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
20namespace boost
21{
22
23
24
25
26 struct planar_face_traversal_visitor
27 {
28 void begin_traversal()
29 {}
30
31 void begin_face()
32 {}
33
34 template <typename Edge>
35 void next_edge(Edge)
36 {}
37
38 template <typename Vertex>
39 void next_vertex(Vertex)
40 {}
41
42 void end_face()
43 {}
44
45 void end_traversal()
46 {}
47
48 };
49
50
51
52
53
54 template<typename Graph,
55 typename PlanarEmbedding,
56 typename Visitor,
57 typename EdgeIndexMap>
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>
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

source code of boost/boost/graph/planar_face_traversal.hpp