[Qt-interest] High-performance transparent overlay widget?

[Ben Bridgwater]

Hi,
I have a realtime Qt application (audio spectrogram) that has need for 
some overlay graphics (cross-hair cursor, maybe a litle text) on top of 
a frequently repainted widget (complete repaint/scroll at least 10x per 
second).

I know I could just use a transparent child widget as an overlay, but if 
I do that then I'm going to take a big CPU hit due to the software 
compositing being done by Qt internally (combining the transparent 
overlay with it's background widget).

Is there any way to implement a transparent overlay in Qt, without 
coding in OpenGL, that would be hardware accelerated? Is there anything 
like a "QOverlayWidget" in the works, or will the transparent OpenGL 
support in Qt 4.5 provide hardware accelerated compositing of child 
and/or overlapping windows?

Ben