add methods to exporter for accessing halfedges for vertices and faces and for accessing next halfface, incident vertex and incident face for halfedges

src/OpenMesh/Core/IO/exporter/BaseExporter.hh

@@ -110,6 +110,14 @@ public:
   virtual unsigned int
   get_vhandles(FaceHandle _fh,
 	       std::vector<VertexHandle>& _vhandles) const=0;
+
+  // information needed for a halfedge based data structure such as OpenMesh
+  virtual int get_halfedge_id(VertexHandle _vh) = 0;
+  virtual int get_halfedge_id(FaceHandle _vh) = 0;
+  virtual int get_next_halfedge_id(HalfedgeHandle _heh) = 0;
+  virtual int get_to_vertex_id(HalfedgeHandle _heh) = 0;
+  virtual int get_face_id(HalfedgeHandle _heh) = 0;
+
   ///
   /// \brief getHeh returns the HalfEdgeHandle that belongs to the face
   ///  specified by _fh and has a toVertexHandle that corresponds to _vh.

src/OpenMesh/Core/IO/exporter/ExporterT.hh

@@ -230,6 +230,31 @@ public:
     return count;
   }
 
+  int get_halfedge_id(VertexHandle _vh) override
+  {
+    return mesh_.halfedge_handle(_vh).idx();
+  }
+
+  int get_halfedge_id(FaceHandle _fh) override
+  {
+    return mesh_.halfedge_handle(_fh).idx();
+  }
+
+  int get_next_halfedge_id(HalfedgeHandle _heh) override
+  {
+    return mesh_.next_halfedge_handle(_heh).idx();
+  }
+
+  int get_to_vertex_id(HalfedgeHandle _heh) override
+  {
+    return mesh_.to_vertex_handle(_heh).idx();
+  }
+
+  int get_face_id(HalfedgeHandle _heh) override
+  {
+    return mesh_.face_handle(_heh).idx();
+  }
+
   unsigned int get_face_texcoords(std::vector<Vec2f>& _hehandles) const
   {
     unsigned int count(0);