Updated tutorial on deleting geometry.

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@264 fdac6126-5c0c-442c-9429-916003d36597

Doc/tutorial_07b.docu

@@ -4,7 +4,7 @@ This small example shows how to remove faces and vertices from a mesh.
 
 We basically use the geometry created in \ref tutorial_01.
 
-If we want our mesh class to be able to remove vertices, faces or (half-) edges
+If we want our mesh class to be able to remove vertices, faces or edges
 we have to extend the default traits for our mesh class.
 Vertices, faces and (half-)edges need the OpenMesh::Attributes::Status attribute
 which is used to hold the flag "deleted" if an element is deleted.
@@ -18,6 +18,18 @@ The struct which defines the mesh traits then looks like this:
 After having created the geometry of the cube one can delete faces and vertices
 by simply calling delete_vertices() (delete_faces() or delete_edges() respectively).
 
+Note that there is actually no way to delete halfedges directly since they are automatically
+affected when the parent edge is marked as deleted!
+
+The status whether an element is marked as deleted can be requested by
+
+\code
+mesh.status(handle).deleted();  // true if element handle is marked as deleted
+                                // false otherwise
+\endcode
+
+where handle is either a vertex-, edge- or face-handle.
+
 In this example we delete all faces except one and the corresponding vertices.
 The code looks like this