title: GTK focus-out-event
body: <p>I am showing a user a popup menu when they right click.</p>
  
  <p>According to the popup behaviour, I want to destroy the popup when it looses focus(when user clicks outside the popup window). For that I tried to connect the popup window to "<strong>focus-out-event</strong>", using Glade. But for some reason, that event is not getting fired. I tried to print something on the terminal when the event is fired, but nothing gets printed.</p>
  
  <p>I am new to Python and GTK, and now I have no clue how to proceed further.</p>
  
  <pre><code>#handler to catch the focus out event
  def on_popup_menu_add_attachment_focus_out_event(self, *args):
      print("Destroying the popup.....")
  </code></pre>
  
  <p><strong>focus-out-signal and its handler</strong>
  <img src="https://i.stack.imgur.com/QPgh3.png" alt="enter image description here"></p>