WId QWidget::winId () const
Returns the window system identifier of the widget.
Portable in principle, but if you use it you are probably about to do something non-portable. Be careful.
If a widget is non-native (alien) and winId() is invoked on it, that widget will be provided a native handle.
On Mac OS X, the type returned depends on which framework Qt was linked against. If Qt is using Carbon, the {WId} is actually an HIViewRef. If Qt is using Cocoa, {WId} is a pointer to an NSView.
This value may change at run-time. An event with type QEvent::WinIdChange will be sent to the widget following a change in window system identifier.
