path: root/src/corelib/kernel/qabstractitemmodel.cpp

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#include "qabstractitemmodel.h"
#include <private/qabstractitemmodel_p.h>
#include <qdatastream.h>
#include <qstringlist.h>
#include <qsize.h>
#include <qmimedata.h>
#include <qdebug.h>
#include <qvector.h>
#include <qstack.h>
#include <qbitarray.h>

#include <limits.h>

QT_BEGIN_NAMESPACE

QPersistentModelIndexData *QPersistentModelIndexData::create(const QModelIndex &index)
{
    Q_ASSERT(index.isValid()); // we will _never_ insert an invalid index in the list
    QPersistentModelIndexData *d = 0;
    QAbstractItemModel *model = const_cast<QAbstractItemModel *>(index.model());
    QHash<QModelIndex, QPersistentModelIndexData *> &indexes = model->d_func()->persistent.indexes;
    const QHash<QModelIndex, QPersistentModelIndexData *>::iterator it = indexes.find(index);
    if (it != indexes.end()) {
        d = (*it);
    } else {
        d = new QPersistentModelIndexData(index);
        indexes.insert(index, d);
    }
    Q_ASSERT(d);
    return d;
}

void QPersistentModelIndexData::destroy(QPersistentModelIndexData *data)
{
    Q_ASSERT(data);
    Q_ASSERT(data->ref == 0);
    QAbstractItemModel *model = const_cast<QAbstractItemModel *>(data->model);
    // a valid persistent model index with a null model pointer can only happen if the model was destroyed
    if (model) {
        QAbstractItemModelPrivate *p = model->d_func();
        Q_ASSERT(p);
        p->removePersistentIndexData(data);
    }
    delete data;
}

/*!
  \class QPersistentModelIndex

  \brief The QPersistentModelIndex class is used to locate data in a data model.

  \ingroup model-view

  A QPersistentModelIndex is a model index that can be stored by an
  application, and later used to access information in a model.
  Unlike the QModelIndex class, it is safe to store a
  QPersistentModelIndex since the model will ensure that references
  to items will continue to be valid as long as they can be accessed
  by the model.

  It is good practice to check that persistent model indexes are valid
  before using them.

  \sa {Model/View Programming}, QModelIndex, QAbstractItemModel
*/


/*!
  \fn QPersistentModelIndex::QPersistentModelIndex()

  \internal
*/

QPersistentModelIndex::QPersistentModelIndex()
    : d(0)
{
}

/*!
  \fn QPersistentModelIndex::QPersistentModelIndex(const QPersistentModelIndex &other)

  Creates a new QPersistentModelIndex that is a copy of the \a other persistent
  model index.
*/

QPersistentModelIndex::QPersistentModelIndex(const QPersistentModelIndex &other)
    : d(other.d)
{
    if (d) d->ref.ref();
}

/*!
    Creates a new QPersistentModelIndex that is a copy of the model \a index.
*/

QPersistentModelIndex::QPersistentModelIndex(const QModelIndex &index)
    : d(0)
{
    if (index.isValid()) {
        d = QPersistentModelIndexData::create(index);
        d->ref.ref();
    }
}

/*!
    \fn QPersistentModelIndex::~QPersistentModelIndex()

    \internal
*/

QPersistentModelIndex::~QPersistentModelIndex()
{
    if (d && !d->ref.deref()) {
        QPersistentModelIndexData::destroy(d);
        d = 0;
    }
}

/*!
  Returns true if this persistent model index is equal to the \a other
  persistent model index; otherwise returns false.

  All values in the persistent model index are used when comparing
  with another persistent model index.
*/

bool QPersistentModelIndex::operator==(const QPersistentModelIndex &other) const
{
    if (d && other.d)
        return d->index == other.d->index;
    return d == other.d;
}

/*!
    \since 4.1

    Returns true if this persistent model index is smaller than the \a other
    persistent model index; otherwise returns false.

    All values in the persistent model index are used when comparing
    with another persistent model index.
*/

bool QPersistentModelIndex::operator<(const QPersistentModelIndex &other) const
{
    if (d && other.d)
        return d->index < other.d->index;

    return d < other.d;
}

/*!
    \fn bool QPersistentModelIndex::operator!=(const QPersistentModelIndex &other) const
    \since 4.2

    Returns true if this persistent model index is not equal to the \a
    other persistent model index; otherwise returns false.
*/

/*!
    Sets the persistent model index to refer to the same item in a model
    as the \a other persistent model index.
*/

QPersistentModelIndex &QPersistentModelIndex::operator=(const QPersistentModelIndex &other)
{
    if (d == other.d)
        return *this;
    if (d && !d->ref.deref())
        QPersistentModelIndexData::destroy(d);
    d = other.d;
    if (d) d->ref.ref();
    return *this;
}

/*!
    Sets the persistent model index to refer to the same item in a model
    as the \a other model index.
*/

QPersistentModelIndex &QPersistentModelIndex::operator=(const QModelIndex &other)
{
    if (d && !d->ref.deref())
        QPersistentModelIndexData::destroy(d);
    if (other.isValid()) {
        d = QPersistentModelIndexData::create(other);
        if (d) d->ref.ref();
    } else {
        d = 0;
    }
    return *this;
}

/*!
  \fn QPersistentModelIndex::operator const QModelIndex&() const

  Cast operator that returns a const QModelIndex&.
*/

QPersistentModelIndex::operator const QModelIndex&() const
{
    static const QModelIndex invalid;
    if (d)
        return d->index;
    return invalid;
}

/*!
    \fn bool QPersistentModelIndex::operator==(const QModelIndex &other) const

    Returns true if this persistent model index refers to the same location as
    the \a other model index; otherwise returns false.
    Note that all values in the persistent model index are used when comparing
    with another model index.
*/

bool QPersistentModelIndex::operator==(const QModelIndex &other) const
{
    if (d)
        return d->index == other;
    return !other.isValid();
}

/*!
    \fn bool QPersistentModelIndex::operator!=(const QModelIndex &other) const

    Returns true if this persistent model index does not refer to the same
    location as the \a other model index; otherwise returns false.
*/

bool QPersistentModelIndex::operator!=(const QModelIndex &other) const
{
    if (d)
        return d->index != other;
    return other.isValid();
}

/*!
    \fn int QPersistentModelIndex::row() const

    Returns the row this persistent model index refers to.
*/

int QPersistentModelIndex::row() const
{
    if (d)
        return d->index.row();
    return -1;
}

/*!
    \fn int QPersistentModelIndex::column() const

    Returns the column this persistent model index refers to.
*/

int QPersistentModelIndex::column() const
{
    if (d)
        return d->index.column();
    return -1;
}

/*!
    \fn void *QPersistentModelIndex::internalPointer() const

    \internal

    Returns a \c{void} \c{*} pointer used by the model to associate the index with
    the internal data structure.
*/

void *QPersistentModelIndex::internalPointer() const
{
    if (d)
        return d->index.internalPointer();
    return 0;
}

/*!
    \fn void *QPersistentModelIndex::internalId() const

    \internal

    Returns a \c{qint64} used by the model to associate the index with
    the internal data structure.
*/

qint64 QPersistentModelIndex::internalId() const
{
    if (d)
        return d->index.internalId();
    return 0;
}

/*!
  Returns the parent QModelIndex for this persistent index, or
  QModelIndex() if it has no parent.

  \sa child() sibling() model()
*/
QModelIndex QPersistentModelIndex::parent() const
{
    if (d)
        return d->index.parent();
    return QModelIndex();
}

/*!
  Returns the sibling at \a row and \a column or an invalid
  QModelIndex if there is no sibling at this position.

  \sa parent() child()
*/

QModelIndex QPersistentModelIndex::sibling(int row, int column) const
{
    if (d)
        return d->index.sibling(row, column);
    return QModelIndex();
}

/*!
  Returns the child of the model index that is stored in the given
  \a row and \a column.

  \sa parent() sibling()
*/

QModelIndex QPersistentModelIndex::child(int row, int column) const
{
    if (d)
        return d->index.child(row, column);
    return QModelIndex();
}

/*!
  Returns the data for the given \a role for the item referred to by the index.

  \sa Qt::ItemDataRole, QAbstractItemModel::setData()
*/
QVariant QPersistentModelIndex::data(int role) const
{
    if (d)
        return d->index.data(role);
    return QVariant();
}

/*!
  \since 4.2

  Returns the flags for the item referred to by the index.
*/
Qt::ItemFlags QPersistentModelIndex::flags() const
{
    if (d)
        return d->index.flags();
    return 0;
}

/*!
  Returns the model that the index belongs to.
*/
const QAbstractItemModel *QPersistentModelIndex::model() const
{
    if (d)
        return d->index.model();
    return 0;
}

/*!
    \fn bool QPersistentModelIndex::isValid() const

    Returns true if this persistent model index is valid; otherwise returns
    false.
    A valid index belongs to a model, and has non-negative row and column numbers.

    \sa model(), row(), column()
*/

bool QPersistentModelIndex::isValid() const
{
    return d && d->index.isValid();
}

#ifndef QT_NO_DEBUG_STREAM
QDebug operator<<(QDebug dbg, const QModelIndex &idx)
{
#ifndef Q_BROKEN_DEBUG_STREAM
    dbg.nospace() << "QModelIndex(" << idx.row() << ',' << idx.column()
                  << ',' << idx.internalPointer() << ',' << idx.model() << ')';
    return dbg.space();
#else
    qWarning("This compiler doesn't support streaming QModelIndex to QDebug");
    return dbg;
    Q_UNUSED(idx);
#endif
}

QDebug operator<<(QDebug dbg, const QPersistentModelIndex &idx)
{
    if (idx.d)
        dbg << idx.d->index;
    else
        dbg << QModelIndex();
    return dbg;
}
#endif

class QEmptyItemModel : public QAbstractItemModel
{
public:
    explicit QEmptyItemModel(QObject *parent = 0) : QAbstractItemModel(parent) {}
    QModelIndex index(int, int, const QModelIndex &) const { return QModelIndex(); }
    QModelIndex parent(const QModelIndex &) const { return QModelIndex(); }
    int rowCount(const QModelIndex &) const { return 0; }
    int columnCount(const QModelIndex &) const { return 0; }
    bool hasChildren(const QModelIndex &) const { return false; }
    QVariant data(const QModelIndex &, int) const { return QVariant(); }
};

Q_GLOBAL_STATIC(QEmptyItemModel, qEmptyModel)

QAbstractItemModel *QAbstractItemModelPrivate::staticEmptyModel()
{
    return qEmptyModel();
}

void QAbstractItemModelPrivate::removePersistentIndexData(QPersistentModelIndexData *data)
{
    if (data->index.isValid()) {
        int removed = persistent.indexes.remove(data->index);
        Q_ASSERT_X(removed == 1, "QPersistentModelIndex::~QPersistentModelIndex",
                   "persistent model indexes corrupted"); //maybe the index was somewhat invalid?
        // This assert may happen if the model use changePersistentIndex in a way that could result on two
        // QPersistentModelIndex pointing to the same index.
        Q_UNUSED(removed);
    }
    // make sure our optimization still works
    for (int i = persistent.moved.count() - 1; i >= 0; --i) {
        int idx = persistent.moved[i].indexOf(data);
        if (idx >= 0)
            persistent.moved[i].remove(idx);
    }
    // update the references to invalidated persistent indexes
    for (int i = persistent.invalidated.count() - 1; i >= 0; --i) {
        int idx = persistent.invalidated[i].indexOf(data);
        if (idx >= 0)
            persistent.invalidated[i].remove(idx);
    }

}

void QAbstractItemModelPrivate::rowsAboutToBeInserted(const QModelIndex &parent,
                                                      int first, int last)
{
    Q_Q(QAbstractItemModel);
    Q_UNUSED(last);
    QVector<QPersistentModelIndexData *> persistent_moved;
    if (first < q->rowCount(parent)) {
        for (QHash<QModelIndex, QPersistentModelIndexData *>::const_iterator it = persistent.indexes.constBegin();
             it != persistent.indexes.constEnd(); ++it) {
            QPersistentModelIndexData *data = *it;
            const QModelIndex &index = data->index;
            if (index.row() >= first && index.isValid() && index.parent() == parent) {
                persistent_moved.append(data);
            }
        }
    }
    persistent.moved.push(persistent_moved);
}

void QAbstractItemModelPrivate::rowsInserted(const QModelIndex &parent,
                                             int first, int last)
{
    QVector<QPersistentModelIndexData *> persistent_moved = persistent.moved.pop();
    int count = (last - first) + 1; // it is important to only use the delta, because the change could be nested
    for (QVector<QPersistentModelIndexData *>::const_iterator it = persistent_moved.constBegin();
         it != persistent_moved.constEnd(); ++it) {
        QPersistentModelIndexData *data = *it;
        QModelIndex old = data->index;
        persistent.indexes.erase(persistent.indexes.find(old));
        data->index = q_func()->index(old.row() + count, old.column(), parent);
        if (data->index.isValid()) {
            persistent.insertMultiAtEnd(data->index, data);
        } else {
            qWarning() << "QAbstractItemModel::endInsertRows:  Invalid index (" << old.row() + count << ',' << old.column() << ") in model" << q_func();
        }
    }
}

void QAbstractItemModelPrivate::rowsAboutToBeRemoved(const QModelIndex &parent,
                                                     int first, int last)
{
    QVector<QPersistentModelIndexData *>  persistent_moved;
    QVector<QPersistentModelIndexData *>  persistent_invalidated;
    // find the persistent indexes that are affected by the change, either by being in the removed subtree
    // or by being on the same level and below the removed rows
    for (QHash<QModelIndex, QPersistentModelIndexData *>::const_iterator it = persistent.indexes.constBegin();
         it != persistent.indexes.constEnd(); ++it) {
        QPersistentModelIndexData *data = *it;
        bool level_changed = false;
        QModelIndex current = data->index;
        while (current.isValid()) {
            QModelIndex current_parent = current.parent();
            if (current_parent == parent) { // on the same level as the change
                if (!level_changed && current.row() > last) // below the removed rows
                    persistent_moved.append(data);
                else if (current.row() <= last && current.row() >= first) // in the removed subtree
                    persistent_invalidated.append(data);
                break;
            }
            current = current_parent;
            level_changed = true;
        }
    }

    persistent.moved.push(persistent_moved);
    persistent.invalidated.push(persistent_invalidated);
}

void QAbstractItemModelPrivate::rowsRemoved(const QModelIndex &parent,
                                            int first, int last)
{
    QVector<QPersistentModelIndexData *> persistent_moved = persistent.moved.pop();
    int count = (last - first) + 1; // it is important to only use the delta, because the change could be nested
    for (QVector<QPersistentModelIndexData *>::const_iterator it = persistent_moved.constBegin();
         it != persistent_moved.constEnd(); ++it) {
        QPersistentModelIndexData *data = *it;
        QModelIndex old = data->index;
        persistent.indexes.erase(persistent.indexes.find(old));
        data->index = q_func()->index(old.row() - count, old.column(), parent);
        if (data->index.isValid()) {
            persistent.insertMultiAtEnd(data->index, data);
        } else {
            qWarning() << "QAbstractItemModel::endRemoveRows:  Invalid index (" << old.row() - count << ',' << old.column() << ") in model" << q_func();
        }
    }
    QVector<QPersistentModelIndexData *> persistent_invalidated = persistent.invalidated.pop();
    for (QVector<QPersistentModelIndexData *>::const_iterator it = persistent_invalidated.constBegin();
         it != persistent_invalidated.constEnd(); ++it) {
        QPersistentModelIndexData *data = *it;
        persistent.indexes.erase(persistent.indexes.find(data->index));
        data->index = QModelIndex();
        data->model = 0;
    }
}

void QAbstractItemModelPrivate::columnsAboutToBeInserted(const QModelIndex &parent,
                                                         int first, int last)
{
    Q_Q(QAbstractItemModel);
    Q_UNUSED(last);
    QVector<QPersistentModelIndexData *> persistent_moved;
    if (first < q->columnCount(parent)) {
        for (QHash<QModelIndex, QPersistentModelIndexData *>::const_iterator it = persistent.indexes.constBegin();
             it != persistent.indexes.constEnd(); ++it) {
            QPersistentModelIndexData *data = *it;
            const QModelIndex &index = data->index;
            if (index.column() >= first && index.isValid() && index.parent() == parent)
                persistent_moved.append(data);
        }
    }
    persistent.moved.push(persistent_moved);
}

void QAbstractItemModelPrivate::columnsInserted(const QModelIndex &parent,
                                                int first, int last)
{
    QVector<QPersistentModelIndexData *> persistent_moved = persistent.moved.pop();
    int count = (last - first) + 1; // it is important to only use the delta, because the change could be nested
    for (QVector<QPersistentModelIndexData *>::const_iterator it = persistent_moved.constBegin();
         it != persistent_moved.constEnd(); ++it) {
        QPersistentModelIndexData *data = *it;
        QModelIndex old = data->index;
        persistent.indexes.erase(persistent.indexes.find(old));
        data->index = q_func()->index(old.row(), old.column() + count, parent);
        if (data->index.isValid()) {
            persistent.insertMultiAtEnd(data->index, data);
        } else {
            qWarning() << "QAbstractItemModel::endInsertColumns:  Invalid index (" << old.row() << ',' << old.column() + count << ") in model" << q_func();
        }
     }
}

void QAbstractItemModelPrivate::columnsAboutToBeRemoved(const QModelIndex &parent,
                                                        int first, int last)
{
    QVector<QPersistentModelIndexData *> persistent_moved;
    QVector<QPersistentModelIndexData *> persistent_invalidated;
    // find the persistent indexes that are affected by the change, either by being in the removed subtree
    // or by being on the same level and to the right of the removed columns
    for (QHash<QModelIndex, QPersistentModelIndexData *>::const_iterator it = persistent.indexes.constBegin();
         it != persistent.indexes.constEnd(); ++it) {
        QPersistentModelIndexData *data = *it;
        bool level_changed = false;
        QModelIndex current = data->index;
        while (current.isValid()) {
            QModelIndex current_parent = current.parent();
            if (current_parent == parent) { // on the same level as the change
                if (!level_changed && current.column() > last) // right of the removed columns
                    persistent_moved.append(data);
                else if (current.column() <= last && current.column() >= first) // in the removed subtree
                    persistent_invalidated.append(data);
                break;
            }
            current = current_parent;
            level_changed = true;
        }
    }

    persistent.moved.push(persistent_moved);
    persistent.invalidated.push(persistent_invalidated);

}

void QAbstractItemModelPrivate::columnsRemoved(const QModelIndex &parent,
                                               int first, int last)
{
    QVector<QPersistentModelIndexData *> persistent_moved = persistent.moved.pop();
    int count = (last - first) + 1; // it is important to only use the delta, because the change could be nested
    for (QVector<QPersistentModelIndexData *>::const_iterator it = persistent_moved.constBegin();
         it != persistent_moved.constEnd(); ++it) {
        QPersistentModelIndexData *data = *it;
        QModelIndex old = data->index;
        persistent.indexes.erase(persistent.indexes.find(old));
        data->index = q_func()->index(old.row(), old.column() - count, parent);
        if (data->index.isValid()) {
            persistent.insertMultiAtEnd(data->index, data);
        } else {
            qWarning() << "QAbstractItemModel::endRemoveColumns:  Invalid index (" << old.row() << ',' << old.column() - count << ") in model" << q_func();
        }
    }
    QVector<QPersistentModelIndexData *> persistent_invalidated = persistent.invalidated.pop();
    for (QVector<QPersistentModelIndexData *>::const_iterator it = persistent_invalidated.constBegin();
         it != persistent_invalidated.constEnd(); ++it) {
        QPersistentModelIndexData *data = *it;
        persistent.indexes.erase(persistent.indexes.find(data->index));
        data->index = QModelIndex();
        data->model = 0;
    }
}

/*!
    \class QModelIndex

    \brief The QModelIndex class is used to locate data in a data model.

    \ingroup model-view
    \mainclass

    This class is used as an index into item models derived from
    QAbstractItemModel. The index is used by item views, delegates, and
    selection models to locate an item in the model.

    New QModelIndex objects are created by the model using the
    QAbstractItemModel::createIndex() function. An \e invalid model index
    can be constructed with the QModelIndex constructor. Invalid indexes are
    often used as parent indexes when referring to top-level items in a model.

    Model indexes refer to items in models, and contain all the information
    required to specify their locations in those models. Each index is located
    in a given row and column, and may have a parent index; use row(), column(),
    and parent() to obtain this information. Each top-level item in a model is
    represented by a model index that does not have a parent index - in this
    case, parent() will return an invalid model index, equivalent to an index
    constructed with the zero argument form of the QModelIndex() constructor.

    To obtain a model index that refers to an existing item in a model, call
    QAbstractItemModel::index() with the required row and column
    values, and the model index of the parent. When referring to
    top-level items in a model, supply QModelIndex() as the parent index.

    The model() function returns the model that the index references as a
    QAbstractItemModel.
    The child() function is used to examine the items held beneath the index
    in the model.
    The sibling() function allows you to traverse items in the model on the
    same level as the index.

    \note Model indexes should be used immediately and then discarded. You
    should not rely on indexes to remain valid after calling model functions
    that change the structure of the model or delete items. If you need to
    keep a model index over time use a QPersistentModelIndex.

    \sa \link model-view-programming.html Model/View Programming\endlink QPersistentModelIndex QAbstractItemModel
*/

/*!
    \fn QModelIndex::QModelIndex()

    Creates a new empty model index.
    This type of model index is used to indicate
    that the position in the model is invalid.

    \sa isValid() QAbstractItemModel
*/

/*!
    \fn QModelIndex::QModelIndex(int row, int column, void *data, const QAbstractItemModel *model)

    \internal

    Creates a new model index at the given \a row and \a column,
    pointing to some \a data.
*/

/*!
    \fn QModelIndex::QModelIndex(const QModelIndex &other)

    Creates a new model index that is a copy of the \a other model
    index.
*/

/*!
    \fn QModelIndex::~QModelIndex()

    Destroys the model index.
*/

/*!
    \fn int QModelIndex::row() const

    Returns the row this model index refers to.
*/


/*!
    \fn int QModelIndex::column() const

    Returns the column this model index refers to.
*/


/*!
    \fn void *QModelIndex::internalPointer() const

    Returns a \c{void} \c{*} pointer used by the model to associate
    the index with the internal data structure.

    \sa QAbstractItemModel::createIndex()
*/

/*!
    \fn void *QModelIndex::internalId() const

    Returns a \c{qint64} used by the model to associate
    the index with the internal data structure.

    \sa QAbstractItemModel::createIndex()
*/

/*!
    \fn bool QModelIndex::isValid() const

    Returns true if this model index is valid; otherwise returns false.
    A valid index belongs to a model, and has non-negative row and column numbers.

    \sa model(), row(), column()
*/

/*!
    \fn const QAbstractItemModel *QModelIndex::model() const

    Returns a pointer to the model containing the item that this index
    refers to.

    You receive a const pointer to the model because calls to
    non-const functions of the model might invalidate the model index
    - and possibly crash your application.
*/

/*!
    \fn QModelIndex QModelIndex::sibling(int row, int column) const

    Returns the sibling at \a row and \a column or an invalid
    QModelIndex if there is no sibling at this position.

    \sa parent() child()
*/

/*!
    \fn QModelIndex QModelIndex::child(int row, int column) const

    Returns the child of the model index that is stored in the given
    \a row and \a column.

    \sa parent() sibling()
*/

/*!
    \fn QVariant QModelIndex::data(int role) const

    Returns the data for the given \a role for the item referred to by the index.
*/

/*!
    \fn Qt::ItemFlags QModelIndex::flags() const
    \since 4.2

    Returns the flags for the item referred to by the index.
*/

/*!
    \fn bool QModelIndex::operator==(const QModelIndex &other) const

    Returns true if this model index refers to the same location as
    the \a other model index; otherwise returns false.
    Note that all values in the model index are used when comparing
    with another model index.
*/


/*!
    \fn bool QModelIndex::operator!=(const QModelIndex &other) const

    Returns true if this model index does not refer to the same
    location as the \a other model index; otherwise returns false.
*/


/*!
  \fn QModelIndex QModelIndex::parent() const

  Returns the parent of the model index, or QModelIndex() if it has no
  parent.

  \sa child() sibling() model()
*/

/*!
    \class QAbstractItemModel

    \brief The QAbstractItemModel class provides the abstract interface for
    item model classes.

    \ingroup model-view
    \mainclass

    The QAbstractItemModel class defines the standard interface that item
    models must use to be able to interoperate with other components in the
    model/view architecture. It is not supposed to be instantiated directly.
    Instead, you should subclass it to create new models.

    The QAbstractItemModel class is one of the \l{Model/View Classes}
    and is part of Qt's \l{Model/View Programming}{model/view framework}.

    If you need a model to use with a QListView or a QTableView, you should
    consider subclassing QAbstractListModel or QAbstractTableModel instead of
    this class.

    The underlying data model is exposed to views and delegates as a hierarchy
    of tables. If you do not make use of the hierarchy, then the model is a
    simple table of rows and columns. Each item has a unique index specified by
    a QModelIndex.

    \img modelindex-no-parent.png

    Every item of data that can be accessed via a model has an associated model
    index. You can obtain this model index using the index() function. Each
    index may have a sibling() index; child items have a parent() index.

    Each item has a number of data elements associated with it and they can be
    retrieved by specifying a role (see \l Qt::ItemDataRole) to the model's
    data() function. Data for all available roles can be obtained at the same
    time using the itemData() function.

    Data for each role is set using a particular \l Qt::ItemDataRole. Data for
    individual roles are set individually with setData(), or they can be set
    for all roles with setItemData().

    Items can be queried with flags() (see \l Qt::ItemFlag) to see if they can
    be selected, dragged, or manipulated in other ways.

    If an item has child objects, hasChildren() returns true for the
    corresponding index.

    The model has a rowCount() and a columnCount() for each level of the
    hierarchy. Rows and columns can be inserted and removed with insertRows(),
    insertColumns(), removeRows(), and removeColumns().

    The model emits signals to indicate changes. For example, dataChanged() is
    emitted whenever items of data made available by the model are changed.
    Changes to the headers supplied by the model cause headerDataChanged() to
    be emitted. If the structure of the underlying data changes, the model can
    emit layoutChanged() to indicate to any attached views that they should
    redisplay any items shown, taking the new structure into account.

    The items available through the model can be searched for particular data
    using the match() function.

    To sort the model, you can use sort().


    \section1 Subclassing

    \note Some general guidelines for subclassing models are available in the
    \l{Model Subclassing Reference}.

    When subclassing QAbstractItemModel, at the very least you must implement
    index(), parent(), rowCount(), columnCount(), and data(). These functions
    are used in all read-only models, and form the basis of editable models.

    You can also reimplement hasChildren() to provide special behavior for
    models where the implementation of rowCount() is expensive. This makes it
    possible for models to restrict the amount of data requested by views, and
    can be used as a way to implement lazy population of model data.

    To enable editing in your model, you must also implement setData(), and
    reimplement flags() to ensure that \c ItemIsEditable is returned.  You can
    also reimplement headerData() and setHeaderData() to control the way the
    headers for your model are presented.

    The dataChanged() and headerDataChanged() signals must be emitted
    explicitly when reimplementing the setData() and setHeaderData() functions,
    respectively.

    Custom models need to create model indexes for other components to use. To
    do this, call createIndex() with suitable row and column numbers for the
    item, and an identifier for it, either as a pointer or as an integer value.
    The combination of these values must be unique for each item. Custom models
    typically use these unique identifiers in other reimplemented functions to
    retrieve item data and access information about the item's parents and
    children. See the \l{Simple Tree Model Example} for more information about
    unique identifiers.

    It is not necessary to support every role defined in Qt::ItemDataRole.
    Depending on the type of data contained within a model, it may only be
    useful to implement the data() function to return valid information for
    some of the more common roles. Most models provide at least a textual
    representation of item data for the Qt::DisplayRole, and well-behaved
    models should also provide valid information for the Qt::ToolTipRole and
    Qt::WhatsThisRole. Supporting these roles enables models to be used with
    standard Qt views. However, for some models that handle highly-specialized
    data, it may be appropriate to provide data only for user-defined roles.

    Models that provide interfaces to resizable data structures can provide
    implementations of insertRows(), removeRows(), insertColumns(),and
    removeColumns(). When implementing these functions, it is important to
    notify any connected views about changes to the model's dimensions both
    \e before and \e after they occur:

    \list
        \o An insertRows() implementation must call beginInsertRows() \e before
           inserting new rows into the data structure, and endInsertRows()
           \e{immediately afterwards}.
        \o An insertColumns() implementation must call beginInsertColumns()
           \e before inserting new columns into the data structure, and
           endInsertColumns() \e{immediately afterwards}.
        \o A removeRows() implementation must call beginRemoveRows() \e before
           the rows are removed from the data structure, and endRemoveRows()
           \e{immediately afterwards}.
        \o A removeColumns() implementation must call beginRemoveColumns()
           \e before the columns are removed from the data structure, and
           endRemoveColumns() \e{immediately afterwards}.
    \endlist

    The \e private signals that these functions emit give attached components
    the chance to take action before any data becomes unavailable. The
    encapsulation of the insert and remove operations with these begin and end
    functions also enables the model to manage \l{QPersistentModelIndex}
    {persistent model indexes} correctly. \bold{If you want selections to be
    handled properly, you must ensure that you call these functions.} If you
    insert or remove an item with children, you do not need to call these
    functions for the child items. In other words, the parent item will take
    care of its child items.

    To create models that populate incrementally, you can reimplement
    fetchMore() and canFetchMore(). If the reimplementation of fetchMore() adds
    rows to the model, \l{QAbstractItemModel::}{beginInsertRows()} and
    \l{QAbstractItemModel::}{endInsertRows()} must be called.

    \sa {Model Classes}, {Model Subclassing Reference}, QModelIndex,
        QAbstractItemView, {Using Drag and Drop with Item Views},
        {Simple DOM Model Example},
        {Simple Tree Model Example}, {Editable Tree Model Example},
        {Fetch More Example}
*/

/*!
    \fn QModelIndex QAbstractItemModel::index(int row, int column, const QModelIndex &parent) const = 0

    Returns the index of the item in the model specified by the given \a row,
    \a column and \a parent index.

    When reimplementing this function in a subclass, call createIndex() to generate
    model indexes that other components can use to refer to items in your model.

    \sa createIndex()
*/

/*!
    \fn bool QAbstractItemModel::insertColumn(int column, const QModelIndex &parent)

    Inserts a single column before the given \a column in the child items of
    the \a parent specified. Returns true if the column is inserted; otherwise
    returns false.

    \sa insertColumns() insertRow() removeColumn()
*/

/*!
    \fn bool QAbstractItemModel::insertRow(int row, const QModelIndex &parent)

    Inserts a single row before the given \a row in the child items of the
    \a parent specified. Returns true if the row is inserted; otherwise
    returns false.

    \sa insertRows() insertColumn() removeRow()
*/

/*!
    \fn QObject *QAbstractItemModel::parent() const
    \internal
*/

/*!
    \fn QModelIndex QAbstractItemModel::parent(const QModelIndex &index) const = 0

    Returns the parent of the model item with the given \a index, or QModelIndex()
    if it has no parent.

    A common convention used in models that expose tree data structures is that
    only items in the first column have children. For that case, when reimplementing
    this function in a subclass the column of the returned QModelIndex would be 0.

    \note When reimplementing this function in a subclass, be careful to avoid
    calling QModelIndex member functions, such as QModelIndex::parent(), since
    indexes belonging to your model will simply call your implementation, leading
    to infinite recursion.

    \sa createIndex()
*/

/*!
    \fn bool QAbstractItemModel::removeColumn(int column, const QModelIndex &parent)

    Removes the given \a column from the child items of the \a parent specified.
    Returns true if the column is removed; otherwise returns false.

    \sa removeColumns(), removeRow(), insertColumn()
*/

/*!
    \fn bool QAbstractItemModel::removeRow(int row, const QModelIndex &parent)

    Removes the given \a row from the child items of the \a parent specified.
    Returns true if the row is removed; otherwise returns false.

    The removeRow() is a convenience function that calls removeRows().
    The QAbstractItemModel implementation of removeRows does nothing.

    \sa removeRows(), removeColumn(), insertRow()
*/

/*!
    \fn void QAbstractItemModel::headerDataChanged(Qt::Orientation orientation, int first, int last)

    This signal is emitted whenever a header is changed. The \a orientation
    indicates whether the horizontal or vertical header has changed. The
    sections in the header from the \a first to the \a last need to be updated.

    Note that this signal must be emitted explicitly when
    reimplementing the setHeaderData() function.

    If you are changing the number of columns or rows you don't need
    to emit this signal, but use the begin/end functions (see the
    section on subclassing in the QAbstractItemModel class description
    for details).

    \sa headerData(), setHeaderData(), dataChanged()
*/

/*!
    \fn void QAbstractItemModel::layoutAboutToBeChanged()
    \since 4.2

    This signal is emitted just before the layout of a model is changed.
    Components connected to this signal use it to adapt to changes
    in the model's layout.

    Subclasses should update any persistent model indexes after emitting
    layoutAboutToBeChanged().

    \sa layoutChanged(), changePersistentIndex()
*/

/*!
    \fn void QAbstractItemModel::layoutChanged()

    This signal is emitted whenever the layout of items exposed by the model
    has changed; for example, when the model has been sorted. When this signal is
    received by a view, it should update the layout of items to reflect this
    change.

    When subclassing QAbstractItemModel or QAbstractProxyModel, ensure that
    you emit layoutAboutToBeChanged() before changing the order of items or
    altering the structure of the data you expose to views, and emit
    layoutChanged() after changing the layout.

    Subclasses should update any persistent model indexes before
    emitting layoutChanged().

    \sa layoutAboutToBeChanged(), dataChanged(), headerDataChanged(), reset(), changePersistentIndex()
*/

/*!
    Constructs an abstract item model with the given \a parent.
*/
QAbstractItemModel::QAbstractItemModel(QObject *parent)
    : QObject(*new QAbstractItemModelPrivate, parent)
{
}

/*!
  \internal
*/
QAbstractItemModel::QAbstractItemModel(QAbstractItemModelPrivate &dd, QObject *parent)
    : QObject(dd, parent)
{
}

/*!
    Destroys the abstract item model.
*/
QAbstractItemModel::~QAbstractItemModel()
{
    d_func()->invalidatePersistentIndexes();
}

/*!
    \fn QModelIndex QAbstractItemModel::sibling(int row, int column, const QModelIndex &index) const

    Returns the sibling at \a row and \a column for the item at \a index, or
    an invalid QModelIndex if there is no sibling at that location.

    sibling() is just a convenience function that finds the item's parent, and
    uses it to retrieve the index of the child item in the specified \a row
    and \a column.

    \sa index(), QModelIndex::row(), QModelIndex::column()
*/


/*!
    \fn int QAbstractItemModel::rowCount(const QModelIndex &parent) const

    Returns the number of rows under the given \a parent.   When the parent
    is valid it means that rowCount is returning the number of children of parent.

    \bold{Tip:} When implementing a table based model, rowCount() should return 0 when
    the parent is valid.

    \sa columnCount()
*/

/*!
    \fn int QAbstractItemModel::columnCount(const QModelIndex &parent) const

    Returns the number of columns for the children of the given \a parent.

    In most subclasses, the number of columns is independent of the
    \a parent. For example:

    \snippet examples/itemviews/simpledommodel/dommodel.cpp 2

    \bold{Tip:} When implementing a table based model, columnCount() should return 0 when
    the parent is valid.

    \sa rowCount()
*/

/*!
    \fn void QAbstractItemModel::dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight)

    This signal is emitted whenever the data in an existing item changes.

    If the items are of the same parent, the affected ones are those between
    \a topLeft and \a bottomRight inclusive. If the items do not have the same
    parent, the behavior is undefined.

    When reimplementing the setData() function, this signal must be emitted
    explicitly.

    \sa headerDataChanged(), setData(), layoutChanged()
*/

/*!
    \fn void QAbstractItemModel::rowsInserted(const QModelIndex &parent, int start, int end)

    This signal is emitted after rows have been inserted into the
    model. The new items are those between \a start and \a end
    inclusive, under the given \a parent item.

    \bold{Note:} Components connected to this signal use it to adapt to changes
    in the model's dimensions. It can only be emitted by the QAbstractItemModel
    implementation, and cannot be explicitly emitted in subclass code.

    \sa insertRows(), beginInsertRows()
*/

/*!
    \fn void QAbstractItemModel::rowsAboutToBeInserted(const QModelIndex &parent, int start, int end)

    This signal is emitted just before rows are inserted into the
    model. The new items will be positioned between \a start and \a end
    inclusive, under the given \a parent item.

    \bold{Note:} Components connected to this signal use it to adapt to changes
    in the model's dimensions. It can only be emitted by the QAbstractItemModel
    implementation, and cannot be explicitly emitted in subclass code.

    \sa insertRows(), beginInsertRows()
*/

/*!
    \fn void QAbstractItemModel::rowsRemoved(const QModelIndex &parent, int start, int end)

    This signal is emitted after rows have been removed from the
    model. The removed items are those between \a start and \a end
    inclusive, under the given \a parent item.

    \bold{Note:} Components connected to this signal use it to adapt to changes
    in the model's dimensions. It can only be emitted by the QAbstractItemModel
    implementation, and cannot be explicitly emitted in subclass code.

    \sa removeRows(), beginRemoveRows()
*/

/*!
    \fn void QAbstractItemModel::rowsAboutToBeRemoved(const QModelIndex &parent, int start, int end)

    This signal is emitted just before rows are removed from the
    model. The items that will be removed are those between \a start and \a end
    inclusive, under the given \a parent item.

    \bold{Note:} Components connected to this signal use it to adapt to changes
    in the model's dimensions. It can only be emitted by the QAbstractItemModel
    implementation, and cannot be explicitly emitted in subclass code.

    \sa removeRows(), beginRemoveRows()
*/

/*!
    \fn void QAbstractItemModel::columnsInserted(const QModelIndex &parent, int start, int end)

    This signal is emitted after columns have been inserted into the
    model. The new items are those between \a start and \a end
    inclusive, under the given \a parent item.

    \bold{Note:} Components connected to this signal use it to adapt to changes
    in the model's dimensions. It can only be emitted by the QAbstractItemModel
    implementation, and cannot be explicitly emitted in subclass code.

    \sa insertColumns(), beginInsertColumns()
*/

/*!
    \fn void QAbstractItemModel::columnsAboutToBeInserted(const QModelIndex &parent, int start, int end)

    This signal is emitted just before columns are inserted into the
    model. The new items will be positioned between \a start and \a end
    inclusive, under the given \a parent item.

    \bold{Note:} Components connected to this signal use it to adapt to changes
    in the model's dimensions. It can only be emitted by the QAbstractItemModel
    implementation, and cannot be explicitly emitted in subclass code.

    \sa insertColumns(), beginInsertColumns()
*/

/*!
    \fn void QAbstractItemModel::columnsRemoved(const QModelIndex &parent, int start, int end)

    This signal is emitted after columns have been removed from the
    model. The removed items are those between \a start and \a end
    inclusive, under the given \a parent item.

    \bold{Note:} Components connected to this signal use it to adapt to changes
    in the model's dimensions. It can only be emitted by the QAbstractItemModel
    implementation, and cannot be explicitly emitted in subclass code.

    \sa removeColumns(), beginRemoveColumns()
*/

/*!
    \fn void QAbstractItemModel::columnsAboutToBeRemoved(const QModelIndex &parent, int start, int end)

    This signal is emitted just before columns are removed
    from the model. The items to be removed are those between \a start and
    \a end inclusive, under the given \a parent item.

    \bold{Note:} Components connected to this signal use it to adapt to changes
    in the model's dimensions. It can only be emitted by the QAbstractItemModel
    implementation, and cannot be explicitly emitted in subclass code.

    \sa removeColumns(), beginRemoveColumns()
*/

/*!
  Returns true if the model returns a valid QModelIndex for \a row and
  \a column with \a parent, otherwise returns false.
*/
bool QAbstractItemModel::hasIndex(int row, int column, const QModelIndex &parent) const
{
    if (row < 0 || column < 0)
        return false;
    return row < rowCount(parent) && column < columnCount(parent);
}


/*!
  Returns true if \a parent has any children; otherwise returns false.
  Use rowCount() on the parent to find out the number of children.

  \sa parent() index()
*/
bool QAbstractItemModel::hasChildren(const QModelIndex &parent) const
{
    return (rowCount(parent) > 0) && (columnCount(parent) > 0);
}


/*!
    Returns a map with values for all predefined roles in the model
    for the item at the given \a index.

    Reimplemented this function if you want to extend the default behavior
    of this function to include custom roles in the map.

    \sa Qt::ItemDataRole, data()
*/
QMap<int, QVariant> QAbstractItemModel::itemData(const QModelIndex &index) const
{
    QMap<int, QVariant> roles;
    for (int i = 0; i < Qt::UserRole; ++i) {
        QVariant variantData = data(index, i);
        if (variantData.type() != QVariant::Invalid)
            roles.insert(i, variantData);
    }
    return roles;
}

/*!
    Sets the \a role data for the item at \a index to \a value.
    Returns true if successful; otherwise returns false.

    The dataChanged() signal should be emitted if the data was successfully set.

    The base class implementation returns false. This function and
    data() must be reimplemented for editable models. Note that the
    dataChanged() signal must be emitted explicitly when
    reimplementing this function.

    \sa Qt::ItemDataRole, data(), itemData()
*/
bool QAbstractItemModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    Q_UNUSED(index);
    Q_UNUSED(value);
    Q_UNUSED(role);
    return false;
}

/*!
    \fn QVariant QAbstractItemModel::data(const QModelIndex &index, int role) const = 0

    Returns the data stored under the given \a role for the item referred to
    by the \a index.

    \note If you do not have a value to return, return an \bold invalid
    QVariant() instead of returning 0.

    \sa Qt::ItemDataRole, setData(), headerData()
*/

/*!
    Sets the role data for the item at \a index to the associated value in
    \a roles, for every Qt::ItemDataRole. Returns true if successful; otherwise
    returns false.

    Roles that are not in \a roles will not be modified.

    \sa setData() data() itemData()
*/
bool QAbstractItemModel::setItemData(const QModelIndex &index, const QMap<int, QVariant> &roles)
{
    bool b = true;
    for (QMap<int, QVariant>::ConstIterator it = roles.begin(); it != roles.end(); ++it)
        b = b && setData(index, it.value(), it.key());
    return b;
}

/*!
    Returns a list of MIME types that can be used to describe a list of
    model indexes.

    \sa mimeData()
*/
QStringList QAbstractItemModel::mimeTypes() const
{
    QStringList types;
    types << QLatin1String("application/x-qabstractitemmodeldatalist");
    return types;
}

/*!
    Returns an object that contains serialized items of data corresponding to the
    list of \a indexes specified. The formats used to describe the encoded data
    is obtained from the mimeTypes() function.

    If the list of indexes is empty, or there are no supported MIME types,
    0 is returned rather than a serialized empty list.

    \sa mimeTypes(), dropMimeData()
*/
QMimeData *QAbstractItemModel::mimeData(const QModelIndexList &indexes) const
{
    if (indexes.count() <= 0)
        return 0;
    QStringList types = mimeTypes();
    if (types.isEmpty())
        return 0;
    QMimeData *data = new QMimeData();
    QString format = types.at(0);
    QByteArray encoded;
    QDataStream stream(&encoded, QIODevice::WriteOnly);
    encodeData(indexes, stream);
    data->setData(format, encoded);
    return data;
}

/*!
    Handles the \a data supplied by a drag and drop operation that ended with
    the given \a action. Returns true if the data and action can be handled
    by the model; otherwise returns false.

    Although the specified \a row, \a column and \a parent indicate the location of
    an item in the model where the operation ended, it is the responsibility of the
    view to provide a suitable location for where the data should be inserted.

    For instance, a drop action on an item in a QTreeView can result in new items
    either being inserted as children of the item specified by \a row, \a column,
    and \a parent, or as siblings of the item.

    When row and column are -1 it means that it is up to the model to decide
    where to place the data.  This can occur in a tree when data is dropped
    on a parent.  Models will usually append the data to the parent in this case.

    Returns true if the dropping was successful otherwise false.

    \sa supportedDropActions(), {Using Drag and Drop with Item Views}
*/
bool QAbstractItemModel::dropMimeData(const QMimeData *data, Qt::DropAction action,
                                      int row, int column, const QModelIndex &parent)
{
    // check if the action is supported
    if (!data || !(action == Qt::CopyAction || action == Qt::MoveAction))
        return false;
    // check if the format is supported
    QStringList types = mimeTypes();
    if (types.isEmpty())
        return false;
    QString format = types.at(0);
    if (!data->hasFormat(format))
        return false;
    if (row > rowCount(parent))
        row = rowCount(parent);
    if (row == -1)
        row = rowCount(parent);
    if (column == -1)
        column = 0;
    // decode and insert
    QByteArray encoded = data->data(format);
    QDataStream stream(&encoded, QIODevice::ReadOnly);
    return decodeData(row, column, parent, stream);
}

/*!
  \since 4.2

  Returns the drop actions supported by this model.

  The default implementation returns Qt::CopyAction. Reimplement this
  function if you wish to support additional actions. Note that you
  must also reimplement the dropMimeData() function to handle the
  additional operations.

  \sa dropMimeData(), Qt::DropActions, {Using Drag and Drop with Item
  Views}
*/
Qt::DropActions QAbstractItemModel::supportedDropActions() const
{
    return Qt::CopyAction;
}

/*!
  Returns the actions supported by the data in this model.

  The default implementation returns supportedDropActions() unless
  specific values have been set with setSupportedDragActions().

  supportedDragActions() is used by QAbstractItemView::startDrag() as
  the default values when a drag occurs.

  \sa Qt::DropActions, {Using Drag and Drop with Item Views}
*/
Qt::DropActions QAbstractItemModel::supportedDragActions() const
{
    // ### Qt 5: make this virtual or these properties
    Q_D(const QAbstractItemModel);
    if (d->supportedDragActions != -1)
        return d->supportedDragActions;
    return supportedDropActions();
}

/*!
    \since 4.2

    Sets the supported drag \a actions for the items in the model.

    \sa supportedDragActions(), {Using Drag and Drop with Item Views}
*/
void QAbstractItemModel::setSupportedDragActions(Qt::DropActions actions)
{
    Q_D(QAbstractItemModel);
    d->supportedDragActions = actions;
}

/*!
  On models that support this, inserts \a count rows into the model before the
  given \a row.  The items in the new row will be children of the item
  represented by the \a parent model index.

  If \a row is 0, the rows are prepended to any existing rows in the parent.
  If \a row is rowCount(), the rows are appended to any existing rows in the
  parent.
  If \a parent has no children, a single column with \a count rows is inserted.

  Returns true if the rows were successfully inserted; otherwise returns
  false.

  The base class implementation does nothing and returns false.

  If you implement your own model, you can reimplement this function
  if you want to support insertions. Alternatively, you can provide
  you own API for altering the data.

  \sa insertColumns(), removeRows(), beginInsertRows(), endInsertRows()
*/
bool QAbstractItemModel::insertRows(int, int, const QModelIndex &)
{
    return false;
}

/*!
  On models that support this, inserts \a count new columns into the model
  before the given \a column.  The items in each new column will be children
  of the item represented by the \a parent model index.

  If \a column is 0, the columns are prepended to any existing columns.
  If \a column is columnCount(), the columns are appended to any existing
  columns.
  If \a parent has no children, a single row with \a count columns is inserted.

  Returns true if the columns were successfully inserted; otherwise returns
  false.

  The base class implementation does nothing and returns false.

  If you implement your own model, you can reimplement this function
  if you want to support insertions. Alternatively, you can provide
  you own API for altering the data.

  \sa insertRows(), removeColumns(), beginInsertColumns(), endInsertColumns()
*/
bool QAbstractItemModel::insertColumns(int, int, const QModelIndex &)
{
    return false;
}

/*!
    On models that support this, removes \a count rows starting with the given
    \a row under parent \a parent from the model. Returns true if the rows
    were successfully removed; otherwise returns false.

    The base class implementation does nothing and returns false.

    If you implement your own model, you can reimplement this function
    if you want to support removing. Alternatively, you can provide
    you own API for altering the data.

    \sa removeRow(), removeColumns(), insertColumns(), beginRemoveRows(), endRemoveRows()
*/
bool QAbstractItemModel::removeRows(int, int, const QModelIndex &)
{
    return false;
}

/*!
    On models that support this, removes \a count columns starting with the
    given \a column under parent \a parent from the model. Returns true if the
    columns were successfully removed; otherwise returns false.

    The base class implementation does nothing and returns false.

    If you implement your own model, you can reimplement this function
    if you want to support removing. Alternatively, you can provide
    you own API for altering the data.

    \sa removeColumn(), removeRows(), insertColumns(), beginRemoveColumns(), endRemoveColumns()
*/
bool QAbstractItemModel::removeColumns(int, int, const QModelIndex &)
{
    return false;
}

/*!
    Fetches any available data for the items with the parent specified by the
    \a parent index.

    Reimplement this if you are populating your model incrementally.

    The default implementation does nothing.

    \sa canFetchMore()
*/
void QAbstractItemModel::fetchMore(const QModelIndex &)
{
    // do nothing
}

/*!
    Returns true if there is more data available for \a parent; otherwise returns
    false.
    
    The default implementation always returns false.

    If canFetchMore() returns true, QAbstractItemView will call fetchMore().
    However, the fetchMore() function is only called when the model is being
    populated incrementally.

    \sa fetchMore()
*/
bool QAbstractItemModel::canFetchMore(const QModelIndex &) const
{
    return false;
}

/*!
    Returns the item flags for the given \a index.

    The base class implementation returns a combination of flags that
    enables the item (\c ItemIsEnabled) and allows it to be
    selected (\c ItemIsSelectable).

    \sa Qt::ItemFlags
*/
Qt::ItemFlags QAbstractItemModel::flags(const QModelIndex &index) const
{
    Q_D(const QAbstractItemModel);
    if (!d->indexValid(index))
        return 0;

    return Qt::ItemIsSelectable|Qt::ItemIsEnabled;
}

/*!
    Sorts the model by \a column in the given \a order.

    The base class implementation does nothing.
*/
void QAbstractItemModel::sort(int column, Qt::SortOrder order)
{
    Q_UNUSED(column);
    Q_UNUSED(order);
    // do nothing
}

/*!
  Returns a model index for the buddy of the item represented by \a index.
  When the user wants to edit an item, the view will call this function to
  check whether another item in the model should be edited instead, and
  construct a delegate using the model index returned by the buddy item.

  In the default implementation each item is its own buddy.
*/
QModelIndex QAbstractItemModel::buddy(const QModelIndex &index) const
{
    return index;
}

/*!
    Returns a list of indexes for the items in the column of the \a
    start index where the data stored under the given \a role matches
    the specified \a value. The way the search is performed is defined
    by the \a flags given. The list that is returned may be empty.

    The search starts from the \a start index, and continues until the
    number of matching data items equals \a hits, the search reaches
    the last row, or the search reaches \a start again, depending on
    whether \c MatchWrap is specified in \a flags. If you want to search
    for all matching items, use \a hits = -1.

    By default, this function will perform a wrapping, string-based comparison
    on all items, searching for items that begin with the search term specified
    by \a value.
    
    \note The default implementation of this function only searches columns,
    This function can be reimplemented to include other search behavior.
*/
QModelIndexList QAbstractItemModel::match(const QModelIndex &start, int role,
                                          const QVariant &value, int hits,
                                          Qt::MatchFlags flags) const
{
    QModelIndexList result;
    uint matchType = flags & 0x0F;
    Qt::CaseSensitivity cs = flags & Qt::MatchCaseSensitive ? Qt::CaseSensitive : Qt::CaseInsensitive;
    bool recurse = flags & Qt::MatchRecursive;
    bool wrap = flags & Qt::MatchWrap;
    bool allHits = (hits == -1);
    QString text; // only convert to a string if it is needed
    QModelIndex p = parent(start);
    int from = start.row();
    int to = rowCount(p);

    // iterates twice if wrapping
    for (int i = 0; (wrap && i < 2) || (!wrap && i < 1); ++i) {
        for (int r = from; (r < to) && (allHits || result.count() < hits); ++r) {
            QModelIndex idx = index(r, start.column(), p);
            if (!idx.isValid())
                 continue;
            QVariant v = data(idx, role);
            // QVariant based matching
            if (matchType == Qt::MatchExactly) {
                if (value == v)
                    result.append(idx);
            } else { // QString based matching
                if (text.isEmpty()) // lazy conversion
                    text = value.toString();
                QString t = v.toString();
                switch (matchType) {
                case Qt::MatchRegExp:
                    if (QRegExp(text, cs).exactMatch(t))
                        result.append(idx);
                    break;
                case Qt::MatchWildcard:
                    if (QRegExp(text, cs, QRegExp::Wildcard).exactMatch(t))
                        result.append(idx);
                    break;
                case Qt::MatchStartsWith:
                    if (t.startsWith(text, cs))
                        result.append(idx);
                    break;
                case Qt::MatchEndsWith:
                    if (t.endsWith(text, cs))
                        result.append(idx);
                    break;
                case Qt::MatchFixedString:
                    if (t.compare(text, cs) == 0)
                        result.append(idx);
                    break;
                case Qt::MatchContains:
                default:
                    if (t.contains(text, cs))
                        result.append(idx);
                }
            }
            if (recurse && hasChildren(idx)) { // search the hierarchy
                result += match(index(0, idx.column(), idx), role,
                                (text.isEmpty() ? value : text),
                                (allHits ? -1 : hits - result.count()), flags);
            }
        }
        // prepare for the next iteration
        from = 0;
        to = start.row();
    }
    return result;
}

/*!
    Returns the row and column span of the item represented by \a index.

    Note: span is not used currently, but will be in the future.
*/

QSize QAbstractItemModel::span(const QModelIndex &) const
{
    return QSize(1, 1);
}

/*!
  Called to let the model know that it should submit whatever it has cached
  to the permanent storage. Typically used for row editing.

  Returns false on error, otherwise true.
*/

bool QAbstractItemModel::submit()
{
    return true;
}

/*!
  Called to let the model know that it should discard whatever it has cached.
  Typically used for row editing.
*/

void QAbstractItemModel::revert()
{
    // do nothing
}

/*!
  Returns the data for the given \a role and \a section in the header
  with the specified \a orientation.

  For horizontal headers, the section number corresponds to the column
  number of items shown beneath it. For vertical headers, the section
  number typically to the row number of items shown alongside it.

  \sa Qt::ItemDataRole, setHeaderData(), QHeaderView
*/

QVariant QAbstractItemModel::headerData(int section, Qt::Orientation orientation, int role) const
{
    Q_UNUSED(orientation);
    if (role == Qt::DisplayRole)
        return section + 1;
    return QVariant();
}

/*!
  Sets the data for the given \a role and \a section in the header with
  the specified \a orientation to the \a value supplied.
  Returns true if the header's data was updated; otherwise returns false.

  Note that the headerDataChanged() signal must be emitted explicitly
  when reimplementing this function.

  \sa Qt::ItemDataRole, headerData()
*/

bool QAbstractItemModel::setHeaderData(int section, Qt::Orientation orientation,
                                       const QVariant &value, int role)
{
    Q_UNUSED(section);
    Q_UNUSED(orientation);
    Q_UNUSED(value);
    Q_UNUSED(role);
    return false;
}

/*!
    \fn QModelIndex QAbstractItemModel::createIndex(int row, int column, void *ptr) const

    Creates a model index for the given \a row and \a column with the internal pointer \a ptr.

    Note that when you are using a QSortFilterProxyModel its indexes have their own
    internal pointer.  It is not advisable to access the internal pointer in the index
    outside of the model.  Use the data() function instead.

    This function provides a consistent interface that model subclasses must
    use to create model indexes.
*/

/*!
    \fn QModelIndex QAbstractItemModel::createIndex(int row, int column, int id) const
    \obsolete

    Use QModelIndex QAbstractItemModel::createIndex(int row, int column, quint32 id) instead.
*/

/*!
    \fn QModelIndex QAbstractItemModel::createIndex(int row, int column, quint32 id) const

    Creates a model index for the given \a row and \a column with the internal
    identifier, \a id.

    This function provides a consistent interface that model subclasses must
    use to create model indexes.
    \sa QModelIndex::internalId()
*/

/*!
  \internal
*/
void QAbstractItemModel::encodeData(const QModelIndexList &indexes, QDataStream &stream) const
{
    QModelIndexList::ConstIterator it = indexes.begin();
    for (; it != indexes.end(); ++it)
        stream << (*it).row() << (*it).column() << itemData(*it);
}

/*!
  \internal
 */
bool QAbstractItemModel::decodeData(int row, int column, const QModelIndex &parent,
                                    QDataStream &stream)
{
    int top = INT_MAX;
    int left = INT_MAX;
    int bottom = 0;
    int right = 0;
    QVector<int> rows, columns;
    QVector<QMap<int, QVariant> > data;

    while (!stream.atEnd()) {
        int r, c;
        QMap<int, QVariant> v;
        stream >> r >> c >> v;
        rows.append(r);
        columns.append(c);
        data.append(v);
        top = qMin(r, top);
        left = qMin(c, left);
        bottom = qMax(r, bottom);
        right = qMax(c, right);
    }

    // insert the dragged items into the table, use a bit array to avoid overwriting items,
    // since items from different tables can have the same row and column
    int dragRowCount = 0;
    int dragColumnCount = right - left + 1;

    // Compute the number of continuous rows upon insertion and modify the rows to match
    QVector<int> rowsToInsert(bottom + 1);
    for (int i = 0; i < rows.count(); ++i)
        rowsToInsert[rows.at(i)] = 1;
    for (int i = 0; i < rowsToInsert.count(); ++i) {
        if (rowsToInsert[i] == 1){
            rowsToInsert[i] = dragRowCount;
            ++dragRowCount;
        }
    }
    for (int i = 0; i < rows.count(); ++i)
        rows[i] = top + rowsToInsert[rows[i]];

    QBitArray isWrittenTo(dragRowCount * dragColumnCount);

    // make space in the table for the dropped data
    int colCount = columnCount(parent);
    if (colCount == 0) {
        insertColumns(colCount, dragColumnCount - colCount, parent);
        colCount = columnCount(parent);
    }
    insertRows(row, dragRowCount, parent);

    row = qMax(0, row);
    column = qMax(0, column);

    QVector<QPersistentModelIndex> newIndexes(data.size());
    // set the data in the table
    for (int j = 0; j < data.size(); ++j) {
        int relativeRow = rows.at(j) - top;
        int relativeColumn = columns.at(j) - left;
        int destinationRow = relativeRow + row;
        int destinationColumn = relativeColumn + column;
        int flat = (relativeRow * dragColumnCount) + relativeColumn;
        // if the item was already written to, or we just can't fit it in the table, create a new row
        if (destinationColumn >= colCount || isWrittenTo.testBit(flat)) {
            destinationColumn = qBound(column, destinationColumn, colCount - 1);
            destinationRow = row + dragRowCount;
            insertRows(row + dragRowCount, 1, parent);
            flat = (dragRowCount * dragColumnCount) + relativeColumn;
            isWrittenTo.resize(++dragRowCount * dragColumnCount);
        }
        if (!isWrittenTo.testBit(flat)) {
            newIndexes[j] = index(destinationRow, destinationColumn, parent);
            isWrittenTo.setBit(flat);
        }
    }

    for(int k = 0; k < newIndexes.size(); k++) {
        if (newIndexes.at(k).isValid())
            setItemData(newIndexes.at(k), data.at(k));
    }

    return true;
}

/*!
    Begins a row insertion operation.

    When reimplementing insertRows() in a subclass, you must call this
    function \e before inserting data into the model's underlying data
    store.

    The \a parent index corresponds to the parent into which the new
    rows are inserted; \a first and \a last are the row numbers that the
    new rows will have after they have been inserted.

    \table 80%
    \row \o \inlineimage modelview-begin-insert-rows.png Inserting rows
    \o Specify the first and last row numbers for the span of rows
       you want to insert into an item in a model.

    For example, as shown in the diagram, we insert three rows before
    row 2, so \a first is 2 and \a last is 4:
    \snippet doc/src/snippets/code/src_corelib_kernel_qabstractitemmodel.cpp 0
    This inserts the three new rows as rows 2, 3, and 4.
    \row
    \o \inlineimage modelview-begin-append-rows.png Appending rows
    \o To append rows, insert them after the last row.

    For example, as shown in the diagram, we append two rows to a
    collection of 4 existing rows (ending in row 3), so \a first is 4
    and \a last is 5:
    \snippet doc/src/snippets/code/src_corelib_kernel_qabstractitemmodel.cpp 1
    This appends the two new rows as rows 4 and 5.
    \endtable

    \sa endInsertRows()
*/
void QAbstractItemModel::beginInsertRows(const QModelIndex &parent, int first, int last)
{
    Q_ASSERT(first >= 0);
    Q_ASSERT(last >= first);
    Q_D(QAbstractItemModel);
    d->changes.push(QAbstractItemModelPrivate::Change(parent, first, last));
    emit rowsAboutToBeInserted(parent, first, last);
    d->rowsAboutToBeInserted(parent, first, last);
}

/*!
    Ends a row insertion operation.

    When reimplementing insertRows() in a subclass, you must call this
    function \e after inserting data into the model's underlying data
    store.

    \sa beginInsertRows()
*/
void QAbstractItemModel::endInsertRows()
{
    Q_D(QAbstractItemModel);
    QAbstractItemModelPrivate::Change change = d->changes.pop();
    d->rowsInserted(change.parent, change.first, change.last);
    emit rowsInserted(change.parent, change.first, change.last);
}

/*!
    Begins a row removal operation.

    When reimplementing removeRows() in a subclass, you must call this
    function \e before removing data from the model's underlying data
    store.

    The \a parent index corresponds to the parent from which the new
    rows are removed; \a first and \a last are the row numbers of the
    rows to be removed.

    \table 80%
    \row \o \inlineimage modelview-begin-remove-rows.png Removing rows
    \o Specify the first and last row numbers for the span of rows
       you want to remove from an item in a model.

    For example, as shown in the diagram, we remove the two rows from
    row 2 to row 3, so \a first is 2 and \a last is 3:
    \snippet doc/src/snippets/code/src_corelib_kernel_qabstractitemmodel.cpp 2
    \endtable

    \sa endRemoveRows()
*/
void QAbstractItemModel::beginRemoveRows(const QModelIndex &parent, int first, int last)
{
    Q_ASSERT(first >= 0);
    Q_ASSERT(last >= first);
    Q_D(QAbstractItemModel);
    d->changes.push(QAbstractItemModelPrivate::Change(parent, first, last));
    emit rowsAboutToBeRemoved(parent, first, last);
    d->rowsAboutToBeRemoved(parent, first, last);
}

/*!
    Ends a row removal operation.

    When reimplementing removeRows() in a subclass, you must call this
    function \e after removing data from the model's underlying data
    store.

    \sa beginRemoveRows()
*/
void QAbstractItemModel::endRemoveRows()
{
    Q_D(QAbstractItemModel);
    QAbstractItemModelPrivate::Change change = d->changes.pop();
    d->rowsRemoved(change.parent, change.first, change.last);
    emit rowsRemoved(change.parent, change.first, change.last);
}

/*!
    Begins a column insertion operation.

    When reimplementing insertColumns() in a subclass, you must call this
    function \e before inserting data into the model's underlying data
    store.

    The \a parent index corresponds to the parent into which the new
    columns are inserted; \a first and \a last are the column numbers of
    the new columns will have after they have been inserted.

    \table 80%
    \row \o \inlineimage modelview-begin-insert-columns.png Inserting columns
    \o Specify the first and last column numbers for the span of columns
       you want to insert into an item in a model.

    For example, as shown in the diagram, we insert three columns before
    column 4, so \a first is 4 and \a last is 6:
    \snippet doc/src/snippets/code/src_corelib_kernel_qabstractitemmodel.cpp 3
    This inserts the three new columns as columns 4, 5, and 6.
    \row
    \o \inlineimage modelview-begin-append-columns.png Appending columns
    \o To append columns, insert them after the last column.

    For example, as shown in the diagram, we append three columns to a
    collection of six existing columns (ending in column 5), so \a first
    is 6 and \a last is 8:
    \snippet doc/src/snippets/code/src_corelib_kernel_qabstractitemmodel.cpp 4
    This appends the two new columns as columns 6, 7, and 8.
    \endtable

    \sa endInsertColumns()
*/
void QAbstractItemModel::beginInsertColumns(const QModelIndex &parent, int first, int last)
{
    Q_ASSERT(first >= 0);
    Q_ASSERT(last >= first);
    Q_D(QAbstractItemModel);
    d->changes.push(QAbstractItemModelPrivate::Change(parent, first, last));
    emit columnsAboutToBeInserted(parent, first, last);
    d->columnsAboutToBeInserted(parent, first, last);
}

/*!
    Ends a column insertion operation.

    When reimplementing insertColumns() in a subclass, you must call this
    function \e after inserting data into the model's underlying data
    store.

    \sa beginInsertColumns()
*/
void QAbstractItemModel::endInsertColumns()
{
    Q_D(QAbstractItemModel);
    QAbstractItemModelPrivate::Change change = d->changes.pop();
    d->columnsInserted(change.parent, change.first, change.last);
    emit columnsInserted(change.parent, change.first, change.last);
}

/*!
    Begins a column removal operation.

    When reimplementing removeColumns() in a subclass, you must call this
    function \e before removing data from the model's underlying data
    store.

    The \a parent index corresponds to the parent from which the new
    columns are removed; \a first and \a last are the column numbers of
    the first and last columns to be removed.

    \table 80%
    \row \o \inlineimage modelview-begin-remove-columns.png Removing columns
    \o Specify the first and last column numbers for the span of columns
       you want to remove from an item in a model.

    For example, as shown in the diagram, we remove the three columns
    from column 4 to column 6, so \a first is 4 and \a last is 6:
    \snippet doc/src/snippets/code/src_corelib_kernel_qabstractitemmodel.cpp 5
    \endtable

    \sa endRemoveColumns()
*/
void QAbstractItemModel::beginRemoveColumns(const QModelIndex &parent, int first, int last)
{
    Q_ASSERT(first >= 0);
    Q_ASSERT(last >= first);
    Q_D(QAbstractItemModel);
    d->changes.push(QAbstractItemModelPrivate::Change(parent, first, last));
    emit columnsAboutToBeRemoved(parent, first, last);
    d->columnsAboutToBeRemoved(parent, first, last);
}

/*!
    Ends a column removal operation.

    When reimplementing removeColumns() in a subclass, you must call this
    function \e after removing data from the model's underlying data
    store.

    \sa beginRemoveColumns()
*/
void QAbstractItemModel::endRemoveColumns()
{
    Q_D(QAbstractItemModel);
    QAbstractItemModelPrivate::Change change = d->changes.pop();
    d->columnsRemoved(change.parent, change.first, change.last);
    emit columnsRemoved(change.parent, change.first, change.last);
}

/*!
    Resets the model to its original state in any attached views.

    \note The view to which the model is attached to will be reset as well.

    When a model is reset it means that any previous data reported from the
    model is now invalid and has to be queried for again.

    When a model radically changes its data it can sometimes be easier to just
    call this function rather than emit dataChanged() to inform other
    components when the underlying data source, or its structure, has changed.

    \sa modelAboutToBeReset(), modelReset()
*/
void QAbstractItemModel::reset()
{
    Q_D(QAbstractItemModel);
    emit modelAboutToBeReset();
    d->invalidatePersistentIndexes();
    emit modelReset();
}

/*!
  Changes the QPersistentModelIndex that is equal to the given \a from
  model index to the given \a to model index.

  If no persistent model index equal to the given \a from model index was
  found, nothing is changed.

  \sa persistentIndexList(), changePersistentIndexList()
*/
void QAbstractItemModel::changePersistentIndex(const QModelIndex &from, const QModelIndex &to)
{
    Q_D(QAbstractItemModel);
    if (d->persistent.indexes.isEmpty())
        return;
    // find the data and reinsert it sorted
    const QHash<QModelIndex, QPersistentModelIndexData *>::iterator it = d->persistent.indexes.find(from);
    if (it != d->persistent.indexes.end()) {
        QPersistentModelIndexData *data = *it;
        d->persistent.indexes.erase(it);
        data->index = to;
        if (to.isValid())
            d->persistent.insertMultiAtEnd(to, data);
        else
            data->model = 0;
    }
}

/*!
  \since 4.1

  Changes the QPersistentModelIndexes that is equal to the indexes in the given \a from
  model index list to the given \a to model index list.

  If no persistent model indexes equal to the indexes in the given \a from model index list
  was found, nothing is changed.

  \sa persistentIndexList(), changePersistentIndex()
*/
void QAbstractItemModel::changePersistentIndexList(const QModelIndexList &from,
                                                   const QModelIndexList &to)
{
    Q_D(QAbstractItemModel);
    if (d->persistent.indexes.isEmpty())
        return;
    QVector<QPersistentModelIndexData *> toBeReinserted;
    toBeReinserted.reserve(to.count());
    for (int i = 0; i < from.count(); ++i) {
        if (from.at(i) == to.at(i))
            continue;
        const QHash<QModelIndex, QPersistentModelIndexData *>::iterator it = d->persistent.indexes.find(from.at(i));
        if (it != d->persistent.indexes.end()) {
            QPersistentModelIndexData *data = *it;
            d->persistent.indexes.erase(it);
            data->index = to.at(i);
            if (data->index.isValid())
                toBeReinserted << data;
            else
                data->model = 0;
        }
    }

    for (QVector<QPersistentModelIndexData *>::const_iterator it = toBeReinserted.constBegin();
         it != toBeReinserted.constEnd() ; ++it) {
        QPersistentModelIndexData *data = *it;
        d->persistent.insertMultiAtEnd(data->index, data);
    }
}

/*!
  \since 4.2

  Returns the list of indexes stored as persistent indexes in the model.
*/
QModelIndexList QAbstractItemModel::persistentIndexList() const
{
    Q_D(const QAbstractItemModel);
    QModelIndexList result;
    for (QHash<QModelIndex, QPersistentModelIndexData *>::const_iterator it = d->persistent.indexes.constBegin();
         it != d->persistent.indexes.constEnd(); ++it) {
        QPersistentModelIndexData *data = *it;
        result.append(data->index);
    }
    return result;
}


/*!
    \class QAbstractTableModel
    \brief The QAbstractTableModel class provides an abstract model that can be
    subclassed to create table models.

    \ingroup model-view

    QAbstractTableModel provides a standard interface for models that represent
    their data as a two-dimensional array of items. It is not used directly,
    but must be subclassed.

    Since the model provides a more specialized interface than
    QAbstractItemModel, it is not suitable for use with tree views, although
    it can be used to provide data to a QListView. If you need to represent
    a simple list of items, and only need a model to contain a single column
    of data, subclassing the QAbstractListModel may be more appropriate.

    The rowCount() and columnCount() functions return the dimensions of the
    table. To retrieve a model index corresponding to an item in the model, use
    index() and provide only the row and column numbers.

    \section1 Subclassing

    \bold{Note:} Some general guidelines for subclassing models are
    available in the \l{Model Subclassing Reference}.

    When subclassing QAbstractTableModel, you must implement rowCount(),
    columnCount(), and data(). Default implementations of the index() and
    parent() functions are provided by QAbstractTableModel.
    Well behaved models will also implement headerData().

    Editable models need to implement setData(), and implement flags() to
    return a value containing
    \l{Qt::ItemFlags}{Qt::ItemIsEditable}.

    Models that provide interfaces to resizable data structures can
    provide implementations of insertRows(), removeRows(), insertColumns(),
    and removeColumns(). When implementing these functions, it is
    important to call the appropriate functions so that all connected views
    are aware of any changes:

    \list
    \o An insertRows() implementation must call beginInsertRows()
       \e before inserting new rows into the data structure, and it must
       call endInsertRows() \e{immediately afterwards}.
    \o An insertColumns() implementation must call beginInsertColumns()
       \e before inserting new columns into the data structure, and it must
       call endInsertColumns() \e{immediately afterwards}.
    \o A removeRows() implementation must call beginRemoveRows()
       \e before the rows are removed from the data structure, and it must
       call endRemoveRows() \e{immediately afterwards}.
    \o A removeColumns() implementation must call beginRemoveColumns()
       \e before the columns are removed from the data structure, and it must
       call endRemoveColumns() \e{immediately afterwards}.
    \endlist

    \sa {Model Classes}, {Model Subclassing Reference}, QAbstractItemModel,
        QAbstractListModel,
        {Pixelator Example}
*/

/*!
    Constructs an abstract table model for the given \a parent.
*/

QAbstractTableModel::QAbstractTableModel(QObject *parent)
    : QAbstractItemModel(parent)
{

}

/*!
    \internal

    Constructs an abstract table model with \a dd and the given \a parent.
*/

QAbstractTableModel::QAbstractTableModel(QAbstractItemModelPrivate &dd, QObject *parent)
    : QAbstractItemModel(dd, parent)
{

}

/*!
    Destroys the abstract table model.
*/

QAbstractTableModel::~QAbstractTableModel()
{

}

/*!
    \fn QModelIndex QAbstractTableModel::index(int row, int column, const QModelIndex &parent = QModelIndex()) const

    Returns the index of the data in \a row and \a column with \a parent.

    \sa parent()
*/

QModelIndex QAbstractTableModel::index(int row, int column, const QModelIndex &parent) const
{
    return hasIndex(row, column, parent) ? createIndex(row, column, 0) : QModelIndex();
}

/*!
    \fn QModelIndex QAbstractTableModel::parent(const QModelIndex &index) const

    Returns the parent of the model item with the given \a index.

    \sa index() hasChildren()
*/

QModelIndex QAbstractTableModel::parent(const QModelIndex &) const
{
    return QModelIndex();
}

bool QAbstractTableModel::hasChildren(const QModelIndex &parent) const
{
    if (parent.model() == this || !parent.isValid())
        return rowCount(parent) > 0 && columnCount(parent) > 0;
    return false;
}

/*!
    \class QAbstractListModel
    \brief The QAbstractListModel class provides an abstract model that can be
    subclassed to create one-dimensional list models.

    \ingroup model-view

    QAbstractListModel provides a standard interface for models that represent
    their data as a simple non-hierarchical sequence of items. It is not used
    directly, but must be subclassed.

    Since the model provides a more specialized interface than
    QAbstractItemModel, it is not suitable for use with tree views; you will
    need to subclass QAbstractItemModel if you want to provide a model for
    that purpose. If you need to use a number of list models to manage data,
    it may be more appropriate to subclass QAbstractTableModel class instead.

    Simple models can be created by subclassing this class and implementing
    the minimum number of required functions. For example, we could implement
    a simple read-only QStringList-based model that provides a list of strings
    to a QListView widget. In such a case, we only need to implement the
    rowCount() function to return the number of items in the list, and the
    data() function to retrieve items from the list.

    Since the model represents a one-dimensional structure, the rowCount()
    function returns the total number of items in the model. The columnCount()
    function is implemented for interoperability with all kinds of views, but
    by default informs views that the model contains only one column.

    \section1 Subclassing

    \bold{Note:} Some general guidelines for subclassing models are
    available in the \l{Model Subclassing Reference}.

    When subclassing QAbstractListModel, you must provide implementations
    of the rowCount() and data() functions. Well behaved models also provide
    a headerData() implementation.

    For editable list models, you must also provide an implementation of
    setData(), implement the flags() function so that it returns a value
    containing \l{Qt::ItemFlags}{Qt::ItemIsEditable}.

    Note that QAbstractListModel provides a default implementation of
    columnCount() that informs views that there is only a single column
    of items in this model.

    Models that provide interfaces to resizable list-like data structures
    can provide implementations of insertRows() and removeRows(). When
    implementing these functions, it is important to call the appropriate
    functions so that all connected views are aware of any changes:

    \list
    \o An insertRows() implementation must call beginInsertRows()
       \e before inserting new rows into the data structure, and it must
       call endInsertRows() \e{immediately afterwards}.
    \o A removeRows() implementation must call beginRemoveRows()
       \e before the rows are removed from the data structure, and it must
       call endRemoveRows() \e{immediately afterwards}.
    \endlist

    \sa {Model Classes}, {Model Subclassing Reference}, QAbstractItemView,
        QAbstractTableModel, {Item Views Puzzle Example}
*/

/*!
    Constructs an abstract list model with the given \a parent.
*/

QAbstractListModel::QAbstractListModel(QObject *parent)
    : QAbstractItemModel(parent)
{

}

/*!
    \internal

    Constructs an abstract list model with \a dd and the given \a parent.
*/

QAbstractListModel::QAbstractListModel(QAbstractItemModelPrivate &dd, QObject *parent)
    : QAbstractItemModel(dd, parent)
{

}

/*!
    Destroys the abstract list model.
*/

QAbstractListModel::~QAbstractListModel()
{

}

/*!
    \fn QModelIndex QAbstractListModel::index(int row, int column, const QModelIndex &parent = QModelIndex()) const

    Returns the index of the data in \a row and \a column with \a parent.

    \sa parent()
*/

QModelIndex QAbstractListModel::index(int row, int column, const QModelIndex &parent) const
{
    return hasIndex(row, column, parent) ? createIndex(row, column, 0) : QModelIndex();
}

/*!
    Returns the parent of the model item with the given \a index.

    \sa index() hasChildren()
*/

QModelIndex QAbstractListModel::parent(const QModelIndex & /* index */) const
{
    return QModelIndex();
}

/*!
    \internal

    Returns the number of columns in the list with the given \a parent.

    \sa rowCount()
*/

int QAbstractListModel::columnCount(const QModelIndex &parent) const
{
    return parent.isValid() ? 0 : 1;
}

bool QAbstractListModel::hasChildren(const QModelIndex &parent) const
{
    return parent.isValid() ? false : (rowCount() > 0);
}

/*!
    \typedef QModelIndexList
    \relates QModelIndex

    Synonym for QList<QModelIndex>.
*/

/*!
  \reimp
*/
bool QAbstractTableModel::dropMimeData(const QMimeData *data, Qt::DropAction action,
                                       int row, int column, const QModelIndex &parent)
{
    if (!data || !(action == Qt::CopyAction || action == Qt::MoveAction))
        return false;

    QStringList types = mimeTypes();
    if (types.isEmpty())
        return false;
    QString format = types.at(0);
    if (!data->hasFormat(format))
        return false;

    QByteArray encoded = data->data(format);
    QDataStream stream(&encoded, QIODevice::ReadOnly);

    // if the drop is on an item, replace the data in the items
    if (parent.isValid() && row == -1 && column == -1) {
        int top = INT_MAX;
        int left = INT_MAX;
        QVector<int> rows, columns;
        QVector<QMap<int, QVariant> > data;

        while (!stream.atEnd()) {
            int r, c;
            QMap<int, QVariant> v;
            stream >> r >> c >> v;
            rows.append(r);
            columns.append(c);
            data.append(v);
            top = qMin(r, top);
            left = qMin(c, left);
        }

        for (int i = 0; i < data.size(); ++i) {
            int r = (rows.at(i) - top) + parent.row();
            int c = (columns.at(i) - left) + parent.column();
            if (hasIndex(r, c))
                setItemData(index(r, c), data.at(i));
        }

        return true;
    }

    // otherwise insert new rows for the data
    return decodeData(row, column, parent, stream);
}

/*!
  \reimp
*/
bool QAbstractListModel::dropMimeData(const QMimeData *data, Qt::DropAction action,
                                      int row, int column, const QModelIndex &parent)
{
    if (!data || !(action == Qt::CopyAction || action == Qt::MoveAction))
        return false;

    QStringList types = mimeTypes();
    if (types.isEmpty())
        return false;
    QString format = types.at(0);
    if (!data->hasFormat(format))
        return false;

    QByteArray encoded = data->data(format);
    QDataStream stream(&encoded, QIODevice::ReadOnly);

    // if the drop is on an item, replace the data in the items
    if (parent.isValid() && row == -1 && column == -1) {
        int top = INT_MAX;
        int left = INT_MAX;
        QVector<int> rows, columns;
        QVector<QMap<int, QVariant> > data;

        while (!stream.atEnd()) {
            int r, c;
            QMap<int, QVariant> v;
            stream >> r >> c >> v;
            rows.append(r);
            columns.append(c);
            data.append(v);
            top = qMin(r, top);
            left = qMin(c, left);
        }

        for (int i = 0; i < data.size(); ++i) {
            int r = (rows.at(i) - top) + parent.row();
            if (columns.at(i) == left && hasIndex(r, 0))
                setItemData(index(r), data.at(i));
        }

        return true;
    }

    if (row == -1)
        row = rowCount(parent);

    // otherwise insert new rows for the data
    return decodeData(row, column, parent, stream);
}

/*!
    \fn QAbstractItemModel::modelAboutToBeReset()
    \since 4.2

    This signal is emitted when reset() is called, before the model's internal
    state (e.g. persistent model indexes) has been invalidated.

    \sa reset(), modelReset()
*/

/*!
    \fn QAbstractItemModel::modelReset()
    \since 4.1

    This signal is emitted when reset() is called, after the model's internal
    state (e.g. persistent model indexes) has been invalidated.

    \sa reset(), modelAboutToBeReset()
*/

/*!
    \fn bool QModelIndex::operator<(const QModelIndex &other) const
    \since 4.1

    Returns true if this model index is smaller than the \a other
    model index; otherwise returns false.
*/

/*!
    \fn uint qHash(const QPersistentModelIndex &index)
    \since 4.5

    Returns a hash of the QPersistentModelIndex
 */


/*!
    \internal
    QHash::insertMulti insert the value before the old value. and find() return the new value.
    We need insertMultiAtEnd because we don't want to overwrite the old one, which should be removed later

    There should be only one instance QPersistentModelIndexData per index, but in some intermediate state there may be
    severals of PersistantModelIndex pointing to the same index, but one is already updated, and the other one is not.
    This make sure than when updating the first one we don't overwrite the second one in the hash, and the second one
    will be updated right later.
 */
void QAbstractItemModelPrivate::Persistent::insertMultiAtEnd(const QModelIndex& key, QPersistentModelIndexData *data)
{
    QHash<QModelIndex,QPersistentModelIndexData *>::iterator newIt =
            indexes.insertMulti(key, data);
    QHash<QModelIndex,QPersistentModelIndexData *>::iterator it = newIt + 1;
    while (it != indexes.end() && it.key() == key) {
        qSwap(*newIt,*it);
        newIt = it;
        ++it;
    }
}

QT_END_NAMESPACE