make sure face index maps are identical when clipping with a plane

Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/clip.h

@@ -456,6 +456,26 @@ clip(      TriangleMesh& tm,
   return internal::clip_open_impl(tm, clipper, np_tm, np_c);
 }
 
+namespace internal{
+template <class TriangleMesh, class NamedParameters>
+bool dispatch_clip_call(TriangleMesh& tm, TriangleMesh& clipper,
+                        const NamedParameters& np, Tag_false)
+{
+  return clip(tm, clipper,
+              np.face_index_map(get(CGAL::dynamic_face_property_t<std::size_t>(), tm)),
+              parameters::face_index_map(get(CGAL::dynamic_face_property_t<std::size_t>(), clipper)));
+}
+
+template <class TriangleMesh, class NamedParameters>
+bool dispatch_clip_call(TriangleMesh& tm, TriangleMesh& clipper,
+                        const NamedParameters& np, Tag_true)
+{
+  return clip(tm, clipper,
+              np.face_index_map(get(face_index, tm)),
+              parameters::face_index_map(get(face_index, clipper)));
+}
+}
+
 /**
   * \ingroup PMP_corefinement_grp
   * clips `tm` by keeping the part that is on the negative side of `plane` (side opposite to its normal vector).
@@ -478,10 +498,6 @@ clip(      TriangleMesh& tm,
   * @param np optional sequence of \ref pmp_namedparameters "Named Parameters" among the ones listed below
   *
   * \cgalNamedParamsBegin
-  *   \cgalParamBegin{face_index_map} a property map containing the index of each face of `tm`.
-  *     Note that if the property map is writable, the indices of the faces
-  *     of `tm` will be set after the refining of `tm` with the intersection with `plane`.
-  *   \cgalParamEnd
   *   \cgalParamBegin{new_face_visitor} a class model of `PMPCorefinementNewFaceVisitor`
   *                                     that is used to track the creation of new faces.
   *   \cgalParamEnd
@@ -534,10 +550,13 @@ bool clip(      TriangleMesh& tm,
     default:
       break;
   }
-  return clip(tm, clipper, np, parameters::all_default());
+  // dispatch is needed because face index map for tm and clipper have to be of the same time
+  return internal::dispatch_clip_call(tm, clipper,
+                                      np, CGAL::graph_has_property<TriangleMesh, CGAL::face_index_t>());
 }
 
 /// \cond SKIP_IN_MANUAL
+
 // convenience overloads
 template <class TriangleMesh,
           class NamedParameters>