gnome-flashback: add option to remove gnome-panel, auto-generate wmName

[chpatrick]

I wanted to remove the wmName option since it would fail if it wasn't in the right format. I also added a flag to disable the GNOME panel.

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[worldofpeace]

you should use mkRemovedOption~

[chpatrick]

Unfortunately I don't think that works because the option is in a submodule. I added an assertion.

[bitonic]

@worldofpeace friendly bump, this is very useful if you want to run gnome flashback and a tiling WM such as i3.

[jtojnar]

A benefit of human readable name is that it is clearer in the logs.

[chpatrick]

I think this is better for the user, since this name is only needed internally and this way it can't be named in a way that breaks things.

[jtojnar]

Alternately, we might use slugify wmLabel as the default value for the name and make it optional. Possibly suffix it with the hash to avoid conflicts.

slugify =
  let
    allowed = lib.lowerChars ++ lib.upperChars ++ lib.stringToCharacters "1234567890-_";
  in
    lib.stringAsChars (c: if builtins.elem c allowed then c else "_");

[jtojnar]

And types.strMatching "[a-zA-Z0-9_-]+" for the option would work.

[chpatrick]

I think it's fine how it is now. This identifier is only needed to get GNOME to find it internally, and exposing it would be a leaky abstraction IMO.

[jtojnar]

Actually, I just remembered that the identifier is needed for auto-login (services.xserver.displayManager.defaultSession) so this is technically another BC break.

[jtojnar]

Yeah, this is not particularly nice:

trace: Default graphical session, 'gnome-flashback-xmonad', not found.
Valid names for 'services.xserver.displayManager.defaultSession' are:
  gnome
  gnome-xorg
  gnome-flashback-Metacity-4175ca004519ae58f559894fbcaadd3f
  gnome-flashback-XMonad-8382231e25a9fde7159467bbc610bdbf
  sm.puri.Phosh

[nh2]

BC break

@jtojnar What's "BC"?

[jtojnar]

@nh2 backwards compatibility

[chpatrick]

@jtojnar OK fair enough, I put the wmName back in.

[jtojnar]

But generally, it looks okay so if you do not think these are worth addressing, we can merge it as is.

[chpatrick]

I've tried it on top of latest master but the custom session doesn't seem to work due to some systemd issues. I don't really know too much about that stuff, could you maybe take a look @worldofpeace?

[jtojnar]

They left the project. I will try to take a look when I have some more time.

[jtojnar]

Do you have any error message?

[chpatrick]

@jtojnar I'm not sure what the exact thing is, but the WM doesn't seem to start. The systemd unit we use in the gnome-flashback is now in a directory instead of a file. I changed cp to copy the service.conf file inside, but I don't know if that's actually correct.

[jtojnar]

Oh, I see.

The systemd units containing @ sign in the name are instantiated templates, the name before @ being the name of the original unit.

I suspect that before, the whole gnome-session@gnome-flashback-metacity.target instance created by systemd was being replaced by the one from the package, which can lead to the flashback instance being outdated.

Likely, to prevent that, upstream decided to switch to drop-in overrides, which use the original instance auto-created by systemd from gnome-session@.target and only override few specific fields listed in the .conf file.

So I would just copy what is now in the package, just like we did before. Do not forget to adjust to the new unit name.

[chpatrick]

@jtojnar OK, it seems to work now!

[jtojnar]

The docs should be updated as well. Otherwise, looks good.

[jtojnar]

Can confirm that it works, thanks.

[B4dM4n]

This PR enables many Gnome services by default without setting any gnome related option:

services.xserver.desktopManager.gnome.flashback.enableMetacity = mkOption {
  default = true;
}
->
flashbackEnabled = cfg.flashback.enableMetacity || length cfg.flashback.customSessions > 0;
->
mkIf (cfg.enable || flashbackEnabled) {
      services.gnome.core-os-services.enable = true;
      services.gnome.core-shell.enable = true;
      services.gnome.core-utilities.enable = mkDefault true;
}

I noticed this because it breaks any configuration with networking.wireless.enable = true:

nix-instantiate ./nixos --arg configuration '{
  fileSystems."/".fsType = "tmpfs";
  boot.loader.grub.device = "/dev/null";
  networking.wireless.enable = true;
}'

error:
       Failed assertions:
       - You can not use networking.networkmanager with networking.wireless.
       Except if you mark some interfaces as <literal>unmanaged</literal> by NetworkManager.

[chpatrick]

@jtojnar I know there were plans to allow enabling flashback but not gnome shell, was this done? If not, we should only apply flashback configs if gnome is enabled right?

[jtojnar]

Sorry about that, I forgot we do not have a separate flashback.enable option. Reverted back to mkEnableOption in b2f86e6.