> The desirable quantity is the result not the mechanics specifically that one can simply open windows on any display and move them between monitors without worrying about scaling.

Then next time don't bring up compatibility when you talk about the benefits of staying on X11. :) You are breaking the legacy programs anyway by forcing LoDPI programs to remain un-upscaled and therefore unusable on HiDPI displays.

> Well only with xwayland do you ever need to do so.

I am sorry, but the problem I mentioned exists as well on a pure X11 setup.

And the "solution" for this problem, on this setup, is to scale up the entire desktop (blurriness everywhere) which is decidedly worse than XWayland where only a single window is affected, assuming your other HiDPI-aware programs run natively on Wayland (which, from my experience, is pretty much true -- after all, HiDPI programs most likely are still actively developed).

The only other viable choice on a pure-X11 setup is a non-solution: just live with the tiny UI whenever you are using HiDPI-unaware programs.

Either you bring up documentation showing people that X11 has something akin to Wayland's buffer_scale event, or consider this discussion finished. It is tiring to talk to a brick wall.