Avoid direct access to the main context events queue

The GQueue that stores the global events queue is handled all over the
place:

  • the structure is created in _clutter_backend_init_events();
  • the queue is handled in clutter-event.c, clutter-stage.c and
    clutter-backend.c;
  • ClutterStage::dispose cleans up the events associated with
    the stage being destroyed;
  • the queue is destroyed in ClutterBackend::dispose.

Since we need to have access to it in different places we cannot put it
inside ClutterBackendPrivate, hence it should stay in ClutterMainContext;
but we should still manage it from just one place - preferably by the
ClutterEvent API only.

clutter/clutter-backend.c

@@ -87,19 +87,11 @@ static void
 clutter_backend_dispose (GObject *gobject)
 {
   ClutterBackendPrivate *priv = CLUTTER_BACKEND (gobject)->priv;
-  ClutterMainContext *clutter_context;
 
-  clutter_context = _clutter_context_get_default ();
-
-  if (clutter_context && clutter_context->events_queue)
-    {
-      g_queue_foreach (clutter_context->events_queue,
-                       (GFunc) clutter_event_free,
-                       NULL);
-      g_queue_free (clutter_context->events_queue);
-      clutter_context->events_queue = NULL;
-    }
+  /* clear the events still in the queue of the main context */
+  _clutter_clear_events_queue ();
 
+  /* remove all event translators */
   if (priv->event_translators != NULL)
     {
       g_list_free (priv->event_translators);
@@ -552,8 +544,6 @@ _clutter_backend_init_events (ClutterBackend *backend)
   g_return_if_fail (CLUTTER_IS_BACKEND (backend));
   g_return_if_fail (clutter_context != NULL);
 
-  clutter_context->events_queue = g_queue_new ();
-
   klass = CLUTTER_BACKEND_GET_CLASS (backend);
   if (klass->init_events)
     klass->init_events (backend);

clutter/clutter-event.c

@@ -793,7 +793,7 @@ clutter_event_get (void)
 {
   ClutterMainContext *context = _clutter_context_get_default ();
 
-  if (!context->events_queue)
+  if (context->events_queue == NULL)
     return NULL;
 
   if (g_queue_is_empty (context->events_queue))
@@ -835,9 +835,11 @@ _clutter_event_push (const ClutterEvent *event,
   ClutterMainContext *context = _clutter_context_get_default ();
   ClutterInputDevice *device;
 
-  /* FIXME: check queue is valid */
   g_assert (context != NULL);
 
+  if (context->events_queue == NULL)
+    context->events_queue = g_queue_new ();
+
   /* disabled devices don't propagate events */
   device = clutter_event_get_device (event);
   if (device != NULL)
@@ -893,7 +895,7 @@ clutter_events_pending (void)
 
   g_return_val_if_fail (context != NULL, FALSE);
 
-  if (!context->events_queue)
+  if (context->events_queue == NULL)
     return FALSE;
 
   return g_queue_is_empty (context->events_queue) == FALSE;

clutter/clutter-main.c

@@ -3267,3 +3267,47 @@ clutter_get_default_text_direction (void)
 {
   return clutter_text_direction;
 }
+
+/*< private >
+ * clutter_clear_events_queue:
+ *
+ * Clears the events queue stored in the main context.
+ */
+void
+_clutter_clear_events_queue (void)
+{
+  ClutterMainContext *context = _clutter_context_get_default ();
+
+  if (context->events_queue != NULL)
+    {
+      g_queue_foreach (context->events_queue,
+                       (GFunc) clutter_event_free,
+                       NULL);
+      g_queue_free (context->events_queue);
+      context->events_queue = NULL;
+    }
+}
+
+void
+_clutter_clear_events_queue_for_stage (ClutterStage *stage)
+{
+  ClutterMainContext *context = _clutter_context_get_default ();
+  GList *l, *next;
+
+  if (context->events_queue == NULL)
+    return;
+
+  /* Remove any pending events for this stage from the event queue */
+  for (l = context->events_queue->head; l; l = next)
+    {
+      ClutterEvent *event = l->data;
+
+      next = l->next;
+
+      if (event->any.stage == stage)
+        {
+          g_queue_delete_link (context->events_queue, l);
+          clutter_event_free (event);
+        }
+    }
+}

clutter/clutter-private.h

@@ -189,6 +189,10 @@ gboolean      _clutter_feature_init (GError **error);
 /* Reinjecting queued events for processing */
 void _clutter_process_event (ClutterEvent *event);
 
+/* clears the event queue inside the main context */
+void _clutter_clear_events_queue           (void);
+void _clutter_clear_events_queue_for_stage (ClutterStage *stage);
+
 /* Picking code */
 ClutterActor *_clutter_do_pick (ClutterStage    *stage,
 				gint             x,

clutter/clutter-stage.c

@@ -1163,29 +1163,14 @@ clutter_stage_dispose (GObject *object)
 {
   ClutterStage        *stage = CLUTTER_STAGE (object);
   ClutterStagePrivate *priv = stage->priv;
-  ClutterStageManager *stage_manager = clutter_stage_manager_get_default ();
-  ClutterMainContext  *context;
-  GList               *l, *next;
+  ClutterStageManager *stage_manager;
 
   clutter_actor_hide (CLUTTER_ACTOR (object));
 
+  stage_manager = clutter_stage_manager_get_default ();
   _clutter_stage_manager_remove_stage (stage_manager, stage);
 
-  context = _clutter_context_get_default ();
-
-  /* Remove any pending events for this stage from the event queue */
-  for (l = context->events_queue->head; l; l = next)
-    {
-      ClutterEvent *event = l->data;
-
-      next = l->next;
-
-      if (event->any.stage == stage)
-        {
-          g_queue_delete_link (context->events_queue, l);
-          clutter_event_free (event);
-        }
-    }
+  _clutter_clear_events_queue_for_stage (stage);
 
   if (priv->impl != NULL)
     {
@@ -1204,7 +1189,7 @@ clutter_stage_finalize (GObject *object)
   ClutterStage *stage = CLUTTER_STAGE (object);
   ClutterStagePrivate *priv = stage->priv;
 
-  g_queue_foreach (priv->event_queue, (GFunc)clutter_event_free, NULL);
+  g_queue_foreach (priv->event_queue, (GFunc) clutter_event_free, NULL);
   g_queue_free (priv->event_queue);
 
   g_free (priv->title);