title: Selection area in Qt widget
body: <p>I wrote this post, because I have a problem with selection area.</p>
  
  <p>If you click on your windows desktop, and drag mouse, you will see selection area. I'm trying to achieve generally similar thing. </p>
  
  <p>Do you have any ideas, how to achieve this?</p>
  
  <p>Thanks for any suggestion. </p>