visibility-group: Use a GWeakNotify instead of the destroy signal

for automatic widget removal.

This doesn't depend on the widget still being a valid object
when the notify function is called, only a valid pointer.

libxapp/xapp-visibility-group.c

@@ -4,8 +4,6 @@
 #define DEBUG_FLAG XAPP_DEBUG_VISIBILITY_GROUP
 #include "xapp-debug.h"
 
-static void widget_destroyed (XAppVisibilityGroup *group, GObject *object);
-
 XAppVisibilityGroup *xapp_visibility_group_copy (const XAppVisibilityGroup *group);
 void xapp_visibility_group_free (XAppVisibilityGroup *group);
 
@@ -43,8 +41,8 @@ xapp_visibility_group_copy (const XAppVisibilityGroup *group)
 }
 
 static void
-widget_destroyed (XAppVisibilityGroup *group,
-  GObject *object)
+widget_disposed (XAppVisibilityGroup *group,
+ GObject *object)
 {
  DEBUG ("Widget destroyed callback: %p", object);
  group->widgets = g_slist_remove (group->widgets, (gpointer) object);
@@ -61,8 +59,7 @@ add_one_widget (XAppVisibilityGroup *group,
  DEBUG ("Add one widget: %p", widget);
 
  group->widgets = g_slist_prepend (group->widgets, (gpointer) widget);
-
- g_signal_connect (widget, "destroy", G_CALLBACK (widget_destroyed), group);
+ g_object_weak_ref (G_OBJECT (widget), (GWeakNotify) widget_disposed, group);
 
  g_object_set (widget,
  "visible", group->visible,
@@ -93,7 +90,7 @@ remove_one_widget (XAppVisibilityGroup *group,
 
  DEBUG ("Remove one widget: %p", widget);
 
- g_signal_handlers_disconnect_by_func (widget, widget_destroyed, group);
+ g_object_weak_unref (G_OBJECT (widget), (GWeakNotify) widget_disposed, group);
  group->widgets = g_slist_remove (group->widgets, ptr->data);
 
  return TRUE;
@@ -106,7 +103,7 @@ remove_widgets (XAppVisibilityGroup *group)
 
  for (l = group->widgets; l != NULL; l = l->next)
  {
- g_signal_handlers_disconnect_by_func (GTK_WIDGET (l->data), widget_destroyed, group);
+ remove_one_widget (group, GTK_WIDGET (l->data));
  }
 
  g_clear_pointer (&group->widgets, g_slist_free);