WebView2 created from C++/WinRT does not render

[kasperisager]

Describe the bug

Consider the following C++ application:

struct App : public ApplicationT<App, IXamlMetadataProvider> {
  void
  OnLaunched (LaunchActivatedEventArgs const &) {
    Resources().MergedDictionaries().Append(XamlControlsResources());

    WebView2 web_view;
    web_view.Source(Uri(L"https://github.com"));

    Window window;
    window.Content(web_view);
    window.Activate();
  }

  XamlControlsXamlMetaDataProvider provider;

  IXamlType
  GetXamlType (hstring const &name) {
    return provider.GetXamlType(name);
  }

  IXamlType
  GetXamlType (TypeName const &type) {
    return provider.GetXamlType(type);
  }

  com_array<XmlnsDefinition>
  GetXmlnsDefinitions () {
    return provider.GetXmlnsDefinitions();
  }
};

int
main () {
  init_apartment();

  Application::Start([] (auto &&) { make<App>(); });
}

When run, the web view isn't rendered and I instead see a blank window. The NavigationStarting event also doesn't fire, but I do see a <exe>.WebView2 directory created.

Steps to reproduce the bug

1. Compile and run the code above.

Expected behavior

No response

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.4.4: 1.4.231219000

Windows version

Windows 11 (22H2): Build 22621

Additional context

If relevant, this is the manifest used:

<?xml version="1.0" encoding="utf-8"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
  <assemblyIdentity name="App" version="1.0.0.0" />

  <application xmlns="urn:schemas-microsoft-com:asm.v3">
    <windowsSettings>
      <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2</dpiAwareness>
    </windowsSettings>
  </application>

  <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
    <application>
      <maxversiontested Id="10.0.18362.1"/>
      <supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}" />
    </application>
  </compatibility>
</assembly>

[github-actions]

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Please view the issues below to see if they solve your problem, and if the issue describes your problem please consider closing this one. Thank you!

Closed similar issues:

• [WinUI3][C++/WinRT] WebView2 menu issues (#6958), similarity score: 0.73
• Cannot include WebView2 Control in Windows App SDK preview 3 C++ App (#6314), similarity score: 0.71

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[kasperisager]

I've updated my code example per #9265 (comment) and am still not seeing the web view.

[kasperisager]

The cause seems to be initialising COM for multi-threaded object concurrency as apartment-threaded object concurrency seems to fix it:

init_apartment(apartment_type::single_threaded);

It's actually right there in the documentation as well:

The WebView2 control is based on the Component Object Model (COM) and must run on a Single Threaded Apartments (STA) thread.

https://learn.microsoft.com/en-us/microsoft-edge/webview2/concepts/threading-model