Main loop and Events

gtk_set_locale ()

gchar*      gtk_set_locale                  (void);

Initializes internationalization support for GTK+. gtk_init() automatically does this, so there is typically no point in calling this function.

If you are calling this function because you changed the locale after GTK+ is was initialized, then calling this function may help a bit. (Note, however, that changing the locale after GTK+ is initialized may produce inconsistent results and is not really supported.)

In detail - sets the current locale according to the program environment. This is the same as calling the C library function setlocale (LC_ALL, "") but also takes care of the locale specific setup of the windowing system used by GDK.

gtk_disable_setlocale ()

void        gtk_disable_setlocale           (void);

Prevents gtk_init() and gtk_init_check() 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 ISO language code 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.

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

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 GUI 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.

gtk_exit ()

void        gtk_exit                        (gint error_code);

Terminates the program and returns the given exit code to the caller. This function will shut down the GUI and free all resources allocated for GTK+.

gtk_events_pending ()

gint        gtk_events_pending              (void);

Checks if any events are pending. This can be used to update the GUI and invoke timeouts etc. while doing some time intensive computation.

	/* computation going on */
...
        while (gtk_events_pending ())
	  gtk_main_iteration ();
...
	/* computation continued */

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. This can be useful when calling gtk_quit_add().

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 dependent 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:

1. Compress enter/leave notify events. If the event passed build an enter/leave pair together with the next event (peeked from GDK) both events are thrown away. This is to avoid a backlog of (de-)highlighting widgets crossed by the pointer.

2. Find the widget which got the event. If the widget can't be determined the event is thrown away unless it belongs to a INCR transaction. In that case it is passed to gtk_selection_incr_event().

3. Then the event is passed on a stack so you can query the currently handled event with gtk_get_current_event().

4. The event is sent to a widget. If a grab is active all events for widgets that are not in the contained in the grab widget are sent to the latter with a few exceptions:

   • Deletion and destruction events are still sent to the event widget for obvious reasons.

   • Events which directly relate to the visual representation of the event widget.

   • Leave events are delivered to the event widget if there was an enter event delivered to it before without the paired leave event.

   • Drag events are not redirected because it is unclear what the semantics of that would be.

   Another point of interest might be that all key events are first passed through the key snooper functions if there are any. Read the description of gtk_key_snooper_install() if you need this feature.

5. After finishing the delivery the event is popped from the event stack.

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 with the argc and argv cleaned from any arguments that GTK+ handles itself.

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...

#include <gtk/gtk.h>

int
main (int argc, char **argv)
{
  GtkWidget     *win, *but;

  gtk_init( &argc, &argv );

  win = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  g_signal_connect (GTK_OBJECT(win), "delete-event", 
                    G_CALLBACK (gtk_true), NULL);
  g_signal_connect (GTK_OBJECT(win), "destroy", 
		    G_CALLBACK (gtk_main_quit), NULL);

  but = gtk_button_new_with_label ("Close yourself. I mean it!");
  g_signal_connect_swapped (GTK_OBJECT (but), "clicked", 
		  G_CALLBACK (gtk_object_destroy), (gpointer) win);
  gtk_container_add (GTK_CONTAINER (win), but);

  gtk_widget_show_all (win);
  gtk_main ();
  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.

gtk_grab_get_current ()

GtkWidget*  gtk_grab_get_current            (void);

Queries the current grab.

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().

gtk_init_add ()

void        gtk_init_add                    (GtkFunction function,
                                             gpointer data);

Registers a function to be called when the mainloop is started.

gtk_quit_add_destroy ()

void        gtk_quit_add_destroy            (guint main_level,
                                             GtkObject *object);

Trigger destruction of object in case the mainloop at level main_level is quit.

gtk_quit_add ()

guint       gtk_quit_add                    (guint main_level,
                                             GtkFunction function,
                                             gpointer data);

Registers a function to be called when an instance of the mainloop is left.

gtk_quit_add_full ()

guint       gtk_quit_add_full               (guint main_level,
                                             GtkFunction function,
                                             GtkCallbackMarshal marshal,
                                             gpointer data,
                                             GtkDestroyNotify destroy);

Registers a function to be called when an instance of the mainloop is left. In comparison to gtk_quit_add() this function adds the possibility to pass a marshaller and a function to be called when the quit handler is freed.

The former can be used to run interpreted code instead of a compiled function while the latter can be used to free the information stored in data (while you can do this in function as well)... So this function will mostly be used by GTK+ wrappers for languages other than C.

gtk_quit_remove ()

void        gtk_quit_remove                 (guint quit_handler_id);

Removes a quit handler by it's identifier.

gtk_quit_remove_by_data ()

void        gtk_quit_remove_by_data         (gpointer data);

Removes a quit handler identified by it's data field.

gtk_timeout_add_full ()

guint       gtk_timeout_add_full            (guint32 interval,
                                             GtkFunction function,
                                             GtkCallbackMarshal marshal,
                                             gpointer data,
                                             GtkDestroyNotify destroy);

Registers a function to be called periodically. The function will be called repeatedly after interval milliseconds until it returns FALSE at which point the timeout is destroyed and will not be called again.

gtk_timeout_add ()

guint       gtk_timeout_add                 (guint32 interval,
                                             GtkFunction function,
                                             gpointer data);

Registers a function to be called periodically. The function will be called repeatedly after interval milliseconds until it returns FALSE at which point the timeout is destroyed and will not be called again.

gtk_timeout_remove ()

void        gtk_timeout_remove              (guint timeout_handler_id);

Removes the given timeout destroying all information about it.

gtk_idle_add ()

guint       gtk_idle_add                    (GtkFunction function,
                                             gpointer data);

Causes the mainloop to call the given function whenever no events with higher priority are to be processed. The default priority is GTK_PRIORITY_DEFAULT, which is rather low.

gtk_idle_add_priority ()

guint       gtk_idle_add_priority           (gint priority,
                                             GtkFunction function,
                                             gpointer data);

Like gtk_idle_add() this function allows you to have a function called when the event loop is idle. The difference is that you can give a priority different from GTK_PRIORITY_DEFAULT to the idle function.

gtk_idle_add_full ()

guint       gtk_idle_add_full               (gint priority,
                                             GtkFunction function,
                                             GtkCallbackMarshal marshal,
                                             gpointer data,
                                             GtkDestroyNotify destroy);

Like gtk_idle_add() this function allows you to have a function called when the event loop is idle. The difference is that you can give a priority different from GTK_PRIORITY_DEFAULT to the idle function.

gtk_idle_remove ()

void        gtk_idle_remove                 (guint idle_handler_id);

Removes the idle function with the given id.

gtk_idle_remove_by_data ()

void        gtk_idle_remove_by_data         (gpointer data);

Removes the idle function identified by the user data.

gtk_input_add_full ()

guint       gtk_input_add_full              (gint source,
                                             GdkInputCondition condition,
                                             GdkInputFunction function,
                                             GtkCallbackMarshal marshal,
                                             gpointer data,
                                             GtkDestroyNotify destroy);

Registers a function to be called when a condition becomes true on a file descriptor.

gtk_input_remove ()

void        gtk_input_remove                (guint input_handler_id);

Removes the function with the given id.

GTK_PRIORITY_REDRAW

#define GTK_PRIORITY_REDRAW     (G_PRIORITY_HIGH_IDLE + 20)

Use this priority for redrawing related stuff. It is used internally by GTK+ to do pending redraws. This priority is lower than GTK_PRIORITY_RESIZE to avoid redrawing a widget just before resizing (and therefore redrawing it again).

GTK_PRIORITY_RESIZE

#define GTK_PRIORITY_RESIZE     (G_PRIORITY_HIGH_IDLE + 10)

Use this priority for resizing related stuff. It is used internally by GTK+ to compute the sizes of widgets. This priority is higher than GTK_PRIORITY_REDRAW to avoid resizing a widget which was just redrawn.

GTK_PRIORITY_HIGH

#define GTK_PRIORITY_HIGH       G_PRIORITY_HIGH

Use this for high priority timeouts. This priority is never used inside GTK+ so everything running at this priority will be running before anything inside the toolkit.

GTK_PRIORITY_INTERNAL

#define GTK_PRIORITY_INTERNAL   GTK_PRIORITY_REDRAW

This priority is for GTK+ internal stuff. Don't use it in your applications.

GTK_PRIORITY_DEFAULT

#define GTK_PRIORITY_DEFAULT	G_PRIORITY_DEFAULT_IDLE

Default priority for idle functions.

GTK_PRIORITY_LOW

#define GTK_PRIORITY_LOW	G_PRIORITY_LOW

Priority for very unimportant background tasks.

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.

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 get a "clicked" signal from GtkButton, the current event will be the GdkEventButton that triggered the "clicked" signal. The returned event must be freed with gdk_event_free(). If there is no current event, the function returns NULL.

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_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. Consider asking on the mailing list for better ways to achieve your goals. For example, use gdk_window_invalidate_rect() or gtk_widget_queue_draw() instead of making up expose events.