Move scroll elasticity files from blink to content

content/renderer/input/input_scroll_elasticity_controller.cc

+/*
+ * Copyright (C) 2011 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 "platform/mac/ScrollElasticityController.h"
+
+// #include "platform/PlatformWheelEvent.h"
+// #include <sys/sysctl.h>
+// #include <sys/time.h>
+
+#if USE(RUBBER_BANDING)
+
+static NSTimeInterval systemUptime()
+{
+    if ([[NSProcessInfo processInfo] respondsToSelector:@selector(systemUptime)])
+        return [[NSProcessInfo processInfo] systemUptime];
+
+    // Get how long system has been up. Found by looking getting "boottime" from the kernel.
+    static struct timeval boottime = {0, 0};
+    if (!boottime.tv_sec) {
+        int mib[2] = {CTL_KERN, KERN_BOOTTIME};
+        size_t size = sizeof(boottime);
+        if (-1 == sysctl(mib, 2, &boottime, &size, 0, 0))
+            boottime.tv_sec = 0;
+    }
+    struct timeval now;
+    if (boottime.tv_sec && -1 != gettimeofday(&now, 0)) {
+        struct timeval uptime;
+        timersub(&now, &boottime, &uptime);
+        NSTimeInterval result = uptime.tv_sec + (uptime.tv_usec / 1E+6);
+        return result;
+    }
+    return 0;
+}
+
+namespace blink {
+
+static const float scrollVelocityZeroingTimeout = 0.10f;
+static const float rubberbandDirectionLockStretchRatio = 1;
+static const float rubberbandMinimumRequiredDeltaBeforeStretch = 10;
+
+static const float rubberbandStiffness = 20;
+static const float rubberbandAmplitude = 0.31f;
+static const float rubberbandPeriod = 1.6f;
+
+static float elasticDeltaForTimeDelta(float initialPosition, float initialVelocity, float elapsedTime)
+{
+    float amplitude = rubberbandAmplitude;
+    float period = rubberbandPeriod;
+    float criticalDampeningFactor = expf((-elapsedTime * rubberbandStiffness) / period);
+
+    return (initialPosition + (-initialVelocity * elapsedTime * amplitude)) * criticalDampeningFactor;
+}
+
+static float elasticDeltaForReboundDelta(float delta)
+{
+    float stiffness = std::max(rubberbandStiffness, 1.0f);
+    return delta / stiffness;
+}
+
+static float reboundDeltaForElasticDelta(float delta)
+{
+    return delta * rubberbandStiffness;
+}
+
+static float scrollWheelMultiplier()
+{
+    static float multiplier = -1;
+    if (multiplier < 0) {
+        multiplier = [[NSUserDefaults standardUserDefaults] floatForKey:@"NSScrollWheelMultiplier"];
+        if (multiplier <= 0)
+            multiplier = 1;
+    }
+    return multiplier;
+}
+
+ScrollElasticityController::ScrollElasticityController(ScrollElasticityControllerClient* client)
+    : m_client(client)
+    , m_inScrollGesture(false)
+    , m_hasScrolled(false)
+    , m_momentumScrollInProgress(false)
+    , m_ignoreMomentumScrolls(false)
+    , m_lastMomentumScrollTimestamp(0)
+    , m_startTime(0)
+    , m_snapRubberbandTimerIsActive(false)
+{
+}
+
+bool ScrollElasticityController::handleWheelEvent(const PlatformWheelEvent& wheelEvent)
+{
+    if (wheelEvent.phase() == PlatformWheelEventPhaseMayBegin)
+        return false;
+
+    if (wheelEvent.phase() == PlatformWheelEventPhaseBegan) {
+        m_inScrollGesture = true;
+        m_hasScrolled = false;
+        m_momentumScrollInProgress = false;
+        m_ignoreMomentumScrolls = false;
+        m_lastMomentumScrollTimestamp = 0;
+        m_momentumVelocity = FloatSize();
+
+        IntSize stretchAmount = m_client->stretchAmount();
+        m_stretchScrollForce.setWidth(reboundDeltaForElasticDelta(stretchAmount.width()));
+        m_stretchScrollForce.setHeight(reboundDeltaForElasticDelta(stretchAmount.height()));
+        m_overflowScrollDelta = FloatSize();
+
+        stopSnapRubberbandTimer();
+
+        // TODO(erikchen): Use the commented out line once Chromium uses the return value correctly.
+        // crbug.com/375512
+        // return shouldHandleEvent(wheelEvent);
+
+        // This logic is incorrect, since diagonal wheel events are not consumed.
+        if (m_client->pinnedInDirection(FloatSize(-wheelEvent.deltaX(), 0))) {
+            if (wheelEvent.deltaX() > 0 && !wheelEvent.canRubberbandLeft())
+                return false;
+            if (wheelEvent.deltaX() < 0 && !wheelEvent.canRubberbandRight())
+                return false;
+        }
+
+        return true;
+    }
+
+    if (wheelEvent.phase() == PlatformWheelEventPhaseEnded || wheelEvent.phase() == PlatformWheelEventPhaseCancelled) {
+        snapRubberBand();
+        return m_hasScrolled;
+    }
+
+    bool isMomentumScrollEvent = (wheelEvent.momentumPhase() != PlatformWheelEventPhaseNone);
+    if (m_ignoreMomentumScrolls && (isMomentumScrollEvent || m_snapRubberbandTimerIsActive)) {
+        if (wheelEvent.momentumPhase() == PlatformWheelEventPhaseEnded) {
+            m_ignoreMomentumScrolls = false;
+            return true;
+        }
+        return false;
+    }
+
+    if (!shouldHandleEvent(wheelEvent))
+        return false;
+
+    float deltaX = m_overflowScrollDelta.width() - wheelEvent.deltaX();
+    float deltaY = m_overflowScrollDelta.height() - wheelEvent.deltaY();
+    float eventCoalescedDeltaX = -wheelEvent.deltaX();
+    float eventCoalescedDeltaY = -wheelEvent.deltaY();
+
+    // Reset overflow values because we may decide to remove delta at various points and put it into overflow.
+    m_overflowScrollDelta = FloatSize();
+
+    IntSize stretchAmount = m_client->stretchAmount();
+    bool isVerticallyStretched = stretchAmount.height();
+    bool isHorizontallyStretched = stretchAmount.width();
+
+    // Slightly prefer scrolling vertically by applying the = case to deltaY
+    if (fabsf(deltaY) >= fabsf(deltaX))
+        deltaX = 0;
+    else
+        deltaY = 0;
+
+    bool shouldStretch = false;
+
+    PlatformWheelEventPhase momentumPhase = wheelEvent.momentumPhase();
+
+    // If we are starting momentum scrolling then do some setup.
+    if (!m_momentumScrollInProgress && (momentumPhase == PlatformWheelEventPhaseBegan || momentumPhase == PlatformWheelEventPhaseChanged)) {
+        m_momentumScrollInProgress = true;
+        // Start the snap rubber band timer if it's not running. This is needed to
+        // snap back from the over scroll caused by momentum events.
+        if (!m_snapRubberbandTimerIsActive && m_startTime == 0)
+            snapRubberBand();
+    }
+
+    CFTimeInterval timeDelta = wheelEvent.timestamp() - m_lastMomentumScrollTimestamp;
+    if (m_inScrollGesture || m_momentumScrollInProgress) {
+        if (m_lastMomentumScrollTimestamp && timeDelta > 0 && timeDelta < scrollVelocityZeroingTimeout) {
+            m_momentumVelocity.setWidth(eventCoalescedDeltaX / (float)timeDelta);
+            m_momentumVelocity.setHeight(eventCoalescedDeltaY / (float)timeDelta);
+            m_lastMomentumScrollTimestamp = wheelEvent.timestamp();
+        } else {
+            m_lastMomentumScrollTimestamp = wheelEvent.timestamp();
+            m_momentumVelocity = FloatSize();
+        }
+
+        if (isVerticallyStretched) {
+            if (!isHorizontallyStretched && m_client->pinnedInDirection(FloatSize(deltaX, 0))) {
+                // Stretching only in the vertical.
+                if (deltaY != 0 && (fabsf(deltaX / deltaY) < rubberbandDirectionLockStretchRatio))
+                    deltaX = 0;
+                else if (fabsf(deltaX) < rubberbandMinimumRequiredDeltaBeforeStretch) {
+                    m_overflowScrollDelta.setWidth(m_overflowScrollDelta.width() + deltaX);
+                    deltaX = 0;
+                } else
+                    m_overflowScrollDelta.setWidth(m_overflowScrollDelta.width() + deltaX);
+            }
+        } else if (isHorizontallyStretched) {
+            // Stretching only in the horizontal.
+            if (m_client->pinnedInDirection(FloatSize(0, deltaY))) {
+                if (deltaX != 0 && (fabsf(deltaY / deltaX) < rubberbandDirectionLockStretchRatio))
+                    deltaY = 0;
+                else if (fabsf(deltaY) < rubberbandMinimumRequiredDeltaBeforeStretch) {
+                    m_overflowScrollDelta.setHeight(m_overflowScrollDelta.height() + deltaY);
+                    deltaY = 0;
+                } else
+                    m_overflowScrollDelta.setHeight(m_overflowScrollDelta.height() + deltaY);
+            }
+        } else {
+            // Not stretching at all yet.
+            if (m_client->pinnedInDirection(FloatSize(deltaX, deltaY))) {
+                if (fabsf(deltaY) >= fabsf(deltaX)) {
+                    if (fabsf(deltaX) < rubberbandMinimumRequiredDeltaBeforeStretch) {
+                        m_overflowScrollDelta.setWidth(m_overflowScrollDelta.width() + deltaX);
+                        deltaX = 0;
+                    } else
+                        m_overflowScrollDelta.setWidth(m_overflowScrollDelta.width() + deltaX);
+                }
+                shouldStretch = true;
+            }
+        }
+    }
+
+    if (deltaX != 0 || deltaY != 0) {
+        m_hasScrolled = true;
+        if (!(shouldStretch || isVerticallyStretched || isHorizontallyStretched)) {
+            if (deltaY != 0) {
+                deltaY *= scrollWheelMultiplier();
+                m_client->immediateScrollBy(FloatSize(0, deltaY));
+            }
+            if (deltaX != 0) {
+                deltaX *= scrollWheelMultiplier();
+                m_client->immediateScrollBy(FloatSize(deltaX, 0));
+            }
+        } else {
+            if (!m_client->allowsHorizontalStretching()) {
+                deltaX = 0;
+                eventCoalescedDeltaX = 0;
+            } else if ((deltaX != 0) && !isHorizontallyStretched && !m_client->pinnedInDirection(FloatSize(deltaX, 0))) {
+                deltaX *= scrollWheelMultiplier();
+
+                m_client->immediateScrollByWithoutContentEdgeConstraints(FloatSize(deltaX, 0));
+                deltaX = 0;
+            }
+
+            if (!m_client->allowsVerticalStretching()) {
+                deltaY = 0;
+                eventCoalescedDeltaY = 0;
+            } else if ((deltaY != 0) && !isVerticallyStretched && !m_client->pinnedInDirection(FloatSize(0, deltaY))) {
+                deltaY *= scrollWheelMultiplier();
+
+                m_client->immediateScrollByWithoutContentEdgeConstraints(FloatSize(0, deltaY));
+                deltaY = 0;
+            }
+
+            IntSize stretchAmount = m_client->stretchAmount();
+
+            if (m_momentumScrollInProgress) {
+                if ((m_client->pinnedInDirection(FloatSize(eventCoalescedDeltaX, eventCoalescedDeltaY)) || (fabsf(eventCoalescedDeltaX) + fabsf(eventCoalescedDeltaY) <= 0)) && m_lastMomentumScrollTimestamp) {
+                    m_ignoreMomentumScrolls = true;
+                    m_momentumScrollInProgress = false;
+                    snapRubberBand();
+                }
+            }
+
+            m_stretchScrollForce.setWidth(m_stretchScrollForce.width() + deltaX);
+            m_stretchScrollForce.setHeight(m_stretchScrollForce.height() + deltaY);
+
+            FloatSize dampedDelta(ceilf(elasticDeltaForReboundDelta(m_stretchScrollForce.width())), ceilf(elasticDeltaForReboundDelta(m_stretchScrollForce.height())));
+
+            m_client->immediateScrollByWithoutContentEdgeConstraints(dampedDelta - stretchAmount);
+        }
+    }
+
+    if (m_momentumScrollInProgress && momentumPhase == PlatformWheelEventPhaseEnded) {
+        m_momentumScrollInProgress = false;
+        m_ignoreMomentumScrolls = false;
+        m_lastMomentumScrollTimestamp = 0;
+    }
+
+    return true;
+}
+
+static inline float roundTowardZero(float num)
+{
+    return num > 0 ? ceilf(num - 0.5f) : floorf(num + 0.5f);
+}
+
+static inline float roundToDevicePixelTowardZero(float num)
+{
+    float roundedNum = roundf(num);
+    if (fabs(num - roundedNum) < 0.125)
+        num = roundedNum;
+
+    return roundTowardZero(num);
+}
+
+void ScrollElasticityController::snapRubberBandTimerFired()
+{
+    if (!m_momentumScrollInProgress || m_ignoreMomentumScrolls) {
+        CFTimeInterval timeDelta = [NSDate timeIntervalSinceReferenceDate] - m_startTime;
+
+        if (m_startStretch == FloatSize()) {
+            m_startStretch = m_client->stretchAmount();
+            if (m_startStretch == FloatSize()) {
+                stopSnapRubberbandTimer();
+
+                m_stretchScrollForce = FloatSize();
+                m_startTime = 0;
+                m_origOrigin = FloatPoint();
+                m_origVelocity = FloatSize();
+                return;
+            }
+
+            m_origOrigin = m_client->absoluteScrollPosition() - m_startStretch;
+            m_origVelocity = m_momentumVelocity;
+
+            // Just like normal scrolling, prefer vertical rubberbanding
+            if (fabsf(m_origVelocity.height()) >= fabsf(m_origVelocity.width()))
+                m_origVelocity.setWidth(0);
+
+            // Don't rubber-band horizontally if it's not possible to scroll horizontally
+            if (!m_client->canScrollHorizontally())
+                m_origVelocity.setWidth(0);
+
+            // Don't rubber-band vertically if it's not possible to scroll vertically
+            if (!m_client->canScrollVertically())
+                m_origVelocity.setHeight(0);
+        }
+
+        FloatPoint delta(roundToDevicePixelTowardZero(elasticDeltaForTimeDelta(m_startStretch.width(), -m_origVelocity.width(), (float)timeDelta)),
+                         roundToDevicePixelTowardZero(elasticDeltaForTimeDelta(m_startStretch.height(), -m_origVelocity.height(), (float)timeDelta)));
+
+        if (fabs(delta.x()) >= 1 || fabs(delta.y()) >= 1) {
+            m_client->immediateScrollByWithoutContentEdgeConstraints(FloatSize(delta.x(), delta.y()) - m_client->stretchAmount());
+
+            FloatSize newStretch = m_client->stretchAmount();
+
+            m_stretchScrollForce.setWidth(reboundDeltaForElasticDelta(newStretch.width()));
+            m_stretchScrollForce.setHeight(reboundDeltaForElasticDelta(newStretch.height()));
+        } else {
+            m_client->adjustScrollPositionToBoundsIfNecessary();
+
+            stopSnapRubberbandTimer();
+            m_stretchScrollForce = FloatSize();
+            m_startTime = 0;
+            m_startStretch = FloatSize();
+            m_origOrigin = FloatPoint();
+            m_origVelocity = FloatSize();
+        }
+    } else {
+        m_startTime = [NSDate timeIntervalSinceReferenceDate];
+        m_startStretch = FloatSize();
+    }
+}
+
+bool ScrollElasticityController::isRubberBandInProgress() const
+{
+    if (!m_inScrollGesture && !m_momentumScrollInProgress && !m_snapRubberbandTimerIsActive)
+        return false;
+
+    return !m_client->stretchAmount().isZero();
+}
+
+void ScrollElasticityController::stopSnapRubberbandTimer()
+{
+    m_client->stopSnapRubberbandTimer();
+    m_snapRubberbandTimerIsActive = false;
+}
+
+void ScrollElasticityController::snapRubberBand()
+{
+    CFTimeInterval timeDelta = systemUptime() - m_lastMomentumScrollTimestamp;
+    if (m_lastMomentumScrollTimestamp && timeDelta >= scrollVelocityZeroingTimeout)
+        m_momentumVelocity = FloatSize();
+
+    m_inScrollGesture = false;
+
+    if (m_snapRubberbandTimerIsActive)
+        return;
+
+    m_startStretch = FloatSize();
+    m_origOrigin = FloatPoint();
+    m_origVelocity = FloatSize();
+
+    // If there's no momentum scroll or stretch amount, no need to start the timer.
+    if (!m_momentumScrollInProgress && m_client->stretchAmount() == FloatSize()) {
+        m_startTime = 0;
+        m_stretchScrollForce = FloatSize();
+        return;
+    }
+
+    m_startTime = [NSDate timeIntervalSinceReferenceDate];
+    m_client->startSnapRubberbandTimer();
+    m_snapRubberbandTimerIsActive = true;
+}
+
+bool ScrollElasticityController::shouldHandleEvent(const PlatformWheelEvent& wheelEvent)
+{
+    // Once any scrolling has happened, all future events should be handled.
+    if (m_hasScrolled)
+        return true;
+
+    // The event can't cause scrolling to start if its delta is 0.
+    if (wheelEvent.deltaX() == 0 && wheelEvent.deltaY() == 0)
+        return false;
+
+    // If the client isn't pinned, then the event is guaranteed to cause scrolling.
+    if (!m_client->pinnedInDirection(FloatSize(-wheelEvent.deltaX(), 0)))
+        return true;
+
+    // If the event is pinned, then the client can't scroll, but it might rubber band.
+    // Check if the event allows rubber banding.
+    if (wheelEvent.deltaY() == 0) {
+        if (wheelEvent.deltaX() > 0 && !wheelEvent.canRubberbandLeft())
+            return false;
+        if (wheelEvent.deltaX() < 0 && !wheelEvent.canRubberbandRight())
+            return false;
+    }
+
+    // The event is going to either cause scrolling or rubber banding.
+    return true;
+}
+
+} // namespace blink
+
+#endif // USE(RUBBER_BANDING)