SwayOSD udev rules

modules/hardware/brightness.nix

@@ -4,11 +4,17 @@ with builtins;
 with lib;
 let cfg = config.modules.hardware.brightness;
 in {
-	options.modules.hardware.brightness = {
-		enable = mkEnableOption "brightness";
-	};
+  options.modules.hardware.brightness = {
+    enable = mkEnableOption "brightness";
+  };
 
-	config = mkIf cfg.enable {
-		environment.systemPackages = with pkgs; [ brightnessctl ];
-	};
+  config = mkIf cfg.enable {
+    environment.systemPackages = with pkgs; [ brightnessctl ];
+
+    # SwayOSD brightness controls don't work without this
+    # See https://github.com/ErikReider/SwayOSD?tab=readme-ov-file#brightness-control
+    # (it should essentially give access to `/sys/class/backlight/*/brightness` to the `video` group)
+    services.udev.packages = with pkgs; [ swayosd ];
+    # note: SwayOSD doesn't even give you an error message when this isn't set correctly
+  };
 }