Apply GNOME shell styling to GDM ✨

This has some other benefits too:
- No messing around with extensions and DConf settings
- The custom theme is compiled into a gresource file for efficiency

However it does cause the GNOME shell package to be compiled from scratch.

modules/gnome/default.nix

@@ -9,26 +9,29 @@ let
   };
 
   theme = pkgs.stdenv.mkDerivation {
-    name = "stylix-gnome-shell.css";
+    name = "stylix-gnome-shell";
 
     src = pkgs.fetchurl {
       url = "mirror://gnome/sources/gnome-shell/43/gnome-shell-43.2.tar.xz";
       sha256 = "52/UvpNCQQ7p+9zday2Bxv8GDnyMxaDxyuanq6JdGGA=";
     };
-    sourceRoot = "gnome-shell-43.2/data/theme";
 
     patches = [ ./shell.patch ];
     postPatch = ''
-      rm gnome-shell-sass/{_colors.scss,_palette.scss}
-      cp ${colors} gnome-shell-sass/_colors.scss
+      rm data/theme/gnome-shell-sass/{_colors.scss,_palette.scss}
+      cp ${colors} data/theme/gnome-shell-sass/_colors.scss
     '';
 
-    nativeBuildInputs = with pkgs; [ sass ];
+    nativeBuildInputs = with pkgs; [ sass glib.dev ];
     buildPhase = ''
-      sass gnome-shell.scss >$out
+      sass data/theme/gnome-shell.scss >data/theme/gnome-shell.css
+      # cp data/theme/gnome-shell.css data/theme/gnome-shell-high-contrast.css
+      glib-compile-resources --sourcedir=data/theme data/gnome-shell-theme.gresource.xml
     '';
 
-    installPhase = "true";
+    installPhase = ''
+      mv data/gnome-shell-theme.gresource $out
+    '';
   };
 
 in {
@@ -49,16 +52,6 @@ in {
           if config.stylix.polarity == "dark"
           then "prefer-dark"
           else "default";
-
-        "org/gnome/shell/extensions/user-theme".name = "Stylix";
-      };
-
-      xdg.dataFile."themes/Stylix/gnome-shell/gnome-shell.css" = {
-        source = theme;
-        onChange = ''
-          gnome-extensions disable [email protected]
-          gnome-extensions enable [email protected]
-        '';
       };
     })];
 
@@ -68,5 +61,15 @@ in {
     # "${pkgs.gnome.gnome-backgrounds}/path/to/your/preferred/background"
     # which will then download the pack regardless of its exclusion below.
     environment.gnome.excludePackages = [ pkgs.gnome.gnome-backgrounds ];
+
+    nixpkgs.overlays = [(self: super: {
+      gnome = super.gnome.overrideScope' (gnomeSelf: gnomeSuper: {
+        gnome-shell = gnomeSuper.gnome-shell.overrideAttrs (oldAttrs: {
+          postFixup = ''
+            cp ${theme} $out/share/gnome-shell/gnome-shell-theme.gresource
+          '';
+        });
+      });
+    })];
   };
 }

modules/gnome/shell.patch

@@ -1,7 +1,7 @@
-diff --git a/gnome-shell-sass/_drawing.scss b/gnome-shell-sass/_drawing.scss
+diff --git a/data/theme/gnome-shell-sass/_drawing.scss b/data/theme/gnome-shell-sass/_drawing.scss
 index 7c8959e2c..6066def91 100644
---- a/gnome-shell-sass/_drawing.scss
-+++ b/gnome-shell-sass/_drawing.scss
+--- a/data/theme/gnome-shell-sass/_drawing.scss
++++ b/data/theme/gnome-shell-sass/_drawing.scss
 @@ -248,7 +248,7 @@
      &:insensitive {
        @include button(insensitive);
@@ -11,10 +11,10 @@ index 7c8959e2c..6066def91 100644
      }
    }
  }
-diff --git a/gnome-shell-sass/widgets/_dash.scss b/gnome-shell-sass/widgets/_dash.scss
+diff --git a/data/theme/gnome-shell-sass/widgets/_dash.scss b/data/theme/gnome-shell-sass/widgets/_dash.scss
 index 8f5d5f939..f3a7e1029 100644
---- a/gnome-shell-sass/widgets/_dash.scss
-+++ b/gnome-shell-sass/widgets/_dash.scss
+--- a/data/theme/gnome-shell-sass/widgets/_dash.scss
++++ b/data/theme/gnome-shell-sass/widgets/_dash.scss
 @@ -1,6 +1,6 @@
  /* Dash */
 
@@ -23,10 +23,10 @@ index 8f5d5f939..f3a7e1029 100644
  $dash_placeholder_size: 32px;
  $dash_padding: $base_padding*2; // 12px
  $dash_border_radius: $modal_radius + $dash_padding;
-diff --git a/gnome-shell-sass/widgets/_message-list.scss b/gnome-shell-sass/widgets/_message-list.scss
+diff --git a/data/theme/gnome-shell-sass/widgets/_message-list.scss b/data/theme/gnome-shell-sass/widgets/_message-list.scss
 index 5196661c1..663e754bd 100644
---- a/gnome-shell-sass/widgets/_message-list.scss
-+++ b/gnome-shell-sass/widgets/_message-list.scss
+--- a/data/theme/gnome-shell-sass/widgets/_message-list.scss
++++ b/data/theme/gnome-shell-sass/widgets/_message-list.scss
 @@ -128,7 +128,7 @@
    }
 
@@ -67,10 +67,10 @@ index 5196661c1..663e754bd 100644
      border: 1px solid transparent;
      border-radius: $base_border_radius;
      icon-size: $large_icon_size !important; // 32px
-diff --git a/gnome-shell-sass/widgets/_panel.scss b/gnome-shell-sass/widgets/_panel.scss
+diff --git a/data/theme/gnome-shell-sass/widgets/_panel.scss b/data/theme/gnome-shell-sass/widgets/_panel.scss
 index fd3e7d2da..051eefbfe 100644
---- a/gnome-shell-sass/widgets/_panel.scss
-+++ b/gnome-shell-sass/widgets/_panel.scss
+--- a/data/theme/gnome-shell-sass/widgets/_panel.scss
++++ b/data/theme/gnome-shell-sass/widgets/_panel.scss
 @@ -1,7 +1,7 @@
  /* Top Bar */
  // a.k.a. the panel
@@ -80,10 +80,10 @@ index fd3e7d2da..051eefbfe 100644
  $panel_fg_color: if($variant == 'light', lighten($bg_color, 10%), darken($fg_color, 5%));
  $panel_height: 2.2em;
  $panel_transition_duration: 250ms; // same as the overview transition duration
-diff --git a/gnome-shell-sass/widgets/_popovers.scss b/gnome-shell-sass/widgets/_popovers.scss
+diff --git a/data/theme/gnome-shell-sass/widgets/_popovers.scss b/data/theme/gnome-shell-sass/widgets/_popovers.scss
 index 138a4fc0f..ccd020a0f 100644
---- a/gnome-shell-sass/widgets/_popovers.scss
-+++ b/gnome-shell-sass/widgets/_popovers.scss
+--- a/data/theme/gnome-shell-sass/widgets/_popovers.scss
++++ b/data/theme/gnome-shell-sass/widgets/_popovers.scss
 @@ -37,22 +37,22 @@
    &:rtl {padding-right: $base_padding;}
 
@@ -140,10 +140,10 @@ index 138a4fc0f..ccd020a0f 100644
    }
 
    .popup-menu-section {
-diff --git a/gnome-shell-sass/widgets/_quick-settings.scss b/gnome-shell-sass/widgets/_quick-settings.scss
+diff --git a/data/theme/gnome-shell-sass/widgets/_quick-settings.scss b/data/theme/gnome-shell-sass/widgets/_quick-settings.scss
 index b429a2dc5..858f286a2 100644
---- a/gnome-shell-sass/widgets/_quick-settings.scss
-+++ b/gnome-shell-sass/widgets/_quick-settings.scss
+--- a/data/theme/gnome-shell-sass/widgets/_quick-settings.scss
++++ b/data/theme/gnome-shell-sass/widgets/_quick-settings.scss
 @@ -81,9 +81,12 @@
        icon-size: $base_icon_size*1.5; // a non-standard symbolic size but ok
        border-radius: 999px;