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CanvasCaptureMediaStream.h (4522B)

      1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
      2 /* This Source Code Form is subject to the terms of the Mozilla Public
      3 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
      4 * You can obtain one at http://mozilla.org/MPL/2.0/. */
      5 
      6 #ifndef mozilla_dom_CanvasCaptureMediaStream_h_
      7 #define mozilla_dom_CanvasCaptureMediaStream_h_
      8 
      9 #include "DOMMediaStream.h"
     10 #include "PrincipalHandle.h"
     11 #include "mozilla/dom/HTMLCanvasElement.h"
     12 
     13 class nsIPrincipal;
     14 
     15 namespace mozilla {
     16 class DOMMediaStream;
     17 class SourceMediaTrack;
     18 
     19 namespace layers {
     20 class Image;
     21 }  // namespace layers
     22 
     23 namespace dom {
     24 class CanvasCaptureMediaStream;
     25 class HTMLCanvasElement;
     26 class OutputStreamFrameListener;
     27 
     28 /*
     29 * The CanvasCaptureMediaStream is a MediaStream subclass that provides a video
     30 * track containing frames from a canvas. See an architectural overview below.
     31 *
     32 * ----------------------------------------------------------------------------
     33 *     === Main Thread ===              __________________________
     34 *                                     |                          |
     35 *                                     | CanvasCaptureMediaStream |
     36 *                                     |__________________________|
     37 *                                                  |
     38 *                                                  | RequestFrame()
     39 *                                                  v
     40 *                                       ________________________
     41 *  ________   FrameCaptureRequested?   |                        |
     42 * |        | ------------------------> |   OutputStreamDriver   |
     43 * | Canvas |  SetFrameCapture()        | (FrameCaptureListener) |
     44 * |________| ------------------------> |________________________|
     45 *                                                  |
     46 *                                                  | SetImage() -
     47 *                                                  | AppendToTrack()
     48 *                                                  |
     49 *                                                  v
     50 *                                      __________________________
     51 *                                     |                          |
     52 *                                     |  MTG / SourceMediaTrack  |
     53 *                                     |__________________________|
     54 * ----------------------------------------------------------------------------
     55 */
     56 
     57 /*
     58 * Base class for drivers of the output stream.
     59 * It is up to each sub class to implement the NewFrame() callback of
     60 * FrameCaptureListener.
     61 */
     62 class OutputStreamDriver : public FrameCaptureListener {
     63 public:
     64  OutputStreamDriver(SourceMediaTrack* aSourceStream,
     65                     const PrincipalHandle& aPrincipalHandle);
     66 
     67  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(OutputStreamDriver);
     68 
     69  /*
     70   * Called from js' requestFrame() when it wants the next painted frame to be
     71   * explicitly captured.
     72   */
     73  virtual void RequestFrameCapture() = 0;
     74 
     75  /*
     76   * Sub classes can SetImage() to update the image being appended to the
     77   * output stream. It will be appended on the next NotifyPull from MTG.
     78   */
     79  void SetImage(RefPtr<layers::Image>&& aImage, const TimeStamp& aTime);
     80 
     81  /*
     82   * Ends the track in mSourceStream when we know there won't be any more images
     83   * requested for it.
     84   */
     85  void EndTrack();
     86 
     87  const RefPtr<SourceMediaTrack> mSourceStream;
     88  const PrincipalHandle mPrincipalHandle;
     89 
     90 protected:
     91  virtual ~OutputStreamDriver();
     92 };
     93 
     94 class CanvasCaptureMediaStream : public DOMMediaStream {
     95 public:
     96  CanvasCaptureMediaStream(nsPIDOMWindowInner* aWindow,
     97                           HTMLCanvasElement* aCanvas);
     98 
     99  NS_DECL_ISUPPORTS_INHERITED
    100  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(CanvasCaptureMediaStream,
    101                                           DOMMediaStream)
    102 
    103  nsresult Init(const dom::Optional<double>& aFPS, nsIPrincipal* aPrincipal);
    104 
    105  JSObject* WrapObject(JSContext* aCx,
    106                       JS::Handle<JSObject*> aGivenProto) override;
    107 
    108  // WebIDL
    109  HTMLCanvasElement* Canvas() const { return mCanvas; }
    110  void RequestFrame();
    111 
    112  dom::FrameCaptureListener* FrameCaptureListener();
    113 
    114  /**
    115   * Stops capturing for this stream at mCanvas.
    116   */
    117  void StopCapture();
    118 
    119  SourceMediaTrack* GetSourceStream() const;
    120 
    121 protected:
    122  ~CanvasCaptureMediaStream();
    123 
    124 private:
    125  RefPtr<HTMLCanvasElement> mCanvas;
    126  RefPtr<OutputStreamDriver> mOutputStreamDriver;
    127 };
    128 
    129 }  // namespace dom
    130 }  // namespace mozilla
    131 
    132 #endif /* mozilla_dom_CanvasCaptureMediaStream_h_ */