title: Creating Gtk.ApplicationWindow from glade
body: <p>I'm using Python 3.6, and I'm trying to create an application window from a glade xml file like this:</p>
  
  <pre><code>builder = Gtk.Builder()
  builder.add_from_file("ui/window.glade")
  win = builder.get_object("window1")
  win.set_application(self)
  win.set_position(Gtk.WindowPosition.CENTER)
  win.show_all()
  </code></pre>
  
  <p>However, this way the window does not retain the menu bar, that I set in the application do_startup, like this:</p>
  
  <pre><code>builder.add_from_file("ui/menu.glade")
  set_menubar(self.builder.get_object("menubar"))
  </code></pre>
  
  <p>However, if I try to create a window with this class:</p>
  
  <pre><code>class MyWindow(Gtk.ApplicationWindow):
  
      def __init__(self, app):
          Gtk.Window.__init__(self, title="MyTitle", application=app)
          self.set_position(Gtk.WindowPosition.CENTER)
          self.set_default_size(600, 500)
  
  # application do_activate function
  win = MyWindow(self)
  win.show_all()
  </code></pre>
  
  <p>the menu is shown. How can I add the menu to the window created from Gtk.Builder? Is there a better way to accomplish this?</p>