SPAR/AIModule/BWTA/vendors/CGAL/CGAL/Sweep_line_2/Arr_batched_pl_sl_visitor.h

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// Copyright (c) 2005  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/Sweep_line_2/Arr_batched_pl_sl_visitor.h $
// $Id: Arr_batched_pl_sl_visitor.h 40007 2007-08-23 13:51:38Z efif $
// 
//
// Author(s)     : Baruch Zukerman <baruchzu@post.tau.ac.il>
//                 Ron Wein <wein@post.tau.ac.il>

#ifndef CGAL_ARR_BATCHED_PL_SL_VISITOR_H
#define CGAL_ARR_BATCHED_PL_SL_VISITOR_H

CGAL_BEGIN_NAMESPACE

#include <CGAL/Object.h>

template <class Helper_, class OutputIterator_>
class Arr_batched_pl_sl_visitor :
  public Helper_::Base_visitor
{
public:

  typedef Helper_                                      Helper;
  typedef OutputIterator_                              OutputIterator;

  typedef typename Helper::Traits_2                    Traits_2;
  typedef typename Helper::Arrangement_2               Arrangement_2;
  typedef typename Helper::Base_visitor                Base;
  typedef typename Helper::Event                       Event;
  typedef typename Helper::Subcurve                    Subcurve;

protected:

  typedef typename Base::Status_line_iterator           Status_line_iterator;
  typedef typename Arrangement_2::Halfedge_const_handle Halfedge_const_handle;
  typedef typename Arrangement_2::Vertex_const_handle   Vertex_const_handle;

  // Data members:
  Helper                   m_helper;    // The helper class.
  OutputIterator          *m_out;       // An output iterator for the result.

public:

  Arr_batched_pl_sl_visitor (const Arrangement_2 *arr,
                             OutputIterator *oi) :
    m_helper (arr),
    m_out (oi)
  {}
  
  /* A notification issued before the sweep process starts. */
  void before_sweep ();

  bool after_handle_event (Event* event,
                           Status_line_iterator above,
                           bool on_above);
};

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

//-----------------------------------------------------------------------------
// A notification issued before the sweep process starts.
//
template <class Hlpr, class OutIt>
void Arr_batched_pl_sl_visitor<Hlpr, OutIt>::before_sweep ()
{
  // We just have to notify the helper that the sweep process now starts.
  m_helper.before_sweep();

  return;
}

//-----------------------------------------------------------------------------
// A notification invoked after the sweep-line finishes handling the given
// event.
//
template <class Hlpr, class OutIt>
bool Arr_batched_pl_sl_visitor<Hlpr, OutIt>::after_handle_event
    (Event* event,
     Status_line_iterator above, bool on_above)
{
  // Notify the helper on the event.
  m_helper.after_handle_event (event);

  // We are only interested in events associated with query points:
  if (! event->is_query())
    return true;

  // Check on what kind of feature does the current query point lie.
  if (event->is_action())
  {
    // The query point coincides with an isolated arrangement vertex:
    Vertex_const_handle  vh = event->point().vertex_handle();
      
    *(*m_out) = std::make_pair (event->point().base(), 
                                CGAL::make_object(vh));
    ++(*m_out);
    return (true);
  }

  if (event->has_right_curves() || event->has_left_curves())
  {
    // The point is located on an arrangement vertex:
    Vertex_const_handle  vh;

    if (event->has_right_curves())
    {
      // Take the target vertex of one of the halfedges to the right.
      Subcurve              *sc = *(event->right_curves_begin());
      Halfedge_const_handle  he = sc->last_curve().halfedge_handle();

      vh = he->target();
    }
    else
    {
      // Take the source vertex of one of the halfedges to the right.
      Subcurve              *sc = *(event->left_curves_begin());
      Halfedge_const_handle  he = sc->last_curve().halfedge_handle();

      vh = he->source();
    }

    *(*m_out) = std::make_pair (event->point().base(), 
                                CGAL::make_object (vh));
    ++(*m_out);
    return (true);
  }

  if (above == this->status_line_end())
  {
    // There are no valid edges above the query point, so we use the helper
    // class to obtain the current top face.
    *(*m_out) = std::make_pair (event->point().base(),
                                CGAL::make_object (m_helper.top_face()));
    ++(*m_out);
    return (true);
  }

  if (on_above)
  {
    // The query point lies on the halfedge associated with the subcurve
    // that the status-line iterator refers to.
    Halfedge_const_handle  he = (*above)->last_curve().halfedge_handle();
      
    *(*m_out) = std::make_pair (event->point().base(),
                                CGAL::make_object (he));
    ++(*m_out);
    return (true);
  }

  // If we reached here, the status-line iterator refers to a halfedge above
  // the query point, such that the query point is located in the incident
  // face of this halfedge.
  Halfedge_const_handle  he = (*above)->last_curve().halfedge_handle();

  *(*m_out) = std::make_pair (event->point().base(),
                              CGAL::make_object (he->face()));
  ++(*m_out);
  return (true);
}

CGAL_END_NAMESPACE

#endif