title: How to create a draggable (borderless and titleless) top level window in QT
body: <p>I'd appreciate help creating a top-level window in Qt with the following characteristics. The window must be:</p>
  
  <ol>
  <li>Borderless, titleless and lie on top of all other windows on the desktop (easy)</li>
  <li>Draggable by clicking and dragging anywhere inside it (this what I need help with) </li>
  <li>Constrained to the top border of the desktop while dragging (relatively easy)</li>
  </ol>
  
  <p>Basically, I'm trying to collapse our QT application to a top-level icon on the top border of the desktop.</p>