Make MetaBackroungGroup class derivable (Mutter 3.32)

make-metabackgroundgroup-derivable.patch

diff --git a/src/compositor/meta-background-group.c b/src/compositor/meta-background-group.c
index f3c125ab0390e8fb046a4ae917fd330cdfc20912..e30b8af4c8c1e97a4d7b640a93bcb0c8dd70ea47 100644
--- a/src/compositor/meta-background-group.c
+++ b/src/compositor/meta-background-group.c
@@ -19,11 +19,6 @@
 #include "compositor/meta-cullable.h"
 #include "meta/meta-background-group.h"
 
-struct _MetaBackgroundGroup
-{
-  ClutterActor parent;
-};
-
 static void cullable_iface_init (MetaCullableInterface *iface);
 
 G_DEFINE_TYPE_WITH_CODE (MetaBackgroundGroup, meta_background_group, CLUTTER_TYPE_ACTOR,
diff --git a/src/meta/meta-background-group.h b/src/meta/meta-background-group.h
index accbb3e0f5e0eac064ba6a0864913ec3421c180d..b43fcb94ade8eadb409b43ac15e440ab3e1359a1 100644
--- a/src/meta/meta-background-group.h
+++ b/src/meta/meta-background-group.h
@@ -10,10 +10,15 @@
 #define META_TYPE_BACKGROUND_GROUP (meta_background_group_get_type ())
 
 META_EXPORT
-G_DECLARE_FINAL_TYPE (MetaBackgroundGroup,
-                      meta_background_group,
-                      META, BACKGROUND_GROUP,
-                      ClutterActor)
+G_DECLARE_DERIVABLE_TYPE (MetaBackgroundGroup,
+                          meta_background_group,
+                          META, BACKGROUND_GROUP,
+                          ClutterActor)
+
+struct _MetaBackgroundGroupClass
+{
+  ClutterActorClass parent_class;
+};
 
 META_EXPORT
 ClutterActor *meta_background_group_new (void);