Add indexed sweep with isolated points

Arrangement_on_surface_2/include/CGAL/Arr_overlay_2.h

@@ -297,8 +297,16 @@ overlay(const Arrangement_on_surface_2<GeometryTraitsA_2, TopologyTraitsA>& arr1
 
   // Clear the result arrangement and perform the sweep to construct it.
   arr.clear();
-  surface_sweep.sweep(xcvs_vec.begin(), xcvs_vec.end(),
+  if (std::is_same<typename Agt2::Base_traits_2::Bottom_side_category,
-                      pts_vec.begin(), pts_vec.end());
+      Arr_contracted_side_tag>::value)
+    surface_sweep.sweep(xcvs_vec.begin(), xcvs_vec.end(),
+                        pts_vec.begin(), pts_vec.end());
+  else
+    surface_sweep.indexed_sweep (xcvs_vec,
+                                 Indexed_sweep_accessor
+                                 <Arr_a, Arr_b, Ovl_x_monotone_curve_2>
+                                 (arr1, arr2),
+                                 pts_vec.begin(), pts_vec.end());
   xcvs_vec.clear();
   pts_vec.clear();
 }

Surface_sweep_2/include/CGAL/No_intersection_surface_sweep_2.h

@@ -322,6 +322,24 @@ public:
     m_visitor->after_sweep();
   }
 
+  template <typename EdgeRange, typename Accessor,
+            typename PointInputIterator>
+  void indexed_sweep (const EdgeRange& edges,
+                      const Accessor& accessor,
+                      PointInputIterator action_points_begin,
+                      PointInputIterator action_points_end)
+  {
+    m_visitor->before_sweep();
+    accessor.before_init();
+    _init_indexed_sweep(edges, accessor);
+    accessor.after_init();
+    _init_points(action_points_begin, action_points_end, Event::ACTION);
+    //m_visitor->after_init();
+    _sweep();
+    _complete_sweep();
+    m_visitor->after_sweep();
+  }
+
   /*! Get an iterator for the first subcurve in the status line. */
   Status_line_iterator status_line_begin() { return m_statusLine.begin(); }