dismiss popups when toplevel deactivates in embedded scenarios (#18527)

Author: emmauss

src/Avalonia.Controls/Primitives/Popup.cs

@@ -14,6 +14,7 @@
 using Avalonia.Platform;
 using Avalonia.VisualTree;
 using Avalonia.Media;
+using Avalonia.Interactivity;
 
 namespace Avalonia.Controls.Primitives
 {
@@ -460,13 +461,13 @@ public void Open()
             SubscribeToEventHandler<Control, EventHandler<VisualTreeAttachmentEventArgs>>(placementTarget, TargetDetached,
                 (x, handler) => x.DetachedFromVisualTree += handler,
                 (x, handler) => x.DetachedFromVisualTree -= handler).DisposeWith(handlerCleanup);
-            
+
             if (topLevel is Window window && window.PlatformImpl != null)
             {
                 SubscribeToEventHandler<Window, EventHandler>(window, WindowDeactivated,
                     (x, handler) => x.Deactivated += handler,
                     (x, handler) => x.Deactivated -= handler).DisposeWith(handlerCleanup);
-                
+
                 SubscribeToEventHandler<IWindowImpl, Action>(window.PlatformImpl, WindowLostFocus,
                     (x, handler) => x.LostFocus += handler,
                     (x, handler) => x.LostFocus -= handler).DisposeWith(handlerCleanup);
@@ -500,6 +501,12 @@ public void Open()
                         (x, handler) => x.Closed -= handler).DisposeWith(handlerCleanup);
                 }
             }
+            else if (topLevel is { } tl && tl.PlatformImpl is ITopLevelImpl pimpl)
+            {
+                SubscribeToEventHandler<ITopLevelImpl, Action>(pimpl, TopLevelLostPlatformFocus,
+                    (x, handler) => x.LostFocus += handler,
+                    (x, handler) => x.LostFocus -= handler).DisposeWith(handlerCleanup);
+            }
 
             InputManager.Instance?.Process.Subscribe(ListenForNonClientClick).DisposeWith(handlerCleanup);
 
@@ -963,6 +970,14 @@ private void ParentClosed(object? sender, EventArgs e)
             }
         }
 
+        private void TopLevelLostPlatformFocus()
+        {
+            if (IsLightDismissEnabled)
+            {
+                Close();
+            }
+        }
+
         private void PlacementTargetTransformChanged(Visual v, Matrix? matrix)
         {
             if (_openState is not null)