Function subtract_retain_largest

src/svgfill/src/arrange_polygons.cpp:148–166

template <typename T>
boost::optional<Polygon_2> subtract_retain_largest(const T& lhs, const T& rhs) {
    std::vector<Polygon_with_holes_2> result;
    boost::optional<Polygon_2> mp;

    CGAL::difference(lhs, rhs, std::back_inserter(result));

    std::sort(result.begin(), result.end(), [](const Polygon_with_holes_2& a, const Polygon_with_holes_2& b) {
        return a.outer_boundary().area() < b.outer_boundary().area();
    });

    if (result.size() > 0) {
        if (result.front().has_holes()) {
            return boost::none;
        }
        return result.front().outer_boundary();
    }

    return boost::none;
}

Polygon_2 circ_to_poly(typename Arrangement_2::Ccb_halfedge_const_circulator circ)
{