Ugly move with a top-level setMasked widget

[nooky59]

Hi,

I've searching a lot in the forum but I don't think I've found something interesting regarding it.

I have made a simple top-level wndow with a custom shape using a QLabel, a QPixmap and the so famous setPixmap et SetMask(pixmap.mask()).

I've too, as in the shaped clock example, implemented the mouseMoveEvent and mousePressEvent in order to move the window.

It seems to really sucks if I move the window over some other apps (for example Visual Studio or Firefox). A picture is better than words (as it's hard to explain for a non native english people ;o)) so look at the attached image.

This effect is drastically intensified if I move the mouse fast but even if I try to move slowly, this problem appears really soon...

However, if I move it on the Windows desktop, it move smoothly !

I wonder if it's related to Qt as I've tried a fancy WinAMP skin and this problem were here too but a lot lesser visible.

Is there a way I can solve it ?

Curiously, with a star example I've found on this forum, there is no problem even if the source code is the same ! Could it be due to the size of the image or if the source PNG is not smoothly anti-aliased on the edge of the shape ?