setMask Problems

I need to cut in half a widget a few times, so I decided to use masks, the only thing is that I can't get them to work with rectangles.
So this does not work:

Code:

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QRegion maskedRegion(0,0,width(),height()/2);
setMask(maskedRegion);

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However, this does (but doesn't get me what I want seeing as its an ellipse):

Code:

---

QRegion maskedRegion(0,0,width(),height()/2,QRegion::Ellipse);
setMask(maskedRegion);

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Right now I call these from outside a resize event, however when I tried from within one all I got was a black section where the mask should have been.


Is there some method that I have to call afterwards of something? I've tried update and repaint but no success.

Could you, by any chance, provide something compilable we can test ourselves?

I found out it was compiz, I ran the same program with kwin and the masking was fine, apparently compiz has problems with masks.

Thanks anyways :-)