| /* |
| * Copyright (C) 2022 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 |
| * notice, this list of conditions and the following disclaimer. |
| * 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 |
| * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * 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, |
| * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY |
| * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #include "config.h" |
| #include "FrameRateAligner.h" |
| |
| namespace WebCore { |
| |
| FrameRateAligner::FrameRateAligner() = default; |
| |
| FrameRateAligner::~FrameRateAligner() = default; |
| |
| static ReducedResolutionSeconds idealTimeForNextUpdate(ReducedResolutionSeconds firstUpdateTime, ReducedResolutionSeconds lastUpdateTime, FramesPerSecond frameRate) |
| { |
| ReducedResolutionSeconds interval(1.0 / frameRate); |
| auto timeUntilNextUpdate = (lastUpdateTime - firstUpdateTime) % interval; |
| return lastUpdateTime + interval - timeUntilNextUpdate; |
| } |
| |
| void FrameRateAligner::beginUpdate(ReducedResolutionSeconds timestamp, std::optional<FramesPerSecond> timelineFrameRate) |
| { |
| // We record the timestamp for this new update such that in updateFrameRate() |
| // we can compare against it to identify animations that should be sampled |
| // for this current update. |
| m_timestamp = timestamp; |
| |
| const auto nextUpdateTimeEpsilon = 1_ms; |
| for (auto& [frameRate, data] : m_frameRates) { |
| // We can reset isNew to false for all entries since they were already present |
| // in the previous update. |
| data.isNew = false; |
| |
| // If the timeline frame rate is the same as this animation frame rate, then |
| // we don't need to compute the next ideal sample time. |
| if (timelineFrameRate == frameRate) { |
| data.lastUpdateTime = timestamp; |
| continue; |
| } |
| |
| // If the next ideal sample time for this frame rate aligns with the current timestamp |
| // or is already behind the current timestamp, we can set the last update time to the |
| // current timestamp, which will indicate in updateFrameRate() that animations using |
| // this frame rate should be sampled in the current update. |
| auto nextUpdateTime = idealTimeForNextUpdate(data.firstUpdateTime, data.lastUpdateTime, frameRate); |
| if ((nextUpdateTime - nextUpdateTimeEpsilon) <= timestamp) |
| data.lastUpdateTime = timestamp; |
| } |
| } |
| |
| auto FrameRateAligner::updateFrameRate(FramesPerSecond frameRate) -> ShouldUpdate |
| { |
| auto it = m_frameRates.find(frameRate); |
| |
| if (it != m_frameRates.end()) { |
| // We're dealing with a frame rate for which we've sampled animations before. |
| // If the last update time for this frame rate is the current timestamp, this |
| // means we've established in beginUpdate() that animations for this frame rate |
| // should be sampled. |
| return it->value.lastUpdateTime == m_timestamp ? ShouldUpdate::Yes : ShouldUpdate::No; |
| } |
| |
| // We're dealing with a frame rate we didn't see in the previous update. In this case, |
| // we'll allow animations to be sampled right away. Later, in finishUpdate(), we'll |
| // make sure to reset the last update time to align this new frame rate with other |
| // compatible frame rates. |
| m_frameRates.set(frameRate, FrameRateData { m_timestamp, m_timestamp }); |
| return ShouldUpdate::Yes; |
| } |
| |
| // For two frame rates to be aligned, one must be the multitple of the other, or vice versa. |
| static bool frameRatesCanBeAligned(FramesPerSecond a, FramesPerSecond b) |
| { |
| return (a > b && a % b == 0) || (b > a && b % a == 0); |
| } |
| |
| void FrameRateAligner::finishUpdate() |
| { |
| // Iterate through the frame rates to find new entries and set their first update time |
| // in a way that future updates will be synchronized with other animations with that |
| // frame rate. |
| for (auto& [frameRate, data] : m_frameRates) { |
| if (!data.isNew) |
| continue; |
| |
| // Look for the compatible frame rate with the highest value. |
| std::optional<FramesPerSecond> highestCompatibleFrameRate; |
| for (auto& [potentiallyCompatibleFrameRate, potentiallyCompatibleData] : m_frameRates) { |
| if (potentiallyCompatibleData.isNew) |
| continue; |
| |
| if (frameRatesCanBeAligned(frameRate, potentiallyCompatibleFrameRate)) { |
| if (!highestCompatibleFrameRate || *highestCompatibleFrameRate > potentiallyCompatibleFrameRate) |
| highestCompatibleFrameRate = potentiallyCompatibleFrameRate; |
| } |
| } |
| |
| // If we don't find any compatible frame rate, we can leave the last update time as-is |
| // and use the current timestamp as the basis from which we'll align animations for this |
| // frame rate. |
| if (highestCompatibleFrameRate) |
| data.firstUpdateTime = m_frameRates.get(*highestCompatibleFrameRate).firstUpdateTime; |
| } |
| } |
| |
| std::optional<Seconds> FrameRateAligner::timeUntilNextUpdateForFrameRate(FramesPerSecond frameRate, ReducedResolutionSeconds timestamp) const |
| { |
| auto it = m_frameRates.find(frameRate); |
| if (it == m_frameRates.end()) |
| return std::nullopt; |
| |
| auto& data = it->value; |
| return idealTimeForNextUpdate(data.firstUpdateTime, data.lastUpdateTime, frameRate) - timestamp; |
| } |
| |
| std::optional<FramesPerSecond> FrameRateAligner::maximumFrameRate() const |
| { |
| std::optional<FramesPerSecond> maximumFrameRate; |
| for (auto frameRate : m_frameRates.keys()) { |
| if (!maximumFrameRate || *maximumFrameRate < frameRate) |
| maximumFrameRate = frameRate; |
| } |
| return maximumFrameRate; |
| } |
| |
| } // namespace WebCore |
| |