static bool Visible_cb(IntPtr inst, IntPtr child_model, IntPtr iter)
 {
     try {
         TreeModelFilter __obj = GLib.Object.GetObject(inst, false) as TreeModelFilter;
         bool            __result;
         __result = __obj.OnVisible(Gtk.TreeModelAdapter.GetObject(child_model, false), Gtk.TreeIter.New(iter));
         return(__result);
     } catch (Exception e) {
         GLib.ExceptionManager.RaiseUnhandledException(e, true);
         // NOTREACHED: above call does not return.
         throw e;
     }
 }