From 12354e46d49ea49a3aab1df2e11610f3de965746 Mon Sep 17 00:00:00 2001
From: benstevens48 <ben@nebstone.co.uk>
Date: Fri, 4 Dec 2020 12:51:39 +0000
Subject: [PATCH 1/2] change last seen parent to weak ref

---
 winrt/lib/xaml/BaseControl.h            | 15 ++++++++++++---
 winrt/lib/xaml/CanvasSwapChainPanel.cpp | 13 +++++++++++--
 winrt/lib/xaml/CanvasSwapChainPanel.h   |  2 +-
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/winrt/lib/xaml/BaseControl.h b/winrt/lib/xaml/BaseControl.h
index 1839f9022..4167d632b 100644
--- a/winrt/lib/xaml/BaseControl.h
+++ b/winrt/lib/xaml/BaseControl.h
@@ -134,7 +134,7 @@ namespace ABI { namespace Microsoft { namespace Graphics { namespace Canvas { na
 
         RenderTarget m_currentRenderTarget;
 
-        ComPtr<IDependencyObject> m_lastSeenParent;
+        WeakRef m_lastSeenParent;
 
         ComPtr<ICanvasDevice> m_customDevice;
 
@@ -233,7 +233,10 @@ namespace ABI { namespace Microsoft { namespace Graphics { namespace Canvas { na
             return ExceptionBoundary(
                 [&]
                 {
-                    RemoveFromVisualTreeImpl(m_lastSeenParent.Get(), As<IUIElement>(GetControl()).Get());
+                    if (!m_lastSeenParent) {
+                        return;
+                    }
+                    RemoveFromVisualTreeImpl(LockWeakRef<IDependencyObject>(m_lastSeenParent).Get(), As<IUIElement>(GetControl()).Get());
                 });
         }
 
@@ -913,7 +916,13 @@ namespace ABI { namespace Microsoft { namespace Graphics { namespace Canvas { na
 
         void UpdateLastSeenParent()
         {
-            As<IFrameworkElement>(GetControl()->GetComposableBase())->get_Parent(&m_lastSeenParent);
+            ComPtr<IDependencyObject> parent;
+            As<IFrameworkElement>(GetControl()->GetComposableBase())->get_Parent(&parent);
+            if (!parent) {
+                m_lastSeenParent.Reset();
+                return;
+            }
+            m_lastSeenParent = AsWeak(parent.Get());
         }
 
         HRESULT OnUnloaded(IInspectable*, IRoutedEventArgs*)
diff --git a/winrt/lib/xaml/CanvasSwapChainPanel.cpp b/winrt/lib/xaml/CanvasSwapChainPanel.cpp
index 51e42fb55..0efcb0797 100644
--- a/winrt/lib/xaml/CanvasSwapChainPanel.cpp
+++ b/winrt/lib/xaml/CanvasSwapChainPanel.cpp
@@ -88,7 +88,13 @@ HRESULT CanvasSwapChainPanel::OnLoaded(IInspectable*, IRoutedEventArgs*)
     return ExceptionBoundary(
         [&]
         {
-            As<IFrameworkElement>(GetComposableBase())->get_Parent(&m_lastSeenParent);
+            ComPtr<IDependencyObject> parent;
+            As<IFrameworkElement>(GetComposableBase())->get_Parent(&parent);
+            if (!parent) {
+                m_lastSeenParent.Reset();
+                return;
+            }
+            m_lastSeenParent = AsWeak(parent.Get());
         });
 }
 
@@ -130,7 +136,10 @@ IFACEMETHODIMP CanvasSwapChainPanel::RemoveFromVisualTree()
     return ExceptionBoundary(
         [&]
         {
-            RemoveFromVisualTreeImpl(m_lastSeenParent.Get(), As<IUIElement>(this).Get());
+            if (!m_lastSeenParent) {
+                return;
+            }
+            RemoveFromVisualTreeImpl(LockWeakRef<IDependencyObject>(m_lastSeenParent).Get(), As<IUIElement>(this).Get());
         });
 }
 
diff --git a/winrt/lib/xaml/CanvasSwapChainPanel.h b/winrt/lib/xaml/CanvasSwapChainPanel.h
index 9e958a919..a43101be4 100644
--- a/winrt/lib/xaml/CanvasSwapChainPanel.h
+++ b/winrt/lib/xaml/CanvasSwapChainPanel.h
@@ -39,7 +39,7 @@ namespace ABI { namespace Microsoft { namespace Graphics { namespace Canvas { na
         std::shared_ptr<ICanvasSwapChainPanelAdapter> m_adapter;
 
         ComPtr<ICanvasSwapChain> m_canvasSwapChain;
-        ComPtr<IDependencyObject> m_lastSeenParent;
+        WeakRef m_lastSeenParent;
 
     public:
         CanvasSwapChainPanel(std::shared_ptr<ICanvasSwapChainPanelAdapter> adapter);

From 9da469426d07d2c571256420291f8a0346f3a636 Mon Sep 17 00:00:00 2001
From: benstevens48 <ben@nebstone.co.uk>
Date: Sat, 5 Dec 2020 16:21:28 +0000
Subject: [PATCH 2/2] fix failing unit test

---
 winrt/lib/xaml/BaseControl.h            | 3 ++-
 winrt/lib/xaml/CanvasSwapChainPanel.cpp | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/winrt/lib/xaml/BaseControl.h b/winrt/lib/xaml/BaseControl.h
index 4167d632b..0b8cb4b07 100644
--- a/winrt/lib/xaml/BaseControl.h
+++ b/winrt/lib/xaml/BaseControl.h
@@ -233,10 +233,11 @@ namespace ABI { namespace Microsoft { namespace Graphics { namespace Canvas { na
             return ExceptionBoundary(
                 [&]
                 {
+                    auto control = As<IUIElement>(GetControl()); //Do this first because the unit tests expect a failure when this cast fails.
                     if (!m_lastSeenParent) {
                         return;
                     }
-                    RemoveFromVisualTreeImpl(LockWeakRef<IDependencyObject>(m_lastSeenParent).Get(), As<IUIElement>(GetControl()).Get());
+                    RemoveFromVisualTreeImpl(LockWeakRef<IDependencyObject>(m_lastSeenParent).Get(), control.Get());
                 });
         }
 
diff --git a/winrt/lib/xaml/CanvasSwapChainPanel.cpp b/winrt/lib/xaml/CanvasSwapChainPanel.cpp
index 0efcb0797..2a4a05804 100644
--- a/winrt/lib/xaml/CanvasSwapChainPanel.cpp
+++ b/winrt/lib/xaml/CanvasSwapChainPanel.cpp
@@ -136,10 +136,11 @@ IFACEMETHODIMP CanvasSwapChainPanel::RemoveFromVisualTree()
     return ExceptionBoundary(
         [&]
         {
+            auto control = As<IUIElement>(this); //Do this first because the unit tests expect a failure when this cast fails.
             if (!m_lastSeenParent) {
                 return;
             }
-            RemoveFromVisualTreeImpl(LockWeakRef<IDependencyObject>(m_lastSeenParent).Get(), As<IUIElement>(this).Get());
+            RemoveFromVisualTreeImpl(LockWeakRef<IDependencyObject>(m_lastSeenParent).Get(), control.Get());
         });
 }