NixOS-Config/modules/system/services/general/greetd/default.nix

{ config, pkgs, ... }:
{
  services.greetd = {
    enable = config.system.desktop.enable;
    restart = true;
    settings = {
      terminal = {
        vt = 2;
        switch = true;
      };
      default_session.command = "${pkgs.greetd.tuigreet}/bin/tuigreet";
    };
  };

  environment.etc."greetd/environments".text = let
    initScript = ''
      if ${pkgs.pciutils}/bin/lspci -k | grep "in use: nvidia" &> /dev/null; then
        export LIBVA_DRIVER_NAME=nvidia
        export GBM_BACKEND=nvidia-drm
        export __GLX_VENDOR_LIBRARY_NAME=nvidia
      else
        :
      fi
    '';
  in ''
    ${pkgs.writeScript "startsway" ''
      ${initScript}
      export QT_QPA_PLATFORM="wayland;xcb"
      export XDG_CURRENT_DESKTOP=sway
      sway --unsupported-gpu
    ''}
    ${pkgs.writeScript "startniri" ''
      ${initScript}
      export QT_QPA_PLATFORM=wayland
      export XDG_CURRENT_DESKTOP=niri
      niri-session
    ''}
  '';
}