Menubars with new api

[Russell Shaw <rjshaw netspace net au>]

Hi,
I'm trying to make a menubar widget with the first menu named "File", which
contains a menu item named "Open":

  GtkUIManager *manager=gtk_ui_manager_new();
  guint mid=gtk_ui_manager_new_merge_id(manager);
  gtk_ui_manager_add_ui(
           manager,
           mid,
           "/menubar",
           NULL,
           <action>,                // what do i use for <action> ?
           GTK_UI_MANAGER_MENUBAR,
           TRUE
  );

What do i do now? I've looked at testaction.c, but it's still not so clear.