message: add simple missing function in surface mesh
diff: @@ -283,11 +283,22 @@ namespace RINGMesh
  * @brief Gets the number of all polygons in the whole Mesh.
  */
  virtual index_t nb_polygons() const = 0;
  +
  /*!
  * @brief Gets the number of vertices in the polygon \param polygon_id.
  * @param[in] polygon_id polygon index
  */
  virtual index_t nb_polygon_vertices( index_t polygon_id ) const = 0;
  +
  + /*!
  + * @brief Gets the number of edges in the polygon \param polygon_id.
  + * @param[in] polygon_id polygon index
  + */
  + index_t nb_polygon_edges( index_t polygon_id ) const
  + {
  + return nb_polygon_vertices( polygon_id );
  + }
  +
  /*!
  * @brief Gets the next vertex index in the polygon vertex
  * \param polygon_local_vertex.
  @@ -403,12 +414,14 @@ namespace RINGMesh
  const PolygonLocalEdge& polygon_local_edge ) const = 0;
  virtual GEO::AttributesManager& polygon_attribute_manager() const = 0;
  +
  /*!
  * @brief Tests whether all the polygons are triangles. when all the
  * polygons are triangles, storage and access is optimized.
  * @return True if all polygons are triangles and False otherwise.
  */
  virtual bool polygons_are_simplicies() const = 0;
  +
  /*!
  * return true if the polygon \param polygon_id is a triangle
  */
  