title: Gtk Spinner Not Appearing
body: <p>I'm trying to get a Gtk::Spinner object to display while calculations are in progress but nothing appears to be happening. The snippet of code looks like...</p>
  
  <pre><code>{
      Gtk::Spinner spinner;
      spinner.start (); 
      // do some work...
      spinner.stop ();
  }
  </code></pre>
  
  <p>I'd have thought the spinner needed to know which dialogue it appears over but I can't see any way of feeding that into the object. Does anyone know where I could find a worked example? I can find the Gtk documentation in many places, but that isn't helping much.</p>