Fix brightness HUD not working on macOS Tahoe 26.5

The brightness HUD broke on Tahoe because Apple deprecated/changed the
DisplayServices private framework and stopped posting the BezelEngine
distributed notifications that Atoll relied on for change detection.

This commit:
- Adds CoreBrightnessDisplayClient using Apple's CoreBrightness framework
  (mirrors the existing KeyboardBrightnessClient pattern) as the primary
  brightness read/write path
- Falls back gracefully to DisplayServices then IODisplay if CoreBrightness
  is unavailable
- Adds a lightweight polling fallback (150ms) so the HUD fires even when
  no distributed notifications are posted (Control Center, Touch Bar, auto-
  brightness changes)
- Registers the new com.apple.CoreBrightness.DisplayBrightnessChanged
  notification
- Fixes deprecated kIOMasterPortDefault → kIOMainPortDefault in
  SystemDisplayManager.swift

Fixes #452

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

DynamicIsland/helpers/CoreBrightnessDisplayClient.swift

@@ -0,0 +1,82 @@
+/*
+ * Atoll (DynamicIsland)
+ * Copyright (C) 2024-2026 Atoll Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import Foundation
+import ObjectiveC.runtime
+
+final class CoreBrightnessDisplayClient {
+    static let shared = CoreBrightnessDisplayClient()
+
+    private static let builtInDisplayID: UInt64 = 0
+
+    private var clientInstance: NSObject?
+    private let getSelector = NSSelectorFromString("brightnessForDisplay:")
+    private let setSelector = NSSelectorFromString("setBrightness:forDisplay:")
+    private let notificationSelector = NSSelectorFromString("setNotificationBlock:")
+
+    var onBrightnessChange: ((Float) -> Void)?
+    private var available = false
+
+    private init() {
+        var loaded = false
+        let bundlePaths = [
+            "/System/Library/PrivateFrameworks/CoreBrightness.framework",
+            "/System/Library/PrivateFrameworks/CoreBrightness.framework/CoreBrightness"
+        ]
+        for path in bundlePaths where !loaded {
+            if let bundle = Bundle(path: path) {
+                loaded = bundle.load()
+            }
+        }
+        guard loaded, let cls = NSClassFromString("DisplayBrightnessClient") as? NSObject.Type else {
+            NSLog("⚠️ CoreBrightnessDisplayClient: DisplayBrightnessClient class not found")
+            return
+        }
+        clientInstance = cls.init()
+        available = clientInstance != nil
+    }
+
+    var isAvailable: Bool { available }
+
+    func currentBrightness() -> Float? {
+        guard let clientInstance,
+              let getter: BrightnessGetter = methodIMP(on: clientInstance, selector: getSelector, as: BrightnessGetter.self)
+        else { return nil }
+        let value = getter(clientInstance, getSelector, Self.builtInDisplayID)
+        guard value >= 0, value <= 1 else { return nil }
+        return value
+    }
+
+    func setBrightness(_ value: Float) -> Bool {
+        guard let clientInstance,
+              let setter: BrightnessSetter = methodIMP(on: clientInstance, selector: setSelector, as: BrightnessSetter.self)
+        else { return false }
+        return setter(clientInstance, setSelector, value, Self.builtInDisplayID).boolValue
+    }
+
+    private typealias BrightnessGetter = @convention(c) (NSObject, Selector, UInt64) -> Float
+    private typealias BrightnessSetter = @convention(c) (NSObject, Selector, Float, UInt64) -> ObjCBool
+
+    private func methodIMP<T>(on object: NSObject, selector: Selector, as type: T.Type) -> T? {
+        guard let cls = object_getClass(object),
+              let method = class_getInstanceMethod(cls, selector)
+        else { return nil }
+        let imp = method_getImplementation(method)
+        return unsafeBitCast(imp, to: T.self)
+    }
+}

DynamicIsland/managers/SystemDisplayManager.swift

@@ -46,7 +46,7 @@ class SystemDisplayManager {
 
     private static func getStandardDisplayBrightness() throws -> Float {
         var brightness: float_t = 1
-        let service = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("IODisplayConnect"))
+        let service = IOServiceGetMatchingService(kIOMainPortDefault, IOServiceMatching("IODisplayConnect"))
         defer {
             IOObjectRelease(service)
         }

DynamicIsland/managers/SystemMediaControllers.swift

@@ -476,6 +476,10 @@ final class SystemBrightnessController {
     private let maximumBrightnessAnimationDuration: TimeInterval = 0.3
     private let brightnessAnimationDurationScale: TimeInterval = 1.6
     private var lastEmittedBrightness: Float = 0.5
+    private let coreBrightnessClient = CoreBrightnessDisplayClient.shared
+    private var pollTimer: Timer?
+    private let pollInterval: TimeInterval = 0.15
+    private let pollChangeThreshold: Float = 0.005
 
     private init() {
         registerExternalNotifications()
@@ -484,12 +488,15 @@ final class SystemBrightnessController {
 
     func start() {
         notifyCurrentBrightness()
+        startPollingIfNeeded()
     }
 
     func stop() {
         onBrightnessChange = nil
         brightnessAnimationTimer?.invalidate()
         brightnessAnimationTimer = nil
+        pollTimer?.invalidate()
+        pollTimer = nil
     }
 
     func adjust(by delta: Float) {
@@ -506,6 +513,9 @@ final class SystemBrightnessController {
     }
 
     var currentBrightness: Float {
+        if let level = coreBrightnessClient.currentBrightness() {
+            return level
+        }
         if let level = getBrightnessViaDisplayServices() {
             return level
         }
@@ -583,6 +593,9 @@ final class SystemBrightnessController {
 
     private func applyBrightness(_ value: Float) {
         let clamped = max(0, min(1, value))
+        if coreBrightnessClient.setBrightness(clamped) {
+            return
+        }
         if setBrightnessViaDisplayServices(clamped) {
             return
         }
@@ -667,7 +680,8 @@ final class SystemBrightnessController {
         let names = [
             Notification.Name("com.apple.BezelEngine.BrightnessChanged"),
             Notification.Name("com.apple.BezelServices.BrightnessChanged"),
-            Notification.Name("com.apple.controlcenter.display.brightness")
+            Notification.Name("com.apple.controlcenter.display.brightness"),
+            Notification.Name("com.apple.CoreBrightness.DisplayBrightnessChanged")
         ]
         observers = names.map { name in
             DistributedNotificationCenter.default().addObserver(forName: name, object: nil, queue: .main) { [weak self] _ in
@@ -677,8 +691,20 @@ final class SystemBrightnessController {
         notificationsInstalled = true
     }
 
+    private func startPollingIfNeeded() {
+        guard pollTimer == nil else { return }
+        pollTimer = Timer.scheduledTimer(withTimeInterval: pollInterval, repeats: true) { [weak self] _ in
+            guard let self else { return }
+            let system = self.currentBrightness
+            if abs(system - self.lastEmittedBrightness) > self.pollChangeThreshold {
+                self.emitBrightnessChange(value: system)
+            }
+        }
+    }
+
     deinit {
         brightnessAnimationTimer?.invalidate()
+        pollTimer?.invalidate()
         observers.forEach { DistributedNotificationCenter.default().removeObserver($0) }
     }
 }