linear_resampling.cc | Explore in Territory

// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/base/prediction/linear_resampling.h"

#include <algorithm>

#include "base/feature_list.h"
#include "base/metrics/field_trial_params.h"
#include "base/strings/string_number_conversions.h"
#include "ui/base/ui_base_features.h"

namespace ui {

namespace {
// Minimum time difference between last two consecutive events before attempting
// to resample.
constexpr auto kResampleMinDelta = …;
// Maximum time to predict forward from the last event, to avoid predicting too
// far into the future. This time is further bounded by 50% of the last time
// delta.
constexpr auto kResampleMaxPrediction = …;
// Align events to a few milliseconds before frame_time. This is to make the
// resampling either doing interpolation or extrapolating a closer future time
// so that resampled result is more accurate and has less noise. This adds some
// latency during resampling but a few ms should be fine.
constexpr auto kResampleLatency = …;
// The optimal prediction anticipation from experimentation: In the study
// https://bit.ly/3iyQf8V we found that, on a machine with VSync at 60Hz, adding
// 1/2 * frame_interval (on top of kResampleLatency) minimizes the Lag on touch
// scrolling. + 1/2 * (1/60) - 5ms = 3.3ms.
constexpr auto kResampleLatencyExperimental = …;

// Get position at |sample_time| by linear interpolate/extrapolate a and b.
inline gfx::PointF lerp(const InputPredictor::InputData& a,
                        const InputPredictor::InputData& b,
                        base::TimeTicks sample_time) { … }

}  // namespace

LinearResampling::LinearResampling() { … }

LinearResampling::~LinearResampling() { … }

const char* LinearResampling::GetName() const { … }

void LinearResampling::Reset() { … }

void LinearResampling::Update(const InputData& new_input) { … }

bool LinearResampling::HasPrediction() const { … }

std::unique_ptr<InputPredictor::InputData> LinearResampling::GeneratePrediction(
    base::TimeTicks frame_time,
    base::TimeDelta frame_interval) { … }

base::TimeDelta LinearResampling::TimeInterval() const { … }

base::TimeDelta LinearResampling::LatencyCalculator::GetResampleLatency(
    base::TimeDelta frame_interval) { … }

base::TimeDelta LinearResampling::LatencyCalculator::CalculateLatency() { … }

}  // namespace ui
chromium/ui/base/prediction/linear_resampling.cc
