source: trunk/src/declarative/graphicsitems/qdeclarativepositioners.cpp@ 1147

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#include "private/qdeclarativepositioners_p.h"
#include "private/qdeclarativepositioners_p_p.h"

#include <qdeclarative.h>
#include <qdeclarativestate_p.h>
#include <qdeclarativestategroup_p.h>
#include <qdeclarativestateoperations_p.h>
#include <qdeclarativeinfo.h>
#include <QtCore/qmath.h>

#include <QDebug>
#include <QCoreApplication>

QT_BEGIN_NAMESPACE

static const QDeclarativeItemPrivate::ChangeTypes watchedChanges
    = QDeclarativeItemPrivate::Geometry
    | QDeclarativeItemPrivate::SiblingOrder
    | QDeclarativeItemPrivate::Visibility
    | QDeclarativeItemPrivate::Opacity
    | QDeclarativeItemPrivate::Destroyed;

void QDeclarativeBasePositionerPrivate::watchChanges(QGraphicsObject *other)
{
    if (QGraphicsItemPrivate::get(other)->isDeclarativeItem) {
        QDeclarativeItemPrivate *otherPrivate = static_cast<QDeclarativeItemPrivate*>(QGraphicsItemPrivate::get(other));
        otherPrivate->addItemChangeListener(this, watchedChanges);
    } else {
        Q_Q(QDeclarativeBasePositioner);
        QObject::connect(other, SIGNAL(widthChanged()), q, SLOT(graphicsWidgetGeometryChanged()));
        QObject::connect(other, SIGNAL(heightChanged()), q, SLOT(graphicsWidgetGeometryChanged()));
        QObject::connect(other, SIGNAL(opacityChanged()), q, SLOT(graphicsWidgetGeometryChanged()));
        QObject::connect(other, SIGNAL(visibleChanged()), q, SLOT(graphicsWidgetGeometryChanged()));
    }
}

void QDeclarativeBasePositionerPrivate::unwatchChanges(QGraphicsObject* other)
{
    if (QGraphicsItemPrivate::get(other)->isDeclarativeItem) {
        QDeclarativeItemPrivate *otherPrivate = static_cast<QDeclarativeItemPrivate*>(QGraphicsItemPrivate::get(other));
        otherPrivate->removeItemChangeListener(this, watchedChanges);
    } else {
        Q_Q(QDeclarativeBasePositioner);
        QObject::disconnect(other, SIGNAL(widthChanged()), q, SLOT(graphicsWidgetGeometryChanged()));
        QObject::disconnect(other, SIGNAL(heightChanged()), q, SLOT(graphicsWidgetGeometryChanged()));
        QObject::disconnect(other, SIGNAL(opacityChanged()), q, SLOT(graphicsWidgetGeometryChanged()));
        QObject::disconnect(other, SIGNAL(visibleChanged()), q, SLOT(graphicsWidgetGeometryChanged()));
    }
}

void QDeclarativeBasePositioner::graphicsWidgetGeometryChanged()
{
    prePositioning();
}

/*!
    \internal
    \class QDeclarativeBasePositioner
    \brief The QDeclarativeBasePositioner class provides a base for QDeclarativeGraphics layouts.

    To create a QDeclarativeGraphics Positioner, simply subclass QDeclarativeBasePositioner and implement
    doLayout(), which is automatically called when the layout might need
    updating. In doLayout() use the setX and setY functions from QDeclarativeBasePositioner, and the
    base class will apply the positions along with the appropriate transitions. The items to
    position are provided in order as the protected member positionedItems.

    You also need to set a PositionerType, to declare whether you are positioning the x, y or both
    for the child items. Depending on the chosen type, only x or y changes will be applied.

    Note that the subclass is responsible for adding the spacing in between items.
*/
QDeclarativeBasePositioner::QDeclarativeBasePositioner(PositionerType at, QDeclarativeItem *parent)
    : QDeclarativeItem(*(new QDeclarativeBasePositionerPrivate), parent)
{
    Q_D(QDeclarativeBasePositioner);
    d->init(at);
}

QDeclarativeBasePositioner::QDeclarativeBasePositioner(QDeclarativeBasePositionerPrivate &dd, PositionerType at, QDeclarativeItem *parent)
    : QDeclarativeItem(dd, parent)
{
    Q_D(QDeclarativeBasePositioner);
    d->init(at);
}

QDeclarativeBasePositioner::~QDeclarativeBasePositioner()
{
    Q_D(QDeclarativeBasePositioner);
    for (int i = 0; i < positionedItems.count(); ++i)
        d->unwatchChanges(positionedItems.at(i).item);
    positionedItems.clear();
}

int QDeclarativeBasePositioner::spacing() const
{
    Q_D(const QDeclarativeBasePositioner);
    return d->spacing;
}

void QDeclarativeBasePositioner::setSpacing(int s)
{
    Q_D(QDeclarativeBasePositioner);
    if (s==d->spacing)
        return;
    d->spacing = s;
    prePositioning();
    emit spacingChanged();
}

QDeclarativeTransition *QDeclarativeBasePositioner::move() const
{
    Q_D(const QDeclarativeBasePositioner);
    return d->moveTransition;
}

void QDeclarativeBasePositioner::setMove(QDeclarativeTransition *mt)
{
    Q_D(QDeclarativeBasePositioner);
    if (mt == d->moveTransition)
        return;
    d->moveTransition = mt;
    emit moveChanged();
}

QDeclarativeTransition *QDeclarativeBasePositioner::add() const
{
    Q_D(const QDeclarativeBasePositioner);
    return d->addTransition;
}

void QDeclarativeBasePositioner::setAdd(QDeclarativeTransition *add)
{
    Q_D(QDeclarativeBasePositioner);
    if (add == d->addTransition)
        return;

    d->addTransition = add;
    emit addChanged();
}

void QDeclarativeBasePositioner::componentComplete()
{
    Q_D(QDeclarativeBasePositioner);
    QDeclarativeItem::componentComplete();
    positionedItems.reserve(d->QGraphicsItemPrivate::children.count());
    prePositioning();
    reportConflictingAnchors();
}

QVariant QDeclarativeBasePositioner::itemChange(GraphicsItemChange change,
                                       const QVariant &value)
{
    Q_D(QDeclarativeBasePositioner);
    if (change == ItemChildAddedChange){
        QGraphicsItem* item = value.value<QGraphicsItem*>();
        QGraphicsObject* child = 0;
        if(item)
            child = item->toGraphicsObject();
        if (child)
            prePositioning();
    } else if (change == ItemChildRemovedChange) {
        QGraphicsItem* item = value.value<QGraphicsItem*>();
        QGraphicsObject* child = 0;
        if(item)
            child = item->toGraphicsObject();
        if (child) {
            QDeclarativeBasePositioner::PositionedItem posItem(child);
            int idx = positionedItems.find(posItem);
            if (idx >= 0) {
                d->unwatchChanges(child);
                positionedItems.remove(idx);
            }
            prePositioning();
        }
    }
    return QDeclarativeItem::itemChange(change, value);
}

void QDeclarativeBasePositioner::prePositioning()
{
    Q_D(QDeclarativeBasePositioner);
    if (!isComponentComplete())
        return;

    if (d->doingPositioning)
        return;

    d->queuedPositioning = false;
    d->doingPositioning = true;
    //Need to order children by creation order modified by stacking order
    QList<QGraphicsItem *> children = d->QGraphicsItemPrivate::children;
    qSort(children.begin(), children.end(), d->insertionOrder);

    QPODVector<PositionedItem,8> oldItems;
    positionedItems.copyAndClear(oldItems);
    for (int ii = 0; ii < children.count(); ++ii) {
        QGraphicsObject *child = children.at(ii)->toGraphicsObject();
        if (!child)
            continue;
        QGraphicsItemPrivate *childPrivate = static_cast<QGraphicsItemPrivate*>(QGraphicsItemPrivate::get(child));
        PositionedItem *item = 0;
        PositionedItem posItem(child);
        int wIdx = oldItems.find(posItem);
        if (wIdx < 0) {
            d->watchChanges(child);
            positionedItems.append(posItem);
            item = &positionedItems[positionedItems.count()-1];
            item->isNew = true;
            if (child->opacity() <= 0.0 || childPrivate->explicitlyHidden || !childPrivate->width() || !childPrivate->height())
                item->isVisible = false;
        } else {
            item = &oldItems[wIdx];
            // Items are only omitted from positioning if they are explicitly hidden
            // i.e. their positioning is not affected if an ancestor is hidden.
            if (child->opacity() <= 0.0 || childPrivate->explicitlyHidden || !childPrivate->width() || !childPrivate->height()) {
                item->isVisible = false;
            } else if (!item->isVisible) {
                item->isVisible = true;
                item->isNew = true;
            } else {
                item->isNew = false;
            }
            positionedItems.append(*item);
        }
    }
    QSizeF contentSize;
    doPositioning(&contentSize);
    if(d->addTransition || d->moveTransition)
        finishApplyTransitions();
    d->doingPositioning = false;
    //Set implicit size to the size of its children
    setImplicitHeight(contentSize.height());
    setImplicitWidth(contentSize.width());
}

void QDeclarativeBasePositioner::positionX(int x, const PositionedItem &target)
{
    Q_D(QDeclarativeBasePositioner);
    if(d->type == Horizontal || d->type == Both){
        if (target.isNew) {
            if (!d->addTransition)
                target.item->setX(x);
            else
                d->addActions << QDeclarativeAction(target.item, QLatin1String("x"), QVariant(x));
        } else if (x != target.item->x()) {
            if (!d->moveTransition)
                target.item->setX(x);
            else
                d->moveActions << QDeclarativeAction(target.item, QLatin1String("x"), QVariant(x));
        }
    }
}

void QDeclarativeBasePositioner::positionY(int y, const PositionedItem &target)
{
    Q_D(QDeclarativeBasePositioner);
    if(d->type == Vertical || d->type == Both){
        if (target.isNew) {
            if (!d->addTransition)
                target.item->setY(y);
            else
                d->addActions << QDeclarativeAction(target.item, QLatin1String("y"), QVariant(y));
        } else if (y != target.item->y()) {
            if (!d->moveTransition)
                target.item->setY(y);
            else
                d->moveActions << QDeclarativeAction(target.item, QLatin1String("y"), QVariant(y));
        }
    }
}

void QDeclarativeBasePositioner::finishApplyTransitions()
{
    Q_D(QDeclarativeBasePositioner);
    // Note that if a transition is not set the transition manager will
    // apply the changes directly, in the case add/move aren't set
    d->addTransitionManager.transition(d->addActions, d->addTransition);
    d->moveTransitionManager.transition(d->moveActions, d->moveTransition);
    d->addActions.clear();
    d->moveActions.clear();
}

/*!
  \qmlclass Column QDeclarativeColumn
  \ingroup qml-positioning-elements
  \since 4.7
  \brief The Column item arranges its children vertically.
  \inherits Item

  The Column item positions its child items so that they are vertically
  aligned and not overlapping.

  Spacing between items can be added using the \l spacing property.
  Transitions can be used for cases where items managed by a Column are
  added or moved. These are stored in the \l add and \l move properties
  respectively.

  See \l{Using QML Positioner and Repeater Items} for more details about this item and other
  related items.

  \section1 Example Usage

  The following example positions differently shaped rectangles using a Column
  item.

  \image verticalpositioner_example.png

  \snippet doc/src/snippets/declarative/column/vertical-positioner.qml document

  \section1 Using Transitions

  Transitions can be used to animate items that are added to, moved within,
  or removed from a Column item. The \l add and \l move properties can be set to
  the transitions that will be applied when items are added to, removed from,
  or re-positioned within a Column item.

  The use of transitions with positioners is described in more detail in the
  \l{Using QML Positioner and Repeater Items#Using Transitions}{Using QML
  Positioner and Repeater Items} document.

  \image verticalpositioner_transition.gif

  \qml
  Column {
      spacing: 2
      add: ...
      move: ...
      ...
  }
  \endqml

  \section1 Limitations

  Note that the positioner assumes that the x and y positions of its children
  will not change. If you manually change the x or y properties in script, bind
  the x or y properties, use anchors on a child of a positioner, or have the
  height of a child depend on the position of a child, then the
  positioner may exhibit strange behavior. If you need to perform any of these
  actions, consider positioning the items without the use of a Column.

  Items with a width or height of 0 will not be positioned.

  \sa Row, Grid, Flow, {declarative/positioners}{Positioners example}
*/
/*!
    \qmlproperty Transition Column::add

    This property holds the transition to be applied when adding an
    item to the positioner. The transition will only be applied to the
    added item(s).  Positioner transitions will only affect the
    position (x, y) of items.

    For a positioner, adding an item can mean that either the object
    has been created or reparented, and thus is now a child or the
    positioner, or that the object has had its opacity increased from
    zero, and thus is now visible.

    \sa move
*/
/*!
    \qmlproperty Transition Column::move

    This property holds the transition to apply when moving an item
    within the positioner.  Positioner transitions will only affect
    the position (x, y) of items.

    This transition can be performed when other items are added or removed
    from the positioner, or when items resize themselves.

    \image positioner-move.gif

    \qml
    Column {
        move: Transition {
            NumberAnimation {
                properties: "y"
                easing.type: Easing.OutBounce
            }
        }
    }
    \endqml

    \sa add, {declarative/positioners}{Positioners example}
*/
/*!
  \qmlproperty int Column::spacing

  The spacing is the amount in pixels left empty between adjacent
  items. The default spacing is 0.

  \sa Grid::spacing
*/
QDeclarativeColumn::QDeclarativeColumn(QDeclarativeItem *parent)
: QDeclarativeBasePositioner(Vertical, parent)
{
}

void QDeclarativeColumn::doPositioning(QSizeF *contentSize)
{
    int voffset = 0;

    for (int ii = 0; ii < positionedItems.count(); ++ii) {
        const PositionedItem &child = positionedItems.at(ii);
        if (!child.item || !child.isVisible)
            continue;

        if(child.item->y() != voffset)
            positionY(voffset, child);

        contentSize->setWidth(qMax(contentSize->width(), QGraphicsItemPrivate::get(child.item)->width()));

        voffset += QGraphicsItemPrivate::get(child.item)->height();
        voffset += spacing();
    }

    contentSize->setHeight(voffset - spacing());
}

void QDeclarativeColumn::reportConflictingAnchors()
{
    QDeclarativeBasePositionerPrivate *d = static_cast<QDeclarativeBasePositionerPrivate*>(QDeclarativeBasePositionerPrivate::get(this));
    for (int ii = 0; ii < positionedItems.count(); ++ii) {
        const PositionedItem &child = positionedItems.at(ii);
        if (child.item && QGraphicsItemPrivate::get(child.item)->isDeclarativeItem) {
            QDeclarativeAnchors *anchors = QDeclarativeItemPrivate::get(static_cast<QDeclarativeItem *>(child.item))->_anchors;
            if (anchors) {
                QDeclarativeAnchors::Anchors usedAnchors = anchors->usedAnchors();
                if (usedAnchors & QDeclarativeAnchors::TopAnchor ||
                    usedAnchors & QDeclarativeAnchors::BottomAnchor ||
                    usedAnchors & QDeclarativeAnchors::VCenterAnchor ||
                    anchors->fill() || anchors->centerIn()) {
                    d->anchorConflict = true;
                    break;
                }
            }
        }
    }
    if (d->anchorConflict) {
        qmlInfo(this) << "Cannot specify top, bottom, verticalCenter, fill or centerIn anchors for items inside Column";
    }
}

/*!
  \qmlclass Row QDeclarativeRow
  \ingroup qml-positioning-elements
  \since 4.7
  \brief The Row item arranges its children horizontally.
  \inherits Item

  The Row item positions its child items so that they are horizontally
  aligned and not overlapping. 

  Use \l spacing to set the spacing between items in a Row, and use the
  \l add and \l move properties to set the transitions that should be applied
  when items are added to, removed from, or re-positioned within the Row.

  See \l{Using QML Positioner and Repeater Items} for more details about this item and other
  related items.

  \section1 Example Usage

  The following example lays out differently shaped rectangles using a Row.

  \image horizontalpositioner_example.png

  \snippet doc/src/snippets/declarative/row/row.qml document

  \section1 Using Transitions

  Transitions can be used to animate items that are added to, moved within,
  or removed from a Grid item. The \l add and \l move properties can be set to
  the transitions that will be applied when items are added to, removed from,
  or re-positioned within a Row item.

  \section1 Limitations

  Note that the positioner assumes that the x and y positions of its children
  will not change. If you manually change the x or y properties in script, bind
  the x or y properties, use anchors on a child of a positioner, or have the
  width of a child depend on the position of a child, then the
  positioner may exhibit strange behaviour. If you need to perform any of these
  actions, consider positioning the items without the use of a Row.

  Items with a width or height of 0 will not be positioned.

  \sa Column, Grid, Flow, {declarative/positioners}{Positioners example}
*/
/*!
    \qmlproperty Transition Row::add

    This property holds the transition to be applied when adding an
    item to the positioner. The transition will only be applied to the
    added item(s).  Positioner transitions will only affect the
    position (x, y) of items.

    For a positioner, adding an item can mean that either the object
    has been created or reparented, and thus is now a child or the
    positioner, or that the object has had its opacity increased from
    zero, and thus is now visible.

    \sa move
*/
/*!
    \qmlproperty Transition Row::move

    This property holds the transition to be applied when moving an
    item within the positioner. Positioner transitions will only affect
    the position (x, y) of items.

    This transition can be performed when other items are added or removed
    from the positioner, or when items resize themselves.

    \qml
    Row {
        id: positioner
        move: Transition {
            NumberAnimation {
                properties: "x"
                ease: "easeOutBounce"
            }
        }
    }
    \endqml

    \sa add, {declarative/positioners}{Positioners example}
*/
/*!
  \qmlproperty int Row::spacing

  The spacing is the amount in pixels left empty between adjacent
  items. The default spacing is 0.

  \sa Grid::spacing
*/
QDeclarativeRow::QDeclarativeRow(QDeclarativeItem *parent)
: QDeclarativeBasePositioner(Horizontal, parent)
{
}

void QDeclarativeRow::doPositioning(QSizeF *contentSize)
{
    int hoffset = 0;

    for (int ii = 0; ii < positionedItems.count(); ++ii) {
        const PositionedItem &child = positionedItems.at(ii);
        if (!child.item || !child.isVisible)
            continue;

        if(child.item->x() != hoffset)
            positionX(hoffset, child);

        contentSize->setHeight(qMax(contentSize->height(), QGraphicsItemPrivate::get(child.item)->height()));

        hoffset += QGraphicsItemPrivate::get(child.item)->width();
        hoffset += spacing();
    }

    contentSize->setWidth(hoffset - spacing());
}

void QDeclarativeRow::reportConflictingAnchors()
{
    QDeclarativeBasePositionerPrivate *d = static_cast<QDeclarativeBasePositionerPrivate*>(QDeclarativeBasePositionerPrivate::get(this));
    for (int ii = 0; ii < positionedItems.count(); ++ii) {
        const PositionedItem &child = positionedItems.at(ii);
        if (child.item && QGraphicsItemPrivate::get(child.item)->isDeclarativeItem) {
            QDeclarativeAnchors *anchors = QDeclarativeItemPrivate::get(static_cast<QDeclarativeItem *>(child.item))->_anchors;
            if (anchors) {
                QDeclarativeAnchors::Anchors usedAnchors = anchors->usedAnchors();
                if (usedAnchors & QDeclarativeAnchors::LeftAnchor ||
                    usedAnchors & QDeclarativeAnchors::RightAnchor ||
                    usedAnchors & QDeclarativeAnchors::HCenterAnchor ||
                    anchors->fill() || anchors->centerIn()) {
                    d->anchorConflict = true;
                    break;
                }
            }
        }
    }
    if (d->anchorConflict)
        qmlInfo(this) << "Cannot specify left, right, horizontalCenter, fill or centerIn anchors for items inside Row";
}

/*!
  \qmlclass Grid QDeclarativeGrid
  \ingroup qml-positioning-elements
  \since 4.7
  \brief The Grid item positions its children in a grid.
  \inherits Item

  The Grid item positions its child items so that they are
  aligned in a grid and are not overlapping. 

  The grid positioner calculates a grid of rectangular cells of sufficient
  size to hold all items, placing the items in the cells, from left to right
  and top to bottom. Each item is positioned in the top-left corner of its
  cell with position (0, 0).

  A Grid defaults to four columns, and as many rows as are necessary to
  fit all child items. The number of rows and columns can be constrained
  by setting the \l rows and \l columns properties.

  Spacing can be added between child items by setting the \l spacing
  property. The amount of spacing applied will be the same in the
  horizontal and vertical directions.

  See \l{Using QML Positioner and Repeater Items} for more details about this item and other
  related items.

  \section1 Example Usage

  The following example demonstrates this.

  \image gridLayout_example.png

  \snippet doc/src/snippets/declarative/grid/grid.qml document

  \section1 Using Transitions

  Transitions can be used to animate items that are added to, moved within,
  or removed from a Grid item. The \l add and \l move properties can be set to
  the transitions that will be applied when items are added to, removed from,
  or re-positioned within a Grid item.

  \section1 Limitations

  Note that the positioner assumes that the x and y positions of its children
  will not change. If you manually change the x or y properties in script, bind
  the x or y properties, use anchors on a child of a positioner, or have the
  width or height of a child depend on the position of a child, then the
  positioner may exhibit strange behaviour. If you need to perform any of these
  actions, consider positioning the items without the use of a Grid.

  Items with a width or height of 0 will not be positioned.

  \sa Flow, Row, Column, {declarative/positioners}{Positioners example}
*/
/*!
    \qmlproperty Transition Grid::add

    This property holds the transition to be applied when adding an
    item to the positioner. The transition will only be applied to the
    added item(s).  Positioner transitions will only affect the
    position (x, y) of items.

    For a positioner, adding an item can mean that either the object
    has been created or reparented, and thus is now a child or the
    positioner, or that the object has had its opacity increased from
    zero, and thus is now visible.

    \sa move
*/
/*!
    \qmlproperty Transition Grid::move

    This property holds the transition to be applied when moving an
    item within the positioner. Positioner transitions will only affect
    the position (x, y) of items.

    This transition can be performed when other items are added or removed
    from the positioner, or when items resize themselves.

    \qml
    Grid {
        move: Transition {
            NumberAnimation {
                properties: "x,y"
                ease: "easeOutBounce"
            }
        }
    }
    \endqml

    \sa add, {declarative/positioners}{Positioners example}
*/
/*!
  \qmlproperty int Grid::spacing

  The spacing is the amount in pixels left empty between adjacent
  items. The default spacing is 0.

  The below example places a Grid containing a red, a blue and a
  green rectangle on a gray background. The area the grid positioner
  occupies is colored white. The positioner on the left has the
  no spacing (the default), and the positioner on the right has
  a spacing of 6.

  \inlineimage qml-grid-no-spacing.png
  \inlineimage qml-grid-spacing.png

  \sa rows, columns
*/
QDeclarativeGrid::QDeclarativeGrid(QDeclarativeItem *parent) :
    QDeclarativeBasePositioner(Both, parent), m_rows(-1), m_columns(-1), m_flow(LeftToRight)
{
}

/*!
    \qmlproperty int Grid::columns

    This property holds the number of columns in the grid. The default
    number of columns is 4.

    If the grid does not have enough items to fill the specified
    number of columns, some columns will be of zero width.
*/

/*!
    \qmlproperty int Grid::rows
    This property holds the number of rows in the grid.

    If the grid does not have enough items to fill the specified
    number of rows, some rows will be of zero width.
*/

void QDeclarativeGrid::setColumns(const int columns)
{
    if (columns == m_columns)
        return;
    m_columns = columns;
    prePositioning();
    emit columnsChanged();
}

void QDeclarativeGrid::setRows(const int rows)
{
    if (rows == m_rows)
        return;
    m_rows = rows;
    prePositioning();
    emit rowsChanged();
}

/*!
    \qmlproperty enumeration Grid::flow
    This property holds the flow of the layout.

    Possible values are:

    \list
    \o Grid.LeftToRight (default) - Items are positioned next to
       to each other from left to right, then wrapped to the next line.
    \o Grid.TopToBottom - Items are positioned next to each
       other from top to bottom, then wrapped to the next column.
    \endlist
*/
QDeclarativeGrid::Flow QDeclarativeGrid::flow() const
{
    return m_flow;
}

void QDeclarativeGrid::setFlow(Flow flow)
{
    if (m_flow != flow) {
        m_flow = flow;
        prePositioning();
        emit flowChanged();
    }
}

void QDeclarativeGrid::doPositioning(QSizeF *contentSize)
{

    int c = m_columns;
    int r = m_rows;
    //Is allocating the extra QPODVector too much overhead?
    QPODVector<PositionedItem, 8> visibleItems;//we aren't concerned with invisible items
    visibleItems.reserve(positionedItems.count());
    for(int i=0; i<positionedItems.count(); i++)
        if(positionedItems[i].item && positionedItems[i].isVisible)
            visibleItems.append(positionedItems[i]);

    int numVisible = visibleItems.count();
    if (m_columns <= 0 && m_rows <= 0){
        c = 4;
        r = (numVisible+3)/4;
    } else if (m_rows <= 0){
        r = (numVisible+(m_columns-1))/m_columns;
    } else if (m_columns <= 0){
        c = (numVisible+(m_rows-1))/m_rows;
    }

    QList<int> maxColWidth;
    QList<int> maxRowHeight;
    int childIndex =0;
    if (m_flow == LeftToRight) {
        for (int i=0; i < r; i++){
            for (int j=0; j < c; j++){
                if (j==0)
                    maxRowHeight << 0;
                if (i==0)
                    maxColWidth << 0;

                if (childIndex == visibleItems.count())
                    break;

                const PositionedItem &child = visibleItems.at(childIndex++);
                QGraphicsItemPrivate *childPrivate = QGraphicsItemPrivate::get(child.item);
                if (childPrivate->width() > maxColWidth[j])
                    maxColWidth[j] = childPrivate->width();
                if (childPrivate->height() > maxRowHeight[i])
                    maxRowHeight[i] = childPrivate->height();
            }
        }
    } else {
        for (int j=0; j < c; j++){
            for (int i=0; i < r; i++){
                if (j==0)
                    maxRowHeight << 0;
                if (i==0)
                    maxColWidth << 0;

                if (childIndex == positionedItems.count())
                    break;

                const PositionedItem &child = visibleItems.at(childIndex++);
                QGraphicsItemPrivate *childPrivate = QGraphicsItemPrivate::get(child.item);
                if (childPrivate->width() > maxColWidth[j])
                    maxColWidth[j] = childPrivate->width();
                if (childPrivate->height() > maxRowHeight[i])
                    maxRowHeight[i] = childPrivate->height();
            }
        }
    }

    int xoffset=0;
    int yoffset=0;
    int curRow =0;
    int curCol =0;
    for (int i = 0; i < visibleItems.count(); ++i) {
        const PositionedItem &child = visibleItems.at(i);
        if((child.item->x()!=xoffset)||(child.item->y()!=yoffset)){
            positionX(xoffset, child);
            positionY(yoffset, child);
        }

        if (m_flow == LeftToRight) {
            contentSize->setWidth(qMax(contentSize->width(), xoffset + QGraphicsItemPrivate::get(child.item)->width()));
            contentSize->setHeight(yoffset + maxRowHeight[curRow]);

            xoffset+=maxColWidth[curCol]+spacing();
            curCol++;
            curCol%=c;
            if (!curCol){
                yoffset+=maxRowHeight[curRow]+spacing();
                xoffset=0;
                curRow++;
                if (curRow>=r)
                    break;
            }
        } else {
            contentSize->setHeight(qMax(contentSize->height(), yoffset + QGraphicsItemPrivate::get(child.item)->height()));
            contentSize->setWidth(xoffset + maxColWidth[curCol]);

            yoffset+=maxRowHeight[curRow]+spacing();
            curRow++;
            curRow%=r;
            if (!curRow){
                xoffset+=maxColWidth[curCol]+spacing();
                yoffset=0;
                curCol++;
                if (curCol>=c)
                    break;
            }
        }
    }
}

void QDeclarativeGrid::reportConflictingAnchors()
{
    QDeclarativeBasePositionerPrivate *d = static_cast<QDeclarativeBasePositionerPrivate*>(QDeclarativeBasePositionerPrivate::get(this));
    for (int ii = 0; ii < positionedItems.count(); ++ii) {
        const PositionedItem &child = positionedItems.at(ii);
        if (child.item && QGraphicsItemPrivate::get(child.item)->isDeclarativeItem) {
            QDeclarativeAnchors *anchors = QDeclarativeItemPrivate::get(static_cast<QDeclarativeItem *>(child.item))->_anchors;
            if (anchors && (anchors->usedAnchors() || anchors->fill() || anchors->centerIn())) {
                d->anchorConflict = true;
                break;
            }
        }
    }
    if (d->anchorConflict)
        qmlInfo(this) << "Cannot specify anchors for items inside Grid";
}

/*!
  \qmlclass Flow QDeclarativeFlow
  \ingroup qml-positioning-elements
  \since 4.7
  \brief The Flow item arranges its children side by side, wrapping as necessary.
  \inherits Item

  The Flow item positions its child items like words on a page, wrapping them
  to create rows or columns of items that do not overlap.

  Spacing between items can be added using the \l spacing property.
  Transitions can be used for cases where items managed by a Column are
  added or moved. These are stored in the \l add and \l move properties
  respectively.

  See \l{Using QML Positioner and Repeater Items} for more details about this item and other
  related items.

  \section1 Example Usage

  The following example positions \l Text items within a parent item using
  a Flow item.

  \image qml-flow-snippet.png

  \snippet doc/src/snippets/declarative/flow.qml flow item

  \section1 Using Transitions

  Transitions can be used to animate items that are added to, moved within,
  or removed from a Flow item. The \l add and \l move properties can be set to
  the transitions that will be applied when items are added to, removed from,
  or re-positioned within a Flow item.

  The use of transitions with positioners is described in more detail in the
  \l{Using QML Positioner and Repeater Items#Using Transitions}{Using QML
  Positioner and Repeater Items} document.

  \section1 Limitations

  Note that the positioner assumes that the x and y positions of its children
  will not change. If you manually change the x or y properties in script, bind
  the x or y properties, use anchors on a child of a positioner, or have the
  width or height of a child depend on the position of a child, then the
  positioner may exhibit strange behaviour.  If you need to perform any of these
  actions, consider positioning the items without the use of a Flow.

  Items with a width or height of 0 will not be positioned.

  \sa Column, Row, Grid, {declarative/positioners}{Positioners example}
*/
/*!
    \qmlproperty Transition Flow::add

    This property holds the transition to be applied when adding an
    item to the positioner. The transition will only be applied to the
    added item(s).  Positioner transitions will only affect the
    position (x, y) of items.

    For a positioner, adding an item can mean that either the object
    has been created or reparented, and thus is now a child or the
    positioner, or that the object has had its opacity increased from
    zero, and thus is now visible.

    \sa move
*/
/*!
    \qmlproperty Transition Flow::move

    This property holds the transition to be applied when moving an
    item within the positioner. Positioner transitions will only affect
    the position (x, y) of items.

    This transition can be performed when other items are added or removed
    from the positioner, or when items resize themselves.

    \qml
    Flow {
        id: positioner
        move: Transition {
            NumberAnimation {
                properties: "x,y"
                ease: "easeOutBounce"
            }
        }
    }
    \endqml

    \sa add, {declarative/positioners}{Positioners example}
*/
/*!
  \qmlproperty int Flow::spacing

  spacing is the amount in pixels left empty between each adjacent
  item, and defaults to 0.

  \sa Grid::spacing
*/

class QDeclarativeFlowPrivate : public QDeclarativeBasePositionerPrivate
{
    Q_DECLARE_PUBLIC(QDeclarativeFlow)

public:
    QDeclarativeFlowPrivate()
        : QDeclarativeBasePositionerPrivate(), flow(QDeclarativeFlow::LeftToRight)
    {}

    QDeclarativeFlow::Flow flow;
};

QDeclarativeFlow::QDeclarativeFlow(QDeclarativeItem *parent)
: QDeclarativeBasePositioner(*(new QDeclarativeFlowPrivate), Both, parent)
{
    Q_D(QDeclarativeFlow);
    // Flow layout requires relayout if its own size changes too.
    d->addItemChangeListener(d, QDeclarativeItemPrivate::Geometry);
}

/*!
    \qmlproperty enumeration Flow::flow
    This property holds the flow of the layout.

    Possible values are:

    \list
    \o Flow.LeftToRight (default) - Items are positioned next to
    to each other from left to right until the width of the Flow
    is exceeded, then wrapped to the next line.
    \o Flow.TopToBottom - Items are positioned next to each
    other from top to bottom until the height of the Flow is exceeded,
    then wrapped to the next column.
    \endlist
*/
QDeclarativeFlow::Flow QDeclarativeFlow::flow() const
{
    Q_D(const QDeclarativeFlow);
    return d->flow;
}

void QDeclarativeFlow::setFlow(Flow flow)
{
    Q_D(QDeclarativeFlow);
    if (d->flow != flow) {
        d->flow = flow;
        prePositioning();
        emit flowChanged();
    }
}

void QDeclarativeFlow::doPositioning(QSizeF *contentSize)
{
    Q_D(QDeclarativeFlow);

    int hoffset = 0;
    int voffset = 0;
    int linemax = 0;

    for (int i = 0; i < positionedItems.count(); ++i) {
        const PositionedItem &child = positionedItems.at(i);
        if (!child.item || !child.isVisible)
            continue;

        QGraphicsItemPrivate *childPrivate = QGraphicsItemPrivate::get(child.item);
        if (d->flow == LeftToRight)  {
            if (widthValid() && hoffset && hoffset + childPrivate->width() > width()) {
                hoffset = 0;
                voffset += linemax + spacing();
                linemax = 0;
            }
        } else {
            if (heightValid() && voffset && voffset + childPrivate->height() > height()) {
                voffset = 0;
                hoffset += linemax + spacing();
                linemax = 0;
            }
        }

        if(child.item->x() != hoffset || child.item->y() != voffset){
            positionX(hoffset, child);
            positionY(voffset, child);
        }

        contentSize->setWidth(qMax(contentSize->width(), hoffset + childPrivate->width()));
        contentSize->setHeight(qMax(contentSize->height(), voffset + childPrivate->height()));

        if (d->flow == LeftToRight)  {
            hoffset += childPrivate->width();
            hoffset += spacing();
            linemax = qMax(linemax, qCeil(childPrivate->height()));
        } else {
            voffset += childPrivate->height();
            voffset += spacing();
            linemax = qMax(linemax, qCeil(childPrivate->width()));
        }
    }
}

void QDeclarativeFlow::reportConflictingAnchors()
{
    Q_D(QDeclarativeFlow);
    for (int ii = 0; ii < positionedItems.count(); ++ii) {
        const PositionedItem &child = positionedItems.at(ii);
        if (child.item && QGraphicsItemPrivate::get(child.item)->isDeclarativeItem) {
            QDeclarativeAnchors *anchors = QDeclarativeItemPrivate::get(static_cast<QDeclarativeItem *>(child.item))->_anchors;
            if (anchors && (anchors->usedAnchors() || anchors->fill() || anchors->centerIn())) {
                d->anchorConflict = true;
                break;
            }
        }
    }
    if (d->anchorConflict)
        qmlInfo(this) << "Cannot specify anchors for items inside Flow";
}

QT_END_NAMESPACE