C++ VPoint::next方法代码示例

/*!The method uses #_shape1 and #_shape2 structure as an input data and produces
one or more polygons representing the result of the logical OR between the 
input polygons. Method returns false if no output shapes are generated, and
true otherwise*/
bool logicop::logic::OR(pcollection& plycol) {
   bool result = false;
   VPoint* centinel = NULL;
   if (0 == _crossp) {
      // If there are no crossing points found, this still does not mean
      // that the operation will fail. Polygons might be fully overlapping...
      // Check that a random point from poly1 is inside poly2 ...
      if       (_shape1->inside(_poly2)) centinel = _shape2;
      // ... if not, check that a random point from poly2 is inside poly1 ...
      else if (_shape2->inside(_poly1)) centinel = _shape1;
      // ... if not - polygons does not have any common area
      else return false;
      // If we've got here means that one of the polygons is completely 
      // overlapped by the other one. So we need to return the outer one
      pointlist *shgen = new pointlist();
      VPoint* vpnt = centinel;
      do {
         shgen->push_back(TP(vpnt->cp()->x(), vpnt->cp()->y()));
         vpnt = vpnt->next();
      }while (centinel != vpnt);
      plycol.push_back(shgen);
      return true;
   }
   pcollection lclcol; // local collection of the resulting shapes
   // get first external and non crossing  point
   centinel = getFirstOutside(_poly2, _shape1);
   if (NULL == centinel) centinel = getFirstOutside(_poly1, _shape2);
   assert(centinel);   
   VPoint* collector = centinel;
   bool direction = true; /*next*/
   do {
      if (0 == collector->visited()) {
         pointlist *shgen = new pointlist();
         VPoint* pickup = collector;
         direction = (0 == lclcol.size());
         do {
            pickup = pickup->follower(direction);
            shgen->push_back(TP(pickup->cp()->x(), pickup->cp()->y()));
         } while (pickup != collector);
         direction = true;
         lclcol.push_back(shgen);
         result = true;
      }
      collector = collector->next();
   } while (collector != centinel);
   if (!result) return result;
   // Convert all collected shapes to a single normalized polygon
   pointlist* respoly = lclcol.front();lclcol.pop_front();
   while (0 < lclcol.size()) {
      respoly = hole2simple(*respoly, *(lclcol.front()));
      lclcol.pop_front();
   }   
   plycol.push_back(respoly);
   return result;
}

/*!If more than one logical operatoin has to be executed over the input shapes
the raw data #_shape1 and #_shape2 can be reused, but has to be recycled beforehand
This method is traversing both fields and invokes VPoint::reset_visited() in 
order to reinitialize the CPoint::_visited fields*/
void logicop::logic::reset_visited() {
   VPoint* centinel = _shape1;
   VPoint* looper = centinel;
   do {
      looper->reset_visited();
      looper = looper->next();
   }  while (centinel != looper);
   centinel = _shape2;
   looper = centinel;
   do {
      looper->reset_visited();
      looper = looper->next();
   }  while (centinel != looper);
}

/*! This method returns properly sorted dual linked list of all vertices 
(including crossing ones) of this segment collection. The method should be 
called after normalize(). The list created here is used as a source data when
the new polygons are generated. All logic operations are using this data. This
is effectively the input polygon vertices and the crossing points lined-up
conterclockwise*/
logicop::VPoint* logicop::segmentlist::dump_points() {
   logicop::VPoint* vlist = NULL;
   for (unsigned i = 0; i < _segs.size(); i++)
      _segs[i]->dump_points(vlist);
   logicop::VPoint* lastV = vlist;
   VPoint* centinel = NULL;
   while (vlist->prev())  {
      if (-1 == vlist->visited()) centinel = vlist;
      vlist = vlist->prev();
   }   
   lastV->set_next(vlist);
   vlist->set_prev(lastV);
   if (NULL != centinel) {
      VPoint* vwork = centinel;
      do {
         if (-1 == vwork->visited()) {
            //here visited == 0 means only that the object is Cpoint.
            VPoint* tbdel = NULL;
            if ((*vwork->cp()) == (*vwork->prev()->cp())) {
               tbdel = vwork->prev();
               vwork->set_prev(vwork->prev()->prev());
               vwork->prev()->set_next(vwork);
            }
            else if ((*vwork->cp()) == (*vwork->next()->cp())) {
               tbdel = vwork->next();
               vwork->set_next(vwork->next()->next());
               vwork->next()->set_prev(vwork);
            }
            vwork = vwork->next();
            if (tbdel) delete tbdel;   
         }
         else vwork = vwork->next();
      } while (centinel != vwork);
   }   
   return vlist;
}