Disable margin when using QMdiArea

[vql]

At the moment, I am converting my program from using QWorkspace to QMdiArea. But I have the problem. Because I am at home, and I don't have Qt. So I use 2 other programs to show the difference.

Please see the window frame:

QMdiArea:


QWorkspace:


Please help me how to remove margin in QMdiArea. Thanks.

[jacek]

This margin might be introduced by the layout, not MDI area.