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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
commit | 26a029d407be480d791972afb5975cf62c9360a6 (patch) | |
tree | f435a8308119effd964b339f76abb83a57c29483 /gfx/layers/apz/src/AndroidFlingPhysics.cpp | |
parent | Initial commit. (diff) | |
download | firefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz firefox-26a029d407be480d791972afb5975cf62c9360a6.zip |
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'gfx/layers/apz/src/AndroidFlingPhysics.cpp')
-rw-r--r-- | gfx/layers/apz/src/AndroidFlingPhysics.cpp | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/gfx/layers/apz/src/AndroidFlingPhysics.cpp b/gfx/layers/apz/src/AndroidFlingPhysics.cpp new file mode 100644 index 0000000000..d18f4be4d4 --- /dev/null +++ b/gfx/layers/apz/src/AndroidFlingPhysics.cpp @@ -0,0 +1,218 @@ +/* -*- 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 "AndroidFlingPhysics.h" + +#include <cmath> + +#include "mozilla/ClearOnShutdown.h" +#include "mozilla/StaticPrefs_apz.h" +#include "mozilla/StaticPtr.h" + +namespace mozilla { +namespace layers { + +// The fling physics calculations implemented here are adapted from +// Chrome's implementation of fling physics on Android: +// https://cs.chromium.org/chromium/src/ui/events/android/scroller.cc?rcl=3ae3aaff927038a5c644926842cb0c31dea60c79 + +static double ComputeDeceleration(float aDPI) { + const float kFriction = 0.84f; + const float kGravityEarth = 9.80665f; + return kGravityEarth // g (m/s^2) + * 39.37f // inch/meter + * aDPI // pixels/inch + * kFriction; +} + +// == std::log(0.78f) / std::log(0.9f) +const float kDecelerationRate = 2.3582018f; + +// Default friction constant in android.view.ViewConfiguration. +static float GetFlingFriction() { + return StaticPrefs::apz_android_chrome_fling_physics_friction(); +} + +// Tension lines cross at (GetInflexion(), 1). +static float GetInflexion() { + // Clamp the inflexion to the range [0,1]. Values outside of this range + // do not make sense in the physics model, and for negative values the + // approximation used to compute the spline curve does not converge. + const float inflexion = + StaticPrefs::apz_android_chrome_fling_physics_inflexion(); + if (inflexion < 0.0f) { + return 0.0f; + } + if (inflexion > 1.0f) { + return 1.0f; + } + return inflexion; +} + +// Fling scroll is stopped when the scroll position is |kThresholdForFlingEnd| +// pixels or closer from the end. +static float GetThresholdForFlingEnd() { + return StaticPrefs::apz_android_chrome_fling_physics_stop_threshold(); +} + +static double ComputeSplineDeceleration(ParentLayerCoord aVelocity, + double aTuningCoeff) { + float velocityPerSec = aVelocity * 1000.0f; + return std::log(GetInflexion() * velocityPerSec / + (GetFlingFriction() * aTuningCoeff)); +} + +static TimeDuration ComputeFlingDuration(ParentLayerCoord aVelocity, + double aTuningCoeff) { + const double splineDecel = ComputeSplineDeceleration(aVelocity, aTuningCoeff); + const double timeSeconds = std::exp(splineDecel / (kDecelerationRate - 1.0)); + return TimeDuration::FromSeconds(timeSeconds); +} + +static ParentLayerCoord ComputeFlingDistance(ParentLayerCoord aVelocity, + double aTuningCoeff) { + const double splineDecel = ComputeSplineDeceleration(aVelocity, aTuningCoeff); + return GetFlingFriction() * aTuningCoeff * + std::exp(kDecelerationRate / (kDecelerationRate - 1.0) * splineDecel); +} + +struct SplineConstants { + public: + SplineConstants() { + const float kStartTension = 0.5f; + const float kEndTension = 1.0f; + const float kP1 = kStartTension * GetInflexion(); + const float kP2 = 1.0f - kEndTension * (1.0f - GetInflexion()); + + float xMin = 0.0f; + for (int i = 0; i < kNumSamples; i++) { + const float alpha = static_cast<float>(i) / kNumSamples; + + float xMax = 1.0f; + float x, tx, coef; + // While the inflexion can be overridden by the user, it's clamped to + // [0,1]. For values in this range, the approximation algorithm below + // should converge in < 20 iterations. For good measure, we impose an + // iteration limit as well. + static const int sIterationLimit = 100; + int iterations = 0; + while (iterations++ < sIterationLimit) { + x = xMin + (xMax - xMin) / 2.0f; + coef = 3.0f * x * (1.0f - x); + tx = coef * ((1.0f - x) * kP1 + x * kP2) + x * x * x; + if (FuzzyEqualsAdditive(tx, alpha)) { + break; + } + if (tx > alpha) { + xMax = x; + } else { + xMin = x; + } + } + mSplinePositions[i] = coef * ((1.0f - x) * kStartTension + x) + x * x * x; + } + mSplinePositions[kNumSamples] = 1.0f; + } + + void CalculateCoefficients(float aTime, float* aOutDistanceCoef, + float* aOutVelocityCoef) { + *aOutDistanceCoef = 1.0f; + *aOutVelocityCoef = 0.0f; + const int index = static_cast<int>(kNumSamples * aTime); + if (index < kNumSamples) { + const float tInf = static_cast<float>(index) / kNumSamples; + const float dInf = mSplinePositions[index]; + const float tSup = static_cast<float>(index + 1) / kNumSamples; + const float dSup = mSplinePositions[index + 1]; + *aOutVelocityCoef = (dSup - dInf) / (tSup - tInf); + *aOutDistanceCoef = dInf + (aTime - tInf) * *aOutVelocityCoef; + } + } + + private: + static const int kNumSamples = 100; + float mSplinePositions[kNumSamples + 1]; +}; + +StaticAutoPtr<SplineConstants> gSplineConstants; + +/* static */ +void AndroidFlingPhysics::InitializeGlobalState() { + gSplineConstants = new SplineConstants(); + ClearOnShutdown(&gSplineConstants); +} + +void AndroidFlingPhysics::Init(const ParentLayerPoint& aStartingVelocity, + float aPLPPI) { + mVelocity = aStartingVelocity.Length(); + // We should not have created a fling animation if there is no velocity. + MOZ_ASSERT(mVelocity != 0.0f); + const double tuningCoeff = ComputeDeceleration(aPLPPI); + mTargetDuration = ComputeFlingDuration(mVelocity, tuningCoeff); + MOZ_ASSERT(!mTargetDuration.IsZero()); + mDurationSoFar = TimeDuration(); + mLastPos = ParentLayerPoint(); + mCurrentPos = ParentLayerPoint(); + float coeffX = + mVelocity == 0 ? 1.0f : aStartingVelocity.x.value / mVelocity.value; + float coeffY = + mVelocity == 0 ? 1.0f : aStartingVelocity.y.value / mVelocity.value; + mTargetDistance = ComputeFlingDistance(mVelocity, tuningCoeff); + mTargetPos = + ParentLayerPoint(mTargetDistance * coeffX, mTargetDistance * coeffY); + const float hyp = mTargetPos.Length(); + if (FuzzyEqualsAdditive(hyp, 0.0f)) { + mDeltaNorm = ParentLayerPoint(1, 1); + } else { + mDeltaNorm = ParentLayerPoint(mTargetPos.x / hyp, mTargetPos.y / hyp); + } +} +void AndroidFlingPhysics::Sample(const TimeDuration& aDelta, + ParentLayerPoint* aOutVelocity, + ParentLayerPoint* aOutOffset) { + float newVelocity; + if (SampleImpl(aDelta, &newVelocity)) { + *aOutOffset = (mCurrentPos - mLastPos); + *aOutVelocity = ParentLayerPoint(mDeltaNorm.x * newVelocity, + mDeltaNorm.y * newVelocity); + mLastPos = mCurrentPos; + } else { + *aOutOffset = (mTargetPos - mLastPos); + *aOutVelocity = ParentLayerPoint(); + } +} + +bool AndroidFlingPhysics::SampleImpl(const TimeDuration& aDelta, + float* aOutVelocity) { + mDurationSoFar += aDelta; + if (mDurationSoFar >= mTargetDuration) { + return false; + } + + const float timeRatio = + mDurationSoFar.ToSeconds() / mTargetDuration.ToSeconds(); + float distanceCoef = 1.0f; + float velocityCoef = 0.0f; + gSplineConstants->CalculateCoefficients(timeRatio, &distanceCoef, + &velocityCoef); + + // The caller expects the velocity in pixels per _millisecond_. + *aOutVelocity = + velocityCoef * mTargetDistance / mTargetDuration.ToMilliseconds(); + + mCurrentPos = mTargetPos * distanceCoef; + + ParentLayerPoint remainder = mTargetPos - mCurrentPos; + const float threshold = GetThresholdForFlingEnd(); + if (fabsf(remainder.x) < threshold && fabsf(remainder.y) < threshold) { + return false; + } + + return true; +} + +} // namespace layers +} // namespace mozilla |