@6thC You call it "Ridiculing", I call it "common sense" or "relevancy". Thank you for your help and contribution.
@raven-worx First: there's nothing free in life.
Second: Qt is not free. Opensource and licensed products don't mean free, far from that.
Third: I am not a Qt API developer, it's not my job.
Don't get mad but here I have a real question for you: would you accept to be slapped for free?
@Snotboogie Thanks a lot for the hint.
Since a solution through Qt does not exist we have to use win32 API for Windows platforms. This function works pretty well for me (windows 8 & 8.1):
setWindowLongPtr(hwnd, GWL_EXSTYLE, WS_EX_NOACTIVATE);
setAttribute(Qt::WA_X11DoNotAcceptFocus); was working fine. But only for Qt 4.8, I have not tried it on Qt 5s yet.