GDK Reference Manual
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# General

## Name

General -- library initialization and miscellaneous functions.

## Synopsis

    #include <gdk/gdk.h>

    void        gdk_init                        (gint *argc,
                                                 gchar ***argv);
    gboolean    gdk_init_check                  (gint *argc,
                                                 gchar ***argv);
    void        gdk_parse_args                  (gint *argc,
                                                 gchar ***argv);
    gchar*      gdk_get_display_arg_name        (void);
    gchar*      gdk_set_locale                  (void);
    void        gdk_set_sm_client_id            (const gchar *sm_client_id);
    void        gdk_exit                        (gint error_code);

    G_CONST_RETURN char* gdk_get_program_class  (void);
    void        gdk_set_program_class           (const char *program_class);

    gchar*      gdk_get_display                 (void);

    void        gdk_flush                       (void);

    gint        gdk_screen_width                (void);
    gint        gdk_screen_height               (void);
    gint        gdk_screen_width_mm             (void);
    gint        gdk_screen_height_mm            (void);

    GdkGrabStatus gdk_pointer_grab              (GdkWindow *window,
                                                 gboolean owner_events,
                                                 GdkEventMask event_mask,
                                                 GdkWindow *confine_to,
                                                 GdkCursor *cursor,
                                                 guint32 time);
    enum        GdkGrabStatus;
    void        gdk_pointer_ungrab              (guint32 time);
    gboolean    gdk_pointer_is_grabbed          (void);
    void        gdk_set_double_click_time       (guint msec);

    GdkGrabStatus gdk_keyboard_grab             (GdkWindow *window,
                                                 gboolean owner_events,
                                                 guint32 time);
    void        gdk_keyboard_ungrab             (guint32 time);

    void        gdk_beep                        (void);

    gboolean    gdk_get_use_xshm                (void);
    void        gdk_set_use_xshm                (gboolean use_xshm);

    void        gdk_error_trap_push             (void);
    gint        gdk_error_trap_pop              (void);

    #define     GDK_WINDOWING_X11
    #define     GDK_WINDOWING_WIN32
    #define     GDK_WINDOWING_FB

## Description

This section describes the GDK initialization functions and miscellaneous utility functions.

## Details

### gdk_init ()

    void        gdk_init                        (gint *argc,
                                                 gchar ***argv);

Initializes the GDK library and connects to the X server. If initialization fails, a warning message is output and the application terminates with a call to `exit(1)`.

Any arguments used by GDK are removed from the array and `argc` and `argv` are updated accordingly.

GTK+ initializes GDK in gtk_init() and so this function is not usually needed by GTK+ applications.

`argc` : | the number of command line arguments.
`argv` : | the array of command line arguments.

### gdk_init_check ()

    gboolean    gdk_init_check                  (gint *argc,
                                                 gchar ***argv);

Initializes the GDK library and connects to the X server, returning `TRUE` on success.

Any arguments used by GDK are removed from the array and `argc` and `argv` are updated accordingly.

GTK+ initializes GDK in gtk_init() and so this function is not usually needed by GTK+ applications.

`argc` : | the number of command line arguments.
`argv` : | the array of command line arguments.
Returns : | `TRUE` if initialization succeeded.

### gdk_parse_args ()

    void        gdk_parse_args                  (gint *argc,
                                                 gchar ***argv);

Parse command line arguments, and store for future use by calls to gdk_open_display().

Any arguments used by GDK are removed from the array and `argc` and `argv` are updated accordingly.

You shouldn't call this function explicitely if you are using gtk_init(), gtk_init_check(), gdk_init(), or gdk_init_check().

`argc` : | the number of command line arguments.
`argv` : | the array of command line arguments.

### gdk_get_display_arg_name ()

    gchar*      gdk_get_display_arg_name        (void);

Gets the display name specified in the command line arguments passed to gdk_init() or gdk_parse_args(), if any.

Returns : | the display name, if specified explicitely, otherwise `NULL`

### gdk_set_locale ()

    gchar*      gdk_set_locale                  (void);

Initializes the support for internationalization by calling the `setlocale()` system call. This function is called by gtk_set_locale() and so GTK+ applications should use that instead.

The locale to use is determined by the `LANG` environment variable, so to run an application in a certain locale you can do something like this:

      export LANG="fr"
      ... run application ...

If the locale is not supported by X then it is reset to the standard "C" locale.

Returns : | the resulting locale.

### gdk_set_sm_client_id ()

    void        gdk_set_sm_client_id            (const gchar *sm_client_id);

Sets the `SM_CLIENT_ID` property on the application's leader window so that the window manager can save the application's state using the X11R6 ICCCM session management protocol.

See the X Session Management Library documentation for more information on session management and the Inter-Client Communication Conventions Manual (ICCCM) for information on the `WM_CLIENT_LEADER` property. (Both documents are part of the X Window System distribution.)

`sm_client_id` : | the client id assigned by the session manager when the connection was opened, or `NULL` to remove the property.

### gdk_exit ()

    void        gdk_exit                        (gint error_code);

Warning
`gdk_exit` is deprecated and should not be used in newly-written code.

Exits the application using the `exit()` system call.

This routine is provided mainly for backwards compatibility, since it used to perform tasks necessary to exit the application cleanly. Those tasks are now performed in a function which is automatically called on exit (via the use of g_atexit()).

`error_code` : | the error code to pass to the `exit()` call.

### gdk_get_program_class ()

    G_CONST_RETURN char* gdk_get_program_class  (void);

Gets the program class. Unless the program class has explicitly been set with gdk_set_program_class() or with the `--class` commandline option, the default value is the program name (determined with g_get_prgname()) with the first character converted to uppercase.

Returns : | the program class.

### gdk_set_program_class ()

    void        gdk_set_program_class           (const char *program_class);

Sets the program class. The X11 backend uses the program class to set the class name part of the `WM_CLASS` property on toplevel windows; see the ICCCM.

`program_class` : | a string.

### gdk_get_display ()

    gchar*      gdk_get_display                 (void);

Gets the name of the display, which usually comes from the `DISPLAY` environment variable or the `--display` command line option.

Returns : | the name of the display.

### gdk_flush ()

    void        gdk_flush                       (void);

Flushes the X output buffer and waits until all requests have been processed by the server. This is rarely needed by applications. It's main use is for trapping X errors with gdk_error_trap_push() and gdk_error_trap_pop().

### gdk_screen_width ()

    gint        gdk_screen_width                (void);

Returns the width of the default screen in pixels.

Returns : | the width of the default screen in pixels.

### gdk_screen_height ()

    gint        gdk_screen_height               (void);

Returns the height of the default screen in pixels.

Returns : | the height of the default screen in pixels.

### gdk_screen_width_mm ()

    gint        gdk_screen_width_mm             (void);

Returns the width of the default screen in millimeters. Note that on many X servers this value will not be correct.

Returns : | the width of the default screen in millimeters, though it is not always correct.

### gdk_screen_height_mm ()

    gint        gdk_screen_height_mm            (void);

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

Returns : | the height of the default screen in millimeters, though it is not always correct.

### gdk_pointer_grab ()

    GdkGrabStatus gdk_pointer_grab              (GdkWindow *window,
                                                 gboolean owner_events,
                                                 GdkEventMask event_mask,
                                                 GdkWindow *confine_to,
                                                 GdkCursor *cursor,
                                                 guint32 time);

Grabs the pointer (usually a mouse) so that all events are passed to this application until the pointer is ungrabbed with gdk_pointer_ungrab(), or the grab window becomes unviewable. This overrides any previous pointer grab by this client.

Pointer grabs are used for operations which need complete control over mouse events, even if the mouse leaves the application. For example in GTK+ it is used for Drag and Drop, for dragging the handle in the GtkHPaned and GtkVPaned widgets, and for resizing columns in GtkCList widgets.

Note that if the event mask of an X window has selected both button press and button release events, then a button press event will cause an automatic pointer grab until the button is released. X does this automatically since most applications expect to receive button press and release events in pairs. It is equivalent to a pointer grab on the window with `owner_events` set to `TRUE`.

`window` : | the GdkWindow which will own the grab (the grab window).
`owner_events` : | if `FALSE` then all pointer events are reported with respect to `window` and are only reported if selected by `event_mask`. If `TRUE` then pointer events for this application are reported as normal, but pointer events outside this application are reported with respect to `window` and only if selected by `event_mask`. In either mode, unreported events are discarded.
`event_mask` : | specifies the event mask, which is used in accordance with `owner_events`.
`confine_to` : | If non-`NULL`, the pointer will be confined to this window during the grab. If the pointer is outside `confine_to`, it will automatically be moved to the closest edge of `confine_to` and enter and leave events will be generated as necessary.
`cursor` : | the cursor to display while the grab is active. If this is `NULL` then the normal cursors are used for `window` and its descendants, and the cursor for `window` is used for all other windows.
`time` : | the timestamp of the event which led to this pointer grab. This usually comes from a GdkEventButton struct, though `GDK_CURRENT_TIME` can be used if the time isn't known.
Returns : | `GDK_GRAB_SUCCESS` if the grab was successful.

### enum GdkGrabStatus

    typedef enum
    {
      GDK_GRAB_SUCCESS         = 0,
      GDK_GRAB_ALREADY_GRABBED = 1,
      GDK_GRAB_INVALID_TIME    = 2,
      GDK_GRAB_NOT_VIEWABLE    = 3,
      GDK_GRAB_FROZEN          = 4
    } GdkGrabStatus;

Returned by gdk_pointer_grab() and gdk_keyboard_grab() to indicate success or the reason for the failure of the grab attempt.

`GDK_GRAB_SUCCESS` | the resource was successfully grabbed.
`GDK_GRAB_ALREADY_GRABBED` | the resource is actively grabbed by another client.
`GDK_GRAB_INVALID_TIME` | the resource was grabbed more recently than the specified time.
`GDK_GRAB_NOT_VIEWABLE` | the grab window or the `confine_to` window are not viewable.
`GDK_GRAB_FROZEN` | the resource is frozen by an active grab of another client.

### gdk_pointer_ungrab ()

    void        gdk_pointer_ungrab              (guint32 time);

`time` : | a timestamp from a GdkEvent, or `GDK_CURRENT_TIME` if no timestamp is available. Ungrabs the pointer, if it is grabbed by this application.

### gdk_pointer_is_grabbed ()

    gboolean    gdk_pointer_is_grabbed          (void);

Returns `TRUE` if the pointer is currently grabbed by this application.

Note that this does not take the inmplicit pointer grab on button presses into account.

Returns : | `TRUE` if the pointer is currently grabbed by this application.*

### gdk_set_double_click_time ()

    void        gdk_set_double_click_time       (guint msec);

Set the double click time for the default display. See gdk_display_set_double_click_time(). Applications should NOT set this, it is a global user-configured setting.

`msec` : | double click time in milliseconds (thousandths of a second)

### gdk_keyboard_grab ()

    GdkGrabStatus gdk_keyboard_grab             (GdkWindow *window,
                                                 gboolean owner_events,
                                                 guint32 time);

Grabs the keyboard so that all events are passed to this application until the keyboard is ungrabbed with gdk_keyboard_ungrab(). This overrides any previous keyboard grab by this client.

`window` : | the GdkWindow which will own the grab (the grab window).
`owner_events` : | if `FALSE` then all keyboard events are reported with respect to `window`. If `TRUE` then keyboard events for this application are reported as normal, but keyboard events outside this application are reported with respect to `window`. Both key press and key release events are always reported, independant of the event mask set by the application.
`time` : | a timestamp from a GdkEvent, or `GDK_CURRENT_TIME` if no timestamp is available.
Returns : | `GDK_GRAB_SUCCESS` if the grab was successful.

### gdk_keyboard_ungrab ()

    void        gdk_keyboard_ungrab             (guint32 time);

Ungrabs the keyboard, if it is grabbed by this application.

`time` : | a timestamp from a GdkEvent, or `GDK_CURRENT_TIME` if no timestamp is available.

### gdk_beep ()

    void        gdk_beep                        (void);

Emits a short beep.

### gdk_get_use_xshm ()

    gboolean    gdk_get_use_xshm                (void);

Warning
`gdk_get_use_xshm` is deprecated and should not be used in newly-written code.

Returns `TRUE` if GDK will attempt to use the MIT-SHM shared memory extension.

The shared memory extension is used for GdkImage, and consequently for GdkRGB. It enables much faster drawing by communicating with the X server through SYSV shared memory calls. However, it can only be used if the X client and server are on the same machine and the server supports it.

Returns : | `TRUE` if use of the MIT shared memory extension will be attempted.

### gdk_set_use_xshm ()

    void        gdk_set_use_xshm                (gboolean use_xshm);

Warning
`gdk_set_use_xshm` is deprecated and should not be used in newly-written code.

Sets whether the use of the MIT shared memory extension should be attempted. This function is mainly for internal use. It is only safe for an application to set this to `FALSE`, since if it is set to `TRUE` and the server does not support the extension it may cause warning messages to be output.

`use_xshm` : | `TRUE` if use of the MIT shared memory extension should be attempted.

### gdk_error_trap_push ()

    void        gdk_error_trap_push             (void);

This function allows X errors to be trapped instead of the normal behavior of exiting the application. It should only be used if it is not possible to avoid the X error in any other way.

Example 1. Trapping an X error.

      gdk_error_trap_push ();

      /* ... Call the X function which may cause an error here ... */

      /* Flush the X queue to catch errors now. */
      gdk_flush ();

      if (gdk_error_trap_pop ())
        {
          /* ... Handle the error here ... */
        }

### gdk_error_trap_pop ()

    gint        gdk_error_trap_pop              (void);

Removes the X error trap installed with gdk_error_trap_push().

Returns : | the X error code, or 0 if no error occurred.

### GDK_WINDOWING_X11

    #define GDK_WINDOWING_X11

This macro is defined if GDK is configured to use the X backend.

### GDK_WINDOWING_WIN32

    #define GDK_WINDOWING_WIN32

This macro is defined if GDK is configured to use the Win32 backend.

### GDK_WINDOWING_FB

    #define GDK_WINDOWING_FB

This macro is defined if GDK is configured to use the Linux framebuffer backend.

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