src/libvpsc/generate-constraints.cpp

   1 /**
   2  * \brief Functions to automatically generate constraints for the
   3  * rectangular node overlap removal problem.
   4  *
   5  * Authors:
   6  *   Tim Dwyer <tgdwyer@gmail.com>
   7  *
   8  * Copyright (C) 2005 Authors
   9  *
  10  * Released under GNU LGPL.  Read the file 'COPYING' for more information.
  11  */
  12
  13 #include <set>
  14 #include <cassert>
  15 #include "generate-constraints.h"
  16 #include "constraint.h"
  17
  18 #include "isnan.h" /* Include last */
  19
  20 using std::set;
  21 using std::vector;
  22
  23 namespace vpsc {
  24 std::ostream& operator <<(std::ostream &os, const Rectangle &r) {
  25         os << "{"<<r.minX<<","<<r.maxX<<","<<r.minY<<","<<r.maxY<<"},";
  26         return os;
  27 }
  28
  29 Rectangle::Rectangle(double x, double X, double y, double Y)
  30 : minX(x),maxX(X),minY(y),maxY(Y) {
  31                 assert(x<=X);
  32                 assert(y<=Y);
  33 }
  34
  35 struct Node;
  36 struct CmpNodePos { bool operator()(const Node* u, const Node* v) const; };
  37
  38 typedef set<Node*,CmpNodePos> NodeSet;
  39
  40 struct Node {
  41         Variable *v;
  42         Rectangle *r;
  43         double pos;
  44         Node *firstAbove, *firstBelow;
  45         NodeSet *leftNeighbours, *rightNeighbours;
  46         Node(Variable *v, Rectangle *r, double p) : v(v),r(r),pos(p) {
  47                 firstAbove=firstBelow=NULL;
  48                 leftNeighbours=rightNeighbours=NULL;
  49                 assert(r->width()<1e40);
  50         }
  51         ~Node() {
  52                 delete leftNeighbours;
  53                 delete rightNeighbours;
  54         }
  55         void addLeftNeighbour(Node *u) {
  56                 leftNeighbours->insert(u);
  57         }
  58         void addRightNeighbour(Node *u) {
  59                 rightNeighbours->insert(u);
  60         }
  61         void setNeighbours(NodeSet *left, NodeSet *right) {
  62                 leftNeighbours=left;
  63                 rightNeighbours=right;
  64                 for(NodeSet::iterator i=left->begin();i!=left->end();++i) {
  65                         Node *v=*(i);
  66                         v->addRightNeighbour(this);
  67                 }
  68                 for(NodeSet::iterator i=right->begin();i!=right->end();++i) {
  69                         Node *v=*(i);
  70                         v->addLeftNeighbour(this);
  71                 }
  72         }
  73 };
  74 bool CmpNodePos::operator() (const Node* u, const Node* v) const {
  75         if (u->pos < v->pos) {
  76                 return true;
  77         }
  78         if (v->pos < u->pos) {
  79                 return false;
  80         }
  81         if (isNaN(u->pos) != isNaN(v->pos)) {
  82                 return isNaN(u->pos);
  83         }
  84         return u < v;
  85
  86         /* I don't know how important it is to handle NaN correctly
  87          * (e.g. we probably handle it badly in other code anyway, and
  88          * in any case the best we can hope for is to reduce the
  89          * badness of other nodes).
  90          *
  91          * Nevertheless, we try to do the right thing here and in
  92          * event comparison.  The issue is that (on platforms with
  93          * ieee floating point comparison) NaN compares neither less
  94          * than nor greater than any other number, yet sort wants a
  95          * well-defined ordering.  In particular, we want to ensure
  96          * transitivity of equivalence, which normally wouldn't be
  97          * guaranteed if the "middle" item in the transitivity
  98          * involves a NaN.  (NaN is neither less than nor greater than
  99          * other numbers, so tends to be considered as equal to all
 100          * other numbers: even unequal numbers.)
 101          */
 102 }
 103
 104 NodeSet* getLeftNeighbours(NodeSet &scanline,Node *v) {
 105         NodeSet *leftv = new NodeSet;
 106         NodeSet::iterator i=scanline.find(v);
 107         while(i--!=scanline.begin()) {
 108                 Node *u=*(i);
 109                 if(u->r->overlapX(v->r)<=0) {
 110                         leftv->insert(u);
 111                         return leftv;
 112                 }
 113                 if(u->r->overlapX(v->r)<=u->r->overlapY(v->r)) {
 114                         leftv->insert(u);
 115                 }
 116         }
 117         return leftv;
 118 }
 119 NodeSet* getRightNeighbours(NodeSet &scanline,Node *v) {
 120         NodeSet *rightv = new NodeSet;
 121         NodeSet::iterator i=scanline.find(v);
 122         for(++i;i!=scanline.end(); ++i) {
 123                 Node *u=*(i);
 124                 if(u->r->overlapX(v->r)<=0) {
 125                         rightv->insert(u);
 126                         return rightv;
 127                 }
 128                 if(u->r->overlapX(v->r)<=u->r->overlapY(v->r)) {
 129                         rightv->insert(u);
 130                 }
 131         }
 132         return rightv;
 133 }
 134
 135 typedef enum {Open, Close} EventType;
 136 struct Event {
 137         EventType type;
 138         Node *v;
 139         double pos;
 140         Event(EventType t, Node *v, double p) : type(t),v(v),pos(p) {};
 141 };
 142 Event **events;
 143 int compare_events(const void *a, const void *b) {
 144         Event *ea=*(Event**)a;
 145         Event *eb=*(Event**)b;
 146         if(ea->v->r==eb->v->r) {
 147                 // when comparing opening and closing from the same rect
 148                 // open must come first
 149                 if(ea->type==Open) return -1;
 150                 return 1;
 151         } else if(ea->pos > eb->pos) {
 152                 return 1;
 153         } else if(ea->pos < eb->pos) {
 154                 return -1;
 155         } else if(isNaN(ea->pos) != isNaN(ea->pos)) {
 156                 /* See comment in CmpNodePos. */
 157                 return ( isNaN(ea->pos)
 158                          ? -1
 159                          : 1 );
 160         }
 161         return 0;
 162 }
 163
 164 /**
 165  * Prepares constraints in order to apply VPSC horizontally.  Assumes variables have already been created.
 166  * useNeighbourLists determines whether or not a heuristic is used to deciding whether to resolve
 167  * all overlap in the x pass, or leave some overlaps for the y pass.
 168  */
 169 int generateXConstraints(const int n, Rectangle** rs, Variable** vars, Constraint** &cs, const bool useNeighbourLists) {
 170         events=new Event*[2*n];
 171         int i,m,ctr=0;
 172         for(i=0;i<n;i++) {
 173                 vars[i]->desiredPosition=rs[i]->getCentreX();
 174                 Node *v = new Node(vars[i],rs[i],rs[i]->getCentreX());
 175                 events[ctr++]=new Event(Open,v,rs[i]->getMinY());
 176                 events[ctr++]=new Event(Close,v,rs[i]->getMaxY());
 177         }
 178         qsort((Event*)events, (size_t)2*n, sizeof(Event*), compare_events );
 179
 180         NodeSet scanline;
 181         vector<Constraint*> constraints;
 182         for(i=0;i<2*n;i++) {
 183                 Event *e=events[i];
 184                 Node *v=e->v;
 185                 if(e->type==Open) {
 186                         scanline.insert(v);
 187                         if(useNeighbourLists) {
 188                                 v->setNeighbours(
 189                                         getLeftNeighbours(scanline,v),
 190                                         getRightNeighbours(scanline,v)
 191                                 );
 192                         } else {
 193                                 NodeSet::iterator it=scanline.find(v);
 194                                 if(it--!=scanline.begin()) {
 195                                         Node *u=*it;
 196                                         v->firstAbove=u;
 197                                         u->firstBelow=v;
 198                                 }
 199                                 it=scanline.find(v);
 200                                 if(++it!=scanline.end()) {
 201                                         Node *u=*it;
 202                                         v->firstBelow=u;
 203                                         u->firstAbove=v;
 204                                 }
 205                         }
 206                 } else {
 207                         // Close event
 208                         int r;
 209                         if(useNeighbourLists) {
 210                                 for(NodeSet::iterator i=v->leftNeighbours->begin();
 211                                         i!=v->leftNeighbours->end();i++
 212                                 ) {
 213                                         Node *u=*i;
 214                                         double sep = (v->r->width()+u->r->width())/2.0;
 215                                         constraints.push_back(new Constraint(u->v,v->v,sep));
 216                                         r=u->rightNeighbours->erase(v);
 217                                 }
 218
 219                                 for(NodeSet::iterator i=v->rightNeighbours->begin();
 220                                         i!=v->rightNeighbours->end();i++
 221                                 ) {
 222                                         Node *u=*i;
 223                                         double sep = (v->r->width()+u->r->width())/2.0;
 224                                         constraints.push_back(new Constraint(v->v,u->v,sep));
 225                                         r=u->leftNeighbours->erase(v);
 226                                 }
 227                         } else {
 228                                 Node *l=v->firstAbove, *r=v->firstBelow;
 229                                 if(l!=NULL) {
 230                                         double sep = (v->r->width()+l->r->width())/2.0;
 231                                         constraints.push_back(new Constraint(l->v,v->v,sep));
 232                                         l->firstBelow=v->firstBelow;
 233                                 }
 234                                 if(r!=NULL) {
 235                                         double sep = (v->r->width()+r->r->width())/2.0;
 236                                         constraints.push_back(new Constraint(v->v,r->v,sep));
 237                                         r->firstAbove=v->firstAbove;
 238                                 }
 239                         }
 240                         r=scanline.erase(v);
 241                         delete v;
 242                 }
 243                 delete e;
 244         }
 245         delete [] events;
 246         cs=new Constraint*[m=constraints.size()];
 247         for(i=0;i<m;i++) cs[i]=constraints[i];
 248         return m;
 249 }
 250
 251 /**
 252  * Prepares constraints in order to apply VPSC vertically to remove ALL overlap.
 253  */
 254 int generateYConstraints(const int n, Rectangle** rs, Variable** vars, Constraint** &cs) {
 255         events=new Event*[2*n];
 256         int ctr=0,i,m;
 257         for(i=0;i<n;i++) {
 258                 vars[i]->desiredPosition=rs[i]->getCentreY();
 259                 Node *v = new Node(vars[i],rs[i],rs[i]->getCentreY());
 260                 events[ctr++]=new Event(Open,v,rs[i]->getMinX());
 261                 events[ctr++]=new Event(Close,v,rs[i]->getMaxX());
 262         }
 263         qsort((Event*)events, (size_t)2*n, sizeof(Event*), compare_events );
 264         NodeSet scanline;
 265         vector<Constraint*> constraints;
 266         for(i=0;i<2*n;i++) {
 267                 Event *e=events[i];
 268                 Node *v=e->v;
 269                 if(e->type==Open) {
 270                         scanline.insert(v);
 271                         NodeSet::iterator i=scanline.find(v);
 272                         if(i--!=scanline.begin()) {
 273                                 Node *u=*i;
 274                                 v->firstAbove=u;
 275                                 u->firstBelow=v;
 276                         }
 277                         i=scanline.find(v);
 278                         if(++i!=scanline.end())  {
 279                                 Node *u=*i;
 280                                 v->firstBelow=u;
 281                                 u->firstAbove=v;
 282                         }
 283                 } else {
 284                         // Close event
 285                         Node *l=v->firstAbove, *r=v->firstBelow;
 286                         if(l!=NULL) {
 287                                 double sep = (v->r->height()+l->r->height())/2.0;
 288                                 constraints.push_back(new Constraint(l->v,v->v,sep));
 289                                 l->firstBelow=v->firstBelow;
 290                         }
 291                         if(r!=NULL) {
 292                                 double sep = (v->r->height()+r->r->height())/2.0;
 293                                 constraints.push_back(new Constraint(v->v,r->v,sep));
 294                                 r->firstAbove=v->firstAbove;
 295                         }
 296                         scanline.erase(v);
 297                         delete v;
 298                 }
 299                 delete e;
 300         }
 301         delete [] events;
 302         cs=new Constraint*[m=constraints.size()];
 303         for(i=0;i<m;i++) cs[i]=constraints[i];
 304         return m;
 305 }
 306 }