nixpkgs/nixos/modules/services/x11/imwheel.nix

{
  config,
  lib,
  pkgs,
  ...
}:
with lib;
let
  cfg = config.services.xserver.imwheel;
in
{
  options = {
    services.xserver.imwheel = {
      enable = mkEnableOption "IMWheel service";

      extraOptions = mkOption {
        type = types.listOf types.str;
        default = [ "--buttons=45" ];
        example = [ "--debug" ];
        description = ''
          Additional command-line arguments to pass to
          {command}`imwheel`.
        '';
      };

      rules = mkOption {
        type = types.attrsOf types.str;
        default = { };
        example = literalExpression ''
          {
            ".*" = '''
              None,      Up,   Button4, 8
              None,      Down, Button5, 8
              Shift_L,   Up,   Shift_L|Button4, 4
              Shift_L,   Down, Shift_L|Button5, 4
              Control_L, Up,   Control_L|Button4
              Control_L, Down, Control_L|Button5
            ''';
          }
        '';
        description = ''
          Window class translation rules.
          /etc/X11/imwheelrc is generated based on this config
          which means this config is global for all users.
          See [official man pages](https://imwheel.sourceforge.net/imwheel.1.html)
          for more information.
        '';
      };
    };
  };

  config = mkIf cfg.enable {
    environment.systemPackages = [ pkgs.imwheel ];

    environment.etc."X11/imwheel/imwheelrc".source = pkgs.writeText "imwheelrc" (
      concatStringsSep "\n\n" (mapAttrsToList (rule: conf: "\"${rule}\"\n${conf}") cfg.rules)
    );

    systemd.user.services.imwheel = {
      description = "imwheel service";
      wantedBy = [ "graphical-session.target" ];
      partOf = [ "graphical-session.target" ];
      serviceConfig = {
        ExecStart =
          "${pkgs.imwheel}/bin/imwheel "
          + escapeShellArgs (
            [
              "--detach"
              "--kill"
            ]
            ++ cfg.extraOptions
          );
        ExecStop = "${pkgs.procps}/bin/pkill imwheel";
        RestartSec = 3;
        Restart = "always";
      };
    };
  };
}