chromium/cc/trees/frame_rate_estimator.h

// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_TREES_FRAME_RATE_ESTIMATOR_H_
#define CC_TREES_FRAME_RATE_ESTIMATOR_H_

#include <cstdint>

#include "base/task/sequenced_task_runner.h"
#include "base/task/single_thread_task_runner.h"
#include "base/time/time.h"
#include "cc/base/delayed_unique_notifier.h"
#include "cc/cc_export.h"

namespace cc {

// The class is used to decide the preferred begin frame rate which related
// compositor frame sink should send based on video conference mode,
// NotifyInputEvent, WillDraw and DidNotProduceFrame. It will enter
// InputPriorityMode in the next 250ms(kInputPriorityDelay) if
// NotifyInputEvent() is called and exit after the delay. Throttling is
// disabled in InputPriorityMode despite other conditions.
// 1. In video conference mode(features::kReducedFrameRateEstimation, enabled by
// default):
// The frame rate will be throttled to half of the default when：
//   Video conference mode is set and
//   the last drawn consecutive_frames_with_min_delta_ <
//   4(kMinNumOfFramesWithMinDelta).
// The throttling will be stopped when:
//   Video conference mode is unset or
//   the last drawn consecutive_frames_with_min_delta_ >= 4.
// 2. In consecutive didNotProduceFrame
// mode(features::kThrottleFrameRateOnManyDidNotProduceFrame):
// The frame rate will be throttled to half of the default when：
//   The num_did_not_produce_frame_since_last_draw_ >
//   4(kNumDidNotProduceFrameBeforeThrottle).
// The throttling will be stopped when:
//   There's a drawn frame.
class CC_EXPORT FrameRateEstimator { … };

}  // namespace cc

#endif  // CC_TREES_FRAME_RATE_ESTIMATOR_H_