Alt text:
Twitter post by Daniel Feldman (@d_feldman): Linux is the only major operating system to support diagonal mode (credit [Twitter] @xssfox). Image shows an untrawide monitor rotated about 45 degrees, with a horizontal IDE window taking up a bottom triangle. A web browser and settings menu above it are organized creating a window shape almost like a stepped pyramid.
Edit: alt text
Rotating the display by a custom angle is possible through xrandr on X.org.
There's no Wayland protocol for custom angle rotation, and I don't expect anyone to create a protocol extension without a use-case.
My wild guess: Theoretically it should be possible for a compositor to support similar custom rotation, as applications simply draw to their surface (window), without knowing how and where it is displayed on the viewport (display).
But it might require quite a bit of work, depending on the project, so I don't expect to ever see custom rotation on anything besides smaller/niche compositors.
[1] https://unix.stackexchange.com/questions/552138/rotate-a-display-by-custom-angle#552140
Puh-lease. It's Wayland; the devs fully and honestly expect every app developer (eg.: calc, Libreoffice, notepad.exe) to implement custom angle rotation on their own.
[gestures at thread] Does this not count??? 😁
Seriously, though: I suspect there might be non-novelty use-cases in mobile devices, especially things like smart watches. Those aren't beyond the scope of Wayland in the long run, are they?
Ok I was joking with the images but now that I think about it this would likely be pretty useful to have on smart watches with circular displays.
E.g. having the watch face rotating to face towards the wearer would be a pretty neat concept. Definitely something I'd want a toggle for though.
Smart watches tend to be microcontroller class devices because even though you can fit something powerful in there, powering it and heat dissipation make it silly.
The usual embedded-type application for wayland that it's even especially designed for is automotive: Things without window management but not particularly hardware-restrained. Also think public transit ticket machines, ATMs, such things. In that sense, from wayland's perspective android is already desktop.