Anyway, try it, if you find anything how to stop the window from being moved via titlebar using Qt (as per OP's question) let me know, it may come handy
Will do.

Just one thing - its not QObject::move() but QWidget::move() - since QObject has no visual representation.

EDIT:
That's largery true, except when OS is moving the window using native api
That is something I don't understand.
Since Qt is drawing the window, how can the OS move it without Qt drawing it. (thus knowing about it).