WPF - Update CleanupElement when PresentationSource changes

- If the CleanupElement is a Window then move it to the new Window

Author: amaitland

CefSharp.Wpf.Example/ChangeParentWindow.xaml

@@ -0,0 +1,24 @@
+<Window x:Class="CefSharp.Wpf.Example.ChangeParentWindow"
+        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        mc:Ignorable="d"
+        Title="ChangeParentWindow" Height="600" Width="800" WindowStartupLocation="CenterScreen" WindowState="Maximized">
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="Auto" />
+            <RowDefinition Height="*" />
+        </Grid.RowDefinitions>
+        <Grid.ColumnDefinitions>
+            <ColumnDefinition />
+            <ColumnDefinition />
+        </Grid.ColumnDefinitions>
+        <StackPanel Orientation="Horizontal" Grid.ColumnSpan="2">
+            <Button Content="Open browser in new Window" Click="OnAddBrowser" />
+            <Button Content="Re-Parent Browser and Close Window" Click="OnRemoveBrowser" />
+        </StackPanel>
+        <Border Grid.Row="1" Grid.Column="0" x:Name="StaticBrowser" />
+        <Border Grid.Row="1" x:Name="BrowserSite" Grid.Column="1" />
+    </Grid>
+</Window>

CefSharp.Wpf.Example/ChangeParentWindow.xaml.cs

@@ -0,0 +1,57 @@
+// Copyright © 2022 The CefSharp Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
+
+using System.Windows;
+
+namespace CefSharp.Wpf.Example
+{
+    /// <summary>
+    /// Interaction logic for ChangeParentWindow.xaml
+    /// </summary>
+    public partial class ChangeParentWindow : Window
+    {
+        private ChromiumWebBrowser browser;
+        private Window newWindow;
+
+        public ChangeParentWindow()
+        {
+            InitializeComponent();
+
+            StaticBrowser.Child = new ChromiumWebBrowser("http://www.msn.net");
+        }
+
+        private void OnAddBrowser(object sender, RoutedEventArgs e)
+        {
+            if (browser == null)
+            {
+                browser = new ChromiumWebBrowser("http://www.msn.net");
+            }
+
+            if (newWindow == null)
+            {
+                newWindow = new Window
+                {
+                    Owner = this,
+                    Content = browser,
+                    WindowStartupLocation = WindowStartupLocation.CenterOwner
+                };
+
+                newWindow.Show();
+            }
+        }
+
+        private void OnRemoveBrowser(object sender, RoutedEventArgs e)
+        {
+            if (newWindow != null)
+            {
+                newWindow.Content = null;
+                newWindow.Close();
+                newWindow = null;
+            }
+
+            BrowserSite.Child = browser;
+        }
+    }
+}
+

CefSharp.Wpf/ChromiumWebBrowser.cs

@@ -1655,6 +1655,19 @@ private void PresentationSourceChangedHandler(object sender, SourceChangedEventA
                     window.StateChanged += OnWindowStateChanged;
                     window.LocationChanged += OnWindowLocationChanged;
                     sourceWindow = window;
+
+                    if (CleanupElement == null)
+                    {
+                        CleanupElement = window;
+                    }
+                    else if(CleanupElement is Window parent)
+                    {
+                        //If the CleanupElement is a window then move it to the new Window
+                        if(parent != window)
+                        {
+                            CleanupElement = window;
+                        }
+                    }
                 }
 
                 browserScreenLocation = GetBrowserScreenLocation();
@@ -1941,11 +1954,6 @@ private void OnIsVisibleChanged(object sender, DependencyPropertyChangedEventArg
         /// <param name="routedEventArgs">The <see cref="RoutedEventArgs"/> instance containing the event data.</param>
         private void OnLoaded(object sender, RoutedEventArgs routedEventArgs)
         {
-            if (CleanupElement == null)
-            {
-                CleanupElement = Window.GetWindow(this);
-            }
-
             // TODO: Consider making the delay here configurable.
             tooltipTimer = new DispatcherTimer(
                 TimeSpan.FromSeconds(0.5),