qtile: install proper session .desktop files for both xorg and wayland

[arjan-s]

Description of changes

This PR modifies the qtile package to install the provided session desktop files for login managers.
That in turn allows us to add the package to services.displayManager.sessionPackages when the NixOS module is enabled.
After that, both the Xorg and Wayland sessions will be available from login (display) managers, instead of just one session that's hard coded to a specific backend (via the now removed option backend).

Additionally, this fixes the services.xserver.windowManager.qtile.finalPackage assignment to use the qtile package instead of building a whole new env.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[Sigmanificient]

When running nix-build -A qtile-unwrapped.passthru.tests.qtile

error: Default graphical session, 'none+qtile', not found.
       Valid names for 'services.displayManager.defaultSession' are:
         qtile
         none+icewm

[Sigmanificient]

build my whole system with your branch, seems to work:

[arjan-s]

Thanks! This PR changed the session names, that's why the test is failing.
Since these changes work on both our systems, I'll just fix the test.

Another todo I thought of after submitting is marking the now-removed backend option deprecated, so people having that in their configs get a nice message.

[Sigmanificient]

Another todo I thought of after submitting is marking the now-removed backend option deprecated, so people having that in their configs get a nice message.

Yes this would be nice

[arjan-s]

Both done!

[arjan-s]

Looking at this again, I'm afraid the configFile option should be deprecated too. But that could break the way some people configure their system, especially those who don't use home-manager (which can write ~/.config/qtile/config.py).
We can't easily modify the session files that are now installed by the package, so the 'old' method isn't feasible I think.
I'm hoping others have ideas about this...? Perhaps a good solution would be a link to the provided config in the system-wide config dir (qtile docs here)?

[Sigmanificient]

it look after into the .desktop pr, indead would break the configFile option.

Setting to /etc/xdg would work, but for users that used previous configFile options, it may not be the cleanest especially one multiple users system.

I'm a bit new to options, could the desktop file be wrapped in it's own derivation, with something like this?

postPatch = ''
  substituteInPlace resources/qtile.desktop \
    --replace-fail "qtile start" "qtile start --config ${cfg.configFile}"
'';

[arjan-s]

Actually, my idea was to do something like this:

environment.etc."qtile/config.py".source = lib.optional (cfg.configFile != null) cfg.configFile;

This would create a link in /etc/xdg/qtile/config.py to the user's provided config (in the nix store).

[arjan-s]

Done. I believe this is ready to test (again).

[arjan-s]

Converted to draft, because after testing I found that the logic regarding the wrapper and systemPackages isn't right. I'll have to dive deeper to get to a point where it just works.

[arjan-s]

Okay, I believe I have now (finally) arrived at a working and much cleaner solution!

• I removed the wrapper since we weren't actually using it anyway (we built a separate new env for display managers and we added the unwrapped package to environment.systemPackages).
• The extraPackages are now nicely added to the dependencies of Qtile itself, making qtile: Fix QTile restart environment #299843 a thing of the past (I hope).
• The finalPackage (which optionally contains qtile-extras and other dependencies) is used for both display managers and added to $PATH (the latter makes commands like qtile check work).
• If a configFile is provided, it is symlinked to /etc/xdg/qtile/config.py, which is automatically used by Qtile if ~/.config/qtile/config.py isn't found.

[drupol]

LGTM

[jwijenbergh]

Thanks a lot for making these changes. Looks good to me. Should we maybe move qtile later to programs.qtile? Most wayland compositors do that, but I'm not sure for qtile as it also supports x11