delete event和destroy信号

0. 有关g_signal和gtk_signal

    g_signal_emit之后，立即会调用g_signal_connect注册的回调函数。

    gtk的signal也是gsignal, 当main_loop中收到x的event后，x_event->gdk_event  ->g_signal

 

    如delete_event和destroy两个gtk的信号实际定义如下：

    Object_signals[DESTROY] = G_signal_new(“destroy”, G_TYPE_FROM_CLASS(gobject_class),G_SIGNAL_RUN_CLEANUP | G_SIGNAL_NO_RECURSE| G_SIGNAL_NO_HOOKS, G_STRUCT_OFFSET(GtkObjectClass, destroy), NULL, NULL, _gtk_marshal_VOID__VOID,G_TYPE_NONE, 0);Widget_signals[DELETE_EVENT] = g_signal_new(“delete_event”, G_TYPE_FROM_CLASS(gobject_class),G_SIGNAL_RUN_LAST,G_STRUCT_OFFSET(GtkWidgetClass, delete_event),_gtk_boolean_handled_accumulator, NULL,_gtk_marshal_BOOLEAN__BOXED,G_TYPE_BOOLEAN, 1,GDK_TYPE_EVENT | G_SIGNAL_TYPE_STATIC_SCOPE); 

   它们一个是GObject的信号(destroy)，一个是widget的信号（delete_event)

 

1. delete event的产生

 （1） main_loop中收到x_event ClientMessage -->gdk_event GDK_CLIENT_EVENT

gdk_event_translate(GdkDisplay *display, GdkEvent *event, XEvent *xevent, gboolean return_exposes){.. Switch(xevent->type){…Case ClientMessage://将event转成GDK_CLIENT_EVENT类型…}

 

（2） gdk_event GDK_CLIENT_EVENT --> gdk_event GDK_DELETE

     当收到client event后， 通过函数gdk_wm_protocols_filter判断其为WM_DELETE_WINDOW后，会进到  gtk_main_do_event中：

 gtk_main_do_event(GdkEvent *event){…Case GDK_DELETE:G_object_ref(event_widget);If(!window_group->grabs || gtk_widget_get_toplevel(window_group->grabs->data) == event_widget && !gtk_widget_event(event_widget, event)){Gtk_widget_destroy(event_widget);G_object_unref(event_widget);Break;}…} 

 

（3）gdk_event GDK_DELETE -->g_signal DELETE_EVENT

gtk_widget_event(widget, event)-> gtk_widget_event_internal(widget, event)#define WIDGET_REALIZED_FOR_EVENT(widget, event)/(event->type == GDK_FOCUS_CHANGE || GTK_WIDGET_REALIZED(widget))gtk_widget_event_internal(GtkWidget *widget, GdkEvent *event){If(!event_window_is_still_viewable(event))Return TRUE;g_object_ref(widget);g_signal_emit(widget, widget_signals[EVENT], 0, event, &return_val);...return_val |= ! WIDGET_REALIZED_FOR_EVENT(widget, event);if(!return_val)g_signal_emit(widget, widget_signals[DELETE_EVENT], 0, event, &return_val);...iIf(WIDGET_REALIZED_FOR_EVENT(widget, event) g_signal_emit(widget, widget_signals[EVENT_AFTER], 0, event);else return_val = TRUE;g_object_unref(widget);return return_val;}

 

2. destroy signal的产生过程

 （1）当gtk_widget_destroy(widget)调用后，gtk_object_destroy(object)被调用

voidGtk_object_destroy(GtkObject *object){If(!(GTK_OBJECT_FLAGS(object) & GTK_IN_DESTRUCTION)G_object_run_dispose(G_OBJECT(object))

（2）g_object_run_dispose

voidg_object_run_dispose(GObject *object){ g_object_ref(object); G_OBJECT_GET_CLASS(object)->dispose(object); g_object_unref(object);}

(3) 调用gtk Object的dispose函数gtk_object_dispose

GtkObject中， gobject_class->dispose= gtk_object_dispose

static voidgtk_object_dispose(GObject *gobject){GtkObject *object = GTK_OBJECT(gobject);if(!(GTK_OBJECT_FLAGS(object) & GTK_IN_DESTRUCTION){GTK_OBJECT_SET_FLAG(object, GTK_IN_DESTRUCTION);g_signal_emit(object, object_signals[DESTROY], 0);GTK_OBJECT_UNSET_FLAGS(object, GTK_IN_DESTRUCTION);}G_OBJECT_CLASS(parent_class)->dispose(gobject);}

(4)上一步发出的DESTROY信号，gtk_object连接了一个默认的处理函数gtk_object_real_destroy

 

 

从上面的1（2）中的代码，可以看到，delete_event的回调函数返回FALSE时，gtk_widget_destroy会被调用，进而触发destroy信号的发出