On my Linux/Wayland (reproduces on Windows 10 as well) with DPI scaling set to 200%, QIcon does not automatically use the `@2x` Hi DPI pixmaps.
I have created a simple reproducer to demo the issue. It contains a QListView widget in icon mode with an icon size of 64x64. Attached to the widget is a simple model with the following `data()` method:
In the resources there are two icons: `icon64.png` which is 64x64 pixels and `firstname.lastname@example.org` which is 128x128 pixels.
I would expect the 128x128 version to be used. Actually the 64x64 version in shown, resulting in poor image quality.
When porting the attached reproducer to Qt5 and enabling `AA_UseHighDpiPixmaps`, the issue disappears. So it seems to me this is a Qt6 regression.