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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_PEERCONNECTION_VSYNC_TICK_PROVIDER_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_PEERCONNECTION_VSYNC_TICK_PROVIDER_H_
#include <memory>
#include "base/functional/bind.h"
#include "base/functional/callback.h"
#include "base/functional/callback_forward.h"
#include "base/memory/raw_ref.h"
#include "base/memory/scoped_refptr.h"
#include "base/memory/weak_ptr.h"
#include "base/task/sequenced_task_runner.h"
#include "base/thread_annotations.h"
#include "base/time/time.h"
#include "third_party/blink/renderer/platform/peerconnection/vsync_provider.h"
#include "third_party/webrtc_overrides/metronome_source.h"
#include "third_party/webrtc_overrides/timer_based_tick_provider.h"
namespace blink {
// Tick provider that normally generates ticks based on callbacks from VSync
// notifications requested from a VSyncProvider. If VSyncs cease to be reported
// (such as when the tab is occluded), ticks are instead provided by a supplied
// default tick provider. When VSyncs are found to be reported again, the class
// switches back to be driven by them.
//
// After construction, all access including destruction must happen on the
// `sequence` specified on construction.
class PLATFORM_EXPORT VSyncTickProvider : public MetronomeSource::TickProvider {
public:
// The VSync frequency is at least 30 Hz under RTC conferencing in Chromium,
// but can be higher depending on animation complexity on the web page.
static constexpr base::TimeDelta kVSyncTickPeriod = base::Hertz(30);
// Create using a begin frame provider.
static scoped_refptr<VSyncTickProvider> Create(
VSyncProvider& vsync_provider,
scoped_refptr<base::SequencedTaskRunner> sequence,
scoped_refptr<MetronomeSource::TickProvider> default_tick_provider);
~VSyncTickProvider() override;
// TickProvider overrides.
void RequestCallOnNextTick(base::OnceClosure callback) override;
base::TimeDelta TickPeriod() override;
private:
VSyncTickProvider(
VSyncProvider& vsync_provider,
scoped_refptr<base::SequencedTaskRunner> sequence,
scoped_refptr<MetronomeSource::TickProvider> default_tick_provider);
void Initialize();
// Requests a callback to OnVSync.
void ScheduleVSync();
// Requests a callback to OnTick.
void ScheduleDefaultTick();
// Called on tick from the default provider.
void OnDefaultTick();
// Called on vsync from the vsync provider.
void OnVSync();
// Processes a tick, i.e. calls out to the requested callback, if present.
void MaybeCalloutToClient();
// Called on tab visibility changes from the vsync provider.
void OnTabVisibilityChange(bool visible);
enum class State {
// The provider is driven by the default provider.
kDrivenByDefault,
// The provider is switching to be driven by vsyncs, but is still awaiting a
// first vsync callback from the provider and drives using default callbacks
// until then.
kAwaitingVSync,
// The provider is driven solely by vsyncs.
kDrivenByVSync
};
const raw_ref<VSyncProvider> vsync_provider_;
const scoped_refptr<base::SequencedTaskRunner> sequence_;
SEQUENCE_CHECKER(sequence_checker_);
// The default tick provider, used when the tab is occluded.
const scoped_refptr<MetronomeSource::TickProvider> default_tick_provider_
GUARDED_BY_CONTEXT(sequence_checker_);
// The currently scheduled tick callback.
WTF::Vector<base::OnceClosure> tick_callbacks_
GUARDED_BY_CONTEXT(sequence_checker_);
// The state of this tick provider.
State state_ GUARDED_BY_CONTEXT(sequence_checker_) = State::kDrivenByDefault;
// Weak factory used to cancel old installed callbacks.
base::WeakPtrFactory<VSyncTickProvider> weak_tick_factory_{this};
base::WeakPtrFactory<VSyncTickProvider> weak_factory_{this};
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_PEERCONNECTION_VSYNC_TICK_PROVIDER_H_
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