App-aware display scaling?

Let’s say there is an app that does support display scaling, but I want it to not scale at all, or scale differently than the rest of the system, or, more simply, to make the shell and the applications to use different UI scale factors.

Let’s say there’s one application where I really need to make pixel measurements, maybe a 2D videogame, or an ancient webapp, AFAIK, I currently I can’t do that and have fractional scaling at the same time.

umm, if they are XWayland apps, you can use force_zero_scaling for that. Native wayland apps handle scaling themselves.