Fix some issues

src/modules/powerdisplay/PowerDisplay.Lib/Drivers/DDC/DdcCiController.cs

@@ -181,7 +181,7 @@ namespace PowerDisplay.Common.Drivers.DDC
                     if (DdcCiNative.TryGetVCPFeature(monitor.Handle, VcpCodeSelectColorPreset, out uint current, out uint max))
                     {
                         var presetName = VcpValueNames.GetFormattedName(0x14, (int)current);
-                        Logger.LogInfo($"[{monitor.Id}] Color temperature via 0x14: {presetName}");
+                        Logger.LogDebug($"[{monitor.Id}] Color temperature via 0x14: {presetName}");
                         return new BrightnessInfo((int)current, 0, (int)max);
                     }
 
@@ -266,7 +266,7 @@ namespace PowerDisplay.Common.Drivers.DDC
                     if (DdcCiNative.TryGetVCPFeature(monitor.Handle, VcpCodeInputSource, out uint current, out uint max))
                     {
                         var sourceName = VcpValueNames.GetFormattedName(0x60, (int)current);
-                        Logger.LogInfo($"[{monitor.Id}] Input source via 0x60: {sourceName}");
+                        Logger.LogDebug($"[{monitor.Id}] Input source via 0x60: {sourceName}");
                         return new BrightnessInfo((int)current, 0, (int)max);
                     }
 
@@ -322,7 +322,7 @@ namespace PowerDisplay.Common.Drivers.DDC
                                 var verifyName = VcpValueNames.GetFormattedName(0x60, (int)verifyValue);
                                 if (verifyValue == (uint)inputSource)
                                 {
-                                    Logger.LogInfo($"[{monitor.Id}] Input source verified: {verifyName} (0x{verifyValue:X2})");
+                                    Logger.LogDebug($"[{monitor.Id}] Input source verified: {verifyName} (0x{verifyValue:X2})");
                                 }
                                 else
                                 {
@@ -409,7 +409,7 @@ namespace PowerDisplay.Common.Drivers.DDC
 
                         if (!string.IsNullOrEmpty(capsString))
                         {
-                            Logger.LogInfo($"Got capabilities string (length: {capsString.Length})");
+                            Logger.LogDebug($"Got capabilities string (length: {capsString.Length})");
                             return capsString;
                         }
                     }

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

@@ -16,8 +16,21 @@ namespace PowerDisplay.Common.Services
     /// Centralized service for managing PowerDisplay profiles storage and retrieval.
     /// Provides unified access to profile data for PowerDisplay, Settings UI, and LightSwitch modules.
     /// Thread-safe and AOT-compatible.
-    /// Implements <see cref="IProfileService"/> for dependency injection support.
     /// </summary>
+    /// <remarks>
+    /// <para><b>Design Note:</b> This class provides both static and instance-based access patterns:</para>
+    /// <list type="bullet">
+    ///   <item><description>Static methods: Direct access for backward compatibility with existing code. Thread-safe with internal locking.</description></item>
+    ///   <item><description>Instance methods (via <see cref="IProfileService"/>): For dependency injection consumers. Delegates to static methods internally.</description></item>
+    /// </list>
+    /// <para><b>Usage Guidelines:</b></para>
+    /// <list type="bullet">
+    ///   <item><description>New code should prefer DI: <c>serviceProvider.GetService&lt;IProfileService&gt;()</c></description></item>
+    ///   <item><description>Or use the singleton: <c>ProfileService.Instance.LoadProfiles()</c></description></item>
+    ///   <item><description>Static methods remain available for backward compatibility</description></item>
+    /// </list>
+    /// <para>All access patterns are thread-safe and share the same underlying lock.</para>
+    /// </remarks>
     public class ProfileService : IProfileService
     {
         private const string LogPrefix = "[ProfileService]";

src/modules/powerdisplay/PowerDisplay.Lib/Utils/EventHelper.cs

@@ -0,0 +1,47 @@
+// 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.Threading;
+using ManagedCommon;
+
+namespace PowerDisplay.Common.Utils
+{
+    /// <summary>
+    /// Helper class for Windows named event operations.
+    /// Provides unified event signaling with consistent error handling and logging.
+    /// </summary>
+    public static class EventHelper
+    {
+        /// <summary>
+        /// Signals a named event. Creates the event if it doesn't exist.
+        /// </summary>
+        /// <param name="eventName">The name of the event to signal.</param>
+        /// <returns>True if the event was signaled successfully, false otherwise.</returns>
+        public static bool SignalEvent(string eventName)
+        {
+            if (string.IsNullOrEmpty(eventName))
+            {
+                Logger.LogWarning("[EventHelper] SignalEvent called with null or empty event name");
+                return false;
+            }
+
+            try
+            {
+                using var eventHandle = new EventWaitHandle(
+                    false,
+                    EventResetMode.AutoReset,
+                    eventName);
+                eventHandle.Set();
+                Logger.LogDebug($"[EventHelper] Signaled event: {eventName}");
+                return true;
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"[EventHelper] Failed to signal event '{eventName}': {ex.Message}");
+                return false;
+            }
+        }
+    }
+}

src/modules/powerdisplay/PowerDisplay/Configuration/AppConstants.cs

@@ -34,5 +34,60 @@ namespace PowerDisplay.Configuration
             /// </summary>
             public const string ExternalMonitorGlyph = "\uE7F4";
         }
+
+        /// <summary>
+        /// DDC/CI protocol constants
+        /// </summary>
+        public static class Ddc
+        {
+            /// <summary>
+            /// Retry delay between DDC/CI operations in milliseconds
+            /// </summary>
+            public const int RetryDelayMs = 100;
+
+            /// <summary>
+            /// Maximum number of retries for DDC/CI operations
+            /// </summary>
+            public const int MaxRetries = 3;
+
+            /// <summary>
+            /// Timeout for getting monitor capabilities in milliseconds
+            /// </summary>
+            public const int CapabilitiesTimeoutMs = 5000;
+
+            // VCP Codes
+            /// <summary>VCP code for Brightness (0x10)</summary>
+            public const byte VcpBrightness = 0x10;
+
+            /// <summary>VCP code for Contrast (0x12)</summary>
+            public const byte VcpContrast = 0x12;
+
+            /// <summary>VCP code for Select Color Preset / Color Temperature (0x14)</summary>
+            public const byte VcpColorTemperature = 0x14;
+
+            /// <summary>VCP code for Input Source (0x60)</summary>
+            public const byte VcpInputSource = 0x60;
+        }
+
+        /// <summary>
+        /// Process synchronization constants
+        /// </summary>
+        public static class Process
+        {
+            /// <summary>
+            /// Timeout for waiting for process ready signal in milliseconds
+            /// </summary>
+            public const int StartupTimeoutMs = 5000;
+
+            /// <summary>
+            /// Polling interval when waiting for process ready in milliseconds
+            /// </summary>
+            public const int ReadyPollIntervalMs = 100;
+
+            /// <summary>
+            /// Fallback delay when event-based synchronization fails in milliseconds
+            /// </summary>
+            public const int FallbackDelayMs = 500;
+        }
     }
 }

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

@@ -26,6 +26,12 @@ namespace PowerDisplay
     public partial class App : Application
 #pragma warning restore CA1001
     {
+        /// <summary>
+        /// Event name for signaling that PowerDisplay process is ready.
+        /// Must match the constant in C++ PowerDisplayModuleInterface.
+        /// </summary>
+        private const string ProcessReadyEventName = "Local\\PowerToys_PowerDisplay_Ready";
+
         private readonly ISettingsUtils _settingsUtils = new SettingsUtils();
         private Window? _mainWindow;
         private int _powerToysRunnerPid;
@@ -106,6 +112,10 @@ namespace PowerDisplay
                 RegisterViewModelEvent(Constants.ApplyColorTemperaturePowerDisplayEvent(), vm => vm.ApplyColorTemperatureFromSettings(), "ApplyColorTemperature");
                 RegisterViewModelEvent(Constants.ApplyProfilePowerDisplayEvent(), vm => vm.ApplyProfileFromSettings(), "ApplyProfile");
 
+                // Signal that process is ready to receive events
+                // This allows the C++ module to wait for initialization instead of using hardcoded Sleep
+                SignalProcessReady();
+
                 // Monitor Runner process (backup exit mechanism)
                 if (_powerToysRunnerPid > 0)
                 {
@@ -354,5 +364,26 @@ namespace PowerDisplay
             _trayIconService?.Destroy();
             Environment.Exit(0);
         }
+
+        /// <summary>
+        /// Signal that PowerDisplay process is ready to receive events.
+        /// Uses a ManualReset event so the C++ module can wait on it.
+        /// </summary>
+        private static void SignalProcessReady()
+        {
+            try
+            {
+                using var readyEvent = new EventWaitHandle(
+                    false,
+                    EventResetMode.ManualReset,
+                    ProcessReadyEventName);
+                readyEvent.Set();
+                Logger.LogInfo("Signaled process ready event");
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"Failed to signal process ready event: {ex.Message}");
+            }
+        }
     }
 }

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

@@ -5,6 +5,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using ManagedCommon;
 using Microsoft.PowerToys.Settings.UI.Library;
@@ -19,7 +20,7 @@ namespace PowerDisplay.ViewModels;
 /// </summary>
 public partial class MainViewModel
 {
-    private async Task InitializeAsync()
+    private async Task InitializeAsync(CancellationToken cancellationToken = default)
     {
         try
         {
@@ -27,7 +28,7 @@ public partial class MainViewModel
             IsScanning = true;
 
             // Discover monitors
-            var monitors = await _monitorManager.DiscoverMonitorsAsync(_cancellationTokenSource.Token);
+            var monitors = await _monitorManager.DiscoverMonitorsAsync(cancellationToken);
 
             // Update UI on the dispatcher thread
             _dispatcherQueue.TryEnqueue(() =>

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

@@ -10,6 +10,7 @@ using ManagedCommon;
 using Microsoft.PowerToys.Settings.UI.Library;
 using PowerDisplay.Common.Models;
 using PowerDisplay.Common.Services;
+using PowerDisplay.Common.Utils;
 using PowerDisplay.Serialization;
 using PowerToys.Interop;
 
@@ -621,21 +622,8 @@ public partial class MainViewModel
     /// </summary>
     private void SignalMonitorsRefreshEvent()
     {
-        try
+        EventHelper.SignalEvent(Constants.RefreshPowerDisplayMonitorsEvent());
-        {
+        Logger.LogInfo("Signaled refresh monitors event to Settings UI");
-            using (var eventHandle = new System.Threading.EventWaitHandle(
-                false,
-                System.Threading.EventResetMode.AutoReset,
-                Constants.RefreshPowerDisplayMonitorsEvent()))
-            {
-                eventHandle.Set();
-                Logger.LogInfo("Signaled refresh monitors event to Settings UI");
-            }
-        }
-        catch (Exception ex)
-        {
-            Logger.LogError($"Failed to signal refresh monitors event: {ex.Message}");
-        }
     }
 
     /// <summary>

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

@@ -80,7 +80,7 @@ public partial class MainViewModel : INotifyPropertyChanged, IDisposable
         LoadProfiles();
 
         // Start initial discovery
-        _ = InitializeAsync();
+        _ = InitializeAsync(_cancellationTokenSource.Token);
     }
 
     public ObservableCollection<MonitorViewModel> Monitors

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

@@ -404,6 +404,13 @@ public partial class MonitorViewModel : INotifyPropertyChanged, IDisposable
     /// <param name="orientation">Orientation: 0=normal, 1=90°, 2=180°, 3=270°</param>
     public async Task SetRotationAsync(int orientation)
     {
+        // Validate orientation range (0=normal, 1=90°, 2=180°, 3=270°)
+        if (orientation < 0 || orientation > 3)
+        {
+            Logger.LogWarning($"[{HardwareId}] Invalid rotation value: {orientation}. Must be 0-3.");
+            return;
+        }
+
         // If already at this orientation, do nothing
         if (CurrentRotation == orientation)
         {

src/modules/powerdisplay/PowerDisplayModuleInterface/Constants.h

@@ -4,4 +4,9 @@ namespace PowerDisplayConstants
 {
     // Name of the powertoy module.
     inline const std::wstring ModuleKey = L"PowerDisplay";
+
+    // Process synchronization constants
+    inline const wchar_t* ProcessReadyEventName = L"Local\\PowerToys_PowerDisplay_Ready";
+    constexpr DWORD ProcessReadyTimeoutMs = 5000;
+    constexpr DWORD FallbackDelayMs = 500;
 }

src/modules/powerdisplay/PowerDisplayModuleInterface/dllmain.cpp

@@ -185,6 +185,38 @@ private:
         }
     }
 
+    // Helper method to wait for PowerDisplay.exe process to be ready
+    // Uses a named event for precise synchronization instead of hardcoded Sleep
+    void wait_for_process_ready()
+    {
+        HANDLE readyEvent = OpenEventW(SYNCHRONIZE, FALSE, PowerDisplayConstants::ProcessReadyEventName);
+        if (readyEvent)
+        {
+            Logger::trace(L"Waiting for PowerDisplay process ready signal...");
+            DWORD waitResult = WaitForSingleObject(readyEvent, PowerDisplayConstants::ProcessReadyTimeoutMs);
+            CloseHandle(readyEvent);
+
+            if (waitResult == WAIT_OBJECT_0)
+            {
+                Logger::trace(L"PowerDisplay process ready signal received");
+            }
+            else if (waitResult == WAIT_TIMEOUT)
+            {
+                Logger::warn(L"PowerDisplay process ready timeout after {}ms", PowerDisplayConstants::ProcessReadyTimeoutMs);
+            }
+            else
+            {
+                Logger::warn(L"WaitForSingleObject failed with error: {}", GetLastError());
+            }
+        }
+        else
+        {
+            // Fallback: if cannot open event, use a shorter delay
+            Logger::warn(L"Could not open PowerDisplay ready event, using fallback delay");
+            Sleep(PowerDisplayConstants::FallbackDelayMs);
+        }
+    }
+
 public:
     PowerDisplayModule()
     {
@@ -332,9 +364,8 @@ public:
                 {
                     Logger::trace(L"PowerDisplay process not running, launching before applying color temperature");
                     launch_process();
-                    // Wait for process to initialize and register event listeners
+                    // Wait for process to signal ready
-                    // This prevents race condition where event is set before process is ready
+                    wait_for_process_ready();
-                    Sleep(1000);
                 }
 
                 if (m_hApplyColorTemperatureEvent)
@@ -364,8 +395,8 @@ public:
                 {
                     Logger::trace(L"PowerDisplay process not running, launching before applying profile");
                     launch_process();
-                    // Wait for process to initialize and register event listeners
+                    // Wait for process to signal ready
-                    Sleep(1000);
+                    wait_for_process_ready();
                 }
 
                 if (m_hApplyProfileEvent)

src/settings-ui/Settings.UI/ViewModels/PowerDisplayViewModel.cs

@@ -142,11 +142,7 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
                 {
                     // Explicitly signal PowerDisplay to refresh tray icon
                     // This is needed because set_config() doesn't signal SettingsUpdatedEvent to avoid UI refresh issues
-                    using var eventHandle = new System.Threading.EventWaitHandle(
+                    EventHelper.SignalEvent(Constants.SettingsUpdatedPowerDisplayEvent());
-                        false,
-                        System.Threading.EventResetMode.AutoReset,
-                        Constants.SettingsUpdatedPowerDisplayEvent());
-                    eventHandle.Set();
                     Logger.LogInfo($"ShowSystemTrayIcon changed to {value}, signaled SettingsUpdatedPowerDisplayEvent");
                 }
             }
@@ -396,19 +392,8 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
         /// </summary>
         private void SignalSettingsUpdated()
         {
-            try
+            EventHelper.SignalEvent(Constants.SettingsUpdatedPowerDisplayEvent());
-            {
+            Logger.LogInfo("Signaled SettingsUpdatedPowerDisplayEvent for feature visibility change");
-                using var eventHandle = new System.Threading.EventWaitHandle(
-                    false,
-                    System.Threading.EventResetMode.AutoReset,
-                    Constants.SettingsUpdatedPowerDisplayEvent());
-                eventHandle.Set();
-                Logger.LogInfo("Signaled SettingsUpdatedPowerDisplayEvent for feature visibility change");
-            }
-            catch (Exception ex)
-            {
-                Logger.LogError($"Failed to signal SettingsUpdatedPowerDisplayEvent: {ex.Message}");
-            }
         }
 
         public void Launch()
@@ -513,7 +498,8 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
                     for (int i = Monitors.Count - 1; i >= 0; i--)
                     {
                         var existingMonitor = Monitors[i];
-                        if (updatedMonitorsDict.TryGetValue(existingMonitor.InternalName, out var updatedMonitor))
+                        if (updatedMonitorsDict.TryGetValue(existingMonitor.InternalName, out var updatedMonitor)
+                            && updatedMonitor != null)
                         {
                             // Monitor still exists - update its properties in place
                             Logger.LogInfo($"[ReloadMonitors] Updating existing monitor: {existingMonitor.InternalName}");
@@ -661,13 +647,7 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
                         profile.Name));
 
                 // Signal PowerDisplay to apply profile
-                using (var eventHandle = new System.Threading.EventWaitHandle(
+                EventHelper.SignalEvent(Constants.ApplyProfilePowerDisplayEvent());
-                    false,
-                    System.Threading.EventResetMode.AutoReset,
-                    Constants.ApplyProfilePowerDisplayEvent()))
-                {
-                    eventHandle.Set();
-                }
 
                 Logger.LogInfo($"Profile '{profile.Name}' applied successfully");
             }