gnome: use overlay.nix

Author: awwpotato

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
+            ];
+          });
+        }
+      );
+}