qquickflickable.cpp

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// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qquickflickable_p.h"
#include "qquickflickable_p_p.h"
#include "qquickflickablebehavior_p.h"
#include "qquickwindow.h"
#include "qquickwindow_p.h"
#include "qquickmousearea_p.h"
#if QT_CONFIG(quick_draganddrop)
#include "qquickdrag_p.h"
#endif
 
#include <QtQuick/private/qquickpointerhandler_p.h>
#include <QtQuick/private/qquicktransition_p.h>
#include <private/qqmlglobal_p.h>
 
#include <QtQml/qqmlinfo.h>
#include <QtGui/qevent.h>
#include <QtGui/qguiapplication.h>
#include <QtGui/private/qguiapplication_p.h>
#include <QtGui/private/qeventpoint_p.h>
#include <QtGui/qstylehints.h>
#include <QtCore/qmath.h>
#include <qpa/qplatformtheme.h>
 
#include <math.h>
#include <cmath>
 
QT_BEGIN_NAMESPACE
 
Q_DECLARE_LOGGING_CATEGORY(lcHandlerParent)
Q_LOGGING_CATEGORY(lcFlickable, "qt.quick.flickable")
Q_LOGGING_CATEGORY(lcFilter, "qt.quick.flickable.filter")
Q_LOGGING_CATEGORY(lcReplay, "qt.quick.flickable.replay")
Q_LOGGING_CATEGORY(lcWheel, "qt.quick.flickable.wheel")
Q_LOGGING_CATEGORY(lcVel, "qt.quick.flickable.velocity")
 
// RetainGrabVelocity is the maxmimum instantaneous velocity that
// will ensure the Flickable retains the grab on consecutive flicks.
static const int RetainGrabVelocity = 100;
 
static qreal EaseOvershoot(qreal t) {
    return qAtan(t);
}
 
QQuickFlickableVisibleArea::QQuickFlickableVisibleArea(QQuickFlickable *parent)
    : QObject(parent), flickable(parent), m_xPosition(0.), m_widthRatio(0.)
    , m_yPosition(0.), m_heightRatio(0.)
{
}
 
qreal QQuickFlickableVisibleArea::widthRatio() const
{
    return m_widthRatio;
}
 
qreal QQuickFlickableVisibleArea::xPosition() const
{
    return m_xPosition;
}
 
qreal QQuickFlickableVisibleArea::heightRatio() const
{
    return m_heightRatio;
}
 
qreal QQuickFlickableVisibleArea::yPosition() const
{
    return m_yPosition;
}
 
void QQuickFlickableVisibleArea::updateVisible()
{
    QQuickFlickablePrivate *p = QQuickFlickablePrivate::get(flickable);
 
    bool changeX = false;
    bool changeY = false;
    bool changeWidth = false;
    bool changeHeight = false;
 
    // Vertical
    const qreal viewheight = flickable->height();
    const qreal maxyextent = -flickable->maxYExtent() + flickable->minYExtent();
    const qreal maxYBounds = maxyextent + viewheight;
    qreal pagePos = 0;
    qreal pageSize = 0;
    if (!qFuzzyIsNull(maxYBounds)) {
        qreal y = p->pixelAligned ? std::round(p->vData.move.value()) : p->vData.move.value();
        pagePos = (-y + flickable->minYExtent()) / maxYBounds;
        pageSize = viewheight / maxYBounds;
    }
 
    if (pageSize != m_heightRatio) {
        m_heightRatio = pageSize;
        changeHeight = true;
    }
    if (pagePos != m_yPosition) {
        m_yPosition = pagePos;
        changeY = true;
    }
 
    // Horizontal
    const qreal viewwidth = flickable->width();
    const qreal maxxextent = -flickable->maxXExtent() + flickable->minXExtent();
    const qreal maxXBounds = maxxextent + viewwidth;
    if (!qFuzzyIsNull(maxXBounds)) {
        qreal x = p->pixelAligned ? std::round(p->hData.move.value()) : p->hData.move.value();
        pagePos = (-x + flickable->minXExtent()) / maxXBounds;
        pageSize = viewwidth / maxXBounds;
    } else {
        pagePos = 0;
        pageSize = 0;
    }
 
    if (pageSize != m_widthRatio) {
        m_widthRatio = pageSize;
        changeWidth = true;
    }
    if (pagePos != m_xPosition) {
        m_xPosition = pagePos;
        changeX = true;
    }
 
    if (changeX)
        emit xPositionChanged(m_xPosition);
    if (changeY)
        emit yPositionChanged(m_yPosition);
    if (changeWidth)
        emit widthRatioChanged(m_widthRatio);
    if (changeHeight)
        emit heightRatioChanged(m_heightRatio);
}
 
 
class QQuickFlickableReboundTransition : public QQuickTransitionManager
{
public:
    QQuickFlickableReboundTransition(QQuickFlickable *f, const QString &name)
        : flickable(f), axisData(nullptr), propName(name), active(false)
    {
    }
 
    ~QQuickFlickableReboundTransition()
    {
        flickable = nullptr;
    }
 
    bool startTransition(QQuickFlickablePrivate::AxisData *data, qreal toPos) {
        QQuickFlickablePrivate *fp = QQuickFlickablePrivate::get(flickable);
        if (!fp->rebound || !fp->rebound->enabled())
            return false;
        active = true;
        axisData = data;
        axisData->transitionTo = toPos;
        axisData->transitionToSet = true;
 
        actions.clear();
        actions << QQuickStateAction(fp->contentItem, propName, toPos);
        QQuickTransitionManager::transition(actions, fp->rebound, fp->contentItem);
        return true;
    }
 
    bool isActive() const {
        return active;
    }
 
    void stopTransition() {
        if (!flickable || !isRunning())
            return;
        QQuickFlickablePrivate *fp = QQuickFlickablePrivate::get(flickable);
        if (axisData == &fp->hData)
            axisData->move.setValue(-flickable->contentX());
        else
            axisData->move.setValue(-flickable->contentY());
        active = false;
        cancel();
    }
 
protected:
    void finished() override {
        if (!flickable)
            return;
        axisData->move.setValue(axisData->transitionTo);
        QQuickFlickablePrivate *fp = QQuickFlickablePrivate::get(flickable);
        active = false;
 
        if (!fp->hData.transitionToBounds->isActive()
                && !fp->vData.transitionToBounds->isActive()) {
            flickable->movementEnding();
        }
    }
 
private:
    QQuickStateOperation::ActionList actions;
    QQuickFlickable *flickable;
    QQuickFlickablePrivate::AxisData *axisData;
    QString propName;
    bool active;
};
 
QQuickFlickablePrivate::AxisData::~AxisData()
{
    delete transitionToBounds;
}
 
class QQuickFlickableContentItem : public QQuickItem
{
    bool contains(const QPointF &point) const override
    {
        const QQuickItem *flickable = parentItem();
        const QPointF posInFlickable = flickable->mapFromItem(this, point);
        return flickable->contains(posInFlickable);
    }
};
 
QQuickFlickablePrivate::QQuickFlickablePrivate()
  : contentItem(new QQuickFlickableContentItem)
    , hData(this, &QQuickFlickablePrivate::setViewportX)
    , vData(this, &QQuickFlickablePrivate::setViewportY)
    , hMoved(false), vMoved(false)
    , stealMouse(false), pressed(false)
    , scrollingPhase(false), interactive(true), calcVelocity(false)
    , pixelAligned(false)
    , syncDrag(false)
    , lastPosTime(-1)
    , lastPressTime(0)
    , deceleration(QGuiApplicationPrivate::platformTheme()->themeHint(QPlatformTheme::FlickDeceleration).toReal())
    , wheelDeceleration(15000)
    , maxVelocity(QGuiApplicationPrivate::platformTheme()->themeHint(QPlatformTheme::FlickMaximumVelocity).toReal())
    , delayedPressEvent(nullptr), pressDelay(0), fixupDuration(400)
    , flickBoost(1.0), initialWheelFlickDistance(qApp->styleHints()->wheelScrollLines() * 24)
    , fixupMode(Normal), vTime(0), visibleArea(nullptr)
    , flickableDirection(QQuickFlickable::AutoFlickDirection)
    , boundsBehavior(QQuickFlickable::DragAndOvershootBounds)
    , boundsMovement(QQuickFlickable::FollowBoundsBehavior)
    , rebound(nullptr)
{
    const int wheelDecelerationEnv = qEnvironmentVariableIntValue("QT_QUICK_FLICKABLE_WHEEL_DECELERATION");
    if (wheelDecelerationEnv > 0)
        wheelDeceleration = wheelDecelerationEnv;
}
 
void QQuickFlickablePrivate::init()
{
    Q_Q(QQuickFlickable);
    QQml_setParent_noEvent(contentItem, q);
    contentItem->setParentItem(q);
    qmlobject_connect(&timeline, QQuickTimeLine, SIGNAL(completed()),
                      q, QQuickFlickable, SLOT(timelineCompleted()));
    qmlobject_connect(&velocityTimeline, QQuickTimeLine, SIGNAL(completed()),
                      q, QQuickFlickable, SLOT(velocityTimelineCompleted()));
    q->setAcceptedMouseButtons(Qt::LeftButton);
    q->setAcceptTouchEvents(true);
    q->setFiltersChildMouseEvents(true);
    q->setFlag(QQuickItem::ItemIsViewport);
    QQuickItemPrivate *viewportPrivate = QQuickItemPrivate::get(contentItem);
    viewportPrivate->addItemChangeListener(this, QQuickItemPrivate::Geometry);
    setSizePolicy(QLayoutPolicy::Preferred, QLayoutPolicy::Preferred);
}
 
qreal QQuickFlickablePrivate::overShootDistance(qreal velocity) const
{
    if (maxVelocity <= 0)
        return 0;
 
    return qMin(qreal(QML_FLICK_OVERSHOOT), velocity / 3);
}
 
void QQuickFlickablePrivate::AxisData::addVelocitySample(qreal v, qreal maxVelocity)
{
    if (v > maxVelocity)
        v = maxVelocity;
    else if (v < -maxVelocity)
        v = -maxVelocity;
    velocityBuffer.append(v);
    if (velocityBuffer.count() > QML_FLICK_SAMPLEBUFFER)
        velocityBuffer.remove(0);
}
 
void QQuickFlickablePrivate::AxisData::updateVelocity()
{
    velocity = 0;
    if (velocityBuffer.count() > QML_FLICK_DISCARDSAMPLES) {
        int count = velocityBuffer.count()-QML_FLICK_DISCARDSAMPLES;
        for (int i = 0; i < count; ++i) {
            qreal v = velocityBuffer.at(i);
            velocity += v;
        }
        velocity /= count;
    }
}
 
void QQuickFlickablePrivate::itemGeometryChanged(QQuickItem *item, QQuickGeometryChange change, const QRectF &oldGeom)
{
    Q_Q(QQuickFlickable);
    if (item == contentItem) {
        Qt::Orientations orient;
        if (change.xChange())
            orient |= Qt::Horizontal;
        if (change.yChange())
            orient |= Qt::Vertical;
        if (orient) {
            q->viewportMoved(orient);
            const QPointF deltaMoved = item->position() - oldGeom.topLeft();
            if (hData.contentPositionChangedExternallyDuringDrag)
                hData.pressPos += deltaMoved.x();
            if (vData.contentPositionChangedExternallyDuringDrag)
                vData.pressPos += deltaMoved.y();
        }
        if (orient & Qt::Horizontal)
            emit q->contentXChanged();
        if (orient & Qt::Vertical)
            emit q->contentYChanged();
    }
}
 
bool QQuickFlickablePrivate::flickX(QEvent::Type eventType, qreal velocity)
{
    Q_Q(QQuickFlickable);
    return flick(hData, q->minXExtent(), q->maxXExtent(), q->width(), fixupX_callback, eventType, velocity);
}
 
bool QQuickFlickablePrivate::flickY(QEvent::Type eventType, qreal velocity)
{
    Q_Q(QQuickFlickable);
    return flick(vData, q->minYExtent(), q->maxYExtent(), q->height(), fixupY_callback, eventType, velocity);
}
 
bool QQuickFlickablePrivate::flick(AxisData &data, qreal minExtent, qreal maxExtent, qreal,
                                   QQuickTimeLineCallback::Callback fixupCallback,
                                   QEvent::Type eventType, qreal velocity)
{
    Q_Q(QQuickFlickable);
    qreal maxDistance = -1;
    data.fixingUp = false;
    // -ve velocity means list is moving up
    if (velocity > 0) {
        maxDistance = qAbs(minExtent - data.move.value());
        data.flickTarget = minExtent;
    } else {
        maxDistance = qAbs(maxExtent - data.move.value());
        data.flickTarget = maxExtent;
    }
    if (maxDistance > 0 || boundsBehavior & QQuickFlickable::OvershootBounds) {
        qreal v = velocity;
        if (maxVelocity != -1 && maxVelocity < qAbs(v)) {
            if (v < 0)
                v = -maxVelocity;
            else
                v = maxVelocity;
        }
 
        qreal accel = eventType == QEvent::Wheel ? wheelDeceleration : deceleration;
        qCDebug(lcFlickable) << "choosing deceleration" << accel << "for" << eventType;
        // adjust accel so that we hit a full pixel
        qreal v2 = v * v;
        qreal dist = v2 / (accel * 2.0);
        if (v > 0)
            dist = -dist;
        qreal target = std::round(data.move.value() - dist);
        dist = -target + data.move.value();
        accel = v2 / (2.0f * qAbs(dist));
 
        resetTimeline(data);
        if (!data.inOvershoot) {
            if (boundsBehavior & QQuickFlickable::OvershootBounds)
                timeline.accel(data.move, v, accel);
            else
                timeline.accel(data.move, v, accel, maxDistance);
        }
        timeline.callback(QQuickTimeLineCallback(&data.move, fixupCallback, this));
 
        if (&data == &hData)
            return !hData.flicking && q->xflick();
        else if (&data == &vData)
            return !vData.flicking && q->yflick();
        return false;
    } else {
        resetTimeline(data);
        fixup(data, minExtent, maxExtent);
        return false;
    }
}
 
void QQuickFlickablePrivate::fixupY_callback(void *data)
{
    ((QQuickFlickablePrivate *)data)->fixupY();
}
 
void QQuickFlickablePrivate::fixupX_callback(void *data)
{
    ((QQuickFlickablePrivate *)data)->fixupX();
}
 
void QQuickFlickablePrivate::fixupX()
{
    Q_Q(QQuickFlickable);
    if (!q->isComponentComplete())
        return; //Do not fixup from initialization values
    fixup(hData, q->minXExtent(), q->maxXExtent());
}
 
void QQuickFlickablePrivate::fixupY()
{
    Q_Q(QQuickFlickable);
    if (!q->isComponentComplete())
        return; //Do not fixup from initialization values
    fixup(vData, q->minYExtent(), q->maxYExtent());
}
 
void QQuickFlickablePrivate::adjustContentPos(AxisData &data, qreal toPos)
{
    Q_Q(QQuickFlickable);
    switch (fixupMode) {
    case Immediate:
        timeline.set(data.move, toPos);
        break;
    case ExtentChanged:
        // The target has changed. Don't start from the beginning; just complete the
        // second half of the animation using the new extent.
        timeline.move(data.move, toPos, QEasingCurve(QEasingCurve::OutExpo), 3*fixupDuration/4);
        data.fixingUp = true;
        break;
    default: {
            if (data.transitionToBounds && data.transitionToBounds->startTransition(&data, toPos)) {
                q->movementStarting();
                data.fixingUp = true;
            } else {
                qreal dist = toPos - data.move;
                timeline.move(data.move, toPos - dist/2, QEasingCurve(QEasingCurve::InQuad), fixupDuration/4);
                timeline.move(data.move, toPos, QEasingCurve(QEasingCurve::OutExpo), 3*fixupDuration/4);
                data.fixingUp = true;
            }
        }
    }
}
 
void QQuickFlickablePrivate::resetTimeline(AxisData &data)
{
    timeline.reset(data.move);
    if (data.transitionToBounds)
        data.transitionToBounds->stopTransition();
}
 
void QQuickFlickablePrivate::clearTimeline()
{
    timeline.clear();
    if (hData.transitionToBounds)
        hData.transitionToBounds->stopTransition();
    if (vData.transitionToBounds)
        vData.transitionToBounds->stopTransition();
}
 
void QQuickFlickablePrivate::fixup(AxisData &data, qreal minExtent, qreal maxExtent)
{
    if (data.move.value() >= minExtent || maxExtent > minExtent) {
        resetTimeline(data);
        if (data.move.value() != minExtent) {
            adjustContentPos(data, minExtent);
        }
    } else if (data.move.value() <= maxExtent) {
        resetTimeline(data);
        adjustContentPos(data, maxExtent);
    } else if (-std::round(-data.move.value()) != data.move.value()) {
        // We could animate, but since it is less than 0.5 pixel it's probably not worthwhile.
        resetTimeline(data);
        qreal val = data.move.value();
        if (std::abs(std::round(val) - val) < 0.25) // round small differences
            val = std::round(val);
        else if (data.smoothVelocity.value() > 0) // continue direction of motion for larger
            val = std::ceil(val);
        else if (data.smoothVelocity.value() < 0)
            val = std::floor(val);
        else // otherwise round
            val = std::round(val);
        timeline.set(data.move, val);
    }
    data.inOvershoot = false;
    fixupMode = Normal;
    data.vTime = timeline.time();
}
 
static bool fuzzyLessThanOrEqualTo(qreal a, qreal b)
{
    if (a == 0.0 || b == 0.0) {
        // qFuzzyCompare is broken
        a += 1.0;
        b += 1.0;
    }
    return a <= b || qFuzzyCompare(a, b);
}
 
void QQuickFlickablePrivate::updateBeginningEnd()
{
    Q_Q(QQuickFlickable);
    bool atXBeginningChange = false, atXEndChange = false;
    bool atYBeginningChange = false, atYEndChange = false;
 
    // Vertical
    const qreal maxyextent = -q->maxYExtent();
    const qreal minyextent = -q->minYExtent();
    const qreal ypos = pixelAligned ? -std::round(vData.move.value()) : -vData.move.value();
    bool atBeginning = fuzzyLessThanOrEqualTo(ypos, std::ceil(minyextent));
    bool atEnd = fuzzyLessThanOrEqualTo(std::floor(maxyextent), ypos);
 
    if (atBeginning != vData.atBeginning) {
        vData.atBeginning = atBeginning;
        atYBeginningChange = true;
        if (!vData.moving && atBeginning)
            vData.smoothVelocity.setValue(0);
    }
    if (atEnd != vData.atEnd) {
        vData.atEnd = atEnd;
        atYEndChange = true;
        if (!vData.moving && atEnd)
            vData.smoothVelocity.setValue(0);
    }
 
    // Horizontal
    const qreal maxxextent = -q->maxXExtent();
    const qreal minxextent = -q->minXExtent();
    const qreal xpos = pixelAligned ? -std::round(hData.move.value()) : -hData.move.value();
    atBeginning = fuzzyLessThanOrEqualTo(xpos, std::ceil(minxextent));
    atEnd = fuzzyLessThanOrEqualTo(std::floor(maxxextent), xpos);
 
    if (atBeginning != hData.atBeginning) {
        hData.atBeginning = atBeginning;
        atXBeginningChange = true;
        if (!hData.moving && atBeginning)
            hData.smoothVelocity.setValue(0);
    }
    if (atEnd != hData.atEnd) {
        hData.atEnd = atEnd;
        atXEndChange = true;
        if (!hData.moving && atEnd)
            hData.smoothVelocity.setValue(0);
    }
 
    if (vData.extentsChanged) {
        vData.extentsChanged = false;
        qreal originY = q->originY();
        if (vData.origin != originY) {
            vData.origin = originY;
            emit q->originYChanged();
        }
    }
 
    if (hData.extentsChanged) {
        hData.extentsChanged = false;
        qreal originX = q->originX();
        if (hData.origin != originX) {
            hData.origin = originX;
            emit q->originXChanged();
        }
    }
 
    if (atXEndChange || atYEndChange || atXBeginningChange || atYBeginningChange)
        emit q->isAtBoundaryChanged();
    if (atXEndChange)
        emit q->atXEndChanged();
    if (atXBeginningChange)
        emit q->atXBeginningChanged();
    if (atYEndChange)
        emit q->atYEndChanged();
    if (atYBeginningChange)
        emit q->atYBeginningChanged();
 
    if (visibleArea)
        visibleArea->updateVisible();
}
 
QQuickFlickable::QQuickFlickable(QQuickItem *parent)
  : QQuickItem(*(new QQuickFlickablePrivate), parent)
{
    Q_D(QQuickFlickable);
    d->init();
}
 
QQuickFlickable::QQuickFlickable(QQuickFlickablePrivate &dd, QQuickItem *parent)
  : QQuickItem(dd, parent)
{
    Q_D(QQuickFlickable);
    d->init();
}
 
QQuickFlickable::~QQuickFlickable()
{
}
 
qreal QQuickFlickable::contentX() const
{
    Q_D(const QQuickFlickable);
    return -d->contentItem->x();
}
 
void QQuickFlickable::setContentX(qreal pos)
{
    Q_D(QQuickFlickable);
    d->hData.explicitValue = true;
    d->resetTimeline(d->hData);
    d->hData.vTime = d->timeline.time();
    if (isMoving() || isFlicking())
        movementEnding(true, false);
    if (!qFuzzyCompare(-pos, d->hData.move.value())) {
        d->hData.contentPositionChangedExternallyDuringDrag = d->hData.dragging;
        d->hData.move.setValue(-pos);
        d->hData.contentPositionChangedExternallyDuringDrag = false;
    }
}
 
qreal QQuickFlickable::contentY() const
{
    Q_D(const QQuickFlickable);
    return -d->contentItem->y();
}
 
void QQuickFlickable::setContentY(qreal pos)
{
    Q_D(QQuickFlickable);
    d->vData.explicitValue = true;
    d->resetTimeline(d->vData);
    d->vData.vTime = d->timeline.time();
    if (isMoving() || isFlicking())
        movementEnding(false, true);
    if (!qFuzzyCompare(-pos, d->vData.move.value())) {
        d->vData.contentPositionChangedExternallyDuringDrag = d->vData.dragging;
        d->vData.move.setValue(-pos);
        d->vData.contentPositionChangedExternallyDuringDrag = false;
    }
}
 
bool QQuickFlickable::isInteractive() const
{
    Q_D(const QQuickFlickable);
    return d->interactive;
}
 
void QQuickFlickable::setInteractive(bool interactive)
{
    Q_D(QQuickFlickable);
    if (interactive != d->interactive) {
        d->interactive = interactive;
        if (!interactive) {
            d->cancelInteraction();
        }
        emit interactiveChanged();
    }
}
 
qreal QQuickFlickable::horizontalVelocity() const
{
    Q_D(const QQuickFlickable);
    return d->hData.smoothVelocity.value();
}
 
qreal QQuickFlickable::verticalVelocity() const
{
    Q_D(const QQuickFlickable);
    return d->vData.smoothVelocity.value();
}
 
bool QQuickFlickable::isAtXEnd() const
{
    Q_D(const QQuickFlickable);
    return d->hData.atEnd;
}
 
bool QQuickFlickable::isAtXBeginning() const
{
    Q_D(const QQuickFlickable);
    return d->hData.atBeginning;
}
 
bool QQuickFlickable::isAtYEnd() const
{
    Q_D(const QQuickFlickable);
    return d->vData.atEnd;
}
 
bool QQuickFlickable::isAtYBeginning() const
{
    Q_D(const QQuickFlickable);
    return d->vData.atBeginning;
}
 
QQuickItem *QQuickFlickable::contentItem() const
{
    Q_D(const QQuickFlickable);
    return d->contentItem;
}
 
QQuickFlickableVisibleArea *QQuickFlickable::visibleArea()
{
    Q_D(QQuickFlickable);
    if (!d->visibleArea) {
        d->visibleArea = new QQuickFlickableVisibleArea(this);
        d->visibleArea->updateVisible(); // calculate initial ratios
    }
    return d->visibleArea;
}
 
QQuickFlickable::FlickableDirection QQuickFlickable::flickableDirection() const
{
    Q_D(const QQuickFlickable);
    return d->flickableDirection;
}
 
void QQuickFlickable::setFlickableDirection(FlickableDirection direction)
{
    Q_D(QQuickFlickable);
    if (direction != d->flickableDirection) {
        d->flickableDirection = direction;
        emit flickableDirectionChanged();
    }
}
 
bool QQuickFlickable::pixelAligned() const
{
    Q_D(const QQuickFlickable);
    return d->pixelAligned;
}
 
void QQuickFlickable::setPixelAligned(bool align)
{
    Q_D(QQuickFlickable);
    if (align != d->pixelAligned) {
        d->pixelAligned = align;
        emit pixelAlignedChanged();
    }
}
 
bool QQuickFlickable::synchronousDrag() const
{
    Q_D(const QQuickFlickable);
    return d->syncDrag;
}
 
void QQuickFlickable::setSynchronousDrag(bool v)
{
    Q_D(QQuickFlickable);
    if (v != d->syncDrag) {
        d->syncDrag = v;
        emit synchronousDragChanged();
    }
}
 
QVector2D QQuickFlickablePrivate::firstPointLocalVelocity(QPointerEvent *event)
{
    QTransform transform = windowToItemTransform();
    // rotate and scale the velocity vector from scene to local
    return QVector2D(transform.map(event->point(0).velocity().toPointF()) - transform.map(QPointF()));
}
 
qint64 QQuickFlickablePrivate::computeCurrentTime(QInputEvent *event) const
{
    if (0 != event->timestamp())
        return event->timestamp();
    if (!timer.isValid())
        return 0LL;
    return timer.elapsed();
}
 
qreal QQuickFlickablePrivate::devicePixelRatio() const
{
    return (window ? window->effectiveDevicePixelRatio() : qApp->devicePixelRatio());
}
 
void QQuickFlickablePrivate::handlePressEvent(QPointerEvent *event)
{
    Q_Q(QQuickFlickable);
    timer.start();
    if (interactive && timeline.isActive()
        && ((qAbs(hData.smoothVelocity.value()) > RetainGrabVelocity && !hData.fixingUp && !hData.inOvershoot)
            || (qAbs(vData.smoothVelocity.value()) > RetainGrabVelocity && !vData.fixingUp && !vData.inOvershoot))) {
        stealMouse = true; // If we've been flicked then steal the click.
        int flickTime = timeline.time();
        if (flickTime > 600) {
            // too long between flicks - cancel boost
            hData.continuousFlickVelocity = 0;
            vData.continuousFlickVelocity = 0;
            flickBoost = 1.0;
        } else {
            hData.continuousFlickVelocity = -hData.smoothVelocity.value();
            vData.continuousFlickVelocity = -vData.smoothVelocity.value();
            if (flickTime > 300) // slower flicking - reduce boost
                flickBoost = qMax(1.0, flickBoost - 0.5);
        }
    } else {
        stealMouse = false;
        hData.continuousFlickVelocity = 0;
        vData.continuousFlickVelocity = 0;
        flickBoost = 1.0;
    }
    q->setKeepMouseGrab(stealMouse);
 
    maybeBeginDrag(computeCurrentTime(event), event->points().first().position(),
                   event->isSinglePointEvent() ? static_cast<QSinglePointEvent *>(event)->buttons()
                                               : Qt::NoButton);
}
 
void QQuickFlickablePrivate::maybeBeginDrag(qint64 currentTimestamp, const QPointF &pressPosn, Qt::MouseButtons buttons)
{
    Q_Q(QQuickFlickable);
    clearDelayedPress();
    // consider dragging only when event is left mouse button or touch event which has no button
    pressed = buttons.testFlag(Qt::LeftButton) || (buttons == Qt::NoButton);
 
    if (hData.transitionToBounds)
        hData.transitionToBounds->stopTransition();
    if (vData.transitionToBounds)
        vData.transitionToBounds->stopTransition();
    if (!hData.fixingUp)
        resetTimeline(hData);
    if (!vData.fixingUp)
        resetTimeline(vData);
 
    hData.reset();
    vData.reset();
    hData.dragMinBound = q->minXExtent() - hData.startMargin;
    vData.dragMinBound = q->minYExtent() - vData.startMargin;
    hData.dragMaxBound = q->maxXExtent() + hData.endMargin;
    vData.dragMaxBound = q->maxYExtent() + vData.endMargin;
    fixupMode = Normal;
    lastPos = QPointF();
    pressPos = pressPosn;
    hData.pressPos = hData.move.value();
    vData.pressPos = vData.move.value();
    const bool wasFlicking = hData.flicking || vData.flicking;
    hData.flickingWhenDragBegan = hData.flicking;
    vData.flickingWhenDragBegan = vData.flicking;
    if (hData.flicking) {
        hData.flicking = false;
        emit q->flickingHorizontallyChanged();
    }
    if (vData.flicking) {
        vData.flicking = false;
        emit q->flickingVerticallyChanged();
    }
    if (wasFlicking)
        emit q->flickingChanged();
    lastPosTime = lastPressTime = currentTimestamp;
    vData.velocityTime.start();
    hData.velocityTime.start();
}
 
void QQuickFlickablePrivate::drag(qint64 currentTimestamp, QEvent::Type eventType, const QPointF &localPos,
                                  const QVector2D &deltas, bool overThreshold, bool momentum,
                                  bool velocitySensitiveOverBounds, const QVector2D &velocity)
{
    Q_Q(QQuickFlickable);
    bool rejectY = false;
    bool rejectX = false;
 
    bool keepY = q->yflick();
    bool keepX = q->xflick();
 
    bool stealY = false;
    bool stealX = false;
    if (eventType == QEvent::MouseMove) {
        stealX = stealY = stealMouse;
    } else if (eventType == QEvent::Wheel) {
        stealX = stealY = scrollingPhase;
    }
 
    bool prevHMoved = hMoved;
    bool prevVMoved = vMoved;
 
    qint64 elapsedSincePress = currentTimestamp - lastPressTime;
    qCDebug(lcFlickable).nospace() << currentTimestamp << ' ' << eventType << " drag @ " << localPos.x() << ',' << localPos.y()
                                   << " \u0394 " << deltas.x() << ',' << deltas.y() << " vel " << velocity.x() << ',' << velocity.y()
                                   << " thrsld? " << overThreshold << " momentum? " << momentum << " velSens? " << velocitySensitiveOverBounds
                                   << " sincePress " << elapsedSincePress;
 
    if (q->yflick()) {
        qreal dy = deltas.y();
        if (overThreshold || elapsedSincePress > 200) {
            if (!vMoved)
                vData.dragStartOffset = dy;
            qreal newY = dy + vData.pressPos - (syncDrag ? 0 : vData.dragStartOffset);
            // Recalculate bounds in case margins have changed, but use the content
            // size estimate taken at the start of the drag in case the drag causes
            // the estimate to be altered
            const qreal minY = vData.dragMinBound + vData.startMargin;
            const qreal maxY = vData.dragMaxBound - vData.endMargin;
            if (!(boundsBehavior & QQuickFlickable::DragOverBounds)) {
                if (fuzzyLessThanOrEqualTo(newY, maxY)) {
                    newY = maxY;
                    rejectY = vData.pressPos == maxY && vData.move.value() == maxY && dy < 0;
                }
                if (fuzzyLessThanOrEqualTo(minY, newY)) {
                    newY = minY;
                    rejectY |= vData.pressPos == minY && vData.move.value() == minY && dy > 0;
                }
            } else {
                qreal vel = velocity.y() / QML_FLICK_OVERSHOOTFRICTION;
                if (vel > 0. && vel > vData.velocity)
                    vData.velocity = qMin(velocity.y() / QML_FLICK_OVERSHOOTFRICTION, maxVelocity);
                else if (vel < 0. && vel < vData.velocity)
                    vData.velocity = qMax(velocity.y() / QML_FLICK_OVERSHOOTFRICTION, -maxVelocity);
                if (newY > minY) {
                    // Overshoot beyond the top.  But don't wait for momentum phase to end before returning to bounds.
                    if (momentum && vData.atBeginning) {
                        if (!vData.inRebound) {
                            vData.inRebound = true;
                            q->returnToBounds();
                        }
                        return;
                    }
                    if (velocitySensitiveOverBounds) {
                        qreal overshoot = (newY - minY) * vData.velocity / maxVelocity / QML_FLICK_OVERSHOOTFRICTION;
                        overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
                        newY = minY + overshoot;
                    } else {
                        newY = minY + (newY - minY) / 2;
                    }
                } else if (newY < maxY && maxY - minY <= 0) {
                    // Overshoot beyond the bottom.  But don't wait for momentum phase to end before returning to bounds.
                    if (momentum && vData.atEnd) {
                        if (!vData.inRebound) {
                            vData.inRebound = true;
                            q->returnToBounds();
                        }
                        return;
                    }
                    if (velocitySensitiveOverBounds) {
                        qreal overshoot = (newY - maxY) * vData.velocity / maxVelocity / QML_FLICK_OVERSHOOTFRICTION;
                        overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
                        newY = maxY - overshoot;
                    } else {
                        newY = maxY + (newY - maxY) / 2;
                    }
                }
            }
            if (!rejectY && stealMouse && dy != 0.0 && dy != vData.previousDragDelta) {
                clearTimeline();
                vData.move.setValue(newY);
                vMoved = true;
            }
            if (!rejectY && overThreshold)
                stealY = true;
 
            if ((newY >= minY && vData.pressPos == minY && vData.move.value() == minY && dy > 0)
                        || (newY <= maxY && vData.pressPos == maxY && vData.move.value() == maxY && dy < 0)) {
                keepY = false;
            }
        }
        vData.previousDragDelta = dy;
    }
 
    if (q->xflick()) {
        qreal dx = deltas.x();
        if (overThreshold || elapsedSincePress > 200) {
            if (!hMoved)
                hData.dragStartOffset = dx;
            qreal newX = dx + hData.pressPos - (syncDrag ? 0 : hData.dragStartOffset);
            const qreal minX = hData.dragMinBound + hData.startMargin;
            const qreal maxX = hData.dragMaxBound - hData.endMargin;
            if (!(boundsBehavior & QQuickFlickable::DragOverBounds)) {
                if (fuzzyLessThanOrEqualTo(newX, maxX)) {
                    newX = maxX;
                    rejectX = hData.pressPos == maxX && hData.move.value() == maxX && dx < 0;
                }
                if (fuzzyLessThanOrEqualTo(minX, newX)) {
                    newX = minX;
                    rejectX |= hData.pressPos == minX && hData.move.value() == minX && dx > 0;
                }
            } else {
                qreal vel = velocity.x() / QML_FLICK_OVERSHOOTFRICTION;
                if (vel > 0. && vel > hData.velocity)
                    hData.velocity = qMin(velocity.x() / QML_FLICK_OVERSHOOTFRICTION, maxVelocity);
                else if (vel < 0. && vel < hData.velocity)
                    hData.velocity = qMax(velocity.x() / QML_FLICK_OVERSHOOTFRICTION, -maxVelocity);
                if (newX > minX) {
                    // Overshoot beyond the left.  But don't wait for momentum phase to end before returning to bounds.
                    if (momentum && hData.atBeginning) {
                        if (!hData.inRebound) {
                            hData.inRebound = true;
                            q->returnToBounds();
                        }
                        return;
                    }
                    if (velocitySensitiveOverBounds) {
                        qreal overshoot = (newX - minX) * hData.velocity / maxVelocity / QML_FLICK_OVERSHOOTFRICTION;
                        overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
                        newX = minX + overshoot;
                    } else {
                        newX = minX + (newX - minX) / 2;
                    }
                } else if (newX < maxX && maxX - minX <= 0) {
                    // Overshoot beyond the right.  But don't wait for momentum phase to end before returning to bounds.
                    if (momentum && hData.atEnd) {
                        if (!hData.inRebound) {
                            hData.inRebound = true;
                            q->returnToBounds();
                        }
                        return;
                    }
                    if (velocitySensitiveOverBounds) {
                        qreal overshoot = (newX - maxX) * hData.velocity / maxVelocity / QML_FLICK_OVERSHOOTFRICTION;
                        overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
                        newX = maxX - overshoot;
                    } else {
                        newX = maxX + (newX - maxX) / 2;
                    }
                }
            }
 
            if (!rejectX && stealMouse && dx != 0.0 && dx != hData.previousDragDelta) {
                clearTimeline();
                hData.move.setValue(newX);
                hMoved = true;
            }
 
            if (!rejectX && overThreshold)
                stealX = true;
 
            if ((newX >= minX && vData.pressPos == minX && vData.move.value() == minX && dx > 0)
                        || (newX <= maxX && vData.pressPos == maxX && vData.move.value() == maxX && dx < 0)) {
                keepX = false;
            }
        }
        hData.previousDragDelta = dx;
    }
 
    stealMouse = stealX || stealY;
    if (stealMouse) {
        if ((stealX && keepX) || (stealY && keepY))
            q->setKeepMouseGrab(true);
        clearDelayedPress();
    }
 
    if (rejectY) {
        vData.velocityBuffer.clear();
        vData.velocity = 0;
    }
    if (rejectX) {
        hData.velocityBuffer.clear();
        hData.velocity = 0;
    }
 
    if (momentum && !hData.flicking && !vData.flicking)
        flickingStarted(hData.velocity != 0, vData.velocity != 0);
    draggingStarting();
 
    if ((hMoved && !prevHMoved) || (vMoved && !prevVMoved))
        q->movementStarting();
 
    lastPosTime = currentTimestamp;
    if (q->yflick() && !rejectY)
        vData.addVelocitySample(velocity.y(), maxVelocity);
    if (q->xflick() && !rejectX)
        hData.addVelocitySample(velocity.x(), maxVelocity);
    lastPos = localPos;
}
 
void QQuickFlickablePrivate::handleMoveEvent(QPointerEvent *event)
{
    Q_Q(QQuickFlickable);
    if (!interactive || lastPosTime == -1 ||
            (event->isSinglePointEvent() && !static_cast<QSinglePointEvent *>(event)->buttons().testFlag(Qt::LeftButton)))
        return;
 
    qint64 currentTimestamp = computeCurrentTime(event);
    const auto &firstPoint = event->points().first();
    const auto &pos = firstPoint.position();
    const QVector2D deltas = QVector2D(pos - q->mapFromGlobal(firstPoint.globalPressPosition()));
    const QVector2D velocity = firstPointLocalVelocity(event);
    bool overThreshold = false;
 
    if (event->pointCount() == 1) {
        if (q->yflick())
            overThreshold |= QQuickDeliveryAgentPrivate::dragOverThreshold(deltas.y(), Qt::YAxis, firstPoint);
        if (q->xflick())
            overThreshold |= QQuickDeliveryAgentPrivate::dragOverThreshold(deltas.x(), Qt::XAxis, firstPoint);
    } else {
        qCDebug(lcFilter) << q->objectName() << "ignoring multi-touch" << event;
    }
 
    drag(currentTimestamp, event->type(), pos, deltas, overThreshold, false, false, velocity);
}
 
void QQuickFlickablePrivate::handleReleaseEvent(QPointerEvent *event)
{
    Q_Q(QQuickFlickable);
    stealMouse = false;
    q->setKeepMouseGrab(false);
    pressed = false;
 
    // if we drag then pause before release we should not cause a flick.
    qint64 elapsed = computeCurrentTime(event) - lastPosTime;
 
    vData.updateVelocity();
    hData.updateVelocity();
 
    draggingEnding();
 
    if (lastPosTime == -1)
        return;
 
    hData.vTime = vData.vTime = timeline.time();
 
    bool canBoost = false;
    const auto pos = event->points().first().position();
    const auto pressPos = q->mapFromGlobal(event->points().first().globalPressPosition());
    const QVector2D eventVelocity = firstPointLocalVelocity(event);
    qCDebug(lcVel) << event->deviceType() << event->type() << "velocity" << event->points().first().velocity() << "transformed to local" << eventVelocity;
 
    qreal vVelocity = 0;
    if (elapsed < 100 && vData.velocity != 0.) {
        vVelocity = (event->device()->capabilities().testFlag(QInputDevice::Capability::Velocity)
                ? eventVelocity.y() : vData.velocity);
    }
    if ((vData.atBeginning && vVelocity > 0.) || (vData.atEnd && vVelocity < 0.)) {
        vVelocity /= 2;
    } else if (vData.continuousFlickVelocity != 0.0
               && vData.viewSize/q->height() > QML_FLICK_MULTIFLICK_RATIO
               && ((vVelocity > 0) == (vData.continuousFlickVelocity > 0))
               && qAbs(vVelocity) > QML_FLICK_MULTIFLICK_THRESHOLD) {
        // accelerate flick for large view flicked quickly
        canBoost = true;
    }
 
    qreal hVelocity = 0;
    if (elapsed < 100 && hData.velocity != 0.) {
        hVelocity = (event->device()->capabilities().testFlag(QInputDevice::Capability::Velocity)
                     ? eventVelocity.x() : hData.velocity);
    }
    if ((hData.atBeginning && hVelocity > 0.) || (hData.atEnd && hVelocity < 0.)) {
        hVelocity /= 2;
    } else if (hData.continuousFlickVelocity != 0.0
               && hData.viewSize/q->width() > QML_FLICK_MULTIFLICK_RATIO
               && ((hVelocity > 0) == (hData.continuousFlickVelocity > 0))
               && qAbs(hVelocity) > QML_FLICK_MULTIFLICK_THRESHOLD) {
        // accelerate flick for large view flicked quickly
        canBoost = true;
    }
 
    flickBoost = canBoost ? qBound(1.0, flickBoost+0.25, QML_FLICK_MULTIFLICK_MAXBOOST) : 1.0;
    const int flickThreshold = QGuiApplicationPrivate::platformTheme()->themeHint(QPlatformTheme::FlickStartDistance).toInt();
 
    bool anyPointGrabbed = event->points().constEnd() !=
            std::find_if(event->points().constBegin(),event->points().constEnd(),
                [q, event](const QEventPoint &point) { return event->exclusiveGrabber(point) == q; });
 
    bool flickedVertically = false;
    vVelocity *= flickBoost;
    const bool isVerticalFlickAllowed = anyPointGrabbed &&
            q->yflick() && qAbs(vVelocity) > _q_MinimumFlickVelocity &&
            qAbs(pos.y() - pressPos.y()) > flickThreshold;
    if (isVerticalFlickAllowed) {
        velocityTimeline.reset(vData.smoothVelocity);
        vData.smoothVelocity.setValue(-vVelocity);
        flickedVertically = flickY(event->type(), vVelocity);
    }
 
    bool flickedHorizontally = false;
    hVelocity *= flickBoost;
    const bool isHorizontalFlickAllowed = anyPointGrabbed &&
            q->xflick() && qAbs(hVelocity) > _q_MinimumFlickVelocity &&
            qAbs(pos.x() - pressPos.x()) > flickThreshold;
    if (isHorizontalFlickAllowed) {
        velocityTimeline.reset(hData.smoothVelocity);
        hData.smoothVelocity.setValue(-hVelocity);
        flickedHorizontally = flickX(event->type(), hVelocity);
    }
 
    if (!isVerticalFlickAllowed)
        fixupY();
 
    if (!isHorizontalFlickAllowed)
        fixupX();
 
    flickingStarted(flickedHorizontally, flickedVertically);
    if (!isViewMoving()) {
        q->movementEnding();
    } else {
        if (flickedVertically)
            vMoved = true;
        if (flickedHorizontally)
            hMoved = true;
        q->movementStarting();
    }
}
 
void QQuickFlickable::mousePressEvent(QMouseEvent *event)
{
    Q_D(QQuickFlickable);
    if (d->interactive && !d->replayingPressEvent && d->wantsPointerEvent(event)) {
        if (!d->pressed)
            d->handlePressEvent(event);
        event->accept();
    } else {
        QQuickItem::mousePressEvent(event);
    }
}
 
void QQuickFlickable::mouseMoveEvent(QMouseEvent *event)
{
    Q_D(QQuickFlickable);
    if (d->interactive && d->wantsPointerEvent(event)) {
        d->handleMoveEvent(event);
        event->accept();
    } else {
        QQuickItem::mouseMoveEvent(event);
    }
}
 
void QQuickFlickable::mouseReleaseEvent(QMouseEvent *event)
{
    Q_D(QQuickFlickable);
    if (d->interactive && d->wantsPointerEvent(event)) {
        if (d->delayedPressEvent) {
            d->replayDelayedPress();
 
            auto &firstPoint = event->point(0);
            if (const auto *grabber = event->exclusiveGrabber(firstPoint); grabber && grabber->isQuickItemType()) {
                // Since we sent the delayed press to the window, we need to resend the release to the window too.
                // We're not copying or detaching, so restore the original event position afterwards.
                const auto oldPosition = firstPoint.position();
                QMutableEventPoint::setPosition(firstPoint, event->scenePosition());
                QCoreApplication::sendEvent(window(), event);
                QMutableEventPoint::setPosition(firstPoint, oldPosition);
            }
 
            // And the event has been consumed
            d->stealMouse = false;
            d->pressed = false;
            return;
        }
 
        d->handleReleaseEvent(event);
        event->accept();
    } else {
        QQuickItem::mouseReleaseEvent(event);
    }
}
 
void QQuickFlickable::touchEvent(QTouchEvent *event)
{
    Q_D(QQuickFlickable);
 
    if (event->type() == QEvent::TouchCancel) {
        if (d->interactive && d->wantsPointerEvent(event))
            d->cancelInteraction();
        else
            QQuickItem::touchEvent(event);
        return;
    }
 
    bool unhandled = false;
    const auto &firstPoint = event->points().first();
    switch (firstPoint.state()) {
    case QEventPoint::State::Pressed:
        if (d->interactive && !d->replayingPressEvent && d->wantsPointerEvent(event)) {
            if (!d->pressed)
                d->handlePressEvent(event);
            event->accept();
        } else {
            unhandled = true;
        }
        break;
    case QEventPoint::State::Updated:
        if (d->interactive && d->wantsPointerEvent(event)) {
            d->handleMoveEvent(event);
            event->accept();
        } else {
            unhandled = true;
        }
        break;
    case QEventPoint::State::Released:
        if (d->interactive && d->wantsPointerEvent(event)) {
            if (d->delayedPressEvent) {
                d->replayDelayedPress();
 
                const auto &firstPoint = event->point(0);
                if (const auto *grabber = event->exclusiveGrabber(firstPoint); grabber && grabber->isQuickItemType()) {
                    // Since we sent the delayed press to the window, we need to resend the release to the window too.
                    QScopedPointer<QPointerEvent> localizedEvent(
                            QQuickDeliveryAgentPrivate::clonePointerEvent(event, firstPoint.scenePosition()));
                    QCoreApplication::sendEvent(window(), localizedEvent.data());
                }
 
                // And the event has been consumed
                d->stealMouse = false;
                d->pressed = false;
                return;
            }
 
            d->handleReleaseEvent(event);
            event->accept();
        } else {
            unhandled = true;
        }
        break;
    case QEventPoint::State::Stationary:
    case QEventPoint::State::Unknown:
        break;
    }
    if (unhandled)
        QQuickItem::touchEvent(event);
}
 
#if QT_CONFIG(wheelevent)
void QQuickFlickable::wheelEvent(QWheelEvent *event)
{
    Q_D(QQuickFlickable);
    if (!d->interactive || !d->wantsPointerEvent(event)) {
        QQuickItem::wheelEvent(event);
        return;
    }
    qCDebug(lcWheel) << event->device() << event << event->source();
    event->setAccepted(false);
    qint64 currentTimestamp = d->computeCurrentTime(event);
    switch (event->phase()) {
    case Qt::ScrollBegin:
        d->scrollingPhase = true;
        d->accumulatedWheelPixelDelta = QVector2D();
        d->vData.velocity = 0;
        d->hData.velocity = 0;
        d->timer.start();
        d->maybeBeginDrag(currentTimestamp, event->position());
        d->lastPosTime = -1;
        break;
    case Qt::NoScrollPhase: // default phase with an ordinary wheel mouse
    case Qt::ScrollUpdate:
        if (d->scrollingPhase)
            d->pressed = true;
        break;
    case Qt::ScrollMomentum:
        d->pressed = false;
        d->scrollingPhase = false;
        d->draggingEnding();
        if (isMoving())
            event->accept();
        d->lastPosTime = -1;
        break;
    case Qt::ScrollEnd:
        d->pressed = false;
        d->scrollingPhase = false;
        d->draggingEnding();
        event->accept();
        returnToBounds();
        d->lastPosTime = -1;
        d->stealMouse = false;
        if (!d->velocityTimeline.isActive() && !d->timeline.isActive())
            movementEnding(true, true);
        return;
    }
 
    qreal elapsed = qreal(currentTimestamp - d->lastPosTime) / qreal(1000);
    if (elapsed <= 0) {
        d->lastPosTime = currentTimestamp;
        qCDebug(lcWheel) << "insufficient elapsed time: can't calculate velocity" << elapsed;
        return;
    }
 
    if (event->source() == Qt::MouseEventNotSynthesized || event->pixelDelta().isNull() || event->phase() == Qt::NoScrollPhase) {
        // no pixel delta (physical mouse wheel, or "dumb" touchpad), so use angleDelta
        int xDelta = event->angleDelta().x();
        int yDelta = event->angleDelta().y();
 
        if (d->wheelDeceleration > _q_MaximumWheelDeceleration) {
            const qreal wheelScroll = -qApp->styleHints()->wheelScrollLines() * 24;
            // If wheelDeceleration is very large, i.e. the user or the platform does not want to have any mouse wheel
            // acceleration behavior, we want to move a distance proportional to QStyleHints::wheelScrollLines()
            if (yflick() && yDelta != 0) {
                d->moveReason = QQuickFlickablePrivate::Mouse; // ItemViews will set fixupMode to Immediate in fixup() without this.
                d->vMoved = true;
                qreal scrollPixel = (-yDelta / 120.0 * wheelScroll);
                if (scrollPixel > 0) { // Forward direction (away from user)
                    if (d->vData.move.value() >= minYExtent())
                        d->vMoved = false;
                } else { // Backward direction (towards user)
                    if (d->vData.move.value() <= maxYExtent())
                        d->vMoved = false;
                }
                if (d->vMoved) {
                    if (d->boundsBehavior == QQuickFlickable::StopAtBounds) {
                        const qreal estContentPos = scrollPixel + d->vData.move.value();
                        if (scrollPixel > 0) { // Forward direction (away from user)
                            if (estContentPos > minYExtent())
                                scrollPixel = minYExtent() - d->vData.move.value();
                        } else { // Backward direction (towards user)
                            if (estContentPos < maxYExtent())
                                scrollPixel = maxYExtent() - d->vData.move.value();
                        }
                    }
                    d->resetTimeline(d->vData);
                    movementStarting();
                    d->timeline.moveBy(d->vData.move, scrollPixel, QEasingCurve(QEasingCurve::OutExpo), 3*d->fixupDuration/4);
                    d->vData.fixingUp = true;
                    d->timeline.callback(QQuickTimeLineCallback(&d->vData.move, QQuickFlickablePrivate::fixupY_callback, d));
                }
                event->accept();
            }
            if (xflick() && xDelta != 0) {
                d->moveReason = QQuickFlickablePrivate::Mouse; // ItemViews will set fixupMode to Immediate in fixup() without this.
                d->hMoved = true;
                qreal scrollPixel = (-xDelta / 120.0 * wheelScroll);
                if (scrollPixel > 0) { // Forward direction (away from user)
                    if (d->hData.move.value() >= minXExtent())
                        d->hMoved = false;
                } else { // Backward direction (towards user)
                    if (d->hData.move.value() <= maxXExtent())
                        d->hMoved = false;
                }
                if (d->hMoved) {
                    if (d->boundsBehavior == QQuickFlickable::StopAtBounds) {
                        const qreal estContentPos = scrollPixel + d->hData.move.value();
                        if (scrollPixel > 0) { // Forward direction (away from user)
                            if (estContentPos > minXExtent())
                                scrollPixel = minXExtent() - d->hData.move.value();
                        } else { // Backward direction (towards user)
                            if (estContentPos < maxXExtent())
                                scrollPixel = maxXExtent() - d->hData.move.value();
                        }
                    }
                    d->resetTimeline(d->hData);
                    movementStarting();
                    d->timeline.moveBy(d->hData.move, scrollPixel, QEasingCurve(QEasingCurve::OutExpo), 3*d->fixupDuration/4);
                    d->hData.fixingUp = true;
                    d->timeline.callback(QQuickTimeLineCallback(&d->hData.move, QQuickFlickablePrivate::fixupX_callback, d));
                }
                event->accept();
            }
        } else {
            // wheelDeceleration is set to some reasonable value: the user or the platform wants to have
            // the classic Qt Quick mouse wheel acceleration behavior.
            // For a single "clicky" wheel event (angleDelta +/- 120),
            // we want flick() to end up moving a distance proportional to QStyleHints::wheelScrollLines().
            // The decel algo from there is
            // qreal dist = v2 / (accel * 2.0);
            // i.e. initialWheelFlickDistance = (120 / dt)^2 / (deceleration * 2)
            // now solve for dt:
            // dt = 120 / sqrt(deceleration * 2 * initialWheelFlickDistance)
            if (!isMoving())
                elapsed = 120 / qSqrt(d->wheelDeceleration * 2 * d->initialWheelFlickDistance);
            if (yflick() && yDelta != 0) {
                qreal instVelocity = yDelta / elapsed;
                // if the direction has changed, start over with filtering, to allow instant movement in the opposite direction
                if ((instVelocity < 0 && d->vData.velocity > 0) || (instVelocity > 0 && d->vData.velocity < 0))
                    d->vData.velocityBuffer.clear();
                d->vData.addVelocitySample(instVelocity, d->maxVelocity);
                d->vData.updateVelocity();
                if ((yDelta > 0 && contentY() > -minYExtent()) || (yDelta < 0 && contentY() < -maxYExtent())) {
                    const bool newFlick = d->flickY(event->type(), d->vData.velocity);
                    if (newFlick && (d->vData.atBeginning != (yDelta > 0) || d->vData.atEnd != (yDelta < 0))) {
                        d->flickingStarted(false, true);
                        d->vMoved = true;
                        movementStarting();
                    }
                    event->accept();
                }
            }
            if (xflick() && xDelta != 0) {
                qreal instVelocity = xDelta / elapsed;
                // if the direction has changed, start over with filtering, to allow instant movement in the opposite direction
                if ((instVelocity < 0 && d->hData.velocity > 0) || (instVelocity > 0 && d->hData.velocity < 0))
                    d->hData.velocityBuffer.clear();
                d->hData.addVelocitySample(instVelocity, d->maxVelocity);
                d->hData.updateVelocity();
                if ((xDelta > 0 && contentX() > -minXExtent()) || (xDelta < 0 && contentX() < -maxXExtent())) {
                    const bool newFlick = d->flickX(event->type(), d->hData.velocity);
                    if (newFlick && (d->hData.atBeginning != (xDelta > 0) || d->hData.atEnd != (xDelta < 0))) {
                        d->flickingStarted(true, false);
                        d->hMoved = true;
                        movementStarting();
                    }
                    event->accept();
                }
            }
        }
    } else {
        // use pixelDelta (probably from a trackpad): this is where we want to be on most platforms eventually
        int xDelta = event->pixelDelta().x();
        int yDelta = event->pixelDelta().y();
 
        QVector2D velocity(xDelta / elapsed, yDelta / elapsed);
        d->accumulatedWheelPixelDelta += QVector2D(event->pixelDelta());
        // Try to drag if 1) we already are dragging or flicking, or
        // 2) the flickable is free to flick both directions, or
        // 3) the movement so far has been mostly horizontal AND it's free to flick horizontally, or
        // 4) the movement so far has been mostly vertical AND it's free to flick vertically.
        // Otherwise, wait until the next event.  Wheel events with pixel deltas tend to come frequently.
        if (isMoving() || isFlicking() || (yflick() && xflick())
                || (xflick() && qAbs(d->accumulatedWheelPixelDelta.x()) > qAbs(d->accumulatedWheelPixelDelta.y() * 2))
                || (yflick() && qAbs(d->accumulatedWheelPixelDelta.y()) > qAbs(d->accumulatedWheelPixelDelta.x() * 2))) {
            d->drag(currentTimestamp, event->type(), event->position(), d->accumulatedWheelPixelDelta,
                    true, !d->scrollingPhase, true, velocity);
            event->accept();
        } else {
            qCDebug(lcWheel) << "not dragging: accumulated deltas" << d->accumulatedWheelPixelDelta <<
                                "moving?" << isMoving() << "can flick horizontally?" << xflick() << "vertically?" << yflick();
        }
    }
    d->lastPosTime = currentTimestamp;
 
    if (!event->isAccepted())
        QQuickItem::wheelEvent(event);
}
#endif
 
bool QQuickFlickablePrivate::isInnermostPressDelay(QQuickItem *i) const
{
    Q_Q(const QQuickFlickable);
    QQuickItem *item = i;
    while (item) {
        QQuickFlickable *flick = qobject_cast<QQuickFlickable*>(item);
        if (flick && flick->pressDelay() > 0 && flick->isInteractive()) {
            // Found the innermost flickable with press delay - is it me?
            return (flick == q);
        }
        item = item->parentItem();
    }
    return false;
}
 
void QQuickFlickablePrivate::captureDelayedPress(QQuickItem *item, QPointerEvent *event)
{
    Q_Q(QQuickFlickable);
    if (!q->window() || pressDelay <= 0)
        return;
 
    // Only the innermost flickable should handle the delayed press; this allows
    // flickables up the parent chain to all see the events in their filter functions
    if (!isInnermostPressDelay(item))
        return;
 
    delayedPressEvent = QQuickDeliveryAgentPrivate::clonePointerEvent(event);
    delayedPressEvent->setAccepted(false);
    delayedPressTimer.start(pressDelay, q);
    qCDebug(lcReplay) << "begin press delay" << pressDelay << "ms with" << delayedPressEvent;
}
 
void QQuickFlickablePrivate::clearDelayedPress()
{
    if (delayedPressEvent) {
        delayedPressTimer.stop();
        qCDebug(lcReplay) << "clear delayed press" << delayedPressEvent;
        delete delayedPressEvent;
        delayedPressEvent = nullptr;
    }
}
 
void QQuickFlickablePrivate::replayDelayedPress()
{
    Q_Q(QQuickFlickable);
    if (delayedPressEvent) {
        // Losing the grab will clear the delayed press event; take control of it here
        QScopedPointer<QPointerEvent> event(delayedPressEvent);
        delayedPressEvent = nullptr;
        delayedPressTimer.stop();
 
        // If we have the grab, release before delivering the event
        if (QQuickWindow *window = q->window()) {
            auto da = deliveryAgentPrivate();
            da->allowChildEventFiltering = false; // don't allow re-filtering during replay
            replayingPressEvent = true;
            auto &firstPoint = event->point(0);
            // At first glance, it's weird for delayedPressEvent to already have a grabber;
            // but on press, filterMouseEvent() took the exclusive grab, and that's stored
            // in the device-specific EventPointData instance in QPointingDevicePrivate::activePoints,
            // not in the event itself.  If this Flickable is still the grabber of that point on that device,
            // that's the reason; but now it doesn't need that grab anymore.
            if (event->exclusiveGrabber(firstPoint) == q)
                event->setExclusiveGrabber(firstPoint, nullptr);
 
            qCDebug(lcReplay) << "replaying" << event.data();
            // Put scenePosition into position, for the sake of QQuickWindowPrivate::translateTouchEvent()
            // TODO remove this if we remove QQuickWindowPrivate::translateTouchEvent()
            QMutableEventPoint::setPosition(firstPoint, firstPoint.scenePosition());
            // Send it through like a fresh press event, and let QQuickWindow
            // (more specifically, QQuickWindowPrivate::deliverPressOrReleaseEvent)
            // find the item or handler that should receive it, as usual.
            QCoreApplication::sendEvent(window, event.data());
            qCDebug(lcReplay) << "replay done";
 
            // We're done with replay, go back to normal delivery behavior
            replayingPressEvent = false;
            da->allowChildEventFiltering = true;
        }
    }
}
 
//XXX pixelAligned ignores the global position of the Flickable, i.e. assumes Flickable itself is pixel aligned.
 
void QQuickFlickablePrivate::setViewportX(qreal x)
{
    Q_Q(QQuickFlickable);
    qreal effectiveX = pixelAligned ? -std::round(-x) : x;
 
    const qreal maxX = q->maxXExtent();
    const qreal minX = q->minXExtent();
 
    if (boundsMovement == int(QQuickFlickable::StopAtBounds))
        effectiveX = qBound(maxX, effectiveX, minX);
 
    contentItem->setX(effectiveX);
    if (contentItem->x() != effectiveX)
        return; // reentered
 
    qreal overshoot = 0.0;
    if (x <= maxX)
        overshoot = maxX - x;
    else if (x >= minX)
        overshoot = minX - x;
 
    if (overshoot != hData.overshoot) {
        hData.overshoot = overshoot;
        emit q->horizontalOvershootChanged();
    }
}
 
void QQuickFlickablePrivate::setViewportY(qreal y)
{
    Q_Q(QQuickFlickable);
    qreal effectiveY = pixelAligned ? -std::round(-y) : y;
 
    const qreal maxY = q->maxYExtent();
    const qreal minY = q->minYExtent();
 
    if (boundsMovement == int(QQuickFlickable::StopAtBounds))
        effectiveY = qBound(maxY, effectiveY, minY);
 
    contentItem->setY(effectiveY);
    if (contentItem->y() != effectiveY)
        return; // reentered
 
    qreal overshoot = 0.0;
    if (y <= maxY)
        overshoot = maxY - y;
    else if (y >= minY)
        overshoot = minY - y;
 
    if (overshoot != vData.overshoot) {
        vData.overshoot = overshoot;
        emit q->verticalOvershootChanged();
    }
}
 
void QQuickFlickable::timerEvent(QTimerEvent *event)
{
    Q_D(QQuickFlickable);
    if (event->timerId() == d->delayedPressTimer.timerId()) {
        d->delayedPressTimer.stop();
        if (d->delayedPressEvent) {
            d->replayDelayedPress();
        }
    }
}
 
qreal QQuickFlickable::minYExtent() const
{
    Q_D(const QQuickFlickable);
    return d->vData.startMargin;
}
 
qreal QQuickFlickable::minXExtent() const
{
    Q_D(const QQuickFlickable);
    return d->hData.startMargin;
}
 
/* returns -ve */
qreal QQuickFlickable::maxXExtent() const
{
    Q_D(const QQuickFlickable);
    return qMin<qreal>(minXExtent(), width() - vWidth() - d->hData.endMargin);
}
/* returns -ve */
qreal QQuickFlickable::maxYExtent() const
{
    Q_D(const QQuickFlickable);
    return qMin<qreal>(minYExtent(), height() - vHeight() - d->vData.endMargin);
}
 
void QQuickFlickable::componentComplete()
{
    Q_D(QQuickFlickable);
    QQuickItem::componentComplete();
    if (!d->hData.explicitValue && d->hData.startMargin != 0.)
        setContentX(-minXExtent());
    if (!d->vData.explicitValue && d->vData.startMargin != 0.)
        setContentY(-minYExtent());
    if (lcWheel().isDebugEnabled() || lcVel().isDebugEnabled()) {
        d->timeline.setObjectName(QLatin1String("timeline for Flickable ") + objectName());
        d->velocityTimeline.setObjectName(QLatin1String("velocity timeline for Flickable ") + objectName());
    }
}
 
void QQuickFlickable::viewportMoved(Qt::Orientations orient)
{
    Q_D(QQuickFlickable);
    if (orient & Qt::Vertical)
        d->viewportAxisMoved(d->vData, minYExtent(), maxYExtent(), d->fixupY_callback);
    if (orient & Qt::Horizontal)
        d->viewportAxisMoved(d->hData, minXExtent(), maxXExtent(), d->fixupX_callback);
    d->updateBeginningEnd();
}
 
void QQuickFlickablePrivate::viewportAxisMoved(AxisData &data, qreal minExtent, qreal maxExtent,
                                           QQuickTimeLineCallback::Callback fixupCallback)
{
    if (!scrollingPhase && (pressed || calcVelocity)) {
        int elapsed = data.velocityTime.restart();
        if (elapsed > 0) {
            qreal velocity = (data.lastPos - data.move.value()) * 1000 / elapsed;
            if (qAbs(velocity) > 0) {
                velocityTimeline.reset(data.smoothVelocity);
                velocityTimeline.set(data.smoothVelocity, velocity);
                qCDebug(lcVel) << "touchpad scroll phase: velocity" << velocity;
            }
        }
    } else {
        if (timeline.time() > data.vTime) {
            velocityTimeline.reset(data.smoothVelocity);
            int dt = timeline.time() - data.vTime;
            if (dt > 2) {
                qreal velocity = (data.lastPos - data.move.value()) * 1000 / dt;
                if (!qFuzzyCompare(data.smoothVelocity.value(), velocity))
                    qCDebug(lcVel) << "velocity" << data.smoothVelocity.value() << "->" << velocity
                                   << "computed as (" << data.lastPos << "-" << data.move.value() << ") * 1000 / ("
                                   << timeline.time() << "-" << data.vTime << ")";
                data.smoothVelocity.setValue(velocity);
            }
        }
    }
 
    if (!data.inOvershoot && !data.fixingUp && data.flicking
            && (data.move.value() > minExtent || data.move.value() < maxExtent)
            && qAbs(data.smoothVelocity.value()) > 10) {
        // Increase deceleration if we've passed a bound
        qreal overBound = data.move.value() > minExtent
                ? data.move.value() - minExtent
                : maxExtent - data.move.value();
        data.inOvershoot = true;
        qreal maxDistance = overShootDistance(qAbs(data.smoothVelocity.value())) - overBound;
        resetTimeline(data);
        if (maxDistance > 0)
            timeline.accel(data.move, -data.smoothVelocity.value(), deceleration*QML_FLICK_OVERSHOOTFRICTION, maxDistance);
        timeline.callback(QQuickTimeLineCallback(&data.move, fixupCallback, this));
    }
 
    data.lastPos = data.move.value();
    data.vTime = timeline.time();
}
 
void QQuickFlickable::geometryChange(const QRectF &newGeometry, const QRectF &oldGeometry)
{
    Q_D(QQuickFlickable);
    QQuickItem::geometryChange(newGeometry, oldGeometry);
 
    bool changed = false;
    if (newGeometry.width() != oldGeometry.width()) {
        changed = true; // we must update visualArea.widthRatio
        if (d->hData.viewSize < 0)
            d->contentItem->setWidth(width() - d->hData.startMargin - d->hData.endMargin);
        // Make sure that we're entirely in view.
        if (!d->pressed && !d->hData.moving && !d->vData.moving) {
            d->fixupMode = QQuickFlickablePrivate::Immediate;
            d->fixupX();
        }
    }
    if (newGeometry.height() != oldGeometry.height()) {
        changed = true; // we must update visualArea.heightRatio
        if (d->vData.viewSize < 0)
            d->contentItem->setHeight(height() - d->vData.startMargin - d->vData.endMargin);
        // Make sure that we're entirely in view.
        if (!d->pressed && !d->hData.moving && !d->vData.moving) {
            d->fixupMode = QQuickFlickablePrivate::Immediate;
            d->fixupY();
        }
    }
 
    if (changed)
        d->updateBeginningEnd();
}
 
void QQuickFlickable::flick(qreal xVelocity, qreal yVelocity)
{
    Q_D(QQuickFlickable);
    d->hData.reset();
    d->vData.reset();
    d->hData.velocity = xVelocity;
    d->vData.velocity = yVelocity;
    d->hData.vTime = d->vData.vTime = d->timeline.time();
 
    const bool flickedX = xflick() && !qFuzzyIsNull(xVelocity) && d->flickX(QEvent::TouchUpdate, xVelocity);
    const bool flickedY = yflick() && !qFuzzyIsNull(yVelocity) && d->flickY(QEvent::TouchUpdate, yVelocity);
 
    if (flickedX)
        d->hMoved = true;
    if (flickedY)
        d->vMoved = true;
    movementStarting();
    d->flickingStarted(flickedX, flickedY);
}
 
void QQuickFlickablePrivate::flickingStarted(bool flickingH, bool flickingV)
{
    Q_Q(QQuickFlickable);
    if (!flickingH && !flickingV)
        return;
 
    bool wasFlicking = hData.flicking || vData.flicking;
    if (flickingH && !hData.flicking) {
        hData.flicking = true;
        emit q->flickingHorizontallyChanged();
    }
    if (flickingV && !vData.flicking) {
        vData.flicking = true;
        emit q->flickingVerticallyChanged();
    }
    if (!wasFlicking && (hData.flicking || vData.flicking)) {
        emit q->flickingChanged();
        emit q->flickStarted();
    }
}
 
void QQuickFlickable::cancelFlick()
{
    Q_D(QQuickFlickable);
    d->resetTimeline(d->hData);
    d->resetTimeline(d->vData);
    movementEnding();
}
 
void QQuickFlickablePrivate::data_append(QQmlListProperty<QObject> *prop, QObject *o)
{
    if (!prop || !prop->data)
        return;
 
    if (QQuickItem *i = qmlobject_cast<QQuickItem *>(o)) {
        i->setParentItem(static_cast<QQuickFlickablePrivate*>(prop->data)->contentItem);
    } else if (QQuickPointerHandler *pointerHandler = qmlobject_cast<QQuickPointerHandler *>(o)) {
        static_cast<QQuickFlickablePrivate*>(prop->data)->addPointerHandler(pointerHandler);
    } else {
        o->setParent(prop->object); // XXX todo - do we want this?
    }
}
 
qsizetype QQuickFlickablePrivate::data_count(QQmlListProperty<QObject> *)
{
    // XXX todo
    return 0;
}
 
QObject *QQuickFlickablePrivate::data_at(QQmlListProperty<QObject> *, qsizetype)
{
    // XXX todo
    return nullptr;
}
 
void QQuickFlickablePrivate::data_clear(QQmlListProperty<QObject> *)
{
    // XXX todo
}
 
QQmlListProperty<QObject> QQuickFlickable::flickableData()
{
    Q_D(QQuickFlickable);
    return QQmlListProperty<QObject>(this, (void *)d, QQuickFlickablePrivate::data_append,
                                             QQuickFlickablePrivate::data_count,
                                             QQuickFlickablePrivate::data_at,
                                             QQuickFlickablePrivate::data_clear);
}
 
QQmlListProperty<QQuickItem> QQuickFlickable::flickableChildren()
{
    Q_D(QQuickFlickable);
    return QQuickItemPrivate::get(d->contentItem)->children();
}
 
QQuickFlickable::BoundsBehavior QQuickFlickable::boundsBehavior() const
{
    Q_D(const QQuickFlickable);
    return d->boundsBehavior;
}
 
void QQuickFlickable::setBoundsBehavior(BoundsBehavior b)
{
    Q_D(QQuickFlickable);
    if (b == d->boundsBehavior)
        return;
    d->boundsBehavior = b;
    emit boundsBehaviorChanged();
}
 
QQuickTransition *QQuickFlickable::rebound() const
{
    Q_D(const QQuickFlickable);
    return d->rebound;
}
 
void QQuickFlickable::setRebound(QQuickTransition *transition)
{
    Q_D(QQuickFlickable);
    if (transition) {
        if (!d->hData.transitionToBounds)
            d->hData.transitionToBounds = new QQuickFlickableReboundTransition(this, QLatin1String("x"));
        if (!d->vData.transitionToBounds)
            d->vData.transitionToBounds = new QQuickFlickableReboundTransition(this, QLatin1String("y"));
    }
    if (d->rebound != transition) {
        d->rebound = transition;
        emit reboundChanged();
    }
}
 
qreal QQuickFlickable::contentWidth() const
{
    Q_D(const QQuickFlickable);
    return d->hData.viewSize;
}
 
void QQuickFlickable::setContentWidth(qreal w)
{
    Q_D(QQuickFlickable);
    if (d->hData.viewSize == w)
        return;
    d->hData.viewSize = w;
    if (w < 0)
        d->contentItem->setWidth(width() - d->hData.startMargin - d->hData.endMargin);
    else
        d->contentItem->setWidth(w);
    d->hData.markExtentsDirty();
    // Make sure that we're entirely in view.
    if (!d->pressed && !d->hData.moving && !d->vData.moving) {
        d->fixupMode = QQuickFlickablePrivate::Immediate;
        d->fixupX();
    } else if (!d->pressed && d->hData.fixingUp) {
        d->fixupMode = QQuickFlickablePrivate::ExtentChanged;
        d->fixupX();
    }
    emit contentWidthChanged();
    d->updateBeginningEnd();
}
 
qreal QQuickFlickable::contentHeight() const
{
    Q_D(const QQuickFlickable);
    return d->vData.viewSize;
}
 
void QQuickFlickable::setContentHeight(qreal h)
{
    Q_D(QQuickFlickable);
    if (d->vData.viewSize == h)
        return;
    d->vData.viewSize = h;
    if (h < 0)
        d->contentItem->setHeight(height() - d->vData.startMargin - d->vData.endMargin);
    else
        d->contentItem->setHeight(h);
    d->vData.markExtentsDirty();
    // Make sure that we're entirely in view.
    if (!d->pressed && !d->hData.moving && !d->vData.moving) {
        d->fixupMode = QQuickFlickablePrivate::Immediate;
        d->fixupY();
    } else if (!d->pressed && d->vData.fixingUp) {
        d->fixupMode = QQuickFlickablePrivate::ExtentChanged;
        d->fixupY();
    }
    emit contentHeightChanged();
    d->updateBeginningEnd();
}
 
qreal QQuickFlickable::topMargin() const
{
    Q_D(const QQuickFlickable);
    return d->vData.startMargin;
}
 
void QQuickFlickable::setTopMargin(qreal m)
{
    Q_D(QQuickFlickable);
    if (d->vData.startMargin == m)
        return;
    d->vData.startMargin = m;
    d->vData.markExtentsDirty();
    if (!d->pressed && !d->hData.moving && !d->vData.moving) {
        d->fixupMode = QQuickFlickablePrivate::Immediate;
        d->fixupY();
    }
    emit topMarginChanged();
    d->updateBeginningEnd();
}
 
qreal QQuickFlickable::bottomMargin() const
{
    Q_D(const QQuickFlickable);
    return d->vData.endMargin;
}
 
void QQuickFlickable::setBottomMargin(qreal m)
{
    Q_D(QQuickFlickable);
    if (d->vData.endMargin == m)
        return;
    d->vData.endMargin = m;
    d->vData.markExtentsDirty();
    if (!d->pressed && !d->hData.moving && !d->vData.moving) {
        d->fixupMode = QQuickFlickablePrivate::Immediate;
        d->fixupY();
    }
    emit bottomMarginChanged();
    d->updateBeginningEnd();
}
 
qreal QQuickFlickable::leftMargin() const
{
    Q_D(const QQuickFlickable);
    return d->hData.startMargin;
}
 
void QQuickFlickable::setLeftMargin(qreal m)
{
    Q_D(QQuickFlickable);
    if (d->hData.startMargin == m)
        return;
    d->hData.startMargin = m;
    d->hData.markExtentsDirty();
    if (!d->pressed && !d->hData.moving && !d->vData.moving) {
        d->fixupMode = QQuickFlickablePrivate::Immediate;
        d->fixupX();
    }
    emit leftMarginChanged();
    d->updateBeginningEnd();
}
 
qreal QQuickFlickable::rightMargin() const
{
    Q_D(const QQuickFlickable);
    return d->hData.endMargin;
}
 
void QQuickFlickable::setRightMargin(qreal m)
{
    Q_D(QQuickFlickable);
    if (d->hData.endMargin == m)
        return;
    d->hData.endMargin = m;
    d->hData.markExtentsDirty();
    if (!d->pressed && !d->hData.moving && !d->vData.moving) {
        d->fixupMode = QQuickFlickablePrivate::Immediate;
        d->fixupX();
    }
    emit rightMarginChanged();
    d->updateBeginningEnd();
}
 
qreal QQuickFlickable::originY() const
{
    Q_D(const QQuickFlickable);
    return -minYExtent() + d->vData.startMargin;
}
 
qreal QQuickFlickable::originX() const
{
    Q_D(const QQuickFlickable);
    return -minXExtent() + d->hData.startMargin;
}
 
 
void QQuickFlickable::resizeContent(qreal w, qreal h, QPointF center)
{
    Q_D(QQuickFlickable);
    const qreal oldHSize = d->hData.viewSize;
    const qreal oldVSize = d->vData.viewSize;
    const bool needToUpdateWidth = w != oldHSize;
    const bool needToUpdateHeight = h != oldVSize;
    d->hData.viewSize = w;
    d->vData.viewSize = h;
    d->contentItem->setSize(QSizeF(w, h));
    if (needToUpdateWidth)
        emit contentWidthChanged();
    if (needToUpdateHeight)
        emit contentHeightChanged();
 
    if (center.x() != 0) {
        qreal pos = center.x() * w / oldHSize;
        setContentX(contentX() + pos - center.x());
    }
    if (center.y() != 0) {
        qreal pos = center.y() * h / oldVSize;
        setContentY(contentY() + pos - center.y());
    }
    d->updateBeginningEnd();
}
 
void QQuickFlickable::returnToBounds()
{
    Q_D(QQuickFlickable);
    d->fixupX();
    d->fixupY();
}
 
qreal QQuickFlickable::vWidth() const
{
    Q_D(const QQuickFlickable);
    if (d->hData.viewSize < 0)
        return width();
    else
        return d->hData.viewSize;
}
 
qreal QQuickFlickable::vHeight() const
{
    Q_D(const QQuickFlickable);
    if (d->vData.viewSize < 0)
        return height();
    else
        return d->vData.viewSize;
}
 
bool QQuickFlickable::xflick() const
{
    Q_D(const QQuickFlickable);
    const int contentWidthWithMargins = d->contentItem->width() + d->hData.startMargin + d->hData.endMargin;
    if ((d->flickableDirection & QQuickFlickable::AutoFlickIfNeeded) && (contentWidthWithMargins > width()))
        return true;
    if (d->flickableDirection == QQuickFlickable::AutoFlickDirection)
        return std::floor(qAbs(contentWidthWithMargins - width()));
    return d->flickableDirection & QQuickFlickable::HorizontalFlick;
}
 
bool QQuickFlickable::yflick() const
{
    Q_D(const QQuickFlickable);
    const int contentHeightWithMargins = d->contentItem->height() + d->vData.startMargin + d->vData.endMargin;
    if ((d->flickableDirection & QQuickFlickable::AutoFlickIfNeeded) && (contentHeightWithMargins > height()))
        return true;
    if (d->flickableDirection == QQuickFlickable::AutoFlickDirection)
        return std::floor(qAbs(contentHeightWithMargins - height()));
    return d->flickableDirection & QQuickFlickable::VerticalFlick;
}
 
void QQuickFlickable::mouseUngrabEvent()
{
    Q_D(QQuickFlickable);
    // if our mouse grab has been removed (probably by another Flickable),
    // fix our state
    if (!d->replayingPressEvent)
        d->cancelInteraction();
}
 
void QQuickFlickablePrivate::cancelInteraction()
{
    Q_Q(QQuickFlickable);
    if (pressed) {
        clearDelayedPress();
        pressed = false;
        draggingEnding();
        stealMouse = false;
        q->setKeepMouseGrab(false);
        fixupX();
        fixupY();
        if (!isViewMoving())
            q->movementEnding();
    }
}
 
void QQuickFlickablePrivate::addPointerHandler(QQuickPointerHandler *h)
{
    Q_Q(const QQuickFlickable);
    qCDebug(lcHandlerParent) << "reparenting handler" << h << "to contentItem of" << q;
    h->setParent(contentItem);
    QQuickItemPrivate::get(contentItem)->addPointerHandler(h);
}
 
bool QQuickFlickable::filterPointerEvent(QQuickItem *receiver, QPointerEvent *event)
{
    const bool isTouch = QQuickDeliveryAgentPrivate::isTouchEvent(event);
    if (!(QQuickDeliveryAgentPrivate::isMouseEvent(event) || isTouch ||
          QQuickDeliveryAgentPrivate::isTabletEvent(event)))
        return false; // don't filter hover events or wheel events, for example
    Q_ASSERT_X(receiver != this, "", "Flickable received a filter event for itself");
    Q_D(QQuickFlickable);
    // If a touch event contains a new press point, don't steal right away: watch the movements for a while
    if (isTouch && static_cast<QTouchEvent *>(event)->touchPointStates().testFlag(QEventPoint::State::Pressed))
        d->stealMouse = false;
    // If multiple touchpoints are within bounds, don't grab: it's probably meant for multi-touch interaction in some child
    if (event->pointCount() > 1) {
        qCDebug(lcFilter) << objectName() << "ignoring multi-touch" << event << "for" << receiver;
        d->stealMouse = false;
    } else {
        qCDebug(lcFilter) << objectName() << "filtering" << event << "for" << receiver;
    }
 
    const auto &firstPoint = event->points().first();
 
    if (event->pointCount() == 1 && event->exclusiveGrabber(firstPoint) == this) {
        // We have an exclusive grab (since we're e.g dragging), but at the same time, we have
        // a child with a passive grab (which is why this filter is being called). And because
        // of that, we end up getting the same pointer events twice; First in our own event
        // handlers (because of the grab), then once more in here, since we filter the child.
        // To avoid processing the event twice (e.g avoid calling handleReleaseEvent once more
        // from below), we mark the event as filtered, and simply return.
        event->setAccepted(true);
        return true;
    }
 
    QPointF localPos = mapFromScene(firstPoint.scenePosition());
    bool receiverDisabled = receiver && !receiver->isEnabled();
    bool stealThisEvent = d->stealMouse;
    bool receiverKeepsGrab = receiver && (receiver->keepMouseGrab() || receiver->keepTouchGrab());
    bool receiverRelinquishGrab = false;
 
    // Special case for MouseArea, try to guess what it does with the event
    if (auto *mouseArea = qmlobject_cast<QQuickMouseArea *>(receiver)) {
        bool preventStealing = mouseArea->preventStealing();
#if QT_CONFIG(quick_draganddrop)
        if (mouseArea->drag() && mouseArea->drag()->target())
            preventStealing = true;
#endif
        if (!preventStealing && receiverKeepsGrab) {
            receiverRelinquishGrab = !receiverDisabled
                    || (QQuickDeliveryAgentPrivate::isMouseEvent(event)
                        && firstPoint.state() == QEventPoint::State::Pressed
                        && (receiver->acceptedMouseButtons() & static_cast<QMouseEvent *>(event)->button()));
            if (receiverRelinquishGrab)
                receiverKeepsGrab = false;
        }
    }
 
    if ((stealThisEvent || contains(localPos)) && (!receiver || !receiverKeepsGrab || receiverDisabled)) {
        QScopedPointer<QPointerEvent> localizedEvent(QQuickDeliveryAgentPrivate::clonePointerEvent(event, localPos));
        localizedEvent->setAccepted(false);
        switch (firstPoint.state()) {
        case QEventPoint::State::Updated:
            d->handleMoveEvent(localizedEvent.data());
            break;
        case QEventPoint::State::Pressed:
            d->handlePressEvent(localizedEvent.data());
            d->captureDelayedPress(receiver, event);
            // never grab the pointing device on press during filtering: do it later, during a move
            d->stealMouse = false;
            stealThisEvent = false;
            break;
        case QEventPoint::State::Released:
            d->handleReleaseEvent(localizedEvent.data());
            stealThisEvent = d->stealMouse;
            break;
        case QEventPoint::State::Stationary:
        case QEventPoint::State::Unknown:
            break;
        }
        if ((receiver && stealThisEvent && !receiverKeepsGrab && receiver != this) || receiverDisabled) {
            d->clearDelayedPress();
            event->setExclusiveGrabber(firstPoint, this);
        } else if (d->delayedPressEvent) {
            event->setExclusiveGrabber(firstPoint, this);
        }
 
        const bool filtered = !receiverRelinquishGrab && (stealThisEvent || d->delayedPressEvent || receiverDisabled);
        if (filtered) {
            event->setAccepted(true);
        }
        return filtered;
    } else if (d->lastPosTime != -1) {
        d->lastPosTime = -1;
        returnToBounds();
    }
    if (firstPoint.state() == QEventPoint::State::Released || (receiverKeepsGrab && !receiverDisabled)) {
        // mouse released, or another item has claimed the grab
        d->lastPosTime = -1;
        d->clearDelayedPress();
        d->stealMouse = false;
        d->pressed = false;
    }
    return false;
}
 
bool QQuickFlickable::childMouseEventFilter(QQuickItem *i, QEvent *e)
{
    Q_D(QQuickFlickable);
    QPointerEvent *pointerEvent = e->isPointerEvent() ? static_cast<QPointerEvent *>(e) : nullptr;
 
    auto wantsPointerEvent_helper = [this, d, i, pointerEvent]() {
        Q_ASSERT(pointerEvent);
        QQuickDeliveryAgentPrivate::localizePointerEvent(pointerEvent, this);
        const bool wants = d->wantsPointerEvent(pointerEvent);
        // re-localize event back to \a i before returning
        QQuickDeliveryAgentPrivate::localizePointerEvent(pointerEvent, i);
        return wants;
    };
 
    if (!isVisible() || !isEnabled() || !isInteractive() ||
            (pointerEvent && !wantsPointerEvent_helper())) {
        d->cancelInteraction();
        return QQuickItem::childMouseEventFilter(i, e);
    }
 
    if (e->type() == QEvent::UngrabMouse) {
        Q_ASSERT(e->isSinglePointEvent());
        auto spe = static_cast<QSinglePointEvent *>(e);
        const QObject *grabber = spe->exclusiveGrabber(spe->points().first());
        qCDebug(lcFilter) << "filtering UngrabMouse" << spe->points().first() << "for" << i << "grabber is" << grabber;
        if (grabber != this)
            mouseUngrabEvent(); // A child has been ungrabbed
    } else if (pointerEvent) {
        return filterPointerEvent(i, pointerEvent);
    }
 
    return QQuickItem::childMouseEventFilter(i, e);
}
 
qreal QQuickFlickable::maximumFlickVelocity() const
{
    Q_D(const QQuickFlickable);
    return d->maxVelocity;
}
 
void QQuickFlickable::setMaximumFlickVelocity(qreal v)
{
    Q_D(QQuickFlickable);
    if (v == d->maxVelocity)
        return;
    d->maxVelocity = v;
    emit maximumFlickVelocityChanged();
}
 
qreal QQuickFlickable::flickDeceleration() const
{
    Q_D(const QQuickFlickable);
    return d->deceleration;
}
 
void QQuickFlickable::setFlickDeceleration(qreal deceleration)
{
    Q_D(QQuickFlickable);
    if (deceleration == d->deceleration)
        return;
    d->deceleration = qMax(0.001, deceleration);
    emit flickDecelerationChanged();
}
 
bool QQuickFlickable::isFlicking() const
{
    Q_D(const QQuickFlickable);
    return d->hData.flicking ||  d->vData.flicking;
}
 
bool QQuickFlickable::isFlickingHorizontally() const
{
    Q_D(const QQuickFlickable);
    return d->hData.flicking;
}
 
bool QQuickFlickable::isFlickingVertically() const
{
    Q_D(const QQuickFlickable);
    return d->vData.flicking;
}
 
bool QQuickFlickable::isDragging() const
{
    Q_D(const QQuickFlickable);
    return d->hData.dragging ||  d->vData.dragging;
}
 
bool QQuickFlickable::isDraggingHorizontally() const
{
    Q_D(const QQuickFlickable);
    return d->hData.dragging;
}
 
bool QQuickFlickable::isDraggingVertically() const
{
    Q_D(const QQuickFlickable);
    return d->vData.dragging;
}
 
void QQuickFlickablePrivate::draggingStarting()
{
    Q_Q(QQuickFlickable);
    bool wasDragging = hData.dragging || vData.dragging;
    if (hMoved && !hData.dragging) {
        hData.dragging = true;
        emit q->draggingHorizontallyChanged();
    }
    if (vMoved && !vData.dragging) {
        vData.dragging = true;
        emit q->draggingVerticallyChanged();
    }
    if (!wasDragging && (hData.dragging || vData.dragging)) {
        emit q->draggingChanged();
        emit q->dragStarted();
    }
}
 
void QQuickFlickablePrivate::draggingEnding()
{
    Q_Q(QQuickFlickable);
    const bool wasDragging = hData.dragging || vData.dragging;
    if (hData.dragging) {
        hData.dragging = false;
        emit q->draggingHorizontallyChanged();
    }
    if (vData.dragging) {
        vData.dragging = false;
        emit q->draggingVerticallyChanged();
    }
    if (wasDragging) {
        if (!hData.dragging && !vData.dragging) {
            emit q->draggingChanged();
            emit q->dragEnded();
        }
        hData.inRebound = false;
        vData.inRebound = false;
    }
}
 
bool QQuickFlickablePrivate::isViewMoving() const
{
    if (timeline.isActive()
            || (hData.transitionToBounds && hData.transitionToBounds->isActive())
            || (vData.transitionToBounds && vData.transitionToBounds->isActive()) ) {
        return true;
    }
    return false;
}
 
int QQuickFlickable::pressDelay() const
{
    Q_D(const QQuickFlickable);
    return d->pressDelay;
}
 
void QQuickFlickable::setPressDelay(int delay)
{
    Q_D(QQuickFlickable);
    if (d->pressDelay == delay)
        return;
    d->pressDelay = delay;
    emit pressDelayChanged();
}
 
bool QQuickFlickable::isMoving() const
{
    Q_D(const QQuickFlickable);
    return d->hData.moving || d->vData.moving;
}
 
bool QQuickFlickable::isMovingHorizontally() const
{
    Q_D(const QQuickFlickable);
    return d->hData.moving;
}
 
bool QQuickFlickable::isMovingVertically() const
{
    Q_D(const QQuickFlickable);
    return d->vData.moving;
}
 
void QQuickFlickable::velocityTimelineCompleted()
{
    Q_D(QQuickFlickable);
    if ( (d->hData.transitionToBounds && d->hData.transitionToBounds->isActive())
         || (d->vData.transitionToBounds && d->vData.transitionToBounds->isActive()) ) {
        return;
    }
    // With subclasses such as GridView, velocityTimeline.completed is emitted repeatedly:
    // for example setting currentIndex results in a visual "flick" which the user
    // didn't initiate directly. We don't want to end movement repeatedly, and in
    // that case movementEnding will happen after the sequence of movements ends.
    if (d->vData.flicking)
        movementEnding();
    d->updateBeginningEnd();
}
 
void QQuickFlickable::timelineCompleted()
{
    Q_D(QQuickFlickable);
    if ( (d->hData.transitionToBounds && d->hData.transitionToBounds->isActive())
         || (d->vData.transitionToBounds && d->vData.transitionToBounds->isActive()) ) {
        return;
    }
    movementEnding();
    d->updateBeginningEnd();
}
 
void QQuickFlickable::movementStarting()
{
    Q_D(QQuickFlickable);
    bool wasMoving = d->hData.moving || d->vData.moving;
    if (d->hMoved && !d->hData.moving) {
        d->hData.moving = true;
        emit movingHorizontallyChanged();
    }
    if (d->vMoved && !d->vData.moving) {
        d->vData.moving = true;
        emit movingVerticallyChanged();
    }
 
    if (!wasMoving && (d->hData.moving || d->vData.moving)) {
        emit movingChanged();
        emit movementStarted();
#if QT_CONFIG(accessibility)
        if (QAccessible::isActive()) {
            QAccessibleEvent ev(this, QAccessible::ScrollingStart);
            QAccessible::updateAccessibility(&ev);
        }
#endif
    }
}
 
void QQuickFlickable::movementEnding()
{
    movementEnding(true, true);
}
 
void QQuickFlickable::movementEnding(bool hMovementEnding, bool vMovementEnding)
{
    Q_D(QQuickFlickable);
 
    // emit flicking signals
    const bool wasFlicking = d->hData.flicking || d->vData.flicking;
    if (hMovementEnding && d->hData.flicking) {
        d->hData.flicking = false;
        emit flickingHorizontallyChanged();
    }
    if (vMovementEnding && d->vData.flicking) {
        d->vData.flicking = false;
        emit flickingVerticallyChanged();
    }
    if (wasFlicking && (!d->hData.flicking || !d->vData.flicking)) {
        emit flickingChanged();
        emit flickEnded();
    } else if (d->hData.flickingWhenDragBegan || d->vData.flickingWhenDragBegan) {
        d->hData.flickingWhenDragBegan = !hMovementEnding;
        d->vData.flickingWhenDragBegan = !vMovementEnding;
        emit flickEnded();
    }
 
    // emit moving signals
    bool wasMoving = isMoving();
    if (hMovementEnding && d->hData.moving
            && (!d->pressed && !d->stealMouse)) {
        d->hData.moving = false;
        d->hMoved = false;
        emit movingHorizontallyChanged();
    }
    if (vMovementEnding && d->vData.moving
            && (!d->pressed && !d->stealMouse)) {
        d->vData.moving = false;
        d->vMoved = false;
        emit movingVerticallyChanged();
    }
    if (wasMoving && !isMoving()) {
        emit movingChanged();
        emit movementEnded();
#if QT_CONFIG(accessibility)
        if (QAccessible::isActive()) {
            QAccessibleEvent ev(this, QAccessible::ScrollingEnd);
            QAccessible::updateAccessibility(&ev);
        }
#endif
    }
 
    if (hMovementEnding) {
        d->hData.fixingUp = false;
        d->hData.smoothVelocity.setValue(0);
        d->hData.previousDragDelta = 0.0;
    }
    if (vMovementEnding) {
        d->vData.fixingUp = false;
        d->vData.smoothVelocity.setValue(0);
        d->vData.previousDragDelta = 0.0;
    }
}
 
void QQuickFlickablePrivate::updateVelocity()
{
    Q_Q(QQuickFlickable);
    emit q->horizontalVelocityChanged();
    emit q->verticalVelocityChanged();
}
 
qreal QQuickFlickable::horizontalOvershoot() const
{
    Q_D(const QQuickFlickable);
    return d->hData.overshoot;
}
 
qreal QQuickFlickable::verticalOvershoot() const
{
    Q_D(const QQuickFlickable);
    return d->vData.overshoot;
}
 
QQuickFlickable::BoundsMovement QQuickFlickable::boundsMovement() const
{
    Q_D(const QQuickFlickable);
    return d->boundsMovement;
}
 
void QQuickFlickable::setBoundsMovement(BoundsMovement movement)
{
    Q_D(QQuickFlickable);
    if (d->boundsMovement == movement)
        return;
 
    d->boundsMovement = movement;
    emit boundsMovementChanged();
}
 
QT_END_NAMESPACE
 
#include "moc_qquickflickable_p_p.cpp"
 
#include "moc_qquickflickable_p.cpp"