GApplication: GIO Reference Manual

## GApplication GApplication — Core application class |

## Functions

gboolean | g_application_id_is_valid ()
GApplication * | g_application_new ()
const gchar * | g_application_get_application_id ()
void | g_application_set_application_id ()
guint | g_application_get_inactivity_timeout ()
void | g_application_set_inactivity_timeout ()
GApplicationFlags | g_application_get_flags ()
void | g_application_set_flags ()
const gchar * | g_application_get_resource_base_path ()
void | g_application_set_resource_base_path ()
GDBusConnection * | g_application_get_dbus_connection ()
const gchar * | g_application_get_dbus_object_path ()
void | g_application_set_action_group ()
gboolean | g_application_get_is_registered ()
gboolean | g_application_get_is_remote ()
gboolean | g_application_register ()
void | g_application_hold ()
void | g_application_release ()
void | g_application_quit ()
void | g_application_activate ()
void | g_application_open ()
void | g_application_send_notification ()
void | g_application_withdraw_notification ()
int | g_application_run ()
void | g_application_add_main_option_entries ()
void | g_application_add_main_option ()
void | g_application_add_option_group ()
void | g_application_set_default ()
GApplication * | g_application_get_default ()
void | g_application_mark_busy ()
void | g_application_unmark_busy ()
gboolean | g_application_get_is_busy ()
void | g_application_bind_busy_property ()
void | g_application_unbind_busy_property ()

## Properties

GActionGroup * | action-group | Write
gchar * | application-id | Read / Write / Construct
GApplicationFlags | flags | Read / Write
guint | inactivity-timeout | Read / Write
gboolean | is-busy | Read
gboolean | is-registered | Read
gboolean | is-remote | Read
gchar * | resource-base-path | Read / Write

## Signals

void | activate | Run Last
gint | command-line | Run Last
gint | handle-local-options | Run Last
void | open | Run Last
void | shutdown | Run Last
void | startup | Run First

## Types and Values

| GApplication
struct | GApplicationClass
enum | GApplicationFlags

## Object Hierarchy

        GObject
        ╰── GApplication

## Implemented Interfaces

GApplication implements GActionGroup and GActionMap.

## Includes

    #include <gio/gio.h>

## Description

A GApplication is the foundation of an application. It wraps some low-level platform-specific services and is intended to act as the foundation for higher-level application classes such as GtkApplication or MxApplication. In general, you should not use this class outside of a higher level framework.

GApplication provides convenient life cycle management by maintaining a "use count" for the primary application instance. The use count can be changed using `g_application_hold()` and `g_application_release()`. If it drops to zero, the application exits. Higher-level classes such as GtkApplication employ the use count to ensure that the application stays alive as long as it has any opened windows.

Another feature that GApplication (optionally) provides is process uniqueness. Applications can make use of this functionality by providing a unique application ID. If given, only one application with this ID can be running at a time per session. The session concept is platform-dependent, but corresponds roughly to a graphical desktop login. When your application is launched again, its arguments are passed through platform communication to the already running program. The already running instance of the program is called the "primary instance"; for non-unique applications this is the always the current instance. On Linux, the D-Bus session bus is used for communication.

The use of GApplication differs from some other commonly-used uniqueness libraries (such as libunique) in important ways. The application is not expected to manually register itself and check if it is the primary instance. Instead, the `main()` function of a GApplication should do very little more than instantiating the application instance, possibly connecting signal handlers, then calling `g_application_run()`. All checks for uniqueness are done internally. If the application is the primary instance then the startup signal is emitted and the mainloop runs. If the application is not the primary instance then a signal is sent to the primary instance and `g_application_run()` promptly returns. See the code examples below.

If used, the expected form of an application identifier is very close to that of of a DBus bus name. Examples include: "com.example.MyApp", "org.example.internal-apps.Calculator". For details on valid application identifiers, see `g_application_id_is_valid()`.

On Linux, the application identifier is claimed as a well-known bus name on the user's session bus. This means that the uniqueness of your application is scoped to the current session. It also means that your application may provide additional services (through registration of other object paths) at that bus name. The registration of these object paths should be done with the shared GDBus session bus. Note that due to the internal architecture of GDBus, method calls can be dispatched at any time (even if a main loop is not running). For this reason, you must ensure that any object paths that you wish to register are registered before GApplication attempts to acquire the bus name of your application (which happens in `g_application_register()`). Unfortunately, this means that you cannot use `g_application_get_is_remote()` to decide if you want to register object paths.

GApplication also implements the GActionGroup and GActionMap interfaces and lets you easily export actions by adding them with `g_action_map_add_action()`. When invoking an action by calling `g_action_group_activate_action()` on the application, it is always invoked in the primary instance. The actions are also exported on the session bus, and GIO provides the GDBusActionGroup wrapper to conveniently access them remotely. GIO provides a GDBusMenuModel wrapper for remote access to exported GMenuModels.

There is a number of different entry points into a GApplication:

- via 'Activate' (i.e. just starting the application)

- via 'Open' (i.e. opening some files)

- by handling a command-line

- via activating an action

The “startup” signal lets you handle the application initialization for all of these in a single place.

Regardless of which of these entry points is used to start the application, GApplication passes some "platform data from the launching instance to the primary instance, in the form of a GVariant dictionary mapping strings to variants. To use platform data, override the `before_emit` or `after_emit` virtual functions in your GApplication subclass. When dealing with GApplicationCommandLine objects, the platform data is directly available via `g_application_command_line_get_cwd()`, `g_application_command_line_get_environ()` and `g_application_command_line_get_platform_data()`.

As the name indicates, the platform data may vary depending on the operating system, but it always includes the current directory (key "cwd"), and optionally the environment (ie the set of environment variables and their values) of the calling process (key "environ"). The environment is only added to the platform data if the `G_APPLICATION_SEND_ENVIRONMENT` flag is set. GApplication subclasses can add their own platform data by overriding the `add_platform_data` virtual function. For instance, GtkApplication adds startup notification data in this way.

To parse commandline arguments you may handle the “command-line” signal or override the `local_command_line()` vfunc, to parse them in either the primary instance or the local instance, respectively.

For an example of opening files with a GApplication, see gapplication-example-open.c.

For an example of using actions with GApplication, see gapplication-example-actions.c.

For an example of using extra D-Bus hooks with GApplication, see gapplication-example-dbushooks.c.

## Functions

### g_application_id_is_valid ()

    gboolean
    g_application_id_is_valid (const gchar *application_id);

Checks if `application_id` is a valid application identifier.

A valid ID is required for calls to `g_application_new()` and `g_application_set_application_id()`.

For convenience, the restrictions on application identifiers are reproduced here:

- Application identifiers must contain only the ASCII characters "A-Z[0-9]_-." and must not begin with a digit.

- Application identifiers must contain at least one '.' (period) character (and thus at least three elements).

- Application identifiers must not begin or end with a '.' (period) character.

- Application identifiers must not contain consecutive '.' (period) characters.

- Application identifiers must not exceed 255 characters.

#### Parameters

application_id | a potential application identifier |

#### Returns

`TRUE` if `application_id` is valid

### g_application_new ()

    GApplication *
    g_application_new (const gchar *application_id,
                       GApplicationFlags flags);

Creates a new GApplication instance.

If non-`NULL`, the application id must be valid. See `g_application_id_is_valid()`.

If no application ID is given then some features of GApplication (most notably application uniqueness) will be disabled.

#### Parameters

application_id | the application id. | [allow-none]
flags | the application flags |

#### Returns

a new GApplication instance

### g_application_get_application_id ()

    const gchar *
    g_application_get_application_id (GApplication *application);

Gets the unique identifier for `application` .

#### Parameters

application | a GApplication |

#### Returns

the identifier for `application` , owned by `application`

Since: 2.28

### g_application_set_application_id ()

    void
    g_application_set_application_id (GApplication *application,
                                      const gchar *application_id);

Sets the unique identifier for `application` .

The application id can only be modified if `application` has not yet been registered.

If non-`NULL`, the application id must be valid. See `g_application_id_is_valid()`.

#### Parameters

application | a GApplication |
application_id | the identifier for `application` . | [allow-none]

Since: 2.28

### g_application_get_inactivity_timeout ()

    guint
    g_application_get_inactivity_timeout (GApplication *application);

Gets the current inactivity timeout for the application.

This is the amount of time (in milliseconds) after the last call to `g_application_release()` before the application stops running.

#### Parameters

application | a GApplication |

#### Returns

the timeout, in milliseconds

Since: 2.28

### g_application_set_inactivity_timeout ()

    void
    g_application_set_inactivity_timeout (GApplication *application,
                                          guint inactivity_timeout);

Sets the current inactivity timeout for the application.

This is the amount of time (in milliseconds) after the last call to `g_application_release()` before the application stops running.

This call has no side effects of its own. The value set here is only used for next time `g_application_release()` drops the use count to zero. Any timeouts currently in progress are not impacted.

#### Parameters

application | a GApplication |
inactivity_timeout | the timeout, in milliseconds |

Since: 2.28

### g_application_get_flags ()

    GApplicationFlags
    g_application_get_flags (GApplication *application);

Gets the flags for `application` .

See GApplicationFlags.

#### Parameters

application | a GApplication |

#### Returns

the flags for `application`

Since: 2.28

### g_application_set_flags ()

    void
    g_application_set_flags (GApplication *application,
                             GApplicationFlags flags);

Sets the flags for `application` .

The flags can only be modified if `application` has not yet been registered.

See GApplicationFlags.

#### Parameters

application | a GApplication |
flags | the flags for `application` |

Since: 2.28

### g_application_get_resource_base_path ()

    const gchar *
    g_application_get_resource_base_path (GApplication *application);

Gets the resource base path of `application` .

See `g_application_set_resource_base_path()` for more information.

#### Parameters

application | a GApplication |

#### Returns

the base resource path, if one is set.

[nullable]

Since: 2.42

### g_application_set_resource_base_path ()

    void
    g_application_set_resource_base_path (GApplication *application,
                                          const gchar *resource_path);

Sets (or unsets) the base resource path of `application` .

The path is used to automatically load various application resources such as menu layouts and action descriptions. The various types of resources will be found at fixed names relative to the given base path.

By default, the resource base path is determined from the application ID by prefixing '/' and replacing each '.' with '/'. This is done at the time that the GApplication object is constructed. Changes to the application ID after that point will not have an impact on the resource base path.

As an example, if the application has an ID of "org.example.app" then the default resource base path will be "/org/example/app". If this is a GtkApplication (and you have not manually changed the path) then Gtk will then search for the menus of the application at "/org/example/app/gtk/menus.ui".

See GResource for more information about adding resources to your application.

You can disable automatic resource loading functionality by setting the path to `NULL`.

Changing the resource base path once the application is running is not recommended. The point at which the resource path is consulted for forming paths for various purposes is unspecified.

#### Parameters

application | a GApplication |
resource_path | the resource path to use. | [nullable]

Since: 2.42

### g_application_get_dbus_connection ()

    GDBusConnection *
    g_application_get_dbus_connection (GApplication *application);

Gets the GDBusConnection being used by the application, or `NULL`.

If GApplication is using its D-Bus backend then this function will return the GDBusConnection being used for uniqueness and communication with the desktop environment and other instances of the application.

If GApplication is not using D-Bus then this function will return `NULL`. This includes the situation where the D-Bus backend would normally be in use but we were unable to connect to the bus.

This function must not be called before the application has been registered. See `g_application_get_is_registered()`.

#### Parameters

application | a GApplication |

#### Returns

a GDBusConnection, or `NULL`.

[transfer none]

Since: 2.34

### g_application_get_dbus_object_path ()

    const gchar *
    g_application_get_dbus_object_path (GApplication *application);

Gets the D-Bus object path being used by the application, or `NULL`.

If GApplication is using its D-Bus backend then this function will return the D-Bus object path that GApplication is using. If the application is the primary instance then there is an object published at this path. If the application is not the primary instance then the result of this function is undefined.

If GApplication is not using D-Bus then this function will return `NULL`. This includes the situation where the D-Bus backend would normally be in use but we were unable to connect to the bus.

This function must not be called before the application has been registered. See `g_application_get_is_registered()`.

#### Parameters

application | a GApplication |

#### Returns

the object path, or `NULL`

Since: 2.34

### g_application_set_action_group ()

    void
    g_application_set_action_group (GApplication *application,
                                    GActionGroup *action_group);

`g_application_set_action_group` has been deprecated since version 2.32 and should not be used in newly-written code.

Use the GActionMap interface instead. Never ever mix use of this API with use of GActionMap on the same `application` or things will go very badly wrong. This function is known to introduce buggy behaviour (ie: signals not emitted on changes to the action group), so you should really use GActionMap instead.

This used to be how actions were associated with a GApplication. Now there is GActionMap for that.

#### Parameters

application | a GApplication |
action_group | a GActionGroup, or `NULL`. | [allow-none]

Since: 2.28

### g_application_get_is_registered ()

    gboolean
    g_application_get_is_registered (GApplication *application);

Checks if `application` is registered.

An application is registered if `g_application_register()` has been successfully called.

#### Parameters

application | a GApplication |

#### Returns

`TRUE` if `application` is registered

Since: 2.28

### g_application_get_is_remote ()

    gboolean
    g_application_get_is_remote (GApplication *application);

Checks if `application` is remote.

If `application` is remote then it means that another instance of application already exists (the 'primary' instance). Calls to perform actions on `application` will result in the actions being performed by the primary instance.

The value of this property cannot be accessed before `g_application_register()` has been called. See `g_application_get_is_registered()`.

#### Parameters

application | a GApplication |

#### Returns

`TRUE` if `application` is remote

Since: 2.28

### g_application_register ()

    gboolean
    g_application_register (GApplication *application,
                            GCancellable *cancellable,
                            GError **error);

Attempts registration of the application.

This is the point at which the application discovers if it is the primary instance or merely acting as a remote for an already-existing primary instance. This is implemented by attempting to acquire the application identifier as a unique bus name on the session bus using GDBus.

If there is no application ID or if `G_APPLICATION_NON_UNIQUE` was given, then this process will always become the primary instance.

Due to the internal architecture of GDBus, method calls can be dispatched at any time (even if a main loop is not running). For this reason, you must ensure that any object paths that you wish to register are registered before calling this function.

If the application has already been registered then `TRUE` is returned with no work performed.

The “startup” signal is emitted if registration succeeds and `application` is the primary instance (including the non-unique case).

In the event of an error (such as `cancellable` being cancelled, or a failure to connect to the session bus), `FALSE` is returned and `error` is set appropriately.

Note: the return value of this function is not an indicator that this instance is or is not the primary instance of the application. See `g_application_get_is_remote()` for that.

#### Parameters

application | a GApplication |
cancellable | a GCancellable, or `NULL`. | [allow-none]
error | a pointer to a NULL GError, or `NULL` |

#### Returns

`TRUE` if registration succeeded

Since: 2.28

### g_application_hold ()

    void
    g_application_hold (GApplication *application);

Increases the use count of `application` .

Use this function to indicate that the application has a reason to continue to run. For example, `g_application_hold()` is called by GTK+ when a toplevel window is on the screen.

To cancel the hold, call `g_application_release()`.

#### Parameters

application | a GApplication |

### g_application_release ()

    void
    g_application_release (GApplication *application);

Decrease the use count of `application` .

When the use count reaches zero, the application will stop running.

Never call this function except to cancel the effect of a previous call to `g_application_hold()`.

#### Parameters

application | a GApplication |

### g_application_quit ()

    void
    g_application_quit (GApplication *application);

Immediately quits the application.

Upon return to the mainloop, `g_application_run()` will return, calling only the 'shutdown' function before doing so.

The hold count is ignored.

The result of calling `g_application_run()` again after it returns is unspecified.

#### Parameters

application | a GApplication |

Since: 2.32

### g_application_activate ()

    void
    g_application_activate (GApplication *application);

Activates the application.

In essence, this results in the “activate” signal being emitted in the primary instance.

The application must be registered before calling this function.

#### Parameters

application | a GApplication |

Since: 2.28

### g_application_open ()

    void
    g_application_open (GApplication *application,
                        GFile **files,
                        gint n_files,
                        const gchar *hint);

Opens the given files.

In essence, this results in the “open” signal being emitted in the primary instance.

`n_files` must be greater than zero.

`hint` is simply passed through to the ::open signal. It is intended to be used by applications that have multiple modes for opening files (eg: "view" vs "edit", etc). Unless you have a need for this functionality, you should use "".

The application must be registered before calling this function and it must have the `G_APPLICATION_HANDLES_OPEN` flag set.

#### Parameters

application | a GApplication |
files | an array of GFiles to open. | [array length=n_files]
n_files | the length of the `files` array |
hint | a hint (or ""), but never `NULL` |

Since: 2.28

### g_application_send_notification ()

    void
    g_application_send_notification (GApplication *application,
                                     const gchar *id,
                                     GNotification *notification);

Sends a notification on behalf of `application` to the desktop shell. There is no guarantee that the notification is displayed immediately, or even at all.

Notifications may persist after the application exits. It will be D-Bus-activated when the notification or one of its actions is activated.

Modifying `notification` after this call has no effect. However, the object can be reused for a later call to this function.

`id` may be any string that uniquely identifies the event for the application. It does not need to be in any special format. For example, "new-message" might be appropriate for a notification about new messages.

If a previous notification was sent with the same `id` , it will be replaced with `notification` and shown again as if it was a new notification. This works even for notifications sent from a previous execution of the application, as long as `id` is the same string.

`id` may be `NULL`, but it is impossible to replace or withdraw notifications without an id.

If `notification` is no longer relevant, it can be withdrawn with `g_application_withdraw_notification()`.

#### Parameters

application | a GApplication |
id | id of the notification, or `NULL`. | [allow-none]
notification | the GNotification to send |

Since: 2.40

### g_application_withdraw_notification ()

    void
    g_application_withdraw_notification (GApplication *application,
                                         const gchar *id);

Withdraws a notification that was sent with `g_application_send_notification()`.

This call does nothing if a notification with `id` doesn't exist or the notification was never sent.

This function works even for notifications sent in previous executions of this application, as long `id` is the same as it was for the sent notification.

Note that notifications are dismissed when the user clicks on one of the buttons in a notification or triggers its default action, so there is no need to explicitly withdraw the notification in that case.

#### Parameters

application | a GApplication |
id | id of a previously sent notification |

Since: 2.40

### g_application_run ()

    int
    g_application_run (GApplication *application,
                       int argc,
                       char **argv);

Runs the application.

This function is intended to be run from `main()` and its return value is intended to be returned by `main()`. Although you are expected to pass the `argc` , `argv` parameters from `main()` to this function, it is possible to pass `NULL` if `argv` is not available or commandline handling is not required. Note that on Windows, `argc` and `argv` are ignored, and `g_win32_get_command_line()` is called internally (for proper support of Unicode commandline arguments).

GApplication will attempt to parse the commandline arguments. You can add commandline flags to the list of recognised options by way of `g_application_add_main_option_entries()`. After this, the “handle-local-options” signal is emitted, from which the application can inspect the values of its GOptionEntrys.

“handle-local-options” is a good place to handle options such as `--version`, where an immediate reply from the local process is desired (instead of communicating with an already-running instance). A “handle-local-options” handler can stop further processing by returning a non-negative value, which then becomes the exit status of the process.

What happens next depends on the flags: if `G_APPLICATION_HANDLES_COMMAND_LINE` was specified then the remaining commandline arguments are sent to the primary instance, where a “command-line” signal is emitted. Otherwise, the remaining commandline arguments are assumed to be a list of files. If there are no files listed, the application is activated via the “activate” signal. If there are one or more files, and `G_APPLICATION_HANDLES_OPEN` was specified then the files are opened via the “open” signal.

If you are interested in doing more complicated local handling of the commandline then you should implement your own GApplication subclass and override `local_command_line()`. In this case, you most likely want to return `TRUE` from your `local_command_line()` implementation to suppress the default handling. See gapplication-example-cmdline2.c for an example.

If, after the above is done, the use count of the application is zero then the exit status is returned immediately. If the use count is non-zero then the default main context is iterated until the use count falls to zero, at which point 0 is returned.

If the `G_APPLICATION_IS_SERVICE` flag is set, then the service will run for as much as 10 seconds with a use count of zero while waiting for the message that caused the activation to arrive. After that, if the use count falls to zero the application will exit immediately, except in the case that `g_application_set_inactivity_timeout()` is in use.

This function sets the prgname (`g_set_prgname()`), if not already set, to the basename of argv[0].

Since 2.40, applications that are not explicitly flagged as services or launchers (ie: neither `G_APPLICATION_IS_SERVICE` or `G_APPLICATION_IS_LAUNCHER` are given as flags) will check (from the default handler for local_command_line) if "--gapplication-service" was given in the command line. If this flag is present then normal commandline processing is interrupted and the `G_APPLICATION_IS_SERVICE` flag is set. This provides a "compromise" solution whereby running an application directly from the commandline will invoke it in the normal way (which can be useful for debugging) while still allowing applications to be D-Bus activated in service mode. The D-Bus service file should invoke the executable with "--gapplication-service" as the sole commandline argument. This approach is suitable for use by most graphical applications but should not be used from applications like editors that need precise control over when processes invoked via the commandline will exit and what their exit status will be.

#### Parameters

application | a GApplication |
argc | the argc from `main()` (or 0 if `argv` is `NULL`) |
argv | the argv from `main()`, or `NULL`. | [array length=argc][allow-none]

#### Returns

the exit status

Since: 2.28

### g_application_add_main_option_entries ()

    void
    g_application_add_main_option_entries (GApplication *application,
                                           const GOptionEntry *entries);

Adds main option entries to be handled by `application` .

This function is comparable to `g_option_context_add_main_entries()`.

After the commandline arguments are parsed, the “handle-local-options” signal will be emitted. At this point, the application can inspect the values pointed to by `arg_data` in the given GOptionEntrys.

Unlike GOptionContext, GApplication supports giving a `NULL` `arg_data` for a non-callback GOptionEntry. This results in the argument in question being packed into a GVariantDict which is also passed to “handle-local-options”, where it can be inspected and modified. If `G_APPLICATION_HANDLES_COMMAND_LINE` is set, then the resulting dictionary is sent to the primary instance, where `g_application_command_line_get_options_dict()` will return it. This "packing" is done according to the type of the argument -- booleans for normal flags, strings for strings, bytestrings for filenames, etc. The packing only occurs if the flag is given (ie: we do not pack a "false" GVariant in the case that a flag is missing).

In general, it is recommended that all commandline arguments are parsed locally. The options dictionary should then be used to transmit the result of the parsing to the primary instance, where `g_variant_dict_lookup()` can be used. For local options, it is possible to either use `arg_data` in the usual way, or to consult (and potentially remove) the option from the options dictionary.

This function is new in GLib 2.40. Before then, the only real choice was to send all of the commandline arguments (options and all) to the primary instance for handling. GApplication ignored them completely on the local side. Calling this function "opts in" to the new behaviour, and in particular, means that unrecognised options will be treated as errors. Unrecognised options have never been ignored when `G_APPLICATION_HANDLES_COMMAND_LINE` is unset.

If “handle-local-options” needs to see the list of filenames, then the use of `G_OPTION_REMAINING` is recommended. If `arg_data` is `NULL` then `G_OPTION_REMAINING` can be used as a key into the options dictionary. If you do use `G_OPTION_REMAINING` then you need to handle these arguments for yourself because once they are consumed, they will no longer be visible to the default handling (which treats them as filenames to be opened).

#### Parameters

application | a GApplication |
entries | (array zero-terminated=1) (element-type GOptionEntry) a `NULL`-terminated list of GOptionEntrys |

Since: 2.40

### g_application_add_main_option ()

    void
    g_application_add_main_option (GApplication *application,
                                   const char *long_name,
                                   char short_name,
                                   GOptionFlags flags,
                                   GOptionArg arg,
                                   const char *description,
                                   const char *arg_description);

Add an option to be handled by `application` .

Calling this function is the equivalent of calling `g_application_add_main_option_entries()` with a single GOptionEntry that has its arg_data member set to `NULL`.

The parsed arguments will be packed into a GVariantDict which is passed to “handle-local-options”. If `G_APPLICATION_HANDLES_COMMAND_LINE` is set, then it will also be sent to the primary instance. See `g_application_add_main_option_entries()` for more details.

See GOptionEntry for more documentation of the arguments.

#### Parameters

application | the GApplication |
long_name | the long name of an option used to specify it in a commandline |
short_name | the short name of an option |
flags | flags from GOptionFlags |
arg | the type of the option, as a GOptionArg |
description | the description for the option in `--help` output |
arg_description | the placeholder to use for the extra argument parsed by the option in `--help` output. | [nullable]

Since: 2.42

### g_application_add_option_group ()

    void
    g_application_add_option_group (GApplication *application,
                                    GOptionGroup *group);

Adds a GOptionGroup to the commandline handling of `application` .

This function is comparable to `g_option_context_add_group()`.

Unlike `g_application_add_main_option_entries()`, this function does not deal with `NULL` `arg_data` and never transmits options to the primary instance.

The reason for that is because, by the time the options arrive at the primary instance, it is typically too late to do anything with them. Taking the GTK option group as an example: GTK will already have been initialised by the time the “command-line” handler runs. In the case that this is not the first-running instance of the application, the existing instance may already have been running for a very long time.

This means that the options from GOptionGroup are only really usable in the case that the instance of the application being run is the first instance. Passing options like `--display=` or `--gdk-debug=` on future runs will have no effect on the existing primary instance.

Calling this function will cause the options in the supplied option group to be parsed, but it does not cause you to be "opted in" to the new functionality whereby unrecognised options are rejected even if `G_APPLICATION_HANDLES_COMMAND_LINE` was given.

#### Parameters

application | the GApplication |
group | a GOptionGroup |

Since: 2.40

### g_application_set_default ()

    void
    g_application_set_default (GApplication *application);

Sets or unsets the default application for the process, as returned by `g_application_get_default()`.

This function does not take its own reference on `application` . If `application` is destroyed then the default application will revert back to `NULL`.

#### Parameters

application | the application to set as default, or `NULL`. | [allow-none]

Since: 2.32

### g_application_get_default ()

    GApplication *
    g_application_get_default (void);

Returns the default GApplication instance for this process.

Normally there is only one GApplication per process and it becomes the default when it is created. You can exercise more control over this by using `g_application_set_default()`.

If there is no default application then `NULL` is returned.

#### Returns

the default application for this process, or `NULL`.

[transfer none]

Since: 2.32

### g_application_mark_busy ()

    void
    g_application_mark_busy (GApplication *application);

Increases the busy count of `application` .

Use this function to indicate that the application is busy, for instance while a long running operation is pending.

The busy state will be exposed to other processes, so a session shell will use that information to indicate the state to the user (e.g. with a spinner).

To cancel the busy indication, use `g_application_unmark_busy()`.

#### Parameters

application | a GApplication |

Since: 2.38

### g_application_unmark_busy ()

    void
    g_application_unmark_busy (GApplication *application);

Decreases the busy count of `application` .

When the busy count reaches zero, the new state will be propagated to other processes.

This function must only be called to cancel the effect of a previous call to `g_application_mark_busy()`.

#### Parameters

application | a GApplication |

Since: 2.38

### g_application_get_is_busy ()

    gboolean
    g_application_get_is_busy (GApplication *application);

Gets the application's current busy state, as set through `g_application_mark_busy()` or `g_application_bind_busy_property()`.

#### Parameters

application | a GApplication |

#### Returns

`TRUE` if `application` is currenty marked as busy

Since: 2.44

### g_application_bind_busy_property ()

    void
    g_application_bind_busy_property (GApplication *application,
                                      gpointer object,
                                      const gchar *property);

Marks `application` as busy (see `g_application_mark_busy()`) while `property` on `object` is `TRUE`.

The binding holds a reference to `application` while it is active, but not to `object` . Instead, the binding is destroyed when `object` is finalized.

#### Parameters

application | a GApplication |
object | a GObject. | [type GObject.Object]
property | the name of a boolean property of `object` |

Since: 2.44

### g_application_unbind_busy_property ()

    void
    g_application_unbind_busy_property (GApplication *application,
                                        gpointer object,
                                        const gchar *property);

Destroys a binding between `property` and the busy state of `application` that was previously created with `g_application_bind_busy_property()`.

#### Parameters

application | a GApplication |
object | a GObject. | [type GObject.Object]
property | the name of a boolean property of `object` |

Since: 2.44

## Types and Values

### GApplication

    typedef struct _GApplication GApplication;

GApplication is an opaque data structure and can only be accessed using the following functions.

Since: 2.28

### struct GApplicationClass

    struct GApplicationClass {
      /* signals */
      void                      (* startup)             (GApplication              *application);

      void                      (* activate)            (GApplication              *application);

      void                      (* open)                (GApplication              *application,
                                                         GFile                    **files,
                                                         gint                       n_files,
                                                         const gchar               *hint);

      int                       (* command_line)        (GApplication              *application,
                                                         GApplicationCommandLine   *command_line);

      /* vfuncs */

      /**
       * GApplicationClass::local_command_line:
       * @application: a #GApplication
       * @arguments: (inout) (array zero-terminated=1): array of command line arguments
       * @exit_status: (out): exit status to fill after processing the command line.
       *
       * This virtual function is always invoked in the local instance. It
       * gets passed a pointer to a %NULL-terminated copy of @argv and is
       * expected to remove arguments that it handled (shifting up remaining
       * arguments).
       *
       * The last argument to local_command_line() is a pointer to the @status
       * variable which can used to set the exit status that is returned from
       * g_application_run().
       *
       * See g_application_run() for more details on #GApplication startup.
       *
       * Returns: %TRUE if the commandline has been completely handled
       */
      gboolean                  (* local_command_line)  (GApplication              *application,
                                                         gchar                   ***arguments,
                                                         int                       *exit_status);

      void                      (* before_emit)         (GApplication              *application,
                                                         GVariant                  *platform_data);
      void                      (* after_emit)          (GApplication              *application,
                                                         GVariant                  *platform_data);
      void                      (* add_platform_data)   (GApplication              *application,
                                                         GVariantBuilder           *builder);
      void                      (* quit_mainloop)       (GApplication              *application);
      void                      (* run_mainloop)        (GApplication              *application);
      void                      (* shutdown)            (GApplication              *application);

      gboolean                  (* dbus_register)       (GApplication              *application,
                                                         GDBusConnection           *connection,
                                                         const gchar               *object_path,
                                                         GError                   **error);
      void                      (* dbus_unregister)     (GApplication              *application,
                                                         GDBusConnection           *connection,
                                                         const gchar               *object_path);
      gint                      (* handle_local_options)(GApplication              *application,
                                                         GVariantDict              *options);
    };

Virtual function table for GApplication.

#### Members

`startup` () | invoked on the primary instance immediately after registration |
`activate` () | invoked on the primary instance when an activation occurs |
`open` () | invoked on the primary instance when there are files to open |
`command_line` () | invoked on the primary instance when a command-line is not handled locally |
`local_command_line` () | invoked (locally) when the process has been invoked via commandline execution (as opposed to, say, D-Bus activation - which is not currently supported by GApplication). The virtual function has the chance to inspect (and possibly replace) the list of command line arguments. See `g_application_run()` for more information. |
`before_emit` () | invoked on the primary instance before 'activate', 'open', 'command-line' or any action invocation, gets the 'platform data' from the calling instance |
`after_emit` () | invoked on the primary instance after 'activate', 'open', 'command-line' or any action invocation, gets the 'platform data' from the calling instance |
`add_platform_data` () | invoked (locally) to add 'platform data' to be sent to the primary instance when activating, opening or invoking actions |
`quit_mainloop` () | Used to be invoked on the primary instance when the use count of the application drops to zero (and after any inactivity timeout, if requested). Not used anymore since 2.32 |
`run_mainloop` () | Used to be invoked on the primary instance from `g_application_run()` if the use-count is non-zero. Since 2.32, GApplication is iterating the main context directly and is not using `run_mainloop` anymore |
`shutdown` () | invoked only on the registered primary instance immediately after the main loop terminates |
`dbus_register` () | invoked locally during registration, if the application is using its D-Bus backend. You can use this to export extra objects on the bus, that need to exist before the application tries to own the bus name. The function is passed the GDBusConnection to to session bus, and the object path that GApplication will use to export is D-Bus API. If this function returns `TRUE`, registration will proceed; otherwise registration will abort. Since: 2.34 |
`dbus_unregister` () | invoked locally during unregistration, if the application is using its D-Bus backend. Use this to undo anything done by the `dbus_register` vfunc. Since: 2.34 |
`handle_local_options` () | invoked locally after the parsing of the commandline options has occurred. |

Since: 2.28

### enum GApplicationFlags

Flags used to define the behaviour of a GApplication.

#### Members

G_APPLICATION_FLAGS_NONE | Default |
G_APPLICATION_IS_SERVICE | Run as a service. In this mode, registration fails if the service is already running, and the application will initially wait up to 10 seconds for an initial activation message to arrive. |
G_APPLICATION_IS_LAUNCHER | Don't try to become the primary instance. |
G_APPLICATION_HANDLES_OPEN | This application handles opening files (in the primary instance). Note that this flag only affects the default implementation of `local_command_line()`, and has no effect if `G_APPLICATION_HANDLES_COMMAND_LINE` is given. See `g_application_run()` for details. |
G_APPLICATION_HANDLES_COMMAND_LINE | This application handles command line arguments (in the primary instance). Note that this flag only affect the default implementation of `local_command_line()`. See `g_application_run()` for details. |
G_APPLICATION_SEND_ENVIRONMENT | Send the environment of the launching process to the primary instance. Set this flag if your application is expected to behave differently depending on certain environment variables. For instance, an editor might be expected to use the <envar>GIT_COMMITTER_NAME</envar> environment variable when editing a git commit message. The environment is available to the “command-line” signal handler, via `g_application_command_line_getenv()`. |
G_APPLICATION_NON_UNIQUE | Make no attempts to do any of the typical single-instance application negotiation, even if the application ID is given. The application neither attempts to become the owner of the application ID nor does it check if an existing owner already exists. Everything occurs in the local process. Since: 2.30. |

Since: 2.28

## Property Details

### The `“action-group”` property

      “action-group”             GActionGroup *

The group of actions that the application exports.

Flags: Write

### The `“application-id”` property

      “application-id”           gchar *

The unique identifier for the application.

Flags: Read / Write / Construct

Default value: NULL

### The `“flags”` property

      “flags”                    GApplicationFlags

Flags specifying the behaviour of the application.

Flags: Read / Write

### The `“inactivity-timeout”` property

      “inactivity-timeout”       guint

Time (ms) to stay alive after becoming idle.

Flags: Read / Write

Default value: 0

### The `“is-busy”` property

      “is-busy”                  gboolean

Whether the application is currently marked as busy through `g_application_mark_busy()` or `g_application_bind_busy_property()`.

Flags: Read

Default value: FALSE

Since: 2.44

### The `“is-registered”` property

      “is-registered”            gboolean

If g_application_register() has been called.

Flags: Read

Default value: FALSE

### The `“is-remote”` property

      “is-remote”                gboolean

If this application instance is remote.

Flags: Read

Default value: FALSE

### The `“resource-base-path”` property

      “resource-base-path”       gchar *

The base resource path for the application.

Flags: Read / Write

Default value: NULL

## Signal Details

### The `“activate”` signal

    void
    user_function (GApplication *application,
                   gpointer      user_data)

The ::activate signal is emitted on the primary instance when an activation occurs. See `g_application_activate()`.

#### Parameters

application | the application |
user_data | user data set when the signal handler was connected. |

Flags: Run Last

### The `“command-line”` signal

    gint
    user_function (GApplication            *application,
                   GApplicationCommandLine *command_line,
                   gpointer                 user_data)

The ::command-line signal is emitted on the primary instance when a commandline is not handled locally. See `g_application_run()` and the GApplicationCommandLine documentation for more information.

#### Parameters

application | the application |
command_line | a GApplicationCommandLine representing the passed commandline |
user_data | user data set when the signal handler was connected. |

#### Returns

An integer that is set as the exit status for the calling process. See `g_application_command_line_set_exit_status()`.

Flags: Run Last

### The `“handle-local-options”` signal

    gint
    user_function (GApplication *application,
                   GVariantDict *options,
                   gpointer      user_data)

The ::handle-local-options signal is emitted on the local instance after the parsing of the commandline options has occurred.

You can add options to be recognised during commandline option parsing using `g_application_add_main_option_entries()` and `g_application_add_option_group()`.

Signal handlers can inspect `options` (along with values pointed to from the `arg_data` of an installed GOptionEntrys) in order to decide to perform certain actions, including direct local handling (which may be useful for options like --version).

In the event that the application is marked `G_APPLICATION_HANDLES_COMMAND_LINE` the "normal processing" will send the `option` dictionary to the primary instance where it can be read with `g_application_command_line_get_options()`. The signal handler can modify the dictionary before returning, and the modified dictionary will be sent.

In the event that `G_APPLICATION_HANDLES_COMMAND_LINE` is not set, "normal processing" will treat the remaining uncollected command line arguments as filenames or URIs. If there are no arguments, the application is activated by `g_application_activate()`. One or more arguments results in a call to `g_application_open()`.

If you want to handle the local commandline arguments for yourself by converting them to calls to `g_application_open()` or `g_action_group_activate_action()` then you must be sure to register the application first. You should probably not call `g_application_activate()` for yourself, however: just return -1 and allow the default handler to do it for you. This will ensure that the `--gapplication-service` switch works properly (i.e. no activation in that case).

Note that this signal is emitted from the default implementation of `local_command_line()`. If you override that function and don't chain up then this signal will never be emitted.

You can override `local_command_line()` if you need more powerful capabilities than what is provided here, but this should not normally be required.

#### Parameters

application | the application |
options | the options dictionary |
user_data | user data set when the signal handler was connected. |

#### Returns

an exit code. If you have handled your options and want to exit the process, return a non-negative option, 0 for success, and a positive value for failure. To continue, return -1 to let the default option processing continue.

Flags: Run Last

Since: 2.40

### The `“open”` signal

    void
    user_function (GApplication *application,
                   gpointer      files,
                   gint          n_files,
                   gchar        *hint,
                   gpointer      user_data)

The ::open signal is emitted on the primary instance when there are files to open. See `g_application_open()` for more information.

#### Parameters

application | the application |
files | an array of GFiles. | [array length=n_files][element-type GFile]
n_files | the length of `files` |
hint | a hint provided by the calling instance |
user_data | user data set when the signal handler was connected. |

Flags: Run Last

### The `“shutdown”` signal

    void
    user_function (GApplication *application,
                   gpointer      user_data)

The ::shutdown signal is emitted only on the registered primary instance immediately after the main loop terminates.

#### Parameters

application | the application |
user_data | user data set when the signal handler was connected. |

Flags: Run Last

### The `“startup”` signal

    void
    user_function (GApplication *application,
                   gpointer      user_data)

The ::startup signal is emitted on the primary instance immediately after registration. See `g_application_register()`.

#### Parameters

application | the application |
user_data | user data set when the signal handler was connected. |

Flags: Run First