components/viz/service/performance_hint/hint_session.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 COMPONENTS_VIZ_SERVICE_PERFORMANCE_HINT_HINT_SESSION_H_
#define COMPONENTS_VIZ_SERVICE_PERFORMANCE_HINT_HINT_SESSION_H_

#include <memory>

#include "base/containers/flat_set.h"
#include "base/threading/platform_thread.h"
#include "components/viz/service/viz_service_export.h"

namespace viz {

// This is a wrapper for the Android `android.os.PerformanceHintManager` APIs
// used to provide hints to the OS on rendering performance, so the OS can
// ramp CPU performance up or down on demand.
// This header is platform-agnostic though it's only implemented on Android

class VIZ_SERVICE_EXPORT HintSession {
 public:
  virtual ~HintSession() = default;

  virtual void UpdateTargetDuration(base::TimeDelta target_duration) = 0;

  // `actual_duration` is compared to `target_duration` in `CreateSession` to
  // determine the performance of a frame.
  virtual void ReportCpuCompletionTime(base::TimeDelta actual_duration) = 0;
};

class VIZ_SERVICE_EXPORT HintSessionFactory {
 public:
  // `permanent_thread_ids` are thread IDs that will be present in all
  // HintSessions.
  // Can return nullptr which can be used as feature detection.
  static std::unique_ptr<HintSessionFactory> Create(
      base::flat_set<base::PlatformThreadId> permanent_thread_ids);

  virtual ~HintSessionFactory() = default;

  // `transient_thread_ids` are added to `permanent_thread_ids` to create this
  // session. Chanting `transient_thread_ids` still requires deleting and
  // recreating the session.
  // `target_duration` is compared to `actual_duration` in
  // `ReportCpuCompletionTime` to determine the performance of a frame.
  virtual std::unique_ptr<HintSession> CreateSession(
      base::flat_set<base::PlatformThreadId> transient_thread_ids,
      base::TimeDelta target_duration) = 0;

  // Issue an early hint to wake up some session.
  virtual void WakeUp() = 0;
};

}  // namespace viz

#endif  // COMPONENTS_VIZ_SERVICE_PERFORMANCE_HINT_HINT_SESSION_H_