Arrangement_on_surface_2/generic_curve_data.cpp

 
// Associating a name attribute with segments using the generic curve-data
// traits.
 
#include <CGAL/basic.h>
#include <CGAL/Arr_curve_data_traits_2.h>
 
#include "arr_polylines.h"
 
using Name = std::string;               // The name-field type.
 
struct Merge_names {
  Name operator() (const Name& s1, const Name& s2) const
  { return (s1 + " " + s2); }
};
 
using Ex_traits = CGAL::Arr_curve_data_traits_2<Traits, Name, Merge_names>;
 
using Ex_polyline = Ex_traits::Curve_2;
using Ex_x_monotone_polyline = Ex_traits::X_monotone_curve_2;
using Ex_arrangement = CGAL::Arrangement_2<Ex_traits>;
 
int main() {
  // Construct an arrangement of four polylines named A--D.
  Ex_traits traits;
  Ex_arrangement arr(&traits);
  auto ctr_curve = traits.construct_curve_2_object();
 
  Point pts1[5] =
    {Point(0, 0), Point(2, 4), Point(3, 3), Point(4, 4), Point(6, 0)};
  insert(arr, Ex_polyline(ctr_curve(pts1, pts1 + 5), "A"));
 
  Point pts2[3] = {Point(1, 5), Point(3, 3), Point(5, 5)};
  insert(arr, Ex_polyline(ctr_curve(pts2, pts2 + 3), "B"));
 
  Point pts3[4] = {Point(1, 0), Point(2, 2), Point(4, 2), Point(5, 0)};
  insert(arr, Ex_polyline(ctr_curve(pts3, pts3 + 4), "C"));
 
  Point pts4[2] = {Point(0, 2), Point(6, 2)};
  insert(arr, Ex_polyline(ctr_curve(pts4, pts4 + 2), "D"));
 
  // Print all edges that correspond to an overlapping polyline.
  std::cout << "The overlapping subcurves:\n";
  for (auto eit = arr.edges_begin(); eit != arr.edges_end(); ++eit) {
    if (eit->curve().data().length() > 1) {
      std::cout << "  [" << eit->curve() << "]  "
                << "named: " << eit->curve().data() << std::endl;
 
      // Modify the curve associated with the edge.
      arr.modify_edge(eit, Ex_x_monotone_polyline(eit->curve(), "overlap"));
    }
  }
  return 0;
}