add e17 desktop manager

desktop-manager is a bit misleading in this case as there is no
session yet and most apps are still missing. This can eventually
grow further once more e17 apps get packaged for nix.

However, for now, I need to initialize some e17 dbus services to
have the "terminology" terminal emulator provide gfx previews.

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

@@ -17,7 +17,7 @@ in
   # Note: the order in which desktop manager modules are imported here
   # determines the default: later modules (if enabled) are preferred.
   # E.g., if KDE is enabled, it supersedes xterm.
-  imports = [ ./none.nix ./xterm.nix ./xfce.nix ./gnome.nix ./kde4.nix ];
+  imports = [ ./none.nix ./xterm.nix ./xfce.nix ./gnome.nix ./kde4.nix ./e17.nix ];
 
   options = {
 

modules/services/x11/desktop-managers/e17.nix

@@ -0,0 +1,30 @@
+{ config, pkgs, ... }:
+
+with pkgs.lib;
+
+let
+
+  xcfg = config.services.xserver;
+  cfg = xcfg.desktopManager.e17;
+
+in
+
+{
+  options = {
+
+    services.xserver.desktopManager.e17.enable = mkOption {
+      default = false;
+      example = true;
+      description = "Enable support for the E17 desktop environment.";
+    };
+
+  };
+
+
+  config = mkIf (xcfg.enable && cfg.enable) {
+
+    services.dbus.packages = [ pkgs.e17.ethumb ];
+
+  };
+
+}