dark theme

home/shihaam.nix

@@ -10,6 +10,7 @@
     ./nano.nix
     ./obs.nix
     ./sway.nix
+    ./theme.nix
   ];
 
   home.username = "shihaam";

home/theme.nix

@@ -0,0 +1,61 @@
+# Dark theme for GTK and Qt apps.
+#
+# There is no desktop environment on this machine to hand apps a theme, so
+# every toolkit has to be told separately:
+#
+#   GTK2      ~/.gtkrc-2.0 + GTK2_RC_FILES -- adw-gtk3 has no GTK2 variant, so
+#             old apps get Adwaita-dark from gnome-themes-extra instead.
+#   GTK3      gtk-3.0/settings.ini (gtk-theme-name + prefer-dark).
+#   GTK4      libadwaita apps ignore gtk-theme-name; they follow the
+#             color-scheme=prefer-dark that the gtk3 module also writes into
+#             dconf, which is why programs.dconf.enable is on system-side.
+#   Electron/ Chromium, Brave, Firefox and friends ask the settings portal for
+#   browsers  color-scheme, and xdg-desktop-portal-gtk answers from that same
+#             dconf key.
+#   Qt5/Qt6   qt5ct/qt6ct, because nixpkgs builds qtbase without the qgtk3
+#             platform theme (withGtk3 = false), so QT_QPA_PLATFORMTHEME=gtk3
+#             would silently do nothing.
+{ pkgs, ... }:
+
+{
+  gtk = {
+    enable = true;
+    colorScheme = "dark";
+
+    theme = {
+      name = "adw-gtk3-dark";
+      package = pkgs.adw-gtk3;
+    };
+
+    iconTheme = {
+      name = "Adwaita";
+      package = pkgs.adwaita-icon-theme;
+    };
+
+    gtk2.theme = {
+      name = "Adwaita-dark";
+      package = pkgs.gnome-themes-extra;
+    };
+  };
+
+  qt = {
+    enable = true;
+    platformTheme.name = "qtct";
+
+    # Pulls adwaita-qt{,6} in without setting QT_STYLE_OVERRIDE -- that
+    # variable makes qt5ct/qt6ct skip their own config entirely.
+    style.package = [ pkgs.adwaita-qt pkgs.adwaita-qt6 ];
+
+    qt5ctSettings.Appearance = {
+      style = "Adwaita-Dark";
+      icon_theme = "Adwaita";
+      standard_dialogs = "xdgdesktopportal";
+    };
+
+    qt6ctSettings.Appearance = {
+      style = "Adwaita-Dark";
+      icon_theme = "Adwaita";
+      standard_dialogs = "xdgdesktopportal";
+    };
+  };
+}

hosts/la2410/configuration.nix

@@ -250,9 +250,17 @@ security.doas.extraRules = [
      default = [ "wlr" "gtk" ];
      "org.freedesktop.impl.portal.ScreenCast" = [ "wlr" ];
      "org.freedesktop.impl.portal.Screenshot" = [ "wlr" ];
+     # How browsers and Electron apps learn the dark preference; wlr has no
+     # Settings implementation, so it has to be pinned to gtk explicitly.
+     "org.freedesktop.impl.portal.Settings" = [ "gtk" ];
    };
  };
 
+ # GTK4/libadwaita apps and the settings portal read the dark preference out
+ # of dconf (see home/theme.nix), which needs a real dconf backend -- there is
+ # no desktop environment here to enable one.
+ programs.dconf.enable = true;
+
  programs.waybar.enable = true;
 programs.xfconf.enable = true;