dom/media/CanvasCaptureMediaStream.h

   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 "mozilla/dom/HTMLCanvasElement.h"
  11 #include "PrincipalHandle.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_ */