README.md

Win32CaptureSample

A simple sample using the Windows.Graphics.Capture APIs in a Win32 application.

Points of interest

Here are some places you should look at in the code to learn the following:

• Capture a window given its window handle. App::StartCapture(HWND)
• Capture a monitor given its monitor handle. App::StartCapture(HMONITOR)
• Show the system provided picker and capture the selected window/monitor. App::StartCaptureWithPickerAsync()
• Setting up the Windows.Graphics.Capture API. SimpleCapture::SimpleCapture()
• Processing frames received from the frame pool. SimpleCapture::OnFrameArrived(Direct3D11CaptureFramePool, IInspectable)
• Taking a snapshot CaptureSnapshot::TakeAsync(IDirect3DDevice, GraphicsCaptureItem) and App::TakeSnapshotAsync() for capturing and encoding respectively.

Win32 vs UWP

For the most part, using the API is the same between Win32 and UWP. However, there are some small differences.

1. The GraphicsCapturePicker won't be able to infer your window in a Win32 application, so you'll have to QI for IInitializeWithWindow and provide your window's HWND.
2. Direct3D11CaptureFramePool requires a DispatcherQueue much like the Composition APIs. You'll need to create a dispatcher for your thread. Alternatively you can use Direct3D11CaptureFramePool::CreateFreeThreaded to create the frame pool. Doing so will remove the DispatcherQueue requirement, but the FrameArrived event will be called from an arbitrary thread.

Create vs CreateFreeThreaded

You might have noticed that there are two ways to create the Direct3D11CaptureFramePool in the code (SimpleCapture::SimpleCapture and CaptureSnapshot::TakeAsync). As the name suggests, the method you use to create the frame pool dictates its threading behavior.

Creating the frame pool using Direct3D11CaptureFramePool::Create ensures that the frame pool's FrameArrived event will always call you back on the thread the frame pool was created on. In order to do this, the frame pool requires that a DispatcherQueue be associated with the thread, much like the Windows::UI::Composition::Compositor object.

Creating the frame pool using Direct3D11CaptureFramePool::CreateFreeThreaded, on the other hand, does not require the presence of a DispatcherQueue. However, in return, the frame pool's FrameArrived event will call you back on an arbitrary thread. Additionally, your callback must be agile (this should only effect those using the raw WinRT ABI).