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diff --git a/Source/WebCore/page/scrolling/ScrollingMomentumCalculator.cpp b/Source/WebCore/page/scrolling/ScrollingMomentumCalculator.cpp
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+/*
+ * Copyright (C) 2016 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. AND ITS CONTRIBUTORS ``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 ITS 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 "ScrollingMomentumCalculator.h"
+
+#include "FloatPoint.h"
+#include "FloatSize.h"
+
+namespace WebCore {
+
+static const Seconds scrollSnapAnimationDuration = 1_s;
+static inline float projectedInertialScrollDistance(float initialWheelDelta)
+{
+    // On macOS 10.10 and earlier, we don't have a platform scrolling momentum calculator, so we instead approximate the scroll destination
+    // by multiplying the initial wheel delta by a constant factor. By running a few experiments (i.e. logging scroll destination and initial
+    // wheel delta for many scroll gestures) we determined that this is a reasonable way to approximate where scrolling will take us without
+    // using _NSScrollingMomentumCalculator.
+    const static double inertialScrollPredictionFactor = 16.7;
+    return inertialScrollPredictionFactor * initialWheelDelta;
+}
+
+ScrollingMomentumCalculator::ScrollingMomentumCalculator(const FloatSize& viewportSize, const FloatSize& contentSize, const FloatPoint& initialOffset, const FloatSize& initialDelta, const FloatSize& initialVelocity)
+    : m_initialDelta(initialDelta)
+    , m_initialVelocity(initialVelocity)
+    , m_initialScrollOffset(initialOffset.x(), initialOffset.y())
+    , m_viewportSize(viewportSize)
+    , m_contentSize(contentSize)
+{
+}
+
+void ScrollingMomentumCalculator::setRetargetedScrollOffset(const FloatSize& target)
+{
+    if (m_retargetedScrollOffset && m_retargetedScrollOffset == target)
+        return;
+
+    m_retargetedScrollOffset = target;
+    retargetedScrollOffsetDidChange();
+}
+
+FloatSize ScrollingMomentumCalculator::predictedDestinationOffset()
+{
+    float initialOffsetX = clampTo<float>(m_initialScrollOffset.width() + projectedInertialScrollDistance(m_initialDelta.width()), 0, m_contentSize.width() - m_viewportSize.width());
+    float initialOffsetY = clampTo<float>(m_initialScrollOffset.height() + projectedInertialScrollDistance(m_initialDelta.height()), 0, m_contentSize.height() - m_viewportSize.height());
+    return { initialOffsetX, initialOffsetY };
+}
+
+#if !HAVE(NSSCROLLING_FILTERS)
+
+std::unique_ptr<ScrollingMomentumCalculator> ScrollingMomentumCalculator::create(const FloatSize& viewportSize, const FloatSize& contentSize, const FloatPoint& initialOffset, const FloatSize& initialDelta, const FloatSize& initialVelocity)
+{
+    return std::make_unique<BasicScrollingMomentumCalculator>(viewportSize, contentSize, initialOffset, initialDelta, initialVelocity);
+}
+
+void ScrollingMomentumCalculator::setPlatformMomentumScrollingPredictionEnabled(bool)
+{
+}
+
+#endif
+
+BasicScrollingMomentumCalculator::BasicScrollingMomentumCalculator(const FloatSize& viewportSize, const FloatSize& contentSize, const FloatPoint& initialOffset, const FloatSize& initialDelta, const FloatSize& initialVelocity)
+    : ScrollingMomentumCalculator(viewportSize, contentSize, initialOffset, initialDelta, initialVelocity)
+{
+}
+
+FloatSize BasicScrollingMomentumCalculator::linearlyInterpolatedOffsetAtProgress(float progress)
+{
+    return m_initialScrollOffset + progress * (retargetedScrollOffset() - m_initialScrollOffset);
+}
+
+FloatSize BasicScrollingMomentumCalculator::cubicallyInterpolatedOffsetAtProgress(float progress) const
+{
+    ASSERT(!m_forceLinearAnimationCurve);
+    FloatSize interpolatedPoint;
+    for (int i = 0; i < 4; ++i)
+        interpolatedPoint += std::pow(progress, i) * m_snapAnimationCurveCoefficients[i];
+
+    return interpolatedPoint;
+}
+
+FloatPoint BasicScrollingMomentumCalculator::scrollOffsetAfterElapsedTime(Seconds elapsedTime)
+{
+    if (m_momentumCalculatorRequiresInitialization) {
+        initializeSnapProgressCurve();
+        initializeInterpolationCoefficientsIfNecessary();
+        m_momentumCalculatorRequiresInitialization = false;
+    }
+
+    float progress = animationProgressAfterElapsedTime(elapsedTime);
+    auto offsetAsSize = m_forceLinearAnimationCurve ? linearlyInterpolatedOffsetAtProgress(progress) : cubicallyInterpolatedOffsetAtProgress(progress);
+    return FloatPoint(offsetAsSize.width(), offsetAsSize.height());
+}
+
+Seconds BasicScrollingMomentumCalculator::animationDuration()
+{
+    return scrollSnapAnimationDuration;
+}
+
+/**
+ * Computes and sets coefficients required for interpolated snapping when scrolling in 2 dimensions, given
+ * initial conditions (the initial and target vectors, along with the initial wheel delta as a vector). The
+ * path is a cubic Bezier curve of the form p(s) = INITIAL + (C_1 * s) + (C_2 * s^2) + (C_3 * s^3) where each
+ * C_i is a 2D vector and INITIAL is the vector representing the initial scroll offset. s is a real in the
+ * interval [0, 1] indicating the "progress" of the curve (i.e. how much of the curve has been traveled).
+ *
+ * The curve has 4 control points, the first and last of which are the initial and target points, respectively.
+ * The distances between adjacent control points are constrained to be the same, making the convex hull an
+ * isosceles trapezoid with 3 sides of equal length. Additionally, the vector from the first control point to
+ * the second points in the same direction as the initial scroll delta. These constraints ensure two properties:
+ *     1. The direction of the snap animation at s=0 will be equal to the direction of the initial scroll delta.
+ *     2. Points at regular intervals of s will be evenly spread out.
+ *
+ * If the initial scroll direction is orthogonal to or points in the opposite direction as the vector from the
+ * initial point to the target point, initialization returns early and sets the curve to animate directly to the
+ * snap point without cubic interpolation.
+ *
+ * FIXME: This should be refactored to use UnitBezier.
+ */
+void BasicScrollingMomentumCalculator::initializeInterpolationCoefficientsIfNecessary()
+{
+    m_forceLinearAnimationCurve = true;
+    float initialDeltaMagnitude = m_initialDelta.diagonalLength();
+    if (initialDeltaMagnitude < 1) {
+        // The initial wheel delta is so insignificant that we're better off considering this to have the same effect as finishing a scroll gesture with no momentum.
+        // Thus, cubic interpolation isn't needed here.
+        return;
+    }
+
+    FloatSize startToEndVector = retargetedScrollOffset() - m_initialScrollOffset;
+    float startToEndDistance = startToEndVector.diagonalLength();
+    if (!startToEndDistance) {
+        // The start and end positions are the same, so we shouldn't try to interpolate a path.
+        return;
+    }
+
+    float cosTheta = (m_initialDelta.width() * startToEndVector.width() + m_initialDelta.height() * startToEndVector.height()) / (initialDeltaMagnitude * startToEndDistance);
+    if (cosTheta <= 0) {
+        // It's possible that the user is not scrolling towards the target snap offset (for instance, scrolling against a corner when 2D scroll snapping).
+        // In this case, just let the scroll offset animate to the target without computing a cubic curve.
+        return;
+    }
+
+    float sideLength = startToEndDistance / (2.0f * cosTheta + 1.0f);
+    FloatSize controlVector1 = m_initialScrollOffset + sideLength * m_initialDelta / initialDeltaMagnitude;
+    FloatSize controlVector2 = controlVector1 + (sideLength * startToEndVector / startToEndDistance);
+    m_snapAnimationCurveCoefficients[0] = m_initialScrollOffset;
+    m_snapAnimationCurveCoefficients[1] = 3 * (controlVector1 - m_initialScrollOffset);
+    m_snapAnimationCurveCoefficients[2] = 3 * (m_initialScrollOffset - 2 * controlVector1 + controlVector2);
+    m_snapAnimationCurveCoefficients[3] = 3 * (controlVector1 - controlVector2) - m_initialScrollOffset + retargetedScrollOffset();
+    m_forceLinearAnimationCurve = false;
+}
+
+static const float framesPerSecond = 60.0f;
+
+/**
+ * Computes and sets parameters required for tracking the progress of a snap animation curve, interpolated
+ * or linear. The progress curve s(t) maps time t to progress s; both variables are in the interval [0, 1].
+ * The time input t is 0 when the current time is the start of the animation, t = 0, and 1 when the current
+ * time is at or after the end of the animation, t = m_scrollSnapAnimationDuration.
+ *
+ * In this exponential progress model, s(t) = A - A * b^(-kt), where k = 60T is the number of frames in the
+ * animation (assuming 60 FPS and an animation duration of T) and A, b are reals greater than or equal to 1.
+ * Also note that we are given the initial progress, a value indicating the portion of the curve which our
+ * initial scroll delta takes us. This is important when matching the initial speed of the animation to the
+ * user's initial momentum scrolling speed. Let this initial progress amount equal v_0. I clamp this initial
+ * progress amount to a minimum or maximum value.
+ *
+ * A is referred to as the curve magnitude, while b is referred to as the decay factor. We solve for A and b,
+ * keeping the following constraints in mind:
+ *     1. s(0) = 0
+ *     2. s(1) = 1
+ *     3. s(1/k) = v_0
+ *
+ * First, observe that s(0) = 0 holds for appropriate values of A, b. Solving for the remaining constraints
+ * yields a nonlinear system of two equations. In lieu of a purely analytical solution, an alternating
+ * optimization scheme is used to approximate A and b. This technique converges quickly (within 5 iterations
+ * or so) for appropriate values of v_0. The optimization terminates early when the decay factor changes by
+ * less than a threshold between one iteration and the next.
+ */
+void BasicScrollingMomentumCalculator::initializeSnapProgressCurve()
+{
+    static const int maxNumScrollSnapParameterEstimationIterations = 10;
+    static const float scrollSnapDecayFactorConvergenceThreshold = 0.001;
+    static const float initialScrollSnapCurveMagnitude = 1.1;
+    static const float minScrollSnapInitialProgress = 0.1;
+    static const float maxScrollSnapInitialProgress = 0.5;
+
+    FloatSize alignmentVector = m_initialDelta * (retargetedScrollOffset() - m_initialScrollOffset);
+    float initialProgress;
+    if (alignmentVector.width() + alignmentVector.height() > 0)
+        initialProgress = clampTo(m_initialDelta.diagonalLength() / (retargetedScrollOffset() - m_initialScrollOffset).diagonalLength(), minScrollSnapInitialProgress, maxScrollSnapInitialProgress);
+    else
+        initialProgress = minScrollSnapInitialProgress;
+
+    float previousDecayFactor = 1.0f;
+    m_snapAnimationCurveMagnitude = initialScrollSnapCurveMagnitude;
+    for (int i = 0; i < maxNumScrollSnapParameterEstimationIterations; ++i) {
+        m_snapAnimationDecayFactor = m_snapAnimationCurveMagnitude / (m_snapAnimationCurveMagnitude - initialProgress);
+        m_snapAnimationCurveMagnitude = 1.0f / (1.0f - std::pow(m_snapAnimationDecayFactor, -framesPerSecond * scrollSnapAnimationDuration.value()));
+        if (std::abs(m_snapAnimationDecayFactor - previousDecayFactor) < scrollSnapDecayFactorConvergenceThreshold)
+            break;
+
+        previousDecayFactor = m_snapAnimationDecayFactor;
+    }
+}
+
+float BasicScrollingMomentumCalculator::animationProgressAfterElapsedTime(Seconds elapsedTime) const
+{
+    float timeProgress = clampTo<float>(elapsedTime / scrollSnapAnimationDuration, 0, 1);
+    return std::min(1.0, m_snapAnimationCurveMagnitude * (1.0 - std::pow(m_snapAnimationDecayFactor, -framesPerSecond * scrollSnapAnimationDuration.value() * timeProgress)));
+}
+
+}; // namespace WebCore