title: QT4: Transparent Window with rounded corners
body: <h3>How can I create a partially transparent window with rounded borders (no standard borders)?</h3>
  
  <p>(I used <code>Qt::FramelessWindowHint</code> to disable standard borders)</p>
  
  <p>I tried stylesheets, but <code>border-radius</code> and <code>opacity</code> doesn't seem to have any effect on the window, it only works on children of the enclosing widget.</p>
  
  <p>My second idea was to make the window fully transparent (with <code>setWindowOpacity</code>), and then add an additional widget with rounded corners (since <code>border-radius</code> works on the children), and then group all my other widgets into that widget. But that does not work since <code>setWindowOpacity</code> affects all children as well (I haven't found a way to change this behaviour).</p>
  
  <p>And any ways to make the outer window transparent I could think of (like stylesheets <code>opacity</code>) don't work properly (I only get a black box instead of a transparent window)</p>
  
  <p><b>Any help would be highly appreciated.</b></p>