After showing a context menu on a QGLWidget under Windows Vista, the window is only partly repainted.

To reproduce, turn off all visual effects in Windows Vista or Windows 7 and start the boxes demo. Right click the white cube in any of the corners to get a context menu, click outside it or press escape to close it. After the menu disappears, only the part of the widget that was under the menu ever gets repainted, even though the whole widget should be repainted continuously. To repaint the whole widget again, it must be moved, be resized, lose focus, or pop up a new context menu.

I am not able to reproduce the bug in a simpler program. See mail task for details and another way to reproduce the bug.

The bug cannot be reproduced on Windows XP.

Workaround: Call SetWindowRgn(widget.winId(), 0, FALSE) before painting.