From 38218aca4f19c3f253567a8ea3fb06e4d89aa278 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mael=20Rouxel-Labb=C3=A9?=
 <mael.rouxel.labbe@geometryfactory.com>
Date: Tue, 22 Sep 2020 15:28:40 +0200
Subject: [PATCH 1/2] Fix deleting elements (degenerate faces) that might be
 further in the range

---
 .../CGAL/Polygon_mesh_processing/repair.h     | 38 ++++++-------------
 1 file changed, 12 insertions(+), 26 deletions(-)

diff --git a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/repair.h b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/repair.h
index bab4589b1b1..1dc090cf96d 100644
--- a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/repair.h
+++ b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/repair.h
@@ -1243,37 +1243,23 @@ bool remove_degenerate_faces(const FaceRange& face_range,
   // Ignore faces with null edges
   if(!all_removed)
   {
-    std::map<edge_descriptor, bool> are_degenerate_edges;
-
-    for(face_descriptor fd : degenerate_face_set)
+    typename std::set<face_descriptor>::iterator it = degenerate_face_set.begin();
+    while(it != degenerate_face_set.end())
     {
-      for(halfedge_descriptor hd : halfedges_around_face(halfedge(fd, tmesh), tmesh))
+      bool has_degenerate_edge = false;
+      for(halfedge_descriptor hd : halfedges_around_face(halfedge(*it, tmesh), tmesh))
       {
-        edge_descriptor ed = edge(hd, tmesh);
-        std::pair<typename std::map<edge_descriptor, bool>::iterator, bool> is_insert_successful =
-          are_degenerate_edges.insert(std::make_pair(ed, false));
-
-        bool is_degenerate = false;
-        if(is_insert_successful.second)
+        const edge_descriptor ed = edge(hd, tmesh);
+        if(is_degenerate_edge(ed, tmesh, np))
         {
-          // did not previously exist in the map, so actually have to check if it is degenerate
-          if(traits.equal_3_object()(get(vpmap, target(ed, tmesh)), get(vpmap, source(ed, tmesh))))
-            is_degenerate = true;
-        }
-
-        is_insert_successful.first->second = is_degenerate;
-
-        if(is_degenerate)
-        {
-          halfedge_descriptor h = halfedge(ed, tmesh);
-          if(!is_border(h, tmesh))
-            degenerate_face_set.erase(face(h, tmesh));
-
-          h = opposite(h, tmesh);
-          if(!is_border(h, tmesh))
-            degenerate_face_set.erase(face(h, tmesh));
+          has_degenerate_edge = true;
+          it = degenerate_face_set.erase(it);
+          break;
         }
       }
+
+      if(!has_degenerate_edge)
+        ++it;
     }
   }
 

From 0b3143ea5c6e4862b95c9d573fc7af154fb7c79d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mael=20Rouxel-Labb=C3=A9?=
 <mael.rouxel.labbe@geometryfactory.com>
Date: Tue, 22 Sep 2020 15:30:57 +0200
Subject: [PATCH 2/2] Also test degenerate element removal with EPECK

---
 .../remove_degeneracies_test.cpp              | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/Polygon_mesh_processing/test/Polygon_mesh_processing/remove_degeneracies_test.cpp b/Polygon_mesh_processing/test/Polygon_mesh_processing/remove_degeneracies_test.cpp
index ab5778ec5f8..7d5e93c3f13 100644
--- a/Polygon_mesh_processing/test/Polygon_mesh_processing/remove_degeneracies_test.cpp
+++ b/Polygon_mesh_processing/test/Polygon_mesh_processing/remove_degeneracies_test.cpp
@@ -1,4 +1,5 @@
 #include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
 
 #include <CGAL/Surface_mesh.h>
 #include <CGAL/Polyhedron_3.h>
@@ -16,9 +17,7 @@
 namespace PMP = CGAL::Polygon_mesh_processing;
 
 typedef CGAL::Exact_predicates_inexact_constructions_kernel     EPICK;
-
-typedef CGAL::Surface_mesh<EPICK::Point_3>                      Surface_mesh;
-typedef CGAL::Polyhedron_3<EPICK>                               Polyhedron;
+typedef CGAL::Exact_predicates_exact_constructions_kernel       EPECK;
 
 template <typename K, typename EdgeRange, typename FaceRange, typename Mesh>
 void detect_degeneracies(const EdgeRange& edge_range,
@@ -38,7 +37,7 @@ void detect_degeneracies(const EdgeRange& edge_range,
 
   dedges.clear();
   PMP::degenerate_edges(edge_range, mesh, std::inserter(dedges, dedges.begin()), CGAL::parameters::all_default());
-  std::cout << "\t" << dedges.size() << " degenerate edges vs " <<  expected_dedges_n << std::endl;
+  std::cout << "\t" << dedges.size() << " degenerate edges, expected " <<  expected_dedges_n << std::endl;
   assert(dedges.size() == expected_dedges_n);
 
   // API tests
@@ -49,7 +48,7 @@ void detect_degeneracies(const EdgeRange& edge_range,
 
   dfaces.clear();
   PMP::degenerate_faces(face_range, mesh, std::back_inserter(dfaces), CGAL::parameters::all_default());
-  std::cout << "\t" << dfaces.size() << " degenerate faces vs " << expected_dfaces_n << std::endl;
+  std::cout << "\t" << dfaces.size() << " degenerate faces, expected " << expected_dfaces_n << std::endl;
   assert(dfaces.size() == expected_dfaces_n);
 }
 
@@ -238,10 +237,16 @@ void test()
 int main()
 {
   std::cout << "EPICK SM TESTS" << std::endl;
-  test<EPICK, Surface_mesh>();
+  test<EPICK, CGAL::Surface_mesh<EPICK::Point_3> >();
 
   std::cout << "EPICK POLYHEDRON TESTS" << std::endl;
-  test<EPICK, Polyhedron>();
+  test<EPICK, CGAL::Polyhedron_3<EPICK>>();
+
+  std::cout << "EPICK SM TESTS" << std::endl;
+  test<EPECK, CGAL::Surface_mesh<EPECK::Point_3> >();
+
+  std::cout << "EPECK POLYHEDRON TESTS" << std::endl;
+  test<EPECK, CGAL::Polyhedron_3<EPECK> >();
 
   return EXIT_SUCCESS;
 }