gnome: use overlay.nix

Author: awwpotato

modules/gnome/nixos.nix

@@ -4,14 +4,6 @@
   config,
   ...
 }:
-
-let
-  theme = pkgs.callPackage ./theme.nix {
-    inherit (config.lib.stylix) colors;
-    inherit (config.stylix) inputs;
-  };
-
-in
 {
   options.stylix.targets.gnome.enable =
     config.lib.stylix.mkEnableTarget "GNOME and GDM" true;
@@ -34,25 +26,6 @@ in
         # which will then download the pack regardless of its exclusion below.
         environment.gnome.excludePackages = [ pkgs.gnome-backgrounds ];
 
-        nixpkgs.overlays = [
-          (_: super: {
-            gnome-shell = super.gnome-shell.overrideAttrs (oldAttrs: {
-              # Themes are usually applied via an extension, but extensions are
-              # not available on the login screen. The only way to change the
-              # theme there is by replacing the default.
-              postFixup =
-                (oldAttrs.postFixup or "")
-                + ''
-                  cp ${theme}/share/gnome-shell/gnome-shell-theme.gresource \
-                    $out/share/gnome-shell/gnome-shell-theme.gresource
-                '';
-              patches = (oldAttrs.patches or [ ]) ++ [
-                ./shell_remove_dark_mode.patch
-              ];
-            });
-          })
-        ];
-
         # Cursor settings are usually applied via Home Manager,
         # but the login screen uses a separate database.
         environment.systemPackages = lib.mkIf (config.stylix.cursor != null) [

modules/gnome/overlay.nix

@@ -0,0 +1,40 @@
+{
+  lib,
+  pkgs,
+  config,
+  options,
+  ...
+}:
+let
+  theme = pkgs.callPackage ./theme.nix {
+    inherit (config.lib.stylix) colors;
+    inherit (config.stylix) inputs;
+  };
+in
+{
+  overlay =
+    lib.mkIf
+      (
+        pkgs.stdenv.hostPlatform.canExecute pkgs.gnome-shell
+        && options.stylix.targets ? gnome
+        && config.stylix.targets.gnome.enable
+      )
+      (
+        _: super: {
+          gnome-shell = super.gnome-shell.overrideAttrs (oldAttrs: {
+            # Themes are usually applied via an extension, but extensions are
+            # not available on the login screen. The only way to change the
+            # theme there is by replacing the default.
+            postFixup =
+              (oldAttrs.postFixup or "")
+              + ''
+                cp ${theme}/share/gnome-shell/gnome-shell-theme.gresource \
+                  $out/share/gnome-shell/gnome-shell-theme.gresource
+              '';
+            patches = (oldAttrs.patches or [ ]) ++ [
+              ./shell_remove_dark_mode.patch
+            ];
+          });
+        }
+      );
+}