services.gnome.gnome-settings-daemon: allow disabling of arbitrary plugins

[deepfire]

In pursuit of minimising the Gnome desktop footprint one might be tempted to reduce the number of services that gnome-settings-daemon starts.

We can observe those by invoking systemctl --all --user | grep SettingsDaemon

This allows build-time subsetting of systemd services that are installed into the system by gnome-settings-daemon to handle its plugins.

Note that the set of plugin-induced systemd services that gnome-system-daemon injects is not controlled by its NixOS packaging and service definition -- instead it is a direct consequence exclusively controlled by its build process.

Description of changes

We patch the Meson build description in the plugins subdir to allow subsetting of the plugins.

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/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 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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[jtojnar]

Thanks for the pull request. Unfortunately, I do not think this is something we want to support:

• the feature will be only useful for a tiny minority of users
• it makes it too easy to shoot oneself into one’s foot
  • get a broken system
  • change options that trigger larger packager rebuilds can be confusing
• it can be relatively easily achieved by an overlay
• the option description adds non-negligible maintenance cost for updates

[deepfire]

it can be relatively easily achieved by an overlay

Maybe indeed that's a better option -- can you explain a bit more?

[jtojnar]

People can just apply the patches to gnome.gnome-settings-daemon using an overlay in their own config.

[deepfire]

On your point of demand: It looks as if there is at least some, for trimming down the Gnome stack:

• Disable optional dependencies in Nautilus (and other GNOME packages) #278468
• Make NetworkManager plugins optional #137338

We can sure discuss ways to reduce the maintenance overhead.