is it possible to attach an DesktopWindowXamlSource instance to an AppWindow?

[oldoldman]

Hi guys,
I found that I can get the HWND of an AppWindow by means of calling Windowing_GetWindowFromWindowId, that inspired me to verify if I can attach an DesktopWindowXamlSource instance to the HWND, so I have the following code. The creation of XamlIsLand always failed with 0x8000ffff. Any suggestion? Many thanks!

static void loadFrameworkUdk() {
  auto mod = GetModuleHandle("Microsoft.Internal.FrameworkUdk.dll");
  if (!mod) {
    mod = LoadLibrary("Microsoft.Internal.FrameworkUdk.dll");
  }
  if (mod) {
    GetWindowFromWindowId = (pfn_GetWindowFromWindowId)GetProcAddress(mod,"Windowing_GetWindowFromWindowId");
  }
}

int WinMain(HINSTANCE,HINSTANCE,PSTR,int) {
  winrt::init_apartment(winrt::apartment_type::single_threaded);
  loadFrameworkUdk();
  auto win = AppWindow::Create();
  HWND hwnd;
  auto hr = GetWindowFromWindowId(win.Id().Value,&hwnd);
  try {
    DesktopWindowXamlSource XamlIsLand;
    auto native = XamlIsLand.try_as<IDesktopWindowXamlSourceNative>();
    winrt::check_hresult(native->AttachToWindow(hwnd));
    auto btn = Button();
    btn.Content(winrt::box_value(L"Button"));
    XamlIsLand.Content(btn);
  } catch (winrt::hresult_error e) {
    printf("error 0x%x\n",int32_t(e.code()));
  }
      
  win.Title(L"WIN32 & WINUI 3");
  auto bar = win.TitleBar();
  auto bgc = Colors::DeepSkyBlue();
  bar.BackgroundColor(bgc);
  bar.ButtonBackgroundColor(bgc);
  bar.ExtendsContentIntoTitleBar(true);
  win.Resize({400,300});
  win.Show();
  
  auto ctl = DispatcherQueueController::CreateOnCurrentThread();
  auto que = ctl.DispatcherQueue();
  auto tkn = win.Destroying(
  [&](AppWindow const&,fnd::IInspectable const&) {
    que.EnqueueEventLoopExit();
  }); 
      
  que.RunEventLoop();
  ctl.ShutdownQueue();
  win.Destroying(tkn);
}

int main() {
  WinMain(nullptr,nullptr,nullptr,0);
}

[oldoldman]

It works by create a SxS manifest as follow

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
  <assemblyIdentity version="1.0.0.0" name="winui32" type="win32"/>
  <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
    <application>
      <maxversiontested Id="10.0.18226.0"/>
      <supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}" />
    </application>
  </compatibility>
</assembly>