QGraphicsPixmapItem is shifting while zooming and panning

[korai]

I am using Qt and QGIS API to create a GUI. I added a marker/icon to the QGraphicsScene as Pixmap item.

mpMapCanvas = new QgsMapCanvas(); 
scene = mpMapCanvas->scene();
QPixmap pixmap = QPixmap(":/mapMarker.png");
icon = new QGraphicsPixmapItem(pixmap);
scene->addItem(icon);

icon->setPos(pointf.x(), pointf.y());   // pointf is a point (coordinates) in type QPointF
icon->show();

When zooming and panning, the item is shifting. To solve this problem, I tried

icon->setFlag(QGraphicsPixmapItem::ItemIgnoresTransformations,true);

How can I prevent the shifting of the icon while zooming, panning etc. using C++ or Python? I want to fix its position.

[Pl45m4]

@korai said in QGraphicsPixmapItem is shifting while zooming and panning:

How can I prevent the shifting

What do you mean by "shifting"?
If you zoom the scene, you need to re-calculate the position of the item, when you want to keep it "static".

[korai]

@Pl45m4 Thank you for your answer. When I put the marker for example here:

If I zoom, then the marker shifts to another place on the map (here somewhere in the top left):

Like you said, I need to re-calculate the position, although I set its position when I put it with the following code:
icon->setPos(pointf.x(), pointf.y());

What should I do to re-calculate its position according to zooming/panning?