My application (on Win32) had a CPU hogging problem that went away when I set the main window to opaque. I needed it transparent to be able to draw nice rounded corners, but because of that, about 50% of CPU was used up in its paint routine. I have a lot of GUI updates in subcomponents, at least 10 times/sec, and I fear that this is why the main window keeps repainting. But by setting main window to opaque, CPU went down to below 5%.
Any ideas on how to minimize repaints, and still be able to draw nice round corners??