BrightnessManager: add per-monitor brightness management

Author: garaevdi

src/DBus.vala

@@ -23,7 +23,20 @@ public class Gala.DBus {
                 try {
                     connection.register_object ("/io/elementary/gala", WindowDragProvider.get_instance ());
 #if HAS_MUTTER50
-                    connection.register_object ("/io/elementary/gala/BrightnessManager", new BrightnessManager (wm.get_display ()));
+                    connection.register_object ("/io/elementary/gala/BrightnessManager", brightness_manager);
+                    brightness_manager.monitor_added.connect ((monitor_brightness) => {
+                        try {
+                            var id = connection.register_object (@"/io/elementary/gala/BrightnessManager/$(monitor_brightness.get_monitor_serial ())", monitor_brightness);
+                            return id;
+                        } catch (Error e) {
+                            warning (e.message);
+                            return null;
+                        }
+                    });
+                    brightness_manager.monitor_removed.connect ((connection_id) => {
+                        connection.unregister_object (connection_id);
+                    });
+                    brightness_manager.update_available_backlights ();
 #endif
                 } catch (Error e) {
                     warning (e.message);

src/Misc/BrightnessManager.vala

@@ -8,31 +8,37 @@
 #if HAS_MUTTER50
 [DBus (name = "io.elementary.gala.BrightnessManager")]
 public class Gala.BrightnessManager : GLib.Object {
+    [DBus (visible = false)]
+    public signal uint? monitor_added (MonitorBrightness monitor_brightness);
+    [DBus (visible = false)]
+    public signal void monitor_removed (uint connection_id);
+
+    private int _brightness;
     public int brightness {
         get {
-            if (backlight == null) {
+            if (exposed_monitors.size () == 0)
                 return -1;
-            }
-            int min, max;
-            int value;
-            backlight.get_brightness_info (out min, out max);
-            value = backlight.get_brightness ();
-            return ((value - min) * 100) / (max - min);
+
+
+            return _brightness;
         }
         set {
-            if (brightness == value || backlight == null) {
+            if (_brightness == value || exposed_monitors.size () == 0)
                 return;
-            }
-            int min, max;
-            backlight.get_brightness_info (out min, out max);
-            backlight.set_brightness ((int) (value * (max - min) / 100) + min);
+
+            foreach (var monitor_brightness in exposed_monitors.get_values ())
+                monitor_brightness.brightness = value;
+
+            _brightness = value;
         }
     }
 
     [DBus (visible = false)]
     public unowned Meta.Display display { private get; construct; }
+
+    private GLib.HashTable<unowned Meta.Monitor, MonitorBrightness> exposed_monitors;
+    private GLib.HashTable<unowned Meta.Monitor, uint> connection_ids;
     private unowned Meta.MonitorManager monitor_manager;
-    private unowned Meta.Backlight? backlight;
 
     public BrightnessManager (Meta.Display display) {
         Object (
@@ -43,6 +49,11 @@ public class Gala.BrightnessManager : GLib.Object {
     construct {
         monitor_manager = display.get_context ().get_backend ().get_monitor_manager ();
         monitor_manager.monitors_changed.connect (update_available_backlights);
+        exposed_monitors = new GLib.HashTable<unowned Meta.Monitor, MonitorBrightness> (null, null);
+        connection_ids = new GLib.HashTable<unowned Meta.Monitor, uint> (null, null);
+
+        // TODO: bind to value from gschema
+        _brightness = 100;
 
         var keybinding_settings = new GLib.Settings ("io.elementary.desktop.wm.keybindings");
         display.add_keybinding ("brightness-brighter", keybinding_settings, Meta.KeyBindingFlags.NONE, () => {
@@ -51,16 +62,39 @@ public class Gala.BrightnessManager : GLib.Object {
         display.add_keybinding ("brightness-dimmer", keybinding_settings, Meta.KeyBindingFlags.NONE, () => {
             brightness -= 5;
         });
-
-        update_available_backlights ();
     }
 
-    private void update_available_backlights () {
-        backlight = null;
+    [DBus (visible = false)]
+    public void update_available_backlights () {
         unowned var monitors = monitor_manager.get_monitors ();
+        var new_monitors = monitors.copy ();
+        var old_monitors = exposed_monitors.get_keys ();
         foreach (unowned var monitor in monitors) {
-            if (monitor.is_primary () && monitor.is_active ()) {
-                backlight = monitor.get_backlight ();
+            if (monitor.get_backlight () == null)
+                continue;
+
+            if (old_monitors.find (monitor) != null) {
+                old_monitors.remove (monitor);
+                new_monitors.remove (monitor);
+            }
+        }
+
+        if (new_monitors.length () > 0) {
+            foreach (var monitor in new_monitors) {
+                var monitor_brightness = new MonitorBrightness (monitor);
+                var connection_id = monitor_added (monitor_brightness);
+                if (connection_id != null) {
+                    exposed_monitors.insert (monitor, monitor_brightness);
+                    connection_ids.insert (monitor, connection_id);
+                }
+            }
+        }
+
+        if (old_monitors.length () > 0) {
+            foreach (var monitor in old_monitors) {
+                monitor_removed (connection_ids.get (monitor));
+                exposed_monitors.remove (monitor);
+                connection_ids.remove (monitor);
             }
         }
     }

src/Misc/MonitorBrightness.vala

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2026 elementary, Inc. (https://elementary.io)
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ * Authored by: Denis Garaev <garaevdi@outlook.com>
+ */
+
+#if HAS_MUTTER50
+[DBus (name = "io.elementary.gala.BrightnessManager.Monitor")]
+public class Gala.MonitorBrightness : GLib.Object {
+    [DBus (visible = false)]
+    public unowned Meta.Monitor monitor { get; construct; }
+
+    public int brightness {
+        get {
+            if (backlight == null)
+                return -1;
+
+            int min, max;
+            int value;
+            backlight.get_brightness_info (out min, out max);
+            value = backlight.get_brightness ();
+            return ((value - min) * 100) / (max - min);
+        }
+        set {
+            if (brightness == value || backlight == null)
+                return;
+
+            int min, max;
+            backlight.get_brightness_info (out min, out max);
+            backlight.set_brightness ((int) (value * (max - min) / 100) + min);
+        }
+    }
+
+    private unowned Meta.Backlight? backlight;
+
+    public MonitorBrightness (Meta.Monitor monitor) {
+        Object (
+            monitor: monitor
+        );
+    }
+
+    construct {
+        backlight = monitor.get_backlight ();
+    }
+
+    [DBus (visible = false)]
+    public string get_monitor_serial () {
+        return monitor.get_serial ();
+    }
+}
+#endif

src/WindowManager.vala

@@ -93,6 +93,10 @@ namespace Gala {
 
         private LockScreenManager lock_screen_manager;
 
+#if HAS_MUTTER50
+        private BrightnessManager brightness_manager;
+#endif
+
         private Gee.LinkedList<ModalProxy> modal_stack = new Gee.LinkedList<ModalProxy> ();
 
         private Gee.HashSet<Meta.WindowActor> minimizing = new Gee.HashSet<Meta.WindowActor> ();

src/meson.build

@@ -31,6 +31,7 @@ gala_bin_sources = files(
     'Misc/DesktopIntegration.vala',
     'Misc/InputMethod.vala',
     'Misc/KeyboardManager.vala',
+    'Misc/MonitorBrightness.vala',
     'Misc/LockScreenManager.vala',
     'Misc/NotificationsManager.vala',
     'Misc/NotificationStack.vala',