Rounding Error in QGraphicsView / QGraphicsScene

I debugged about the reason, that our application sometimes shows a cursor indicating to move an object, while when the mouse is pressed a selection frame is created. This problem only occurs in some situations when the mouse is pressed on the bottom most position of i.e. a QGraphicsPathItem which contains a rectangle.

I found that the screen coordinates passed to

QGraphicsView::mousePressEvent(event);

as event->pos(); has a y-value which differs by 1 from the values recalculated in

QGraphicsScenePrivate::itemsAtPosition

See the stack below:

QRectF::QRectF(const QPointF & atopLeft, const QSizeF & asize) Line 626    C++
QGraphicsScenePrivate::itemsAtPosition(const QPoint & screenPos, const QPointF & scenePos, QWidget * widget) Line 1100    C++
QGraphicsScenePrivate::dispatchHoverEvent(QGraphicsSceneHoverEvent * hoverEvent) Line 3772    C++
QGraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent * mouseEvent) Line 3957    C++
QGraphicsScene::event(QEvent * event) Line 3320    C++
QApplicationPrivate::notify_helper(QObject * receiver, QEvent * e) Line 3290    C++
QApplication::notify(QObject * receiver, QEvent * e) Line 3241    C++
QCoreApplication::notifyInternal2(QObject * receiver, QEvent * event) Line 1118    C++
QCoreApplication::sendSpontaneousEvent(QObject * receiver, QEvent * event) Line 1551    C++
qt_sendSpontaneousEvent(QObject * receiver, QEvent * event) Line 3683    C++
QGraphicsView::mousePressEvent(QMouseEvent * event) Line 3233    C++
 

The event passed to QGraphicsView::mousePressEvent reports

pos = { x = 316, y = 600 }

The value passed as the first parameter to  const QRectF pointRect in QGraphicsScenePrivate::itemsAtPosition is

atopLeft = { x = 316.00000000000000, y = 601.00000000000000 }

And not 600.

Of course this only is a minor deviation but we build a application for the graphics industry and in this case this is somewhat disturbing.