I am implementing a graphics view to display a motion captured point trace. I use a QGraphicsPathItem for the trace, and a QGraphicsEllipseItem to indicate the current position. The user has to be able to zoom and pan the view, but the current position indicator has to stay the same size in pixels.

So I decided to use the QGraphicsItem::ItemIgnoresTransformations flag on the ellipse so it ignores the scaling of the view. It works as intended, but on Mac OS there are redrawing artifacts (the ellipse stays on screen until a full redraw). I'm not sure why the artifacts are not present in Windows, but my guess is that this is an issue with the boundingRect of the item which misbehaves in combination with the QGraphicsItem::ItemIgnoresTransformations flag.

Is this a know issue? Are there any good workarounds? Maybe creating a custom implementation for the "non-scalable dot", ignoring the scaling in the boundingRect method, is the best way? Are there better ways to draw dots instead of a QGraphicsEllipseItem?