зеркало из https://github.com/mozilla/gecko-dev.git
92 строки
2.8 KiB
C++
92 строки
2.8 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
|
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
|
|
/* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
|
|
|
|
#include "ScrollVelocityQueue.h"
|
|
|
|
#include "mozilla/StaticPrefs.h"
|
|
#include "nsPresContext.h"
|
|
#include "nsRefreshDriver.h"
|
|
|
|
namespace mozilla {
|
|
namespace layout {
|
|
|
|
void ScrollVelocityQueue::Sample(const nsPoint& aScrollPosition) {
|
|
float flingSensitivity = StaticPrefs::ScrollSnapPredictionSensitivity();
|
|
int maxVelocity = StaticPrefs::ScrollSnapPredictionMaxVelocity();
|
|
maxVelocity = nsPresContext::CSSPixelsToAppUnits(maxVelocity);
|
|
int maxOffset = maxVelocity * flingSensitivity;
|
|
TimeStamp currentRefreshTime =
|
|
mPresContext->RefreshDriver()->MostRecentRefresh();
|
|
if (mSampleTime.IsNull()) {
|
|
mAccumulator = nsPoint();
|
|
} else {
|
|
uint32_t durationMs = (currentRefreshTime - mSampleTime).ToMilliseconds();
|
|
if (durationMs > StaticPrefs::APZVelocityRelevanceTime()) {
|
|
mAccumulator = nsPoint();
|
|
mQueue.Clear();
|
|
} else if (durationMs == 0) {
|
|
mAccumulator += aScrollPosition - mLastPosition;
|
|
} else {
|
|
nsPoint velocity = mAccumulator * 1000 / durationMs;
|
|
velocity.Clamp(maxVelocity);
|
|
mQueue.AppendElement(std::make_pair(durationMs, velocity));
|
|
mAccumulator = aScrollPosition - mLastPosition;
|
|
}
|
|
}
|
|
mAccumulator.Clamp(maxOffset);
|
|
mSampleTime = currentRefreshTime;
|
|
mLastPosition = aScrollPosition;
|
|
TrimQueue();
|
|
}
|
|
|
|
void ScrollVelocityQueue::TrimQueue() {
|
|
if (mSampleTime.IsNull()) {
|
|
// There are no samples, nothing to do here.
|
|
return;
|
|
}
|
|
|
|
TimeStamp currentRefreshTime =
|
|
mPresContext->RefreshDriver()->MostRecentRefresh();
|
|
nsPoint velocity;
|
|
uint32_t timeDelta = (currentRefreshTime - mSampleTime).ToMilliseconds();
|
|
for (int i = mQueue.Length() - 1; i >= 0; i--) {
|
|
timeDelta += mQueue[i].first;
|
|
if (timeDelta >= StaticPrefs::APZVelocityRelevanceTime()) {
|
|
// The rest of the samples have expired and should be dropped
|
|
for (; i >= 0; i--) {
|
|
mQueue.RemoveElementAt(0);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void ScrollVelocityQueue::Reset() {
|
|
mAccumulator = nsPoint();
|
|
mSampleTime = TimeStamp();
|
|
mQueue.Clear();
|
|
}
|
|
|
|
/**
|
|
Calculate the velocity of the scroll frame, in appunits / second.
|
|
*/
|
|
nsPoint ScrollVelocityQueue::GetVelocity() {
|
|
TrimQueue();
|
|
if (mQueue.Length() == 0) {
|
|
// If getting the scroll velocity before any scrolling has occurred,
|
|
// the velocity must be (0, 0)
|
|
return nsPoint();
|
|
}
|
|
nsPoint velocity;
|
|
for (int i = mQueue.Length() - 1; i >= 0; i--) {
|
|
velocity += mQueue[i].second;
|
|
}
|
|
return velocity / mQueue.Length();
|
|
;
|
|
}
|
|
|
|
} // namespace layout
|
|
} // namespace mozilla
|