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[KHartmann <>]

<http://cgal-discuss.949826.n4.nabble.com/file/n4661783/TwoSquares.png> 


I'm adding two intersecting squares to an arrangement.
Then I traverse the half-edges of the outer boundary 
for each face in the arrangement.

I get the correct number of half-edges, but the target 
vertex of a half-edge isn't always the source vertex
of the next half-edge.

I wouldn't expect this result from reading the help
documentation.  What am I doing wrong?

My program is listed below.  Along with the output.


----- Output of Program -------------

Face outer boundary:
(15.000000, 15.000000) - (10.000000, 15.000000)
(10.000000, 15.000000) - (10.000000, 10.000000)
(10.000000, 10.000000) - (15.000000, 10.000000)
(15.000000, 10.000000) - (15.000000, 15.000000)

Face outer boundary:
(15.000000, 15.000000) - (10.000000, 15.000000)
(15.000000, 10.000000) - (15.000000, 15.000000)
(15.000000, 10.000000) - (25.000000, 10.000000)
(25.000000, 10.000000) - (25.000000, 25.000000)
(25.000000, 25.000000) - (10.000000, 25.000000)
(10.000000, 25.000000) - (10.000000, 15.000000)

Face outer boundary:
(0.000000, 15.000000) - (0.000000, 0.000000)
(0.000000, 0.000000) - (15.000000, 0.000000)
(15.000000, 0.000000) - (15.000000, 10.000000)
(10.000000, 10.000000) - (15.000000, 10.000000)
(10.000000, 15.000000) - (10.000000, 10.000000)
(10.000000, 15.000000) - (0.000000, 15.000000)



----- Program ---------------


#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Polygon_2.h>
#include <CGAL/Polygon_with_holes_2.h>
#include <CGAL/Polygon_set_2.h>

#include <CGAL/Arr_batched_point_location.h>

typedef CGAL::Lazy_kernel<CGAL::Simple_cartesian&lt;CGAL::Gmpq> >   Kernel;  
typedef Kernel::Point_2                                   Point_2;
typedef CGAL::Polygon_2<Kernel>                           Polygon_2;
typedef CGAL::Polygon_with_holes_2<Kernel>               
Polygon_with_holes_2;
typedef CGAL::Polygon_set_2<Kernel>                       Polygon_set_2;

typedef Kernel::Circle_2                                  Circle_2;
typedef CGAL::Gps_circle_segment_traits_2<Kernel>         Traits_2;
typedef CGAL::General_polygon_set_2<Traits_2>             Gen_Polygon_set_2;
typedef Traits_2::General_polygon_2                       Gen_Polygon_2;
typedef Traits_2::General_polygon_with_holes_2           
Gen_Polygon_with_holes_2;
typedef Traits_2::Curve_2                                 Curve_2;
typedef Traits_2::X_monotone_curve_2                     
X_monotone_curve_2;

typedef Gen_Polygon_set_2::Arrangement_2                  Arrangement_2;
typedef Gen_Polygon_set_2::Arrangement_2::Point_2         Arr_Point_2;
typedef CGAL::Arr_point_location_result<Arrangement_2>   
Point_location_result;
typedef CGAL::Arr_walk_along_line_point_location<Arrangement_2> Walk_pl;
typedef std::pair<Arr_Point_2, Point_location_result::Type>   Query_result;


int main()
{
  Arrangement_2 arr;

  Point_2 p1( 10.0, 10.0 );
  Point_2 p2( 25.0, 10.0 );
  Point_2 p3( 25.0, 25.0 );
  Point_2 p4( 10.0, 25.0 );

  Point_2 p5( 0.0, 0.0 );
  Point_2 p6( 15.0, 0.0 );
  Point_2 p7( 15.0, 15.0 );
  Point_2 p8( 0.0, 15.0 );

  X_monotone_curve_2 s1( p1, p2 );
  X_monotone_curve_2 s2( p2, p3 );
  X_monotone_curve_2 s3( p3, p4 );
  X_monotone_curve_2 s4( p4, p1 );

  X_monotone_curve_2 s5( p5, p6 );
  X_monotone_curve_2 s6( p6, p7 );
  X_monotone_curve_2 s7( p7, p8 );
  X_monotone_curve_2 s8( p8, p5 );

  CGAL::insert (arr, s1);
  CGAL::insert (arr, s2);
  CGAL::insert (arr, s3);
  CGAL::insert (arr, s4);

  CGAL::insert (arr, s5);
  CGAL::insert (arr, s6);
  CGAL::insert (arr, s7);
  CGAL::insert (arr, s8);

  Arrangement_2::Face_const_iterator fit;
  for (fit = arr.faces_begin(); fit != arr.faces_end(); ++fit)
  {
    Arrangement_2::Face_const_handle f = fit;

    if (f->is_unbounded())
      continue;

    Arrangement_2::Ccb_halfedge_const_circulator startLoc = f->outer_ccb();
    Arrangement_2::Ccb_halfedge_const_circulator currLoc = startLoc;
    Arrangement_2::Halfedge_const_handle halfEdge;

    fprintf( stdout, "Face outer boundary:\n" );
    do
    {
      halfEdge = currLoc;
      const X_monotone_curve_2& curve = halfEdge->curve();

      fprintf( stdout, "(%lf, %lf) - (%lf, %lf)\n", 
        CGAL::to_double( curve.source().x() ),
        CGAL::to_double( curve.source().y() ),
        CGAL::to_double( curve.target().x() ),
        CGAL::to_double( curve.target().y() ) );

      ++currLoc;
    } while (currLoc != startLoc);
    fprintf( stdout, "\n");
  }

  return 0;
}





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