{ config, pkgs, ... }: with pkgs.lib; let cfg = config.services.xserver.windowManager.twm; in { ###### interface options = { services.xserver.windowManager.twm.enable = mkOption { default = false; description = "Enable the twm window manager."; }; }; ###### implementation config = mkIf cfg.enable { services.xserver.windowManager.session = singleton { name = "twm"; start = '' ${pkgs.xorg.twm}/bin/twm & waitPID=$! ''; }; environment.x11Packages = [ pkgs.xorg.twm ]; }; }