Planar Face Visitor Concept

This concept defines the visitor interface for planar_face_traversal. Users can define a class with the Planar Face Visitor interface and pass an object of the class to planar_face_traversal, thereby augmenting the actions taken during the traversal. Note that objects passed to planar_face_traversal are passed by reference.

Notation

`V`	A type that is a model of Planar Face Visitor.
`vis`	An object of type `V`.
`G`	A type that is a model of Graph.
`e`	An object of type `boost::graph_traits<G>::edge_descriptor`.
`v`	An object of type `boost::graph_traits<G>::vertex_descriptor`.

Valid Expressions

Name	Expression	Return Type	Description
Begin Traversal	`vis.begin_traversal()`	`void`	This is invoked once per traversal, before the traversal begins.
Begin Face	`vis.begin_face()`	`void`	This is invoked once for each face, before any vertices or edges on the face are visited.
Next Vertex	`vis.next_vertex(v)`	`void`	This is invoked when a vertex is encountered while traversing a face.
Next Edge	`vis.next_edge(e)`	`void`	This is invoked when an edge is encountered while traversing a face.
End Face	`vis.end_face()`	`void`	This is invoked once for each face, after all vertices and edges on the face are visited.
End Traversal	`vis.end_traversal()`	`void`	This is invoked once per traversal, after the traversal ends.

Models

The file planar_face_traversal.hpp contains a class planar_face_traversal_visitor that implements empty actions for all event points of a Planar Face Visitor. In the case where only a few of the event points of Planar Face Visitor need to be implemented, one can derive from planar_face_traversal_visitor and only implement the necessary event points.
The implementation of make_maximal_planar uses a triangulation_visitor that is a model of Planar Face Visitor.