add the FVWM window manager

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

@@ -17,6 +17,7 @@ in
       ./xmonad.nix
       ./i3.nix
       ./xbmc.nix
+      ./fvwm.nix
     ];
 
   options = {

modules/services/x11/window-managers/fvwm.nix

@@ -0,0 +1,42 @@
+{ config, pkgs, ... }:
+
+with pkgs.lib;
+
+let
+
+  cfg = config.services.xserver.windowManager.fvwm;
+
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    services.xserver.windowManager.fvwm.enable = mkOption {
+      default = false;
+      description = "Enable the FVWM window manager.";
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = mkIf cfg.enable {
+
+    services.xserver.windowManager.session = singleton
+      { name = "fvwm";
+        start =
+          ''
+            ${pkgs.fvwm}/bin/fvwm &
+            waitPID=$!
+          '';
+      };
+
+    environment.x11Packages = [ pkgs.fvwm ];
+
+  };
+
+}