title: How to get a signal when layout has changed in Awesome Wm
body: <p>Is is possible to capture the layout change in Awesome 3.5 like this for the tags ( for example):</p>
  
  <pre><code>screen[s]:connect_signal("tag::history::update", function()                     
     --do some stuff when virtual desktop has changed
  end
  </code></pre>
  
  <p>If so how do you do it?</p>