How can I start a UWP (Xaml) application from a Core application in its own thread?

Question

How can I start a UWP (Xaml) application from a Core application in its own thread?

I would like to have both a UWP xaml application (called my_xaml_app) and a UWP Core application (called my_core_app) running in the same program in their own respective thread.

So far I have tried the following approach:

my_core_app::my_core_app()
{
    ViewProviderFactory viewProviderFactory;
    winrt::Windows::ApplicationModel::Core::CoreApplication::Run(viewProviderFactory);
}

winrt::Windows::Foundation::IAsyncAction init_core_app()
 {
        co_await winrt::resume_background();
        my_core_app coreApp;
 }

int __stdcall wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)
{
      init_core_app();

      winrt::Windows::UI::Xaml::Application::Start(
      [](auto &&)
      {
          winrt::make<winrt::my_xaml_app::implementation::App>();
      });

      return 0;
 }

I didnt include the details of how my_core_app and my_xaml_app are instantiated but you can assume that they do work correctly since they launch correctly if I start them alone by themselves from the main thread.

In the code above, my_xaml_app starts correctly because it is called from the main thread. However my_core_app fails to start and reports the following errors:

WinRT originate error - 0x8001010E : 'The Application Object must initially be accessed from the multi-thread apartment.'.

The application called an interface that was marshalled for a different thread.

Microsoft C++ exception: winrt::hresult_wrong_thread at memory location 0x00000040E4EFE6E8

Is this something that is possible and if so how can it be done?

xaml

uwp

com

c++-winrt

asked on Stack Overflow Sep 17, 2018 by

mbl • edited Sep 17, 2018 by

IInspectable

2 Answers

to initialize from main thread initially you can use CoreDispatcher

below is the sample code from the docs of running the app from CoreDispatcher

// App.cpp
...
// An implementation of IFrameworkView::Run.
void Run()
{
    CoreWindow window{ CoreWindow::GetForCurrentThread() };
    window.Activate();

    CoreDispatcher dispatcher{ window.Dispatcher() };
    dispatcher.ProcessEvents(CoreProcessEventsOption::ProcessUntilQuit);
}

// The CoreApplication::Run call indirectly calls the App::Run function above.
int __stdcall wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)
{
    CoreApplication::Run(App());
}

answered on Stack Overflow Sep 17, 2018 by

touseefbsb • edited Sep 17, 2018 by

IInspectable

The error message is showing the internals of how COM apartments work. A single process can only have one MTA apartment. It is not possible to have two MTA threads in the same process.

That said, you can launch the application in another process and that would work.

answered on Stack Overflow Oct 15, 2018 by

Nathan • edited Oct 15, 2018 by

Brad Larson

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