Calling update() from paintEvent()

[wonder.mice]

As for your other doubt - if the application doesn't have the CPU, it won't process events. If you click on the window decoration which is not a part of the application but rather the windowing system, you might take away CPU from the application and it can't do anything about it. Conclusions are yours to draw.

It's nonsense. So you want to say, that when I click on window decoration in Windows everything stopped? =)))) You can take a look on Windows native applications like Clock or Media Player for example - they work even if you click on their caption. More over, slots connected to timer still works in this case. It is very bad design if GUI is dead while user holding mouse button on caption or looking on system menu opened with Alt+Space.

And if you want calling update() from paintEvent() is implemented in Qt composition demo, so this way is not that bad. BTW.