part of the Xkb standard:

  • <X11/XKBlib.h>

    XKBlib.h is the main header file for Xkb; it declares constants, types, and
    functions.

  • <X11/extensions/XKBstr.h>

    XKBstr.h declares types and constants for Xkb. It is included automatically
    from <X11/XKBlib.h>; you should never need to reference it directly in your
    application code.

  • <X11/extensions/XKB.h>

    XKB.h defines constants for Xkb. It is included automatically from <X11/
    XKBstr.h>; you should never need to reference it directly in your
    application code.

  • <X11/extensions/XKBgeom.h>

    XKBgeom.h declares types, symbolic constants, and functions for
    manipulating keyboard geometry descriptions.

Extension Name

The name of the Xkb extension is given in <X11/extensions/Xkb.h>:

#define XkbName "XKEYBOARD"

Most extensions to the X protocol are initialized by calling XInitExtension and
passing the extension name. However, as explained in section 2.4, Xkb requires
a more complex initialization sequence, and a client program should not call
XInitExtension directly.

Determining Library Compatibility

If an application is dynamically linked, both the X server and the client-side
X library must contain the Xkb extension in order for the client to use the Xkb
extension capabilities. Therefore a dynamically linked application must check
both the library and the server for compatibility before using Xkb function
calls. A properly written program must check for compatibility between the
version of the Xkb library that is dynamically loaded and the one used when the
application was built. It must then check the server version for compatibility
with the version of Xkb in the library.

If your application is statically linked, you must still check for server
compatibility and may check library compatibility. (It is possible to compile
against one set of header files and link against a different, incompatible,
version of the library, although this should not normally occur.)

To determine the compatibility of a library at runtime, call XkbLibraryVersion.

Bool XkbLibraryVersion(int *lib_major_in_out, int *lib_minor_in_out);

lib_major_in_out specifies and returns the major Xkb library version.

lib_minor_in_out specifies and returns the minor Xkb library version.

Pass the symbolic value XkbMajorVersion in lib_major_in_out and XkbMinorVersion
in lib_minor_in_out. These arguments represent the version of the library used
at compile time. The XkbLibraryVersion function backfills the major and minor
version numbers of the library used at run time in lib_major_in_out and
lib_minor_in_out. If the versions of the compile time and run time libraries
are compatible, XkbLibraryVersion returns True, otherwise, it returns False.

In addition, in order to use the Xkb extension, you must ensure that the
extension is present in the server and that the server supports the version of
the extension expected by the client. Use XkbQueryExtension to do this, as
described in the next section.

Initializing the Keyboard Extension

Call XkbQueryExtension to check for the presence and compatibility of the
extension in the server and to initialize the extension. Because of potential
version mismatches, you cannot use the generic extension mechanism functions
(XQueryExtension and XInitExtension) for checking for the presence of, and
initializing the Xkb extension.

You must call XkbQueryExtension or XkbOpenDisplay before using any other Xkb
library interfaces, unless such usage is explicitly allowed in the interface
description in this document. The exceptions are: XkbIgnoreExtension,
XkbLibraryVersion, and a handful of audible-bell functions. You should not use
any other Xkb functions if the extension is not present or is uninitialized. In
general, calls to Xkb library functions made prior to initializing the Xkb
extension cause BadAccess protocol errors.

XkbQueryExtension both determines whether a compatible Xkb extension is present
in the X server and initializes the extension when it is present.

Bool XkbQueryExtension(Display *dpy, int *opcode_rtrn, int *event_rtrn, int
*error_rtrn, int *major_in_out, int *minor_in_out);

dpy          connection to the X server

opcode_rtrn  backfilled with the major extension opcode

event_rtrn   backfilled with the extension base event code

error_rtrn   backfilled with the extension base error code

major_in_out compile time lib major version in, server major version out

minor_in_out compile time lib min version in, server minor version out

The XkbQueryExtension function determines whether a compatible version of the X
Keyboard Extension is present in the server. If a compatible extension is
present, XkbQueryExtension returns True; otherwise, it returns False.

If a compatible version of Xkb is present, XkbQueryExtension initializes the
extension. It backfills the major opcode for the keyboard extension in
opcode_rtrn, the base event code in event_rtrn, the base error code in
error_rtrn, and the major and minor version numbers of the extension in
major_in_out and minor_in_out. The major opcode is reported in the req_major
fields of some Xkb events. For a discussion of the base event code, see section
4.1.

As a convenience, you can use the function XkbOpenDisplay to perform these
three tasks at once: open a connection to an X server, check for a compatible
version of the Xkb extension in both the library and the server, and initialize
the extension for use.

Display *XkbOpenDisplay(char *display_name, int *event_rtrn, int *error_rtrn,
int *major_in_out, int *minor_in_out, int *reason_rtrn);

display_name hardware display name, which determines the display and
             communications domain to be used

event_rtrn   backfilled with the extension base event code

error_rtrn   backfilled with the extension base error code

major_in_out compile time lib major version in, server major version out

minor_in_out compile time lib minor version in, server minor version out

reason_rtrn  backfilled with a status code

XkbOpenDisplay is a convenience function that opens an X display connection and
initializes the X keyboard extension. In all cases, upon return reason_rtrn
contains a status value indicating success or the type of failure. If
major_in_out and minor_in_out are not NULL, XkbOpenDisplay first calls
XkbLibraryVersion to determine whether the client library is compatible,
passing it the values pointed to by major_in_out and minor_in_out. If the
library is incompatible, XkbOpenDisplay backfills major_in_out and minor_in_out
with the major and minor extension versions of the library being used and
returns NULL. If the library is compatible, XkbOpenDisplay next calls
XOpenDisplay with the display_name. If this fails, the function returns NULL.
If successful, XkbOpenDisplay calls XkbQueryExtension and backfills the major
and minor Xkb server extension version numbers in major_in_out and minor_in_out
. If the server extension version is not compatible with the library extension
version or if the server extension is not present, XkbOpenDisplay closes the
display and returns NULL. When successful, the function returns the display
connection.

The possible values for reason_rtrn are:

  • XkbOD_BadLibraryVersion indicates XkbLibraryVersion returned False.

  • XkbOD_ConnectionRefused indicates the display could not be opened.

  • XkbOD_BadServerVersion indicates the library and the server have
    incompatible extension versions.

  • XkbOD_NonXkbServer indicates the extension is not present in the X server.

  • XkbOD_Success indicates that the function succeeded.

Disabling the Keyboard Extension

If a server supports the Xkb extension, the X library normally implements
preXkb keyboard functions using the Xkb keyboard description and state. The
server Xkb keyboard state may differ from the preXkb keyboard state. This
difference does not affect most clients, but there are exceptions. To allow
these clients to work properly, you may instruct the extension not to use Xkb
functionality.

Call XkbIgnoreExtension to prevent core X library keyboard functions from using
the X Keyboard Extension. You must call XkbIgnoreExtension before you open a
server connection; Xkb does not provide a way to enable or disable use of the
extension once a connection is established.

Bool XkbIgnoreExtension(Bool ignore);

ignore True means ignore the extension

XkbIgnoreExtension tells the X library whether to use the X Keyboard Extension
on any subsequently opened X display connections. If ignore is True, the
library does not initialize the Xkb extension when it opens a new display. This
forces the X server to use compatibility mode and communicate with the client
using only core protocol requests and events. If ignore is False, the library
treats subsequent calls to XOpenDisplay normally and uses Xkb extension
requests, events, and state. Do not explicitly use Xkb on a connection for
which it is disabled. XkbIgnoreExtension returns False if it was unable to
apply the ignore request.

Protocol Errors

Many of the Xkb extension library functions described in this document can
cause the X server to report an error, referred to in this document as a BadXxx
protocol error, where Xxx is some name. These errors are fielded in the normal
manner, by the default Xlib error handler or one replacing it. Note that X
protocol errors are not necessarily reported immediately because of the
buffering of X protocol requests in Xlib and the server.

Table 2.1 lists the protocol errors that can be generated, and their causes.

Table 2.1. Xkb Protocol Errors

┌─────────────────┬───────────────────────────────────────────────────────────┐
│Error            │Cause                                                      │
├─────────────────┼───────────────────────────────────────────────────────────┤
│BadAccess        │The Xkb extension has not been properly initialized        │
├─────────────────┼───────────────────────────────────────────────────────────┤
│BadKeyboard      │The device specified was not a valid core or input         │
│                 │extension device                                           │
├─────────────────┼───────────────────────────────────────────────────────────┤
│BadImplementation│Invalid reply from server                                  │
├─────────────────┼───────────────────────────────────────────────────────────┤
│BadAlloc         │Unable to allocate storage                                 │
├─────────────────┼───────────────────────────────────────────────────────────┤
│                 │A compatible version of Xkb was not available in the server│
│BadMatch         │or an argument has correct type and range, but is otherwise│
│                 │invalid                                                    │
├─────────────────┼───────────────────────────────────────────────────────────┤
│BadValue         │An argument is out of range                                │
├─────────────────┼───────────────────────────────────────────────────────────┤
│BadAtom          │A name is neither a valid Atom or None                     │
├─────────────────┼───────────────────────────────────────────────────────────┤
│BadDevice        │Device, Feedback Class, or Feedback ID invalid             │
└─────────────────┴───────────────────────────────────────────────────────────┘


The Xkb extension adds a single protocol error, BadKeyboard, to the core
protocol error set. This error code will be reported as the error_rtrn when
XkbQueryExtension is called. When a BadKeyboard error is reported in an 
XErrorEvent, additional information is reported in the resourceid field. The
most significant byte of the resource_id is a further refinement of the error
cause, as defined in Table 2.2. The least significant byte will contain the
device, class, or feedback ID as indicated in the table.

Table 2.2. BadKeyboard Protocol Error resource_id Values

┌────────────────┬─────┬────────────────────────────────────────────┬─────────┐
│high-order byte │value│meaning                                     │low-order│
│                │     │                                            │byte     │
├────────────────┼─────┼────────────────────────────────────────────┼─────────┤
│XkbErr_BadDevice│0xff │device not found                            │device ID│
├────────────────┼─────┼────────────────────────────────────────────┼─────────┤
│XkbErr_BadClass │0xfe │device found, but it is of the wrong class  │class ID │
├────────────────┼─────┼────────────────────────────────────────────┼─────────┤
│XkbErr_BadId    │0xfd │device found, class ok, but device does not │feedback │
│                │     │contain a feedback with the indicated ID    │ID       │
└────────────────┴─────┴────────────────────────────────────────────┴─────────┘


Display and Device Specifications in Function Calls

Where a connection to the server is passed as an argument (Display*) and an 
XkbDescPtr is also passed as an argument, the Display* argument must match the
dpy field of the XkbDescRec pointed to by the XkbDescPtr argument, or else the
dpy field of the XkbDescRec must be NULL. If they don’t match or the dpy field
is not NULL, a BadMatch error is returned (either in the return value or a
backfilled Status variable). Upon successful return, the dpy field of the 
XkbDescRec always contains the Display* value passed in.

The Xkb extension can communicate with the X input extension if it is present.
Consequently, there can potentially be more than one input device connected to
the server. Most Xkb library calls that require communicating with the server
involve both a server connection (Display * dpy) and a device identifier
(unsigned int device_spec). In some cases, the device identifier is implicit
and is taken as the device_spec field of an XkbDescRec structure passed as an
argument.

The device identifier can specify any X input extension device with a KeyClass
component, or it can specify the constant, XkbUseCoreKbd. The use of 
XkbUseCoreKbd allows applications to indicate the core keyboard without having
to determine its device identifier.

Where an Xkb device identifier is passed as an argument and an XkbDescPtr is
also passed as an argument, if either the argument or the XkbDescRec
device_spec field is XkbUseCoreKbd, and if the function returns successfully,
the XkbDescPtr device_spec field will have been converted from XkbUseCoreKbd to
a real Xkb device ID. If the function does not complete successfully, the
device_spec field remains unchanged. Subsequently, the device id argument must
match the device_spec field of the XkbDescPtr argument. If they don’t match, a 
BadMatch error is returned (either in the return value or a backfilled Status
variable).

When the Xkb extension in the server hands an application a device identifier
to use for the keyboard, that ID is the input extension identifier for the
device if the server supports the X Input Extension. If the server does not
support the input extension, the meaning of the identifier is undefined — the
only guarantee is that when you use XkbUseCoreKbd, XkbUseCoreKbd will work and
the identifier returned by the server will refer to the core keyboard device.

Chapter 3. Data Structures

Table of Contents

Allocating Xkb Data Structures
Adding Data and Editing Data Structures
Making Changes to the Server’s Keyboard Description
Tracking Keyboard Changes in the Server
Freeing Data Structures

An Xkb keyboard description consists of a variety of data structures, each of
which describes some aspect of the keyboard. Although each data structure has
its own peculiarities, there are a number of features common to nearly all Xkb
structures. This chapter describes these common features and techniques for
manipulating them.

Many Xkb data structures are interdependent; changing a field in one might
require changes to others. As an additional complication, some Xkb library
functions allocate related components as a group to reduce fragmentation and
allocator overhead. In these cases, simply allocating and freeing fields of Xkb
structures might corrupt program memory. Creating and destroying such
structures or keeping them properly synchronized during editing is complicated
and error prone.

Xkb provides functions and macros to allocate and free all major data
structures. You should use them instead of allocating and freeing the
structures yourself.

Allocating Xkb Data Structures

Xkb provides functions, known as allocators, to create and initialize Xkb data
structures. In most situations, the Xkb functions that read a keyboard
description from the server call these allocators automatically. As a result,
you will seldom have to directly allocate or initialize Xkb data structures.

However, if you need to enlarge an existing structure or construct a keyboard
definition from scratch, you may need to allocate and initialize Xkb data
structures directly. Each major Xkb data structure has its own unique
allocator. The allocator functions share common features: allocator functions
for structures with optional components take as an input argument a mask of
subcomponents to be allocated. Allocators for data structures containing
variable-length data take an argument specifying the initial length of the
data.

You may call an allocator to change the size of the space allocated for
variable-length data. When you call an allocator with an existing data
structure as a parameter, the allocator does not change the data in any of the
fields, with one exception: variable-length data might be moved. The allocator
resizes the allocated memory if the current size is too small. This normally
involves allocating new memory, copying existing data to the newly allocated
memory, and freeing the original memory. This possible reallocation is
important to note because local variables pointing into Xkb data structures
might be invalidated by calls to allocator functions.

Adding Data and Editing Data Structures

You should edit most data structures via the Xkb-supplied helper functions and
macros, although a few data structures can be edited directly. The helper
functions and macros make sure everything is initialized and interdependent
values are properly updated for those Xkb structures that have
interdependencies. As a general rule, if there is a helper function or macro to
edit the data structure, use it. For example, increasing the width of a type
requires you to resize every key that uses that type. This is complicated and
ugly, which is why there’s an XkbResizeKeyType function.

Many Xkb data structures have arrays whose size is reported by two fields. The
first field, whose name is usually prefixed by sz_, represents the total number
of elements that can be stored in the array. The second field, whose name is
usually prefixed by num_, specifies the number of elements currently stored
there. These arrays typically represent data whose total size cannot always be
determined when the array is created. In these instances, the usual way to
allocate space and add data is as follows:

  • Call the allocator function with some arbitrary size, as a hint.

  • For those arrays that have an Xkb...Add... function, call it each time you
    want to add new data to the array. The function expands the array if
    necessary.

For example, call:

XkbAllocGeomShapes(geom,4)

to say “I’ll need space for four new shapes in this geometry.” This makes sure
that sz_shapes − num_shapes >= 4, and resizes the shapes array if it isn’t. If
this function succeeds, you are guaranteed to have space for the number of
shapes you need.

When you call an editing function for a structure, you do not need to check for
space, because the function automatically checks the sz_ and num_ fields of the
array, resizes the array if necessary, adds the entry to the array, and then
updates the num_ field.

Making Changes to the Server’s Keyboard Description

In Xkb, as in the core protocol, the client and server have independent copies
of the data structures that describe the keyboard. The recommended way to
change some aspect of the keyboard mapping in the X server is to edit a local
copy of the Xkb keyboard description and then send only the changes to the X
server. This method helps eliminate the need to transfer the entire keyboard
description or even an entire data structure for only minor changes.

To help you keep track of the changes you make to a local copy of the keyboard
description, Xkb provides separate special changes data structures for each
major Xkb data structure. These data structures do not contain the actual
changed values: they only indicate the changes that have been made to the
structures that actually describe the keyboard.

When you wish to change the keyboard description in the server, you first
modify a local copy of the keyboard description and then flag the modifications
in an appropriate changes data structure. When you finish editing the local
copy of the keyboard description, you pass your modified version of the
keyboard description and the modified changes data structure to an Xkb
function. This function uses the modified keyboard description and changes
structure to pass only the changed information to the server. Note that
modifying the keyboard description but not setting the appropriate flags in the
changes data structure causes indeterminate behavior.

Tracking Keyboard Changes in the Server

The server reports all changes in its keyboard description to any interested
clients via special Xkb events. Just as clients use special changes data
structures to change the keyboard description in the server, the server uses
special changes data structures to tell a client what changed in the server’s
keyboard description.

Unlike clients, however, the server does not always pass the new values when it
reports changes to its copy of the keyboard description. Instead, the server
only passes a changes data structure when it reports changes to its keyboard
description. This is done for efficiency reasons — some clients do not always
need to update their copy of the keyboard description with every report from
the server.

When your client application receives a report from the server indicating the
keyboard description has changed, you can determine the set of changes by
passing the event to an Xkb function that “notes” event information in the
corresponding changes data structure. These “note changes” functions are
defined for all major Xkb components, and their names have the form XkbNote(
{Component}Changes), where Component is the name of a major Xkb component such
as Map or Names. When you want to copy these changes from the server into a
local copy of the keyboard description, use the corresponding XkbGet(
{Component}Changes) function, passing it the changes structure. The function
then retrieves only the changed structures from the server and copies the
modified pieces into the local keyboard description.

Freeing Data Structures

For the same reasons you should not directly use malloc to allocate Xkb data
structures, you should not free Xkb data structures or components directly
using free or Xfree. Xkb provides functions to free the various data structures
and their components. Always use the free functions supplied by Xkb. There is
no guarantee that any particular field can be safely freed by free or Xfree.

Chapter 4. Xkb Events

Table of Contents

Xkb Event Types
Xkb Event Data Structures
Selecting Xkb Events

    Event Masks

Unified Xkb Event Type

The primary way the X server communicates with clients is by sending X events
to them. Some events are sent to all clients, while others are sent only to
clients that have requested them. Some of the events that can be requested are
associated with a particular window and are only sent to those clients who have
both requested the event and specified the window in which the event occurred.

The Xkb extension uses events to communicate the keyboard status to interested
clients. These events are not associated with a particular window. Instead, all
Xkb keyboard status events are reported to all interested clients, regardless
of which window currently has the keyboard focus and regardless of the grab
state of the keyboard.^[2]

The X server reports the events defined by the Xkb extension to your client
application only if you have requested them. You may request Xkb events by
calling either XkbSelectEvents or XkbSelectEventDetails. XkbSelectEvents
requests Xkb events by their event type and causes them to be reported to your
client application under all circumstances. You can specify a finer granularity
for event reporting by using XkbSelectEventDetails; in this case events are
reported only when the specific detail conditions you specify have been met.

Xkb Event Types

The Xkb Extension adds new event types to the X protocol definition. An Xkb
event type is defined by two fields in the X event data structure. One is the
type field, containing the base event code. This base event code is a value the
X server assigns to each X extension at runtime and that identifies the
extension that generated the event; thus, the event code in the type field
identifies the event as an Xkb extension event, rather than an event from
another extension or a core X protocol event. You can obtain the base event
code via a call to XkbQueryExtension or XkbOpenDisplay. The second field is the
Xkb event type, which contains a value uniquely identifying each different Xkb
event type. Possible values are defined by constants declared in the header
file <X11/extensions/Xkb.h>.

Table 4.1 lists the categories of events defined by Xkb and their associated
event types, as defined in Xkb.h. Each event is described in more detail in the
section referenced for that event.

Table 4.1. Xkb Event Types

┌────────────────────────┬───────────────────────────────────────┬───────┐
│Event Type              │Conditions Generating Event            │Section│
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbNewKeyboardNotify    │Keyboard geometry; keycode range change│19     │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbMapNotify            │Keyboard mapping change                │14.4   │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbStateNotify          │Keyboard state change                  │5.4    │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbControlsNotify       │Keyboard controls state change         │10.11  │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbIndicatorStateNotify │Keyboard indicators state change       │8.5    │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbIndicatorMapNotify   │Keyboard indicators map change         │8.5    │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbNamesNotify          │Keyboard name change                   │18.5   │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbCompatMapNotify      │Keyboard compatibility map change      │17.5   │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbBellNotify           │Keyboard bell generated                │9.4    │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbActionMessage        │Keyboard action message                │16.1.11│
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbAccessXNotify        │AccessX state change                   │10.6.4 │
├────────────────────────┼───────────────────────────────────────┼───────┤
│XkbExtensionDeviceNotify│Extension device change                │21.6   │
└────────────────────────┴───────────────────────────────────────┴───────┘


Xkb Event Data Structures

Xkb reports each event it generates in a unique structure holding the data
values needed to describe the conditions the event is reporting. However, all
Xkb events have certain things in common. These common features are contained
in the same fields at the beginning of all Xkb event structures and are
described in the XkbAnyEvent structure:

typedef struct {
    int             type;        /* Xkb extension base event code */
    unsigned long   serial;      /* X server serial number for event */
    Bool            send_event;  /* True ⇒ synthetically generated */
    Display *       display;     /* server connection where event generated */
    Time            time;        /* server time when event generated */
    int             xkb_type;    /* Xkb minor event code */
    unsigned int    device;      /* Xkb device ID, will not be XkbUseCoreKbd */
} XkbAnyEvent;

For any Xkb event, the type field is set to the base event code for the Xkb
extension, assigned by the server to all Xkb extension events. The serial,
send_event, and display fields are as described for all X11 events. The time
field is set to the time when the event was generated and is expressed in
milliseconds. The xkb_type field contains the minor extension event code, which
is the extension event type, and is one of the values listed in Table 4.1. The
device field contains the keyboard device identifier associated with the event.
This is never XkbUseCoreKbd, even if the request that generated the event
specified a device of XkbUseCoreKbd. If the request that generated the event
specified XkbUseCoreKbd, device contains a value assigned by the server to
specify the core keyboard. If the request that generated the event specified an
X input extension device, device contains that same identifier.

Other data fields specific to individual Xkb events are described in subsequent
chapters where the events are described.

Selecting Xkb Events

Xkb events are selected using an event mask, much the same as normal core X
events are selected. However, unlike selecting core X events, where you must
specify the selection status (on or off) for all possible event types whenever
you wish to change the selection criteria for any one event, Xkb allows you to
restrict the specification to only the event types you wish to change. This
means that you do not need to remember the event selection values for all
possible types each time you want to change one of them.

Many Xkb event types are generated under several different circumstances. When
selecting to receive an Xkb event, you may specify either that you want it
delivered under all circumstances, or that you want it delivered only for a
subset of the possible circumstances.

You can also deselect an event type that was previously selected for, using the
same granularity.

Xkb provides two functions to select and deselect delivery of Xkb events.
XkbSelectEvents allows you to select or deselect delivery of more than one Xkb
event type at once. Events selected using XkbSelectEvents are delivered to your
program under all circumstances that generate the events. To restrict delivery
of an event to a subset of the conditions under which it occurs, use
XkbSelectEventDetails. XkbSelectEventDetails only allows you to change the
selection conditions for a single event at a time, but it provides a means of
fine-tuning the conditions under which the event is delivered.

To select and / or deselect for delivery of one or more Xkb events and have
them delivered under all conditions, use XkbSelectEvents.

Bool XkbSelectEvents(Display *display, unsigned int device_spec, unsigned long
int bits_to_change, unsigned long int values_for_bits);

display         connection to the X server

device_spec     device ID, or XkbUseCoreKbd

bits_to_change  determines events to be selected / deselected

values_for_bits 1⇒select, 0→deselect; for events in bits_to_change

This request changes the Xkb event selection mask for the keyboard specified by
device_spec.

Each Xkb event that can be selected is represented by a bit in the
bits_to_change and values_for_bits masks. Only the event selection bits
specified by the bits_to_change parameter are affected; any unspecified bits
are left unchanged. To turn on event selection for an event, set the bit for
the event in the bits_to_change parameter and set the corresponding bit in the
values_for_bits parameter. To turn off event selection for an event, set the
bit for the event in the bits_to_change parameter and do not set the
corresponding bit in the values_for_bits parameter. The valid values for both
of these parameters are an inclusive bitwise OR of the masks shown in Table 4.2
. There is no interface to return your client’s current event selection mask.
Clients cannot set other clients’ event selection masks.

If a bit is not set in the bits_to_change parameter, but the corresponding bit
is set in the values_for_bits parameter, a BadMatch protocol error results. If
an undefined bit is set in either the bits_to_change or the values_for_bits
parameter, a BadValue protocol error results.

All event selection bits are initially zero for clients using the Xkb
extension. Once you set some bits, they remain set for your client until you
clear them via another call to XkbSelectEvents.

XkbSelectEvents returns False if the Xkb extension has not been initialized and
True otherwise.

To select or deselect for a specific Xkb event and optionally place conditions
on when events of that type are reported to your client, use
XkbSelectEventDetails. This allows you to exercise a finer granularity of
control over delivery of Xkb events with XkbSelectEvents.

Bool XkbSelectEventDetails(Display *display, unsigned int device_spec, unsigned
int event_type, unsigned long int bits_to_change, unsigned long int
values_for_bits);

display         connection to the X server

device_spec     device ID, or XkbUseCoreKbd

event_type      Xkb event type of interest

bits_to_change  event selection details

values_for_bits values for bits selected by bits_to_change

While XkbSelectEvents allows multiple events to be selected,
XkbSelectEventDetails changes the selection criteria for a single type of Xkb
event. The interpretation of the bits_to_change and values_for_bits masks
depends on the event type in question.

XkbSelectEventDetails changes the Xkb event selection mask for the keyboard
specified by device_spec and the Xkb event specified by event_type. To turn on
event selection for an event detail, set the bit for the detail in the
bits_to_change parameter and set the corresponding bit in the values_for_bits
parameter. To turn off event detail selection for a detail, set the bit for the
detail in the bits_to_change parameter and do not set the corresponding bit in
the values_for_bits parameter.

If an invalid event type is specified, a BadValue protocol error results. If a
bit is not set in the bits_to_change parameter, but the corresponding bit is
set in the values_for_bits parameter, a BadMatch protocol error results. If an
undefined bit is set in either the bits_to_change or the values_for_bits
parameter, a BadValue protocol error results.

For each type of Xkb event, the legal event details that you can specify in the
XkbSelectEventDetails request are listed in the chapters that describe each
event in detail.

Event Masks

The X server reports the events defined by Xkb to your client application only
if you have requested them via a call to XkbSelectEvents or
XkbSelectEventDetails. Specify the event types in which you are interested in a
mask, as described in section 4.3.

Table 4.2 lists the event mask constants that can be specified with the
XkbSelectEvents request and the circumstances in which the mask should be
specified.

Table 4.2. XkbSelectEvents Mask Constants

┌────────────────────────────┬────────┬───────────────────────────────┐
│Event Mask                  │Value   │Notification Wanted            │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbNewKeyboardNotifyMask    │(1L<<0) │Keyboard geometry change       │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbMapNotifyMask            │(1L<<1) │Keyboard mapping change        │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbStateNotifyMask          │(1L<<2) │Keyboard state change          │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbControlsNotifyMask       │(1L<<3) │Keyboard control change        │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbIndicatorStateNotifyMask │(1L<<4) │Keyboard indicator state change│
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbIndicatorMapNotifyMask   │(1L<<5) │Keyboard indicator map change  │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbNamesNotifyMask          │(1L<<6) │Keyboard name change           │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbCompatMapNotifyMask      │(1L<<7) │Keyboard compat map change     │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbBellNotifyMask           │(1L<<8) │Bell                           │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbActionMessageMask        │(1L<<9) │Action message                 │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbAccessXNotifyMask        │(1L<<10)│AccessX features               │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbExtensionDeviceNotifyMask│(1L<<11)│Extension device               │
├────────────────────────────┼────────┼───────────────────────────────┤
│XkbAllEventsMask            │(0xFFF) │All Xkb events                 │
└────────────────────────────┴────────┴───────────────────────────────┘


Unified Xkb Event Type

The XkbEvent structure is a union of the individual structures declared for
each Xkb event type and for the core protocol XEvent type. Given an XkbEvent
structure, you may use the type field to determine if the event is an Xkb event
(type equals the Xkb base event code; see section 2.4). If the event is an Xkb
event, you may then use the any.xkb_type field to determine the type of Xkb
event and thereafter access the event-dependent components using the union
member corresponding to the particular Xkb event type.

typedef union _XkbEvent {
      int                            type;
      XkbAnyEvent                    any;
      XkbStateNotifyEvent            state;
      XkbMapNotifyEvent              map;
      XkbControlsNotifyEvent         ctrls;
      XkbIndicatorNotifyEvent        indicators;
      XkbBellNotifyEvent             bell;
      XkbAccessXNotifyEvent          accessx;
      XkbNamesNotifyEvent            names;
      XkbCompatMapNotifyEvent        compat;
      XkbActionMessageEvent          message;
      XkbExtensionDeviceNotifyEvent  device;
      XkbNewKeyboardNotifyEvent      new_kbd;
      XEvent                         core;
} XkbEvent;

This unified Xkb event type includes a normal XEvent as used by the core
protocol, so it is straightforward for applications that use Xkb events to call
the X library event functions without having to cast every reference. For
example, to get the next event, you can simply declare a variable of type 
XkbEvent and call:

XNextEvent(dpy,&xkbev.core);


━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

^[2] The one exception to this rule is the XkbExtensionDeviceNotify event
report that is sent when a client attempts to use an unsupported feature of an
X Input Extension device (see section 21.4).

Chapter 5. Keyboard State

Table of Contents

Keyboard State Description
Changing the Keyboard State

    Changing Modifiers
    Changing Groups

Determining Keyboard State
Tracking Keyboard State

Keyboard state encompasses all of the transitory information necessary to map a
physical key press or release to an appropriate event. The Xkb keyboard state
consists of primitive components and additional derived components that are
maintained for efficiency reasons. Figure 5.1 shows the components of Xkb
keyboard state and their relationships.

Figure 5.1. Xkb State


Keyboard State Description

The Xkb keyboard state is comprised of the state of all keyboard modifiers, the
keyboard group, and the state of the pointer buttons. These are grouped into
the following components:

  • The locked group and locked modifiers

  • The latched group and latched modifiers

  • The base group and base modifiers

  • The effective group and effective modifiers

  • The state of the core pointer buttons

The modifiers are Shift, Lock, Control, and Mod1 – Mod5, as defined by the core
protocol. A modifier can be thought of as a toggle that is either set or unset.
All modifiers are initially unset. When a modifier is locked, it is set and
remains set for all future key events, until it is explicitly unset. A latched
modifier is set, but automatically unsets after the next key event that does
not change the keyboard state. Locked and latched modifier state can be changed
by keyboard activity or via Xkb extension library functions.

The Xkb extension provides support for keysym groups, as defined by ISO9995:

      A logical state of a keyboard providing access to a collection of
Group characters. A group usually contains a set of characters that logically
      belong together and that may be arranged on several shift levels within
      that group.

The Xkb extension supports up to four keysym groups. Groups are named beginning
with one and indexed beginning with zero. All group states are indicated using
the group index. At any point in time, there is zero or one locked group, zero
or one latched group, and one base group. When a group is locked, it supersedes
any previous locked group and remains the locked group for all future key
events, until a new group is locked. A latched group applies only to the next
key event that does not change the keyboard state. The locked and latched group
can be changed by keyboard activity or via Xkb extension library functions.

Changing to a different group changes the keyboard state to produce characters
from a different group. Groups are typically used to switch between keysyms of
different languages and locales.

The pointer buttons are Button1 – Button5, as defined by the core protocol.

The base group and base modifiers represent keys that are physically or
logically down. These and the pointer buttons can be changed by keyboard
activity and not by Xkb requests. It is possible for a key to be logically
down, but not physically down, and neither latched nor locked. ^[3]

The effective modifiers are the bitwise union of the locked, latched, and the
base modifiers.

The effective group is the arithmetic sum of the group indices of the latched
group, locked group, and base group, which is then normalized by some function.
The result is a meaningful group index.

n = number of keyboard groups, 1<= n <= 4
0 <= any of locked, latched, or base group < n
effective group = f(locked group + latched group + base group)

The function f ensures that the effective group is within range. The precise
function is specified for the keyboard and can be retrieved through the
keyboard description. It may wrap around, clamp down, or default. Few
applications will actually examine the effective group, and far fewer still
will examine the locked, latched, and base groups.

There are two circumstances under which groups are normalized:

 1. The global locked or effective group changes. In this case, the changed
    group is normalized into range according to the settings of the groups_wrap
    field of the XkbControlsRec structure for the keyboard (see section 10.7.1
    ).

 2. The Xkb library is interpreting an event with an effective group that is
    legal for the keyboard as a whole, but not for the key in question. In this
    case, the group to use for this event only is determined using the
    group_info field of the key symbol mapping (XkbSymMapRec) for the event
    key.

Each nonmodifier key on a keyboard has zero or more symbols, or keysyms,
associated with it. These are the logical symbols that the key can generate
when it is pressed. The set of all possible keysyms for a keyboard is divided
into groups. Each key is associated with zero or more groups; each group
contains one or more symbols. When a key is pressed, the determination of which
symbol for the key is selected is based on the effective group and the shift
level, which is determined by which modifiers are set.

A client that does not explicitly call Xkb functions, but that otherwise makes
use of an X library containing the Xkb extension, will have keyboard state
represented in bits 0 – 14 of the state field of events that report modifier
and button state. Such a client is said to be Xkb-capable. A client that does
explicitly call Xkb functions is an Xkb-aware client. The Xkb keyboard state
includes information derived from the effective state and from two server
parameters that can be set through the keyboard extension. The following
components of keyboard state pertain to Xkb-capable and Xkb-aware clients:

  • lookup state: lookup group and lookup modifiers

  • grab state: grab group and grab modifiers

The lookup modifiers and lookup group are represented in the state field of
core X events. The modifier state and keycode of a key event are used to
determine the symbols associated with the event. For KeyPress and KeyRelease
events, the lookup modifiers are computed as:

   ((base | latched | locked) & ~server_internal_modifiers)

Otherwise the lookup modifiers are computed as:

   (((base | latched | (locked & ~ignore_locks)) & ~server_internal_modifiers)

The lookup group is the same as the effective group.

When an Xkb-capable or Xkb-aware client wishes to map a keycode to a keysym, it
should use the lookup state — the lookup group and the lookup modifiers.

The grab state is the state used when matching events to passive grabs. If the
event activates a grab, the grab modifiers and grab group are represented in
the state field of core X events; otherwise, the lookup state is used. The grab
modifiers are computed as:

   (((base | latched | (locked & ~ignore_locks)) & ~server_internal_modifiers)

If the server’s IgnoreGroupLock control (see section 10.7.3) is not set, the
grab group is the same as the effective group. Otherwise, the grab group is
computed from the base group and latched group, ignoring the locked group.

The final three components of Xkb state are applicable to clients that are not
linked with an Xlib containing the X keyboard extension library and therefore
are not aware of the keyboard extension (Xkb-unaware clients):

  • The compatibility modifier state

  • The compatibility lookup modifier state

  • The compatibility grab modifier state

The X11 protocol interpretation of modifiers does not include direct support
for multiple groups. When an Xkb-extended X server connects to an Xkb-unaware
client, the compatibility states remap the keyboard group into a core modifier
whenever possible. The compatibility state corresponds to the effective
modifier and effective group state, with the group remapped to a modifier. The
compatibility lookup and grab states correspond to the lookup and grab states,
respectively, with the group remapped to a modifier. The compatibility lookup
state is reported in events that do not trigger passive grabs; otherwise, the
compatibility grab state is reported.

Changing the Keyboard State

Changing Modifiers

The functions in this section that change the use of modifiers use a mask in
the parameter affect. It is a bitwise inclusive OR of the legal modifier masks:

Table 5.1. Real Modifier Masks

Mask
ShiftMask
LockMask
ControlMask
Mod1Mask
Mod2Mask
Mod3Mask
Mod4Mask
Mod5Mask


To lock and unlock any of the eight real keyboard modifiers, use
XkbLockModifiers:

Bool XkbLockModifiers(Display *display, unsigned int device_spec, unsigned int
affect, unsigned int values);

display     connection to the X server

device_spec device ID, or XkbUseCoreKbd

affect      mask of real modifiers whose lock state is to change

values      1 ⇒ lock, 0 ⇒ unlock; only for modifiers selected by affect

XkbLockModifiers sends a request to the server to lock the real modifiers
selected by both affect and values and to unlock the real modifiers selected by
affect but not selected by values. XkbLockModifiers does not wait for a reply
from the server. It returns True if the request was sent, and False otherwise.

To latch and unlatch any of the eight real keyboard modifiers, use
XkbLatchModifiers:

Bool XkbLatchModifiers(Display *display, unsigned int device_spec, unsigned int
affect, unsigned int values);

display     connection to the X server

device_spec device ID, or XkbUseCoreKbd

affect      mask of modifiers whose latch state is to change

values      1 ⇒ latch, 0 ⇒ unlatch; only for mods selected by affect

XkbLatchModifiers sends a request to the server to latch the real modifiers
selected by both affect and values and to unlatch the real modifiers selected
by affect but not selected by values. XkbLatchModifiers does not wait for a
reply from the server. It returns True if the request was sent, and False
otherwise.

Changing Groups

Reference the keysym group indices with these symbolic constants:

Table 5.2. Symbolic Group Names

┌───────────────┬─────┐
│Symbolic Name  │Value│
├───────────────┼─────┤
│XkbGroup1Index │0    │
├───────────────┼─────┤
│XkbGroup2Index │1    │
├───────────────┼─────┤
│XkbGroup3Index │2    │
├───────────────┼─────┤
│XkbGroup4Index │3    │
└───────────────┴─────┘


To lock the keysym group, use XkbLockGroup.

Bool XkbLockGroup(Display *display, unsigned int device_spec, unsigned int
group);

display     connection to the X server

device_spec device ID, or XkbUseCoreKbd

group       index of the keysym group to lock

XkbLockGroup sends a request to the server to lock the specified group and does
not wait for a reply. It returns True if the request was sent and False
otherwise.

To latch the keysym group, use XkbLatchGroup.

Bool XkbLatchGroup(Display *display, unsigned int device_spec, unsigned int
group);

display     connection to the X server

device_spec device ID, or XkbUseCoreKbd

group       index of the keysym group to latch

XkbLatchGroup sends a request to the server to latch the specified group and
does not wait for a reply. It returns True if the request was sent and False
otherwise.

Determining Keyboard State

Xkb keyboard state may be represented in an XkbStateRec structure:

typedef struct {
    unsigned char      group;                /* effective group index */
    unsigned char      base_group;           /* base group index */
    unsigned char      latched_group;        /* latched group index */
    unsigned char      locked_group;         /* locked group index */
    unsigned char      mods;                 /* effective modifiers */
    unsigned char      base_mods;            /* base modifiers */
    unsigned char      latched_mods;         /* latched modifiers */
    unsigned char      locked_mods;          /* locked modifiers */
    unsigned char      compat_state;         /* effective group ⇒ modifiers */
    unsigned char      grab_mods;            /* modifiers used for grabs */
    unsigned char      compat_grab_mods;     /* mods used for compatibility
                                                mode grabs */
    unsigned char      lookup_mods;          /* mods used to lookup symbols */
    unsigned char      compat_lookup_mods;   /* mods used for compatibility
                                                lookup */
    unsigned short     ptr_buttons;          /* 1 bit ⇒ corresponding
                                                pointer btn is down */
} XkbStateRec, *XkbStatePtr;

To obtain the keyboard state, use XkbGetState.

Status XkbGetState(Display *display, unsigned int device_spec, XkbStatePtr
state_return);

display      connection to the X server

device_spec  device ID, or XkbUseCoreKbd

state_return backfilled with Xkb state

The XkbGetState function queries the server for the current keyboard state,
waits for a reply, and then backfills state_return with the results.

All group values are expressed as group indices in the range [0..3]. Modifiers
and the compatibility modifier state values are expressed as the bitwise union
of the core X11 modifier masks. The pointer button state is reported as in the
core X11 protocol.

Tracking Keyboard State

The Xkb extension reports XkbStateNotify events to clients wanting notification
whenever the Xkb state changes. The changes reported include changes to any
aspect of the keyboard state: when a modifier is set or unset, when the current
group changes, or when a pointer button is pressed or released. As with all Xkb
events, XkbStateNotify events are reported to all interested clients without
regard to the current keyboard input focus or grab state.

There are many different types of Xkb state changes. Xkb defines an event
detail mask corresponding to each type of change. The event detail masks are
listed in Table 5.3.

Table 5.3. XkbStateNotify Event Detail Masks

┌─────────────────────────┬──────────┐
│Mask                     │Value     │
├─────────────────────────┼──────────┤
│XkbModifierStateMask     │(1L << 0) │
├─────────────────────────┼──────────┤
│XkbModifierBaseMask      │(1L << 1) │
├─────────────────────────┼──────────┤
│XkbModifierLatchMask     │(1L << 2) │
├─────────────────────────┼──────────┤
│XkbModifierLockMask      │(1L << 3) │
├─────────────────────────┼──────────┤
│XkbGroupStateMask        │(1L << 4) │
├─────────────────────────┼──────────┤
│XkbGroupBaseMask         │(1L << 5) │
├─────────────────────────┼──────────┤
│XkbGroupLatchMask        │(1L << 6) │
├─────────────────────────┼──────────┤
│XkbGroupLockMask         │(1L << 7) │
├─────────────────────────┼──────────┤
│XkbCompatStateMask       │(1L << 8) │
├─────────────────────────┼──────────┤
│XkbGrabModsMask          │(1L << 9) │
├─────────────────────────┼──────────┤
│XkbCompatGrabModsMask    │(1L << 10)│
├─────────────────────────┼──────────┤
│XkbLookupModsMask        │(1L << 11)│
├─────────────────────────┼──────────┤
│XkbCompatLookupModsMask  │(1L << 12)│
├─────────────────────────┼──────────┤
│XkbPointerButtonMask     │(1L << 13)│
├─────────────────────────┼──────────┤
│XkbAllStateComponentsMask│(0x3fff)  │
└─────────────────────────┴──────────┘


To track changes in the keyboard state for a particular device, select to
receive XkbStateNotify events by calling either XkbSelectEvents or
XkbSelectEventDetails (see section 4.3).

To receive XkbStateNotify events under all possible conditions, use
XkbSelectEvents and pass XkbStateNotifyMask in both bits_to_change and
values_for_bits.

To receive XkbStateNotify events only under certain conditions, use
XkbSelectEventDetails using XkbStateNotify as the event_type and specifying the
desired state changes in bits_to_change and values_for_bits using mask bits
from Table 5.3.

The structure for XkbStateNotify events is:

typedef struct {
    int            type;            /* Xkb extension base event code */
    unsigned long  serial;          /* X server serial number for event */
    Bool           send_event;      /* True ⇒ synthetically generated */
    Display *      display;         /* server connection where event generated */
    Time           time;            /* server time when event generated */
    int            xkb_type;        /* XkbStateNotify */
    int            device;          /* Xkb device ID,
                                       will not be XkbUseCoreKbd */
    unsigned int   changed;         /* bits indicating what has changed */
    int            group;           /* group index of effective group */
    int            base_group;      /* group index of base group */
    int            latched_group;   /* group index of latched group */
    int            locked_group;    /* group index of locked group */
    unsigned int   mods;            /* effective modifiers */
    unsigned int   base_mods;       /* base modifiers */
    unsigned int   latched_mods;    /* latched modifiers */
    unsigned int   locked_mods;     /* locked modifiers */
    int            compat_state;    /* computed compatibility state */
    unsigned char  grab_mods;       /* modifiers used for grabs */
    unsigned char  compat_grab_mods; /* modifiers used for compatibility grabs */
    unsigned char  lookup_mods;     /* modifiers used to lookup symbols */
    unsigned char  compat_lookup_mods; /* mods used for compatibility look up */
    int            ptr_buttons;     /* core pointer buttons */
    KeyCode        keycode;         /* keycode causing event,
                                       0 if programmatic */
    char           event_type;      /* core event if req_major or req_minor
                                       non zero */
    char           req_major;       /* major request code if program trigger,
                                       else 0 */
    char           req_minor;       /* minor request code if program trigger,
                                       else 0 */
} XkbStateNotifyEvent;

When you receive an XkbStateNotify event, the changed field indicates which
elements of keyboard state have changed. This will be the bitwise inclusive OR
of one or more of the XkbStateNotify event detail masks shown in Table 5.3. All
fields reported in the event are valid, but only those indicated in changed
have changed values.

The group field is the group index of the effective keysym group. The
base_group, latched_group, and locked_group fields are set to a group index
value representing the base group, the latched group, and the locked group,
respectively. The X server can set the modifier and compatibility state fields
to a union of the core modifier mask bits; this union represents the
corresponding modifier states. The ptr_buttons field gives the state of the
core pointer buttons as a mask composed of an inclusive OR of zero or more of
the core pointer button masks.

Xkb state changes can occur either in response to keyboard activity or under
application control. If a key event caused the state change, the keycode field
gives the keycode of the key event, and the event_type field is set to either 
KeyPress or KeyRelease. If a pointer button event caused the state change, the
keycode field is zero, and the event_type field is set to either ButtonPress or
ButtonRelease. Otherwise, the major and minor codes of the request that caused
the state change are given in the req_major and req_minor fields, and the
keycode field is zero. The req_major value is the same as the major extension
opcode.


━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

^[3] Keys may be logically down when they are physically up because of their
electrical properties or because of the keyboard extension in the X server
having filtered the key release, for esoteric reasons.

Chapter 6. Complete Keyboard Description

Table of Contents

The XkbDescRec Structure
Obtaining a Keyboard Description from the Server
Tracking Changes to the Keyboard Description in the Server
Allocating and Freeing a Keyboard Description

The complete Xkb description for a keyboard device is accessed using a single
structure containing pointers to major Xkb components. This chapter describes
this single structure and provides references to other sections of this
document that discuss the major Xkb components in detail.

The XkbDescRec Structure

The complete description of an Xkb keyboard is given by an XkbDescRec. The
component structures in the XkbDescRec represent the major Xkb components
outlined in Figure 1.1.

typedef struct {
    struct _XDisplay *  display;        /* connection to X server */
    unsigned short      flags;          /* private to Xkb, do not modify */
    unsigned short      device_spec;    /* device of interest */
    KeyCode             min_key_code;   /* minimum keycode for device */
    KeyCode             max_key_code;   /* maximum keycode for device */
    XkbControlsPtr      ctrls;          /* controls */
    XkbServerMapPtr     server;         /* server keymap */
    XkbClientMapPtr     map;            /* client keymap */
    XkbIndicatorPtr     indicators;     /* indicator map */
    XkbNamesPtr         names;          /* names for all components */
    XkbCompatMapPtr     compat;         /* compatibility map */
    XkbGeometryPtr      geom;           /* physical geometry of keyboard */
} XkbDescRec, *XkbDescPtr;

The display field points to an X display structure. The flags field is private
to the library: modifying flags may yield unpredictable results. The
device_spec field specifies the device identifier of the keyboard input device,
or XkbUseCoreKbd, which specifies the core keyboard device. The min_key_code
and max_key_code fields specify the least and greatest keycode that can be
returned by the keyboard.

The other fields specify structure components of the keyboard description and
are described in detail in other sections of this document. Table 6.1
identifies the subsequent sections of this document that discuss the individual
components of the XkbDescRec.

Table 6.1. XkbDescRec Component References

┌────────────────┬───────────────────────────────────────┐
│XkbDescRec Field│For more info                          │
├────────────────┼───────────────────────────────────────┤
│ctrls           │Chapter 10, Keyboard Controls          │
├────────────────┼───────────────────────────────────────┤
│server          │Chapter 16, Xkb Server Keyboard Mapping│
├────────────────┼───────────────────────────────────────┤
│map             │Chapter 15, Xkb Client Keyboard Mapping│
├────────────────┼───────────────────────────────────────┤
│indicators      │Chapter 8, Indicators                  │
├────────────────┼───────────────────────────────────────┤
│names           │Chapter 18, Symbolic Names             │
├────────────────┼───────────────────────────────────────┤
│compat          │Chapter 17, The Xkb Compatibility Map  │
├────────────────┼───────────────────────────────────────┤
│geom            │Chapter 13, Keyboard Geometry          │
└────────────────┴───────────────────────────────────────┘


Each structure component has a corresponding mask bit that is used in function
calls to indicate that the structure should be manipulated in some manner, such
as allocating it or freeing it. These masks and their relationships to the
fields in the XkbDescRec are shown in Table 6.2.

Table 6.2. Mask Bits for XkbDescRec

┌────────────────────┬────────────────┬───────┐
│Mask Bit            │XkbDescRec Field│Value  │
├────────────────────┼────────────────┼───────┤
│XkbControlsMask     │ctrls           │(1L<<0)│
├────────────────────┼────────────────┼───────┤
│XkbServerMapMask    │server          │(1L<<1)│
├────────────────────┼────────────────┼───────┤
│XkbIClientMapMask   │map             │(1L<<2)│
├────────────────────┼────────────────┼───────┤
│XkbIndicatorMapMask │indicators      │(1L<<3)│
├────────────────────┼────────────────┼───────┤
│XkbNamesMask        │names           │(1L<<4)│
├────────────────────┼────────────────┼───────┤
│XkbCompatMapMask    │compat          │(1L<<5)│
├────────────────────┼────────────────┼───────┤
│XkbGeometryMask     │geom            │(1L<<6)│
├────────────────────┼────────────────┼───────┤
│XkbAllComponentsMask│All Fields      │(0x7f) │
└────────────────────┴────────────────┴───────┘


Obtaining a Keyboard Description from the Server

To retrieve one or more components of a keyboard device description, use
XkbGetKeyboard (see also XkbGetKeyboardByName).

XkbDescPtr XkbGetKeyboard(Display *display, unsigned int which, unsigned int
device_spec);

display     connection to X server

which       mask indicating components to return

device_spec device for which to fetch description, or XkbUseCoreKbd

XkbGetKeyboard allocates and returns a pointer to a keyboard description. It
queries the server for those components specified in the which parameter for
device device_spec and copies the results to the XkbDescRec it allocated. The
remaining fields in the keyboard description are set to NULL. The valid masks
for which are those listed in Table 6.2.

XkbGetKeyboard can generate BadAlloc protocol errors.

To free the returned keyboard description, use XkbFreeKeyboard (see section 6.4
).

Tracking Changes to the Keyboard Description in the Server

The server can generate events whenever its copy of the keyboard description
for a device changes. Refer to section 14.4 for detailed information on
tracking changes to the keyboard description.

Allocating and Freeing a Keyboard Description

Applications seldom need to directly allocate a keyboard description; calling
XkbGetKeyboard usually suffices. In the event you need to create a keyboard
description from scratch, however, use XkbAllocKeyboard rather than directly
calling malloc or Xmalloc.

XkbDescRec *XkbAllocKeyboard(void);

If XkbAllocKeyboard fails to allocate the keyboard description, it returns NULL
. Otherwise, it returns a pointer to an empty keyboard description structure.
The device_spec field will have been initialized to XkbUseCoreKbd. You may then
either fill in the structure components or use Xkb functions to obtain values
for the structure components from a keyboard device.

To destroy either an entire an XkbDescRec or just some of its members, use
XkbFreeKeyboard.

void XkbFreeKeyboard(XkbDescPtr xkb, unsigned int which, Bool free_all);

xkb      keyboard description with components to free

which    mask selecting components to free

free_all True ⇒ free all components and xkb

XkbFreeKeyboard frees the components of xkb specified by which and sets the
corresponding values to NULL. If free_all is True, XkbFreeKeyboard frees every
non- NULL component of xkb and then frees the xkb structure itself.

Chapter 7. Virtual Modifiers

Table of Contents

Virtual Modifier Names and Masks
Modifier Definitions
Binding Virtual Modifiers to Real Modifiers
Virtual Modifier Key Mapping

    Inactive Modifier Sets

Conventions
Example

The core protocol specifies that certain keysyms, when bound to modifiers,
affect the rules of keycode to keysym interpretation for all keys; for example,
when the Num_Lock keysym is bound to some modifier, that modifier is used to
select between shifted and unshifted state for the numeric keypad keys. The
core protocol does not provide a convenient way to determine the mapping of
modifier bits (in particular Mod1 through Mod5) to keysyms such as Num_Lock and
Mode_switch. Using the core protocol only, a client application must retrieve
and search the modifier map to determine the keycodes bound to each modifier,
and then retrieve and search the keyboard mapping to determine the keysyms
bound to the keycodes. It must repeat this process for all modifiers whenever
any part of the modifier mapping is changed.

Xkb alleviates these problems by defining virtual modifiers. In addition to the
eight core modifiers, referred to as the real modifiers, Xkb provides a set of
sixteen named virtual modifiers. Each virtual modifier can be bound to any set
of the real modifiers ( Shift, Lock, Control, and Mod1 – Mod5).

The separation of function from physical modifier bindings makes it easier to
specify more clearly the intent of a binding. X servers do not all assign
modifiers the same way — for example, Num_Lock might be bound to Mod2 for one
vendor and to Mod4 for another. This makes it cumbersome to automatically remap
the keyboard to a desired configuration without some kind of prior knowledge
about the keyboard layout and bindings. With XKB, applications can use virtual
modifiers to specify the desired behavior, without regard for the actual
physical bindings in effect.

Virtual Modifier Names and Masks

Virtual modifiers are named by converting their string name to an X Atom and
storing the Atom in the names.vmods array in an XkbDescRec structure (see
section 6.1). The position of a name Atom in the names.vmods array defines the
bit position used to represent the virtual modifier and also the index used
when accessing virtual modifier information in arrays: the name in the i-th (0
relative) entry of names.vmods is the i-th virtual modifier, represented by the
mask (1<<i). Throughout Xkb, various functions have a parameter that is a mask
representing virtual modifier choices. In each case, the i-th bit (0 relative)
of the mask represents the i-th virtual modifier.

To set the name of a virtual modifier, use XkbSetNames, using 
XkbVirtualModNamesMask in which and the name in the xkb argument; to retrieve
indicator names, use XkbGetNames. These functions are discussed in Chapter 18, 
Symbolic Names.

Modifier Definitions

An Xkb modifier definition enumerates a collection of real and virtual
modifiers but does not in itself bind those modifiers to any particular key or
to each other. Modifier definitions are included in a number of structures in
the keyboard description to define the collection of modifiers that affect or
are affected by some other entity. A modifier definition is relevant only in
the context of some other entity such as an indicator map, a control, or a key
type. (See section 8.2.2, section 10.8, and section 15.2.)

typedef struct _XkbMods {
    unsigned char   mask;       /* real_mods | vmods mapped to real modifiers */
    unsigned char   real_mods;  /* real modifier bits */
    unsigned short  vmods;      /* virtual modifier bits */
} XkbModsRec, *XkbModsPtr;

An Xkb modifier definition consists of a set of bit masks corresponding to the
eight real modifiers (real_mods); a similar set of bitmasks corresponding to
the 16 named virtual modifiers (vmods); and an effective mask (mask). The
effective mask represents the set of all real modifiers that can logically be
set either by setting any of the real modifiers or by setting any of the
virtual modifiers in the definition. mask is derived from the real and virtual
modifiers and should never be explicitly changed — it contains all of the real
modifiers specified in the definition (real_mods) plus any real modifiers that
are bound to the virtual modifiers specified in the definition (vmods). The
binding of the virtual modifiers to real modifiers is exterior to the modifier
definition. Xkb automatically recomputes the mask field of modifier definitions
as necessary. Whenever you access a modifier definition that has been retrieved
using an Xkb library function, the mask field will be correct for the keyboard
mapping of interest.

Binding Virtual Modifiers to Real Modifiers

The binding of virtual modifiers to real modifiers is defined by the
server.vmods array in an XkbDescRec structure. Each entry contains the real
modifier bits that are bound to the virtual modifier corresponding to the
entry. The overall relationship of fields dealing with virtual modifiers in the
server keyboard description are shown in Figure 16.2.

Virtual Modifier Key Mapping

Xkb maintains a virtual modifier mapping, which lists the virtual modifiers
associated with, or bound to, each key. The real modifiers bound to a virtual
modifier always include all of the modifiers bound to any of the keys that
specify that virtual modifier in their virtual modifier mapping. The
server.vmodmap array indicates which virtual modifiers are bound to each key;
each entry is a bitmask for the virtual modifier bits. The server.vmodmap array
is indexed by keycode.

The vmodmap and vmods members of the server map are the “master” virtual
modifier definitions. Xkb automatically propagates any changes to these fields
to all other fields that use virtual modifier mappings (see section 16.4).

For example, if Mod3 is bound to the Num_Lock key by the core protocol modifier
mapping, and the NumLock virtual modifier is bound to they Num_Lock key by the
virtual modifier mapping, Mod3 is added to the set of modifiers associated with
NumLock.

The virtual modifier mapping is normally updated whenever actions are
automatically applied to symbols (see section 16.4 for details), and few
applications should need to change the virtual modifier mapping explicitly.

Use XkbGetMap (see section 14.2) to get the virtual modifiers from the server
or use XkbGetVirtualMods (see section 16.4.1) to update a local copy of the
virtual modifiers bindings from the server. To set the binding of a virtual
modifier to a real modifier, use XkbSetMap (see section 14.3).

To determine the mapping of virtual modifiers to core X protocol modifiers, use
XkbVirtualModsToReal.

Bool XkbVirtualModsToReal(XkbDescPtr xkb, unsigned int virtual_mask, unsigned
int *mask_rtrn);

xkb          keyboard description for input device

virtual_mask virtual modifier mask to translate

mask_rtrn    backfilled with real modifiers

If the keyboard description defined by xkb includes bindings for virtual
modifiers, XkbVirtualModsToReal uses those bindings to determine the set of
real modifiers that correspond to the set of virtual modifiers specified in
virtual_mask. The virtual_mask parameter is a mask specifying the virtual
modifiers to translate; the i-th bit (0 relative) of the mask represents the
i-th virtual modifier. If mask_rtrn is non- NULL, XkbVirtualModsToReal
backfills it with the resulting real modifier mask. If the keyboard description
in xkb does not include virtual modifier bindings, XkbVirtualModsToReal returns
False; otherwise, it returns True.

Note

It is possible for a local (client-side) keyboard description (the xkb
parameter) to not contain any virtual modifier information (simply because the
client has not requested it) while the server’s corresponding definition may
contain virtual modifier information.

Inactive Modifier Sets

An unbound virtual modifier is one that is not bound to any real modifier (
server->vmods [virtual_modifier_index] is zero).

Some Xkb operations ignore modifier definitions in which the virtual modifiers
are unbound. Consider this example:

        if (state matches {Shift}) Do OneThing;
        if (state matches {Shift+NumLock}) Do Another;

If the NumLock virtual modifier is not bound to any real modifiers, the
effective masks for these two cases are identical (that is, contain only Shift
). When it is essential to distinguish between OneThing and Another, Xkb
considers only those modifier definitions for which all virtual modifiers are
bound.

Conventions

The Xkb extension does not require any specific virtual modifier names.
However, everyone benefits if the same names are used for common modifiers. The
following names are suggested:

NumLock
ScrollLock
Alt
Meta
AltGr
LevelThree

Example

If the second (0-relative) entry in names.vmods contains the Atom for
"NumLock", then 0x4 (1<<2) is the virtual modifier bit for the NumLock virtual
modifier. If server.vmods [2] contains Mod3Mask, then the NumLock virtual
modifier is bound to the Mod3 real modifier.

A virtual modifier definition for this example would have:

     real_mods = 0
     vmods = 0x4 (NumLock named virtual modifier)
     mask = 0x20 (Mod3Mask)

Continuing the example, if the keyboard has a Num_Lock keysym bound to the key
with keycode 14, and the NumLock virtual modifier is bound to this key,
server.vmodmap[14] contains 0x4.

Finally, if the keyboard also used the real Mod1 modifier for numeric lock
operations, the modifier definition below would represent the situation where
either the key bound to Mod1 or the NumLock virtual modifier could be used for
this purpose:

     real_mods = 0x8 (Mod1Mask)
     vmods = 0x4 (NumLock named virtual modifier)
     mask = 0x28 (Mod1Mask | Mod3Mask)

Chapter 8. Indicators

Table of Contents

Indicator Names
Indicator Data Structures

    XkbIndicatorRec
    XkbIndicatorMapRec

Getting Information About Indicators

    Getting Indicator State
    Getting Indicator Information by Index
    Getting Indicator Information by Name

Changing Indicator Maps and State

    Effects of Explicit Changes on Indicators
    Changing Indicator Maps by Index
    Changing Indicator Maps by Name

Tracking Changes to Indicator State or Map
Allocating and Freeing Indicator Maps

Although the core X implementation supports up to 32 LEDs on an input device,
it does not provide any linkage between the state of the LEDs and the logical
state of the input device. For example, most keyboards have a CapsLock LED, but
X does not provide a mechanism to make the LED automatically follow the logical
state of the CapsLock key.

Furthermore, the core X implementation does not provide clients with the
ability to determine what bits in the led_mask field of the XKeyboardState map
to the particular LEDs on the keyboard. For example, X does not provide a
method for a client to determine what bit to set in the led_mask field to turn
on the Scroll Lock LED or whether the keyboard even has a Scroll Lock LED.

Xkb provides indicator names and programmable indicators to help solve these
problems. Using Xkb, clients can determine the names of the various indicators,
determine and control the way that the individual indicators should be updated
to reflect keyboard changes, and determine which of the 32 keyboard indicators
reported by the protocol are actually present on the keyboard. Clients may also
request immediate notification of changes to the state of any subset of the
keyboard indicators, which makes it straightforward to provide an on-screen “
virtual” LED panel. This chapter describes Xkb indicators and the functions
used for manipulating them.

Indicator Names

Xkb provides the capability of symbolically naming indicators. Xkb itself
doesn’t use these symbolic names for anything; they are there only to help make
the keyboard description comprehensible to humans. To set the names of specific
indicators, use XkbSetNames as discussed in Chapter 18, Symbolic Names. Then
set the map using XkbSetMap (see section 14.3) or XkbSetNamedDeviceIndicator
(below). To retrieve indicator names, use XkbGetNames (Chapter 18, Symbolic
Names).

Indicator Data Structures

Use the indicator description record, XkbIndicatorRec, and its indicator map, 
XkbIndicatorMapRec, to inquire about and control most indicator properties and
behaviors.

XkbIndicatorRec

The description for all the Xkb indicators is held in the indicators field of
the complete keyboard description (see Chapter 6, Complete Keyboard Description
), which is defined as follows:

#define      XkbNumIndicators      32

typedef struct {
    unsigned long           phys_indicators;            /* LEDs existence */
    XkbIndicatorMapRec      maps[XkbNumIndicators];     /* indicator maps */
} XkbIndicatorRec, *XkbIndicatorPtr;

This structure contains the phys_indicators field, which relates some
information about the correspondence between indicators and physical LEDs on
the keyboard, and an array of indicator maps, one map per indicator.

The phys_indicators field indicates which indicators are bound to physical LEDs
on the keyboard; if a bit is set in phys_indicators, then the associated
indicator has a physical LED associated with it. This field is necessary
because some indicators may not have corresponding physical LEDs on the
keyboard. For example, most keyboards have an LED for indicating the state of 
CapsLock, but most keyboards do not have an LED that indicates the current
group. Because phys_indicators describes a physical characteristic of the
keyboard, you cannot directly change it under program control. However, if a
client program loads a completely new keyboard description via
XkbGetKeyboardByName, or if a new keyboard is attached and the X implementation
notices, phys_indicators changes if the indicators for the new keyboard are
different.

XkbIndicatorMapRec

Each indicator has its own set of attributes that specify whether clients can
explicitly set its state and whether it tracks the keyboard state. The
attributes of each indicator are held in the maps array, which is an array of 
XkbIndicatorRec structures:

typedef struct {
    unsigned char  flags;         /* how the indicator can be changed */
    unsigned char  which_groups;  /* match criteria for groups */
    unsigned char  groups;        /* which keyboard groups the indicator watches */
    unsigned char  which_mods;    /* match criteria for modifiers */
    XkbModsRec     mods;          /* which modifiers the indicator watches */
    unsigned int   ctrls;         /* which controls the indicator watches */
} XkbIndicatorMapRec, *XkbIndicatorMapPtr;

This indicator map specifies for each indicator:

  • The conditions under which the keyboard modifier state affects the
    indicator

  • The conditions under which the keyboard group state affects the indicator

  • The conditions under which the state of the boolean controls affects the
    indicator

  • The effect (if any) of attempts to explicitly change the state of the
    indicator using the functions XkbSetControls or XChangeKeyboardControl

For more information on the effects of explicit changes to indicators and the
relationship to the indicator map, see section 8.4.1.

XkbIndicatorMapRec flags field

The flags field specifies the conditions under which the indicator can be
changed and the effects of changing the indicator. The valid values for flags
and their effects are shown in Table 8.1.

Table 8.1. XkbIndicatorMapRec flags Field

┌─────────────────┬────┬──────────────────────────────────────────────────────┐
│Value            │    │Effect                                                │
├─────────────────┼────┼──────────────────────────────────────────────────────┤
│XkbIM_NoExplicit │(1L │Client applications cannot change the state of the    │
│                 │<<7)│indicator.                                            │
├─────────────────┼────┼──────────────────────────────────────────────────────┤
│                 │    │Xkb does not automatically change the value of the    │
│XkbIM_NoAutomatic│(1L │indicator based upon a change in the keyboard state,  │
│                 │<<6)│regardless of the values for the other fields of the  │
│                 │    │indicator map.                                        │
├─────────────────┼────┼──────────────────────────────────────────────────────┤
│XkbIM_LEDDrivesKB│(1L │A client application changing the state of the        │
│                 │<<5)│indicator causes the state of the keyboard to change. │
└─────────────────┴────┴──────────────────────────────────────────────────────┘


Note that if XkbIM_NoAutomatic is not set, by default the indicator follows the
keyboard state.

If XkbIM_LEDDrivesKB is set and XkbIM_NoExplicit is not, and if you call a
function which updates the server’s image of the indicator map (such as
XkbSetIndicatorMap or XkbSetNamedDeviceIndicator), Xkb changes the keyboard
state and controls to reflect the other fields of the indicator map, as
described in the remainder of this section. If you attempt to explicitly change
the value of an indicator for which XkbIM_LEDDrivesKB is absent or for which 
XkbIM_NoExplicit is present, keyboard state or controls are unaffected.

For example, a keyboard designer may want to make the CapsLock LED controllable
only by the server, but allow the Scroll Lock LED to be controlled by client
applications. To do so, the keyboard designer could set the XkbIM_NoExplicit
flag for the CapsLock LED, but not set it for the Scroll Lock LED. Or the
keyboard designer may wish to allow the CapsLock LED to be controlled by both
the server and client applications and also have the server to automatically
change the CapsLock modifier state whenever a client application changes the 
CapsLock LED. To do so, the keyboard designer would not set the 
XkbIM_NoExplicit flag, but would instead set the XkbIM_LEDDrivesKB flag.

The remaining fields in the indicator map specify the conditions under which
Xkb automatically turns an indicator on or off (only if XkbIM_NoAutomatic is
not set). If these conditions match the keyboard state, Xkb turns the indicator
on. If the conditions do not match, Xkb turns the indicator off.

XkbIndicatorMapRec which_groups and groups fields

The which_groups and the groups fields of an indicator map determine how the
keyboard group state affects the corresponding indicator. The which_groups
field controls the interpretation of groups and may contain any one of the
following values:

#define XkbIM_UseNone             0
#define XkbIM_UseBase             (1L << 0)
#define XkbIM_UseLatched          (1L << 1)
#define XkbIM_UseLocked           (1L << 2)
#define XkbIM_UseEffective        (1L << 3)
#define XkbIM_UseAnyGroup         XkbIM_UseLatched | XkbIM_UseLocked |
                                  XkbIM_UseEffective

The groups field specifies what keyboard groups an indicator watches and is the
bitwise inclusive OR of the following valid values:

#define XkbGroup1Mask            (1<<0)
#define XkbGroup2Mask            (1<<1)
#define XkbGroup3Mask            (1<<2)
#define XkbGroup4Mask            (1<<3)
#define XkbAnyGroupMask          (1<<7)
#define XkbAllGroupsMask         (0xf)

If XkbIM_NoAutomatic is not set (the keyboard drives the indicator), the effect
of which_groups and groups is shown in Table 8.2.

Table 8.2. XkbIndicatorMapRec which_groups and groups, Keyboard Drives
Indicator

┌──────────────────┬──────────────────────────────────────────────────────────┐
│which_groups      │Effect                                                    │
├──────────────────┼──────────────────────────────────────────────────────────┤
│XkbIM_UseNone     │The groups field and the current keyboard group state are │
│                  │ignored.                                                  │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │If groups is nonzero, the indicator is lit whenever the   │
│XkbIM_UseBase     │base keyboard group is nonzero. If groups is zero, the    │
│                  │indicator is lit whenever the base keyboard group is zero.│
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │If groups is nonzero, the indicator is lit whenever the   │
│XkbIM_UseLatched  │latched keyboard group is nonzero. If groups is zero, the │
│                  │indicator is lit whenever the latched keyboard group is   │
│                  │zero.                                                     │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The groups field is interpreted as a mask. The indicator  │
│XkbIM_UseLocked   │is lit when the current locked keyboard group matches one │
│                  │of the bits that are set in groups.                       │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The groups field is interpreted as a mask. The indicator  │
│XkbIM_UseEffective│is lit when the current effective keyboard group matches  │
│                  │one of the bits that are set in groups.                   │
└──────────────────┴──────────────────────────────────────────────────────────┘


The effect of which_groups and groups when you change an indicator for which 
XkbIM_LEDDrivesKB is set (the indicator drives the keyboard) is shown in Table
8.3. The “New State” column refers to the new state to which you set the
indicator.

Table 8.3. XkbIndicatorMapRec which_groups and groups, Indicator Drives
Keyboard

┌──────────────────┬─────┬────────────────────────────────────────────────────┐
│which_groups      │New  │Effect on Keyboard Group State                      │
│                  │State│                                                    │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│XkbIM_UseNone     │On or│No effect                                           │
│                  │Off  │                                                    │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│XkbIM_UseBase     │On or│No effect                                           │
│                  │Off  │                                                    │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│                  │     │The groups field is treated as a group mask. The    │
│XkbIM_UseLatched  │On   │keyboard group latch is changed to the lowest       │
│                  │     │numbered group specified in groups; if groups is    │
│                  │     │empty, the keyboard group latch is changed to zero. │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│                  │     │The groups field is treated as a group mask. If the │
│                  │     │indicator is explicitly extinguished, keyboard group│
│XkbIM_UseLatched  │Off  │latch is changed to the lowest numbered group not   │
│                  │     │specified in groups; if groups is zero, the keyboard│
│                  │     │group latch is set to the index of the highest legal│
│                  │     │keyboard group.                                     │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│XkbIM_UseLocked or│     │If the groups mask is empty, group is not changed;  │
│XkbIM_UseEffective│On   │otherwise, the locked keyboard group is changed to  │
│                  │     │the lowest numbered group specified in groups.      │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│                  │     │Locked keyboard group is changed to the lowest      │
│XkbIM_UseLocked or│Off  │numbered group that is not specified in the groups  │
│XkbIM_UseEffective│     │mask, or to Group1 if the groups mask contains all  │
│                  │     │keyboard groups.                                    │
└──────────────────┴─────┴────────────────────────────────────────────────────┘


XkbIndicatorMapRec which_mods and mods fields

The mods field specifies what modifiers an indicator watches. The mods field is
an Xkb modifier definition, XkbModsRec, as described in section 7.2, which can
specify both real and virtual modifiers. The mods field takes effect even if
some or all of the virtual indicators specified in mods are unbound. To specify
the mods field, in general, assign the modifiers of interest to mods.real_mods
and the virtual modifiers of interest to mods.vmods. You can disregard the
mods.mask field unless your application needs to interpret the indicator map
directly (that is, to simulate automatic indicator behavior on its own).
Relatively few applications need to do so, but if you find it necessary, you
can either read the indicator map back from the server after you update it (the
server automatically updates the mask field whenever any of the real or virtual
modifiers are changed in the modifier definition) or you can use
XkbVirtualModsToReal to determine the proper contents for the mask field,
assuming that the XkbDescRec contains the virtual modifier definitions.

which_mods specifies what criteria Xkb uses to determine a match with the
corresponding mods field by specifying one or more components of the Xkb
keyboard state. If XkbIM_NoAutomatic is not set (the keyboard drives the
indicator), the indicator is lit whenever any of the modifiers specified in the
mask field of the mods modifier definition are also set in any of the current
keyboard state components specified by which_mods. Remember that the mask field
is comprised of all of the real modifiers specified in the definition plus any
real modifiers that are bound to the virtual modifiers specified in the
definition. (See Chapter 5, Keyboard State for more information on the keyboard
state and Chapter 7, Virtual Modifiers for more information on virtual
modifiers.) Use a bitwise inclusive OR of the following values to compose a
value for which_mods:

#define XkbIM_UseNone             0
#define XkbIM_UseBase             (1L << 0)
#define XkbIM_UseLatched          (1L << 1)
#define XkbIM_UseLocked           (1L << 2)
#define XkbIM_UseEffective        (1L << 3)
#define XkbIM_UseCompat           (1L << 4)
#define XkbIM_UseAnyMods          XkbIM_UseBase | XkbIM_UseLatched |
                                  XkbIM_UseLocked | XkbIM_UseEffective |
                                  XkbIM_UseCompat

If XkbIM_NoAutomatic is not set (the keyboard drives the indicator), the effect
of which_mods and mods is shown in Table 8.4

Table 8.4. XkbIndicatorMapRec which_mods and mods, Keyboard Drives Indicator

┌──────────────────┬──────────────────────────────────────────────────────────┐
│which_mods        │Effect on Keyboard Modifiers                              │
├──────────────────┼──────────────────────────────────────────────────────────┤
│XkbIM_UseNone     │The mods field and the current keyboard modifier state are│
│                  │ignored.                                                  │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The indicator is lit when any of the modifiers specified  │
│                  │in the mask field of mods are on in the keyboard base     │
│XkbIM_UseBase     │state. If both mods.real_mods and mods.vmods are zero, the│
│                  │indicator is lit when the base keyboard state contains no │
│                  │modifiers.                                                │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The indicator is lit when any of the modifiers specified  │
│XkbIM_UseLatched  │in the mask field of mods are latched. If both            │
│                  │mods.real_mods and mods.vmods are zero, the indicator is  │
│                  │lit when none of the modifier keys are latched.           │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The indicator is lit when any of the modifiers specified  │
│XkbIM_UseLocked   │in the mask field of mods are locked. If both             │
│                  │mods.real_mods and mods.vmods are zero, the indicator is  │
│                  │lit when none of the modifier keys are locked.            │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The indicator is lit when any of the modifiers specified  │
│                  │in the mask field of mods are in the effective keyboard   │
│XkbIM_UseEffective│state. If both mods.real_mods and mods.vmods are zero, the│
│                  │indicator is lit when the effective keyboard state        │
│                  │contains no modifiers.                                    │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The indicator is lit when any of the modifiers specified  │
│                  │in the mask field of mods are in the keyboard             │
│XkbIM_UseCompat   │compatibility state. If both mods.real_mods and mods.vmods│
│                  │are zero, the indicator is lit when the keyboard          │
│                  │compatibility state contains no modifiers.                │
└──────────────────┴──────────────────────────────────────────────────────────┘


The effect on the keyboard modifiers of which_mods and mods when you change an
indicator for which XkbIM_LEDDrivesKB is set (the indicator drives the
keyboard) is shown in Table 8.5. The “New State” column refers to the new state
to which you set the indicator.

Table 8.5. XkbIndicatorMapRec which_mods and mods, Indicator Drives Keyboard

┌─────────────────────────┬─────┬─────────────────────────────────────────────┐
│which_mods               │New  │Effect on Keyboard Modifiers                 │
│                         │State│                                             │
├─────────────────────────┼─────┼─────────────────────────────────────────────┤
│XkbIM_UseNone or         │On or│No Effect                                    │
│XkbIM_UseBase            │Off  │                                             │
├─────────────────────────┼─────┼─────────────────────────────────────────────┤
│XkbIM_UseLatched         │On   │Any modifiers specified in the mask field of │
│                         │     │mods are added to the latched modifiers.     │
├─────────────────────────┼─────┼─────────────────────────────────────────────┤
│XkbIM_UseLatched         │Off  │Any modifiers specified in the mask field of │
│                         │     │mods are removed from the latched modifiers. │
├─────────────────────────┼─────┼─────────────────────────────────────────────┤
│XkbIM_UseLocked,         │     │Any modifiers specified in the mask field of │
│XkbIM_UseCompat, or      │On   │mods are added to the locked modifiers.      │
│XkbIM_UseEffective       │     │                                             │
├─────────────────────────┼─────┼─────────────────────────────────────────────┤
│XkbIM_UseLocked          │Off  │Any modifiers specified in the mask field of │
│                         │     │mods are removed from the locked modifiers.  │
├─────────────────────────┼─────┼─────────────────────────────────────────────┤
│XkbIM_UseCompat or       │     │Any modifiers specified in the mask field of │
│XkbIM_UseEffective       │Off  │mods are removed from both the locked and    │
│                         │     │latched modifiers.                           │
└─────────────────────────┴─────┴─────────────────────────────────────────────┘


XkbIndicatorMapRec ctrls field

The ctrls field specifies what controls (see Chapter 10, Keyboard Controls) the
indicator watches and is composed using the bitwise inclusive OR of the
following values:

#define XkbRepeatKeysMask           (1L << 0)
#define XkbSlowKeysMask             (1L << 1)
#define XkbBounceKeysMask           (1L << 2)
#define XkbStickyKeysMask           (1L << 3)
#define XkbMouseKeysMask            (1L << 4)
#define XkbMouseKeysAccelMask       (1L << 5)
#define XkbAccessXKeysMask          (1L << 6)
#define XkbAccessXTimeoutMask       (1L << 7)
#define XkbAccessXFeedbackMask      (1L << 8)
#define XkbAudibleBellMask          (1L << 9)
#define XkbOverlay1Mask             (1L << 10)
#define XkbOverlay2Mask             (1L << 11)
#define XkbAllBooleanCtrlsMask      (0x00001FFF)

Xkb lights the indicator whenever any of the boolean controls specified in
ctrls is enabled.

Getting Information About Indicators

Xkb allows applications to obtain information about indicators using two
different methods. The first method, which is similar to the core X
implementation, uses a mask to specify the indicators. The second method, which
is more suitable for applications concerned with interoperability, uses
indicator names. The correspondence between the indicator name and the bit
position in masks is as follows: one of the parameters returned from
XkbGetNamedDeviceIndicator is an index that is the bit position to use in any
function call that requires a mask of indicator bits, as well as the
indicator’s index into the XkbIndicatorRec array of indicator maps.

Getting Indicator State

Because the state of the indicators is relatively volatile, the keyboard
description does not hold the current state of the indicators. To obtain the
current state of the keyboard indicators, use XkbGetIndicatorState.

Status XkbGetIndicatorState(Display *display, unsigned int device_spec,
unsigned int *state_return);

display      connection to the X server

device_spec  device ID, or XkbUseCoreKbd

state_return backfilled with a mask of the indicator state

XkbGetIndicatorState queries the display for the state of the indicators on the
device specified by the device_spec. For each indicator that is “turned on” on
the device, the associated bit is set in state_return. If a compatible version
of the Xkb extension is not available in the server, XkbGetIndicatorState
returns a BadMatch error. Otherwise, it sends the request to the X server,
places the state of the indicators into state_return, and returns Success. Thus
the value reported by XkbGetIndicatorState is identical to the value reported
by the core protocol.

Getting Indicator Information by Index

To get the map for one or more indicators, using a mask to specify the
indicators, use XkbGetIndicatorMap.

Status XkbGetIndicatorMap(Display *dpy, unsigned int which, XkbDescPtr desc);

dpy   connection to the X server

which mask of indicators for which maps should be returned

desc  keyboard description to be updated

XkbGetIndicatorMap obtains the maps from the server for only those indicators
specified by the which mask and copies the values into the keyboard description
specified by desc. If the indicators field of the desc parameter is NULL,
XkbGetIndicatorMap allocates and initializes it.

XkbGetIndicatorMap can generate BadAlloc, BadLength, BadMatch, and 
BadImplementation errors.

To free the indicator maps, use XkbFreeIndicatorMaps (see section 8.6).

Getting Indicator Information by Name

Xkb also allows applications to refer to indicators by name. Use XkbGetNames to
get the indicator names (see Chapter 18, Symbolic Names). Using names
eliminates the need for hard-coding bitmask values for particular keyboards.
For example, instead of using vendor-specific constants such as 
WSKBLed_ScrollLock mask on Digital workstations or XLED_SCROLL_LOCK on Sun
workstations, you can instead use XkbGetNamedDeviceIndicator or
XkbGetNamedIndicator to look up information on the indicator named “Scroll
Lock.”

Use XkbGetNamedDeviceIndicator to look up the indicator map and other
information for an indicator by name on a specific device.

Bool XkbGetNamedDeviceIndicator(Display *dpy, unsigned int device_spec,
unsigned int led_class, unsigned int led_id, Atom name, int *ndx_rtrn, Bool
*state_rtrn, XkbIndicatorMapPtr map_rtrn, Bool *real_rtrn);

dpy         connection to the X server

device_spec keyboard device ID, or XkbUseCoreKbd

led_class   feedback class, or XkbDfltXIClass

led_id      feedback ID, or XkbDfltXIId

name        name of the indicator to be retrieved

ndx_rtrn    backfilled with the index of the retrieved indicator

state_rtrn  backfilled with the current state of the retrieved indicator

map_rtrn    backfilled with the mapping for the retrieved indicator

real_rtrn   backfilled with True if the named indicator is real (physical)

If the device specified by device_spec with feedback specified by led_class and
led_id has an indicator named name, XkbGetNamedDeviceIndicator returns True and
populates the rest of the parameters with information about the indicator.
Otherwise, XkbGetNamedDeviceIndicator returns False.

The ndx_rtrn field returns the zero-based index of the named indicator. This
index is the bit position to use in any function call that requires a mask of
indicator bits, as well as the indicator’s index into the XkbIndicatorRec array
of indicator maps. state_rtrn returns the current state of the named indicator
(True = on, False = off). map_rtrn returns the indicator map for the named
indicator. In addition, if the indicator is mapped to a physical LED, the
real_rtrn parameter is set to True.

Each of the "_rtrn" arguments is optional; you can pass NULL for any unneeded "
_rtrn" arguments.

XkbGetNamedDeviceIndicator can generate BadAtom and BadImplementation errors.

As a convenience function, Xkb provides a function to get information about
indicators with the default class and identifier on the default device:
XkbGetNamedIndicator.

Bool XkbGetNamedIndicator(Display *dpy, Atom name, int *ndx_rtrn, Bool
*state_rtrn, XkbIndicatorMapPtr map_rtrn, Bool *real_rtrn);

dpy        connection to the X server

name       name of the indicator to be retrieved

ndx_rtrn   backfilled with the index of the retrieved indicator

state_rtrn backfilled with the current state of the retrieved indicator

map_rtrn   backfilled with the mapping for the retrieved indicator

real_rtrn  backfilled with True if the named indicator is real (physical)

XkbGetNamedIndicator calls XkbGetNamedDeviceIndicator with the specified
parameters, a device_spec of XkbUseCoreKbd, a led_class of XkbDfltXIClass, and
a led_id of XkbDfltXIId, and returns the value which was returned by
XkbGetNamedDeviceIndicator.

Changing Indicator Maps and State

Just as you can get the indicator map using a mask or using an indicator name,
so you can change it using a mask or a name.

Note

You cannot change the phys_indicators field of the indicators structure. The
only way to change the phys_indicators field is to change the keyboard map.

To make changes to indicator maps and state, change a local copy of the
indicator maps and use XkbSetIndicatorMap or XkbSetNamedDeviceIndicator.

Effects of Explicit Changes on Indicators

This section discusses the effects of explicitly changing indicators depending
upon different settings in the indicator map. See Table 8.3 and Table 8.5 for
information on the effects of the indicator map fields when explicit changes
are made.

If XkbIM_LEDDrivesKB is set and XkbIM_NoExplicit is not, and if you call a
function that updates the server’s image of the indicator map (such as
XkbSetIndicatorMap or XkbSetNamedDeviceIndicator), Xkb changes the keyboard
state and controls to reflect the other fields of the indicator map. If you
attempt to explicitly change the value of an indicator for which 
XkbIM_LEDDrivesKB is absent or for which XkbIM_NoExplicit is present, keyboard
state or controls are unaffected.

If neither XkbIM_NoAutomatic nor XkbIM_NoExplicit is set in an indicator map,
Xkb honors any request to change the state of the indicator, but the new state
might be immediately superseded by automatic changes to the indicator state if
the keyboard state or controls change.

The effects of changing an indicator that drives the keyboard are cumulative;
it is possible for a single change to affect keyboard group, modifiers, and
controls simultaneously.

If you change an indicator for which both the XkbIM_LEDDrivesKB and 
XkbIM_NoAutomatic flags are specified, Xkb applies the keyboard changes
specified in the other indicator map fields and changes the indicator to
reflect the state that was explicitly requested. The indicator remains in the
new state until it is explicitly changed again.

If the XkbIM_NoAutomatic flag is not set and XkbIM_LEDDrivesKB is set, Xkb
applies the changes specified in the other indicator map fields and sets the
state of the indicator to the values specified by the indicator map. Note that
it is possible in this case for the indicator to end up in a different state
than the one that was explicitly requested. For example, Xkb does not
extinguish an indicator with which_mods of XkbIM_UseBase and mods of Shift if,
at the time Xkb processes the request to extinguish the indicator, one of the 
Shift keys is physically depressed.

If you explicitly light an indicator for which XkbIM_LEDDrivesKB is set, Xkb
enables all of the boolean controls specified in the ctrls field of its
indicator map. Explicitly extinguishing such an indicator causes Xkb to disable
all of the boolean controls specified in ctrls.

Changing Indicator Maps by Index

To update the maps for one or more indicators, first modify a local copy of the
keyboard description, then use XkbSetIndicatorMap to download the changes to
the server:

Bool XkbSetIndicatorMap(Display *dpy, unsigned int which, XkbDescPtr desc);

dpy   connection to the X server

which mask of indicators to change

desc  keyboard description from which the maps are taken

For each bit set in the which parameter, XkbSetIndicatorMap sends the
corresponding indicator map from the desc parameter to the server.

Changing Indicator Maps by Name

XkbSetNamedDeviceIndicator and XkbSetNamedIndicator can do several related
things:

  • Name an indicator if it is not already named

  • Toggle the state of the indicator

  • Set the indicator to a specified state

  • Set the indicator map for the indicator

BoolXkbSetNamedDeviceIndicator(Display *dpy, unsigned int device_spec, unsigned
int led_class, unsigned int led_id, Atom name, Bool change_state, Bool state,
Bool create_new, XkbIndicatorMapPtr map);

dpy          connection to the X server

device_spec  device ID, or XkbUseCoreKbd

led_class    feedback class, or XkbDfltXIClass

led_id       feedback ID, or XkbDfltXIId

name         name of the indicator to change

change_state whether to change the indicator state or not

state        desired new state for the indicator

create_new   whether a new indicator with the specified name should be created
             when necessary

map          new map for the indicator

If a compatible version of the Xkb extension is not available in the server,
XkbSetNamedDeviceIndicator returns False. Otherwise, it sends a request to the
X server to change the indicator specified by name and returns True.

If change_state is True, XkbSetNamedDeviceIndicator tells the server to change
the state of the named indicator to the value specified by state. If
change_state is False, state is not used.

If an indicator with the name specified by name does not already exist, the
create_new parameter tells the server whether it should create a new named
indicator. If create_new is True, the server finds the first indicator that
doesn’t have a name and gives it the name specified by name.

If the optional parameter, map, is not NULL, XkbSetNamedDeviceIndicator tells
the server to change the indicator’s map to the values specified in map.

XkbSetNamedDeviceIndicator can generate BadAtom and BadImplementation errors.
In addition, it can also generate XkbIndicatorStateNotify (see section 8.5), 
XkbIndicatorMapNotify, and XkbNamesNotify events (see section 18.5).

As a convenience function, Xkb provides a function to set information about
indicators with the default class and identifier on the default device:
XkbSetNamedIndicator.

BoolXkbSetNamedIndicator(Display *dpy, Atom name, Bool change_state, Bool
state, Bool create_new, XkbIndicatorMapPtr map);

dpy          connection to the X server

name         name of the indicator to change

change_state whether to change the indicator state or not

state        desired new state for the indicator

create_new   whether a new indicator with the specified name should be created
             when necessary

map          new map for the indicator

XkbSetNamedIndicator calls XkbSetNamedDeviceIndicator with the specified
parameters, a device_spec of XkbUseCoreKbd, a led_class of XkbDfltXIClass, and
a led_id of XkbDfltXIId, and returns the value which was returned by
XkbSetNamedDeviceIndicator.

Tracking Changes to Indicator State or Map

Whenever an indicator changes state, the server sends XkbIndicatorStateNotify
events to all interested clients. Similarly, whenever an indicator’s map
changes, the server sends XkbIndicatorMapNotify events to all interested
clients.

To receive XkbIndicatorStateNotify events, use XkbSelectEvents (see section 4.3
) with both the bits_to_change and values_for_bits parameters containing 
XkbIndicatorStateNotifyMask. To receive XkbIndicatorMapNotify events, use
XkbSelectEvents with XkbIndicatorMapNotifyMask.

To receive events for only specific indicators, use XkbSelectEventDetails. Set
the event_type parameter to XkbIndicatorStateNotify or XkbIndicatorMapNotify,
and set both the bits_to_change and values_for_bits detail parameters to a mask
where each bit specifies one indicator, turning on those bits that specify the
indicators for which you want to receive events.

Both types of indicator events use the same structure:

typedef struct _XkbIndicatorNotify {
    int            type;        /* Xkb extension base event code */
    unsigned long  serial;      /* X server serial number for event */
    Bool           send_event;  /* True ⇒ synthetically generated */
    Display *      display;     /* server connection where event generated */
    Time           time;        /* server time when event generated */
    int            xkb_type;    /* specifies state or map notify */
    int            device;      /* Xkb device ID, will not be XkbUseCoreKbd */
    unsigned int   changed;     /* mask of indicators with new state or map */
    unsigned int   state;       /* current state of all indicators */
} XkbIndicatorNotifyEvent;

xkb_type is either XkbIndicatorStateNotify or XkbIndicatorMapNotify, depending
on whether the event is a XkbIndicatorStateNotify event or 
XkbIndicatorMapNotify, event.

The changed parameter is a mask that is the bitwise inclusive OR of the
indicators that have changed. If the event is of type XkbIndicatorMapNotify,
changed reports the maps that changed. If the event is of type 
XkbIndicatorStateNotify, changed reports the indicators that have changed
state. state is a mask that specifies the current state of all indicators,
whether they have changed or not, for both XkbIndicatorStateNotify and 
XkbIndicatorMapNotify events.

Allocating and Freeing Indicator Maps

Most applications do not need to directly allocate the indicators member of the
keyboard description record (the keyboard description record is described in
Chapter 6, Complete Keyboard Description). If the need arises, however, use
XkbAllocIndicatorMaps.

Status XkbAllocIndicatorMaps(XkbDescPtr xkb);

xkb keyboard description structure

The xkb parameter must point to a valid keyboard description. If it doesn’t,
XkbAllocIndicatorMaps returns a BadMatch error. Otherwise,
XkbAllocIndicatorMaps allocates and initializes the indicators member of the
keyboard description record and returns Success. If XkbAllocIndicatorMaps was
unable to allocate the indicators record, it reports a BadAlloc error.

To free memory used by the indicators member of an XkbDescRec structure, use
XkbFreeIndicatorMaps.

void XkbFreeIndicatorMaps(XkbDescPtr xkb);

xkb keyboard description structure

If the indicators member of the keyboard description record pointed to by xkb
is not NULL, XkbFreeIndicatorMaps frees the memory associated with the
indicators member of xkb.

Chapter 9. Bells

Table of Contents

Bell Names
Audible Bells
Bell Functions

    Generating Named Bells
    Generating Named Bell Events
    Forcing a Server-Generated Bell

Detecting Bells

The core X protocol allows only applications to explicitly sound the system
bell with a given duration, pitch, and volume. Xkb extends this capability by
allowing clients to attach symbolic names to bells, disable audible bells, and
receive an event whenever the keyboard bell is rung. For the purposes of this
document, the audible bell is defined to be the system bell, or the default
keyboard bell, as opposed to any other audible sound generated elsewhere in the
system.

You can ask to receive XkbBellNotify events (see section 9.4) when any client
rings any one of the following:

  • The default bell

  • Any bell on an input device that can be specified by a bell_class and
    bell_id pair

  • Any bell specified only by an arbitrary name. (This is, from the server’s
    point of view, merely a name, and not connected with any physical
    sound-generating device. Some client application must generate the sound,
    or visual feedback, if any, that is associated with the name.)

You can also ask to receive XkbBellNotify events when the server rings the
default bell or if any client has requested events only (without the bell
sounding) for any of the bell types previously listed.

You can disable audible bells on a global basis (to set the AudibleBell
control, see Chapter 10, Keyboard Controls). For example, a client that
replaces the keyboard bell with some other audible cue might want to turn off
the AudibleBell control to prevent the server from also generating a sound and
avoid cacophony. If you disable audible bells and request to receive 
XkbBellNotify events, you can generate feedback different from the default
bell.

You can, however, override the AudibleBell control by calling one of the
functions that force the ringing of a bell in spite of the setting of the 
AudibleBell control — XkbForceDeviceBell or XkbForceBell (see section 9.3.3).
In this case the server does not generate a bell event.

Just as some keyboards can produce keyclicks to indicate when a key is pressed
or repeating, Xkb can provide feedback for the controls by using special beep
codes. The AccessXFeedback control is used to configure the specific types of
operations that generate feedback. See section 10.6.3 for a discussion on 
AccessXFeedback control.

This chapter describes bell names, the functions used to generate named bells,
and the events the server generates for bells.

Bell Names

You can associate a name to an act of ringing a bell by converting the name to
an Atom and then using this name when you call the functions listed in this
chapter. If an event is generated as a result, the name is then passed to all
other clients interested in receiving XkbBellNotify events. Note that these are
arbitrary names and that there is no binding to any sounds. Any sounds or other
effects (such as visual bells on the screen) must be generated by a client
application upon receipt of the bell event containing the name. There is no
default name for the default keyboard bell. The server does generate some
predefined bells for the AccessX controls (see section 10.6.3). These named
bells are shown in Table 9.1; the name is included in any bell event sent to
clients that have requested to receive XkbBellNotify events.

Table 9.1. Predefined Bells

┌────────────────────────────────────────────────────┬──────────────────┐
│Action                                              │Named Bell        │
├────────────────────────────────────────────────────┼──────────────────┤
│Indicator turned on                                 │AX_IndicatorOn    │
├────────────────────────────────────────────────────┼──────────────────┤
│Indicator turned off                                │AX_IndicatorOff   │
├────────────────────────────────────────────────────┼──────────────────┤
│More than one indicator changed state               │AX_IndicatorChange│
├────────────────────────────────────────────────────┼──────────────────┤
│Control turned on                                   │AX_FeatureOn      │
├────────────────────────────────────────────────────┼──────────────────┤
│Control turned off                                  │AX_FeatureOff     │
├────────────────────────────────────────────────────┼──────────────────┤
│More than one control changed state                 │AX_FeatureChange  │
├────────────────────────────────────────────────────┼──────────────────┤
│SlowKeys and BounceKeys about to be turned on or off│AX_SlowKeysWarning│
├────────────────────────────────────────────────────┼──────────────────┤
│SlowKeys key pressed                                │AX_SlowKeyPress   │
├────────────────────────────────────────────────────┼──────────────────┤
│SlowKeys key accepted                               │AX_SlowKeyAccept  │
├────────────────────────────────────────────────────┼──────────────────┤
│SlowKeys key rejected                               │AX_SlowKeyReject  │
├────────────────────────────────────────────────────┼──────────────────┤
│Accepted SlowKeys key released                      │AX_SlowKeyRelease │
├────────────────────────────────────────────────────┼──────────────────┤
│BounceKeys key rejected                             │AX_BounceKeyReject│
├────────────────────────────────────────────────────┼──────────────────┤
│StickyKeys key latched                              │AX_StickyLatch    │
├────────────────────────────────────────────────────┼──────────────────┤
│StickyKeys key locked                               │AX_StickyLock     │
├────────────────────────────────────────────────────┼──────────────────┤
│StickyKeys key unlocked                             │AX_StickyUnlock   │
└────────────────────────────────────────────────────┴──────────────────┘


Audible Bells

Using Xkb you can generate bell events that do not necessarily ring the system
bell. This is useful if you need to use an audio server instead of the system
beep. For example, when an audio client starts, it could disable the audible
bell (the system bell) and then listen for XkbBellNotify events (see section
9.4). When it receives a XkbBellNotify event, the audio client could then send
a request to an audio server to play a sound.

You can control the audible bells feature by passing the XkbAudibleBellMask to
XkbChangeEnabledControls (see section 10.1.1). If you set XkbAudibleBellMask
on, the server rings the system bell when a bell event occurs. This is the
default. If you set XkbAudibleBellMask off and a bell event occurs, the server
does not ring the system bell unless you call XkbForceDeviceBell or
XkbForceBell (see section 9.3.3).

Audible bells are also part of the per-client auto-reset controls. For more
information on auto-reset controls, see section 10.1.2.

Bell Functions

Use the functions described in this section to ring bells and to generate bell
events.

The input extension has two types of feedbacks that can generate bells — bell
feedback and keyboard feedback. Some of the functions in this section have
bell_class and bell_id parameters; set them as follows: Set bell_class to 
BellFeedbackClass or KbdFeedbackClass. A device can have more than one feedback
of each type; set bell_id to the particular bell feedback of bell_class type.

Table 9.2 shows the conditions that cause a bell to sound or an 
XkbBellNotifyEvent to be generated when a bell function is called.

Table 9.2. Bell Sounding and Bell Event Generating

┌──────────────────┬───────────┬─────────────────┬────────────────────────────┐
│Function called   │AudibleBell│Server sounds a  │Server sends an             │
│                  │           │bell             │XkbBellNotifyEvent          │
├──────────────────┼───────────┼─────────────────┼────────────────────────────┤
│XkbDeviceBell     │On         │Yes              │Yes                         │
├──────────────────┼───────────┼─────────────────┼────────────────────────────┤
│XkbDeviceBell     │Off        │No               │Yes                         │
├──────────────────┼───────────┼─────────────────┼────────────────────────────┤
│XkbBell           │On         │Yes              │Yes                         │
├──────────────────┼───────────┼─────────────────┼────────────────────────────┤
│XkbBell           │Off        │No               │Yes                         │
├──────────────────┼───────────┼─────────────────┼────────────────────────────┤
│XkbDeviceBellEvent│On or Off  │No               │Yes                         │
├──────────────────┼───────────┼─────────────────┼────────────────────────────┤
│XkbBellEvent      │On or Off  │No               │Yes                         │
├──────────────────┼───────────┼─────────────────┼────────────────────────────┤
│XkbDeviceForceBell│On or Off  │Yes              │No                          │
├──────────────────┼───────────┼─────────────────┼────────────────────────────┤
│XkbForceBell      │On or Off  │Yes              │No                          │
└──────────────────┴───────────┴─────────────────┴────────────────────────────┘


Generating Named Bells

To ring the bell on an X input extension device or the default keyboard, use
XkbDeviceBell.

Bool XkbDeviceBell(Display *display, Window window, unsigned int device_spec,
unsigned int bell_class, unsigned int bell_id, int percent, Atom name);

display     connection to the X server

window      window for which the bell is generated, or None

device_spec device ID, or XkbUseCoreKbd

bell_class  X input extension bell class of the bell to be rung

bell_id     X input extension bell ID of the bell to be rung

percent     bell volume, from −100 to 100 inclusive

name        a name for the bell, or NULL

Set percent to be the volume relative to the base volume for the keyboard as
described for XBell.

Note that bell_class and bell_id indicate the bell to physically ring. name is
simply an arbitrary moniker for the client application’s use.

To determine the current feedback settings of an extension input device, use
XGetFeedbackControl. See the X input extension documentation for more
information on XGetFeedbackControl and related data structures.

If a compatible keyboard extension is not present in the X server,
XkbDeviceBell immediately returns False. Otherwise, XkbDeviceBell rings the
bell as specified for the display and keyboard device and returns True. If you
have disabled the audible bell, the server does not ring the system bell,
although it does generate a XkbBellNotify event.

You can call XkbDeviceBell without first initializing the keyboard extension.

As a convenience function, Xkb provides a function to ring the bell on the
default keyboard: XkbBell.

Bool XkbBell(Display *display, Window window, int percent, Atom name);

display connection to the X server

window  event window, or None

percent relative volume, which can range from −100 to 100 inclusive

name    a bell name, or NULL

If a compatible keyboard extension isn’t present in the X server, XkbBell calls
XBell with the specified display and percent, and returns False. Otherwise,
XkbBell calls XkbDeviceBell with the specified display, window, percent, and
name, a device_spec of XkbUseCoreKbd, a bell_class of XkbDfltXIClass, and a
bell_id of XkbDfltXIId, and returns True.

If you have disabled the audible bell, the server does not ring the system
bell, although it does generate a XkbBellNotify event.

You can call XkbBell without first initializing the keyboard extension.

Generating Named Bell Events

Using Xkb, you can also generate a named bell event that does not ring any
bell. This allows you to do things such as generate events when your
application starts.

For example, if an audio client listens for these types of bells, it can
produce a “whoosh” sound when it receives a named bell event to indicate a
client just started. In this manner, applications can generate start-up
feedback and not worry about producing annoying beeps if an audio server is not
running.

To cause a bell event for an X input extension device or for the keyboard,
without ringing the corresponding bell, use XkbDeviceBellEvent.

Bool XkbDeviceBellEvent(Display *display, Window window, unsigned int
device_spec, unsigned int bell_class, unsigned int bell_id, int percent, Atom
name);

display     connection to the X server

window      event window, or None

device_spec device ID, or XkbUseCoreKbd

bell_class  input extension bell class for the event

bell_id     input extension bell ID for the event

percent     volume for the bell, which can range from −100 to 100 inclusive

name        a bell name, or NULL

If a compatible keyboard extension isn’t present in the X server,
XkbDeviceBellEvent immediately returns False. Otherwise, XkbDeviceBellEvent
causes an XkbBellNotify event to be sent to all interested clients and returns 
True. Set percent to be the volume relative to the base volume for the keyboard
as described for XBell.

In addition, XkbDeviceBellEvent may generate Atom protocol errors as well as 
XkbBellNotify events. You can call XkbBell without first initializing the
keyboard extension.

As a convenience function, Xkb provides a function to cause a bell event for
the keyboard without ringing the bell: XkbBellEvent.

Bool XkbBellEvent(Display *display, Window window, int percent, Atom name);

display connection to the X server

window  the event window, or None

percent relative volume, which can range from −100 to 100 inclusive

name    a bell name, or NULL

If a compatible keyboard extension isn’t present in the X server, XkbBellEvent
immediately returns False. Otherwise, XkbBellEvent calls XkbDeviceBellEvent
with the specified display, window, percent, and name, a device_spec of 
XkbUseCoreKbd, a bell_class of XkbDfltXIClass, and a bell_id of XkbDfltXIId,
and returns what XkbDeviceBellEvent returns.

XkbBellEvent generates a XkbBellNotify event.

You can call XkbBellEvent without first initializing the keyboard extension.

Forcing a Server-Generated Bell

To ring the bell on any keyboard, overriding user preference settings for
audible bells, use XkbForceDeviceBell.

Bool XkbForceDeviceBell(Display *display, Window window, unsigned int
device_spec, unsigned int bell_class, unsigned int bell_id, int percent);

display     connection to the X server

window      event window, or None

device_spec device ID, or XkbUseCoreKbd

bell_class  input extension class of the bell to be rung

bell_id     input extension ID of the bell to be rung

percent     relative volume, which can range from −100 to 100 inclusive

If a compatible keyboard extension isn’t present in the X server,
XkbForceDeviceBell immediately returns False. Otherwise, XkbForceDeviceBell
rings the bell as specified for the display and keyboard device and returns 
True. Set percent to be the volume relative to the base volume for the keyboard
as described for XBell. There is no name parameter because XkbForceDeviceBell
does not cause an XkbBellNotify event.

You can call XkbBell without first initializing the keyboard extension.

To ring the bell on the default keyboard, overriding user preference settings
for audible bells, use XkbForceBell.

Bool XkbForceBell(Display *display, int percent);

display connection to the X server

percent volume for the bell, which can range from −100 to 100 inclusive

If a compatible keyboard extension isn’t present in the X server, XkbForceBell
calls XBell with the specified display and percent and returns False.
Otherwise, XkbForceBell calls XkbForceDeviceBell with the specified display and
percent, device_spec = XkbUseCoreKbd, bell_class = XkbDfltXIClass, bell_id = 
XkbDfltXIId, window = None, and name = NULL, and returns what
XkbForceDeviceBell returns.

XkbForceBell does not cause an XkbBellNotify event.

You can call XkbBell without first initializing the keyboard extension.

Detecting Bells

Xkb generates XkbBellNotify events for all bells except for those resulting
from calls to XkbForceDeviceBell and XkbForceBell. To receive XkbBellNotify
events under all possible conditions, pass XkbBellNotifyMask in both the
bits_to_change and values_for_bits parameters to XkbSelectEvents (see section
4.3).

The XkbBellNotify event has no event details. It is either selected or it is
not. However, you can call XkbSelectEventDetails using XkbBellNotify as the
event_type and specifying XkbAllBellEventsMask in bits_to_change and
values_for_bits. This has the same effect as a call to XkbSelectEvents.

The structure for the XkbBellNotify event type contains:

typedef struct _XkbBellNotify {
    int             type;        /* Xkb extension base event code */
    unsigned long   serial;      /* X server serial number for event */
    Bool            send_event;  /* True ⇒ synthetically generated */
    Display *       display;     /* server connection where event generated */
    Time            time;        /* server time when event generated */
    int             xkb_type;    /* XkbBellNotify */
    unsigned int    device;      /* Xkb device ID, will not be XkbUseCoreKbd */
    int             percent;     /* requested volume as % of max */
    int             pitch;       /* requested pitch in Hz */
    int             duration;    /* requested duration in microseconds */
    unsigned int    bell_class;  /* X input extension feedback class */
    unsigned int    bell_id;     /* X input extension feedback ID */
    Atom            name;        /* "name" of requested bell */
    Window          window;      /* window associated with event */
    Bool            event_only;  /* False → the server did not produce a beep */
} XkbBellNotifyEvent;

If your application needs to generate visual bell feedback on the screen when
it receives a bell event, use the window ID in the XkbBellNotifyEvent, if
present.

Chapter 10. Keyboard Controls

Table of Contents

Controls that Enable and Disable Other Controls

    The EnabledControls Control
    The AutoReset Control

Control for Bell Behavior

    The AudibleBell Control

Controls for Repeat Key Behavior

    The PerKeyRepeat Control
    The RepeatKeys Control
    The DetectableAutorepeat Control

Controls for Keyboard Overlays (Overlay1 and Overlay2 Controls)
Controls for Using the Mouse from the Keyboard

    The MouseKeys Control
    The MouseKeysAccel Control

Controls for Better Keyboard Access by Physically Impaired Persons

    The AccessXKeys Control
    The AccessXTimeout Control
    The AccessXFeedback Control
    AccessXNotify Events
    StickyKeys, RepeatKeys, and MouseKeys Events
    The SlowKeys Control
    The BounceKeys Control
    The StickyKeys Control

Controls for General Keyboard Mapping

    The GroupsWrap Control
    The IgnoreLockMods Control
    The IgnoreGroupLock Control
    The InternalMods Control

The XkbControlsRec Structure

     

Querying Controls
Changing Controls

    The XkbControlsChangesRec Structure

Tracking Changes to Keyboard Controls
Allocating and Freeing an XkbControlsRec
The Miscellaneous Per-client Controls

The Xkb extension is composed of two parts: a server extension, and a
client-side X library extension. This chapter discusses functions used to
modify controls effecting the behavior of the server portion of the Xkb
extension. Chapter 11, X Library Controls discusses functions used to modify
controls that affect only the behavior of the client portion of the extension;
those controls are known as Library Controls.

Xkb contains control features that affect the entire keyboard, known as global
keyboard controls. Some of the controls may be selectively enabled and
disabled; these controls are known as the Boolean Controls. Boolean Controls
can be turned on or off under program control and can also be automatically set
to an on or off condition when a client program exits. The remaining controls,
known as the Non-Boolean Controls, are always active. The XkbControlsRec
structure describes the current state of most of the global controls and the
attributes effecting the behavior of each of these Xkb features. This chapter
describes the Xkb controls and how to manipulate them.

There are two possible components for each of the Boolean Controls: attributes
describing how the control should work, and a state describing whether the
behavior as a whole is enabled or disabled. The attributes and state for most
of these controls are held in the XkbControlsRec structure (see section 10.8).

You can manipulate the Xkb controls individually, via convenience functions, or
as a whole. To treat them as a group, modify an XkbControlsRec structure to
describe all of the changes to be made, and then pass that structure and
appropriate flags to an Xkb library function, or use a XkbControlsChangesRec
(see section 10.10.1) to reduce network traffic. When using a convenience
function to manipulate one control individually, you do not use an 
XkbControlsRec structure directly.

The Xkb controls are grouped as shown in Table 10.1.

Table 10.1. Xkb Keyboard Controls

┌────────────────────────────────────────┬──────────────────────┬─────────────┐
│Type of Control                         │Control Name          │Boolean      │
│                                        │                      │Control?     │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│Controls for enabling and disabling     │EnabledControls       │No           │
│other controls                          │                      │             │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │AutoReset             │No           │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│Control for bell behavior               │AudibleBell           │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│Controls for repeat key behavior        │PerKeyRepeat          │No           │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │RepeatKeys            │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │DetectableAutorepeat  │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│Controls for keyboard overlays          │Overlay1              │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │Overlay2              │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│Controls for using the mouse from the   │MouseKeys             │Boolean      │
│keyboard                                │                      │             │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │MouseKeysAccel        │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│Controls for better keyboard access by  │AccessXFeedback       │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│physically impaired persons             │AccessXKeys           │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │AccessXTimeout        │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │BounceKeys            │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │SlowKeys              │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │StickyKeys            │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│Controls for general keyboard mapping   │GroupsWrap            │No           │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │IgnoreGroupLock       │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │IgnoreLockMods        │No           │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │InternalMods          │No           │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│Miscellaneous per-client controls       │GrabsUseXKBState      │Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │LookupStateWhenGrabbed│Boolean      │
├────────────────────────────────────────┼──────────────────────┼─────────────┤
│                                        │SendEventUsesXKBState │Boolean      │
└────────────────────────────────────────┴──────────────────────┴─────────────┘


The individual categories and controls are described first, together with
functions for manipulating them. A description of the XkbControlsRec structure
and the general functions for dealing with all of the controls at once follow
at the end of the chapter.

Controls that Enable and Disable Other Controls

Enable and disable the boolean controls under program control by using the 
EnabledControls control; enable and disable them upon program exit by
configuring the AutoReset control.

The EnabledControls Control

The EnabledControls control is a bit mask where each bit that is turned on
means the corresponding control is enabled, and when turned off, disabled. It
corresponds to the enabled_ctrls field of an XkbControlsRec structure (see
section 10.8). The bits describing which controls are turned on or off are
defined in Table 10.7.

Use XkbChangeEnabledControls to manipulate the EnabledControls control.

Bool XkbChangeEnabledControls(Display *dpy, unsigned int device_spec, unsigned
int mask, unsigned int values);

dpy         connection to X server

device_spec keyboard device to modify

mask        1 bit → controls to enable / disable

values      1 bit ⇒ enable, 0 bit ⇒ disable

The mask parameter specifies the boolean controls to be enabled or disabled,
and the values mask specifies the new state for those controls. Valid values
for both of these masks are composed of a bitwise inclusive OR of bits taken
from the set of mask bits in Table 10.7, using only those masks with “ok” in
the enabled_ctrls column.

If the X server does not support a compatible version of Xkb or the Xkb
extension has not been properly initialized, XkbChangeEnabledControls returns 
False; otherwise, it sends the request to the X server and returns True.

Note that the EnabledControls control only enables and disables controls; it
does not configure them. Some controls, such as the AudibleBell control, have
no configuration attributes and are therefore manipulated solely by enabling
and disabling them. Others, however, have additional attributes to configure
their behavior. For example, the RepeatControl control uses repeat_delay and
repeat_interval fields to describe the timing behavior of keys that repeat. The
RepeatControl behavior is turned on or off depending on the value of the 
XkbRepeatKeysMask bit, but you must use other means, as described in this
chapter, to configure its behavior in detail.

The AutoReset Control

You can configure the boolean controls to automatically be enabled or disabled
when a program exits. This capability is controlled via two masks maintained in
the X server on a per-client basis. There is no client-side Xkb data structure
corresponding to these masks. Whenever the client exits for any reason, any
boolean controls specified in the auto-reset mask are set to the corresponding
value from the auto-reset values mask. This makes it possible for clients to
"clean up after themselves" automatically, even if abnormally terminated. The
bits used in the masks correspond to the EnabledControls control bits.

For example, a client that replaces the keyboard bell with some other audible
cue might want to turn off the AudibleBell control to prevent the server from
also generating a sound and avoid cacophony. If the client were to exit without
resetting the AudibleBell control, the user would be left without any feedback
at all. Setting AudibleBell in both the auto-reset mask and auto-reset values
guarantees that the audible bell will be turned back on when the client exits.

To get the current values of the auto-reset controls, use
XkbGetAutoResetControls.

Bool XkbGetAutoResetControls(Display *dpy, unsigned int *auto_ctrls, unsigned
int *auto_values);

dpy         connection to X server

auto_ctrls  specifies which bits in auto_values are relevant

auto_values 1 bit ⇒ corresponding control has auto-reset on

XkbGetAutoResetControls backfills auto_ctrls and auto_values with the AutoReset
control attributes for this particular client. It returns True if successful,
and False otherwise.

To change the current values of the AutoReset control attributes, use
XkbSetAutoResetControls.

Bool XkbSetAutoResetControls(Display *dpy, unsigned int changes, unsigned int
*auto_ctrls, unsigned int *auto_values);

dpy         connection to X server

changes     controls for which to change auto-reset values

auto_ctrls  controls from changes that should auto reset

auto_values 1 bit ⇒ auto-reset on

XkbSetAutoResetControls changes the auto-reset status and associated auto-reset
values for the controls selected by changes. For any control selected by
changes, if the corresponding bit is set in auto_ctrls, the control is
configured to auto-reset when the client exits. If the corresponding bit in
auto_values is on, the control is turned on when the client exits; if zero, the
control is turned off when the client exits. For any control selected by
changes, if the corresponding bit is not set in auto_ctrls, the control is
configured to not reset when the client exits. For example:

To leave the auto-reset controls for StickyKeys the way they are:

    ok = XkbSetAutoResetControls(dpy, 0, 0, 0);

To change the auto-reset controls so that StickyKeys are unaffected when the
client exits:

    ok = XkbSetAutoResetControls(dpy, XkbStickyKeysMask, 0, 0);

To change the auto-reset controls so that StickyKeys are turned off when the
client exits:

    ok = XkbSetAutoResetControls(dpy, XkbStickyKeysMask, XkbStickyKeysMask, 0);

To change the auto-reset controls so that StickyKeys are turned on when the
client exits:

    ok = XkbSetAutoResetControls(dpy, XkbStickyKeysMask, XkbStickyKeysMask,
                                 XkbStickyKeysMask);

XkbSetAutoResetControls backfills auto_ctrls and auto_values with the
auto-reset controls for this particular client. Note that all of the bits are
valid in the returned values, not just the ones selected in the changes mask.

Control for Bell Behavior

The X server’s generation of sounds is controlled by the AudibleBell control.
Configuration of different bell sounds is discussed in Chapter 9, Bells.

The AudibleBell Control

The AudibleBell control is a boolean control that has no attributes. As such,
you may enable and disable it using either the EnabledControls control or the 
AutoReset control discussed in section 10.1.1. When enabled, protocol requests
to generate a sound result in the X server actually producing a real sound;
when disabled, requests to the server to generate a sound are ignored unless
the sound is forced. See section 9.2.

Controls for Repeat Key Behavior

The repeating behavior of keyboard keys is governed by three controls, the 
PerKeyRepeat control, which is always active, and the RepeatKeys and 
DetectableAutorepeat controls, which are boolean controls that may be enabled
and disabled. PerKeyRepeat determines which keys are allowed to repeat. 
RepeatKeys governs the behavior of an individual key when it is repeating. 
DetectableAutorepeat allows a client to detect when a key is repeating as a
result of being held down.

The PerKeyRepeat Control

The PerKeyRepeat control is a bitmask long enough to contain a bit for each key
on the device; it determines which individual keys are allowed to repeat. The
Xkb PerKeyRepeat control provides no functionality different from that
available via the core X protocol. There are no convenience functions in Xkb
for manipulating this control. The PerKeyRepeat control settings are carried in
the per_key_repeat field of an XkbControlsRec structure, discussed in section
10.8.

The RepeatKeys Control

The core protocol allows only control over whether or not the entire keyboard
or individual keys should auto-repeat when held down. RepeatKeys is a boolean
control that extends this capability by adding control over the delay until a
key begins to repeat and the rate at which it repeats. RepeatKeys is coupled
with the core auto-repeat control: when RepeatKeys is enabled or disabled, the
core auto-repeat is enabled or disabled and vice versa.

Auto-repeating keys are controlled by two attributes. The first, timeout, is
the delay after the initial press of an auto-repeating key and the first
generated repeat event. The second, interval, is the delay between all
subsequent generated repeat events. As with all boolean controls, configuring
the attributes that determine how the control operates does not automatically
enable the control as a whole; see section 10.1.

To get the current attributes of the RepeatKeys control for a keyboard device,
use XkbGetAutoRepeatRate.

Bool XkbGetAutoRepeatRate(Display *display, unsigned int device_spec, unsigned
int *timeout_rtrn, unsigned int *interval_rtrn);

display       connection to X server

device_spec   desired device ID, or XkbUseCoreKbd

timeout_rtrn  backfilled with initial repeat delay, ms

interval_rtrn backfilled with subsequent repeat delay, ms

XkbGetAutoRepeatRate queries the server for the current values of the 
RepeatControls control attributes, backfills timeout_rtrn and interval_rtrn
with them, and returns True. If a compatible version of the Xkb extension is
not available in the server XkbGetAutoRepeatRate returns False.

To set the attributes of the RepeatKeys control for a keyboard device, use
XkbSetAutoRepeatRate.

Bool XkbSetAutoRepeatRate(Display *display, unsigned int device_spec, unsigned
int timeout, unsigned int interval);

display     connection to X server

device_spec device to configure, or XkbUseCoreKbd

timeout     initial delay, ms

interval    delay between repeats, ms

XkbSetAutoRepeatRate sends a request to the X server to configure the 
AutoRepeat control attributes to the values specified in timeout and interval.

XkbSetAutoRepeatRate does not wait for a reply; it normally returns True.
Specifying a zero value for either timeout or interval causes the server to
generate a BadValue protocol error. If a compatible version of the Xkb
extension is not available in the server, XkbSetAutoRepeatRate returns False.

The DetectableAutorepeat Control

Auto-repeat is the generation of multiple key events by a keyboard when the
user presses a key and holds it down. Keyboard hardware and device-dependent X
server software often implement auto-repeat by generating multiple KeyPress
events with no intervening KeyRelease event. The standard behavior of the X
server is to generate a KeyRelease event for every KeyPress event. If the
keyboard hardware and device-dependent software of the X server implement
auto-repeat by generating multiple KeyPress events, the device-independent part
of the X server by default synthetically generates a KeyRelease event after
each KeyPress event. This provides predictable behavior for X clients, but does
not allow those clients to detect the fact that a key is auto-repeating.

Xkb allows clients to request detectable auto-repeat. If a client requests and
the server supports DetectableAutorepeat, Xkb generates KeyRelease events only
when the key is physically released. If DetectableAutorepeat is not supported
or has not been requested, the server synthesizes a KeyRelease event for each
repeating KeyPress event it generates.

DetectableAutorepeat, unlike the other controls in this chapter, is not
contained in the XkbControlsRec structure, nor can it be enabled or disabled
via the EnabledControls control. Instead, query and set DetectableAutorepeat
using XkbGetDetectableAutorepeat and XkbSetDetectableAutorepeat.

DetectableAutorepeat is a condition that applies to all keyboard devices for a
client’s connection to a given X server; it cannot be selectively set for some
devices and not for others. For this reason, none of the Xkb library functions
involving DetectableAutorepeat involve a device specifier.

To determine whether or not the server supports DetectableAutorepeat, use
XkbGetDetectableAutorepeat.

Bool XkbGetDetectableAutorepeat(Display *display, Bool *supported_rtrn);

display        connection to X server

supported_rtrn backfilled True if DetectableAutorepeat supported

XkbGetDetectableAutorepeat queries the server for the current state of 
DetectableAutorepeat and waits for a reply. If supported_rtrn is not NULL, it
backfills supported_rtrn with True if the server supports DetectableAutorepeat,
and False otherwise. XkbGetDetectableAutorepeat returns the current state of 
DetectableAutorepeat for the requesting client: True if DetectableAutorepeat is
set, and False otherwise.

To set DetectableAutorepeat, use XkbSetDetectableAutorepeat. This request
affects all keyboard activity for the requesting client only; other clients
still see the expected nondetectable auto-repeat behavior, unless they have
requested otherwise.

Bool XkbSetDetectableAutorepeat(Display *display, Bool detectable, Bool
*supported_rtrn);

display        connection to X server

detectable     True ⇒ set DetectableAutorepeat

supported_rtrn backfilled True if DetectableAutorepeat supported

XkbSetDetectableAutorepeat sends a request to the server to set 
DetectableAutorepeat on for the current client if detectable is True, and off
it detectable is False; it then waits for a reply. If supported_rtrn is not 
NULL, XkbSetDetectableAutorepeat backfills supported_rtrn with True if the
server supports DetectableAutorepeat, and False if it does not.
XkbSetDetectableAutorepeat returns the current state of DetectableAutorepeat
for the requesting client: True if DetectableAutorepeat is set, and False
otherwise.

Controls for Keyboard Overlays (Overlay1 and Overlay2 Controls)

A keyboard overlay allows some subset of the keyboard to report alternate
keycodes when the overlay is enabled. For example, a keyboard overlay can be
used to simulate a numeric or editing keypad on a keyboard that does not
actually have one by reusing some portion of the keyboard as an overlay. This
technique is very common on portable computers and embedded systems with small
keyboards.

Xkb includes direct support for two keyboard overlays, using the Overlay1 and 
Overlay2 controls. When Overlay1 is enabled, all of the keys that are members
of the first keyboard overlay generate an alternate keycode. When Overlay2 is
enabled, all of the keys that are members of the second keyboard overlay
generate an alternate keycode. The two overlays are mutually exclusive; any
particular key may be in at most one overlay. Overlay1 and Overlay2 are boolean
controls. As such, you may enable and disable them using either the 
EnabledControls control or the AutoReset control discussed in section 10.1.1.

To specify the overlay to which a key belongs and the alternate keycode it
should generate when that overlay is enabled, assign it either the 
XkbKB_Overlay1 or XkbKB_Overlay2 key behaviors, as described in section 16.2.

Controls for Using the Mouse from the Keyboard

Using Xkb, it is possible to configure the keyboard to allow simulation of the
X pointer device. This simulation includes both movement of the pointer itself
and press and release events associated with the buttons on the pointer. Two
controls affect this behavior: the MouseKeys control determines whether or not
simulation of the pointer device is active, as well as configuring the default
button; the MouseKeysAccel control determines the movement characteristics of
the pointer when simulated via the keyboard. Both of them are boolean controls;
as such, you may enable and disable them using either the EnabledControls
control or the AutoReset control discussed in section 10.1.1. The individual
keys that simulate different aspects of the pointer device are determined by
the keyboard mapping, discussed in Chapter 16, Xkb Server Keyboard Mapping.

The MouseKeys Control

The MouseKeys control allows a user to control all the mouse functions from the
keyboard. When MouseKeys are enabled, all keys with MouseKeys actions bound to
them generate core pointer events instead of normal KeyPress and KeyRelease
events.

The MouseKeys control has a single attribute, mk_dflt_btn that specifies the
core button number to be used by mouse keys actions that do not explicitly
specify a button. There is no convenience function for getting or setting the
attribute; instead use XkbGetControls and XkbSetControls (see section 10.9 and
section 10.10).

Note

MouseKeys can also be turned on and off by pressing the key combination
necessary to produce an XK_Pointer_EnableKeys keysym. The de facto default
standard for this is Shift+Alt+NumLock, but this may vary depending on the
keymap.

The MouseKeysAccel Control

When the MouseKeysAccel control is enabled, the effect of a key-activated
pointer motion action changes as a key is held down. If the control is
disabled, pressing a mouse-pointer key yields one mouse event. When 
MouseKeysAccel is enabled, mouse movement is defined by an initial distance
specified in the XkbSA_MovePtr action and the following fields in the 
XkbControlsRec structure (see section 10.8).

Table 10.2. MouseKeysAccel Fields

┌──────────────┬──────────────────────────────────────────────────────────────┐
│Field         │Function                                                      │
├──────────────┼──────────────────────────────────────────────────────────────┤
│mk_delay      │Time (ms) between the initial key press and the first repeated│
│              │motion event                                                  │
├──────────────┼──────────────────────────────────────────────────────────────┤
│mk_interval   │Time (ms) between repeated motion events                      │
├──────────────┼──────────────────────────────────────────────────────────────┤
│mk_time_to_max│Number of events (count) before the pointer reaches maximum   │
│              │speed                                                         │
├──────────────┼──────────────────────────────────────────────────────────────┤
│mk_max_speed  │The maximum speed (in pixels per event) the pointer reaches   │
├──────────────┼──────────────────────────────────────────────────────────────┤
│mk_curve      │The ramp used to reach maximum pointer speed                  │
└──────────────┴──────────────────────────────────────────────────────────────┘


There are no convenience functions to query or change the attributes of the 
MouseKeysAccel control; instead use XkbGetControls and XkbSetControls (see
section 10.9 and section 10.10).

The effects of the attributes of the MouseKeysAccel control depend on whether
the XkbSA_MovePtr action (see section 16.1) specifies relative or absolute
pointer motion.

Absolute Pointer Motion

If an XkbSA_MovePtr action specifies an absolute position for one of the
coordinates but still allows acceleration, all repeated events contain any
absolute coordinates specified in the action. For example, if the XkbSA_MovePtr
action specifies an absolute position for the X direction, but a relative
motion for the Y direction, the pointer accelerates in the Y direction, but
stays at the same X position.

Relative Pointer Motion

If the XkbSA_MovePtr action specifies relative motion, the initial event always
moves the cursor the distance specified in the action. After mk_delay
milliseconds, a second motion event is generated, and another occurs every
mk_interval milliseconds until the user releases the key.

Between the time of the second motion event and mk_time_to_max intervals, the
change in pointer distance per interval increases with each interval. After
mk_time_to_max intervals have elapsed, the change in pointer distance per
interval remains the same and is calculated by multiplying the original
distance specified in the action by mk_max_speed.

For example, if the XkbSA_MovePtr action specifies a relative motion in the X
direction of 5, mk_delay =160, mk_interval =40, mk_time_to_max =30, and
mk_max_speed =30, the following happens when the user presses the key:

  • The pointer immediately moves 5 pixels in the X direction when the key is
    pressed.

  • After 160 milliseconds (mk_delay), and every 40 milliseconds thereafter (
    mk_interval), the pointer moves in the X direction.

  • The distance in the X direction increases with each interval until 30
    intervals ( mk_time_to_max) have elapsed.

  • After 30 intervals, the pointer stops accelerating, and moves 150 pixels (
    mk_max_speed * the original distance) every interval thereafter, until the
    key is released.

The increase in pointer difference for each interval is a function of mk_curve.
Events after the first but before maximum acceleration has been achieved are
accelerated according to the formula:

Where action_delta is the relative motion specified by the XkbSA_MovePtr
action, mk_max_speed and mk_time_to_max are parameters to the MouseKeysAccel
control, and the curveFactor is computed using the MouseKeysAccel mk_curve
parameter as follows:

With the result that a mk_curve of zero causes the distance moved to increase
linearly from action_delta to

. A negative mk_curve causes an initial sharp increase in acceleration that
tapers off, and a positive curve yields a slower initial increase in
acceleration followed by a sharp increase as the number of pointer events
generated by the action approaches mk_time_to_max. The legal values for
mk_curve are between −1000 and 1000.

A distance vs. time graph of the pointer motion is shown in Figure 10.1.

Figure 10.1. MouseKeys Acceleration


Controls for Better Keyboard Access by Physically Impaired Persons

The Xkb extension includes several controls specifically aimed at making
keyboard use more effective for physically impaired people. All of these
controls are boolean controls and may be individually enabled and disabled, as
well as configured to tune their specific behavior. The behavior of these
controls is based on the AccessDOS package ^[4].

The AccessXKeys Control

Enabling or disabling the keyboard controls through a graphical user interface
may be impossible for people who need to use the controls. For example, a user
who needs SlowKeys (see section 10.6.6) may not even be able to start the
graphical application, let alone use it, if SlowKeys is not enabled. To allow
easier access to some of the controls, the AccessXKeys control provides a set
of special key sequences similar to those available in AccessDOS.

When the AccessXKeys control is enabled, the user can turn controls on or off
from the keyboard by entering the following standard key sequences:

  • Holding down a Shift key by itself for eight seconds toggles the SlowKeys
    control.

  • Pressing and releasing the left or right Shift key five times in a row,
    without any intervening key events and with less than 30 seconds delay
    between consecutive presses, toggles the state of the StickyKeys control.

  • Simultaneously operating two or more modifier keys deactivates the 
    StickyKeys control.

When the AccessXKeys control is disabled, Xkb does not look for the above
special key sequences.

Some of these key sequences optionally generate audible feedback of the change
in state, as described in section 10.6.3, or XkbControlsNotify events,
described in section 10.11.

The AccessXTimeout Control

In environments where computers are shared, features such as SlowKeys present a
problem: if SlowKeys is on, the keyboard can appear to be unresponsive because
keys are not accepted until they are held for a certain period of time. To help
solve this problem, Xkb provides an AccessXTimeout control to automatically
change the enabled/disabled state of any boolean controls and to change the
value of the AccessXKeys and AccessXFeedback control attributes if the keyboard
is idle for a specified period of time.

When a timeout as specified by AccessXTimeout occurs and a control is
consequently modified, Xkb generates an XkbControlsNotify event. For more
information on XkbControlsNotify events, refer to section 10.11.

There are no convenience functions in Xkb for manipulating this control. The 
AccessXTimeout control settings are carried in the ax_timeout, axt_opts_mask,
axt_opts_values, axt_ctrls_mask, and axt_ctrls_values fields of an 
XkbControlsRec structure, discussed in section 10.8.

The AccessXFeedback Control

Just as some keyboards can produce keyclicks to indicate when a key is pressed
or repeating, Xkb can provide feedback for the controls by using special beep
codes. Use the AccessXFeedback control to configure the specific types of
operations that generate feedback.

There is no convenience function for modifying the AccessXFeedback control,
although the feedback as a whole can be enabled or disabled just as other
boolean controls are (see section 10.1). Individual beep codes are turned on or
off by modifying the following bits in the ax_options field of an 
XkbControlsRec structure and using XkbSetControls (see section 10.10):

Table 10.3. AccessXFeedback Masks

┌────────────────────────────┬─────────────────────────┬──────────────────────┐
│Action                      │Beep Code                │ax_options bit        │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│LED turned on               │High-pitched beep        │XkbAX_IndicatorFBMask │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│LED turned off              │Low-pitched beep         │XkbAX_IndicatorFBMask │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│More than one LED changed   │Two high-pitched beeps   │XkbAX_IndicatorFBMask │
│state                       │                         │                      │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│Control turned on           │Rising tone              │XkbAX_FeatureFBMask   │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│Control turned off          │Falling tone             │XkbAX_FeatureFBMask   │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│More than one control       │Two high-pitched beeps   │XkbAX_FeatureFBMask   │
│changed state               │                         │                      │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│SlowKeys and BounceKeys     │Three high-pitched beeps │XkbAX_SlowWarnFBMask  │
│about to be turned on or off│                         │                      │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│SlowKeys key pressed        │Medium-pitched beep      │XkbAX_SKPressFBMask   │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│SlowKeys key accepted       │Medium-pitched beep      │XkbAX_SKAcceptFBMask  │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│SlowKeys key rejected       │Low-pitched beep         │XkbAX_SKRejectFBMask  │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│Accepted SlowKeys key       │Medium-pitched beep      │XkbAX_SKReleaseFBMask │
│released                    │                         │                      │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│BounceKeys key rejected     │Low-pitched beep         │XkbAX_BKRejectFBMask  │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│StickyKeys key latched      │Low-pitched beep followed│XkbAX_StickyKeysFBMask│
│                            │by high-pitched beep     │                      │
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│StickyKeys key locked       │High-pitched beep        │XkbAX_StickyKeysFBMask│
├────────────────────────────┼─────────────────────────┼──────────────────────┤
│StickyKeys key unlocked     │Low-pitched beep         │XkbAX_StickyKeysFBMask│
└────────────────────────────┴─────────────────────────┴──────────────────────┘


Implementations that cannot generate continuous tones may generate multiple
beeps instead of falling and rising tones; for example, they can generate a
high-pitched beep followed by a low-pitched beep instead of a continuous
falling tone. Other implementations can only ring the bell with one fixed
pitch. In these cases, use the XkbAX_DumbBellFBMask bit of ax_options to
indicate that the bell can only ring with a fixed pitch.

When any of the above feedbacks occur, Xkb may generate a XkbBellNotify event
(see section 9.4).

AccessXNotify Events

The server can generate XkbAccessXNotify events for some of the global keyboard
controls. The structure for the XkbAccessXNotify event type is as follows:

typedef struct {
    int             type;            /* Xkb extension base event code */
    unsigned long   serial;          /* X server serial number for event */
    Bool            send_event;      /* True ⇒ synthetically generated */
    Display *       display;         /* server connection where event generated */
    Time            time;            /* server time when event generated */
    int             xkb_type;        /* XkbAccessXNotify */
    int             device;          /* Xkb device ID, will not be XkbUseCoreKbd */
    int             detail;          /* XkbAXN_* */
    KeyCode         keycode;         /* key of event */
    int             slowKeysDelay;   /* current SlowKeys delay */
    int             debounceDelay;   /* current debounce delay */
} XkbAccessXNotifyEvent;

The detail field describes what AccessX event just occurred and can be any of
the values in Table 10.4.

Table 10.4. AccessXNotify Events

┌─────────────────┬───────────────────────────────────────────────────────────┐
│detail           │Reason                                                     │
├─────────────────┼───────────────────────────────────────────────────────────┤
│XkbAXN_SKPress   │A key was pressed when SlowKeys was enabled.               │
├─────────────────┼───────────────────────────────────────────────────────────┤
│XkbAXN_SKAccept  │A key was accepted (held longer than the SlowKeys delay).  │
├─────────────────┼───────────────────────────────────────────────────────────┤
│XkbAXN_SKRelease │An accepted SlowKeys key was released.                     │
├─────────────────┼───────────────────────────────────────────────────────────┤
│XkbAXN_SKReject  │A key was rejected (released before the SlowKeys delay     │
│                 │expired).                                                  │
├─────────────────┼───────────────────────────────────────────────────────────┤
│XkbAXN_BKAccept  │A key was accepted by BounceKeys.                          │
├─────────────────┼───────────────────────────────────────────────────────────┤
│XkbAXN_BKReject  │A key was rejected (pressed before the BounceKeys delay    │
│                 │expired).                                                  │
├─────────────────┼───────────────────────────────────────────────────────────┤
│XkbAXN_AXKWarning│AccessXKeys is about to turn on/off StickyKeys or          │
│                 │BounceKeys.                                                │
└─────────────────┴───────────────────────────────────────────────────────────┘


The keycode field reports the keycode of the key for which the event occurred.
If the action is related to SlowKeys, the slowKeysDelay field contains the
current SlowKeys acceptance delay. If the action is related to BounceKeys, the
debounceDelay field contains the current BounceKeys debounce delay.

Selecting for AccessX Events

To receive XkbAccessXNotify events under all possible conditions, use
XkbSelectEvents (see section 4.3) and pass XkbAccessXNotifyMask in both
bits_to_change and values_for_bits.

To receive XkbStateNotify events only under certain conditions, use
XkbSelectEventDetails using XkbAccessXNotify as the event_type and specifying
the desired state changes in bits_to_change and values_for_bits using mask bits
from Table 10.5.

Table 10.5. AccessXNotify Event Details

┌─────────────────────────────┬──────┬────────────────────────────────────────┐
│XkbAccessXNotify Event       │Value │Circumstances                           │
│Details                      │      │                                        │
├─────────────────────────────┼──────┼────────────────────────────────────────┤
│XkbAXN_SKPressMask           │(1<<0)│Slow key press notification wanted      │
├─────────────────────────────┼──────┼────────────────────────────────────────┤
│XkbAXN_SKAcceptMask          │(1<<1)│Slow key accept notification wanted     │
├─────────────────────────────┼──────┼────────────────────────────────────────┤
│XkbAXN_SKRejectMask          │(1<<2)│Slow key reject notification wanted     │
├─────────────────────────────┼──────┼────────────────────────────────────────┤
│XkbAXN_SKReleaseMask         │(1<<3)│Slow key release notification wanted    │
├─────────────────────────────┼──────┼────────────────────────────────────────┤
│XkbAXN_BKAcceptMask          │(1<<4)│Bounce key accept notification wanted   │
├─────────────────────────────┼──────┼────────────────────────────────────────┤
│XkbAXN_BKRejectMask          │(1<<5)│Bounce key reject notification wanted   │
├─────────────────────────────┼──────┼────────────────────────────────────────┤
│XkbAXN_AXKWarningMask        │(1<<6)│AccessX warning notification wanted     │
├─────────────────────────────┼──────┼────────────────────────────────────────┤
│XkbAXN_AllEventsMask         │(0x7f)│All AccessX features notifications      │
│                             │      │wanted                                  │
└─────────────────────────────┴──────┴────────────────────────────────────────┘


StickyKeys, RepeatKeys, and MouseKeys Events

The StickyKeys, RepeatKeys, and MouseKeys controls do not generate specific
events. Instead, the latching, unlatching, locking, or unlocking of modifiers
using StickyKeys generates XkbStateNotify events as described in section 5.4.
Repeating keys generate normal KeyPress and KeyRelease events, though the
auto-repeat can be detected using DetectableAutorepeat (see section 10.3.3).
Finally, MouseKeys generates pointer events identical to those of the core
pointer device.

The SlowKeys Control

Some users may accidentally bump keys while moving a hand or typing stick
toward the key they want. Usually, the keys that are accidentally bumped are
just hit for a very short period of time. The SlowKeys control helps filter
these accidental bumps by telling the server to wait a specified period, called
the SlowKeys acceptance delay, before delivering key events. If the key is
released before this period elapses, no key events are generated. Users can
then bump any number of keys on their way to the one they want without
accidentally getting those characters. Once they have reached the key they
want, they can then hold the desired key long enough for the computer to accept
it. SlowKeys is a boolean control with one configurable attribute.

When the SlowKeys control is active, the server reports the initial key press,
subsequent acceptance or rejection, and release of any key to interested
clients by sending an appropriate AccessXNotify event (see section 10.6.4).

There are no convenience functions in Xkb for manipulating this control. The 
SlowKeys control settings are carried in the slow_keys_delay field of an 
XkbControlsRec structure, discussed in section 10.8.

The BounceKeys Control

Some users may accidentally “bounce” on a key when they release it. They press
it once, then accidentally press it again after they release it. The BounceKeys
control temporarily disables a key after it has been pressed, effectively “
debouncing” the keyboard. The period of time the key is disabled after it is
released is known as the BounceKeys delay. BounceKeys is a boolean control.

When the BounceKeys control is active, the server reports acceptance or
rejection of any key to interested clients by sending an appropriate 
AccessXNotify event (see section 10.6.4).

There are no convenience functions in Xkb for manipulating this control. The 
BounceKeys control settings are carried in the debounce_delay field of an 
XkbControlsRec structure, discussed in section 10.8.

The StickyKeys Control

Some people find it difficult or even impossible to press two keys at once. For
example, a one-fingered typist or someone using a mouth stick cannot press the 
Shift and 1 keys at the same time. The StickyKeys control solves this problem
by changing the behavior of the modifier keys. With StickyKeys, the user can
first press a modifier, release it, then press another key. For example, to get
an exclamation point on a PC-style keyboard, the user can press the Shift key,
release it, and then press the 1 key.

StickyKeys also allows users to lock modifier keys without requiring special
locking keys. When StickyKeys is enabled, a modifier is latched when the user
presses it just once. The user can press a modifier twice in a row to lock it,
and then unlock it by pressing it one more time.

When a modifier is latched, it becomes unlatched when the user presses a
nonmodifier key or a pointer button. For instance, to enter the sequence Shift+
Control+Z the user could press and release the Shift key to latch it, then
press and release the Control key to latch it, and finally press and release
the Z key. Because the Control key is a modifier key, pressing it does not
unlatch the Shift key. Thus, after the user presses the Control key, both the 
Shift and Control modifiers are latched. When the user presses the Z key, the
effect is as though the user had pressed Shift+Control+Z. In addition, because
the Z key is not a modifier key, the Shift and Control modifiers are unlatched.

Locking a modifier key means that the modifier affects any key or pointer
button the user presses until the user unlocks it or it is unlocked
programmatically. For example, to enter the sequence ("XKB") on a keyboard
where ‘(’ is a shifted ‘9’, ‘)’ is a shifted ‘0’, and ‘"’ is a shifted single
quote, the user could press and release the Shift key twice to lock the Shift
modifier. Then, when the user presses the 9, ', x, k, b, ', and 0 keys in
sequence, it generates ("XKB"). To unlock the Shift modifier, the user can
press and release the Shift key.

StickyKeys is a boolean control with two separate attributes that may be
individually configured: one to automatically disable it, and one to control
the latching behavior of modifier keys.

StickyKeys Options

The StickyKeys control has two options that can be accessed via the ax_options
of an XkbControlsRec structure (see section 10.8). The first option, TwoKeys,
specifies whether StickyKeys should automatically turn off when two keys are
pressed at the same time. This feature is useful for shared computers so people
who do not want them do not need to turn StickyKeys off if a previous user left
StickyKeys on. The second option, LatchToLock, specifies whether or not 
StickyKeys locks a modifier when pressed twice in a row.

There are no convenience functions in Xkb for manipulating this control. The 
StickyKeys control settings are carried in the ax_options field of an 
XkbControlsRec structure, discussed in section 10.8.

Controls for General Keyboard Mapping

There are several controls that apply to the keyboard mapping in general. They
control handling of out-of-range group indices and how modifiers are processed
and consumed in the server. These are:

GroupsWrap
IgnoreGroupLock
IgnoreLockMods
InternalMods

IgnoreGroupLock is a boolean control; the rest are always active.

Without the modifier processing options provided by Xkb, passive grabs set via
translations in a client (for example, Alt<KeyPress>space) do not trigger if
any modifiers other than those specified by the translation are set. This
results in problems in the user interface when either NumLock or a secondary
keyboard group is active. The IgnoreLockMods and IgnoreGroupLock controls make
it possible to avoid this behavior without exhaustively specifying a grab for
every possible modifier combination.

The GroupsWrap Control

The GroupsWrap control determines how illegal groups are handled on a global
basis. There are a number of valid keyboard sequences that can cause the
effective group number to go out of range. When this happens, the group must be
normalized back to a valid number. The GroupsWrap control specifies how this is
done.

When dealing with group numbers, all computations are done using the group
index, which is the group number minus one. There are three different
algorithms; the GroupsWrap control specifies which one is used:

  • XkbRedirectIntoRange

    All invalid group numbers are converted to a valid group number by taking
    the last four bits of the GroupsWrap control and using them as the group
    index. If the result is still out of range, Group one is used.

  • XkbClampIntoRange

    All invalid group numbers are converted to the nearest valid group number.
    Group numbers larger than the highest supported group number are mapped to
    the highest supported group; those less than one are mapped to group one.

  • XkbWrapIntoRange

    All invalid group numbers are converted to a valid group number using
    integer modulus applied to the group index.

There are no convenience functions for manipulating the GroupsWrap control.
Manipulate the GroupsWrap control via the groups_wrap field in the 
XkbControlsRec structure, then use XkbSetControls and XkbGetControls (see
section 10.9 and section 10.10) to query and change this control.

Note

See also section 15.3.2 or a discussion of the related field, group_info, which
also normalizes a group under certain circumstances.

The IgnoreLockMods Control

The core protocol does not provide a way to exclude specific modifiers from
grab calculations, with the result that locking modifiers sometimes have
unanticipated side effects.

The IgnoreLockMods control specifies modifiers that should be excluded from
grab calculations. These modifiers are also not reported in any core events
except KeyPress and KeyRelease events that do not activate a passive grab and
that do not occur while a grab is active.

Manipulate the IgnoreLockMods control via the ignore_lock field in the 
XkbControlsRec structure, then use XkbSetControls and XkbGetControls (see
section 10.9 and section 10.10) to query and change this control.
Alternatively, use XkbSetIgnoreLockMods.

To set the modifiers that, if locked, are not to be reported in matching events
to passive grabs, use XkbSetIgnoreLockMods.

Bool XkbSetIgnoreLockMods(Display *display, unsigned int device_spec, unsigned
int affect_real, unsigned int real_values, unsigned int affect_virtual,
unsigned int virtual_values);

display        connection to the X server

device_spec    device ID, or XkbUseCoreKbd

affect_real    mask of real modifiers affected by this call

real_values    values for affected real modifiers (1⇒set, 0⇒unset)

affect_virtual mask of virtual modifiers affected by this call

virtual_values values for affected virtual modifiers (1⇒set, 0⇒unset)

XkbSetIgnoreLockMods sends a request to the server to change the server’s 
IgnoreLockMods control. affect_real and real_values are masks of real modifier
bits indicating which real modifiers are to be added and removed from the
server’s IgnoreLockMods control. Modifiers selected by both affect_real and
real_values are added to the server’s IgnoreLockMods control; those selected by
affect_real but not by real_values are removed from the server’s IgnoreLockMods
control. Valid values for affect_real and real_values consist of any
combination of the eight core modifier bits: ShiftMask, LockMask, ControlMask, 
Mod1Mask – Mod5Mask. affect_virtual and virtual_values are masks of virtual
modifier bits indicating which virtual modifiers are to be added and removed
from the server’s IgnoreLockMods control. Modifiers selected by both
affect_virtual and virtual_values are added to the server’s IgnoreLockMods
control; those selected by affect_virtual but not by virtual_values are removed
from the server’s IgnoreLockMods control. See section 7.1 for a discussion of
virtual modifier masks to use in affect_virtual and virtual_values.
XkbSetIgnoreLockMods does not wait for a reply from the server. It returns True
if the request was sent, and False otherwise.

The IgnoreGroupLock Control

The IgnoreGroupLock control is a boolean control with no attributes. If
enabled, it specifies that the locked state of the keyboard group should not be
considered when activating passive grabs.

Because IgnoreGroupLock is a boolean control with no attributes, use the
general boolean controls functions (see section 10.1) to change its state.

The InternalMods Control

The core protocol does not provide any means to prevent a modifier from being
reported in events sent to clients; Xkb, however makes this possible via the 
InternalMods control. It specifies modifiers that should be consumed by the
server and not reported to clients. When a key is pressed and a modifier that
has its bit set in the InternalMods control is reported to the server, the
server uses the modifier when determining the actions to apply for the key. The
server then clears the bit, so it is not actually reported to the client. In
addition, modifiers specified in the InternalMods control are not used to
determine grabs and are not used to calculate core protocol compatibility
state.

Manipulate the InternalMods control via the internal field in the 
XkbControlsRec structure, using XkbSetControls and XkbGetControls (see section
10.9 and section 10.10). Alternatively, use XkbSetServerInternalMods.

To set the modifiers that are consumed by the server before events are
delivered to the client, use XkbSetServerInternalMods.

Bool XkbSetServerInternalMods(Display *display, unsigned int device_spec,
unsigned int affect_real, unsigned int real_values, unsigned int
affect_virtual, unsigned int virtual_values);

display        connection to the X server

device_spec    ‘device ID, or XkbUseCoreKbd

affect_real    mask of real modifiers affected by this call

real_values    values for affected real modifiers (1⇒set, 0⇒unset)

affect_virtual mask of virtual modifiers affected by this call

virtual_values values for affected virtual modifiers (1⇒set, 0⇒unset)

XkbSetServerInternalMods sends a request to the server to change the internal
modifiers consumed by the server. affect_real and real_values are masks of real
modifier bits indicating which real modifiers are to be added and removed from
the server’s internal modifiers control. Modifiers selected by both affect_real
and real_values are added to the server’s internal modifiers control; those
selected by affect_real but not by real_values are removed from the server’s
internal modifiers mask. Valid values for affect_real and real_values consist
of any combination of the eight core modifier bits: ShiftMask, LockMask, 
ControlMask, Mod1Mask – Mod5Mask. affect_virtual and virtual_values are masks
of virtual modifier bits indicating which virtual modifiers are to be added and
removed from the server’s internal modifiers control. Modifiers selected by
both affect_virtual and virtual_values are added to the server’s internal
modifiers control; those selected by affect_virtual but not by virtual_values
are removed from the server’s internal modifiers control. See section 7.1 for a
discussion of virtual modifier masks to use in affect_virtual and
virtual_values. XkbSetServerInternalMods does not wait for a reply from the
server. It returns True if the request was sent and False otherwise.

The XkbControlsRec Structure

Many of the individual controls described in sections 10.1 through 10.7 may be
manipulated via convenience functions discussed in those sections. Some of
them, however, have no convenience functions. The XkbControlsRec structure
allows the manipulation of one or more of the controls in a single operation
and to track changes to any of them in conjunction with the XkbGetControls and
XkbSetControls functions. This is the only way to manipulate those controls
that have no convenience functions.

The XkbControlsRec structure is defined as follows:

#define      XkbMaxLegalKeyCode       255
#define      XkbPerKeyBitArraySize    ((XkbMaxLegalKeyCode+1)/8)

typedef struct {
    unsigned char     mk_dflt_btn;       /* default button for
                                             keyboard driven mouse */
    unsigned char     num_groups;        /* number of keyboard groups */
    unsigned char     groups_wrap;       /* how to wrap out-of-bounds groups */
    XkbModsRec        internal;          /* defines server internal modifiers */
    XkbModsRec        ignore_lock;       /* modifiers to ignore when
                                             checking for grab */
    unsigned int      enabled_ctrls;     /* 1 bit ⇒ corresponding
                                             boolean control enabled */
    unsigned short    repeat_delay;      /* ms delay until first repeat */
    unsigned short    repeat_interval;   /* ms delay between repeats */
    unsigned short    slow_keys_delay;   /* ms minimum time key must be
                                             down to be ok */
    unsigned short    debounce_delay;    /* ms delay before key reactivated */
    unsigned short    mk_delay;          /* ms delay to second mouse
                                             motion event */
    unsigned short    mk_interval;       /* ms delay between repeat mouse
                                             events */
    unsigned short    mk_time_to_max;    /* # intervals until constant
                                             mouse move */
    unsigned short    mk_max_speed;      /* multiplier for maximum mouse speed */
    short             mk_curve;          /* determines mouse move curve type */
    unsigned short    ax_options;        /* 1 bit ⇒ Access X option enabled */
    unsigned short    ax_timeout;        /* seconds until Access X disabled */
    unsigned short    axt_opts_mask;     /* 1 bit ⇒ options to reset
                                             on Access X timeout */
    unsigned short    axt_opts_values;   /* 1 bit ⇒ turn option on, 0⇒ off */
    unsigned int      axt_ctrls_mask;    /* which bits in enabled_ctrls
                                             to modify */
    unsigned int      axt_ctrls_values;  /* values for new bits in
                                             enabled_ctrls */
    unsigned char     per_key_repeat[XkbPerKeyBitArraySize];
                                         /* per key auto repeat */
} XkbControlsRec, *XkbControlsPtr;

The general-purpose functions that work with the XkbControlsRec structure use a
mask to specify which controls are to be manipulated. Table 10.6 lists these
controls, the masks used to select them in the general function calls (which
parameter), and the data fields in the XkbControlsRec structure that comprise
each of the individual controls. Also listed are the bit used to turn boolean
controls on and off and the section where each control is described in more
detail.

Table 10.6. Xkb Controls

┌─────────────────────┬──────────────────────┬──────────────────────┬───────────────────────┬───────┐
│                     │Control Selection Mask│Relevant              │Boolean Control        │       │
│Control              │(which parameter)     │XkbControlsRec Data   │enabled_ctrls bit      │Section│
│                     │                      │Fields                │                       │       │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│AccessXFeedback      │XkbAccessXFeedbackMask│ax_options:           │XkbAccessXFeedback­Mask│10.6.3 │
│                     │                      │XkbAX_*FBMask         │                       │       │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│AccessXKeys          │                      │                      │XkbAccessXKeys­Mask    │10.6.1 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│                     │                      │ax_timeout            │                       │       │
│                     │                      │                      │                       │       │
│                     │                      │axt_opts_mask         │                       │       │
│                     │                      │                      │                       │       │
│AccessXTimeout       │XkbAccessXTimeoutMask │axt_opts_values       │XkbAccessXTimeout­Mask │10.6.2 │
│                     │                      │                      │                       │       │
│                     │                      │axt_ctrls_mask        │                       │       │
│                     │                      │                      │                       │       │
│                     │                      │axt_ctrls_values      │                       │       │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│AudibleBell          │                      │                      │XkbAudibleBellMask     │9.2    │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│AutoReset            │                      │                      │                       │10.1.2 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│BounceKeys           │XkbBounceKeysMask     │debounce_delay        │XkbBounceKeysMask      │10.6.7 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│Detectable-Autorepeat│                      │                      │                       │10.3.3 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│EnabledControls      │XkbControlsEnabledMask│enabled_ctrls         │Non-Boolean Control    │10.1.1 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│GroupsWrap           │XkbGroupsWrapMask     │groups_wrap           │Non-Boolean Control    │10.7.1 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│IgnoreGroupLock      │                      │                      │XkbIgnoreGroupLock­Mask│10.7.3 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│IgnoreLockMods       │XkbIgnoreLockModsMask │ignore_lock           │Non-Boolean Control    │5.1    │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│InternalMods         │XkbInternalModsMask   │internal              │Non-Boolean Control    │5.1    │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│MouseKeys            │XkbMouseKeysMask      │mk_dflt_btn           │XkbMouseKeysMask       │10.5.1 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│                     │                      │mk_delay              │                       │       │
│                     │                      │                      │                       │       │
│                     │                      │mk_interval           │                       │       │
│                     │                      │                      │                       │       │
│MouseKeysAccel       │XkbMouseKeysAccelMask │mk_time_to_max        │XkbMouseKeysAccel­Mask │10.5.2 │
│                     │                      │                      │                       │       │
│                     │                      │mk_max_speed          │                       │       │
│                     │                      │                      │                       │       │
│                     │                      │mk_curve              │                       │       │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│Overlay1             │                      │                      │XkbOverlay1Mask        │10.4   │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│Overlay2             │                      │                      │XkbOverlay2Mask        │10.4   │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│PerKeyRepeat         │XkbPerKeyRepeatMask   │per_key_repeat        │Non-Boolean Control    │10.3.1 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│                     │                      │repeat_delay          │                       │       │
│RepeatKeys           │XkbRepeatKeysMask     │                      │XkbRepeatKeysMask      │10.3   │
│                     │                      │repeat_interval       │                       │       │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│SlowKeys             │XkbSlowKeysMask       │slow_keys_delay       │XkbSlowKeysMask        │10.6.6 │
├─────────────────────┼──────────────────────┼──────────────────────┼───────────────────────┼───────┤
│                     │                      │ax_options:           │                       │       │
│                     │                      │                      │                       │       │
│StickyKeys           │XkbStickyKeysMask     │XkbAX_Two­KeysMask    │XkbStickyKeysMask      │10.6.8 │
│                     │                      │                      │                       │       │
│                     │                      │XkbAX_Latch­ToLockMask│                       │       │
└─────────────────────┴──────────────────────┴──────────────────────┴───────────────────────┴───────┘


Table 10.7 shows the actual values for the individual mask bits used to select
controls for modification and to enable and disable the control. Note that the
same mask bit is used to specify general modifications to the parameters used
to configure the control (which), and to enable and disable the control (
enabled_ctrls). The anomalies in the table (no “ok” in column) are for controls
that have no configurable attributes; and for controls that are not boolean
controls and therefore cannot be enabled or disabled.

Table 10.7. Controls Mask Bits

┌──────────────────────┬─────────────┬─────────────┬──────────────────────────┐
│Mask Bit              │which or     │enabled_ctrls│Value                     │
│                      │changed_ctrls│             │                          │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbRepeatKeysMask     │ok           │ok           │(1L<<0)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbSlowKeysMask       │ok           │ok           │(1L<<1)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbBounceKeysMask     │ok           │ok           │(1L<<2)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbStickyKeysMask     │ok           │ok           │(1L<<3)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbMouseKeysMask      │ok           │ok           │(1L<<4)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbMouseKeysAccelMask │ok           │ok           │(1L<<5)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbAccessXKeysMask    │ok           │ok           │(1L<<6)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbAccessXTimeoutMask │ok           │ok           │(1L<<7)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbAccessXFeedbackMask│ok           │ok           │(1L<<8)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbAudibleBellMask    │             │ok           │(1L<<9)                   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbOverlay1Mask       │             │ok           │(1L<<10)                  │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbOverlay2Mask       │             │ok           │(1L<<11)                  │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbIgnoreGroupLockMask│             │ok           │(1L<<12)                  │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbGroupsWrapMask     │ok           │             │(1L<<27)                  │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbInternalModsMask   │ok           │             │(1L<<28)                  │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbIgnoreLockModsMask │ok           │             │(1L<<29)                  │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbPerKeyRepeatMask   │ok           │             │(1L<<30)                  │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbControlsEnabledMask│ok           │             │(1L<<31)                  │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbAccessXOptionsMask │ok           │ok           │(XkbStickyKeysMask |      │
│                      │             │             │XkbAccessXFeedbackMask)   │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbAllBooleanCtrlsMask│             │ok           │(0x00001FFF)              │
├──────────────────────┼─────────────┼─────────────┼──────────────────────────┤
│XkbAllControlsMask    │ok           │             │(0xF8001FFF)              │
└──────────────────────┴─────────────┴─────────────┴──────────────────────────┘


The individual fields of the XkbControlsRec structure are defined as follows.

mk_dflt_btn

mk_dflt_btn is an attribute of the MouseKeys control (see section 10.5). It
specifies the mouse button number to use for keyboard simulated mouse button
operations. Its value should be one of the core symbols Button1 – Button5.

num_groups

num_groups is not a part of any control, but is reported in the XkbControlsRec
structure whenever any of its components are fetched from the server. It
reports the number of groups the particular keyboard configuration uses and is
computed automatically by the server whenever the keyboard mapping changes.

groups_wrap

groups_wrap is an attribute of the GroupsWrap control (see section 10.7.1). It
specifies the handling of illegal groups on a global basis. Valid values for
groups_wrap are shown in Table 10.8.

Table 10.8. GroupsWrap options (groups_wrap field)

┌─────────────────────────┬──────┐
│groups_wrap symbolic name│value │
├─────────────────────────┼──────┤
│XkbWrapIntoRange         │(0x00)│
├─────────────────────────┼──────┤
│XkbClampIntoRange        │(0x40)│
├─────────────────────────┼──────┤
│XkbRedirectIntoRange     │(0x80)│
└─────────────────────────┴──────┘


When groups_wrap is set to XkbRedirectIntoRange, its four low-order bits
specify the index of the group to use.

internal

internal is an attribute of the InternalMods control (see section 10.7.4). It
specifies modifiers to be consumed in the server and not passed on to clients
when events are reported. Valid values consist of any combination of the eight
core modifier bits: ShiftMask, LockMask, ControlMask, Mod1Mask – Mod5Mask.

ignore_lock

ignore_lock is an attribute of the IgnoreLockMods control (see section 10.7.2).
It specifies modifiers to be ignored in grab calculations. Valid values consist
of any combination of the eight core modifier bits: ShiftMask, LockMask, 
ControlMask, Mod1Mask – Mod5Mask.

enabled_ctrls

enabled_ctrls is an attribute of the EnabledControls control (see section
10.1.1). It contains one bit per boolean control. Each bit determines whether
the corresponding control is enabled or disabled; a one bit means the control
is enabled. The mask bits used to enable these controls are listed in Table
10.7, using only those masks with “ok” in the enabled_ctrls column.

repeat_delay and repeat_interval

repeat_delay and repeat_interval are attributes of the RepeatKeys control (see
section 10.3.2). repeat_delay is the initial delay before a key begins
repeating, in milliseconds; repeat_interval is the delay between subsequent key
events, in milliseconds.

slow_keys_delay

slow_keys_delay is an attribute of the SlowKeys control (see section 10.6.6).
Its value specifies the SlowKeys acceptance delay period in milliseconds before
a key press is accepted by the server.

debounce_delay

debounce_delay is an attribute of the BounceKeys control (see section 10.6.7).
Its value specifies the BounceKeys delay period in milliseconds for which the
key is disabled after having been pressed before another press of the same key
is accepted by the server.

mk_delay, mk_interval, mk_time_to_max, mk_max_speed, and mk_curve

mk_delay, mk_interval, mk_time_to_max, mk_max_speed, and mk_curve are
attributes of the MouseKeysAccel control. Refer to section 10.5.2 for a
description of these fields and the units involved.

ax_options

The ax_options field contains attributes used to configure two different
controls, the StickyKeys control (see section 10.6.8) and the AccessXFeedback
control (see section 10.6.3). The ax_options field is a bitmask and may include
any combination of the bits defined in Table 10.9.

Table 10.9. Access X Enable/Disable Bits (ax_options field)

┌────────────────┬──────────────────────┬──────────┐
│Access X Control│ax_options bit        │value     │
├────────────────┼──────────────────────┼──────────┤
│AccessXFeedback │XkbAX_SKPressFBMask   │(1L<<0)   │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_SKAcceptFBMask  │(1L << 1) │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_FeatureFBMask   │(1L << 2) │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_SlowWarnFBMask  │(1L << 3) │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_IndicatorFBMask │(1L << 4) │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_StickyKeysFBMask│(1L << 5) │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_SKReleaseFBMask │(1L << 8) │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_SKRejectFBMask  │(1L << 9) │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_BKRejectFBMask  │(1L << 10)│
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_DumbBellFBMask  │(1L << 11)│
├────────────────┼──────────────────────┼──────────┤
│StickyKeys      │XkbAX_TwoKeysMask     │(1L << 6) │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_LatchToLockMask │(1L << 7) │
├────────────────┼──────────────────────┼──────────┤
│                │XkbAX_AllOptionsMask  │(0xFFF)   │
└────────────────┴──────────────────────┴──────────┘


The fields pertaining to each control are relevant only when the control is
enabled (XkbAccessXFeedbackMask or XkbStickyKeysMask bit is turned on in the
enabled_ctrls field).

Xkb provides a set of convenience macros for working with the ax_options field
of an XkbControlsRec structure:

#define      XkbAX_NeedOption(c,w)      ((c)->ax_options & (w))

The XkbAX_NeedOption macro is useful for determining whether a particular
AccessX option is enabled or not. It accepts a pointer to an XkbControlsRec
structure and a valid mask bit from Table 10.9. If the specified mask bit in
the ax_options field of the controls structure is set, the macro returns the
mask bit. Otherwise, it returns zero. Thus,

    XkbAX_NeedOption(ctlrec, XkbAX_LatchToLockMask)

is nonzero if the latch to lock transition for latching keys is enabled, and
zero if it is disabled. Note that XkbAX_NeedOption only determines whether or
not the particular capability is configured to operate; the 
XkbAccessXFeedbackMask bit must also be turned on in enabled_ctrls for the
capability to actually be functioning.

#define      XkbAX_AnyFeedback(c) \
                 ((c)->enabled_ctrls & XkbAccessXFeedbackMask)

The XkbAX_AnyFeedback macro accepts a pointer to an XkbControlsRec structure
and tells whether the AccessXFeedback control is enabled or not. If the 
AccessXFeedback control is enabled, the macro returns XkbAccessXFeedbackMask.
Otherwise, it returns zero.

#define      XkbAX_NeedFeedback(c,w) \
                 (XkbAX_AnyFeedback(c) && XkbAX_NeedOption(c,w))

The XkbAX_NeedFeedback macro is useful for determining if both the 
AccessXFeedback control and a particular AccessX feedback option are enabled.
The macro accepts a pointer to an XkbControlsRec structure and a feedback
option from the table above. If both the AccessXFeedback control and the
specified feedback option are enabled, the macro returns True. Otherwise it
returns False.

ax_timeout, axt_opts_mask, axt_opts_values, axt_ctrls_mask, and
axt_ctrls_values

ax_timeout, axt_opts_mask, axt_opts_values, axt_ctrls_mask, and
axt_ctrls_values are attributes of the AccessXTimeout control. Refer to section
10.6.2 for a description of these fields and the units involved.

per_key_repeat

The per_key_repeat field mirrors the auto_repeats field of the core protocol 
XKeyboardState structure: changing the auto_repeats field automatically changes
per_key_repeat and vice versa. It is provided for convenience and to reduce
protocol traffic. For example, to obtain the individual repeat key behavior as
well as the repeat delay and rate, use XkbGetControls. If the per_key_repeat
were not in this structure, you would have to call both XGetKeyboardControl and
XkbGetControls to get this information. The bits correspond to keycodes. The
first seven keys (keycodes 1–7) are indicated in per_key_repeat[0], with bit
position 0 (low order) corresponding to the fictitious keycode 0. Following
array elements correspond to 8 keycodes per element. A 1 bit indicates that the
key is a repeating key.

Querying Controls

Use XkbGetControls to find the current state of Xkb server controls.

Status XkbGetControls(Display *display, unsigned long which, XkbDescPtr xkb);

display connection to X server

which   mask of controls requested

xkb     keyboard description for controls information

XkbGetControls queries the server for the requested control information, waits
for a reply, and then copies the server’s values for the requested information
into the ctrls structure of the xkb argument. Only those components specified
by the which parameter are copied. Valid values for which are any combination
of the masks listed in Table 10.7 that have “ok” in the which column.

If xkb->ctrls is NULL, XkbGetControls allocates and initializes it before
obtaining the values specified by which. If xkb->ctrls is not NULL,
XkbGetControls modifies only those portions of xkb->ctrls corresponding to the
values specified by which.

XkbGetControls returns Success if successful; otherwise, it returns BadAlloc if
it cannot obtain sufficient storage, BadMatch if xkb is NULL or which is empty,
or BadImplementation.

To free the ctrls member of a keyboard description, use XkbFreeControls (see
section 10.12)

The num_groups field in the ctrls structure is always filled in by
XkbGetControls, regardless of which bits are selected by which.

Changing Controls

There are two ways to make changes to controls: either change a local copy
keyboard description and call XkbSetControls, or, to reduce network traffic,
use an XkbControlsChangesRec structure and call XkbChangeControls.

To change the state of one or more controls, first modify the ctrls structure
in a local copy of the keyboard description and then use XkbSetControls to copy
those changes to the X server.

Bool XkbSetControls(Display *display, unsigned long which, XkbDescPtr xkb);

display connection to X server

which   mask of controls to change

xkb     ctrls field contains new values to be set

For each bit that is set in the which parameter, XkbSetControls sends the
corresponding values from the xkb->ctrls field to the server. Valid values for
which are any combination of the masks listed in Table 10.7 that have “ok” in
the which column.

If xkb->ctrls is NULL, the server does not support a compatible version of Xkb,
or the Xkb extension has not been properly initialized, XkbSetControls returns 
False. Otherwise, it sends the request to the X server and returns True.

Note that changes to attributes of controls in the XkbControlsRec structure are
apparent only when the associated control is enabled, although the
corresponding values are still updated in the X server. For example, the
repeat_delay and repeat_interval fields are ignored unless the RepeatKeys
control is enabled (that is, the X server’s equivalent of xkb->ctrls has 
XkbRepeatKeysMask set in enabled_ctrls). It is permissible to modify the
attributes of a control in one call to XkbSetControls and enable the control in
a subsequent call. See section 10.1.1 for more information on enabling and
disabling controls.

Note that the enabled_ctrls field is itself a control — the EnabledControls
control. As such, to set a specific configuration of enabled and disabled
boolean controls, you must set enabled_ctrls to the appropriate bits to enable
only the controls you want and disable all others, then specify the 
XkbControlsEnabledMask in a call to XkbSetControls. Because this is somewhat
awkward if all you want to do is enable and disable controls, and not modify
any of their attributes, a convenience function is also provided for this
purpose (XkbChangeEnabledControls, section 10.1.1).

The XkbControlsChangesRec Structure

The XkbControlsChangesRec structure allows applications to track modifications
to an XkbControlsRec structure and thereby reduce the amount of traffic sent to
the server. The same XkbControlsChangesRec structure may be used in several
successive modifications to the same XkbControlsRec structure, then
subsequently used to cause all of the changes, and only the changes, to be
propagated to the server. The XkbControlsChangesRec structure is defined as
follows:

typedef struct _XkbControlsChanges {
    unsigned int changed_ctrls;          /* bits indicating changed
                                             control data */
    unsigned int enabled_ctrls_changes;  /* bits indicating
                                             enabled/disabled controls */
    Bool         num_groups_changed;     /* True if number of keyboard
                                             groups changed */
} XkbControlsChangesRec, *XkbControlsChangesPtr;

The changed_ctrls field is a mask specifying which logical sets of data in the
controls structure have been modified. In this context, modified means set,
that is, if a value is set to the same value it previously contained, it has
still been modified, and is noted as changed. Valid values for changed_ctrls
are any combination of the masks listed in Table 10.7 that have “ok” in the
changed_ctrls column. Setting a bit implies the corresponding data fields from
the “Relevant XkbControlsRec Data Fields” column in Table 10.6 have been
modified. The enabled_ctrls_changes field specifies which bits in the
enabled_ctrls field have changed. If the number of keyboard groups has changed,
the num_groups_changed field is set to True.

If you have an Xkb description with controls that have been modified and an 
XkbControlsChangesRec that describes the changes that have been made, the
XkbChangeControls function provides a flexible method for updating the controls
in a server to match those in the changed keyboard description.

Bool XkbChangeControls(Display *dpy, XkbDescPtr xkb, XkbControlsChangesPtr
changes);

dpy     connection to X server

xkb     keyboard description with changed xkb->ctrls

changes which parts of xkb->ctrls have changed

XkbChangeControls copies any controls fields specified by changes from the
keyboard description controls structure, xkb->ctrls, to the server specified by
dpy.

Tracking Changes to Keyboard Controls

Whenever a field in the controls structure changes in the server’s keyboard
description, the server sends an XkbControlsNotify event to all interested
clients.To receive XkbControlsNotify events under all possible conditions, use
XkbSelectEvents (see section 4.3) and pass XkbControlsNotifyMask in both
bits_to_change and values_for_bits.

To receive XkbControlsNotify events only under certain conditions, use
XkbSelectEventDetails using XkbControlsNotify as the event_type and specifying
the desired state changes in bits_to_change and values_for_bits using mask bits
from Table 10.7.

The structure for the XkbControlsNotify event is defined as follows:

typedef struct {
    int            type;          /* Xkb extension base event code */
    unsigned long  serial;        /* X server serial number for event */
    Bool           send_event;    /* True ⇒ synthetically generated */
    Display *      display;       /* server connection where event generated */
    Time           time;          /* server time when event generated */
    int            xkb_type;      /* XkbCompatMapNotify */
    int            device;        /* Xkb device ID,
                                     will not be XkbUseCoreKbd */
    unsigned int   changed_ctrls; /* bits indicating which controls
                                     data have changed */
    unsigned int   enabled_ctrls; /* controls currently enabled in server */
    unsigned int   enabled_ctrl_changes;  /* bits indicating
                                             enabled/disabled controls */
    int            num_groups;    /* current number of keyboard groups */
    KeyCode        keycode;       /* != 0 ⇒ keycode of key causing change */
    char           event_type;    /* Type of event causing change */
    char           req_major;     /* major event code of event causing change */
    char           req_minor;     /* minor event code of event causing change */
} XkbControlsNotifyEvent;

The changed_ctrls field specifies the controls components that have changed and
consists of bits taken from the masks defined in Table 10.7 with “ok” in the
changed_ctrls column.

The controls currently enabled in the server are reported in the enabled_ctrls
field. If any controls were just enabled or disabled (that is, the contents of
the enabled_ctrls field changed), they are flagged in the enabled_ctrl_changes
field. The valid bits for these fields are the masks listed in Table 10.7 with 
“ok” in the enabled_ctrls column. The num_groups field reports the number of
groups bound to the key belonging to the most number of groups and is
automatically updated when the keyboard mapping changes.

If the change was caused by a request from a client, the keycode and event_type
fields are set to zero and the req_major and req_minor fields identify the
request. The req_major value is the same as the major extension opcode.
Otherwise, event_type is set to the type of event that caused the change (one
of KeyPress, KeyRelease, DeviceKeyPress, DeviceKeyRelease, ButtonPress or 
ButtonRelease), and req_major and req_minor are undefined. If event_type is 
KeyPress, KeyRelease, DeviceKeyPress, or DeviceKeyRelease, the keycode field is
set to the key that caused the change. If event_type is ButtonPress or 
ButtonRelease, keycode contains the button number.

When a client receives an XkbControlsNotify event, it can note the changes in a
changes structure using XkbNoteControlsChanges.

void XkbNoteControlsChanges(XkbControlsChangesPtr changes,
XkbControlsNotifyEvent *new, unsigned int wanted);

changes records changes indicated by new

new     tells which things have changed

wanted  tells which parts of new to record in changes

The wanted parameter is a bitwise inclusive OR of bits taken from the set of
masks specified in Table 10.7 with “ok” in the changed_ctrls column.
XkbNoteControlsChanges copies any changes reported in new and specified in
wanted into the changes record specified by changes.

Use XkbGetControlsChanges to update a local copy of a keyboard description with
the changes previously noted by one or more calls to XkbNoteControlsChanges.

Status XkbGetControlsChanges(Display *dpy, XkbDescPtr xkb, XkbNameChangesPtr
changes);

dpy     connection to X server

xkb     xkb->ctrls will be updated

changes indicates which parts of xkb->ctrls to update

XkbGetControlsChanges examines the changes parameter, queries the server for
the necessary information, and copies the results into the xkb->ctrls keyboard
description. If the ctrls field of xkb is NULL, XkbGetControlsChanges allocates
and initializes it. To free the ctrls field, use XkbFreeControls (see section
10.12).

XkbGetControlsChanges returns Success if successful and can generate BadAlloc, 
BadImplementation, and BadMatch errors.

Allocating and Freeing an XkbControlsRec

The need to allocate an XkbControlsRec structure seldom arises; Xkb creates one
when an application calls XkbGetControls or a related function. For those
situations where there is not an XkbControlsRec structure allocated in the 
XkbDescRec, allocate one by calling XkbAllocControls.

Status XkbAllocControls(XkbDescPtr xkb, unsigned int which);

xkb   Xkb description in which to allocate ctrls rec

which mask of components of ctrls to allocate

XkbAllocControls allocates the ctrls field of the xkb parameter, initializes
all fields to zero, and returns Success. If the ctrls field is not NULL,
XkbAllocControls simply returns Success. If xkb is NULL, XkbAllocControls
reports a BadMatch error. If the ctrls field could not be allocated, it reports
a BadAlloc error.

The which mask specifies the individual fields of the ctrls structure to be
allocated and can contain any of the valid masks defined in Table 10.7. Because
none of the currently existing controls have any structures associated with
them, which is currently of little practical value in this call.

To free memory used by the ctrls member of an XkbDescRec structure, use
XkbFreeControls:

void XkbFreeControls(XkbDescPtr xkb, unsigned int which, Bool free_all);

xkb      Xkb description in which to free controls components

which    mask of components of ctrls to free

free_all True ⇒ free everything + ctrls itself

XkbFreeControls frees the specified components of the ctrls field in the xkb
keyboard description and sets the corresponding structure component values to 
NULL or zero. The which mask specifies the fields of ctrls to be freed and can
contain any of the controls components specified in Table 10.7.

If free_all is True, XkbFreeControls frees every non- NULL structure component
in the controls, frees the XkbControlsRec structure referenced by the ctrls
member of xkb, and sets ctrls to NULL.

The Miscellaneous Per-client Controls

You can configure the boolean per-client controls which affect the state
reported in button and key events. See section 12.1.1, 12.3, 12.5, and 16.3.11
of the XKB Protocol specification for more details.

To get the current values of the per-client controls, use
XkbGetPerClientControls.

Bool XkbGetPerClientControls(Display *dpy, unsigned int *ctrls);

dpy   connection to X server

ctrls 1 bit ⇒ corresponding control is on

XkbGetPerClientControls backfills ctrls with the per-client control attributes
for this particular client. It returns True if successful, and False otherwise.

To change the current values of the per-client control attributes, use
XkbSetPerClientControls.

Bool XkbSetPerClientControls(Display *dpy, unsigned int change, unsigned int
*value);

dpy    connection to X server

change 1 bit ⇒ change control

value  1 bit ⇒ control on

XkbSetPerClientControls changes the per-client values for the controls selected
by change to the corresponding value in value. Legal values for change and
value are: XkbPCF_GrabsUseXKBStateMask, XkbPCF_LookupStateWhenGrabbed, and
XkbPCF_SendEventUsesXKBState. More than one control may be changed at one time
by OR-ing the values together. XkbSetPerClientControls backfills value with the
per-client control attributes for this particular client. It returns True if
successful, and False otherwise.


━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

^[4] AccessDOS provides access to the DOS operating system for people with
physical impairments and was developed by the Trace R&D Center at the
University of Wisconsin. For more information on AccessDOS, contact the Trace R
&D Center, Waisman Center and Department of Industrial Engineering, University
of Wisconsin-Madison WI 53705-2280. Phone: 608-262-6966. e-mail:
info@trace.wisc.edu.

Chapter 11. X Library Controls

Table of Contents

Controls Affecting Keycode-to-String Translation

    ForceLatin1Lookup
    ConsumeLookupMods
    AlwaysConsumeShiftAndLock

Controls Affecting Compose Processing

    ConsumeKeysOnComposeFail
    ComposeLED
    BeepOnComposeFail

Controls Effecting Event Delivery

    IgnoreNewKeyboards

Manipulating the Library Controls

    Determining Which Library Controls are Implemented
    Determining the State of the Library Controls
    Changing the State of the Library Controls

The Xkb extension is composed of two parts: a server extension, and a
client-side X library extension. Chapter 10, Keyboard Controls discusses
functions used to modify controls affecting the behavior of the server portion
of the Xkb extension. This chapter discusses functions used to modify controls
that affect only the behavior of the client portion of the extension; these
controls are known as Library Controls.

All of the Library Controls are boolean flags that may be enabled and disabled.
The controls can be divided into several categories:

  • Controls affecting general string lookups

  • Controls affecting compose processing

  • Controls affecting event delivery

There are two types of string lookups performed by XLookupString. The first
type involves translating a single keycode into a string; the controls in the
first category affect this type of lookup. The second type involves translating
a series of keysyms into a string; the controls in the second category affect
this type of lookup.

An Xkb implementation is required to support the programming interface for all
of the controls. However, an implementation may choose not to support the
semantics associated with the controls that deal with compose processing. In
this case, a program that accesses these controls should still function
normally; however, the feedback that would normally occur with the controls
enabled may be missing.

Controls Affecting Keycode-to-String Translation

The first type of string lookups, which are here called simple string lookups,
involves translating a single keycode into a string. Because these simple
lookups involve only a single keycode, all of the information needed to do the
translation is contained in the keyboard state in a single event. The controls
affecting simple string lookups are:

ForceLatin1Lookup
ConsumeLookupMods
LevelOneUsesShiftAndLock

ForceLatin1Lookup

If the ForceLatin1Lookup control is enabled, XLookupString only returns strings
using the Latin1 character set. If ForceLatin1Lookup is not enabled,
XLookupString can return characters that are not in the Latin1 set. By default,
this control is disabled, allowing characters outside of the Latin1 set to be
returned.

ConsumeLookupMods

Simple string lookups in XLookupString involve two different translation
phases. The first phase translates raw device keycodes to individual keysyms.
The second phase attempts to map the resulting keysym into a string of one or
more characters. In the first phase, some of the modifiers are normally used to
determine the appropriate shift level for a key.

The ConsumeLookupMods control determines whether or not XLookupString consumes
the modifiers it uses during the first phase of processing (mapping a keycode
to a keysym). When a modifier is consumed, it is effectively removed from the
working copy of the keyboard state information XLookupString is using and
appears to be unset for the remainder of the processing.

If the ConsumeLookupMods control is enabled, XLookupString does not use the
modifiers used to translate the keycode of the event to a keysym when it is
determining the string associated with a keysym. For example, assume the keymap
for the ‘A’ key only contains the shift modifier and the ConsumeLookupMods
control is enabled. If a user presses the Shift key and the A key while the 
Num_Lock key is locked, XLookupString uses the Shift modifier when mapping the
keycode for the ‘a’ key to the keysym for ‘A’; subsequently, it only uses the 
NumLock modifier when determining the string associated with the keysym ‘A’.

If the ConsumeLookupMods control is not enabled, XLookupString uses all of the
event modifiers to determine the string associated with a keysym. This behavior
mirrors the behavior of XLookupString in the core implementation.

The ConsumeLookupMods control is unset by default. For more information on
modifier consumption, refer to Chapter 12, Interpreting Key Events.

AlwaysConsumeShiftAndLock

The AlwaysConsumeShiftAndLock control, if enabled, forces XLookupString to
consume the Shift and Lock modifiers when processing all keys, even if the
definition for the key type does not specify these modifiers. The 
AlwaysConsumeShiftAndLock control is unset by default. See section 15.2 for a
discussion of key types.

Controls Affecting Compose Processing

The second type of string lookup performed by XLookupString involves
translating a series of keysyms into a string. Because these lookups can
involve more than one key event, they require XLookupString to retain some
state information between successive calls. The process of mapping a series of
keysyms to a string is known as compose processing. The controls affecting
compose processing are:

ConsumeKeysOnComposeFail
ComposeLED
BeepOnComposeFail

Because different vendors have historically used different algorithms to
implement compose processing, and these algorithms may be incompatible with the
semantics required by the Xkb compose processing controls, implementation of
the compose processing controls is optional in an Xkb implementation.

ConsumeKeysOnComposeFail

Some compose processing algorithms signal the start of a compose sequence by a
key event meaning “start compose”. ^[5] The subsequent key events should
normally result in a valid composition yielding a valid translation to a
string. If the subsequent key events do not have a valid translation, some
decision must be made about what to do with the key events that were processed
while attempting the compose. The ConsumeKeysOnComposeFail control allows a
client to specify what happens with the key events XLookupString has been
considering when it reaches a dead end in a compose sequence.

If the ConsumeKeysOnComposeFail control is set, all keys associated with a
failed compose sequence should be consumed (discarded). If the 
ConsumeKeysOnComposeFail control is not set, the key events associated with a
failed compose sequence should be processed as a normal sequence of key events.

The ConsumeKeysOnComposeFail control is disabled by default.

ComposeLED

The ComposeLED control allows a client to specify whether or not an indicator
should be set and cleared to provide feedback when compose processing is in
progress. The control does not specify which indicator should be used; the
mapping for this is up to the individual implementation. If the ComposeLED
control is enabled, it specifies that an indicator should be set when a compose
sequence is in progress and cleared when one is not in progress. The ComposeLED
control is disabled by default.

While the Xkb extension does not specify the type of type of indicator to be
used when the ComposeLED control is implemented, a consistent convention
between implementations is to everyone’s benefit. If a named indicator is used
for this purpose, the recommended name is “Compose”. Note that some
implementations may use an unnamed, custom hardware LED for this purpose.

BeepOnComposeFail

The BeepOnComposeFail control allows a client to specify whether or not a bell
should be activated to provide feedback when a compose sequence fails. The
control does not specify the type of bell that should be used; the mapping for
this is up to the individual implementation. If the BeepOnComposeFail control
is enabled, it specifies that a bell should be activated when a compose
sequence fails. The BeepOnComposeFail control is disabled by default. If
implemented, the bell should be activated using XkbBell or XkbDeviceBell.

While the Xkb extension does not specify the type of bell to be used when the 
BeepOnComposeFail control is implemented, a consistent convention between
implementations is to everyone’s benefit. If a named bell is used for this
purpose, the recommended name is “ComposeFail”.

Controls Effecting Event Delivery

IgnoreNewKeyboards

When Xkb is initialized, it implicitly forces requests for NewKeyboardNotify
events. These events may be used by the Xkb library extension internally; they
are normally translated into core protocol MappingNotify events before being
passed to the client. While delivering the event to the client is appropriate
in most cases, it is not appropriate for some clients that maintain per-key
data structures. This is because once the server has sent a NewKeyboardNotify
event, it is free to send the client events for all keys in the new range and
that range may be outside of the per-key data structures the client is
maintaining.

The IgnoreNewKeyboards control, if enabled, prevents Xkb from mapping 
NewKeyboardNotify events to core MappingNotify events and passing them to the
client. The control is initially disabled.

Manipulating the Library Controls

The Library Controls are manipulated using functions that deal with bitmasks to
indicate which controls to manipulate. The controls are identified by the masks
defined in Table 11.1.

Table 11.1. Library Control Masks

┌───────────────────────────────┬────────────┐
│Library Control Mask           │Value       │
├───────────────────────────────┼────────────┤
│XkbLC_ForceLatin1Lookup        │(1 << 0)    │
├───────────────────────────────┼────────────┤
│XkbLC_ConsumeLookupMods        │(1 << 1)    │
├───────────────────────────────┼────────────┤
│XkbLC_AlwaysConsumeShiftAndLock│(1 << 2)    │
├───────────────────────────────┼────────────┤
│XkbLC_IgnoreNewKeyboards       │(1 << 3)    │
├───────────────────────────────┼────────────┤
│XkbLC_ConsumeKeysOnComposeFail │(1 << 29)   │
├───────────────────────────────┼────────────┤
│XkbLC_ComposeLED               │(1 << 30)   │
├───────────────────────────────┼────────────┤
│XkbLC_BeepOnComposeFail        │(1 << 31)   │
├───────────────────────────────┼────────────┤
│XkbLC_AllControls              │(0xc0000007)│
└───────────────────────────────┴────────────┘


Determining Which Library Controls are Implemented

To determine which Library Controls are actually implemented, use
XkbXlibControlsImplemented.

unsigned int XkbXlibControlsImplemented(Display *display);

display connection to X server

XkbXlibControlsImplemented returns a bitmask indicating the controls actually
implemented in the Xkb library and is composed of an inclusive OR of bits from
Table 11.1.

Determining the State of the Library Controls

To determine the current state of the Library Controls, use XkbGetXlibControls.

unsigned int XkbGetXlibControls(Display *display);

display connection to X server

XkbGetXlibControls returns the current state of the Library Controls as a bit
mask that is an inclusive OR of the control masks from Table 11.1 for the
controls that are enabled. For the optional compose processing controls, the
fact that a control is enabled does not imply that it is actually implemented.

Changing the State of the Library Controls

To change the state of the Library Controls, use XkbSetXlibControls.

Bool XkbSetXlibControls(Display *display, unsigned long bits_to_change,
unsigned long values_for_bits);

display         connection to X server

bits_to_change  selects controls to be modified

values_for_bits turns selected controls on (1) or off (0)

XkbSetXlibControls modifies the state of the controls selected by
bits_to_change; only the controls selected by bits_to_change are modified. If
the bit corresponding to a control is on in bits_to_change and also on in
values_for_bits, the control is enabled. If the bit corresponding to a control
is on in bits_to_change but off in values_for_bits, the control is disabled.
bits_to_change should be an inclusive OR of bits from Table 11.1.


━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

^[5] Another possibility is to have the compose processing simply be the result
of a finite state acceptor; a compose sequence would never fail for a properly
written finite state acceptor.

Chapter 12. Interpreting Key Events

Table of Contents

Effects of Xkb on the Core X Library

    Effects of Xkb on Event State
    Effects of Xkb on MappingNotify Events
    X Library Functions Affected by Xkb

Xkb Event and Keymap Functions

Xkb provides functions to help developers interpret key events without having
to directly interpret Xkb data structures. Xkb also modifies the behavior of
several core X library functions.

Effects of Xkb on the Core X Library

When support for Xkb is built into the X library, the XOpenDisplay function
looks for a compatible version of Xkb on the server. If it finds a compatible
version, it initializes the extension and enables implicit support for Xkb in a
number of X library functions. This makes it possible for clients to take
advantage of nearly all Xkb features without having to be rewritten or even
recompiled, if they are built with shared libraries. This implicit support is
invisible to most clients, but it can have side effects, so the extension
includes ways to control or disable it.

Effects of Xkb on Event State

Because XOpenDisplay initializes Xkb, some events contain an Xkb description of
the keyboard state instead of that normally used by the core protocol. See
section 17.1.1 for more information about the differences between Xkb keyboard
state and that reported by the core protocol.

Effects of Xkb on MappingNotify Events

When Xkb is missing or disabled, the X library tracks changes to the keyboard
mapping using MappingNotify events. Whenever the keyboard mapping is changed,
the server sends all clients a MappingNotify event to report the change. When a
client receives a MappingNotify event, it is supposed to call
XRefreshKeyboardMapping to update the keyboard description used internally by
the X library.

The X Keyboard Extension uses XkbMapNotify and XkbNewKeyboardNotify events to
track changes to the keyboard mapping. When an Xkb-aware client receives either
event, it should call XkbRefreshKeyboardMapping to update the keyboard
description used internally by the X library. To avoid duplicate events, the X
server does not send core protocol MappingNotify events to a client that has
selected for XkbMapNotify events.

The implicit support for Xkb selects for XkbMapNotify events. This means that
clients that do not explicitly use Xkb but that are using a version of the X
library that has implicit support for Xkb do not receive MappingNotify events
over the wire. Clients that were not written with Xkb in mind do not recognize
or properly handle the new Xkb events, so the implicit support converts them to
MappingNotify events that report approximately the same information, unless the
client has explicitly selected for the Xkb version of the event.

An Xkb-capable X server does not send events from keys that fall outside the
legal range of keycodes expected by that client. Once the server sends a client
an XkbNewKeyboardNotify event, it reports events from all keys because it
assumes that any client that has received an XkbNewKeyboardNotify event expects
key events from the new range of keycodes. The implicit support for Xkb asks
for XkbNewKeyboardNotify events, so the range of keycodes reported to the
client might vary without the client’s knowledge. Most clients don’t really
care about the range of legal keycodes, but some clients maintain information
about each key and might have problems with events that come from unexpected
keys. Such clients can set the XkbLC_IgnoreNewKeyboards library control (see
section 11.3.1) to prevent the implicit support from requesting notification of
changes to the legal range of keycodes.

X Library Functions Affected by Xkb

The following X library functions are modified by Xkb:

XKeycodeToKeysym
XKeysymToKeycode
XLookupKeysym
XLookupString
XRefreshKeyboardMapping
XRebindKeysym

The implicit support for Xkb replaces a number of X library functions with
versions that understand and use the X Keyboard Extension. In most cases, the
semantics of the new versions are identical to those of the old, but there are
occasional visible differences. This section lists all of the functions that
are affected and the differences in behavior, if any, that are visible to
clients.

The XKeycodeToKeysym function reports the keysym associated with a particular
index for a single key. The index specifies a column of symbols in the core
keyboard mapping (that is, as reported by the core protocol GetKeyboardMapping
request). The order of the symbols in the core mapping does not necessarily
correspond to the order of the symbols used by Xkb; section 17.1.3 describes
the differences.

The XKeysymToKeycode function reports a keycode to which a particular keysym is
bound. When Xkb is missing or disabled, this function looks in each column of
the core keyboard mapping in turn and returns the lowest numbered key that
matches in the lowest numbered group. When Xkb is present, this function uses
the Xkb ordering for symbols instead.

The XLookupKeysym function reports the symbol in a specific column of the key
associated with an event. Whether or not Xkb is present, the column specifies
an index into the core symbol mapping.

The XLookupString function reports the symbol and string associated with a key
event, taking into account the keycode and keyboard state as reported in the
event. When Xkb is disabled or missing, XLookupString uses the rules specified
by the core protocol and reports only ISO Latin-1 characters. When Xkb is
present, XLookupString uses the explicit keyboard group, key types, and rules
specified by Xkb. When Xkb is present, XLookupString is allowed, but not
required, to return strings in character sets other than ISO Latin-1, depending
on the current locale. If any key bindings are defined, XLookupString does not
use any consumed modifiers (see section 11.1.2 and section 15.2) to determine
matching bindings.

The XRefreshKeyboardMapping function updates the X library’s internal
representation of the keyboard to reflect changes reported via MappingNotify
events. When Xkb is missing or disabled, this function reloads the entire
modifier map or keyboard mapping. When Xkb is present, the implicit Xkb support
keeps track of the changed components reported by each XkbMapNotify event and
updates only those pieces of the keyboard description that have changed. If the
implicit support has not noted any keyboard mapping changes,
XRefreshKeyboardMapping updates the entire keyboard description.

The XRebindKeysym function associates a string with a keysym and a set of
modifiers. Xkb does not directly change this function, but it does affect the
way that the state reported in the event is compared to the state specified to
XRebindKeysym. When Xkb is missing or disabled, XLookupString returns the
specified string if the modifiers in the event exactly match the modifiers from
this call. When Xkb is present, any modifiers used to determine the keysym are
consumed and are not used to look up the string.

Xkb Event and Keymap Functions

To find the keysym bound to a particular key at a specified group and shift
level, use XkbKeycodeToKeysym.

KeySym XkbKeycodeToKeysym(Display *dpy, KeyCode kc, unsigned int group,
unsigned int level);

dpy   connection to X server

kc    key of interest

group group of interest

level shift level of interest

XkbKeycodeToKeysym returns the keysym bound to a particular group and shift
level for a particular key on the core keyboard. If kc is not a legal keycode
for the core keyboard, or if group or level are out of range for the specified
key, XkbKeycodeToKeysym returns NoSymbol.

To find the set of modifiers bound to a particular keysym on the core keyboard,
use XkbKeysymToModifiers.

unsigned int XkbKeysymToModifiers(Display *dpy, KeySym ks);

dpy connection to X server

ks  keysym of interest

XkbKeysymToModifiers finds the set of modifiers currently bound to the keysym
ks on the core keyboard. The value returned is the mask of modifiers bound to
the keysym ks. If no modifiers are bound to the keysym, XkbKeysymToModifiers
returns zero; otherwise, it returns the inclusive OR of zero or more of the
following: ShiftMask, ControlMask, LockMask, Mod1Mask, Mod2Mask, Mod3Mask, 
Mod4Mask, and Mod5Mask.

Use XkbLookupKeySym to find the symbol associated with a key for a particular
state.

Bool XkbLookupKeySym(Display *dpy, KeyCode key, unsigned int state, unsigned
int *mods_rtrn, KeySym *sym_rtrn);

dpy       connection to X server

key       key for which symbols are to be found

state     state for which symbol should be found

mods_rtrn backfilled with consumed modifiers

sym_rtrn  backfilled with symbol associated with key + state

XkbLookupKeySym is the equivalent of the core XLookupKeySym function. For the
core keyboard, given a keycode key and an Xkb state state, XkbLookupKeySym
returns the symbol associated with the key in sym_rtrn and the list of
modifiers that should still be applied in mods_rtrn. The state parameter is the
state from a KeyPress or KeyRelease event. XkbLookupKeySym returns True if it
succeeds.

Use XkbLookupKeyBinding to find the string bound to a key by XRebindKeysym.
XkbLookupKeyBinding is the equivalent of the core XLookupString function.

int XkbLookupKeyBinding(Display *dpy, KeySym sym, unsigned int state, char
*buf, int nbytes, int *extra_rtrn);

dpy        connection to server

sym        symbol to be looked up

state      state for which string is to be looked up

buf        buffer into which returned string is written

nbytes     size of buffer in bytes

extra_rtrn backfilled with number bytes overflow

XRebindKeysym binds an ASCII string to a specified keysym, so that the string
and keysym are returned when the key is pressed and a specified list of
modifiers are also being held down. XkbLookupKeyBinding returns in buf the
string associated with the keysym sym and modifier state state. buf is NULL
terminated unless there’s an overflow. If the string returned is larger than
nbytes, a count of bytes that does not fit into the buffer is returned in
extra_rtrn. XkbTranslateKeySym returns the number of bytes that it placed into
buf.

To find the string and symbol associated with a keysym for a given keyboard
state, use XkbTranslateKeySym.

int XkbTranslateKeySym(Display *dpy, KeySym *sym_inout, unsigned int mods, char
*buf, int nbytes, int *extra_rtrn);

dpy        connection to X server

sym_inout  symbol to be translated; result of translation

mods       modifiers to apply to sym_inout

buf        buffer into which returned string is written

nbytes     size of buffer in bytes

extra_rtrn number of bytes overflow

XkbTranslateKeySym applies the transformations specified in mods to the symbol
specified by sym_inout. It returns in buf the string, if any, associated with
the keysym for the current locale. If the transformations in mods changes the
keysym, sym_inout is updated accordingly. If the string returned is larger than
nbytes, a count of bytes that does not fit into the buffer is returned in
extra_rtrn. XkbTranslateKeySym returns the number of bytes it placed into buf.

To update the keyboard description that is internal to the X library, use
XkbRefreshKeyboardMapping.

Status XkbRefreshKeyboardMapping(XkbMapNotifyEvent *event);

event event initiating remapping

XkbRefreshKeyboardMapping is the Xkb equivalent of the core
XRefreshKeyboardMapping function. It requests that the X server send the
current key mapping information to this client. A client usually invokes
XkbRefreshKeyboardMapping after receiving an XkbMapNotify event.
XkbRefreshKeyboardMapping returns Success if it succeeds and BadMatch if the
event is not an Xkb event.

The XkbMapNotify event can be generated when some client calls XkbSetMap,
XkbChangeMap, XkbGetKeyboardByName, or any of the standard X library functions
that change the keyboard mapping or modifier mapping.

To translate a keycode to a key symbol and modifiers, use XkbTranslateKeyCode.

Bool XkbTranslateKeyCode(XkbDescPtr xkb, KeyCode key, unsigned int mods,
unsigned int *mods_rtrn, KeySym *keysym_rtrn);

xkb         keyboard description to use for translation

key         keycode to translate

mods        modifiers to apply when translating key

mods_rtrn   backfilled with consumed modifiers

keysym_rtrn keysym resulting from translation

mods_rtrn is backfilled with the modifiers consumed by the translation process.
mods is a bitwise inclusive OR of the legal modifier masks: ShiftMask, LockMask
, ControlMask, Mod1Mask, Mod2Mask, Mod3Mask, Mod4Mask, Mod5Mask. The 
AlwaysConsumeShiftAndLock library control (see section 11.1.3), if enabled,
causes XkbTranslateKeyCode to consume shift and lock. XkbTranslateKeyCode
returns True if the translation resulted in a keysym, and False if it resulted
in NoSymbol.

Chapter 13. Keyboard Geometry

Table of Contents

Shapes and Outlines
Sections
Rows and Keys
Doodads
Overlay Rows and Overlay Keys
Drawing a Keyboard Representation
Geometry Data Structures

    DoodadRec Structures

Getting Keyboard Geometry From the Server
Using Keyboard Geometry
Adding Elements to a Keyboard Geometry
Allocating and Freeing Geometry Components

The Xkb description of a keyboard includes an optional keyboard geometry that
describes the physical appearance of the keyboard. Keyboard geometry describes
the shape, location, and color of all keyboard keys or other visible keyboard
components such as indicators. The information contained in a keyboard geometry
is sufficient to allow a client program to draw an accurate two-dimensional
image of the keyboard.

You can retrieve a keyboard geometry from an X server that supports Xkb, or you
can allocate it from scratch and initialize it in a client program. The
keyboard geometry need not have any correspondence with the physical keyboard
that is connected to the X server.

Geometry measurements are specified in mm/10 units. The origin (0,0) is in the
top left corner of the keyboard image. A component’s own origin is also its
upper left corner. In some cases a component needs to be drawn rotated. For
example, a special keyboard may have a section of keys arranged in rows in a
rectangular area, but the entire rectangle may not be in alignment with the
rest of the keyboard, and instead, it is rotated from horizontal by 30°.
Rotation for a geometry object is specified in 1/10° increments about its
origin. An example of a keyboard with rotated sections is shown in Figure 13.1.

Figure 13.1. Rotated Keyboard Sections


Some geometry components include a priority, which indicates the order in which
overlapping objects should be drawn. Objects should be drawn in order from
highest priority (0) to lowest (255).

The keyboard geometry’s top-level description is stored in a XkbGeometryRec
structure. This structure contains three types of information:

 1. Lists of items, not used to draw the basic keyboard, but indexed by the
    geometry descriptions that comprise the entire keyboard geometry (colors,
    geometry properties, key aliases, shapes)

 2. A number of singleton items that describe the keyboard as a whole (keyboard
    name, width and height, a color for the keyboard as a whole, and a color
    for keyboard key labels)

 3. A list of the keyboard’s sections and nonkey doodads

The top-level geometry is described in more detail in the following.

The lists of items used by components of the keyboard geometry description is
as follows:

  • The top-level keyboard geometry description includes a list of up to 
    XkbGeomMaxColors (32) color names. A color name is a string whose
    interpretation is not specified by Xkb. The XkbColorRec structure provides
    a field for this name as well as a pixel field. The pixel field is a
    convenient place for an application to store a pixel value or color
    definition, if it needs to. All other geometry data structures refer to
    colors using their indices in this global list.

  • The top-level keyboard geometry description includes a list of geometry
    properties. A geometry property associates an arbitrary string with an
    equally arbitrary name. Geometry properties can be used to provide hints to
    programs that display images of keyboards, but they are not interpreted by
    Xkb. No other geometry structures refer to geometry properties. As an
    example of a possible use of properties, consider the pause/break key on
    most PC keyboards: the “break” symbol is usually on the front of the key
    and is often a different color. A program might set a property to:

    LBL_PAUS = "{Pause/top/black,Break/front/red}"

    and use the property information to draw the key with a front label as well
    as a top label.

  • The top-level keyboard geometry description includes a list of key aliases
    (see Chapter 18, Symbolic Names). Key aliases allow the keyboard layout
    designer to assign multiple key names to a single key.

    Note

    Key aliases defined in the geometry component of a keyboard mapping
    override those defined in the keycodes component of the server database,
    which are stored in the XkbNamesRec (xkb->names). Therefore, consider the
    key aliases defined by the geometry before considering key aliases supplied
    by the keycodes.

  • The top-level keyboard geometry description includes a list of shapes;
    other keyboard components refer to shapes by their index in this list. A
    shape consists of an arbitrary name of type Atom and one or more
    closed-polygon outlines. All points in an outline are specified relative to
    the origin of its enclosing shape, that is, whichever shape that contains
    this outline in its list of outlines. One outline is the primary outline.
    The primary outline is by default the first outline, or it can be
    optionally specified by the primary field in the XkbShapeRec structure. A
    keyboard display application can generate a simpler but still accurate
    keyboard image by displaying only the primary outlines for each shape.
    Nonrectangular keys must include a rectangular approximation as one of the
    outlines associated with the shape. The approximation is not normally
    displayed but can be used by very simple keyboard display applications to
    generate a recognizable but degraded image of the keyboard.

The XkbGeometryRec top-level geometry description contains the following
information that pertains to the keyboard as a whole:

  • A keyboard symbolic name of type Atom to help users identify the keyboard.

  • The width and height of the keyboard, in mm/10. For nonrectangular
    keyboards, the width and height describe the smallest bounding box that
    encloses the outline of the keyboard.

  • The base color of the keyboard is the predominant color on the keyboard and
    is used as the default color for any components whose color is not
    explicitly specified.

  • The label color is the color used to draw the labels on most of the
    keyboard keys.

  • The label font is a string that describes the font used to draw labels on
    most keys; label fonts are arbitrary strings, because Xkb does not specify
    the format or name space for font names.

The keyboard is subdivided into named sections of related keys and doodads. The
sections and doodads on the keyboard are listed in the XkbGeometryRec top-level
keyboard geometry description. A section is composed of keys that are
physically together and logically related. Figure 13.2 shows a keyboard that is
divided into four sections. A doodad describes some visible aspect of the
keyboard that is not a key and is not a section.

Figure 13.2. Keyboard with Four Sections


Shapes and Outlines

A shape, used to draw keyboard components and stored in a XkbShapeRec
structure, has:

  • An arbitrary name of type Atom.

  • Bounds (two x and y coordinates) that describe the corners of a rectangle
    containing the shape’s top surface outline.

  • A list of one or more outlines (described below).

  • Optional pointers to a primary and an approximation outline (described
    below). If either of these pointers is NULL, the default primary/
    approximation outline is the first one in the list of outlines for the
    shape.

An outline, stored in a XkbOutlineRec structure, is a list of one or more
points that describes a single closed-polygon, as follows:

  • A list with a single point describes a rectangle with one corner at the
    origin of the shape (0,0) and the opposite corner at the specified point.

  • A list of two points describes a rectangle with one corner at the position
    specified by the first point and the opposite corner at the position
    specified by the second point.

  • A list of three or more points describes an arbitrary polygon. If
    necessary, the polygon is automatically closed by connecting the last point
    in the list with the first.

  • A nonzero value for the corner_radius field specifies that the corners of
    the polygon should be drawn as circles with the specified radius.

All points in an outline are specified relative to the origin of the enclosing
shape. Points in an outline may have negative values for the X and Y
coordinate.

One outline is the primary outline; a keyboard display application can generate
a simple but still accurate keyboard image by displaying only the primary
outlines for each shape. The default primary outline is the first in a shape’s
list of outlines. If the primary field of the XkbShapeRec structure is not NULL
, it points to the primary outline. A rectangular approximation must be
included for nonrectangular keys as one of the outlines associated with the
shape; the approximation is not normally displayed but can be used by very
simple keyboard display applications to generate a recognizable but degraded
image of the keyboard.

Sections

As previously noted, a keyboard is subdivided into sections of related keys.
Each section has its own coordinate system — if a section is rotated, the
coordinates of any components within the section are interpreted relative to
the edges that were on the top and left before rotation. The components that
make up a section, stored in a XkbSectionRec, include:

  • An arbitrary name of type Atom.

  • A priority, to indicate drawing order. 0 is the highest priority, 255 the
    lowest.

  • Origin of the section, relative to the origin of the keyboard.

  • The width and height and the angle of rotation.

  • A list of rows. A row is a list of horizontally or vertically adjacent
    keys. Horizontal rows parallel the (prerotation) top of the section, and
    vertical rows parallel the (prerotation) left of the section. All keys in a
    horizontal row share a common top coordinate; all keys in a vertical row
    share a left coordinate. Figure 13.3 shows the alpha section from the
    keyboard shown in Figure 13.2, divided into rows. Rows and keys are defined
    below.

Figure 13.3. Rows in a Section


  • An optional list of doodads; any type of doodad can be enclosed within a
    section. Position and angle of rotation are relative to the origin and
    angle of rotation of the sections that contain them. Priority for doodads
    in a section is relative to the other components of the section, not to the
    keyboard as a whole.

  • An optional overlay with a name of type Atom and a list of overlay rows
    (described below).

  • Bounds (two x and y coordinates) that describe the corners of a rectangle
    containing the entire section.

Rows and Keys

A row description (XkbRowRec) consists of the coordinates of its origin
relative to its enclosing section, a flag indicating whether the row is
horizontal or vertical, and a list of keys in the row.

A key description (XkbKeyRec) consists of a key name, a shape, a key color, and
a gap. The key name should correspond to one of the keys named in the keyboard
names description, the shape specifies the appearance of the key, and the key
color specifies the color of the key (not the label on the key; the label color
is stored in the XkbGeometryRec). Keys are normally drawn immediately adjacent
to one another from left to right (or top to bottom) within a row. The gap
field specifies the distance between a key and its predecessor.

Doodads

Doodads can be global to the keyboard or part of a section. Doodads have
symbolic names of arbitrary length. The only doodad name whose interpretation
is specified by Xkb is “Edges”, which, if present, describes the outline of the
entire keyboard.

Each doodad’s origin is stored in fields named left and top, which are the
coordinates of the doodad’s origin relative to its enclosing object, whether it
be a section or the top-level keyboard. The priority for doodads that are
listed in the top-level geometry is relative to the other doodads listed in the
top-level geometry and the sections listed in the top-level geometry. The
priority for doodads listed in a section are relative to the other components
of the section. Each doodad is stored in a structure with a type field, which
specifies the type of doodad.

Xkb supports five types of doodads:

  • An indicator doodad describes one of the physical keyboard indicators.
    Indicator doodads specify the shape of the indicator, the indicator color
    when it is lit (on_color) and the indicator color when it is dark (
    off_color).

  • An outline doodad describes some aspect of the keyboard to be drawn as one
    or more hollow, closed polygons. Outline doodads specify the shape, color,
    and angle of rotation about the doodad origin at which they should be
    drawn.

  • A solid doodad describes some aspect of the keyboard to be drawn as one or
    more filled polygons. Solid doodads specify the shape, color, and angle of
    rotation about the doodad origin at which they should be drawn.

  • A text doodad describes a text label somewhere on the keyboard. Text
    doodads specify the label string, the font and color to use when drawing
    the label, and the angle of rotation of the doodad about its origin.

  • A logo doodad is a catch-all, which describes some other visible element of
    the keyboard. A logo doodad is essentially an outline doodad with an
    additional symbolic name that describes the element to be drawn. If a
    keyboard display program recognizes the symbolic name, it can draw
    something appropriate within the bounding region of the shape specified in
    the doodad. If the symbolic name does not describe a recognizable image, it
    should draw an outline using the specified shape, outline, and angle of
    rotation. The Xkb extension does not specify the interpretation of logo
    names.

The structures these doodads are stored in and the values of the type fields
are shown in Table 13.1.

Table 13.1. Doodad Types

┌────────────────┬─────────────────────┬──────────────────┐
│Doodad          │Structure            │Type              │
├────────────────┼─────────────────────┼──────────────────┤
│indicator doodad│XkbIndicatorDoodadRec│XkbIndicatorDoodad│
├────────────────┼─────────────────────┼──────────────────┤
│outline doodad  │XkbShapeDoodadRec    │XkbOutlineDoodad  │
├────────────────┼─────────────────────┼──────────────────┤
│solid doodad    │XkbShapeDoodadRec    │XkbSolidDoodad    │
├────────────────┼─────────────────────┼──────────────────┤
│text doodad     │XkbTextDoodadRec     │XkbTextDoodad     │
├────────────────┼─────────────────────┼──────────────────┤
│logo doodad     │XkbLogoDoodadRec     │XkbLogoDoodad     │
└────────────────┴─────────────────────┴──────────────────┘


Overlay Rows and Overlay Keys

An overlay row (XkbOverlayRowRec) contains a pointer to the row it overlays and
a list of overlay keys.

Each overlay key definition (XkbOverlayKeyRec) indicates a key that can yield
multiple keycodes and consists of a field named under, which specifies the
primary name of the key and a field named over, which specifies the name for
the key when the overlay keycode is selected. The key specified in under must
be a member of the section that contains the overlay key definition, while the
key specified in over must not be.

Drawing a Keyboard Representation

To draw a representation of the keyboard, draw in the following order:

     Draw the top-level keyboard as a rectangle, using its width and height.
     For each component (section or doodad) of the top-level geometry, in priority order:
        If component is a section
           For each row, in the order it appears in the section
              Draw keys in the order they appear in the row
           Draw doodads within the section in priority order.
        Else draw doodad

Geometry Data Structures

In the following figures, a solid arrow denotes a pointer to an array of
structures or a singleton structure. A dotted arrow denotes an index or a
pointer into the array.

Figure 13.4. Xkb Geometry Data Structures


Figure 13.5. Xkb Geometry Data Structures (Doodads)


Figure 13.6. Xkb Geometry Data Structures (Overlays)


typedef struct _XkbGeometry {    /* top-level keyboard geometry structure */
    Atom              name;            /* keyboard name */
    unsigned short    width_mm;        /* keyboard width in ^mm/[10] */
    unsigned short    height_mm;       /* keyboard height in ^mm/[10] */
    char *            label_font;      /* font for key labels */
    XkbColorPtr       label_color;     /* color for key labels
                                          - pointer into colors array */
    XkbColorPtr       base_color;      /* color for basic keyboard
                                          - pointer into colors array */
    unsigned short    sz_properties;   /* size of properties array */
    unsigned short    sz_colors;       /* size of colors array */
    unsigned short    sz_shapes;       /* size of shapes array */
    unsigned short    sz_sections;     /* size of sections array */
    unsigned short    sz_doodads;      /* size of doodads array */
    unsigned short    sz_key_aliases;  /* size of key aliases array */
    unsigned short    num_properties;  /* number of properties in the
                                           properties array */
    unsigned short    num_colors;      /* number of colors in the
                                           colors array */
    unsigned short    num_shapes;      /* number of shapes in the
                                           shapes array */
    unsigned short    num_sections;    /* number of sections in the
                                           sections array */
    unsigned short    num_doodads;     /* number of doodads in the
                                           doodads array */
    unsigned short    num_key_aliases; /* number of key aliases in the
                                           key_aliases array */
    XkbPropertyPtr    properties;      /* properties array */
    XkbColorPtr       colors;          /* colors array */
    XkbShapePtr       shapes;          /* shapes array */
    XkbSectionPtr     sections;        /* sections array */
    XkbDoodadPtr      doodads;         /* doodads array */
    XkbKeyAliasPtr    key_aliases;     /* key aliases array */
} XkbGeometryRec, *XkbGeometryPtr;

The doodads array is only for doodads not contained in any of the sections that
has its own doodads. The key aliases contained in the key_aliases array take
precedence over any defined in the keycodes component of the keyboard
description.

typedef struct _XkbProperty {
    char *      name;                   /* property name */
    char *      value;                  /* property value */
} XkbPropertyRec, *XkbPropertyPtr;

typedef struct _XkbColor {
    unsigned int      pixel;            /* color */
    char *            spec;             /* color name */
} XkbColorRec, *XkbColorPtr;

typedef struct _XkbKeyAliasRec {
    char      real[XkbKeyNameLength];   /* real name of the key */
    char      alias[XkbKeyNameLength];  /* alias for the key */
} XkbKeyAliasRec, *XkbKeyAliasPtr;

typedef struct _XkbPoint {              /* x, y coordinates */
    short      x;
    short      y;
} XkbPointRec, *XkbPointPtr;

typedef struct _XkbOutline {
    unsigned short      num_points;     /* number of points in the outline */
    unsigned short      sz_points;      /* size of the points array */
    unsigned short      corner_radius;  /* draw corners as circles
                                           with this radius */
    XkbPointPtr         points;         /* array of points defining
                                           the outline */
} XkbOutlineRec, *XkbOutlinePtr;

typedef struct _XkbBounds {
    short      x1, y1;       /* upper left corner of the bounds, in ^mm/[10] */
    short      x2, y2;       /* lower right corner of the bounds, in ^mm/[10] */
} XkbBoundsRec, *XkbBoundsPtr;

typedef struct _XkbShape {
    Atom              name;             /* shape’s name */
    unsigned short    num_outlines;     /* number of outlines for the shape */
    unsigned short    sz_outlines;      /* size of the outlines array */
    XkbOutlinePtr     outlines;         /* array of outlines for the shape */
    XkbOutlinePtr     approx;           /* pointer into the array to the
                                           approximating outline */
    XkbOutlinePtr     primary;          /* pointer into the array to the
                                           primary outline */
    XkbBoundsRec      bounds;           /* bounding box for the shape;
                                           encompasses all outlines */
} XkbShapeRec, *XkbShapePtr;

If approx and/or primary is NULL, the default value is used. The default
primary outline is the first element in the outlines array, as is the default
approximating outline.

typedef struct _XkbKey {           /* key in a row */
    XkbKeyNameRec    name;         /* key name */
    short            gap;          /* gap in ^mm/[10] from previous key in row */
    unsigned char    shape_ndx;    /* index of shape for key */
    unsigned char    color_ndx;    /* index of color for key body */
} XkbKeyRec, *XkbKeyPtr;

typedef struct _XkbRow {           /* row in a section */
    short               top;       /* top coordinate of row origin,
                                      relative to section’s origin */
    short               left;      /* left coordinate of row origin,
                                      relative to section’s origin */
    unsigned short      num_keys;  /* number of keys in the keys array */
    unsigned short      sz_keys;   /* size of the keys array */
    int                 vertical;  /* True ⇒vertical row,
                                      False ⇒horizontal row */
    XkbKeyPtr           keys;      /* array of keys in the row */
    XkbBoundsRec        bounds;    /* bounding box for the row */
} XkbRowRec, *XkbRowPtr;

top and left are in ^mm/[10].

typedef struct _XkbOverlayRec {
    Atom              name;           /* overlay name */
    XkbSectionPtr     section_under;  /* the section under this overlay */
    unsigned short    num_rows;       /* number of rows in the rows array */
    unsigned short    sz_rows;        /* size of the rows array */
    XkbOverlayRowPtr  rows;           /* array of rows in the overlay */
    XkbBoundsPtr      bounds;         /* bounding box for the overlay */
} XkbOverlayRec, *XkbOverlayPtr;

typedef struct _XkbOverlayRow {
    unsigned short      row_under;    /* index into the row under this
                                         overlay row */
    unsigned short      num_keys;     /* number of keys in the keys array */
    unsigned short      sz_keys;      /* size of the keys array */
    XkbOverlayKeyPtr    keys;         /* array of keys in the overlay row */
} XkbOverlayRowRec, *XkbOverlayRowPtr;

row_under is an index into the array of rows in the section under this overlay.
The section under this overlay row is the one pointed to by section_under in
this overlay row’s XkbOverlayRec.

typedef struct _XkbOverlayKey {
    XkbKeyNameRec      over;      /* name of this overlay key */
    XkbKeyNameRec      under;     /* name of the key under this overlay key */
} XkbOverlayKeyRec, *XkbOverlayKeyPtr;

typedef struct _XkbSection {
    Atom            name;          /* section name */
    unsigned char   priority;      /* drawing priority, 0⇒highest, 255⇒lowest */
    short           top;           /* top coordinate of section origin */
    short           left;          /* left coordinate of row origin */
    unsigned short  width;         /* section width, in ^mm/[10] */
    unsigned short  height;        /* section height, in ^mm/[10] */
    short           angle;         /* angle of section rotation,
                                      counterclockwise */
    unsigned short  num_rows;      /* number of rows in the rows array */
    unsigned short  num_doodads;   /* number of doodads in the doodads array */
    unsigned short  num_overlays;  /* number of overlays in the overlays array */
    unsigned short  sz_rows;       /* size of the rows array */
    unsigned short  sz_doodads;    /* size of the doodads array */
    unsigned short  sz_overlays;   /* size of the overlays array */
    XkbRowPtr       rows;          /* section rows array */
    XkbDoodadPtr    doodads;       /* section doodads array */
    XkbBoundsRec    bounds;        /* bounding box for the section,
                                      before rotation */
    XkbOverlayPtr   overlays;      /* section overlays array */
} XkbSectionRec, *XkbSectionPtr;

top and left are the origin of the section, relative to the origin of the
keyboard, in ^mm/[10]. angle is in ^1/[10] degrees.

DoodadRec Structures

The doodad arrays in the XkbGeometryRec and the XkbSectionRec may contain any
of the doodad structures and types shown in Table 13.1.

The doodad structures form a union:

typedef union _XkbDoodad {
      XkbAnyDoodadRec        any;
      XkbShapeDoodadRec      shape;
      XkbTextDoodadRec       text;
      XkbIndicatorDoodadRec  indicator;
      XkbLogoDoodadRec       logo;
} XkbDoodadRec, *XkbDoodadPtr;

The top and left coordinates of each doodad are the coordinates of the origin
of the doodad relative to the keyboard’s origin if the doodad is in the 
XkbGeometryRec doodad array, and with respect to the section’s origin if the
doodad is in a XkbSectionRec doodad array. The color_ndx or on_color_ndx and
off_color_ndx fields are color indices into the XkbGeometryRec’s color array
and are the colors to draw the doodads with. Similarly, the shape_ndx fields
are indices into the XkbGeometryRec’s shape array.

typedef struct _XkbShapeDoodad {
    Atom             name;         /* doodad name */
    unsigned char    type;         /* XkbOutlineDoodad
                                      or XkbSolidDoodad */
    unsigned char    priority;     /* drawing priority,
                                       0⇒highest, 255⇒lowest */
    short            top;          /* top coordinate, in ^mm/[10] */
    short            left;         /* left coordinate, in ^mm/[10] */
    short            angle;        /* angle of rotation, clockwise,
                                      in ^1/[10] degrees */
    unsigned short   color_ndx;    /* doodad color */
    unsigned short   shape_ndx;    /* doodad shape */
} XkbShapeDoodadRec, *XkbShapeDoodadPtr;

typedef struct _XkbTextDoodad {
    Atom             name;         /* doodad name */
    unsigned char    type;         /* XkbTextDoodad */
    unsigned char    priority;     /* drawing priority,
                                     0⇒highest, 255⇒lowest */
    short            top;          /* top coordinate, in ^mm/[10] */
    short            left;         /* left coordinate, in ^mm/[10] */
    short            angle;        /* angle of rotation, clockwise,
                                      in ^1/[10] degrees */
    short            width;        /* width in ^mm/[10] */
    short            height;       /* height in ^mm/[10] */
    unsigned short   color_ndx;    /* doodad color */
    char *           text;         /* doodad text */
    char *           font;         /* arbitrary font name for doodad text */
} XkbTextDoodadRec, *XkbTextDoodadPtr;

typedef struct _XkbIndicatorDoodad {
    Atom             name;         /* doodad name */
    unsigned char    type;         /* XkbIndicatorDoodad */
    unsigned char    priority;     /* drawing priority, 0⇒highest, 255⇒lowest */
    short            top;          /* top coordinate, in ^mm/[10] */
    short            left;         /* left coordinate, in ^mm/[10] */
    short            angle;        /* angle of rotation, clockwise,
                                      in ^1/[10] degrees */
    unsigned short   shape_ndx;    /* doodad shape */
    unsigned short   on_color_ndx; /* color for doodad if indicator is on */
    unsigned short   off_color_ndx;/* color for doodad if indicator is off */
} XkbIndicatorDoodadRec, *XkbIndicatorDoodadPtr;

typedef struct _XkbLogoDoodad {
    Atom             name;         /* doodad name */
    unsigned char    type;         /* XkbLogoDoodad */
    unsigned char    priority;     /* drawing priority, 0⇒highest, 255⇒lowest */
    short            top;          /* top coordinate, in ^mm/[10] */
    short            left;         /* left coordinate, in ^mm/[10] */
    short            angle;        /* angle of rotation, clockwise,
                                      in ^1/[10] degrees */
    unsigned short   color_ndx;    /* doodad color */
    unsigned short   shape_ndx;    /* doodad shape */
    char *           logo_name;    /* text for logo */
} XkbLogoDoodadRec, *XkbLogoDoodadPtr

Getting Keyboard Geometry From the Server

You can load a keyboard geometry as part of the keyboard description returned
by XkbGetKeyboard. However, if a keyboard description has been previously
loaded, you can instead obtain the geometry by calling the XkbGetGeometry. In
this case, the geometry returned is the one associated with the keyboard whose
device ID is contained in the keyboard description.

To load a keyboard geometry if you already have the keyboard description, use
XkbGetGeometry.

Status XkbGetGeometry(Display *dpy, XkbDescPtr xkb);

dpy connection to the X server

xkb keyboard description that contains the ID for the keyboard and into which
    the geometry should be loaded

XkbGetGeometry can return BadValue, BadImplementation, BadName, BadAlloc, or 
BadLength errors or Success if it succeeds.

It is also possible to load a keyboard geometry by name. The X server maintains
a database of keyboard components (see Chapter 20, Server Database of Keyboard
Components). To load a keyboard geometry description from this database by
name, use XkbGetNamedGeometry.

Status XkbGetNamedGeometry(Display *dpy, XkbDescPtr xkb, Atom name);

dpy  connection to the X server

xkb  keyboard description into which the geometry should be loaded

name name of the geometry to be loaded

XkbGetNamedGeometry can return BadName if the name cannot be found.

Using Keyboard Geometry

Xkb provides a number of convenience functions to help use a keyboard geometry.
These include functions to return the bounding box of a shape’s top surface and
to update the bounding box of a shape row or section.

A shape is made up of a number of outlines. Each outline is a polygon made up
of a number of points. The bounding box of a shape is a rectangle that contains
all the outlines of that shape.

Figure 13.7. Key Surface, Shape Outlines, and Bounding Box


To determine the bounding box of the top surface of a shape, use
XkbComputeShapeTop.

Bool XkbComputeShapeTop(XkbShapePtr shape, XkbBoundsPtr bounds_rtrn);

shape       shape to be examined

bounds_rtrn backfilled with the bounding box for the shape

XkbComputeShapeTop returns a BoundsRec that contains two x and y coordinates.
These coordinates describe the corners of a rectangle that contains the outline
that describes the top surface of the shape. The top surface is defined to be
the approximating outline if the approx field of shape is not NULL. If approx
is NULL, the top surface is defined as the last outline in the shape’s array of
outlines. XkbComputeShapeTop returns False if shape is NULL or if there are no
outlines for the shape; otherwise, it returns True.

A ShapeRec contains a BoundsRec that describes the bounds of the shape. If you
add or delete an outline to or from a shape, the bounding box must be updated.
To update the bounding box of a shape, use XkbComputeShapeBounds.

Bool XkbComputeShapeBounds(XkbShapePtr shape);

shape shape to be examined

XkbComputeShapeBounds updates the BoundsRec contained in the shape by examining
all the outlines of the shape and setting the BoundsRec to the minimum x and
minimum y, and maximum x and maximum y values found in those outlines.
XkbComputeShapeBounds returns False if shape is NULL or if there are no
outlines for the shape; otherwise, it returns True.

If you add or delete a key to or from a row, or if you update the shape of one
of the keys in that row, you may need to update the bounding box of that row.
To update the bounding box of a row, use XkbComputeRowBounds.

Bool XkbComputeRowBounds(XkbGeometryPtr geom, XkbSectionPtr section, XkbRowPtr
row);

geom    geometry that contains the section

section section that contains the row

row     row to be examined and updated

XkbComputeRowBounds checks the bounds of all keys in the row and updates the
bounding box of the row if necessary. XkbComputeRowBounds returns False if any
of the arguments is NULL; otherwise, it returns True.

If you add or delete a row to or from a section, or if you change the geometry
of any of the rows in that section, you may need to update the bounding box for
that section. To update the bounding box of a section, use
XkbComputeSectionBounds.

Bool XkbComputeSectionBounds(XkbGeometryPtr geom, XkbSectionPtr section);

geom    geometry that contains the section

section section to be examined and updated

XkbComputeSectionBounds examines all the rows of the section and updates the
bounding box of that section so that it contains all rows.
XkbComputeSectionBounds returns False if any of the arguments is NULL;
otherwise, it returns True.

Keys that can generate multiple keycodes may be associated with multiple names.
Such keys have a primary name and an alternate name. To find the alternate name
by using the primary name for a key that is part of an overlay, use
XkbFindOverlayForKey.

char *XkbFindOverlayForKey(XkbGeometryPtr geom, XkbSectionPtr section, char
*under);

geom    geometry that contains the section

section section to be searched for matching keys

under   .primary name of the key to be considered

XkbFindOverlayForKey uses the primary name of the key, under, to look up the
alternate name, which it returns.

Adding Elements to a Keyboard Geometry

Xkb provides functions to add a single new element to the top-level keyboard
geometry. In each case the num_* fields of the corresponding structure is
incremented by 1. These functions do not change sz_* unless there is no more
room in the array. Some of these functions fill in the values of the element’s
structure from the arguments. For other functions, you must explicitly write
code to fill the structure’s elements.

The top-level geometry description includes a list of geometry properties. A
geometry property associates an arbitrary string with an equally arbitrary
name. Programs that display images of keyboards can use geometry properties as
hints, but they are not interpreted by Xkb. No other geometry structures refer
to geometry properties.

To add one property to an existing keyboard geometry description, use
XkbAddGeomProperty.

XkbPropertyPtr XkbAddGeomProperty(XkbGeometryPtr geom, char *name, char
*value);

geom  geometry to be updated

name  name of the new property

value value for the new property

XkbAddGeomProperty adds one property with the specified name and value to the
keyboard geometry specified by geom. XkbAddGeomProperty returns NULL if any of
the parameters is empty or if it was not able to allocate space for the
property. To allocate space for an arbitrary number of properties, use the
XkbAllocGeomProps function.

To add one key alias to an existing keyboard geometry description, use
XkbAddGeomKeyAlias.

XkbKeyAliasPtr XkbAddGeomKeyAlias(XkbGeometryPtr geom, char *alias, char
*real);

geom  geometry to be updated

alias alias to be added

real  real name to be bound to the new alias

XkbAddGeomKeyAlias adds one key alias with the value alias to the geometry
geom, and associates it with the key whose real name is real.
XkbAddGeomKeyAlias returns NULL if any of the parameters is empty or if it was
not able to allocate space for the alias. To allocate space for an arbitrary
number of aliases, use the XkbAllocGeomKeyAliases function.

To add one color name to an existing keyboard geometry description, use
XkbAddGeomColor.

XkbColorPtr XkbAddGeomColor(XkbGeometryPtr geom, char *spec, unsigned int
pixel);

geom  geometry to be updated

spec  color to be added

pixel color to be added

XkbAddGeomColor adds the specified color name and pixel to the specified
geometry geom. The top-level geometry description includes a list of up to 
MaxColors (32) color names. A color name is a string whose interpretation is
not specified by Xkb and neither is the pixel value’s interpretation. All other
geometry data structures refer to colors using their indices in this global
list or pointers to colors in this list. XkbAddGeomColor returns NULL if any of
the parameters is empty or if it was not able to allocate space for the color.
To allocate space for an arbitrary number of colors to a geometry, use the
XkbAllocGeomColors function.

To add one outline to an existing shape, use XkbAddGeomOutline.

XkbOutlinePtr XkbAddGeomOutline(XkbShapePtr shape, int sz_points);

shape     shape to be updated

sz_points number of points to be reserved

An outline consists of an arbitrary number of points. XkbAddGeomOutline adds an
outline to the specified shape by reserving sz_points points for it. The new
outline is allocated and zeroed. XkbAddGeomOutline returns NULL if any of the
parameters is empty or if it was not able to allocate space. To allocate space
for an arbitrary number of outlines to a shape, use XkbAllocGeomOutlines.

To add a shape to a keyboard geometry, use XkbAddGeomShape.

XkbShapePtr XkbAddGeomShape(XkbGeometryPtr geom, Atom name, int sz_outlines);

geom        geometry to be updated

name        name of the new shape

sz_outlines number of outlines to be reserved

A geometry contains an arbitrary number of shapes, each of which is made up of
an arbitrary number of outlines. XkbAddGeomShape adds a shape to a geometry
geom by allocating space for sz_outlines outlines for it and giving it the name
specified by name. If a shape with name name already exists in the geometry, a
pointer to the existing shape is returned. XkbAddGeomShape returns NULL if any
of the parameters is empty or if it was not able to allocate space. To allocate
space for an arbitrary number of geometry shapes, use XkbAllocGeomShapes.

To add one key at the end of an existing row of keys, use XkbAddGeomKey.

XkbKeyPtr XkbAddGeomKey(XkbRowPtr row);

row row to be updated

Keys are grouped into rows. XkbAddGeomKey adds one key to the end of the
specified row. The key is allocated and zeroed. XkbAddGeomKey returns NULL if
row is empty or if it was not able to allocate space for the key. To allocate
space for an arbitrary number of keys to a row, use XkbAllocGeomKeys.

To add one section to an existing keyboard geometry, use XkbAddGeomSection.

XkbSectionPtr XkbAddGeomSection(XkbGeometryPtr geom, Atom name, int sz_rows,
int sz_doodads, int sz_overlays);

geom        geometry to be updated

name        name of the new section

sz_rows     number of rows to reserve in the section

sz_doodads  number of doodads to reserve in the section

sz_overlays number of overlays to reserve in the section

A keyboard geometry contains an arbitrary number of sections. XkbAddGeomSection
adds one section to an existing keyboard geometry geom. The new section
contains space for the number of rows, doodads, and overlays specified by
sz_rows, sz_doodads, and sz_overlays. The new section is allocated and zeroed
and given the name specified by name. If a section with name name already
exists in the geometry, a pointer to the existing section is returned.
XkbAddGeomSection returns NULL if any of the parameters is empty or if it was
not able to allocate space for the section. To allocate space for an arbitrary
number of sections to a geometry, use XkbAllocGeomSections.

To add a row to a section, use XkbAddGeomRow.

XkbRowPtr XkbAddGeomRow(XkbSectionPtr section, int sz_keys);

section section to be updated

sz_keys number of keys to be reserved

One of the components of a keyboard geometry section is one or more rows of
keys. XkbAddGeomRow adds one row to the specified section. The newly created
row contains space for the number of keys specified in sz_keys. They are
allocated and zeroed, but otherwise uninitialized. XkbAddGeomRow returns NULL
if any of the parameters is empty or if it was not able to allocate space for
the row. To allocate space for an arbitrary number of rows to a section, use
the XkbAllocGeomRows function.

To add one doodad to a section of a keyboard geometry or to the top-level
geometry, use XkbAddGeomDoodad.

XkbDoodadPtr XkbAddGeomDoodad(XkbGeometryPtr geom, XkbSectionPtr section, Atom
name);

geom    geometry to which the doodad is added

section section, if any, to which the doodad is added

name    name of the new doodad

A doodad describes some visible aspect of the keyboard that is not a key and is
not a section. XkbAddGeomDoodad adds a doodad with name specified by name to
the geometry geom if section is NULL or to the section of the geometry
specified by section if section is not NULL. XkbAddGeomDoodad returns NULL if
any of the parameters is empty or if it was not able to allocate space for the
doodad. If there is already a doodad with the name name in the doodad array for
the geometry (if section is NULL) or the section (if section is non- NULL), a
pointer to that doodad is returned. To allocate space for an arbitrary number
of doodads to a section, use the XkbAllocGeomSectionDoodads function. To
allocate space for an arbitrary number of doodads to a keyboard geometry, use
the XkbAllocGeomDoodads function.

To add one overlay to a section, use XkbAddGeomOverlay.

XkbOverlayPtr XkbAddGeomOverlay(XkbSectionPtr section, Atom name, int sz_rows);

section section to which an overlay will be added

name    name of the overlay

sz_rows number of rows to reserve in the overlay

XkbAddGeomOverlay adds an overlay with the specified name to the specified
section. The new overlay is created with space allocated for sz_rows rows. If
an overlay with name name already exists in the section, a pointer to the
existing overlay is returned. XkbAddGeomOverlay returns NULL if any of the
parameters is empty or if it was not able to allocate space for the overlay. To
allocate space for an arbitrary number of overlays to a section, use the
XkbAllocGeomOverlay function.

To add a row to an existing overlay, use XkbAddGeomOverlayRow.

XkbOverlayRowPtr XkbAddGeomOverlayRow(XkbOverlayPtr overlay, XkbRowPtr
row_under, int sz_keys);

overlay   overlay to be updated

row_under row to be overlaid in the section overlay overlays

sz_keys   number of keys to reserve in the row

XkbAddGeomOverlayRow adds one row to the overlay. The new row contains space
for sz_keys keys. If row_under specifies a row that doesn’t exist on the
underlying section, XkbAddGeomOverlayRow returns NULL and doesn’t change the
overlay. XkbAddGeomOverlayRow returns NULL if any of the parameters is empty or
if it was not able to allocate space for the overlay.

To add a key to an existing overlay row, use XkbAddGeomOverlayKey.

XkbOverlayKeyPtr XkbAddGeomOverlayKey(XkbOverlayPtr overlay, XkbRowPtr row,
char *under);

overlay overlay to be updated

row     row in overlay to be updated

under   primary name of the key to be considered

XkbAddGeomOverlayKey adds one key to the row in the overlay. If there is no key
named under in the row of the underlying section, XkbAddGeomOverlayKey returns 
NULL.

Allocating and Freeing Geometry Components

Xkb provides a number of functions to allocate and free subcomponents of a
keyboard geometry. Use these functions to create or modify keyboard geometries.
Note that these functions merely allocate space for the new element(s), and it
is up to you to fill in the values explicitly in your code. These allocation
functions increase sz_* but never touch num_* (unless there is an allocation
failure, in which case they reset both sz_* and num_* to zero). These functions
return Success if they succeed, BadAlloc if they are not able to allocate
space, or BadValue if a parameter is not as expected.

To allocate space for an arbitrary number of outlines to a shape, use
XkbAllocGeomOutlines.

Status XkbAllocGeomOutlines(XkbShapePtr shape, int num_needed);

shape      shape for which outlines should be allocated

num_needed number of new outlines required

XkbAllocGeomOutlines allocates space for num_needed outlines in the specified
shape. The outlines are not initialized.

To free geometry outlines, use XkbFreeGeomOutlines.

void XkbFreeGeomOutlines(XkbShapePtr shape, int first, int count, Bool
free_all);

shape    shape in which outlines should be freed

first    first outline to be freed

count    number of outlines to be freed

free_all True ⇒ all outlines are freed

If free_all is True, all outlines are freed regardless of the value of first or
count. Otherwise, count outlines are freed beginning with the one specified by
first.

To allocate space for an arbitrary number of keys to a row, use
XkbAllocGeomKeys.

Status XkbAllocGeomKeys(XkbRowPtr row, int num_needed);

row        row to which keys should be allocated

num_needed number of new keys required

XkbAllocGeomKeys allocates num_needed keys and adds them to the row. No
initialization of the keys is done.

To free geometry keys, use XkbFreeGeomKeys.

void XkbFreeGeomKeys(XkbRowPtr row, int first, int count, Bool free_all);

row      row in which keys should be freed

first    first key to be freed

count    number of keys to be freed

free_all True ⇒ all keys are freed

If free_all is True, all keys are freed regardless of the value of first or
count. Otherwise, count keys are freed beginning with the one specified by
first.

To allocate geometry properties, use XkbAllocGeomProps.

Status XkbAllocGeomProps(XkbGeometryPtr geom, int num_needed);

geom       geometry for which properties should be allocated

num_needed number of new properties required

XkbAllocGeomProps allocates space for num_needed properties and adds them to
the specified geometry geom. No initialization of the properties is done. A
geometry property associates an arbitrary string with an equally arbitrary
name. Geometry properties can be used to provide hints to programs that display
images of keyboards, but they are not interpreted by Xkb. No other geometry
structures refer to geometry properties.

To free geometry properties, use XkbFreeGeomProperties.

void XkbFreeGeomProperties(XkbGeometryPtr geom, int first, int count, Bool
free_all);

geom     geometry in which properties should be freed

first    first property to be freed

count    number of properties to be freed

free_all True ⇒ all properties are freed

If free_all is True, all properties are freed regardless of the value of first
or count. Otherwise, count properties are freed beginning with the one
specified by first.

To allocate geometry key aliases, use XkbAllocGeomKeyAliases.

Status XkbAllocGeomKeyAliases(XkbGeometryPtr geom, int num_needed);

geom       geometry for which key aliases should be allocated

num_needed number of new key aliases required

XkbAllocGeomKeyAliases allocates space for num_needed key aliases and adds them
to the specified geometry geom. A key alias is a pair of strings that
associates an alternate name for a key with the real name for that key.

To free geometry key aliases, use XkbFreeGeomKeyAliases.

void XkbFreeGeomKeyAliases(XkbGeometryPtr geom, int first, int count, Bool
free_all);

geom     geometry in which key aliases should be freed

first    first key alias to be freed

count    number of key aliases to be freed

free_all True ⇒ all key aliases are freed

If free_all is True, all aliases in the top level of the specified geometry
geom are freed regardless of the value of first or count. Otherwise, count
aliases in geom are freed beginning with the one specified by first.

To allocate geometry colors, use XkbAllocGeomColors.

Status XkbAllocGeomColors(XkbGeometryPtr geom, int num_needed);

geom       geometry for which colors should be allocated

num_needed number of new colors required.

XkbAllocGeomColors allocates space for num_needed colors and adds them to the
specified geometry geom. A color name is a string whose interpretation is not
specified by Xkb. All other geometry data structures refer to colors using
their indices in this global list or pointers to colors in this list.

To free geometry colors, use XkbFreeGeomColors.

void XkbFreeGeomColors(XkbGeometryPtr geom, int first, int count, Bool
free_all);

geom     geometry in which colors should be freed

first    first color to be freed

count    number of colors to be freed

free_all True ⇒ all colors are freed

If free_all is True, all colors are freed regardless of the value of first or
count. Otherwise, count colors are freed beginning with the one specified by
first.

To allocate points in an outline, use XkbAllocGeomPoints.

Status XkbAllocGeomPoints(XkbOutlinePtr outline, int num_needed);

outline    outline for which points should be allocated

num_needed number of new points required

XkbAllocGeomPoints allocates space for num_needed points in the specified
outline. The points are not initialized.

To free points in a outline, use XkbFreeGeomPoints.

void XkbFreeGeomPoints(XkbOutlinePtr outline, int first, int count, Bool
free_all);

outline  outline in which points should be freed

first    first point to be freed.

count    number of points to be freed

free_all True ⇒ all points are freed

If free_all is True, all points are freed regardless of the value of first and
count. Otherwise, the number of points specified by count are freed, beginning
with the point specified by first in the specified outline.

To allocate space for an arbitrary number of geometry shapes, use
XkbAllocGeomShapes.

Status XkbAllocGeomShapes(XkbGeometryPtr geom, int num_needed);

geom       geometry for which shapes should be allocated

num_needed number of new shapes required

XkbAllocGeomShapes allocates space for num_needed shapes in the specified
geometry geom. The shapes are not initialized.

To free geometry shapes, use XkbFreeGeomShapes.

void XkbFreeGeomShapes(XkbGeometryPtr geom, int first, int count, Bool
free_all);

geom     geometry in which shapes should be freed

first    first shape to be freed

count    number of shapes to be freed

free_all True ⇒ all shapes are freed

If free_all is True, all shapes in the geometry are freed regardless of the
values of first and count. Otherwise, count shapes are freed, beginning with
the shape specified by first.

To allocate geometry sections, use XkbAllocGeomSections.

Status XkbAllocGeomSections(XkbGeometryPtr geom, int num_needed);

geom       geometry for which sections should be allocated

num_needed number of new sections required

XkbAllocGeomSections allocates num_needed sections and adds them to the
geometry geom. No initialization of the sections is done.

To free geometry sections, use XkbFreeGeomSections.

void XkbFreeGeomSections(XkbGeometryPtr geom, int first, int count, Bool
free_all);

geom     geometry in which sections should be freed

first    first section to be freed.

count    number of sections to be freed

free_all True ⇒ all sections are freed

If free_all is True, all sections are freed regardless of the value of first
and count. Otherwise, the number of sections specified by count are freed,
beginning with the section specified by first in the specified geometry.

To allocate rows in a section, use XkbAllocGeomRows.

Status XkbAllocGeomRows(XkbSectionPtr section, int num_needed);

section    section for which rows should be allocated

num_needed number of new rows required

XkbAllocGeomRows allocates num_needed rows and adds them to the section. No
initialization of the rows is done.

To free rows in a section, use XkbFreeGeomRows.

void XkbFreeGeomRows(XkbSectionPtr section, int first, int count, Bool
free_all);

section  section in which rows should be freed

first    first row to be freed.

count    number of rows to be freed

free_all True ⇒ all rows are freed

If free_all is True, all rows are freed regardless of the value of first and
count. Otherwise, the number of rows specified by count are freed, beginning
with the row specified by first in the specified section.

To allocate overlays in a section, use XkbAllocGeomOverlays.

Status XkbAllocGeomOverlays(XkbSectionPtr section, int num_needed);

section    section for which overlays should be allocated

num_needed number of new overlays required

XkbAllocGeomOverlays allocates num_needed overlays and adds them to the
section. No initialization of the overlays is done.

To free rows in an section, use XkbFreeGeomOverlays.

void XkbFreeGeomOverlays(XkbSectionPtr section, int first, int count, Bool
free_all);

section  section in which overlays should be freed

first    first overlay to be freed.

count    number of overlays to be freed

free_all True ⇒ all overlays are freed

If free_all is True, all overlays are freed regardless of the value of first
and count. Otherwise, the number of overlays specified by count are freed,
beginning with the overlay specified by first in the specified section.

To allocate rows in a overlay, use XkbAllocGeomOverlayRows.

Status XkbAllocGeomOverlayRows(XkbOverlayPtr overlay, int num_needed);

overlay    overlay for which rows should be allocated

num_needed number of new rows required

XkbAllocGeomOverlayRows allocates num_needed rows and adds them to the overlay.
No initialization of the rows is done.

To free rows in an overlay, use XkbFreeGeomOverlayRows.

void XkbFreeGeomOverlayRows(XkbSectionPtr overlay, int first, int count, Bool
free_all);

overlay  section in which rows should be freed

first    first row to be freed.

count    number of rows to be freed

free_all True ⇒ all rows are freed

If free_all is True, all rows are freed regardless of the value of first and
count. Otherwise, the number of rows specified by count are freed, beginning
with the row specified by first in the specified overlay.

To allocate keys in an overlay row, use XkbAllocGeomOverlayKeys.

Status XkbAllocGeomOverlayKeys(XkbOverlayRowPtr row, int num_needed);

row        row for which keys should be allocated

num_needed number of new rows required

XkbAllocGeomOverlayKeys allocates num_needed keys and adds them to the row. No
initialization of the keys is done.

To free keys in an overlay row, use XkbFreeGeomOverlayKeys.

void XkbFreeGeomOverlayKeys(XkbOverlayRowPtr row, int first, int count, Bool
free_all);

row      row in which keys should be freed

first    first key to be freed.

count    number of keys to be freed

free_all True ⇒ all keys are freed

If free_all is True, all keys are freed regardless of the value of first and
count. Otherwise, the number of keys specified by count are freed, beginning
with the key specified by first in the specified row.

To allocate doodads that are global to a keyboard geometry, use
XkbAllocGeomDoodads.

Status XkbAllocGeomDoodads(XkbGeometryPtr geom, int num_needed);

geom       geometry for which doodads should be allocated

num_needed number of new doodads required

XkbAllocGeomDoodads allocates num_needed doodads and adds them to the specified
geometry geom. No initialization of the doodads is done.

To allocate doodads that are specific to a section, use
XkbAllocGeomSectionDoodads.

Status XkbAllocGeomSectionDoodads(XkbSectionPtr section, int num_needed);

section    section for which doodads should be allocated

num_needed number of new doodads required

XkbAllocGeomSectionDoodads allocates num_needed doodads and adds them to the
specified section. No initialization of the doodads is done.

To free geometry doodads, use XkbFreeGeomDoodads.

void XkbFreeGeomDoodads(XkbDoodadPtr doodads, int count, Bool free_all);

doodads  doodads to be freed

count    number of doodads to be freed

free_all True ⇒ all doodads are freed

If free_all is True, all doodads in the array are freed, regardless of the
value of count. Otherwise, count doodads are freed.

To allocate an entire geometry, use XkbAllocGeometry.

Status XkbAllocGeometry(XkbDescPtr xkb, XkbGeometrySizesPtr sizes);

xkb   keyboard description for which geometry is to be allocated

sizes initial sizes for all geometry components

XkbAllocGeometry allocates a keyboard geometry and adds it to the keyboard
description specified by xkb. The keyboard description should be obtained via
the XkbGetKeyboard or XkbAllockeyboard functions. The sizes parameter specifies
the number of elements to be reserved for the subcomponents of the keyboard
geometry and can be zero or more. These subcomponents include the properties,
colors, shapes, sections, and doodads.

To free an entire geometry, use XkbFreeGeometry.

void XkbFreeGeometry(XkbGeometryPtr geom, unsigned int which, Bool free_all);

geom     geometry to be freed

which    mask of geometry components to be freed

free_all True ⇒ the entire geometry is freed.

The values of which and free_all determine how much of the specified geometry
is freed. The valid values for which are:

#define      XkbGeomPropertiesMask  (1<<0)
#define      XkbGeomColorsMask      (1<<1)
#define      XkbGeomShapesMask      (1<<2)
#define      XkbGeomSectionsMask    (1<<3)
#define      XkbGeomDoodadsMask     (1<<4)
#define      XkbGeomAllMask         (0x1f)

If free_all is True, the entire geometry is freed regardless of the value of
which. Otherwise, the portions of the geometry specified by which are freed.

Chapter 14. Xkb Keyboard Mapping

Table of Contents

Notation and Terminology

    Core Implementation
    Xkb Implementation

Getting Map Components from the Server
Changing Map Components in the Server

    The XkbMapChangesRec Structure

Tracking Changes to Map Components
Allocating and Freeing Client and Server Maps

    Allocating an Empty Client Map
    Freeing a Client Map
    Allocating an Empty Server Map
    Freeing a Server Map

The Xkb keyboard mapping contains all the information the server and clients
need to interpret key events. This chapter provides an overview of the
terminology used to describe an Xkb keyboard mapping and introduces common
utilities for manipulating the keyboard mapping.

The mapping consists of two components, a server map and a client map. The
client map is the collection of information a client needs to interpret key
events from the keyboard. It contains a global list of key types and an array
of key symbol maps, each of which describes the symbols bound to a key and the
rules to be used to interpret those symbols. The server map contains the
information the server needs to interpret key events. This includes actions and
behaviors for each key, explicit components for a key, and the virtual
modifiers and the per-key virtual modifier mapping.

For detailed information on particular components of the keyboard map, refer to
Chapter 15, Xkb Client Keyboard Mapping, and Chapter 16, Xkb Server Keyboard
Mapping.

Notation and Terminology

The graphic characters or control functions that may be accessed by one key are
logically arranged in groups and levels, where group and level are defined as
in the ISO9995 standard:

       A logical state of a keyboard providing access to a collection of
Group: graphic characters. Usually these graphic characters logically belong
       together and may be arranged on several levels within a group.

       One of several states (normally 2 or 3) governing which graphic
Level: character is produced when a graphic key is actuated. In certain cases
       the level may also affect function keys.

These definitions, taken from the ISO standard, refer to graphic keys and
characters. In the context of Xkb, Group and Level are not constrained to
graphic keys and characters; they may be used with any key to access any
character the key is capable of generating.

Level is often referred to as “Shift Level”. Levels are numbered sequentially
starting at one.

Note

Shift level is derived from the modifier state, but not necessarily in the same
way for all keys. For example, the Shift modifier selects shift level 2 on most
keys, but for keypad keys the modifier bound to Num_Lock (that is, the NumLock
virtual modifier) also selects shift level 2.

For example, consider the following key (the gray characters indicate symbols
that are implied or expected but are not actually engraved on the key):

Figure 14.1. Shift Levels and Groups


This key has two groups, indicated by the columns, and each group has two shift
levels. For the first group (Group1), the symbol shift level one is a, and the
symbol for shift level two is A. For the second group, the symbol for shift
level one is æ, and the symbol for shift level two is Æ.

Core Implementation

The standard interpretation rules for the core X keymap only allow clients to
access keys such as the one shown in Figure 14.1. That is, clients using the
standard interpretation rules can only access one of four keysyms for any given
KeyPress event — two different symbols in two different groups.

In general, the Shift modifier, the Lock modifier, and the modifier bound to
the Num_Lock key are used to change between shift level 1 and shift level 2. To
switch between groups, the core implementation uses the modifier bound to the 
Mode_switch key. When the Mode_switch modifier is set, the keyboard is
logically in Group 2. When the Mode_switch modifier is not set, the keyboard is
logically in Group 1.

The core implementation does not clearly specify the behavior of keys. For
example, the locking behavior of the CapsLock and Num_Lock keys depends on the
vendor.

Xkb Implementation

Xkb extends the core implementation by providing access to up to four keyboard
groups with up to 63 shift levels per key ^[6]. In addition, Xkb provides
precise specifications regarding the behavior of keys. In Xkb, modifier state
and the current group are independent (with the exception of compatibility
mapping, discussed in Chapter 17, The Xkb Compatibility Map).

Xkb handles switching between groups via key actions, independent of any
modifier state information. Key actions are in the server map component and are
described in detail in section 16.1.4.

Xkb handles shift levels by associating a key type with each group on each key.
Each key type defines the shift levels available for the groups on keys of its
type and specifies the modifier combinations necessary to access each level.

For example, Xkb allows key types where the Control modifier can be used to
access the shift level two of a key. Key types are in the client map component
and are described in detail in section 15.2.

Xkb provides precise specification of the behavior of a key using key
behaviors. Key behaviors are in the server map component and are described in
detail in section 16.2.

Getting Map Components from the Server

Xkb provides two functions to obtain the keyboard mapping components from the
server. The first function, XkbGetMap, allocates an XkbDescRec structure,
retrieves mapping components from the server, and stores them in the XkbDescRec
structure it just allocated. The second function, XkbGetUpdatedMap, retrieves
mapping components from the server and stores them in an XkbDescRec structure
that has previously been allocated.

To allocate an XkbDescRec structure and populate it with the server’s keyboard
client map and server map, use XkbGetMap. XkbGetMap is similar to
XkbGetKeyboard (see section 6.2), but is used only for obtaining the address of
an XkbDescRec structure that is populated with keyboard mapping components. It
allows finer control over which substructures of the keyboard mapping
components are to be populated. XkbGetKeyboard always returns fully populated
components, while XkbGetMap can be instructed to return a partially populated
component.

XkbDescPtr XkbGetMap(Display *display, unsigned int which, unsigned int
device_spec);

display     connection to X server

which       mask selecting subcomponents to populate

device_spec device_id, or XkbUseCoreKbd

The which mask is a bitwise inclusive OR of the masks defined in Table 14.1.
Only those portions of the keyboard server map and the keyboard client maps
that are specified in which are allocated and populated.

In addition to allocating and obtaining the server map and the client map,
XkbGetMap also sets the device_spec, the min_key_code, and max_key_code fields
of the keyboard description.

XkbGetMap is synchronous; it queries the server for the desired information,
waits for a reply, and then returns. If successful, XkbGetMap returns a pointer
to the XkbDescRec structure it allocated. If unsuccessful, XkbGetMap returns 
NULL. When unsuccessful, one of the following protocol errors is also
generated: BadAlloc (unable to allocate the XkbDescRec structure), BadValue
(some mask bits in which are undefined), or BadImplementation (a compatible
version of the Xkb extension is not available in the server). To free the
returned data, use XkbFreeClientMap.

Xkb also provides convenience functions to get partial component definitions
from the server. These functions are specified in the “convenience functions”
column in Table 14.1. Refer to the sections listed in the table for more
information on these functions.

Table 14.1. Xkb Mapping Component Masks and Convenience Functions

┌─────────────────────────┬─────┬──────┬───────────┬────────────────────────────┬───────┐
│Mask                     │Value│Map   │Fields     │Convenience Functions       │Section│
├─────────────────────────┼─────┼──────┼───────────┼────────────────────────────┼───────┤
│                         │     │      │           │XkbGetKeyTypes              │       │
│                         │     │      │types      │                            │       │
│                         │(1   │      │           │XkbResizeKeyType            │       │
│XkbKeyTypesMask          │<<0) │client│size_types │                            │15.2   │
│                         │     │      │           │XkbCopyKeyType              │       │
│                         │     │      │num_types  │                            │       │
│                         │     │      │           │XkbCopyKeyTypes             │       │
├─────────────────────────┼─────┼──────┼───────────┼────────────────────────────┼───────┤
│                         │     │      │syms       │                            │       │
│                         │     │      │           │XkbGetKeySyms               │       │
│                         │(1   │      │size_syms  │                            │       │
│XkbKeySymsMask           │<<1) │client│           │XkbResizeKeySyms            │15.3   │
│                         │     │      │num_syms   │                            │       │
│                         │     │      │           │XkbChangeTypes­OfKey        │       │
│                         │     │      │key_sym_map│                            │       │
├─────────────────────────┼─────┼──────┼───────────┼────────────────────────────┼───────┤
│XkbModifierMapMask       │(1   │client│modmap     │XkbGetKeyModifier­Map       │15.4   │
│                         │<<2) │      │           │                            │       │
├─────────────────────────┼─────┼──────┼───────────┼────────────────────────────┼───────┤
│XkbExplicitComponentsMask│(1   │server│explicit   │XkbGetKeyExplicit­Components│16.3   │
│                         │<<3) │      │           │                            │       │
├─────────────────────────┼─────┼──────┼───────────┼────────────────────────────┼───────┤
│                         │     │      │key_acts   │                            │       │
│                         │     │      │           │                            │       │
│                         │(1   │      │acts       │XkbGetKeyActions            │       │
│XkbKeyActionsMask        │<<4) │server│           │                            │16.1   │
│                         │     │      │num_acts   │XkbResizeKey­Actions        │       │
│                         │     │      │           │                            │       │
│                         │     │      │size_acts  │                            │       │
├─────────────────────────┼─────┼──────┼───────────┼────────────────────────────┼───────┤
│XkbKeyBehaviorsMask      │(1   │server│behaviors  │XkbGetKey­Behaviors         │16.2   │
│                         │<<5) │      │           │                            │       │
├─────────────────────────┼─────┼──────┼───────────┼────────────────────────────┼───────┤
│XkbVirtualModsMask       │(1   │server│vmods      │XkbGetVirtualMods           │16.4   │
│                         │<<6) │      │           │                            │       │
├─────────────────────────┼─────┼──────┼───────────┼────────────────────────────┼───────┤
│XkbVirtualModMapMask     │(1   │server│vmodmap    │XkbGetVirtualMod­Map        │16.4   │
│                         │<<7) │      │           │                            │       │
└─────────────────────────┴─────┴──────┴───────────┴────────────────────────────┴───────┘


Xkb defines combinations of these masks for convenience:

#define  XkbResizableInfoMask      (XkbKeyTypesMask)
#define  XkbAllClientInfoMask      (XkbKeyTypesMask | XkbKeySymsMask |
                                    XkbModifierMapMask)
#define  XkbAllServerInfoMask      (XkbExplicitComponentsMask |
                                    XkbKeyActionsMask| XkbKeyBehaviorsMask |
                                    XkbVirtualModsMask | XkbVirtualModMapMask)
#define  XkbAllMapComponentsMask   (XkbAllClientInfoMask|XkbAllServerInfoMask)

Key types, symbol maps, and actions are all interrelated: changes in one
require changes in the others. The convenience functions make it easier to edit
these components and handle the interdependencies.

To update the client or server map information in an existing keyboard
description, use XkbGetUpdatedMap.

Status XkbGetUpdatedMap(Display *display, unsigned int which, XkbDescPtr xkb);

display connection to X server

which   mask selecting subcomponents to populate

xkb     keyboard description to be updated

The which parameter is a bitwise inclusive OR of the masks in Table 14.1. If
the needed components of the xkb structure are not already allocated,
XkbGetUpdatedMap allocates them. XkbGetUpdatedMap fetches the requested
information for the device specified in the XkbDescRec passed in the xkb
parameter.

XkbGetUpdatedMap is synchronous; it queries the server for the desired
information, waits for a reply, and then returns. If successful,
XkbGetUpdatedMap returns Success. If unsuccessful, XkbGetUpdatedMap returns one
of the following: BadAlloc (unable to allocate a component in the XkbDescRec
structure), BadValue (some mask bits in which are undefined), BadImplementation
(a compatible version of the Xkb extension is not available in the server or
the reply from the server was invalid).

Changing Map Components in the Server

There are two ways to make changes to map components: either change a local
copy of the keyboard map and call XkbSetMap to send the modified map to the
server, or, to reduce network traffic, use an XkbMapChangesRec structure and
call XkbChangeMap.

Bool XkbSetMap(Display *dpy, unsigned int which, XkbDescPtr xkb);

dpy   connection to X server

which mask selecting subcomponents to update

xkb   description from which new values are taken

Use XkbSetMap to send a complete new set of values for entire components (for
example, all symbols, all actions, and so on) to the server. The which
parameter specifies the components to be sent to the server, and is a bitwise
inclusive OR of the masks listed in Table 14.1. The xkb parameter is a pointer
to an XkbDescRec structure and contains the information to be copied to the
server. For each bit set in the which parameter, XkbSetMap takes the
corresponding structure values from the xkb parameter and sends it to the
server specified by dpy.

If any components specified by which are not present in the xkb parameter,
XkbSetMap returns False. Otherwise, it sends the update request to the server
and returns True. XkbSetMap can generate BadAlloc, BadLength, and BadValue
protocol errors.

Key types, symbol maps, and actions are all interrelated; changes in one
require changes in the others. Xkb provides functions to make it easier to edit
these components and handle the interdependencies. Table 14.1 lists these
helper functions and provides a pointer to where they are defined.

The XkbMapChangesRec Structure

Use the XkbMapChangesRec structure to identify and track partial modifications
to the mapping components and to reduce the amount of traffic between the
server and clients.

typedef struct _XkbMapChanges {
    unsigned short    changed;              /* identifies valid components
                                               in structure */
    KeyCode           min_key_code;         /* lowest numbered keycode for
                                               device */
    KeyCode           max_key_code;         /* highest numbered keycode for
                                               device */
    unsigned char     first_type;           /* index of first key type
                                               modified */
    unsigned char     num_types;            /* # types modified */
    KeyCode           first_key_sym;        /* first key whose key_sym_map
                                               changed */
    unsigned char     num_key_syms;         /* # key_sym_map
                                               entries changed */
    KeyCode           first_key_act;        /* first key whose key_acts
                                               entry changed */
    unsigned char     num_key_acts;         /* # key_acts
                                               entries changed */
    KeyCode           first_key_behavior;   /* first key whose behaviors
                                               changed */
    unsigned char     num_key_behaviors;    /* # behaviors
                                               entries changed */
    KeyCode           first_key_explicit;   /* first key whose explicit
                                               entry changed */
    unsigned char     num_key_explicit;     /* # explicit
                                               entries changed */
    KeyCode           first_modmap_key;     /* first key whose modmap
                                               entry changed */
    unsigned char     num_modmap_keys;      /* # modmap
                                               entries changed */
    KeyCode           first_vmodmap_key;    /* first key whose vmodmap
                                               changed */
    unsigned char     num_vmodmap_keys;     /* # vmodmap
                                               entries changed */
    unsigned char     pad1;                 /* reserved */
    unsigned short    vmods;                /* mask indicating which vmods
                                               changed */
} XkbMapChangesRec, *XkbMapChangesPtr;

The changed field identifies the map components that have changed in an 
XkbDescRec structure and may contain any of the bits in Table 14.1, which are
also shown in Table 14.2. Every 1 bit in changed also identifies which other
fields in the XkbMapChangesRec structure contain valid values, as indicated in
Table 14.2. The min_key_code and max_key_code fields are for reference only;
they are ignored on any requests sent to the server and are always updated by
the server whenever it returns the data for an XkbMapChangesRec.

Table 14.2. XkbMapChangesRec Masks

┌─────────────────────────┬───────────────────┬───────────────────────────────┐
│                         │Valid              │XkbDescRec Field Containing    │
│Mask                     │XkbMapChangesRec   │Changed Data                   │
│                         │Fields             │                               │
├─────────────────────────┼───────────────────┼───────────────────────────────┤
│                         │first_type,        │map->type[first_type] .. map-> │
│XkbKeyTypesMask          │num_types          │type[first_type + num_types -  │
│                         │                   │1]                             │
├─────────────────────────┼───────────────────┼───────────────────────────────┤
│                         │                   │map->key_sym_map[first_key_sym]│
│XkbKeySymsMask           │first_key_sym,     │.. map->key_sym_map            │
│                         │num_key_syms       │[first_key_sym + num_key_syms -│
│                         │                   │1]                             │
├─────────────────────────┼───────────────────┼───────────────────────────────┤
│                         │first_modmap_key,  │map->modmap[first_modmap_key]  │
│XkbModifierMapMask       │num_modmap_keys    │.. map->modmap[first_modmap_key│
│                         │                   │+ num_modmap_keys - 1]         │
├─────────────────────────┼───────────────────┼───────────────────────────────┤
│                         │                   │server->explicit               │
│                         │first_key_explicit,│[first_key_explicit] ..        │
│XkbExplicitComponentsMask│num_key_explicit   │server->explicit               │
│                         │                   │[first_key_explicit +          │
│                         │                   │num_key_explicit - 1]          │
├─────────────────────────┼───────────────────┼───────────────────────────────┤
│                         │                   │server->key_acts[first_key_act]│
│XkbKeyActionsMask        │first_key_act,     │.. server->key_acts            │
│                         │num_key_acts       │[first_key_act + num_key_acts -│
│                         │                   │1]                             │
├─────────────────────────┼───────────────────┼───────────────────────────────┤
│                         │                   │server->behaviors              │
│                         │first_key_behavior,│[first_key_behavior] ..        │
│XkbKeyBehaviorsMask      │num_key_behaviors  │server->behaviors              │
│                         │                   │[first_key_behavior +          │
│                         │                   │num_key_behaviors - 1]         │
├─────────────────────────┼───────────────────┼───────────────────────────────┤
│XkbVirtualModsMask       │vmods              │server->vmods[*]               │
├─────────────────────────┼───────────────────┼───────────────────────────────┤
│                         │                   │server->vmodmap                │
│XkbVirtualModMapMask     │first_vmodmap_key, │[first_vmodmap_key] .. server->│
│                         │num_vmodmap_keys   │vmodmap[first_vmodmap_key +    │
│                         │                   │num_vmodmap_keys - 1]          │
└─────────────────────────┴───────────────────┴───────────────────────────────┘


To update only partial components of a keyboard description, modify the
appropriate fields in the server and map components of a local copy of the
keyboard description, then call XkbChangeMap with an XkbMapChangesRec structure
indicating which components have changed.

Bool XkbChangeMap(Display *dpy, XkbDescPtr xkb, XkbMapChangesPtr changes);

dpy     connection to X server

xkb     description from which new values are taken

changes identifies component parts to update

XkbChangeMap copies any components specified by the changes structure from the
keyboard description, xkb, to the X server specified by dpy.

If any components specified by changes are not present in the xkb parameter,
XkbChangeMap returns False. Otherwise, it sends a request to the server and
returns True.

XkbChangeMap can generate BadAlloc, BadLength, and BadValue protocol errors.

Tracking Changes to Map Components

The Xkb extension reports XkbMapNotify events to clients wanting notification
whenever a map component of the Xkb description for a device changes. There are
many different types of Xkb keyboard map changes. Xkb uses an event detail mask
to identify each type of change. The event detail masks are identical to the
masks listed in Table 14.1.

To receive XkbMapNotify events under all possible conditions, use
XkbSelectEvents (see section 4.3) and pass XkbMapNotifyMask in both
bits_to_change and values_for_bits.

To receive XkbMapNotify events only under certain conditions, use
XkbSelectEventDetails using XkbMapNotify as the event_type and specifying the
desired map changes in bits_to_change and values_for_bits using mask bits from
Table 14.1.

The structure for XkbMapNotify events is:

typedef struct {
    int            type;         /* Xkb extension base event code */
    unsigned long  serial;       /* X server serial number for event */
    Bool           send_event;   /* True ⇒ synthetically generated */
    Display *      display;      /* server connection where event generated */
    Time           time;         /* server time when event generated */
    int            xkb_type;     /* XkbMapNotify */
    int            device;       /* Xkb device ID, will not be XkbUseCoreKbd */
    unsigned int   changed;      /* identifies valid fields in rest of event */
    unsigned int   resized;      /* reserved */
    int            first_type;   /* index of first key type modified */
    int            num_types     /* # types modified */
    KeyCode        min_key_code; /* minimum keycode for device */
    KeyCode        max_key_code; /* maximum keycode for device */
    KeyCode        first_key_sym; /* first key whose key_sym_map changed */
    KeyCode        first_key_act; /* first key whose key_acts entry changed */
    KeyCode        first_key_behavior; /* first key whose behaviors changed */
    KeyCode        first_key_explicit; /* first key whose explicit entry changed */
    KeyCode        first_modmap_key;   /* first key whose modmap entry changed */
    KeyCode        first_vmodmap_key;  /* first key whose vmodmap entry changed */
    int            num_key_syms;       /* # key_sym_map entries changed */
    int            num_key_acts;       /* # key_acts entries changed */
    int            num_key_behaviors;  /* # behaviors entries changed */
    int            num_key_explicit;   /* # explicit entries changed */
    int            num_modmap_keys;    /* # modmap entries changed */
    int            num_vmodmap_keys;   /* # vmodmap entries changed */
    unsigned int   vmods;              /* mask indicating which vmods changed */
} XkbMapNotifyEvent;

The changed field specifies the map components that have changed and is the
bitwise inclusive OR of the mask bits defined in Table 14.1. The other fields
in this event are interpreted as the like-named fields in an XkbMapChangesRec
(see section 14.3.1). The XkbMapNotifyEvent structure also has an additional
resized field that is reserved for future use.

Allocating and Freeing Client and Server Maps

Calling XkbGetMap (see section 14.2) should be sufficient for most applications
to get client and server maps. As a result, most applications do not need to
directly allocate client and server maps.

If you change the number of key types or construct map components without
loading the necessary components from the X server, do not allocate any map
components directly using malloc or Xmalloc. Instead, use the Xkb allocators,
XkbAllocClientMap, and XkbAllocServerMap.

Similarly, use the Xkb destructors, XkbFreeClientMap, and XkbFreeServerMap
instead of free or Xfree.

Allocating an Empty Client Map

To allocate and initialize an empty client map description record, use
XkbAllocClientMap.

Status XkbAllocClientMap(XkbDescPtr xkb, unsigned int which, unsigned int
type_count);

xkb        keyboard description in which to allocate client map

which      mask selecting map components to allocate

type_count value of num_types field in map to be allocated

XkbAllocClientMap allocates and initializes an empty client map in the map
field of the keyboard description specified by xkb. The which parameter
specifies the particular components of the client map structure to allocate and
is a mask composed by a bitwise inclusive OR of one or more of the masks shown
in Table 14.3.

Table 14.3. XkbAllocClientMap Masks

┌──────────────────┬──────────────────────────────────────────────────────────┐
│Mask              │Effect                                                    │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The type_count field specifies the number of entries to   │
│XkbKeyTypesMask   │preallocate for the types field of the client map. If the │
│                  │type_count field is less than XkbNumRequiredTypes (see    │
│                  │section 15.2.1), returns BadValue.                        │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The min_key_code and max_key_code fields of the xkb       │
│                  │parameter are used to allocate the syms and key_sym_map   │
│XkbKeySymsMask    │fields of the client map. The fields are allocated to     │
│                  │contain the maximum number of entries necessary for       │
│                  │max_key_code − min_key_code + 1 keys.                     │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │The min_key_code and max_key_code fields of the xkb       │
│                  │parameter are used to allocate the modmap field of the    │
│XkbModifierMapMask│client map. The field is allocated to contain the maximum │
│                  │number of entries necessary for max_key_code −            │
│                  │min_key_code + 1 keys.                                    │
└──────────────────┴──────────────────────────────────────────────────────────┘


Note

The min_key_code and max_key_code fields of the xkb parameter must be legal
values if the XkbKeySymsMask or XkbModifierMapMask masks are set in the which
parameter. If they are not valid, XkbAllocClientMap returns BadValue.

If the client map of the keyboard description is not NULL, and any fields are
already allocated in the client map, XkbAllocClientMap does not overwrite the
existing values; it simply ignores that part of the request. The only exception
is the types array. If type_count is greater than the current num_types field
of the client map, XkbAllocClientMap resizes the types array and resets the
num_types field accordingly.

If XkbAllocClientMap is successful, it returns Success. Otherwise, it can
return either BadMatch, BadAlloc, or BadValue errors.

Freeing a Client Map

To free memory used by the client map member of an XkbDescRec structure, use
XkbFreeClientMap.

void XkbFreeClientMap(XkbDescPtr xkb, unsigned int which, Bool free_all);

xkb      keyboard description containing client map to free

which    mask identifying components of map to free

free_all True ⇒ free all client components and map itself

XkbFreeClientMap frees the components of client map specified by which in the 
XkbDescRec structure specified by the xkb parameter and sets the corresponding
structure component values to NULL. The which parameter specifies a combination
of the client map masks shown in Table 14.3.

If free_all is True, which is ignored; XkbFreeClientMap frees every non- NULL
structure component in the client map, frees the XkbClientMapRec structure
referenced by the map member of the xkb parameter, and sets the map member to 
NULL.

Allocating an Empty Server Map

To allocate and initialize an empty server map description record, use
XkbAllocServerMap.

Status XkbAllocServerMap(XkbDescPtr xkb, unsigned int which, unsigned int
count_acts);

xkb        keyboard description in which to allocate server map

which      mask selecting map components to allocate

count_acts value of num_acts field in map to be allocated

XkbAllocServerMap allocates and initializes an empty server map in the server
field of the keyboard description specified by xkb. The which parameter
specifies the particular components of the server map structure to allocate, as
specified in Table 14.4.

Table 14.4. XkbAllocServerMap Masks

┌─────────────────────────┬───────────────────────────────────────────────────┐
│Mask                     │Effect                                             │
├─────────────────────────┼───────────────────────────────────────────────────┤
│                         │The min_key_code and max_key_code fields of the xkb│
│XkbExplicitComponentsMask│parameter are used to allocate the explicit field  │
│                         │of the server map.                                 │
├─────────────────────────┼───────────────────────────────────────────────────┤
│                         │The min_key_code and max_key_code fields of the xkb│
│XkbKeyActionsMask        │parameter are used to allocate the key_acts field  │
│                         │of the server map. The count_acts parameter is used│
│                         │to allocate the acts field of the server map.      │
├─────────────────────────┼───────────────────────────────────────────────────┤
│                         │The min_key_code and max_key_code fields of the xkb│
│XkbKeyBehaviorsMask      │parameter are used to allocate the behaviors field │
│                         │of the server map.                                 │
├─────────────────────────┼───────────────────────────────────────────────────┤
│                         │The min_key_code and max_key_code fields of the xkb│
│XkbVirtualModMapMask     │parameter are used to allocate the vmodmap field of│
│                         │the server map.                                    │
└─────────────────────────┴───────────────────────────────────────────────────┘


Note

The min_key_code and max_key_code fields of the xkb parameter must be legal
values. If they are not valid, XkbAllocServerMap returns BadValue.

If the server map of the keyboard description is not NULL and any fields are
already allocated in the server map, XkbAllocServerMap does not overwrite the
existing values. The only exception is with the acts array. If the count_acts
parameter is greater than the current num_acts field of the server map,
XkbAllocServerMap resizes the acts array and resets the num_acts field
accordingly.

If XkbAllocServerMap is successful, it returns Success. Otherwise, it can
return either BadMatch or BadAlloc errors.

Freeing a Server Map

To free memory used by the server member of an XkbDescRec structure, use
XkbFreeServerMap.

void XkbFreeServerMap(XkbDescPtr xkb, unsigned int which, Bool free_all);

xkb      keyboard description containing server map to free

which    mask identifying components of map to free

free_all True ⇒ free all server map components and server itself

The XkbFreeServerMap function frees the specified components of server map in
the XkbDescRec structure specified by the xkb parameter and sets the
corresponding structure component values to NULL. The which parameter specifies
a combination of the server map masks and is a bitwise inclusive OR of the
masks listed in Table 14.4. If free_all is True, which is ignored and
XkbFreeServerMap frees every non- NULL structure component in the server map,
frees the XkbServerMapRec structure referenced by the server member of the xkb
parameter, and sets the server member to NULL.


━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

^[6] The core implementation restricts the number of symbols per key to 255.
With four groups, this allows for up to 63 symbols (or shift levels) per group.
Most keys will only have a few shift levels.

Chapter 15. Xkb Client Keyboard Mapping

Table of Contents

The XkbClientMapRec Structure
Key Types

    The Canonical Key Types
    Getting Key Types from the Server
    Changing the Number of Levels in a Key Type
    Copying Key Types

Key Symbol Map

    Per-Key Key Type Indices
    Per-Key Group Information
    Key Width
    Offset in to the Symbol Map
    Getting the Symbol Map for Keys from the Server
    Changing the Number of Groups and Types Bound to a Key
    Changing the Number of Symbols Bound to a Key

The Per-Key Modifier Map

    Getting the Per-Key Modifier Map from the Server

The Xkb client map for a keyboard is the collection of information a client
needs to interpret key events from the keyboard. It contains a global list of
key types and an array of key symbol maps, each of which describes the symbols
bound to a key and the rules to be used to interpret those symbols.

Figure 15.1 shows the relationships between elements in the client map:

Figure 15.1. Xkb Client Map


The XkbClientMapRec Structure

The map field of the complete Xkb keyboard description (see section 6.1) is a
pointer to the Xkb client map, which is of type XkbClientMapRec:

typedef struct {                   /* Client Map */
    unsigned char   size_types;    /* # occupied entries in types */
    unsigned char   num_types;     /* # entries in types */
    XkbKeyTypePtr   types;         /* vector of key types used by this keymap */
    unsigned short  size_syms;     /* length of the syms array */
    unsigned short  num_syms;      /* # entries in syms */
    KeySym *        syms;          /* linear 2d tables of keysyms, 1 per key */
    XkbSymMapPtr    key_sym_map;   /* 1 per keycode, maps keycode to syms */
    unsigned char * modmap;        /* 1 per keycode, real mods bound to key */
} XkbClientMapRec, *XkbClientMapPtr;

The following sections describe each of the elements of the XkbClientMapRec
structure in more detail.

Key Types

Key types are used to determine the shift level of a key given the current
state of the keyboard. The set of all possible key types for the Xkb keyboard
description are held in the types field of the client map, whose total size is
stored in size_types, and whose total number of valid entries is stored in
num_types. Key types are defined using the following structures:

typedef struct {                     /* Key Type */
    XkbModsRec        mods;          /* modifiers used to compute shift level */
    unsigned char     num_levels;    /* total # shift levels, do not
                                        modify directly */
    unsigned char     map_count;     /* # entries in map, preserve
                                        (if non-NULL) */
    XkbKTMapEntryPtr  map;           /* vector of modifiers for each
                                        shift level */
    XkbModsPtr        preserve;      /* mods to preserve for
                                        corresponding map entry */
    Atom              name;          /* name of key type */
    Atom *            level_names;   /* array of names of each shift level */
} XkbKeyTypeRec, *XkbKeyTypePtr;

typedef struct {                     /* Modifiers for a key type */
    Bool              active;        /* True ⇒ entry active when
                                        determining shift level */
    unsigned char     level;         /* shift level if modifiers match mods */
    XkbModsRec        mods;          /* mods needed for this level to be
                                        selected */
} XkbKTMapEntryRec, *XkbKTMapEntryPtr;

The mods field of a key type is an XkbModsRec (see section 7.2) specifying the
modifiers the key type uses when calculating the shift level, and can be
composed of both the core modifiers and virtual modifiers. To set the modifiers
associated with a key type, modify the real_mods and vmods fields of the mods 
XkbModsRec accordingly. The mask field of the XkbModsRec is reserved for use by
Xkb and is calculated from the real_mods and vmods fields.

The num_levels field holds the total number of shift levels for the key type.
Xkb uses num_levels to ensure the array of symbols bound to a key is large
enough. Do not modify num_levels directly to change the number if shift levels
for a key type. Instead, use XkbResizeKeyType (see section 15.2.3).

The map field is a vector of XkbKTMapEntryRec structures, with map_count
entries, that specify the modifier combinations for each possible shift level.
Each map entry contains an active field, a mods field, and a level field. The
active field determines whether the modifier combination listed in the mods
field should be considered when determining shift level. If active is False,
this map entry is ignored. If active is True, the level field of the map entry
specifies the shift level to use when the current modifier combination matches
the combination specified in the mods field of the map entry.

Any combination of modifiers not explicitly listed somewhere in the map yields
shift level one. In addition, map entries specifying unbound virtual modifiers
are not considered.

Any modifiers specified in mods are normally consumed by XkbTranslateKeyCode
(see section 12.1.3). For those rare occasions a modifier should be considered
despite having been used to look up a symbol, key types include an optional
preserve field. If a preserve member of a key type is not NULL, it represents a
list of modifiers where each entry corresponds directly to one of the key
type’s map. Each entry lists the modifiers that should not be consumed if the
matching map entry is used to determine shift level.

Each shift level has a name and these names are held in the level_names array,
whose length is num_levels. The type itself also has a name, which is held in
the name field.

For example, consider how the server handles the following possible symbolic
description of a possible key type (note that the format used to specify
keyboard mappings in the server database is not specified by the Xkb extension,
although this format is one possible example):

Table 15.1. Example Key Type

┌──────────────────────────────────┬─────────────────────────────────┐
│Symbolic Description              │Key Type Data Structure          │
├──────────────────────────────────┼─────────────────────────────────┤
│type "ALPHATHREE" {               │Xkb->map->types[i].name          │
├──────────────────────────────────┼─────────────────────────────────┤
│modifiers = Shift+Lock+LevelThree;│Xkb->map->types[i].mods          │
├──────────────────────────────────┼─────────────────────────────────┤
│map[None]= Level1;                │Xkb->map->types[i].map[0]        │
├──────────────────────────────────┼─────────────────────────────────┤
│map[Lock]= Level1;                │Xkb->map->types[i].map[1]        │
├──────────────────────────────────┼─────────────────────────────────┤
│map[Shift]= Level2;               │Xkb->map->types[i].map[2]        │
├──────────────────────────────────┼─────────────────────────────────┤
│map[LevelThree]= Level3;          │Xkb->map->types[i].map[3]        │
├──────────────────────────────────┼─────────────────────────────────┤
│map[Shift+LevelThree]= Level3;    │Xkb->map->types[i].map[4]        │
├──────────────────────────────────┼─────────────────────────────────┤
│preserve[None]= None;             │Xkb->map->types[i].preserve[0]   │
├──────────────────────────────────┼─────────────────────────────────┤
│preserve[Lock]= Lock;             │Xkb->map->types[i].preserve[1]   │
├──────────────────────────────────┼─────────────────────────────────┤
│preserve[Shift]= None;            │Xkb->map->types[i].preserve[2]   │
├──────────────────────────────────┼─────────────────────────────────┤
│preserve[LevelThree]= None;       │Xkb->map->types[i].preserve[3]   │
├──────────────────────────────────┼─────────────────────────────────┤
│preserve[Shift+Level3]= None;     │Xkb->map->types[i].preserve[4]   │
├──────────────────────────────────┼─────────────────────────────────┤
│level_name[Level1]= "Base";       │Xkb->map->types[i].level_names[0]│
├──────────────────────────────────┼─────────────────────────────────┤
│level_name[Level2]= "Caps";       │Xkb->map->types[i].level_names[1]│
├──────────────────────────────────┼─────────────────────────────────┤
│level_name[Level3]= "Level3";     │Xkb->map->types[i].level_names[2]│
├──────────────────────────────────┼─────────────────────────────────┤
│};                                │                                 │
└──────────────────────────────────┴─────────────────────────────────┘


The name of the example key type is "ALPHATHREE," and the modifiers it pays
attention to are Shift, Lock, and the virtual modifier LevelThree. There are
three shift levels. The name of shift level one is "Base," the name of shift
level two is "Caps," and the name of shift level three is "Level3."

Given the combination of the map and preserve specifications, there are five
map entries. The first map entry specifies that shift level one is to be used
if no modifiers are set. The second entry specifies the Lock modifier alone
also yields shift level one. The third entry specifies the Shift modifier alone
yields shift level two. The fourth and fifth entries specify that the virtual 
LevelThree modifier alone, or in combination with the Shift modifier, yields
shift level three.

Note

Shift level three can be reached only if the virtual modifier LevelThree is
bound to a real modifier (see section 16.4). If LevelThree is not bound to a
real modifier, the map entries associated with it are ignored.

Because the Lock modifier is to be preserved for further event processing, the
preserve list is not NULL and parallels the map list. All preserve entries,
except for the one corresponding to the map entry that specifies the Lock
modifier, do not list any modifiers. For the map entry that specifies the Lock
modifier, the corresponding preserve list entry lists the Lock modifier,
meaning do not consume the Lock modifier. In this particular case, the
preserved modifier is passed to Xlib translation functions and causes them to
notice that the Lock modifier is set; consequently, the Xlib functions apply
the appropriate capitalization rules to the symbol. Because this preserve entry
is set only for a modifier that yields shift level one, the capitalization
occurs only for level-one symbols.

The Canonical Key Types

Xkb allows up to XkbMaxKeyTypes (255) key types to be defined, but requires at
least XkbNumRequiredTypes (4) predefined types to be in a key map. These
predefined key types are referred to as the canonical key types and describe
the types of keys available on most keyboards. The definitions for the
canonical key types are held in the first XkbNumRequiredTypes entries of the
types field of the client map and are indexed using the following constants:

XkbOneLevelIndex
XkbTwoLevelIndex
XkbAlphabeticIndex
XkbKeypadIndex

ONE_LEVEL

The ONE_LEVEL key type describes groups that have only one symbol. The default
ONE_LEVEL key type has no map entries and does not pay attention to any
modifiers. A symbolic representation of this key type could look like the
following:


    type "ONE_LEVEL" {
          modifiers = None;
          map[None]= Level1;
          level_name[Level1]= "Any";
    };

The description of the ONE_LEVEL key type is stored in the types [ 
XkbOneLevelIndex ] entry of the client key map.

TWO_LEVEL

The TWO_LEVEL key type describes groups that consist of two symbols but are
neither alphabetic nor numeric keypad keys. The default TWO_LEVEL type uses
only the Shift modifier. It returns shift level two if Shift is set, and level
one if it is not. A symbolic representation of this key type could look like
the following:


    type "TWO_LEVEL" {
          modifiers = Shift;
          map[Shift]= Level2;
          level_name[Level1]= "Base";
          level_name[Level2]= "Shift";
    };

The description of the TWO_LEVEL key type is stored in the types [ 
XkbTwoLevelIndex ] entry of the client key map.

ALPHABETIC

The ALPHABETIC key type describes groups consisting of two symbols: the
lowercase form of a symbol followed by the uppercase form of the same symbol.
The default ALPHABETIC type implements locale-sensitive “Shift cancels CapsLock
” behavior using both the Shift and Lock modifiers as follows:

  • If Shift and Lock are both set, the default ALPHABETIC type yields level
    one.

  • If Shift alone is set, it yields level two.

  • If Lock alone is set, it yields level one, but preserves the Lock modifier
    so Xlib notices and applies the appropriate capitalization rules. The Xlib
    functions are locale-sensitive and apply different capitalization rules for
    different locales.

  • If neither Shift nor Lock is set, it yields level one.

A symbolic representation of this key type could look like the following:


    type "ALPHABETIC" {
          modifiers = Shift+Lock;
          map[Shift]= Level2;
          preserve[Lock]= Lock;
          level_name[Level1]= "Base";
          level_name[Level2]= "Caps";
    };

The description of the ALPHABETIC key type is stored in the types [ 
XkbAlphabeticIndex ] entry of the client key map.

KEYPAD

The KEYPAD key type describes groups that consist of two symbols, at least one
of which is a numeric keypad symbol. The numeric keypad symbol is assumed to
reside at level two. The default KEYPAD key type implements “Shift cancels
NumLock” behavior using the Shift modifier and the real modifier bound to the
virtual modifier named “NumLock”, known as the NumLock modifier, as follows:

  • If Shift and NumLock are both set, the default KEYPAD type yields level
    one.

  • If Shift alone is set, it yields level two.

  • If NumLock alone is set, it yields level two.

  • If neither Shift nor NumLock is set, it yields level one.

A symbolic representation of this key type could look like the following:


    type "KEYPAD" {
          modifiers = Shift+NumLock;
          map[None]= Level1;
          map[Shift]= Level2;
          map[NumLock]= Level2;
          map[Shift+NumLock]= Level1;
          level_name[Level1]= "Base";
          level_name[Level2]= "Caps";
    };

The description of the KEYPAD key type is stored in the types [ XkbKeypadIndex
] entry of the client key map.

Initializing the Canonical Key Types in a New Client Map

To set the definitions of the canonical key types in a client map to their
default values, use XkbInitCanonicalKeyTypes.

Status XkbInitCanonicalKeyTypes(XkbDescPtr xkb, unsigned int which, int
keypadVMod);

xkb        keyboard description containing client map to initialize

which      mask of types to initialize

keypadVMod index of NumLock virtual modifier

XkbInitCanonicalKeyTypes initializes the first XkbNumRequiredTypes key types of
the keyboard specified by the xkb parameter to their default values. The which
parameter specifies what canonical key types to initialize and is a bitwise
inclusive OR of the following masks: XkbOneLevelMask, XkbTwoLevelMask, 
XkbAlphabeticMask, and XkbKeypadMask. Only those canonical types specified by
the which mask are initialized.

If XkbKeypadMask is set in the which parameter, XkbInitCanonicalKeyTypes looks
up the NumLock named virtual modifier to determine which virtual modifier to
use when initializing the KEYPAD key type. If the NumLock virtual modifier does
not exist, XkbInitCanonicalKeyTypes creates it.

XkbInitCanonicalKeyTypes normally returns Success. It returns BadAccess if the
Xkb extension has not been properly initialized, and BadAccess if the xkb
parameter is not valid.

Getting Key Types from the Server

To obtain the list of available key types in the server’s keyboard mapping, use
XkbGetKeyTypes.

Status XkbGetKeyTypes(Display *dpy, unsigned int first, unsigned int num,
XkbDescPtr xkb);

dpy   connection to X server

first index to first type to get, 0 ⇒ 1st type

num   number of key types to be returned

xkb   keyboard description containing client map to update

Note

XkbGetKeyTypes is used to obtain descriptions of the key types themselves, not
the key types bound to individual keys. To obtain the key types bound to an
individual key, refer to the key_sym_map field of the client map (see section
15.3.1).

XkbGetKeyTypes queries the server for the desired types, waits for a reply, and
returns the desired types in the xkb->map->types. If successful, it returns
Success.

XkbGetKeyTypes returns BadAccess if the Xkb extension has not been properly
initialized and BadValue if the combination of first and num results in numbers
out of valid range.

Changing the Number of Levels in a Key Type

To change the number of levels in a key type, use XkbResizeKeyType.

Status XkbResizeKeyType(XkbDescPtr xkb, int type_ndx, int map_count, Bool
want_preserve, int new_num_lvls);

xkb           keyboard description containing client map to update

type_ndx      index in xkb->map->types of type to change

map_count     total # of map entries needed for the type

want_preserve True ⇒ list of preserved modifiers is necessary

new_num_lvls  new max # of levels for type

XkbResizeKeyType changes the type specified by xkb->map->types [ type_ndx ],
and reallocates the symbols and actions bound to all keys that use the type, if
necessary. XkbResizeKeyType updates only the local copy of the types in xkb; to
update the server’s copy for the physical device, use XkbSetMap or XkbChangeMap
after calling XkbResizeKeyType.

The map_count parameter specifies the total number of map entries needed for
the type, and can be zero or greater. If map_count is zero, XkbResizeKeyType
frees the existing map and preserve entries for the type if they exist and sets
them to NULL.

The want_preserve parameter specifies whether a preserve list for the key
should be created. If want_preserve is True, the preserve list with map_count
entries is allocated or reallocated if it already exists. Otherwise, if
want_preserve is False, the preserve field is freed if necessary and set to 
NULL.

The new_num_lvls parameter specifies the new maximum number of shift levels for
the type and is used to calculate and resize the symbols and actions bound to
all keys that use the type.

If type_ndx does not specify a legal type, new_num_lvls is less than 1, or the
map_count is less than zero, XkbResizeKeyType returns BadValue. If
XkbResizeKeyType encounters any problems with allocation, it returns BadAlloc.
Otherwise, it returns Success.

Copying Key Types

Use XkbCopyKeyType and XkbCopyKeyTypes to copy one or more XkbKeyTypeRec
structures.

Status XkbCopyKeyType(XkbKeyTypePtr from, XkbKeyTypePtr into);

from pointer to XkbKeyTypeRec to be copied

into pointer to XkbKeyTypeRec to be changed

XkbCopyKeyType copies the key type specified by from to the key type specified
by into. Both must point to legal XkbKeyTypeRec structures. Xkb assumes from
and into point to different places. As a result, overlaps can be fatal.
XkbCopyKeyType frees any existing map, preserve, and level_names in into prior
to copying. If any allocation errors occur while copying from to into,
XkbCopyKeyType returns BadAlloc. Otherwise, XkbCopyKeyType copies from to into
and returns Success.

Status XkbCopyKeyTypes(XkbKeyTypePtr from, XkbKeyTypePtr into, int num_types);

from      pointer to array of XkbKeyTypeRecs to copy

into      pointer to array of XkbKeyTypeRecs to change

num_types number of types to copy

XkbCopyKeyTypes copies num_types XkbKeyTypeRec structures from the array
specified by from into the array specified by into. It is intended for copying
between, rather than within, keyboard descriptions, so it doesn’t check for
overlaps. The same rules that apply to the from and into parameters in
XkbCopyKeyType apply to each entry of the from and into arrays of
XkbCopyKeyTypes. If any allocation errors occur while copying from to into,
XkbCopyKeyTypes returns BadAlloc. Otherwise, XkbCopyKeyTypes copies from to
into and returns Success.

Key Symbol Map

The entire list of key symbols for the keyboard mapping is held in the syms
field of the client map. Whereas the core keyboard mapping is a two-dimensional
array of KeySyms whose rows are indexed by keycode, the syms field of Xkb is a
linear list of KeySyms that needs to be indexed uniquely for each key. This
section describes the key symbol map and the methods for determining the
symbols bound to a key.

The reason the syms field is a linear list of KeySyms is to reduce the memory
consumption associated with a keymap; because Xkb allows individual keys to
have multiple shift levels and a different number of groups per key, a single
two-dimensional array of KeySyms would potentially be very large and sparse.
Instead, Xkb provides a small two-dimensional array of KeySyms for each key. To
store all of these individual arrays, Xkb concatenates each array together in
the syms field of the client map.

In order to determine which KeySyms in the syms field are associated with each
keycode, the client map contains an array of key symbol mappings, held in the
key_sym_map field. The key_sym_map field is an array of XkbSymMapRec structures
indexed by keycode. The key_sym_map array has min_key_code unused entries at
the start to allow direct indexing using a keycode. All keycodes falling
between the minimum and maximum legal keycodes, inclusive, have key_sym_map
arrays, whether or not any key actually yields that code. The KeySymMapRec
structure is defined as follows:

#define XkbNumKbdGroups            4
#define XkbMaxKbdGroup            (XkbNumKbdGroups-1)

typedef struct {                 /* map to keysyms for a single keycode */
    unsigned char     kt_index[XkbNumKbdGroups];
                                         /* key type index for each group */
    unsigned char     group_info;        /* # of groups and out of range
                                            group handling */
    unsigned char     width;             /* max # of shift levels for key */
    unsigned short    offset;            /* index to keysym table in
                                            syms array */
} XkbSymMapRec, *XkbSymMapPtr;

These fields are described in detail in the following sections.

Per-Key Key Type Indices

The kt_index array of the XkbSymMapRec structure contains the indices of the
key types (see section 15.2) for each possible group of symbols associated with
the key. To obtain the index of a key type or the pointer to a key type, Xkb
provides the following macros, to access the key types:

Note

The array of key types is of fixed width and is large enough to hold key types
for the maximum legal number of groups (XkbNumKbdGroups, currently four); if a
key has fewer than XkbNumKbdGroups groups, the extra key types are reported but
ignored.

int XkbKeyKeyTypeIndex(XkbDescPtr xkb, KeyCode keycode, int group);

xkb     Xkb description of interest

keycode keycode of interest

group   group index

XkbKeyKeyTypeIndex computes an index into the types vector of the client map in
xkb from the given keycode and group index.

XkbKeyTypePtr XkbKeyKeyType(XkbDescPtr xkb, KeyCode keycode, int group);

xkb     Xkb description of interest

keycode keycode of interest

group   group index

XkbKeyKeyType returns a pointer to the key type in the types vector of the
client map in xkb corresponding to the given keycode and group index.

Per-Key Group Information

The group_info field of an XkbSymMapRec is an encoded value containing the
number of groups of symbols bound to the key as well as the specification of
the treatment of out-of-range groups. It is legal for a key to have zero
groups, in which case it also has zero symbols and all events from that key
yield NoSymbol. To obtain the number of groups of symbols bound to the key, use
XkbKeyNumGroups. To change the number of groups bound to a key, use
XkbChangeTypesOfKey (see section 15.3.6). To obtain a mask that determines the
treatment of out-of-range groups, use XkbKeyGroupInfo and
XkbOutOfRangeGroupInfo.

The keyboard controls (see Chapter 10, Keyboard Controls) contain a groups_wrap
field specifying the handling of illegal groups on a global basis. That is,
when the user performs an action causing the effective group to go out of the
legal range, the groups_wrap field specifies how to normalize the effective
keyboard group to a group that is legal for the keyboard as a whole, but there
is no guarantee that the normalized group will be within the range of legal
groups for any individual key. The per-key group_info field specifies how a key
treats a legal effective group if the key does not have a type specified for
the group of concern. For example, the Enter key usually has just one group
defined. If the user performs an action causing the global keyboard group to
change to Group2, the group_info field for the Enter key describes how to
handle this situation.

Out-of-range groups for individual keys are mapped to a legal group using the
same options as are used for the overall keyboard group. The particular type of
mapping used is controlled by the bits set in the group_info flag, as shown in
Table 15.2. See section 10.7.1 for more details on the normalization methods in
this table.

Table 15.2. group_info Range Normalization

┌──────────────────────┬────────────────────┐
│Bits set in group_info│Normalization method│
├──────────────────────┼────────────────────┤
│XkbRedirectIntoRange  │XkbRedirectIntoRange│
├──────────────────────┼────────────────────┤
│XkbClampIntoRange     │XkbClampIntoRange   │
├──────────────────────┼────────────────────┤
│none of the above     │XkbWrapIntoRange    │
└──────────────────────┴────────────────────┘


Xkb provides the following macros to access group information:

int XkbKeyNumGroups(XkbDescPtr xkb, KeyCode keycode);

xkb     Xkb description of interest

keycode keycode of interest

XkbKeyNumGroups returns the number of groups of symbols bound to the key
corresponding to keycode.

unsigned char XkbKeyGroupInfo(XkbDescPtr xkb, KeyCode keycode);

xkb     Xkb description of interest

keycode keycode of interest

XkbKeyGroupInfo returns the group_info field from the XkbSymMapRec structure
associated with the key corresponding to keycode.

unsigned char XkbOutOfRangeGroupInfo(unsigned char grp_inf);

grp_inf group_info field of XkbSymMapRec

XkbOutOfRangeGroupInfo returns only the out-of-range processing information
from the group_info field of an XkbSymMapRec structure.

unsigned char XkbOutOfRangeGroupNumber(unsigned char grp_inf);

grp_inf group_info field of XkbSymMapRec

XkbOutOfRangeGroupNumber returns the out-of-range group number, represented as
a group index, from the group_info field of an XkbSymMapRec structure.

Key Width

The maximum number of shift levels for a type is also referred to as the width
of a key type. The width field of the key_sym_map entry for a key contains the
width of the widest type associated with the key. The width field cannot be
explicitly changed; it is updated automatically whenever the symbols or set of
types bound to a key are changed.

Offset in to the Symbol Map

The key width and number of groups associated with a key are used to form a
small two-dimensional array of KeySyms for a key. This array may be different
sizes for different keys. The array for a single key is stored as a linear
list, in row-major order. The arrays for all of the keys are stored in the syms
field of the client map. There is one row for each group associated with a key
and one column for each level. The index corresponding to a given group and
shift level is computed as:


     idx = group_index * key_width + shift_level

The offset field of the key_sym_map entry for a key is used to access the
beginning of the array.

Xkb provides the following macros for accessing the width for individual keys,
as well as macros for accessing the two-dimensional array of symbols bound to
the key:

int XkbKeyGroupsWidth(XkbDescPtr xkb, KeyCode keycode);

xkb     Xkb description of interest

keycode keycode of interest

XkbKeyGroupsWidth computes the maximum width associated with the key
corresponding to keycode.

int XkbKeyGroupWidth(XkbDescPtr xkb, KeyCode keycode, int grp);

xkb     Xkb description of interest

keycode keycode of interest

grp     group of interest

XkbKeyGroupWidth computes the width of the type associated with the group grp
for the key corresponding to keycode.

int XkbKeyNumSyms(XkbDescPtr xkb, KeyCode keycode);

xkb     Xkb description of interest

keycode keycode of interest

XkbKeyNumSyms returns the total number of keysyms for the key corresponding to
keycode.

KeySym *XkbKeySymsPtr(XkbDescPtr xkb, KeyCode keycode);

xkb     Xkb description of interest

keycode keycode of interest

XkbKeySymsPtr returns the pointer to the two-dimensional array of keysyms for
the key corresponding to keycode.

KeySym XkbKeySymEntry(XkbDescPtr xkb, KeyCode keycode, int shift, int grp);

xkb     Xkb description of interest

keycode keycode of interest

shift   shift level of interest

grp     group of interest

XkbKeySymEntry returns the KeySym corresponding to shift level shift and group
grp from the two-dimensional array of keysyms for the key corresponding to
keycode

Getting the Symbol Map for Keys from the Server

To obtain the symbols for a subset of the keys in a keyboard description, use
XkbGetKeySyms:

Status XkbGetKeySyms(Display *dpy, unsigned int first, unsigned int num,
XkbDescPtr xkb);

dpy   connection to X server

first keycode of first key to get

num   number of keycodes for which syms desired

xkb   Xkb description to be updated

XkbGetKeySyms sends a request to the server to obtain the set of keysyms bound
to num keys starting with the key whose keycode is first. It waits for a reply
and returns the keysyms in the map.syms field of xkb. If successful,
XkbGetKeySyms returns Success. The xkb parameter must be a pointer to a valid
Xkb keyboard description.

If the client map in the xkb parameter has not been allocated, XkbGetKeySyms
allocates and initializes it before obtaining the symbols.

If a compatible version of Xkb is not available in the server or the Xkb
extension has not been properly initialized, XkbGetKeySyms returns BadAccess.
If num is less than 1 or greater than XkbMaxKeyCount, XkbGetKeySyms returns 
BadValue. If any allocation errors occur, XkbGetKeySyms returns BadAlloc.

Changing the Number of Groups and Types Bound to a Key

To change the number of groups and the types bound to a key, use
XkbChangeTypesOfKey.

Status XkbChangeTypesOfKey(XkbDescPtr xkb, int key, int n_groups, unsigned int
groups, int *new_types_in, XkbMapChangesPtr p_changes);

xkb          keyboard description to be changed

key          keycode for key of interest

n_groups     new number of groups for key

groups       mask indicating groups to change

new_types_in indices for new groups specified in groups

p_changes    notes changes made to xkb

XkbChangeTypesOfKey reallocates the symbols and actions bound to the key, if
necessary, and initializes any new symbols or actions to NoSymbol or NoAction,
as appropriate. If the p_changes parameter is not NULL, XkbChangeTypesOfKey
adds the XkbKeySymsMask to the changes field of p_changes and modifies the
first_key_sym and num_key_syms fields of p_changes to include the key that was
changed. See section 14.3.1 for more information on the XkbMapChangesPtr
structure. If successful, XkbChangeTypesOfKey returns Success.

The n_groups parameter specifies the new number of groups for the key. The
groups parameter is a mask specifying the groups for which new types are
supplied and is a bitwise inclusive OR of the following masks: XkbGroup1Mask, 
XkbGroup2Mask, XkbGroup3Mask, and XkbGroup4Mask.

The new_types_in parameter is an integer array of length n_groups. Each entry
represents the type to use for the associated group and is an index into xkb->
map->types. The new_types_in array is indexed by group index; if n_groups is
four and groups only has XkbGroup1Mask and XkbGroup3Mask set, new_types_in
looks like this:


     new_types_in[0] = type for Group1
     new_types_in[1] = ignored
     new_types_in[2] = type for Group3
     new_types_in[3] = ignored

For convenience, Xkb provides the following constants to use as indices to the
groups:

Table 15.3. Group Index Constants

┌───────────────┬─────┐
│Constant Name  │Value│
├───────────────┼─────┤
│XkbGroup1Index │0    │
├───────────────┼─────┤
│XkbGroup2Index │1    │
├───────────────┼─────┤
│XkbGroup3Index │2    │
├───────────────┼─────┤
│XkbGroup4Index │3    │
└───────────────┴─────┘


If the Xkb extension has not been properly initialized, XkbChangeTypesOfKey
returns BadAccess. If the xkb parameter it not valid (that is, it is NULL or it
does not contain a valid client map), XkbChangeTypesOfKey returns BadMatch. If
the key is not a valid keycode, n_groups is greater than XkbNumKbdGroups, or
the groups mask does not contain any of the valid group mask bits,
XkbChangeTypesOfKey returns BadValue. If it is necessary to resize the key
symbols or key actions arrays and any allocation errors occur,
XkbChangeTypesOfKey returns BadAlloc.

Changing the Number of Symbols Bound to a Key

To change the number of symbols bound to a key, use XkbResizeKeySyms.

KeySym *XkbResizeKeySyms(XkbDescRec *xkb, int key, int needed);

xkb    keyboard description to be changed

key    keycode for key to modify

needed new number of keysyms required for key

XkbResizeKeySyms reserves the space needed for needed keysyms and returns a
pointer to the beginning of the new array that holds the keysyms. It adjusts
the offset field of the key_sym_map entry for the key if necessary and can also
change the syms, num_syms, and size_syms fields of xkb->map if it is necessary
to reallocate the syms array. XkbResizeKeySyms does not modify either the width
or number of groups associated with the key.

If needed is greater than the current number of keysyms for the key,
XkbResizeKeySyms initializes all new keysyms in the array to NoSymbol.

Because the number of symbols needed by a key is normally computed as width *
number of groups, and XkbResizeKeySyms does not modify either the width or
number of groups for the key, a discrepancy exists upon return from
XkbResizeKeySyms between the space allocated for the keysyms and the number
required. The unused entries in the list of symbols returned by
XkbResizeKeySyms are not preserved across future calls to any of the map
editing functions, so you must update the key symbol mapping (which updates the
width and number of groups for the key) before calling another allocator
function. A call to XkbChangeTypesOfKey will update the mapping.

If any allocation errors occur while resizing the number of symbols bound to
the key, XkbResizeKeySyms returns NULL.

Note

A change to the number of symbols bound to a key should be accompanied by a
change in the number of actions bound to a key. Refer to section 16.1.16 for
more information on changing the number of actions bound to a key.

The Per-Key Modifier Map

The modmap entry of the client map is an array, indexed by keycode, specifying
the real modifiers bound to a key. Each entry is a mask composed of a bitwise
inclusive OR of the legal real modifiers: ShiftMask, LockMask, ControlMask, 
Mod1Mask, Mod2Mask, Mod3Mask, Mod4Mask, and Mod5Mask. If a bit is set in a
modmap entry, the corresponding key is bound to that modifier.

Pressing or releasing the key bound to a modifier changes the modifier set and
unset state. The particular manner in which the modifier set and unset state
changes is determined by the behavior and actions assigned to the key (see
Chapter 16, Xkb Server Keyboard Mapping).

Getting the Per-Key Modifier Map from the Server

To update the modifier map for one or more of the keys in a keyboard
description, use XkbGetKeyModifierMap.

Status XkbGetKeyModifierMap(Display *dpy, unsigned int first, unsigned int num,
XkbDescPtr xkb);

dpy   connection to X server

first keycode of first key to get

num   number of keys for which information is desired

xkb   keyboard description to update

XkbGetKeyModifierMap sends a request to the server for the modifier mappings
for num keys starting with the key whose keycode is first. It waits for a reply
and places the results in the xkb->map->modmap array. If successful,
XkbGetKeyModifierMap returns Success.

If the map component of the xkb parameter has not been allocated,
XkbGetKeyModifierMap allocates and initializes it.

If a compatible version of Xkb is not available in the server or the Xkb
extension has not been properly initialized, XkbGetKeySyms returns BadAccess.
If any allocation errors occur while obtaining the modifier map,
XkbGetKeyModifierMap returns BadAlloc.

Chapter 16. Xkb Server Keyboard Mapping

Table of Contents

Key Actions

    The XkbAction Structure
    The XkbAnyAction Structure
    Actions for Changing Modifiers’ State
    Actions for Changing Group State
    Actions for Moving the Pointer
    Actions for Simulating Pointer Button Press and Release
    Actions for Changing the Pointer Button Simulated
    Actions for Locking Modifiers and Group
    Actions for Changing the Active Screen
    Actions for Changing Boolean Controls State
    Actions for Generating Messages
    Actions for Generating a Different Keycode
    Actions for Generating DeviceButtonPress and DeviceButtonRelease
    Actions for Simulating Events from Device Valuators
    Obtaining Key Actions for Keys from the Server
    Changing the Number of Actions Bound to a Key

Key Behavior

    Radio Groups
    The XkbBehavior Structure
    Obtaining Key Behaviors for Keys from the Server

Explicit Components—Avoiding Automatic Remapping by the Server

    Obtaining Explicit Components for Keys from the Server

Virtual Modifier Mapping

    Obtaining Virtual Modifier Bindings from the Server
    Obtaining Per-Key Virtual Modifier Mappings from the Server

The server field of the complete Xkb keyboard description (see section 6.1) is
a pointer to the Xkb server map.

Figure 16.1 shows the relationships between elements in the server map:

Figure 16.1. Server Map Relationships


The Xkb server map contains the information the server needs to interpret key
events and is of type XkbServerMapRec:

#define XkbNumVirtualMods            16

typedef struct {                       /* Server Map */
    unsigned short     num_acts;       /* # of occupied entries in acts */
    unsigned short     size_acts;      /* # of entries in acts */
    XkbAction *        acts;           /* linear 2d tables of key actions,
                                          1 per keycode */
    XkbBehavior *      behaviors;      /* key behaviors, 1 per keycode */
    unsigned short *   key_acts;       /* index into acts, 1 per keycode */
    unsigned char *    explicit;       /* explicit overrides of core
                                          remapping, 1 per key */
    unsigned char      vmods[XkbNumVirtualMods];  /* real mods bound
                                                     to virtual mods */
    unsigned short *   vmodmap;        /* virtual mods bound to key,
                                          1 per keycode */
} XkbServerMapRec, *XkbServerMapPtr;

The num_acts, size_acts, acts, and key_acts fields specify the key actions,
defined in section 16.1. The behaviors field describes the behavior for each
key and is defined in section 16.2. The explicit field describes the explicit
components for a key and is defined in section 16.3. The vmods and the vmodmap
fields describe the virtual modifiers and the per-key virtual modifier mapping
and are defined in section 16.4.

Key Actions

A key action defines the effect key presses and releases have on the internal
state of the server. For example, the expected key action associated with
pressing the Shift key is to set the Shift modifier. There is zero or one key
action associated with each keysym bound to each key.

Just as the entire list of key symbols for the keyboard mapping is held in the
syms field of the client map, the entire list of key actions for the keyboard
mapping is held in the acts array of the server map. The total size of acts is
specified by size_acts, and the number of entries is specified by num_acts.

The key_acts array, indexed by keycode, describes the actions associated with a
key. The key_acts array has min_key_code unused entries at the start to allow
direct indexing using a keycode. If a key_acts entry is zero, it means the key
does not have any actions associated with it. If an entry is not zero, the
entry represents an index into the acts field of the server map, much as the
offset field of a KeySymMapRec structure is an index into the syms field of the
client map.

The reason the acts field is a linear list of XkbActions is to reduce the
memory consumption associated with a keymap. Because Xkb allows individual keys
to have multiple shift levels and a different number of groups per key, a
single two-dimensional array of KeySyms would potentially be very large and
sparse. Instead, Xkb provides a small two-dimensional array of XkbActions for
each key. To store all of these individual arrays, Xkb concatenates each array
together in the acts field of the server map.

The key action structures consist only of fields of type char or unsigned char.
This is done to optimize data transfer when the server sends bytes over the
wire. If the fields are anything but bytes, the server has to sift through all
of the actions and swap any nonbyte fields. Because they consist of nothing but
bytes, it can just copy them out.

Xkb provides the following macros, to simplify accessing information pertaining
to key actions:

Bool XkbKeyHasActions(XkbDescPtr xkb, KeyCode keycode);

xkb     Xkb description of interest

keycode keycode of interest

XkbKeyHasActions returns True if the key corresponding to keycode has any
actions associated with it; otherwise, it returns False.

int XkbKeyNumActions(XkbDescPtr xkb, KeyCode keycode);

xkb     Xkb description of interest

keycode keycode of interest

XkbKeyNumActions computes the number of actions associated with the key
corresponding to keycode. This should be the same value as the result of
XkbKeyNumSyms (see section 15.3.3).

XkbKeyActionPtr XkbKeyActionsPtr(XkbDescPtr xkb, KeyCode keycode);

xkb     Xkb description of interest

keycode keycode of interest

XkbKeyActionsPtr returns a pointer to the two-dimensional array of key actions
associated with the key corresponding to keycode. Use XkbKeyActionsPtr only if
the key actually has some actions associated with it, that is, XkbKeyNumActions
(xkb, keycode) returns something greater than zero.

XkbAction XkbKeyAction(XkbDescPtr xkb, KeyCode keycode, int idx);

xkb     Xkb description of interest

keycode keycode of interest

idx     index for group and shift level

XkbKeyAction returns the key action indexed by idx in the two-dimensional array
of key actions associated with the key corresponding to keycode. idx may be
computed from the group and shift level of interest as follows:


     idx = group_index * key_width + shift_level

XkbAction XkbKeyActionEntry(XkbDescPtr xkb, KeyCode keycode, int shift, int
grp);

xkb     Xkb description of interest

keycode keycode of interest

shift   shift level within group

grp     group index for group of interest

XkbKeyActionEntry returns the key action corresponding to group grp and shift
level shift from the two-dimensional table of key actions associated with the
key corresponding to keycode.

The XkbAction Structure

The description for an action is held in an XkbAction structure, which is a
union of all possible Xkb action types:

typedef union _XkbAction {
    XkbAnyAction              any;
    XkbModAction              mods;
    XkbGroupAction            group;
    XkbISOAction              iso;
    XkbPtrAction              ptr;
    XkbPtrBtnAction           btn;
    XkbPtrDfltAction          dflt;
    XkbSwitchScreenAction     screen;
    XkbCtrlsAction            ctrls;
    XkbMessageAction          msg;
    XkbRedirectKeyAction      redirect;
    XkbDeviceBtnAction        devbtn;
    XkbDeviceValuatorAction   devval;
    unsigned char             type;
} XkbAction;

The type field is provided for convenience and is the same as the type field in
the individual structures. The following sections describe the individual
structures for each action in detail.

The XkbAnyAction Structure

The XkbAnyAction structure is a convenience structure that refers to any of the
actions:

#define      XkbAnyActionDataSize       7

typedef struct _XkbAnyAction {
    unsigned char    type;            /* type of action; determines interpretation for data */
    unsigned char    data[XkbAnyActionDataSize];
} XkbAnyAction;

The data field represents a structure for an action, and its interpretation
depends on the type field. The valid values for the type field, and the data
structures associated with them are shown in Table 16.1:

Table 16.1. Action Types

┌────────────────────┬──────────────────────────────────────┬─────────┬───────┐
│                    │                                      │XkbAction│       │
│Type                │Structure for Data                    │Union    │Section│
│                    │                                      │Member   │       │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│                    │XkbSA_NoAction means the server does  │         │       │
│XkbSA_NoAction      │not perform an action for the key;    │any      │       │
│                    │this action does not have an          │         │       │
│                    │associated data structure.            │         │       │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_SetMods       │                                      │         │       │
│                    │                                      │         │       │
│XkbSA_LatchMods     │XkbModAction                          │mods     │16.1.3 │
│                    │                                      │         │       │
│XkbSA_LockMods      │                                      │         │       │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_SetGroup      │                                      │         │       │
│                    │                                      │         │       │
│XkbSA_LatchGroup    │XkbGroupAction                        │group    │16.1.4 │
│                    │                                      │         │       │
│XkbSA_LockGroup     │                                      │         │       │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_MovePtr       │XkbPtrAction                          │ptr      │16.1.5 │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_PtrBtn        │                                      │         │       │
│                    │XkbPtrBtnAction                       │btn      │16.1.6 │
│XkbSA_LockPtrBtn    │                                      │         │       │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_SetPtrDflt    │XkbPtrDfltAction                      │dflt     │16.1.7 │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_ISOLock       │XkbISOAction                          │iso      │16.1.8 │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_SwitchScreen  │XkbSwitchScreenAction                 │screen   │16.1.9 │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_SetControls   │                                      │         │       │
│                    │XkbCtrlsAction                        │ctrls    │16.1.10│
│XkbSA_LockControls  │                                      │         │       │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_ActionMessage │XkbMessageAction                      │msg      │16.1.11│
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_RedirectKey   │XkbRedirectKeyAction                  │redirect │16.1.12│
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_DeviceBtn     │                                      │         │       │
│                    │XkbDeviceBtnAction                    │devbtn   │16.1.13│
│XkbSA_LockDeviceBtn │                                      │         │       │
├────────────────────┼──────────────────────────────────────┼─────────┼───────┤
│XkbSA_DeviceValuator│XkbDeviceValuatorAction               │devval   │16.1.14│
└────────────────────┴──────────────────────────────────────┴─────────┴───────┘


Actions for Changing Modifiers’ State

Actions associated with the XkbModAction structure change the state of the
modifiers when keys are pressed and released (see Chapter 7, Virtual Modifiers
for a discussion of modifiers):

typedef struct _XkbModAction {
    unsigned char     type;         /* XkbSA_{Set|Latch|Lock}Mods */
    unsigned char     flags;        /* with type, controls the effect
                                       on modifiers */
    unsigned char     mask;         /* same as mask field of
                                       a modifier description */
    unsigned char     real_mods;    /* same as real_mods field of
                                       a modifier description */
    unsigned char     vmods1;       /* derived from vmods field of
                                       a modifier description */
    unsigned char     vmods2;       /* derived from vmods field of
                                       a modifier description */
} XkbModAction;

In the following description, the term action modifiers means the real modifier
bits associated with this action. Depending on the value of flags (see Table
16.3), these are designated either in the mask field of the XkbModAction
structure itself or the real modifiers bound to the key for which the action is
being used. In the latter case, this is the client map->modmap [ keycode ]
field.

The type field can have any of the values shown in Table 16.2.

Table 16.2. Modifier Action Types

┌───────────────┬─────────────────────────────────────────────────────────────┐
│Type           │Effect                                                       │
├───────────────┼─────────────────────────────────────────────────────────────┤
│               │  • A key press adds any action modifiers to the keyboard’s  │
│               │    base modifiers.                                          │
│               │                                                             │
│               │  • A key release clears any action modifiers in the         │
│XkbSA_SetMods  │    keyboard’s base modifiers, provided no other key         │
│               │    affecting the same modifiers is logically down.          │
│               │                                                             │
│               │  • If no other keys are physically depressed when this key  │
│               │    is released, and XkbSA_ClearLocks is set in the flags    │
│               │    field, the key release unlocks any action modifiers.     │
├───────────────┼─────────────────────────────────────────────────────────────┤
│               │  • Key press and key release events have the same effect as │
│               │    for XkbSA_SetMods; if no keys are physically depressed   │
│               │    when this key is released, key release events have the   │
│               │    following additional effects:                            │
│               │                                                             │
│               │  • Modifiers unlocked due to XkbSA_ClearLocks have no       │
│XkbSA_LatchMods│    further effect.                                          │
│               │                                                             │
│               │  • If XkbSA_LatchToLock is set in the flags field, a key    │
│               │    release locks and then unlatches any remaining action    │
│               │    modifiers that are already latched.                      │
│               │                                                             │
│               │  • A key release latches any action modifiers not used by   │
│               │    the XkbSA_ClearLocks and XkbSA_LatchToLock flags.        │
├───────────────┼─────────────────────────────────────────────────────────────┤
│               │  • A key press sets the base state of any action modifiers. │
│               │    If XkbSA_LockNoLock is set in the flags field, a key     │
│               │    press also sets the locked state of any action modifiers.│
│               │                                                             │
│XkbSA_LockMods │  • A key release clears any action modifiers in the         │
│               │    keyboard’s base modifiers, provided no other key that    │
│               │    affects the same modifiers is down. If XkbSA_LockNoUnlock│
│               │    is not set in the flags field, and any of the action     │
│               │    modifiers were locked before the corresponding key press │
│               │    occurred, a key release unlocks them.                    │
└───────────────┴─────────────────────────────────────────────────────────────┘


The flags field is composed of the bitwise inclusive OR of the masks shown in
Table 16.3. A general meaning is given in the table, but the exact meaning
depends on the action type.

Table 16.3. Modifier Action Flags

┌───────────────────┬─────────────────────────────────────────────────────────┐
│Flag               │Meaning                                                  │
├───────────────────┼─────────────────────────────────────────────────────────┤
│                   │If set, the action modifiers are determined by the       │
│                   │modifiers bound by the modifier mapping of the key.      │
│XkbSA_UseModMapMods│Otherwise, the action modifiers are set to the modifiers │
│                   │specified by the mask, real_mods, vmods1, and vmods2     │
│                   │fields.                                                  │
├───────────────────┼─────────────────────────────────────────────────────────┤
│                   │If set and no keys are physically depressed when this key│
│XkbSA_ClearLocks   │transition occurs, the server unlocks any action         │
│                   │modifiers.                                               │
├───────────────────┼─────────────────────────────────────────────────────────┤
│                   │If set, and the action type is XkbSA_LatchMods, the      │
│XkbSA_LatchToLock  │server locks the action modifiers if they are already    │
│                   │latched.                                                 │
├───────────────────┼─────────────────────────────────────────────────────────┤
│XkbSA_LockNoLock   │If set, and the action type is XkbSA_LockMods, the server│
│                   │only unlocks the action modifiers.                       │
├───────────────────┼─────────────────────────────────────────────────────────┤
│XkbSA_LockNoUnlock │If set, and the action is XkbSA_LockMods, the server only│
│                   │locks the action modifiers.                              │
└───────────────────┴─────────────────────────────────────────────────────────┘


If XkbSA_UseModMapMods is not set in the flags field, the mask, real_mods,
vmods1, and vmods2 fields are used to determine the action modifiers. Otherwise
they are ignored and the modifiers bound to the key (client map->modmap [
keycode ]) are used instead.

The mask, real_mods, vmods1, and vmods2 fields represent the components of an
Xkb modifier description (see section 7.2). While the mask and real_mods fields
correspond directly to the mask and real_mods fields of an Xkb modifier
description, the vmods1 and vmods2 fields are combined to correspond to the
vmods field of an Xkb modifier description. Xkb provides the following macros,
to convert between the two formats:

unsigned short XkbModActionVMods(XkbAction act);

act action from which to extract virtual mods

XkbModActionVMods returns the vmods1 and vmods2 fields of act converted to the
vmods format of an Xkb modifier description.

void XkbSetModActionVMods(XkbAction act, unsigned short vmods);

act   action in which to set vmods

vmods virtual mods to set

XkbSetModActionVMods sets the vmods1 and vmods2 fields of act using the vmods
format of an Xkb modifier description.

Note

Despite the fact that the first parameter of these two macros is of type
XkbAction, these macros may be used only with Actions of type XkbModAction and 
XkbISOAction.

Actions for Changing Group State

Actions associated with the XkbGroupAction structure change the current group
state when keys are pressed and released (see Chapter 5, Keyboard State for a
description of groups and keyboard state):

typedef struct _XkbGroupAction {
    unsigned char   type;       /* XkbSA_{Set|Latch|Lock}Group */
    unsigned char   flags;      /* with type , controls the effect on groups */
    char            group_XXX;  /* represents a group index or delta */
} XkbGroupAction;

The type field can have any of the following values:

Table 16.4. Group Action Types

┌────────────────┬────────────────────────────────────────────────────────────┐
│Type            │Effect                                                      │
├────────────────┼────────────────────────────────────────────────────────────┤
│                │  • If the XkbSA_GroupAbsolute bit is set in the flags      │
│                │    field, key press events change the base keyboard group  │
│                │    to the group specified by the group_XXX field.          │
│                │    Otherwise, key press events change the base keyboard    │
│                │    group by adding the group_XXX field to the base keyboard│
│                │    group. In either case, the resulting effective keyboard │
│                │    group is brought back into range depending on the value │
│                │    of the groups_wrap field of the controls structure (see │
│                │    section 10.7.1).                                        │
│XkbSA_SetGroup  │                                                            │
│                │  • If a key with an XkbSA_ISOLock action (see section      │
│                │    16.1.8) is pressed while this key is down, the key      │
│                │    release of this key has no effect. Otherwise, the key   │
│                │    release cancels the effects of the key press.           │
│                │                                                            │
│                │  • If the XkbSA_ClearLocks bit is set in the flags field,  │
│                │    and no keys are physically depressed when this key is   │
│                │    released, the key release also sets the locked keyboard │
│                │    group to Group1.                                        │
├────────────────┼────────────────────────────────────────────────────────────┤
│                │  • Key press and key release events have the same effect as│
│                │    for XkbSA_SetGroup; if no keys are physically depressed │
│                │    when this key is released, key release events have the  │
│                │    following additional effects.                           │
│                │                                                            │
│                │  • If the XkbSA_LatchToLock bit is set in the flags field  │
│                │    and the latched keyboard group index is nonzero, the key│
│XkbSA_LatchGroup│    release adds the delta applied by the corresponding key │
│                │    press to the locked keyboard group and subtracts it from│
│                │    the latched keyboard group. The locked and effective    │
│                │    keyboard group are brought back into range according to │
│                │    the value of the groups_wrap field of the controls      │
│                │    structure.                                              │
│                │                                                            │
│                │  • Otherwise, the key press adds the key press delta to the│
│                │    latched keyboard group.                                 │
├────────────────┼────────────────────────────────────────────────────────────┤
│                │  • If the XkbSA_GroupAbsolute is set in the flags field,   │
│                │    key press events set the locked keyboard group to the   │
│                │    group specified by the group_XXX field. Otherwise, key  │
│                │    press events add the group specified by the group_XXX   │
│XkbSA_LockGroup │    field to the locked keyboard group. In either case, the │
│                │    resulting locked and effective keyboard groups are      │
│                │    brought back into range depending on the value of the   │
│                │    groups_wrap field of the controls structure.            │
│                │                                                            │
│                │  • A key release has no effect.                            │
└────────────────┴────────────────────────────────────────────────────────────┘


The flags field is composed of the bitwise inclusive OR of the masks shown in
Table 16.5. A general meaning is given in the table, but the exact meaning
depends on the action type.

Table 16.5. Group Action Flags

┌───────────────────┬─────────────────────────────────────────────────────────┐
│Flag               │Meaning                                                  │
├───────────────────┼─────────────────────────────────────────────────────────┤
│                   │If set and no keys are physically depressed when this key│
│XkbSA_ClearLocks   │transition occurs, the server sets the locked keyboard   │
│                   │group to Group1 on a key release.                        │
├───────────────────┼─────────────────────────────────────────────────────────┤
│XkbSA_LatchToLock  │If set, and the action type is XkbSA_LatchGroup, the     │
│                   │server locks the action group if it is already latched.  │
├───────────────────┼─────────────────────────────────────────────────────────┤
│                   │If set, the group_XXX field represents an absolute group │
│XkbSA_GroupAbsolute│number. Otherwise, it represents a group delta to be     │
│                   │added to the current group to determine the new group    │
│                   │number.                                                  │
└───────────────────┴─────────────────────────────────────────────────────────┘


The group_XXX field represents a signed character. Xkb provides the following
macros to convert between a signed integer value and a signed character:

int XkbSAGroup(XkbAction act);

act action from which to extract group

XkbSAGroup returns the group_XXX field of act converted to a signed int.

void XkbSASetGroup(XkbAction act, int grp);

act action from which to set group

grp group index to set in group_XXX

XkbSASetGroup sets the group_XXX field of act from the group index grp.

Note

Despite the fact that the first parameter of these two macros is of type
XkbAction, these macros may only be used with Actions of type XkbGroupAction
and XkbISOAction.

Actions for Moving the Pointer

Actions associated with the XkbPtrAction structure move the pointer when keys
are pressed and released:

typedef struct _XkbPtrAction {
    unsigned char      type;      /* XkbSA_MovePtr */
    unsigned char      flags;     /* determines type of pointer motion */
    unsigned char      high_XXX;  /* x coordinate, high bits */
    unsigned char      low_XXX;   /* y coordinate, low bits */
    unsigned char      high_YYY;  /* x coordinate, high bits */
    unsigned char      low_YYY;   /* y coordinate, low bits */
} XkbPtrAction;

If the MouseKeys control is not enabled (see section 10.5.1), KeyPress and 
KeyRelease events are treated as though the action is XkbSA_NoAction.

If the MouseKeys control is enabled, a server action of type XkbSA_MovePtr
instructs the server to generate core pointer MotionNotify events rather than
the usual KeyPress event, and the corresponding KeyRelease event disables any
mouse keys timers that were created as a result of handling the XkbSA_MovePtr
action.

The type field of the XkbPtrAction structure is always XkbSA_MovePtr.

The flags field is a bitwise inclusive OR of the masks shown in Table 16.6.

Table 16.6. Pointer Action Types

┌────────────────────┬────────────────────────────────────────────────────────┐
│Action Type         │Meaning                                                 │
├────────────────────┼────────────────────────────────────────────────────────┤
│                    │If not set, and the MouseKeysAccel control is enabled   │
│XkbSA_NoAcceleration│(see section 10.5.2), the KeyPress initiates a mouse    │
│                    │keys timer for this key; every time the timer expires,  │
│                    │the cursor moves.                                       │
├────────────────────┼────────────────────────────────────────────────────────┤
│                    │If set, the X portion of the structure specifies the new│
│XkbSA_MoveAbsoluteX │pointer X coordinate. Otherwise, the X portion is added │
│                    │to the current pointer X coordinate to determine the new│
│                    │pointer X coordinate.                                   │
├────────────────────┼────────────────────────────────────────────────────────┤
│                    │If set, the Y portion of the structure specifies the new│
│XkbSA_MoveAbsoluteY │pointer Y coordinate. Otherwise, the Y portion is added │
│                    │to the current pointer Y coordinate to determine the new│
│                    │pointer Y coordinate.                                   │
└────────────────────┴────────────────────────────────────────────────────────┘


Each of the X and Y coordinates of the XkbPtrAction structure is composed of
two signed 16-bit values, that is, the X coordinate is composed of high_XXX and
low_XXX, and similarly for the Y coordinate. Xkb provides the following macros,
to convert between a signed integer and two signed 16-bit values in 
XkbPtrAction structures:

int XkbPtrActionX(XkbPtrAction act);

act action from which to extract X

XkbPtrActionX returns the high_XXX and low_XXX fields of act converted to a
signed int.

int XkbPtrActionY(XkbPtrAction act);

act action from which to extract Y

XkbPtrActionY returns the high_YYY and low_YYY fields of act converted to a
signed int.

void XkbSetPtrActionX(XkbPtrAction act, int x);

act action in which to set X

x   new value to set

XkbSetPtrActionX sets the high_XXX and low_XXX fields of act from the signed
integer value x.

void XkbSetPtrActionY(XkbPtrAction act, int y);

act action in which to set Y

y   new value to set

XkbSetPtrActionX sets the high_YYY and low_YYY fields of act from the signed
integer value y.

Actions for Simulating Pointer Button Press and Release

Actions associated with the XkbPtrBtnAction structure simulate the press and
release of pointer buttons when keys are pressed and released:

typedef struct _XkbPtrBtnAction {
    unsigned char   type;     /* XkbSA_PtrBtn, XkbSA_LockPtrBtn */
    unsigned char   flags;    /* with type, controls the effect
                                 on pointer buttons */
    unsigned char   count;    /* controls number of ButtonPress and
                                 ButtonRelease events */
    unsigned char   button;   /* pointer button to simulate */
} XkbPtrBtnAction;

If the MouseKeys (see section 10.5.1) control is not enabled, KeyPress and 
KeyRelease events are treated as though the action is XkbSA_NoAction.

The type field can have any one of the values shown in Table 16.7.

Table 16.7. Pointer Button Action Types

┌────────────────┬────────────────────────────────────────────────────────────┐
│Type            │Effect                                                      │
├────────────────┼────────────────────────────────────────────────────────────┤
│                │  • If XkbSA_UseDfltButton is set in the flags field, the   │
│                │    event is generated for the pointer button specified by  │
│                │    the mk_dflt_btn attribute of the MouseKeys control (see │
│                │    section 10.5.1). Otherwise, the event is generated for  │
│                │    the button specified by the button field.               │
│                │                                                            │
│                │  • If the mouse button specified for this action is        │
│                │    logically down, the key press and corresponding key     │
│                │    release are ignored and have no effect. Otherwise, a key│
│XkbSA_PtrBtn    │    press causes one or more core pointer button events     │
│                │    instead of the usual KeyPress event. If count is zero, a│
│                │    key press generates a single ButtonPress event; if count│
│                │    is greater than zero, a key press generates count pairs │
│                │    of ButtonPress and ButtonRelease events.                │
│                │                                                            │
│                │  • If count is zero, a key release generates a core pointer│
│                │    ButtonRelease that matches the event generated by the   │
│                │    corresponding KeyPress; if count is nonzero, a key      │
│                │    release does not cause a ButtonRelease event. A key     │
│                │    release never generates a key KeyRelease event.         │
├────────────────┼────────────────────────────────────────────────────────────┤
│                │  • If the button specified by the MouseKeys default button │
│                │    or button is not locked, a key press causes a           │
│                │    ButtonPress event instead of a KeyPress event and locks │
│                │    the button. If the button is already locked or if       │
│                │    XkbSA_LockNoUnlock is set in the flags field, a key     │
│                │    press is ignored and has no effect.                     │
│XkbSA_LockPtrBtn│                                                            │
│                │  • If the corresponding key press was ignored, and if      │
│                │    XkbSA_LockNoLock is not set in the flags field, a key   │
│                │    release generates a ButtonRelease event instead of a    │
│                │    KeyRelease event and unlocks the specified button. If   │
│                │    the corresponding key press locked a button, the key    │
│                │    release is ignored and has no effect.                   │
└────────────────┴────────────────────────────────────────────────────────────┘


The flags field is composed of the bitwise inclusive OR of the masks shown in
Table 16.8. A general meaning is given in the table, but the exact meaning
depends on the action type:

Table 16.8. Pointer Button Action Flags

┌───────────────────┬─────────────────────────────────────────────────────────┐
│Flag               │Meaning                                                  │
├───────────────────┼─────────────────────────────────────────────────────────┤
│                   │If set, the action uses the pointer button specified by  │
│XkbSA_UseDfltButton│the mk_dflt_btn attribute of the MouseKeys control (see  │
│                   │section 10.5.1). Otherwise, the action uses the pointer  │
│                   │button specified by the button field.                    │
├───────────────────┼─────────────────────────────────────────────────────────┤
│XkbSA_LockNoLock   │If set, and the action type is XkbSA_LockPtrBtn, the     │
│                   │server only unlocks the pointer button.                  │
├───────────────────┼─────────────────────────────────────────────────────────┤
│XkbSA_LockNoUnlock │If set, and the action type is XkbSA_LockPtrBtn, the     │
│                   │server only locks the pointer button.                    │
└───────────────────┴─────────────────────────────────────────────────────────┘


Actions for Changing the Pointer Button Simulated

Actions associated with the XkbPtrDfltAction structure change the mk_dflt_btn
attribute of the MouseKeys control (see section 10.5.1):

typedef struct _XkbPtrDfltAction {
    unsigned char   type;      /* XkbSA_SetPtrDflt */
    unsigned char   flags;     /* controls the pointer button number */
    unsigned char   affect;    /* XkbSA_AffectDfltBtn */
    char            valueXXX;  /* new default button member */
} XkbPtrDfltAction;

If the MouseKeys control is not enabled, KeyPress and KeyRelease events are
treated as though the action is XkbSA_NoAction. Otherwise, this action changes
the mk_dflt_btn attribute of the MouseKeys control.

The type field of the XkbPtrDfltAction structure should always be 
XkbSA_SetPtrDflt.

The flags field is composed of the bitwise inclusive OR of the values shown in
Table 16.9 (currently there is only one value defined).

Table 16.9. Pointer Default Flags

┌─────────────────────┬───────────────────────────────────────────────────────┐
│Flag                 │Meaning                                                │
├─────────────────────┼───────────────────────────────────────────────────────┤
│                     │If set, the value field represents an absolute pointer │
│XkbSA_DfltBtnAbsolute│button. Otherwise, the value field represents the      │
│                     │amount to be added to the current default button.      │
└─────────────────────┴───────────────────────────────────────────────────────┘


The affect field specifies what changes as a result of this action. The only
valid value for the affect field is XkbSA_AffectDfltBtn.

The valueXXX field is a signed character that represents the new button value
for the mk_dflt_btn attribute of the MouseKeys control (see section 10.5.1). If
XkbSA_DfltBtnAbsolute is set in flags, valueXXX specifies the button to be
used; otherwise, valueXXX specifies the amount to be added to the current
default button. In either case, illegal button choices are wrapped back around
into range. Xkb provides the following macros, to convert between the integer
and signed character values in XkbPtrDfltAction structures:

int XkbSAPtrDfltValue(XkbAction act);

act action from which to extract group

XkbSAPtrDfltValue returns the valueXXX field of act converted to a signed int.

void XkbSASetPtrDfltValue(XkbPtrDfltAction act, int val);

act action in which to set valueXXX

val value to set in valueXXX

XkbSASetPtrDfltValue sets the valueXXX field of act from val.

Actions for Locking Modifiers and Group

Actions associated with the XkbISOAction structure lock modifiers and the group
according to the ISO9995 specification.

Operated by itself, the XkbISOAction is just a caps lock. Operated
simultaneously with another modifier key, it transforms the other key into a
locking key. For example, press ISO_Lock, press and release Control_L, release 
ISO_Lock ends up locking the Control modifier.

The default behavior is to convert:

{Set,Latch}Mods to: LockMods
{Set,Latch}Group to: LockGroup
SetPtrBtn to: LockPtrBtn
SetControls to: LockControls

The affects field allows you to turn those effects on or off individually. Set 
XkbSA_ISONoAffectMods to disable the first, XkbSA_ISONoAffectGroup to disable
the second, and so forth.

typedef struct _XkbISOAction {
    unsigned char   type;        /* XkbSA_ISOLock */
    unsigned char   flags;       /* controls changes to group or
                                    modifier state */
    unsigned char   mask;        /* same as mask field of
                                    a modifier description */
    unsigned char   real_mods;   /* same as real_mods field of
                                    a modifier description */
    char            group_XXX;   /* group index or delta group */
    unsigned char   affect;      /* specifies whether to affect
                                    mods, group, ptrbtn, or controls */
    unsigned char   vmods1;      /* derived from vmods field of
                                    a modifier description */
    unsigned char   vmods2;      /* derived from vmods field of
                                    a modifier description */
} XkbISOAction;

The type field of the XkbISOAction structure should always be XkbSA_ISOLock.

The interpretation of the flags field depends on whether the 
XkbSA_ISODfltIsGroup is set in the flags field or not.

If the XkbSA_ISODfltIsGroup is set in the flags field, the action is used to
change the group state. The remaining valid bits of the flags field are
composed of a bitwise inclusive OR using the masks shown in Table 16.10.

Table 16.10. ISO Action Flags when XkbSA_ISODfltIsGroup is Set

┌──────────────────────┬──────────────────────────────────────────────────────┐
│Flag                  │Meaning                                               │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If set, the action is used to change the base group   │
│                      │state. Must be set for the remaining bits in this     │
│                      │table to carry their interpretations.                 │
│                      │                                                      │
│XkbSA_ISODfltIsGroup  │A key press sets the base group as specified by the   │
│                      │group_XXX field and the XkbSA_GroupAbsolute bit of the│
│                      │flags field (see section Note). If no other actions   │
│                      │are transformed by the XkbSA_ISOLock action, a key    │
│                      │release locks the group. Otherwise, a key release     │
│                      │clears group set by the key press.                    │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If set, the group_XXX field represents an absolute    │
│XkbSA_GroupAbsolute   │group number. Otherwise, it represents a group delta  │
│                      │to be added to the current group to determine the new │
│                      │group number.                                         │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If not set, any XkbSA_SetMods or XkbSA_LatchMods      │
│XkbSA_ISONoAffectMods │actions that occur simultaneously with the            │
│                      │XkbSA_ISOLock action are treated as XkbSA_LockMods    │
│                      │actions instead.                                      │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If not set, any XkbSA_SetGroup or XkbSA_LatchGroup    │
│XkbSA_ISONoAffectGroup│actions that occur simultaneously with the            │
│                      │XkbSA_ISOLock action are treated as XkbSA_LockGroup   │
│                      │actions instead.                                      │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If not set, any XkbSA_PtrBtn actions that occur       │
│XkbSA_ISONoAffectPtr  │simultaneously with the XkbSA_ISOLock action are      │
│                      │treated as XkbSA_LockPtrBtn actions instead.          │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If not set, any XkbSA_SetControls actions that occur  │
│XkbSA_ISONoAffectCtrls│simultaneously with the XkbSA_ISOLock action are      │
│                      │treated as XkbSA_LockControls actions instead.        │
└──────────────────────┴──────────────────────────────────────────────────────┘


If the XkbSA_ISODfltIsGroup is not set in the flags field, the action is used
to change the modifier state and the remaining valid bits of the flags field
are composed of a bitwise inclusive OR using the masks shown in Table 16.11.

Table 16.11. ISO Action Flags when XkbSA_ISODfltIsGroup is Not Set

┌──────────────────────┬──────────────────────────────────────────────────────┐
│Flag                  │Meaning                                               │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If not set, action is used to change the base modifier│
│                      │state. Must not be set for the remaining bits in this │
│                      │table to carry their interpretations.                 │
│                      │                                                      │
│                      │A key press sets the action modifiers in the          │
│XkbSA_ISODfltIsGroup  │keyboard’s base modifiers using the mask, real_mods,  │
│                      │vmods1, and vmods2 fields (see section 16.1.3). If no │
│                      │other actions are transformed by the XkbSA_ISOLock    │
│                      │action, a key release locks the action modifiers.     │
│                      │Otherwise, a key release clears the base modifiers set│
│                      │by the key press.                                     │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If set, the action modifiers are determined by the    │
│                      │modifiers bound by the modifier mapping of the key.   │
│XkbSA_UseModMapMods   │Otherwise, the action modifiers are set to the        │
│                      │modifiers specified by the mask, real_mods, vmods1,   │
│                      │and vmods2 fields.                                    │
├──────────────────────┼──────────────────────────────────────────────────────┤
│XkbSA_LockNoLock      │If set, the server only unlocks the action modifiers. │
├──────────────────────┼──────────────────────────────────────────────────────┤
│XkbSA_LockNoUnlock    │If set, the server only locks the action modifiers.   │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If not set, any XkbSA_SetMods or XkbSA_LatchMods      │
│XkbSA_ISONoAffectMods │actions that occur simultaneously with the            │
│                      │XkbSA_ISOLock action are treated as XkbSA_LockMods    │
│                      │actions instead.                                      │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If not set, any XkbSA_SetGroup or XkbSA_LatchGroup    │
│XkbSA_ISONoAffectGroup│actions that occur simultaneously with the            │
│                      │XkbSA_ISOLock action are treated as XkbSA_LockGroup   │
│                      │actions instead.                                      │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If not set, any XkbSA_PtrBtn actions that occur       │
│XkbSA_ISONoAffectPtr  │simultaneously with the XkbSA_ISOLock action are      │
│                      │treated as XkbSA_LockPtrBtn actions instead.          │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If not set, any XkbSA_SetControls actions that occur  │
│XkbSA_ISONoAffectCtrls│simultaneously with the XkbSA_ISOLock action are      │
│                      │treated as XkbSA_LockControls actions instead.        │
└──────────────────────┴──────────────────────────────────────────────────────┘


The group_XXX field represents a signed character. Xkb provides macros to
convert between a signed integer value and a signed character as shown in
section Note.

The mask, real_mods, vmods1, and vmods2 fields represent the components of an
Xkb modifier description (see section 7.2). While the mask and real_mods fields
correspond directly to the mask and real_mods fields of an Xkb modifier
description, the vmods1 and vmods2 fields are combined to correspond to the
vmods field of an Xkb modifier description. Xkb provides macros to convert
between the two formats as shown in section 16.1.3.

The affect field is composed of a bitwise inclusive OR using the masks shown in
Table 16.11.

Table 16.12. ISO Action Affect Field Values

┌──────────────────────┬──────────────────────────────────────────────────────┐
│Affect                │Meaning                                               │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If XkbSA_ISONoAffectMods is not set, any SA_SetMods or│
│XkbSA_ISONoAffectMods │SA_LatchMods actions occurring simultaneously with the│
│                      │XkbISOAction are treated as SA_LockMods instead.      │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If XkbSA_ISONoAffectGroup is not set, any SA_SetGroup │
│XkbSA_ISONoAffectGroup│or SA_LatchGroup actions occurring simultaneously with│
│                      │the XkbISOAction are treated as SA_LockGroup instead. │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If XkbSA_ISONoAffectPtr is not set, any SA_PtrBtn     │
│XkbSA_ISONoAffectPtr  │actions occurring simultaneously with the XkbISOAction│
│                      │are treated as SA_LockPtrBtn instead.                 │
├──────────────────────┼──────────────────────────────────────────────────────┤
│                      │If XkbSA_ISONoAffectCtrls is not set, any             │
│XkbSA_ISONoAffectCtrls│SA_SetControls actions occurring simultaneously with  │
│                      │the XkbISOAction are treated as SA_LockControls       │
│                      │instead.                                              │
└──────────────────────┴──────────────────────────────────────────────────────┘


Actions for Changing the Active Screen

Actions associated with the XkbSwitchScreenAction action structure change the
active screen on a multiscreen display:

Note

This action is optional. Servers are free to ignore the action or any of its
flags if they do not support the requested behavior. If the action is ignored,
it behaves like XkbSA_NoAction. Otherwise, key press and key release events do
not generate an event.

typedef struct _XkbSwitchScreenAction {
    unsigned char   type;        /* XkbSA_SwitchScreen */
    unsigned char   flags;       /* controls screen switching */
    char            screenXXX;   /* screen number or delta */
} XkbSwitchScreenAction;

The type field of the XkbSwitchScreenAction structure should always be 
XkbSA_SwitchScreen.

The flags field is composed of the bitwise inclusive OR of the masks shown in
Table 16.13.

Table 16.13. Switch Screen Action Flags

┌───────────────────────┬─────────────────────────────────────────────────────┐
│Flag                   │Meaning                                              │
├───────────────────────┼─────────────────────────────────────────────────────┤
│                       │If set, the screenXXX field represents the index of  │
│XkbSA_SwitchAbsolute   │the new screen. Otherwise, it represents an offset   │
│                       │from the current screen to the new screen.           │
├───────────────────────┼─────────────────────────────────────────────────────┤
│                       │If not set, the action should switch to another      │
│XkbSA_SwitchApplication│screen on the same server. Otherwise, it should      │
│                       │switch to another X server or application that shares│
│                       │the same physical display.                           │
└───────────────────────┴─────────────────────────────────────────────────────┘


The screenXXX field is a signed character value that represents either the
relative or absolute screen index, depending on the state of the 
XkbSA_SwitchAbsolute bit in the flags field. Xkb provides the following macros
to convert between the integer and signed character value for screen numbers in
XkbSwitchScreenAction structures:

int XkbSAScreen(XkbSwitchScreenAction act);

act action from which to extract screen

XkbSAScreen returns the screenXXX field of act converted to a signed int.

void XkbSASetScreen(XkbSwitchScreenAction act, int s);

act action in which to set screenXXX

s   value to set in screenXXX

XkbSASetScreen sets the screenXXX field of act from s.

Actions for Changing Boolean Controls State

Actions associated with the XkbCtrlsAction structure change the state of the
boolean controls (see section 10.1):

typedef struct _XkbCtrlsAction {
    unsigned char     type;        /* XkbSA_SetControls,
                                      XkbSA_LockControls */
    unsigned char     flags;       /* with type, controls enabling
                                      and disabling of controls */
    unsigned char     ctrls3;      /* ctrls0 through ctrls3
                                      represent the boolean controls */
    unsigned char     ctrls2;      /* ctrls0 through ctrls3
                                      represent the boolean controls */
    unsigned char     ctrls1;      /* ctrls0 through ctrls3
                                      represent the boolean controls */
    unsigned char     ctrls0;      /* ctrls0 through ctrls3
                                      represent the boolean controls */
} XkbCtrlsAction;

The type field can have any one of the values shown in Table 16.14.

Table 16.14. Controls Action Types

┌──────────────────┬──────────────────────────────────────────────────────────┐
│Type              │Effect                                                    │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │  • A key press enables any boolean controls specified in │
│                  │    the ctrls fields that were not already enabled at the │
│                  │    time of the key press.                                │
│                  │                                                          │
│XkbSA_SetControls │  • A key release disables any controls enabled by the key│
│                  │    press.                                                │
│                  │                                                          │
│                  │  • This action can cause XkbControlsNotify events (see   │
│                  │    section 10.1).                                        │
├──────────────────┼──────────────────────────────────────────────────────────┤
│                  │  • If the XkbSA_LockNoLock bit is not set in the flags   │
│                  │    field, a key press enables any controls specified in  │
│                  │    the ctrls fields that were not already enabled at the │
│                  │    time of the key press.                                │
│                  │                                                          │
│XkbSA_LockControls│  • If the XkbSA_LockNoUnlock bit is not set in the flags │
│                  │    field, a key release disables any controls specified  │
│                  │    in the ctrls fields that were not already disabled at │
│                  │    the time of the key press.                            │
│                  │                                                          │
│                  │  • This action can cause XkbControlsNotify events (see   │
│                  │    section 10.1).                                        │
└──────────────────┴──────────────────────────────────────────────────────────┘


The flags field is composed of the bitwise inclusive OR of the masks shown in
Table 16.15.

Table 16.15. Control Action Flags

┌──────────────────┬──────────────────────────────────────────────────────────┐
│Flag              │Meaning                                                   │
├──────────────────┼──────────────────────────────────────────────────────────┤
│XkbSA_LockNoLock  │If set, and the action type is XkbSA_LockControls, the    │
│                  │server only disables controls.                            │
├──────────────────┼──────────────────────────────────────────────────────────┤
│XkbSA_LockNoUnlock│If set, and the action type is XkbSA_LockControls, the    │
│                  │server only enables controls.                             │
└──────────────────┴──────────────────────────────────────────────────────────┘


The XkbSA_SetControls action implements a key that enables a boolean control
when pressed and disables it when released. The XkbSA_LockControls action is
used to implement a key that toggles the state of a boolean control each time
it is pressed and released. The XkbSA_LockNoLock and XkbSA_LockNoUnlock flags
allow modifying the toggling behavior to only unlock or only lock the boolean
control.

The ctrls0, ctrls1, ctrls2, and ctrls3 fields represent the boolean controls in
the enabled_ctrls field of the controls structure (see section 10.1). Xkb
provides the following macros, to convert between the two formats:

unsigned int XkbActionCtrls(XkbCtrlsAction act);

act action from which to extract controls

XkbActionCtrls returns the ctrls fields of act converted to an unsigned int.

void XkbActionSetCtrls(XkbCtrlsAction act, unsigned int ctrls);

act   action in which to set ctrls0-ctrls3

ctrls value to set in ctrls0-ctrls3

XkbActionSetCtrls sets the ctrls0 through ctrls3 fields of act from ctrls.

Actions for Generating Messages

Actions associated with the XkbMessageAction structure generate 
XkbActionMessage events:

#define             XkbActionMessageLength                  6

typedef struct _XkbMessageAction {
    unsigned char   type;             /* XkbSA_ActionMessage */
    unsigned char   flags;            /* controls event generation via
                                         key presses and releases */
    unsigned char   message[XkbActionMessageLength];    /* message */
} XkbMessageAction;

The type field of the XkbMessageAction structure should always be 
XkbSA_ActionMessage.

The flags field is composed of the bitwise inclusive OR of the masks shown in
Table 16.16.

Table 16.16. Message Action Flags

┌────────────────────────┬────────────────────────────────────────────────────┐
│Flag                    │Meaning                                             │
├────────────────────────┼────────────────────────────────────────────────────┤
│                        │If set, key press events generate an                │
│XkbSA_MessageOnPress    │XkbActionMessage event that reports the keycode,    │
│                        │event type, and contents of the message field.      │
├────────────────────────┼────────────────────────────────────────────────────┤
│                        │If set, key release events generate an              │
│XkbSA_MessageOnRelease  │XkbActionMessage event that reports the keycode,    │
│                        │event type, and contents of the message field.      │
├────────────────────────┼────────────────────────────────────────────────────┤
│                        │If set, key press and key release events generate   │
│XkbSA_MessageGenKeyEvent│KeyPress and KeyRelease events, regardless of       │
│                        │whether they generate XkbActionMessage events.      │
└────────────────────────┴────────────────────────────────────────────────────┘


The message field is an array of XkbActionMessageLength unsigned characters and
may be set to anything the keymap designer wishes.

Detecting Key Action Messages

To receive XkbActionMessage events by calling either XkbSelectEvents or
XkbSelectEventDetails (see section 4.3).

To receive XkbActionMessage events under all possible conditions, use
XkbSelectEvents and pass XkbActionMessageMask in both bits_to_change and
values_for_bits.

The XkbActionMessage event has no event details. However, you can call
XkbSelectEventDetails using XkbActionMessage as the event_type and specifying 
XkbAllActionMessagesMask in bits_to_change and values_for_bits. This has the
same effect as a call to XkbSelectEvents.

The structure for the XkbActionMessage event is defined as follows:

typedef struct _XkbActionMessage {
    int            type;             /* Xkb extension base event code */
    unsigned long  serial;           /* X server serial number for event */
    Bool           send_event;       /* True ⇒ synthetically generated */
    Display *      display;          /* server connection where event generated */
    Time           time;             /* server time when event generated */
    int            xkb_type;         /* XkbActionMessage */
    int            device;           /* Xkb device ID,
                                        will not be XkbUseCoreKbd */
    KeyCode        keycode;          /* keycode of key triggering event */
    Bool           press;            /* True ⇒ key press,
                                        False ⇒ release */
    Bool           key_event_follows;/* True ⇒ KeyPress/KeyRelease follows */
    char           message[XkbActionMessageLength+1];  /* message text */
} XkbActionMessageEvent;

The keycode is the keycode of the key that was pressed or released. The press
field specifies whether the event was the result of a key press or key release.

The key_event_follows specifies whether a KeyPress (if press is True) or 
KeyRelease (if press is False) event is also sent to the client. As with all
other Xkb events, XkbActionMessageEvents are delivered to all clients
requesting them, regardless of the current keyboard focus. However, the 
KeyPress or KeyRelease event that conditionally follows an 
XkbActionMessageEvent is sent only to the client selected by the current
keyboard focus. key_event_follows is True only for the client that is actually
sent the following KeyPress or KeyRelease event.

The message field is set to the message specified in the action and is
guaranteed to be NULL -terminated; the Xkb extension forces a NULL into message
[ XkbActionMessageLength ].

Actions for Generating a Different Keycode

Actions associated with the XkbRedirectKeyAction structure generate KeyPress
and KeyRelease events containing a keycode different from the key that was
pressed or released:

typedef struct      _XkbRedirectKeyAction {
    unsigned char      type;          /* XkbSA_RedirectKey */
    unsigned char      new_key;       /* keycode to be put in event */
    unsigned char      mods_mask;     /* mask of real mods to be reset */
    unsigned char      mods;          /* mask of real mods to take values from */
    unsigned char      vmods_mask0;   /* first half of mask of virtual mods
                                         to be reset */
    unsigned char      vmods_mask1;   /* other half of mask of virtual mods
                                         to be reset */
    unsigned char      vmods0;        /* first half of mask of virtual mods
                                         to take values from */
    unsigned char      vmods1;        /* other half of mask of virtual mods
                                         to take values from */
} XkbRedirectKeyAction;

The type field for the XkbRedirectKeyAction structure should always be 
XkbSA_RedirectKey.

Key presses cause a KeyPress event for the key specified by the new_key field
instead of the actual key. The state reported in this event reports the current
effective modifiers changed as follows: any real modifiers selected by the
mods_mask field are set to corresponding values from the mods field. Any real
modifiers bound to the virtual modifiers specified by the vmods_mask0 and
vmods_mask1 fields are either set or cleared, depending on the corresponding
values in the vmods0 and vmods1 fields. If the real and virtual modifier
definitions specify conflicting values for a single modifier, the real modifier
definition has priority.

Key releases cause a KeyRelease event for the key specified by the new_key
field instead of the actual key. The state for this event consists of the
effective keyboard modifiers at the time of the release, changed as described
previously.

The XkbSA_RedirectKey action normally redirects to another key on the same
device as the key that caused the event, unless that device does not belong to
the input extension KeyClass, in which case this action causes an event on the
core keyboard device. (The input extension categorizes devices by breaking them
into classes. Keyboards, and other input devices with keys, are classified as
KeyClass devices by the input extension.)

The vmods_mask0 and vmods_mask1 fields actually represent one vmods_mask value,
as described in Chapter 7, Virtual Modifiers. Xkb provides the following
macros, to convert between the two formats:

unsigned int XkbSARedirectVModsMask(XkbRedirectKeyAction act);

act action from which to extract vmods

XkbSARedirectVModsMask returns the vmods_mask0 and vmods_mask1 fields of act
converted to an unsigned int.

void XkbSARedirectSetVModsMask(XkbRedirectKeyAction act, unsigned int vm);

act action in which to set vmods

vm  new value for virtual modifier mask

XkbSARedirectSetVModsMask sets the vmods_mask0 and vmods_mask1 fields of act
from vm.

Similarly, the vmods0 and vmods1 fields actually represent one vmods value, as
described in Chapter 7, Virtual Modifiers. To convert between the two formats,
Xkb provides the following convenience macros:

unsigned int XkbSARedirectVMods(XkbRedirectKeyAction act);

act action from which to extract vmods

XkbSARedirectVModsMask returns the vmods0 and vmods1 fields of act converted to
an unsigned int.

void XkbSARedirectSetVMods(XkbRedirectKeyAction act, unsigned int v);

act action in which to set vmods

v   new value for virtual modifiers

XkbSARedirectSetVModsMask sets the vmods0 and vmods1 of act from v.

Actions for Generating DeviceButtonPress and DeviceButtonRelease

Actions associated with XkbDeviceBtnAction structures generate 
DeviceButtonPress and DeviceButtonRelease events instead of normal KeyPress and
KeyRelease events:

typedef struct _XkbDeviceBtnAction {
    unsigned char    type;      /* XkbSA_DeviceBtn, XkbSA_LockDeviceBtn */
    unsigned char    flags;     /* with type, specifies locking or unlocking */
    unsigned char    count;     /* controls number of DeviceButtonPress
                                   and Release events */
    unsigned char    button;    /* index of button on device */
    unsigned char    device;    /* device ID of an X input extension device */
} XkbDeviceBtnAction;

The type field can have any one of the values shown in Table 16.17.

Table 16.17. Device Button Action Types

┌───────────────────┬─────────────────────────────────────────────────────────┐
│Type               │Effect                                                   │
├───────────────────┼─────────────────────────────────────────────────────────┤
│                   │  • If the button specified by this action is logically  │
│                   │    down, the key press and corresponding release are    │
│                   │    ignored and have no effect. If the device or button  │
│                   │    specified by this action are illegal, this action    │
│                   │    behaves like XkbSA_NoAction.                         │
│                   │                                                         │
│                   │  • Otherwise, key presses cause one or more input       │
│                   │    extension device events instead of the usual key     │
│                   │    press event. If the count field is zero, a key press │
│XkbSA_DeviceBtn    │    generates a single DeviceButtonPress event. If count │
│                   │    is greater than zero, a key press event generates    │
│                   │    count pairs of DeviceButtonPress and                 │
│                   │    DeviceButtonRelease events.                          │
│                   │                                                         │
│                   │  • If count is zero, a key release generates an input   │
│                   │    extension DeviceButtonRelease event that matches the │
│                   │    event generated by the corresponding key press. If   │
│                   │    count is nonzero, a key release does not cause a     │
│                   │    DeviceButtonRelease event. Key releases never cause  │
│                   │    KeyRelease events.                                   │
├───────────────────┼─────────────────────────────────────────────────────────┤
│                   │  • If the device or button specified by this action are │
│                   │    illegal, this action behaves like XkbSA_NoAction.    │
│                   │                                                         │
│                   │  • Otherwise, if the specified button is not locked and │
│                   │    the XkbSA_LockNoLock bit is not set in the flags     │
│                   │    field, a key press generates an input extension      │
│                   │    DeviceButtonPress event instead of a KeyPress event  │
│                   │    and locks the button. If the button is already locked│
│XkbSA_LockDeviceBtn│    or if XkbSA_LockNoLock bit is set in the flags field,│
│                   │    the key press is ignored and has no effect.          │
│                   │                                                         │
│                   │  • If the corresponding key press was ignored, and if   │
│                   │    the XkbSA_LockNoUnlock bit is not set in the flags   │
│                   │    field, a key release generates an input extension    │
│                   │    DeviceButtonRelease event instead of a KeyRelease    │
│                   │    event and unlocks the button. If the corresponding   │
│                   │    key press locked a button, the key release is ignored│
│                   │    and has no effect.                                   │
└───────────────────┴─────────────────────────────────────────────────────────┘


The flags field is composed of the bitwise inclusive OR of the masks shown in
Table 16.18.

Table 16.18. Device Button Action Flags

┌──────────────────┬──────────────────────────────────────────────────────────┐
│Flag              │Meaning                                                   │
├──────────────────┼──────────────────────────────────────────────────────────┤
│XkbSA_LockNoLock  │If set, and the action type is XkbSA_LockDeviceBtn, the   │
│                  │server only unlocks the button.                           │
├──────────────────┼──────────────────────────────────────────────────────────┤
│XkbSA_LockNoUnlock│If set, and the action type is XkbSA_LockDeviceBtn, the   │
│                  │server only locks the button.                             │
└──────────────────┴──────────────────────────────────────────────────────────┘


Actions for Simulating Events from Device Valuators

A valuator manipulates a range of values for some entity, like a mouse axis, a
slider or a dial. Actions associated with XkbDeviceValuatorAction structures
are used to simulate events from one or two input extension device valuators.

typedef struct _XkbDeviceValuatorAction {
    unsigned char    type;        /* XkbSA_DeviceValuator */
    unsigned char    device;      /* device ID */
    unsigned char    v1_what;     /* determines how valuator is
                                     to behave for valuator 1 */
    unsigned char    v1_ndx;      /* specifies a real valuator */
    unsigned char    v1_value;    /* the value for valuator 1 */
    unsigned char    v2_what;     /* determines how valuator is
                                     to behave for valuator 2 */
    unsigned char    v2_ndx;      /* specifies a real valuator */
    unsigned char    v2_value;    /* the value for valuator 1 */
} XkbDeviceValuatorAction;

If device is illegal or if neither v1_ndx nor v2_ndx specifies a legal
valuator, this action behaves like XkbSA_NoAction.

The low four bits of v1_what and v2_what specify the corresponding scale value
(denoted val<n>Scale in Table 16.17), if needed. The high four bits of v1_what
and v2_what specify the operation to perform to set the values. The high four
bits of v1_what and v2_what can have the values shown in Table 16.17; the use
of val<n>Scale is shown in that table also.

Table 16.19. Device Valuator v<n>_what High Bits Values

┌────────────────────┬────────────────────────────────────────────────────┐
│Value of high bits  │Effect                                              │
├────────────────────┼────────────────────────────────────────────────────┤
│XkbSA_IgnoreVal     │No action                                           │
├────────────────────┼────────────────────────────────────────────────────┤
│XkbSA_SetValMin     │v<n>_value is set to its minimum legal value.       │
├────────────────────┼────────────────────────────────────────────────────┤
│XkbSA_SetValCenter  │v<n>_valueis centered (to (max-min)/2).             │
├────────────────────┼────────────────────────────────────────────────────┤
│XkbSA_SetValMax     │v<n>_value is set to its maximum legal value.       │
├────────────────────┼────────────────────────────────────────────────────┤
│XkbSA_SetValRelative│v<n>_value * (2 val<n>Scale) is added to v<n>_value.│
├────────────────────┼────────────────────────────────────────────────────┤
│XkbSA_SetValAbsolute│v<n>_value is set to (2 val<n>Scale).               │
└────────────────────┴────────────────────────────────────────────────────┘


Illegal values for XkbSA_SetValRelative or XkbSA_SetValAbsolute are clamped
into range. Note that all of these possibilities are legal for absolute
valuators. For relative valuators, only XkbSA_SetValRelative is permitted. Part
of the input extension description of a device is the range of legal values for
all absolute valuators, whence the maximum and minimum legal values shown in
Table 16.17.

The following two masks are provided as a convenience to select either portion
of v1_what or v2_what:

#define XkbSA_ValOpMask         (0x70)
#define XkbSA_ValScaleMask      (0x07)

v1_ndx and v2_ndx specify valuators that actually exists. For example, most
mice have two valuators (x and y axes) so the only legal values for a mouse
would be 0 and 1. For a dial box with eight dials, any value in the range 0..7
would be correct.

Obtaining Key Actions for Keys from the Server

To update the actions (the key_acts array) for a subset of the keys in a
keyboard description, use XkbGetKeyActions.

Status XkbGetKeyActions(Display *dpy, unsigned int first, unsigned int num,
XkbDescPtr xkb);

dpy   connection to X server

first keycode of first key of interest

num   number of keys desired

xkb   pointer to keyboard description where result is stored

XkbGetKeyActions sends a request to the server to obtain the actions for num
keys on the keyboard starting with key first. It waits for a reply and returns
the actions in the server->key_acts field of xkb. If successful,
XkbGetKeyActions returns Success. The xkb parameter must be a pointer to a
valid Xkb keyboard description.

If the server map in the xkb parameter has not been allocated, XkbGetKeyActions
allocates and initializes it before obtaining the actions.

If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, XkbGetKeyActions returns BadAccess. If num
is less than 1 or greater than XkbMaxKeyCount, XkbGetKeyActions returns 
BadValue. If any allocation errors occur, XkbGetKeyActions returns BadAlloc.

Changing the Number of Actions Bound to a Key

To change the number of actions bound to a key, use XkbResizeKeyActions.

XkbAction *XkbResizeKeyActions(XkbDescRec *xkb, int key, int needed);

xkb    keyboard description to change

key    keycode of key to change

needed new number of actions required

The xkb parameter points to the keyboard description containing the key whose
number of actions is to be changed. The key parameter is the keycode of the key
to change, and needed specifies the new number of actions required for the key.

XkbResizeKeyActions reserves the space needed for the actions and returns a
pointer to the beginning of the new array that holds the actions. It can change
the acts, num_acts, and size_acts fields of xkb->server if it is necessary to
reallocate the acts array.

If needed is greater than the current number of keysyms for the key,
XkbResizeKeyActions initializes all new actions in the array to NoAction.

Because the number of actions needed by a key is normally computed as width *
number of groups, and XkbResizeKeyActions does not modify either the width or
number of groups for the key, a discrepancy exists on return from
XkbResizeKeyActions between the space allocated for the actions and the number
required. The unused entries in the list of actions returned by
XkbResizeKeyActions are not preserved across future calls to any of the map
editing functions, so you must update the key actions (which updates the width
and number of groups for the key) before calling another allocator function. A
call to XkbChangeTypesOfKey updates these.

If any allocation errors occur while resizing the number of actions bound to
the key, XkbResizeKeyActions returns NULL.

Note

A change to the number of actions bound to a key should be accompanied by a
change in the number of symbols bound to a key. Refer to section 15.3.7 for
more information on changing the number of symbols bound to a key.

Key Behavior

Key behavior refers to the demeanor of a key. For example, the expected
behavior of the CapsLock key is that it logically locks when pressed, and then
logically unlocks when pressed again.

Radio Groups

Keys that belong to the same radio group have the XkbKB_RadioGroup type in the
type field and the radio group index specified in the data field in the 
XkbBehavior structure. If the radio group has a name in the XkbNamesRec
structure, the radio group index is the index into the radio_group array in the
XkbNamesRec structure. A radio group key when pressed stays logically down
until another key in the radio group is pressed, when the first key becomes
logically up and the new key becomes logically down. Setting the 
XkbKB_RGAllowNone bit in the behavior for all of the keys of the radio group
means that pressing the logically down member of the radio group causes it to
logically release, in which case none of the keys of the radio group would be
logically down. If XkbKB_RGAllowNone is not set, there is no way to release the
logically down member of the group.

The low five bits of the data field of the XkbBehavior structure are the group
number, the high three bits are flags. The only flag currently defined is:

#define      XkbKB_RGAllowNone      0x80

The XkbBehavior Structure

The behaviors field of the server map is an array of XkbBehavior structures,
indexed by keycode, and contains the behavior for each key. The XkbBehavior
structure is defined as follows:

typedef struct _XkbBehavior {
    unsigned char  type;              /* behavior type + optional
                                         XkbKB_Permanent bit */
    unsigned char  data;
} XkbBehavior;

The type field specifies the Xkb behavior, and the value of the data field
depends on the type. Xkb supports the key behaviors shown in Table 16.20.

Table 16.20. Key Behaviors

┌────────────────┬────────────────────────────────────────────────────────────┐
│Type            │Effect                                                      │
├────────────────┼────────────────────────────────────────────────────────────┤
│XkbKB_Default   │Press and release events are processed normally. The data   │
│                │field is unused.                                            │
├────────────────┼────────────────────────────────────────────────────────────┤
│                │If a key is logically up (that is, the corresponding bit of │
│                │the core key map is cleared) when it is pressed, the key    │
│XkbKB_Lock      │press is processed normally and the corresponding release is│
│                │ignored. If the key is logically down when pressed, the key │
│                │press is ignored but the corresponding release is processed │
│                │normally. The data field is unused.                         │
├────────────────┼────────────────────────────────────────────────────────────┤
│                │If another member of the radio group is logically down (all │
│                │members of the radio group have the same index, specified in│
│                │data) when a key is pressed, the server synthesizes a key   │
│                │release for the member that is logically down and then      │
│                │processes the new key press event normally.                 │
│                │                                                            │
│XkbKB_RadioGroup│If the key itself is logically down when pressed, the key   │
│                │press event is ignored, but the processing of the           │
│                │corresponding key release depends on the value of the       │
│                │XkbKB_RGAllowNone bit in flags. If it is set, the key       │
│                │release is processed normally; otherwise, the key release is│
│                │also ignored.                                               │
│                │                                                            │
│                │All other key release events are ignored.                   │
├────────────────┼────────────────────────────────────────────────────────────┤
│                │If the Overlay1 control is enabled (see section 10.4), data │
│XkbKB_Overlay1  │is interpreted as a keycode, and events from this key are   │
│                │reported as if they came from data’s keycode. Otherwise,    │
│                │press and release events are processed normally.            │
├────────────────┼────────────────────────────────────────────────────────────┤
│                │If the Overlay2 control is enabled (see section 10.4), data │
│XkbKB_Overlay2  │is interpreted as a keycode, and events from this key are   │
│                │reported as if they came from data’s keycode. Otherwise,    │
│                │press and release events are processed normally.            │
└────────────────┴────────────────────────────────────────────────────────────┘


Xkb also provides the mask, XkbKB_Permanent to specify whether the key behavior
type should be simulated by Xkb or whether the key behavior describes an
unalterable physical, electrical, or software aspect of the keyboard. If the 
XkbKB_Permanent bit is not set in the type field, Xkb simulates the behavior in
software. Otherwise, Xkb relies upon the keyboard to implement the behavior.

Obtaining Key Behaviors for Keys from the Server

To obtain the behaviors (the behaviors array) for a subset of the keys in a
keyboard description from the server, use XkbGetKeyBehaviors:

Status XkbGetKeyBehaviors(Display *dpy, unsigned int first, unsigned int num,
XkbDescPtr xkb);

dpy   connection to server

first keycode of first key to get

num   number of keys for which behaviors are desired

xkb   Xkb description to contain the result

XkbGetKeyBehaviors sends a request to the server to obtain the behaviors for
num keys on the keyboard starting with the key whose keycode is first. It waits
for a reply and returns the behaviors in the server->behaviors field of xkb. If
successful, XkbGetKeyBehaviors returns Success.

If the server map in the xkb parameter has not been allocated,
XkbGetKeyBehaviors allocates and initializes it before obtaining the actions.

If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, XkbGetKeyBehaviors returns BadAccess. If num
is less than 1 or greater than XkbMaxKeyCount, XkbGetKeyBehaviors returns 
BadValue. If any allocation errors occur, XkbGetKeyBehaviors returns BadAlloc.

Explicit Components—Avoiding Automatic Remapping by the Server

Whenever a client remaps the keyboard using core protocol requests, Xkb
examines the map to determine likely default values for the components that
cannot be specified using the core protocol (see section 17.1.2 for more
information on how Xkb chooses the default values).

This automatic remapping might replace definitions explicitly requested by an
application, so the Xkb keyboard description defines an explicit components
mask for each key. Any aspects of the automatic remapping listed in the
explicit components mask for a key are not changed by the automatic keyboard
mapping.

The explicit components masks are held in the explicit field of the server map,
which is an array indexed by keycode. Each entry in this array is a mask that
is a bitwise inclusive OR of the values shown in Table 16.21.

Table 16.21. Explicit Component Masks

┌──────────────────┬─────┬────────────────────────────────────────────────────┐
│Bit in Explicit   │Value│Protects Against                                    │
│Mask              │     │                                                    │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│ExplicitKeyType1  │(1   │Automatic determination of the key type associated  │
│                  │<<0) │with Group1.                                        │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│ExplicitKeyType2  │(1   │Automatic determination of the key type associated  │
│                  │<<1) │with Group2.                                        │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│ExplicitKeyType3  │(1   │Automatic determination of the key type associated  │
│                  │<<2) │with Group3.                                        │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│ExplicitKeyType4  │(1   │Automatic determination of the key type associated  │
│                  │<<3) │with Group4.                                        │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│ExplicitInterpret │(1   │Application of any of the fields of a symbol        │
│                  │<<4) │interpretation to the key in question.              │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│ExplicitAutoRepeat│(1   │Automatic determination of auto-repeat status for   │
│                  │<<5) │the key, as specified in a symbol interpretation.   │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│                  │(1   │Automatic assignment of the XkbKB_Lock behavior to  │
│ExplicitBehavior  │<<6) │the key, if the XkbSI_LockingKey flag is set in a   │
│                  │     │symbol interpretation.                              │
├──────────────────┼─────┼────────────────────────────────────────────────────┤
│                  │(1   │Automatic determination of the virtual modifier map │
│ExplicitVModMap   │<<7) │for the key based on the actions assigned to the key│
│                  │     │and the symbol interpretations that match the key.  │
└──────────────────┴─────┴────────────────────────────────────────────────────┘


Obtaining Explicit Components for Keys from the Server

To obtain the explicit components (the explicit array) for a subset of the keys
in a keyboard description, use XkbGetKeyExplicitComponents.

Status XkbGetKeyExplicitComponents(Display *dpy, unsigned int first, unsigned
int num, XkbDescPtr xkb);

dpy   connection to server

first keycode of first key to fetch

num   number of keys for which to get explicit info

xkb   Xkb description in which to put results

XkbGetKeyExplicitComponents sends a request to the server to obtain the
explicit components for num keys on the keyboard starting with key first. It
waits for a reply and returns the explicit components in the server->explicit
array of xkb. If successful, XkbGetKeyExplicitComponents returns Success. The
xkb parameter must be a pointer to a valid Xkb keyboard description.

If the server map in the xkb parameter has not been allocated,
XkbGetKeyExplicitComponents allocates and initializes it before obtaining the
actions.

If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, XkbGetKeyExplicitComponents returns BadMatch
. If num is less than 1 or greater than XkbMaxKeyCount,
XkbGetKeyExplicitComponents returns BadValue. If any allocation errors occur,
XkbGetKeyExplicitComponents returns BadAlloc.

Virtual Modifier Mapping

The vmods member of the server map is a fixed-length array containing 
XkbNumVirtualMods entries. Each entry corresponds to a virtual modifier and
provides the binding of the virtual modifier to the real modifier bits. Each
entry in the vmods array is a bitwise inclusive OR of the legal modifier masks:

ShiftMask
LockMask
ControlMask
Mod1Mask
Mod2Mask
Mod3Mask
Mod4Mask
Mod5Mask

The vmodmap member of the server map is similar to the modmap array of the
client map (see section 15.4), but is used to define the virtual modifier
mapping for each key. Like the modmap member, it is indexed by keycode, and
each entry is a mask representing the virtual modifiers bound to the
corresponding key:

  • Each of the bits in a vmodmap entry represents an index into the vmods
    member. That is, bit 0 of a vmodmap entry refers to index 0 of the vmods
    array, bit 1 refers to index 1, and so on.

  • If a bit is set in the vmodmap entry for a key, that key is bound to the
    corresponding virtual modifier in the vmods array.

The vmodmap and vmods members of the server map are the “master” virtual
modifier definitions. Xkb automatically propagates any changes to these fields
to all other fields that use virtual modifier mappings.

The overall relationship of fields dealing with virtual modifiers in an Xkb
keyboard description are shown in Figure 16.2.

Figure 16.2. Virtual Modifier Relationships


Obtaining Virtual Modifier Bindings from the Server

To obtain a subset of the virtual modifier bindings (the vmods array) in a
keyboard description, use XkbGetVirtualMods:

Status XkbGetVirtualMods(Display *dpy, unsigned int which, XkbDescPtr xkb);

dpy   connection to server

which mask indicating virtual modifier bindings to get

xkb   Xkb description where results will be placed

XkbGetVirtualMods sends a request to the server to obtain the vmods entries for
the virtual modifiers specified in the mask, which, and waits for a reply. See
section 7.1 for a description of how to determine the virtual modifier mask.
For each bit set in which, XkbGetVirtualMods updates the corresponding virtual
modifier definition in the server->vmods array of xkb. The xkb parameter must
be a pointer to a valid Xkb keyboard description. If successful,
XkbGetVirtualMods returns Success.

If the server map has not been allocated in the xkb parameter,
XkbGetVirtualMods allocates and initializes it before obtaining the virtual
modifier bindings.

If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, XkbGetVirtualMods returns BadMatch. Any
errors in allocation cause XkbGetVirtualMods to return BadAlloc.

Obtaining Per-Key Virtual Modifier Mappings from the Server

To obtain the virtual modifier map (the vmodmap array) for a subset of the keys
in a keyboard description, use XkbGetKeyVirtualModMap:

Status XkbGetKeyVirtualModMap(Display *dpy, unsigned int first, unsigned int
num, XkbDescPtr xkb);

dpy   connection to server

first keycode of first key to fetch

num   # keys for which virtual mod maps are desired

xkb   Xkb description where results will be placed

XkbGetKeyVirtualModmap sends a request to the server to obtain the virtual
modifier mappings for num keys on the keyboard starting with key first. It
waits for a reply and returns the virtual modifier mappings in the server->
vmodmap array of xkb. If successful, XkbGetKeyVirtualModMap returns Success.
The xkb parameter must be a pointer to a valid Xkb keyboard description

If the server map in the xkb parameter has not been allocated,
XkbGetKeyVirtualModMap allocates and initializes it before obtaining the
virtual modifier mappings.

If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, XkbGetKeyVirtualModMap returns BadMatch. If
num is less than 1 or greater than XkbMaxKeyCount, XkbGetKeyVirtualModMap
returns BadValue. If any allocation errors occur, XkbGetKeyVirtualModMap
returns BadAlloc.

Chapter 17. The Xkb Compatibility Map

Table of Contents

The XkbCompatMap Structure

    Xkb State to Core Protocol State Transformation
    Core Keyboard Mapping to Xkb Keyboard Mapping Transformation
    Xkb Keyboard Mapping to Core Keyboard Mapping Transformations

Getting Compatibility Map Components From the Server
Using the Compatibility Map
Changing the Server’s Compatibility Map
Tracking Changes to the Compatibility Map
Allocating and Freeing the Compatibility Map

As shown in Figure 17.1, the X server is normally dealing with more than one
client, each of which may be receiving events from the keyboard, and each of
which may issue requests to modify the keyboard in some manner. Each client may
be either Xkb-unaware, Xkb-capable, or Xkb-aware. The server itself may be
either Xkb-aware or Xkb-unaware. If the server is Xkb-unaware, Xkb state and
keyboard mappings are not involved in any manner, and Xkb-aware clients may not
issue Xkb requests to the server. If the server is Xkb-aware, the server must
be able to deliver events and accept requests in which the keyboard state and
mapping are compatible with the mode in which the client is operating.
Consequently, for some situations, conversions must be made between Xkb state /
keyboard mappings and core protocol state / keyboard mappings, and vice versa.

Figure 17.1. Server Interaction with Types of Clients


In addition to these situations involving a single server, there are cases
where a client that deals with multiple servers may need to configure keyboards
on different servers to be similar and the different servers may not all be
Xkb-aware. Finally, a client may be dealing with descriptions of keyboards
(files, and so on) that are based on core protocol and therefore may need to be
able to map these descriptions to Xkb descriptions.

An Xkb-aware server maintains keyboard state and mapping as an Xkb keyboard
state and an Xkb keyboard mapping plus a compatibility map used to convert from
Xkb components to core components and vice versa. In addition, the server also
maintains a core keyboard mapping that approximates the Xkb keyboard mapping.
The core keyboard mapping may be updated piecemeal, on a per-key basis. When
the server receives a core protocol ChangeKeyboardMapping or SetModifierMapping
request, it updates its core keyboard mapping, then uses the compatibility map
to update its Xkb keyboard mapping. When the server receives an XkbSetMap
request, it updates those portions of its Xkb keyboard mapping specified by the
request, then uses its compatibility map to update the corresponding parts of
its core keyboard map. Consequently, the server’s Xkb keyboard map and also its
core keyboard map may contain components that were set directly and others that
were computed. Figure 17.2 illustrates these relationships.

Note

The core keyboard map is contained only in the server, not in any client-side
data structures.

Figure 17.2. Server Derivation of State and Keyboard Mapping Components


There are three kinds of compatibility transformations made by the server:

 1. Xkb State to Core State

    Keyboard state information reported to a client in the state field of
    various core events may be translated from the Xkb keyboard state
    maintained by the server, which includes a group number, to core protocol
    state, which does not.

    In addition, whenever the Xkb state is retrieved, the compat_state,
    compat_grab_mods, and compat_lookup_mods fields of the XkbStateRec returned
    indicate the result of applying the compatibility map to the current Xkb
    state in the server.

 2. Core Keyboard Mapping to Xkb Keyboard Mapping

    After core protocol requests received by the server to change the keyboard
    mapping (ChangeKeyboardMapping and SetModifierMapping) have been applied to
    the server’s core keyboard map, the results must be transformed to achieve
    an equivalent change of the Xkb keyboard mapping maintained by the server.

 3. Xkb Keyboard Mapping to Core Keyboard Mapping

    After Xkb protocol requests received by the server to change the keyboard
    mapping (XkbSetMap) have been applied to the server’s Xkb keyboard map, the
    results are transformed to achieve an approximately equivalent change to
    the core keyboard mapping maintained by the server.

This chapter discusses how a client may modify the compatibility map so that
subsequent transformations have a particular result.

The XkbCompatMap Structure

All configurable aspects of mapping Xkb state and configuration to and from
core protocol state and configuration are defined by a compatibility map,
contained in an XkbCompatMapRec structure; plus a set of explicit override
controls used to prevent particular components of type 2 (core-to-Xkb keyboard
mapping) transformations from automatically occurring. These explicit override
controls are maintained in a separate data structure discussed in section 16.3.

The compat member of an Xkb keyboard description (XkbDescRec) points to the 
XkbCompatMapRec structure:

typedef struct _XkbCompatMapRec {
      XkbSymInterpretPtr sym_interpret;    /* symbol based key semantics */
      XkbModsRec         groups[XkbNumKbdGroups]; /* group ⇒ modifier map */
      unsigned short     num_si;           /* # structures used in
                                                sym_interpret */
      unsigned short     size_si;          /* # structures allocated in
                                                sym_interpret */
} XkbCompatMapRec, *XkbCompatMapPtr;

Figure 17.3. Xkb Compatibility Data Structures


The subsections that follow discuss how the compatibility map and explicit
override controls are used in each of the three cases where compatibility
transformations are made.

Xkb State to Core Protocol State Transformation

As shown in Figure 17.3, there are four group compatibility maps (contained in
groups [0..3]) in the XkbCompatMapRec structure, one per possible Xkb group.
Each group compatibility map is a modifier definition (see section 7.2 for a
description of modifier definitions). The mask component of the definition
specifies which real modifiers should be set in the core protocol state field
when the corresponding group is active. Because only one group is active at any
one time, only one of the four possible transformations is ever applied at any
one point in time. If the device described by the XkbDescRec does not support
four groups, the extra groups fields are present, but undefined.

Normally, the Xkb-aware server reports keyboard state in the state member of
events such as a KeyPress event and ButtonPress event, encoded as follows:

┌─────┬────────────────┐
│bits │meaning         │
├─────┼────────────────┤
│15   │0               │
├─────┼────────────────┤
│13–14│Group index     │
├─────┼────────────────┤
│8–12 │Pointer Buttons │
├─────┼────────────────┤
│0–7  │Modifiers       │
└─────┴────────────────┘

For Xkb-unaware clients, only core protocol keyboard information may be
reported. Because core protocol does not define the group index, the group
index is mapped to modifier bits as specified by the groups [group index] field
of the compatibility map (the bits set in the compatibility map are ORed into
bits 0–7 of the state), and bits 13–14 are reported in the event as zero.

Core Keyboard Mapping to Xkb Keyboard Mapping Transformation

When a core protocol keyboard mapping request is received by the server, the
server’s core keyboard map is updated, and then the Xkb map maintained by the
server is updated. Because a client may have explicitly configured some of the
Xkb keyboard mapping in the server, this automatic regeneration of the Xkb
keyboard mapping from the core protocol keyboard mapping should not modify any
components of the Xkb keyboard mapping that were explicitly set by a client.
The client must set explicit override controls to prevent this from happening
(see section 16.3). The core-to-Xkb mapping is done as follows:

 1. Map the symbols from the keys in the core keyboard map to groups and
    symbols on keys in the Xkb keyboard map. The core keyboard mapping is of
    fixed width, so each key in the core mapping has the same number of symbols
    associated with it. The Xkb mapping allows a different number of symbols to
    be associated with each key; those symbols may be divided into a different
    number of groups (1-4) for each key. For each key, this process therefore
    involves partitioning the fixed number of symbols from the core mapping
    into a set of variable-length groups with a variable number of symbols in
    each group. For example, if the core protocol map is of width five, the
    partition for one key might result in one group with two symbols and
    another with three symbols. A different key might result in two groups with
    two symbols plus a third group with one symbol. The core protocol map
    requires at least two symbols in each of the first two groups.

     a. For each changed key, determine the number of groups represented in the
        new core keyboard map. This results in a tentative group count for each
        key in the Xkb map.

     b. For each changed key, determine the number of symbols in each of the
        groups found in step 1a. There is one explicit override control
        associated with each of the four possible groups for each Xkb key, 
        ExplicitKeyType1 through ExplicitKeyType4. If no explicit override
        control is set for a group, the number of symbols used for that group
        from the core map is two. If the explicit override control is set for a
        group on the key, the number of symbols used for that Xkb group from
        the core map is the width of the Xkb group with one exception: because
        of the core protocol requirement for at least two symbols in each of
        groups one and two, the number of symbols used for groups one and two
        is the maximum of 2 or the width of the Xkb group.

     c. For each changed key, assign the symbols in the core map to the
        appropriate group on the key. If the total number of symbols required
        by the Xkb map for a particular key needs more symbols than the core
        protocol map contains, the additional symbols are taken to be NoSymbol
        keysyms appended to the end of the core set. If the core map contains
        more symbols than are needed by the Xkb map, trailing symbols in the
        core map are discarded. In the absence of an explicit override for
        group one or two, symbols are assigned in order by group; the first
        symbols in the core map are assigned to group one, in order, followed
        by group two, and so on. For example, if the core map contained eight
        symbols per key, and a particular Xkb map contained 2 symbols for G1
        and G2 and three for G3, the symbols would be assigned as (G is group,
        L is shift level):


                  G1L1 G1L2 G2L1 G2L2 G3L1 G3L2 G3L3

        If an explicit override control is set for group one or two, the
        symbols are taken from the core set in a somewhat different order. The
        first four symbols from the core set are assigned to G1L1, G1L2, G2L1,
        G2L2, respectively. If group one requires more symbols, they are taken
        next, and then any additional symbols needed by group two. Group three
        and four symbols are taken in complete sequence after group two. For
        example, a key with four groups and three symbols in each group would
        take symbols from the core set in the following order:


        G1L1 G1L2 G2L1 G2L2 G1L3 G2L3 G3L1 G3L2 G3L3 G4L1 G4L2 G4L3

        As previously noted, the core protocol map requires at lease two
        symbols in groups one and two. Because of this, if an explicit override
        control for an Xkb key is set and group one and / or group two is of
        width one, it is not possible to generate the symbols taken from the
        core protocol set and assigned to position G1L2 and / or G2L2.

     d. For each group on each changed key, assign a key type appropriate for
        the symbols in the group.

     e. For each changed key, remove any empty or redundant groups.

 2. At this point, the groups and their associated symbols have been assigned
    to the corresponding key definitions in the Xkb map.

 3. Apply symbol interpretations to modify key operation. This phase is
    completely skipped if the ExplicitInterpret override control bit is set in
    the explicit controls mask for the Xkb key (see section 16.3).

     a. For each symbol on each changed key, attempt to match the symbol and
        modifiers from the Xkb map to a symbol interpretation describing how to
        generate the symbol.

     b. When a match is found in step 2a, apply the symbol interpretation to
        change the semantics associated with the symbol in the Xkb key map. If
        no match is found, apply a default interpretation.

The symbol interpretations used in step 2 are configurable and may be specified
using XkbSymInterpretRec structures referenced by the sym_interpret field of an
XkbCompatMapRec (see Figure 17.3).

Symbol Interpretations — the XkbSymInterpretRec Structure

Symbol interpretations are used to guide the X server when it modifies the Xkb
keymap in step 2. An initial set of symbol interpretations is loaded by the
server when it starts. A client may add new ones using XkbSetCompatMap (see
section 17.4).

Symbol interpretations result in key semantics being set. When a symbol
interpretation is applied, the following components of server key event
processing may be modified for the particular key involved:

Virtual modifier map
Auto repeat
Key behavior (may be set to XkbKB_Lock)
Key action (see section 16.1)

The XkbSymInterpretRec structure specifies a symbol interpretation:

typedef struct {
    KeySym          sym;          /* keysym of interest or NULL */
    unsigned char   flags;        /* XkbSI_AutoRepeat, XkbSI_LockingKey */
    unsigned char   match;        /* specifies how mods is interpreted */
    unsigned char   mods;         /* modifier bits, correspond to
                                     eight real modifiers */
    unsigned char   virtual_mod;  /* 1 modifier to add to key virtual mod map */
    XkbAnyAction    act;          /* action to bind to symbol position on key */
} XkbSymInterpretRec,*XkbSymInterpretPtr;

If sym is not NULL, it limits the symbol interpretation to keys on which that
particular keysym is selected by the modifiers matching the criteria specified
by mods and match. If sym is NULL, the interpretation may be applied to any
symbol selected on a key when the modifiers match the criteria specified by
mods and match.

match must be one of the values shown in Table 17.1 and specifies how the real
modifiers specified in mods are to be interpreted.

Table 17.1. Symbol Interpretation Match Criteria

┌─────────────────┬─────┬─────────────────────────────────────────────────────┐
│Match Criteria   │Value│Effect                                               │
├─────────────────┼─────┼─────────────────────────────────────────────────────┤
│XkbSI_NoneOf     │(0)  │None of the bits that are on in mods can be set, but │
│                 │     │other bits can be.                                   │
├─────────────────┼─────┼─────────────────────────────────────────────────────┤
│XkbSI_AnyOfOrNone│(1)  │Zero or more of the bits that are on in mods can be  │
│                 │     │set, as well as others.                              │
├─────────────────┼─────┼─────────────────────────────────────────────────────┤
│XkbSI_AnyOf      │(2)  │One or more of the bits that are on in mods can be   │
│                 │     │set, as well as any others.                          │
├─────────────────┼─────┼─────────────────────────────────────────────────────┤
│XkbSI_AllOf      │(3)  │All of the bits that are on in mods must be set, but │
│                 │     │others may be set as well.                           │
├─────────────────┼─────┼─────────────────────────────────────────────────────┤
│XkbSI_Exactly    │(4)  │All of the bits that are on in mods must be set, and │
│                 │     │no other bits may be set.                            │
└─────────────────┴─────┴─────────────────────────────────────────────────────┘


In addition to the above bits, match may contain the XkbSI_LevelOneOnly bit, in
which case the modifier match criteria specified by mods and match applies only
if sym is in level one of its group; otherwise, mods and match are ignored and
the symbol matches a condition where no modifiers are set.

#define XkbSI_LevelOneOnly  (0x80)
/* use mods + match only if sym is level 1 */

If no matching symbol interpretation is found, the server uses a default
interpretation where:

sym =         0
flags =       XkbSI_AutoRepeat
match =       XkbSI_AnyOfOrNone
mods =        0
virtual_mod = XkbNoModifier
act =         SA_NoAction

When a matching symbol interpretation is found in step 2a, the interpretation
is applied to modify the Xkb map as follows.

The act field specifies a single action to be bound to the symbol position; any
key event that selects the symbol causes the action to be taken. Valid actions
are defined in section 16.1.

If the Xkb keyboard map for the key does not have its ExplicitVModMap control
set, the XkbSI_LevelOneOnly bit and symbol position are examined. If the 
XkbSI_LevelOneOnly bit is not set in match or the symbol is in position G1L1,
the virtual_mod field is examined. If virtual_mod is not XkbNoModifier,
virtual_mod specifies a single virtual modifier to be added to the virtual
modifier map for the key. virtual_mod is specified as an index in the range
[0..15].

If the matching symbol is in position G1L1 of the key, two bits in the flags
field potentially specify additional behavior modifications:

#define   XkbSI_AutoRepeat    (1<<0)     /* key repeats if sym
                                            is in position G1L1 */
#define   XkbSI_LockingKey    (1<<1)     /* set KB_Lock behavior
                                            if sym is in psn G1L1 */

If the Xkb keyboard map for the key does not have its ExplicitAutoRepeat
control set, its auto repeat behavior is set based on the value of the 
XkbSI_AutoRepeat bit. If the XkbSI_AutoRepeat bit is set, the auto-repeat
behavior of the key is turned on; otherwise, it is turned off.

If the Xkb keyboard map for the key does not have its ExplicitBehavior control
set, its locking behavior is set based on the value of the XkbSI_LockingKey
bit. If XkbSI_LockingKey is set, the key behavior is set to KB_Lock; otherwise,
it is turned off (see section 16.3).

Xkb Keyboard Mapping to Core Keyboard Mapping Transformations

Whenever the server processes Xkb requests to change the keyboard mapping, it
discards the affected portion of its core keyboard mapping and regenerates it
based on the new Xkb mapping.

When the Xkb mapping for a key is transformed to a core protocol mapping, the
symbols for the core map are taken in the following order from the Xkb map:

G1L1 G1L2 G2L1 G2L2 G1L3-n G2L3-n G3L1-n G4L1-n

If group one is of width one in the Xkb map, G1L2 is taken to be NoSymbol;
similarly, if group two is of width one in the Xkb map, G2L2 is taken to be
NoSymbol.

If the Xkb key map for a particular key has fewer groups than the core
keyboard, the symbols for group one are repeated to fill in the missing core
components. For example, an Xkb key with a single width-three group would be
mapped to a core mapping counting three groups as:

G1L1 G1L2 G1L1 G1L2 G1L3 G1L3 G1L1 G1L2 G1L3

When a core keyboard map entry is generated from an Xkb keyboard map entry, a
modifier mapping is generated as well. The modifier mapping contains all of the
modifiers affected by any of the actions associated with the key combined with
all of the real modifiers associated with any of the virtual modifiers bound to
the key. In addition, if any of the actions associated with the key affect any
component of the keyboard group, all of the modifiers in the mask field of all
of the group compatibility maps are added to the modifier mapping as well.
While an XkbSA_ISOLock action can theoretically affect any modifier, if the Xkb
mapping for a key specifies an XkbSA_ISOLock action, only the modifiers or
group that are set by default are added to the modifier mapping.

Getting Compatibility Map Components From the Server

Use XkbGetCompatMap to fetch any combination of the current compatibility map
components from the server. When another client modifies the compatibility map,
you are notified if you have selected for XkbCompatMapNotify events (see
section 17.5). XkbGetCompatMap is particularly useful when you receive an event
of this type, as it allows you to update your program’s version of the
compatibility map to match the modified version now in the server. If your
program is dealing with multiple servers and needs to configure them all in a
similar manner, the updated compatibility map may be used to reconfigure other
servers.

Note

To make a complete matching configuration you must also update the explicit
override components of the server state.

Status XkbGetCompatMap(Display *display, unsigned int which, XkbDescRec *xkb);

display connection to server

which   mask of compatibility map components to fetch

xkb     keyboard description where results placed

XkbGetCompatMap fetches the components of the compatibility map specified in
which from the server specified by display and places them in the compat
structure of the keyboard description xkb. Valid values for which are an
inclusive OR of the values shown in Table 17.2.

Table 17.2. Compatibility Map Component Masks

┌──────────────────┬──────┬────────────────────────────────┐
│Mask              │Value │Affecting                       │
├──────────────────┼──────┼────────────────────────────────┤
│XkbSymInterpMask  │(1<<0)│Symbol interpretations          │
├──────────────────┼──────┼────────────────────────────────┤
│XkbGroupCompatMask│(1<<1)│Group maps                      │
├──────────────────┼──────┼────────────────────────────────┤
│XkbAllCompatMask  │(0x3) │All compatibility map components│
└──────────────────┴──────┴────────────────────────────────┘


If no compatibility map structure is allocated in xkb upon entry,
XkbGetCompatMap allocates one. If one already exists, its contents are
overwritten with the returned results.

XkbGetCompatMap fetches compatibility map information for the device specified
by the device_spec field of xkb. Unless you have specifically modified this
field, it is the default keyboard device. XkbGetCompatMap returns Success if
successful, BadAlloc if it is unable to obtain necessary storage for either the
return values or work space, BadMatch if the dpy field of the xkb argument is
non- NULL and does not match the display argument, and BadLength under certain
conditions caused by server or Xkb implementation errors.

Using the Compatibility Map

Xkb provides several functions that make it easier to apply the compatibility
map to configure a client-side Xkb keyboard mapping, given a core protocol
representation of part or all of a keyboard mapping. Obtain a core protocol
representation of a keyboard mapping from an actual server (by using
XGetKeyboardMapping, for example), a data file, or some other source.

To update a local Xkb keyboard map to reflect the mapping expressed by a core
format mapping by calling the function XkbUpdateMapFromCore.

Bool XkbUpdateMapFromCore(XkbDescPtr xkb, KeyCode first_key, int num_keys, int
map_width, KeySym *core_keysyms, XkbChangesPtr changes);

xkb          keyboard description to update

first_key    keycode of first key description to update

num_keys     number of key descriptions to update

map_width    width of core protocol keymap

core_keysyms symbols in core protocol keymap

changes      backfilled with changes made to Xkb

XkbUpdateMapFromCore interprets input argument information representing a
keyboard map in core format to update the Xkb keyboard description passed in
xkb. Only a portion of the Xkb map is updated — the portion corresponding to
keys with keycodes in the range first_key through first_key + num_keys - 1. If
XkbUpdateMapFromCore is being called in response to a MappingNotify event,
first_key and num_keys are reported in the MappingNotify event. core_keysyms
contains the keysyms corresponding to the keycode range being updated, in core
keyboard description order. map_width is the number of keysyms per key in
core_keysyms. Thus, the first map_width entries in core_keysyms are for the key
with keycode first_key, the next map_width entries are for key first_key + 1,
and so on.

In addition to modifying the Xkb keyboard mapping in xkb, XkbUpdateMapFromCore
backfills the changes structure whose address is passed in changes to indicate
the modifications that were made. You may then use changes in subsequent calls
such as XkbSetMap, to propagate the local modifications to a server.

When dealing with core keyboard mappings or descriptions, it is sometimes
necessary to determine the Xkb key types appropriate for the symbols bound to a
key in a core keyboard mapping. Use XkbKeyTypesForCoreSymbols for this purpose:

int XkbKeyTypesForCoreSymbols(XkbDescPtr xkb, int map_width, KeySym *core_syms,
unsigned int protected, int *types_inout, KeySym *xkb_syms_rtrn);

xkb           keyboard description in which to place symbols

map_width     width of core protocol keymap in xkb_syms_rtrn

core_syms     core protocol format array of KeySyms

protected     explicit key types

types_inout   backfilled with the canonical types bound to groups one and two
              for the key

xkb_syms_rtrn backfilled with symbols bound to the key in the Xkb mapping

XkbKeyTypesForCoreSymbols expands the symbols in core_syms and types in
types_inout according to the rules specified in section 12 of the core
protocol, then chooses canonical key types (canonical key types are defined in
section 15.2.1) for groups 1 and 2 using the rules specified by the Xkb
protocol and places them in xkb_syms_rtrn, which will be non- NULL.

A core keymap is a two-dimensional array of keysyms. It has map_width columns
and max_key_code rows. XkbKeyTypesForCoreSymbols takes a single row from a core
keymap, determines the number of groups associated with it, the type of each
group, and the symbols bound to each group. The return value is the number of
groups, types_inout has the types for each group, and xkb_syms_rtrn has the
symbols in Xkb order (that is, groups are contiguous, regardless of size).

protected contains the explicitly protected key types. There is one explicit
override control associated with each of the four possible groups for each Xkb
key, ExplicitKeyType1 through ExplicitKeyType4; protected is an inclusive OR of
these controls. map_width is the width of the core keymap and is not dependent
on any Xkb definitions. types_inout is an array of four type indices. On input,
types_inout contains the indices of any types already assigned to the key, in
case they are explicitly protected from change.

Upon return, types_inout contains any automatically selected (that is,
canonical) types plus any protected types. Canonical types are assigned to all
four groups if there are enough symbols to do so. The four entries in
types_inout correspond to the four groups for the key in question.

If the groups mapping does not change, but the symbols assigned to an Xkb
keyboard compatibility map do change, the semantics of the key may be modified.
To apply the new compatibility mapping to an individual key to get its
semantics updated, use XkbApplyCompatMapToKey.

Bool XkbApplyCompatMapToKey(XkbDescPtr xkb, KeyCode key, XkbChangesPtr
changes);

xkb     keyboard description to be updated

key     key to be updated

changes notes changes to the Xkb keyboard description

XkbApplyCompatMapToKey essentially performs the operation described in section
17.1.2 to a specific key. This updates the behavior, actions, repeat status,
and virtual modifier bindings of the key.

Changing the Server’s Compatibility Map

To modify the server’s compatibility map, first modify a local copy of the Xkb
compatibility map, then call XkbSetCompatMap. You may allocate a new
compatibility map for this purpose using XkbAllocCompatMap (see section 17.6).
You may also use a compatibility map from another server, although you need to
adjust the device_spec field in the XkbDescRec accordingly. Note that symbol
interpretations in a compatibility map ( sym_interpret, the vector of 
XkbSymInterpretRec structures) are also allocated using this same function.

Bool XkbSetCompatMap(Display *display, unsigned int which, XkbDescPtr xkb, Bool
update_actions);

display        connection to server

which          mask of compat map components to set

xkb            source for compat map components

update_actions True ⇒ apply to server’s keyboard map

XkbSetCompatMap copies compatibility map information from the keyboard
description in xkb to the server specified in display’s compatibility map for
the device specified by the device_spec field of xkb. Unless you have
specifically modified this field, it is the default keyboard device. which
specifies the compatibility map components to be set, and is an inclusive OR of
the bits shown in Table 17.2.

After updating its compatibility map for the specified device, if
update_actions is True, the server applies the new compatibility map to its
entire keyboard for the device to generate a new set of key semantics,
compatibility state, and a new core keyboard map. If update_actions is False,
the new compatibility map is not used to generate any modifications to the
current device semantics, state, or core keyboard map. One reason for not
applying the compatibility map immediately would be if one server was being
configured to match another on a piecemeal basis; the map should not be applied
until everything is updated. To force an update at a later time, use
XkbSetCompatMap specifying which as zero and update_actions as True.

XkbSetCompatMap returns True if successful and False if unsuccessful. The
server may report problems it encounters when processing the request
subsequently via protocol errors.

To add a symbol interpretation to the list of symbol interpretations in an 
XkbCompatRec, use XkbAddSymInterpret.

XkbSymInterpretPtr XkbAddSymInterpret(XkbDescPtr xkb, XkbSymInterpretPtr si,
Bool updateMap, XkbChangesPtr changes);

xkb       keyboard description to be updated

si        symbol interpretation to be added

updateMap True⇒apply compatibility map to keys

changes   changes are put here

XkbAddSymInterpret adds si to the list of symbol interpretations in xkb. If
updateMap is True, it (re)applies the compatibility map to all of the keys on
the keyboard. If changes is non- NULL, it reports the parts of the keyboard
that were affected (unless updateMap is True, not much changes).
XkbAddSymInterpret returns a pointer to the actual new symbol interpretation in
the list or NULL if it failed.

Tracking Changes to the Compatibility Map

The server automatically generates MappingNotify events when the keyboard
mapping changes. If you wish to be notified of changes to the compatibility
map, you should select for XkbCompatMapNotify events. If you select for 
XkbMapNotify events, you no longer receive the automatically generated 
MappingNotify events. If you subsequently deselect XkbMapNotifyEvent delivery,
you again receive MappingNotify events.

To receive XkbCompatMapNotify events under all possible conditions, use
XkbSelectEvents (see section 4.3) and pass XkbCompatMapNotifyMask in both
bits_to_change and values_for_bits.

To receive XkbCompatMapNotify events only under certain conditions, use
XkbSelectEventDetails using XkbCompatMapNotify as the event_type and specifying
the desired map changes in bits_to_change and values_for_bits using mask bits
from Table 17.2.

Note that you are notified of changes you make yourself, as well as changes
made by other clients.

The structure for the XkbCompatMapNotifyEvent is:

typedef struct {
    int            type;           /* Xkb extension base event code */
    unsigned long  serial;         /* X server serial number for event */
    Bool           send_event;     /* True ⇒
                                      synthetically generated */
    Display *      display;        /* server connection where event generated */
    Time           time;           /* server time when event generated */
    int            xkb_type;       /* XkbCompatMapNotify */
    int            device;         /* Xkb device ID, will not be
                                      XkbUseCoreKbd */
    unsigned int   changed_groups; /* number of group maps changed */
    int            first_si;       /* index to 1st changed symbol
                                      interpretation */
    int            num_si;         /* number of changed symbol
                                      interpretations */
    int            num_total_si;   /* total number of valid symbol
                                      interpretations */
} XkbCompatMapNotifyEvent;

changed_groups is the number of group compatibility maps that have changed. If
you are maintaining a corresponding copy of the compatibility map, or get a
fresh copy from the server using XkbGetCompatMap, changed_groups references
groups [0.. changed_groups -1] in the XkbCompatMapRec structure.

first_si is the index of the first changed symbol interpretation, num_si is the
number of changed symbol interpretations, and num_total_si is the total number
of valid symbol interpretations. If you are maintaining a corresponding copy of
the compatibility map, or get a fresh copy from the server using
XkbGetCompatMap, first_si, num_si, and num_total_si are appropriate for use
with the compat.sym_interpret vector in this structure.

Allocating and Freeing the Compatibility Map

If you are modifying the compatibility map, you need to allocate a new
compatibility map if you do not already have one available. To do so, use
XkbAllocCompatMap.

Status XkbAllocCompatMap(XkbDescPtr xkb, unsigned int which, unsigned int
num_si);

xkb    keyboard description in which to allocate compat map

which  mask of compatibility map components to allocate

num_si number of symbol interpretations to allocate

xkb specifies the keyboard description for which compatibility maps are to be
allocated. The compatibility map is the compat field in this structure.

which specifies the compatibility map components to be allocated (see
XkbGetCompatMap, in section 17.2). which is an inclusive OR of the bits shown
in Table 17.2.

num_si specifies the total number of entries to allocate in the symbol
interpretation vector (xkb.compat.sym_interpret).

Note that symbol interpretations in a compatibility map (the sym_interpret
vector of XkbSymInterpretRec structures) are also allocated using this same
function. To ensure that there is sufficient space in the symbol interpretation
vector for entries to be added, use XkbAllocCompatMap specifying which as 
XkbSymInterpretMask and the number of free symbol interpretations needed in
num_si.

XkbAllocCompatMap returns Success if successful, BadMatch if xkb is NULL, or 
BadAlloc if errors are encountered when attempting to allocate storage.

To free an entire compatibility map or selected portions of one, use
XkbFreeCompatMap.

void XkbFreeCompatMap(XkbDescPtr xkb, unsigned int which, Bool free_map);

xkb      Xkb description in which to free compatibility map

which    mask of compatibility map components to free

free_map True ⇒ free XkbCompatMapRec structure itself

which specifies the compatibility map components to be freed (see
XkbGetCompatMap, in section 17.2). which is an inclusive OR of the bits shown
in Table 17.2

free_map indicates whether the XkbCompatMapRec structure itself should be
freed. If free_map is True, which is ignored, all non- NULL compatibility map
components are freed, and the compat field in the XkbDescRec referenced by xkb
is set to NULL.

Chapter 18. Symbolic Names

Table of Contents

The XkbNamesRec Structure
Symbolic Names Masks
Getting Symbolic Names From the Server
Changing Symbolic Names on the Server

     

Tracking Name Changes
Allocating and Freeing Symbolic Names

The core protocol does not provide any information to clients other than that
actually used to interpret events. This makes it difficult to write an
application that presents the keyboard to a user in an easy-to-understand way.
Such applications have to examine the vendor string and keycodes to determine
the type of keyboard connected to the server and then examine keysyms and
modifier mappings to determine the effects of most modifiers (the Shift, Lock
and Control modifiers are defined by the core protocol but no semantics are
implied for any other modifiers).

To make it easier for applications to present a keyboard to the user, Xkb
supports symbolic names for most components of the keyboard extension. Most of
these symbolic names are grouped into the names component of the keyboard
description.

The XkbNamesRec Structure

The names component of the keyboard description is defined as follows:

#define      XkbKeyNameLength      4
#define      XkbKeyNumVirtualMods  16
#define      XkbKeyNumIndicators   32
#define      XkbKeyNumKbdGroups    4
#define      XkbMaxRadioGroups     32

typedef struct {
    char      name[XkbKeyNameLength];      /* symbolic key names */
} XkbKeyNameRec, *XkbKeyNamePtr;

typedef struct {
    char      real[XkbKeyNameLength];
              /* this key name must be in the keys array */
    char      alias[XkbKeyNameLength];
              /* symbolic key name as alias for the key */
} XkbKeyAliasRec, *XkbKeyAliasPtr;

typedef struct _XkbNamesRec {
    Atom            keycodes;        /* identifies range and meaning
                                        of keycodes */
    Atom            geometry;        /* identifies physical location,
                                        size, and shape of keys */
    Atom            symbols;         /* identifies the symbols logically
                                        bound to the keys */
    Atom            types;           /* identifies the set of key types */
    Atom            compat;          /* identifies actions for keys using
                                        core protocol */
    Atom            vmods[XkbNumVirtualMods]; /* symbolic names for
                                                 virtual modifiers */
    Atom            indicators[XkbNumIndicators]; /* symbolic names
                                                     for indicators */
    Atom            groups[XkbNumKbdGroups];  /* symbolic names for
                                                 keyboard groups */
    XkbKeyNamePtr   keys;            /* symbolic key name array */
    XkbKeyAliasPtr  key_aliases;     /* real/alias symbolic name pairs array */
    Atom *          radio_groups;    /* radio group name array */
    Atom            phys_symbols;    /* identifies the symbols engraved
                                        on the keyboard */
    unsigned char   num_keys;        /* number of keys in the keys array */
    unsigned char   num_key_aliases; /* number of keys in the
                                        key_aliases array */
    unsigned short  num_rg;          /* number of radio groups */
} XkbNamesRec, *XkbNamesPtr;

The keycodes name identifies the range and meaning of the keycodes returned by
the keyboard in question. The geometry name, on the other hand, identifies the
physical location, size and shape of the various keys on the keyboard. As an
example to distinguish between these two names, consider function keys on
PC-compatible keyboards. Function keys are sometimes above the main keyboard
and sometimes to the left of the main keyboard, but the same keycode is used
for the key that is logically F1 regardless of physical position. Thus, all
PC-compatible keyboards share a similar keycodes name but may have different
geometry names.

Note

The keycodes name is intended to be a very general description of the keycodes
returned by a keyboard; a single keycodes name might cover keyboards with
differing numbers of keys provided all keys have the same semantics when
present. For example, 101 and 102 key PC keyboards might use the same name. In
these cases, applications can use the keyboard geometry name to determine which
subset of the named keycodes is in use.

The symbols name identifies the symbols logically bound to the keys. The
symbols name is a human or application-readable description of the intended
locale or usage of the keyboard with these symbols. The phys_symbols name, on
the other hand, identifies the symbols actually engraved on the keyboard. Given
this, the symbols name and phys_symbols names might be different. For example,
the description for a keyboard that has English US engravings, but that is
using Swiss German symbols might have a phys_symbols name of "en_US" and a
symbols name of "de_CH."

The types name provides some information about the set of key types (see
section 15.2) that can be associated with the keyboard. In addition, each key
type can have a name, and each shift level of a type can have a name. Although
these names are stored in the map description with each of the types, they are
accessed using the same methods as the other symbolic names.

The compat name provides some information about the rules used to bind actions
to keys that are changed using core protocol requests.

Xkb provides symbolic names for each of the 4 keyboard groups, 16 virtual
modifiers, 32 keyboard indicators, and 4 keyboard groups. These names are held
in the vmods, indicators, and groups fixed-length arrays.

Each key has a four-byte symbolic name. All of the symbolic key names are held
in the keys array, and num_keys reports the number of entries that are in the
keys array. For each key, the key name links keys with similar functions or in
similar positions on keyboards that report different keycodes. For example, the
F1 key may emit keycode 23 on one keyboard and keycode 86 on another. By naming
this key "FK01" on both keyboards, the keyboard layout designer can reuse parts
of keyboard descriptions for different keyboards.

Key aliases allow the keyboard layout designer to assign multiple key names to
a single key. This allows the keyboard layout designer to refer to keys using
either their position or their “function”. For example, a keyboard layout
designer may wish to refer to the left arrow key on a PC keyboard using the
ISO9995-5 positional specification of A31 or using the functional specification
of LEFT. The key_aliases field holds a variable-length array of real and alias
key name pairs, and the total number of entries in the key_aliases array is
held in num_key_aliases. For each real and alias key name pair, the real field
refers to the a name in the keys array, and the alias field refers to the alias
for that key. Using the previous example, the keyboard designer may use the
name A31 in the keys array, but also define the name LEFT as an alias for A31
in the key_aliases array.

Note

Key aliases defined in the geometry component of a keyboard mapping (see
Chapter 13, Keyboard Geometry) override those defined in the keycodes component
of the server database, which are stored in the XkbNamesRec (xkb->names).
Therefore, consider the key aliases defined by the geometry before considering
key aliases supplied by the XkbNamesRec.

A radio group is a set of keys whose behavior simulates a set of radio buttons.
Once a key in a radio group is pressed, it stays logically depressed until
another key in the group is pressed, at which point the previously depressed
key is logically released. Consequently, at most one key in a radio group can
be logically depressed at one time.

Each radio group in the keyboard description can have a name. These names are
held in the variable-length array radio_groups, and num_rg tells how many
elements are in the radio_groups array.

Symbolic Names Masks

Xkb provides several functions that work with symbolic names. Each of these
functions uses a mask to specify individual fields of the structures described
above. These masks and their relationships to the fields in a keyboard
description are shown in Table 18.1.

Table 18.1. Symbolic Names Masks

┌──────────────────────┬────────┬────────────────┬────────────────────────────┐
│Mask Bit              │Value   │Keyboard        │Field                       │
│                      │        │Component       │                            │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbKeycodesNameMask   │(1<<0)  │Xkb->names      │keycodes                    │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbGeometryNameMask   │(1<<1)  │Xkb->names      │geometry                    │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbSymbolsNameMask    │(1<<2)  │Xkb->names      │symbols                     │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbPhysSymbolsNameMask│(1<<3)  │Xkb->names      │phys_symbols                │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbTypesNameMask      │(1<<4)  │Xkb->names      │type                        │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbCompatNameMask     │(1<<5)  │Xkb->names      │compat                      │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbKeyTypeNamesMask   │(1<<6)  │Xkb->map        │type[*].name                │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbKTLevelNamesMask   │(1<<7)  │Xkb->map        │type[*].lvl_names[*]        │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbIndicatorNamesMask │(1<<8)  │Xkb->names      │indicators[*]               │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbKeyNamesMask       │(1<<9)  │Xkb->names      │keys[*], num_keys           │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbKeyAliasesMask     │(1<<10) │Xkb->names      │key_aliases[*],             │
│                      │        │                │num_key_aliases             │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbVirtualModNamesMask│(1<<11) │Xkb->names      │vmods[*]                    │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbGroupNamesMask     │(1<<12) │Xkb->names      │groups[*]                   │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbRGNamesMask        │(1<<13) │Xkb->names      │radio_groups[*], num_rg     │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│                      │        │                │keycodes,                   │
│                      │        │                │                            │
│                      │        │                │geometry,                   │
│                      │        │                │                            │
│                      │        │                │symbols,                    │
│XkbComponentNamesMask │(0x3f)  │Xkb->names      │                            │
│                      │        │                │physical symbols,           │
│                      │        │                │                            │
│                      │        │                │types, and                  │
│                      │        │                │                            │
│                      │        │                │compatibility map           │
├──────────────────────┼────────┼────────────────┼────────────────────────────┤
│XkbAllNamesMask       │(0x3fff)│Xkb->names      │all name components         │
└──────────────────────┴────────┴────────────────┴────────────────────────────┘


Getting Symbolic Names From the Server

To obtain symbolic names from the server, use XkbGetNames.

Status XkbGetNames(Display *dpy, unsigned int which, XkbDescPtr xkb);

dpy   connection to the X server

which mask of names or map components to be updated

xkb   keyboard description to be updated

XkbGetNames retrieves symbolic names for the components of the keyboard
extension from the X server. The which parameter specifies the name components
to be updated in the xkb parameter, and is the bitwise inclusive OR of the
valid names mask bits defined in Table 18.1.

If the names field of the keyboard description xkb is NULL, XkbGetNames
allocates and initializes the names component of the keyboard description
before obtaining the values specified by which. If the names field of xkb is
not NULL, XkbGetNames obtains the values specified by which and copies them
into the keyboard description xkb.

If the map component of the xkb parameter is NULL, XkbGetNames does not
retrieve type or shift level names, even if XkbKeyTypeNamesMask or 
XkbKTLevelNamesMask are set in which.

XkbGetNames can return Success, or BadAlloc, BadLength, BadMatch, and 
BadImplementation errors.

To free symbolic names, use XkbFreeNames (see section 18.6)

Changing Symbolic Names on the Server

To change the symbolic names in the server, first modify a local copy of the
keyboard description and then use either XkbSetNames, or, to save network
traffic, use a XkbNameChangesRec structure and call XkbChangeNames to download
the changes to the server. XkbSetNames and XkbChangeNames can generate BadAlloc
, BadAtom, BadLength, BadMatch, and BadImplementation errors.

Bool XkbSetNames(Display *dpy, unsigned int which, unsigned int first_type,
unsigned int num_types, XkbDescPtr xkb);

dpy        connection to the X server

which      mask of names or map components to be changed

first_type first type whose name is to be changed

num_types  number of types for which names are to be changed

xkb        keyboard description from which names are to be taken

Use XkbSetNames to change many names at the same time. For each bit set in
which, XkbSetNames takes the corresponding value (or values in the case of
arrays) from the keyboard description xkb and sends it to the server.

The first_type and num_types arguments are used only if XkbKeyTypeNamesMask or 
XkbKTLevelNamesMask is set in which and specify a subset of the types for which
the corresponding names are to be changed. If either or both of these mask bits
are set but the specified types are illegal, XkbSetNames returns False and does
not update any of the names specified in which. The specified types are illegal
if xkb does not include a map component or if first_type and num_types specify
types that are not defined in the keyboard description.

The XkbNameChangesRec Structure

The XkbNameChangesRec allows applications to identify small modifications to
the symbolic names and effectively reduces the amount of traffic sent to the
server:

typedef struct _XkbNameChanges {
    unsigned int       changed;           /* name components that have
                                             changed */
    unsigned char      first_type;        /* first key type with a new name */
    unsigned char      num_types;         /* number of types with new names */
    unsigned char      first_lvl;         /* first key type with new level
                                             names */
    unsigned char      num_lvls;          /* number of key types with new
                                             level names */
    unsigned char      num_aliases;       /* if key aliases changed,
                                             total number of key aliases */
    unsigned char      num_rg;            /* if radio groups changed, total
                                             number of radio groups */
    unsigned char      first_key;         /* first key with a new name */
    unsigned char      num_keys;          /* number of keys with new names */
    unsigned short     changed_vmods;     /* mask of virtual modifiers
                                             for which names have changed */
    unsigned long      changed_indicators;  /* mask of indicators
                                               for which names were changed */
    unsigned char      changed_groups;    /* mask of groups for
                                             which names were changed */
} XkbNameChangesRec, *XkbNameChangesPtr;

The changed field specifies the name components that have changed and is the
bitwise inclusive OR of the valid names mask bits defined in Table 18.1. The
rest of the fields in the structure specify the ranges that have changed for
the various kinds of symbolic names, as shown in Table 18.2.

Table 18.2. XkbNameChanges Fields

┌──────────────────────┬──────────────────┬──────────┬────────────────────┐
│Mask                  │Fields            │Component │Field               │
├──────────────────────┼──────────────────┼──────────┼────────────────────┤
│                      │first_type,       │          │                    │
│XkbKeyTypeNamesMask   │                  │Xkb->map  │type[*].name        │
│                      │num_types         │          │                    │
├──────────────────────┼──────────────────┼──────────┼────────────────────┤
│                      │first_lvl,        │          │                    │
│XkbKTLevelNamesMask   │                  │Xkb->map  │type[*].lvl_names[*]│
│                      │num_lvls          │          │                    │
├──────────────────────┼──────────────────┼──────────┼────────────────────┤
│XkbKeyAliasesMask     │num_aliases       │Xkb->names│key_aliases[*]      │
├──────────────────────┼──────────────────┼──────────┼────────────────────┤
│XkbRGNamesMask        │num_rg            │Xkb->names│radio_groups[*]     │
├──────────────────────┼──────────────────┼──────────┼────────────────────┤
│                      │first_key,        │          │                    │
│XkbKeyNamesMask       │                  │Xkb->names│keys[*]             │
│                      │num_keys          │          │                    │
├──────────────────────┼──────────────────┼──────────┼────────────────────┤
│XkbVirtualModNamesMask│changed_vmods     │Xkb->names│vmods[*]            │
├──────────────────────┼──────────────────┼──────────┼────────────────────┤
│XkbIndicatorNamesMask │changed_indicators│Xkb->names│indicators[*]       │
├──────────────────────┼──────────────────┼──────────┼────────────────────┤
│XkbGroupNamesMask     │changed_groups    │Xkb->names│groups[*]           │
└──────────────────────┴──────────────────┴──────────┴────────────────────┘


XkbChangeNames provides a more flexible method for changing symbolic names than
XkbSetNames and requires the use of an XkbNameChangesRec structure.

Bool XkbChangeNames(Display *dpy, XkbDescPtr xkb, XkbNameChangesPtr changes);

dpy     connection to the X server

xkb     keyboard description from which names are to be taken

changes names map components to be updated on the server

XkbChangeNames copies any names specified by changes from the keyboard
description, xkb, to the X server specified by dpy. XkbChangeNames aborts and
returns False if any illegal type names or type shift level names are specified
by changes.

Tracking Name Changes

Whenever a symbolic name changes in the server’s keyboard description, the
server sends a XkbNamesNotify event to all interested clients. To receive name
notify events, use XkbSelectEvents (see section 4.3) with XkbNamesNotifyMask in
both the bits_to_change and values_for_bits parameters.

To receive events for only specific names, use XkbSelectEventDetails. Set the
event_type parameter to XkbNamesNotify, and set both the bits_to_change and
values_for_bits detail parameter to a mask composed of a bitwise OR of masks in
Table 18.1.

The structure for the XkbNamesNotify event is defined as follows:

typedef struct {
    int             type;           /* Xkb extension base event code */
    unsigned long   serial;         /* X server serial number for event */
    Bool            send_event;     /* True ⇒ synthetically generated */
    Display *       display;        /* server connection where event generated */
    Time            time;           /* server time when event generated */
    int             xkb_type;       /* XkbNamesNotify */
    int             device;         /* Xkb device ID, will not be
                                       XkbUseCoreKbd */
    unsigned int    changed;        /* mask of name components
                                       that have changed */
    int             first_type;     /* first key type with a new name */
    int             num_types;      /* number of types with new names */
    int             first_lvl;      /* first key type with new level names */
    int             num_lvls;       /* number of key types with new level names */
    int             num_aliases;    /* if key aliases changed, total number
                                       of key aliases */
    int             num_radio_groups;  /* if radio groups changed,
                                         total number of radio groups */
    unsigned int    changed_vmods;  /* mask of virtual modifiers for
                                       which names have changed */
    unsigned int    changed_groups; /* mask of groups for
                                       which names were changed */
    unsigned int    changed_indicators;  /* mask of indicators for which
                                              names were changed */
    int             first_key;      /* first key with a new name */
    int             num_keys;       /* number of keys with new names */
} XkbNamesNotifyEvent;

The changed field specifies the name components that have changed and is the
bitwise inclusive OR of the valid names mask bits defined in Table 18.1. The
other fields in this event are interpreted as the like-named fields in an 
XkbNameChangesRec , as previously defined.

When your application receives a XkbNamesNotify event, you can note the changed
names in a changes structure using XkbNoteNameChanges.

void XkbNoteNameChanges(XkbNameChangesPtr old, XkbNamesNotifyEvent *new,
unsigned int wanted);

old    XkbNameChangesRec structure to be updated

new    event from which changes are to be copied

wanted types of names for which changes are to be noted

The wanted parameter is the bitwise inclusive OR of the valid names mask bits
shown in Table 18.1. XkbNoteNameChanges copies any changes that are reported in
new and specified in wanted into the changes record specified by old.

Allocating and Freeing Symbolic Names

Most applications do not need to directly allocate symbolic names structures.
Do not allocate a names structure directly using malloc or Xmalloc if your
application changes the number of key aliases or radio groups or constructs a
symbolic names structure without loading the necessary components from the X
server. Instead use XkbAllocNames.

Status XkbAllocNames(XkbDescPtr xkb, unsigned int which, int num_rg, int
num_key_aliases);

xkb             keyboard description for which names are to be allocated

which           mask of names to be allocated

num_rg          total number of radio group names needed

num_key_aliases total number of key aliases needed

XkbAllocNames can return BadAlloc, BadMatch, and BadValue errors. The which
parameter is the bitwise inclusive OR of the valid names mask bits defined in
Table 18.1.

Do not free symbolic names structures directly using free or XFree. Use
XkbFreeNames instead.

void XkbFreeNames(XkbDescPtr xkb, unsigned int which, Bool free_map);

xkb      keyboard description for which names are to be freed

which    mask of names components to be freed

free_map True ⇒ XkbNamesRec structure itself should be freed

The which parameter is the bitwise inclusive OR of the valid names mask bits
defined in Table 18.1.

Chapter 19. Replacing a Keyboard “On the Fly”

Some operating system and X server implementations allow “hot plugging” of
input devices. When using these implementations, input devices can be unplugged
and new ones plugged in without restarting the software that is using those
devices. There is no provision in the standard X server for notification of
client programs if input devices are unplugged and/or new ones plugged in. In
the case of the X keyboard, this could result in the X server having a keymap
that does not match the new keyboard.

If the X server implementation supports the X input device extension, a client
program may also change the X keyboard programmatically. The
XChangeKeyboardDevice input extension request allows a client to designate an
input extension keyboard device as the X keyboard, in which case the old X
keyboard device becomes inaccessible except via the input device extension. In
this case, core protocol MappingNotify and input extension XChangeDeviceNotify
events are generated to notify all clients that a new keyboard with a new
keymap has been designated.

When a client opens a connection to the X server, the server reports the
minimum and maximum keycodes. The server keeps track of the minimum and maximum
keycodes last reported to each client. When delivering events to a particular
client, the server filters out any events that fall outside of the valid range
for the client.

Xkb provides an XkbNewKeyboardNotify event that reports a change in keyboard
geometry and/or the range of supported keycodes. The server can generate an 
XkbNewKeyboardNotify event when it detects a new keyboard or in response to an
XkbGetKeyboardByName request that loads a new keyboard description. Selecting
for XkbNewKeyboardNotify events allows Xkb-aware clients to be notified
whenever a keyboard change occurs that may affect the keymap.

When a client requests XkbNewKeyboardNotify events, the server compares the
range of keycodes for the current keyboard to the range of keycodes that are
valid for the client. If they are not the same, the server immediately sends
the client an XkbNewKeyboardNotify event. Even if the “new” keyboard is not new
to the server, it is new to this particular client.

When the server sends an XkbNewKeyboardNotify event to a client to inform it of
a new keycode range, it resets the stored range of legal keycodes for the
client to the keycode range reported in the event; it does not reset this range
for the client if it does not sent an XkbNewKeyboardNotify event to a client.
Because Xkb-unaware clients and Xkb-aware clients that do not request 
XkbNewKeyboardNotify events are never sent these events, the server’s notion of
the legal keycode range never changes, and these clients never receive events
from keys that fall outside of their notion of the legal keycode range.

Clients that have not selected to receive XkbNewKeyboardNotify events do,
however, receive the XkbNewKeyboardNotify event when a keyboard change occurs.
Clients that have not selected to receive this event also receive numerous
other events detailing the individual changes that occur when a keyboard change
occurs.

Clients wishing to track changes in min_key_code and max_key_code must watch
for both XkbNewKeyboardNotify and XkbMapNotify events, because a simple mapping
change causes an XkbMapNotify event and may change the range of valid keycodes,
but does not cause an XkbNewKeyboardNotify event. If a client does not select
for XkbNewKeyboardNotify events, the server restricts the range of keycodes
reported to the client.

In addition to filtering out-of-range key events, Xkb:

  • Adjusts core protocol MappingNotify events to refer only to keys that match
    the stored legal range.

  • Reports keyboard mappings for keys that match the stored legal range to
    clients that issue a core protocol GetKeyboardMapping request.

  • Reports modifier mappings only for keys that match the stored legal range
    to clients that issue a core protocol GetModifierMapping request.

  • Restricts the core protocol ChangeKeyboardMapping and SetModifierMapping
    requests to keys that fall inside the stored legal range.

In short, Xkb does everything possible to hide from Xkb-unaware clients the
fact that the range of legal keycodes has changed, because such clients cannot
be expected to deal with them. Xkb events and requests are not modified in this
manner; all Xkb events report the full range of legal keycodes. No requested
Xkb events are discarded, and no Xkb requests have their keycode range clamped.

The structure for the XkbNewKeyboardNotify event is defined as follows:

typedef struct _XkbNewKeyboardNotify {
    int            type;         /* Xkb extension base event code */
    unsigned long  serial;       /* X server serial number for event */
    Bool           send_event;   /* True ⇒ synthetically generated */
    Display *      display;      /* server connection where event generated */
    Time           time;         /* server time when event generated */
    int            xkb_type;     /* XkbNewKeyboardNotify */
    int            device;       /* device ID of new keyboard */
    int            old_device;   /* device ID of old keyboard */
    int            min_key_code; /* min keycode of new keyboard */
    int            max_key_code; /* max keycode of new keyboard */
    int            old_min_key_code; /* min keycode of old keyboard */
    int            old_max_key_code; /* max keycode of old keyboard */
    unsigned int   changed;      /* changed aspects - see masks below */
    char           req_major;    /* major request that caused change */
    char           req_minor;    /* minor request that caused change */
} XkbNewKeyboardNotifyEvent;

To receive name notify events, use XkbSelectEvents (see section 4.3) with 
XkbNewKeyboardNotifyMask in both the bits_to_change and values_for_bits
parameters. To receive events for only specific names, use
XkbSelectEventDetails. Set the event_type parameter to XkbNewKeyboardNotify,
and set both the bits_to_change and values_for_bits detail parameter to a mask
composed of a bitwise OR of masks in Table 19.1.

Table 19.1. XkbNewKeyboardNotifyEvent Details

┌──────────────────────────────┬──────┬───────────────────────────────────────┐
│XkbNewKeyboardNotify Event    │Value │Circumstances                          │
│Details                       │      │                                       │
├──────────────────────────────┼──────┼───────────────────────────────────────┤
│XkbNKN_KeycodesMask           │(1L   │Notification of keycode range changes  │
│                              │<<0)  │wanted                                 │
├──────────────────────────────┼──────┼───────────────────────────────────────┤
│XkbNKN_GeometryMask           │(1L   │Notification of geometry changes wanted│
│                              │<<1)  │                                       │
├──────────────────────────────┼──────┼───────────────────────────────────────┤
│XkbNKN_DeviceIDMask           │(1L   │Notification of device ID changes      │
│                              │<<2)  │wanted                                 │
├──────────────────────────────┼──────┼───────────────────────────────────────┤
│XkbAllNewKeyboardEventsMask   │(0x7) │Includes all of the above masks        │
└──────────────────────────────┴──────┴───────────────────────────────────────┘


The req_major and req_minor fields indicate what type of keyboard change has
occurred.

If req_major and req_minor are zero, the device change was not caused by a
software request to the server — a spontaneous change has occurred, such as
hot-plugging a new device. In this case, device is the device identifier for
the new, current X keyboard device, but no implementation-independent guarantee
can be made about old_device. old_device may be identical to device (an
implementor is permitted to reuse the device specifier when the device
changes); or it may be different. Note that req_major and req_minor being zero
do not necessarily mean that the physical keyboard device has changed; rather,
they only imply a spontaneous change outside of software control (some systems
have keyboards that can change personality at the press of a key).

If the keyboard change is the result of an X Input Extension
ChangeKeyboardDevice request, req_major contains the input extension major
opcode, and req_minor contains the input extension request number for 
X_ChangeKeyboardDevice. In this case, device and old_device are different, with
device being the identifier for the new, current X keyboard device, and
old_device being the identifier for the former device.

If the keyboard change is the result of an XkbGetKeyboardByName function call,
which generates an X_kbGetKbdByName request, req_major contains the Xkb
extension base event code (see section 2.4), and req_minor contains the event
code for the Xkb extension request X_kbGetKbdByName. device contains the device
identifier for the new device, but nothing definitive can be said for
old_device; it may be identical to device, or it may be different, depending on
the implementation.

Chapter 20. Server Database of Keyboard Components

Table of Contents

Component Names
Listing the Known Keyboard Components
Component Hints
Building a Keyboard Description Using the Server Database

The X server maintains a database of keyboard components, identified by
component type. The database contains all the information necessary to build a
complete keyboard description for a particular device, as well as to assemble
partial descriptions. Table 20.1 identifies the component types and the type of
information they contain.

Table 20.1. Server Database Keyboard Components

┌─────────────┬────────────────────────────────┬──────────────────────────────┐
│Component    │Component Primary Contents      │May also contain              │
│Type         │                                │                              │
├─────────────┼────────────────────────────────┼──────────────────────────────┤
│             │Complete keyboard description   │                              │
│             │                                │                              │
│Keymap       │Normally assembled using a      │                              │
│             │complete component from each of │                              │
│             │the other types                 │                              │
├─────────────┼────────────────────────────────┼──────────────────────────────┤
│             │                                │Aliases for some keys         │
│             │Symbolic name for each key      │                              │
│Keycodes     │                                │Symbolic names for indicators │
│             │Minimum and maximum legal       │                              │
│             │keycodes                        │Description of indicators     │
│             │                                │physically present            │
├─────────────┼────────────────────────────────┼──────────────────────────────┤
│             │                                │Real modifier bindings and    │
│Types        │Key types                       │symbolic names for some       │
│             │                                │virtual modifiers             │
├─────────────┼────────────────────────────────┼──────────────────────────────┤
│             │                                │Maps for some indicators      │
│             │Rules used to assign actions to │                              │
│Compatibility│keysyms                         │Real modifier bindings and    │
│             │                                │symbolic names for some       │
│             │                                │virtual modifiers             │
├─────────────┼────────────────────────────────┼──────────────────────────────┤
│             │Symbol mapping for keyboard keys│Explicit actions and behaviors│
│             │                                │for some keys                 │
│Symbols      │Modifier mapping                │                              │
│             │                                │Real modifier bindings and    │
│             │Symbolic names for groups       │symbolic names for some       │
│             │                                │virtual modifiers             │
├─────────────┼────────────────────────────────┼──────────────────────────────┤
│             │                                │Aliases for some keys;        │
│             │                                │overrides keycodes component  │
│             │                                │aliases                       │
│             │                                │                              │
│Geometry     │Layout of the keyboard          │Symbolic names for some       │
│             │                                │indicators                    │
│             │                                │                              │
│             │                                │Description of indicators     │
│             │                                │physically present            │
└─────────────┴────────────────────────────────┴──────────────────────────────┘


While a keymap is a database entry for a complete keyboard description, and
therefore logically different from the individual component database entries,
the rules for processing keymap entries are identical to those for the
individual components. In the discussion that follows, the term component is
used to refer to either individual components or a keymap.

There may be multiple entries for each of the component types. An entry may be
either complete or partial. Partial entries describe only a piece of the
corresponding keyboard component and are designed to be combined with other
entries of the same type to form a complete entry.

For example, a partial symbols map might describe the differences between a
common ASCII keyboard and some national layout. Such a partial map is not
useful on its own because it does not include those symbols that are the same
on both the ASCII and national layouts (such as function keys). On the other
hand, this partial map can be used to configure any ASCII keyboard to use a
national layout.

When a keyboard description is built, the components are processed in the order
in which they appear in Table 20.1; later definitions override earlier ones.

Component Names

Component names have the form “class(member)” where class describes a subset of
the available components for a particular type and the optional member
identifies a specific component from that subset. For example, the name
"atlantis(acme)" for a symbols component might specify the symbols used for the
atlantis national keyboard layout by the vendor "acme." Each class has an
optional default member — references that specify a class but not a member
refer to the default member of the class, if one exists. Xkb places no
constraints on the interpretation of the class and member names used in
component names.

The class and member names are both specified using characters from the Latin-1
character set. Xkb implementations must accept all alphanumeric characters,
minus (‘-’) and underscore (‘_’) in class or member names, and must not accept
parentheses, plus, vertical bar, percent sign, asterisk, question mark, or
white space. The use of other characters is implementation-dependent.

Listing the Known Keyboard Components

You may ask the server for a list of components for one or more component
types. The request takes the form of a set of patterns, one pattern for each of
the component types, including a pattern for the complete keyboard description.
To obtain this list, use XkbListComponents.

XkbComponentListPtr XkbListComponents(Display *dpy, unsigned int device_spec,
XkbComponentNamesPtr ptrns, int *max_inout);

dpy         connection to X server

device_spec device ID, or XkbUseCoreKbd

ptrns       namelist for components of interest

max_inout   max # returned names, # left over

XkbListComponents queries the server for a list of component names matching the
patterns specified in ptrns. It waits for a reply and returns the matching
component names in an XkbComponentListRec structure. When you are done using
the structure, you should free it using XkbFreeComponentList. device_spec
indicates a particular device in which the caller is interested. A server is
allowed (but not required) to restrict its reply to portions of the database
that are relevant for that particular device.

ptrns is a pointer to an XkbComponentNamesRec, described below. Each of the
fields in ptrns contains a pattern naming the components of interest. Each of
the patterns is composed of characters from the ISO Latin1 encoding, but can
contain only parentheses, the wildcard characters ‘?’ and ‘*’, and characters
permitted in a component class or member name (see section 20.1). A pattern may
be NULL, in which case no components for that type is returned. Pattern matches
with component names are case sensitive. The ‘?’ wildcard matches any single
character, except a left or right parenthesis; the ‘*’ wildcard matches any
number of characters, except a left or right parenthesis. If an implementation
allows additional characters in a component class or member name other than
those required by the Xkb extension (see section 20.1), the result of comparing
one of the additional characters to either of the wildcard characters is
implementation-dependent.

If a pattern contains illegal characters, the illegal characters are ignored.
The matching process is carried out as if the illegal characters were omitted
from the pattern.

max_inout is used to throttle the amount of data passed to and from the server.
On input, it specifies the maximum number of names to be returned (the total
number of names in all component categories). Upon return from
XkbListComponents, max_inout contains the number of names that matched the
request but were not returned because of the limit.

The component name patterns used to describe the request are passed to
XkbListComponents using an XkbComponentNamesRec structure. This structure has
no special allocation constraints or interrelationships with other structures;
allocate and free this structure using standard malloc and free calls or their
equivalent:

typedef struct _XkbComponentNames {
    char *       keymap;    /* keymap names */
    char *       keycodes;  /* keycode names */
    char *       types;     /* type names */
    char *       compat;    /* compatibility map names */
    char *       symbols;   /* symbol names */
    char *       geometry;  /* geometry names */
} XkbComponentNamesRec, *XkbComponentNamesPtr;

XkbListComponents returns a pointer to an XkbComponentListRec:

typedef struct _XkbComponentList {
    int                  num_keymaps;     /* number of entries in keymap */
    int                  num_keycodes;    /* number of entries in keycodes */
    int                  num_types;       /* number of entries in types */
    int                  num_compat;      /* number of entries in compat */
    int                  num_symbols;     /* number of entries in symbols */
    int                  num_geometry;    /* number of entries in geometry;
    XkbComponentNamePtr  keymap;          /* keymap names */
    XkbComponentNamePtr  keycodes;        /* keycode names */
    XkbComponentNamePtr  types;           /* type names */
    XkbComponentNamePtr  compat;          /* compatibility map names */
    XkbComponentNamePtr  symbols;         /* symbol names */
    XkbComponentNamePtr  geometry;        /* geometry names */
} XkbComponentListRec, *XkbComponentListPtr;

typedef struct _XkbComponentName {
    unsigned short       flags;           /* hints regarding component name */
    char *               name;            /* name of component */
} XkbComponentNameRec, *XkbComponentNamePtr;

Note that the structure used to specify patterns on input is an 
XkbComponentNamesRec, and that used to hold the individual component names upon
return is an XkbComponentNameRec (no trailing ‘s’ in Name).

When you are done using the structure returned by XkbListComponents, free it
using XkbFreeComponentList.

void XkbFreeComponentList(XkbComponentListPtr list);

list pointer to XkbComponentListRec to free

Component Hints

A set of flags is associated with each component; these flags provide
additional hints about the component’s use. These hints are designated by bit
masks in the flags field of the XkbComponentNameRec structures contained in the
XkbComponentListRec returned from XkbListComponents. The least significant byte
of the flags field has the same meaning for all types of keyboard components;
the interpretation of the most significant byte is dependent on the type of
component. The flags bits are defined in Table 20.2. The symbols hints in Table
20.2 apply only to partial symbols components (those with XkbLC_Partial also
set); full symbols components are assumed to specify all of the pieces.

The alphanumeric, modifier, keypad or function keys symbols hints should
describe the primary intent of the component designer and should not be simply
an exhaustive list of the kinds of keys that are affected. For example,
national keyboard layouts affect primarily alphanumeric keys, but many affect a
few modifier keys as well; such mappings should set only the 
XkbLC_AlphanumericKeys hint. In general, symbols components should set only one
of the four flags ( XkbLC_AlternateGroup may be combined with any of the other
flags).

Table 20.2. XkbComponentNameRec Flags Bits

┌─────────────┬──────────────────────┬──────────────────────────────────┬─────┐
│Component    │Component Hints       │Meaning                           │Value│
│Type         │(flags)               │                                  │     │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│All          │XkbLC_Hidden          │Do not present to user            │(1L  │
│Components   │                      │                                  │<<0) │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│             │XkbLC_Default         │Default member of class           │(1L  │
│             │                      │                                  │<<1) │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│             │XkbLC_Partial         │Partial component                 │(1L  │
│             │                      │                                  │<<2) │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│Keymap       │none                  │                                  │     │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│Keycodes     │none                  │                                  │     │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│Types        │none                  │                                  │     │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│Compatibility│none                  │                                  │     │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│Symbols      │XkbLC_AlphanumericKeys│Bindings primarily for            │(1L  │
│             │                      │alphanumeric keyboard section     │<<8) │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│             │XkbLC_ModifierKeys    │Bindings primarily for modifier   │(1L  │
│             │                      │keys                              │<<9) │
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│             │XkbLC_KeypadKeys      │Bindings primarily for numeric    │(1L  │
│             │                      │keypad keys                       │<<10)│
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│             │XkbLC_FunctionKeys    │Bindings primarily for function   │(1L  │
│             │                      │keys                              │<<11)│
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│             │XkbLC_AlternateGroup  │Bindings for an alternate group   │(1L  │
│             │                      │                                  │<<12)│
├─────────────┼──────────────────────┼──────────────────────────────────┼─────┤
│Geometry     │none                  │                                  │     │
└─────────────┴──────────────────────┴──────────────────────────────────┴─────┘


Building a Keyboard Description Using the Server Database

A client may request that the server fetch one or more components from its
database and use those components to build a new server keyboard description.
The new keyboard description may be built from scratch, or it may be built
starting with the current keyboard description for a particular device. Once
the keyboard description is built, all or part of it may be returned to the
client. The parts returned to the client need not include all of the parts used
to build the description. At the time it requests the server to build a new
keyboard description, a client may also request that the server use the new
description internally to replace the current keyboard description for a
specific device, in which case the behavior of the device changes accordingly.

To build a new keyboard description from a set of named components, and to
optionally have the server use the resulting description to replace an active
one, use XkbGetKeyboardByName.

XkbDescPtr XkbGetKeyboardByName(Display *dpy, unsigned int device_spec,
XkbComponentNamesPtr names, unsigned int want, unsigned int need, Bool load);

dpy         connection to X server

device_spec device ID, or XkbUseCoreKbd

names       names of components to fetch

want        desired structures in returned record

need        mandatory structures in returned record

load        True ⇒ load into device_spec

names contains a set of expressions describing the keyboard components the
server should use to build the new keyboard description. want and need are bit
fields describing the parts of the resulting keyboard description that should
be present in the returned XkbDescRec.

The individual fields in names are component expressions composed of keyboard
component names (no wildcarding as may be used in XkbListComponents), the
special component name symbol ‘%’, and the special operator characters ‘+’ and
‘|’. A component expression is parsed left to right, as follows:

  • The special component name “computed” may be used in keycodes component
    expressions and refers to a component consisting of a set of keycodes
    computed automatically by the server as needed.

  • The special component name “canonical” may be used in types component
    expressions and refers to a partial component defining the four standard
    key types: ALPHABETIC, ONE_LEVEL, TWO_LEVEL, and KEYPAD.

  • The special component name ‘%’ refers to the keyboard description for the
    device specified in device_spec or the keymap names component. If a keymap
    names component is specified that does not begin with ‘+’ or ‘|’ and does
    not contain ‘%’, then ‘%’ refers to the description generated by the keymap
    names component. Otherwise, it refers to the keyboard description for
    device_spec.

  • The ‘+’ operator specifies that the following component should override the
    currently assembled description; any definitions that are present in both
    components are taken from the second.

  • The ‘|’ operator specifies that the next specified component should augment
    the currently assembled description; any definitions that are present in
    both components are taken from the first.

  • If the component expression begins with an operator, a leading ‘%’ is
    implied.

  • If any unknown or illegal characters appear anywhere in the expression, the
    entire expression is invalid and is ignored.

For example, if names->symbols contained the expression "+de", it specifies
that the default member of the "de" class of symbols should be applied to the
current keyboard mapping, overriding any existing definitions (it could also be
written "+de(default)").

Here is a slightly more involved example: the expression "acme(ascii)+de(basic)
|iso9995-3" constructs a German (de) mapping for the ASCII keyboard supplied by
the "acme" vendor. The new definition begins with the symbols for the ASCII
keyboard for Acme (acme(ascii)), overrides them with definitions for the basic
German keyboard (de(basic)), and then applies the definitions from the default
iso9995-3 keyboard ( iso9995-3) to any undefined keys or groups of keys (part
three of the iso9995 standard defines a common set of bindings for the
secondary group, but allows national layouts to override those definitions
where necessary).

Note

The interpretation of the above expression components (acme, ascii, de, basic,
iso9995-3) is not defined by Xkb; only the operations and their ordering are.

Note that the presence of a keymap names component that does not contain ‘%’
(either explicit or implied by virtue of an expression starting with an
operator) indicates a description that is independent of the keyboard
description for the device specified in device_spec. The same is true of
requests in which the keymap names component is empty and all five other names
components contain expressions void of references to ‘%’. Requests of this form
allow you to deal with keyboard definitions independent of any actual device.

The server parses all non- NULL fields in names and uses them to build a
keyboard description. However, before parsing the expressions in names, the
server ORs the bits in want and need together and examines the result in
relationship to the expressions in names. Table 20.3 identifies the components
that are required for each of the possible bits in want or need. If a required
component has not been specified in the names structure (the corresponding
field is NULL), the server substitutes the expression “%”, resulting in the
component values being taken from device_spec. In addition, if load is True,
the server modifies names if necessary (again using a “%” entry) to ensure all
of the following fields are non- NULL: types, keycodes, symbols, and compat.

Table 20.3. Want and Need Mask Bits and Required Names Components

┌────────────────────────┬────────────────────────────────────────────┬───────┐
│want or need mask bit   │Required names Components                   │value  │
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_TypesMask        │Types                                       │(1L<<0)│
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_CompatMapMask    │Compat                                      │(1L<<1)│
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_ClientSymbolsMask│Types + Symbols + Keycodes                  │(1L<<2)│
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_ServerSymbolsMask│Types + Symbols + Keycodes                  │(1L<<3)│
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_SymbolsMask      │Symbols                                     │(1L<<1)│
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_IndicatorMapMask │Compat                                      │(1L<<4)│
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_KeyNamesMask     │Keycodes                                    │(1L<<5)│
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_GeometryMask     │Geometry                                    │(1L<<6)│
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_OtherNamesMask   │Types + Symbols + Keycodes + Compat +       │(1L<<7)│
│                        │Geometry                                    │       │
├────────────────────────┼────────────────────────────────────────────┼───────┤
│XkbGBN_AllComponentsMask│                                            │(0xff) │
└────────────────────────┴────────────────────────────────────────────┴───────┘


need specifies a set of keyboard components that the server must be able to
resolve in order for XkbGetKeyboardByName to succeed; if any of the components
specified in need cannot be successfully resolved, XkbGetKeyboardByName fails.

want specifies a set of keyboard components that the server should attempt to
resolve, but that are not mandatory. If the server is unable to resolve any of
these components, XkbGetKeyboardByName still succeeds. Bits specified in want
that are also specified in need have no effect in the context of want.

If load is True, the server updates its keyboard description for device_spec to
match the result of the keyboard description just built. If load is False, the
server’s description for device device_spec is not updated. In all cases, the
parts specified by want and need from the just-built keyboard description are
returned.

The names structure in an XkbDescRec keyboard description record (see
Chapter 18, Symbolic Names) contains one field for each of the five component
types used to build a keyboard description. When a keyboard description is
built from a set of database components, the corresponding fields in this names
structure are set to match the expressions used to build the component.

The entire process of building a new keyboard description from the server
database of components and returning all or part of it is diagrammed in Figure
20.1:

Figure 20.1. Building a New Keyboard Description from the Server Database


The information returned to the client in the XkbDescRec is essentially the
result of a series of calls to extract information from a fictitious device
whose description matches the one just built. The calls corresponding to each
of the mask bits are summarized in Table 20.4, together with the XkbDescRec
components that are filled in.

Table 20.4. XkbDescRec Components Returned for Values of Want & Needs

┌────────────────────────┬──────────────────┬─────────────────────────────────┐
│Request (want+need)     │Fills in Xkb      │Equivalent Function Call         │
│                        │components        │                                 │
├────────────────────────┼──────────────────┼─────────────────────────────────┤
│XkbGBN_TypesMask        │map.types         │XkbGetUpdatedMap(dpy,            │
│                        │                  │XkbTypesMask, Xkb)               │
├────────────────────────┼──────────────────┼─────────────────────────────────┤
│XkbGBN_ServerSymbolsMask│server            │XkbGetUpdatedMap(dpy,            │
│                        │                  │XkbAllClientInfoMask, Xkb)       │
├────────────────────────┼──────────────────┼─────────────────────────────────┤
│XkbGBN_ClientSymbolsMask│map, including    │XkbGetUpdatedMap(dpy,            │
│                        │map.types         │XkbAllServerInfoMask, Xkb)       │
├────────────────────────┼──────────────────┼─────────────────────────────────┤
│XkbGBN_IndicatorMaps    │indicators        │XkbGetIndicatorMap(dpy,          │
│                        │                  │XkbAllIndicators, Xkb)           │
├────────────────────────┼──────────────────┼─────────────────────────────────┤
│XkbGBN_CompatMapMask    │compat            │XkbGetCompatMap(dpy,             │
│                        │                  │XkbAllCompatMask, Xkb)           │
├────────────────────────┼──────────────────┼─────────────────────────────────┤
│XkbGBN_GeometryMask     │geom              │XkbGetGeometry(dpy, Xkb)         │
├────────────────────────┼──────────────────┼─────────────────────────────────┤
│                        │names.keys        │XkbGetNames(dpy, XkbKeyNamesMask │
│XkbGBN_KeyNamesMask     │                  │| XkbKeyAliasesMask, Xkb)        │
│                        │names.key_aliases │                                 │
├────────────────────────┼──────────────────┼─────────────────────────────────┤
│                        │names.keycodes    │                                 │
│                        │                  │                                 │
│                        │names.geometry    │                                 │
│                        │                  │                                 │
│                        │names.symbols     │                                 │
│                        │                  │                                 │
│                        │names.types       │                                 │
│                        │                  │XkbGetNames(dpy, XkbAllNamesMask │
│                        │map.types         │&                                │
│                        │[*].lvl_names[*]  │                                 │
│XkbGBN_OtherNamesMask   │                  │~(XkbKeyNamesMask |              │
│                        │names.compat      │XkbKeyAliasesMask),              │
│                        │                  │                                 │
│                        │names.vmods       │Xkb)                             │
│                        │                  │                                 │
│                        │names.indicators  │                                 │
│                        │                  │                                 │
│                        │names.groups      │                                 │
│                        │                  │                                 │
│                        │names.radio_groups│                                 │
│                        │                  │                                 │
│                        │names.phys_symbols│                                 │
└────────────────────────┴──────────────────┴─────────────────────────────────┘


There is no way to determine which components specified in want (but not in
need) were actually fetched, other than breaking the call into successive calls
to XkbGetKeyboardByName and specifying individual components.

XkbGetKeyboardByName always sets min_key_code and max_key_code in the returned 
XkbDescRec structure.

XkbGetKeyboardByName is synchronous; it sends the request to the server to
build a new keyboard description and waits for the reply. If successful, the
return value is non-NULL. XkbGetKeyboardByName generates a BadMatch protocol
error if errors are encountered when building the keyboard description.

If you simply want to obtain information about the current keyboard device,
rather than generating a new keyboard description from elements in the server
database, use XkbGetKeyboard (see section 6.2).

XkbDescPtr XkbGetKeyboard(Display *dpy, unsigned int which, unsigned int
device_spec);

dpy         connection to X server

which       mask of components of XkbDescRec of interest

device_spec device ID

XkbGetKeyboard is used to read the current description for one or more
components of a keyboard device. It calls XkbGetKeyboardByName as follows:

XkbGetKeyboardByName ( dpy, device_spec, NULL, which, which, False).

Chapter 21. Attaching Xkb Actions to X Input Extension Devices

Table of Contents

XkbDeviceInfoRec
Querying Xkb Features for Non-KeyClass Input Extension Devices
Allocating, Initializing, and Freeing the XkbDeviceInfoRec Structure
Setting Xkb Features for Non-KeyClass Input Extension Devices
XkbExtensionDeviceNotify Event
Tracking Changes to Extension Devices

The X input extension allows an X server to support multiple keyboards, as well
as other input devices, in addition to the core X keyboard and pointer. The
input extension categorizes devices by grouping them into classes. Keyboards
and other input devices with keys are classified as KeyClass devices by the
input extension. Other types of devices supported by the input extension
include, but are not limited to: mice, tablets, touchscreens, barcode readers,
button boxes, trackballs, identifier devices, data gloves, and eye trackers.
Xkb provides additional control over all X input extension devices, whether
they are KeyClass devices or not, as well as the core keyboard and pointer.

If an X server implements support for both the input extension and Xkb, the
server implementor determines whether interaction between Xkb and the input
extension is allowed. Implementors are free to restrict the effects of Xkb to
only the core X keyboard device or allow interaction between Xkb and the input
extension.

Several types of interaction between Xkb and the input extension are defined by
Xkb. Some or all may be allowed by the X server implementation.

Regardless of whether the server allows interaction between Xkb and the input
extension, the following access is provided:

  • Xkb functionality for the core X keyboard device and its mapping is
    accessed via the functions described in the other chapters of this
    specification.

  • Xkb functionality for the core X pointer device is accessed via the
    XkbGetDeviceInfo and XkbSetDeviceInfo functions described in this chapter.

If all types of interaction are allowed between Xkb and the input extension,
the following additional access is provided:

  • If allowed, Xkb functionality for additional KeyClass devices supported by
    the input extension is accessed via those same functions.

  • If allowed, Xkb functionality for non- KeyClass devices supported by the
    input extension is also accessed via the XkbGetDeviceInfo and
    XkbSetDeviceInfo functions described in this chapter.

Each device has an X Input Extension device ID. Each device may have several
classes of feedback. For example, there are two types of feedbacks that can
generate bells: bell feedback and keyboard feedback (BellFeedbackClass and 
KbdFeedbackClass). A device can have more than one feedback of each type; the
feedback ID identifies the particular feedback within its class.

A keyboard feedback has:

  • Auto-repeat status (global and per key)

  • 32 LEDs

  • A bell

An indicator feedback has:

  • Up to 32 LEDs

If the input extension is present and the server allows interaction between the
input extension and Xkb, then the core keyboard, the core keyboard indicators,
and the core keyboard bells may each be addressed using an appropriate device
spec, class, and ID. The constant XkbDfltXIId may be used as the device ID to
specify the core keyboard indicators for the core indicator feedback. The
particular device ID corresponding to the core keyboard feedback and the core
indicator feedback may be obtained by calling XkbGetDeviceInfo and specifying 
XkbUseCoreKbd as the device_spec; the values will be returned in dflt_kbd_fb
and dflt_led_fb.

If the server does not allow Xkb access to input extension KeyClass devices,
attempts to use Xkb requests with those devices fail with a BadKeyboard error.
Attempts to access non- KeyClass input extension devices via XkbGetDeviceInfo
and XkbSetDeviceInfo fail silently if Xkb access to those devices is not
supported by the X server.

XkbDeviceInfoRec

Information about X Input Extension devices is transferred between a client
program and the Xkb extension in an XkbDeviceInfoRec structure:

typedef struct {
    char *          name;          /* name for device */
    Atom            type;          /* name for class of devices */
    unsigned short  device_spec;   /* device of interest */
    Bool            has_own_state; /* True ⇒ this device has
                                      its own state */
    unsigned short  supported;     /* bits indicating supported capabilities */
    unsigned short  unsupported;   /* bits indicating unsupported capabilities */
    unsigned short  num_btns;      /* number of entries in btn_acts */
    XkbAction *     btn_acts;      /* button actions */
    unsigned short  sz_leds;       /* total number of entries in LEDs vector */
    unsigned short  num_leds;      /* number of valid entries in LEDs vector */
    unsigned short  dflt_kbd_fb;   /* input extension ID of default
                                      (core kbd) indicator */
    unsigned short  dflt_led_fb;   /* input extension ID of default
                                      indicator feedback */
    XkbDeviceLedInfoPtr  leds;     /* LED descriptions */
} XkbDeviceInfoRec, *XkbDeviceInfoPtr;

typedef struct {
    unsigned short  led_class;     /* class for this LED device */
    unsigned short  led_id;        /* ID for this LED device */
    unsigned int    phys_indicators; /* bits for which LEDs physically present */
    unsigned int    maps_present;  /* bits for which LEDs have maps in maps */
    unsigned int    names_present; /* bits for which LEDs are in names */
    unsigned int    state;         /* 1 bit ⇒ corresponding LED is on */
    Atom            names[XkbNumIndicators]; /* names for LEDs */
    XkbIndicatorMapRec  maps;      /* indicator maps for each LED */
} XkbDeviceLedInfoRec, *XkbDeviceLedInfoPtr;

The type field is a registered symbolic name for a class of devices (for
example, "TABLET"). If a device is a keyboard (that is, is a member of KeyClass
), it has its own state, and has_own_state is True. If has_own_state is False,
the state of the core keyboard is used. The supported and unsupported fields
are masks where each bit indicates a capability. The meaning of the mask bits
is listed in Table 21.1, together with the fields in the XkbDeviceInfoRec
structure that are associated with the capability represented by each bit. The
same bits are used to indicate the specific information desired in many of the
functions described subsequently in this section.

Table 21.1. XkbDeviceInfoRec Mask Bits

┌─────────────────────────────┬────────────────┬────────┬──────────────────────────────┐
│Name                         │XkbDeviceInfoRec│Value   │Capability If Set             │
│                             │Fields Effected │        │                              │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│                             │                │        │Clients can use all Xkb       │
│XkbXI_KeyboardsMask          │                │(1L <<  │requests and events with      │
│                             │                │0)      │KeyClass devices supported by │
│                             │                │        │the input device extension.   │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│                             │num_btns        │        │Clients can assign key actions│
│XkbXI_ButtonActionsMask      │                │(1L <<1)│to buttons on non- KeyClass   │
│                             │btn_acts        │        │input extension devices.      │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│                             │                │        │Clients can assign names to   │
│XkbXI_IndicatorNamesMask     │leds->names     │(1L <<2)│indicators on non- KeyClass   │
│                             │                │        │input extension devices.      │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│                             │                │        │Clients can assign indicator  │
│XkbXI_IndicatorMapsMask      │leds->maps      │(1L <<3)│maps to indicators on non-    │
│                             │                │        │KeyClass input extension      │
│                             │                │        │devices.                      │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│                             │                │        │Clients can request the status│
│XkbXI_IndicatorStateMask     │leds->state     │(1L <<4)│of indicators on non- KeyClass│
│                             │                │        │input extension devices.      │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│                             │sz_leds         │        │XkbXI_IndicatorNames­Mask |   │
│                             │                │        │                              │
│XkbXI_IndicatorsMask         │num_leds        │(0x1c)  │XkbXI_IndicatorMaps­Mask |    │
│                             │                │        │                              │
│                             │leds->*         │        │XkbXI_IndicatorState­Mask     │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│XkbXI_UnsupportedFeaturesMask│unsupported     │(1L     │                              │
│                             │                │<<15)   │                              │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│                             │Those selected  │        │XkbXI_Indicators­Mask |       │
│XkbXI_AllDeviceFeaturesMask  │by Value column │(0x1e)  │                              │
│                             │masks           │        │XkbXI_ButtonActions­Mask      │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│                             │Those selected  │        │XkbXI_AllDevice­FeaturesMask |│
│XkbXI_AllFeaturesMask        │by Value column │(0x1f)  │                              │
│                             │masks           │        │XkbXI_Keyboards­Mask          │
├─────────────────────────────┼────────────────┼────────┼──────────────────────────────┤
│                             │Those selected  │        │XkbXI_AllFeatures­Mask |      │
│XkbXI_AllDetailsMask         │by Value column │(0x801f)│                              │
│                             │masks           │        │XkbXI_Unsupported­FeaturesMask│
└─────────────────────────────┴────────────────┴────────┴──────────────────────────────┘


The name, type, has_own_state, supported, and unsupported fields are always
filled in when a valid reply is returned from the server involving an 
XkbDeviceInfoRec. All of the other fields are modified only if the particular
function asks for them.

Querying Xkb Features for Non-KeyClass Input Extension Devices

To determine whether the X server allows Xkb access to particular capabilities
of input devices other than the core X keyboard, or to determine the status of
indicator maps, indicator names or button actions on a non- KeyClass extension
device, use XkbGetDeviceInfo.

XkbDeviceInfoPtr XkbGetDeviceInfo(Display *dpy, unsigned int which, unsigned
int device_spec, unsigned int ind_class, unsigned int ind_id);

dpy         connection to X server

which       mask indicating information to return

device_spec device ID, or XkbUseCoreKbd

ind_class   feedback class for indicator requests

ind_id      feedback ID for indicator requests

XkbGetDeviceInfo returns information about the input device specified by
device_spec. Unlike the device_spec parameter of most Xkb functions,
device_spec does not need to be a keyboard device. It must, however, indicate
either the core keyboard or a valid X Input Extension device.

The which parameter is a mask specifying optional information to be returned.
It is an inclusive OR of one or more of the values from Table 21.1 and causes
the returned XkbDeviceInfoRec to contain values for the corresponding fields
specified in the table.

The XkbDeviceInfoRec returned by XkbGetDeviceInfo always has values for name
(may be a null string, ""), type, supported, unsupported, has_own_state,
dflt_kbd_fb, and dflt_led_fb. Other fields are filled in as specified by which.

Upon return, the supported field will be set to the inclusive OR of zero or
more bits from Table 21.1; each bit set indicates an optional Xkb extension
device feature supported by the server implementation, and a client may modify
the associated behavior.

If the XkbXI_ButtonActionsMask bit is set in which, the XkbDeviceInfoRec
returned will have the button actions (btn_acts field) filled in for all
buttons.

If which includes one of the bits in XkbXI_IndicatorsMask, the feedback class
of the indicators must be specified in ind_class, and the feedback ID of the
indicators must be specified in ind_id. If the request does not include any of
the bits in XkbXI_IndicatorsMask, the ind_class and ind_id parameters are
ignored. The class and ID can be obtained via the input device extension
XListInputDevices request.

If any of the XkbXI_IndicatorsMask bits are set in which, the XkbDeviceInfoRec
returned will have filled in the portions of the leds structure corresponding
to the indicator feedback identified by ind_class and ind_id. The leds vector
of the XkbDeviceInfoRec is allocated if necessary and sz_leds and num_leds
filled in. The led_class, led_id and phys_indicators fields of the leds entry
corresponding to ind_class and ind_id are always filled in. If which contains 
XkbXI_IndicatorNamesMask, the names_present and names fields of the leds
structure corresponding to ind_class and ind_id are returned. If which contains
XkbXI_IndicatorStateMask, the corresponding state field is updated. If which
contains XkbXI_IndicatorMapsMask, the maps_present and maps fields are updated.

Xkb provides convenience functions to request subsets of the information
available via XkbGetDeviceInfo. These convenience functions mirror some of the
mask bits. The functions all take an XkbDeviceInfoPtr as an input argument and
operate on the X Input Extension device specified by the device_spec field of
the structure. Only the parts of the structure indicated in the function
description are updated. The XkbDeviceInfoRec structure used in the function
call can be obtained by calling XkbGetDeviceInfo or can be allocated by calling
XkbAllocDeviceInfo (see section 21.3).

These convenience functions are described as follows.

To query the button actions associated with an X Input Extension device, use
XkbGetDeviceButtonActions.

Status XkbGetDeviceButtonActions(Display *dpy, XkbDeviceInfoPtr device_info,
Bool all_buttons, unsigned int first_button, unsigned int num_buttons);

dpy          connection to X server

device_info  structure to update with results

all_buttons  True ⇒ get information for all buttons

first_button number of first button for which info is desired

num_buttons  number of buttons for which info is desired

XkbGetDeviceButtonActions queries the server for the desired button information
for the device indicated by the device_spec field of device_info and waits for
a reply. If successful, XkbGetDeviceButtonActions backfills the button actions
(btn_acts field of device_info) for only the requested buttons, updates the
name, type, supported, and unsupported fields, and returns Success.

all_buttons, first_button and num_buttons specify the device buttons for which
actions should be returned. Setting all_buttons to True requests actions for
all device buttons; if all_buttons is False, first_button and num_buttons
specify a range of buttons for which actions are requested.

If a compatible version of Xkb is not available in the server or the Xkb
extension has not been properly initialized, XkbGetDeviceButtonActions returns 
BadAccess. If allocation errors occur, a BadAlloc status is returned. If the
specified device (device_info->device_spec) is invalid, a BadKeyboard status is
returned. If the device has no buttons, a BadMatch status is returned. If
first_button and num_buttons specify illegal buttons, a BadValue status is
returned.

To query the indicator names, maps, and state associated with an LED feedback
of an input extension device, use XkbGetDeviceLedInfo.

Status XkbGetDeviceLedInfo(Display *dpy, XkbDeviceInfoPtr device_info, unsigned
int led_class, unsigned int led_id, unsigned int which);

dpy         connection to X server

device_info structure to update with results

led_class   LED feedback class assigned by input extension

led_id      LED feedback ID assigned by input extension

which       mask indicating desired information

XkbGetDeviceLedInfo queries the server for the desired LED information for the
feedback specified by led_class and led_id for the X input extension device
indicated by device_spec->device_info and waits for a reply. If successful,
XkbGetDeviceLedInfo backfills the relevant fields of device_info as determined
by which with the results and returns Success. Valid values for which are the
inclusive OR of any of XkbXI_IndicatorNamesMask, XkbXI_IndicatorMapsMask, and 
XkbXI_IndicatorStateMask.

The fields of device_info that are filled in when this request succeeds are
name, type, supported, and unsupported, and portions of the leds structure
corresponding to led_class and led_id as indicated by the bits set in which.
The device_info->leds vector is allocated if necessary and sz_leds and num_leds
filled in. The led_class, led_id and phys_indicators fields of the device_info
->leds entry corresponding to led_class and led_id are always filled in.

If which contains XkbXI_IndicatorNamesMask, the names_present and names fields
of the device_info->leds structure corresponding to led_class and led_id are
updated, if which contains XkbXI_IndicatorStateMask, the corresponding state
field is updated, and if which contains XkbXI_IndicatorMapsMask, the
maps_present and maps fields are updated.

If a compatible version of Xkb is not available in the server or the Xkb
extension has not been properly initialized, XkbGetDeviceLedInfo returns 
BadAccess. If allocation errors occur, a BadAlloc status is returned. If the
device has no indicators, a BadMatch error is returned. If ledClass or ledID
have illegal values, a BadValue error is returned. If they have legal values
but do not specify a feedback that contains LEDs and is associated with the
specified device, a BadMatch error is returned.

Allocating, Initializing, and Freeing the XkbDeviceInfoRec Structure

To obtain an XkbDeviceInfoRec structure, use XkbGetDeviceInfo or
XkbAllocDeviceInfo.

XkbDeviceInfoPtr XkbAllocDeviceInfo(unsigned int device_spec, unsigned int
n_buttons, unsigned int sz_leds);

device_spec device ID with which structure will be used

n_buttons   number of button actions to allocate space for

sz_leds     number of LED feedbacks to allocate space for

XkbAllocDeviceInfo allocates space for an XkbDeviceInfoRec structure and
initializes that structure’s device_spec field with the device ID specified by
device_spec. If n_buttons is nonzero, n_buttons XkbActions are linked into the 
XkbDeviceInfoRec structure and initialized to zero. If sz_leds is nonzero,
sz_leds XkbDeviceLedInfoRec structures are also allocated and linked into the 
XkbDeviceInfoRec structure. If you request XkbDeviceLedInfoRec structures be
allocated using this request, you must initialize them explicitly.

To initialize an XkbDeviceLedInfoRec structure, use XkbAddDeviceLedInfo.

XkbDeviceLedInfoPtr XkbAddDeviceLedInfo(XkbDeviceInfoPtr device_info, unsigned
int led_class, unsigned int led_id);

device_info structure in which to add LED info

led_class   input extension class for LED device of interest

led_id      input extension ID for LED device of interest

XkbAddDeviceLedInfo first checks to see whether an entry matching led_class and
led_id already exists in the device_info->leds array. If it finds a matching
entry, it returns a pointer to that entry. Otherwise, it checks to be sure
there is at least one empty entry in device_info->leds and extends it if there
is not enough room. It then increments device_info->num_leds and fills in the
next available entry in device_info->leds with led_class and led_id.

If successful, XkbAddDeviceLedInfo returns a pointer to the XkbDeviceLedInfoRec
structure that was initialized. If unable to allocate sufficient storage, or if
device_info points to an invalid XkbDeviceInfoRec structure, or if led_class or
led_id are inappropriate, XkbAddDeviceLedInfo returns NULL.

To allocate additional space for button actions in an XkbDeviceInfoRec
structure, use XkbResizeDeviceButtonActions.

Status XkbResizeDeviceButtonActions(XkbDeviceInfoPtr device_info, unsigned int
new_total);

device_info structure in which to allocate button actions

new_total   new total number of button actions needed

XkbResizeDeviceButtonActions reallocates space, if necessary, to make sure
there is room for a total of new_total button actions in the device_info
structure. Any new entries allocated are zeroed. If successful,
XkbResizeDeviceButtonActions returns Success. If new_total is zero, all button
actions are deleted, device_info->num_btns is set to zero, and device_info->
btn_acts is set to NULL. If device_info is invalid or new_total is greater than
255, BadValue is returned. If a memory allocation failure occurs, a BadAlloc is
returned.

To free an XkbDeviceInfoRec structure, use XkbFreeDeviceInfo.

void XkbFreeDeviceInfo(XkbDeviceInfoPtr device_info, unsigned int which, Bool
free_all);

device_info pointer to XkbDeviceInfoRec in which to free items

which       mask of components of device_info to free

free_all    True ⇒ free everything, including device_info

If free_all is True, the XkbFreeDeviceInfo frees all components of device_info
and the XkbDeviceInfoRec structure pointed to by device_info itself. If
free_all is False, the value of which determines which subcomponents are freed.
which is an inclusive OR of one or more of the values from Table 21.1. If which
contains XkbXI_ButtonActionsMask, all button actions associated with
device_info are freed, device_info->btn_acts is set to NULL, and device_info->
num_btns is set to zero. If which contains all bits in XkbXI_IndicatorsMask,
all XkbDeviceLedInfoRec structures associated with device_info are freed,
device_info->leds is set to NULL, and device_info->sz_leds and device_info->
num_leds are set to zero. If which contains XkbXI_IndicatorMapsMask, all
indicator maps associated with device_info are cleared, but the number of LEDs
and the leds structures themselves are preserved. If which contains 
XkbXI_IndicatorNamesMask, all indicator names associated with device_info are
cleared, but the number of LEDs and the leds structures themselves are
preserved. If which contains XkbXI_IndicatorStateMask, the indicator state
associated with the device_info leds are set to zeros but the number of LEDs
and the leds structures themselves are preserved.

Setting Xkb Features for Non-KeyClass Input Extension Devices

The Xkb extension allows clients to assign any key action to either core
pointer or input extension device buttons. This makes it possible to control
the keyboard or generate keyboard key events from extension devices or from the
core pointer.

Key actions assigned to core X pointer buttons or input extension device
buttons cause key events to be generated as if they had originated from the
core X keyboard.

Xkb implementations are required to support key actions for the buttons of the
core pointer device, but support for actions on extension devices is optional.
Implementations that do not support button actions for extension devices must
not set the XkbXI_ButtonActionsMask bit in the supported field of an 
XkbDeviceInfoRec structure.

If a client attempts to modify valid characteristics of a device using an
implementation that does not support modification of those characteristics, no
protocol error is generated. Instead, the server reports a failure for the
request; it also sends an XkbExtensionDeviceNotify event to the client that
issued the request if the client has selected to receive these events.

To change characteristics of an X Input Extension device in the server, first
modify a local copy of the device structure and then use either
XkbSetDeviceInfo, or, to save network traffic, use an XkbDeviceChangesRec
structure (see section 21.6) and call XkbChangeDeviceInfo to download the
changes to the server.

To modify some or all of the characteristics of an X Input Extension device,
use XkbSetDeviceInfo.

Bool XkbSetDeviceInfo(Display *dpy, unsigned int which, XkbDeviceInfoPtr
device_info);

dpy         connection to X server

which       mask indicating characteristics to modify

device_info structure defining the device and modifications

XkbSetDeviceInfo sends a request to the server to modify the characteristics of
the device specified in the device_info structure. The particular
characteristics modified are identified by the bits set in which and take their
values from the relevant fields in device_info (see Table 21.1).
XkbSetDeviceInfo returns True if the request was successfully sent to the
server. If the X server implementation does not allow interaction between the X
input extension and the Xkb Extension, the function does nothing and returns 
False.

The which parameter specifies which aspects of the device should be changed and
is a bitmask composed of an inclusive OR or one or more of the following bits: 
XkbXI_ButtonActionsMask, XkbXI_IndicatorNamesMask, XkbXI_IndicatorMapsMask. If
the features requested to be manipulated in which are valid for the device, but
the server does not support assignment of one or more of them, that particular
portion of the request is ignored.

If the device specified in device_info->device_spec does not contain buttons
and a request affecting buttons is made, or the device does not contain
indicators and a request affecting indicators is made, a BadMatch protocol
error results.

If the XkbXI_ButtonActionsMask bit is set in the supported mask returned by
XkbGetDeviceInfo, the Xkb extension allows applications to assign key actions
to buttons on input extension devices other than the core keyboard device. If
the XkbXI_ButtonActionsMask is set in which, the actions for all buttons
specified in device_info are set to the XkbActions specified in device_info->
btn_acts. If the number of buttons requested to be updated is not valid for the
device, XkbSetDeviceInfo returns False and a BadValue protocol error results.

If the XkbXI_IndicatorMapsMask and / or XkbXI_IndicatorNamesMask bit is set in
the supported mask returned by XkbGetDeviceInfo, the Xkb extension allows
applications to assign maps and / or names to the indicators of nonkeyboard
extension devices. If supported, maps and / or names can be assigned to all
extension device indicators, whether they are part of a keyboard feedback or
part of an indicator feedback.

If the XkbXI_IndicatorMapsMask and / or XkbXI_IndicatorNamesMask flag is set in
which, the indicator maps and / or names for all device_info->num_leds
indicator devices specified in device_info->leds are set to the maps and / or
names specified in device_info->leds. device_info->leds->led_class and led_id
specify the input extension class and device ID for each indicator device to
modify; if they have invalid values, a BadValue protocol error results and
XkbSetDeviceInfo returns False. If they have legal values but do not specify a
keyboard or indicator class feedback for the device in question, a BadMatch
error results. If any of the values in device_info->leds->names are not a valid
Atom or None, a BadAtom protocol error results.

Xkb provides convenience functions to modify subsets of the information
accessible via XkbSetDeviceInfo. Only the parts of the structure indicated in
the function description are modified. These convenience functions are
described as follows.

To change only the button actions for an input extension device, use
XkbSetDeviceButtonActions.

Bool XkbSetDeviceButtonActions(Display *dpy, XkbDeviceInfoPtr device_info,
unsigned int first_button, unsigned int num_buttons);

dpy          connection to X server

device_info  structure defining the device and modifications

first_button number of first button to update, 0 relative

num_buttons  number of buttons to update

XkbSetDeviceButtonActions assigns actions to the buttons of the device
specified in device_info->device_spec. Actions are assigned to num_buttons
buttons beginning with first_button and are taken from the actions specified in
device_info->btn_acts.

If the server does not support assignment of Xkb actions to extension device
buttons, XkbSetDeviceButtonActions has no effect and returns False. If the
device has no buttons or if first_button or num_buttons specify buttons outside
of the valid range as determined by device_info->num_btns, the function has no
effect and returns False. Otherwise, XkbSetDeviceButtonActions sends a request
to the server to change the actions for the specified buttons and returns True.

If the actual request sent to the server involved illegal button numbers, a 
BadValue protocol error is generated. If an invalid device identifier is
specified in device_info->device_spec, a BadKeyboard protocol error results. If
the actual device specified in device_info->device_spec does not contain
buttons and a request affecting buttons is made, a BadMatch protocol error is
generated.

XkbExtensionDeviceNotify Event

The Xkb extension generates XkbExtensionDeviceNotify events when the status of
an input extension device changes or when an attempt is made to use an Xkb
feature that is not supported by a particular device.

Note

Events indicating an attempt to use an unsupported feature are delivered only
to the client requesting the event.

To track changes to the status of input extension devices or attempts to use
unsupported features of a device, select to receive XkbExtensionDeviceNotify
events by calling either XkbSelectEvents or XkbSelectEventDetails (see section
4.3).

To receive XkbExtensionDeviceNotify events under all possible conditions, call
XkbSelectEvents and pass XkbExtensionDeviceNotifyMask in both bits_to_change
and values_for_bits.

The XkbExtensionDeviceNotify event has no event details. However, you can call
XkbSelectEventDetails using XkbExtensionDeviceNotify as the event_type and
specifying XkbAllExtensionDeviceEventsMask in bits_to_change and
values_for_bits. This has the same effect as a call to XkbSelectEvents.

The structure for XkbExtensionDeviceNotify events is:

typedef struct {
    int            type;           /* Xkb extension base event code */
    unsigned long  serial;         /* X server serial number for event */
    Bool           send_event;     /* True ⇒ synthetically generated */
    Display *      display;        /* server connection where event generated */
    Time           time;           /* server time when event generated */
    int            xkb_type;       /* XkbExtensionDeviceNotifyEvent */
    int            device;         /* Xkb device ID, will not be XkbUseCoreKbd */
    unsigned int   reason;         /* reason for the event */
    unsigned int   supported;      /* mask of supported features */
    unsigned int   unsupported;    /* unsupported features this client
                                      attempted to use */
    int            first_btn;      /* first button that changed */
    int            num_btns;       /* number of buttons that changed */
    unsigned int   leds_defined;   /* indicators with names or maps */
    unsigned int   led_state;      /* current state of the indicators */
    int            led_class;      /* feedback class for LED changes */
    int            led_id;         /* feedback ID for LED changes */
} XkbExtensionDeviceNotifyEvent;

The XkbExtensionDeviceNotify event has fields enabling it to report changes in
the state (on/off) of all of the buttons for a device, but only for one LED
feedback associated with a device. You will get multiple events when more than
one LED feedback changes state or configuration.

Tracking Changes to Extension Devices

Changes to an Xkb extension device may be tracked by listening to 
XkbExtensionDeviceNotify events and accumulating the changes in an 
XkbDeviceChangesRec structure. The changes noted in the structure may then be
used in subsequent operations to update either a server configuration or a
local copy of an Xkb extension device configuration. The changes structure is
defined as follows:

typedef struct _XkbDeviceChanges {
    unsigned int    changed;      /* bits indicating what has changed */
    unsigned short  first_btn;    /* number of first button which changed,
                                     if any */
    unsigned short  num_btns;     /* number of buttons that have changed */
    XkbDeviceLedChangesRec leds;
} XkbDeviceChangesRec, *XkbDeviceChangesPtr;

typedef struct _XkbDeviceLedChanges {
    unsigned short  led_class;    /* class of this indicator feedback bundle */
    unsigned short  led_id;       /* ID of this indicator feedback bundle */
    unsigned int    names;        /* bits indicating which names have changed */
    unsigned int    maps;         /* bits indicating which maps have changed */
    struct _XkbDeviceLedChanges *next; /* link to indicator change record
                                          for next set */
} XkbDeviceLedChangesRec, *XkbDeviceLedChangesPtr;

A local description of the configuration and state of a device may be kept in
an XkbDeviceInfoRec structure. The actual state or configuration of the device
may change because of XkbSetDeviceInfo and XkbSetButtonActions requests made by
clients or by user interaction with the device. The X server sends an
XkbExtensionDeviceNotify event to all interested clients when the state of any
buttons or indicators or the configuration of the buttons or indicators on the
core keyboard or any input extension device changes. The event reports the
state of indicators for a single indicator feedback, and the state of up to 128
buttons. If more than 128 buttons or more than one indicator feedback are
changed, the additional buttons and indicator feedbacks are reported in
subsequent events. Xkb provides functions with which you can track changes to
input extension devices by noting the changes that were made and then
requesting the changed information from the server.

To note device changes reported in an XkbExtensionDeviceNotify event, use
XkbNoteDeviceChanges.

void XkbNoteDeviceChanges(XkbDeviceChangesPtr old,
XkbExtensionDeviceNotifyEvent *new, unsigned int wanted);

old    structure tracking state changes

new    event indicating state changes

wanted mask indicating changes to note

The wanted field specifies the changes that should be noted in old, and is
composed of the bitwise inclusive OR of one or more of the masks from Table
21.1. The reason field of the event in new indicates the types of changes the
event is reporting. XkbNoteDeviceChanges updates the XkbDeviceChangesRec
specified by old with the changes that are both specified in wanted and
contained in new->reason.

To update a local copy of the state and configuration of an X input extension
device with the changes previously noted in an XkbDeviceChangesRec structure,
use XkbGetDeviceInfoChanges.

To query the changes that have occurred in the button actions or indicator
names and indicator maps associated with an input extension device, use
XkbGetDeviceInfoChanges.

Status XkbGetDeviceInfoChanges(Display *dpy, XkbDeviceInfoPtr device_info,
XkbDeviceChangesPtr changes);

dpy         connection to X server

device_info structure to update with results

changes     contains notes of changes that have occurred

The changes->changed field indicates which attributes of the device specified
in changes->device have changed. The parameters describing the changes are
contained in the other fields of changes. XkbGetDeviceInfoChanges uses that
information to call XkbGetDeviceInfo to obtain the current status of those
attributes that have changed. It then updates the local description of the
device in device_info with the new information.

To update the server’s description of a device with the changes noted in an
XkbDeviceChangesRec, use XkbChangeDeviceInfo.

Bool XkbChangeDeviceInfo(Display *dpy, XkbDeviceInfoPtr device_info,
XkbDeviceChangesPtr changes);

dpy         connection to X server

device_info local copy of device state and configuration

changes     note specifying changes in device_info

XkbChangeDeviceInfo updates the server’s description of the device specified in
device_info->device_spec with the changes specified in changes and contained in
device_info. The update is made by an XkbSetDeviceInfo request.

Chapter 22. Debugging Aids

The debugging aids are intended for use primarily by Xkb implementors and are
optional in any implementation.

There are two bitmasks that may be used to control debugging. One bitmask
controls the output of debugging information, and the other controls behavior.
Both bitmasks are initially all zeros.

To change the values of any of the debug controls, use XkbSetDebuggingFlags.

Bool XkbSetDebuggingFlags(Display *display, unsigned int mask, unsigned int
flags, char *msg, unsigned int ctrls_mask, unsigned int ctrls, unsigned int
*ret_flags, unsigned int *ret_ctrls);

display    connection to X server

mask       mask selecting debug output flags to change

flags      values for debug output flags selected by mask

msg        message to print right now

ctrls_mask mask selecting debug controls to change

ctrls      values for debug controls selected by ctrls_mask

ret_flags  resulting state of all debug output flags

ret_ctrls  resulting state of all debug controls

XkbSetDebuggingFlags modifies the debug output flags as specified by mask and
flags, modifies the debug controls flags as specified by ctrls_mask and ctrls,
prints the message msg, and backfills ret_flags and ret_ctrls with the
resulting debug output and debug controls flags.

When bits are set in the debug output masks, mask and flags, Xkb prints debug
information corresponding to each bit at appropriate points during its
processing. The device to which the output is written is
implementation-dependent, but is normally the same device to which X server
error messages are directed; thus the bits that can be set in mask and flags is
implementation-specific. To turn on a debug output selection, set the bit for
the output in the mask parameter and set the corresponding bit in the flags
parameter. To turn off event selection for an event, set the bit for the output
in the mask parameter and do not set the corresponding bit in the flags
parameter.

When bits are set in the debug controls masks, ctrls_mask and ctrls, Xkb
modifies its behavior according to each controls bit. ctrls_mask and ctrls are
related in the same way that mask and flags are. The valid controls bits are
defined in Table 22.1.

Table 22.1. Debug Control Masks

┌──────────────────┬────────┬───────────────────────────────────┐
│Debug Control Mask│Value   │Meaning                            │
├──────────────────┼────────┼───────────────────────────────────┤
│XkbDF_DisableLocks│(1 << 0)│Disable actions that lock modifiers│
└──────────────────┴────────┴───────────────────────────────────┘


XkbSetDebuggingFlags returns True if successful and False otherwise. The only
protocol error it may generate is BadAlloc, if for some reason it is unable to
allocate storage.

XkbSetDebuggingFlags is intended for developer use and may be disabled in
production X servers. If it is disabled, XkbSetDebuggingFlags has no effect and
does not generate any protocol errors.

The message in msg is written immediately. The device to which it is written is
implementation dependent but is normally the same device where X server error
messages are directed.

Glossary

Allocator

    Xkb provides functions, known as allocators, to create and initialize Xkb
    data structures.

Audible Bell

    An audible bell is the sound generated by whatever bell is associated with
    the keyboard or input extension device, as opposed to any other audible
    sound generated elsewhere in the system.

Autoreset Controls

    The autoreset controls configure the boolean controls to automatically be
    enabled or disabled at the time a program exits.

Base Group

    The group in effect as a result of all actions other than a previous lock
    or latch request; the base group is transient. For example, the user
    pressing and holding a group shift key that shifts to Group2 would result
    in the base group being group 2 at that point in time. Initially, base
    group is always Group1.

Base Modifiers

    Modifiers that are turned on as a result of some actions other than
    previous lock or latch requests; base modifiers are transient. For example,
    the user pressing and holding a key bound to the Shift modifier would
    result in Shift being a base modifier at that point in time.

Base Event Code

    A number assigned by the X server at run time that is assigned to the
    extension to identify events from that extension.

Base State

    The base group and base modifiers represent keys that are physically or
    logically down; these constitute the base state.

Boolean Controls

    Global keyboard controls that may be selectively enabled and disabled under
    program control and that may be automatically set to an on or off condition
    upon client program exit.

Canonical Key Types

    The canonical key types are predefined key types that describe the types of
    keys available on most keyboards. The definitions for the canonical key
    types are held in the first XkbNumRequiredTypes entries of the types field
    of the client map and are indexed using the following constants:

      □ XkbOneLevelIndex

      □ XkbTwoLevelIndex

      □ XkbAlphabeticIndex

      □ XkbKeypadIndex

Client Map

    The key mapping information needed to convert arbitrary keycodes to
    symbols.

Compat Name

    The compat name is a string that provides some information about the rules
    used to bind actions to keys that are changed using core protocol requests.

Compatibility State

    When an Xkb-extended X server connects to an Xkb-unaware client, the
    compatibility state remaps the keyboard group into a core modifier whenever
    possible.

Compatibility Grab State

    The grab state that results from applying the compatibility map to the Xkb
    grab state.

Compatibility Map

    The definition of how to map core protocol keyboard state to Xkb keyboard
    state.

Component Expression

    An expression used to describe server keyboard database components to be
    loaded. It describes the order in which the components should be loaded and
    the rules by which duplicate attributes should be resolved.

Compose Processing

    The process of mapping a series of keysyms to a string is known as compose
    processing.

Consumed Modifier

    Xkb normally consumes modifiers in determining the appropriate symbol for
    an event, that is, the modifiers are not considered during any of the later
    stages of event processing. For those rare occasions when a modifier should
    be considered despite having been used to look up a symbol, key types
    include an optional preserve field.

Core Event

    An event created from the core X server.

Detectable Auto-Repeat

    Detectable auto-repeat allows a client to detect an auto-repeating key. If
    a client requests and the server supports detectable auto-repeat, Xkb
    generates KeyRelease events only when the key is physically released. Thus
    the client receives a number of KeyPress events for that key without
    intervening KeyRelease events until the key is finally released, when a 
    KeyRelease event is received.

Effective Group

    The effective group is the arithmetic sum of the locked, latched, and base
    groups. The effective keyboard group is always brought back into range
    depending on the value of the GroupsWrap control for the keyboard. If an
    event occurs with an effective group that is legal for the keyboard as a
    whole, but not for the key in question, the group for that event only is
    normalized using the algorithm specified by the group_info member of the
    key symbol map (XkbSymMapRec).

Effective Mask

    An Xkb modifier definition consists of a set of bit masks corresponding to
    the eight real modifiers; a similar set of bitmasks corresponding to the 16
    named virtual modifiers; and an effective mask. The effective mask
    represents the set of all real modifiers that can logically be set either
    by setting any of the real modifiers or by setting any of the virtual
    modifiers in the definition.

Effective Modifier

    The effective modifiers are the bitwise union of the base, latched and
    locked modifiers.

Extension Device

    Any keyboard or other input device recognized by the X input extension.

Global Keyboard Controls

    Controls that affect the way Xkb generates key events. The controls affect
    all keys, as opposed to per-key controls that are for a single key. Global
    controls include

      □ RepeatKeys Control

      □ DetectableAuto-repeat

      □ SlowKeys

      □ BounceKeys

      □ StickyKeys

      □ MouseKeys

      □ MouseKeysAccel

      □ AccessXKeys

      □ AccessXTimeout

      □ AccessXFeedback

      □ Overlay1

      □ Overlay2

      □ EnabledControls

Grab State

    The grab state is the state used when matching events to passive grabs. It
    consists of the grab group and the grab modifiers.

Group

    See Keysym Group

Group Index

    A number used as the internal representation for a group number. Group1
    through Group 4 have indices of 0 through 3.

Groups Wrap Control

    If a group index exceeds the maximum number of groups permitted for the
    specified keyboard, it is wrapped or truncated back into range as specified
    by the global GroupsWrap control. GroupsWrap can have the following values:

    WrapIntoRange
    ClampIntoRange
    RedirectIntoRange

Key Type

    An attribute of a key that identifies which modifiers affect the shift
    level of a key and the number of groups on the key.

Key Width

    The maximum number of shift levels in any group for the key type associated
    with a key.

Keysym Group

    A keysym group is a logical state of the keyboard providing access to a
    collection of characters. A group usually contains a set of characters that
    logically belong together and that may be arranged on several shift levels
    within that group. For example, Group1 could be the English alphabet, and
    Group2 could be Greek. Xkb supports up to four different groups for an
    input device or keyboard. Groups are in the range 1–4 (Group1–Group4), and
    are often referred to as G1–G4 and indexed as 0–3.

Indicator

    An indicator is a feedback mechanism such as an LED on an input device.
    Using Xkb, a client application can determine the names of the various
    indicators, determine and control the way that the individual indicators
    should be updated to reflect keyboard changes, and determine which of the
    32 keyboard indicators reported by the protocol are actually present on the
    keyboard.

Indicator Feedback

    An indicator feedback describes the state of a bank of up to 32 lights. It
    has a mask where each bit corresponds to a light and an associated value
    mask that specifies which lights are on or off.

Indicator Map

    An indicator has its own set of attributes that specify whether clients can
    explicitly set its state and whether it tracks the keyboard state. The
    indicator map is the collection of these attributes for each indicator and
    is held in the maps array, which is an array of XkbIndicatorRec structures.

Input Extension

    An extension to the core X protocol that allows an X server to support
    multiple keyboards, as well as other input devices, in addition to the core
    X keyboard and pointer. Other types of devices supported by the input
    extension include, but are not limited to: mice, tablets, touchscreens,
    barcode readers, button boxes, trackballs, identifier devices, data gloves,
    and eye trackers.

Key Action

    A key action consists of an operator and some optional data. Once the
    server has applied the global controls and per-key behavior and has decided
    to process a key event, it applies key actions to determine the effects of
    the key on the internal state of the server. Xkb supports actions that do
    the following:

      □ Change base, latched, or locked modifiers or group

      □ Move the core pointer or simulate core pointer button events

      □ Change most aspects of keyboard behavior

      □ Terminate or suspend the server

      □ Send a message to interested clients

      □ Simulate events on other keys

Key Alias

    A key alias is a symbolic name for a specific physical key. Key aliases
    allow the keyboard layout designer to assign multiple key names to a single
    key. This allows the keyboard layout designer to refer to keys using either
    their position or their “function”. Key aliases can be specified both in
    the symbolic names component and in the keyboard geometry. Both sets of
    aliases are always valid, but key alias definitions in the keyboard
    geometry have priority; if both symbolic names and geometry include
    aliases, you should consider the definitions from the geometry before
    considering the definitions from the symbolic names section.

Key Behavior

    The behaviors field of the server map is an array of XkbBehavior, indexed
    by keycode, and contains the behavior for each key. The X server uses key
    behavior to determine whether to process or filter out any given key event;
    key behavior is independent of keyboard modifier or group state. Each key
    has exactly one behavior.

    Key behaviors include:

      □ XkbKB_Default

      □ XkbKB_Lock

      □ XkbKB_RadioGroup

      □ XkbKB_Overlay1

      □ XkbKB_Overlay2

Key Symbol Map

    A key symbol map describes the symbols bound to a key and the rules to be
    used to interpret those symbols. It is an array of XkbSymMapRec structures
    indexed by keycode.

Key Type

    Key types are used to determine the shift level of a key given the current
    state of the keyboard. There is one key type for each group for a key. Key
    types are defined using the XkbKeyTypeRec and XkbKTMapEntryRec structures.
    Xkb allows up to XkbMaxKeyTypes (255) key types to be defined, but requires
    at least XkbNumRequiredTypes (4) predefined types to be in a key map.

Keyboard Bells

    The sound the default bell makes when rung is the system bell or the
    default keyboard bell. Some input devices may have more than one bell,
    identified by bell_class and bell_id.

Keyboard Components

    There are five types of components stored in the X server database of
    keyboard components. They correspond to the >symbols, geometry, keycodes,
    compat, and types symbolic names associated with a keyboard.

Keyboard Feedback

    A keyboard feedback includes the following:

    Keyclick volume
    Bell volume
    Bell pitch
    Bell duration
    Global auto-repeat
    Per key auto-repeat
    32 LEDs

Key Width, Key Type Width

    The maximum number of shift levels for a type is referred to as the width
    of a key type.

Keyboard Geometry

    Keyboard geometry describes the physical appearance of the keyboard,
    including the shape, location, and color of all keyboard keys or other
    visible keyboard components such as indicators and is stored in a 
    XkbGeometryRec structure. The information contained in a keyboard geometry
    is sufficient to allow a client program to draw an accurate two-dimensional
    image of the keyboard.

Keyboard Geometry Name

    The keyboard geometry name describes the physical location, size, and shape
    of the various keys on the keyboard and is part of the XkbNamesRec
    structure.

Keyboard State

    Keyboard state encompasses all of the transitory information necessary to
    map a physical key press or release to an appropriate event.

Keycode

    A numeric value returned to the X server when a key on a keyboard is
    pressed or released, indicating which key is being modulated. Keycode
    numbers are in the range 1 <= keycode <= max, where max is the number of
    physical keys on the device.

Keycode Name

    The keycode name describes the range and meaning of the keycodes returned
    by the keyboard and is part of the XkbNamesRec structure.

Latched Group

    A latched group is a group index that is combined with the base and locked
    group to form the effective group. It applies only to the next key event
    that does not change the keyboard state. The latched group can be changed
    by keyboard activity or via Xkb extension library functions.

Latched Modifier

    Latched modifiers are the set of modifiers that are combined with the base
    modifiers and the locked modifiers to form the effective modifiers. It
    applies only to the next key event that does not change the keyboard state.

LED

    A light emitting diode. However, for the purposes of the X keyboard
    extension specification, a LED is any form of visual two-state indicator
    that is either on or off.

Locked Group

    A locked group is a group index that is combined with the base and latched
    group to form the effective group. When a group is locked, it supersedes
    any previous locked group and remains the locked group for all future key
    events, until a new group is locked. The locked group can be changed by
    keyboard activity or via Xkb extension library functions.

Locked Modifiers

    Locked modifiers are the set of modifiers that are combined with the base
    modifiers and the latched modifiers to form the effective modifiers. A
    locked modifier applies to all future key events until it is explicitly
    unlocked.

Lookup State

    The lookup state is composed of the lookup group and the lookup modifiers,
    and it is the state an Xkb-capable or Xkb-aware client should use to map a
    keycode to a keysym.

Modifier

    A modifier is a logical condition that is either set or unset. The
    modifiers control the Shift Level selected when a key event occurs. Xkb
    supports the core protocol eight modifiers (Shift, Lock, Control, and Mod1
    through Mod5), called the real modifiers. In addition, Xkb extends modifier
    flexibility by providing a set of sixteen named virtual modifiers, each of
    which can be bound to any set of the eight real modifiers.

Modifier Key

    A modifier key is a key whose operation has no immediate effect, but that,
    for as long as it is held down, modifies the effect of other keys. A
    modifier key may be, for example, a shift key or a control key.

Modifier Definition

    An Xkb modifier definition, held in an XkbModsRec, consists of a set of
    real modifiers, a set of virtual modifiers, and an effective mask. The mask
    is the union of the real modifiers and the set of real modifiers to which
    the virtual modifiers map; the mask cannot be explicitly changed.

Nonkeyboard Extension Device

    An input extension device that is not a keyboard. Other types of devices
    supported by the input extension include, but are not limited to: mice,
    tablets, touchscreens, barcode readers, button boxes, trackballs,
    identifier devices, data gloves, and eye trackers.

Outlines

    An outline is a list of one or more points that describes a single closed
    polygon, used in the geometry specification for a keyboard.

Physical Indicator Mask

    The physical indicator mask is a field in the XkbIndicatorRec that
    indicates which indicators are bound to physical LEDs on the keyboard; if a
    bit is set in phys_indicators, then the associated indicator has a physical
    LED associated with it. This field is necessary because some indicators may
    not have corresponding physical LEDs on the keyboard.

Physical Symbol Keyboard Name

    The symbols keyboard name identifies the symbols logically bound to the
    keys. The symbols name is a human or application-readable description of
    the intended locale or usage of the keyboard with these symbols. The
    phys_symbols keyboard name, on the other hand, identifies the symbols
    actually engraved on the keyboard.

Preserved Modifier

    Xkb normally consumes modifiers in determining the appropriate symbol for
    an event, that is, the modifiers are not considered during any of the later
    stages of event processing. For those rare occasions when a modifier should
    be considered despite having been used to look up a symbol, key types
    include an optional preserve field. If a modifier is present in the
    preserve list, it is a preserved modifier.

Radio Group

    A radio group is a set of keys whose behavior simulates a set of radio
    buttons. Once a key in a radio group is pressed, it stays logically
    depressed until another key in the group is pressed, at which point the
    previously depressed key is logically released. Consequently, at most one
    key in a radio group can be logically depressed at one time.

Real Modifier

    Xkb supports the eight core protocol modifiers (Shift, Lock, Control, and 
    Mod1 through Mod5); these are called the real modifiers, as opposed to the
    set of sixteen named virtual modifiers that can be bound to any set of the
    eight real modifiers.

Server Internal Modifiers

    Modifiers that the server uses to determine the appropriate symbol for an
    event; internal modifiers are normally consumed by the server.

Shift Level

    One of several states (normally 2 or 3) governing which graphic character
    is produced when a key is actuated.

Symbol Keyboard Name

    The symbols keyboard name identifies the symbols logically bound to the
    keys. The symbols name is a human or application-readable description of
    the intended locale or usage of the keyboard with these symbols. The
    phys_symbols keyboard name, on the other hand, identifies the symbols
    actually engraved on the keyboard.

Symbolic Name

    Xkb supports symbolic names for most components of the keyboard extension.
    Most of these symbolic names are grouped into the names component of the
    keyboard description.

State Field

    The portion of a client-side core protocol event that holds the modifier,
    group, and button state information pertaining to the event.

Types Name

    The types name provides some information about the set of key types that
    can be associated with the keyboard. In addition, each key type can have a
    name, and each shift level of a type can have a name.

Valuator

    A valuator reports a range of values for some entity, like a mouse axis, a
    slider, or a dial.

Virtual Modifier

    Xkb provides a set of sixteen named virtual modifiers that can be bound to
    any set of the eight real modifiers. Each virtual modifier can be bound to
    any set of the real modifiers (Shift, Lock, Control, and Mod1 – Mod5).

Virtual Modifier Mapping

    Xkb maintains a virtual modifier mapping, which lists the virtual modifiers
    associated with each key.

Xkb-aware Client

    A client application that initializes Xkb extension and is consequently
    bound to an Xlib that includes the Xkb extension.

Xkb-capable Client

    A client application that makes no Xkb extension Xlib calls but is bound to
    an Xlib that includes the Xkb extension.

Xkb-unaware Client

    A client application that makes no Xkb extension Xlib calls and is bound to
    an Xlib that does not include the Xkb extension.

Index

A

action modifiers, Actions for Changing Modifiers’ State
audible bell, Bells
auto-repeat

    controls, Controls for Repeat Key Behavior
    detectable, The DetectableAutorepeat Control

auto-reset mask, The AutoReset Control

B

BadAccess, Initializing the Keyboard Extension
BadKeyboard, Protocol Errors
base group, Keyboard State Description
base modifiers, Keyboard State Description
bell, Bells

    audible, Bells

boolean controls, Keyboard Controls

C

changes data structures, Making Changes to the Server’s Keyboard Description
client map, Xkb Keyboard Mapping, Xkb Client Keyboard Mapping
compose processing, Controls Affecting Compose Processing
controls, Keyboard Controls

    boolean, Keyboard Controls
    library, X Library Controls
    non-boolean, Keyboard Controls
    server, Keyboard Controls

D

detectable auto-repeat, The DetectableAutorepeat Control

E

effective group, Keyboard State Description
effective modifiers, Keyboard State Description
errors, Error Indications, Protocol Errors

    BadAccess, Initializing the Keyboard Extension
    BadKeyboard, Protocol Errors

events, Xkb Events

    MappingNotify, IgnoreNewKeyboards, Effects of Xkb on MappingNotify Events
    mask, Selecting Xkb Events
    NewKeyboardNotify, IgnoreNewKeyboards
    XkbAccessXNotify, AccessXNotify Events
    XkbActionMessage, Detecting Key Action Messages
    XkbAnyEvent, Xkb Event Data Structures
    XkbCompatMapNotify, Tracking Changes to the Compatibility Map
    XkbControlsNotify, Tracking Changes to Keyboard Controls
    XkbEvent, Unified Xkb Event Type
    XkbExtensionDeviceNotify, XkbExtensionDeviceNotify Event
    XkbIndicatorMapNotify, Tracking Changes to Indicator State or Map
    XkbIndicatorStateNotify, Tracking Changes to Indicator State or Map
    XkbMapNotify, Tracking Changes to Map Components
    XkbNamesNotify, Tracking Name Changes
    XkbNewKeyboardNotify, Replacing a Keyboard “On the Fly”
    XkbStateNotify, Tracking Keyboard State

G

grab group, Keyboard State Description
grab modifiers, Keyboard State Description
grab state, Keyboard State Description
group

    base, Keyboard State Description
    effective, Keyboard State Description
    grab, Keyboard State Description
    ISO9995, Keyboard State Description
    keysym, Keyboard State Description, Changing Groups
    lookup, Keyboard State Description
    radio, Radio Groups

group compatibility map, Xkb State to Core Protocol State Transformation

I

indicators, Indicators

K

keyboard description, Xkb Extension Components
keysym groups, Keyboard State Description, Changing Groups

L

level, Notation and Terminology
library controls, X Library Controls
lookup group, Keyboard State Description
lookup modifiers, Keyboard State Description
lookup state, Keyboard State Description

M

map

    client, Xkb Keyboard Mapping, Xkb Client Keyboard Mapping
    group compatibility, Xkb State to Core Protocol State Transformation
    server, Xkb Keyboard Mapping, Xkb Server Keyboard Mapping

mask

    auto-reset, The AutoReset Control
    event, Selecting Xkb Events
    real modifiers, Changing Modifiers

modifier definition, Keyboard State Description
modifiers, Keyboard State Description

    action, Actions for Changing Modifiers’ State
    base, Keyboard State Description
    effective, Keyboard State Description
    grab, Keyboard State Description
    lookup, Keyboard State Description
    names, Conventions
    real, Changing Modifiers, Virtual Modifiers
    virtual, Virtual Modifiers
    virtual mapping, Virtual Modifier Key Mapping

N

non-boolean controls, Keyboard Controls

R

radio group, Radio Groups
real modifiers, Changing Modifiers, Virtual Modifiers

S

server controls, Keyboard Controls
server map, Xkb Keyboard Mapping, Xkb Server Keyboard Mapping
shift level, Notation and Terminology
state

    grab, Keyboard State Description
    lookup, Keyboard State Description

V

valuator, Actions for Simulating Events from Device Valuators
virtual modifier mapping, Virtual Modifier Key Mapping
virtual modifiers, Virtual Modifiers

X

Xkb-aware client, Keyboard State Description
Xkb-capable client, Keyboard State Description
XkbAccessXNotifyEvent, AccessXNotify Events
XkbAction, The XkbAction Structure
XkbActionCtrls, Actions for Changing Boolean Controls State
XkbActionMessageEvent, Detecting Key Action Messages
XkbActionSetCtrls, Actions for Changing Boolean Controls State
XkbAddDeviceLedInfo, Allocating, Initializing, and Freeing the XkbDeviceInfoRec
    Structure
XkbAddGeomColor, Adding Elements to a Keyboard Geometry
XkbAddGeomDoodad, Adding Elements to a Keyboard Geometry
XkbAddGeomKey, Adding Elements to a Keyboard Geometry
XkbAddGeomKeyAlias, Adding Elements to a Keyboard Geometry
XkbAddGeomOutline, Adding Elements to a Keyboard Geometry
XkbAddGeomOverlay, Adding Elements to a Keyboard Geometry
XkbAddGeomOverlayKey, Adding Elements to a Keyboard Geometry
XkbAddGeomOverlayRow, Adding Elements to a Keyboard Geometry
XkbAddGeomProperty, Adding Elements to a Keyboard Geometry
XkbAddGeomRow, Adding Elements to a Keyboard Geometry
XkbAddGeomSection, Adding Elements to a Keyboard Geometry
XkbAddGeomShape, Adding Elements to a Keyboard Geometry
XkbAddSymInterpret, Changing the Server’s Compatibility Map
XkbAllocClientMap, Allocating an Empty Client Map
XkbAllocCompatMap, Allocating and Freeing the Compatibility Map
XkbAllocControls, Allocating and Freeing an XkbControlsRec
XkbAllocDeviceInfo, Allocating, Initializing, and Freeing the XkbDeviceInfoRec
    Structure
XkbAllocGeomColors, Allocating and Freeing Geometry Components
XkbAllocGeomDoodads, Allocating and Freeing Geometry Components
XkbAllocGeometry, Allocating and Freeing Geometry Components
XkbAllocGeomKeyAliases, Allocating and Freeing Geometry Components
XkbAllocGeomKeys, Allocating and Freeing Geometry Components
XkbAllocGeomOutlines, Allocating and Freeing Geometry Components
XkbAllocGeomOverlayKeys, Allocating and Freeing Geometry Components
XkbAllocGeomOverlayRows, Allocating and Freeing Geometry Components
XkbAllocGeomOverlays, Allocating and Freeing Geometry Components
XkbAllocGeomPoints, Allocating and Freeing Geometry Components
XkbAllocGeomProps, Allocating and Freeing Geometry Components
XkbAllocGeomRows, Allocating and Freeing Geometry Components
XkbAllocGeomSectionDoodads, Allocating and Freeing Geometry Components
XkbAllocGeomSections, Allocating and Freeing Geometry Components
XkbAllocGeomShapes, Allocating and Freeing Geometry Components
XkbAllocIndicatorMaps, Allocating and Freeing Indicator Maps
XkbAllocKeyboard, Allocating and Freeing a Keyboard Description
XkbAllocNames, Allocating and Freeing Symbolic Names
XkbAllocServerMap, Allocating an Empty Server Map
XkbAnyAction, The XkbAnyAction Structure
XkbAnyEvent, Xkb Event Data Structures
XkbApplyCompatMapToKey, Using the Compatibility Map
XkbBehavior, The XkbBehavior Structure
XkbBell, Generating Named Bells
XkbBellEvent, Generating Named Bell Events
XkbChangeControls, The XkbControlsChangesRec Structure
XkbChangeDeviceInfo, Tracking Changes to Extension Devices
XkbChangeEnabledControls, The EnabledControls Control
XkbChangeMap, The XkbMapChangesRec Structure
XkbChangeNames, The XkbNameChangesRec Structure
XkbChangeTypesOfKey, Changing the Number of Groups and Types Bound to a Key
XkbClientMapRec, The XkbClientMapRec Structure
XkbCompatMapNotifyEvent, Tracking Changes to the Compatibility Map
XkbCompatMapRec, The XkbCompatMap Structure
XkbComponentListRec, Listing the Known Keyboard Components
XkbComponentNameRec, Listing the Known Keyboard Components
XkbComponentNamesRec, Listing the Known Keyboard Components
XkbComputeRowBounds, Using Keyboard Geometry
XkbComputeSectionBounds, Using Keyboard Geometry
XkbComputeShapeBounds, Using Keyboard Geometry
XkbComputeShapeTop, Using Keyboard Geometry
XkbControlsChangesRec, The XkbControlsChangesRec Structure
XkbControlsNotifyEvent, Tracking Changes to Keyboard Controls
XkbControlsRec, The XkbControlsRec Structure
XkbCopyKeyType, Copying Key Types
XkbCopyKeyTypes, Copying Key Types
XkbCtrlsAction, Actions for Changing Boolean Controls State
XkbDescRec, The XkbDescRec Structure
XkbDeviceBell, Generating Named Bells
XkbDeviceBellEvent, Generating Named Bell Events
XkbDeviceBtnAction, Actions for Generating DeviceButtonPress and
    DeviceButtonRelease
XkbDeviceChangesRec, Tracking Changes to Extension Devices
XkbDeviceInfoRec, XkbDeviceInfoRec
XkbDeviceLedChangesRec, Tracking Changes to Extension Devices
XkbDeviceLedInfoRec, XkbDeviceInfoRec
XkbDeviceValuatorAction, Actions for Simulating Events from Device Valuators
XkbEvent, Unified Xkb Event Type
XkbExtensionDeviceNotifyEvent, XkbExtensionDeviceNotify Event
XkbFindOverlayForKey, Using Keyboard Geometry
XkbForceBell, Forcing a Server-Generated Bell
XkbForceDeviceBell, Forcing a Server-Generated Bell
XkbFreeClientMap, Freeing a Client Map
XkbFreeCompatMap, Allocating and Freeing the Compatibility Map
XkbFreeComponentList, Listing the Known Keyboard Components
XkbFreeControls, Allocating and Freeing an XkbControlsRec
XkbFreeDeviceInfo, Allocating, Initializing, and Freeing the XkbDeviceInfoRec
    Structure
XkbFreeGeomColors, Allocating and Freeing Geometry Components
XkbFreeGeomDoodads, Allocating and Freeing Geometry Components
XkbFreeGeometry, Allocating and Freeing Geometry Components
XkbFreeGeomKeyAliases, Allocating and Freeing Geometry Components
XkbFreeGeomKeys, Allocating and Freeing Geometry Components
XkbFreeGeomOutlines, Allocating and Freeing Geometry Components
XkbFreeGeomOverlayKeys, Allocating and Freeing Geometry Components
XkbFreeGeomOverlayRows, Allocating and Freeing Geometry Components
XkbFreeGeomOverlays, Allocating and Freeing Geometry Components
XkbFreeGeomPoints, Allocating and Freeing Geometry Components
XkbFreeGeomProperties, Allocating and Freeing Geometry Components
XkbFreeGeomRows, Allocating and Freeing Geometry Components
XkbFreeGeomSections, Allocating and Freeing Geometry Components
XkbFreeGeomShapes, Allocating and Freeing Geometry Components
XkbFreeIndicatorMaps, Allocating and Freeing Indicator Maps
XkbFreeKeyboard, Allocating and Freeing a Keyboard Description
XkbFreeNames, Allocating and Freeing Symbolic Names
XkbFreeServerMap, Freeing a Server Map
XkbGeometryRec, Keyboard Geometry
XkbGetAutoRepeatRate, The RepeatKeys Control
XkbGetAutoResetControls, The AutoReset Control
XkbGetCompatMap, Getting Compatibility Map Components From the Server
XkbGetControls, Querying Controls
XkbGetControlsChanges, Tracking Changes to Keyboard Controls
XkbGetDetectableAutorepeat, The DetectableAutorepeat Control
XkbGetDeviceButtonActions, Querying Xkb Features for Non-KeyClass Input
    Extension Devices
XkbGetDeviceInfo, Querying Xkb Features for Non-KeyClass Input Extension
    Devices
XkbGetDeviceInfoChanges, Tracking Changes to Extension Devices
XkbGetDeviceLedInfo, Querying Xkb Features for Non-KeyClass Input Extension
    Devices
XkbGetGeometry, Getting Keyboard Geometry From the Server
XkbGetIndicatorMap, Getting Indicator Information by Index
XkbGetIndicatorState, Getting Indicator State
XkbGetKeyActions, Obtaining Key Actions for Keys from the Server
XkbGetKeyBehaviors, Obtaining Key Behaviors for Keys from the Server
XkbGetKeyboard, Obtaining a Keyboard Description from the Server, Obtaining a
    Keyboard Description from the Server
XkbGetKeyboardByName, Building a Keyboard Description Using the Server Database
XkbGetKeyExplicitComponents, Obtaining Explicit Components for Keys from the
    Server
XkbGetKeyModifierMap, Getting the Per-Key Modifier Map from the Server
XkbGetKeySyms, Getting the Symbol Map for Keys from the Server
XkbGetKeyTypes, Getting Key Types from the Server
XkbGetKeyVirtualModMap, Obtaining Per-Key Virtual Modifier Mappings from the
    Server
XkbGetMap, Getting Map Components from the Server
XkbGetNamedDeviceIndicator, Getting Indicator Information by Name
XkbGetNamedGeometry, Getting Keyboard Geometry From the Server
XkbGetNamedIndicator, Getting Indicator Information by Name
XkbGetNames, Getting Symbolic Names From the Server
XkbGetPerClientControls, The Miscellaneous Per-client Controls
XkbGetState, Determining Keyboard State
XkbGetUpdatedMap, Getting Map Components from the Server
XkbGetVirtualMods, Obtaining Virtual Modifier Bindings from the Server
XkbGetXlibControls, Determining the State of the Library Controls
XkbGroupAction, Actions for Changing Group State
XkbIgnoreExtension, Disabling the Keyboard Extension
XkbIndicatorMapNotifyEvent, Tracking Changes to Indicator State or Map
XkbIndicatorMapRec, XkbIndicatorMapRec
XkbIndicatorRec, XkbIndicatorRec
XkbIndicatorStateNotifyEvent, Tracking Changes to Indicator State or Map
XkbInitCanonicalKeyTypes, Initializing the Canonical Key Types in a New Client
    Map
XkbISOAction, Actions for Locking Modifiers and Group
XkbKeyAction, Key Actions
XkbKeyActionEntry, Key Actions
XkbKeyActionsPtr, Key Actions
XkbKeyAliasRec, The XkbNamesRec Structure
XkbKeycodeToKeysym, Xkb Event and Keymap Functions
XkbKeyGroupInfo, Per-Key Group Information
XkbKeyGroupsWidth, Offset in to the Symbol Map
XkbKeyGroupWidth, Offset in to the Symbol Map
XkbKeyHasActions, Key Actions
XkbKeyKeyType, Per-Key Key Type Indices
XkbKeyKeyTypeIndex, Per-Key Key Type Indices
XkbKeyNameRec, The XkbNamesRec Structure
XkbKeyNumActions, Key Actions
XkbKeyNumGroups, Per-Key Group Information
XkbKeyNumSyms, Offset in to the Symbol Map
XkbKeySymEntry, Offset in to the Symbol Map
XkbKeySymsPtr, Offset in to the Symbol Map
XkbKeysymToModifiers, Xkb Event and Keymap Functions
XkbKeyTypeRec, Key Types
XkbKeyTypesForCoreSymbols, Using the Compatibility Map
XkbKTMapEntryRec, Key Types
XkbLatchGroup, Changing Groups
XkbLatchModifiers, Changing Modifiers
XkbLibraryVersion, Determining Library Compatibility
XkbListComponents, Listing the Known Keyboard Components
XkbLockGroup, Changing Groups
XkbLockModifiers, Changing Modifiers
XkbLookupKeyBinding, Xkb Event and Keymap Functions
XkbLookupKeySym, Xkb Event and Keymap Functions
XkbMapChangesRec, The XkbMapChangesRec Structure
XkbMapNotifyEvent, Tracking Changes to Map Components
XkbMessageAction, Actions for Generating Messages
XkbModAction, Actions for Changing Modifiers’ State
XkbModActionVMods, Actions for Changing Modifiers’ State
XkbModsRec, Modifier Definitions
XkbName, Extension Name
XkbNameChangesRec, The XkbNameChangesRec Structure
XkbNamesNotifyEvent, Tracking Name Changes
XkbNamesRec, The XkbNamesRec Structure
XkbNewKeyboardNotifyEvent, Replacing a Keyboard “On the Fly”
XkbNoteControlsChanges, Tracking Changes to Keyboard Controls
XkbNoteDeviceChanges, Tracking Changes to Extension Devices
XkbNoteNameChanges, Tracking Name Changes
XkbOpenDisplay, Initializing the Keyboard Extension
XkbOutOfRangeGroupInfo, Per-Key Group Information
XkbOutOfRangeGroupNumber, Per-Key Group Information
XkbPtrAction, Actions for Moving the Pointer
XkbPtrActionX, Actions for Moving the Pointer
XkbPtrActionY, Actions for Moving the Pointer
XkbPtrBtnAction, Actions for Simulating Pointer Button Press and Release
XkbPtrDfltAction, Actions for Changing the Pointer Button Simulated
XkbQueryExtension, Initializing the Keyboard Extension
XkbRedirectKeyAction, Actions for Generating a Different Keycode
XkbRefreshKeyboardMapping, Xkb Event and Keymap Functions
XkbResizeDeviceButtonActions, Allocating, Initializing, and Freeing the
    XkbDeviceInfoRec Structure
XkbResizeKeyActions, Changing the Number of Actions Bound to a Key
XkbResizeKeySyms, Changing the Number of Symbols Bound to a Key
XkbResizeKeyType, Changing the Number of Levels in a Key Type
XkbSAGroup, Actions for Changing Group State
XkbSAPtrDfltValue, Actions for Changing the Pointer Button Simulated
XkbSARedirectSetVMods, Actions for Generating a Different Keycode
XkbSARedirectSetVModsMask, Actions for Generating a Different Keycode
XkbSARedirectVMods, Actions for Generating a Different Keycode
XkbSARedirectVModsMask, Actions for Generating a Different Keycode
XkbSAScreen, Actions for Changing the Active Screen
XkbSASetGroup, Actions for Changing Group State
XkbSASetPtrDfltValue, Actions for Changing the Pointer Button Simulated
XkbSASetScreen, Actions for Changing the Active Screen
XkbSelectEventDetails, Selecting Xkb Events
XkbSelectEvents, Selecting Xkb Events
XkbServerMapRec, Xkb Server Keyboard Mapping
XkbSetAutoRepeatRate, The RepeatKeys Control
XkbSetAutoResetControls, The AutoReset Control
XkbSetCompatMap, Changing the Server’s Compatibility Map
XkbSetControls, Changing Controls
XkbSetDebuggingFlags, Debugging Aids
XkbSetDetectableAutorepeat, The DetectableAutorepeat Control
XkbSetDeviceButtonActions, Setting Xkb Features for Non-KeyClass Input
    Extension Devices
XkbSetDeviceInfo, Setting Xkb Features for Non-KeyClass Input Extension Devices
XkbSetIgnoreLockMods, The IgnoreLockMods Control
XkbSetIndicatorMap, Changing Indicator Maps by Index
XkbSetMap, Changing Map Components in the Server
XkbSetModActionVMods, Actions for Changing Modifiers’ State
XkbSetNamedDeviceIndicator, Changing Indicator Maps by Name
XkbSetNamedIndicator, Changing Indicator Maps by Name
XkbSetNames, Changing Symbolic Names on the Server
XkbSetPerClientControls, The Miscellaneous Per-client Controls
XkbSetPtrActionX, Actions for Moving the Pointer
XkbSetPtrActionY, Actions for Moving the Pointer
XkbSetServerInternalMods, The InternalMods Control
XkbSetXlibControls, Changing the State of the Library Controls
XkbStateNotifyEvent, Tracking Keyboard State
XkbStateRec, Determining Keyboard State
XkbSwitchScreenAction, Actions for Changing the Active Screen
XkbSymInterpretRec, Symbol Interpretations — the XkbSymInterpretRec Structure
XkbSymMapRec, Key Symbol Map
XkbTranslateKeyCode, Xkb Event and Keymap Functions
XkbTranslateKeySym, Xkb Event and Keymap Functions
XkbUpdateMapFromCore, Using the Compatibility Map
XkbUseCoreKbd, Display and Device Specifications in Function Calls
XkbVirtualModsToReal, Virtual Modifier Key Mapping
XkbXlibControlsImplemented, Determining Which Library Controls are Implemented
XKeycodeToKeysym, X Library Functions Affected by Xkb
XKeysymToKeycode, X Library Functions Affected by Xkb
XLookupKeysym, X Library Functions Affected by Xkb
XLookupString, X Library Controls, X Library Functions Affected by Xkb
XRebindKeysym, X Library Functions Affected by Xkb
XRefreshKeyboardMapping, X Library Functions Affected by Xkb

