【UWP】让 UWP 自己托管自己 —— Windows App SDK 篇

君无言

众所周知，UWP 使用的窗口模型是 CoreWindow，但是 UWP 本身只是一个应用模型，所以完全可以创建 win32 窗口，那么我们可以不可以创建一个 win32 窗口，然后像 XAML 岛 (XAML Islands) 一样把 XAML 托管上去呢？本篇将讲述如何利用 WAS (Windows App SDK，俗称 WinUI3) 在 UWP 创建一个 XAML 岛窗口。

演示视频：https://x.com/wherewhere7/status/1721570411388039587
由于 WAS 在 win32 应用模型下本身就是个 XAML 岛，所以 WAS 对 XAML 岛的支持要比 WUXC (Windows.UI.Xaml.Controls) 要好多了，接下来的内容大多是将 WAS 中实现窗口的方法迁移到 C#。
首先，不管是 WUXC 还是 WAS 的 XAML 岛都会判断当前的应用模型是否为ClassicDesktop，所以我们需要利用Detours劫持AppPolicyGetWindowingModel方法。具体内容如下：

1. #r "nuget:Detours.Win32Metadata"
2. #r "nuget:Microsoft.Windows.CsWin32"
4. using System;
5. using System.Runtime.CompilerServices;
6. using System.Runtime.InteropServices;
7. using Windows.Win32;
8. using Windows.Win32.Foundation;
9. using Windows.Win32.Storage.Packaging.Appx;
10. using Detours = Microsoft.Detours.PInvoke;
12. /// <summary>
13. /// Represents a hook for the <see cref="PInvoke.AppPolicyGetWindowingModel(HANDLE, AppPolicyWindowingModel*)"/> function.
14. /// </summary>
15. public sealed partial class HookWindowingModel : IDisposable
16. {
17.     /// <summary>
18.     /// The value that indicates whether the class has been disposed.
19.     /// </summary>
20.     private bool disposed;
22.     /// <summary>
23.     /// The reference count for the hook.
24.     /// </summary>
25.     private static int refCount;
27.     /// <summary>
28.     /// The value that represents the current process token.
29.     /// </summary>
30.     private const int currentProcessToken = -6;
32.     /// <remarks>The original <see cref="PInvoke.AppPolicyGetWindowingModel(HANDLE, AppPolicyWindowingModel*)"/> function.</remarks>
33.     /// <inheritdoc cref="PInvoke.AppPolicyGetWindowingModel(HANDLE, AppPolicyWindowingModel*)"/>
34.     private static unsafe delegate* unmanaged[Stdcall]<HANDLE, AppPolicyWindowingModel*, WIN32_ERROR> AppPolicyGetWindowingModel;
36.     /// <summary>
37.     /// Initializes a new instance of the <see cref="HookWindowingModel"/> class.
38.     /// </summary>
39.     public HookWindowingModel()
40.     {
41.         refCount++;
42.         StartHook();
43.     }
45.     /// <summary>
46.     /// Finalizes this instance of the <see cref="HookWindowingModel"/> class.
47.     /// </summary>
48.     ~HookWindowingModel()
49.     {
50.         Dispose();
51.     }
53.     /// <summary>
54.     /// Gets the value that indicates whether the hook is active.
55.     /// </summary>
56.     public static bool IsHooked { get; private set; }
58.     /// <summary>
59.     /// Gets or sets the windowing model to use when the hooked <see cref="PInvoke.AppPolicyGetWindowingModel(HANDLE, AppPolicyWindowingModel*)"/> function is called.
60.     /// </summary>
61.     internal static AppPolicyWindowingModel WindowingModel { get; set; } = AppPolicyWindowingModel.AppPolicyWindowingModel_ClassicDesktop;
63.     /// <summary>
64.     /// Starts the hook for the <see cref="PInvoke.AppPolicyGetWindowingModel(HANDLE, AppPolicyWindowingModel*)"/> function.
65.     /// </summary>
66.     private static unsafe void StartHook()
67.     {
68.         if (!IsHooked)
69.         {
70.             using FreeLibrarySafeHandle library = PInvoke.GetModuleHandle("KERNEL32.dll");
71.             if (!library.IsInvalid && NativeLibrary.TryGetExport(library.DangerousGetHandle(), nameof(PInvoke.AppPolicyGetWindowingModel), out nint appPolicyGetWindowingModel))
72.             {
73.                 void* appPolicyGetWindowingModelPtr = (void*)appPolicyGetWindowingModel;
74.                 delegate* unmanaged[Stdcall]<HANDLE, AppPolicyWindowingModel*, WIN32_ERROR> overrideAppPolicyGetWindowingModel = &OverrideAppPolicyGetWindowingModel;
76.                 _ = Detours.DetourRestoreAfterWith();
78.                 _ = Detours.DetourTransactionBegin();
79.                 _ = Detours.DetourUpdateThread(PInvoke.GetCurrentThread());
80.                 _ = Detours.DetourAttach(ref appPolicyGetWindowingModelPtr, overrideAppPolicyGetWindowingModel);
81.                 _ = Detours.DetourTransactionCommit();
83.                 AppPolicyGetWindowingModel = (delegate* unmanaged[Stdcall]<HANDLE, AppPolicyWindowingModel*, WIN32_ERROR>)appPolicyGetWindowingModelPtr;
84.                 IsHooked = true;
85.             }
86.         }
87.     }
89.     /// <summary>
90.     /// Ends the hook for the <see cref="PInvoke.AppPolicyGetWindowingModel(HANDLE, AppPolicyWindowingModel*)"/> function.
91.     /// </summary>
92.     private static unsafe void EndHook()
93.     {
94.         if (--refCount == 0 && IsHooked)
95.         {
96.             void* appPolicyGetWindowingModelPtr = AppPolicyGetWindowingModel;
97.             delegate* unmanaged[Stdcall]<HANDLE, AppPolicyWindowingModel*, WIN32_ERROR> overrideAppPolicyGetWindowingModel = &OverrideAppPolicyGetWindowingModel;
99.             _ = Detours.DetourTransactionBegin();
100.             _ = Detours.DetourUpdateThread(PInvoke.GetCurrentThread());
101.             _ = Detours.DetourDetach(&appPolicyGetWindowingModelPtr, overrideAppPolicyGetWindowingModel);
102.             _ = Detours.DetourTransactionCommit();
104.             AppPolicyGetWindowingModel = null;
105.             IsHooked = false;
106.         }
107.     }
109.     /// <param name="policy">A pointer to a variable of the <a target="_blank" href="https://docs.microsoft.com/windows/win32/api/appmodel/ne-appmodel-apppolicywindowingmodel">AppPolicyWindowingModel</a> enumerated type.
110.     /// When the function returns successfully, the variable contains the <see cref="WindowingModel"/> when the identified process is current; otherwise, the windowing model of the identified process.</param>
111.     /// <remarks>The overridden <see cref="PInvoke.AppPolicyGetWindowingModel(HANDLE, AppPolicyWindowingModel*)"/> function.</remarks>
112.     /// <inheritdoc cref="PInvoke.AppPolicyGetWindowingModel(HANDLE, AppPolicyWindowingModel*)"/>
113.     [UnmanagedCallersOnly(CallConvs = [typeof(CallConvStdcall)])]
114.     private static unsafe WIN32_ERROR OverrideAppPolicyGetWindowingModel(HANDLE processToken, AppPolicyWindowingModel* policy)
115.     {
116.         if ((int)processToken.Value == currentProcessToken)
117.         {
118.             *policy = WindowingModel;
119.             return WIN32_ERROR.ERROR_SUCCESS;
120.         }
121.         return AppPolicyGetWindowingModel(processToken, policy);
122.     }
124.     /// <inheritdoc/>
125.     public void Dispose()
126.     {
127.         if (!disposed && IsHooked)
128.         {
129.             EndHook();
130.         }
131.         GC.SuppressFinalize(this);
132.         disposed = true;
133.     }
134. }

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准备工作完成，接下来我们就可以创建窗口了，如果顺利的话我们只需要new Microsoft.UI.Xaml.Window()就行了，但是很遗憾，经过测试在 UWP 并不能正常初始化这个类，有可能是我使用的方法不太正确，或许以后可能能找到正常使用的办法，不过现在我们只能去手动创建一个 Win32 窗口了。
首先我们需要新创建一个线程，CoreWindow 线程无法新建 XAML 岛，不过在 XAML 岛线程可以，新建线程只需要用Thread就行了。

1. new Thread(() => { ... });

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WAS 提供了AppWindow来管理 win32 窗口，我们只需要使用它创建一个窗口就行了。

1. AppWindow window = AppWindow.Create();

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接下来我们需要创建 XAML 岛，这时我们就需要利用上面劫持器来劫持获取应用模型的方法了。

1. DispatcherQueueController controller;
2. DesktopWindowXamlSource source;
4. using (HookWindowingModel hook = new())
5. {
6.     controller = DispatcherQueueController.CreateOnCurrentThread();
7.     source = new DesktopWindowXamlSource();
8. }

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然后我们就可以把 XAML 岛糊到之前创建的 AppWindow 上了。

1. source.Initialize(window.Id);
2. DesktopChildSiteBridge bridge = source.SiteBridge;
3. bridge.ResizePolicy = ContentSizePolicy.ResizeContentToParentWindow;
4. bridge.Show();
6. DispatcherQueue dispatcherQueue = controller.DispatcherQueue;
7. window.AssociateWithDispatcherQueue(dispatcherQueue);

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由于 XAML 岛存在的一些特性，当窗口扩展标题栏或者全屏化的时候窗口内容并不会跟着变化，所以我们需要一些小魔法来让它在变化时调整大小。

1. window.Changed += (sender, args) =>
2. {
3.     if (args.DidPresenterChange)
4.     {
5.         bridge.ResizePolicy = ContentSizePolicy.None;
6.         bridge.ResizePolicy = ContentSizePolicy.ResizeContentToParentWindow;
7.     }
8. };

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最后不要忘了保持当前线程，不然这里跑完了窗口就退出了。

1. dispatcherQueue.RunEventLoop();
2. await controller.ShutdownQueueAsync();

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当窗口关闭后记得执行DispatcherQueue.EnqueueEventLoopExit()来释放保持的线程。
最后把之前的东西组合起来，再加点东西：

1. /// <summary>
2. /// Create a new <see cref="DesktopWindow"/> instance.
3. /// </summary>
4. /// <param name="launched">Do something after <see cref="DesktopWindowXamlSource"/> created.</param>
5. /// <returns>The new instance of <see cref="DesktopWindow"/>.</returns>
6. public static Task<DesktopWindow> CreateAsync(Action<DesktopWindowXamlSource> launched)
7. {
8.     TaskCompletionSource<DesktopWindow> taskCompletionSource = new();
10.     new Thread(async () =>
11.     {
12.         try
13.         {
14.             DispatcherQueueController controller;
15.             DesktopWindowXamlSource source;
16.             AppWindow window = AppWindow.Create();
18.             using (HookWindowingModel hook = new())
19.             {
20.                 controller = DispatcherQueueController.CreateOnCurrentThread();
21.                 source = new DesktopWindowXamlSource();
22.             }
24.             source.Initialize(window.Id);
25.             DesktopChildSiteBridge bridge = source.SiteBridge;
26.             bridge.ResizePolicy = ContentSizePolicy.ResizeContentToParentWindow;
27.             bridge.Show();
29.             window.Changed += (sender, args) =>
30.             {
31.                 if (args.DidPresenterChange)
32.                 {
33.                     bridge.ResizePolicy = ContentSizePolicy.None;
34.                     bridge.ResizePolicy = ContentSizePolicy.ResizeContentToParentWindow;
35.                 }
36.             };
38.             DispatcherQueue dispatcherQueue = controller.DispatcherQueue;
39.             window.AssociateWithDispatcherQueue(dispatcherQueue);
40.             TrackWindow(window);
42.             launched(source);
43.             DesktopWindow desktopWindow = new()
44.             {
45.                 AppWindow = window,
46.                 WindowXamlSource = source
47.             };
48.             taskCompletionSource.SetResult(desktopWindow);
50.             dispatcherQueue.RunEventLoop();
51.             await controller.ShutdownQueueAsync();
52.         }
53.         catch (Exception e)
54.         {
55.             taskCompletionSource.SetException(e);
56.         }
57.     })
58.     {
59.         Name = nameof(DesktopWindowXamlSource)
60.     }.Start();
62.     return taskCompletionSource.Task;
63. }
65. /// <summary>
66. /// Create a new <see cref="DesktopWindow"/> instance.
67. /// </summary>
68. /// <param name="dispatcherQueue">The <see cref="DispatcherQueue"/> to provide thread.</param>
69. /// <param name="launched">Do something after <see cref="DesktopWindowXamlSource"/> created.</param>
70. /// <returns>The new instance of <see cref="DesktopWindow"/>.</returns>
71. public static Task<DesktopWindow> CreateAsync(DispatcherQueue dispatcherQueue, Action<DesktopWindowXamlSource> launched)
72. {
73.     TaskCompletionSource<DesktopWindow> taskCompletionSource = new();
75.     _ = dispatcherQueue.TryEnqueue(() =>
76.     {
77.         try
78.         {
79.             DesktopWindowXamlSource source;
80.             AppWindow window = AppWindow.Create();
81.             window.AssociateWithDispatcherQueue(dispatcherQueue);
82.             TrackWindow(window);
84.             using (HookWindowingModel hook = new())
85.             {
86.                 source = new DesktopWindowXamlSource();
87.             }
89.             source.Initialize(window.Id);
90.             DesktopChildSiteBridge bridge = source.SiteBridge;
91.             bridge.ResizePolicy = ContentSizePolicy.ResizeContentToParentWindow;
92.             bridge.Show();
94.             window.Changed += (sender, args) =>
95.             {
96.                 if (args.DidPresenterChange)
97.                 {
98.                     bridge.ResizePolicy = ContentSizePolicy.None;
99.                     bridge.ResizePolicy = ContentSizePolicy.ResizeContentToParentWindow;
100.                 }
101.             };
103.             launched(source);
104.             DesktopWindow desktopWindow = new()
105.             {
106.                 AppWindow = window,
107.                 WindowXamlSource = source
108.             };
109.             taskCompletionSource.SetResult(desktopWindow);
110.         }
111.         catch (Exception e)
112.         {
113.             taskCompletionSource.SetException(e);
114.         }
115.     });
117.     return taskCompletionSource.Task;
118. }
120. private static void TrackWindow(AppWindow window)
121. {
122.     if (ActiveDesktopWindows.ContainsKey(window.DispatcherQueue))
123.     {
124.         ActiveDesktopWindows[window.DispatcherQueue] += 1;
125.     }
126.     else
127.     {
128.         ActiveDesktopWindows[window.DispatcherQueue] = 1;
129.     }
130.     window.Destroying -= AppWindow_Destroying;
131.     window.Destroying += AppWindow_Destroying;
132. }
134. private static void AppWindow_Destroying(AppWindow sender, object args)
135. {
136.     if (ActiveDesktopWindows.TryGetValue(sender.DispatcherQueue, out ulong num))
137.     {
138.         num--;
139.         if (num == 0)
140.         {
141.             ActiveDesktopWindows.Remove(sender.DispatcherQueue);
142.             sender.DispatcherQueue.EnqueueEventLoopExit();
143.             return;
144.         }
145.         ActiveDesktopWindows[sender.DispatcherQueue] = num;
146.     }
147. }
149. private static Dictionary<DispatcherQueue, ulong> ActiveDesktopWindows { get; } = [];

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其中DesktopWindow是用来存放 AppWindow 和 DesktopWindowXamlSource的类，如果不嫌麻烦的话可以包裹成一个和 Microsoft.UI.Xaml.Window一样的东西。
最后附上示例应用：https://github.com/wherewhere/CoreAppUWP/tree/muxc

来源:https://www.cnblogs.com/wherewhere/p/18446822
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