Refactor LightSwitch integration: decouple event handling

Removed LightSwitchListener and ThemeChangedEventArgs. Added LightSwitchService to centralize theme/profile logic. Updated event registration and MainViewModel to handle LightSwitch theme changes via service, decoupling event listening from profile application. Event listening now handled externally.

src/modules/powerdisplay/PowerDisplay.Lib/Services/LightSwitchListener.cs

@@ -1,239 +0,0 @@
-// Copyright (c) Microsoft Corporation
-// The Microsoft Corporation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System;
-using System.IO;
-using System.Text.Json;
-using System.Threading;
-using System.Threading.Tasks;
-using ManagedCommon;
-
-namespace PowerDisplay.Common.Services
-{
-    /// <summary>
-    /// Listens for LightSwitch theme change events and notifies subscribers.
-    /// Encapsulates all LightSwitch integration logic including:
-    /// - Background thread management for event listening (light/dark theme events)
-    /// - LightSwitch settings file parsing
-    /// Theme is determined directly from which event was signaled (not from registry).
-    /// </summary>
-    public sealed partial class LightSwitchListener : IDisposable
-    {
-        private const string LogPrefix = "[LightSwitch Listener]";
-
-        private Thread? _listenerThread;
-        private CancellationTokenSource? _cancellationTokenSource;
-        private bool _disposed;
-
-        /// <summary>
-        /// Fired when LightSwitch signals a theme change and a profile should be applied
-        /// </summary>
-        public event EventHandler<ThemeChangedEventArgs>? ThemeChanged;
-
-        /// <summary>
-        /// Starts the background thread to listen for LightSwitch theme change events
-        /// </summary>
-        public void Start()
-        {
-            if (_listenerThread != null && _listenerThread.IsAlive)
-            {
-                Logger.LogWarning($"{LogPrefix} Listener already running");
-                return;
-            }
-
-            _cancellationTokenSource = new CancellationTokenSource();
-            var token = _cancellationTokenSource.Token;
-
-            _listenerThread = new Thread(() => ListenerThreadProc(token))
-            {
-                IsBackground = true,
-                Name = "LightSwitchEventListener",
-            };
-
-            _listenerThread.Start();
-            Logger.LogInfo($"{LogPrefix} Listener started");
-        }
-
-        /// <summary>
-        /// Stops the background listener thread
-        /// </summary>
-        public void Stop()
-        {
-            if (_cancellationTokenSource == null)
-            {
-                return;
-            }
-
-            _cancellationTokenSource.Cancel();
-
-            if (_listenerThread != null && _listenerThread.IsAlive)
-            {
-                try
-                {
-                    if (!_listenerThread.Join(TimeSpan.FromSeconds(2)))
-                    {
-                        Logger.LogWarning($"{LogPrefix} Listener thread did not stop in time");
-                    }
-                }
-                catch (Exception ex)
-                {
-                    Logger.LogDebug($"{LogPrefix} Error joining listener thread: {ex.Message}");
-                }
-            }
-
-            _listenerThread = null;
-            _cancellationTokenSource.Dispose();
-            _cancellationTokenSource = null;
-
-            Logger.LogInfo($"{LogPrefix} Listener stopped");
-        }
-
-        private void ListenerThreadProc(CancellationToken cancellationToken)
-        {
-            try
-            {
-                Logger.LogInfo($"{LogPrefix} Event listener thread started");
-
-                // Use separate events for light and dark themes to avoid race conditions
-                // where we might read the registry before LightSwitch has updated it
-                using var lightThemeEvent = new EventWaitHandle(false, EventResetMode.AutoReset, PathConstants.LightSwitchLightThemeEventName);
-                using var darkThemeEvent = new EventWaitHandle(false, EventResetMode.AutoReset, PathConstants.LightSwitchDarkThemeEventName);
-
-                var waitHandles = new WaitHandle[] { lightThemeEvent, darkThemeEvent };
-
-                while (!cancellationToken.IsCancellationRequested)
-                {
-                    // Wait for either light or dark theme event (with timeout to allow cancellation check)
-                    int index = WaitHandle.WaitAny(waitHandles, TimeSpan.FromSeconds(1));
-
-                    if (index == WaitHandle.WaitTimeout)
-                    {
-                        continue;
-                    }
-
-                    // Determine theme from which event was signaled
-                    bool isLightMode = index == 0; // 0 = lightThemeEvent, 1 = darkThemeEvent
-                    Logger.LogInfo($"{LogPrefix} Theme event received: {(isLightMode ? "Light" : "Dark")}");
-
-                    // Process the theme change with the known theme
-                    _ = Task.Run(() => ProcessThemeChange(isLightMode), CancellationToken.None);
-                }
-
-                Logger.LogInfo($"{LogPrefix} Event listener thread stopping");
-            }
-            catch (Exception ex)
-            {
-                Logger.LogError($"{LogPrefix} Event listener thread failed: {ex.Message}");
-            }
-        }
-
-        private void ProcessThemeChange(bool isLightMode)
-        {
-            try
-            {
-                Logger.LogInfo($"{LogPrefix} Processing theme change to {(isLightMode ? "light" : "dark")} mode");
-
-                var profileToApply = ReadProfileFromLightSwitchSettings(isLightMode);
-
-                if (string.IsNullOrEmpty(profileToApply) || profileToApply == "(None)")
-                {
-                    Logger.LogInfo($"{LogPrefix} No profile configured for {(isLightMode ? "light" : "dark")} mode");
-                    return;
-                }
-
-                Logger.LogInfo($"{LogPrefix} Requesting profile application: {profileToApply}");
-
-                // Notify subscribers
-                ThemeChanged?.Invoke(this, new ThemeChangedEventArgs(isLightMode, profileToApply));
-            }
-            catch (Exception ex)
-            {
-                Logger.LogError($"{LogPrefix} Failed to process theme change: {ex.Message}");
-            }
-        }
-
-        /// <summary>
-        /// Reads LightSwitch settings and returns the profile name to apply for the given theme.
-        /// The theme is determined by which event was signaled (light or dark), not by reading the registry.
-        /// </summary>
-        /// <param name="isLightMode">Whether the theme is light mode (determined from the signaled event)</param>
-        /// <returns>The profile name to apply, or null if not configured</returns>
-        private static string? ReadProfileFromLightSwitchSettings(bool isLightMode)
-        {
-            try
-            {
-                var settingsPath = PathConstants.LightSwitchSettingsFilePath;
-
-                if (!File.Exists(settingsPath))
-                {
-                    Logger.LogWarning($"{LogPrefix} LightSwitch settings file not found");
-                    return null;
-                }
-
-                var json = File.ReadAllText(settingsPath);
-                var settings = JsonDocument.Parse(json);
-                var root = settings.RootElement;
-
-                if (!root.TryGetProperty("properties", out var properties))
-                {
-                    Logger.LogWarning($"{LogPrefix} LightSwitch settings has no properties");
-                    return null;
-                }
-
-                // Check if monitor settings integration is enabled
-                if (!properties.TryGetProperty("apply_monitor_settings", out var applyMonitorSettingsElement) ||
-                    !applyMonitorSettingsElement.TryGetProperty("value", out var applyValue) ||
-                    !applyValue.GetBoolean())
-                {
-                    Logger.LogInfo($"{LogPrefix} Monitor settings integration is disabled");
-                    return null;
-                }
-
-                // Get the appropriate profile name based on the theme from the event
-                if (isLightMode)
-                {
-                    return GetProfileFromSettings(properties, "enable_light_mode_profile", "light_mode_profile");
-                }
-                else
-                {
-                    return GetProfileFromSettings(properties, "enable_dark_mode_profile", "dark_mode_profile");
-                }
-            }
-            catch (Exception ex)
-            {
-                Logger.LogError($"{LogPrefix} Failed to read LightSwitch settings: {ex.Message}");
-                return null;
-            }
-        }
-
-        private static string? GetProfileFromSettings(
-            JsonElement properties,
-            string enableKey,
-            string profileKey)
-        {
-            if (properties.TryGetProperty(enableKey, out var enableElement) &&
-                enableElement.TryGetProperty("value", out var enableValue) &&
-                enableValue.GetBoolean() &&
-                properties.TryGetProperty(profileKey, out var profileElement) &&
-                profileElement.TryGetProperty("value", out var profileValue))
-            {
-                return profileValue.GetString();
-            }
-
-            return null;
-        }
-
-        public void Dispose()
-        {
-            if (_disposed)
-            {
-                return;
-            }
-
-            Stop();
-            _disposed = true;
-            GC.SuppressFinalize(this);
-        }
-    }
-}

src/modules/powerdisplay/PowerDisplay.Lib/Services/LightSwitchService.cs

@@ -0,0 +1,112 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.IO;
+using System.Text.Json;
+using ManagedCommon;
+
+namespace PowerDisplay.Common.Services
+{
+    /// <summary>
+    /// Service for handling LightSwitch theme change events.
+    /// Provides methods to process theme changes and read LightSwitch settings.
+    /// Event listening is handled externally via NativeEventWaiter.
+    /// </summary>
+    public static class LightSwitchService
+    {
+        private const string LogPrefix = "[LightSwitch]";
+
+        /// <summary>
+        /// Process a theme change event and return the profile name to apply.
+        /// </summary>
+        /// <param name="isLightMode">Whether the theme changed to light mode.</param>
+        /// <returns>The profile name to apply, or null if no profile is configured.</returns>
+        public static string? GetProfileForTheme(bool isLightMode)
+        {
+            try
+            {
+                Logger.LogInfo($"{LogPrefix} Processing theme change to {(isLightMode ? "light" : "dark")} mode");
+
+                var profileToApply = ReadProfileFromLightSwitchSettings(isLightMode);
+
+                if (string.IsNullOrEmpty(profileToApply) || profileToApply == "(None)")
+                {
+                    Logger.LogInfo($"{LogPrefix} No profile configured for {(isLightMode ? "light" : "dark")} mode");
+                    return null;
+                }
+
+                Logger.LogInfo($"{LogPrefix} Profile to apply: {profileToApply}");
+                return profileToApply;
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"{LogPrefix} Failed to process theme change: {ex.Message}");
+                return null;
+            }
+        }
+
+        /// <summary>
+        /// Reads LightSwitch settings and returns the profile name to apply for the given theme.
+        /// </summary>
+        /// <param name="isLightMode">Whether the theme is light mode.</param>
+        /// <returns>The profile name to apply, or null if not configured.</returns>
+        private static string? ReadProfileFromLightSwitchSettings(bool isLightMode)
+        {
+            var settingsPath = PathConstants.LightSwitchSettingsFilePath;
+
+            if (!File.Exists(settingsPath))
+            {
+                Logger.LogWarning($"{LogPrefix} LightSwitch settings file not found");
+                return null;
+            }
+
+            var json = File.ReadAllText(settingsPath);
+            var settings = JsonDocument.Parse(json);
+            var root = settings.RootElement;
+
+            if (!root.TryGetProperty("properties", out var properties))
+            {
+                Logger.LogWarning($"{LogPrefix} LightSwitch settings has no properties");
+                return null;
+            }
+
+            // Check if monitor settings integration is enabled
+            if (!properties.TryGetProperty("apply_monitor_settings", out var applyMonitorSettingsElement) ||
+                !applyMonitorSettingsElement.TryGetProperty("value", out var applyValue) ||
+                !applyValue.GetBoolean())
+            {
+                Logger.LogInfo($"{LogPrefix} Monitor settings integration is disabled");
+                return null;
+            }
+
+            // Get the appropriate profile name based on the theme
+            if (isLightMode)
+            {
+                return GetProfileFromSettings(properties, "enable_light_mode_profile", "light_mode_profile");
+            }
+            else
+            {
+                return GetProfileFromSettings(properties, "enable_dark_mode_profile", "dark_mode_profile");
+            }
+        }
+
+        private static string? GetProfileFromSettings(
+            JsonElement properties,
+            string enableKey,
+            string profileKey)
+        {
+            if (properties.TryGetProperty(enableKey, out var enableElement) &&
+                enableElement.TryGetProperty("value", out var enableValue) &&
+                enableValue.GetBoolean() &&
+                properties.TryGetProperty(profileKey, out var profileElement) &&
+                profileElement.TryGetProperty("value", out var profileValue))
+            {
+                return profileValue.GetString();
+            }
+
+            return null;
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay.Lib/Services/ThemeChangedEventArgs.cs

@@ -1,30 +0,0 @@
-// Copyright (c) Microsoft Corporation
-// The Microsoft Corporation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System;
-
-namespace PowerDisplay.Common.Services
-{
-    /// <summary>
-    /// Event arguments for theme change notifications from LightSwitch
-    /// </summary>
-    public class ThemeChangedEventArgs : EventArgs
-    {
-        /// <summary>
-        /// Gets a value indicating whether the system is currently in light mode
-        /// </summary>
-        public bool IsLightMode { get; }
-
-        /// <summary>
-        /// Gets profile name to apply (null if no profile configured for current theme)
-        /// </summary>
-        public string? ProfileToApply { get; }
-
-        public ThemeChangedEventArgs(bool isLightMode, string? profileToApply)
-        {
-            IsLightMode = isLightMode;
-            ProfileToApply = profileToApply;
-        }
-    }
-}

src/modules/powerdisplay/PowerDisplay/PowerDisplayXAML/App.xaml.cs

@@ -11,6 +11,7 @@ using Microsoft.PowerToys.Telemetry;
 using Microsoft.UI.Dispatching;
 using Microsoft.UI.Xaml;
 using Microsoft.Windows.AppLifecycle;
+using PowerDisplay.Common;
 using PowerDisplay.Helpers;
 using PowerDisplay.Serialization;
 using PowerToys.Interop;
@@ -106,6 +107,10 @@ namespace PowerDisplay
                 RegisterViewModelEvent(Constants.ApplyColorTemperaturePowerDisplayEvent(), vm => vm.ApplyColorTemperatureFromSettings(), "ApplyColorTemperature");
                 RegisterViewModelEvent(Constants.ApplyProfilePowerDisplayEvent(), vm => vm.ApplyProfileFromSettings(), "ApplyProfile");
 
+                // LightSwitch integration - apply profiles when theme changes
+                RegisterViewModelEvent(PathConstants.LightSwitchLightThemeEventName, vm => vm.ApplyLightSwitchProfile(isLightMode: true), "LightSwitch-Light");
+                RegisterViewModelEvent(PathConstants.LightSwitchDarkThemeEventName, vm => vm.ApplyLightSwitchProfile(isLightMode: false), "LightSwitch-Dark");
+
                 // Monitor Runner process (backup exit mechanism)
                 if (_powerToysRunnerPid > 0)
                 {

src/modules/powerdisplay/PowerDisplay/ViewModels/MainViewModel.Settings.cs

@@ -209,11 +209,15 @@ public partial class MainViewModel
     }
 
     /// <summary>
-    /// Handle theme change notification from LightSwitch
+    /// Handle theme change from LightSwitch by applying the appropriate profile.
+    /// Called from App.xaml.cs when LightSwitch theme events are received.
     /// </summary>
-    private void OnLightSwitchThemeChanged(object? sender, ThemeChangedEventArgs e)
+    /// <param name="isLightMode">Whether the theme changed to light mode.</param>
+    public void ApplyLightSwitchProfile(bool isLightMode)
     {
-        if (string.IsNullOrEmpty(e.ProfileToApply))
+        var profileName = LightSwitchService.GetProfileForTheme(isLightMode);
+
+        if (string.IsNullOrEmpty(profileName))
         {
             return;
         }
@@ -222,21 +226,21 @@ public partial class MainViewModel
         {
             try
             {
-                Logger.LogInfo($"[LightSwitch Integration] Applying profile: {e.ProfileToApply}");
+                Logger.LogInfo($"[LightSwitch Integration] Applying profile: {profileName}");
 
                 // Load and apply the profile
                 var profilesData = ProfileService.LoadProfiles();
-                var profile = profilesData.GetProfile(e.ProfileToApply);
+                var profile = profilesData.GetProfile(profileName);
 
                 if (profile == null || !profile.IsValid())
                 {
-                    Logger.LogWarning($"[LightSwitch Integration] Profile '{e.ProfileToApply}' not found or invalid");
+                    Logger.LogWarning($"[LightSwitch Integration] Profile '{profileName}' not found or invalid");
                     return;
                 }
 
                 // Apply the profile
                 await ApplyProfileAsync(profile.MonitorSettings);
-                Logger.LogInfo($"[LightSwitch Integration] Successfully applied profile '{e.ProfileToApply}'");
+                Logger.LogInfo($"[LightSwitch Integration] Successfully applied profile '{profileName}'");
             }
             catch (Exception ex)
             {

src/modules/powerdisplay/PowerDisplay/ViewModels/MainViewModel.cs

@@ -46,7 +46,6 @@ public partial class MainViewModel : INotifyPropertyChanged, IDisposable
     private readonly CancellationTokenSource _cancellationTokenSource;
     private readonly ISettingsUtils _settingsUtils;
     private readonly MonitorStateManager _stateManager;
-    private readonly LightSwitchListener _lightSwitchListener;
     private readonly DisplayChangeWatcher _displayChangeWatcher;
 
     private ObservableCollection<MonitorViewModel> _monitors;
@@ -75,11 +74,6 @@ public partial class MainViewModel : INotifyPropertyChanged, IDisposable
         // Initialize the monitor manager
         _monitorManager = new MonitorManager();
 
-        // Initialize and start LightSwitch integration listener
-        _lightSwitchListener = new LightSwitchListener();
-        _lightSwitchListener.ThemeChanged += OnLightSwitchThemeChanged;
-        _lightSwitchListener.Start();
-
         // Load profiles for quick apply feature
         LoadProfiles();
 
@@ -256,7 +250,6 @@ public partial class MainViewModel : INotifyPropertyChanged, IDisposable
 
         // Dispose all resources safely (don't throw from Dispose)
         SafeDispose(_displayChangeWatcher, "DisplayChangeWatcher");
-        SafeDispose(_lightSwitchListener, "LightSwitchListener");
 
         // Dispose monitor view models
         foreach (var vm in Monitors)