title: QToolTip::showText disappears after mouse release
body: <p>I want to show tool tip on the QGLWidget but i must the call; <code>QToolTip::showText(pos, "Message", qglwidgetPtr, rect(), 5000);</code> 
  in another class.</p>
  
  <p>So, tooltip disappears after releasing the mouse button. If I don't release it, the tooltip disappears after that 5000 msecs. I do not understand the disappear problem. I think it could be trigger disappear QGL widget paint event but i'm not sure. </p>