Main loop and Events

Typical main() function for a GTK+ application

It’s OK to use the GLib main loop directly instead of gtk_main(), though it involves slightly more typing. See GMainLoop in the GLib documentation.

gtk_disable_setlocale ()

void
gtk_disable_setlocale (void);

Prevents gtk_init(), gtk_init_check(), gtk_init_with_args() and gtk_parse_args() from automatically calling setlocale (LC_ALL, ""). You would want to use this function if you wanted to set the locale for your program to something other than the user’s locale, or if you wanted to set different values for different locale categories.

Most programs should not need to call this function.

gtk_get_default_language ()

PangoLanguage *
gtk_get_default_language (void);

Returns the PangoLanguage for the default language currently in effect. (Note that this can change over the life of an application.) The default language is derived from the current locale. It determines, for example, whether GTK+ uses the right-to-left or left-to-right text direction.

This function is equivalent to pango_language_get_default(). See that function for details.

gtk_get_locale_direction ()

GtkTextDirection
gtk_get_locale_direction (void);

Get the direction of the current locale. This is the expected reading direction for text and UI.

This function depends on the current locale being set with setlocale() and will default to setting the GTK_TEXT_DIR_LTR direction otherwise. GTK_TEXT_DIR_NONE will never be returned.

GTK+ sets the default text direction according to the locale during gtk_init(), and you should normally use gtk_widget_get_direction() or gtk_widget_get_default_direction() to obtain the current direcion.

This function is only needed rare cases when the locale is changed after GTK+ has already been initialized. In this case, you can use it to update the default text direction as follows:

Since: 3.12

gtk_parse_args ()

gboolean
gtk_parse_args (int *argc,
                char ***argv);

Parses command line arguments, and initializes global attributes of GTK+, but does not actually open a connection to a display. (See gdk_display_open(), gdk_get_display_arg_name())

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

There is no need to call this function explicitly if you are using gtk_init(), or gtk_init_check().

Note that many aspects of GTK+ require a display connection to function, so this way of initializing GTK+ is really only useful for specialized use cases.

gtk_init ()

void
gtk_init (int *argc,
          char ***argv);

Call this function before using any other GTK+ functions in your GUI applications. It will initialize everything needed to operate the toolkit and parses some standard command line options.

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.

argc and argv are adjusted accordingly so your own code will never see those standard arguments.

Note that there are some alternative ways to initialize GTK+: if you are calling gtk_parse_args(), gtk_init_check(), gtk_init_with_args() or g_option_context_parse() with the option group returned by gtk_get_option_group(), you don’t have to call gtk_init().

And if you are using GtkApplication, you don't have to call any of the initialization functions either; the “startup” handler does it for you.

This function will terminate your program if it was unable to initialize the windowing system for some reason. If you want your program to fall back to a textual interface you want to call gtk_init_check() instead.

Since 2.18, GTK+ calls signal (SIGPIPE, SIG_IGN) during initialization, to ignore SIGPIPE signals, since these are almost never wanted in graphical applications. If you do need to handle SIGPIPE for some reason, reset the handler after gtk_init(), but notice that other libraries (e.g. libdbus or gvfs) might do similar things.

gtk_init_check ()

gboolean
gtk_init_check (int *argc,
                char ***argv);

This function does the same work as gtk_init() with only a single change: It does not terminate the program if the commandline arguments couldn’t be parsed or the windowing system can’t be initialized. Instead it returns FALSE on failure.

This way the application can fall back to some other means of communication with the user - for example a curses or command line interface.

Note that calling any GTK function or instantiating any GTK type after this function returns FALSE results in undefined behavior.

gtk_init_with_args ()

gboolean
gtk_init_with_args (gint *argc,
                    gchar ***argv,
                    const gchar *parameter_string,
                    const GOptionEntry *entries,
                    const gchar *translation_domain,
                    GError **error);

This function does the same work as gtk_init_check(). Additionally, it allows you to add your own commandline options, and it automatically generates nicely formatted --help output. Note that your program will be terminated after writing out the help output.

Since: 2.6

gtk_get_option_group ()

GOptionGroup *
gtk_get_option_group (gboolean open_default_display);

Returns a GOptionGroup for the commandline arguments recognized by GTK+ and GDK.

You should add this group to your GOptionContext with g_option_context_add_group(), if you are using g_option_context_parse() to parse your commandline arguments.

Since: 2.6

gtk_events_pending ()

gboolean
gtk_events_pending (void);

Checks if any events are pending.

This can be used to update the UI and invoke timeouts etc. while doing some time intensive computation.

gtk_main ()

void
gtk_main (void);

Runs the main loop until gtk_main_quit() is called.

You can nest calls to gtk_main(). In that case gtk_main_quit() will make the innermost invocation of the main loop return.

gtk_main_level ()

guint
gtk_main_level (void);

Asks for the current nesting level of the main loop.

gtk_main_quit ()

void
gtk_main_quit (void);

Makes the innermost invocation of the main loop return when it regains control.

gtk_main_iteration ()

gboolean
gtk_main_iteration (void);

Runs a single iteration of the mainloop.

If no events are waiting to be processed GTK+ will block until the next event is noticed. If you don’t want to block look at gtk_main_iteration_do() or check if any events are pending with gtk_events_pending() first.

gtk_main_iteration_do ()

gboolean
gtk_main_iteration_do (gboolean blocking);

Runs a single iteration of the mainloop. If no events are available either return or block depending on the value of blocking .

gtk_main_do_event ()

void
gtk_main_do_event (GdkEvent *event);

Processes a single GDK event.

This is public only to allow filtering of events between GDK and GTK+. You will not usually need to call this function directly.

While you should not call this function directly, you might want to know how exactly events are handled. So here is what this function does with the event:

GtkModuleInitFunc ()

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

Each GTK+ module must have a function gtk_module_init() with this prototype. This function is called after loading the module.

GtkModuleDisplayInitFunc ()

void
(*GtkModuleDisplayInitFunc) (GdkDisplay *display);

A multihead-aware GTK+ module may have a gtk_module_display_init() function with this prototype. GTK+ calls this function for each opened display.

Since: 2.2

gtk_true ()

gboolean
gtk_true (void);

All this function does it to return TRUE.

This can be useful for example if you want to inhibit the deletion of a window. Of course you should not do this as the user expects a reaction from clicking the close icon of the window...

int
main (int argc, char **argv)
{
 GtkWidget *mainwin;
  // Initialize i18n support with bindtextdomain(), etc.

  // ...

  // Initialize the widget set
  gtk_init (&argc, &argv);

  // Create the main window
  mainwin = gtk_window_new (GTK_WINDOW_TOPLEVEL);

  // Set up our GUI elements

  // ...

  // Show the application window
  gtk_widget_show_all (mainwin);

  // Enter the main event loop, and wait for user interaction
  gtk_main ();

  // The user lost interest
  return 0;
}

gtk_false ()

gboolean
gtk_false (void);

Analogical to gtk_true(), this function does nothing but always returns FALSE.

gtk_grab_add ()

void
gtk_grab_add (GtkWidget *widget);

Makes widget the current grabbed widget.

This means that interaction with other widgets in the same application is blocked and mouse as well as keyboard events are delivered to this widget.

If widget is not sensitive, it is not set as the current grabbed widget and this function does nothing.

[method]

gtk_grab_get_current ()

GtkWidget *
gtk_grab_get_current (void);

Queries the current grab of the default window group.

gtk_grab_remove ()

void
gtk_grab_remove (GtkWidget *widget);

Removes the grab from the given widget.

You have to pair calls to gtk_grab_add() and gtk_grab_remove().

If widget does not have the grab, this function does nothing.

[method]

gtk_device_grab_add ()

void
gtk_device_grab_add (GtkWidget *widget,
                     GdkDevice *device,
                     gboolean block_others);

Adds a GTK+ grab on device , so all the events on device and its associated pointer or keyboard (if any) are delivered to widget . If the block_others parameter is TRUE, any other devices will be unable to interact with widget during the grab.

Since: 3.0

gtk_device_grab_remove ()

void
gtk_device_grab_remove (GtkWidget *widget,
                        GdkDevice *device);

Removes a device grab from the given widget.

You have to pair calls to gtk_device_grab_add() and gtk_device_grab_remove().

Since: 3.0

gtk_key_snooper_install ()

guint
gtk_key_snooper_install (GtkKeySnoopFunc snooper,
                         gpointer func_data);

Installs a key snooper function, which will get called on all key events before delivering them normally.

[skip]

GtkKeySnoopFunc ()

gint
(*GtkKeySnoopFunc) (GtkWidget *grab_widget,
                    GdkEventKey *event,
                    gpointer func_data);

Key snooper functions are called before normal event delivery. They can be used to implement custom key event handling.

gtk_key_snooper_remove ()

void
gtk_key_snooper_remove (guint snooper_handler_id);

Removes the key snooper function with the given id.

gtk_get_current_event ()

GdkEvent *
gtk_get_current_event (void);

Obtains a copy of the event currently being processed by GTK+.

For example, if you are handling a “clicked” signal, the current event will be the GdkEventButton that triggered the ::clicked signal.

gtk_get_current_event_time ()

guint32
gtk_get_current_event_time (void);

If there is a current event and it has a timestamp, return that timestamp, otherwise return GDK_CURRENT_TIME.

gtk_get_current_event_state ()

gboolean
gtk_get_current_event_state (GdkModifierType *state);

If there is a current event and it has a state field, place that state field in state and return TRUE, otherwise return FALSE.

gtk_get_current_event_device ()

GdkDevice *
gtk_get_current_event_device (void);

If there is a current event and it has a device, return that device, otherwise return NULL.

gtk_get_event_widget ()

GtkWidget *
gtk_get_event_widget (GdkEvent *event);

If event is NULL or the event was not associated with any widget, returns NULL, otherwise returns the widget that received the event originally.

gtk_propagate_event ()

void
gtk_propagate_event (GtkWidget *widget,
                     GdkEvent *event);

Sends an event to a widget, propagating the event to parent widgets if the event remains unhandled.

Events received by GTK+ from GDK normally begin in gtk_main_do_event(). Depending on the type of event, existence of modal dialogs, grabs, etc., the event may be propagated; if so, this function is used.

gtk_propagate_event() calls gtk_widget_event() on each widget it decides to send the event to. So gtk_widget_event() is the lowest-level function; it simply emits the “event” and possibly an event-specific signal on a widget. gtk_propagate_event() is a bit higher-level, and gtk_main_do_event() is the highest level.

All that said, you most likely don’t want to use any of these functions; synthesizing events is rarely needed. There are almost certainly better ways to achieve your goals. For example, use gdk_window_invalidate_rect() or gtk_widget_queue_draw() instead of making up expose events.

GTK_PRIORITY_RESIZE

#define GTK_PRIORITY_RESIZE (G_PRIORITY_HIGH_IDLE + 10)

Use this priority for functionality related to size allocation.

It is used internally by GTK+ to compute the sizes of widgets. This priority is higher than GDK_PRIORITY_REDRAW to avoid resizing a widget which was just redrawn.