qquicklistview.cpp

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// Copyright (C) 2016 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 "qquicklistview_p.h"
#include "qquickitemview_p_p.h"
#include "qquickflickablebehavior_p.h"
 
#include <private/qqmlobjectmodel_p.h>
#include <QtQml/qqmlexpression.h>
#include <QtQml/qqmlengine.h>
#include <QtQml/qqmlinfo.h>
#include <QtGui/qevent.h>
#include <QtCore/qcoreapplication.h>
#include <QtCore/qmath.h>
 
#include <private/qquicksmoothedanimation_p_p.h>
#include <private/qqmlcomponent_p.h>
 
QT_BEGIN_NAMESPACE
 
#ifndef QML_FLICK_SNAPONETHRESHOLD
#define QML_FLICK_SNAPONETHRESHOLD 30
#endif
 
Q_LOGGING_CATEGORY(lcEvents, "qt.quick.listview.events")
 
class FxListItemSG;
 
class QQuickListViewPrivate : public QQuickItemViewPrivate
{
public:
    Q_DECLARE_PUBLIC(QQuickListView)
    static QQuickListViewPrivate* get(QQuickListView *item) { return item->d_func(); }
 
    Qt::Orientation layoutOrientation() const override;
    bool isContentFlowReversed() const override;
    bool isRightToLeft() const;
    bool isBottomToTop() const;
 
    qreal positionAt(int index) const override;
    qreal endPositionAt(int index) const override;
    qreal originPosition() const override;
    qreal lastPosition() const override;
 
    FxViewItem *itemBefore(int modelIndex) const;
    QString sectionAt(int modelIndex);
    qreal snapPosAt(qreal pos);
    FxViewItem *snapItemAt(qreal pos);
 
    void init() override;
    void clear(bool onDestruction) override;
 
    bool addVisibleItems(qreal fillFrom, qreal fillTo, qreal bufferFrom, qreal bufferTo, bool doBuffer) override;
    bool removeNonVisibleItems(qreal bufferFrom, qreal bufferTo) override;
    void visibleItemsChanged() override;
 
    void removeItem(FxViewItem *item);
 
    FxViewItem *newViewItem(int index, QQuickItem *item) override;
    void initializeViewItem(FxViewItem *item) override;
    bool releaseItem(FxViewItem *item, QQmlInstanceModel::ReusableFlag reusableFlag) override;
    void repositionItemAt(FxViewItem *item, int index, qreal sizeBuffer) override;
    void repositionPackageItemAt(QQuickItem *item, int index) override;
    void resetFirstItemPosition(qreal pos = 0.0) override;
    void adjustFirstItem(qreal forwards, qreal backwards, int) override;
    void updateSizeChangesBeforeVisiblePos(FxViewItem *item, ChangeResult *removeResult) override;
 
    void createHighlight(bool onDestruction = false) override;
    void updateHighlight() override;
    void resetHighlightPosition() override;
    bool movingFromHighlight() override;
 
    void setPosition(qreal pos) override;
    void layoutVisibleItems(int fromModelIndex = 0) override;
 
    bool applyInsertionChange(const QQmlChangeSet::Change &insert, ChangeResult *changeResult, QList<FxViewItem *> *addedItems, QList<MovedItem> *movingIntoView) override;
#if QT_CONFIG(quick_viewtransitions)
    void translateAndTransitionItemsAfter(int afterIndex, const ChangeResult &insertionResult, const ChangeResult &removalResult) override;
#endif
 
    void updateSectionCriteria() override;
    void updateSections() override;
    QQuickItem *getSectionItem(const QString &section);
    void releaseSectionItem(QQuickItem *item);
    void releaseSectionItems();
    void updateInlineSection(FxListItemSG *);
    void updateCurrentSection();
    void updateStickySections();
 
    qreal headerSize() const override;
    qreal footerSize() const override;
    bool showHeaderForIndex(int index) const override;
    bool showFooterForIndex(int index) const override;
    void updateHeader() override;
    void updateFooter() override;
    bool hasStickyHeader() const override;
    bool hasStickyFooter() const override;
 
    void initializeComponentItem(QQuickItem *item) const override;
 
    void changedVisibleIndex(int newIndex) override;
    void initializeCurrentItem() override;
 
    void updateAverage();
 
    void itemGeometryChanged(QQuickItem *item, QQuickGeometryChange change, const QRectF &oldGeometry) override;
    void fixupPosition() override;
    void fixup(AxisData &data, qreal minExtent, qreal maxExtent) override;
    bool flick(QQuickItemViewPrivate::AxisData &data, qreal minExtent, qreal maxExtent, qreal vSize,
               QQuickTimeLineCallback::Callback fixupCallback, QEvent::Type eventType, qreal velocity) override;
 
    QQuickItemViewAttached *getAttachedObject(const QObject *object) const override;
 
    void fixupHeader();
    void fixupHeaderCompleted();
 
    bool wantsPointerEvent(const QPointerEvent *event) override;
 
    QQuickListView::Orientation orient;
    qreal visiblePos;
    qreal averageSize;
    qreal spacing;
    QQuickListView::SnapMode snapMode;
 
    QQuickListView::HeaderPositioning headerPositioning;
    QQuickListView::FooterPositioning footerPositioning;
 
    std::unique_ptr<QSmoothedAnimation> highlightPosAnimator;
    std::unique_ptr<QSmoothedAnimation> highlightWidthAnimator;
    std::unique_ptr<QSmoothedAnimation> highlightHeightAnimator;
    qreal highlightMoveVelocity;
    qreal highlightResizeVelocity;
    int highlightResizeDuration;
 
    QQuickViewSection *sectionCriteria;
    QString currentSection;
    static const int sectionCacheSize = 5;
    QQuickItem *sectionCache[sectionCacheSize];
    QQuickItem *currentSectionItem;
    QString currentStickySection;
    QQuickItem *nextSectionItem;
    QString nextStickySection;
    QString lastVisibleSection;
    QString nextSection;
 
    qreal overshootDist;
 
    qreal desiredViewportPosition;
    qreal fixupHeaderPosition;
    bool headerNeedsSeparateFixup : 1;
    bool desiredHeaderVisible : 1;
 
    bool correctFlick : 1;
    bool inFlickCorrection : 1;
    bool wantedMousePress : 1;
 
    QQuickListViewPrivate()
        : orient(QQuickListView::Vertical)
        , visiblePos(0)
        , averageSize(100.0), spacing(0.0)
        , snapMode(QQuickListView::NoSnap)
        , headerPositioning(QQuickListView::InlineHeader)
        , footerPositioning(QQuickListView::InlineFooter)
        , highlightPosAnimator(nullptr), highlightWidthAnimator(nullptr), highlightHeightAnimator(nullptr)
        , highlightMoveVelocity(400), highlightResizeVelocity(400), highlightResizeDuration(-1)
        , sectionCriteria(nullptr), currentSectionItem(nullptr), nextSectionItem(nullptr)
        , overshootDist(0.0), desiredViewportPosition(0.0), fixupHeaderPosition(0.0)
        , headerNeedsSeparateFixup(false), desiredHeaderVisible(false)
        , correctFlick(false), inFlickCorrection(false), wantedMousePress(false)
    {
        highlightMoveDuration = -1; //override default value set in base class
    }
 
    friend class QQuickViewSection;
 
    static void setSectionHelper(QQmlContext *context, QQuickItem *sectionItem, const QString &section);
};
 
//----------------------------------------------------------------------------
 
QQuickViewSection::QQuickViewSection(QQuickListView *parent)
    : QObject(parent), m_criteria(FullString), m_delegate(nullptr), m_labelPositioning(InlineLabels)
    , m_view(parent ? QQuickListViewPrivate::get(parent) : nullptr)
{
}
 
void QQuickViewSection::setProperty(const QString &property)
{
    if (property != m_property) {
        m_property = property;
        emit propertyChanged();
        // notify view that the contents of the sections must be recalculated
        m_view->updateSectionCriteria();
    }
}
 
void QQuickViewSection::setCriteria(QQuickViewSection::SectionCriteria criteria)
{
    if (criteria != m_criteria) {
        m_criteria = criteria;
        emit criteriaChanged();
        // notify view that the contents of the sections must be recalculated
        m_view->updateSectionCriteria();
    }
}
 
void QQuickViewSection::setDelegate(QQmlComponent *delegate)
{
    if (delegate != m_delegate) {
        if (m_delegate)
            m_view->releaseSectionItems();
        m_delegate = delegate;
        emit delegateChanged();
        m_view->forceLayoutPolish();
    }
}
 
QString QQuickViewSection::sectionString(const QString &value)
{
    if (m_criteria == FirstCharacter)
        return value.isEmpty() ? QString() : value.at(0);
    else
        return value;
}
 
void QQuickViewSection::setLabelPositioning(int l)
{
    if (m_labelPositioning != l) {
        m_labelPositioning = l;
        emit labelPositioningChanged();
        m_view->forceLayoutPolish();
    }
}
 
//----------------------------------------------------------------------------
 
class FxListItemSG : public FxViewItem
{
public:
    FxListItemSG(QQuickItem *i, QQuickListView *v, bool own) : FxViewItem(i, v, own, static_cast<QQuickItemViewAttached*>(qmlAttachedPropertiesObject<QQuickListView>(i))), view(v)
    {
    }
 
    inline QQuickItem *section() const {
        return item && attached ? static_cast<QQuickListViewAttached*>(attached)->m_sectionItem : nullptr;
    }
    void setSection(QQuickItem *s) {
        static_cast<QQuickListViewAttached*>(attached)->m_sectionItem = s;
    }
 
    qreal position() const override {
        if (section()) {
            if (view->orientation() == QQuickListView::Vertical)
                return (view->verticalLayoutDirection() == QQuickItemView::BottomToTop ? -section()->height()-section()->y() : section()->y());
            else
                return (view->effectiveLayoutDirection() == Qt::RightToLeft ? -section()->width()-section()->x() : section()->x());
        } else {
            return itemPosition();
        }
    }
    qreal itemPosition() const {
        if (view->orientation() == QQuickListView::Vertical)
            return (view->verticalLayoutDirection() == QQuickItemView::BottomToTop ? -itemHeight()-itemY() : itemY());
        else
            return (view->effectiveLayoutDirection() == Qt::RightToLeft ? -itemWidth()-itemX() : itemX());
    }
    qreal size() const override {
        if (section())
            return (view->orientation() == QQuickListView::Vertical ? itemHeight()+section()->height() : itemWidth()+section()->width());
        else
            return (view->orientation() == QQuickListView::Vertical ? itemHeight() : itemWidth());
    }
    qreal itemSize() const {
        return (view->orientation() == QQuickListView::Vertical ? itemHeight() : itemWidth());
    }
    qreal sectionSize() const override {
        if (section())
            return (view->orientation() == QQuickListView::Vertical ? section()->height() : section()->width());
        return 0.0;
    }
    qreal endPosition() const override {
        if (view->orientation() == QQuickListView::Vertical) {
            return (view->verticalLayoutDirection() == QQuickItemView::BottomToTop
                    ? -itemY()
                    : itemY() + itemHeight());
        } else {
            return (view->effectiveLayoutDirection() == Qt::RightToLeft
                    ? -itemX()
                    : itemX() + itemWidth());
        }
    }
 
    void setPosition(qreal pos, bool immediate = false, bool resetInactiveAxis = true) {
        // position the section immediately even if there is a transition
        if (section()) {
            if (view->orientation() == QQuickListView::Vertical) {
                if (view->verticalLayoutDirection() == QQuickItemView::BottomToTop)
                    section()->setY(-section()->height()-pos);
                else
                    section()->setY(pos);
            } else {
                if (view->effectiveLayoutDirection() == Qt::RightToLeft)
                    section()->setX(-section()->width()-pos);
                else
                    section()->setX(pos);
            }
        }
        moveTo(pointForPosition(pos, resetInactiveAxis), immediate);
    }
 
    void setSize(qreal size) {
        if (view->orientation() == QQuickListView::Vertical)
            item->setHeight(size);
        else
            item->setWidth(size);
    }
    bool contains(qreal x, qreal y) const override {
        return (x >= itemX() && x < itemX() + itemWidth() &&
                y >= itemY() && y < itemY() + itemHeight());
    }
 
    QQuickListView *view;
 
private:
    QPointF pointForPosition(qreal pos, bool resetInactiveAxis) const {
        if (view->orientation() == QQuickListView::Vertical) {
            if (view->verticalLayoutDirection() == QQuickItemView::BottomToTop) {
                if (section())
                    pos += section()->height();
                return QPointF(resetInactiveAxis ? 0 : itemX(), -itemHeight() - pos);
            } else {
                if (section())
                    pos += section()->height();
                return QPointF(resetInactiveAxis ? 0 : itemX(), pos);
            }
        } else {
            if (view->effectiveLayoutDirection() == Qt::RightToLeft) {
                if (section())
                    pos += section()->width();
                return QPointF(-itemWidth() - pos, resetInactiveAxis ? 0 : itemY());
            } else {
                if (section())
                    pos += section()->width();
                return QPointF(pos, resetInactiveAxis ? 0 : itemY());
            }
        }
    }
};
 
class MutableModelIterator {
public:
    MutableModelIterator(QQmlInstanceModel *model, int iBegin, int iEnd)
        : removedAtIndex(false)
        , backwards(iEnd < iBegin)
    {
        conn = QObject::connect(model, &QQmlInstanceModel::modelUpdated,
                [&] (const QQmlChangeSet &changeSet, bool /*reset*/)
        {
            for (const QQmlChangeSet::Change &rem : changeSet.removes()) {
                idxEnd -= rem.count;
                if (rem.start() <= index) {
                    index -= rem.count;
                    if (index < rem.start() + rem.count)
                        removedAtIndex = true; // model index was removed
                }
            }
            for (const QQmlChangeSet::Change &ins : changeSet.inserts()) {
                idxEnd += ins.count;
                if (ins.start() <= index)
                    index += ins.count;
            }
        }
        );
        index = iBegin;
        idxEnd = iEnd;
    }
 
    bool hasNext() const {
        return backwards ? index > idxEnd : index < idxEnd;
    }
 
    void next() { index += (backwards ? -1 : +1); }
 
    ~MutableModelIterator()
    {
        disconnect();
    }
 
    void disconnect()
    {
        if (conn) {
            QObject::disconnect(conn);
            conn = QMetaObject::Connection();   // set to nullptr
        }
    }
    int index = 0;
    int idxEnd;
    unsigned removedAtIndex : 1;
    unsigned backwards : 1;
private:
    QMetaObject::Connection conn;
};
 
 
//----------------------------------------------------------------------------
 
bool QQuickListViewPrivate::isContentFlowReversed() const
{
    return isRightToLeft() || isBottomToTop();
}
 
Qt::Orientation QQuickListViewPrivate::layoutOrientation() const
{
    return static_cast<Qt::Orientation>(orient);
}
 
bool QQuickListViewPrivate::isRightToLeft() const
{
    Q_Q(const QQuickListView);
    return orient == QQuickListView::Horizontal && q->effectiveLayoutDirection() == Qt::RightToLeft;
}
 
bool QQuickListViewPrivate::isBottomToTop() const
{
    return orient == QQuickListView::Vertical && verticalLayoutDirection == QQuickItemView::BottomToTop;
}
 
// Returns the item before modelIndex, if created.
// May return an item marked for removal.
FxViewItem *QQuickListViewPrivate::itemBefore(int modelIndex) const
{
    if (modelIndex < visibleIndex)
        return nullptr;
    int idx = 1;
    int lastIndex = -1;
    while (idx < visibleItems.size()) {
        FxViewItem *item = visibleItems.at(idx);
        if (item->index != -1)
            lastIndex = item->index;
        if (item->index == modelIndex)
            return visibleItems.at(idx-1);
        ++idx;
    }
    if (lastIndex == modelIndex-1)
        return visibleItems.constLast();
    return nullptr;
}
 
void QQuickListViewPrivate::setPosition(qreal pos)
{
    Q_Q(QQuickListView);
    if (orient == QQuickListView::Vertical) {
        if (isBottomToTop())
            q->QQuickFlickable::setContentY(-pos-size());
        else
            q->QQuickFlickable::setContentY(pos);
    } else {
        if (isRightToLeft())
            q->QQuickFlickable::setContentX(-pos-size());
        else
            q->QQuickFlickable::setContentX(pos);
    }
}
 
qreal QQuickListViewPrivate::originPosition() const
{
    qreal pos = 0;
    if (!visibleItems.isEmpty()) {
        pos = (*visibleItems.constBegin())->position();
        if (visibleIndex > 0)
            pos -= visibleIndex * (averageSize + spacing);
    }
    return pos;
}
 
qreal QQuickListViewPrivate::lastPosition() const
{
    qreal pos = 0;
    if (!visibleItems.isEmpty()) {
        int invisibleCount = INT_MIN;
        int delayRemovedCount = 0;
        for (int i = visibleItems.size()-1; i >= 0; --i) {
            FxViewItem *item = visibleItems.at(i);
            if (item->index != -1) {
                // Find the invisible count after the last visible item with known index
                invisibleCount = model->count() - (item->index + 1 + delayRemovedCount);
                break;
            } else if (item->attached->delayRemove()) {
                ++delayRemovedCount;
            }
        }
        if (invisibleCount == INT_MIN) {
            // All visible items are in delayRemove state
            invisibleCount = model->count();
        }
        pos = (*(visibleItems.constEnd() - 1))->endPosition();
        if (invisibleCount > 0)
            pos += invisibleCount * (averageSize + spacing);
    } else if (model && model->count()) {
        pos = (model->count() * averageSize + (model->count()-1) * spacing);
    }
    return pos;
}
 
qreal QQuickListViewPrivate::positionAt(int modelIndex) const
{
    if (FxViewItem *item = visibleItem(modelIndex)) {
        return item->position();
    }
    if (!visibleItems.isEmpty()) {
        if (modelIndex < visibleIndex) {
            int count = visibleIndex - modelIndex;
            qreal cs = 0;
            if (modelIndex == currentIndex && currentItem) {
                cs = currentItem->size() + spacing;
                --count;
            }
            return (*visibleItems.constBegin())->position() - count * (averageSize + spacing) - cs;
        } else {
            int count = modelIndex - findLastVisibleIndex(visibleIndex) - 1;
            return (*(visibleItems.constEnd() - 1))->endPosition() + spacing + count * (averageSize + spacing);
        }
    }
    return 0;
}
 
qreal QQuickListViewPrivate::endPositionAt(int modelIndex) const
{
    if (FxViewItem *item = visibleItem(modelIndex))
        return item->endPosition();
    if (!visibleItems.isEmpty()) {
        if (modelIndex < visibleIndex) {
            int count = visibleIndex - modelIndex;
            return (*visibleItems.constBegin())->position() - (count - 1) * (averageSize + spacing) - spacing;
        } else {
            int count = modelIndex - findLastVisibleIndex(visibleIndex) - 1;
            return (*(visibleItems.constEnd() - 1))->endPosition() + count * (averageSize + spacing);
        }
    }
    return 0;
}
 
QString QQuickListViewPrivate::sectionAt(int modelIndex)
{
    if (FxViewItem *item = visibleItem(modelIndex))
        return item->attached->section();
 
    QString section;
    if (sectionCriteria && modelIndex >= 0 && modelIndex < itemCount) {
        QString propValue = model->stringValue(modelIndex, sectionCriteria->property());
        section = sectionCriteria->sectionString(propValue);
    }
 
    return section;
}
 
qreal QQuickListViewPrivate::snapPosAt(qreal pos)
{
    if (FxListItemSG *snapItem = static_cast<FxListItemSG*>(snapItemAt(pos)))
        return snapItem->itemPosition();
    if (visibleItems.size()) {
        qreal firstPos = (*visibleItems.constBegin())->position();
        qreal endPos = (*(visibleItems.constEnd() - 1))->position();
        if (pos < firstPos) {
            return firstPos - qRound((firstPos - pos) / averageSize) * averageSize;
        } else if (pos > endPos)
            return endPos + qRound((pos - endPos) / averageSize) * averageSize;
    }
    return qRound((pos - originPosition()) / averageSize) * averageSize + originPosition();
}
 
FxViewItem *QQuickListViewPrivate::snapItemAt(qreal pos)
{
    const qreal velocity = orient == QQuickListView::Vertical ? vData.velocity : hData.velocity;
    FxViewItem *snapItem = nullptr;
    FxViewItem *prevItem = nullptr;
    qreal prevItemSize = 0;
    for (FxViewItem *item : std::as_const(visibleItems)) {
        if (item->index == -1)
            continue;
 
        const FxListItemSG *listItem = static_cast<FxListItemSG *>(item);
        qreal itemTop = listItem->position();
        qreal itemSize = listItem->size();
        if (highlight && itemTop >= pos && listItem->endPosition() <= pos + highlight->size())
            return item;
 
        if (listItem->section() && velocity > 0) {
            if (itemTop + listItem->sectionSize() / 2 >= pos && itemTop - prevItemSize / 2 < pos)
                snapItem = prevItem;
            itemTop = listItem->itemPosition();
            itemSize = listItem->itemSize();
        }
 
        // Middle of item and spacing (i.e. the middle of the distance between this item and the next
        qreal halfwayToNextItem = itemTop + (itemSize+spacing) / 2;
        qreal halfwayToPrevItem = itemTop - (prevItemSize+spacing) / 2;
        if (halfwayToNextItem >= pos && halfwayToPrevItem < pos)
            snapItem = item;
 
        prevItemSize = listItem->itemSize();
        prevItem = item;
    }
    return snapItem;
}
 
void QQuickListViewPrivate::changedVisibleIndex(int newIndex)
{
    visiblePos = positionAt(newIndex);
    visibleIndex = newIndex;
}
 
void QQuickListViewPrivate::init()
{
    QQuickItemViewPrivate::init();
    ::memset(sectionCache, 0, sizeof(QQuickItem*) * sectionCacheSize);
}
 
void QQuickListViewPrivate::clear(bool onDestruction)
{
    for (int i = 0; i < sectionCacheSize; ++i) {
        delete sectionCache[i];
        sectionCache[i] = nullptr;
    }
    visiblePos = 0;
    releaseSectionItem(currentSectionItem);
    currentSectionItem = nullptr;
    releaseSectionItem(nextSectionItem);
    nextSectionItem = nullptr;
    lastVisibleSection = QString();
    QQuickItemViewPrivate::clear(onDestruction);
}
 
FxViewItem *QQuickListViewPrivate::newViewItem(int modelIndex, QQuickItem *item)
{
    Q_Q(QQuickListView);
 
    FxListItemSG *listItem = new FxListItemSG(item, q, false);
    listItem->index = modelIndex;
 
    // initialise attached properties
    if (sectionCriteria) {
        QString propValue = model->stringValue(modelIndex, sectionCriteria->property());
        QString section = sectionCriteria->sectionString(propValue);
        QString prevSection;
        QString nextSection;
        if (modelIndex > 0) {
            if (FxViewItem *item = itemBefore(modelIndex))
                prevSection = item->attached->section();
            else
                prevSection = sectionAt(modelIndex-1);
        }
        if (modelIndex < model->count()-1) {
            nextSection = sectionAt(modelIndex+1);
        }
        listItem->attached->setSections(prevSection, section, nextSection);
    }
 
    return listItem;
}
 
void QQuickListViewPrivate::initializeViewItem(FxViewItem *item)
{
    QQuickItemViewPrivate::initializeViewItem(item);
 
    // need to track current items that are animating
    item->trackGeometry(true);
 
    if (sectionCriteria && sectionCriteria->delegate()) {
        if (QString::compare(item->attached->m_prevSection, item->attached->m_section, Qt::CaseInsensitive))
            updateInlineSection(static_cast<FxListItemSG*>(item));
    }
}
 
bool QQuickListViewPrivate::releaseItem(FxViewItem *item, QQmlInstanceModel::ReusableFlag reusableFlag)
{
    if (!item || !model)
        return QQuickItemViewPrivate::releaseItem(item, reusableFlag);
 
    QPointer<QQuickItem> it = item->item;
    QQuickListViewAttached *att = static_cast<QQuickListViewAttached*>(item->attached);
 
    bool released = QQuickItemViewPrivate::releaseItem(item, reusableFlag);
    if (released && it && att && att->m_sectionItem) {
        QQuickItemPrivate::get(att->m_sectionItem)->removeItemChangeListener(this, QQuickItemPrivate::Geometry);
 
        // We hold no more references to this item
        int i = 0;
        do {
            if (!sectionCache[i]) {
                sectionCache[i] = att->m_sectionItem;
                sectionCache[i]->setVisible(false);
                att->m_sectionItem = nullptr;
                break;
            }
            ++i;
        } while (i < sectionCacheSize);
        delete att->m_sectionItem;
        att->m_sectionItem = nullptr;
    }
 
    return released;
}
 
bool QQuickListViewPrivate::addVisibleItems(qreal fillFrom, qreal fillTo, qreal bufferFrom, qreal bufferTo, bool doBuffer)
{
    qreal itemEnd = visiblePos;
    if (visibleItems.size()) {
        visiblePos = (*visibleItems.constBegin())->position();
        itemEnd = (*(visibleItems.constEnd() - 1))->endPosition() + spacing;
    }
 
    int modelIndex = findLastVisibleIndex();
    bool haveValidItems = modelIndex >= 0;
    modelIndex = modelIndex < 0 ? visibleIndex : modelIndex + 1;
 
    if (haveValidItems && (bufferFrom > itemEnd+averageSize+spacing
        || bufferTo < visiblePos - averageSize - spacing)) {
        // We've jumped more than a page.  Estimate which items are now
        // visible and fill from there.
        int count = (fillFrom - itemEnd) / (averageSize + spacing);
        int newModelIdx = qBound(0, modelIndex + count, model->count());
        count = newModelIdx - modelIndex;
        if (count) {
            releaseVisibleItems(reusableFlag);
            modelIndex = newModelIdx;
            visibleIndex = modelIndex;
            visiblePos = itemEnd + count * (averageSize + spacing);
            itemEnd = visiblePos;
        }
    }
 
    QQmlIncubator::IncubationMode incubationMode = doBuffer ? QQmlIncubator::Asynchronous : QQmlIncubator::AsynchronousIfNested;
 
    bool changed = false;
    FxListItemSG *item = nullptr;
    qreal pos = itemEnd;
    while (modelIndex < model->count() && pos <= fillTo) {
        if (!(item = static_cast<FxListItemSG*>(createItem(modelIndex, incubationMode))))
            break;
        qCDebug(lcItemViewDelegateLifecycle) << "refill: append item" << modelIndex << "pos" << pos << "buffer" << doBuffer << "item" << (QObject *)(item->item);
#if QT_CONFIG(quick_viewtransitions)
        if (!transitioner || !transitioner->canTransition(QQuickItemViewTransitioner::PopulateTransition, true)) // pos will be set by layoutVisibleItems()
#endif
            item->setPosition(pos, true);
        if (item->item)
            QQuickItemPrivate::get(item->item)->setCulled(doBuffer);
        pos += item->size() + spacing;
        visibleItems.append(item);
        ++modelIndex;
        changed = true;
    }
 
    if (doBuffer && requestedIndex != -1) // already waiting for an item
        return changed;
 
    while (visibleIndex > 0 && visibleIndex <= model->count() && visiblePos > fillFrom) {
        if (!(item = static_cast<FxListItemSG*>(createItem(visibleIndex-1, incubationMode))))
            break;
        qCDebug(lcItemViewDelegateLifecycle) << "refill: prepend item" << visibleIndex-1 << "current top pos" << visiblePos << "buffer" << doBuffer << "item" << (QObject *)(item->item);
        --visibleIndex;
        visiblePos -= item->size() + spacing;
#if QT_CONFIG(quick_viewtransitions)
        if (!transitioner || !transitioner->canTransition(QQuickItemViewTransitioner::PopulateTransition, true)) // pos will be set by layoutVisibleItems()
#endif
            item->setPosition(visiblePos, true);
        if (item->item)
            QQuickItemPrivate::get(item->item)->setCulled(doBuffer);
        visibleItems.prepend(item);
        changed = true;
    }
 
    return changed;
}
 
void QQuickListViewPrivate::removeItem(FxViewItem *item)
{
#if QT_CONFIG(quick_viewtransitions)
    if (item->transitionScheduledOrRunning()) {
        qCDebug(lcItemViewDelegateLifecycle) << "\tnot releasing animating item" << item->index << (QObject *)(item->item);
        item->releaseAfterTransition = true;
        releasePendingTransition.append(item);
    } else
#endif
    {
        qCDebug(lcItemViewDelegateLifecycle) << "\treleasing stationary item" << item->index << (QObject *)(item->item);
        releaseItem(item, reusableFlag);
    }
}
 
bool QQuickListViewPrivate::removeNonVisibleItems(qreal bufferFrom, qreal bufferTo)
{
    FxViewItem *item = nullptr;
    bool changed = false;
 
    // Remove items from the start of the view.
    // Zero-sized items shouldn't be removed unless a non-zero-sized item is also being
    // removed, otherwise a zero-sized item is infinitely added and removed over and
    // over by refill().
    int index = 0;
    while (visibleItems.size() > 1 && index < visibleItems.size()
           && (item = visibleItems.at(index)) && item->endPosition() < bufferFrom) {
        if (item->attached->delayRemove())
            break;
 
        if (item->size() > 0) {
            qCDebug(lcItemViewDelegateLifecycle) << "refill: remove first" << visibleIndex << "top end pos" << item->endPosition();
            // remove this item and all zero-sized items before it
            while (item) {
                if (item->index != -1)
                    visibleIndex++;
                visibleItems.removeAt(index);
                removeItem(item);
                if (index == 0)
                    break;
                item = visibleItems.at(--index);
            }
            changed = true;
        } else {
            index++;
        }
    }
 
    while (visibleItems.size() > 1 && (item = visibleItems.constLast()) && item->position() > bufferTo) {
        if (item->attached->delayRemove())
            break;
        qCDebug(lcItemViewDelegateLifecycle) << "refill: remove last" << visibleIndex+visibleItems.size()-1 << item->position() << (QObject *)(item->item);
        visibleItems.removeLast();
        removeItem(item);
        changed = true;
    }
 
    return changed;
}
 
void QQuickListViewPrivate::visibleItemsChanged()
{
    if (visibleItems.size())
        visiblePos = (*visibleItems.constBegin())->position();
    updateAverage();
    if (currentIndex >= 0 && currentItem && !visibleItem(currentIndex)) {
        static_cast<FxListItemSG*>(currentItem)->setPosition(positionAt(currentIndex));
        updateHighlight();
    }
    if (sectionCriteria)
        updateCurrentSection();
    updateUnrequestedPositions();
}
 
void QQuickListViewPrivate::layoutVisibleItems(int fromModelIndex)
{
    if (!visibleItems.isEmpty()) {
        const qreal from = isContentFlowReversed() ? -position()-displayMarginBeginning-size() : position()-displayMarginBeginning;
        const qreal to = isContentFlowReversed() ? -position()+displayMarginEnd : position()+size()+displayMarginEnd;
 
        FxListItemSG *firstItem = static_cast<FxListItemSG *>(visibleItems.constFirst());
        bool fixedCurrent = currentItem && firstItem->item == currentItem->item;
 
#if QT_CONFIG(quick_viewtransitions)
        /* Set position of first item in list view when populate transition is configured, as it doesn't set
           while adding visible item (addVisibleItem()) to the view */
        if (transitioner && transitioner->canTransition(QQuickItemViewTransitioner::PopulateTransition, true))
            resetFirstItemPosition(isContentFlowReversed() ? -firstItem->position()-firstItem->size() : firstItem->position());
#endif
 
        firstVisibleItemPosition = firstItem->position();
        qreal sum = firstItem->size();
        qreal pos = firstItem->position() + firstItem->size() + spacing;
        firstItem->setVisible(firstItem->endPosition() >= from && firstItem->position() <= to);
 
        // setPosition will affect the position of the item, and its section, if it has one.
        // This will prevent them from potentially overlapping.
        if (firstItem->section())
            firstItem->setPosition(firstItem->position());
 
        for (int i=1; i < visibleItems.size(); ++i) {
            FxListItemSG *item = static_cast<FxListItemSG*>(visibleItems.at(i));
            if (item->index >= fromModelIndex) {
                item->setPosition(pos);
                item->setVisible(item->endPosition() >= from && item->position() <= to);
            }
            pos += item->size() + spacing;
            sum += item->size();
            fixedCurrent = fixedCurrent || (currentItem && item->item == currentItem->item);
        }
        averageSize = qRound(sum / visibleItems.size());
 
        // move current item if it is not a visible item.
        if (currentIndex >= 0 && currentItem && !fixedCurrent)
            static_cast<FxListItemSG*>(currentItem)->setPosition(positionAt(currentIndex));
 
        updateCurrentSection();
        updateStickySections();
    }
}
 
void QQuickListViewPrivate::repositionItemAt(FxViewItem *item, int index, qreal sizeBuffer)
{
    static_cast<FxListItemSG *>(item)->setPosition(positionAt(index) + sizeBuffer);
}
 
void QQuickListViewPrivate::repositionPackageItemAt(QQuickItem *item, int index)
{
    Q_Q(QQuickListView);
    qreal pos = position();
    if (orient == QQuickListView::Vertical) {
        if (item->y() + item->height() > pos && item->y() < pos + q->height()) {
            if (isBottomToTop())
                item->setY(-positionAt(index)-item->height());
            else
                item->setY(positionAt(index));
        }
    } else {
        if (item->x() + item->width() > pos && item->x() < pos + q->width()) {
            if (isRightToLeft())
                item->setX(-positionAt(index)-item->width());
            else
                item->setX(positionAt(index));
        }
    }
}
 
void QQuickListViewPrivate::resetFirstItemPosition(qreal pos)
{
    FxListItemSG *item = static_cast<FxListItemSG*>(visibleItems.constFirst());
    item->setPosition(pos);
}
 
void QQuickListViewPrivate::adjustFirstItem(qreal forwards, qreal backwards, int)
{
    if (!visibleItems.size())
        return;
    qreal diff = forwards - backwards;
    static_cast<FxListItemSG*>(visibleItems.constFirst())->setPosition(visibleItems.constFirst()->position() + diff);
}
 
void QQuickListViewPrivate::updateSizeChangesBeforeVisiblePos(FxViewItem *item, ChangeResult *removeResult)
{
    if (item != visibleItems.constFirst())
        QQuickItemViewPrivate::updateSizeChangesBeforeVisiblePos(item, removeResult);
}
 
void QQuickListViewPrivate::createHighlight(bool onDestruction)
{
    bool changed = false;
    if (highlight) {
        if (trackedItem == highlight.get())
            trackedItem = nullptr;
        highlight.reset();
 
        highlightPosAnimator.reset();
        highlightWidthAnimator.reset();
        highlightHeightAnimator.reset();
        highlightPosAnimator = nullptr;
        highlightWidthAnimator = nullptr;
        highlightHeightAnimator = nullptr;
 
        changed = true;
    }
 
    if (onDestruction)
        return;
 
    Q_Q(QQuickListView);
    if (currentItem) {
        QQuickItem *item = createHighlightItem();
        if (item) {
            std::unique_ptr<FxListItemSG> newHighlight
                    = std::make_unique<FxListItemSG>(item, q, true);
            newHighlight->trackGeometry(true);
 
            if (autoHighlight) {
                newHighlight->setSize(static_cast<FxListItemSG*>(currentItem)->itemSize());
                newHighlight->setPosition(static_cast<FxListItemSG*>(currentItem)->itemPosition());
            }
            const QLatin1String posProp(orient == QQuickListView::Vertical ? "y" : "x");
            highlightPosAnimator = std::make_unique<QSmoothedAnimation>();
            highlightPosAnimator->target = QQmlProperty(item, posProp);
            highlightPosAnimator->velocity = highlightMoveVelocity;
            highlightPosAnimator->userDuration = highlightMoveDuration;
 
            highlightWidthAnimator = std::make_unique<QSmoothedAnimation>();
            highlightWidthAnimator->velocity = highlightResizeVelocity;
            highlightWidthAnimator->userDuration = highlightResizeDuration;
            highlightWidthAnimator->target = QQmlProperty(item, QStringLiteral("width"));
 
            highlightHeightAnimator = std::make_unique<QSmoothedAnimation>();
            highlightHeightAnimator->velocity = highlightResizeVelocity;
            highlightHeightAnimator->userDuration = highlightResizeDuration;
            highlightHeightAnimator->target = QQmlProperty(item, QStringLiteral("height"));
 
            highlight = std::move(newHighlight);
            changed = true;
        }
    }
    if (changed)
        emit q->highlightItemChanged();
}
 
void QQuickListViewPrivate::updateHighlight()
{
    applyPendingChanges();
 
    if ((!currentItem && highlight) || (currentItem && !highlight))
        createHighlight();
    bool strictHighlight = haveHighlightRange && highlightRange == QQuickListView::StrictlyEnforceRange;
    if (currentItem && autoHighlight && highlight && (!strictHighlight || !pressed)) {
        // auto-update highlight
        FxListItemSG *listItem = static_cast<FxListItemSG*>(currentItem);
        highlightPosAnimator->to = isContentFlowReversed()
                ? -listItem->itemPosition()-listItem->itemSize()
                : listItem->itemPosition();
        highlightWidthAnimator->to = listItem->item->width();
        highlightHeightAnimator->to = listItem->item->height();
        if (orient == QQuickListView::Vertical) {
            if (highlight->item->width() == 0)
                highlight->item->setWidth(currentItem->item->width());
        } else {
            if (highlight->item->height() == 0)
                highlight->item->setHeight(currentItem->item->height());
        }
 
        highlightPosAnimator->restart();
        highlightWidthAnimator->restart();
        highlightHeightAnimator->restart();
    }
    updateTrackedItem();
}
 
void QQuickListViewPrivate::resetHighlightPosition()
{
    if (highlight && currentItem) {
        static_cast<FxListItemSG*>(highlight.get())->setPosition(
                static_cast<FxListItemSG*>(currentItem)->itemPosition());
    }
}
 
bool QQuickListViewPrivate::movingFromHighlight()
{
    if (!haveHighlightRange || highlightRange != QQuickListView::StrictlyEnforceRange)
        return false;
 
    return (highlightPosAnimator && highlightPosAnimator->isRunning()) ||
           (highlightHeightAnimator && highlightHeightAnimator->isRunning()) ||
           (highlightWidthAnimator && highlightWidthAnimator->isRunning());
}
 
 
QQuickItem * QQuickListViewPrivate::getSectionItem(const QString &section)
{
    Q_Q(QQuickListView);
    QQuickItem *sectionItem = nullptr;
    int i = sectionCacheSize-1;
    while (i >= 0 && !sectionCache[i])
        --i;
    if (i >= 0) {
        sectionItem = sectionCache[i];
        sectionCache[i] = nullptr;
        sectionItem->setVisible(true);
        QQmlContext *context = QQmlEngine::contextForObject(sectionItem)->parentContext();
        setSectionHelper(context, sectionItem, section);
    } else {
        QQmlComponent* delegate = sectionCriteria->delegate();
        const bool reuseExistingContext = delegate->isBound();
        auto delegatePriv = QQmlComponentPrivate::get(delegate);
        QQmlPropertyCache::ConstPtr rootPropertyCache;
 
        QQmlContext *creationContext = sectionCriteria->delegate()->creationContext();
        auto baseContext = creationContext ? creationContext : qmlContext(q);
        // if we need to insert a context property, we need a separate context
        QQmlContext *context = reuseExistingContext ? baseContext : new QQmlContext(baseContext);
        QObject *nobj = delegate->beginCreate(context);
        if (nobj) {
            if (delegatePriv->hadTopLevelRequiredProperties()) {
                delegate->setInitialProperties(nobj, {{QLatin1String("section"), section}});
            } else if (!reuseExistingContext) {
                context->setContextProperty(QLatin1String("section"), section);
            }
            if (!reuseExistingContext)
                QQml_setParent_noEvent(context, nobj);
            sectionItem = qobject_cast<QQuickItem *>(nobj);
            if (!sectionItem) {
                delete nobj;
            } else {
                if (qFuzzyIsNull(sectionItem->z()))
                    sectionItem->setZ(2);
                QQml_setParent_noEvent(sectionItem, contentItem);
                sectionItem->setParentItem(contentItem);
            }
            // sections are not controlled by FxListItemSG, so apply attached properties here
            QQuickItemViewAttached *attached = static_cast<QQuickItemViewAttached*>(qmlAttachedPropertiesObject<QQuickListView>(sectionItem));
            attached->setView(q);
        } else if (!reuseExistingContext) {
            delete context;
        }
        sectionCriteria->delegate()->completeCreate();
    }
 
    if (sectionItem)
        QQuickItemPrivate::get(sectionItem)->addItemChangeListener(this, QQuickItemPrivate::Geometry);
 
    return sectionItem;
}
 
void QQuickListViewPrivate::releaseSectionItem(QQuickItem *item)
{
    if (!item)
        return;
    int i = 0;
 
    QQuickItemPrivate::get(item)->removeItemChangeListener(this, QQuickItemPrivate::Geometry);
 
    do {
        if (!sectionCache[i]) {
            sectionCache[i] = item;
            sectionCache[i]->setVisible(false);
            return;
        }
        ++i;
    } while (i < sectionCacheSize);
    delete item;
}
 
 
void QQuickListViewPrivate::releaseSectionItems()
{
    for (FxViewItem *item : std::as_const(visibleItems)) {
        FxListItemSG *listItem = static_cast<FxListItemSG *>(item);
        if (listItem->section()) {
            qreal pos = listItem->position();
            releaseSectionItem(listItem->section());
            listItem->setSection(nullptr);
            listItem->setPosition(pos);
        }
    }
    for (int i = 0; i < sectionCacheSize; ++i) {
        delete sectionCache[i];
        sectionCache[i] = nullptr;
    }
}
 
void QQuickListViewPrivate::updateInlineSection(FxListItemSG *listItem)
{
    if (!sectionCriteria || !sectionCriteria->delegate())
        return;
    if (QString::compare(listItem->attached->m_prevSection, listItem->attached->m_section, Qt::CaseInsensitive)
            && (sectionCriteria->labelPositioning() & QQuickViewSection::InlineLabels
                || (listItem->index == 0 && sectionCriteria->labelPositioning() & QQuickViewSection::CurrentLabelAtStart))) {
        if (!listItem->section()) {
            qreal pos = listItem->position();
            listItem->setSection(getSectionItem(listItem->attached->m_section));
            listItem->setPosition(pos);
        } else {
            QQmlContext *context = QQmlEngine::contextForObject(listItem->section())->parentContext();
            setSectionHelper(context, listItem->section(), listItem->attached->m_section);
        }
    } else if (listItem->section()) {
        qreal pos = listItem->position();
        releaseSectionItem(listItem->section());
        listItem->setSection(nullptr);
        listItem->setPosition(pos);
    }
}
 
void QQuickListViewPrivate::updateStickySections()
{
    if (!sectionCriteria || !sectionCriteria->delegate()
            || (!sectionCriteria->labelPositioning() && !currentSectionItem && !nextSectionItem))
        return;
 
    bool isFlowReversed = isContentFlowReversed();
    qreal viewPos = isFlowReversed ? -position()-size() : position();
    qreal startPos = hasStickyHeader() ? header->endPosition() : viewPos;
    qreal endPos = hasStickyFooter() ? footer->position() : viewPos + size();
 
    QQuickItem *sectionItem = nullptr;
    QQuickItem *lastSectionItem = nullptr;
    int index = 0;
    while (index < visibleItems.size()) {
        if (QQuickItem *section = static_cast<FxListItemSG *>(visibleItems.at(index))->section()) {
            // Find the current section header and last visible section header
            // and hide them if they will overlap a static section header.
            qreal sectionPos = orient == QQuickListView::Vertical ? section->y() : section->x();
            qreal sectionSize = orient == QQuickListView::Vertical ? section->height() : section->width();
            bool visTop = true;
            if (sectionCriteria->labelPositioning() & QQuickViewSection::CurrentLabelAtStart)
                visTop = isFlowReversed ? -sectionPos-sectionSize >= startPos : sectionPos >= startPos;
            bool visBot = true;
            if (sectionCriteria->labelPositioning() & QQuickViewSection::NextLabelAtEnd)
                visBot = isFlowReversed ? -sectionPos <= endPos : sectionPos + sectionSize < endPos;
            section->setVisible(visBot && visTop);
            if (visTop && !sectionItem)
                sectionItem = section;
            if (isFlowReversed) {
               if (-sectionPos <= endPos)
                    lastSectionItem = section;
            } else {
                if (sectionPos + sectionSize < endPos)
                    lastSectionItem = section;
            }
        }
        ++index;
    }
 
    // Current section header
    if (sectionCriteria->labelPositioning() & QQuickViewSection::CurrentLabelAtStart && isValid() && visibleItems.size()) {
        if (!currentSectionItem) {
            currentSectionItem = getSectionItem(currentSection);
        } else if (QString::compare(currentStickySection, currentSection, Qt::CaseInsensitive)) {
            QQmlContext *context = QQmlEngine::contextForObject(currentSectionItem)->parentContext();
            setSectionHelper(context, currentSectionItem, currentSection);
        }
        currentStickySection = currentSection;
        if (!currentSectionItem)
            return;
 
        qreal sectionSize = orient == QQuickListView::Vertical ? currentSectionItem->height() : currentSectionItem->width();
        bool atBeginning = orient == QQuickListView::Vertical ? (isBottomToTop() ? vData.atEnd : vData.atBeginning) : (isRightToLeft() ? hData.atEnd : hData.atBeginning);
 
        currentSectionItem->setVisible(!atBeginning && (!header || hasStickyHeader() || header->endPosition() < viewPos));
        qreal pos = isFlowReversed ? position() + size() - sectionSize : startPos;
        if (header)
            pos = isFlowReversed ? qMin(-header->endPosition() - sectionSize, pos) : qMax(header->endPosition(), pos);
        if (sectionItem) {
            qreal sectionPos = orient == QQuickListView::Vertical ? sectionItem->y() : sectionItem->x();
            pos = isFlowReversed ? qMax(pos, sectionPos + sectionSize) : qMin(pos, sectionPos - sectionSize);
        }
        if (footer)
            pos = isFlowReversed ? qMax(-footer->position(), pos) : qMin(footer->position() - sectionSize, pos);
        if (orient == QQuickListView::Vertical)
            currentSectionItem->setY(pos);
        else
            currentSectionItem->setX(pos);
    } else if (currentSectionItem) {
        releaseSectionItem(currentSectionItem);
        currentSectionItem = nullptr;
    }
 
    // Next section footer
    if (sectionCriteria->labelPositioning() & QQuickViewSection::NextLabelAtEnd && isValid() && visibleItems.size()) {
        if (!nextSectionItem) {
            nextSectionItem = getSectionItem(nextSection);
        } else if (QString::compare(nextStickySection, nextSection, Qt::CaseInsensitive)) {
            QQmlContext *context = QQmlEngine::contextForObject(nextSectionItem)->parentContext();
            setSectionHelper(context, nextSectionItem, nextSection);
        }
        nextStickySection = nextSection;
        if (!nextSectionItem)
            return;
 
        qreal sectionSize = orient == QQuickListView::Vertical ? nextSectionItem->height() : nextSectionItem->width();
        nextSectionItem->setVisible(!nextSection.isEmpty());
        qreal pos = isFlowReversed ? position() : endPos - sectionSize;
        if (footer)
            pos = isFlowReversed ? qMax(-footer->position(), pos) : qMin(footer->position() - sectionSize, pos);
        if (lastSectionItem) {
            qreal sectionPos = orient == QQuickListView::Vertical ? lastSectionItem->y() : lastSectionItem->x();
            pos = isFlowReversed ? qMin(pos, sectionPos - sectionSize) : qMax(pos, sectionPos + sectionSize);
        }
        if (header)
            pos = isFlowReversed ? qMin(-header->endPosition() - sectionSize, pos) : qMax(header->endPosition(), pos);
        if (orient == QQuickListView::Vertical)
            nextSectionItem->setY(pos);
        else
            nextSectionItem->setX(pos);
    } else if (nextSectionItem) {
        releaseSectionItem(nextSectionItem);
        nextSectionItem = nullptr;
    }
}
 
void QQuickListViewPrivate::updateSections()
{
    Q_Q(QQuickListView);
    if (!q->isComponentComplete())
        return;
 
    QQuickItemViewPrivate::updateSections();
 
    if (sectionCriteria && !visibleItems.isEmpty() && isValid()) {
        QString prevSection;
        if (visibleIndex > 0)
            prevSection = sectionAt(visibleIndex-1);
        QQuickListViewAttached *prevAtt = nullptr;
        int prevIdx = -1;
        int idx = -1;
        for (FxViewItem *item : std::as_const(visibleItems)) {
            QQuickListViewAttached *attached = static_cast<QQuickListViewAttached*>(item->attached);
            attached->setPrevSection(prevSection);
            if (item->index != -1) {
                QString propValue = model->stringValue(item->index, sectionCriteria->property());
                attached->setSection(sectionCriteria->sectionString(propValue));
                idx = item->index;
            }
            updateInlineSection(static_cast<FxListItemSG*>(item));
            if (prevAtt)
                prevAtt->setNextSection(sectionAt(prevIdx+1));
            prevSection = attached->section();
            prevAtt = attached;
            prevIdx = item->index;
        }
        if (prevAtt) {
            if (idx > 0 && idx < model->count()-1)
                prevAtt->setNextSection(sectionAt(idx+1));
            else
                prevAtt->setNextSection(QString());
        }
    }
 
    lastVisibleSection = QString();
}
 
void QQuickListViewPrivate::updateCurrentSection()
{
    Q_Q(QQuickListView);
    if (!sectionCriteria || visibleItems.isEmpty()) {
        if (!currentSection.isEmpty()) {
            currentSection.clear();
            emit q->currentSectionChanged();
        }
        return;
    }
    bool inlineSections = sectionCriteria->labelPositioning() & QQuickViewSection::InlineLabels;
    qreal viewPos = isContentFlowReversed() ? -position()-size() : position();
    qreal startPos = hasStickyHeader() ? header->endPosition() : viewPos;
    int index = 0;
    int modelIndex = visibleIndex;
    while (index < visibleItems.size()) {
        FxViewItem *item = visibleItems.at(index);
        if (item->endPosition() > startPos)
            break;
        if (item->index != -1)
            modelIndex = item->index;
        ++index;
    }
 
    QString newSection = currentSection;
    if (index < visibleItems.size())
        newSection = visibleItems.at(index)->attached->section();
    else
        newSection = (*visibleItems.constBegin())->attached->section();
    if (newSection != currentSection) {
        currentSection = newSection;
        updateStickySections();
        emit q->currentSectionChanged();
    }
 
    if (sectionCriteria->labelPositioning() & QQuickViewSection::NextLabelAtEnd) {
        // Don't want to scan for next section on every movement, so remember
        // the last section in the visible area and only scan for the next
        // section when that changes.  Clearing lastVisibleSection will also
        // force searching.
        QString lastSection = currentSection;
        qreal endPos = hasStickyFooter() ? footer->position() : viewPos + size();
        if (nextSectionItem && !inlineSections)
            endPos -= orient == QQuickListView::Vertical ? nextSectionItem->height() : nextSectionItem->width();
        while (index < visibleItems.size()) {
            FxListItemSG *listItem = static_cast<FxListItemSG *>(visibleItems.at(index));
            if (listItem->itemPosition() >= endPos)
                break;
            if (listItem->index != -1)
                modelIndex = listItem->index;
            lastSection = listItem->attached->section();
            ++index;
        }
 
        if (lastVisibleSection != lastSection) {
            nextSection = QString();
            lastVisibleSection = lastSection;
            for (int i = modelIndex; i < itemCount; ++i) {
                QString section = sectionAt(i);
                if (section != lastSection) {
                    nextSection = section;
                    updateStickySections();
                    break;
                }
            }
        }
    }
}
 
void QQuickListViewPrivate::initializeCurrentItem()
{
    QQuickItemViewPrivate::initializeCurrentItem();
 
    if (currentItem) {
        FxListItemSG *listItem = static_cast<FxListItemSG *>(currentItem);
 
        // don't reposition the item if it is already in the visibleItems list
        FxViewItem *actualItem = visibleItem(currentIndex);
        if (!actualItem) {
            if (currentIndex == visibleIndex - 1 && visibleItems.size()) {
                // We can calculate exact postion in this case
                listItem->setPosition(visibleItems.constFirst()->position() - currentItem->size() - spacing);
            } else {
                // Create current item now and position as best we can.
                // Its position will be corrected when it becomes visible.
                listItem->setPosition(positionAt(currentIndex));
            }
        }
 
        if (visibleItems.isEmpty())
            averageSize = listItem->size();
    }
}
 
void QQuickListViewPrivate::updateAverage()
{
    if (!visibleItems.size())
        return;
    qreal sum = 0.0;
    for (FxViewItem *item : std::as_const(visibleItems))
        sum += item->size();
    averageSize = qRound(sum / visibleItems.size());
}
 
qreal QQuickListViewPrivate::headerSize() const
{
    return header ? header->size() : 0.0;
}
 
qreal QQuickListViewPrivate::footerSize() const
{
    return footer ? footer->size() : 0.0;
}
 
bool QQuickListViewPrivate::showHeaderForIndex(int index) const
{
    return index == 0;
}
 
bool QQuickListViewPrivate::showFooterForIndex(int index) const
{
    return model && index == model->count()-1;
}
 
void QQuickListViewPrivate::updateFooter()
{
    Q_Q(QQuickListView);
    bool created = false;
    if (!footer) {
        QQuickItem *item = createComponentItem(footerComponent, 1.0);
        if (!item)
            return;
        footer = new FxListItemSG(item, q, true);
        footer->trackGeometry(true);
        created = true;
    }
 
    FxListItemSG *listItem = static_cast<FxListItemSG*>(footer);
    if (footerPositioning == QQuickListView::OverlayFooter) {
        listItem->setPosition(isContentFlowReversed() ? -position() - footerSize() : position() + size() - footerSize(), false, false);
    } else if (visibleItems.size()) {
        if (footerPositioning == QQuickListView::PullBackFooter) {
            qreal viewPos = isContentFlowReversed() ? -position() : position() + size();
            // using qBound() would throw an assert here, because max < min is a valid case
            // here, if the list's delegates do not fill the whole view
            qreal clampedPos = qMax(originPosition() - footerSize() + size(), qMin(listItem->position(), lastPosition()));
            listItem->setPosition(qBound(viewPos - footerSize(), clampedPos, viewPos), false, false);
        } else {
            qreal endPos = lastPosition();
            if (findLastVisibleIndex() == model->count()-1) {
                listItem->setPosition(endPos, false, false);
            } else {
                qreal visiblePos = position() + q->height();
                if (endPos <= visiblePos || listItem->position() < endPos)
                    listItem->setPosition(endPos, false, false);
            }
        }
    } else {
        listItem->setPosition(visiblePos, false, false);
    }
 
    if (created)
        emit q->footerItemChanged();
}
 
void QQuickListViewPrivate::fixupHeaderCompleted()
{
    headerNeedsSeparateFixup = false;
    QObjectPrivate::disconnect(&timeline, &QQuickTimeLine::updated, this, &QQuickListViewPrivate::fixupHeader);
}
 
void QQuickListViewPrivate::fixupHeader()
{
    FxListItemSG *listItem = static_cast<FxListItemSG*>(header);
    const bool fixingUp = (orient == QQuickListView::Vertical ? vData : hData).fixingUp;
    if (fixingUp && headerPositioning == QQuickListView::PullBackHeader && visibleItems.size()) {
        int fixupDura = timeline.duration();
        if (fixupDura < 0)
            fixupDura = fixupDuration/2;
        const int t = timeline.time();
 
        const qreal progress = qreal(t)/fixupDura;
        const qreal ultimateHeaderPosition = desiredHeaderVisible ? desiredViewportPosition : desiredViewportPosition - headerSize();
        const qreal headerPosition = fixupHeaderPosition * (1 - progress) + ultimateHeaderPosition * progress;
        const qreal viewPos = isContentFlowReversed() ? -position() - size() : position();
        const qreal clampedPos = qBound(originPosition() - headerSize(), headerPosition, lastPosition() - size());
        listItem->setPosition(qBound(viewPos - headerSize(), clampedPos, viewPos));
    }
}
 
void QQuickListViewPrivate::updateHeader()
{
    Q_Q(QQuickListView);
    bool created = false;
    if (!header) {
        QQuickItem *item = createComponentItem(headerComponent, 1.0);
        if (!item)
            return;
        header = new FxListItemSG(item, q, true);
        header->trackGeometry(true);
        created = true;
    }
 
    FxListItemSG *listItem = static_cast<FxListItemSG*>(header);
    if (headerPositioning == QQuickListView::OverlayHeader) {
        listItem->setPosition(isContentFlowReversed() ? -position() - size() : position(), false, false);
    } else if (visibleItems.size()) {
        const bool fixingUp = (orient == QQuickListView::Vertical ? vData : hData).fixingUp;
        if (headerPositioning == QQuickListView::PullBackHeader) {
            qreal headerPosition = listItem->position();
            const qreal viewPos = isContentFlowReversed() ? -position() - size() : position();
            // Make sure the header is not shown if we absolutely do not have any plans to show it
            if (fixingUp && !headerNeedsSeparateFixup)
                headerPosition = viewPos - headerSize();
            // using qBound() would throw an assert here, because max < min is a valid case
            // here, if the list's delegates do not fill the whole view
            qreal clampedPos = qMax(originPosition() - headerSize(), qMin(headerPosition, lastPosition() - size()));
            listItem->setPosition(qBound(viewPos - headerSize(), clampedPos, viewPos), false, false);
        } else {
            qreal startPos = originPosition();
            if (visibleIndex == 0) {
                listItem->setPosition(startPos - headerSize(), false, false);
            } else {
                if (position() <= startPos || listItem->position() > startPos - headerSize())
                    listItem->setPosition(startPos - headerSize(), false, false);
            }
        }
    } else {
        listItem->setPosition(-headerSize(), false, false);
    }
 
    if (created)
        emit q->headerItemChanged();
}
 
bool QQuickListViewPrivate::hasStickyHeader() const
{
    return header && headerPositioning != QQuickListView::InlineHeader;
}
 
bool QQuickListViewPrivate::hasStickyFooter() const
{
    return footer && footerPositioning != QQuickListView::InlineFooter;
}
 
void QQuickListViewPrivate::initializeComponentItem(QQuickItem *item) const
{
    QQuickListViewAttached *attached = static_cast<QQuickListViewAttached *>(
            qmlAttachedPropertiesObject<QQuickListView>(item));
    if (attached) // can be null for default components (see createComponentItem)
        attached->setView(const_cast<QQuickListView*>(q_func()));
}
 
void QQuickListViewPrivate::itemGeometryChanged(QQuickItem *item, QQuickGeometryChange change,
                                                const QRectF &oldGeometry)
{
    Q_Q(QQuickListView);
 
    QQuickItemViewPrivate::itemGeometryChanged(item, change, oldGeometry);
    if (!q->isComponentComplete())
        return;
 
    if (currentItem && currentItem->item == item) {
        const bool contentFlowReversed = isContentFlowReversed();
        const qreal pos = position();
        const qreal sz = size();
        const qreal from = contentFlowReversed ? -pos - displayMarginBeginning - sz : pos - displayMarginBeginning;
        const qreal to = contentFlowReversed ? -pos + displayMarginEnd : pos + sz + displayMarginEnd;
        QQuickItemPrivate::get(currentItem->item)->setCulled(currentItem->endPosition() < from || currentItem->position() > to);
    }
 
    if (item != contentItem && (!highlight || item != highlight->item)) {
        if ((orient == QQuickListView::Vertical && change.heightChange())
            || (orient == QQuickListView::Horizontal && change.widthChange())) {
 
            // if visibleItems.first() has resized, adjust its pos since it is used to
            // position all subsequent items
            if (visibleItems.size() && item == visibleItems.constFirst()->item) {
                FxListItemSG *listItem = static_cast<FxListItemSG*>(visibleItems.constFirst());
#if QT_CONFIG(quick_viewtransitions)
                if (listItem->transitionScheduledOrRunning())
                    return;
#endif
                if (orient == QQuickListView::Vertical) {
                    const qreal oldItemEndPosition = verticalLayoutDirection == QQuickItemView::BottomToTop ? -oldGeometry.y() : oldGeometry.y() + oldGeometry.height();
                    const qreal heightDiff = item->height() - oldGeometry.height();
                    if (verticalLayoutDirection == QQuickListView::TopToBottom && oldItemEndPosition < q->contentY())
                        listItem->setPosition(listItem->position() - heightDiff, true);
                    else if (verticalLayoutDirection == QQuickListView::BottomToTop && oldItemEndPosition > q->contentY())
                        listItem->setPosition(listItem->position() + heightDiff, true);
                } else {
                    const qreal oldItemEndPosition = q->effectiveLayoutDirection() == Qt::RightToLeft ? -oldGeometry.x() : oldGeometry.x() + oldGeometry.width();
                    const qreal widthDiff = item->width() - oldGeometry.width();
                    if (q->effectiveLayoutDirection() == Qt::LeftToRight && oldItemEndPosition < q->contentX())
                        listItem->setPosition(listItem->position() - widthDiff, true);
                    else if (q->effectiveLayoutDirection() == Qt::RightToLeft && oldItemEndPosition > q->contentX())
                        listItem->setPosition(listItem->position() + widthDiff, true);
                }
            }
            forceLayoutPolish();
        }
    }
}
 
void QQuickListViewPrivate::fixupPosition()
{
    if (orient == QQuickListView::Vertical)
        fixupY();
    else
        fixupX();
}
 
void QQuickListViewPrivate::fixup(AxisData &data, qreal minExtent, qreal maxExtent)
{
    if (orient == QQuickListView::Horizontal && &data == &vData) {
        if (flickableDirection != QQuickFlickable::HorizontalFlick)
            QQuickItemViewPrivate::fixup(data, minExtent, maxExtent);
        return;
    } else if (orient == QQuickListView::Vertical && &data == &hData) {
        if (flickableDirection != QQuickFlickable::VerticalFlick)
            QQuickItemViewPrivate::fixup(data, minExtent, maxExtent);
        return;
    }
 
    // update footer if all visible items have been removed
    if (visibleItems.size() == 0)
        updateFooter();
 
    correctFlick = false;
    fixupMode = moveReason == Mouse ? fixupMode : Immediate;
    bool strictHighlightRange = haveHighlightRange && highlightRange == QQuickListView::StrictlyEnforceRange;
 
    qreal viewPos = isContentFlowReversed() ? -position()-size() : position();
 
    if (snapMode != QQuickListView::NoSnap && moveReason != QQuickListViewPrivate::SetIndex) {
        qreal tempPosition = isContentFlowReversed() ? -position()-size() : position();
        if (snapMode == QQuickListView::SnapOneItem && moveReason == Mouse) {
            // if we've been dragged < averageSize/2 then bias towards the next item
            qreal dist = data.move.value() - data.pressPos;
            qreal bias = 0;
            if (data.velocity > 0 && dist > QML_FLICK_SNAPONETHRESHOLD && dist < averageSize/2)
                bias = averageSize/2;
            else if (data.velocity < 0 && dist < -QML_FLICK_SNAPONETHRESHOLD && dist > -averageSize/2)
                bias = -averageSize/2;
            if (isContentFlowReversed())
                bias = -bias;
            tempPosition -= bias;
        }
 
        qreal snapOffset = 0;
        qreal overlayHeaderOffset = 0;
        bool isHeaderWithinBounds = false;
        if (header) {
            qreal visiblePartOfHeader = header->position() + header->size() - tempPosition;
            isHeaderWithinBounds = visiblePartOfHeader > 0;
            switch (headerPositioning) {
            case QQuickListView::OverlayHeader:
                snapOffset = header->size();
                overlayHeaderOffset = header->size();
                break;
            case QQuickListView::InlineHeader:
                if (isHeaderWithinBounds && tempPosition < originPosition())
                    // For the inline header, we want to snap to the first item
                    // if we're more than halfway down the inline header.
                    // So if we look for an item halfway down of the header
                    snapOffset = header->size() / 2;
                break;
            case QQuickListView::PullBackHeader:
                desiredHeaderVisible = visiblePartOfHeader > header->size()/2;
                if (qFuzzyCompare(header->position(), tempPosition)) {
                    // header was pulled down; make sure it remains visible and snap items to bottom of header
                    snapOffset = header->size();
                } else if (desiredHeaderVisible) {
                    // More than 50% of the header is shown. Show it fully.
                    // Scroll the view so the next item snaps to the header.
                    snapOffset = header->size();
                    overlayHeaderOffset = header->size();
                }
                break;
            }
        }
        FxViewItem *topItem = snapItemAt(tempPosition + snapOffset + highlightRangeStart);
        if (strictHighlightRange && currentItem && (!topItem || (topItem->index != currentIndex && fixupMode == Immediate))) {
            // StrictlyEnforceRange always keeps an item in range
            updateHighlight();
            topItem = currentItem;
        }
        FxViewItem *bottomItem = snapItemAt(tempPosition + snapOffset + highlightRangeEnd);
        if (strictHighlightRange && currentItem && (!bottomItem || (bottomItem->index != currentIndex && fixupMode == Immediate))) {
            // StrictlyEnforceRange always keeps an item in range
            updateHighlight();
            bottomItem = currentItem;
        }
        qreal pos = 0;
        bool isInBounds = -position() > maxExtent && -position() <= minExtent;
 
        if (header && !topItem && isInBounds) {
            // We are trying to pull back further than needed
            switch (headerPositioning) {
            case QQuickListView::OverlayHeader:
                pos = startPosition() - overlayHeaderOffset;
                break;
            case QQuickListView::InlineHeader:
                pos = isContentFlowReversed() ? header->size() - size() : header->position();
                break;
            case QQuickListView::PullBackHeader:
                pos = isContentFlowReversed() ? -size() : startPosition();
                break;
            }
        } else if (topItem && (isInBounds || strictHighlightRange)) {
            if (topItem->index == 0 && header && !hasStickyHeader() && tempPosition+highlightRangeStart < header->position()+header->size()/2 && !strictHighlightRange) {
                pos = isContentFlowReversed() ? -header->position() + highlightRangeStart - size() : (header->position() - highlightRangeStart + header->size());
            } else {
                if (header && headerPositioning == QQuickListView::PullBackHeader) {
                    // We pulled down the header. If it isn't pulled all way down, we need to snap
                    // the header.
                    if (qFuzzyCompare(tempPosition, header->position())) {
                        // It is pulled all way down. Scroll-snap the content, but not the header.
                        if (isContentFlowReversed())
                            pos = -static_cast<FxListItemSG*>(topItem)->itemPosition() + highlightRangeStart - size() + snapOffset;
                        else
                            pos = static_cast<FxListItemSG*>(topItem)->itemPosition() - highlightRangeStart - snapOffset;
                    } else {
                        // Header is not pulled all way down, make it completely visible or hide it.
                        // Depends on how much of the header is visible.
                        if (desiredHeaderVisible) {
                            // More than half of the header is visible - show it.
                            // Scroll so that the topItem is aligned to a fully visible header
                            if (isContentFlowReversed())
                                pos = -static_cast<FxListItemSG*>(topItem)->itemPosition() + highlightRangeStart - size() + headerSize();
                            else
                                pos = static_cast<FxListItemSG*>(topItem)->itemPosition() - highlightRangeStart - headerSize();
                        } else {
                            // Less than half is visible - hide the header. Scroll so
                            // that the topItem is aligned to the top of the view
                            if (isContentFlowReversed())
                                pos = -static_cast<FxListItemSG*>(topItem)->itemPosition() + highlightRangeStart - size();
                            else
                                pos = static_cast<FxListItemSG*>(topItem)->itemPosition() - highlightRangeStart;
                        }
                    }
 
                    headerNeedsSeparateFixup = isHeaderWithinBounds || desiredHeaderVisible;
                    if (headerNeedsSeparateFixup) {
                        // We need to animate the header independently if it starts visible or should end as visible,
                        // since the header should not necessarily follow the content.
                        // Store the desired viewport position.
                        // Also store the header position so we know where to animate the header from (fixupHeaderPosition).
                        // We deduce the desired header position from the desiredViewportPosition variable.
                        pos = qBound(-minExtent, pos, -maxExtent);
                        desiredViewportPosition = isContentFlowReversed() ? -pos - size() : pos;
 
                        FxListItemSG *headerItem = static_cast<FxListItemSG*>(header);
                        fixupHeaderPosition = headerItem->position();
 
                        // follow the same fixup timeline
                        QObjectPrivate::connect(&timeline, &QQuickTimeLine::updated, this, &QQuickListViewPrivate::fixupHeader);
                        QObjectPrivate::connect(&timeline, &QQuickTimeLine::completed, this, &QQuickListViewPrivate::fixupHeaderCompleted);
                    }
                } else if (isContentFlowReversed()) {
                    pos = -static_cast<FxListItemSG*>(topItem)->itemPosition() + highlightRangeStart - size() + overlayHeaderOffset;
                } else {
                    pos = static_cast<FxListItemSG*>(topItem)->itemPosition() - highlightRangeStart - overlayHeaderOffset;
                }
            }
        } else if (bottomItem && isInBounds) {
            if (isContentFlowReversed())
                pos = -static_cast<FxListItemSG*>(bottomItem)->itemPosition() + highlightRangeEnd - size() + overlayHeaderOffset;
            else
                pos = static_cast<FxListItemSG*>(bottomItem)->itemPosition() - highlightRangeEnd - overlayHeaderOffset;
        } else {
            QQuickItemViewPrivate::fixup(data, minExtent, maxExtent);
            return;
        }
        pos = qBound(-minExtent, pos, -maxExtent);
 
        qreal dist = qAbs(data.move + pos);
        if (dist >= 0) {
            // Even if dist == 0 we still start the timeline, because we use the same timeline for
            // moving the header. And we might need to move the header while the content does not
            // need moving
            timeline.reset(data.move);
            if (fixupMode != Immediate) {
                timeline.move(data.move, -pos, QEasingCurve(QEasingCurve::InOutQuad), fixupDuration/2);
                data.fixingUp = true;
            } else {
                timeline.set(data.move, -pos);
            }
            vTime = timeline.time();
        }
    } else if (currentItem && strictHighlightRange && moveReason != QQuickListViewPrivate::SetIndex) {
        updateHighlight();
        qreal pos = static_cast<FxListItemSG*>(currentItem)->itemPosition();
        if (viewPos < pos + static_cast<FxListItemSG*>(currentItem)->itemSize() - highlightRangeEnd)
            viewPos = pos + static_cast<FxListItemSG*>(currentItem)->itemSize() - highlightRangeEnd;
        if (viewPos > pos - highlightRangeStart)
            viewPos = pos - highlightRangeStart;
        if (isContentFlowReversed())
            viewPos = -viewPos-size();
 
        timeline.reset(data.move);
        if (viewPos != position()) {
            if (fixupMode != Immediate) {
                if (fixupMode == ExtentChanged && data.fixingUp)
                    timeline.move(data.move, -viewPos, QEasingCurve(QEasingCurve::OutQuad), fixupDuration/2);
                else
                    timeline.move(data.move, -viewPos, QEasingCurve(QEasingCurve::InOutQuad), fixupDuration/2);
                data.fixingUp = true;
            } else {
                timeline.set(data.move, -viewPos);
            }
        }
        vTime = timeline.time();
    } else {
        QQuickItemViewPrivate::fixup(data, minExtent, maxExtent);
    }
    data.inOvershoot = false;
    fixupMode = Normal;
}
 
bool QQuickListViewPrivate::flick(AxisData &data, qreal minExtent, qreal maxExtent, qreal vSize,
                                        QQuickTimeLineCallback::Callback fixupCallback, QEvent::Type eventType, qreal velocity)
{
    data.fixingUp = false;
    moveReason = Mouse;
    if ((!haveHighlightRange || highlightRange != QQuickListView::StrictlyEnforceRange) && snapMode == QQuickListView::NoSnap) {
        correctFlick = true;
        return QQuickItemViewPrivate::flick(data, minExtent, maxExtent, vSize, fixupCallback, eventType, velocity);
    }
    qreal maxDistance = 0;
    const qreal dataValue =
            isContentFlowReversed() ? -data.move.value() + size() : data.move.value();
 
    // -ve velocity means list is moving up/left
    if (velocity > 0) {
        if (data.move.value() < minExtent) {
            if (snapMode == QQuickListView::SnapOneItem && !hData.flicking && !vData.flicking) {
                // averageSize/2 + 1 - next item
                qreal bias = averageSize / 2 + 1 - (pressed ? data.pressPos : 0);
                if (isContentFlowReversed())
                    bias = -bias;
                data.flickTarget = -snapPosAt(-(dataValue - highlightRangeStart) - bias) + highlightRangeStart;
                maxDistance = qAbs(data.flickTarget - data.move.value());
                velocity = maxVelocity;
            } else {
                maxDistance = qAbs(minExtent - data.move.value());
            }
        }
        if (snapMode == QQuickListView::NoSnap && highlightRange != QQuickListView::StrictlyEnforceRange)
            data.flickTarget = minExtent;
    } else {
        if (data.move.value() > maxExtent) {
            if (snapMode == QQuickListView::SnapOneItem && !hData.flicking && !vData.flicking) {
                // averageSize/2 + 1 - next item
                qreal bias = averageSize / 2 + 1 - (pressed ? data.pressPos : 0);
                if (isContentFlowReversed())
                    bias = -bias;
                data.flickTarget =
                        -snapPosAt(-(dataValue - highlightRangeStart) + bias) + highlightRangeStart;
                maxDistance = qAbs(data.flickTarget - data.move.value());
                velocity = -maxVelocity;
            } else {
                maxDistance = qAbs(maxExtent - data.move.value());
            }
        }
        if (snapMode == QQuickListView::NoSnap && highlightRange != QQuickListView::StrictlyEnforceRange)
            data.flickTarget = maxExtent;
    }
    bool overShoot = boundsBehavior & QQuickFlickable::OvershootBounds;
    if (maxDistance > 0 || overShoot) {
        // These modes require the list to stop exactly on an item boundary.
        // The initial flick will estimate the boundary to stop on.
        // Since list items can have variable sizes, the boundary will be
        // reevaluated and adjusted as we approach the boundary.
        qreal v = velocity;
        if (maxVelocity != -1 && maxVelocity < qAbs(v)) {
            if (v < 0)
                v = -maxVelocity;
            else
                v = maxVelocity;
        }
        if (!hData.flicking && !vData.flicking) {
            // the initial flick - estimate boundary
            qreal accel = eventType == QEvent::Wheel ? wheelDeceleration : deceleration;
            qreal v2 = v * v;
            overshootDist = 0.0;
            // + averageSize/4 to encourage moving at least one item in the flick direction
            qreal dist = v2 / (accel * 2.0) + averageSize/4;
            if (maxDistance > 0)
                dist = qMin(dist, maxDistance);
            if (v > 0)
                dist = -dist;
            if ((maxDistance > 0.0 && v2 / (2.0f * maxDistance) < accel) || snapMode == QQuickListView::SnapOneItem) {
                if (snapMode != QQuickListView::SnapOneItem) {
                    qreal distTemp = isContentFlowReversed() ? -dist : dist;
                    data.flickTarget = -snapPosAt(-(dataValue - highlightRangeStart) + distTemp) + highlightRangeStart;
                }
                data.flickTarget = isContentFlowReversed() ? -data.flickTarget+size() : data.flickTarget;
                if (overShoot) {
                    if (data.flickTarget > minExtent) {
                        overshootDist = overShootDistance(vSize);
                        data.flickTarget += overshootDist;
                    } else if (data.flickTarget < maxExtent) {
                        overshootDist = overShootDistance(vSize);
                        data.flickTarget -= overshootDist;
                    }
                }
                qreal adjDist = -data.flickTarget + data.move.value();
                if (qAbs(adjDist) > qAbs(dist)) {
                    // Prevent painfully slow flicking - adjust velocity to suit flickDeceleration
                    qreal adjv2 = accel * 2.0f * qAbs(adjDist);
                    if (adjv2 > v2) {
                        v2 = adjv2;
                        v = qSqrt(v2);
                        if (dist > 0)
                            v = -v;
                    }
                }
                dist = adjDist;
                accel = v2 / (2.0f * qAbs(dist));
            } else if (overShoot) {
                data.flickTarget = data.move.value() - dist;
                if (data.flickTarget > minExtent) {
                    overshootDist = overShootDistance(vSize);
                    data.flickTarget += overshootDist;
                } else if (data.flickTarget < maxExtent) {
                    overshootDist = overShootDistance(vSize);
                    data.flickTarget -= overshootDist;
                }
            }
            timeline.reset(data.move);
            timeline.accel(data.move, v, accel, maxDistance + overshootDist);
            timeline.callback(QQuickTimeLineCallback(&data.move, fixupCallback, this));
            correctFlick = true;
            return true;
        } else {
            // reevaluate the target boundary.
            qreal newtarget = data.flickTarget;
            if (snapMode != QQuickListView::NoSnap || highlightRange == QQuickListView::StrictlyEnforceRange) {
                qreal tempFlickTarget = isContentFlowReversed() ? -data.flickTarget+size() : data.flickTarget;
                newtarget = -snapPosAt(-(tempFlickTarget - highlightRangeStart)) + highlightRangeStart;
                newtarget = isContentFlowReversed() ? -newtarget+size() : newtarget;
            }
            if (velocity < 0 && newtarget <= maxExtent)
                newtarget = maxExtent - overshootDist;
            else if (velocity > 0 && newtarget >= minExtent)
                newtarget = minExtent + overshootDist;
            if (newtarget == data.flickTarget) { // boundary unchanged - nothing to do
                if (qAbs(velocity) < _q_MinimumFlickVelocity)
                    correctFlick = false;
                return false;
            }
            data.flickTarget = newtarget;
            qreal dist = -newtarget + data.move.value();
            if ((v < 0 && dist < 0) || (v > 0 && dist > 0)) {
                correctFlick = false;
                timeline.reset(data.move);
                fixup(data, minExtent, maxExtent);
                return false;
            }
            timeline.reset(data.move);
            timeline.accelDistance(data.move, v, -dist);
            timeline.callback(QQuickTimeLineCallback(&data.move, fixupCallback, this));
            return false;
        }
    } else {
        correctFlick = false;
        timeline.reset(data.move);
        fixup(data, minExtent, maxExtent);
        return false;
    }
}
 
void QQuickListViewPrivate::setSectionHelper(QQmlContext *context, QQuickItem *sectionItem, const QString &section)
{
    if (!QQmlContextData::get(context)->isInternal() && context->contextProperty(QLatin1String("section")).isValid())
        context->setContextProperty(QLatin1String("section"), section);
    else
        sectionItem->setProperty("section", section);
}
 
QQuickItemViewAttached *QQuickListViewPrivate::getAttachedObject(const QObject *object) const
{
    QObject *attachedObject = qmlAttachedPropertiesObject<QQuickListView>(object);
    return static_cast<QQuickItemViewAttached *>(attachedObject);
}
 
//----------------------------------------------------------------------------
 
QQuickListView::QQuickListView(QQuickItem *parent)
    : QQuickItemView(*(new QQuickListViewPrivate), parent)
{
}
 
QQuickListView::~QQuickListView()
{
}
 
//###Possibly rename these properties, since they are very useful even without a highlight?
void QQuickListView::setHighlightFollowsCurrentItem(bool autoHighlight)
{
    Q_D(QQuickListView);
    if (d->autoHighlight != autoHighlight) {
        if (!autoHighlight) {
            if (d->highlightPosAnimator)
                d->highlightPosAnimator->stop();
            if (d->highlightWidthAnimator)
                d->highlightWidthAnimator->stop();
            if (d->highlightHeightAnimator)
                d->highlightHeightAnimator->stop();
        }
        QQuickItemView::setHighlightFollowsCurrentItem(autoHighlight);
    }
}
 
qreal QQuickListView::spacing() const
{
    Q_D(const QQuickListView);
    return d->spacing;
}
 
void QQuickListView::setSpacing(qreal spacing)
{
    Q_D(QQuickListView);
    if (spacing != d->spacing) {
        d->spacing = spacing;
        d->forceLayoutPolish();
        emit spacingChanged();
    }
}
 
QQuickListView::Orientation QQuickListView::orientation() const
{
    Q_D(const QQuickListView);
    return d->orient;
}
 
void QQuickListView::setOrientation(QQuickListView::Orientation orientation)
{
    Q_D(QQuickListView);
    if (d->orient != orientation) {
        d->orient = orientation;
        if (d->orient == Vertical) {
            if (d->flickableDirection == HorizontalFlick) {
                setFlickableDirection(VerticalFlick);
                if (isComponentComplete())
                    setContentWidth(-1);
            }
            setContentX(0);
        } else {
            if (d->flickableDirection == VerticalFlick) {
                setFlickableDirection(HorizontalFlick);
                if (isComponentComplete())
                    setContentHeight(-1);
            }
            setContentY(0);
        }
        d->regenerate(true);
        emit orientationChanged();
    }
}
 
QQuickViewSection *QQuickListView::sectionCriteria()
{
    Q_D(QQuickListView);
    if (!d->sectionCriteria)
        d->sectionCriteria = new QQuickViewSection(this);
    return d->sectionCriteria;
}
 
QString QQuickListView::currentSection() const
{
    Q_D(const QQuickListView);
    return d->currentSection;
}
 
qreal QQuickListView::highlightMoveVelocity() const
{
    Q_D(const QQuickListView);
    return d->highlightMoveVelocity;
}
 
void QQuickListView::setHighlightMoveVelocity(qreal speed)
{
    Q_D(QQuickListView);
    if (d->highlightMoveVelocity != speed) {
        d->highlightMoveVelocity = speed;
        if (d->highlightPosAnimator)
            d->highlightPosAnimator->velocity = d->highlightMoveVelocity;
        emit highlightMoveVelocityChanged();
    }
}
 
void QQuickListView::setHighlightMoveDuration(int duration)
{
    Q_D(QQuickListView);
    if (d->highlightMoveDuration != duration) {
        if (d->highlightPosAnimator)
            d->highlightPosAnimator->userDuration = duration;
        QQuickItemView::setHighlightMoveDuration(duration);
    }
}
 
qreal QQuickListView::highlightResizeVelocity() const
{
    Q_D(const QQuickListView);
    return d->highlightResizeVelocity;
}
 
void QQuickListView::setHighlightResizeVelocity(qreal speed)
{
    Q_D(QQuickListView);
    if (d->highlightResizeVelocity != speed) {
        d->highlightResizeVelocity = speed;
        if (d->highlightWidthAnimator)
            d->highlightWidthAnimator->velocity = d->highlightResizeVelocity;
        if (d->highlightHeightAnimator)
            d->highlightHeightAnimator->velocity = d->highlightResizeVelocity;
        emit highlightResizeVelocityChanged();
    }
}
 
int QQuickListView::highlightResizeDuration() const
{
    Q_D(const QQuickListView);
    return d->highlightResizeDuration;
}
 
void QQuickListView::setHighlightResizeDuration(int duration)
{
    Q_D(QQuickListView);
    if (d->highlightResizeDuration != duration) {
        d->highlightResizeDuration = duration;
        if (d->highlightWidthAnimator)
            d->highlightWidthAnimator->userDuration = d->highlightResizeDuration;
        if (d->highlightHeightAnimator)
            d->highlightHeightAnimator->userDuration = d->highlightResizeDuration;
        emit highlightResizeDurationChanged();
    }
}
 
QQuickListView::SnapMode QQuickListView::snapMode() const
{
    Q_D(const QQuickListView);
    return d->snapMode;
}
 
void QQuickListView::setSnapMode(SnapMode mode)
{
    Q_D(QQuickListView);
    if (d->snapMode != mode) {
        d->snapMode = mode;
        emit snapModeChanged();
        d->fixupPosition();
    }
}
 
 
QQuickListView::HeaderPositioning QQuickListView::headerPositioning() const
{
    Q_D(const QQuickListView);
    return d->headerPositioning;
}
 
void QQuickListView::setHeaderPositioning(QQuickListView::HeaderPositioning positioning)
{
    Q_D(QQuickListView);
    if (d->headerPositioning != positioning) {
        d->applyPendingChanges();
        d->headerPositioning = positioning;
        if (isComponentComplete()) {
            d->updateHeader();
            d->updateViewport();
            d->fixupPosition();
        }
        emit headerPositioningChanged();
    }
}
 
QQuickListView::FooterPositioning QQuickListView::footerPositioning() const
{
    Q_D(const QQuickListView);
    return d->footerPositioning;
}
 
void QQuickListView::setFooterPositioning(QQuickListView::FooterPositioning positioning)
{
    Q_D(QQuickListView);
    if (d->footerPositioning != positioning) {
        d->applyPendingChanges();
        d->footerPositioning = positioning;
        if (isComponentComplete()) {
            d->updateFooter();
            d->updateViewport();
            d->fixupPosition();
        }
        emit footerPositioningChanged();
    }
}
 
void QQuickListView::viewportMoved(Qt::Orientations orient)
{
    Q_D(QQuickListView);
    QQuickItemView::viewportMoved(orient);
 
    if (!d->itemCount) {
        if (d->hasStickyHeader())
            d->updateHeader();
        if (d->hasStickyFooter())
            d->updateFooter();
        return;
    }
 
    // Recursion can occur due to refill changing the content size.
    if (d->inViewportMoved)
        return;
    d->inViewportMoved = true;
 
    if (yflick()) {
        if (d->isBottomToTop())
            d->bufferMode = d->vData.smoothVelocity < 0 ? QQuickListViewPrivate::BufferAfter : QQuickListViewPrivate::BufferBefore;
        else
            d->bufferMode = d->vData.smoothVelocity < 0 ? QQuickListViewPrivate::BufferBefore : QQuickListViewPrivate::BufferAfter;
    } else {
        if (d->isRightToLeft())
            d->bufferMode = d->hData.smoothVelocity < 0 ? QQuickListViewPrivate::BufferAfter : QQuickListViewPrivate::BufferBefore;
        else
            d->bufferMode = d->hData.smoothVelocity < 0 ? QQuickListViewPrivate::BufferBefore : QQuickListViewPrivate::BufferAfter;
    }
 
    d->refillOrLayout();
 
    // Set visibility of items to eliminate cost of items outside the visible area.
    qreal from = d->isContentFlowReversed() ? -d->position()-d->displayMarginBeginning-d->size() : d->position()-d->displayMarginBeginning;
    qreal to = d->isContentFlowReversed() ? -d->position()+d->displayMarginEnd : d->position()+d->size()+d->displayMarginEnd;
    for (FxViewItem *item : std::as_const(d->visibleItems)) {
        if (item->item)
            QQuickItemPrivate::get(item->item)->setCulled(item->endPosition() < from || item->position() > to);
    }
    if (d->currentItem)
        QQuickItemPrivate::get(d->currentItem->item)->setCulled(d->currentItem->endPosition() < from || d->currentItem->position() > to);
 
    if (d->hData.flicking || d->vData.flicking || d->hData.moving || d->vData.moving)
        d->moveReason = QQuickListViewPrivate::Mouse;
    if (d->moveReason != QQuickListViewPrivate::SetIndex) {
        if (d->haveHighlightRange && d->highlightRange == StrictlyEnforceRange && d->highlight) {
            // reposition highlight
            qreal pos = d->highlight->position();
            qreal viewPos = d->isContentFlowReversed() ? -d->position()-d->size() : d->position();
            if (pos > viewPos + d->highlightRangeEnd - d->highlight->size())
                pos = viewPos + d->highlightRangeEnd - d->highlight->size();
            if (pos < viewPos + d->highlightRangeStart)
                pos = viewPos + d->highlightRangeStart;
            if (pos != d->highlight->position()) {
                d->highlightPosAnimator->stop();
                static_cast<FxListItemSG*>(d->highlight.get())->setPosition(pos);
            } else {
                d->updateHighlight();
            }
 
            // update current index
            if (FxViewItem *snapItem = d->snapItemAt(d->highlight->position())) {
                if (snapItem->index >= 0 && snapItem->index != d->currentIndex)
                    d->updateCurrent(snapItem->index);
            }
        }
    }
 
    if ((d->hData.flicking || d->vData.flicking) && d->correctFlick && !d->inFlickCorrection) {
        d->inFlickCorrection = true;
        // Near an end and it seems that the extent has changed?
        // Recalculate the flick so that we don't end up in an odd position.
        if (yflick() && !d->vData.inOvershoot) {
            if (d->vData.velocity > 0) {
                const qreal minY = minYExtent();
                if ((minY - d->vData.move.value() < height()/2 || d->vData.flickTarget - d->vData.move.value() < height()/2)
                    && minY != d->vData.flickTarget)
                    d->flickY(QEvent::TouchUpdate, -d->vData.smoothVelocity.value());
            } else if (d->vData.velocity < 0) {
                const qreal maxY = maxYExtent();
                if ((d->vData.move.value() - maxY < height()/2 || d->vData.move.value() - d->vData.flickTarget < height()/2)
                    && maxY != d->vData.flickTarget)
                    d->flickY(QEvent::TouchUpdate, -d->vData.smoothVelocity.value());
            }
        }
 
        if (xflick() && !d->hData.inOvershoot) {
            if (d->hData.velocity > 0) {
                const qreal minX = minXExtent();
                if ((minX - d->hData.move.value() < width()/2 || d->hData.flickTarget - d->hData.move.value() < width()/2)
                    && minX != d->hData.flickTarget)
                    d->flickX(QEvent::TouchUpdate, -d->hData.smoothVelocity.value());
            } else if (d->hData.velocity < 0) {
                const qreal maxX = maxXExtent();
                if ((d->hData.move.value() - maxX < width()/2 || d->hData.move.value() - d->hData.flickTarget < width()/2)
                    && maxX != d->hData.flickTarget)
                    d->flickX(QEvent::TouchUpdate, -d->hData.smoothVelocity.value());
            }
        }
        d->inFlickCorrection = false;
    }
    if (d->hasStickyHeader())
        d->updateHeader();
    if (d->hasStickyFooter())
        d->updateFooter();
    if (d->sectionCriteria) {
        d->updateCurrentSection();
        d->updateStickySections();
    }
    d->inViewportMoved = false;
}
 
void QQuickListView::keyPressEvent(QKeyEvent *event)
{
    Q_D(QQuickListView);
    if (d->model && d->model->count() && ((d->interactive && !d->explicitKeyNavigationEnabled)
        || (d->explicitKeyNavigationEnabled && d->keyNavigationEnabled))) {
        if ((d->orient == QQuickListView::Horizontal && !d->isRightToLeft() && event->key() == Qt::Key_Left)
                    || (d->orient == QQuickListView::Horizontal && d->isRightToLeft() && event->key() == Qt::Key_Right)
                    || (d->orient == QQuickListView::Vertical && !d->isBottomToTop() && event->key() == Qt::Key_Up)
                    || (d->orient == QQuickListView::Vertical && d->isBottomToTop() && event->key() == Qt::Key_Down)) {
            if (currentIndex() > 0 || (d->wrap && !event->isAutoRepeat())) {
                decrementCurrentIndex();
                event->accept();
                return;
            } else if (d->wrap) {
                event->accept();
                return;
            }
        } else if ((d->orient == QQuickListView::Horizontal && !d->isRightToLeft() && event->key() == Qt::Key_Right)
                    || (d->orient == QQuickListView::Horizontal && d->isRightToLeft() && event->key() == Qt::Key_Left)
                   || (d->orient == QQuickListView::Vertical && !d->isBottomToTop() && event->key() == Qt::Key_Down)
                   || (d->orient == QQuickListView::Vertical && d->isBottomToTop() && event->key() == Qt::Key_Up)) {
            if (currentIndex() < d->model->count() - 1 || (d->wrap && !event->isAutoRepeat())) {
                incrementCurrentIndex();
                event->accept();
                return;
            } else if (d->wrap) {
                event->accept();
                return;
            }
        }
    }
    event->ignore();
    QQuickItemView::keyPressEvent(event);
}
 
void QQuickListView::geometryChange(const QRectF &newGeometry, const QRectF &oldGeometry)
{
    Q_D(QQuickListView);
 
    if (d->model) {
        // When the view changes size, we force the pool to
        // shrink by releasing all pooled items.
        d->model->drainReusableItemsPool(0);
    }
 
    if (d->isRightToLeft()) {
        // maintain position relative to the right edge
        qreal dx = newGeometry.width() - oldGeometry.width();
        setContentX(contentX() - dx);
    } else if (d->isBottomToTop()) {
        // maintain position relative to the bottom edge
        qreal dy = newGeometry.height() - oldGeometry.height();
        setContentY(contentY() - dy);
    }
    QQuickItemView::geometryChange(newGeometry, oldGeometry);
}
 
void QQuickListView::initItem(int index, QObject *object)
{
    QQuickItemView::initItem(index, object);
 
    // setting the view from the FxViewItem wrapper is too late if the delegate
    // needs access to the view in Component.onCompleted
    QQuickItem *item = qmlobject_cast<QQuickItem*>(object);
    if (item) {
        QQuickListViewAttached *attached = static_cast<QQuickListViewAttached *>(
                qmlAttachedPropertiesObject<QQuickListView>(item));
        if (attached)
            attached->setView(this);
    }
}
 
qreal QQuickListView::maxYExtent() const
{
    Q_D(const QQuickListView);
    if (d->layoutOrientation() == Qt::Horizontal && d->flickableDirection != HorizontalFlick)
        return QQuickFlickable::maxYExtent();
    return QQuickItemView::maxYExtent();
}
 
qreal QQuickListView::maxXExtent() const
{
    Q_D(const QQuickListView);
    if (d->layoutOrientation() == Qt::Vertical && d->flickableDirection != VerticalFlick)
        return QQuickFlickable::maxXExtent();
    return QQuickItemView::maxXExtent();
}
 
void QQuickListView::incrementCurrentIndex()
{
    Q_D(QQuickListView);
    int count = d->model ? d->model->count() : 0;
    if (count && (currentIndex() < count - 1 || d->wrap)) {
        d->moveReason = QQuickListViewPrivate::SetIndex;
        int index = currentIndex()+1;
        setCurrentIndex((index >= 0 && index < count) ? index : 0);
    }
}
 
void QQuickListView::decrementCurrentIndex()
{
    Q_D(QQuickListView);
    int count = d->model ? d->model->count() : 0;
    if (count && (currentIndex() > 0 || d->wrap)) {
        d->moveReason = QQuickListViewPrivate::SetIndex;
        int index = currentIndex()-1;
        setCurrentIndex((index >= 0 && index < count) ? index : count-1);
    }
}
 
void QQuickListViewPrivate::updateSectionCriteria()
{
    Q_Q(QQuickListView);
    if (q->isComponentComplete() && model) {
        QList<QByteArray> roles;
        if (sectionCriteria && !sectionCriteria->property().isEmpty())
            roles << sectionCriteria->property().toUtf8();
        model->setWatchedRoles(roles);
        updateSections();
        if (itemCount)
            forceLayoutPolish();
    }
}
 
bool QQuickListViewPrivate::applyInsertionChange(const QQmlChangeSet::Change &change, ChangeResult *insertResult, QList<FxViewItem *> *addedItems, QList<MovedItem> *movingIntoView)
{
    Q_Q(QQuickListView);
#if QT_CONFIG(quick_viewtransitions)
    Q_UNUSED(movingIntoView)
#endif
    int modelIndex = change.index;
    int count = change.count;
 
    if (q->size().isEmpty() && visibleItems.isEmpty())
        return false;
 
    qreal tempPos = isContentFlowReversed() ? -position()-size() : position();
    int index = visibleItems.size() ? mapFromModel(modelIndex) : 0;
    qreal lastVisiblePos = buffer + displayMarginEnd + tempPos + size();
 
    if (index < 0) {
        int i = visibleItems.size() - 1;
        while (i > 0 && visibleItems.at(i)->index == -1)
            --i;
        if (i == 0 && visibleItems.constFirst()->index == -1) {
            // there are no visible items except items marked for removal
            index = visibleItems.size();
        } else if (visibleItems.at(i)->index + 1 == modelIndex
            && visibleItems.at(i)->endPosition() <= lastVisiblePos) {
            // Special case of appending an item to the model.
            index = visibleItems.size();
        } else {
            if (modelIndex < visibleIndex) {
                // Insert before visible items
                visibleIndex += count;
                for (FxViewItem *item : std::as_const(visibleItems)) {
                    if (item->index != -1 && item->index >= modelIndex)
                        item->index += count;
                }
            }
            return true;
        }
    }
 
    // index can be the next item past the end of the visible items list (i.e. appended)
    qreal pos = 0;
    if (visibleItems.size()) {
        pos = index < visibleItems.size() ? visibleItems.at(index)->position()
                                                : visibleItems.constLast()->endPosition() + spacing;
    }
 
    // Update the indexes of the following visible items.
    for (FxViewItem *item : std::as_const(visibleItems)) {
        if (item->index != -1 && item->index >= modelIndex) {
            item->index += count;
#if QT_CONFIG(quick_viewtransitions)
            if (change.isMove())
                item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::MoveTransition, false);
            else
                item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, false);
#endif
        }
    }
 
    bool visibleAffected = false;
    if (insertResult->visiblePos.isValid() && pos < insertResult->visiblePos) {
        // Insert items before the visible item.
        int insertionIdx = index;
        qreal from = tempPos - displayMarginBeginning - buffer;
 
        if (insertionIdx < visibleIndex) {
            if (pos >= from) {
                // items won't be visible, just note the size for repositioning
                insertResult->sizeChangesBeforeVisiblePos += count * (averageSize + spacing);
            }
        } else {
            MutableModelIterator it(model, modelIndex + count - 1, modelIndex -1);
            for (; it.hasNext() && pos >= from; it.next()) {
                // item is before first visible e.g. in cache buffer
                FxViewItem *item = nullptr;
                if (change.isMove() && (item = currentChanges.removedItems.take(change.moveKey(it.index))))
                    item->index = it.index;
                if (!item)
                    item = createItem(it.index, QQmlIncubator::Synchronous);
                if (!item)
                    return false;
                if (it.removedAtIndex)
                    continue;
 
                visibleAffected = true;
                visibleItems.insert(insertionIdx, item);
                if (insertionIdx == 0)
                    insertResult->changedFirstItem = true;
                if (!change.isMove()) {
                    addedItems->append(item);
#if QT_CONFIG(quick_viewtransitions)
                    if (transitioner)
                        item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, true);
                    else
#endif
                        static_cast<FxListItemSG *>(item)->setPosition(pos, true);
                }
                insertResult->sizeChangesBeforeVisiblePos += item->size() + spacing;
                pos -= item->size() + spacing;
                index++;
            }
        }
 
        int firstOkIdx = -1;
        for (int i = 0; i <= insertionIdx && i < visibleItems.size() - 1; i++) {
            if (visibleItems.at(i)->index + 1 != visibleItems.at(i + 1)->index) {
                firstOkIdx = i + 1;
                break;
            }
        }
        for (int i = 0; i < firstOkIdx; i++) {
            FxViewItem *nvItem = visibleItems.takeFirst();
            addedItems->removeOne(nvItem);
            removeItem(nvItem);
        }
 
    } else {
        MutableModelIterator it(model, modelIndex, modelIndex + count);
        for (; it.hasNext() && pos <= lastVisiblePos; it.next()) {
            visibleAffected = true;
            FxViewItem *item = nullptr;
            if (change.isMove() && (item = currentChanges.removedItems.take(change.moveKey(it.index))))
                item->index = it.index;
#if QT_CONFIG(quick_viewtransitions)
            bool newItem = !item;
#endif
            it.removedAtIndex = false;
            if (!item)
                item = createItem(it.index, QQmlIncubator::Synchronous);
            if (!item)
                return false;
            if (it.removedAtIndex) {
                releaseItem(item, reusableFlag);
                continue;
            }
 
            visibleItems.insert(index, item);
            if (index == 0)
                insertResult->changedFirstItem = true;
            if (change.isMove()) {
                // we know this is a move target, since move displaced items that are
                // shuffled into view due to a move would be added in refill()
#if QT_CONFIG(quick_viewtransitions)
                if (newItem && transitioner && transitioner->canTransition(QQuickItemViewTransitioner::MoveTransition, true))
                    movingIntoView->append(MovedItem(item, change.moveKey(item->index)));
#endif
            } else {
                addedItems->append(item);
#if QT_CONFIG(quick_viewtransitions)
                if (transitioner)
                    item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, true);
                else
#endif
                    static_cast<FxListItemSG *>(item)->setPosition(pos, true);
            }
            insertResult->sizeChangesAfterVisiblePos += item->size() + spacing;
            pos += item->size() + spacing;
            ++index;
        }
        it.disconnect();
 
        if (0 < index && index < visibleItems.size()) {
            FxViewItem *prevItem = visibleItems.at(index - 1);
            FxViewItem *item = visibleItems.at(index);
            if (prevItem->index != item->index - 1) {
                int i = index;
#if QT_CONFIG(quick_viewtransitions)
                qreal prevPos = prevItem->position();
#endif
                while (i < visibleItems.size()) {
                    FxListItemSG *nvItem = static_cast<FxListItemSG *>(visibleItems.takeLast());
                    insertResult->sizeChangesAfterVisiblePos -= nvItem->size() + spacing;
                    addedItems->removeOne(nvItem);
#if QT_CONFIG(quick_viewtransitions)
                    if (nvItem->transitionScheduledOrRunning())
                        nvItem->setPosition(prevPos + (nvItem->index - prevItem->index) * averageSize);
#endif
                    removeItem(nvItem);
                }
            }
        }
    }
 
    updateVisibleIndex();
 
    return visibleAffected;
}
 
#if QT_CONFIG(quick_viewtransitions)
void QQuickListViewPrivate::translateAndTransitionItemsAfter(int afterModelIndex, const ChangeResult &insertionResult, const ChangeResult &removalResult)
{
    Q_UNUSED(insertionResult);
 
    if (!transitioner)
        return;
 
    int markerItemIndex = -1;
    for (int i=0; i<visibleItems.size(); i++) {
        if (visibleItems.at(i)->index == afterModelIndex) {
            markerItemIndex = i;
            break;
        }
    }
    if (markerItemIndex < 0)
        return;
 
    const qreal viewEndPos = isContentFlowReversed() ? -position() : position() + size();
    qreal sizeRemoved = -removalResult.sizeChangesAfterVisiblePos
            - (removalResult.countChangeAfterVisibleItems * (averageSize + spacing));
 
    for (int i=markerItemIndex+1; i<visibleItems.size(); i++) {
        FxListItemSG *listItem = static_cast<FxListItemSG *>(visibleItems.at(i));
        if (listItem->position() >= viewEndPos)
            break;
        if (!listItem->transitionScheduledOrRunning()) {
            qreal pos = listItem->position();
            listItem->setPosition(pos - sizeRemoved);
            listItem->transitionNextReposition(transitioner, QQuickItemViewTransitioner::RemoveTransition, false);
            listItem->setPosition(pos);
        }
    }
}
#endif
 
QQuickListViewAttached *QQuickListView::qmlAttachedProperties(QObject *obj)
{
    return new QQuickListViewAttached(obj);
}
 
bool QQuickListViewPrivate::wantsPointerEvent(const QPointerEvent *event)
{
    Q_Q(const QQuickListView);
    bool ret = true;
 
    QPointF pos = event->points().first().position();
    if (!pos.isNull()) {
        if (auto header = q->headerItem()) {
            if (q->headerPositioning() != QQuickListView::InlineHeader &&
                    header->contains(q->mapToItem(header, pos)))
                ret = false;
        }
        if (auto footer = q->footerItem()) {
            if (q->footerPositioning() != QQuickListView::InlineFooter &&
                    footer->contains(q->mapToItem(footer, pos)))
                ret = false;
        }
    }
 
    switch (event->type()) {
    case QEvent::MouseButtonPress:
        wantedMousePress = ret;
        break;
    case QEvent::MouseMove:
        ret = wantedMousePress;
        break;
    default:
        break;
    }
 
    qCDebug(lcEvents) << q << (ret ? "WANTS" : "DOESN'T want") << event;
    return ret;
}
 
QT_END_NAMESPACE
 
#include "moc_qquicklistview_p.cpp"