GDK 3 Reference Manual: GdkScreen

## GdkScreen GdkScreen — Object representing a physical screen |

## Synopsis

    #include <gdk/gdk.h>

                        GdkScreen;
    GdkScreen *         gdk_screen_get_default              (void);
    GdkVisual *         gdk_screen_get_system_visual        (GdkScreen *screen);
    GdkVisual *         gdk_screen_get_rgba_visual          (GdkScreen *screen);
    gboolean            gdk_screen_is_composited            (GdkScreen *screen);
    GdkWindow *         gdk_screen_get_root_window          (GdkScreen *screen);
    GdkDisplay *        gdk_screen_get_display              (GdkScreen *screen);
    gint                gdk_screen_get_number               (GdkScreen *screen);
    gint                gdk_screen_get_width                (GdkScreen *screen);
    gint                gdk_screen_get_height               (GdkScreen *screen);
    gint                gdk_screen_get_width_mm             (GdkScreen *screen);
    gint                gdk_screen_get_height_mm            (GdkScreen *screen);
    GList *             gdk_screen_list_visuals             (GdkScreen *screen);
    GList *             gdk_screen_get_toplevel_windows     (GdkScreen *screen);
    gchar *             gdk_screen_make_display_name        (GdkScreen *screen);
    gint                gdk_screen_get_n_monitors           (GdkScreen *screen);
    gint                gdk_screen_get_primary_monitor      (GdkScreen *screen);
    void                gdk_screen_get_monitor_geometry     (GdkScreen *screen,
                                                             gint monitor_num,
                                                             GdkRectangle *dest);
    void                gdk_screen_get_monitor_workarea     (GdkScreen *screen,
                                                             gint monitor_num,
                                                             GdkRectangle *dest);
    gint                gdk_screen_get_monitor_at_point     (GdkScreen *screen,
                                                             gint x,
                                                             gint y);
    gint                gdk_screen_get_monitor_at_window    (GdkScreen *screen,
                                                             GdkWindow *window);
    gint                gdk_screen_get_monitor_height_mm    (GdkScreen *screen,
                                                             gint monitor_num);
    gint                gdk_screen_get_monitor_width_mm     (GdkScreen *screen,
                                                             gint monitor_num);
    gchar *             gdk_screen_get_monitor_plug_name    (GdkScreen *screen,
                                                             gint monitor_num);
    gint                gdk_screen_get_monitor_scale_factor (GdkScreen *screen,
                                                             gint monitor_num);
    gboolean            gdk_screen_get_setting              (GdkScreen *screen,
                                                             const gchar *name,
                                                             GValue *value);
    const cairo_font_options_t * gdk_screen_get_font_options
                                                            (GdkScreen *screen);
    void                gdk_screen_set_font_options         (GdkScreen *screen,
                                                             const cairo_font_options_t *options);
    gdouble             gdk_screen_get_resolution           (GdkScreen *screen);
    void                gdk_screen_set_resolution           (GdkScreen *screen,
                                                             gdouble dpi);
    GdkWindow *         gdk_screen_get_active_window        (GdkScreen *screen);
    GList *             gdk_screen_get_window_stack         (GdkScreen *screen);

## Object Hierarchy

      GObject
       +----GdkScreen

## Properties

      "font-options"             gpointer              : Read / Write
      "resolution"               gdouble               : Read / Write

## Signals

      "composited-changed"                             : Run Last
      "monitors-changed"                               : Run Last
      "size-changed"                                   : Run Last

## Description

GdkScreen objects are the GDK representation of the screen on which windows can be displayed and on which the pointer moves. X originally identified screens with physical screens, but nowadays it is more common to have a single GdkScreen which combines several physical monitors (see `gdk_screen_get_n_monitors()`).

GdkScreen is used throughout GDK and GTK+ to specify which screen the top level windows are to be displayed on. it is also used to query the screen specification and default settings such as the default visual (`gdk_screen_get_system_visual()`), the dimensions of the physical monitors (`gdk_screen_get_monitor_geometry()`), etc.

## Details

### GdkScreen

    typedef struct _GdkScreen GdkScreen;

### gdk_screen_get_default ()

    GdkScreen *         gdk_screen_get_default              (void);

Gets the default screen for the default display. (See `gdk_display_get_default()`).

Returns : | a GdkScreen, or `NULL` if there is no default display. [transfer none]

Since 2.2

### gdk_screen_get_system_visual ()

    GdkVisual *         gdk_screen_get_system_visual        (GdkScreen *screen);

Get the system's default visual for `screen`. This is the visual for the root window of the display. The return value should not be freed.

`screen` : | a GdkScreen.
Returns : | the system visual. [transfer none]

Since 2.2

### gdk_screen_get_rgba_visual ()

    GdkVisual *         gdk_screen_get_rgba_visual          (GdkScreen *screen);

Gets a visual to use for creating windows with an alpha channel. The windowing system on which GTK+ is running may not support this capability, in which case `NULL` will be returned. Even if a non-`NULL` value is returned, its possible that the window's alpha channel won't be honored when displaying the window on the screen: in particular, for X an appropriate windowing manager and compositing manager must be running to provide appropriate display.

This functionality is not implemented in the Windows backend.

For setting an overall opacity for a top-level window, see `gdk_window_set_opacity()`.

`screen` : | a GdkScreen
Returns : | a visual to use for windows with an alpha channel or `NULL` if the capability is not available. [transfer none]

Since 2.8

### gdk_screen_is_composited ()

    gboolean            gdk_screen_is_composited            (GdkScreen *screen);

Returns whether windows with an RGBA visual can reasonably be expected to have their alpha channel drawn correctly on the screen.

On X11 this function returns whether a compositing manager is compositing `screen`.

`screen` : | a GdkScreen
Returns : | Whether windows with RGBA visuals can reasonably be expected to have their alpha channels drawn correctly on the screen.

Since 2.10

### gdk_screen_get_root_window ()

    GdkWindow *         gdk_screen_get_root_window          (GdkScreen *screen);

Gets the root window of `screen`.

`screen` : | a GdkScreen
Returns : | the root window. [transfer none]

Since 2.2

### gdk_screen_get_display ()

    GdkDisplay *        gdk_screen_get_display              (GdkScreen *screen);

Gets the display to which the `screen` belongs.

`screen` : | a GdkScreen
Returns : | the display to which `screen` belongs. [transfer none]

Since 2.2

### gdk_screen_get_number ()

    gint                gdk_screen_get_number               (GdkScreen *screen);

Gets the index of `screen` among the screens in the display to which it belongs. (See `gdk_screen_get_display()`)

`screen` : | a GdkScreen
Returns : | the index

Since 2.2

### gdk_screen_get_width ()

    gint                gdk_screen_get_width                (GdkScreen *screen);

Gets the width of `screen` in pixels

`screen` : | a GdkScreen
Returns : | the width of `screen` in pixels.

Since 2.2

### gdk_screen_get_height ()

    gint                gdk_screen_get_height               (GdkScreen *screen);

Gets the height of `screen` in pixels

`screen` : | a GdkScreen
Returns : | the height of `screen` in pixels.

Since 2.2

### gdk_screen_get_width_mm ()

    gint                gdk_screen_get_width_mm             (GdkScreen *screen);

Gets the width of `screen` in millimeters. Note that on some X servers this value will not be correct.

`screen` : | a GdkScreen
Returns : | the width of `screen` in millimeters.

Since 2.2

### gdk_screen_get_height_mm ()

    gint                gdk_screen_get_height_mm            (GdkScreen *screen);

Returns the height of `screen` in millimeters. Note that on some X servers this value will not be correct.

`screen` : | a GdkScreen
Returns : | the heigth of `screen` in millimeters.

Since 2.2

### gdk_screen_list_visuals ()

    GList *             gdk_screen_list_visuals             (GdkScreen *screen);

Lists the available visuals for the specified `screen`. A visual describes a hardware image data format. For example, a visual might support 24-bit color, or 8-bit color, and might expect pixels to be in a certain format.

Call `g_list_free()` on the return value when you're finished with it.

`screen` : | the relevant GdkScreen.
Returns : | a list of visuals; the list must be freed, but not its contents. [transfer container][element-type GdkVisual]

Since 2.2

### gdk_screen_get_toplevel_windows ()

    GList *             gdk_screen_get_toplevel_windows     (GdkScreen *screen);

Obtains a list of all toplevel windows known to GDK on the screen `screen`. A toplevel window is a child of the root window (see `gdk_get_default_root_window()`).

The returned list should be freed with `g_list_free()`, but its elements need not be freed.

`screen` : | The GdkScreen where the toplevels are located.
Returns : | list of toplevel windows, free with `g_list_free()`. [transfer container][element-type GdkWindow]

Since 2.2

### gdk_screen_make_display_name ()

    gchar *             gdk_screen_make_display_name        (GdkScreen *screen);

Determines the name to pass to `gdk_display_open()` to get a GdkDisplay with this screen as the default screen.

`screen` : | a GdkScreen
Returns : | a newly allocated string, free with `g_free()`

Since 2.2

### gdk_screen_get_n_monitors ()

    gint                gdk_screen_get_n_monitors           (GdkScreen *screen);

Returns the number of monitors which `screen` consists of.

`screen` : | a GdkScreen
Returns : | number of monitors which `screen` consists of

Since 2.2

### gdk_screen_get_primary_monitor ()

    gint                gdk_screen_get_primary_monitor      (GdkScreen *screen);

Gets the primary monitor for `screen`. The primary monitor is considered the monitor where the 'main desktop' lives. While normal application windows typically allow the window manager to place the windows, specialized desktop applications such as panels should place themselves on the primary monitor.

If no primary monitor is configured by the user, the return value will be 0, defaulting to the first monitor.

`screen` : | a GdkScreen.
Returns : | An integer index for the primary monitor, or 0 if none is configured.

Since 2.20

### gdk_screen_get_monitor_geometry ()

    void                gdk_screen_get_monitor_geometry     (GdkScreen *screen,
                                                             gint monitor_num,
                                                             GdkRectangle *dest);

Retrieves the GdkRectangle representing the size and position of the individual monitor within the entire screen area.

Monitor numbers start at 0. To obtain the number of monitors of `screen`, use `gdk_screen_get_n_monitors()`.

Note that the size of the entire screen area can be retrieved via `gdk_screen_get_width()` and `gdk_screen_get_height()`.

`screen` : | a GdkScreen
`monitor_num` : | the monitor number
`dest` : | a GdkRectangle to be filled with the monitor geometry. [out][allow-none]

Since 2.2

### gdk_screen_get_monitor_workarea ()

    void                gdk_screen_get_monitor_workarea     (GdkScreen *screen,
                                                             gint monitor_num,
                                                             GdkRectangle *dest);

Retrieves the GdkRectangle representing the size and position of the "work area" on a monitor within the entire screen area.

The work area should be considered when positioning menus and similar popups, to avoid placing them below panels, docks or other desktop components.

Monitor numbers start at 0. To obtain the number of monitors of `screen`, use `gdk_screen_get_n_monitors()`.

`screen` : | a GdkScreen
`monitor_num` : | the monitor number
`dest` : | a GdkRectangle to be filled with the monitor workarea. [out][allow-none]

Since 3.4

### gdk_screen_get_monitor_at_point ()

    gint                gdk_screen_get_monitor_at_point     (GdkScreen *screen,
                                                             gint x,
                                                             gint y);

Returns the monitor number in which the point (`x`,`y`) is located.

`screen` : | a GdkScreen.
`x` : | the x coordinate in the virtual screen.
`y` : | the y coordinate in the virtual screen.
Returns : | the monitor number in which the point (`x`,`y`) lies, or a monitor close to (`x`,`y`) if the point is not in any monitor.

Since 2.2

### gdk_screen_get_monitor_at_window ()

    gint                gdk_screen_get_monitor_at_window    (GdkScreen *screen,
                                                             GdkWindow *window);

Returns the number of the monitor in which the largest area of the bounding rectangle of `window` resides.

`screen` : | a GdkScreen.
`window` : | a GdkWindow
Returns : | the monitor number in which most of `window` is located, or if `window` does not intersect any monitors, a monitor, close to `window`.

Since 2.2

### gdk_screen_get_monitor_height_mm ()

    gint                gdk_screen_get_monitor_height_mm    (GdkScreen *screen,
                                                             gint monitor_num);

Gets the height in millimeters of the specified monitor.

`screen` : | a GdkScreen
`monitor_num` : | number of the monitor, between 0 and gdk_screen_get_n_monitors (screen)
Returns : | the height of the monitor, or -1 if not available

Since 2.14

### gdk_screen_get_monitor_width_mm ()

    gint                gdk_screen_get_monitor_width_mm     (GdkScreen *screen,
                                                             gint monitor_num);

Gets the width in millimeters of the specified monitor, if available.

`screen` : | a GdkScreen
`monitor_num` : | number of the monitor, between 0 and gdk_screen_get_n_monitors (screen)
Returns : | the width of the monitor, or -1 if not available

Since 2.14

### gdk_screen_get_monitor_plug_name ()

    gchar *             gdk_screen_get_monitor_plug_name    (GdkScreen *screen,
                                                             gint monitor_num);

Returns the output name of the specified monitor. Usually something like VGA, DVI, or TV, not the actual product name of the display device.

`screen` : | a GdkScreen
`monitor_num` : | number of the monitor, between 0 and gdk_screen_get_n_monitors (screen)
Returns : | a newly-allocated string containing the name of the monitor, or `NULL` if the name cannot be determined

Since 2.14

### gdk_screen_get_monitor_scale_factor ()

    gint                gdk_screen_get_monitor_scale_factor (GdkScreen *screen,
                                                             gint monitor_num);

Returns the internal scale factor that maps from monitor coordiantes to the actual device pixels. On traditional systems this is 1, but on very high density outputs this can be a higher value (often 2).

This can be used if you want to create pixel based data for a particula monitor, but most of the time you're drawing to a window where it is better to use `gdk_window_get_scale_factor()` instead.

`screen` : | screen to get scale factor for
`monitor_num` : | number of the monitor, between 0 and gdk_screen_get_n_monitors (screen)
Returns : | the scale factor

Since 3.10

### gdk_screen_get_setting ()

    gboolean            gdk_screen_get_setting              (GdkScreen *screen,
                                                             const gchar *name,
                                                             GValue *value);

Retrieves a desktop-wide setting such as double-click time for the GdkScreen `screen`.

FIXME needs a list of valid settings here, or a link to more information.

`screen` : | the GdkScreen where the setting is located
`name` : | the name of the setting
`value` : | location to store the value of the setting
Returns : | `TRUE` if the setting existed and a value was stored in `value`, `FALSE` otherwise.

Since 2.2

### gdk_screen_get_font_options ()

    const cairo_font_options_t * gdk_screen_get_font_options
                                                            (GdkScreen *screen);

Gets any options previously set with `gdk_screen_set_font_options()`.

`screen` : | a GdkScreen
Returns : | the current font options, or `NULL` if no default font options have been set.

Since 2.10

### gdk_screen_set_font_options ()

    void                gdk_screen_set_font_options         (GdkScreen *screen,
                                                             const cairo_font_options_t *options);

Sets the default font options for the screen. These options will be set on any PangoContext's newly created with `gdk_pango_context_get_for_screen()`. Changing the default set of font options does not affect contexts that have already been created.

`screen` : | a GdkScreen
`options` : | a cairo_font_options_t, or `NULL` to unset any previously set default font options. [allow-none]

Since 2.10

### gdk_screen_get_resolution ()

    gdouble             gdk_screen_get_resolution           (GdkScreen *screen);

Gets the resolution for font handling on the screen; see `gdk_screen_set_resolution()` for full details.

`screen` : | a GdkScreen
Returns : | the current resolution, or -1 if no resolution has been set.

Since 2.10

### gdk_screen_set_resolution ()

    void                gdk_screen_set_resolution           (GdkScreen *screen,
                                                             gdouble dpi);

Sets the resolution for font handling on the screen. This is a scale factor between points specified in a PangoFontDescription and cairo units. The default value is 96, meaning that a 10 point font will be 13 units high. (10 * 96. / 72. = 13.3).

`screen` : | a GdkScreen
`dpi` : | the resolution in "dots per inch". (Physical inches aren't actually involved; the terminology is conventional.)

Since 2.10

### gdk_screen_get_active_window ()

    GdkWindow *         gdk_screen_get_active_window        (GdkScreen *screen);

Returns the screen's currently active window.

On X11, this is done by inspecting the _NET_ACTIVE_WINDOW property on the root window, as described in the Extended Window Manager Hints. If there is no currently currently active window, or the window manager does not support the _NET_ACTIVE_WINDOW hint, this function returns `NULL`.

On other platforms, this function may return `NULL`, depending on whether it is implementable on that platform.

The returned window should be unrefed using `g_object_unref()` when no longer needed.

`screen` : | a GdkScreen
Returns : | the currently active window, or `NULL`. [transfer full]

Since 2.10

### gdk_screen_get_window_stack ()

    GList *             gdk_screen_get_window_stack         (GdkScreen *screen);

Returns a GList of GdkWindows representing the current window stack.

On X11, this is done by inspecting the _NET_CLIENT_LIST_STACKING property on the root window, as described in the Extended Window Manager Hints. If the window manager does not support the _NET_CLIENT_LIST_STACKING hint, this function returns `NULL`.

On other platforms, this function may return `NULL`, depending on whether it is implementable on that platform.

The returned list is newly allocated and owns references to the windows it contains, so it should be freed using `g_list_free()` and its windows unrefed using `g_object_unref()` when no longer needed.

`screen` : | a GdkScreen
Returns : | a list of GdkWindows for the current window stack, or `NULL`. [transfer full][element-type GdkWindow]

Since 2.10

## Property Details

### The `"font-options"` property

      "font-options"             gpointer              : Read / Write

The default font options for the screen.

### The `"resolution"` property

      "resolution"               gdouble               : Read / Write

The resolution for fonts on the screen.

Default value: -1

## Signal Details

### The `"composited-changed"` signal

    void                user_function                      (GdkScreen *screen,
                                                            gpointer   user_data)      : Run Last

The ::composited-changed signal is emitted when the composited status of the screen changes

`screen` : | the object on which the signal is emitted
`user_data` : | user data set when the signal handler was connected.

Since 2.10

### The `"monitors-changed"` signal

    void                user_function                      (GdkScreen *screen,
                                                            gpointer   user_data)      : Run Last

The ::monitors-changed signal is emitted when the number, size or position of the monitors attached to the screen change.

Only for X11 and OS X for now. A future implementation for Win32 may be a possibility.

`screen` : | the object on which the signal is emitted
`user_data` : | user data set when the signal handler was connected.

Since 2.14

### The `"size-changed"` signal

    void                user_function                      (GdkScreen *screen,
                                                            gpointer   user_data)      : Run Last

The ::size-changed signal is emitted when the pixel width or height of a screen changes.

`screen` : | the object on which the signal is emitted
`user_data` : | user data set when the signal handler was connected.

Since 2.2