Originally posted by pavlacki
I can ask the delphi's programmer to do anything I want.
I meant you can't delagate Qt's painting routines to Delphi easily.
Either don't use Qt's GUI system at all (you can still paint on QImages) or paint Qt widgets using Qt painting engine. I guess you can implement a painter (using the abstract paining engine) that uses Delphi functions, but you still have to use Qt's event queue -- unless you find a way to transfer Qt events to delphi (for example by calling QApplication::processEvents now and then). An alternative is, as mentioned, to use Qt-made widget as an ActiveX server.
It is probably simpler to use Qt just for painting on images, if you need that functionality and do all the drawing in Delphi without mixing technologies.