Fix Toplevel not losing focus with native implementation deactivates. (#20768)

* add failing test

* query the toplevel of the currently focused control instead when losing focus

src/Avalonia.Controls/TopLevel.cs

@@ -257,8 +257,6 @@ namespace Avalonia.Controls
 
             impl.LostFocus += PlatformImpl_LostFocus;
 
-
-
             if (impl.TryGetFeature<ISystemNavigationManagerImpl>() is { } systemNavigationManager)
             {
                 systemNavigationManager.BackRequested += (_, e) =>
@@ -803,11 +801,7 @@ namespace Avalonia.Controls
 
         void PlatformImpl_LostFocus()
         {
-            var focused = (Visual?)FocusManager?.GetFocusedElement();
-            if (focused == null)
-                return;
-            while (focused.VisualParent != null)
-                focused = focused.VisualParent;
+            var focused = TopLevel.GetTopLevel((Visual?)FocusManager?.GetFocusedElement());
 
             if (focused == this)
                 KeyboardDevice.Instance?.SetFocusedElement(null, NavigationMethod.Unspecified, KeyModifiers.None, false);

tests/Avalonia.Controls.UnitTests/TopLevelTests.cs

@@ -253,6 +253,34 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
+        [Fact]
+        public void TopLevel_Should_Unfocus_When_Impl_Focus_Is_Lost()
+        {
+            using (UnitTestApplication.Start(TestServices.RealFocus))
+            {
+                var impl = CreateMockTopLevelImpl(true);
+                var content = new TextBox()
+                {
+                    Focusable = true
+                };
+                var target = new TestTopLevel(impl.Object)
+                {
+                    Template = CreateTemplate(),
+                    Focusable = true,
+                    Content = content
+                };
+
+                target.LayoutManager.ExecuteInitialLayoutPass();
+
+                content.Focus();
+                Assert.True(content.IsFocused);
+
+                impl.Object.LostFocus?.Invoke();
+
+                Assert.False(content.IsFocused);
+            }
+        }
+
         [Fact]
         public void Reacts_To_Changes_In_Global_Styles()
         {