content/public/browser/render_widget_host_view_frame_subscriber.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CONTENT_PUBLIC_BROWSER_RENDER_WIDGET_HOST_VIEW_FRAME_SUBSCRIBER_H_
   6 #define CONTENT_PUBLIC_BROWSER_RENDER_WIDGET_HOST_VIEW_FRAME_SUBSCRIBER_H_
   7
   8 #include "base/callback.h"
   9 #include "base/time/time.h"
  10
  11 namespace gfx {
  12 class Rect;
  13 class Size;
  14 }  // namespace gfx
  15
  16 namespace media {
  17 class VideoFrame;
  18 }  // namespace media
  19
  20 namespace content {
  21
  22 // Defines an interface for listening to events of frame presentation and to
  23 // instruct the platform layer (i.e. RenderWidgetHostView) to copy a frame.
  24 //
  25 // Further processing is possible (e.g. scale and color space conversion)
  26 // through this interface. See ShouldCaptureFrame() for details.
  27 //
  28 // It is platform dependent which thread this object lives on, but it is
  29 // guaranteed to be used on a single thread.
  30 class RenderWidgetHostViewFrameSubscriber {
  31  public:
  32   virtual ~RenderWidgetHostViewFrameSubscriber() {}
  33
  34   // Called when a captured frame is available or the frame is no longer
  35   // needed by the platform layer.
  36   //
  37   // If |frame_captured| is true then frame provided contains valid content and
  38   // |timestamp| is the time when the frame was painted.
  39   //
  40   // If |frame_captured| is false then the content in frame provided is
  41   // invalid. There was an error during the process of frame capture or the
  42   // platform layer is shutting down. |timestamp| is also invalid in this case.
  43   typedef base::Callback<void(base::TimeTicks /* timestamp */,
  44                               bool /* frame_captured */)> DeliverFrameCallback;
  45
  46   // Called when a new frame is going to be presented at time
  47   // |present_time| with |damage_rect| being the region of the frame that has
  48   // changed since the last frame. The implementation decides whether the
  49   // current frame should be captured or not.
  50   //
  51   // Return true if the current frame should be captured. If so, |storage|
  52   // will be set to hold an appropriately sized and allocated buffer into which
  53   // to copy the frame. The platform presenter will perform scaling and color
  54   // space conversion to fit into the output frame.
  55   //
  56   // Destination format is determined by |storage|, currently only
  57   // media::VideoFrame::YV12 is supported. Platform layer will perform color
  58   // space conversion if needed.
  59   //
  60   // When the frame is available |callback| will be called. It is up to the
  61   // platform layer to decide when to deliver a captured frame.
  62   //
  63   // Return false if the current frame should not be captured.
  64   virtual bool ShouldCaptureFrame(const gfx::Rect& damage_rect,
  65                                   base::TimeTicks present_time,
  66                                   scoped_refptr<media::VideoFrame>* storage,
  67                                   DeliverFrameCallback* callback) = 0;
  68 };
  69
  70 }  // namespace content
  71
  72 #endif  // CONTENT_PUBLIC_BROWSER_RENDER_WIDGET_HOST_VIEW_FRAME_SUBSCRIBER_H_