qquickgridview.cpp

/****************************************************************************
**
** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/
**
** This file is part of the QtQml module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** GNU Lesser General Public License Usage
** This file may be used under the terms of the GNU Lesser General Public
** License version 2.1 as published by the Free Software Foundation and
** appearing in the file LICENSE.LGPL included in the packaging of this
** file. Please review the following information to ensure the GNU Lesser
** General Public License version 2.1 requirements will be met:
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU General
** Public License version 3.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of this
** file. Please review the following information to ensure the GNU General
** Public License version 3.0 requirements will be met:
** http://www.gnu.org/copyleft/gpl.html.
**
** Other Usage
** Alternatively, this file may be used in accordance with the terms and
** conditions contained in a signed written agreement between you and Nokia.
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qquickgridview_p.h"
#include "qquickvisualitemmodel_p.h"
#include "qquickflickable_p_p.h"
#include "qquickitemview_p_p.h"

#include <private/qquicksmoothedanimation_p_p.h>
#include <private/qlistmodelinterface_p.h>

#include <QtGui/qevent.h>
#include <QtCore/qmath.h>
#include <QtCore/qcoreapplication.h>
#include <math.h>
#include "qplatformdefs.h"

QT_BEGIN_NAMESPACE

#ifndef QML_FLICK_SNAPONETHRESHOLD
#define QML_FLICK_SNAPONETHRESHOLD 30
#endif

//#define DEBUG_DELEGATE_LIFECYCLE

//----------------------------------------------------------------------------

class FxGridItemSG : public FxViewItem
{
public:
    FxGridItemSG(QQuickItem *i, QQuickGridView *v, bool own, bool trackGeometry) : FxViewItem(i, own, trackGeometry), view(v) {
        attached = static_cast<QQuickGridViewAttached*>(qmlAttachedPropertiesObject<QQuickGridView>(item));
        if (attached)
            static_cast<QQuickGridViewAttached*>(attached)->setView(view);
        if (trackGeometry) {
            QQuickItemPrivate *itemPrivate = QQuickItemPrivate::get(item);
            itemPrivate->addItemChangeListener(QQuickItemViewPrivate::get(view), QQuickItemPrivate::Geometry);
        }
    }

    ~FxGridItemSG() {
        if (trackGeom) {
            QQuickItemPrivate *itemPrivate = QQuickItemPrivate::get(item);
            itemPrivate->removeItemChangeListener(QQuickItemViewPrivate::get(view), QQuickItemPrivate::Geometry);
        }
    }

    qreal position() const {
        return rowPos();
    }

    qreal endPosition() const {
        return endRowPos();
    }

    qreal size() const {
        return view->flow() == QQuickGridView::LeftToRight ? view->cellHeight() : view->cellWidth();
    }

    qreal sectionSize() const {
        return 0.0;
    }

    qreal rowPos() const {
        if (view->flow() == QQuickGridView::LeftToRight)
            return itemY();
        else
            return (view->effectiveLayoutDirection() == Qt::RightToLeft ? -view->cellWidth()-itemX() : itemX());
    }

    qreal colPos() const {
        if (view->flow() == QQuickGridView::LeftToRight) {
            if (view->effectiveLayoutDirection() == Qt::RightToLeft) {
                qreal colSize = view->cellWidth();
                int columns = view->width()/colSize;
                return colSize * (columns-1) - itemX();
            } else {
                return itemX();
            }
        } else {
            return itemY();
        }
    }
    qreal endRowPos() const {
        if (view->flow() == QQuickGridView::LeftToRight) {
            return itemY() + view->cellHeight();
        } else {
            if (view->effectiveLayoutDirection() == Qt::RightToLeft)
                return -itemX();
            else
                return itemX() + view->cellWidth();
        }
    }
    void setPosition(qreal col, qreal row, bool immediate = false) {
        moveTo(pointForPosition(col, row), immediate);
    }
    bool contains(qreal x, qreal y) const {
        return (x >= itemX() && x < itemX() + view->cellWidth() &&
                y >= itemY() && y < itemY() + view->cellHeight());
    }

    QQuickGridView *view;

private:
    QPointF pointForPosition(qreal col, qreal row) const {
        if (view->effectiveLayoutDirection() == Qt::RightToLeft) {
            if (view->flow() == QQuickGridView::LeftToRight) {
                int columns = view->width()/view->cellWidth();
                return QPointF(view->cellWidth() * (columns-1) - col, row);
            } else {
                return QPointF(-view->cellWidth() - row, col);
            }
        } else {
            if (view->flow() == QQuickGridView::LeftToRight)
                return QPointF(col, row);
            else
                return QPointF(row, col);
        }
    }
};

//----------------------------------------------------------------------------

class QQuickGridViewPrivate : public QQuickItemViewPrivate
{
    Q_DECLARE_PUBLIC(QQuickGridView)

public:
    virtual Qt::Orientation layoutOrientation() const;
    virtual bool isContentFlowReversed() const;
    bool isRightToLeftTopToBottom() const;

    virtual qreal positionAt(int index) const;
    virtual qreal endPositionAt(int index) const;
    virtual qreal originPosition() const;
    virtual qreal lastPosition() const;

    qreal rowSize() const;
    qreal colSize() const;
    qreal colPosAt(int modelIndex) const;
    qreal rowPosAt(int modelIndex) const;
    qreal snapPosAt(qreal pos) const;
    FxViewItem *snapItemAt(qreal pos) const;
    int snapIndex() const;

    void resetColumns();

    virtual bool addVisibleItems(qreal fillFrom, qreal fillTo, bool doBuffer);
    virtual bool removeNonVisibleItems(qreal bufferFrom, qreal bufferTo);

    virtual FxViewItem *newViewItem(int index, QQuickItem *item);
    virtual void initializeViewItem(FxViewItem *item);
    virtual void repositionItemAt(FxViewItem *item, int index, qreal sizeBuffer);
    virtual void repositionPackageItemAt(QQuickItem *item, int index);
    virtual void resetFirstItemPosition(qreal pos = 0.0);
    virtual void adjustFirstItem(qreal forwards, qreal backwards, int changeBeforeVisible);

    virtual void createHighlight();
    virtual void updateHighlight();
    virtual void resetHighlightPosition();

    virtual void setPosition(qreal pos);
    virtual void layoutVisibleItems(int fromModelIndex = 0);
    virtual bool applyInsertionChange(const QQuickChangeSet::Insert &insert, ChangeResult *changeResult, QList<FxViewItem *> *addedItems, QList<MovedItem> *movingIntoView);
    virtual void translateAndTransitionItemsAfter(int afterModelIndex, const ChangeResult &insertionResult, const ChangeResult &removalResult);
    virtual bool needsRefillForAddedOrRemovedIndex(int index) const;

    virtual qreal headerSize() const;
    virtual qreal footerSize() const;
    virtual bool showHeaderForIndex(int index) const;
    virtual bool showFooterForIndex(int index) const;
    virtual void updateHeader();
    virtual void updateFooter();

    virtual void changedVisibleIndex(int newIndex);
    virtual void initializeCurrentItem();

    virtual void updateViewport();
    virtual void fixupPosition();
    virtual void fixup(AxisData &data, qreal minExtent, qreal maxExtent);
    virtual void flick(QQuickItemViewPrivate::AxisData &data, qreal minExtent, qreal maxExtent, qreal vSize,
                        QQuickTimeLineCallback::Callback fixupCallback, qreal velocity);

    QQuickGridView::Flow flow;
    qreal cellWidth;
    qreal cellHeight;
    int columns;
    QQuickGridView::SnapMode snapMode;

    QSmoothedAnimation *highlightXAnimator;
    QSmoothedAnimation *highlightYAnimator;

    QQuickGridViewPrivate()
        : flow(QQuickGridView::LeftToRight)
        , cellWidth(100), cellHeight(100), columns(1)
        , snapMode(QQuickGridView::NoSnap)
        , highlightXAnimator(0), highlightYAnimator(0)
    {}
    ~QQuickGridViewPrivate()
    {
        delete highlightXAnimator;
        delete highlightYAnimator;
    }
};

Qt::Orientation QQuickGridViewPrivate::layoutOrientation() const
{
    return flow == QQuickGridView::LeftToRight ? Qt::Vertical : Qt::Horizontal;
}

bool QQuickGridViewPrivate::isContentFlowReversed() const
{
    return isRightToLeftTopToBottom();
}

bool QQuickGridViewPrivate::isRightToLeftTopToBottom() const
{
    Q_Q(const QQuickGridView);
    return flow == QQuickGridView::TopToBottom && q->effectiveLayoutDirection() == Qt::RightToLeft;
}

void QQuickGridViewPrivate::changedVisibleIndex(int newIndex)
{
    visibleIndex = newIndex / columns * columns;
}

void QQuickGridViewPrivate::setPosition(qreal pos)
{
    Q_Q(QQuickGridView);
    if (flow == QQuickGridView::LeftToRight) {
        q->QQuickFlickable::setContentY(pos);
        q->QQuickFlickable::setContentX(0);
    } else {
        if (q->effectiveLayoutDirection() == Qt::LeftToRight)
            q->QQuickFlickable::setContentX(pos);
        else
            q->QQuickFlickable::setContentX(-pos-size());
        q->QQuickFlickable::setContentY(0);
    }
}

qreal QQuickGridViewPrivate::originPosition() const
{
    qreal pos = 0;
    if (!visibleItems.isEmpty())
        pos = static_cast<FxGridItemSG*>(visibleItems.first())->rowPos() - visibleIndex / columns * rowSize();
    return pos;
}

qreal QQuickGridViewPrivate::lastPosition() const
{
    qreal pos = 0;
    if (model && model->count()) {
        // get end position of last item
        pos = (rowPosAt(model->count() - 1) + rowSize());
    }
    return pos;
}

qreal QQuickGridViewPrivate::positionAt(int index) const
{
    return rowPosAt(index);
}

qreal QQuickGridViewPrivate::endPositionAt(int index) const
{
    return rowPosAt(index) + rowSize();
}

qreal QQuickGridViewPrivate::rowSize() const {
    return flow == QQuickGridView::LeftToRight ? cellHeight : cellWidth;
}
qreal QQuickGridViewPrivate::colSize() const {
    return flow == QQuickGridView::LeftToRight ? cellWidth : cellHeight;
}

qreal QQuickGridViewPrivate::colPosAt(int modelIndex) const
{
    if (FxViewItem *item = visibleItem(modelIndex))
        return static_cast<FxGridItemSG*>(item)->colPos();
    if (!visibleItems.isEmpty()) {
        if (modelIndex == visibleIndex) {
            FxGridItemSG *firstItem = static_cast<FxGridItemSG*>(visibleItems.first());
            return firstItem->colPos();
        } else if (modelIndex < visibleIndex) {
            int count = (visibleIndex - modelIndex) % columns;
            int col = static_cast<FxGridItemSG*>(visibleItems.first())->colPos() / colSize();
            col = (columns - count + col) % columns;
            return col * colSize();
        } else {
            FxGridItemSG *lastItem = static_cast<FxGridItemSG*>(visibleItems.last());
            int count = modelIndex - lastItem->index;
            int col = lastItem->colPos() / colSize();
            col = (col + count) % columns;
            return col * colSize();
        }
    }
    return (modelIndex % columns) * colSize();
}

qreal QQuickGridViewPrivate::rowPosAt(int modelIndex) const
{
    if (FxViewItem *item = visibleItem(modelIndex))
        return static_cast<FxGridItemSG*>(item)->rowPos();
    if (!visibleItems.isEmpty()) {
        if (modelIndex == visibleIndex) {
            FxGridItemSG *firstItem = static_cast<FxGridItemSG*>(visibleItems.first());
            return firstItem->rowPos();
        } else if (modelIndex < visibleIndex) {
            FxGridItemSG *firstItem = static_cast<FxGridItemSG*>(visibleItems.first());
            int firstCol = firstItem->colPos() / colSize();
            int col = visibleIndex - modelIndex + (columns - firstCol - 1);
            int rows = col / columns;
            return firstItem->rowPos() - rows * rowSize();
        } else {
            FxGridItemSG *lastItem = static_cast<FxGridItemSG*>(visibleItems.last());
            int count = modelIndex - lastItem->index;
            int col = lastItem->colPos() + count * colSize();
            int rows = col / (columns * colSize());
            return lastItem->rowPos() + rows * rowSize();
        }
    }
    return (modelIndex / columns) * rowSize();
}


qreal QQuickGridViewPrivate::snapPosAt(qreal pos) const
{
    Q_Q(const QQuickGridView);
    qreal snapPos = 0;
    if (!visibleItems.isEmpty()) {
        qreal highlightStart = highlightRangeStart;
        pos += highlightStart;
        pos += rowSize()/2;
        snapPos = static_cast<FxGridItemSG*>(visibleItems.first())->rowPos() - visibleIndex / columns * rowSize();
        snapPos = pos - fmodf(pos - snapPos, qreal(rowSize()));
        snapPos -= highlightStart;
        qreal maxExtent;
        qreal minExtent;
        if (isRightToLeftTopToBottom()) {
            maxExtent = q->minXExtent()-size();
            minExtent = q->maxXExtent()-size();
        } else {
            maxExtent = flow == QQuickGridView::LeftToRight ? -q->maxYExtent() : -q->maxXExtent();
            minExtent = flow == QQuickGridView::LeftToRight ? -q->minYExtent() : -q->minXExtent();
        }
        if (snapPos > maxExtent)
            snapPos = maxExtent;
        if (snapPos < minExtent)
            snapPos = minExtent;
    }
    return snapPos;
}

FxViewItem *QQuickGridViewPrivate::snapItemAt(qreal pos) const
{
    for (int i = 0; i < visibleItems.count(); ++i) {
        FxViewItem *item = visibleItems.at(i);
        if (item->index == -1)
            continue;
        qreal itemTop = item->position();
        if (itemTop+rowSize()/2 >= pos && itemTop - rowSize()/2 <= pos)
            return item;
    }
    return 0;
}

int QQuickGridViewPrivate::snapIndex() const
{
    int index = currentIndex;
    for (int i = 0; i < visibleItems.count(); ++i) {
        FxGridItemSG *item = static_cast<FxGridItemSG*>(visibleItems.at(i));
        if (item->index == -1)
            continue;
        qreal itemTop = item->position();
        FxGridItemSG *hItem = static_cast<FxGridItemSG*>(highlight);
        if (itemTop >= hItem->rowPos()-rowSize()/2 && itemTop < hItem->rowPos()+rowSize()/2) {
            index = item->index;
            if (item->colPos() >= hItem->colPos()-colSize()/2 && item->colPos() < hItem->colPos()+colSize()/2)
                return item->index;
        }
    }
    return index;
}

void QQuickGridViewPrivate::resetColumns()
{
    Q_Q(QQuickGridView);
    qreal length = flow == QQuickGridView::LeftToRight ? q->width() : q->height();
    columns = (int)qMax((length + colSize()/2) / colSize(), qreal(1.));
}

FxViewItem *QQuickGridViewPrivate::newViewItem(int modelIndex, QQuickItem *item)
{
    Q_Q(QQuickGridView);
    Q_UNUSED(modelIndex);
    return new FxGridItemSG(item, q, false, false);
}

void QQuickGridViewPrivate::initializeViewItem(FxViewItem *item)
{
    QQuickItemViewPrivate::initializeViewItem(item);

    // need to track current items that are animating
    QQuickItemPrivate *itemPrivate = QQuickItemPrivate::get(item->item);
    itemPrivate->addItemChangeListener(this, QQuickItemPrivate::Geometry);
}

bool QQuickGridViewPrivate::addVisibleItems(qreal fillFrom, qreal fillTo, bool doBuffer)
{
    qreal colPos = colPosAt(visibleIndex);
    qreal rowPos = rowPosAt(visibleIndex);
    if (visibleItems.count()) {
        FxGridItemSG *lastItem = static_cast<FxGridItemSG*>(visibleItems.last());
        rowPos = lastItem->rowPos();
        int colNum = qFloor((lastItem->colPos()+colSize()/2) / colSize());
        if (++colNum >= columns) {
            colNum = 0;
            rowPos += rowSize();
        }
        colPos = colNum * colSize();
    }

    int modelIndex = findLastVisibleIndex();
    modelIndex = modelIndex < 0 ? visibleIndex : modelIndex + 1;

    if (visibleItems.count() && (fillFrom > rowPos + rowSize()*2
        || fillTo < rowPosAt(visibleIndex) - rowSize())) {
        // We've jumped more than a page.  Estimate which items are now
        // visible and fill from there.
        int count = (fillFrom - (rowPos + rowSize())) / (rowSize()) * columns;
        for (int i = 0; i < visibleItems.count(); ++i)
            releaseItem(visibleItems.at(i));
        visibleItems.clear();
        modelIndex += count;
        if (modelIndex >= model->count())
            modelIndex = model->count() - 1;
        else if (modelIndex < 0)
            modelIndex = 0;
        modelIndex = modelIndex / columns * columns;
        visibleIndex = modelIndex;
        colPos = colPosAt(visibleIndex);
        rowPos = rowPosAt(visibleIndex);
    }

    int colNum = qFloor((colPos+colSize()/2) / colSize());
    FxGridItemSG *item = 0;
    bool changed = false;

    while (modelIndex < model->count() && rowPos <= fillTo + rowSize()*(columns - colNum)/(columns+1)) {
#ifdef DEBUG_DELEGATE_LIFECYCLE
        qDebug() << "refill: append item" << modelIndex << colPos << rowPos;
#endif
        if (!(item = static_cast<FxGridItemSG*>(createItem(modelIndex, doBuffer))))
            break;
        if (!transitioner || !transitioner->canTransition(QQuickItemViewTransitioner::PopulateTransition, true)) // pos will be set by layoutVisibleItems()
            item->setPosition(colPos, rowPos, true);
        item->item->setVisible(!doBuffer);
        visibleItems.append(item);
        if (++colNum >= columns) {
            colNum = 0;
            rowPos += rowSize();
        }
        colPos = colNum * colSize();
        ++modelIndex;
        changed = true;
    }

    if (doBuffer && requestedIndex != -1) // already waiting for an item
        return changed;

    // Find first column
    if (visibleItems.count()) {
        FxGridItemSG *firstItem = static_cast<FxGridItemSG*>(visibleItems.first());
        rowPos = firstItem->rowPos();
        colNum = qFloor((firstItem->colPos()+colSize()/2) / colSize());
        if (--colNum < 0) {
            colNum = columns - 1;
            rowPos -= rowSize();
        }
    } else {
        colNum = qFloor((colPos+colSize()/2) / colSize());
    }

    // Prepend
    colPos = colNum * colSize();
    while (visibleIndex > 0 && rowPos + rowSize() - 1 >= fillFrom - rowSize()*(colNum+1)/(columns+1)){
#ifdef DEBUG_DELEGATE_LIFECYCLE
        qDebug() << "refill: prepend item" << visibleIndex-1 << "top pos" << rowPos << colPos;
#endif
        if (!(item = static_cast<FxGridItemSG*>(createItem(visibleIndex-1, doBuffer))))
            break;
        --visibleIndex;
        if (!transitioner || !transitioner->canTransition(QQuickItemViewTransitioner::PopulateTransition, true)) // pos will be set by layoutVisibleItems()
            item->setPosition(colPos, rowPos, true);
        item->item->setVisible(!doBuffer);
        visibleItems.prepend(item);
        if (--colNum < 0) {
            colNum = columns-1;
            rowPos -= rowSize();
        }
        colPos = colNum * colSize();
        changed = true;
    }

    return changed;
}

bool QQuickGridViewPrivate::removeNonVisibleItems(qreal bufferFrom, qreal bufferTo)
{
    FxGridItemSG *item = 0;
    bool changed = false;

    while (visibleItems.count() > 1
           && (item = static_cast<FxGridItemSG*>(visibleItems.first()))
                && item->rowPos()+rowSize()-1 < bufferFrom - rowSize()*(item->colPos()/colSize()+1)/(columns+1)) {
        if (item->attached->delayRemove())
            break;
#ifdef DEBUG_DELEGATE_LIFECYCLE
        qDebug() << "refill: remove first" << visibleIndex << "top end pos" << item->endRowPos();
#endif
        if (item->index != -1)
            visibleIndex++;
        visibleItems.removeFirst();
        if (item->transitionScheduledOrRunning()) {
#ifdef DEBUG_DELEGATE_LIFECYCLE
            qDebug() << "\tnot releasing animating item:" << item->index << item->item->objectName();
#endif
            item->releaseAfterTransition = true;
            releasePendingTransition.append(item);
        } else {
            releaseItem(item);
        }
        changed = true;
    }
    while (visibleItems.count() > 1
           && (item = static_cast<FxGridItemSG*>(visibleItems.last()))
                && item->rowPos() > bufferTo + rowSize()*(columns - item->colPos()/colSize())/(columns+1)) {
        if (item->attached->delayRemove())
            break;
#ifdef DEBUG_DELEGATE_LIFECYCLE
        qDebug() << "refill: remove last" << visibleIndex+visibleItems.count()-1;
#endif
        visibleItems.removeLast();
        if (item->transitionScheduledOrRunning()) {
#ifdef DEBUG_DELEGATE_LIFECYCLE
            qDebug() << "\tnot releasing animating item:" << item->index << item->item->objectName();
#endif
            item->releaseAfterTransition = true;
            releasePendingTransition.append(item);
        } else {
            releaseItem(item);
        }
        changed = true;
    }

    return changed;
}

void QQuickGridViewPrivate::updateViewport()
{
    resetColumns();
    QQuickItemViewPrivate::updateViewport();
}

void QQuickGridViewPrivate::layoutVisibleItems(int fromModelIndex)
{
    if (visibleItems.count()) {
        const qreal from = isContentFlowReversed() ? -position() - size() : position();
        const qreal to = isContentFlowReversed() ? -position() : position() + size();

        FxGridItemSG *firstItem = static_cast<FxGridItemSG*>(visibleItems.first());
        qreal rowPos = firstItem->rowPos();
        qreal colPos = firstItem->colPos();
        int col = visibleIndex % columns;
        if (colPos != col * colSize()) {
            colPos = col * colSize();
            firstItem->setPosition(colPos, rowPos);
            firstItem->setVisible(firstItem->rowPos() + rowSize() >= from && firstItem->rowPos() <= to);
        }
        for (int i = 1; i < visibleItems.count(); ++i) {
            FxGridItemSG *item = static_cast<FxGridItemSG*>(visibleItems.at(i));
            if (++col >= columns) {
                col = 0;
                rowPos += rowSize();
            }
            colPos = col * colSize();
            if (item->index >= fromModelIndex) {
                item->setPosition(colPos, rowPos);
                item->setVisible(item->rowPos() + rowSize() >= from && item->rowPos() <= to);
            }
        }
    }
}

void QQuickGridViewPrivate::repositionItemAt(FxViewItem *item, int index, qreal sizeBuffer)
{
    int count = sizeBuffer / rowSize();
    static_cast<FxGridItemSG *>(item)->setPosition(colPosAt(index + count), rowPosAt(index + count));
}

void QQuickGridViewPrivate::repositionPackageItemAt(QQuickItem *item, int index)
{
    Q_Q(QQuickGridView);
    qreal pos = position();
    if (flow == QQuickGridView::LeftToRight) {
        if (item->y() + item->height() > pos && item->y() < pos + q->height())
            item->setPos(QPointF(colPosAt(index), rowPosAt(index)));
    } else {
        if (item->x() + item->width() > pos && item->x() < pos + q->width()) {
            if (isRightToLeftTopToBottom())
                item->setPos(QPointF(-rowPosAt(index)-item->width(), colPosAt(index)));
            else
                item->setPos(QPointF(rowPosAt(index), colPosAt(index)));
        }
    }
}

void QQuickGridViewPrivate::resetFirstItemPosition(qreal pos)
{
    FxGridItemSG *item = static_cast<FxGridItemSG*>(visibleItems.first());
    item->setPosition(0, pos);
}

void QQuickGridViewPrivate::adjustFirstItem(qreal forwards, qreal backwards, int changeBeforeVisible)
{
    if (!visibleItems.count())
        return;

    int moveCount = (forwards - backwards) / rowSize();
    if (moveCount == 0 && changeBeforeVisible != 0)
        moveCount += (changeBeforeVisible % columns) - (columns - 1);

    FxGridItemSG *gridItem = static_cast<FxGridItemSG*>(visibleItems.first());
    gridItem->setPosition(gridItem->colPos(), gridItem->rowPos() + ((moveCount / columns) * rowSize()));
}

void QQuickGridViewPrivate::createHighlight()
{
    Q_Q(QQuickGridView);
    bool changed = false;
    if (highlight) {
        if (trackedItem == highlight)
            trackedItem = 0;
        delete highlight;
        highlight = 0;

        delete highlightXAnimator;
        delete highlightYAnimator;
        highlightXAnimator = 0;
        highlightYAnimator = 0;

        changed = true;
    }

    if (currentItem) {
        QQuickItem *item = createHighlightItem();
        if (item) {
            FxGridItemSG *newHighlight = new FxGridItemSG(item, q, true, true);
            if (autoHighlight)
                resetHighlightPosition();
            highlightXAnimator = new QSmoothedAnimation;
            highlightXAnimator->target = QQmlProperty(item, QLatin1String("x"));
            highlightXAnimator->userDuration = highlightMoveDuration;
            highlightYAnimator = new QSmoothedAnimation;
            highlightYAnimator->target = QQmlProperty(item, QLatin1String("y"));
            highlightYAnimator->userDuration = highlightMoveDuration;

            highlight = newHighlight;
            changed = true;
        }
    }
    if (changed)
        emit q->highlightItemChanged();
}

void QQuickGridViewPrivate::updateHighlight()
{
    applyPendingChanges();

    if ((!currentItem && highlight) || (currentItem && !highlight))
        createHighlight();
    bool strictHighlight = haveHighlightRange && highlightRange == QQuickGridView::StrictlyEnforceRange;
    if (currentItem && autoHighlight && highlight && (!strictHighlight || !pressed)) {
        // auto-update highlight
        highlightXAnimator->to = currentItem->itemX();
        highlightYAnimator->to = currentItem->itemY();
        highlight->item->setWidth(currentItem->item->width());
        highlight->item->setHeight(currentItem->item->height());

        highlightXAnimator->restart();
        highlightYAnimator->restart();
    }
    updateTrackedItem();
}

void QQuickGridViewPrivate::resetHighlightPosition()
{
    if (highlight && currentItem) {
        FxGridItemSG *cItem = static_cast<FxGridItemSG*>(currentItem);
        static_cast<FxGridItemSG*>(highlight)->setPosition(cItem->colPos(), cItem->rowPos());
    }
}

qreal QQuickGridViewPrivate::headerSize() const
{
    if (!header)
        return 0.0;
    return flow == QQuickGridView::LeftToRight ? header->item->height() : header->item->width();
}

qreal QQuickGridViewPrivate::footerSize() const
{
    if (!footer)
        return 0.0;
    return flow == QQuickGridView::LeftToRight? footer->item->height() : footer->item->width();
}

bool QQuickGridViewPrivate::showHeaderForIndex(int index) const
{
    return index / columns == 0;
}

bool QQuickGridViewPrivate::showFooterForIndex(int index) const
{
    return index / columns == (model->count()-1) / columns;
}

void QQuickGridViewPrivate::updateFooter()
{
    Q_Q(QQuickGridView);
    bool created = false;
    if (!footer) {
        QQuickItem *item = createComponentItem(footerComponent);
        if (!item)
            return;
        item->setZ(1);
        footer = new FxGridItemSG(item, q, true, true);
        created = true;
    }

    FxGridItemSG *gridItem = static_cast<FxGridItemSG*>(footer);
    qreal colOffset = 0;
    qreal rowOffset = 0;
    if (q->effectiveLayoutDirection() == Qt::RightToLeft) {
        if (flow == QQuickGridView::TopToBottom)
            rowOffset = gridItem->item->width() - cellWidth;
        else
            colOffset = gridItem->item->width() - cellWidth;
    }
    if (visibleItems.count()) {
        qreal endPos = lastPosition();
        if (findLastVisibleIndex() == model->count()-1) {
            gridItem->setPosition(colOffset, endPos + rowOffset);
        } else {
            qreal visiblePos = isRightToLeftTopToBottom() ? -position() : position() + size();
            if (endPos <= visiblePos || gridItem->endPosition() <= endPos + rowOffset)
                gridItem->setPosition(colOffset, endPos + rowOffset);
        }
    } else {
        gridItem->setPosition(colOffset, rowOffset);
    }

    if (created)
        emit q->footerItemChanged();
}

void QQuickGridViewPrivate::updateHeader()
{
    Q_Q(QQuickGridView);
    bool created = false;
    if (!header) {
        QQuickItem *item = createComponentItem(headerComponent);
        if (!item)
            return;
        item->setZ(1);
        header = new FxGridItemSG(item, q, true, true);
        created = true;
    }

    FxGridItemSG *gridItem = static_cast<FxGridItemSG*>(header);
    qreal colOffset = 0;
    qreal rowOffset = -headerSize();
    if (q->effectiveLayoutDirection() == Qt::RightToLeft) {
        if (flow == QQuickGridView::TopToBottom)
            rowOffset += gridItem->item->width()-cellWidth;
        else
            colOffset = gridItem->item->width()-cellWidth;
    }
    if (visibleItems.count()) {
        qreal startPos = originPosition();
        if (visibleIndex == 0) {
            gridItem->setPosition(colOffset, startPos + rowOffset);
        } else {
            qreal tempPos = isRightToLeftTopToBottom() ? -position()-size() : position();
            qreal headerPos = isRightToLeftTopToBottom() ? gridItem->rowPos() + cellWidth - headerSize() : gridItem->rowPos();
            if (tempPos <= startPos || headerPos > startPos + rowOffset)
                gridItem->setPosition(colOffset, startPos + rowOffset);
        }
    } else {
        if (isRightToLeftTopToBottom())
            gridItem->setPosition(colOffset, rowOffset);
        else
            gridItem->setPosition(colOffset, -headerSize());
    }

    if (created)
        emit q->headerItemChanged();
}

void QQuickGridViewPrivate::initializeCurrentItem()
{
    if (currentItem && currentIndex >= 0) {
        FxGridItemSG *gridItem = static_cast<FxGridItemSG*>(currentItem);
        FxViewItem *actualItem = visibleItem(currentIndex);

        // don't reposition the item if it's about to be transitioned to another position
        if ((!actualItem || !actualItem->transitionScheduledOrRunning()))
            gridItem->setPosition(colPosAt(currentIndex), rowPosAt(currentIndex));
    }
}

void QQuickGridViewPrivate::fixupPosition()
{
    moveReason = Other;
    if (flow == QQuickGridView::LeftToRight)
        fixupY();
    else
        fixupX();
}

void QQuickGridViewPrivate::fixup(AxisData &data, qreal minExtent, qreal maxExtent)
{
    if ((flow == QQuickGridView::TopToBottom && &data == &vData)
        || (flow == QQuickGridView::LeftToRight && &data == &hData))
        return;

    fixupMode = moveReason == Mouse ? fixupMode : Immediate;

    qreal viewPos = isRightToLeftTopToBottom() ? -position()-size() : position();

    bool strictHighlightRange = haveHighlightRange && highlightRange == QQuickGridView::StrictlyEnforceRange;
    if (snapMode != QQuickGridView::NoSnap) {
        qreal tempPosition = isRightToLeftTopToBottom() ? -position()-size() : position();
        if (snapMode == QQuickGridView::SnapOneRow && moveReason == Mouse) {
            // if we've been dragged < rowSize()/2 then bias towards the next row
            qreal dist = data.move.value() - (data.pressPos - data.dragStartOffset);
            qreal bias = 0;
            if (data.velocity > 0 && dist > QML_FLICK_SNAPONETHRESHOLD && dist < rowSize()/2)
                bias = rowSize()/2;
            else if (data.velocity < 0 && dist < -QML_FLICK_SNAPONETHRESHOLD && dist > -rowSize()/2)
                bias = -rowSize()/2;
            if (isRightToLeftTopToBottom())
                bias = -bias;
            tempPosition -= bias;
        }
        FxViewItem *topItem = snapItemAt(tempPosition+highlightRangeStart);
        if (!topItem && strictHighlightRange && currentItem) {
            // StrictlyEnforceRange always keeps an item in range
            updateHighlight();
            topItem = currentItem;
        }
        FxViewItem *bottomItem = snapItemAt(tempPosition+highlightRangeEnd);
        if (!bottomItem && strictHighlightRange && currentItem) {
            // StrictlyEnforceRange always keeps an item in range
            updateHighlight();
            bottomItem = currentItem;
        }
        qreal pos;
        bool isInBounds = -position() > maxExtent && -position() <= minExtent;
        if (topItem && (isInBounds || strictHighlightRange)) {
            qreal headerPos = header ? static_cast<FxGridItemSG*>(header)->rowPos() : 0;
            if (topItem->index == 0 && header && tempPosition+highlightRangeStart < headerPos+headerSize()/2 && !strictHighlightRange) {
                pos = isRightToLeftTopToBottom() ? - headerPos + highlightRangeStart - size() : headerPos - highlightRangeStart;
            } else {
                if (isRightToLeftTopToBottom())
                    pos = qMax(qMin(-topItem->position() + highlightRangeStart - size(), -maxExtent), -minExtent);
                else
                    pos = qMax(qMin(topItem->position() - highlightRangeStart, -maxExtent), -minExtent);
            }
        } else if (bottomItem && isInBounds) {
            if (isRightToLeftTopToBottom())
                pos = qMax(qMin(-bottomItem->position() + highlightRangeEnd - size(), -maxExtent), -minExtent);
            else
                pos = qMax(qMin(bottomItem->position() - highlightRangeEnd, -maxExtent), -minExtent);
        } else {
            QQuickItemViewPrivate::fixup(data, minExtent, maxExtent);
            return;
        }

        qreal dist = qAbs(data.move + pos);
        if (dist > 0) {
            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 (haveHighlightRange && highlightRange == QQuickGridView::StrictlyEnforceRange) {
        if (currentItem) {
            updateHighlight();
            qreal pos = static_cast<FxGridItemSG*>(currentItem)->rowPos();
            if (viewPos < pos + rowSize() - highlightRangeEnd)
                viewPos = pos + rowSize() - highlightRangeEnd;
            if (viewPos > pos - highlightRangeStart)
                viewPos = pos - highlightRangeStart;
            if (isRightToLeftTopToBottom())
                viewPos = -viewPos-size();
            timeline.reset(data.move);
            if (viewPos != position()) {
                if (fixupMode != Immediate) {
                    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;
}

void QQuickGridViewPrivate::flick(AxisData &data, qreal minExtent, qreal maxExtent, qreal vSize,
                                        QQuickTimeLineCallback::Callback fixupCallback, qreal velocity)
{
    Q_Q(QQuickGridView);
    data.fixingUp = false;
    moveReason = Mouse;
    if ((!haveHighlightRange || highlightRange != QQuickGridView::StrictlyEnforceRange)
        && snapMode == QQuickGridView::NoSnap) {
        QQuickItemViewPrivate::flick(data, minExtent, maxExtent, vSize, fixupCallback, velocity);
        return;
    }
    qreal maxDistance = 0;
    qreal dataValue = isRightToLeftTopToBottom() ? -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 == QQuickGridView::SnapOneRow) {
                // if we've been dragged < averageSize/2 then bias towards the next item
                qreal dist = data.move.value() - (data.pressPos - data.dragStartOffset);
                qreal bias = dist < rowSize()/2 ? rowSize()/2 : 0;
                if (isRightToLeftTopToBottom())
                    bias = -bias;
                data.flickTarget = -snapPosAt(-dataValue - bias);
                maxDistance = qAbs(data.flickTarget - data.move.value());
                velocity = maxVelocity;
            } else {
                maxDistance = qAbs(minExtent - data.move.value());
            }
        }
        if (snapMode == QQuickGridView::NoSnap && highlightRange != QQuickGridView::StrictlyEnforceRange)
            data.flickTarget = minExtent;
    } else {
        if (data.move.value() > maxExtent) {
            if (snapMode == QQuickGridView::SnapOneRow) {
                // if we've been dragged < averageSize/2 then bias towards the next item
                qreal dist = data.move.value() - (data.pressPos - data.dragStartOffset);
                qreal bias = -dist < rowSize()/2 ? rowSize()/2 : 0;
                if (isRightToLeftTopToBottom())
                    bias = -bias;
                data.flickTarget = -snapPosAt(-dataValue + bias);
                maxDistance = qAbs(data.flickTarget - data.move.value());
                velocity = -maxVelocity;
            } else {
                maxDistance = qAbs(maxExtent - data.move.value());
            }
        }
        if (snapMode == QQuickGridView::NoSnap && highlightRange != QQuickGridView::StrictlyEnforceRange)
            data.flickTarget = maxExtent;
    }
    bool overShoot = boundsBehavior == QQuickFlickable::DragAndOvershootBounds;
    if (maxDistance > 0 || overShoot) {
        // This mode requires the grid to stop exactly on a row boundary.
        qreal v = velocity;
        if (maxVelocity != -1 && maxVelocity < qAbs(v)) {
            if (v < 0)
                v = -maxVelocity;
            else
                v = maxVelocity;
        }
        qreal accel = deceleration;
        qreal v2 = v * v;
        qreal overshootDist = 0.0;
        if ((maxDistance > 0.0 && v2 / (2.0f * maxDistance) < accel) || snapMode == QQuickGridView::SnapOneRow) {
            // + rowSize()/4 to encourage moving at least one item in the flick direction
            qreal dist = v2 / (accel * 2.0) + rowSize()/4;
            dist = qMin(dist, maxDistance);
            if (v > 0)
                dist = -dist;
            if (snapMode != QQuickGridView::SnapOneRow) {
                qreal distTemp = isRightToLeftTopToBottom() ? -dist : dist;
                data.flickTarget = -snapPosAt(-dataValue + distTemp);
            }
            data.flickTarget = isRightToLeftTopToBottom() ? -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 {
            data.flickTarget = velocity > 0 ? minExtent : maxExtent;
            overshootDist = overShoot ? overShootDistance(vSize) : 0;
        }
        timeline.reset(data.move);
        timeline.accel(data.move, v, accel, maxDistance + overshootDist);
        timeline.callback(QQuickTimeLineCallback(&data.move, fixupCallback, this));
        if (!hData.flicking && q->xflick()) {
            hData.flicking = true;
            emit q->flickingChanged();
            emit q->flickingHorizontallyChanged();
            emit q->flickStarted();
        }
        if (!vData.flicking && q->yflick()) {
            vData.flicking = true;
            emit q->flickingChanged();
            emit q->flickingVerticallyChanged();
            emit q->flickStarted();
        }
    } else {
        timeline.reset(data.move);
        fixup(data, minExtent, maxExtent);
    }
}


//----------------------------------------------------------------------------
/*!
    \qmlclass GridView QQuickGridView
    \inqmlmodule QtQuick 2
    \ingroup qml-view-elements

    \inherits Flickable
    \brief The GridView item provides a grid view of items provided by a model.

    A GridView displays data from models created from built-in QML elements like ListModel
    and XmlListModel, or custom model classes defined in C++ that inherit from
    QAbstractListModel.

    A GridView has a \l model, which defines the data to be displayed, and
    a \l delegate, which defines how the data should be displayed. Items in a
    GridView are laid out horizontally or vertically. Grid views are inherently flickable
    as GridView inherits from \l Flickable.

    \section1 Example Usage

    The following example shows the definition of a simple list model defined
    in a file called \c ContactModel.qml:

    \snippet doc/src/snippets/qml/gridview/ContactModel.qml 0

    \div {class="float-right"}
    \inlineimage gridview-simple.png
    \enddiv

    This model can be referenced as \c ContactModel in other QML files. See \l{QML Modules}
    for more information about creating reusable components like this.

    Another component can display this model data in a GridView, as in the following
    example, which creates a \c ContactModel component for its model, and a \l Column element
    (containing \l Image and \l Text elements) for its delegate.

    \clearfloat
    \snippet doc/src/snippets/qml/gridview/gridview.qml import
    \codeline
    \snippet doc/src/snippets/qml/gridview/gridview.qml classdocs simple

    \div {class="float-right"}
    \inlineimage gridview-highlight.png
    \enddiv

    The view will create a new delegate for each item in the model. Note that the delegate
    is able to access the model's \c name and \c portrait data directly.

    An improved grid view is shown below. The delegate is visually improved and is moved
    into a separate \c contactDelegate component.

    \clearfloat
    \snippet doc/src/snippets/qml/gridview/gridview.qml classdocs advanced

    The currently selected item is highlighted with a blue \l Rectangle using the \l highlight property,
    and \c focus is set to \c true to enable keyboard navigation for the grid view.
    The grid view itself is a focus scope (see \l{qmlfocus#Acquiring Focus and Focus Scopes}{the focus documentation page} for more details).

    Delegates are instantiated as needed and may be destroyed at any time.
    State should \e never be stored in a delegate.

    GridView attaches a number of properties to the root item of the delegate, for example
    \c {GridView.isCurrentItem}.  In the following example, the root delegate item can access
    this attached property directly as \c GridView.isCurrentItem, while the child
    \c contactInfo object must refer to this property as \c wrapper.GridView.isCurrentItem.

    \snippet doc/src/snippets/qml/gridview/gridview.qml isCurrentItem

    \note Views do not set the \l{Item::}{clip} property automatically.
    If the view is not clipped by another item or the screen, it will be necessary
    to set this property to true in order to clip the items that are partially or
    fully outside the view.

    \sa {declarative/modelviews/gridview}{GridView example}
*/

QQuickGridView::QQuickGridView(QQuickItem *parent)
    : QQuickItemView(*(new QQuickGridViewPrivate), parent)
{
}

QQuickGridView::~QQuickGridView()
{
}

void QQuickGridView::setHighlightFollowsCurrentItem(bool autoHighlight)
{
    Q_D(QQuickGridView);
    if (d->autoHighlight != autoHighlight) {
        if (!autoHighlight && d->highlightXAnimator) {
            d->highlightXAnimator->stop();
            d->highlightYAnimator->stop();
        }
        QQuickItemView::setHighlightFollowsCurrentItem(autoHighlight);
    }
}

/*!
    \qmlattachedproperty bool QtQuick2::GridView::isCurrentItem
    This attached property is true if this delegate is the current item; otherwise false.

    It is attached to each instance of the delegate.
*/

/*!
    \qmlattachedproperty GridView QtQuick2::GridView::view
    This attached property holds the view that manages this delegate instance.

    It is attached to each instance of the delegate.

    \snippet doc/src/snippets/qml/gridview/gridview.qml isCurrentItem
*/

/*!
    \qmlattachedproperty bool QtQuick2::GridView::delayRemove
    This attached property holds whether the delegate may be destroyed. It
    is attached to each instance of the delegate. The default value is false.

    It is sometimes necessary to delay the destruction of an item
    until an animation completes. The example delegate below ensures that the
    animation completes before the item is removed from the list.

    \snippet doc/src/snippets/qml/gridview/gridview.qml delayRemove

    If a \l remove transition has been specified, it will not be applied until
    delayRemove is returned to \c false.
*/

/*!
    \qmlattachedsignal QtQuick2::GridView::onAdd()
    This attached handler is called immediately after an item is added to the view.
*/

/*!
    \qmlattachedsignal QtQuick2::GridView::onRemove()
    This attached handler is called immediately before an item is removed from the view.

    If a \l remove transition has been specified, it is applied after
    this signal handler is called, providing that delayRemove is false.
*/


/*!
  \qmlproperty model QtQuick2::GridView::model
  This property holds the model providing data for the grid.

    The model provides the set of data that is used to create the items
    in the view. Models can be created directly in QML using \l ListModel, \l XmlListModel
    or \l VisualItemModel, or provided by C++ model classes. If a C++ model class is
    used, it must be a subclass of \l QAbstractItemModel or a simple list.

  \sa {qmlmodels}{Data Models}
*/

/*!
    \qmlproperty Component QtQuick2::GridView::delegate

    The delegate provides a template defining each item instantiated by the view.
    The index is exposed as an accessible \c index property.  Properties of the
    model are also available depending upon the type of \l {qmlmodels}{Data Model}.

    The number of elements in the delegate has a direct effect on the
    flicking performance of the view.  If at all possible, place functionality
    that is not needed for the normal display of the delegate in a \l Loader which
    can load additional elements when needed.

    The GridView will layout the items based on the size of the root item
    in the delegate.

    \note Delegates are instantiated as needed and may be destroyed at any time.
    State should \e never be stored in a delegate.
*/

/*!
  \qmlproperty int QtQuick2::GridView::currentIndex
  \qmlproperty Item QtQuick2::GridView::currentItem

    The \c currentIndex property holds the index of the current item, and
    \c currentItem holds the current item.  Setting the currentIndex to -1
    will clear the highlight and set currentItem to null.

    If highlightFollowsCurrentItem is \c true, setting either of these
    properties will smoothly scroll the GridView so that the current
    item becomes visible.

    Note that the position of the current item
    may only be approximate until it becomes visible in the view.
*/


/*!
  \qmlproperty Item QtQuick2::GridView::highlightItem

  This holds the highlight item created from the \l highlight component.

  The highlightItem is managed by the view unless
  \l highlightFollowsCurrentItem is set to false.

  \sa highlight, highlightFollowsCurrentItem
*/


/*!
  \qmlproperty int QtQuick2::GridView::count
  This property holds the number of items in the view.
*/


/*!
  \qmlproperty Component QtQuick2::GridView::highlight
  This property holds the component to use as the highlight.

  An instance of the highlight component is created for each view.
  The geometry of the resulting component instance will be managed by the view
  so as to stay with the current item, unless the highlightFollowsCurrentItem property is false.

  \sa highlightItem, highlightFollowsCurrentItem
*/

/*!
  \qmlproperty bool QtQuick2::GridView::highlightFollowsCurrentItem
  This property sets whether the highlight is managed by the view.

    If this property is true (the default value), the highlight is moved smoothly
    to follow the current item.  Otherwise, the
    highlight is not moved by the view, and any movement must be implemented
    by the highlight.

    Here is a highlight with its motion defined by a \l {SpringAnimation} item:

    \snippet doc/src/snippets/qml/gridview/gridview.qml highlightFollowsCurrentItem
*/


/*!
    \qmlproperty int QtQuick2::GridView::highlightMoveDuration
    This property holds the move animation duration of the highlight delegate.

    highlightFollowsCurrentItem must be true for this property
    to have effect.

    The default value for the duration is 150ms.

    \sa highlightFollowsCurrentItem
*/

/*!
    \qmlproperty real QtQuick2::GridView::preferredHighlightBegin
    \qmlproperty real QtQuick2::GridView::preferredHighlightEnd
    \qmlproperty enumeration QtQuick2::GridView::highlightRangeMode

    These properties define the preferred range of the highlight (for the current item)
    within the view. The \c preferredHighlightBegin value must be less than the
    \c preferredHighlightEnd value.

    These properties affect the position of the current item when the view is scrolled.
    For example, if the currently selected item should stay in the middle of the
    view when it is scrolled, set the \c preferredHighlightBegin and
    \c preferredHighlightEnd values to the top and bottom coordinates of where the middle
    item would be. If the \c currentItem is changed programmatically, the view will
    automatically scroll so that the current item is in the middle of the view.
    Furthermore, the behavior of the current item index will occur whether or not a
    highlight exists.

    Valid values for \c highlightRangeMode are:

    \list
    \li GridView.ApplyRange - the view attempts to maintain the highlight within the range.
       However, the highlight can move outside of the range at the ends of the view or due
       to mouse interaction.
    \li GridView.StrictlyEnforceRange - the highlight never moves outside of the range.
       The current item changes if a keyboard or mouse action would cause the highlight to move
       outside of the range.
    \li GridView.NoHighlightRange - this is the default value.
    \endlist
*/


/*!
  \qmlproperty enumeration QtQuick2::GridView::layoutDirection
  This property holds the layout direction of the grid.

    Possible values:

  \list
  \li Qt.LeftToRight (default) - Items will be laid out starting in the top, left corner. The flow is
  dependent on the \l GridView::flow property.
  \li Qt.RightToLeft - Items will be laid out starting in the top, right corner. The flow is dependent
  on the \l GridView::flow property.
  \endlist

  \b Note: If GridView::flow is set to GridView.LeftToRight, this is not to be confused if
  GridView::layoutDirection is set to Qt.RightToLeft. The GridView.LeftToRight flow value simply
  indicates that the flow is horizontal.
*/


/*!
    \qmlproperty enumeration QtQuick2::GridView::effectiveLayoutDirection
    This property holds the effective layout direction of the grid.

    When using the attached property \l {LayoutMirroring::enabled}{LayoutMirroring::enabled} for locale layouts,
    the visual layout direction of the grid will be mirrored. However, the
    property \l {GridView::layoutDirection}{layoutDirection} will remain unchanged.

    \sa GridView::layoutDirection, {LayoutMirroring}{LayoutMirroring}
*/
/*!
  \qmlproperty bool QtQuick2::GridView::keyNavigationWraps
  This property holds whether the grid wraps key navigation

    If this is true, key navigation that would move the current item selection
    past one end of the view instead wraps around and moves the selection to
    the other end of the view.

    By default, key navigation is not wrapped.
*/
/*!
    \qmlproperty int QtQuick2::GridView::cacheBuffer
    This property determines whether delegates are retained outside the
    visible area of the view.

    If non-zero the view may keep as many delegates
    instantiated as will fit within the buffer specified.  For example,
    if in a vertical view the delegate is 20 pixels high, there are 3
    columns and \c cacheBuffer is
    set to 40, then up to 6 delegates above and 6 delegates below the visible
    area may be created/retained.  The buffered delegates are created asynchronously,
    allowing creation to occur across multiple frames and reducing the
    likelihood of skipping frames.  In order to improve painting performance
    delegates outside the visible area have their \l visible property set to
    false until they are moved into the visible area.

    Note that cacheBuffer is not a pixel buffer - it only maintains additional
    instantiated delegates.

    Setting this value can make scrolling the list smoother at the expense
    of additional memory usage.  It is not a substitute for creating efficient
    delegates; the fewer elements in a delegate, the faster a view may be
    scrolled.
*/
void QQuickGridView::setHighlightMoveDuration(int duration)
{
    Q_D(QQuickGridView);
    if (d->highlightMoveDuration != duration) {
        if (d->highlightYAnimator) {
            d->highlightXAnimator->userDuration = duration;
            d->highlightYAnimator->userDuration = duration;
        }
        QQuickItemView::setHighlightMoveDuration(duration);
    }
}

/*!
  \qmlproperty enumeration QtQuick2::GridView::flow
  This property holds the flow of the grid.

    Possible values:

    \list
    \li GridView.LeftToRight (default) - Items are laid out from left to right, and the view scrolls vertically
    \li GridView.TopToBottom - Items are laid out from top to bottom, and the view scrolls horizontally
    \endlist
*/
QQuickGridView::Flow QQuickGridView::flow() const
{
    Q_D(const QQuickGridView);
    return d->flow;
}

void QQuickGridView::setFlow(Flow flow)
{
    Q_D(QQuickGridView);
    if (d->flow != flow) {
        d->flow = flow;
        if (d->flow == LeftToRight) {
            setContentWidth(-1);
            setFlickableDirection(VerticalFlick);
        } else {
            setContentHeight(-1);
            setFlickableDirection(HorizontalFlick);
        }
        setContentX(0);
        setContentY(0);
        d->regenerate();
        emit flowChanged();
    }
}


/*!
  \qmlproperty real QtQuick2::GridView::cellWidth
  \qmlproperty real QtQuick2::GridView::cellHeight

  These properties holds the width and height of each cell in the grid.

  The default cell size is 100x100.
*/
qreal QQuickGridView::cellWidth() const
{
    Q_D(const QQuickGridView);
    return d->cellWidth;
}

void QQuickGridView::setCellWidth(qreal cellWidth)
{
    Q_D(QQuickGridView);
    if (cellWidth != d->cellWidth && cellWidth > 0) {
        d->cellWidth = qMax(qreal(1), cellWidth);
        d->updateViewport();
        emit cellWidthChanged();
        d->forceLayout = true;
        polish();
    }
}

qreal QQuickGridView::cellHeight() const
{
    Q_D(const QQuickGridView);
    return d->cellHeight;
}

void QQuickGridView::setCellHeight(qreal cellHeight)
{
    Q_D(QQuickGridView);
    if (cellHeight != d->cellHeight && cellHeight > 0) {
        d->cellHeight = qMax(qreal(1), cellHeight);
        d->updateViewport();
        emit cellHeightChanged();
        d->forceLayout = true;
        polish();
    }
}
/*!
    \qmlproperty enumeration QtQuick2::GridView::snapMode

    This property determines how the view scrolling will settle following a drag or flick.
    The possible values are:

    \list
    \li GridView.NoSnap (default) - the view stops anywhere within the visible area.
    \li GridView.SnapToRow - the view settles with a row (or column for \c GridView.TopToBottom flow)
    aligned with the start of the view.
    \li GridView.SnapOneRow - the view will settle no more than one row (or column for \c GridView.TopToBottom flow)
    away from the first visible row at the time the mouse button is released.
    This mode is particularly useful for moving one page at a time.
    \endlist

*/
QQuickGridView::SnapMode QQuickGridView::snapMode() const
{
    Q_D(const QQuickGridView);
    return d->snapMode;
}

void QQuickGridView::setSnapMode(SnapMode mode)
{
    Q_D(QQuickGridView);
    if (d->snapMode != mode) {
        d->snapMode = mode;
        emit snapModeChanged();
    }
}


/*!
    \qmlproperty Component QtQuick2::GridView::footer
    This property holds the component to use as the footer.

    An instance of the footer component is created for each view.  The
    footer is positioned at the end of the view, after any items.

    \sa header, footerItem
*/
/*!
    \qmlproperty Component QtQuick2::GridView::header
    This property holds the component to use as the header.

    An instance of the header component is created for each view.  The
    header is positioned at the beginning of the view, before any items.

    \sa footer, headerItem
*/

/*!
    \qmlproperty Item QtQuick2::GridView::headerItem
    This holds the header item created from the \l header component.

    An instance of the header component is created for each view.  The
    header is positioned at the beginning of the view, before any items.

    \sa header, footerItem
*/

/*!
    \qmlproperty Item QtQuick2::GridView::footerItem
    This holds the footer item created from the \l footer component.

    An instance of the footer component is created for each view.  The
    footer is positioned at the end of the view, after any items.

    \sa footer, headerItem
*/

/*!
    \qmlproperty Transition QtQuick2::GridView::populate

    This property holds the transition to apply to the items that are initially created
    for a view.

    It is applied to all items that are created when:

    \list
    \li The view is first created
    \li The view's \l model changes
    \li The view's \l model is \l {QAbstractItemModel::reset}{reset}, if the model is a QAbstractItemModel subclass
    \endlist

    For example, here is a view that specifies such a transition:

    \code
    GridView {
        ...
        populate: Transition {
            NumberAnimation { properties: "x,y"; duration: 1000 }
        }
    }
    \endcode

    When the view is initialized, the view will create all the necessary items for the view,
    then animate them to their correct positions within the view over one second.

    For more details and examples on how to use view transitions, see the ViewTransition
    documentation.

    \sa add, ViewTransition
*/

/*!
    \qmlproperty Transition QtQuick2::GridView::add

    This property holds the transition to apply to items that are added to the view.

    For example, here is a view that specifies such a transition:

    \code
    GridView {
        ...
        add: Transition {
            NumberAnimation { properties: "x,y"; from: 100; duration: 1000 }
        }
    }
    \endcode

    Whenever an item is added to the above view, the item will be animated from the position (100,100)
    to its final x,y position within the view, over one second. The transition only applies to
    the new items that are added to the view; it does not apply to the items below that are
    displaced by the addition of the new items. To animate the displaced items, set the \l displaced
    or \l addDisplaced properties.

    For more details and examples on how to use view transitions, see the ViewTransition
    documentation.

    \note This transition is not applied to the items that are created when the view is initially
    populated, or when the view's \l model changes. In those cases, the \l populate transition is
    applied instead.

    \sa addDisplaced, populate, ViewTransition
*/

/*!
    \qmlproperty Transition QtQuick2::GridView::addDisplaced

    This property holds the transition to apply to items within the view that are displaced by
    the addition of other items to the view.

    For example, here is a view that specifies such a transition:

    \code
    GridView {
        ...
        addDisplaced: Transition {
            NumberAnimation { properties: "x,y"; duration: 1000 }
        }
    }
    \endcode

    Whenever an item is added to the above view, all items beneath the new item are displaced, causing
    them to move down (or sideways, if horizontally orientated) within the view. As this
    displacement occurs, the items' movement to their new x,y positions within the view will be
    animated by a NumberAnimation over one second, as specified. This transition is not applied to
    the new item that has been added to the view; to animate the added items, set the \l add
    property.

    If an item is displaced by multiple types of operations at the same time, it is not defined as to
    whether the addDisplaced, moveDisplaced or removeDisplaced transition will be applied. Additionally,
    if it is not necessary to specify different transitions depending on whether an item is displaced
    by an add, move or remove operation, consider setting the \l displaced property instead.

    For more details and examples on how to use view transitions, see the ViewTransition
    documentation.

    \note This transition is not applied to the items that are created when the view is initially
    populated, or when the view's \l model changes. In those cases, the \l populate transition is
    applied instead.

    \sa displaced, add, populate, ViewTransition
*/
/*!
    \qmlproperty Transition QtQuick2::GridView::move

    This property holds the transition to apply to items in the view that are being moved due
    to a move operation in the view's \l model.

    For example, here is a view that specifies such a transition:

    \code
    GridView {
        ...
        move: Transition {
            NumberAnimation { properties: "x,y"; duration: 1000 }
        }
    }
    \endcode

    Whenever the \l model performs a move operation to move a particular set of indexes, the
    respective items in the view will be animated to their new positions in the view over one
    second. The transition only applies to the items that are the subject of the move operation
    in the model; it does not apply to items below them that are displaced by the move operation.
    To animate the displaced items, set the \l displaced or \l moveDisplaced properties.

    For more details and examples on how to use view transitions, see the ViewTransition
    documentation.

    \sa moveDisplaced, ViewTransition
*/

/*!
    \qmlproperty Transition QtQuick2::GridView::moveDisplaced

    This property holds the transition to apply to items that are displaced by a move operation in
    the view's \l model.

    For example, here is a view that specifies such a transition:

    \code
    GridView {
        ...
        moveDisplaced: Transition {
            NumberAnimation { properties: "x,y"; duration: 1000 }
        }
    }
    \endcode

    Whenever the \l model performs a move operation to move a particular set of indexes, the items
    between the source and destination indexes of the move operation are displaced, causing them
    to move upwards or downwards (or sideways, if horizontally orientated) within the view. As this
    displacement occurs, the items' movement to their new x,y positions within the view will be
    animated by a NumberAnimation over one second, as specified. This transition is not applied to
    the items that are the actual subjects of the move operation; to animate the moved items, set
    the \l move property.

    If an item is displaced by multiple types of operations at the same time, it is not defined as to
    whether the addDisplaced, moveDisplaced or removeDisplaced transition will be applied. Additionally,
    if it is not necessary to specify different transitions depending on whether an item is displaced
    by an add, move or remove operation, consider setting the \l displaced property instead.

    For more details and examples on how to use view transitions, see the ViewTransition
    documentation.

    \sa displaced, move, ViewTransition
*/

/*!
    \qmlproperty Transition QtQuick2::GridView::remove

    This property holds the transition to apply to items that are removed from the view.

    For example, here is a view that specifies such a transition:

    \code
    GridView {
        ...
        remove: Transition {
            ParallelAnimation {
                NumberAnimation { property: "opacity"; to: 0; duration: 1000 }
                NumberAnimation { properties: "x,y"; to: 100; duration: 1000 }
            }
        }
    }
    \endcode

    Whenever an item is removed from the above view, the item will be animated to the position (100,100)
    over one second, and in parallel will also change its opacity to 0. The transition
    only applies to the items that are removed from the view; it does not apply to the items below
    them that are displaced by the removal of the items. To animate the displaced items, set the
    \l displaced or \l removeDisplaced properties.

    Note that by the time the transition is applied, the item has already been removed from the
    model; any references to the model data for the removed index will not be valid.

    Additionally, if the \l delayRemove attached property has been set for a delegate item, the
    remove transition will not be applied until \l delayRemove becomes false again.

    For more details and examples on how to use view transitions, see the ViewTransition
    documentation.

    \sa removeDisplaced, ViewTransition
*/

/*!
    \qmlproperty Transition QtQuick2::GridView::removeDisplaced

    This property holds the transition to apply to items in the view that are displaced by the
    removal of other items in the view.

    For example, here is a view that specifies such a transition:

    \code
    GridView {
        ...
        removeDisplaced: Transition {
            NumberAnimation { properties: "x,y"; duration: 1000 }
        }
    }
    \endcode

    Whenever an item is removed from the above view, all items beneath it are displaced, causing
    them to move upwards (or sideways, if horizontally orientated) within the view. As this
    displacement occurs, the items' movement to their new x,y positions within the view will be
    animated by a NumberAnimation over one second, as specified. This transition is not applied to
    the item that has actually been removed from the view; to animate the removed items, set the
    \l remove property.

    If an item is displaced by multiple types of operations at the same time, it is not defined as to
    whether the addDisplaced, moveDisplaced or removeDisplaced transition will be applied. Additionally,
    if it is not necessary to specify different transitions depending on whether an item is displaced
    by an add, move or remove operation, consider setting the \l displaced property instead.

    For more details and examples on how to use view transitions, see the ViewTransition
    documentation.

    \sa displaced, remove, ViewTransition
*/

/*!
    \qmlproperty Transition QtQuick2::GridView::displaced
    This property holds the generic transition to apply to items that have been displaced by
    any model operation that affects the view.

    This is a convenience for specifying a generic transition for items that are displaced
    by add, move or remove operations, without having to specify the individual addDisplaced,
    moveDisplaced and removeDisplaced properties. For example, here is a view that specifies
    a displaced transition:

    \code
    GridView {
        ...
        displaced: Transition {
            NumberAnimation { properties: "x,y"; duration: 1000 }
        }
    }
    \endcode

    When any item is added, moved or removed within the above view, the items below it are
    displaced, causing them to move down (or sideways, if horizontally orientated) within the
    view. As this displacement occurs, the items' movement to their new x,y positions within
    the view will be animated by a NumberAnimation over one second, as specified.

    If a view specifies this generic displaced transition as well as a specific addDisplaced,
    moveDisplaced or removeDisplaced transition, the more specific transition will be used
    instead of the generic displaced transition when the relevant operation occurs, providing that
    the more specific transition has not been disabled (by setting \l {Transition::enabled}{enabled}
    to false). If it has indeed been disabled, the generic displaced transition is applied instead.

    For more details and examples on how to use view transitions, see the ViewTransition
    documentation.

    \sa addDisplaced, moveDisplaced, removeDisplaced, ViewTransition
*/

void QQuickGridView::viewportMoved()
{
    Q_D(QQuickGridView);
    QQuickItemView::viewportMoved();
    if (!d->itemCount)
        return;
    if (d->inViewportMoved)
        return;
    d->inViewportMoved = true;

    if (yflick())
        d->bufferMode = d->vData.smoothVelocity < 0 ? QQuickItemViewPrivate::BufferBefore : QQuickItemViewPrivate::BufferAfter;
    else if (d->isRightToLeftTopToBottom())
        d->bufferMode = d->hData.smoothVelocity < 0 ? QQuickItemViewPrivate::BufferAfter : QQuickItemViewPrivate::BufferBefore;
    else
        d->bufferMode = d->hData.smoothVelocity < 0 ? QQuickItemViewPrivate::BufferBefore : QQuickItemViewPrivate::BufferAfter;

    d->refill();

    // Set visibility of items to eliminate cost of items outside the visible area.
    qreal from = d->isContentFlowReversed() ? -d->position()-d->size() : d->position();
    qreal to = d->isContentFlowReversed() ? -d->position() : d->position()+d->size();
    for (int i = 0; i < d->visibleItems.count(); ++i) {
        FxGridItemSG *item = static_cast<FxGridItemSG*>(d->visibleItems.at(i));
        item->item->setVisible(item->rowPos() + d->rowSize() >= from && item->rowPos() <= to);
    }
    if (d->currentItem) {
        FxGridItemSG *item = static_cast<FxGridItemSG*>(d->currentItem);
        item->item->setVisible(item->rowPos() + d->rowSize() >= from && item->rowPos() <= to);
    }

    if (d->hData.flicking || d->vData.flicking || d->hData.moving || d->vData.moving)
        d->moveReason = QQuickGridViewPrivate::Mouse;
    if (d->moveReason != QQuickGridViewPrivate::SetIndex) {
        if (d->haveHighlightRange && d->highlightRange == StrictlyEnforceRange && d->highlight) {
            // reposition highlight
            qreal pos = d->highlight->position();
            qreal viewPos = d->isRightToLeftTopToBottom() ? -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->highlightXAnimator->stop();
                d->highlightYAnimator->stop();
                static_cast<FxGridItemSG*>(d->highlight)->setPosition(static_cast<FxGridItemSG*>(d->highlight)->colPos(), pos);
            } else {
                d->updateHighlight();
            }

            // update current index
            int idx = d->snapIndex();
            if (idx >= 0 && idx != d->currentIndex) {
                d->updateCurrent(idx);
                if (d->currentItem && static_cast<FxGridItemSG*>(d->currentItem)->colPos() != static_cast<FxGridItemSG*>(d->highlight)->colPos() && d->autoHighlight) {
                    if (d->flow == LeftToRight)
                        d->highlightXAnimator->to = d->currentItem->itemX();
                    else
                        d->highlightYAnimator->to = d->currentItem->itemY();
                }
            }
        }
    }

    d->inViewportMoved = false;
}

void QQuickGridView::keyPressEvent(QKeyEvent *event)
{
    Q_D(QQuickGridView);
    if (d->model && d->model->count() && d->interactive) {
        d->moveReason = QQuickGridViewPrivate::SetIndex;
        int oldCurrent = currentIndex();
        switch (event->key()) {
        case Qt::Key_Up:
            moveCurrentIndexUp();
            break;
        case Qt::Key_Down:
            moveCurrentIndexDown();
            break;
        case Qt::Key_Left:
            moveCurrentIndexLeft();
            break;
        case Qt::Key_Right:
            moveCurrentIndexRight();
            break;
        default:
            break;
        }
        if (oldCurrent != currentIndex()) {
            event->accept();
            return;
        }
    }
    event->ignore();
    QQuickItemView::keyPressEvent(event);
}

void QQuickGridView::geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry)
{
    Q_D(QQuickGridView);
    d->resetColumns();
    QQuickItemView::geometryChanged(newGeometry, oldGeometry);
}

/*!
    \qmlmethod QtQuick2::GridView::moveCurrentIndexUp()

    Move the currentIndex up one item in the view.
    The current index will wrap if keyNavigationWraps is true and it
    is currently at the end. This method has no effect if the \l count is zero.

    \b Note: methods should only be called after the Component has completed.
*/


void QQuickGridView::moveCurrentIndexUp()
{
    Q_D(QQuickGridView);
    const int count = d->model ? d->model->count() : 0;
    if (!count)
        return;
    if (d->flow == QQuickGridView::LeftToRight) {
        if (currentIndex() >= d->columns || d->wrap) {
            int index = currentIndex() - d->columns;
            setCurrentIndex((index >= 0 && index < count) ? index : count-1);
        }
    } else {
        if (currentIndex() > 0 || d->wrap) {
            int index = currentIndex() - 1;
            setCurrentIndex((index >= 0 && index < count) ? index : count-1);
        }
    }
}

/*!
    \qmlmethod QtQuick2::GridView::moveCurrentIndexDown()

    Move the currentIndex down one item in the view.
    The current index will wrap if keyNavigationWraps is true and it
    is currently at the end. This method has no effect if the \l count is zero.

    \b Note: methods should only be called after the Component has completed.
*/
void QQuickGridView::moveCurrentIndexDown()
{
    Q_D(QQuickGridView);
    const int count = d->model ? d->model->count() : 0;
    if (!count)
        return;
    if (d->flow == QQuickGridView::LeftToRight) {
        if (currentIndex() < count - d->columns || d->wrap) {
            int index = currentIndex()+d->columns;
            setCurrentIndex((index >= 0 && index < count) ? index : 0);
        }
    } else {
        if (currentIndex() < count - 1 || d->wrap) {
            int index = currentIndex() + 1;
            setCurrentIndex((index >= 0 && index < count) ? index : 0);
        }
    }
}

/*!
    \qmlmethod QtQuick2::GridView::moveCurrentIndexLeft()

    Move the currentIndex left one item in the view.
    The current index will wrap if keyNavigationWraps is true and it
    is currently at the end. This method has no effect if the \l count is zero.

    \b Note: methods should only be called after the Component has completed.
*/
void QQuickGridView::moveCurrentIndexLeft()
{
    Q_D(QQuickGridView);
    const int count = d->model ? d->model->count() : 0;
    if (!count)
        return;
    if (effectiveLayoutDirection() == Qt::LeftToRight) {
        if (d->flow == QQuickGridView::LeftToRight) {
            if (currentIndex() > 0 || d->wrap) {
                int index = currentIndex() - 1;
                setCurrentIndex((index >= 0 && index < count) ? index : count-1);
            }
        } else {
            if (currentIndex() >= d->columns || d->wrap) {
                int index = currentIndex() - d->columns;
                setCurrentIndex((index >= 0 && index < count) ? index : count-1);
            }
        }
    } else {
        if (d->flow == QQuickGridView::LeftToRight) {
            if (currentIndex() < count - 1 || d->wrap) {
                int index = currentIndex() + 1;
                setCurrentIndex((index >= 0 && index < count) ? index : 0);
            }
        } else {
            if (currentIndex() < count - d->columns || d->wrap) {
                int index = currentIndex() + d->columns;
                setCurrentIndex((index >= 0 && index < count) ? index : 0);
            }
        }
    }
}


/*!
    \qmlmethod QtQuick2::GridView::moveCurrentIndexRight()

    Move the currentIndex right one item in the view.
    The current index will wrap if keyNavigationWraps is true and it
    is currently at the end. This method has no effect if the \l count is zero.

    \b Note: methods should only be called after the Component has completed.
*/
void QQuickGridView::moveCurrentIndexRight()
{
    Q_D(QQuickGridView);
    const int count = d->model ? d->model->count() : 0;
    if (!count)
        return;
    if (effectiveLayoutDirection() == Qt::LeftToRight) {
        if (d->flow == QQuickGridView::LeftToRight) {
            if (currentIndex() < count - 1 || d->wrap) {
                int index = currentIndex() + 1;
                setCurrentIndex((index >= 0 && index < count) ? index : 0);
            }
        } else {
            if (currentIndex() < count - d->columns || d->wrap) {
                int index = currentIndex()+d->columns;
                setCurrentIndex((index >= 0 && index < count) ? index : 0);
            }
        }
    } else {
        if (d->flow == QQuickGridView::LeftToRight) {
            if (currentIndex() > 0 || d->wrap) {
                int index = currentIndex() - 1;
                setCurrentIndex((index >= 0 && index < count) ? index : count-1);
            }
        } else {
            if (currentIndex() >= d->columns || d->wrap) {
                int index = currentIndex() - d->columns;
                setCurrentIndex((index >= 0 && index < count) ? index : count-1);
            }
        }
    }
}

bool QQuickGridViewPrivate::applyInsertionChange(const QQuickChangeSet::Insert &change, ChangeResult *insertResult, QList<FxViewItem *> *addedItems, QList<MovedItem> *movingIntoView)
{
    Q_Q(QQuickGridView);

    int modelIndex = change.index;
    int count = change.count;

    int index = visibleItems.count() ? mapFromModel(modelIndex) : 0;

    if (index < 0) {
        int i = visibleItems.count() - 1;
        while (i > 0 && visibleItems.at(i)->index == -1)
            --i;
        if (visibleItems.at(i)->index + 1 == modelIndex) {
            // Special case of appending an item to the model.
            index = visibleItems.count();
        } else {
            if (modelIndex <= visibleIndex) {
                // Insert before visible items
                visibleIndex += count;
                for (int i = 0; i < visibleItems.count(); ++i) {
                    FxViewItem *item = visibleItems.at(i);
                    if (item->index != -1 && item->index >= modelIndex)
                        item->index += count;
                }
            }
            return true;
        }
    }

    qreal tempPos = isRightToLeftTopToBottom() ? -position()-size()+q->width()+1 : position();
    qreal colPos = 0;
    qreal rowPos = 0;
    int colNum = 0;
    if (visibleItems.count()) {
        if (index < visibleItems.count()) {
            FxGridItemSG *gridItem = static_cast<FxGridItemSG*>(visibleItems.at(index));
            colPos = gridItem->colPos();
            rowPos = gridItem->rowPos();
            colNum = qFloor((colPos+colSize()/2) / colSize());
        } else {
            // appending items to visible list
            FxGridItemSG *gridItem = static_cast<FxGridItemSG*>(visibleItems.at(index-1));
            rowPos = gridItem->rowPos();
            colNum = qFloor((gridItem->colPos()+colSize()/2) / colSize());
            if (++colNum >= columns) {
                colNum = 0;
                rowPos += rowSize();
            }
            colPos = colNum * colSize();
        }
    }

    // Update the indexes of the following visible items.
    for (int i = 0; i < visibleItems.count(); ++i) {
        FxViewItem *item = visibleItems.at(i);
        if (item->index != -1 && item->index >= modelIndex) {
            item->index += count;
            if (change.isMove())
                item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::MoveTransition, false);
            else
                item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, false);
        }
    }

    int prevVisibleCount = visibleItems.count();
    if (insertResult->visiblePos.isValid() && rowPos < insertResult->visiblePos) {
        // Insert items before the visible item.
        int insertionIdx = index;
        int i = count - 1;
        int from = tempPos - buffer;

        while (i >= 0) {
            if (rowPos > from && insertionIdx < visibleIndex) {
                // item won't be visible, just note the size for repositioning
                insertResult->countChangeBeforeVisible++;
            } else {
                // item is before first visible e.g. in cache buffer
                FxViewItem *item = 0;
                if (change.isMove() && (item = currentChanges.removedItems.take(change.moveKey(modelIndex + i))))
                    item->index = modelIndex + i;
                if (!item)
                    item = createItem(modelIndex + i);
                if (!item)
                    return false;

                item->item->setVisible(true);
                visibleItems.insert(insertionIdx, item);
                if (insertionIdx == 0)
                    insertResult->changedFirstItem = true;
                if (!change.isMove()) {
                    addedItems->append(item);
                    item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, true);
                }
                insertResult->sizeChangesBeforeVisiblePos += rowSize();
            }

            if (--colNum < 0 ) {
                colNum = columns - 1;
                rowPos -= rowSize();
            }
            colPos = colNum * colSize();
            index++;
            i--;
        }
    } else {
        int i = 0;
        int to = buffer+tempPos+size()-1;
        while (i < count && rowPos <= to + rowSize()*(columns - colNum)/qreal(columns+1)) {
            FxViewItem *item = 0;
            if (change.isMove() && (item = currentChanges.removedItems.take(change.moveKey(modelIndex + i))))
                item->index = modelIndex + i;
            bool newItem = !item;
            if (!item)
                item = createItem(modelIndex + i);
            if (!item)
                return false;

            item->item->setVisible(true);
            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 (newItem && transitioner && transitioner->canTransition(QQuickItemViewTransitioner::MoveTransition, true))
                    movingIntoView->append(MovedItem(item, change.moveKey(item->index)));
            } else {
                addedItems->append(item);
                item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, true);
            }
            insertResult->sizeChangesAfterVisiblePos += rowSize();

            if (++colNum >= columns) {
                colNum = 0;
                rowPos += rowSize();
            }
            colPos = colNum * colSize();
            ++index;
            ++i;
        }
    }

    updateVisibleIndex();

    return visibleItems.count() > prevVisibleCount;
}

void QQuickGridViewPrivate::translateAndTransitionItemsAfter(int afterModelIndex, const ChangeResult &insertionResult, const ChangeResult &removalResult)
{
    if (!transitioner)
        return;

    int markerItemIndex = -1;
    for (int i=0; i<visibleItems.count(); i++) {
        if (visibleItems[i]->index == afterModelIndex) {
            markerItemIndex = i;
            break;
        }
    }
    if (markerItemIndex < 0)
        return;

    const qreal viewEndPos = isContentFlowReversed() ? -position() : position() + size();
    int countItemsRemoved = -(removalResult.sizeChangesAfterVisiblePos / rowSize());

    // account for whether first item has changed if < 1 row was removed before visible
    int changeBeforeVisible = insertionResult.countChangeBeforeVisible - removalResult.countChangeBeforeVisible;
    if (changeBeforeVisible != 0)
        countItemsRemoved += (changeBeforeVisible % columns) - (columns - 1);

    countItemsRemoved -= removalResult.countChangeAfterVisibleItems;

    for (int i=markerItemIndex+1; i<visibleItems.count() && visibleItems.at(i)->position() < viewEndPos; i++) {
        FxGridItemSG *gridItem = static_cast<FxGridItemSG *>(visibleItems[i]);
        if (!gridItem->transitionScheduledOrRunning()) {
            qreal origRowPos = gridItem->colPos();
            qreal origColPos = gridItem->rowPos();
            int indexDiff = gridItem->index - countItemsRemoved;
            gridItem->setPosition((indexDiff % columns) * colSize(), (indexDiff / columns) * rowSize());
            gridItem->transitionNextReposition(transitioner, QQuickItemViewTransitioner::RemoveTransition, false);
            gridItem->setPosition(origRowPos, origColPos);
        }
    }
}

bool QQuickGridViewPrivate::needsRefillForAddedOrRemovedIndex(int modelIndex) const
{
    // If we add or remove items before visible items, a layout may be
    // required to ensure item 0 is in the first column.
    return modelIndex < visibleIndex;
}

/*!
    \qmlmethod QtQuick2::GridView::positionViewAtIndex(int index, PositionMode mode)

    Positions the view such that the \a index is at the position specified by
    \a mode:

    \list
    \li GridView.Beginning - position item at the top (or left for \c GridView.TopToBottom flow) of the view.
    \li GridView.Center - position item in the center of the view.
    \li GridView.End - position item at bottom (or right for horizontal orientation) of the view.
    \li GridView.Visible - if any part of the item is visible then take no action, otherwise
    bring the item into view.
    \li GridView.Contain - ensure the entire item is visible.  If the item is larger than
    the view the item is positioned at the top (or left for \c GridView.TopToBottom flow) of the view.
    \endlist

    If positioning the view at the index would cause empty space to be displayed at
    the beginning or end of the view, the view will be positioned at the boundary.

    It is not recommended to use \l {Flickable::}{contentX} or \l {Flickable::}{contentY} to position the view
    at a particular index.  This is unreliable since removing items from the start
    of the view does not cause all other items to be repositioned.
    The correct way to bring an item into view is with \c positionViewAtIndex.

    \b Note: methods should only be called after the Component has completed.  To position
    the view at startup, this method should be called by Component.onCompleted.  For
    example, to position the view at the end:

    \code
    Component.onCompleted: positionViewAtIndex(count - 1, GridView.Beginning)
    \endcode
*/

/*!
    \qmlmethod QtQuick2::GridView::positionViewAtBeginning()
    \qmlmethod QtQuick2::GridView::positionViewAtEnd()

    Positions the view at the beginning or end, taking into account any header or footer.

    It is not recommended to use \l {Flickable::}{contentX} or \l {Flickable::}{contentY} to position the view
    at a particular index.  This is unreliable since removing items from the start
    of the list does not cause all other items to be repositioned, and because
    the actual start of the view can vary based on the size of the delegates.

    \b Note: methods should only be called after the Component has completed.  To position
    the view at startup, this method should be called by Component.onCompleted.  For
    example, to position the view at the end on startup:

    \code
    Component.onCompleted: positionViewAtEnd()
    \endcode
*/

/*!
    \qmlmethod int QtQuick2::GridView::indexAt(int x, int y)

    Returns the index of the visible item containing the point \a x, \a y in content
    coordinates.  If there is no item at the point specified, or the item is
    not visible -1 is returned.

    If the item is outside the visible area, -1 is returned, regardless of
    whether an item will exist at that point when scrolled into view.

    \b Note: methods should only be called after the Component has completed.
*/

/*!
    \qmlmethod Item QtQuick2::GridView::itemAt(int x, int y)

    Returns the visible item containing the point \a x, \a y in content
    coordinates.  If there is no item at the point specified, or the item is
    not visible null is returned.

    If the item is outside the visible area, null is returned, regardless of
    whether an item will exist at that point when scrolled into view.

    \b Note: methods should only be called after the Component has completed.
*/

QQuickGridViewAttached *QQuickGridView::qmlAttachedProperties(QObject *obj)
{
    return new QQuickGridViewAttached(obj);
}

QT_END_NAMESPACE