Something like:

diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 0e4d198..567ac3e 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -10812,6 +10812,8 @@ gtk_widget_propagate_state (GtkWidget    *widget,
             }
         }
 
+      gtk_widget_queue_resize (widget);
+
       g_object_unref (widget);
     }
 }


This is the correct thing to do but it seems to add about 50% more time to propagate a new flag from the toplevel to every widget on widget-factory. Needs more investigation about what is taking up that extra time.