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How to activate an app (DirectX and C++)

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This topic shows how to define the activation experience for a Universal Windows Platform (UWP) DirectX app.

Register the app activation event handler

First, register to handle the CoreApplicationView::Activated event, which is raised when your app is started and initialized by the operating system.

Add this code to your implementation of the IFrameworkView::Initialize method of your view provider (named MyViewProvider in the example):

void App::Initialize(CoreApplicationView^ applicationView)
{
    // Register event handlers for the app lifecycle. This example includes Activated, so that we
    // can make the CoreWindow active and start rendering on the window.
    applicationView->Activated +=
        ref new TypedEventHandler<CoreApplicationView^, IActivatedEventArgs^>(this, &App::OnActivated);
  
  //...

}

Activate the CoreWindow instance for the app

When your app starts, you must obtain a reference to the CoreWindow for your app. CoreWindow contains the window event message dispatcher that your app uses to process window events. Obtain this reference in your callback for the app activation event by calling CoreWindow::GetForCurrentThread. Once you have obtained this reference, activate the main app window by calling CoreWindow::Activate.

void App::OnActivated(CoreApplicationView^ applicationView, IActivatedEventArgs^ args)
{
    // Run() won't start until the CoreWindow is activated.
    CoreWindow::GetForCurrentThread()->Activate();
}

Start processing event message for the main app window

Your callbacks occur as event messages are processed by the CoreDispatcher for the app's CoreWindow. This callback will not be invoked if you do not call CoreDispatcher::ProcessEvents from your app's main loop (implemented in the IFrameworkView::Run method of your view provider).

// This method is called after the window becomes active.
void App::Run()
{
    while (!m_windowClosed)
    {
        if (m_windowVisible)
        {
            CoreWindow::GetForCurrentThread()->Dispatcher->ProcessEvents(CoreProcessEventsOption::ProcessAllIfPresent);

            m_main->Update();

            if (m_main->Render())
            {
                m_deviceResources->Present();
            }
        }
        else
        {
            CoreWindow::GetForCurrentThread()->Dispatcher->ProcessEvents(CoreProcessEventsOption::ProcessOneAndAllPending);
        }
    }
}