1 //=======================================================================
2 // Copyright (c) Aaron Windsor 2007
3 //
4 // Distributed under the Boost Software License, Version 1.0. (See
5 // accompanying file LICENSE_1_0.txt or copy at
6 // http://www.boost.org/LICENSE_1_0.txt)
7 //=======================================================================
8 
9 #ifndef __PLANAR_FACE_TRAVERSAL_HPP__
10 #define __PLANAR_FACE_TRAVERSAL_HPP__
11 
12 #include <vector>
13 #include <set>
14 #include <map>
15 #include <boost/next_prior.hpp>
16 #include <boost/graph/graph_traits.hpp>
17 #include <boost/graph/properties.hpp>
18 
19 
20 namespace boost
21 {
22 
23 
24 
25 
26   struct planar_face_traversal_visitor
27   {
begin_traversalboost::planar_face_traversal_visitor28     void begin_traversal()
29     {}
30 
begin_faceboost::planar_face_traversal_visitor31     void begin_face()
32     {}
33 
34     template <typename Edge>
next_edgeboost::planar_face_traversal_visitor35     void next_edge(Edge)
36     {}
37 
38     template <typename Vertex>
next_vertexboost::planar_face_traversal_visitor39     void next_vertex(Vertex)
40     {}
41 
end_faceboost::planar_face_traversal_visitor42     void end_face()
43     {}
44 
end_traversalboost::planar_face_traversal_visitor45     void end_traversal()
46     {}
47 
48   };
49 
50 
51 
52 
53 
54   template<typename Graph,
55            typename PlanarEmbedding,
56            typename Visitor,
57            typename EdgeIndexMap>
planar_face_traversal(const Graph & g,PlanarEmbedding embedding,Visitor & visitor,EdgeIndexMap em)58   void planar_face_traversal(const Graph& g,
59                              PlanarEmbedding embedding,
60                              Visitor& visitor, EdgeIndexMap em
61                              )
62   {
63     typedef typename graph_traits<Graph>::vertex_descriptor vertex_t;
64     typedef typename graph_traits<Graph>::edge_descriptor edge_t;
65     typedef typename graph_traits<Graph>::vertex_iterator vertex_iterator_t;
66     typedef typename graph_traits<Graph>::edge_iterator edge_iterator_t;
67     typedef typename
68       property_traits<PlanarEmbedding>::value_type embedding_value_t;
69     typedef typename embedding_value_t::const_iterator embedding_iterator_t;
70 
71     typedef typename
72       std::vector< std::set<vertex_t> > distinguished_edge_storage_t;
73     typedef typename
74       std::vector< std::map<vertex_t, edge_t> >
75       distinguished_edge_to_edge_storage_t;
76 
77     typedef typename
78       boost::iterator_property_map
79         <typename distinguished_edge_storage_t::iterator, EdgeIndexMap>
80       distinguished_edge_map_t;
81 
82     typedef typename
83       boost::iterator_property_map
84         <typename distinguished_edge_to_edge_storage_t::iterator, EdgeIndexMap>
85       distinguished_edge_to_edge_map_t;
86 
87     distinguished_edge_storage_t visited_vector(num_edges(g));
88     distinguished_edge_to_edge_storage_t next_edge_vector(num_edges(g));
89 
90     distinguished_edge_map_t visited(visited_vector.begin(), em);
91     distinguished_edge_to_edge_map_t next_edge(next_edge_vector.begin(), em);
92 
93     vertex_iterator_t vi, vi_end;
94     typename std::vector<edge_t>::iterator ei, ei_end;
95     edge_iterator_t fi, fi_end;
96     embedding_iterator_t pi, pi_begin, pi_end;
97 
98     visitor.begin_traversal();
99 
100     // Initialize the next_edge property map. This map is initialized from the
101     // PlanarEmbedding so that get(next_edge, e)[v] is the edge that comes
102     // after e in the clockwise embedding around vertex v.
103 
104     for(boost::tie(vi,vi_end) = vertices(g); vi != vi_end; ++vi)
105       {
106         vertex_t v(*vi);
107         pi_begin = embedding[v].begin();
108         pi_end = embedding[v].end();
109         for(pi = pi_begin; pi != pi_end; ++pi)
110           {
111             edge_t e(*pi);
112             std::map<vertex_t, edge_t> m = get(next_edge, e);
113             m[v] = boost::next(pi) == pi_end ? *pi_begin : *boost::next(pi);
114             put(next_edge, e, m);
115           }
116       }
117 
118     // Take a copy of the edges in the graph here, since we want to accomodate
119     // face traversals that add edges to the graph (for triangulation, in
120     // particular) and don't want to use invalidated edge iterators.
121     // Also, while iterating over all edges in the graph, we single out
122     // any self-loops, which need some special treatment in the face traversal.
123 
124     std::vector<edge_t> self_loops;
125     std::vector<edge_t> edges_cache;
126     std::vector<vertex_t> vertices_in_edge;
127 
128     for(boost::tie(fi,fi_end) = edges(g); fi != fi_end; ++fi)
129       {
130         edge_t e(*fi);
131         edges_cache.push_back(e);
132         if (source(e,g) == target(e,g))
133           self_loops.push_back(e);
134       }
135 
136 
137     // Iterate over all edges in the graph
138     ei_end = edges_cache.end();
139     for(ei = edges_cache.begin(); ei != ei_end; ++ei)
140       {
141 
142         edge_t e(*ei);
143         vertices_in_edge.clear();
144         vertices_in_edge.push_back(source(e,g));
145         vertices_in_edge.push_back(target(e,g));
146 
147         typename std::vector<vertex_t>::iterator vi, vi_end;
148         vi_end = vertices_in_edge.end();
149 
150         //Iterate over both vertices in the current edge
151         for(vi = vertices_in_edge.begin(); vi != vi_end; ++vi)
152           {
153 
154             vertex_t v(*vi);
155             std::set<vertex_t> e_visited = get(visited, e);
156             typename std::set<vertex_t>::iterator e_visited_found
157               = e_visited.find(v);
158 
159             if (e_visited_found == e_visited.end())
160               visitor.begin_face();
161 
162             while (e_visited.find(v) == e_visited.end())
163               {
164                 visitor.next_vertex(v);
165                 visitor.next_edge(e);
166                 e_visited.insert(v);
167                 put(visited, e, e_visited);
168                 v = source(e,g) == v ? target(e,g) : source(e,g);
169                 e = get(next_edge, e)[v];
170                 e_visited = get(visited, e);
171               }
172 
173             if (e_visited_found == e_visited.end())
174               visitor.end_face();
175 
176           }
177 
178       }
179 
180     // Iterate over all self-loops, visiting them once separately
181     // (they've already been visited once, this visitation is for
182     // the "inside" of the self-loop)
183 
184     ei_end = self_loops.end();
185     for(ei = self_loops.begin(); ei != ei_end; ++ei)
186       {
187         visitor.begin_face();
188         visitor.next_edge(*ei);
189         visitor.next_vertex(source(*ei,g));
190         visitor.end_face();
191       }
192 
193     visitor.end_traversal();
194 
195   }
196 
197 
198 
199   template<typename Graph, typename PlanarEmbedding, typename Visitor>
planar_face_traversal(const Graph & g,PlanarEmbedding embedding,Visitor & visitor)200   inline void planar_face_traversal(const Graph& g,
201                                     PlanarEmbedding embedding,
202                                     Visitor& visitor
203                                     )
204   {
205     planar_face_traversal(g, embedding, visitor, get(edge_index, g));
206   }
207 
208 
209 
210 
211 } //namespace boost
212 
213 #endif //__PLANAR_FACE_TRAVERSAL_HPP__
214