id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
10647,backlog in for_each_range.hpp causes incorrect result of disjoint,Petr Doubrava <petr@…>,Barend Gehrels,"simple test program,
Polygon poly2 is entirely within the hole in the polygon poly1, the result of disjonit may be true, but is false.

{{{
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>

#include <assert.h>

void test_polygon_disjoint()
{
    typedef boost::geometry::model::point<double, 2, boost::geometry::cs::cartesian> Point;
    boost::geometry::model::polygon<Point> poly1, poly2;


    boost::geometry::read_wkt(""POLYGON((0.0 0.0, 0.0 5.0, 5.0 5.0, 5.0 0.0, 0.0 0.0)(1.0 1.0, 4.0 1.0, 4.0 4.0, 1.0 4.0, 1.0 1.0))"", poly1);
    boost::geometry::correct(poly1);

    boost::geometry::read_wkt(""POLYGON((2.0 2.0, 2.0 3.0, 3.0 3.0, 3.0 2.0, 2.0 2.0))"", poly2);
    boost::geometry::correct(poly2);

    bool res=boost::geometry::disjoint(poly1,poly2);
    assert(res==true);
    // res is false :-(
}

int main(int argc, char* argv[])
{
  test_polygon_disjoint();
  return 0;
}

}}}

The reason is probably this backlog in boost\geometry\algorithms\detail\for_each_range.hpp

{{{
...
template <typename Polygon, typename Actor>
struct fe_range_polygon
{

    static inline void apply(Polygon & polygon, Actor & actor)
    {
        actor.apply(exterior_ring(polygon));

        // TODO: If some flag says true, also do the inner rings.
        // for convex hull, it's not necessary
    }
};
...
}}}

I created this workaround and disjoint works correctly in this case.

{{{
template <typename Polygon, typename Actor>
struct fe_range_polygon
{
    static inline void apply(Polygon & polygon, Actor & actor)
    {
        actor.apply(exterior_ring(polygon));

        if (actor.has_within) {
            Polygon::inner_container_type::const_iterator it=interior_rings(polygon).begin();
            for (;it!=interior_rings(polygon).end();++it)
            {
               actor.apply(*it);
               if (actor.has_within)
               {
                   actor.has_within = false;
                   break;
               }
           }
       }
   }
};

}}}",Bugs,closed,To Be Determined,geometry,Boost 1.56.0,Problem,fixed,,