QQuickWidget doesn't invoke provided virtual functions for drag-drop

QQuickWidget has the virtual functions dragEnterEvent(), dragMoveEvent(), dragLeaveEvent() and dropEvent(). However, after setting setAcceptDrops(true), and subclassing QQuickWidget it appears these methods are not called.

See also forum topic: http://qt-project.org/forums/viewthread/51669

The suggestion from the forum was to reimplement QWidget::event() and this has revealed that the events are in fact coming through, but the virtual methods are not called and therefore cannot be used.