Ok, I tried it, and it _almost_ works.
Almost means, that I gave the dialog a transparent background color, in order to paint the visible parts my self with a visible color.
The problem is that the invisible color come out not really invisible, but black.
Which explains why my previous try (what I posted above with the atteched image) has that outcome, it basically would work if this would have been a child widget on top of its parent.
I am not sure, but I think it has to do with the fact this is a top level dialog, that has no parents (or the parnt is the desktop).
Also I noticed that in the QtQuarterly issue 16, there is quite a lot about the subject, but it alwasy talks about *child* custom shaped widgets, where as I need a top level one, and I could not find any thing that talks about that...

Any help or ideas are very welcome.

Thanks.