Today I added support for OS X HiDPI resolutions. It turned out to be relatively straightforward, with Qt 5 already doing most of the work for us. Doomsday’s default UI style package was easy to adapt for HiDPI, with a couple of extra factors applied to UI metrics and font sizes. It helped that we had already prepared suitably high-resolution versions of the icons and other graphics used in the revised UI.
I’m very happy about how crisp everything looks on a retina display.