clutter/actor: Add API to check whether actor or clone is on view

The new function returns TRUE if an actor is effectively on the passed
view, where effectively refers to itself or a clone containing itself.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1285

clutter/clutter/clutter-actor.c

@@ -16258,6 +16258,40 @@ clutter_actor_peek_stage_views (ClutterActor *self)
   return self->priv->stage_views;
 }
 
+gboolean
+clutter_actor_is_effectively_on_stage_view (ClutterActor     *self,
+                                            ClutterStageView *view)
+{
+  ClutterActor *actor;
+
+  g_return_val_if_fail (CLUTTER_IS_ACTOR (self), FALSE);
+
+  if (g_list_find (self->priv->stage_views, view))
+    return TRUE;
+
+  for (actor = self; actor; actor = actor->priv->parent)
+    {
+      if (actor->priv->clones)
+        {
+          GHashTableIter iter;
+          gpointer key;
+
+          g_hash_table_iter_init (&iter, actor->priv->clones);
+          while (g_hash_table_iter_next (&iter, &key, NULL))
+            {
+              ClutterActor *clone = key;
+              GList *clone_views;
+
+              clone_views = clutter_actor_peek_stage_views (clone);
+              if (g_list_find (clone_views, view))
+                return TRUE;
+            }
+        }
+    }
+
+  return FALSE;
+}
+
 /**
  * clutter_actor_pick_frame_clock:
  * @self: a #ClutterActor

clutter/clutter/clutter-mutter.h

@@ -39,6 +39,10 @@
 CLUTTER_EXPORT
 GList * clutter_stage_peek_stage_views (ClutterStage *stage);
 
+CLUTTER_EXPORT
+gboolean clutter_actor_is_effectively_on_stage_view (ClutterActor     *self,
+                                                     ClutterStageView *view);
+
 CLUTTER_EXPORT
 void clutter_set_custom_backend_func (ClutterBackend *(* func) (void));