QGraphicsPixmapItem is not correctly updated when the pixmap is big.

I am trying to do an application to work on some of my astrophotos.

But I have issues with the display of the big pictures. I have oversimplified my application to get only the display part and the zoom of an image; you will find it in attachement.

This is done of a QMainWindow with a QMdiArea where every QMdiSubWindow contains a QGraphicsView which shows a QGraphicsScene which contains just one QGraphicsPixmapItem. I do some zoom on this picture.

Please open the project Imager.zip and launch it; then open the file LittlePicture.bmp; if you set the mouse other the picture and play with the wheel of your mouse, this will change the zoom of the picture. In the output of the application you will see that every call to the QGraphicsView::paintEvent() is followed by a call to QGraphicsPixmapItem::paint()

But if now you open the file BigPicture.JPG and then you play with the wheel of the mouse, you will see that not every call to QGraphicsView::paintEvent() are followed by a call to QGraphicsPixmapItem::paint() which of course make the picture disappeared.

Could you please tell me what is going on ? Why did the pixmap is not updated ? What is the relation with the size of the picture ?