Release implicit mouse capture on focus lost (#20574)

* macOS: Release implicit mouse capture on focus lost

* Added native modal test to EmbeddingPage

samples/IntegrationTestApp/Pages/EmbeddingPage.axaml

@@ -16,5 +16,7 @@
       </Popup>
     </StackPanel>
     <Button Name="Reset" Click="Reset_Click">Reset</Button>
+    <Button Name="RunNativeModalSession" Click="RunNativeModalSession_OnClick">Open Native Modal</Button>
+    <TextBox Name="ModalResultTextBox" />
   </StackPanel>
 </UserControl>

samples/IntegrationTestApp/Pages/EmbeddingPage.axaml.cs

@@ -1,10 +1,19 @@
+using System;
+using Avalonia.Automation;
 using Avalonia.Controls;
+using Avalonia.Controls.Embedding;
 using Avalonia.Interactivity;
+using IntegrationTestApp.Embedding;
+using MonoMac.AppKit;
+using MonoMac.CoreGraphics;
+using MonoMac.ObjCRuntime;
 
 namespace IntegrationTestApp;
 
 public partial class EmbeddingPage : UserControl
 {
+    private const long NSModalResponseContinue = -1002;
+
     public EmbeddingPage()
     {
         InitializeComponent();
@@ -19,5 +28,65 @@ public partial class EmbeddingPage : UserControl
     private void Reset_Click(object? sender, RoutedEventArgs e)
     {
         ResetText();
+        ModalResultTextBox.Text = "";
+    }
+
+    private void RunNativeModalSession_OnClick(object? sender, RoutedEventArgs e)
+    {
+        MacHelper.EnsureInitialized();
+
+        var app = NSApplication.SharedApplication;
+        var modalWindow = CreateNativeWindow();
+        var session = app.BeginModalSession(modalWindow);
+
+        while (true)
+        {
+            if (app.RunModalSession(session) != NSModalResponseContinue)
+                break;
+        }
+
+        app.EndModalSession(session);
+    }
+
+    private NSWindow CreateNativeWindow()
+    {
+        var button = new Button
+        {
+            Name = "ButtonInModal",
+            Content = "Button"
+        };
+
+        AutomationProperties.SetAutomationId(button, "ButtonInModal");
+
+        var root = new EmbeddableControlRoot
+        {
+            Width = 200,
+            Height = 200,
+            Content = button
+        };
+        root.Prepare();
+
+        var window = new NSWindow(
+            new CGRect(0, 0, root.Width, root.Height),
+            NSWindowStyle.Titled | NSWindowStyle.Closable,
+            NSBackingStore.Buffered,
+            false);
+
+        window.Identifier = "ModalNativeWindow";
+        window.WillClose += (_, _) => NSApplication.SharedApplication.StopModal();
+
+        button.Click += (_, _) =>
+        {
+            ModalResultTextBox.Text = "Clicked";
+            window.Close();
+        };
+
+        if (root.TryGetPlatformHandle() is not { } handle)
+            throw new InvalidOperationException("Could not get platform handle");
+
+        window.ContentView = (NSView)Runtime.GetNSObject(handle.Handle)!;
+        root.StartRendering();
+
+        return window;
     }
 }

src/Avalonia.Base/Input/MouseDevice.cs

@@ -34,6 +34,8 @@ namespace Avalonia.Input
             _pointer = pointer ?? new Pointer(Pointer.GetNextFreeId(), PointerType.Mouse, true);
         }
 
+        internal Pointer Pointer => _pointer;
+
         internal static TMouseDevice GetOrCreatePrimary<TMouseDevice>() where TMouseDevice : MouseDevice, new()
         {
             if (_primary is TMouseDevice device)

src/Avalonia.Base/Input/Pointer.cs

@@ -77,6 +77,7 @@ namespace Avalonia.Input
             if (oldVisual != null)
                 oldVisual.DetachedFromVisualTree -= OnCaptureDetached;
             Captured = control;
+            CaptureSource = source;
 
             if (source != CaptureSource.Platform)
                 PlatformCapture(control);
@@ -115,6 +116,7 @@ namespace Avalonia.Input
         public IInputElement? Captured { get; private set; }
 
         public PointerType Type { get; }
+
         public bool IsPrimary { get; }
 
         /// <summary>
@@ -124,6 +126,8 @@ namespace Avalonia.Input
 
         public bool IsGestureRecognitionSkipped { get; set; }
 
+        internal CaptureSource CaptureSource { get; private set; } = CaptureSource.Platform;
+
         public void Dispose()
         {
             if (Captured != null)

src/Avalonia.Native/TopLevelImpl.cs

@@ -65,8 +65,8 @@ internal class TopLevelImpl : ITopLevelImpl, IFramebufferPlatformSurface
     private NativeControlHostImpl? _nativeControlHost;
     private PlatformBehaviorInhibition? _platformBehaviorInhibition;
 
-    private readonly MouseDevice? _mouse;
-    private readonly PenDevice? _pen;
+    private readonly MouseDevice _mouse;
+    private readonly PenDevice _pen;
 
     private readonly IKeyboardDevice? _keyboard;
     private readonly ICursorFactory? _cursorFactory;
@@ -480,6 +480,18 @@ internal class TopLevelImpl : ITopLevelImpl, IFramebufferPlatformSurface
         void IAvnTopLevelEvents.LostFocus()
         {
             _parent.LostFocus?.Invoke();
+
+            // macOS doesn't have the concept of mouse capture. If we're losing the focus during an implicit capture
+            // (standard mouse down), we should release it to avoid mouse events going to an old window.
+            var mouse = _parent._mouse;
+            var captured = mouse.Pointer.Captured;
+
+            if (captured is not null &&
+                mouse.Pointer.CaptureSource == CaptureSource.Implicit &&
+                TopLevel.GetTopLevel(captured as Visual)?.PlatformImpl == _parent)
+            {
+                mouse.PlatformCaptureLost();
+            }
         }
 
         AvnDragDropEffects IAvnTopLevelEvents.DragEvent(AvnDragEventType type, AvnPoint position,