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polygon_clipper: detect invalid winding order when in debug mode

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This commit is contained in:
Dane Springmeyer 2013-09-24 21:18:52 -07:00
parent 8ca8b2c64e
commit 0b5d70f926
1 changed files with 9 additions and 2 deletions
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11
include/mapnik/polygon_clipper.hpp
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@ -28,6 +28,7 @@
// mapnik // mapnik
#include <mapnik/box2d.hpp> #include <mapnik/box2d.hpp>
#include <mapnik/debug.hpp>
#include <mapnik/geometry.hpp> #include <mapnik/geometry.hpp>
// boost // boost
@ -101,7 +102,7 @@ struct polygon_clipper
} }
polygon_clipper( box2d<double> const& clip_box,Geometry & geom) polygon_clipper(box2d<double> const& clip_box, Geometry & geom)
: clip_box_(clip_box), : clip_box_(clip_box),
geom_(geom) geom_(geom)
{ {
@ -179,7 +180,13 @@ private:
} }
polygon_list clipped_polygons; polygon_list clipped_polygons;
#ifdef MAPNIK_LOG
double area = boost::geometry::area(subject_poly);
if (area < 0)
{
MAPNIK_LOG_ERROR(polygon_clipper) << "negative area detected for polygon indicating incorrect winding order";
}
#endif
try try
{ {
boost::geometry::intersection(clip_box_, subject_poly, clipped_polygons); boost::geometry::intersection(clip_box_, subject_poly, clipped_polygons);