HRESULT XGameStreamingGetDisplayDetails(
        XGameStreamingClientId client,
        uint32_t maxSupportedPixels,
        float widestSupportedAspectRatio,
        float tallestSupportedAspectRatio,
        XGameStreamingDisplayDetails* displayDetails
)

#define DEFAULT_GAME_WIDTH 1920
#define DEFAULT_GAME_HEIGHT 1080

#define GAME_WIDEST_SUPPORTED_ASPECT_RATIO 21.5f / 9.0f
#define GAME_TALLEST_SUPPORTED_ASPECT_RATIO 16.0f / 10.0f

static uint32_t s_currentStreamWidth = DEFAULT_GAME_WIDTH;
static uint32_t s_currentStreamHeight = DEFAULT_GAME_HEIGHT;

// Option 1: Event driven. Note: be aware of potential threading issues when using the task queue.
void GameStreamingClientManager::OnConnectionStateChanged(XGameStreamingClientId client, XGameStreamingConnectionState connected)
{
    // Other connection work like registering or unregistering for the client properties change events.
    ...

    UpdateResolutionIfNeeded();
}

void GameStreamingClientManager::OnClientPropertiesChanged(
    XGameStreamingClientId client,
    uint32_t updatedPropertiesCount,
    XGameStreamingClientProperty* updatedProperties)
{
    for (uint32_t i = 0; i < updatedPropertiesCount; ++i)
    {
        switch (updatedProperties[i])
        {
        case XGameStreamingClientProperty::DisplayDetails:
        {
            UpdateResolutionIfNeeded();
            break;
        }

        default:
            // A characteristic we are not tracking - do nothing
            break;
        }
    }
}

// Option 2: Polling.

void Game::Update(DX::StepTimer const& timer)
{
    ...

    gameStreamingClientManager->UpdateResolutionIfNeeded();

    ...
}

void GameStreamingClientManager::UpdateResolutionIfNeeded()
{
    bool changeResolution = false;
    bool useDefaultResolution = true;

    // Only use custom resolution when there is only one streaming client connected.
    if (XGameStreamingGetClientCount() == 1)
    {
        XGameStreamingClientId client;
        uint32_t clientsUsed = 0;
        HRESULT hr = XGameStreamingGetClients(1, &client, &clientsUsed);
        if (SUCCEEDED(hr) && clientsUsed == 1)
        {
            XGameStreamingDisplayDetails displayDetails = {};
            hr = XGameStreamingGetDisplayDetails(client, DEFAULT_GAME_WIDTH * DEFAULT_GAME_HEIGHT, GAME_WIDEST_SUPPORTED_ASPECT_RATIO, GAME_TALLEST_SUPPORTED_ASPECT_RATIO, &displayDetails);

            if (SUCCEEDED(hr))
            {
                useDefaultResolution = false;

                // Assuming the game supports all resolutions, use the stream resolution to the preferred dimensions as provided.
                if (s_currentStreamWidth != displayDetails.preferredWidth || s_currentStreamHeight != displayDetails.preferredHeight)
                {
                    changeResolution = true;
                    s_currentStreamWidth = displayDetails.preferredWidth;
                    s_currentStreamHeight = displayDetails.preferredHeight;
                }
            }
            else
            {
                LogFormat(L"XGameStreamingGetDisplayDetails failed %x", hr);
            }
        }
        else
        {
            LogFormat(L"XGameStreamingGetClients failed hr=%x clientsUsed=%d", hr, clientsUsed);
        }
    }

    if (useDefaultResolution)
    {
        if (s_currentStreamWidth != DEFAULT_GAME_WIDTH || s_currentStreamHeight != DEFAULT_GAME_HEIGHT)
        {
            changeResolution = true;
            s_currentStreamWidth = DEFAULT_GAME_WIDTH;
            s_currentStreamHeight = DEFAULT_GAME_HEIGHT;
        }
    }

    if (changeResolution)
    {
        // Update the stream to the new resolution.
        HRESULT hr = XGameStreamingSetResolution(s_currentStreamWidth, s_currentStreamHeight);
        if (SUCCEEDED(hr))
        {
            // Update the game to render at the new resolution.
        }
        else
        {
            LogFormat(L"XGameStreamingSetResolution failed %x", hr);
        }
    }
}