Improve monitor identification accuracy in IdentifyMonitors

Refactored IdentifyMonitors to use Windows API for mapping display areas to monitor numbers via HMONITOR and GDI device names. This ensures correct monitor numbering in identify windows, especially in complex setups. Added detailed logging and only counts successfully created windows.

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

@@ -3,18 +3,23 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 using CommunityToolkit.Mvvm.Input;
 using ManagedCommon;
 using Microsoft.PowerToys.Settings.UI.Library;
+using Microsoft.UI;
 using Microsoft.UI.Dispatching;
 using Microsoft.UI.Windowing;
+using PowerDisplay.Common.Drivers;
+using PowerDisplay.Common.Drivers.DDC;
 using PowerDisplay.Common.Models;
 using PowerDisplay.Common.Services;
 using PowerDisplay.Helpers;
@@ -32,6 +37,10 @@ namespace PowerDisplay.ViewModels;
 [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicProperties | DynamicallyAccessedMemberTypes.PublicMethods)]
 public partial class MainViewModel : INotifyPropertyChanged, IDisposable
 {
+    [LibraryImport("user32.dll", EntryPoint = "GetMonitorInfoW", StringMarshalling = StringMarshalling.Utf16)]
+    [return: MarshalAs(UnmanagedType.Bool)]
+    private static partial bool GetMonitorInfo(IntPtr hMonitor, ref MonitorInfoEx lpmi);
+
     private readonly MonitorManager _monitorManager;
     private readonly DispatcherQueue _dispatcherQueue;
     private readonly CancellationTokenSource _cancellationTokenSource;
@@ -157,39 +166,64 @@ public partial class MainViewModel : INotifyPropertyChanged, IDisposable
     private async Task RefreshAsync() => await RefreshMonitorsAsync();
 
     [RelayCommand]
-    private void IdentifyMonitors()
+    private unsafe void IdentifyMonitors()
     {
         Logger.LogInfo("Identify monitors feature triggered");
 
         try
         {
-            // Get all display areas - use direct indexing to avoid WinRT enumeration issues
+            // Get all display areas
             var displayAreas = DisplayArea.FindAll();
-            int displayCount = displayAreas.Count;
+            Logger.LogDebug($"Found {displayAreas.Count} display areas");
-            Logger.LogDebug($"Found {displayCount} display areas");
 
-            // Get current monitors sorted by MonitorNumber
+            // Get GDI device name to MonitorNumber mapping from QueryDisplayConfig
-            var monitors = _monitorManager.Monitors.OrderBy(m => m.MonitorNumber).ToList();
+            var displayInfoByGdiName = DdcCiNative.GetAllMonitorDisplayInfo()
-            Logger.LogDebug($"Found {monitors.Count} monitors in MonitorManager");
+                .Values
+                .Where(info => info.MonitorNumber > 0)
+                .ToDictionary(info => info.GdiDeviceName, info => info.MonitorNumber, StringComparer.OrdinalIgnoreCase);
+            Logger.LogDebug($"Found {displayInfoByGdiName.Count} monitors with valid MonitorNumber from QueryDisplayConfig");
 
-            for (int index = 0; index < displayCount; index++)
+            // For each DisplayArea, get its HMONITOR, then get GDI device name to find MonitorNumber
+            int windowsCreated = 0;
+            for (int i = 0; i < displayAreas.Count; i++)
             {
-                var displayArea = displayAreas[index];
+                var displayArea = displayAreas[i];
 
-                // Get monitor number: prefer MonitorManager's number, fall back to index+1
+                // Convert DisplayId to HMONITOR
-                int monitorNumber = (index < monitors.Count)
+                var hMonitor = Win32Interop.GetMonitorFromDisplayId(displayArea.DisplayId);
-                    ? monitors[index].MonitorNumber
+                if (hMonitor == IntPtr.Zero)
-                    : index + 1;
+                {
+                    Logger.LogDebug($"DisplayArea[{i}]: Failed to get HMONITOR");
+                    continue;
+                }
 
-                Logger.LogDebug($"Creating identify window for monitor {monitorNumber} on display area {index}");
+                // Get GDI device name from HMONITOR
+                var monitorInfo = new MonitorInfoEx { CbSize = (uint)sizeof(MonitorInfoEx) };
+                if (!GetMonitorInfo(hMonitor, ref monitorInfo))
+                {
+                    Logger.LogDebug($"DisplayArea[{i}]: GetMonitorInfo failed");
+                    continue;
+                }
 
-                // Create and position window
+                var gdiDeviceName = monitorInfo.GetDeviceName();
+
+                // Look up MonitorNumber by GDI device name
+                if (!displayInfoByGdiName.TryGetValue(gdiDeviceName, out int monitorNumber))
+                {
+                    Logger.LogDebug($"DisplayArea[{i}]: No MonitorNumber found for GDI device '{gdiDeviceName}'");
+                    continue;
+                }
+
+                Logger.LogDebug($"DisplayArea[{i}]: GDI='{gdiDeviceName}' -> MonitorNumber={monitorNumber}");
+
+                // Create and position identify window
                 var identifyWindow = new IdentifyWindow(monitorNumber);
                 identifyWindow.PositionOnDisplay(displayArea);
                 identifyWindow.Activate();
+                windowsCreated++;
             }
 
-            Logger.LogInfo($"Created {displayCount} identify windows");
+            Logger.LogInfo($"Created {windowsCreated} identify windows");
         }
         catch (Exception ex)
         {