Fix program not shutting down when using Ubuntu app menu.

Ensure that an idle event is generated after a menu event even when the latter
comes, via DBUS, from the out of process app menu and not from a real GTK menu.

Closes #15122.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73737 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/menu.cpp

@@ -537,6 +537,14 @@ static void menuitem_activate(GtkWidget*, wxMenuItem* item)
 
     wxMenu* menu = item->GetMenu();
     menu->SendEvent(id, item->IsCheckable() ? item->IsChecked() : -1);
+
+    // A lot of existing code, including any program that closes its main
+    // window from a menu handler and expects the program to exit -- as our own
+    // minimal sample -- relies on getting an idle event after a menu event.
+    // But when using Ubuntu Unity detached menus, we get called from a DBUS
+    // handler called from g_timeout_dispatch() and Glib doesn't send us any
+    // idle events after it. So ask explicitly for an idle event to get one.
+    wxWakeUpIdle();
 }
 }