void TileLayer::resize(const QSize &size, const QPoint &offset)
{
    if (this->size() == size && offset.isNull())
        return;

    QScopedPointer<TileLayer> newLayer(new TileLayer(QString(), 0, 0, size.width(), size.height()));

    // Copy over the preserved part
    QRect area = mBounds.translated(-position() + offset).intersected(newLayer->rect());
    for (int y = area.top(); y <= area.bottom(); ++y)
        for (int x = area.left(); x <= area.right(); ++x)
            newLayer->setCell(x, y, cellAt(x - offset.x(), y - offset.y()));

    mChunks = newLayer->mChunks;
    mBounds = newLayer->mBounds;
    setSize(size);
}