Source/WebCore/platform/graphics/AnimationFrameRate.h

/*
 * Copyright (C) 2020 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
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 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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 */

#pragma once

#include <wtf/OptionSet.h>
#include <wtf/Seconds.h>

namespace WTF {
class TextStream;
}

namespace WebCore {

using FramesPerSecond = unsigned;

enum class ThrottlingReason : uint8_t {
    VisuallyIdle                    = 1 << 0,
    OutsideViewport                 = 1 << 1,
    LowPowerMode                    = 1 << 2,
    NonInteractedCrossOriginFrame   = 1 << 3,
};

// Allow a little more than 60fps to make sure we can at least hit that frame rate.
constexpr const Seconds FullSpeedAnimationInterval { 15_ms };
// Allow a little more than 30fps to make sure we can at least hit that frame rate.
constexpr const Seconds HalfSpeedThrottlingAnimationInterval { 30_ms };
constexpr const Seconds AggressiveThrottlingAnimationInterval { 10_s };
constexpr const int IntervalThrottlingFactor { 2 };

constexpr const FramesPerSecond FullSpeedFramesPerSecond = 60;
constexpr const FramesPerSecond HalfSpeedThrottlingFramesPerSecond = 30;

WEBCORE_EXPORT FramesPerSecond framesPerSecondNearestFullSpeed(FramesPerSecond);

// This will return std::nullopt if throttling results in a frequency < 1fps.
WEBCORE_EXPORT std::optional<FramesPerSecond> preferredFramesPerSecond(OptionSet<ThrottlingReason>, std::optional<FramesPerSecond> nominalFramesPerSecond, bool preferFrameRatesNear60FPS);

WEBCORE_EXPORT Seconds preferredFrameInterval(OptionSet<ThrottlingReason>, std::optional<FramesPerSecond> nominalFramesPerSecond, bool preferFrameRatesNear60FPS);

WEBCORE_EXPORT FramesPerSecond preferredFramesPerSecondFromInterval(Seconds);

WEBCORE_EXPORT WTF::TextStream& operator<<(WTF::TextStream&, const OptionSet<ThrottlingReason>&);

} // namespace WebCore