I'm just playing around with QPainter and get the following message on the console:

QPainter::setCompositionMode(), composition modes not supported on device

whenever I use QPainter::setCompositionMode(). For example, I tried

painter.setCompositionMode(QPainter::CompositionMo de_SourceOver);

What else do I need to set up on my system. I am using Qt 4.0.1 on an X11 based linux box