1 files changed, 90 insertions, 0 deletions
diff --git a/Source/WebCore/page/scrolling/ScrollingMomentumCalculator.h b/Source/WebCore/page/scrolling/ScrollingMomentumCalculator.h
new file mode 100644
index 000000000..a82afaa66
--- /dev/null
+++ b/Source/WebCore/page/scrolling/ScrollingMomentumCalculator.h
@@ -0,0 +1,90 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#if ENABLE(CSS_SCROLL_SNAP)
+
+#include "AxisScrollSnapOffsets.h"
+#include "PlatformWheelEvent.h"
+#include "ScrollTypes.h"
+#include <wtf/Optional.h>
+#include <wtf/Seconds.h>
+
+namespace WebCore {
+
+class FloatPoint;
+class FloatSize;
+
+class ScrollingMomentumCalculator {
+public:
+    ScrollingMomentumCalculator(const FloatSize& viewportSize, const FloatSize& contentSize, const FloatPoint& initialOffset, const FloatSize& initialDelta, const FloatSize& initialVelocity);
+    static std::unique_ptr<ScrollingMomentumCalculator> create(const FloatSize& viewportSize, const FloatSize& contentSize, const FloatPoint& initialOffset, const FloatSize& initialDelta, const FloatSize& initialVelocity);
+    WEBCORE_EXPORT static void setPlatformMomentumScrollingPredictionEnabled(bool);
+    virtual ~ScrollingMomentumCalculator() { }
+
+    virtual FloatPoint scrollOffsetAfterElapsedTime(Seconds) = 0;
+    virtual Seconds animationDuration() = 0;
+    virtual FloatSize predictedDestinationOffset();
+    void setRetargetedScrollOffset(const FloatSize&);
+
+protected:
+    const FloatSize& retargetedScrollOffset() const { return m_retargetedScrollOffset.value(); }
+    virtual void retargetedScrollOffsetDidChange() { }
+
+    FloatSize m_initialDelta;
+    FloatSize m_initialVelocity;
+    FloatSize m_initialScrollOffset;
+    FloatSize m_viewportSize;
+    FloatSize m_contentSize;
+
+private:
+    std::optional<FloatSize> m_retargetedScrollOffset;
+};
+
+class BasicScrollingMomentumCalculator final : public ScrollingMomentumCalculator {
+public:
+    BasicScrollingMomentumCalculator(const FloatSize& viewportSize, const FloatSize& contentSize, const FloatPoint& initialOffset, const FloatSize& initialDelta, const FloatSize& initialVelocity);
+
+private:
+    FloatPoint scrollOffsetAfterElapsedTime(Seconds) final;
+    Seconds animationDuration() final;
+    void initializeInterpolationCoefficientsIfNecessary();
+    void initializeSnapProgressCurve();
+    float animationProgressAfterElapsedTime(Seconds) const;
+    FloatSize linearlyInterpolatedOffsetAtProgress(float progress);
+    FloatSize cubicallyInterpolatedOffsetAtProgress(float progress) const;
+
+    float m_snapAnimationCurveMagnitude { 0 };
+    float m_snapAnimationDecayFactor { 0 };
+    FloatSize m_snapAnimationCurveCoefficients[4] { };
+    bool m_forceLinearAnimationCurve { false };
+    bool m_momentumCalculatorRequiresInitialization { true };
+    std::optional<FloatSize> m_predictedDestinationOffset;
+};
+
+} // namespace WebCore
+
+#endif // ENABLE(CSS_SCROLL_SNAP)