See the example project.
If the blue rectangle is dragged fast on high Dpi screen it partly disappears.
This does not occur with non-high Dpi screen.
If GraphicsView::setViewportUpdateMode(QGraphicsView::FullViewportUpdate); is used the rectangles seem to stay visible on both screen types.
Users example(qr_test.zip) has also been attached.
Here is the user comment:
"If you run the example and drag a rectangle fast in a repeatedly circular motion you should notice artefacts.
it doesnt look like a perfect rectangle anymore - partly disjoint. It seems that if I add the "invalidate()" to "tJvGvScene::mouseMoveEvent()" that the artefact disappears."