QGraphicsRectItem::pos() function returns something that is not expected?

Question

I have this simple piece of code in a class constructor which is inherited from QGraphicsScene :

setSceneRect(0,0,800,800);
addRect(sceneRect());
QGraphicsRectItem*r1 = addRect(200, 0, 5, 5);
qDebug()<<r1->pos();

Here I add a rect at pos(200,0) but qDebug() prints QPointF(0, 0)! I'm totally confused. Even scenePos returns (0,0)! Is it true?!

score 0 · Accepted Answer · answered Dec 21 '13 at 12:53

The rect is at position (200, 0) inside the item's coordinate system, but the item itself is at (0,0) in its parent's coordinate system.

The QGraphicsScene::addRect() documentation explains this:

Note that the item's geometry is provided in item coordinates, and its position is initialized to (0, 0). For example, if a QRect(50, 50, 100, 100) is added, its top-left corner will be at (50, 50) relative to the origin in the items coordinate system.

Alternatively, you can add a rectangle at 0, 0, 5, 5) and move the item afterwards, to get the result you expected:

QGraphicsRectItem* r1 = addRect(0, 0, 5, 5);
r1->setPos(200, 0);

QGraphicsRectItem::pos() function returns something that is not expected?

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