QWidget WindowContainer breaks parent relation

Preconditions:
You have a GUI made of QWidgets and a QWindow which will be integrated in your GUI with the createWindowContainer() method. This may be e.g. a QDockWidget *dockWidget and a QGLView *graphicsView which will be glued together with dockWidget->setWidget(createWindowContainer(graphicsView));
This will lead to an object hierarchy in the form of
dockWidget - someWidgetWindow - graphicsView.

If I iterate upwards through the hierarchy starting from the QGLView as following:
QObject *parentObject = graphicsView;
while (parentObject)

I would expect to come to the dockWidget, but this would not happen.

The container class created by the createWindowContainer() call seems to be a QWidgetWindow which has a widget() method to work around this, but this class is completely private - so there's no opportunity to call this method, do a qobject_cast<QWindowWidget> etc.