nixpkgs/nixos/modules/services/x11/hardware/cmt.nix

{
  config,
  lib,
  pkgs,
  ...
}:

with lib;

let

  cfg = config.services.xserver.cmt;
  etcPath = "X11/xorg.conf.d";

in
{

  options = {

    services.xserver.cmt = {
      enable = mkOption {
        type = types.bool;
        default = false;
        description = "Enable chrome multitouch input (cmt). Touchpad drivers that are configured for chromebooks.";
      };
      models = mkOption {
        type = types.enum [
          "atlas"
          "banjo"
          "candy"
          "caroline"
          "cave"
          "celes"
          "clapper"
          "cyan"
          "daisy"
          "elan"
          "elm"
          "enguarde"
          "eve"
          "expresso"
          "falco"
          "gandof"
          "glimmer"
          "gnawty"
          "heli"
          "kevin"
          "kip"
          "leon"
          "lulu"
          "orco"
          "pbody"
          "peppy"
          "pi"
          "pit"
          "puppy"
          "quawks"
          "rambi"
          "samus"
          "snappy"
          "spring"
          "squawks"
          "swanky"
          "winky"
          "wolf"
          "auron_paine"
          "auron_yuna"
          "daisy_skate"
          "nyan_big"
          "nyan_blaze"
          "veyron_jaq"
          "veyron_jerry"
          "veyron_mighty"
          "veyron_minnie"
          "veyron_speedy"
        ];
        example = "banjo";
        description = ''
          Which models to enable cmt for. Enter the Code Name for your Chromebook.
          Code Name can be found at <https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices>.
        '';
      };
    }; # closes services
  }; # closes options

  config = mkIf cfg.enable {

    services.xserver.modules = [ pkgs.xf86_input_cmt ];

    environment.etc = {
      "${etcPath}/40-touchpad-cmt.conf" = {
        source = "${pkgs.chromium-xorg-conf}/40-touchpad-cmt.conf";
      };
      "${etcPath}/50-touchpad-cmt-${cfg.models}.conf" = {
        source = "${pkgs.chromium-xorg-conf}/50-touchpad-cmt-${cfg.models}.conf";
      };
      "${etcPath}/60-touchpad-cmt-${cfg.models}.conf" = {
        source = "${pkgs.chromium-xorg-conf}/60-touchpad-cmt-${cfg.models}.conf";
      };
    };

    assertions = [
      {
        assertion = !config.services.libinput.enable;
        message = ''
          cmt and libinput are incompatible, meaning you cannot enable them both.
          To use cmt you need to disable libinput with `services.libinput.enable = false`
          If you haven't enabled it in configuration.nix, it's enabled by default on a
          different xserver module.
        '';
      }
    ];
  };
}