title: Resize QWidget to hold just the current widgets, when the set of widgets change
body: <p>Let's say there is a <code>QWidget</code> whose layout is vertical. This layout has a button (bt1) and another layout (<code>hLayout</code>).</p>
  
  <p>The app works so that clicking in bt1 add/remove a button from <code>hLayout</code>.</p>
  
  <p>The first time the button is added the window gets bigger (width increase) to hold the new button. Next click hides the button. But hiding the button does not make the window shrink. I would like to have the same size as before the button was added.</p>
  
  <p>Whats the approach to properly shrink the window when the button is removed? Or more generally, what's the approach to make the window get just enough size?</p>