QIcon doc suggests using files to create Hi DPI icons. but if that's not possible, because you programmatically create QPixMaps, or because your existing subsystem uses QPixMaps for everything, or any other valid reason, then it is not possible to create Hi DPI QIcons.
When attempting to create QIcon from QPixMap, you'd expect to be able to do this:
and have the aspect ratio to be preserved in the icon, but it is not
previously reported here, but then ignored for some reason?