HiDPI support for X11 apps

[wmww]

When HiDPI support lands X11 apps will get scaled up, but will be low resolution. From sway I know it's possible to scale them correctly. Not a priority at the moment.

[RAOF]

FWIW, KWin also fails to correctly scale HiDPI apps.

This is annoying, as CLion is an XWayland app and so is all blurry on my laptop 😀

[wmww]

Attaching these two X PRs, which seem relevant (though hopefully we'll have a solution before they merge): https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/111, https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/432

[wmww]

It seems I was incorrect in the call earlier today. Sway does not support HiDPI on XWayland. It seems the change I was thinking of that caused my problem to go away was me purchasing a normal DPI laptop.

The status quo is that there is no way to know the scale of an XWayland app, so all XWayland apps must be scaled the same. Currently Sway requests them render at 1x scale and then stretches the buffers. This gives consistent but blurry results.

There is a proposal to requests the correct scale and assume apps respect it. Apps that don't respect X11 scaling will then render smol.

This tradeoff exists when running X11 natively as well, either all apps are lower resolution or some apps are not scaled. I assume GNOME is taking the latter approach, and that's what we want to do until a real fix is ready on the X11 side (which could be a very long time). I will look into how to do that.

EDIT: actually that sway proposal depends on the X11 PRs, but everything else I said holds.