QAbstractProxyModel and QTreeView

[niko]

I want to create a Proxy Model - as a first step I tried to create a Proxy that should behave exaclty like the sourceModel:

class Proxy : public QAbstractProxyModel
{
    Q_OBJECT
 
public:
 
    Proxy(QObject* parent = 0) : QAbstractProxyModel(parent) { }
 
    QModelIndex mapFromSource ( const QModelIndex & sourceIndex ) const
    {
        return sourceIndex;
    }
 
    QModelIndex mapToSource ( const QModelIndex & proxyIndex ) const
    {
        return proxyIndex;
    }
 
    int rowCount(const QModelIndex& parent) const
    {
        return sourceModel()->rowCount(parent);
    }
 
    int columnCount(const QModelIndex& parent) const
    {
        return sourceModel()->columnCount(parent);
    }
 
    QModelIndex index(int row, int col, const QModelIndex& parent) const
    {
        return sourceModel()->index(row, col, parent);
    }
    QModelIndex parent(const QModelIndex& index) const
    {
        return parent(index);
    }
};

class Proxy : public QAbstractProxyModel
{
    Q_OBJECT

public:

    Proxy(QObject* parent = 0) : QAbstractProxyModel(parent) { }

    QModelIndex mapFromSource ( const QModelIndex & sourceIndex ) const
    {
        return sourceIndex;
    }

    QModelIndex mapToSource ( const QModelIndex & proxyIndex ) const
    {
        return proxyIndex;
    }

    int rowCount(const QModelIndex& parent) const
    {
        return sourceModel()->rowCount(parent);
    }

    int columnCount(const QModelIndex& parent) const
    {
        return sourceModel()->columnCount(parent);
    }

    QModelIndex index(int row, int col, const QModelIndex& parent) const
    {
        return sourceModel()->index(row, col, parent);
    }
    QModelIndex parent(const QModelIndex& index) const
    {
        return parent(index);
    }
};

To copy to clipboard, switch view to plain text mode 

So far one thing is unclear to me: why do I have to implement rowCount, columnCount, index and parent? Why isn't this done in QAbstractProxyModel?

when using my proxy with the simpletreemodel-example this way:

int main(int argc, char *argv[])
{
    Q_INIT_RESOURCE(simpletreemodel);
 
    QApplication app(argc, argv);
 
    QFile file(":/default.txt");
    file.open(QIODevice::ReadOnly);
    TreeModel model(file.readAll());
    file.close();
 
    Proxy proxy;
    proxy.setSourceModel(&model);
 
    QTreeView view;
    view.setModel(&proxy);
    view.setWindowTitle(QObject::tr("Simple Tree Model"));
    view.show();
    return app.exec();
}

int main(int argc, char *argv[])
{
    Q_INIT_RESOURCE(simpletreemodel);

    QApplication app(argc, argv);

    QFile file(":/default.txt");
    file.open(QIODevice::ReadOnly);
    TreeModel model(file.readAll());
    file.close();

    Proxy proxy;
    proxy.setSourceModel(&model);

    QTreeView view;
    view.setModel(&proxy);
    view.setWindowTitle(QObject::tr("Simple Tree Model"));
    view.show();
    return app.exec();
}

To copy to clipboard, switch view to plain text mode 

I get a messed-up tree - see attached screenshot.
Using a QTableView however works!

please help
niko