Update DesktopWindowXamlSource to describe how to avoid leaks

windows.ui.xaml.hosting/desktopwindowxamlsource.md

@@ -21,7 +21,7 @@ Equivalent WinUI class: [Microsoft.UI.Xaml.Hosting.DesktopWindowXamlSource](/win
 
 If you create a **DesktopWindowXamlSource** object before you create the [Windows.UI.Xaml.UIElement](../windows.ui.xaml/uielement.md) objects that will be hosted in it, the framework for hosting [Windows.UI.Xaml.UIElement](../windows.ui.xaml/uielement.md) content makes sure all the objects are initialized to the same thread. If you create the [Windows.UI.Xaml.UIElement](../windows.ui.xaml/uielement.md) objects before you create the **DesktopWindowXamlSource** object in which they will be hosted, you must call [WindowsXamlManager.InitializeForCurrentThread](windowsxamlmanager_initializeforcurrentthread_14911797.md) before you instantiate the [Windows.UI.Xaml.UIElement](../windows.ui.xaml/uielement.md) objects.
 
-Because **DesktopWindowXamlSource** derives from [IClosable](../windows.foundation/iclosable.md), so it is recommended that you **Close** it (**Dispose** it in .NET) when you’re finished with it.
+**DesktopWindowXamlSource** derives from [IClosable](../windows.foundation/iclosable.md). To avoid a leak that results from a cycle between it and **WindowsXamlManager** you must call **Close** (**Dispose** it in .NET) before you release **WindowsXamlManager**.
 
 ## -see-also
 [Using the UWP XAML hosting API in a desktop application](/windows/uwp/xaml-platform/using-the-xaml-hosting-api)

windows.ui.xaml.hosting/windowsxamlmanager_initializeforcurrentthread_14911797.md

@@ -19,11 +19,25 @@ Equivalent WinUI method: [Microsoft.UI.Xaml.Hosting.WindowsXamlManager.Initializ
 An object that contains a reference to the UWP XAML framework.
 
 ## -remarks
-Call this method to initialize the internal UWP XAML framework for the current thread in a desktop application in which you want to host [Windows.UI.Xaml.UIElement](../windows.ui.xaml/uielement.md) objects in a [DesktopWindowXamlSource](desktopwindowxamlsource.md). You only need to explicitly call this method if your application creates the **Windows.UI.Xaml.UIElement** objects before it creates the **DesktopWindowXamlSource** object that will host them. Your application should typically should call this method when the parent UI object that hosts the **DesktopWindowXamlSource** is instantiated.
+Call this method to initialize the internal UWP XAML framework for the current thread in a desktop application in which you want to host [Windows.UI.Xaml.UIElement](../windows.ui.xaml/uielement.md) objects in a [DesktopWindowXamlSource](desktopwindowxamlsource.md). Call this method if your application creates the **Windows.UI.Xaml.UIElement** objects before it creates the **DesktopWindowXamlSource** object that will host them, or if your program uses XAML from more than one thread. 
 
-If you create a **DesktopWindowXamlSource** object before you create the **Windows.UI.Xaml.UIElement** objects that will be hosted in it, you don’t need to call this method. In this scenario, the UWP XAML framework will be initialized for you when you instantiate the **DesktopWindowXamlSource** object.
+This method must be called before creating the **DesktopWindowXamlSource** on the thread.
 
-This method returns a [WindowsXamlManager](windowsxamlmanager.md) object that contains a reference to the UWP XAML framework. You can create as many **WindowsXamlManager** objects as you want on a given thread. However, because each object holds a reference to the UWP XAML framework, you should **Close** (**Dispose** in .NET) the objects to ensure that XAML resources are eventually released.
+This method returns a [WindowsXamlManager](windowsxamlmanager.md) object that contains a reference to the UWP XAML framework for the current thread. It is safe to call this method multiple times, it will return the same instance if one is active.
+You must destroy the instance after destroying the **DesktopWindowXamlSource** instances. Note, after releasing this object a message loop must be run to finish the resource rundown, otherwise the associated resources will be leaked.
+
+```cpp
+
+// Break the cycle between the WindowsXamlManager and the DesktopWindowXamlSource.
+m_xamlSource.Close();
+m_xamlManager = nullptr;
+
+// Drain the message queue after releasing WindowsXamlManager since rundown is async
+while (PeekMessageW(&msg, nullptr, 0, 0, PM_REMOVE))
+{
+    ::DispatchMessageW(&msg);
+}
+```
 
 ## -see-also