KDChartAbstractProxyModel.cpp

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/****************************************************************************
**
** This file is part of the KD Chart library.
**
** SPDX-FileCopyrightText: 2001 Klarälvdalens Datakonsult AB, a KDAB Group company <info@kdab.com>
**
** SPDX-License-Identifier: MIT
**
****************************************************************************/
 
#include "KDChartAbstractProxyModel.h"
 
#include <QDebug>
 
#include <KDABLibFakes>
 
#ifdef __GNUC__
#if __GNUC__ > 3
#define MAY_ALIAS __attribute__((__may_alias__))
#endif
#else
#define MAY_ALIAS
#endif
 
namespace KDChart {
 
AbstractProxyModel::AbstractProxyModel(QObject *parent)
    : QAbstractProxyModel(parent)
{
}
 
// Allows access to QModelIndex's private data via type punning and a compatible data layout.
// Due to inlining in Qt and no d-pointer, it is safe to assume that the layout won't change except
// between major Qt versions. As it happens, the layout is the same in Qt4 and Qt5.
// The only change is void * -> quintptr.
struct MAY_ALIAS KDPrivateModelIndex
{
    int r, c;
    void *p;
    const QAbstractItemModel *m;
};
 
QModelIndex AbstractProxyModel::mapFromSource(const QModelIndex &sourceIndex) const
{
    if (!sourceIndex.isValid())
        return QModelIndex();
    // qDebug() << "sourceIndex.model()="<<sourceIndex.model();
    // qDebug() << "model()="<<sourceModel();
    Q_ASSERT(sourceIndex.model() == sourceModel());
 
    // Create an index that preserves the internal pointer from the source;
    // this way AbstractProxyModel preserves the structure of the source model
    return createIndex(sourceIndex.row(), sourceIndex.column(), sourceIndex.internalPointer());
}
 
QModelIndex AbstractProxyModel::mapToSource(const QModelIndex &proxyIndex) const
{
    if (!sourceModel() || !proxyIndex.isValid())
        return QModelIndex();
    if (proxyIndex.model() != this)
        qDebug() << proxyIndex.model() << this;
    Q_ASSERT(proxyIndex.model() == this);
    // So here we need to create a source index which holds that internal pointer.
    // No way to pass it to sourceModel()->index... so we have to do the ugly way:
    QModelIndex sourceIndex;
    auto *hack = reinterpret_cast<KDPrivateModelIndex *>(&sourceIndex);
    hack->r = proxyIndex.row();
    hack->c = proxyIndex.column();
    hack->p = proxyIndex.internalPointer();
    hack->m = sourceModel();
    Q_ASSERT(sourceIndex.isValid());
    return sourceIndex;
}
 
QModelIndex AbstractProxyModel::index(int row, int col, const QModelIndex &index) const
{
    if (!sourceModel())
        return QModelIndex();
    return mapFromSource(sourceModel()->index(row, col, mapToSource(index)));
}
 
QModelIndex AbstractProxyModel::parent(const QModelIndex &index) const
{
    if (!sourceModel())
        return QModelIndex();
    return mapFromSource(sourceModel()->parent(mapToSource(index)));
}
}