From f21ab5a1a112a0692c3ee3b26ddccca13512bf98 Mon Sep 17 00:00:00 2001
From: Guillaume Damiand <guillaume.damiand@liris.cnrs.fr>
Date: Thu, 14 Oct 2021 17:48:43 +0200
Subject: [PATCH] When cells have id, store the max id.

---
 .../include/CGAL/Cell_attribute.h             | 23 +++++++++++++++----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/Combinatorial_map/include/CGAL/Cell_attribute.h b/Combinatorial_map/include/CGAL/Cell_attribute.h
index 4409b2ebfe3..99b502ec202 100644
--- a/Combinatorial_map/include/CGAL/Cell_attribute.h
+++ b/Combinatorial_map/include/CGAL/Cell_attribute.h
@@ -14,6 +14,7 @@
 
 #include <CGAL/tags.h>
 #include <CGAL/assertions.h>
+#include <cstddef>
 
 namespace CGAL {
 
@@ -83,15 +84,27 @@ namespace CGAL {
     const std::size_t& id() const
     { return m_id; }
 
-  protected:
-    void set_id(std::size_t id)
-    { m_id=id; }
+    static const std::size_t& max_id()
+    { return m_max_id; }
 
   protected:
-    /// id of the cell
-    std::size_t m_id;
+    void set_id(std::size_t id)
+    {
+      m_id=id;
+      if (m_id+1>m_max_id) { m_max_id=m_id+1; }
+    }
+
+    static void reset_max_id()
+    { m_max_id=0; }
+
+  protected:
+    std::size_t m_id; ///< id of the cell
+    static std::size_t m_max_id; ///< max id used (warning: never decreases)
   };
 
+  template <class WithId>
+  std::size_t Add_id<WithId>::m_max_id=0;
+
   /// If the tag WithId is false, we do not add id to cells.
   template <>
   class Add_id<Tag_false>