+ /* this resets focus to the first focusable parent of the given widget,
+ * or, if there is no focusable parent, cancels focus in the toplevel
+ * window that the given widget is packed into (if there is one).
+ */
+
+ if (!w) {
+ return;
+ }
+
+ Gtk::Widget* top = w->get_toplevel();
+
+ if (!top || !top->is_toplevel()) {
+ return;
+ }
+
+ w = w->get_parent ();
+
+ while (w) {
+ if (w->get_can_focus ()) {
+ Window* win = dynamic_cast<Window*> (top);
+ win->set_focus (*w);
+ return;
+ }
+ w = w->get_parent ();
+ }
+
+ /* no focusable parent found, cancel focus in top level window.
+ C++ API cannot be used for this. Thanks, references.
+ */
+
+ gtk_window_set_focus (GTK_WINDOW(top->gobj()), 0);
+