From 38c44cf11bd15f8907c8f985ec3f73699e8124c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Loriot?= <sebastien.loriot@cgal.org>
Date: Tue, 5 Jun 2018 13:45:23 +0200
Subject: [PATCH] make sure face index maps are identical when clipping with a
 plane

---
 .../CGAL/Polygon_mesh_processing/clip.h       | 29 +++++++++++++++----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/clip.h b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/clip.h
index 66c45b11b77..ff8fb03e910 100644
--- a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/clip.h
+++ b/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>