title: Draw Rectangular overlay on QWidget at click
body: <p>in my project i use a <code>EventFilter</code> for widgets, that are in a <code>QHBoxLayout</code>.</p>
  
  <p>If i clicked on an a widget, i want to draw a transparent overlay with blue color over the clicked widget.
  Is there a way to implement this?</p>
  
  <p>greetings</p>