Improve performance, thread safety, and resource handling

Enhanced monitor initialization with parallelism in `MonitorManager.cs` for better performance. Added cancellation support to `NativeEventWaiter.cs` with `CancellationToken` and timeout handling. Introduced thread safety in `PhysicalMonitorHandleManager.cs` using locks to prevent race conditions.

Updated `PowerDisplayViewModel.cs` to include proper resource cleanup with `CancellationTokenSource` and improved memory management. Added necessary namespaces for threading and asynchronous operations. General code improvements for readability, maintainability, and reliability.

src/modules/powerdisplay/PowerDisplay/Core/MonitorManager.cs

@@ -104,9 +104,12 @@ namespace PowerDisplay.Core
                 var results = await Task.WhenAll(discoveryTasks);
 
                 // Collect all discovered monitors
+                var allMonitors = new List<Monitor>();
+
                 foreach (var (controller, monitors) in results)
                 {
-                    foreach (var monitor in monitors)
+                    // Initialize monitors in parallel
+                    var initTasks = monitors.Select(async monitor =>
                     {
                         // Verify if monitor can be controlled
                         if (await controller.CanControlMonitorAsync(monitor, cancellationToken))
@@ -165,9 +168,14 @@ namespace PowerDisplay.Core
                                 }
                             }
 
-                            newMonitors.Add(monitor);
-                        }
+                            return monitor;
                         }
+
+                        return null;
+                    });
+
+                    var initializedMonitors = await Task.WhenAll(initTasks);
+                    newMonitors.AddRange(initializedMonitors.Where(m => m != null));
                 }
 
                 // Update monitor list

src/modules/powerdisplay/PowerDisplay/Helpers/NativeEventWaiter.cs

@@ -19,15 +19,16 @@ namespace PowerDisplay.Helpers
         /// </summary>
         /// <param name="eventName">Name of the Windows Event to wait for</param>
         /// <param name="callback">Callback to invoke when event is signaled</param>
-        public static void WaitForEventLoop(string eventName, Action callback)
+        /// <param name="cancellationToken">Token to cancel the wait loop</param>
+        public static void WaitForEventLoop(string eventName, Action callback, CancellationToken cancellationToken)
         {
             var dispatcherQueue = DispatcherQueue.GetForCurrentThread();
             var t = new Thread(() =>
             {
-                var eventHandle = new EventWaitHandle(false, EventResetMode.AutoReset, eventName);
-                while (true)
+                using var eventHandle = new EventWaitHandle(false, EventResetMode.AutoReset, eventName);
+                while (!cancellationToken.IsCancellationRequested)
                 {
-                    if (eventHandle.WaitOne())
+                    if (eventHandle.WaitOne(500))
                     {
                         dispatcherQueue.TryEnqueue(() => callback());
                     }

src/modules/powerdisplay/PowerDisplay/Native/DDC/PhysicalMonitorHandleManager.cs

@@ -17,12 +17,15 @@ namespace PowerDisplay.Native.DDC
     {
         // Mapping: deviceKey -> physical handle
         private readonly Dictionary<string, IntPtr> _deviceKeyToHandleMap = new();
+        private readonly object _lock = new();
         private bool _disposed;
 
         /// <summary>
         /// Get physical handle for monitor using stable deviceKey
         /// </summary>
         public IntPtr GetPhysicalHandle(Monitor monitor)
+        {
+            lock (_lock)
             {
                 // Primary lookup: use stable deviceKey from EnumDisplayDevices
                 if (!string.IsNullOrEmpty(monitor.DeviceKey) &&
@@ -30,6 +33,7 @@ namespace PowerDisplay.Native.DDC
                 {
                     return handle;
                 }
+            }
 
             // Fallback: use direct handle from monitor object
             if (monitor.Handle != IntPtr.Zero)
@@ -51,6 +55,8 @@ namespace PowerDisplay.Native.DDC
                 return (newHandle, false);
             }
 
+            lock (_lock)
+            {
                 // Try to reuse existing handle if it's still valid
                 if (_deviceKeyToHandleMap.TryGetValue(deviceKey, out var existingHandle) &&
                     existingHandle != IntPtr.Zero &&
@@ -64,6 +70,7 @@ namespace PowerDisplay.Native.DDC
 
                     return (existingHandle, true);
                 }
+            }
 
             return (newHandle, false);
         }
@@ -72,6 +79,8 @@ namespace PowerDisplay.Native.DDC
         /// Update the handle mapping with new handles
         /// </summary>
         public void UpdateHandleMap(Dictionary<string, IntPtr> newHandleMap)
+        {
+            lock (_lock)
             {
                 // Clean up unused handles before updating
                 CleanupUnusedHandles(newHandleMap);
@@ -83,6 +92,7 @@ namespace PowerDisplay.Native.DDC
                     _deviceKeyToHandleMap[kvp.Key] = kvp.Value;
                 }
             }
+        }
 
         /// <summary>
         /// Clean up handles that are no longer in use

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

@@ -10,6 +10,7 @@ using System.IO;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Text.Json;
+using System.Threading;
 using System.Threading.Tasks;
 using System.Windows;
 
@@ -72,7 +73,8 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
                 {
                     Logger.LogInfo("Received refresh monitors event from PowerDisplay.exe");
                     ReloadMonitorsFromSettings();
-                });
+                },
+                _cancellationTokenSource.Token);
         }
 
         private void InitializeEnabledValue()
@@ -284,6 +286,10 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
                 _monitors.CollectionChanged -= Monitors_CollectionChanged;
             }
 
+            _cancellationTokenSource.Cancel();
+            _cancellationTokenSource.Dispose();
+            GC.SuppressFinalize(this);
+
             base.Dispose();
         }
 
@@ -447,6 +453,7 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
         private PowerDisplaySettings _settings;
         private ObservableCollection<MonitorInfo> _monitors;
         private bool _hasMonitors;
+        private CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
 
         public void RefreshEnabledState()
         {