clutter: Change _clutter_process_event name/signature

Avoid using the ClutterEvent stage field, and pass the stage
explicitly. Also rename to clutter_stage_process_event(), so that
its ownership/namespace is clearer.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3153>

clutter/clutter/clutter-event-private.h

@@ -10,7 +10,8 @@ void            _clutter_event_set_pointer_emulated     (ClutterEvent       *eve
 
 /* Reinjecting queued events for processing */
 CLUTTER_EXPORT
-void            _clutter_process_event                  (ClutterEvent       *event);
+void            clutter_stage_process_event             (ClutterStage *stage,
+                                                         ClutterEvent *event);
 
 CLUTTER_EXPORT
 gboolean        _clutter_event_process_filters          (ClutterEvent *event,

clutter/clutter/clutter-main.c

@@ -887,29 +887,22 @@ _clutter_process_event_details (ClutterActor        *stage,
 }
 
 /*
- * _clutter_process_event
+ * clutter_stage_process_event
  * @event: a #ClutterEvent.
  *
  * Does the actual work of processing an event that was queued earlier
  * out of clutter_stage_handle_event().
  */
 void
-_clutter_process_event (ClutterEvent *event)
+clutter_stage_process_event (ClutterStage *stage,
+                             ClutterEvent *event)
 {
   ClutterMainContext *context;
-  ClutterActor *stage;
   ClutterSeat *seat;
 
   context = _clutter_context_get_default ();
   seat = clutter_backend_get_default_seat (context->backend);
 
-  stage = CLUTTER_ACTOR (event->any.stage);
-  if (stage == NULL)
-    {
-      CLUTTER_NOTE (EVENT, "Discarding event without a stage set");
-      return;
-    }
-
   /* push events on a stack, so that we don't need to
    * add an event parameter to all signals that can be emitted within
    * an event chain
@@ -917,7 +910,7 @@ _clutter_process_event (ClutterEvent *event)
   context->current_event = g_slist_prepend (context->current_event, event);
 
   clutter_seat_handle_event_post (seat, event);
-  _clutter_process_event_details (stage, context, event);
+  _clutter_process_event_details (CLUTTER_ACTOR (stage), context, event);
 
   context->current_event = g_slist_delete_link (context->current_event, context->current_event);
 }

clutter/clutter/clutter-stage.c

@@ -769,7 +769,7 @@ _clutter_stage_process_queued_events (ClutterStage *stage)
             }
         }
 
-      _clutter_process_event (event);
+      clutter_stage_process_event (stage, event);
 
     next_event:
       clutter_event_free (event);