ext/OGDF/src/planarity/SimpleEmbedder.cpp

   1 /*
   2  * $Revision: 2599 $
   3  *
   4  * last checkin:
   5  *   $Author: chimani $
   6  *   $Date: 2012-07-15 22:39:24 +0200 (So, 15. Jul 2012) $
   7  ***************************************************************/
   8
   9 /** \file
  10  * \brief A simple embedder algorithm.
  11  *
  12  * \author Thorsten Kerkhof
  13  *
  14  * \par License:
  15  * This file is part of the Open Graph Drawing Framework (OGDF).
  16  *
  17  * \par
  18  * Copyright (C)<br>
  19  * See README.txt in the root directory of the OGDF installation for details.
  20  *
  21  * \par
  22  * This program is free software; you can redistribute it and/or
  23  * modify it under the terms of the GNU General Public License
  24  * Version 2 or 3 as published by the Free Software Foundation;
  25  * see the file LICENSE.txt included in the packaging of this file
  26  * for details.
  27  *
  28  * \par
  29  * This program is distributed in the hope that it will be useful,
  30  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  31  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  32  * GNU General Public License for more details.
  33  *
  34  * \par
  35  * You should have received a copy of the GNU General Public
  36  * License along with this program; if not, write to the Free
  37  * Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  38  * Boston, MA 02110-1301, USA.
  39  *
  40  * \see  http://www.gnu.org/copyleft/gpl.html
  41  ***************************************************************/
  42
  43 #include <ogdf/planarity/SimpleEmbedder.h>
  44
  45 namespace ogdf {
  46
  47         void SimpleEmbedder::call(Graph& G, adjEntry& adjExternal)
  48         {
  49                 OGDF_ASSERT(isPlanar(G));
  50
  51                 //----------------------------------------------------------
  52                 //
  53                 // determine embedding of G
  54                 //
  55
  56                 // We currently compute any embedding and choose the maximal face
  57                 // as external face
  58
  59                 // if we use FixedEmbeddingInserter, we have to re-use the computed
  60                 // embedding, otherwise crossing nodes can turn into "touching points"
  61                 // of edges (alternatively, we could compute a new embedding and
  62                 // finally "remove" such unnecessary crossings).
  63                 adjExternal = 0;
  64                 if(!G.representsCombEmbedding())
  65                         planarEmbed(G);
  66
  67                 if (G.numberOfEdges() > 0)
  68                 {
  69                         CombinatorialEmbedding E(G);
  70                         //face fExternal = E.maximalFace();
  71                         face fExternal = findBestExternalFace(G, E);
  72                         adjExternal = fExternal->firstAdj();
  73                 }
  74         }
  75
  76
  77         face SimpleEmbedder::findBestExternalFace(
  78                 const PlanRep& PG,
  79                 const CombinatorialEmbedding& E)
  80         {
  81                 FaceArray<int> weight(E);
  82
  83                 face f;
  84                 forall_faces(f,E)
  85                         weight[f] = f->size();
  86
  87                 node v;
  88                 forall_nodes(v,PG)
  89                 {
  90                         if(PG.typeOf(v) != Graph::generalizationMerger)
  91                                 continue;
  92
  93                         adjEntry adj;
  94                         forall_adj(adj,v) {
  95                                 if(adj->theEdge()->source() == v)
  96                                         break;
  97                         }
  98
  99                         OGDF_ASSERT(adj->theEdge()->source() == v);
 100
 101                         node w = adj->theEdge()->target();
 102                         bool isBase = true;
 103
 104                         adjEntry adj2;
 105                         forall_adj(adj2, w) {
 106                                 edge e = adj2->theEdge();
 107                                 if(e->target() != w && PG.typeOf(e) == Graph::generalization) {
 108                                         isBase = false;
 109                                         break;
 110                                 }
 111                         }
 112
 113                         if(isBase == false)
 114                                 continue;
 115
 116                         face f1 = E.leftFace(adj);
 117                         face f2 = E.rightFace(adj);
 118
 119                         weight[f1] += v->indeg();
 120                         if(f2 != f1)
 121                                 weight[f2] += v->indeg();
 122                 }
 123
 124                 face fBest = E.firstFace();
 125                 forall_faces(f,E)
 126                         if(weight[f] > weight[fBest])
 127                                 fBest = f;
 128
 129                 return fBest;
 130         }
 131
 132 } // end namespace ogdf