1 files changed, 4 insertions, 2 deletions
diff --git a/libs/gtkmm2ext/gtkmm2ext/visibility_tracker.h b/libs/gtkmm2ext/gtkmm2ext/visibility_tracker.h
index f4ed62bb21..1256448efd 100644
--- a/libs/gtkmm2ext/gtkmm2ext/visibility_tracker.h
+++ b/libs/gtkmm2ext/gtkmm2ext/visibility_tracker.h
@@ -28,7 +28,7 @@ namespace GTK {
 
 namespace Gtkmm2ext {
 
-class VisibilityTracker {
+class VisibilityTracker : public virtual sigc::trackable {
   public:
     VisibilityTracker (Gtk::Window&);
     virtual ~VisibilityTracker() {}
@@ -39,8 +39,10 @@ class VisibilityTracker {
     bool not_visible() const;
     bool partially_visible() const;
 
+    Gtk::Window& window () const { return _window; }
+
   private:
-    Gtk::Window& window;
+    Gtk::Window& _window;
     GdkVisibilityState _visibility;
     bool handle_visibility_notify_event (GdkEventVisibility*);
 };