make Item::child_changed() virtual

diff --git a/libs/canvas/canvas/item.h b/libs/canvas/canvas/item.h
index 4c0366b859e3a1a4e249783c446f2452f436fe94..c7f8a0e043d5d5c8a399994b627ede4d557a37bc 100644 (file)
--- a/libs/canvas/canvas/item.h
+++ b/libs/canvas/canvas/item.h
@@ -200,7 +200,7 @@ public:
        void raise_child_to_top (Item *);
        void raise_child (Item *, int);
        void lower_child_to_bottom (Item *);
-       void child_changed ();
+       virtual void child_changed ();
 
        static int default_items_per_cell;