Qt在Ubuntu20.4版本上无法获取触摸屏按压的尺寸

Qt在Ubuntu20.4版本上无法获取触摸屏按压的尺寸,代码如下：

bool GraphicsView::viewportEvent(QEvent *event)
{
QEvent::Type type = event->type();

if(type == QEvent::TouchBegin || type == QEvent::TouchUpdate

QTouchEvent *pTouchEvent = static_cast(event);
QList touchPoints = pTouchEvent->touchPoints();

int nId = 0;
QColor penColor;

foreach (const QTouchEvent::TouchPoint tp, touchPoints)

{ qDebug() << "id" << tp.id() << "size" << tp.ellipseDiameters() << "position" << tp.pos(); }

return true;
}

return QGraphicsView::viewportEvent(event);

}