NixOs module: add option to use UWSM

[meck]

This is mostly adapted from the equivelent nixpgks hyprland option.

USWM gives better options for delaying start of dependent systemd units (waybar and such). And handles
putting processes in slices.

[nullcubee]

This is what I have in my config, not sure if this is intended behavior or not, but it does work and would simplify this a bit:

Suggested change

	binPath = nixpkgs.lib.getExe (
	pkgs.writeShellScriptBin "niriSession" ''
	exec /run/current-system/sw/bin/niri --session
	''
	);
	binPath = "/run/current-system/sw/bin/niri -- --session";

[Brisingr05]

I'm surprised this works, since the -- should come before the compositor command and args¹.

Footnotes

1. https://github.com/Vladimir-csp/uwsm?tab=readme-ov-file#syntax-and-behavior ↩

[meck]

It seems uwsm parses
uwsm start -S -F /run/current-system/sw/bin/niri -- --session and
uwsm start -S -F -- /run/current-system/sw/bin/niri --session
the same way, I guess it could be changed but it doesn't feel like a behavior that should be relied on.

i guess the best would be to add programs.uwsm.waylandCompositors.*.args in nixpkgs

[Brisingr05]

handles putting processes in slices.

FYI niri started using niri-session already does this for programs started using spawn-at-startup in the config, niri keybinds, or niri msg action spawn, but yes, UWSM definitely gives more flexibility.

[Brisingr05]

Suggested change

	prettyName = "Niri";
	comment = "Niri compositor managed by UWSM";
	prettyName = "niri";
	comment = "niri compositor managed by UWSM";

Small nitpick but the "n" isn't meant to be capitalized according to the niri dev.