xserver: dwm as a window manager

nixos/modules/services/x11/window-managers/default.nix

@@ -12,6 +12,7 @@ in
     ./bspwm.nix
     ./clfswm.nix
     ./compiz.nix
+    ./dwm.nix
     ./fluxbox.nix
     ./herbstluftwm.nix
     ./i3.nix

nixos/modules/services/x11/window-managers/dwm.nix

@@ -0,0 +1,37 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.services.xserver.windowManager.dwm;
+
+in
+
+{
+
+  ###### interface
+
+  options = {
+    services.xserver.windowManager.dwm.enable = mkEnableOption "dwm";
+  };
+
+
+  ###### implementation
+
+  config = mkIf cfg.enable {
+
+    services.xserver.windowManager.session = singleton
+      { name = "dwm";
+        start =
+          ''
+            ${pkgs.dwm}/bin/dwm &
+            waitPID=$!
+          '';
+      };
+
+    environment.systemPackages = [ pkgs.dwm ];
+
+  };
+
+}