Proxy model for filtering only the 1st level children in a treemodel. Assumes 1 column, 2 level tree.

ChildrenFilteringProxyModel.cpp

/**
Proxy model for filtering only the 1st level children in a treemodel. Assumes 1 column, 2 level tree.

If the source model is:
Parent 1
- child 1
- child 2
Parent 2
- child 4
- child 5

Then this proxy model will be:
child 1
child 2
child 3
child 4
child 5

*/

QModelIndex ProxyModel::index( int row, int column, const QModelIndex& parent ) const
{
    if ( !hasIndex( row, column, parent ) )
        return QModelIndex();

    return createIndex( row, 0 );
}

int ProxyModel::rowCount( const QModelIndex& /* parent */ ) const
{
    int count = 0;
    for ( int i = 0; i < sourceModel()->rowCount(); ++i ) {
        QModelIndex parent = sourceModel()->index( i, 0 );
        count += sourceModel()->rowCount( parent );
    }
    return count;
}

QModelIndex ProxyModel::mapFromSource( const QModelIndex& sourceIndex ) const
{
    if ( !sourceIndex.isValid() )
        return QModelIndex();

    if ( !sourceIndex.parent().isValid() )
        return QModelIndex();

    int count = 0;
    for ( int i = 0; i < sourceIndex.parent().row(); ++i ) {
        QModelIndex parent = sourceModel()->index( i, 0 );
        count += sourceModel()->rowCount( parent );
    }
    count += sourceIndex.row();
    return index( count, 0 );
}

QModelIndex ProxyModel::mapToSource( const QModelIndex& proxyIndex ) const
{
    int proxy_row = proxyIndex.row();
    int count = 0;
    QModelIndex parent;
    bool found = false;

    //locate the parent index which contains proxy_row
    for ( int i = 0; i < sourceModel()->rowCount(); ++i ) {
        parent = sourceModel()->index( i, 0 );
        count += sourceModel()->rowCount( parent );
        if ( count > proxy_row ) {
            count = sourceModel()->rowCount( parent );
            found = true;
            break;
        }
    }
    if ( !found ) {
        qDebug() << "source model parent not found";
        return QModelIndex();
    }
//     qDebug() << proxy_row <<"%" << count << "=" << proxy_row % count;
    return sourceModel()->index( proxy_row % count, 0, parent );
}