Refactor tiling layout type (#354)

- Move conversion to JSON to apply function of tiles
- Made options of tiling layout not optional
- Added example for `layout.id`

modules/kwin.nix

@@ -82,13 +82,12 @@ let
   tilingLayoutType = types.submodule {
     options = {
       id = mkOption {
-        type = with types; nullOr str;
-        default = null;
+        type = types.str;
         description = "The id of the layout.";
+        example = "cf5c25c2-4217-4193-add6-b5971cb543f2";
       };
       tiles = mkOption {
-        type = with types; nullOr (attrsOf anything);
-        default = null;
+        type = with types; attrsOf anything;
         example = {
           layoutDirection = "horizontal";
           tiles = [
@@ -109,6 +108,7 @@ let
             }
           ];
         };
+        apply = builtins.toJSON;
       };
     };
   };
@@ -678,7 +678,7 @@ in
         "Tiling/${cfg.kwin.tiling.layout.id}" = {
           tiles =  {
             escapeValue = false;
-            value = builtins.toJSON cfg.kwin.tiling.layout.tiles;
+            value = cfg.kwin.tiling.layout.tiles;
           };
         };
       })