Revert "clutter: Drop Event.get_source"

We'll need this API again when adding ClutterGesture.

This reverts commit 6032be04a0.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2389>

clutter/clutter/clutter-event.c

@@ -510,6 +510,27 @@ clutter_event_get_position (const ClutterEvent *event,
 
 }
 
+/**
+ * clutter_event_get_source:
+ * @event: a #ClutterEvent
+ *
+ * Retrieves the source #ClutterActor the event originated from, or
+ * NULL if the event has no source.
+ *
+ * Return value: (transfer none): a #ClutterActor
+ */
+ClutterActor *
+clutter_event_get_source (const ClutterEvent *event)
+{
+  g_return_val_if_fail (event != NULL, NULL);
+
+  if (event->type == CLUTTER_ENTER ||
+      event->type == CLUTTER_LEAVE)
+    return event->crossing.source;
+
+  return NULL;
+}
+
 /**
  * clutter_event_get_flags:
  * @event: a #ClutterEvent

clutter/clutter/clutter-event.h

@@ -170,6 +170,8 @@ ClutterInputDevice *    clutter_event_get_source_device         (const ClutterEv
 CLUTTER_EXPORT
 ClutterInputDeviceTool *clutter_event_get_device_tool           (const ClutterEvent     *event);
 
+CLUTTER_DEPRECATED
+ClutterActor *          clutter_event_get_source                (const ClutterEvent     *event);
 CLUTTER_EXPORT
 ClutterInputDeviceType  clutter_event_get_device_type           (const ClutterEvent     *event);
 CLUTTER_EXPORT