/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* 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_GFX_IMAGECOMPOSITE_H

#define MOZILLA_GFX_IMAGECOMPOSITE_H

#include "CompositableHost.h"           // for CompositableTextureHostRef

#include "mozilla/gfx/2D.h"

#include "mozilla/TimeStamp.h"          // for TimeStamp

#include "nsTArray.h"

namespace mozilla {

namespace layers {

/**

 * Implements Image selection logic.

 */

class ImageComposite

{

public:

  static const float BIAS_TIME_MS;

  explicit ImageComposite();

  ~ImageComposite();

  int32_t GetFrameID()

  {

    const TimedImage* img = ChooseImage();

    return img ? img->mFrameID : -1;

  }

  int32_t GetProducerID()

  {

    const TimedImage* img = ChooseImage();

    return img ? img->mProducerID : -1;

  }

  int32_t GetLastFrameID() const { return mLastFrameID; }

  int32_t GetLastProducerID() const { return mLastProducerID; }

  uint32_t GetDroppedFramesAndReset()

  {

    uint32_t dropped = mDroppedFrames;

    mDroppedFrames = 0;

    return dropped;

  }

  enum Bias {

    // Don't apply bias to frame times

    BIAS_NONE,

    // Apply a negative bias to frame times to keep them before the vsync time

    BIAS_NEGATIVE,

    // Apply a positive bias to frame times to keep them after the vsync time

    BIAS_POSITIVE,

  };

protected:

  void UpdateBias(size_t aImageIndex);

  virtual TimeStamp GetCompositionTime() const = 0;

  struct TimedImage {

    CompositableTextureHostRef mTextureHost;

    TimeStamp mTimeStamp;

    gfx::IntRect mPictureRect;

    int32_t mFrameID;

    int32_t mProducerID;

  };

  /**

   * ChooseImage is guaranteed to return the same TimedImage every time it's

   * called during the same composition, up to the end of Composite() ---

   * it depends only on mImages, mCompositor->GetCompositionTime(), and mBias.

   * mBias is updated at the end of Composite().

   */

  const TimedImage* ChooseImage();

  int ChooseImageIndex();

  const TimedImage* GetImage(size_t aIndex) const;

  size_t ImagesCount() const { return mImages.Length(); }

  const nsTArray<TimedImage>& Images() const { return mImages; }

  void RemoveImagesWithTextureHost(TextureHost* aTexture);

  void ClearImages();

  void SetImages(nsTArray<TimedImage>&& aNewImages);

  int32_t mLastFrameID;

  int32_t mLastProducerID;

private:

  nsTArray<TimedImage> mImages;

  TimeStamp GetBiasedTime(const TimeStamp& aInput) const;

  // Scan new images and look for common ones in the existing mImages array.

  // Will determine if an image has been dropped through gaps between images and

  // adjust mDroppedFrames accordingly.

  // Return the index of what the last returned image would have been.

  uint32_t ScanForLastFrameIndex(const nsTArray<TimedImage>& aNewImages);

  /**

   * Bias to apply to the next frame.

   */

  Bias mBias;

  uint32_t mDroppedFrames;

  uint32_t mLastChosenImageIndex;

};

} // namespace layers

} // namespace mozilla

#endif // MOZILLA_GFX_IMAGECOMPOSITE_H