[mike_hearn]

macOS actually has the best support for that. DMG files are mountable disk images and the contents can be compressed with LZMA or some Apple-specific codecs that are quite good. Opening them mounts them into the kernel and then there's random access. Even code signatures are checked JIT during page faults.

The main problem with DMGs is the poor UX, and very slow mount/verification times. Users can start the app from the DMG and it will seem to work, but be unable to update. They forget to unmount the "drive" or don't know how. The format is also undocumented and a PITA to work with as it's basically a full filesystem, which also has to be signed and notarized independently and that's super slow too. So it makes the whole build process a lot slower.

There's quite some low hanging fruit here that I might experiment with soon. I have a design in mind already.