SPAR/AIModule/BWTA/vendors/CGAL/CGAL/Arr_topology_traits/Arr_unb_planar_construction_helper.h

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// Copyright (c) 1997  Tel-Aviv University (Israel).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org); you may redistribute it under
// the terms of the Q Public License version 1.0.
// See the file LICENSE.QPL distributed with CGAL.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL: svn+ssh://scm.gforge.inria.fr/svn/cgal/branches/CGAL-3.5-branch/Arrangement_on_surface_2/include/CGAL/Arr_topology_traits/Arr_unb_planar_construction_helper.h $
// $Id: Arr_unb_planar_construction_helper.h 49772 2009-06-03 21:25:53Z eric $
// 
//
// Author(s)     : Baruch Zukerman <baruchzu@post.tau.ac.il>
//                 Ron Wein        <wein@post.tau.ac.il>
//                 Efi Fogel       <efif@post.tau.ac.il>

#ifndef CGAL_ARR_UNB_PLANAR_CONSTRUCTION_HELPER_H
#define CGAL_ARR_UNB_PLANAR_CONSTRUCTION_HELPER_H

#include <CGAL/Sweep_line_empty_visitor.h>
#include <CGAL/Unique_hash_map.h>

CGAL_BEGIN_NAMESPACE

template <class Traits_, class Arrangement_, class Event_, class Subcurve_> 
class Arr_unb_planar_construction_helper
{
public:

  typedef Traits_                                      Traits_2;
  typedef Arrangement_                                 Arrangement_2;
  typedef Event_                                       Event;
  typedef Subcurve_                                    Subcurve;

  typedef typename Traits_2::X_monotone_curve_2        X_monotone_curve_2;
  typedef typename Traits_2::Point_2                   Point_2;

  typedef Sweep_line_empty_visitor<Traits_2, Subcurve, Event>
                                                       Base_visitor;

  typedef typename Arrangement_2::Halfedge_handle      Halfedge_handle;
  typedef typename Arrangement_2::Face_handle          Face_handle;
  
  typedef typename Subcurve::Halfedge_indices_list     Indices_list;
  typedef Unique_hash_map<Halfedge_handle, 
                          Indices_list>                Halfedge_indices_map;

protected:

  typedef typename Arrangement_2::Topology_traits      Topology_traits;
  typedef typename Arrangement_2::Vertex_handle        Vertex_handle;

  // Data members:
  Topology_traits         *m_top_traits;  // The topology-traits class.
  Arr_accessor<Arrangement_2>
                           m_arr_access;  // An arrangement accessor.

  Halfedge_handle          m_lh;          // The current left fictitious
                                          // halfedge (on x = -oo).
  Halfedge_handle          m_th;          // The current top fictitious
                                          // halfedge (on y = +oo).
  Halfedge_handle          m_bh;          // The current bottom fictitious
                                          // halfedge (on y = -oo).
  Halfedge_handle          m_rh;          // The current right fictitious
                                          // halfedge (on x = +oo).

  Indices_list      m_subcurves_at_ubf;       // Indices of the curves that
                                              // "see" m_th from below.
  Event*            m_prev_minus_inf_x_event; // The previous event at x = -oo.
  Event*            m_prev_plus_inf_y_event;  // The previous event at y = +oo.

  Halfedge_indices_map    *m_he_ind_map_p;    // A pointer to a map of
                                              // halfedges to indices lists
                                              // (stored in the visitor class).
  
public:
 
  Arr_unb_planar_construction_helper (Arrangement_2 *arr) :
    m_top_traits (arr->topology_traits()),
    m_arr_access (*arr),
    m_prev_minus_inf_x_event (NULL),
    m_prev_plus_inf_y_event (NULL),
    m_he_ind_map_p (NULL)
  {}

  virtual ~Arr_unb_planar_construction_helper(){}



  /* A notification issued before the sweep process starts. */
  virtual void before_sweep ();

  virtual void before_handle_event (Event* event);

  virtual void add_subcurve (Halfedge_handle /* he */,
                             Subcurve* /* sc */)
  {
    return;
  }

  void add_subcurve_in_top_face (unsigned int index)
  {
    m_subcurves_at_ubf.push_back (index);
    return;
  }

  void before_deallocate_event (Event* event)
  {
    // The last event at y = +oo may be deallocated if it has no incident
    // right subcurves, so we should not keep a pointer to it.
    if (event == m_prev_plus_inf_y_event)
      m_prev_plus_inf_y_event = NULL;

    return;
  }
  
  void set_halfedge_indices_map (Halfedge_indices_map& table)
  {
    m_he_ind_map_p = &table;
    return;
  }

  bool swap_predecessors (Event* event) const
  {
    // If we insert an edge whose right end lies on the top edge of the
    // ficititous bounding rectangle, we have to flip the order of predecessor
    // halfegdes.
    return ((event->parameter_space_in_x() == ARR_INTERIOR) &&
            (event->parameter_space_in_y() == ARR_TOP_BOUNDARY));
  }

  Face_handle top_face () const
  {
    return (m_th->face());
  }
};

//-----------------------------------------------------------------------------
// Memeber-function definitions:
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// A notification issued before the sweep process starts.
//
template <class Tr, class Arr, class Evnt, class Sbcv> 
void Arr_unb_planar_construction_helper<Tr,Arr,Evnt,Sbcv>::before_sweep ()
{
  // Obtain the four fictitious vertices that form the "corners" of the
  // fictitious face in the DCEL.
  Vertex_handle    v_bl = Vertex_handle (m_top_traits->bottom_left_vertex());
  Vertex_handle    v_tl = Vertex_handle (m_top_traits->top_left_vertex());
  Vertex_handle    v_br = Vertex_handle (m_top_traits->bottom_right_vertex());
  Vertex_handle    v_tr = Vertex_handle (m_top_traits->top_right_vertex());
  
  // Get the fictitous halfedges incident to these vertices, representing
  // the left, right, top and bottom edges of the fictitious face.
  //
  //              m_th
  //  v_tl (.)<----------(.) v_tr
  //        |             ^
  //   m_lh |             | m_rh
  //        v             |
  //  v_bl (.)---------->(.) v_br
  //              m_bh
  //
  m_lh = v_tl->incident_halfedges();
  
  if(m_lh->source() != v_bl)
    m_lh = m_lh->next();
  else
    m_lh = m_lh->twin();
  
  m_bh = m_lh->next();
  m_rh = m_bh->next();
  m_th = m_rh->next();

  CGAL_assertion_code (
    Face_handle  fict_face = Face_handle (m_top_traits->fictitious_face());
  );
  CGAL_assertion (m_lh->direction() == ARR_RIGHT_TO_LEFT);
  CGAL_assertion (m_lh->face() != fict_face);
  CGAL_assertion (m_lh->source() == v_tl && m_lh->target() == v_bl);
  
  CGAL_assertion (m_bh->direction() == ARR_LEFT_TO_RIGHT);
  CGAL_assertion (m_bh->face() != fict_face);
  CGAL_assertion (m_bh->source() == v_bl && m_bh->target() == v_br);
  
  CGAL_assertion (m_rh->direction() == ARR_LEFT_TO_RIGHT);
  CGAL_assertion (m_rh->face() != fict_face);
  CGAL_assertion (m_rh->source() == v_br && m_rh->target() == v_tr);
  
  CGAL_assertion (m_th->direction() == ARR_RIGHT_TO_LEFT);
  CGAL_assertion (m_th->face() != fict_face);
  CGAL_assertion (m_th->source() == v_tr && m_th->target() == v_tl);
}

//-----------------------------------------------------------------------------
// A notification invoked before the sweep-line starts handling the given
// event.
//
template <class Tr, class Arr, class Evnt, class Sbcv> 
void Arr_unb_planar_construction_helper<Tr,Arr,Evnt,Sbcv>::
before_handle_event (Event* event)
{
  if (event->is_closed())
    return;

  // As the event lieas at infinity, it must have only one (right or left)
  // incident curve.
  CGAL_assertion(((event->number_of_left_curves() == 0) &&
                  (event->number_of_right_curves() == 1)) ||
                 ((event->number_of_left_curves() == 1) &&
                  (event->number_of_right_curves() == 0)));
  Arr_curve_end                  ind = (event->number_of_left_curves() == 0 &&
                                        event->number_of_right_curves() == 1) ?
    ARR_MIN_END : ARR_MAX_END;
  const X_monotone_curve_2&  xc = (ind == ARR_MIN_END) ?
    (*(event->right_curves_begin()))->last_curve() :
    (*(event->left_curves_begin()))->last_curve();

  const Arr_parameter_space        ps_x = event->parameter_space_in_x();
  const Arr_parameter_space        ps_y = event->parameter_space_in_y();

  // Create a vertex at infinity and split the corresponding fictitious edge.
  Vertex_handle v_at_inf =
    m_arr_access.create_boundary_vertex (xc, ind, ps_x, ps_y, false);

  switch (ps_x) {
   case ARR_LEFT_BOUNDARY:
    // The event lies on the left fictitious halfedge.
    m_arr_access.split_fictitious_edge(m_lh, v_at_inf);
    event->set_halfedge_handle(m_lh);

    // Update the incident halfedge of the previous vertex at x = -oo
    // (m_lh used to be incident to it, but now we have split it).
    if (m_prev_minus_inf_x_event != NULL)
      m_prev_minus_inf_x_event->set_halfedge_handle(m_lh->next());
    m_prev_minus_inf_x_event = event;
    return;

   case ARR_RIGHT_BOUNDARY:
    // The event lies on the right fictitious halfedge.
    m_arr_access.split_fictitious_edge(m_rh, v_at_inf);
    event->set_halfedge_handle(m_rh);
    m_rh = m_rh->next();
    return;

  case ARR_INTERIOR:
    break;

  default:
    CGAL_error();
  }

  switch (ps_y) {
   case ARR_BOTTOM_BOUNDARY:
    // The event lies on the bottom fictitious halfedge.
    m_arr_access.split_fictitious_edge(m_bh, v_at_inf);
    event->set_halfedge_handle(m_bh);
    m_bh = m_bh->next();
    return;

   case ARR_TOP_BOUNDARY:
    {
      // The event lies on the top fictitious halfedge.
      m_arr_access.split_fictitious_edge(m_th, v_at_inf);
      event->set_halfedge_handle(m_th);

      // Update the incident halfedge of the previous vertex at y = +oo
      // (m_th used to be incident to it, but now we have split it).
      if(m_prev_plus_inf_y_event != NULL)
        m_prev_plus_inf_y_event->set_halfedge_handle(m_th->next());
      m_prev_plus_inf_y_event = event;

      // Associate all curve indices of subcurves that "see" m_th from
      // below with the left portion of the split halfedge (m_th->next()).
      if (m_he_ind_map_p != NULL)
      {
        Indices_list& list_ref = (*m_he_ind_map_p)[m_th->next()];
        list_ref.clear();
        list_ref.splice (list_ref.end(), m_subcurves_at_ubf);
      }
      else
      {
        m_subcurves_at_ubf.clear();
      }
      CGAL_assertion (m_subcurves_at_ubf.empty());
    }
    return;

  case ARR_INTERIOR:
  default:
    // We are not supposed to reach here at all.
    CGAL_error();
  }

  return;
}

CGAL_END_NAMESPACE

#endif