There is an interesting Qt blog about support of high DPI displays: https://blog.qt.io/blog/2016/01/26/high ... in-qt-5-6/
An interesting fact is that it can be tested on any hardware, i.e. also on low resolution displays. All what must be set is the environment QT_SCALE_FACTOR=1.5 (or any other value) before starting the application.
This way I could reproduce the issue issue #0003130 where the rubberband has an offset.