From c8bd154c015b914e171a326481fef6532bc943de Mon Sep 17 00:00:00 2001
From: reunion-maestro-bot <reunion-maestro-bot@microsoft.com>
Date: Fri, 1 Mar 2024 07:26:29 +0000
Subject: [PATCH] Syncing content from committish
 f7a64ff105945fb702b0709dd193f886a1eca128

---
 Directory.Build.props                         |  13 +
 .../AnnotatedScrollBar/AnnotatedScrollBar.cpp |   8 +-
 controls/dev/Collections/Vector.h             | 112 +++++-
 .../dev/Materials/Acrylic/AcrylicBrush.cpp    |  11 +-
 .../Repeater/APITests/ItemTemplateTests.cs    |  62 ++++
 .../ItemTemplateSamples/ItemTemplateDemo.xaml | 207 +++++------
 .../TeachingTipFocusTestPageElements.cs       |   9 +
 .../InteractionTests/TeachingTipTests.cs      |  68 ++++
 controls/dev/TeachingTip/TeachingTip.cpp      |  24 +-
 controls/dev/TeachingTip/TeachingTip.h        |   1 +
 .../TestUI/TeachingTip-FocusBehavior.md       |  13 +
 .../TestUI/TeachingTipFocusPage.xaml          |   2 +-
 .../dev/TreeView/TestUI/TreeViewPage.xaml     |  25 +-
 .../dev/TreeView/TestUI/TreeViewPage.xaml.cs  |  38 +-
 controls/dev/TreeView/ViewModel.cpp           | 348 +++++++++---------
 controls/dev/TreeView/ViewModel.h             |  84 ++++-
 .../xcp/components/comptree/DCompTreeHost.cpp |  40 +-
 .../components/comptree/inc/DCompTreeHost.h   |   1 +
 dxaml/xcp/core/core/elements/depends.cpp      |   4 +-
 dxaml/xcp/core/dll/xcpcore.cpp                |   2 +-
 dxaml/xcp/core/inc/InputServices.h            |  73 +++-
 dxaml/xcp/core/inc/VisualTree.h               |  12 +
 dxaml/xcp/core/input/InputServices.cpp        | 236 ++++++++----
 .../core/microsoft.ui.xaml.coretypes2.idl     |   5 +
 dxaml/xcp/dxaml/lib/CascadingMenuHelper.cpp   |  18 +-
 dxaml/xcp/dxaml/lib/DXamlCore.cpp             |  27 +-
 dxaml/xcp/dxaml/lib/DesktopWindowImpl.cpp     |   7 +-
 .../lib/DesktopWindowXamlSource_Partial.cpp   |  26 ++
 .../lib/DesktopWindowXamlSource_Partial.h     |   5 +-
 dxaml/xcp/dxaml/lib/FlyoutBase_partial.cpp    |  23 +-
 .../dxaml/lib/FrameworkElement_partial.cpp    |  17 +-
 dxaml/xcp/dxaml/lib/InputSiteAdapter.h        |   4 +-
 dxaml/xcp/dxaml/lib/JupiterWindow.cpp         |   6 -
 dxaml/xcp/dxaml/lib/synonyms.g.h              |   1 +
 .../DesktopWindowXamlSource.g.cpp             |  22 ++
 .../DesktopWindowXamlSource.g.h               |  12 +
 .../XamlOM/Model/Microsoft.UI.Xaml.Hosting.cs |  17 +-
 .../XamlOM/Model/Microsoft.UI.Xaml.cs         |  22 --
 eng/Version.Details.xml                       |  12 +-
 .../CppWinRT/CppWinRT_AppPass1.cs             |   6 +
 .../CppWinRT/CppWinRT_AppPass1.tt             |   6 +
 .../CppWinRT/CppWinRT_BindingInfoPass1.cs     |   6 +
 .../CppWinRT/CppWinRT_BindingInfoPass1.tt     |   6 +
 .../CppWinRT/CppWinRT_PagePass1.cs            |   9 +-
 .../CppWinRT/CppWinRT_PagePass1.tt            |   7 +
 .../CppWinRT/CppWinRT_TypeInfoPass1.cs        |   4 +
 .../CppWinRT/CppWinRT_TypeInfoPass1.tt        |   4 +
 .../CppWinRT/CppWinRT_TypeInfoPass1Impl.cs    |   5 +
 .../CppWinRT/CppWinRT_TypeInfoPass1Impl.tt    |   5 +
 .../CppWinRT/CppWinRT_TypeInfoPass2.cs        |   3 +-
 .../CppWinRT/CppWinRT_TypeInfoPass2.tt        |   5 +
 .../CppWinRT_XamlMetaDataProviderPass1.cs     |   5 +
 .../CppWinRT_XamlMetaDataProviderPass1.tt     |   5 +
 .../CodeGenerators/PageDefinition.cs          |  39 +-
 .../CodeGenerators/TypeInfoDefinition.cs      |  18 +-
 55 files changed, 1265 insertions(+), 485 deletions(-)
 create mode 100644 controls/dev/TeachingTip/TestUI/TeachingTip-FocusBehavior.md

diff --git a/Directory.Build.props b/Directory.Build.props
index 678a9bb54f..6dfc4fe649 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -21,6 +21,19 @@
     <ShouldUnsetParentConfigurationAndPlatform>false</ShouldUnsetParentConfigurationAndPlatform>
   </PropertyGroup>
 
+  <!-- Import LKG VC Toolset, if enabled (LkgVcTools* env vars set)-->
+  <Import Project="$(NugetPackageDirectory)\$(LkgVcToolsName)\$(LkgVcToolsVersion)\build\native\$(LkgVcToolsName).props" 
+    Condition="'$(MSBuildProjectExtension)' == '.vcxproj' and '$(LkgVcToolsName)$(LkgVcToolsVersion)' != '' and
+      Exists('$(NugetPackageDirectory)\$(LkgVcToolsName)\$(LkgVcToolsVersion)\build\native\$(LkgVcToolsName).props')" />
+  <Target Name="LkgEnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild" 
+    Condition="'$(MSBuildProjectExtension)' == '.vcxproj' and '$(LkgVcToolsName)$(LkgVcToolsVersion)' != ''">
+    <PropertyGroup>
+      <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
+    </PropertyGroup>
+    <Error Condition="!Exists('$(NugetPackageDirectory)\$(LkgVcToolsName)\$(LkgVcToolsVersion)\build\native\$(LkgVcToolsName).props')" 
+      Text="$([System.String]::Format('$(ErrorText)', '$(NugetPackageDirectory)\$(LkgVcToolsName)\$(LkgVcToolsVersion)\build\native\$(LkgVcToolsName).props'))" />
+  </Target>
+
   <!--
     Every project in this repository should include the root Directory.Build.props file. This allows us to create a 
     single place where we can share common build infrastructure, without creating MSBuild duplicate import errors.
diff --git a/controls/dev/AnnotatedScrollBar/AnnotatedScrollBar.cpp b/controls/dev/AnnotatedScrollBar/AnnotatedScrollBar.cpp
index f6c14b2480..6d7f768a1b 100644
--- a/controls/dev/AnnotatedScrollBar/AnnotatedScrollBar.cpp
+++ b/controls/dev/AnnotatedScrollBar/AnnotatedScrollBar.cpp
@@ -302,6 +302,12 @@ void AnnotatedScrollBar::QueueLayoutLabels(unsigned int millisecondWait)
         auto weakThis = get_weak();
         auto runLayoutLabelsAction = [weakThis]()
         {
+            if (winrt::WindowsXamlManager::GetForCurrentThread() == nullptr)
+            {
+                // Exit early if Xaml core has already shut down.
+                return;
+            }
+
             if (auto strongThis = weakThis.get())
             {
                 strongThis->m_labelsDebounce.clear();
@@ -315,7 +321,7 @@ void AnnotatedScrollBar::QueueLayoutLabels(unsigned int millisecondWait)
 
 void AnnotatedScrollBar::LayoutLabels()
 {
-    auto labelsGrid = m_labelsGrid.get();
+    auto labelsGrid = m_labelsGrid.safe_get();
     if (!labelsGrid)
     {
         return;
diff --git a/controls/dev/Collections/Vector.h b/controls/dev/Collections/Vector.h
index 76ad3b7c79..eddecb9b60 100644
--- a/controls/dev/Collections/Vector.h
+++ b/controls/dev/Collections/Vector.h
@@ -6,15 +6,15 @@
 #include "VectorChangedEventArgs.h"
 #include <algorithm>
 
-// Nearly all Vector need to set DependencyObjectBase flag 
+// Nearly all Vector need to set DependencyObjectBase flag
 // to make DependencyObject as ComposableBase
 // Otherwise we may hit memory leak when interact with .net.
 // One exception is AcrylicBrush::CreateAcrylicBrushWorker
 // because we know we don't have memory leak.
 enum class VectorFlag {
     None = 0, // not Observable, not Bindable and not DependencyObjectBase
-    Observable = 1, 
-    DependencyObjectBase = 2, 
+    Observable = 1,
+    DependencyObjectBase = 2,
     Bindable = 4,
     NoTrackerRef = 8
 };
@@ -121,7 +121,7 @@ struct ObservableTraits<T, true, isBindable>
         winrt::BindableVectorChangedEventHandler,
         winrt::VectorChangedEventHandler<T>
     >::type;
-    
+
     using EventToken = typename winrt::event_token;
 
     static void RaiseEvent(EventSource* e, SenderType sender, winrt::CollectionChange collectionChange, uint32_t index)
@@ -223,6 +223,53 @@ struct VectorInnerImpl
         return false;
     }
 
+    bool IndexOf_OptimizedForRemove(typename T_type const& value, uint32_t& index)
+    {
+        index = 0;
+
+        if (m_optimizedIndexOf_StartNextSearchAt >= m_vector.size())
+        {
+            if (m_vector.size() == 0)
+            {
+                m_optimizedIndexOf_StartNextSearchAt = 0;
+            }
+            else
+            {
+                m_optimizedIndexOf_StartNextSearchAt = static_cast<unsigned int>(m_vector.size() - 1);
+            }
+        }
+
+        const auto& searchFor = wrap(value);
+
+        auto it = std::find(m_vector.begin() + m_optimizedIndexOf_StartNextSearchAt, m_vector.end(), searchFor);
+        bool found = (it != m_vector.end());
+        if (!found && m_optimizedIndexOf_StartNextSearchAt > 0)
+        {
+            // Note: if std::find fails, it returns the second iterator and not always the end of the vector.
+            it = std::find(m_vector.begin(), m_vector.begin() + m_optimizedIndexOf_StartNextSearchAt, searchFor);
+            found = (it != m_vector.begin() + m_optimizedIndexOf_StartNextSearchAt);
+        }
+
+        if (found)
+        {
+            index = (uint32_t)(it - m_vector.begin());
+            if (index > 0)
+            {
+                // Next time we search start near this index. We assume that the remove is being processed from the end
+                // of the vector towards index 0, so the next item being removed is probably at "index - 1". Start the
+                // next search there.
+                m_optimizedIndexOf_StartNextSearchAt = index - 1;
+            }
+            else
+            {
+                m_optimizedIndexOf_StartNextSearchAt = index;
+            }
+            return true;
+        }
+
+        return false;
+    }
+
     uint32_t GetMany(uint32_t const startIndex, winrt::array_view<T_type> values)
     {
         if (startIndex >= m_vector.size())
@@ -255,7 +302,7 @@ struct VectorInnerImpl
         {
             throw winrt::hresult_out_of_bounds();
         }
-        
+
     }
 
     void RemoveAt(uint32_t const index)
@@ -313,6 +360,35 @@ struct VectorInnerImpl
 
     std::vector<T_Storage> m_vector;
     ITrackerHandleManager* m_trackerHandleManager{ nullptr };
+
+    //
+    // IndexOf optimization for scenarios where lots of items are removed from a large vector, such as unchecking a
+    // selected subtree in a large TreeView
+    //
+    // e.g. A TreeView has a single root with 10 children, each with 10,000 children inside them. The entire TreeView
+    // is selected, and the user unchecks one of the 10 first-level children. The SelectedItems vector of the TreeView
+    // has all 100,000 (roughly - it includes the parent nodes too) items, and we're going to remove 10,000. TreeView's
+    // deselection logic makes sure an item is selected before removing it from the SelectedItems vector, and it does
+    // this with an IndexOf. So naively, unchecking one top-level child is going to run 10,000 IndexOf operations into
+    // a vector of 100,000. If the child being unchecked is near the end of the TreeView, then its entries are near the
+    // end of the vector of 100,000, and each IndexOf will have to search linearly to the end of the vector, making the
+    // operation extremely slow.
+    //
+    // Instead, we optimize by starting the search not at index 0 but partway through the list, specifically near where
+    // we found a previous hit. The assumption is that all 10,000 items being unchecked were checked when the top-level
+    // child was checked, so they're all next to each other in the SelectedItems vector, and we can find them quickly
+    // if we start near where we found the previous hit.
+    //
+    // Note that it's _near_ the previous hit and not _at_ the previous hit because of another optimization. Removing
+    // 10,000 items means shuffling the vector 10,000 times, which is also a slow operation. The last item being removed
+    // is going to be shuffled up 9,999 times only to be deleted in the end. To avoid wasted shuffling, we iterate the
+    // child collection backwards when deselecting. But this also means IndexOf can't start the next search at the same
+    // index but rather at that index - 1. In this example, item 89,999 was just removed, and next we're going to remove
+    // item 89,998. Starting the next search at index 89,999 actualy has the worst performance, because it guarantees that
+    // we're going to search linearly from 89,999 to the end of the vector, then wrap around at the beginning and search
+    // through every item in the vector before finding our hit at the last possible index 89,998.
+    //
+    unsigned int m_optimizedIndexOf_StartNextSearchAt = 0;
 };
 
 // Vector Inner implementation with Observable function
@@ -341,7 +417,7 @@ struct ObservableVectorInnerImpl:
             Traits::RaiseEvent(m_pIVectorExternal->GetVectorEventSource(), sender, collectionChange, index);
         }
     }
-    
+
     winrt::event_token AddEventHandler(EventHandler const& handler)
     {
         return Traits::AddEventHandler(m_pIVectorExternal->GetVectorEventSource(), handler);
@@ -389,7 +465,7 @@ struct ComposableBasePointersImplTType
     using WinRTBaseFactoryInterface = typename winrt::IDependencyObjectFactory;
 };
 
-template <> 
+template <>
 struct ComposableBasePointersImplTType<false>
 {
     using WinRTBase = typename winrt::IInspectable;
@@ -417,7 +493,7 @@ struct VectorOptionsBase: VectorInterfaceHelper<T, isBindable>, ComposableBasePo
 
 template <typename T, bool isObservable, bool isBindable, bool isDependencyObjectBase, bool isNoTrackerRef>
 struct VectorOptions: VectorOptionsBase<T, isObservable, isBindable, isDependencyObjectBase, isNoTrackerRef>
-{ 
+{
 };
 
 template <typename T, bool isObservable, bool isDependencyObjectBase, bool isNoTrackerRef>
@@ -532,7 +608,7 @@ struct VectorOptionsFromFlag :
         } \
     private:
 
-// Implement IVectorOwner, also define the Inner Vector and Event Source 
+// Implement IVectorOwner, also define the Inner Vector and Event Source
 #define Implement_Vector_External(Options) \
     private: \
         using VectorInnerType = ObservableVectorInnerImpl<##Options##>; \
@@ -552,7 +628,7 @@ struct VectorOptionsFromFlag :
     Implement_IVector_Modify_Functions(##Options##) \
     Implement_IIterator(##Options##) \
     Implement_IObservable(##Options##) \
-    Implement_Vector_External(##Options##) 
+    Implement_Vector_External(##Options##)
 
 // Implement all interfaces for IXXVector/IXXIterator/IXXObservable except those which will modify the vector
 // Like TreeViewNode, we need do additional work before Add/Remove/Modify the vector
@@ -560,14 +636,14 @@ struct VectorOptionsFromFlag :
     Implement_IVector_Read_Functions(##Options##) \
     Implement_IIterator(##Options##) \
     Implement_IObservable(##Options##) \
-    Implement_Vector_External(##Options##) 
+    Implement_Vector_External(##Options##)
 
 // Implement all interfaces for IXXVector/IXXIterator/IXXObservable except those which will modify the vector
 // Like TreeViewNode, we need do additional work before Add/Remove/Modify the vector
 #define Implement_Vector_Read_NoObservable(Options) \
     Implement_IVector_Read_Functions(##Options##) \
     Implement_IIterator(##Options##) \
-    Implement_Vector_External(##Options##) 
+    Implement_Vector_External(##Options##)
 
 
 template <typename T, bool isObservable, bool isBindable, bool isDependencyObjectBase, bool isNoTrackerRef, typename Options = VectorOptions<T, isObservable, isBindable, isDependencyObjectBase, isNoTrackerRef>>
@@ -602,8 +678,8 @@ class VectorBase :
 };
 
 
-template<typename T, 
-    int flags = MakeVectorParam<VectorFlag::Observable, VectorFlag::DependencyObjectBase>(), 
+template<typename T,
+    int flags = MakeVectorParam<VectorFlag::Observable, VectorFlag::DependencyObjectBase>(),
     typename Helper = VectorFlagHelper<flags>>
 class Vector :
     public VectorBase<T, Helper::isObservable, Helper::isBindable, Helper::isDependencyObjectBase, Helper::isNoTrackerRef>
@@ -613,18 +689,18 @@ class Vector :
     Vector(uint32_t capacity) : VectorBase<T, Helper::isObservable, Helper::isBindable, Helper::isDependencyObjectBase, Helper::isNoTrackerRef>(capacity) {}
 
     // The same copy of data for NavigationView split into two parts in top navigationview. So two or more vectors are created to provide multiple datasource for controls.
-    // InspectingDataSource is converting C# collections to Vector<winrt::IInspectable>. When GetAt(index) for things like string, a new IInspectable is always returned by C# projection. 
+    // InspectingDataSource is converting C# collections to Vector<winrt::IInspectable>. When GetAt(index) for things like string, a new IInspectable is always returned by C# projection.
     // ListView use indexOf for selection, so a copied/filtered view of C# collection doesn't work for SelectedItem(s) anymore because IInspectable comparsion always return false.
-    // As a workaround, the copied/filtered vector requires others help to IndexOf the orignial C# collection. 
+    // As a workaround, the copied/filtered vector requires others help to IndexOf the orignial C# collection.
     // So the comparison is done by C# vector other than Inspectable directly comparision. Here is an example:
-    // Raw data A is: Home-Apps-Music-Sports 
+    // Raw data A is: Home-Apps-Music-Sports
     // data is splitted two vectors: B and C. B includes Homes, and C includes Apps-Music-Sports
     // Music is the selected item. SplitDataSource is the class help to manage the raw data and provides splitted vectors to ListViews
     // ListView call C.indexOf("Music")
     //                  C ask SplitDataSource.IndexOf
     //                      SplitDataSource calls A.IndexOf (C# provided it)
     //                      SpiltDataSource help to convert the indexInRawData to indexInC
-    //                  return index in C    
+    //                  return index in C
     Vector(std::function<int(typename T const& value)> indexOfFunction) : m_indexOfFunction(indexOfFunction)
     {
         if (m_indexOfFunction)
diff --git a/controls/dev/Materials/Acrylic/AcrylicBrush.cpp b/controls/dev/Materials/Acrylic/AcrylicBrush.cpp
index 68be52dc2c..e76181852e 100644
--- a/controls/dev/Materials/Acrylic/AcrylicBrush.cpp
+++ b/controls/dev/Materials/Acrylic/AcrylicBrush.cpp
@@ -81,7 +81,14 @@ winrt::CompositionAnimation AcrylicBrush::MakeColorAnimation(const winrt::Color&
 {
     auto animation = compositor.CreateColorKeyFrameAnimation();
     animation.InsertKeyFrame(1.0, color);
-    animation.Duration(duration.count() == 0 ? winrt::TimeSpan::duration(1 * 10000) : duration);     // Zero duration KeyFrameAnimations not supported, use 1ms duration in that case.
+    if (SharedHelpers::IsAnimationsEnabled())
+    {
+        animation.Duration(duration.count() == 0 ? winrt::TimeSpan::duration(1 * 10000) : duration);     // Zero duration KeyFrameAnimations not supported, use 1ms duration in that case.
+    }
+    else
+    {
+        animation.Duration(1ms); // shortest allowed to minimize CPU use
+    }
     return animation;
 }
 
@@ -95,7 +102,7 @@ winrt::CompositionAnimation AcrylicBrush::MakeFloatAnimation(
     auto animation = compositor.CreateScalarKeyFrameAnimation();
     animation.InsertKeyFrame(0.0, fromValue);
     animation.InsertKeyFrame(1.0, toValue, easing);
-    animation.Duration(duration);
+    animation.Duration(SharedHelpers::IsAnimationsEnabled() ? duration : 1ms); // 1m is shortest allowed, minimize CPU use
     return animation;
 }
 
diff --git a/controls/dev/Repeater/APITests/ItemTemplateTests.cs b/controls/dev/Repeater/APITests/ItemTemplateTests.cs
index 318ff6e4d8..2b20655ce3 100644
--- a/controls/dev/Repeater/APITests/ItemTemplateTests.cs
+++ b/controls/dev/Repeater/APITests/ItemTemplateTests.cs
@@ -250,6 +250,67 @@ public void ValidateRecyclingElementFactoryWithSingleTemplate()
             });
         }
 
+        [TestMethod]
+        public void ValidateDataTemplateWithElementNameBinding()
+        {
+            const int numItems = 5;
+            ItemsRepeater itemsRepeater = null;
+
+            RunOnUIThread.Execute(() =>
+            {
+                var dataTemplate = XamlReader.Load(
+                    @"<DataTemplate xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'>
+                        <TextBlock Text='{Binding}' Tag='{Binding ElementName=siblingTextBlock, Path=Text}'/>
+                    </DataTemplate>") as DataTemplate;
+
+                var stackPanel = new StackPanel()
+                {
+                    Name = "stackPanel",
+                    Width = 200
+                };
+
+                var siblingTextBlock = new TextBlock()
+                {
+                    Name = "siblingTextBlock",
+                    Text = "DataSource"
+                };
+
+                itemsRepeater = new ItemsRepeater()
+                {
+                    Name = "itemsRepeater",
+                    ItemsSource = Enumerable.Range(0, numItems).Select(i => i.ToString()),
+                    Layout = new StackLayout(),
+                    ItemTemplate = dataTemplate
+                };
+
+                stackPanel.Children.Add(siblingTextBlock);
+                stackPanel.Children.Add(itemsRepeater);
+
+                Content = stackPanel;
+
+                Content.UpdateLayout();
+            });
+
+            IdleSynchronizer.Wait();
+
+            RunOnUIThread.Execute(() =>
+            {
+                Verify.AreEqual(numItems, VisualTreeHelper.GetChildrenCount(itemsRepeater));
+
+                for (int i = 0; i < numItems; i++)
+                {
+                    var itemTextBlock = itemsRepeater.TryGetElement(i) as TextBlock;
+
+                    Verify.IsNotNull(itemTextBlock);
+                    Verify.AreEqual(i.ToString(), itemTextBlock.Text);
+                    Verify.AreEqual("DataSource", itemTextBlock.Tag);
+                }
+
+                itemsRepeater.ItemsSource = null;
+                Content.UpdateLayout();
+            });
+        }
+
         [TestMethod]
         [TestProperty("IsolationLevel", "Method")] // Task 28232821: DCPP Test: ItemsRepeater tests are running in isolation mode due to test instability.
         public void ValidateDataTemplateAsItemTemplate()
@@ -635,6 +696,7 @@ public void VerifyNullTemplateGivesMeaningfullError()
                 Content = null;
             });
         }
+
         private ItemsRepeaterScrollHost CreateAndInitializeRepeater(
             object itemsSource,
             Layout layout,
diff --git a/controls/dev/Repeater/TestUI/Samples/ItemTemplateSamples/ItemTemplateDemo.xaml b/controls/dev/Repeater/TestUI/Samples/ItemTemplateSamples/ItemTemplateDemo.xaml
index 41a873d542..273f12cb1d 100644
--- a/controls/dev/Repeater/TestUI/Samples/ItemTemplateSamples/ItemTemplateDemo.xaml
+++ b/controls/dev/Repeater/TestUI/Samples/ItemTemplateSamples/ItemTemplateDemo.xaml
@@ -7,114 +7,111 @@
     xmlns:controls="using:Microsoft.UI.Xaml.Controls"
     Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
     <Page.Resources>
-        <controls:RecyclePool x:Name="recyclePool" />
-        <controls:StackLayout x:Name="stackLayout" />
+        <RecyclePool x:Name="recyclePool"/>
+        <StackLayout x:Name="stackLayout"/>
     </Page.Resources>
-    <Grid>
-        <Grid.ColumnDefinitions>
-            <ColumnDefinition Width="auto" />
-            <ColumnDefinition Width="auto" />
-            <ColumnDefinition Width="auto" />
-            <ColumnDefinition Width="auto" />
-            <ColumnDefinition Width="auto" />
-        </Grid.ColumnDefinitions>
-        <StackPanel>
-            <TextBlock Text="DataTemplate Sample:"/>
-            <controls:ItemsRepeaterScrollHost Height="400" Width="150">
-                <ScrollViewer>
-                    <controls:ItemsRepeater x:Name="repeater0"
-                                            ItemsSource="{x:Bind Data}"
-                                            Layout="{StaticResource stackLayout}">
-                        <controls:ItemsRepeater.ItemTemplate>
-                            <DataTemplate>
-                                <TextBlock Text="{Binding}" />
-                            </DataTemplate>
-                        </controls:ItemsRepeater.ItemTemplate>
-                    </controls:ItemsRepeater>
-                </ScrollViewer>
-            </controls:ItemsRepeaterScrollHost>
-        </StackPanel>
-        <StackPanel Grid.Column="1">
-            <TextBlock Text="DataTemplateSelector Sample:"/>
-            <controls:ItemsRepeaterScrollHost Height="400" Width="150">
-                <ScrollViewer>
-                    <controls:ItemsRepeater x:Name="repeater1" 
-                                            ItemsSource="{x:Bind Data}"
-                                            Layout="{StaticResource stackLayout}">
-                        <controls:ItemsRepeater.ItemTemplate>
-                            <local:MySelector>
-                                <local:MySelector.TemplateOdd>
-                                    <DataTemplate>
-                                        <TextBlock Text="{Binding}" Foreground="Red"/>
-                                    </DataTemplate>
-                                </local:MySelector.TemplateOdd>
-                                <local:MySelector.TemplateEven>
-                                    <DataTemplate>
-                                        <TextBlock Text="{Binding}" Foreground="Green"/>
-                                    </DataTemplate>
-                                </local:MySelector.TemplateEven>
-                            </local:MySelector>
-                        </controls:ItemsRepeater.ItemTemplate>
-                    </controls:ItemsRepeater>
-                </ScrollViewer>
-            </controls:ItemsRepeaterScrollHost>
-        </StackPanel>
-        <StackPanel Grid.Column="2">
-            <TextBlock Text="ElementFactory Single Template Sample:"/>
-            <controls:ItemsRepeaterScrollHost Height="400" Width="150">
-                <ScrollViewer>
-                    <controls:ItemsRepeater x:Name="repeater2" 
-                                            ItemsSource="{x:Bind Data}"
-                                            Layout="{StaticResource stackLayout}">
-                        <controls:ItemsRepeater.ItemTemplate>
-                            <controls:RecyclingElementFactory RecyclePool="{StaticResource recyclePool}">
-                                <DataTemplate x:Key="item">
-                                    <TextBlock Text="{Binding}" />
-                                </DataTemplate>
-                            </controls:RecyclingElementFactory>
-                        </controls:ItemsRepeater.ItemTemplate>
-                    </controls:ItemsRepeater>
-                </ScrollViewer>
-            </controls:ItemsRepeaterScrollHost>
-        </StackPanel>
-        <StackPanel Grid.Column="3">
-            <TextBlock Text="ElementFactory Multiple Template Sample:"/>
-            <controls:ItemsRepeaterScrollHost Height="400" Width="150">
-                <ScrollViewer>
-                    <controls:ItemsRepeater x:Name="repeater4" 
-                                            ItemsSource="{x:Bind Data}"
-                                            Layout="{StaticResource stackLayout}">
-                        <controls:ItemsRepeater.ItemTemplate>
-                            <controls:RecyclingElementFactory 
-                                RecyclePool="{StaticResource recyclePool}"
-                                SelectTemplateKey="OnSelectTemplateKey">
-                                <DataTemplate x:Key="odd">
-                                    <TextBlock Text="{Binding}" Foreground="Red" />
+    <Grid ColumnDefinitions="170, 170, 170, 170, 170, 170" RowDefinitions="Auto, Auto">
+        <TextBlock Text="DataTemplate Sample:" TextWrapping="WrapWholeWords" Margin="10"/>
+        <ItemsRepeaterScrollHost Height="400" Margin="10" Grid.Row="1">
+            <ScrollViewer>
+                <ItemsRepeater x:Name="itemsRepeater0"
+                    ItemsSource="{x:Bind Data}"
+                    Layout="{StaticResource stackLayout}">
+                    <ItemsRepeater.ItemTemplate>
+                        <DataTemplate>
+                            <TextBlock Text="{Binding}"/>
+                        </DataTemplate>
+                    </ItemsRepeater.ItemTemplate>
+                </ItemsRepeater>
+            </ScrollViewer>
+        </ItemsRepeaterScrollHost>
+
+        <TextBlock Text="DataTemplateSelector Sample:" TextWrapping="WrapWholeWords" Margin="10" Grid.Column="1"/>
+        <ItemsRepeaterScrollHost Height="400" Margin="10" Grid.Column="1" Grid.Row="1">
+            <ScrollViewer>
+                <ItemsRepeater x:Name="itemsRepeater1" 
+                    ItemsSource="{x:Bind Data}"
+                    Layout="{StaticResource stackLayout}">
+                    <ItemsRepeater.ItemTemplate>
+                        <local:MySelector>
+                            <local:MySelector.TemplateOdd>
+                                <DataTemplate>
+                                    <TextBlock Text="{Binding}" Foreground="Red"/>
                                 </DataTemplate>
-                                <DataTemplate x:Key="even">
-                                    <TextBlock Text="{Binding}" Foreground="Green" />
+                            </local:MySelector.TemplateOdd>
+                            <local:MySelector.TemplateEven>
+                                <DataTemplate>
+                                    <TextBlock Text="{Binding}" Foreground="Green"/>
                                 </DataTemplate>
-                            </controls:RecyclingElementFactory>
-                        </controls:ItemsRepeater.ItemTemplate>
-                    </controls:ItemsRepeater>
-                </ScrollViewer>
-            </controls:ItemsRepeaterScrollHost>
-        </StackPanel>
-        <StackPanel Grid.Column="4">
-            <TextBlock Text="DataTemplate clear count checking:"/>
-            <controls:ItemsRepeaterScrollHost Height="400" Width="150">
-                <ScrollViewer>
-                    <controls:ItemsRepeater x:Name="repeater3" 
-                                            ItemsSource="{x:Bind Numbers}"
-                                            Layout="{StaticResource stackLayout}">
-                        <controls:ItemsRepeater.ItemTemplate>
-                            <DataTemplate x:DataType="local:MyData" >
-                                <local:DisposableUserControl Number="{x:Bind number}"/>
+                            </local:MySelector.TemplateEven>
+                        </local:MySelector>
+                    </ItemsRepeater.ItemTemplate>
+                </ItemsRepeater>
+            </ScrollViewer>
+        </ItemsRepeaterScrollHost>
+
+        <TextBlock Text="ElementFactory Single Template Sample:" TextWrapping="WrapWholeWords" Margin="10" Grid.Column="2"/>
+        <ItemsRepeaterScrollHost Height="400" Margin="10" Grid.Column="2" Grid.Row="1">
+            <ScrollViewer>
+                <ItemsRepeater x:Name="itemsRepeater2" 
+                    ItemsSource="{x:Bind Data}"
+                    Layout="{StaticResource stackLayout}">
+                    <ItemsRepeater.ItemTemplate>
+                        <RecyclingElementFactory RecyclePool="{StaticResource recyclePool}">
+                            <DataTemplate x:Key="item">
+                                <TextBlock Text="{Binding}"/>
+                            </DataTemplate>
+                        </RecyclingElementFactory>
+                    </ItemsRepeater.ItemTemplate>
+                </ItemsRepeater>
+            </ScrollViewer>
+        </ItemsRepeaterScrollHost>
+
+        <TextBlock Text="ElementFactory Multiple Template Sample:" TextWrapping="WrapWholeWords" Margin="10" Grid.Column="3"/>
+        <ItemsRepeaterScrollHost Height="400" Margin="10" Grid.Column="3" Grid.Row="1">
+            <ScrollViewer>
+                <ItemsRepeater x:Name="itemsRepeater3" 
+                    ItemsSource="{x:Bind Data}"
+                    Layout="{StaticResource stackLayout}">
+                    <ItemsRepeater.ItemTemplate>
+                        <RecyclingElementFactory 
+                            RecyclePool="{StaticResource recyclePool}"
+                            SelectTemplateKey="OnSelectTemplateKey">
+                            <DataTemplate x:Key="odd">
+                                <TextBlock Text="{Binding}" Foreground="Red"/>
+                            </DataTemplate>
+                            <DataTemplate x:Key="even">
+                                <TextBlock Text="{Binding}" Foreground="Green"/>
                             </DataTemplate>
-                        </controls:ItemsRepeater.ItemTemplate>
-                    </controls:ItemsRepeater>
-                </ScrollViewer>
-            </controls:ItemsRepeaterScrollHost>
-        </StackPanel>
+                        </RecyclingElementFactory>
+                    </ItemsRepeater.ItemTemplate>
+                </ItemsRepeater>
+            </ScrollViewer>
+        </ItemsRepeaterScrollHost>
+        
+        <TextBlock Text="DataTemplate clear count checking:" TextWrapping="WrapWholeWords" Margin="10" Grid.Column="4"/>
+        <ItemsRepeaterScrollHost Height="400" Margin="10" Grid.Column="4" Grid.Row="1">
+            <ScrollViewer>
+                <ItemsRepeater x:Name="itemsRepeater4" 
+                    ItemsSource="{x:Bind Numbers}"
+                    Layout="{StaticResource stackLayout}">
+                    <ItemsRepeater.ItemTemplate>
+                        <DataTemplate x:DataType="local:MyData" >
+                            <local:DisposableUserControl Number="{x:Bind number}"/>
+                        </DataTemplate>
+                    </ItemsRepeater.ItemTemplate>
+                </ItemsRepeater>
+            </ScrollViewer>
+        </ItemsRepeaterScrollHost>
+
+        <TextBlock x:Name="tbl5" Tag="Binding Source" Text="DataTemplate with ElementName Binding:" TextWrapping="WrapWholeWords" Margin="10" Grid.Column="5"/>
+        <ItemsRepeater x:Name="itemsRepeater5" Height="400" Margin="10" Grid.Column="5" Grid.Row="1"
+            ItemsSource="{x:Bind Numbers}">
+            <ItemsRepeater.ItemTemplate>
+                <DataTemplate>
+                    <Button x:Name="itemsRepeaterChildButton5" Content="{Binding ElementName=tbl5, Path=Tag}"/>
+                </DataTemplate>
+            </ItemsRepeater.ItemTemplate>
+        </ItemsRepeater>
     </Grid>
 </Page>
diff --git a/controls/dev/TeachingTip/InteractionTests/TeachingTipFocusTestPageElements.cs b/controls/dev/TeachingTip/InteractionTests/TeachingTipFocusTestPageElements.cs
index 50f12ba3e0..5a4c0632cd 100644
--- a/controls/dev/TeachingTip/InteractionTests/TeachingTipFocusTestPageElements.cs
+++ b/controls/dev/TeachingTip/InteractionTests/TeachingTipFocusTestPageElements.cs
@@ -47,6 +47,15 @@ public CheckBox GetIsLightDismissEnabledCheckBox()
         }
         private CheckBox isLightDismissEnabledCheckBox;
 
+        public UIObject GetTeachingTipCloseButton()
+        {
+            ElementCache.Clear();
+            var element = GetElement(ref teachingTipCloseButton, "Close TeachingTip");
+            teachingTipCloseButton = null;
+            return element;
+        }
+        private UIObject teachingTipCloseButton;
+
         private T GetElement<T>(ref T element, string elementName) where T : UIObject
         {
             if (element == null)
diff --git a/controls/dev/TeachingTip/InteractionTests/TeachingTipTests.cs b/controls/dev/TeachingTip/InteractionTests/TeachingTipTests.cs
index 298d83bbef..f7fc9ece60 100644
--- a/controls/dev/TeachingTip/InteractionTests/TeachingTipTests.cs
+++ b/controls/dev/TeachingTip/InteractionTests/TeachingTipTests.cs
@@ -1126,6 +1126,74 @@ public void VerifyTeachingTipButtonsNameAutomationProperty()
             }
         }
 
+        [TestMethod]
+        [TestProperty("TestSuite", "C")]
+        public void VerifyTeachingTipGetsFocus()
+        {
+            using (var setup = new TestSetupHelper(new[] { "TeachingTip Tests", "TeachingTipFocus Test" }))
+            {
+                var elements = new TeachingTipFocusTestPageElements();
+                var openTeachingTipButton = elements.GetOpenButton();
+
+                FocusHelper.SetFocus(openTeachingTipButton);
+                OpenTeachingTip();
+
+                Log.Comment("Verify that an opened teaching tip get focus on F6");
+                Verify.IsTrue(openTeachingTipButton.HasKeyboardFocus);
+                KeyboardHelper.PressKey(Key.F6);
+                Wait.ForIdle();
+                var closeButton = elements.GetTeachingTipCloseButton();
+                Verify.IsTrue(closeButton.HasKeyboardFocus);
+                KeyboardHelper.PressKey(Key.F6);
+                Wait.ForIdle();
+                Verify.IsTrue(openTeachingTipButton.HasKeyboardFocus);
+
+                Log.Comment("Switch to light-dismissable teaching tip.");
+                CloseTeachingTipProgrammatically();
+                EnableLightDismiss();
+
+                Log.Comment("Verify that a light-dismissable teaching tip gets focus on opening");
+                Verify.IsTrue(openTeachingTipButton.HasKeyboardFocus);
+                OpenTeachingTip();
+                Wait.ForIdle();
+                closeButton = elements.GetTeachingTipCloseButton();
+                Verify.IsTrue(closeButton.HasKeyboardFocus);
+                KeyboardHelper.PressKey(Key.Escape);
+                Wait.ForIdle();
+                Verify.IsTrue(openTeachingTipButton.HasKeyboardFocus);
+
+                void OpenTeachingTip()
+                {
+                    if (elements.GetIsOpenCheckBox().ToggleState != ToggleState.On)
+                    {
+                        openTeachingTipButton.InvokeAndWait();
+                        WaitForChecked(elements.GetIsOpenCheckBox());
+                        WaitForChecked(elements.GetIsIdleCheckBox());
+                    }
+                }
+
+                void CloseTeachingTipProgrammatically()
+                {
+                    if (elements.GetIsOpenCheckBox().ToggleState != ToggleState.Off)
+                    {
+                        elements.GetCloseButton().InvokeAndWait();
+                        WaitForUnchecked(elements.GetIsOpenCheckBox());
+                        WaitForChecked(elements.GetIsIdleCheckBox());
+                    }
+                }
+
+                void EnableLightDismiss()
+                {
+                    var isLightDismissEnabledCheckBox = elements.GetIsLightDismissEnabledCheckBox();
+                    if (isLightDismissEnabledCheckBox.ToggleState != ToggleState.On)
+                    {
+                        isLightDismissEnabledCheckBox.Check();
+                        WaitForChecked(isLightDismissEnabledCheckBox);
+                    }
+                }
+            }
+        }
+
         private void CloseOpenAndCloseWithJustKeyboardViaF6()
         {
             KeyboardHelper.PressKey(Key.F6);
diff --git a/controls/dev/TeachingTip/TeachingTip.cpp b/controls/dev/TeachingTip/TeachingTip.cpp
index 70d608df9b..74b4ba92a0 100644
--- a/controls/dev/TeachingTip/TeachingTip.cpp
+++ b/controls/dev/TeachingTip/TeachingTip.cpp
@@ -1038,6 +1038,7 @@ void TeachingTip::OnIsLightDismissEnabledChanged()
         {
             lightDismissIndicatorPopup.IsLightDismissEnabled(true);
             m_lightDismissIndicatorPopupClosedRevoker = lightDismissIndicatorPopup.Closed(winrt::auto_revoke, { this, &TeachingTip::OnLightDismissIndicatorPopupClosed });
+            m_lightDismissIndicatorPopupPreviewKeyDownForF6Revoker = lightDismissIndicatorPopup.PreviewKeyDown(winrt::auto_revoke, { this, &TeachingTip::OnF6PreviewKeyDownClicked });
         }
     }
     else
@@ -1048,6 +1049,7 @@ void TeachingTip::OnIsLightDismissEnabledChanged()
             lightDismissIndicatorPopup.IsLightDismissEnabled(false);
         }
         m_lightDismissIndicatorPopupClosedRevoker.revoke();
+        m_lightDismissIndicatorPopupPreviewKeyDownForF6Revoker.revoke();
     }
     UpdateButtonsState();
 }
@@ -1183,6 +1185,16 @@ bool TeachingTip::HandleF6Clicked(bool fromPopup)
     }
     else if (!hasFocusInSubtree && !fromPopup)
     {
+        if (IsLightDismissEnabled())
+        {
+            auto focusable = winrt::FocusManager::FindFirstFocusableElement(m_rootElement.get());
+            if (focusable)
+            {
+                SetFocus(focusable, winrt::FocusState::Keyboard);
+                return true;
+            }
+        }
+
         const winrt::Button f6Button = [this]() -> winrt::Button
         {
             auto firstButton = m_closeButton.get();
@@ -1289,6 +1301,15 @@ void TeachingTip::OnPopupOpened(const winrt::IInspectable&, const winrt::IInspec
 
         winrt::get_self<TeachingTipAutomationPeer>(teachingTipPeer)->RaiseWindowOpenedEvent(notificationString);
     }
+
+    if(IsLightDismissEnabled())
+    {
+        auto focusable = winrt::FocusManager::FindFirstFocusableElement(m_rootElement.get());
+        if (focusable)
+        {
+            SetFocus(focusable, winrt::FocusState::Programmatic);
+        }
+    }
 }
 
 void TeachingTip::OnPopupClosed(const winrt::IInspectable&, const winrt::IInspectable&)
@@ -2110,8 +2131,7 @@ winrt::Rect TeachingTip::GetWindowBounds()
     {
         return winrt::Rect{ 0, 0, xamlRoot.Size().Width, xamlRoot.Size().Height };
     }
-
-    return winrt::CoreWindow::GetForCurrentThread().Bounds();
+    return winrt::Rect{ 0, 0, 0, 0 };
 }
 
 std::array<winrt::TeachingTipPlacementMode, 13> TeachingTip::GetPlacementFallbackOrder(winrt::TeachingTipPlacementMode preferredPlacement)
diff --git a/controls/dev/TeachingTip/TeachingTip.h b/controls/dev/TeachingTip/TeachingTip.h
index 6c06800cc6..6403589498 100644
--- a/controls/dev/TeachingTip/TeachingTip.h
+++ b/controls/dev/TeachingTip/TeachingTip.h
@@ -65,6 +65,7 @@ class TeachingTip :
     winrt::UIElement::PreviewKeyDown_revoker m_previewKeyDownForF6Revoker{};
     // This handler is not required for Winui3 because the framework bug this works around has been fixed.
     winrt::UIElement::PreviewKeyDown_revoker m_popupPreviewKeyDownForF6Revoker{};
+    winrt::UIElement::PreviewKeyDown_revoker m_lightDismissIndicatorPopupPreviewKeyDownForF6Revoker{};
     winrt::Button::Click_revoker m_closeButtonClickedRevoker{};
     winrt::Button::Click_revoker m_alternateCloseButtonClickedRevoker{};
     winrt::Button::Click_revoker m_actionButtonClickedRevoker{};
diff --git a/controls/dev/TeachingTip/TestUI/TeachingTip-FocusBehavior.md b/controls/dev/TeachingTip/TestUI/TeachingTip-FocusBehavior.md
new file mode 100644
index 0000000000..23ddc23ebe
--- /dev/null
+++ b/controls/dev/TeachingTip/TestUI/TeachingTip-FocusBehavior.md
@@ -0,0 +1,13 @@
+# Teaching Tip - Focus Behavior
+
+### Non-light-dismiss TeachingTip:
+- When it opens, it does not take focus.
+- You can manually move focus to the teaching tip by pressing f6.
+- You can move focus back to the main page by pressing f6 again. 
+- Focus moves back to the element that previously had focus before the teaching tip opened.
+
+### For a light-dismiss teaching tip:
+- When it opens it does take focus.
+- Once focus moves out of the teaching tip, it will close (due to light dismiss). 
+- You can move focus out of the teaching tip with f6 or esc.
+- When the teachingtip closes, focus moves back to the element in the page that originally had focus.
diff --git a/controls/dev/TeachingTip/TestUI/TeachingTipFocusPage.xaml b/controls/dev/TeachingTip/TestUI/TeachingTipFocusPage.xaml
index c41bad000c..cd94ded3be 100644
--- a/controls/dev/TeachingTip/TestUI/TeachingTipFocusPage.xaml
+++ b/controls/dev/TeachingTip/TestUI/TeachingTipFocusPage.xaml
@@ -12,7 +12,7 @@
     Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
 
     <Grid Margin="10">
-        <muxc:TeachingTip x:Name="TestTeachingTip" Title="Title" IsLightDismissEnabled="{x:Bind (x:Boolean)IsLightDismissEnabledCheckBox.IsChecked, Mode=OneWay}" />
+        <muxc:TeachingTip x:Name="TestTeachingTip" Title="Title" IsLightDismissEnabled="{x:Bind (x:Boolean)IsLightDismissEnabledCheckBox.IsChecked, Mode=OneWay}" CloseButtonContent="Close TeachingTip"/>
 
         <StackPanel>
             <TextBlock Text="TeachingTip special focus test page" Style="{StaticResource SubtitleTextBlockStyle}" Margin="0,0,0,15"/>
diff --git a/controls/dev/TreeView/TestUI/TreeViewPage.xaml b/controls/dev/TreeView/TestUI/TreeViewPage.xaml
index 1f944aa5df..b373f20af5 100644
--- a/controls/dev/TreeView/TestUI/TreeViewPage.xaml
+++ b/controls/dev/TreeView/TestUI/TreeViewPage.xaml
@@ -19,6 +19,7 @@
                 <ColumnDefinition Width="Auto"/>
                 <ColumnDefinition Width="1*"/>
                 <ColumnDefinition Width="1*"/>
+                <ColumnDefinition Width="1*"/>
             </Grid.ColumnDefinitions>
             <ScrollViewer>
                 <StackPanel>
@@ -113,7 +114,7 @@
             <ScrollViewer Grid.Column="2">
                 <StackPanel x:Name="ContentModeTestStackPanel">
 
-                    <muxcontrols:TreeView 
+                    <muxcontrols:TreeView
                         x:Name="ContentModeTestTreeView"
                         AutomationProperties.Name="ContentModeTestTreeView"
                         HorizontalAlignment="Left"
@@ -122,7 +123,7 @@
                         ItemsSource="{x:Bind TestTreeViewItemsSource}">
                         <muxcontrols:TreeView.ItemTemplate>
                             <DataTemplate x:DataType="local:TreeViewItemSource">
-                                <muxcontrols:TreeViewItem 
+                                <muxcontrols:TreeViewItem
                                     ItemsSource="{x:Bind Children}"
                                     Content="{x:Bind Content}"
                                     IsExpanded="{x:Bind IsExpanded, Mode=TwoWay}"
@@ -131,7 +132,7 @@
                         </muxcontrols:TreeView.ItemTemplate>
                     </muxcontrols:TreeView>
 
-                    <muxcontrols:TreeView 
+                    <muxcontrols:TreeView
                         x:Name="ContentModeTestTreeView2"
                         AutomationProperties.Name="ContentModeTestTreeView2"
                         HorizontalAlignment="Left"
@@ -139,7 +140,7 @@
                         ItemsSource="{Binding TestTreeView2ItemsSource}">
                         <muxcontrols:TreeView.ItemTemplate>
                             <DataTemplate>
-                                <muxcontrols:TreeViewItem 
+                                <muxcontrols:TreeViewItem
                                     ItemsSource="{Binding Children}"
                                     Content="{Binding Content}"
                                     IsExpanded="{Binding IsExpanded, Mode=TwoWay}"
@@ -156,6 +157,22 @@
                     </Border>
                 </StackPanel>
             </ScrollViewer>
+
+            <ScrollViewer Grid.Column="3">
+                <StackPanel x:Name="PerfScenarioStackPanel">
+
+                    <Button Content="Load big tree view (SLOW on chk)" Click="LoadPerfTreeView_Click" />
+
+                    <muxcontrols:TreeView
+                        x:Name="PerfScenarioTreeView"
+                        SelectionMode="Multiple"
+                        HorizontalAlignment="Left"
+                        Width="400" Height="800">
+                    </muxcontrols:TreeView>
+
+                </StackPanel>
+            </ScrollViewer>
+
         </Grid>
         <Grid Grid.Row="1">
             <Grid.ColumnDefinitions>
diff --git a/controls/dev/TreeView/TestUI/TreeViewPage.xaml.cs b/controls/dev/TreeView/TestUI/TreeViewPage.xaml.cs
index 9702ee3b44..9d4dfb129b 100644
--- a/controls/dev/TreeView/TestUI/TreeViewPage.xaml.cs
+++ b/controls/dev/TreeView/TestUI/TreeViewPage.xaml.cs
@@ -262,7 +262,7 @@ private string GetRootNodeChildrenOrder(TreeView tree)
                 {
                     pendingNodes.Push(currentNode.Children[size - 1 - i]);
                 }
-                
+
                 result.Add(GetNodeContent(currentNode));
             }
 
@@ -517,7 +517,7 @@ private void Item_DragEnter(object sender, DragEventArgs e)
         private async void TreeView_Drop(object sender, DragEventArgs e)
         {
             try
-            { 
+            {
                 var text = await e.DataView.GetTextAsync();
                 Results.Text = "Dropped: " + text;
             }
@@ -582,7 +582,7 @@ private void TestTreeView_DragItemsStarting(TreeView sender, TreeViewDragItemsSt
                     items.Append(node.Content.ToString());
                 }
             }
-            
+
             e.Data.SetText(items.ToString());
             e.Data.RequestedOperation = DataPackageOperation.Copy;
         }
@@ -646,7 +646,7 @@ private void ModifySecondLevelOfNode_Click(object sender, RoutedEventArgs e)
                 var y0 = new TreeViewNode { Content = "THIS IS NEW" };
                 var root0 = _visualRoot.Children[0];
                 root0.Children[0] = y0;
-            }            
+            }
         }
 
         private void SetRoot1HasUnrealizedChildren_Click(object sender, RoutedEventArgs e)
@@ -762,7 +762,7 @@ private String GetDraggedItemsNames(IEnumerable<object> items)
                     names.Append(node.Content.ToString());
                 }
             }
-            
+
             return names.ToString();
         }
 
@@ -918,7 +918,7 @@ private void ClearNodes_Click(object sender, RoutedEventArgs e)
         private void AddRootNode_Click(object sender, RoutedEventArgs e)
         {
             try
-            { 
+            {
                 if (IsInContentMode())
                 {
                     var newNode = new TreeViewItemSource() { Content = "Root" + TestTreeViewItemsSource.Count };
@@ -1023,8 +1023,32 @@ private void SelectRoot2Item_Click(object sender, RoutedEventArgs e)
         }
         private void ReadBindingResult_Click(object sender, RoutedEventArgs e)
         {
-            Results.Text = ((TwoWayBoundButton.Content as TreeViewNode).Content as string) 
+            Results.Text = ((TwoWayBoundButton.Content as TreeViewNode).Content as string)
                 + ";" + (TestTreeView.SelectedItem as TreeViewNode).Content as string;
         }
+
+        private void LoadPerfTreeView_Click(object sender, RoutedEventArgs e)
+        {
+            TreeViewNode rootNode = new TreeViewNode() { Content = "Root" };
+            for (int level1Index = 0; level1Index < 10; level1Index++)
+            {
+                TreeViewNode level1 = new TreeViewNode()
+                {
+                    Content = level1Index,
+                };
+                rootNode.Children.Add(level1);
+
+                for (int level2Index = 0; level2Index < 5000; level2Index++)
+                {
+                    TreeViewNode level2 = new TreeViewNode()
+                    {
+                        Content = level1Index + "_" + level2Index,
+                    };
+                    level1.Children.Add(level2);
+                }
+            }
+            PerfScenarioTreeView.RootNodes.Clear();
+            PerfScenarioTreeView.RootNodes.Add(rootNode);
+        }
     }
 }
diff --git a/controls/dev/TreeView/ViewModel.cpp b/controls/dev/TreeView/ViewModel.cpp
index 968dda522a..943a528dc4 100644
--- a/controls/dev/TreeView/ViewModel.cpp
+++ b/controls/dev/TreeView/ViewModel.cpp
@@ -15,137 +15,124 @@
 // i.e. the node is already gone when we get to ItemRemoved callback.
 #pragma region SelectedTreeNodeVector
 
-typedef typename VectorOptionsFromFlag<winrt::TreeViewNode, MakeVectorParam<VectorFlag::Observable, VectorFlag::DependencyObjectBase>()> SelectedTreeNodeVectorOptions;
-
-class SelectedTreeNodeVector :
-    public ReferenceTracker<
-    SelectedTreeNodeVector,
-    reference_tracker_implements_t<typename SelectedTreeNodeVectorOptions::VectorType>::type,
-    typename TreeViewNodeVectorOptions::IterableType,
-    typename TreeViewNodeVectorOptions::ObservableVectorType>,
-    public TreeViewNodeVectorOptions::IVectorOwner
+bool SelectedTreeNodeVector::IndexOf_OptimizedForRemove(winrt::TreeViewNode const& node, uint32_t& index)
 {
-    Implement_Vector_Read(SelectedTreeNodeVectorOptions)
-
-private:
-    winrt::weak_ref<ViewModel> m_viewModel{ nullptr };
+    return GetVectorInnerImpl()->IndexOf_OptimizedForRemove(node, index);
+}
 
-    void UpdateSelection(winrt::TreeViewNode const& node, TreeNodeSelectionState state)
+void SelectedTreeNodeVector::UpdateSelection(winrt::TreeViewNode const& node, TreeNodeSelectionState state)
+{
+    if (winrt::get_self<TreeViewNode>(node)->SelectionState() != state)
     {
-        if (winrt::get_self<TreeViewNode>(node)->SelectionState() != state)
+        if (auto viewModel = m_viewModel.get())
         {
-            if (auto viewModel = m_viewModel.get())
-            {
-                viewModel->UpdateSelection(node, state);
-                viewModel->NotifyContainerOfSelectionChange(node, state);
-            }
+            viewModel->UpdateSelection(node, state);
+            viewModel->NotifyContainerOfSelectionChange(node, state);
         }
     }
+}
 
-public:
-    void SetViewModel(ViewModel& viewModel)
-    {
-        m_viewModel = viewModel.get_weak();
-    }
-
-    void Append(winrt::TreeViewNode const& node)
-    {
-        InsertAt(Size(), node);
-    }
+void SelectedTreeNodeVector::SetViewModel(ViewModel& viewModel)
+{
+    m_viewModel = viewModel.get_weak();
+}
 
-    void InsertAt(unsigned int index, winrt::TreeViewNode const& node)
-    {
-        // UpdateSelection will call InsertAtCore
-        UpdateSelection(node, TreeNodeSelectionState::Selected);
-    }
+void SelectedTreeNodeVector::Append(winrt::TreeViewNode const& node)
+{
+    InsertAt(Size(), node);
+}
 
-    void SetAt(unsigned int index, winrt::TreeViewNode const& node)
-    {
-        RemoveAt(index);
-        InsertAt(index, node);
-    }
+void SelectedTreeNodeVector::InsertAt(unsigned int index, winrt::TreeViewNode const& node)
+{
+    // UpdateSelection will call InsertAtCore_NoContainsCheck
+    UpdateSelection(node, TreeNodeSelectionState::Selected);
+}
 
-    void RemoveAt(unsigned int index)
-    {
-        auto inner = GetVectorInnerImpl();
-        auto oldNode = winrt::get_self<TreeViewNode>(inner->GetAt(index));
-        // UpdateSelection will call RemoveAtCore
-        UpdateSelection(*oldNode, TreeNodeSelectionState::UnSelected);
-    }
+void SelectedTreeNodeVector::SetAt(unsigned int index, winrt::TreeViewNode const& node)
+{
+    RemoveAt(index);
+    InsertAt(index, node);
+}
 
-    void RemoveAtEnd()
-    {
-        RemoveAt(Size() - 1);
-    }
+void SelectedTreeNodeVector::RemoveAt(unsigned int index)
+{
+    auto inner = GetVectorInnerImpl();
+    auto oldNode = winrt::get_self<TreeViewNode>(inner->GetAt(index));
+    // UpdateSelection will call RemoveAtCore
+    UpdateSelection(*oldNode, TreeNodeSelectionState::UnSelected);
+}
 
-    void ReplaceAll(winrt::array_view<winrt::TreeViewNode const> nodes)
-    {
-        Clear();
+void SelectedTreeNodeVector::RemoveAtEnd()
+{
+    RemoveAt(Size() - 1);
+}
 
-        for (auto const& node : nodes)
-        {
-            Append(node);
-        }
-    }
+void SelectedTreeNodeVector::ReplaceAll(winrt::array_view<winrt::TreeViewNode const> nodes)
+{
+    Clear();
 
-    void Clear()
+    for (auto const& node : nodes)
     {
-        while (Size() > 0)
-        {
-            RemoveAtEnd();
-        }
+        Append(node);
     }
+}
 
-    bool Contains(winrt::TreeViewNode const& node)
+void SelectedTreeNodeVector::Clear()
+{
+    while (Size() > 0)
     {
-        uint32_t index;
-        return GetVectorInnerImpl()->IndexOf(node, index);
+        RemoveAtEnd();
     }
+}
+
+bool SelectedTreeNodeVector::Contains(winrt::TreeViewNode const& node)
+{
+    uint32_t index;
+    return GetVectorInnerImpl()->IndexOf(node, index);
+}
+
+// Default write methods will trigger TreeView visual updates.
+// If you want to update vector content without notifying TreeViewNodes, use "core" version of the methods.
+void SelectedTreeNodeVector::InsertAtCore_NoContainsCheck(unsigned int index, winrt::TreeViewNode const& node)
+{
+    MUX_ASSERT(!Contains(node));
+
+    GetVectorInnerImpl()->InsertAt(index, node);
 
-    // Default write methods will trigger TreeView visual updates.
-    // If you want to update vector content without notifying TreeViewNodes, use "core" version of the methods.
-    void InsertAtCore(unsigned int index, winrt::TreeViewNode const& node)
+    // Keep SelectedItems and SelectedNodes in sync
+    if (auto viewModel = m_viewModel.get())
     {
-        if (!Contains(node))
+        auto selectedItems = viewModel->GetSelectedItems();
+        if (selectedItems.Size() != Size())
         {
-            GetVectorInnerImpl()->InsertAt(index, node);
-
-            // Keep SelectedItems and SelectedNodes in sync
-            if (auto viewModel = m_viewModel.get())
+            if (auto listControl = viewModel->ListControl())
             {
-                auto selectedItems = viewModel->GetSelectedItems();
-                if (selectedItems.Size() != Size())
+                if (auto item = winrt::get_self<TreeViewList>(listControl)->ItemFromNode(node))
                 {
-                    if (auto listControl = viewModel->ListControl())
-                    {
-                        if (auto item = winrt::get_self<TreeViewList>(listControl)->ItemFromNode(node))
-                        {
-                            selectedItems.InsertAt(index, item);
-                            viewModel->TrackItemSelected(item);
-                        }
-                    }
+                    winrt::get_self<SelectedItemsVector>(selectedItems)->InsertAt_NoContainsCheck(index, item);
+                    viewModel->TrackItemSelected(item);
                 }
             }
         }
     }
+}
 
-    void RemoveAtCore(unsigned int index)
-    {
-        GetVectorInnerImpl()->RemoveAt(index);
+void SelectedTreeNodeVector::RemoveAtCore(unsigned int index)
+{
+    GetVectorInnerImpl()->RemoveAt(index);
 
-        // Keep SelectedItems and SelectedNodes in sync
-        if (auto viewModel = m_viewModel.get())
+    // Keep SelectedItems and SelectedNodes in sync
+    if (auto viewModel = m_viewModel.get())
+    {
+        auto selectedItems = viewModel->GetSelectedItems();
+        if (selectedItems.Size() != Size())
         {
-            auto selectedItems = viewModel->GetSelectedItems();
-            if (selectedItems.Size() != Size())
-            {
-                const auto item = selectedItems.GetAt(index);
-                selectedItems.RemoveAt(index);
-                viewModel->TrackItemUnselected(item);
-            }
+            const auto item = selectedItems.GetAt(index);
+            selectedItems.RemoveAt(index);
+            viewModel->TrackItemUnselected(item);
         }
     }
-};
+}
 
 #pragma endregion
 
@@ -153,106 +140,100 @@ class SelectedTreeNodeVector :
 // we can't use vector change events because the event already happened when event hander gets called.
 #pragma region SelectedItemsVector
 
-typedef typename VectorOptionsFromFlag<winrt::IInspectable, MakeVectorParam<VectorFlag::Observable, VectorFlag::DependencyObjectBase>()> SelectedItemsVectorOptions;
+bool SelectedItemsVector::IndexOf_OptimizedForRemove(winrt::IInspectable const& node, uint32_t& index)
+{
+    return GetVectorInnerImpl()->IndexOf_OptimizedForRemove(node, index);
+}
 
-class SelectedItemsVector :
-    public ReferenceTracker<
-    SelectedItemsVector,
-    reference_tracker_implements_t<typename SelectedItemsVectorOptions::VectorType>::type,
-    typename SelectedItemsVectorOptions::IterableType,
-    typename SelectedItemsVectorOptions::ObservableVectorType>,
-    public SelectedItemsVectorOptions::IVectorOwner
+void SelectedItemsVector::SetViewModel(ViewModel& viewModel)
 {
-    Implement_Vector_Read(SelectedItemsVectorOptions)
+    m_viewModel = viewModel.get_weak();
+}
 
-private:
-    winrt::weak_ref<ViewModel> m_viewModel{ nullptr };
+void SelectedItemsVector::Append(winrt::IInspectable const& item)
+{
+    InsertAt(Size(), item);
+}
 
-public:
-    void SetViewModel(ViewModel& viewModel)
+void SelectedItemsVector::InsertAt(unsigned int index, winrt::IInspectable const& item)
+{
+    if (!Contains(item))
     {
-        m_viewModel = viewModel.get_weak();
+        InsertAt_NoContainsCheck(index, item);
     }
+}
 
-    void Append(winrt::IInspectable const& item)
-    {
-        InsertAt(Size(), item);
-    }
+void SelectedItemsVector::InsertAt_NoContainsCheck(unsigned int index, winrt::IInspectable const& item)
+{
+    MUX_ASSERT(!Contains(item));
+    GetVectorInnerImpl()->InsertAt(index, item);
 
-    void InsertAt(unsigned int index, winrt::IInspectable const& item)
+    // Keep SelectedNodes and SelectedItems in sync
+    if (auto viewModel = m_viewModel.get())
     {
-        if (!Contains(item))
+        auto selectedNodes = viewModel->GetSelectedNodes();
+        if (selectedNodes.Size() != Size())
         {
-            GetVectorInnerImpl()->InsertAt(index, item);
-
-            // Keep SelectedNodes and SelectedItems in sync
-            if (auto viewModel = m_viewModel.get())
+            if (auto listControl = viewModel->ListControl())
             {
-                auto selectedNodes = viewModel->GetSelectedNodes();
-                if (selectedNodes.Size() != Size())
+                if (auto node = winrt::get_self<TreeViewList>(listControl)->NodeFromItem(item))
                 {
-                    if (auto listControl = viewModel->ListControl())
-                    {
-                        if (auto node = winrt::get_self<TreeViewList>(listControl)->NodeFromItem(item))
-                        {
-                            selectedNodes.InsertAt(index, node);
-                        }
-                    }
+                    selectedNodes.InsertAt(index, node);
                 }
             }
         }
     }
+}
 
-    void SetAt(unsigned int index, winrt::IInspectable const& item)
-    {
-        RemoveAt(index);
-        InsertAt(index, item);
-    }
+void SelectedItemsVector::SetAt(unsigned int index, winrt::IInspectable const& item)
+{
+    RemoveAt(index);
+    InsertAt(index, item);
+}
 
-    void RemoveAt(unsigned int index)
-    {
-        GetVectorInnerImpl()->RemoveAt(index);
+void SelectedItemsVector::RemoveAt(unsigned int index)
+{
+    GetVectorInnerImpl()->RemoveAt(index);
 
-        // Keep SelectedNodes and SelectedItems in sync
-        if (auto viewModel = m_viewModel.get())
+    // Keep SelectedNodes and SelectedItems in sync
+    if (auto viewModel = m_viewModel.get())
+    {
+        auto selectedNodes = viewModel->GetSelectedNodes();
+        if (Size() != selectedNodes.Size())
         {
-            auto selectedNodes = viewModel->GetSelectedNodes();
-            if (Size() != selectedNodes.Size())
-            {
-                selectedNodes.RemoveAt(index);
-            }
+            selectedNodes.RemoveAt(index);
         }
     }
+}
 
-    void RemoveAtEnd()
-    {
-        RemoveAt(Size() - 1);
-    }
-
-    void ReplaceAll(winrt::array_view<winrt::IInspectable const> items)
-    {
-        Clear();
+void SelectedItemsVector::RemoveAtEnd()
+{
+    RemoveAt(Size() - 1);
+}
 
-        for (auto const& node : items)
-        {
-            Append(node);
-        }
-    }
+void SelectedItemsVector::ReplaceAll(winrt::array_view<winrt::IInspectable const> items)
+{
+    Clear();
 
-    void Clear()
+    for (auto const& node : items)
     {
-        while (Size() > 0)
-        {
-            RemoveAtEnd();
-        }
+        Append(node);
     }
+}
 
-    bool Contains(winrt::IInspectable const& item)
+void SelectedItemsVector::Clear()
+{
+    while (Size() > 0)
     {
-        uint32_t index;
-        return GetVectorInnerImpl()->IndexOf(item, index);
+        RemoveAtEnd();
     }
-};
+}
+
+bool SelectedItemsVector::Contains(winrt::IInspectable const& item)
+{
+    uint32_t index;
+    return GetVectorInnerImpl()->IndexOf(item, index);
+}
 
 #pragma endregion
 
@@ -503,7 +484,7 @@ void ViewModel::Append(winrt::IInspectable const& value)
 {
     GetVectorInnerImpl()->Append(value);
     winrt::TreeViewNode newNode = value.as<winrt::TreeViewNode>();
-    
+
     // Hook up events and save tokens
     auto tvnNewNode = winrt::get_self<TreeViewNode>(newNode);
     m_collectionChangedEventTokenVector.push_back(tvnNewNode->ChildrenChanged({ this, &ViewModel::TreeViewNodeVectorChanged }));
@@ -773,7 +754,7 @@ void ViewModel::UpdateNodeSelection(winrt::TreeViewNode const& selectNode, TreeN
         switch (selectionState)
         {
         case TreeNodeSelectionState::Selected:
-            selectedNodes->InsertAtCore(selectedNodes->Size(), selectNode);
+            selectedNodes->InsertAtCore_NoContainsCheck(selectedNodes->Size(), selectNode);
             m_selectedNodeChildrenChangedEventTokenVector.push_back(winrt::get_self<TreeViewNode>(selectNode)->ChildrenChanged({ this, &ViewModel::SelectedNodeChildrenChanged }));
             break;
 
@@ -809,11 +790,26 @@ void ViewModel::UpdateSelectionStateOfDescendants(winrt::TreeViewNode const& tar
 {
     if (selectionState == TreeNodeSelectionState::PartialSelected) return;
 
-    for (auto const& childNode : targetNode.Children())
+    // For unselecting items, we process the list backwards. This prevents an item from being repeatedly shuffled
+    // towards the front of the list only to be removed at the end anyway.
+    if (selectionState == TreeNodeSelectionState::UnSelected)
+    {
+        for (int i = targetNode.Children().Size() - 1; i >= 0; i--)
+        {
+            const auto& childNode = targetNode.Children().GetAt(i);
+            UpdateSelectionStateOfDescendants(childNode, selectionState);
+            UpdateNodeSelection(childNode, selectionState);
+            NotifyContainerOfSelectionChange(childNode, selectionState);
+        }
+    }
+    else
     {
-        UpdateNodeSelection(childNode, selectionState);
-        UpdateSelectionStateOfDescendants(childNode, selectionState);
-        NotifyContainerOfSelectionChange(childNode, selectionState);
+        for (auto const& childNode : targetNode.Children())
+        {
+            UpdateNodeSelection(childNode, selectionState);
+            UpdateSelectionStateOfDescendants(childNode, selectionState);
+            NotifyContainerOfSelectionChange(childNode, selectionState);
+        }
     }
 }
 
@@ -912,7 +908,7 @@ winrt::TreeViewNode ViewModel::GetAssociatedNode(winrt::IInspectable item)
             return treeViewImpl->GetAssociatedNode(item);
         }
     }
-    
+
     return nullptr;
 }
 
@@ -929,7 +925,7 @@ void ViewModel::TreeViewNodeVectorChanged(winrt::TreeViewNode const& sender, win
     switch (collectionChange)
     {
         // Reset case, commonly seen when a TreeNode is cleared.
-        // removes all nodes that need removing then 
+        // removes all nodes that need removing then
         // toggles a collapse / expand to ensure order.
     case (winrt::CollectionChange::Reset):
     {
diff --git a/controls/dev/TreeView/ViewModel.h b/controls/dev/TreeView/ViewModel.h
index 265b9b94e1..b53842a292 100644
--- a/controls/dev/TreeView/ViewModel.h
+++ b/controls/dev/TreeView/ViewModel.h
@@ -8,7 +8,7 @@
 using TreeNodeSelectionState = TreeViewNode::TreeNodeSelectionState;
 using ViewModelVectorOptions = VectorOptionsFromFlag<winrt::IInspectable, MakeVectorParam<VectorFlag::Observable, VectorFlag::DependencyObjectBase>()>;
 
-class ViewModel : 
+class ViewModel :
     public ReferenceTracker<
         ViewModel,
         reference_tracker_implements_t<typename ViewModelVectorOptions::VectorType>::type,
@@ -113,3 +113,85 @@ class ViewModel :
     void BeginSelectionChanges();
     void EndSelectionChanges();
 };
+
+
+// Need to update node selection states on UI before vector changes.
+// Listen on vector change events don't solve the problem because the event already happened when the event handler gets called.
+// i.e. the node is already gone when we get to ItemRemoved callback.
+#pragma region SelectedTreeNodeVector
+
+typedef typename VectorOptionsFromFlag<winrt::TreeViewNode, MakeVectorParam<VectorFlag::Observable, VectorFlag::DependencyObjectBase>()> SelectedTreeNodeVectorOptions;
+
+class SelectedTreeNodeVector :
+    public ReferenceTracker<
+        SelectedTreeNodeVector,
+        reference_tracker_implements_t<typename SelectedTreeNodeVectorOptions::VectorType>::type,
+        typename TreeViewNodeVectorOptions::IterableType,
+        typename TreeViewNodeVectorOptions::ObservableVectorType>,
+    public TreeViewNodeVectorOptions::IVectorOwner
+{
+    Implement_Vector_Read(SelectedTreeNodeVectorOptions)
+
+private:
+    winrt::weak_ref<ViewModel> m_viewModel{ nullptr };
+
+    void UpdateSelection(winrt::TreeViewNode const& node, TreeNodeSelectionState state);
+
+public:
+    void SetViewModel(ViewModel& viewModel);
+    void Append(winrt::TreeViewNode const& node);
+    void InsertAt(unsigned int index, winrt::TreeViewNode const& node);
+    void SetAt(unsigned int index, winrt::TreeViewNode const& node);
+    void RemoveAt(unsigned int index);
+    void RemoveAtEnd();
+    void ReplaceAll(winrt::array_view<winrt::TreeViewNode const> nodes);
+    void Clear();
+    bool Contains(winrt::TreeViewNode const& node);
+
+    std::function<bool(winrt::TreeViewNode const& value, uint32_t& index)> GetCustomIndexOfFunction() override { return [this](winrt::TreeViewNode const& value, uint32_t& index) { return IndexOf_OptimizedForRemove(value, index); }; }
+    bool IndexOf_OptimizedForRemove(winrt::TreeViewNode const& node, uint32_t& index);
+
+    // Default write methods will trigger TreeView visual updates.
+    // If you want to update vector content without notifying TreeViewNodes, use "core" version of the methods.
+    void InsertAtCore_NoContainsCheck(unsigned int index, winrt::TreeViewNode const& node);
+    void RemoveAtCore(unsigned int index);
+};
+
+#pragma endregion
+
+// Similar to SelectedNodesVector above, we need to make decisions before the item is inserted or removed.
+// we can't use vector change events because the event already happened when event hander gets called.
+#pragma region SelectedItemsVector
+
+typedef typename VectorOptionsFromFlag<winrt::IInspectable, MakeVectorParam<VectorFlag::Observable, VectorFlag::DependencyObjectBase>()> SelectedItemsVectorOptions;
+
+class SelectedItemsVector :
+    public ReferenceTracker<
+    SelectedItemsVector,
+    reference_tracker_implements_t<typename SelectedItemsVectorOptions::VectorType>::type,
+    typename SelectedItemsVectorOptions::IterableType,
+    typename SelectedItemsVectorOptions::ObservableVectorType>,
+    public SelectedItemsVectorOptions::IVectorOwner
+{
+    Implement_Vector_Read(SelectedItemsVectorOptions)
+
+private:
+    winrt::weak_ref<ViewModel> m_viewModel{ nullptr };
+
+public:
+    void SetViewModel(ViewModel& viewModel);
+    void Append(winrt::IInspectable const& item);
+    void InsertAt(unsigned int index, winrt::IInspectable const& item);
+    void InsertAt_NoContainsCheck(unsigned int index, winrt::IInspectable const& item);
+    void SetAt(unsigned int index, winrt::IInspectable const& item);
+    void RemoveAt(unsigned int index);
+    void RemoveAtEnd();
+    void ReplaceAll(winrt::array_view<winrt::IInspectable const> items);
+    void Clear();
+    bool Contains(winrt::IInspectable const& item);
+
+    std::function<bool(winrt::IInspectable const& value, uint32_t& index)> GetCustomIndexOfFunction() override { return [this](winrt::IInspectable const& value, uint32_t& index) { return IndexOf_OptimizedForRemove(value, index); }; }
+    bool IndexOf_OptimizedForRemove(winrt::IInspectable const& node, uint32_t& index);
+};
+
+#pragma endregion
diff --git a/dxaml/xcp/components/comptree/DCompTreeHost.cpp b/dxaml/xcp/components/comptree/DCompTreeHost.cpp
index d8091a2b60..0a13a939e4 100644
--- a/dxaml/xcp/components/comptree/DCompTreeHost.cpp
+++ b/dxaml/xcp/components/comptree/DCompTreeHost.cpp
@@ -1099,6 +1099,14 @@ _Check_return_ HRESULT DCompTreeHost::ConnectXamlIslandTargetRoots()
 
                 renderData.contentConnected = true;
 
+                // If this is our first island and we need a Frame visual then add it here.  Note that at this point the
+                // commit has already been done so we need to recommit.
+                if (m_needsFrameRateVisual)
+                {
+                    ShowUIThreadCounters();
+                    IFC_RETURN(CommitMainDevice());
+                }
+
                 continue;
             }
         }
@@ -1667,6 +1675,8 @@ void DCompTreeHost::UpdateUIThreadCounters(
 
 void DCompTreeHost::ShowUIThreadCounters()
 {
+    m_needsFrameRateVisual = false;  // We are setting up the frame visual here.
+
     if (m_frameRateVisual) return; // Already have one and don't need another;
 
     wrl::ComPtr<WUComp::IContainerVisual> hostVisual = m_hwndVisual;
@@ -1682,6 +1692,15 @@ void DCompTreeHost::ShowUIThreadCounters()
             wrl::ComPtr<WUComp::IVisual> rootVisual = iter->first->GetRootVisual();
             LPCWSTR ROOT_HOST_TAG = L"_XAML_Root_Frame_Host";
 
+            // If we don't have a root visual then this frame is being rendered before have completely set up our environment This can happen on the first
+            // frame or a frame where all existing islands are torn down and a new one is added.  If so, we have to wait until the visual is setup as
+            // our root visual.
+            if (!rootVisual)
+            {
+                m_needsFrameRateVisual = true;
+                return;
+            }
+
             // We want to add the frame rate visual as a sibling to the root visual, but in our initial configuration, we have added the Xaml root visual as
             // the root of the content island.  So we start by attempting to get the parent of the root visual and if null is returned, we know that our
             // our root visual is directly under the content island and so we create our own container visual to be used as the content island root and
@@ -2697,15 +2716,26 @@ void DCompTreeHost::RemoveXamlIslandTarget(_In_ CXamlIslandRoot* xamlIslandRoot)
 {
     // Remove render data for XamlIslandRoot, if it exists
     auto islandData = m_islandRenderData.find(xamlIslandRoot);
-    if (islandData != m_islandRenderData.end())
-    {
-        m_islandRenderData.erase(islandData);
-    }
-    else
+
+    if (islandData == m_islandRenderData.end())
     {
         // Islands should already have render data
         IFCFAILFAST(E_FAIL);
     }
+
+    // If this is the first island and we are showing frame data, then remove it and reshow it on the next island
+    bool refreshFrameRateVisual = m_frameRateVisual && islandData == m_islandRenderData.begin();
+    if (refreshFrameRateVisual)
+    {
+        HideUIThreadCounters();
+    }
+    
+    m_islandRenderData.erase(islandData);
+
+    if (refreshFrameRateVisual)
+    {
+        ShowUIThreadCounters();
+    }
 }
 
 _Check_return_ HRESULT DCompTreeHost::GetPointerSourceForElement(
diff --git a/dxaml/xcp/components/comptree/inc/DCompTreeHost.h b/dxaml/xcp/components/comptree/inc/DCompTreeHost.h
index 22adbfe02f..aa53397f88 100644
--- a/dxaml/xcp/components/comptree/inc/DCompTreeHost.h
+++ b/dxaml/xcp/components/comptree/inc/DCompTreeHost.h
@@ -525,6 +525,7 @@ class DCompTreeHost : public CXcpObjectBase<IObject>
     bool m_disableAtlas;
     bool m_useExplicitAtlasHint;
     bool m_isInitialized;
+    bool m_needsFrameRateVisual = false;
 
     XRECTF m_backgroundRect;
 
diff --git a/dxaml/xcp/core/core/elements/depends.cpp b/dxaml/xcp/core/core/elements/depends.cpp
index 741771f9d9..7ebc7bddea 100644
--- a/dxaml/xcp/core/core/elements/depends.cpp
+++ b/dxaml/xcp/core/core/elements/depends.cpp
@@ -335,8 +335,8 @@ wrl::ComPtr<ixp::IIslandInputSitePartner> CDependencyObject::GetElementIslandInp
         }
     }
 
-    // By default, return the application-wide IslandInputSite that was registered with InputServices on startup.
-    return coreServices->GetInputServices()->GetApplicationIslandInputSite();
+    // By default, return the primary IslandInputSite that was registered with InputServices on startup.
+    return coreServices->GetInputServices()->GetPrimaryRegisteredIslandInputSite();
 }
 
 HWND CDependencyObject::GetElementPositioningWindow()
diff --git a/dxaml/xcp/core/dll/xcpcore.cpp b/dxaml/xcp/core/dll/xcpcore.cpp
index 8714216947..649dddace1 100644
--- a/dxaml/xcp/core/dll/xcpcore.cpp
+++ b/dxaml/xcp/core/dll/xcpcore.cpp
@@ -8376,7 +8376,7 @@ _Check_return_ HRESULT CCoreServices::RecoverFromDeviceLost()
             // explicitly cleaned up.
             if (cleanupDComp && m_inputServices)
             {
-                m_inputServices->ResetCrossSlideService();
+                m_inputServices->ResetAllCrossSlideServices();
             }
         }
 
diff --git a/dxaml/xcp/core/inc/InputServices.h b/dxaml/xcp/core/inc/InputServices.h
index 34117cc385..80dc26d98d 100644
--- a/dxaml/xcp/core/inc/InputServices.h
+++ b/dxaml/xcp/core/inc/InputServices.h
@@ -400,8 +400,9 @@ class CInputServices final
     void SetCoreWindow(_In_ wuc::ICoreWindow* pCoreWindow);
     wuc::ICoreWindow* GetCoreWindow() const;
 
-    void SetApplicationIslandInputSite(_In_ ixp::IIslandInputSitePartner* pIslandInputSite);
-    wrl::ComPtr<ixp::IIslandInputSitePartner> GetApplicationIslandInputSite() const { return m_islandInputSite; }
+    void RegisterIslandInputSite(_In_ ixp::IIslandInputSitePartner* pIslandInputSite);
+    void UnregisterIslandInputSite(_In_ ixp::IIslandInputSitePartner* pIslandInputSite);
+    wrl::ComPtr<ixp::IIslandInputSitePartner> GetPrimaryRegisteredIslandInputSite() const;
 
     void SetLastInputDeviceType(XPointerInputType deviceType)
     {
@@ -833,7 +834,7 @@ class CInputServices final
     _Check_return_ HRESULT UpdateCursor(_In_ CDependencyObject* pVisualInTargetIsland, _In_ XINT32 bUnset = FALSE);
 
     void Reset();
-    void ResetCrossSlideService();
+    void ResetAllCrossSlideServices();
     void DestroyPointerObjects();
 
     _Check_return_ HRESULT ObjectLeavingTree(_In_ CDependencyObject *pObject);
@@ -1078,7 +1079,7 @@ class CInputServices final
 
     bool CanDMContainerInitialize() const
     {
-        return (nullptr != m_islandInputSite);
+        return !m_islandInputSiteRegistrations.empty();
     }
 
     bool CanDMContainerInitialize(_In_ CUIElement* const dmContainer) const
@@ -1560,23 +1561,71 @@ class CInputServices final
     xvector<CSecondaryContentRelationship*>* m_pSecondaryContentRelationshipsToBeApplied;
 
     xchainedmap<CUIElement*, IPALDirectManipulationService*>* m_pDMServices;
-    IPALDirectManipulationService* m_pDMCrossSlideService; // Common DM manager used to handle all cross-slide viewports for cross-slide support
-    std::shared_ptr<DirectManipulationServiceSharedState> m_DMServiceSharedState;
+    std::shared_ptr<DirectManipulationServiceSharedState> m_DMServiceSharedState; // This is per-thread shared state, not per-ContentIsland.
 
     XUINT32 m_cCrossSlideContainers; // Number of registered cross-slide containers.
     std::unique_ptr<std::vector < xref::weakref_ptr<CUIElement>>> m_pDMContainersNeedingInitialization;
-    
-    wrl::ComPtr<ixp::IIslandInputSitePartner> m_islandInputSite;
+
+    // The DMCrossSlideService can only be shared across CUIElements on the *same* ContentIsland.
+    // Each ContentIsland has its own IslandInputSite and therefore its own underlying Input HWND.
+    // InputServices is per-thread, but each thread can have multiple ContentIslands.
+    // We cannot use just one IslandInputRegistration across different ContentIslands.
+    struct IslandInputSiteRegistration
+    {
+        explicit IslandInputSiteRegistration(ixp::IIslandInputSitePartner* islandInputSite) : m_islandInputSite{ islandInputSite } {}
+
+        [[nodiscard]] bool Match(ixp::IIslandInputSitePartner* islandInputSite) const
+        {
+            if (nullptr == islandInputSite)
+            {
+                return false;
+            }
+
+            wrl::ComPtr<ixp::IIslandInputSitePartner> querySite{ islandInputSite };
+            wrl::ComPtr<IUnknown> querySiteAsIUnknown{ nullptr };
+            FAIL_FAST_IF_FAILED(querySite.As(&querySiteAsIUnknown));
+
+            wrl::ComPtr<IUnknown> mySiteAsIUnknown{ nullptr };
+            FAIL_FAST_IF_FAILED(m_islandInputSite.As(&mySiteAsIUnknown));
+            return (mySiteAsIUnknown.Get() == querySiteAsIUnknown.Get());
+        }
+
+        [[nodiscard]] bool Match(CUIElement* uiElement) const
+        {
+            if (nullptr == uiElement)
+            {
+                return false;
+            }
+            return Match(uiElement->GetElementIslandInputSite().Get());
+        }
+
+        [[nodiscard]] wrl::ComPtr<ixp::IIslandInputSitePartner> IslandInputSite() const { return m_islandInputSite; }
+
+        [[nodiscard]] wrl::ComPtr<IPALDirectManipulationService> DMCrossSlideService() const { return m_DMCrossSlideService; }
+        void DMCrossSlideService(_In_ IPALDirectManipulationService* pDMCrossSlideService) { m_DMCrossSlideService = pDMCrossSlideService; }
+
+        [[nodiscard]] bool ShouldRegisterDMViewportCallback() const { return m_shouldRegisterDMViewportCallback; }
+        void ShouldRegisterDMViewportCallback(bool shouldRegisterDMViewportCallback) { m_shouldRegisterDMViewportCallback = shouldRegisterDMViewportCallback; }
+
+    private:
+        wrl::ComPtr<ixp::IIslandInputSitePartner> m_islandInputSite { nullptr };
+        wrl::ComPtr<IPALDirectManipulationService> m_DMCrossSlideService{ nullptr }; // Common DM manager used to handle all cross-slide viewports for cross-slide support per ContentIsland.
+
+        // For deciding whether or not DMViewportHandler needs to be registered on a CrossSlide viewport. True if at least one UIElement is draggable.
+        bool m_shouldRegisterDMViewportCallback = false;
+    };
+    std::vector<IslandInputSiteRegistration> m_islandInputSiteRegistrations;
+    IslandInputSiteRegistration& GetIslandInputSiteRegistrationForUIElement(CUIElement* pUIElement);
+    IPALDirectManipulationService* GetDMCrossSlideServiceNoRefForUIElement(_In_ CUIElement* pUIElement) const;
+
+    // For deciding whether or not DMViewportHandler needs to be registered on a CrossSlide viewport. True if at least one UIElement is draggable and no IslandInputSite has yet been registered.
+    bool m_shouldRegisterPrimaryDMViewportCallback = false;
 
 #ifdef DM_DEBUG
     bool m_fIsDMInfoTracingEnabled : 1;
     bool m_fIsDMVerboseInfoTracingEnabled : 1;
 #endif // DM_DEBUG
 
-    // for deciding whether or not DMViewportHandler needs to be registered
-    // on a CrossSlide viewport. True if at least one UIElement is draggable.
-    bool m_shouldRegisterDMViewportCallback = false;
-
     // Holds on to DM content/shared transform for sticky headers as we synchronize changing their curves
     std::vector<DMDeferredRelease> m_vecDeferredRelease;
 
diff --git a/dxaml/xcp/core/inc/VisualTree.h b/dxaml/xcp/core/inc/VisualTree.h
index 1c7a328a5a..d18ebd5ae9 100644
--- a/dxaml/xcp/core/inc/VisualTree.h
+++ b/dxaml/xcp/core/inc/VisualTree.h
@@ -134,6 +134,9 @@ class VisualTree final
 
     xref::details::control_block* EnsureControlBlock();
 
+    void SetShouldConstrainPopupsToWorkArea(bool value) { m_shouldConstrainPopupsToWorkArea = value; }
+    bool ShouldConstrainPopupsToWorkArea() const { return m_shouldConstrainPopupsToWorkArea; }
+
 private:
     static VisualTree* GetVisualTreeViaTreeWalkNoRef(_In_ CDependencyObject* element, LookupOptions options = LookupOptions::WarningIfNotFound);
 
@@ -192,6 +195,15 @@ class VisualTree final
     // True if the VisualTree is serving as the main visual tree for a XAML app.  Otherwise, it's for a XamlIslandRoot
     bool IsMainVisualTree() { return m_rootVisual != nullptr; }
 
+    //
+    // DesktopWindowXamlSource.ShouldConstrainPopupsToWorkArea property - normally Xaml places all popups inside the
+    // work area of the display, which is the portion of the screen not obscured by the system taskbar or by application
+    // desktop toolbars (see "SPI_GETWORKAREA" and DisplayArea.WorkArea). This is a problem for docked components that
+    // can and want to open popups outside the work area, so we have those components mark their DWXSes and have Xaml
+    // constrain their popups to the display bounds instead.
+    //
+    bool m_shouldConstrainPopupsToWorkArea { true };
+
     bool m_bIsRootScrollViewerAddedToRoot : 1;
     bool m_shutdownInProgress : 1;
     bool m_isShutdown : 1;
diff --git a/dxaml/xcp/core/input/InputServices.cpp b/dxaml/xcp/core/input/InputServices.cpp
index 5ad1e0bb30..00eedc48c8 100644
--- a/dxaml/xcp/core/input/InputServices.cpp
+++ b/dxaml/xcp/core/input/InputServices.cpp
@@ -97,10 +97,8 @@ CInputServices::Init(_In_ CCoreServices *pCoreService)
     m_pSecondaryContentRelationshipsToBeApplied = NULL;
 
     m_pDMServices = NULL;
-    m_pDMCrossSlideService = NULL;
     m_DMServiceSharedState = std::make_shared<DirectManipulationServiceSharedState>();
     m_cCrossSlideContainers = 0;
-    m_islandInputSite = nullptr;
 
     if (!static_cast<CCoreServices*>(pCoreService)->IsTSF3Enabled())
     {
@@ -122,7 +120,8 @@ void CInputServices::Reset()
 {
     ReleaseInterface(m_pEventManager);
 
-    ReleaseInterface(m_pDMCrossSlideService);
+    ResetAllCrossSlideServices();
+    m_islandInputSiteRegistrations.clear();
     IGNOREHR(DeleteDMViewports());
     IGNOREHR(DeleteDMCrossSlideViewports());
     IGNOREHR(DeleteSecondaryContentRelationshipsToBeApplied());
@@ -135,37 +134,108 @@ void CInputServices::Reset()
     m_pCoreService = nullptr;
 }
 
-void CInputServices::ResetCrossSlideService()
+void CInputServices::ResetAllCrossSlideServices()
 {
-    if (m_pDMCrossSlideService)
+    for (auto& islandInputSiteRegistration : m_islandInputSiteRegistrations)
     {
-        m_pDMCrossSlideService->DeactivateDirectManipulationManager();
-        ReleaseInterface(m_pDMCrossSlideService);
+        auto cpDMCrossSlideService = islandInputSiteRegistration.DMCrossSlideService();
+        if (nullptr != cpDMCrossSlideService)
+        {
+            cpDMCrossSlideService->DeactivateDirectManipulationManager();
+            islandInputSiteRegistration.DMCrossSlideService(nullptr);
+        }
     }
 }
 
-void CInputServices::SetApplicationIslandInputSite(_In_ ixp::IIslandInputSitePartner* pIslandInputSite)
+void CInputServices::RegisterIslandInputSite(_In_ ixp::IIslandInputSitePartner* pIslandInputSite)
 {
-    wrl::ComPtr<IUnknown> previousIslandInputSiteAsIUnknown{ nullptr };
-    if (nullptr != m_islandInputSite)
+    auto iter = std::find_if(
+        m_islandInputSiteRegistrations.cbegin(),
+        m_islandInputSiteRegistrations.cend(),
+        [&pIslandInputSite](IslandInputSiteRegistration const& entry) { return entry.Match(pIslandInputSite); });
+
+    if (iter == m_islandInputSiteRegistrations.end())
     {
-        FAIL_FAST_IF_FAILED(m_islandInputSite.As(&previousIslandInputSiteAsIUnknown));
+        // Not yet registered.
+        m_islandInputSiteRegistrations.push_back(IslandInputSiteRegistration{ pIslandInputSite });
+        if (m_shouldRegisterPrimaryDMViewportCallback)
+        {
+            // This will only be true if we had no IslandInputSites registered when a CUIElement tried to register a CrossSlide DManip container.
+            // Transfer the pending callback to the registration entry we just added.
+            m_islandInputSiteRegistrations.at(0).ShouldRegisterDMViewportCallback(true);
+            m_shouldRegisterPrimaryDMViewportCallback = false;
+        }
     }
+}
 
-    m_islandInputSite = pIslandInputSite;
+void CInputServices::UnregisterIslandInputSite(_In_ ixp::IIslandInputSitePartner* pIslandInputSite)
+{
+    auto iter = std::find_if(
+        m_islandInputSiteRegistrations.begin(),
+        m_islandInputSiteRegistrations.end(),
+        [&pIslandInputSite](IslandInputSiteRegistration const& entry) { return entry.Match(pIslandInputSite); });
 
-    wrl::ComPtr<IUnknown> newIslandInputSiteAsIUnknown{ nullptr };
-    if (nullptr != m_islandInputSite)
+    if (iter != m_islandInputSiteRegistrations.end())
     {
-        FAIL_FAST_IF_FAILED(m_islandInputSite.As(&newIslandInputSiteAsIUnknown));
+        // Found a match, clean up the DMCrossSlideService, if any.
+        auto cpDMCrossSlideService = iter->DMCrossSlideService();
+        if (nullptr != cpDMCrossSlideService)
+        {
+            cpDMCrossSlideService->DeactivateDirectManipulationManager();
+            iter->DMCrossSlideService(nullptr);
+        }
+
+        // Delete the registration entry.
+        m_islandInputSiteRegistrations.erase(iter);
     }
+}
 
-    if (previousIslandInputSiteAsIUnknown.Get() != newIslandInputSiteAsIUnknown.Get())
+wrl::ComPtr<ixp::IIslandInputSitePartner> CInputServices::GetPrimaryRegisteredIslandInputSite() const
+{
+    if (m_islandInputSiteRegistrations.empty())
     {
-        // The cross slide service directly references the IslandInputSite we created it with
-        // so if the IslandInputSite changes, we need to recreate the service.
-        ResetCrossSlideService();
+        return nullptr;
     }
+
+    // Return the oldest registered IslandInputSite with input services that is still valid for this thread.
+    return m_islandInputSiteRegistrations.at(0).IslandInputSite();
+}
+
+CInputServices::IslandInputSiteRegistration& CInputServices::GetIslandInputSiteRegistrationForUIElement(CUIElement* pUIElement)
+{
+    auto iter = std::find_if(
+        m_islandInputSiteRegistrations.begin(),
+        m_islandInputSiteRegistrations.end(),
+        [&pUIElement](IslandInputSiteRegistration const& entry) { return entry.Match(pUIElement); });
+
+    // If the CUIElement is not yet on a ContentIsland, CUIElement->GetElementIslandInputSite (used in the Match function) will return the
+    // "Primary" IslandInputSite as a fallback which corresponds to the "main", "first", or "oldest valid" IslandInputSite
+    // registered with InputServices (i.e. the first element in m_islandInputSiteRegistrations).
+    // It calls the CInputServices::GetPrimaryRegisteredIslandInputSite() just above. See depends.cpp for CDependencyObject::GetElementIslandInputSite.
+    // If m_islandInputSiteRegistrations is empty, we handle this as a special case, see CInputServices::RegisterDirectManipulationCrossSlideContainer.
+    //
+    // This is fragile, since it does mean the CUIElement could be placed on a different ContentIsland leading to potentially
+    // wonky DManip behavior. However, it does match existing behavior.
+    //
+    // We should *never* be in a situation where a CUIElement *has* an ElementIslandInputSite via a XamlIslandRoot that has somehow not already been registered.
+    FAIL_FAST_IF(iter == m_islandInputSiteRegistrations.end());
+
+    return *iter;
+}
+
+IPALDirectManipulationService* CInputServices::GetDMCrossSlideServiceNoRefForUIElement(_In_ CUIElement* pUIElement) const
+{
+    auto iter = std::find_if(
+        m_islandInputSiteRegistrations.cbegin(),
+        m_islandInputSiteRegistrations.cend(),
+        [&pUIElement](IslandInputSiteRegistration const& entry) { return entry.Match(pUIElement); });
+
+    if (iter != m_islandInputSiteRegistrations.cend())
+    {
+        return iter->DMCrossSlideService().Get();
+    }
+
+    return nullptr;
 }
 
 //------------------------------------------------------------------------
@@ -3016,10 +3086,13 @@ CInputServices::GetUnderlyingInputHwndFromIslandInputSite(_In_opt_ ixp::IIslandI
     if (nullptr != pIslandInputSite)
     {
         ABI::Microsoft::UI::WindowId inputWindowId;
-        IFCFAILFAST(pIslandInputSite->get_UnderlyingInputWindowId(&inputWindowId));
-        HWND inputHwnd;
-        IFCFAILFAST(Windowing_GetWindowFromWindowId(inputWindowId, &inputHwnd));
-        return inputHwnd;
+        if (S_OK == pIslandInputSite->get_UnderlyingInputWindowId(&inputWindowId))
+        {
+            // The IslandInputSite might already be closed, in which case we should just return nullptr since there is no valid HWND.
+            HWND inputHwnd;
+            IFCFAILFAST(Windowing_GetWindowFromWindowId(inputWindowId, &inputHwnd));
+            return inputHwnd;
+        }
     }
 
     return nullptr;
@@ -3138,20 +3211,32 @@ CInputServices::RegisterDirectManipulationCrossSlideContainer(
 
         IFC(pDMCrossSlideContainer->CanDrag(&fIsDraggable));
 
-        if (fIsDraggable && !m_shouldRegisterDMViewportCallback)
+        if (fIsDraggable && m_islandInputSiteRegistrations.empty())
         {
-            if (m_pDMCrossSlideService == nullptr)
-            {
-                // Register DMViewportCallback when DMCrossSlideService is set up.
-                m_shouldRegisterDMViewportCallback = true;
-            }
-            else
+            // No IslandInputSites have been registered yet! That means this CUIElement isn't yet in a tree connected to any ContentIsland.
+            // Warning: potential fragility - continuing the existing assumption that the CUIElement will eventually be placed on the first
+            // ContentIsland that will register its IslandInputSite with InputServices. If it is placed on a different ContentIsland, DManip
+            // will likely not work.
+            m_shouldRegisterPrimaryDMViewportCallback = true;
+        }
+        else
+        {
+            auto& islandInputSiteRegistration = GetIslandInputSiteRegistrationForUIElement(pDMCrossSlideContainer);
+            if (fIsDraggable && !islandInputSiteRegistration.ShouldRegisterDMViewportCallback())
             {
-                // if DMViewportCallback is not already registered on m_pDMCrossSlideService when DMCrossSlideService is already set up.
-                xref_ptr<IXcpDirectManipulationViewportEventHandler> spDirectManipulationViewportEventHandler;
+                if (islandInputSiteRegistration.DMCrossSlideService() == nullptr)
+                {
+                    // Register DMViewportCallback when DMCrossSlideService is set up.
+                    islandInputSiteRegistration.ShouldRegisterDMViewportCallback(true);
+                }
+                else
+                {
+                    // if DMViewportCallback is not already registered on DMCrossSlideService when DMCrossSlideService is already set up.
+                    xref_ptr<IXcpDirectManipulationViewportEventHandler> spDirectManipulationViewportEventHandler;
 
-                IFC(GetDirectManipulationViewportEventHandler(spDirectManipulationViewportEventHandler.ReleaseAndGetAddressOf()));
-                IFC(m_pDMCrossSlideService->RegisterViewportEventHandler(spDirectManipulationViewportEventHandler.get()));
+                    IFC(GetDirectManipulationViewportEventHandler(spDirectManipulationViewportEventHandler.ReleaseAndGetAddressOf()));
+                    IFC(islandInputSiteRegistration.DMCrossSlideService()->RegisterViewportEventHandler(spDirectManipulationViewportEventHandler.get()));
+                }
             }
         }
 
@@ -3230,12 +3315,13 @@ CInputServices::DirectManipulationCrossSlideContainerCompleted(
     ASSERT(pCrossSlideViewport);
     if (pCrossSlideViewport)
     {
-        ASSERT(m_pDMCrossSlideService);
+        auto* pDMCrossSlideService = GetDMCrossSlideServiceNoRefForUIElement(pDMCrossSlideContainer);
+        ASSERT(pDMCrossSlideService);
 
         IFC(pCrossSlideViewport->GetContactIdCount(&cContactIds));
         if (cContactIds > 0)
         {
-            IFC(m_pDMCrossSlideService->ReleaseAllContacts(pCrossSlideViewport));
+            IFC(pDMCrossSlideService->ReleaseAllContacts(pCrossSlideViewport));
         }
 
         IFC(UnregisterCrossSlideViewport(pCrossSlideViewport));
@@ -3363,14 +3449,15 @@ CInputServices::UpdateCrossSlideViewportConfigurations(
                     configuration = static_cast<XDMConfigurations>(configuration & (XcpDMConfigurationPanX | XcpDMConfigurationPanY));
                     if (configuration == XcpDMConfigurationPanX || configuration == XcpDMConfigurationPanY)
                     {
-                        ASSERT(m_pDMCrossSlideService);
-                        IFC_RETURN(m_pDMCrossSlideService->AddViewportConfiguration(
+                        auto* pDMCrossSlideService = GetDMCrossSlideServiceNoRefForUIElement(pViewport->GetDMContainerNoRef());
+                        ASSERT(pDMCrossSlideService);
+                        IFC_RETURN(pDMCrossSlideService->AddViewportConfiguration(
                             pCrossSlideViewport,
                             TRUE /*fIsCrossSlideViewport*/,
                             FALSE /*fIsDragDrop*/,
                             configuration));
                         // fCausedRunningStatus is ignored because we don't track cross-slide viewport statuses.
-                        IFC_RETURN(m_pDMCrossSlideService->EnableViewport(pCrossSlideViewport, fCausedRunningStatus));
+                        IFC_RETURN(pDMCrossSlideService->EnableViewport(pCrossSlideViewport, fCausedRunningStatus));
                         IFC_RETURN(AddCrossSlideViewportContactId(pointerId, pCrossSlideViewport, pfContactFailure));
                         if (*pfContactFailure)
                         {
@@ -3553,32 +3640,36 @@ CInputServices::InitializeDirectManipulationContainers()
 
         // Only pre-create the DM manager dedicated to cross-slide viewports when a DManip container
         // and real viewport is instantiated.
-        if (!m_pDMCrossSlideService)
+        for (auto& islandInputSiteRegistration : m_islandInputSiteRegistrations)
         {
-            // Pre-create a DM manager for potential cross-slide handling, using cross-slide viewports
-            IFC_RETURN(gps->GetDirectManipulationService(m_DMServiceSharedState, &m_pDMCrossSlideService));
-            ASSERT(m_pDMCrossSlideService);
+            if (!islandInputSiteRegistration.DMCrossSlideService())
+            {
+                // Pre-create a DM manager for potential cross-slide handling, using cross-slide viewports
+                wrl::ComPtr<IPALDirectManipulationService> cpDMCrossSlideService{ nullptr };
+                IFC_RETURN(gps->GetDirectManipulationService(m_DMServiceSharedState, &cpDMCrossSlideService));
+                ASSERT(cpDMCrossSlideService);
 
 #ifdef DM_DEBUG
-            if (m_fIsDMInfoTracingEnabled)
-            {
-                IGNOREHR(gps->DebugTrace(static_cast<XDebugTraceType>(XCP_TRACE_DM_INPUT_MANAGER | DMIM_DBG) /*traceType*/, L"DMIM[0x%p]:  InitializeDirectManipulationContainers. Created m_pDMCrossSlideService=0x%p. m_cCrossSlideContainers=%d.",
-                    this, m_pDMCrossSlideService, m_cCrossSlideContainers));
-            }
+                if (m_fIsDMInfoTracingEnabled)
+                {
+                    IGNOREHR(gps->DebugTrace(static_cast<XDebugTraceType>(XCP_TRACE_DM_INPUT_MANAGER | DMIM_DBG) /*traceType*/, L"DMIM[0x%p]:  InitializeDirectManipulationContainers. Created cpDMCrossSlideService=0x%p. m_cCrossSlideContainers=%d.",
+                        this, cpDMCrossSlideService.Get(), m_cCrossSlideContainers));
+                }
 #endif // DM_DEBUG
-            // CInputServices is storing an IslandInputSite which is a per-tree (XamlIslandRoot) object, but CInputServices is a per-thread type.
-            // This is matching the previous behavior where CInputServices was storing an application hwnd directly set via XamlIslandRoot.
-            // Does this need to be refined to hold some sort of map structure to map XamlIslandRoots<->IslandInputSites?
-            // Right now the last XamlIslandRoot created on a thread will end up setting the "application" IslandInputSite on CInputServices.
-            IFC_RETURN(m_pDMCrossSlideService->EnsureDirectManipulationManager(m_islandInputSite.Get(), TRUE /*fIsForCrossSlideViewports*/));
-            IFC_RETURN(m_pDMCrossSlideService->ActivateDirectManipulationManager());
 
-            if (m_shouldRegisterDMViewportCallback)
-            {
-                xref_ptr<IXcpDirectManipulationViewportEventHandler> spDirectManipulationViewportEventHandler;
+                IFC_RETURN(cpDMCrossSlideService->EnsureDirectManipulationManager(islandInputSiteRegistration.IslandInputSite().Get(), TRUE /*fIsForCrossSlideViewports*/));
+                IFC_RETURN(cpDMCrossSlideService->ActivateDirectManipulationManager());
+
+                if (islandInputSiteRegistration.ShouldRegisterDMViewportCallback())
+                {
+                    xref_ptr<IXcpDirectManipulationViewportEventHandler> spDirectManipulationViewportEventHandler;
+
+                    IFC_RETURN(GetDirectManipulationViewportEventHandler(spDirectManipulationViewportEventHandler.ReleaseAndGetAddressOf()));
+                    IFC_RETURN(cpDMCrossSlideService->RegisterViewportEventHandler(spDirectManipulationViewportEventHandler.get()));
+                }
 
-                IFC_RETURN(GetDirectManipulationViewportEventHandler(spDirectManipulationViewportEventHandler.ReleaseAndGetAddressOf()));
-                IFC_RETURN(m_pDMCrossSlideService->RegisterViewportEventHandler(spDirectManipulationViewportEventHandler.get()));
+                // Success! Store our IslandInputSite specific DMCrossSlideService.
+                islandInputSiteRegistration.DMCrossSlideService(cpDMCrossSlideService.Get());
             }
         }
 
@@ -3587,7 +3678,7 @@ CInputServices::InitializeDirectManipulationContainers()
         auto position = std::partition(m_pDMContainersNeedingInitialization->begin(), m_pDMContainersNeedingInitialization->end(),
             [](const xref::weakref_ptr<CUIElement>& elem)
         {
-            // Only keep containers that are inactive or do not have a valid window handle
+            // Only keep containers that are inactive or do not have a valid IslandInputSite.
             auto pDMContainer = elem.lock();
             return pDMContainer && (!pDMContainer->IsActive() || !pDMContainer->CanDMContainerInitialize());
         });
@@ -5279,8 +5370,9 @@ CInputServices::SetDirectManipulationCrossSlideContainer(
 
     IFC_RETURN(pElement->CanDrag(&fIsDraggable));
 
+    auto* pDMCrossSlideService = GetDMCrossSlideServiceNoRefForUIElement(pElement);
     if (pElement->GetIsDirectManipulationCrossSlideContainer()
-        && !(fIsDraggable && ((m_pDMCrossSlideService && m_pDMCrossSlideService->GetHasDragDropViewport()) || !pElement->IsEnabled())))
+        && !(fIsDraggable && ((pDMCrossSlideService && pDMCrossSlideService->GetHasDragDropViewport()) || !pElement->IsEnabled())))
     {
         // This element needs a cross-slide viewport - it needs a first shot at recognizing gestures or manipulations.
         // Once the first DragDrop CrossSlideContainer is set up, we will treat the rest as regular containers.
@@ -5351,7 +5443,8 @@ CInputServices::SetDirectManipulationCrossSlideContainer(
     IFCPTR(pfContactFailure);
     *pfContactFailure = FALSE;
 
-    if (m_pDMCrossSlideService)
+    auto* pDMCrossSlideService = GetDMCrossSlideServiceNoRefForUIElement(pDMCrossSlideContainer);
+    if (pDMCrossSlideService)
     {
         // Check if a DM cross-slide viewport was already created for this element
         IFC(GetCrossSlideViewport(pDMCrossSlideContainer, &pCrossSlideViewport));
@@ -5389,13 +5482,13 @@ CInputServices::SetDirectManipulationCrossSlideContainer(
                 }
 #endif // DM_DEBUG
 
-                IFC(m_pDMCrossSlideService->AddViewportConfiguration(
+                IFC(pDMCrossSlideService->AddViewportConfiguration(
                     pCrossSlideViewport,
                     TRUE /*fIsCrossSlideViewport*/,
                     fIsDraggable /*fIsDragDrop*/,
                     configuration));
                 // fCausedRunningStatus is ignored because we don't track cross-slide viewport statuses.
-                IFC(m_pDMCrossSlideService->EnableViewport(pCrossSlideViewport, fCausedRunningStatus));
+                IFC(pDMCrossSlideService->EnableViewport(pCrossSlideViewport, fCausedRunningStatus));
 #ifdef DM_DEBUG
                 if (m_fIsDMInfoTracingEnabled)
                 {
@@ -5487,9 +5580,10 @@ CInputServices::AddCrossSlideViewportContactId(
     IFCPTR(pfContactFailure);
     *pfContactFailure = FALSE;
 
-    ASSERT(m_pDMCrossSlideService);
+    auto* pDMCrossSlideService = GetDMCrossSlideServiceNoRefForUIElement(pCrossSlideViewport->GetDMContainerNoRef());
+    ASSERT(pDMCrossSlideService);
 
-    IFC(m_pDMCrossSlideService->SetContact(pCrossSlideViewport, pointerId, pfContactFailure));
+    IFC(pDMCrossSlideService->SetContact(pCrossSlideViewport, pointerId, pfContactFailure));
     ExitOnSetContactFailure(*pfContactFailure);
 
     IFC(pCrossSlideViewport->AddContactId(pointerId));
@@ -5972,7 +6066,8 @@ CInputServices::UnregisterCrossSlideViewport(
 
     if (m_pCrossSlideViewports)
     {
-        ASSERT(m_pDMCrossSlideService);
+        auto* pDMCrossSlideService = GetDMCrossSlideServiceNoRefForUIElement(pCrossSlideViewport->GetDMContainerNoRef());
+        ASSERT(pDMCrossSlideService);
 
         for (XUINT32 iCrossSlideViewport = 0; iCrossSlideViewport < m_pCrossSlideViewports->size(); iCrossSlideViewport++)
         {
@@ -5981,7 +6076,7 @@ CInputServices::UnregisterCrossSlideViewport(
 
             if (pCrossSlideViewportTmp == pCrossSlideViewport)
             {
-                IFC_RETURN(m_pDMCrossSlideService->UnregisterViewport(pCrossSlideViewport));
+                IFC_RETURN(pDMCrossSlideService->UnregisterViewport(pCrossSlideViewport));
 
                 IFC_RETURN(m_pCrossSlideViewports->erase(iCrossSlideViewport));
                 ReleaseInterface(pCrossSlideViewport);
@@ -7326,9 +7421,10 @@ CInputServices::ProcessDirectManipulationViewportStatusUpdate(
     }
 #endif // DM_DEBUG
 
-    if (m_pDMCrossSlideService)
+    auto* pDMCrossSlideService = GetDMCrossSlideServiceNoRefForUIElement(pViewport->GetDMContainerNoRef());
+    if (pDMCrossSlideService)
     {
-        IFC(m_pDMCrossSlideService->GetDragDropViewport(&pDragDropViewportHandle));
+        IFC(pDMCrossSlideService->GetDragDropViewport(&pDragDropViewportHandle));
         if (pViewport == pDragDropViewportHandle)
         {
             // Drag drop viewport doesn't handle Viewport status update
diff --git a/dxaml/xcp/dxaml/idl/winrt/core/microsoft.ui.xaml.coretypes2.idl b/dxaml/xcp/dxaml/idl/winrt/core/microsoft.ui.xaml.coretypes2.idl
index f46b8ff7ad..e946f80cbd 100644
--- a/dxaml/xcp/dxaml/idl/winrt/core/microsoft.ui.xaml.coretypes2.idl
+++ b/dxaml/xcp/dxaml/idl/winrt/core/microsoft.ui.xaml.coretypes2.idl
@@ -4181,6 +4181,11 @@ namespace Microsoft.UI.Xaml.Hosting
         event Windows.Foundation.TypedEventHandler<Microsoft.UI.Xaml.Hosting.DesktopWindowXamlSource,Microsoft.UI.Xaml.Hosting.DesktopWindowXamlSourceGotFocusEventArgs> GotFocus;
         Microsoft.UI.Xaml.Hosting.XamlSourceFocusNavigationResult NavigateFocus(Microsoft.UI.Xaml.Hosting.XamlSourceFocusNavigationRequest request);
         void Initialize(Microsoft.UI.WindowId parentWindowId);
+    
+        [contract(Microsoft.UI.Xaml.WinUIContract, 6)]
+        {
+            Boolean ShouldConstrainPopupsToWorkArea;
+        }
     };
 
     [contract(Microsoft.UI.Xaml.WinUIContract, 5)]
diff --git a/dxaml/xcp/dxaml/lib/CascadingMenuHelper.cpp b/dxaml/xcp/dxaml/lib/CascadingMenuHelper.cpp
index 03cd1200e0..b32d952d9c 100644
--- a/dxaml/xcp/dxaml/lib/CascadingMenuHelper.cpp
+++ b/dxaml/xcp/dxaml/lib/CascadingMenuHelper.cpp
@@ -385,13 +385,19 @@ _Check_return_ HRESULT CascadingMenuHelper::OnKeyDown(_In_ xaml_input::IKeyRoute
         auto key = wsy::VirtualKey_None;
         IFC_RETURN(args->get_Key(&key));
 
-        // Show the sub menu with the enter, space, or right arrow keys
-        if (key == wsy::VirtualKey_Enter ||
-            key == wsy::VirtualKey_Right ||
-            key == wsy::VirtualKey_Space)
+        wuc::CorePhysicalKeyStatus keyStatus;
+        IFC_RETURN(args->get_KeyStatus(&keyStatus));
+
+        if (!keyStatus.IsMenuKeyDown)
         {
-            IFC_RETURN(OpenSubMenu());
-            IFC_RETURN(args->put_Handled(TRUE));
+            // Show the sub menu with the enter, space, or right arrow keys
+            if (key == wsy::VirtualKey_Enter ||
+                key == wsy::VirtualKey_Right ||
+                key == wsy::VirtualKey_Space)
+            {
+                IFC_RETURN(OpenSubMenu());
+                IFC_RETURN(args->put_Handled(TRUE));
+            }            
         }
     }
 
diff --git a/dxaml/xcp/dxaml/lib/DXamlCore.cpp b/dxaml/xcp/dxaml/lib/DXamlCore.cpp
index 9a8c79de90..429d911c8c 100644
--- a/dxaml/xcp/dxaml/lib/DXamlCore.cpp
+++ b/dxaml/xcp/dxaml/lib/DXamlCore.cpp
@@ -324,7 +324,7 @@ DXamlCore::GetAssociatedWindowNoRef(
         return S_FALSE;
     }
 
-    // Retrieve the hosting HWND from the XamlRoot. 
+    // Retrieve the hosting HWND from the XamlRoot.
     // As above, it is possible that the element is hosted inside of a XamlIsland, which means that
     // it will have a XamlRoot but not a hosting HWND. This is essentially equivalent to a UIElement
     // being created in code behind, as a XamlIsland is used to host Xaml content inside of an app
@@ -3786,12 +3786,25 @@ DXamlCore::CalculateAvailableMonitorRect(
                 *inputPaneOccludeRectScreenLogical = inputPaneOccludeRectScreenLogicalTemp;
             }
 
-            wf::Rect availableMonitorRectScreenLogical = {
-                monitorInfo.rcWork.left / scale,
-                monitorInfo.rcWork.top / scale,
-                (monitorInfo.rcWork.right - monitorInfo.rcWork.left) / scale,
-                (monitorInfo.rcWork.bottom - monitorInfo.rcWork.top) / scale
-            };
+            wf::Rect availableMonitorRectScreenLogical = {};
+            if (visualTree->ShouldConstrainPopupsToWorkArea())
+            {
+                availableMonitorRectScreenLogical = {
+                    monitorInfo.rcWork.left / scale,
+                    monitorInfo.rcWork.top / scale,
+                    (monitorInfo.rcWork.right - monitorInfo.rcWork.left) / scale,
+                    (monitorInfo.rcWork.bottom - monitorInfo.rcWork.top) / scale
+                    };
+            }
+            else
+            {
+                availableMonitorRectScreenLogical = {
+                    monitorInfo.rcMonitor.left / scale,
+                    monitorInfo.rcMonitor.top / scale,
+                    (monitorInfo.rcMonitor.right - monitorInfo.rcMonitor.left) / scale,
+                    (monitorInfo.rcMonitor.bottom - monitorInfo.rcMonitor.top) / scale
+                    };
+            }
 
             wf::Rect intersectionRectScreenLogical = availableMonitorRectScreenLogical;
 
diff --git a/dxaml/xcp/dxaml/lib/DesktopWindowImpl.cpp b/dxaml/xcp/dxaml/lib/DesktopWindowImpl.cpp
index cabbd43329..b54bb40846 100644
--- a/dxaml/xcp/dxaml/lib/DesktopWindowImpl.cpp
+++ b/dxaml/xcp/dxaml/lib/DesktopWindowImpl.cpp
@@ -1286,7 +1286,12 @@ _Check_return_ HRESULT DesktopWindowImpl::SetTitleBarImpl(_In_ xaml::IUIElement*
 
 IFACEMETHODIMP DesktopWindowImpl::get_SystemBackdrop(_Outptr_result_maybenull_ ABI::Windows::UI::Composition::ICompositionBrush** systemBackdropBrush)
 {
-    IFC_RETURN(m_desktopWindowXamlSource->get_SystemBackdrop(systemBackdropBrush));
+    *systemBackdropBrush = nullptr;
+
+    if (m_desktopWindowXamlSource)
+    {
+        IFC_RETURN(m_desktopWindowXamlSource->get_SystemBackdrop(systemBackdropBrush));
+    }
 
     return S_OK;
 }
diff --git a/dxaml/xcp/dxaml/lib/DesktopWindowXamlSource_Partial.cpp b/dxaml/xcp/dxaml/lib/DesktopWindowXamlSource_Partial.cpp
index 747af3e0bf..79377adb92 100644
--- a/dxaml/xcp/dxaml/lib/DesktopWindowXamlSource_Partial.cpp
+++ b/dxaml/xcp/dxaml/lib/DesktopWindowXamlSource_Partial.cpp
@@ -675,6 +675,32 @@ HRESULT DesktopWindowXamlSource::get_HasFocusImpl(_Out_ boolean* pValue)
     return S_OK;
 }
 
+_Check_return_ HRESULT DesktopWindowXamlSource::get_ShouldConstrainPopupsToWorkAreaImpl(_Outptr_ boolean* pValue)
+{
+    *pValue = true;
+
+    // Note: XamlIslandRoot won't have a ContentRoot (and VisualTree) if it's closing. No-op this case.
+    auto coreXamlIsland = static_cast<CXamlIslandRoot*>(m_spXamlIsland.Cast<XamlIslandRoot>()->GetHandle());
+    auto visualTreeNoRef = coreXamlIsland->GetVisualTreeNoRef();
+    if (visualTreeNoRef)
+    {
+        *pValue = visualTreeNoRef->ShouldConstrainPopupsToWorkArea();
+    }
+    return S_OK;
+}
+
+_Check_return_ HRESULT DesktopWindowXamlSource::put_ShouldConstrainPopupsToWorkAreaImpl(_In_opt_ boolean value)
+{
+    // Note: XamlIslandRoot won't have a ContentRoot (and VisualTree) if it's closing. No-op this case.
+    auto coreXamlIsland = static_cast<CXamlIslandRoot*>(m_spXamlIsland.Cast<XamlIslandRoot>()->GetHandle());
+    auto visualTreeNoRef = coreXamlIsland->GetVisualTreeNoRef();
+    if (visualTreeNoRef)
+    {
+        visualTreeNoRef->SetShouldConstrainPopupsToWorkArea(!!value);
+    }
+    return S_OK;
+}
+
 _Check_return_
 HRESULT DesktopWindowXamlSource::GetGotFocusEventSourceNoRef(_Outptr_ GotFocusEventSourceType** ppEventSource)
 {
diff --git a/dxaml/xcp/dxaml/lib/DesktopWindowXamlSource_Partial.h b/dxaml/xcp/dxaml/lib/DesktopWindowXamlSource_Partial.h
index af6e04756d..de62045444 100644
--- a/dxaml/xcp/dxaml/lib/DesktopWindowXamlSource_Partial.h
+++ b/dxaml/xcp/dxaml/lib/DesktopWindowXamlSource_Partial.h
@@ -39,7 +39,7 @@ namespace DirectUI
         _Check_return_ HRESULT get_ContentImpl(_Outptr_ xaml::IUIElement** ppValue);
         _Check_return_ HRESULT put_ContentImpl(_In_opt_ xaml::IUIElement* pValue);
 
-        _Check_return_ HRESULT get_SiteBridgeImpl(_Outptr_result_maybenull_ ixp::IDesktopChildSiteBridge** ppValue);        
+        _Check_return_ HRESULT get_SiteBridgeImpl(_Outptr_result_maybenull_ ixp::IDesktopChildSiteBridge** ppValue);
 
         _Check_return_ HRESULT NavigateFocusImpl(
             _In_ xaml_hosting::IXamlSourceFocusNavigationRequest* request,
@@ -47,6 +47,9 @@ namespace DirectUI
 
         _Check_return_ HRESULT get_HasFocusImpl(_Out_ boolean* pResult);
 
+        _Check_return_ HRESULT get_ShouldConstrainPopupsToWorkAreaImpl(_Outptr_ boolean* pValue);
+        _Check_return_ HRESULT put_ShouldConstrainPopupsToWorkAreaImpl(_In_opt_ boolean value);
+
         _Check_return_ HRESULT GetGotFocusEventSourceNoRef(_Outptr_ GotFocusEventSourceType** ppEventSource) override;
         _Check_return_ HRESULT GetTakeFocusRequestedEventSourceNoRef(_Outptr_ TakeFocusRequestedEventSourceType** ppEventSource) override;
 
diff --git a/dxaml/xcp/dxaml/lib/FlyoutBase_partial.cpp b/dxaml/xcp/dxaml/lib/FlyoutBase_partial.cpp
index 021418c619..16e8dd0d98 100644
--- a/dxaml/xcp/dxaml/lib/FlyoutBase_partial.cpp
+++ b/dxaml/xcp/dxaml/lib/FlyoutBase_partial.cpp
@@ -1061,14 +1061,7 @@ _Check_return_ HRESULT FlyoutBase::ShowAtWithOptionsImpl(
         m_exclusionRect = RectUtil::CreateEmptyRect();
     }
 
-    if (showMode != xaml_primitives::FlyoutShowMode_Auto)
-    {
-        IFC_RETURN(UpdateStateToShowMode(showMode));
-    }
-    else
-    {
-        IFC_RETURN(UpdateStateToShowMode(xaml_primitives::FlyoutShowMode_Standard));
-    }
+    IFC_RETURN(UpdateStateToShowMode(showMode));
 
     if (placement != xaml_primitives::FlyoutPlacementMode_Auto)
     {
@@ -1856,11 +1849,14 @@ _Check_return_ HRESULT FlyoutBase::PerformPlacement(
     }
 
 
-
-    if (presenterSize.Width != presenterRect.Width ||
-        presenterSize.Height != presenterRect.Height)
+    if (presenterSize.Width != presenterRect.Width)
     {
         IFC(pPresenterAsControl->put_Width(presenterRect.Width));
+        m_presenterResized = true;
+    }
+
+    if (presenterSize.Height != presenterRect.Height)
+    {
         IFC(pPresenterAsControl->put_Height(presenterRect.Height));
         m_presenterResized = true;
     }
@@ -3878,6 +3874,11 @@ _Check_return_ HRESULT FlyoutBase::GetPresenterSize(_Out_ wf::Size* value)
 
 _Check_return_ HRESULT FlyoutBase::UpdateStateToShowMode(xaml_primitives::FlyoutShowMode showMode)
 {
+    if (showMode == xaml_primitives::FlyoutShowMode_Auto)
+    {
+        showMode = xaml_primitives::FlyoutShowMode_Standard;
+    }
+
     IFC_RETURN(put_ShowMode(showMode));
 
     bool oldShouldHideIfPointerMovesAway = m_shouldHideIfPointerMovesAway;
diff --git a/dxaml/xcp/dxaml/lib/FrameworkElement_partial.cpp b/dxaml/xcp/dxaml/lib/FrameworkElement_partial.cpp
index d4e2ba292b..a6bb948ed3 100644
--- a/dxaml/xcp/dxaml/lib/FrameworkElement_partial.cpp
+++ b/dxaml/xcp/dxaml/lib/FrameworkElement_partial.cpp
@@ -1147,13 +1147,15 @@ _Check_return_ HRESULT FrameworkElement::FindNameInPage(
         }
         else
         {
-
             // ListBoxItem(s) inside of an ItemsControl do not have a
-            // templated parent, so the TemplatedParent chain is broken
-            // to work around this we get their parent and if it is a panel
+            // templated parent, so the TemplatedParent chain is broken.
+            // To work around this, we get their parent and if it is a panel
             // serving as an ItemsHost in an ItemsControl then we use that panel
             // as the next step in the chain. The Panel will have the TemplatedParent
             // set since it is created from a Template by the ItemsPresenter.
+            // A MUXC ItemsRepeater may not have a TemplatedParent either, so that
+            // panel is used as the next step in the chain as well. This allows its
+            // ItemTemplate to use ElementName-based bindings to elements outside its scope.
             IFC_RETURN(current->GetInheritanceParent(&templatedParentAsDO));
             if (!templatedParentAsDO)
             {
@@ -1166,8 +1168,13 @@ _Check_return_ HRESULT FrameworkElement::FindNameInPage(
 
             if (panel)
             {
+                // Two kinds of panels get special treatment:
+                // - items host for an ItemsControl,
+                // - MUXC ItemsRepeater
+                // In both cases, ElementName-based bindings need to be able to successfully find elements outside the ItemsControl or ItemsRepeater respectively.
                 IFC_RETURN(panel->get_IsItemsHost(&fIsItemsHost));
-                if (fIsItemsHost)
+                if (fIsItemsHost ||
+                    static_cast<CFrameworkElement*>(templatedParentAsDO->GetHandle())->GetClassName().Equals(XSTRING_PTR_EPHEMERAL(L"Microsoft.UI.Xaml.Controls.ItemsRepeater")))
                 {
                     current = templatedParentAsDO.Cast<FrameworkElement>();
                 }
@@ -1180,10 +1187,8 @@ _Check_return_ HRESULT FrameworkElement::FindNameInPage(
         }
     }
 
-
     foundElementValue.CopyTo<IInspectable>(ppObj);
     return S_OK;
-
 }
 
 _Check_return_
diff --git a/dxaml/xcp/dxaml/lib/InputSiteAdapter.h b/dxaml/xcp/dxaml/lib/InputSiteAdapter.h
index 2aacebbcfa..c174b8cdd6 100644
--- a/dxaml/xcp/dxaml/lib/InputSiteAdapter.h
+++ b/dxaml/xcp/dxaml/lib/InputSiteAdapter.h
@@ -23,8 +23,6 @@ class InputSiteAdapter
 
     void Initialize(_In_ ixp::IContentIsland* contentIsland, _In_ CContentRoot* contentRoot, _In_ CJupiterWindow* jupiterWindow);
 
-    void RegisterApplicationIslandInputSiteWithInputServicesForDManip();
-    void UnregisterApplicationIslandInputSiteWithInputServicesForDManip();
     wrl::ComPtr<ixp::IIslandInputSitePartner> GetIslandInputSite() const { return m_islandInputSite; }
 
     _Check_return_ HRESULT SetFocus();
@@ -73,6 +71,8 @@ class InputSiteAdapter
     void SubscribeToInputKeyboardSourceEvents();
     void SubscribeToInputPointerSourceEvents();
     void UnsubscribeToInputEvents();
+    void RegisterIslandInputSiteWithInputServicesForDManip();
+    void UnregisterIslandInputSiteWithInputServicesForDManip();
 
     _Check_return_ HRESULT OnCharacterReceived(_Inout_ ixp::ICharacterReceivedEventArgs *args);
     _Check_return_ HRESULT OnKeyDown(_In_ ixp::IKeyEventArgs *pArgs);
diff --git a/dxaml/xcp/dxaml/lib/JupiterWindow.cpp b/dxaml/xcp/dxaml/lib/JupiterWindow.cpp
index 76aca36dab..3008bd517f 100644
--- a/dxaml/xcp/dxaml/lib/JupiterWindow.cpp
+++ b/dxaml/xcp/dxaml/lib/JupiterWindow.cpp
@@ -1433,16 +1433,10 @@ void CJupiterWindow::EnsureInputSiteAdapterForCoreWindow(_In_ ixp::IContentIslan
 
     m_inputSiteAdapter = std::make_unique<InputSiteAdapter>();
     m_inputSiteAdapter->Initialize(coreWindowContentIsland, GetCoreWindowContentRootNoRef(), this);
-    m_inputSiteAdapter->RegisterApplicationIslandInputSiteWithInputServicesForDManip();
 }
 
 void CJupiterWindow::UninitializeInputSiteAdapterForCoreWindow()
 {
-    if (nullptr != m_inputSiteAdapter)
-    {
-        m_inputSiteAdapter->UnregisterApplicationIslandInputSiteWithInputServicesForDManip();
-    }
-
     m_inputSiteAdapter = nullptr;
 }
 
diff --git a/dxaml/xcp/dxaml/lib/synonyms.g.h b/dxaml/xcp/dxaml/lib/synonyms.g.h
index a19374bf4a..7d99c8619b 100644
--- a/dxaml/xcp/dxaml/lib/synonyms.g.h
+++ b/dxaml/xcp/dxaml/lib/synonyms.g.h
@@ -561,6 +561,7 @@ namespace DirectUISynonyms
     typedef ABI::Microsoft::UI::Xaml::Documents::ITypography ITypography;
     typedef ABI::Microsoft::UI::Xaml::Documents::IUnderline IUnderline;
     typedef ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource IDesktopWindowXamlSource;
+    typedef ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource2 IDesktopWindowXamlSource2;
     typedef ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSourceGotFocusEventArgs IDesktopWindowXamlSourceGotFocusEventArgs;
     typedef ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSourceTakeFocusRequestedEventArgs IDesktopWindowXamlSourceTakeFocusRequestedEventArgs;
     typedef ABI::Microsoft::UI::Xaml::Hosting::IElementCompositionPreview IElementCompositionPreview;
diff --git a/dxaml/xcp/dxaml/lib/winrtgeneratedclasses/DesktopWindowXamlSource.g.cpp b/dxaml/xcp/dxaml/lib/winrtgeneratedclasses/DesktopWindowXamlSource.g.cpp
index 6f289d08e6..a4c2361f7e 100644
--- a/dxaml/xcp/dxaml/lib/winrtgeneratedclasses/DesktopWindowXamlSource.g.cpp
+++ b/dxaml/xcp/dxaml/lib/winrtgeneratedclasses/DesktopWindowXamlSource.g.cpp
@@ -42,6 +42,10 @@ HRESULT DirectUI::DesktopWindowXamlSourceGenerated::QueryInterfaceImpl(_In_ REFI
     {
         *ppObject = static_cast<ABI::Windows::Foundation::IClosable*>(this);
     }
+    else if (InlineIsEqualGUID(iid, __uuidof(ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource2)))
+    {
+        *ppObject = ctl::interface_cast<ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource2>(this);
+    }
     else
     {
         RRETURN(ctl::WeakReferenceSource::QueryInterfaceImpl(iid, ppObject));
@@ -79,6 +83,24 @@ _Check_return_ HRESULT STDMETHODCALLTYPE DirectUI::DesktopWindowXamlSourceGenera
 Cleanup:
     RRETURN(hr);
 }
+_Check_return_ HRESULT STDMETHODCALLTYPE DirectUI::DesktopWindowXamlSourceGenerated::get_ShouldConstrainPopupsToWorkArea(_Out_ BOOLEAN* pValue)
+{
+    HRESULT hr = S_OK;
+    ARG_VALIDRETURNPOINTER(pValue);
+    
+    IFC(static_cast<DesktopWindowXamlSource*>(this)->get_ShouldConstrainPopupsToWorkAreaImpl(pValue));
+Cleanup:
+    RRETURN(hr);
+}
+_Check_return_ HRESULT STDMETHODCALLTYPE DirectUI::DesktopWindowXamlSourceGenerated::put_ShouldConstrainPopupsToWorkArea(_In_ BOOLEAN value)
+{
+    HRESULT hr = S_OK;
+    
+    
+    IFC(static_cast<DesktopWindowXamlSource*>(this)->put_ShouldConstrainPopupsToWorkAreaImpl(value));
+Cleanup:
+    RRETURN(hr);
+}
 _Check_return_ HRESULT STDMETHODCALLTYPE DirectUI::DesktopWindowXamlSourceGenerated::get_SiteBridge(_Outptr_result_maybenull_ ABI::Microsoft::UI::Content::IDesktopChildSiteBridge** ppValue)
 {
     HRESULT hr = S_OK;
diff --git a/dxaml/xcp/dxaml/lib/winrtgeneratedclasses/DesktopWindowXamlSource.g.h b/dxaml/xcp/dxaml/lib/winrtgeneratedclasses/DesktopWindowXamlSource.g.h
index d5d58a257f..c03072cb62 100644
--- a/dxaml/xcp/dxaml/lib/winrtgeneratedclasses/DesktopWindowXamlSource.g.h
+++ b/dxaml/xcp/dxaml/lib/winrtgeneratedclasses/DesktopWindowXamlSource.g.h
@@ -35,6 +35,14 @@ namespace ctl
         IFACEMETHOD(add_TakeFocusRequested)(_In_ ABI::Windows::Foundation::ITypedEventHandler<ABI::Microsoft::UI::Xaml::Hosting::DesktopWindowXamlSource*, ABI::Microsoft::UI::Xaml::Hosting::DesktopWindowXamlSourceTakeFocusRequestedEventArgs*>* pValue, _Out_ EventRegistrationToken* pToken) override { return This()->add_TakeFocusRequested(pValue, pToken); }
         IFACEMETHOD(remove_TakeFocusRequested)(_In_ EventRegistrationToken token) override { return This()->remove_TakeFocusRequested(token); }
     };
+    template<typename impl_type>
+    class interface_forwarder< ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource2, impl_type> final
+        : public ctl::iinspectable_forwarder_base< ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource2, impl_type>
+    {
+        impl_type* This() { return this->This_helper<impl_type>(); }
+        IFACEMETHOD(get_ShouldConstrainPopupsToWorkArea)(_Out_ BOOLEAN* pValue) override { return This()->get_ShouldConstrainPopupsToWorkArea(pValue); }
+        IFACEMETHOD(put_ShouldConstrainPopupsToWorkArea)(_In_ BOOLEAN value) override { return This()->put_ShouldConstrainPopupsToWorkArea(value); }
+    };
 }
 #pragma endregion
 
@@ -50,6 +58,7 @@ namespace DirectUI
         , public ctl::forwarder_holder< ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource, DesktopWindowXamlSourceGenerated >
         , public ABI::Microsoft::UI::Composition::ICompositionSupportsSystemBackdrop
         , public ABI::Windows::Foundation::IClosable
+        , public ctl::forwarder_holder< ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource2, DesktopWindowXamlSourceGenerated >
     {
         friend class DirectUI::DesktopWindowXamlSource;
 
@@ -59,6 +68,7 @@ namespace DirectUI
             INTERFACE_ENTRY(DesktopWindowXamlSourceGenerated, ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource)
             INTERFACE_ENTRY(DesktopWindowXamlSourceGenerated, ABI::Microsoft::UI::Composition::ICompositionSupportsSystemBackdrop)
             INTERFACE_ENTRY(DesktopWindowXamlSourceGenerated, ABI::Windows::Foundation::IClosable)
+            INTERFACE_ENTRY(DesktopWindowXamlSourceGenerated, ABI::Microsoft::UI::Xaml::Hosting::IDesktopWindowXamlSource2)
         END_INTERFACE_MAP(DesktopWindowXamlSourceGenerated, ctl::WeakReferenceSource)
 
     public:
@@ -74,6 +84,8 @@ namespace DirectUI
         _Check_return_ HRESULT STDMETHODCALLTYPE get_Content(_Outptr_result_maybenull_ ABI::Microsoft::UI::Xaml::IUIElement** ppValue);
         _Check_return_ HRESULT STDMETHODCALLTYPE put_Content(_In_opt_ ABI::Microsoft::UI::Xaml::IUIElement* pValue);
         _Check_return_ HRESULT STDMETHODCALLTYPE get_HasFocus(_Out_ BOOLEAN* pValue);
+        _Check_return_ HRESULT STDMETHODCALLTYPE get_ShouldConstrainPopupsToWorkArea(_Out_ BOOLEAN* pValue);
+        _Check_return_ HRESULT STDMETHODCALLTYPE put_ShouldConstrainPopupsToWorkArea(_In_ BOOLEAN value);
         _Check_return_ HRESULT STDMETHODCALLTYPE get_SiteBridge(_Outptr_result_maybenull_ ABI::Microsoft::UI::Content::IDesktopChildSiteBridge** ppValue);
         _Check_return_ HRESULT STDMETHODCALLTYPE get_SystemBackdrop(_Outptr_result_maybenull_ ABI::Microsoft::UI::Xaml::Media::ISystemBackdrop** ppValue);
         _Check_return_ HRESULT STDMETHODCALLTYPE put_SystemBackdrop(_In_opt_ ABI::Microsoft::UI::Xaml::Media::ISystemBackdrop* pValue);
diff --git a/dxaml/xcp/tools/XCPTypesAutoGen/XamlOM/Model/Microsoft.UI.Xaml.Hosting.cs b/dxaml/xcp/tools/XCPTypesAutoGen/XamlOM/Model/Microsoft.UI.Xaml.Hosting.cs
index 041a8a4991..e73359a2f7 100644
--- a/dxaml/xcp/tools/XCPTypesAutoGen/XamlOM/Model/Microsoft.UI.Xaml.Hosting.cs
+++ b/dxaml/xcp/tools/XCPTypesAutoGen/XamlOM/Model/Microsoft.UI.Xaml.Hosting.cs
@@ -246,6 +246,7 @@ public bool WasFocusMoved
     };
 
     [Contract(typeof(WinUIContract), 5)]
+    [Platform(2, typeof(Microsoft.UI.Xaml.WinUIContract), 6)]
     [DXamlIdlGroup("coretypes2")]
     [CodeGen(partial: true)]
     [FrameworkTypePattern]
@@ -290,6 +291,16 @@ public Microsoft.UI.Xaml.Media.SystemBackdrop SystemBackdrop
             set;
         }
 
+        [CodeGen(CodeGenLevel.IdlAndPartialStub)]
+        [PropertyKind(PropertyKind.PropertyOnly)]
+        [TypeTable(IsExcludedFromDXaml = true)]
+        [Version(2)]
+        public bool ShouldConstrainPopupsToWorkArea
+        {
+            get;
+            set;
+        }
+
         public XamlSourceFocusNavigationResult NavigateFocus(XamlSourceFocusNavigationRequest request)
         {
             return default(XamlSourceFocusNavigationResult);
@@ -309,8 +320,8 @@ public void Initialize(Microsoft.UI.WindowId parentWindowId)
         [CodeGen(CodeGenLevel.IdlAndPartialStub)]
         [PropertyKind(PropertyKind.PropertyOnly)]
         [TypeTable(IsExcludedFromDXaml = true)]
-        public Microsoft.UI.Content.DesktopChildSiteBridge SiteBridge 
-        { 
+        public Microsoft.UI.Content.DesktopChildSiteBridge SiteBridge
+        {
             get;
         }
     }
@@ -353,7 +364,7 @@ public static WindowsXamlManager InitializeForCurrentThread()
         [CodeGen(CodeGenLevel.IdlAndPartialStub)]
         [TypeTable(IsExcludedFromDXaml = true)]
 	    public static WindowsXamlManager GetForCurrentThread()
-        { 
+        {
             return default(WindowsXamlManager);
         }
     }
diff --git a/dxaml/xcp/tools/XCPTypesAutoGen/XamlOM/Model/Microsoft.UI.Xaml.cs b/dxaml/xcp/tools/XCPTypesAutoGen/XamlOM/Model/Microsoft.UI.Xaml.cs
index c4907704d7..691faea3df 100644
--- a/dxaml/xcp/tools/XCPTypesAutoGen/XamlOM/Model/Microsoft.UI.Xaml.cs
+++ b/dxaml/xcp/tools/XCPTypesAutoGen/XamlOM/Model/Microsoft.UI.Xaml.cs
@@ -2706,18 +2706,6 @@ public Windows.Foundation.Boolean FailFastOnErrors
             set;
         }
 
-        [CodeGen(CodeGenLevel.IdlAndPartialStub)]
-        [AllowCrossThreadAccess]
-        [TypeTable(IsExcludedFromDXaml = true, IsExcludedFromCore = true)]
-        [PropertyKind(PropertyKind.PropertyOnly)]
-        [VelocityFeature("Feature_ExperimentalApi")]
-        public LayoutCycleTracingLevel LayoutCycleTracing
-        {
-            get;
-            set;
-        }
-
-        [CodeGen(CodeGenLevel.IdlAndPartialStub)]
         [Version(3)]
         [CodeGen(CodeGenLevel.IdlAndPartialStub)]
         [AllowCrossThreadAccess]
@@ -2740,16 +2728,6 @@ public LayoutCycleDebugBreakLevel LayoutCycleDebugBreakLevel
             set;
         }
 
-        [AllowCrossThreadAccess]
-        [TypeTable(IsExcludedFromDXaml = true, IsExcludedFromCore = true)]
-        [PropertyKind(PropertyKind.PropertyOnly)]
-        [VelocityFeature("Feature_ExperimentalApi")]
-        public LayoutCycleDebugBreakLevel LayoutCycleDebugBreaks
-        {
-            get;
-            set;
-        }
-
         [AllowCrossThreadAccess]
         public event Microsoft.UI.Xaml.BindingFailedEventHandler BindingFailed;
 
diff --git a/eng/Version.Details.xml b/eng/Version.Details.xml
index e8a05a55ff..662f14ff3c 100644
--- a/eng/Version.Details.xml
+++ b/eng/Version.Details.xml
@@ -2,17 +2,17 @@
 <!-- Copyright (c) Microsoft Corporation. Licensed under the MIT License. See LICENSE in the project root for license information. -->
 <Dependencies>
   <ProductDependencies>
-    <Dependency Name="Microsoft.WindowsAppSDK.Foundation.TransportPackage" Version="1.5.0-20240203.2">
+    <Dependency Name="Microsoft.WindowsAppSDK.Foundation.TransportPackage" Version="1.5.0-20240223.0">
       <Uri>https://dev.azure.com/microsoft/ProjectReunion/_git/WindowsAppSDK</Uri>
-      <Sha>e5cca86cae13e2d76d660b92c2887207ea0d7ae3</Sha>
+      <Sha>f729ae6e9a9d1db8022c4a2be28b93c399f95b8f</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.ProjectReunion.InteractiveExperiences.TransportPackage" Version="1.5.3-CI-26050.1000.240201-1035.1">
+    <Dependency Name="Microsoft.ProjectReunion.InteractiveExperiences.TransportPackage" Version="1.5.4-CI-26061.1000.240215-0823.2">
       <Uri>https://dev.azure.com/microsoft/LiftedIXP/_git/DCPP</Uri>
-      <Sha>2d8e71d8e93b54cebdbab98cf6c48d0393a303eb</Sha>
+      <Sha>ae2b1fa0e5de26d1f5cc3cdbc7ad03a96c110781</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.Internal.InteractiveExperiences" Version="1.5.3-CI-26050.1000.240201-1035.1">
+    <Dependency Name="Microsoft.Internal.InteractiveExperiences" Version="1.5.4-CI-26061.1000.240215-0823.2">
       <Uri>https://dev.azure.com/microsoft/LiftedIXP/_git/DCPP</Uri>
-      <Sha>2d8e71d8e93b54cebdbab98cf6c48d0393a303eb</Sha>
+      <Sha>ae2b1fa0e5de26d1f5cc3cdbc7ad03a96c110781</Sha>
     </Dependency>
     <!-- Microsoft-WinUI-SDK repo (MSBuild and Visual Studio extensions for building, deploying, and debugging packaged applications.)  -->
     <Dependency Name="Microsoft.Build.Msix" Version="1.5.0-zmain.231129.0">
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_AppPass1.cs b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_AppPass1.cs
index e426f41a95..fc137ac352 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_AppPass1.cs
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_AppPass1.cs
@@ -30,6 +30,12 @@ public override string TransformText()
 //     the code is regenerated.
 //------------------------------------------------------------------------------
 
+#include <unknwn.h>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 #include ""winrt/");
             this.Write(this.ToStringHelper.ToStringWithCulture(KnownNamespaces.Xaml));
             this.Write(".h\"\r\n#include \"winrt/");
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_AppPass1.tt b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_AppPass1.tt
index 3cf823cd99..9962bb30c6 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_AppPass1.tt
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_AppPass1.tt
@@ -8,6 +8,12 @@
 //     the code is regenerated.
 //------------------------------------------------------------------------------
 
+#include <unknwn.h>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 #include "winrt/<#=KnownNamespaces.Xaml#>.h"
 #include "winrt/<#=KnownNamespaces.XamlMarkup#>.h"
 #include "winrt/<#=KnownNamespaces.XamlInterop#>.h"
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_BindingInfoPass1.cs b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_BindingInfoPass1.cs
index adc190e204..48600605cb 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_BindingInfoPass1.cs
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_BindingInfoPass1.cs
@@ -32,6 +32,12 @@ public override string TransformText()
 //------------------------------------------------------------------------------
 #pragma once
 
+#include <unknwn.h>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 #include ""winrt/windows.foundation.h""
 #include ""winrt/windows.ui.xaml.interop.h""
 #include ""winrt/microsoft.ui.xaml.controls.h""
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_BindingInfoPass1.tt b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_BindingInfoPass1.tt
index bf30d1c781..20f4b187f6 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_BindingInfoPass1.tt
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_BindingInfoPass1.tt
@@ -10,6 +10,12 @@
 //------------------------------------------------------------------------------
 #pragma once
 
+#include <unknwn.h>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 #include "winrt/windows.foundation.h"
 #include "winrt/windows.ui.xaml.interop.h"
 #include "winrt/microsoft.ui.xaml.controls.h"
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_PagePass1.cs b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_PagePass1.cs
index fbed3dc99e..7f382895e2 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_PagePass1.cs
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_PagePass1.cs
@@ -22,7 +22,8 @@ internal partial class CppWinRT_PagePass1 : CppWinRT_CodeGenerator<PageDefinitio
         /// </summary>
         public override string TransformText()
         {
-            this.Write(@"//------------------------------------------------------------------------------
+            this.Write(@"
+//------------------------------------------------------------------------------
 //     This code was generated by a tool.
 //
 //     Changes to this file may cause incorrect behavior and will be lost if
@@ -30,6 +31,12 @@ public override string TransformText()
 //------------------------------------------------------------------------------
 #pragma once
 
+#include <unknwn.h>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 ");
   foreach (var includeFile in Model.NeededCppWinRTProjectionHeaderFiles) { 
             this.Write("#if __has_include(<");
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_PagePass1.tt b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_PagePass1.tt
index cb5bc19a1c..d81e4bde8f 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_PagePass1.tt
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_PagePass1.tt
@@ -1,5 +1,6 @@
 <#@ template language="C#" inherits="CppWinRT_CodeGenerator<PageDefinition>" visibility="internal" linePragmas="false"#>
 <#@ assembly name="System.Core" #>
+
 //------------------------------------------------------------------------------
 //     This code was generated by a tool.
 //
@@ -8,6 +9,12 @@
 //------------------------------------------------------------------------------
 #pragma once
 
+#include <unknwn.h>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 <#  foreach (var includeFile in Model.NeededCppWinRTProjectionHeaderFiles) { #>
 #if __has_include(<<#=includeFile#>>)
 #include <<#=includeFile#>>
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1.cs b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1.cs
index f8bf202f52..a2136c76d3 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1.cs
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1.cs
@@ -38,6 +38,10 @@ public override string TransformText()
 #include <unknwn.h>
 #include <mutex>
 
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 #include <winrt/Windows.Foundation.h>
 #include <winrt/Windows.Foundation.Collections.h>
 #include ""winrt/");
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1.tt b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1.tt
index 7013ea2fd2..63be8ef1be 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1.tt
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1.tt
@@ -16,6 +16,10 @@
 #include <unknwn.h>
 #include <mutex>
 
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 #include <winrt/Windows.Foundation.h>
 #include <winrt/Windows.Foundation.Collections.h>
 #include "winrt/<#=KnownNamespaces.Xaml#>.h"
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1Impl.cs b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1Impl.cs
index 5a7317d3ab..88c92637b9 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1Impl.cs
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1Impl.cs
@@ -42,6 +42,11 @@ public override string TransformText()
 #include <regex>
 #include <unknwn.h>
 #include <mutex>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 #include ""winrt/windows.foundation.h""
 #include ""winrt/windows.ui.xaml.interop.h""
 #include ""winrt/microsoft.ui.xaml.markup.h""
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1Impl.tt b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1Impl.tt
index 12996b337b..7729de2fa0 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1Impl.tt
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass1Impl.tt
@@ -17,6 +17,11 @@
 #include <regex>
 #include <unknwn.h>
 #include <mutex>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
+
 #include "winrt/windows.foundation.h"
 #include "winrt/windows.ui.xaml.interop.h"
 #include "winrt/microsoft.ui.xaml.markup.h"
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass2.cs b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass2.cs
index 4d32caea59..c17dd0530d 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass2.cs
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass2.cs
@@ -40,7 +40,8 @@ public override string TransformText()
             this.Write(this.ToStringHelper.ToStringWithCulture(ProjectInfo.PrecompiledHeaderFile));
             this.Write("\"\r\n");
   }
-            this.Write("#include <memory>\r\n\r\n");
+            this.Write("#include <memory>\r\n#include <unknwn.h>\r\n\r\n// Undefine GetCurrentTime macro to pre" +
+                    "vent\r\n// conflict with Storyboard::GetCurrentTime\r\n#undef GetCurrentTime\r\n\r\n");
   foreach (var includeFile in Model.NeededCppWinRTProjectionHeaderFiles) { 
             this.Write("#if __has_include(<");
             this.Write(this.ToStringHelper.ToStringWithCulture(includeFile));
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass2.tt b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass2.tt
index eabc1474b6..155c6e7ad9 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass2.tt
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_TypeInfoPass2.tt
@@ -16,6 +16,11 @@
 #include "<#=ProjectInfo.PrecompiledHeaderFile#>"
 <#  }#>
 #include <memory>
+#include <unknwn.h>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
 
 <#  foreach (var includeFile in Model.NeededCppWinRTProjectionHeaderFiles) { #>
 #if __has_include(<<#=includeFile#>>)
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_XamlMetaDataProviderPass1.cs b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_XamlMetaDataProviderPass1.cs
index 267fd070a5..3618aa9eac 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_XamlMetaDataProviderPass1.cs
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_XamlMetaDataProviderPass1.cs
@@ -35,6 +35,11 @@ public override string TransformText()
 #include <functional>
 #include <map>
 #include <vector>
+#include <unknwn.h>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
 
 #include ""XamlTypeInfo.xaml.g.h""
 #include ""XamlMetaDataProvider.g.h""
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_XamlMetaDataProviderPass1.tt b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_XamlMetaDataProviderPass1.tt
index a88f56f02b..e30c0177cf 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_XamlMetaDataProviderPass1.tt
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/CppWinRT/CppWinRT_XamlMetaDataProviderPass1.tt
@@ -13,6 +13,11 @@
 #include <functional>
 #include <map>
 #include <vector>
+#include <unknwn.h>
+
+// Undefine GetCurrentTime macro to prevent
+// conflict with Storyboard::GetCurrentTime
+#undef GetCurrentTime
 
 #include "XamlTypeInfo.xaml.g.h"
 #include "XamlMetaDataProvider.g.h"
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/PageDefinition.cs b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/PageDefinition.cs
index 1e869d1408..e3477a1075 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/PageDefinition.cs
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/PageDefinition.cs
@@ -13,7 +13,7 @@ internal class PageDefinition : Definition
         private List<ConnectionIdElement> _allConnectionIdElements;
         private List<ForwardDeclaringNamespace> _forwardDeclarations;
         private HashSet<string> _neededLocalXamlHeaderFiles = new HashSet<string>();
-        private HashSet<string> _neededCppWinRTProjectionHeaderFiles = new HashSet<string>();
+        private List<string> _neededCppWinRTProjectionHeaderFiles = new List<string>();
         private bool _neededXamlHeaderFilesCalculated = false;
         private string _checksumAlgorithmGuid;
         private IEnumerable<ApiInformation> _allApiInformations;
@@ -191,6 +191,8 @@ public string GetLoadComponentUri(string priIndexName, string xamlRelativePath)
 
         private void EnsureNeededXamlHeaderFilesCalculated()
         {
+            HashSet<string> neededCppWinRTProjectionHeaderFiles;
+
             void addCppWinRTHeaderForTypeIfNecessary(Type type)
             {
                 // If the input type is an array type then we need to use its element type instead
@@ -204,7 +206,7 @@ void addCppWinRTHeaderForTypeIfNecessary(Type type)
                 // convention as they are part of the C++/WinRT project system itself (e.g. base.h)
                 if (adjustedType != null && !XamlSchemaCodeInfo.IsProjectedPrimitiveCppType(adjustedType.FullName))
                 {
-                    _neededCppWinRTProjectionHeaderFiles.Add($"winrt/{adjustedType.Namespace}.h");
+                    neededCppWinRTProjectionHeaderFiles.Add($"winrt/{adjustedType.Namespace}.h");
 
                     if (adjustedType.IsGenericType)
                     {
@@ -218,6 +220,8 @@ void addCppWinRTHeaderForTypeIfNecessary(Type type)
 
             if (!_neededXamlHeaderFilesCalculated)
             {
+                neededCppWinRTProjectionHeaderFiles = new HashSet<string>();
+
                 string headerFile;
                 if (ProjectInfo.ClassToHeaderFileMap.TryGetValue(CodeInfo.ClassName.FullName, out headerFile))
                 {
@@ -226,6 +230,12 @@ void addCppWinRTHeaderForTypeIfNecessary(Type type)
 
                 foreach (XamlFileCodeInfo fileCodeInfo in CodeInfo.PerXamlFileInfo)
                 {
+                    if (fileCodeInfo.ConnectionIdElements.Any())
+                    {
+                        // Need Microsoft.UI.Xaml.Markup.h for IComponentConnector
+                        neededCppWinRTProjectionHeaderFiles.Add("winrt/Microsoft.UI.Xaml.Markup.h");
+                    }
+
                     // iterate over all the fields
                     foreach (FieldDefinition fieldData in from c in fileCodeInfo.ConnectionIdElements
                                                           where c.FieldDefinition != null
@@ -249,6 +259,7 @@ void addCppWinRTHeaderForTypeIfNecessary(Type type)
                     {
                         foreach (EventAssignment xamlEvent in events)
                         {
+                            // Event handler type (e.g. RoutedEventHandler)
                             if (ProjectInfo.ClassToHeaderFileMap.TryGetValue(xamlEvent.EventType.StandardName, out headerFile))
                             {
                                 _neededLocalXamlHeaderFiles.Add(headerFile);
@@ -257,6 +268,16 @@ void addCppWinRTHeaderForTypeIfNecessary(Type type)
                             {
                                 addCppWinRTHeaderForTypeIfNecessary(xamlEvent.EventType?.UnderlyingType);
                             }
+
+                            // Event's declaring type (e.g. MUXC.Primitives.ButtonBase)
+                            if (ProjectInfo.ClassToHeaderFileMap.TryGetValue(xamlEvent.DeclaringType.StandardName, out headerFile))
+                            {
+                                _neededLocalXamlHeaderFiles.Add(headerFile);
+                            }
+                            else
+                            {
+                                addCppWinRTHeaderForTypeIfNecessary(xamlEvent.DeclaringType?.UnderlyingType);
+                            }
                         }
                     }
 
@@ -274,6 +295,20 @@ void addCppWinRTHeaderForTypeIfNecessary(Type type)
                     }
                 }
 
+                // Sort the projection headers by namespace
+                _neededCppWinRTProjectionHeaderFiles = neededCppWinRTProjectionHeaderFiles.OrderBy(
+                    value => 
+                    {
+                        if (value.EndsWith(".h"))
+                        {
+                            return value.Substring(0, value.Length - 2);
+                        }
+                        else
+                        {
+                            return value;
+                        }
+                    }).ToList();
+
                 _neededXamlHeaderFilesCalculated = true;
             }
         }
diff --git a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/TypeInfoDefinition.cs b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/TypeInfoDefinition.cs
index a98529f370..a40ec3be94 100644
--- a/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/TypeInfoDefinition.cs
+++ b/src/XamlCompiler/BuildTasks/Microsoft/Xaml/XamlCompiler/CodeGenerators/TypeInfoDefinition.cs
@@ -14,7 +14,7 @@ internal class TypeInfoDefinition : Definition
         private Dictionary<String, int> _typeInfoIndexes;
         private UInt32[] _typeInfoLookup;
         private List<EnumGenInfo> _enumValues = new List<EnumGenInfo>();
-        private HashSet<string> _neededCppWinRTProjectionHeaderFiles;
+        private List<string> _neededCppWinRTProjectionHeaderFiles;
 
         public TypeInfoDefinition(XamlProjectInfo projectInfo, XamlSchemaCodeInfo schemaInfo)
             : base(projectInfo, schemaInfo)
@@ -294,7 +294,7 @@ public IEnumerable<string> NeededCppWinRTProjectionHeaderFiles
             }
         }
 
-        private HashSet<string> LookupNeededCppWinRTProjectionHeaderFiles()
+        private List<string> LookupNeededCppWinRTProjectionHeaderFiles()
         {
             var headers = new HashSet<string>();
 
@@ -316,7 +316,19 @@ void addCppWinRTHeaderForTypeIfNecessary(Type type)
                 }
             }
 
-            return headers;
+            // Sort the projection headers by namespace
+            return headers.OrderBy(
+                value =>
+                {
+                    if (value.EndsWith(".h"))
+                    {
+                        return value.Substring(0, value.Length - 2);
+                    }
+                    else
+                    {
+                        return value;
+                    }
+                }).ToList();
         }
 
         public String GetterName(int i)