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ImageComposite.h (4676B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      3 /* This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #ifndef MOZILLA_GFX_IMAGECOMPOSITE_H
      8 #define MOZILLA_GFX_IMAGECOMPOSITE_H
      9 
     10 #include "CompositableHost.h"  // for CompositableTextureHostRef
     11 #include "mozilla/gfx/2D.h"
     12 #include "mozilla/TimeStamp.h"  // for TimeStamp
     13 #include "nsTArray.h"
     14 
     15 namespace mozilla {
     16 namespace layers {
     17 
     18 /**
     19 * Implements Image selection logic.
     20 */
     21 class ImageComposite {
     22 public:
     23  static const float BIAS_TIME_MS;
     24 
     25  explicit ImageComposite();
     26  virtual ~ImageComposite();
     27 
     28  int32_t GetFrameID() {
     29    const TimedImage* img = ChooseImage();
     30    return img ? img->mFrameID : -1;
     31  }
     32 
     33  int32_t GetProducerID() {
     34    const TimedImage* img = ChooseImage();
     35    return img ? img->mProducerID : -1;
     36  }
     37 
     38  int32_t GetLastFrameID() const { return mLastFrameID; }
     39  int32_t GetLastProducerID() const { return mLastProducerID; }
     40  uint32_t GetDroppedFramesAndReset() {
     41    uint32_t dropped = mDroppedFrames;
     42    mDroppedFrames = 0;
     43    return dropped;
     44  }
     45 
     46  enum Bias {
     47    // Don't apply bias to frame times
     48    BIAS_NONE,
     49    // Apply a negative bias to frame times to keep them before the vsync time
     50    BIAS_NEGATIVE,
     51    // Apply a positive bias to frame times to keep them after the vsync time
     52    BIAS_POSITIVE,
     53  };
     54 
     55 protected:
     56  virtual TimeStamp GetCompositionTime() const = 0;
     57  virtual CompositionOpportunityId GetCompositionOpportunityId() const = 0;
     58  virtual void AppendImageCompositeNotification(
     59      const ImageCompositeNotificationInfo& aInfo) const = 0;
     60 
     61  struct TimedImage {
     62    CompositableTextureHostRef mTextureHost;
     63    TimeStamp mTimeStamp;
     64    gfx::IntRect mPictureRect;
     65    int32_t mFrameID;
     66    int32_t mProducerID;
     67  };
     68 
     69  /**
     70   * ChooseImage is guaranteed to return the same TimedImage every time it's
     71   * called during the same composition, up to the end of Composite() ---
     72   * it depends only on mImages, mCompositor->GetCompositionTime(), and mBias.
     73   * mBias is updated at the end of Composite().
     74   */
     75  const TimedImage* ChooseImage();
     76  int ChooseImageIndex();
     77  const TimedImage* GetImage(size_t aIndex) const;
     78  size_t ImagesCount() const { return mImages.Length(); }
     79  const nsTArray<TimedImage>& Images() const { return mImages; }
     80 
     81  void RemoveImagesWithTextureHost(TextureHost* aTexture);
     82  void ClearImages();
     83  void SetImages(nsTArray<TimedImage>&& aNewImages);
     84 
     85 protected:
     86  // Send ImageComposite notifications and update the ChooseImage bias.
     87  void OnFinishRendering(int aImageIndex, const TimedImage* aImage,
     88                         base::ProcessId aProcessId,
     89                         const CompositableHandle& aHandle);
     90 
     91  int32_t mLastFrameID = -1;
     92  int32_t mLastProducerID = -1;
     93 
     94 private:
     95  nsTArray<TimedImage> mImages;
     96  TimeStamp GetBiasedTime(const TimeStamp& aInput) const;
     97 
     98  // Called when we know that frames older than aImage will never get another
     99  // chance to be displayed.
    100  // Counts frames in mImages that were skipped, and adds the skipped count to
    101  // mSkippedFramesSinceLastComposite.
    102  void CountSkippedFrames(const TimedImage* aImage);
    103 
    104  // Update mLastFrameID and mLastProducerID, and report dropped frames.
    105  // Returns whether the frame changed.
    106  bool UpdateCompositedFrame(int aImageIndex,
    107                             bool aWasVisibleAtPreviousComposition);
    108 
    109  void UpdateBias(size_t aImageIndex, bool aFrameUpdated);
    110 
    111  // Emit a profiler marker about video frame timestamp jitter.
    112  void DetectTimeStampJitter(const TimedImage* aNewImage);
    113 
    114  /**
    115   * Bias to apply to the next frame.
    116   */
    117  Bias mBias = BIAS_NONE;
    118 
    119  // Video frames that were in mImages but that will never reach the screen.
    120  // This count is reset in UpdateCompositedFrame.
    121  int32_t mSkippedFramesSinceLastComposite = 0;
    122 
    123  // The number of dropped frames since the last call to
    124  // GetDroppedFramesAndReset(). Not all skipped frames are considered "dropped"
    125  // - for example, videos that are scrolled out of view or videos in background
    126  // tabs are expected to skip frames, and those skipped frames are not counted
    127  // as dropped frames.
    128  uint32_t mDroppedFrames = 0;
    129 
    130  // The composition opportunity IDs of the last calls to ChooseImageIndex and
    131  // UpdateCompositedFrame, respectively.
    132  CompositionOpportunityId mLastChooseImageIndexComposition;
    133  CompositionOpportunityId mLastFrameUpdateComposition;
    134 };
    135 
    136 }  // namespace layers
    137 }  // namespace mozilla
    138 
    139 #endif  // MOZILLA_GFX_IMAGECOMPOSITE_H