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/* -*- 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
#include "OvershootDetector.h"
#include "InputData.h"
#include "mozilla/Telemetry.h" // for Telemetry
namespace mozilla {
namespace layers {
const TimeDuration kOvershootInterval = TimeDuration::FromMilliseconds(500);
static Maybe<Side> GetScrollDirection(const ScrollWheelInput& aInput) {
// If the wheel input is scrolling on both axes, we just take the y-axis.
// This is mostly out of laziness, because this code is for experiment
// purposes and just needs to handle the cases that will dominate in the data.
if (aInput.mDeltaY > 0) {
return Some(Side::eSideBottom);
}
if (aInput.mDeltaY < 0) {
return Some(Side::eSideTop);
}
if (aInput.mDeltaX > 0) {
return Some(Side::eSideRight);
}
if (aInput.mDeltaX < 0) {
return Some(Side::eSideLeft);
}
return Nothing();
}
void OvershootDetector::Update(const ScrollWheelInput& aInput) {
TimeStamp inputTime = aInput.mTimeStamp;
Maybe<Side> inputDirection = GetScrollDirection(aInput);
if (mLastTimeStamp && (inputTime - mLastTimeStamp) < kOvershootInterval &&
mLastDirection && inputDirection) {
// The new input we got happened within the kOvershootInterval of the last
// input. Let's see if the direction is reversed; if so, we accumulate to
// telemetry.
bool reversed = false;
switch (*mLastDirection) {
case Side::eSideBottom:
reversed = (*inputDirection == Side::eSideTop);
break;
case Side::eSideTop:
reversed = (*inputDirection == Side::eSideBottom);
break;
case Side::eSideRight:
reversed = (*inputDirection == Side::eSideLeft);
break;
case Side::eSideLeft:
reversed = (*inputDirection == Side::eSideRight);
break;
}
if (reversed) {
Telemetry::ScalarAdd(Telemetry::ScalarID::APZ_SCROLLWHEEL_OVERSHOOT, 1);
}
}
mLastTimeStamp = inputTime;
mLastDirection = inputDirection;
}
} // namespace layers
} // namespace mozilla