Rebase to flake parts #9

modules/desktop/gui.nix

@@ -58,6 +58,14 @@
           xdg.portal.extraPortals =
             [ pkgs.xdg-desktop-portal-gtk ]
             ++ lib.optionals cfg.plasma.enable [ pkgs.kdePackages.xdg-desktop-portal-kde ];
+
+          # Backlight control: `brightnessctl` + its udev rule (auto-loaded from the package's
+          # `lib/udev/rules.d`). The rule grants the `video` group write access to
+          # `/sys/class/backlight/*/brightness`; the user catalog adds desktop users to `video`.
+          # The Hyprland defaults already bind XF86MonBrightness* to brightnessctl, and the Niri
+          # base config does the same — this guarantees the binary is actually present.
+          environment.systemPackages = [ pkgs.brightnessctl ];
+          services.udev.packages = [ pkgs.brightnessctl ];
         })
         (lib.mkIf (guiEnabled && !useGreeter) {
           services.displayManager.sddm = {

modules/desktop/niri/default.nix

@@ -113,6 +113,11 @@ let
           "toggle"
         ];
 
+        # Backlight: relies on `pkgs.brightnessctl` being on PATH (provided by `desktopGui` when
+        # any GUI session is enabled) and the user being in the `video` group (catalog default).
+        "XF86MonBrightnessUp".spawn = [ "brightnessctl" "set" "+5%" ];
+        "XF86MonBrightnessDown".spawn = [ "brightnessctl" "set" "5%-" ];
+
         Print.screenshot = _: { };
         "Ctrl+Print"."screenshot-screen" = _: { };
         "Alt+Print"."screenshot-window" = _: { };