cc/debug/frame_timing_tracker.h

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_DEBUG_FRAME_TIMING_TRACKER_H_
#define CC_DEBUG_FRAME_TIMING_TRACKER_H_

#include <utility>
#include <vector>

#include "base/basictypes.h"
#include "base/containers/hash_tables.h"
#include "base/memory/scoped_ptr.h"
#include "base/time/time.h"

namespace cc {

// This class maintains a history of timestamps and rect IDs to communicate
// frame events back to Blink
// TODO(mpb): Start using this. crbug.com/442554
class FrameTimingTracker {
 public:
  struct CompositeTimingEvent {
    CompositeTimingEvent(int, base::TimeTicks);
    ~CompositeTimingEvent();

    int frame_id;
    base::TimeTicks timestamp;
  };

  using CompositeTimingSet =
      base::hash_map<int, std::vector<CompositeTimingEvent>>;

  static scoped_ptr<FrameTimingTracker> Create();

  ~FrameTimingTracker();

  // This routine takes all of the individual CompositeEvents stored in the
  // tracker and collects them by "rect_id", as in the example below.
  // [ {f_id1,r_id1,t1}, {f_id2,r_id1,t2}, {f_id3,r_id2,t3} ]
  // ====>
  // [ {r_id1,<{f_id1,t1},{f_id2,t2}>}, {r_id2,<{f_id3,t3}>} ]
  scoped_ptr<CompositeTimingSet> GroupCountsByRectId();

  // This routine takes a timestamp and an array of frame_id,rect_id pairs
  // and generates CompositeTimingEvents (frame_id, timestamp) and adds them to
  // internal hash_map keyed on rect_id
  using FrameAndRectIds = std::pair<int, int64_t>;
  void SaveTimeStamps(base::TimeTicks timestamp,
                      const std::vector<FrameAndRectIds>& frame_ids);

 private:
  FrameTimingTracker();

  scoped_ptr<CompositeTimingSet> composite_events_;

  DISALLOW_COPY_AND_ASSIGN(FrameTimingTracker);
};

}  // namespace cc

#endif  // CC_DEBUG_FRAME_TIMING_TRACKER_H_