commit 2aad81259ef832172d65aeaba6401fee857a0f48
author Austin Orion <auorion@microsoft.com> Thu Jan 07 22:34:31 2021
committer Commit Bot <commit-bot@chromium.org> Wed Jan 27 21:17:19 2021
tree 278ea4270c97ffe5ba54b650a79569d52d3a0d14
parent ca5d4a4152df8ee8ba9c7d26461d2dedfc9bd97f

Refactor and implement WgcCapturerWin, a source agnostic capturer.

This change refactors WgcWindowCapturer into WgcCapturerWin, a source
agnostic capturer, and finishes the implementation to enable both window
and screen capture.

This CL depends on another which must complete first:
196622: Add ability to load CreateDirect3DDeviceFromDXGIDevice from
d3d11.dll | https://webrtc-review.googlesource.com/c/src/+/196622

This feature remains off by default behind a build flag, due to it
adding a depency on the Win10 SDK vv10.0.19041 which not all consumers
of WebRTC have upgraded to. A follow up change later will enable the
rtc_enable_win_wgc build flag, but for now it should remain off.

The basic operation of this class is as follows:
Consumers call either WgcCapturerWin::CreateRawWindowCapturer or
CreateRawScreenCapturer to receive a correctly initialized
WgcCapturerWin object suitable for the desired source type.

Callers then indicate via SelectSource and a SourceId the desired
capture target, and the capturer creates an appropriate WgcCaptureSource
for the correct type (window or screen) using the
WgcCaptureSourceFactory supplied at construction.

Next, callers request frames for the currently selected source and the
capturer then creates a WgcCaptureSession and stores it in a map for
more efficient capture of multiple sources.

The WgcCaptureSession is supplied with a GraphicsCaptureItem created by
the WgcCaptureSource. It uses this item to create a
Direct3D11CaptureFramePool and create and start a
GraphicsCaptureSession.

Once started, captured frames will begin to be deposited into the
FramePool. Typically, one would listen for the FrameArrived event and
process the frame then, but due to the synchronous nature of the
DesktopCapturer interface, and to avoid a more complicated multi-
threaded architecture we ignore the FrameArrived event. Instead, we
wait for a request for a frame from the caller, then we check the
FramePool for a frame, and process it on demand.

Processing a frame involves moving the image data from an
ID3D11Texture2D stored in the GPU into a texture that is accessible
from the CPU, and then copying the data into the new WgcDesktopFrame
class. This copy is necessary as otherwise we would need to manage the
lifetimes of the CaptureFrame and ID3D11Texture2D objects, lest the
buffer be invalidated.

Once we've copied the data and returned it to the caller, we can unmap
the texture and exit the scope of the GetFrame method, which will
destruct the CaptureFrame object. At this point, the CaptureSession
will begin capturing a new frame, and will soon deposit it into the
FramePool and we can repeat.

Bug: webrtc:9273
Change-Id: I02263c4fd587df652b04d5267fad8965330d0f5b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/200161
Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@webrtc.org>
Commit-Queue: Austin Orion <auorion@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#33083}