Cleanup of the properties API

Surface_mesh/examples/Surface_mesh/sm_properties.cpp

@@ -29,13 +29,28 @@ int main()
   // give each vertex a name, the default is empty
   Mesh::Property_map<vertex_descriptor,std::string> name;
   bool created;
-  boost::tie(name, created) = m.property_map<vertex_descriptor,std::string>("v:name", "noname");
+  boost::tie(name, created) = m.add_property_map<vertex_descriptor,std::string>("v:name", "noname");
   assert(created);
   // add some names to the vertices
   name[v0] = "hello";
   name[v2] = "world";
 
-  // retrieve the point property
+  {
+    // You can't add a property if it already exists
+    Mesh::Property_map<vertex_descriptor,std::string> name;
+    bool created;
+    boost::tie(name, created) = m.add_property_map<vertex_descriptor,std::string>("v:name", "noname");
+    assert(! created);
+  }
+
+  //  You can't get a property that does not exist
+  Mesh::Property_map<face_descriptor,std::string> gnus;
+  bool found;
+  boost::tie(gnus, found) = m.property_map<face_descriptor,std::string>("v:gnus");
+  assert(! found);
+
+
+  // retrieve the point property for which exists a convenience function
   Mesh::Property_map<vertex_descriptor, K::Point_3> location = m.points();
   BOOST_FOREACH( vertex_descriptor vd, m.vertices()) { 
     std::cout << name[vd] << " @ " << location[vd] << std::endl;

Surface_mesh/include/CGAL/Surface_mesh/Surface_mesh.h

@@ -1897,25 +1897,27 @@ private: //--------------------------------------------------- property handling
 
 #endif
 
-#if 0
     /// adds a property map named `name` with value type `T` and default `t`
-    /// for index type `I`. Returns an invalid property map if a property
-    /// map named `name` already exists.
+    /// for index type `I`. Returns the property map together with a Boolean 
+    /// that is `true` if a new map was created. In case it already exists
+    /// the existing map together with `false` is returned.
 
   
     template<class I, class T>
-    Property_map<I, T>
+      std::pair<Property_map<I, T>, bool>
     add_property_map(const std::string& name, const T t=T()) {
         return (this->*boost::fusion::at_key<I>(pmap_)).template add<T>(name, t);
     }
-#endif
 
-    /// returns a property map named `name` with key type `I` and value type `T`, and a Boolean 
-    /// that is `true` if the property map gets newly created.
+ 
+    /// returns a property map named `name` with key type `I` and value type `T`, 
+    /// and a Boolean that is `true` if the property exists. 
+    /// In case it does not exist the Boolean is `false` and the behavior of
+    /// the property map is undefined.
     template <class I, class T>
-    std::pair<Property_map<I, T>,bool> property_map(const std::string& name, const T& t=T()) const
+    std::pair<Property_map<I, T>,bool> property_map(const std::string& name) const
     {
-      return (this->*boost::fusion::at_key<I>(pmap_)).template get<T>(name, t);
+      return (this->*boost::fusion::at_key<I>(pmap_)).template get<T>(name);
     }