let main window =
  GAction.add_actions window#actions 
    [ GAction.add_action 
        "CallGraph" ~label:"_Show Call Graph" ~callback:show_graph_win];
  ignore
    (window#ui_manager#add_ui_from_string
       "<ui><menubar name='MenuBar'> 
              <menu action='ViewMenu'>
                 <menuitem action='CallGraph'/> 
              </menu>
           </menubar>
       </ui>"
)