def on_menu(self, event):
        '''called on menu event'''
        state = self.state
        if self.popup_menu is not None:
            ret = self.popup_menu.find_selected(event)
            if ret is not None:
                ret.popup_pos = self.popup_pos
                if ret.returnkey == 'fitWindow':
                    self.fit_to_window()
                elif ret.returnkey == 'fullSize':
                    self.full_size()
                else:
                    state.out_queue.put(ret)
                return
        if self.menu is not None:
            ret = self.menu.find_selected(event)
            if ret is not None:
                state.out_queue.put(ret)
                return
called on menu event