Ticket #10642: boostbug.cc

#include <boost/polygon/polygon.hpp>

#include <iostream>
#include <cstdlib>

namespace bp = boost::polygon;
using namespace bp::operators;

typedef bp::polygon_set_data<int> PolygonSet;
typedef bp::polygon_data<PolygonSet::coordinate_type> Polygon;
typedef bp::polygon_traits<Polygon>::point_type Point;

int
main(int argc, char *argv[])
{
    // Small figure with a little hole. Area should be 32.
    const Point points[] = {
        Point(0,0),
        Point(6,0),
        Point(6,4),
        Point(4,6),
        Point(0,6),
        Point(0,0),
        Point(4,4),
        Point(5,4)
    };

    Polygon poly1(&points[0], &points[sizeof(points)/sizeof(points[0])]);
    PolygonSet ps1;
    ps1 += poly1;

    // Boost.Polygon says the area is 30. That is because its internal
    // representation is wrong, as you can confirm by manually
    // examining the result of get() or get_trapezoids().
    std::cout << "poly1 area == " << area(poly1) << "\n";
    std::cout << "ps1 area == " << area(ps1) << "\n";

    // Doubling the coordinates avoids the bug.
    Polygon poly2(poly1);
    scale_up(poly2, 2);
    PolygonSet ps2;
    ps2 += poly2;
    std::cout << "poly2 area == " << area(poly2) << "\n";
    std::cout << "ps2 area == " << area(ps2) << "\n";

    assert(area(poly2) == area(ps2));
    assert(area(poly1) == area(ps1));
}