## GdkScreen

GdkScreen — Object representing a physical screen

## Synopsis

    #include <gdk/gdk.h>

                GdkScreen;
    GdkScreen*  gdk_screen_get_default          (void);
    GdkColormap* gdk_screen_get_default_colormap
                                                (GdkScreen *screen);
    void        gdk_screen_set_default_colormap (GdkScreen *screen,
                                                 GdkColormap *colormap);
    GdkColormap* gdk_screen_get_system_colormap (GdkScreen *screen);
    GdkVisual*  gdk_screen_get_system_visual    (GdkScreen *screen);
    GdkColormap* gdk_screen_get_rgb_colormap    (GdkScreen *screen);
    GdkVisual*  gdk_screen_get_rgb_visual       (GdkScreen *screen);
    GdkColormap* gdk_screen_get_rgba_colormap   (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);
    void        gdk_screen_get_monitor_geometry (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);
    void        gdk_screen_broadcast_client_message
                                                (GdkScreen *screen,
                                                 GdkEvent *event);
    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);

    gboolean    gdk_spawn_on_screen             (GdkScreen *screen,
                                                 const gchar *working_directory,
                                                 gchar **argv,
                                                 gchar **envp,
                                                 GSpawnFlags flags,
                                                 GSpawnChildSetupFunc child_setup,
                                                 gpointer user_data,
                                                 gint *child_pid,
                                                 GError **error);
    gboolean    gdk_spawn_on_screen_with_pipes  (GdkScreen *screen,
                                                 const gchar *working_directory,
                                                 gchar **argv,
                                                 gchar **envp,
                                                 GSpawnFlags flags,
                                                 GSpawnChildSetupFunc child_setup,
                                                 gpointer user_data,
                                                 gint *child_pid,
                                                 gint *standard_input,
                                                 gint *standard_output,
                                                 gint *standard_error,
                                                 GError **error);
    gboolean    gdk_spawn_command_line_on_screen
                                                (GdkScreen *screen,
                                                 const gchar *command_line,
                                                 GError **error);

## Object Hierarchy

      GObject
       +----GdkScreen

## Properties

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

## Signals

    "composited-changed"
                void        user_function      (GdkScreen *screen,
                                                gpointer   user_data)      : Run last
    "size-changed"
                void        user_function      (GdkScreen *screen,
                                                gpointer   user_data)      : Run last

## Description

GdkScreen objects are the GDK representation of a physical screen. It 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 colormap (`gdk_screen_get_default_colormap()`), the screen width (`gdk_screen_get_width()`), etc.

Note that a screen may consist of multiple monitors which are merged to form a large screen area.

## Details

### GdkScreen

    typedef struct _GdkScreen GdkScreen;

This is a currently just a placeholder typedef for the first argument of the `window_at_pointer` function in GdkPointerHooks. It will be used when GDK gets multihead support.

Since 2.2

### 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.

Since 2.2

### gdk_screen_get_default_colormap ()

    GdkColormap* gdk_screen_get_default_colormap
                                                (GdkScreen *screen);

Gets the default colormap for `screen`.

`screen` : | a GdkScreen
Returns : | the default GdkColormap.

Since 2.2

### gdk_screen_set_default_colormap ()

    void        gdk_screen_set_default_colormap (GdkScreen *screen,
                                                 GdkColormap *colormap);

Sets the default `colormap` for `screen`.

`screen` : | a GdkScreen
`colormap` : | a GdkColormap

Since 2.2

### gdk_screen_get_system_colormap ()

    GdkColormap* gdk_screen_get_system_colormap (GdkScreen *screen);

Gets the system's default colormap for `screen`

`screen` : | a GdkScreen
Returns : | the default colormap for `screen`.

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

Since 2.2

### gdk_screen_get_rgb_colormap ()

    GdkColormap* gdk_screen_get_rgb_colormap    (GdkScreen *screen);

Gets the preferred colormap for rendering image data on `screen`. Not a very useful function; historically, GDK could only render RGB image data to one colormap and visual, but in the current version it can render to any colormap and visual. So there's no need to call this function.

`screen` : | a GdkScreen.
Returns : | the preferred colormap

Since 2.2

### gdk_screen_get_rgb_visual ()

    GdkVisual*  gdk_screen_get_rgb_visual       (GdkScreen *screen);

Gets a "preferred visual" chosen by GdkRGB for rendering image data on `screen`. In previous versions of GDK, this was the only visual GdkRGB could use for rendering. In current versions, it's simply the visual GdkRGB would have chosen as the optimal one in those previous versions. GdkRGB can now render to drawables with any visual.

`screen` : | a GdkScreen
Returns : | The GdkVisual chosen by GdkRGB.

Since 2.2

### gdk_screen_get_rgba_colormap ()

    GdkColormap* gdk_screen_get_rgba_colormap   (GdkScreen *screen);

Gets a colormap to use for creating windows or pixmaps 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.

`screen` : | a GdkScreen.
Returns : | a colormap to use for windows with an alpha channel or `NULL` if the capability is not available.

Since 2.8

### gdk_screen_get_rgba_visual ()

    GdkVisual*  gdk_screen_get_rgba_visual      (GdkScreen *screen);

Gets a visual to use for creating windows or pixmaps with an alpha channel. See the docs for `gdk_screen_get_rgba_colormap()` for caveats.

`screen` : | a GdkScreen
Returns : | a visual to use for windows with an alpha channel or `NULL` if the capability is not available.

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

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

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

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()`

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_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.

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

Since 2.2

### 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_broadcast_client_message ()

    void        gdk_screen_broadcast_client_message
                                                (GdkScreen *screen,
                                                 GdkEvent *event);

On X11, sends an X ClientMessage event to all toplevel windows on `screen`.

Toplevel windows are determined by checking for the WM_STATE property, as described in the Inter-Client Communication Conventions Manual (ICCCM). If no windows are found with the WM_STATE property set, the message is sent to all children of the root window.

On Windows, broadcasts a message registered with the name GDK_WIN32_CLIENT_MESSAGE to all top-level windows. The amount of data is limited to one long, i.e. four bytes.

`screen` : | the GdkScreen where the event will be broadcasted.
`event` : | the GdkEvent.

Since 2.2

### 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.

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`.

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`.

Since 2.10

### gdk_spawn_on_screen ()

    gboolean    gdk_spawn_on_screen             (GdkScreen *screen,
                                                 const gchar *working_directory,
                                                 gchar **argv,
                                                 gchar **envp,
                                                 GSpawnFlags flags,
                                                 GSpawnChildSetupFunc child_setup,
                                                 gpointer user_data,
                                                 gint *child_pid,
                                                 GError **error);

Like `g_spawn_async()`, except the child process is spawned in such an environment that on calling `gdk_display_open()` it would be returned a GdkDisplay with `screen` as the default screen.

This is useful for applications which wish to launch an application on a specific screen.

`screen` : | a GdkScreen
`working_directory` : | child's current working directory, or `NULL` to inherit parent's
`argv` : | child's argument vector
`envp` : | child's environment, or `NULL` to inherit parent's
`flags` : | flags from GSpawnFlags
`child_setup` : | function to run in the child just before `exec()`
`user_data` : | user data for `child_setup`
`child_pid` : | return location for child process ID, or `NULL`
`error` : | return location for error
Returns : | `TRUE` on success, `FALSE` if error is set

Since 2.4

### gdk_spawn_on_screen_with_pipes ()

    gboolean    gdk_spawn_on_screen_with_pipes  (GdkScreen *screen,
                                                 const gchar *working_directory,
                                                 gchar **argv,
                                                 gchar **envp,
                                                 GSpawnFlags flags,
                                                 GSpawnChildSetupFunc child_setup,
                                                 gpointer user_data,
                                                 gint *child_pid,
                                                 gint *standard_input,
                                                 gint *standard_output,
                                                 gint *standard_error,
                                                 GError **error);

Like `g_spawn_async_with_pipes()`, except the child process is spawned in such an environment that on calling `gdk_display_open()` it would be returned a GdkDisplay with `screen` as the default screen.

This is useful for applications which wish to launch an application on a specific screen.

`screen` : | a GdkScreen
`working_directory` : | child's current working directory, or `NULL` to inherit parent's
`argv` : | child's argument vector
`envp` : | child's environment, or `NULL` to inherit parent's
`flags` : | flags from GSpawnFlags
`child_setup` : | function to run in the child just before `exec()`
`user_data` : | user data for `child_setup`
`child_pid` : | return location for child process ID, or `NULL`
`standard_input` : | return location for file descriptor to write to child's stdin, or `NULL`
`standard_output` : | return location for file descriptor to read child's stdout, or `NULL`
`standard_error` : | return location for file descriptor to read child's stderr, or `NULL`
`error` : | return location for error
Returns : | `TRUE` on success, `FALSE` if an error was set

Since 2.4

### gdk_spawn_command_line_on_screen ()

    gboolean    gdk_spawn_command_line_on_screen
                                                (GdkScreen *screen,
                                                 const gchar *command_line,
                                                 GError **error);

Like `g_spawn_command_line_async()`, except the child process is spawned in such an environment that on calling `gdk_display_open()` it would be returned a GdkDisplay with `screen` as the default screen.

This is useful for applications which wish to launch an application on a specific screen.

`screen` : | a GdkScreen
`command_line` : | a command line
`error` : | return location for errors
Returns : | `TRUE` on success, `FALSE` if error is set.

Since 2.4

## 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 "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