Double click events not arriving in QGraphicsWidget::windowFrameEvent()

The variable QGraphicsWidgetPrivate::grabbedSection is set in the handler for QEvent::GraphicsSceneMousePress and unset in the handler for QEvent::GraphicsSceneMouseRelease.

The event handling of double clicks looks at follows:

bool QGraphicsWidget::event(QEvent *event)
{
...
case QEvent::GraphicsSceneMouseDoubleClick:
if (d->hasDecoration() && d->grabbedSection != Qt::NoSection)
return windowFrameEvent(event);
break;
...
}

When the mouse button is clicked twice, a mouse press event, a mouse
release event and a mouse double click event arrive. In that moment, the value of
grabbedSection is NoSection, i.e. the condition in the above code snippet is always false.