Quote Originally Posted by fatjuicymole View Post
This is correct behavior on Windows, nothing will be drawn until the window gets a draw event, which can't occur until the sleep function has completed and the event loop continued. Qt will not attempt any drawing event (which includes the window background) until it gets such an event.
Indeed. So this (some kind of Erase Background event being fired & processed) is not the reason for my window to have a white background beneath its real content. Which is the problem I'm trying to solve.

Any idea?

Cheers,
Franz