Pen drawing 1px off when setting QGraphicsItem position with setPos()

For some reason QGraphicsView draws the border of a rect (and possibly other objects) off by one to the right and bottom (see screenshot).
It seems that sometimes this happens without zooming, but zooming a few times at factor 1.2 is the safest way to trigger the issue.

This issue appears only on Mac OS X (tested Carbon, did not test Windows or Cocoa!).

Attached a minimal example that triggers the bug with code comments.