dom/media/CanvasCaptureMediaStream.h
author Marian-Vasile Laza <mlaza@mozilla.com>
Tue, 30 Nov 2021 23:30:59 +0200
changeset 600683 15c1262d6e8f4524fa63dcc9cc2572038ffb3a92
parent 513762 49adcf9a70abc9df4f11a123d181aa7213a20615
permissions -rw-r--r--
Backed out 6 changesets (bug 1715892, bug 1719735) for causing bc test failures. CLOSED TREE Backed out changeset 196952bd8c9c (bug 1715892) Backed out changeset 9105fe01c025 (bug 1715892) Backed out changeset 4c15d1a24ccd (bug 1715892) Backed out changeset 2c328b84285f (bug 1715892) Backed out changeset 8fcdcdf44b62 (bug 1719735) Backed out changeset c48f398e301f (bug 1719735)

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_dom_CanvasCaptureMediaStream_h_
#define mozilla_dom_CanvasCaptureMediaStream_h_

#include "DOMMediaStream.h"
#include "mozilla/dom/HTMLCanvasElement.h"
#include "PrincipalHandle.h"

class nsIPrincipal;

namespace mozilla {
class DOMMediaStream;
class SourceMediaTrack;

namespace layers {
class Image;
}  // namespace layers

namespace dom {
class CanvasCaptureMediaStream;
class HTMLCanvasElement;
class OutputStreamFrameListener;

/*
 * The CanvasCaptureMediaStream is a MediaStream subclass that provides a video
 * track containing frames from a canvas. See an architectural overview below.
 *
 * ----------------------------------------------------------------------------
 *     === Main Thread ===              __________________________
 *                                     |                          |
 *                                     | CanvasCaptureMediaStream |
 *                                     |__________________________|
 *                                                  |
 *                                                  | RequestFrame()
 *                                                  v
 *                                       ________________________
 *  ________   FrameCaptureRequested?   |                        |
 * |        | ------------------------> |   OutputStreamDriver   |
 * | Canvas |  SetFrameCapture()        | (FrameCaptureListener) |
 * |________| ------------------------> |________________________|
 *                                                  |
 *                                                  | SetImage() -
 *                                                  | AppendToTrack()
 *                                                  |
 *                                                  v
 *                                      __________________________
 *                                     |                          |
 *                                     |  MTG / SourceMediaTrack  |
 *                                     |__________________________|
 * ----------------------------------------------------------------------------
 */

/*
 * Base class for drivers of the output stream.
 * It is up to each sub class to implement the NewFrame() callback of
 * FrameCaptureListener.
 */
class OutputStreamDriver : public FrameCaptureListener {
 public:
  OutputStreamDriver(SourceMediaTrack* aSourceStream,
                     const PrincipalHandle& aPrincipalHandle);

  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(OutputStreamDriver);

  /*
   * Sub classes can SetImage() to update the image being appended to the
   * output stream. It will be appended on the next NotifyPull from MTG.
   */
  void SetImage(RefPtr<layers::Image>&& aImage, const TimeStamp& aTime);

  /*
   * Ends the track in mSourceStream when we know there won't be any more images
   * requested for it.
   */
  void EndTrack();

  /*
   * Makes sure any internal resources this driver is holding that may create
   * reference cycles are released.
   */
  virtual void Forget() {}

  const RefPtr<SourceMediaTrack> mSourceStream;
  const PrincipalHandle mPrincipalHandle;

 protected:
  virtual ~OutputStreamDriver();
};

class CanvasCaptureMediaStream : public DOMMediaStream {
 public:
  CanvasCaptureMediaStream(nsPIDOMWindowInner* aWindow,
                           HTMLCanvasElement* aCanvas);

  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(CanvasCaptureMediaStream,
                                           DOMMediaStream)

  nsresult Init(const dom::Optional<double>& aFPS, nsIPrincipal* aPrincipal);

  JSObject* WrapObject(JSContext* aCx,
                       JS::Handle<JSObject*> aGivenProto) override;

  // WebIDL
  HTMLCanvasElement* Canvas() const { return mCanvas; }
  void RequestFrame();

  dom::FrameCaptureListener* FrameCaptureListener();

  /**
   * Stops capturing for this stream at mCanvas.
   */
  void StopCapture();

  SourceMediaTrack* GetSourceStream() const;

 protected:
  ~CanvasCaptureMediaStream();

 private:
  RefPtr<HTMLCanvasElement> mCanvas;
  RefPtr<OutputStreamDriver> mOutputStreamDriver;
};

}  // namespace dom
}  // namespace mozilla

#endif /* mozilla_dom_CanvasCaptureMediaStream_h_ */