Say I have a QGraphicsItem* main as root item and many QGraphicsItem as children.
When all QGrapihicsItem::setCacheMode(DeviceCoordinateCache) and GraphicsEffect applied to the root(main) item, some children item will not be rendered when zooming in.

Note that if I remove caching(NoCache) or don't apply GraphicsEffect, all children will be rendered.

I suspect this is has something to do with viewport/visible rectangle.

Attached is an project that illustrate the problem.