libobs: Add function to force a sceneitem transform update

Useful when you need to modify transform properties of group sub-items
and have the transform available immediately (group sub-items always
automatically defer their transform update to the next frame).

libobs/obs-scene.c

@@ -2885,3 +2885,12 @@ void obs_sceneitem_group_enum_items(obs_sceneitem_t *group,
 	if (scene)
 		obs_scene_enum_items(scene, callback, param);
 }
+
+void obs_sceneitem_force_update_transform(obs_sceneitem_t *item)
+{
+	if (!item)
+		return;
+
+	if (os_atomic_set_bool(&item->update_transform, false))
+		update_item_transform(item, false);
+}

libobs/obs.h

@@ -1427,6 +1427,8 @@ EXPORT void obs_sceneitem_set_scale_filter(obs_sceneitem_t *item,
 EXPORT enum obs_scale_type obs_sceneitem_get_scale_filter(
 		obs_sceneitem_t *item);
 
+EXPORT void obs_sceneitem_force_update_transform(obs_sceneitem_t *item);
+
 EXPORT void obs_sceneitem_defer_update_begin(obs_sceneitem_t *item);
 EXPORT void obs_sceneitem_defer_update_end(obs_sceneitem_t *item);