xresources: add module

This module adds basic support for configuring X resources.

modules/default.nix

@@ -27,6 +27,7 @@ let
     ./services/udiskie.nix
     ./services/xscreensaver.nix
     ./systemd.nix
+    ./xresources.nix
     ./xsession.nix
   ];
 

modules/xresources.nix

@@ -0,0 +1,43 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.xresources;
+
+  formatLine = n: v:
+    let
+      v' =
+        if isBool v then (if v then "true" else "false")
+        else toString v;
+    in
+      "${n}: ${v'}";
+
+in
+
+{
+  options = {
+    xresources.properties = mkOption {
+      type = types.nullOr types.attrs;
+      default = null;
+      example = ''
+        {
+          "XTerm*faceName" = "dejavu sans mono";
+          "Emacs*toolBar" = 0;
+        }
+      '';
+      description = ''
+        X server resources that should be set. If null, then this
+        feature is disabled and no ~/.Xresources link is produced.
+      '';
+    };
+  };
+
+  config = mkIf (cfg.properties != null) {
+    home.file.".Xresources".text =
+      concatStringsSep "\n" (
+        mapAttrsToList formatLine cfg.properties
+      );
+  };
+}