menu2.py

#!/usr/bin/env python

import gi
gi.require_version('Gtk','3.0')
gi.require_version('Keybinder', '3.0')
from gi.repository import Gtk, Gdk, Keybinder

class MenuBar(Gtk.Window):

    def __init__(self, *args):
        super().__init__(*args, name="bar")

        # Create an undecorated dock
        self.set_type_hint(Gdk.WindowTypeHint.DOCK)
        self.set_decorated(False)
        self.connect("delete-event", Gtk.main_quit)

        action_group = Gtk.ActionGroup("my_actions")
        action_group.add_actions([
            ("numbers", None, "Numbers", None, None, None),
            ("one", None, "One", None, None, self.callback),
            ("two", None, "Two", None, None, self.callback),
            ("shapes", None, "Shapes", None, None, None),
            ("triangle", None, "Triangle", None, None, self.callback),
            ("square", None, "Square", None, None, self.callback)
        ])

        uimanager = Gtk.UIManager()
        uimanager.insert_action_group(action_group)
        uimanager.add_ui_from_string("""
        <ui>
          <menubar name='MenuBar'>
            <menu name='default' action='numbers'>
              <menuitem action='one' />
              <menuitem action='two' />
            </menu>
            <menu action='shapes'>
              <menuitem action='triangle' />
              <menuitem action='square' />
            </menu>
          </menubar>
        </ui>
        """)

        box = Gtk.Box();
        menubar =  uimanager.get_widget("/MenuBar")
        box.pack_start(menubar, False, False, 0)
        self.add(box)

        item = Gtk.MenuItem()
        item.set_label('Colours')
        menu = Gtk.Menu()
        self.menu = menu
        item.set_submenu(menu)
        menubar.append(item)

        item = Gtk.MenuItem()
        item.set_label('Red')
        item.connect('activate',self.callback)
        menu.append(item)

        item = Gtk.MenuItem()
        item.set_label('Blue')
        item.connect('activate',self.callback)
        menu.add(item)

        # Bind hotkey
        keystr = "Menu"
        Keybinder.init()
        Keybinder.bind(keystr, self.keybinder_callback, "Keystring %s (user data)" % keystr)

        # For keybinder_callback
        self.anchor = box # popup_at_widget
        self.menubar = menubar
        self.menu =  uimanager.get_widget("/MenuBar/default")

    def callback(self, obj):
        print("You chose %s (%s)" % (obj.get_label(), type(obj)))

    def keybinder_callback(self, keystr, user_data):
        print("Handling", keystr, user_data)
        print("Event time:", Keybinder.get_current_event_time())
        #self.menu.popup(None,None,None,None,1,Keybinder.get_current_event_time())
        #self.menu.popup_at_widget(self.anchor,Gdk.Gravity.SOUTH_WEST,Gdk.Gravity.NORTH_WEST,None)
        self.menubar.select_item(self.menu)

MenuBar().show_all()

# Control-C termination https://bugzilla.gnome.org/show_bug.cgi?id=622084
from gi.repository import GLib
GLib.MainLoop().run()