cgal/Straight_skeleton_2/include/CGAL/Polygon_offset_builder_2.h

// Copyright (c) 2005-2008 Fernando Luis Cacciola Carballal. All rights reserved.
//
// This file is part of CGAL (www.cgal.org).
//
// $URL$
// $Id$
// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s)     : Fernando Cacciola <fernando_cacciola@ciudad.com.ar>
//
#ifndef CGAL_POLYGON_OFFSET_BUILDER_2_H
#define CGAL_POLYGON_OFFSET_BUILDER_2_H 1

#include <CGAL/license/Straight_skeleton_2.h>

#include <CGAL/Straight_skeleton_2/Straight_skeleton_aux.h>
#include <CGAL/Polygon_offset_builder_traits_2.h>

#include <optional>
#include <memory>

#include <vector>

namespace CGAL {

template<class Traits_, class SSkel_>
struct Default_polygon_offset_builder_2_visitor
{
  typedef Traits_ Traits ;
  typedef SSkel_  SSkel ;

  typedef typename SSkel::Halfedge_const_handle Halfedge_const_handle ;
  typedef typename SSkel::Vertex_const_handle   Vertex_const_handle ;

  typedef typename Traits::FT      FT ;
  typedef typename Traits::Point_2 Point_2 ;

  void on_construction_started ( FT ) const {}

  void on_offset_contour_started() const {}

  void on_offset_point ( Point_2 const&, Halfedge_const_handle ) const {}

  Point_2 on_offset_point_overflowed( Halfedge_const_handle aBisector ) const
  {
    ::CGAL::warning_fail( "", __FILE__, __LINE__, "! Unable to compute polygon offset point due to overflow !" ) ;
    return aBisector->vertex()->point() ;
  }

  void on_offset_contour_finished ( bool /*is_complete*/ ) const {}

  void on_construction_finished () const {}

  void on_error( char const* ) const {}
} ;

template<class Ss_, class Traits_, class Container_, class Visitor_ = Default_polygon_offset_builder_2_visitor<Traits_,Ss_> >
class Polygon_offset_builder_2
{
public :

  typedef Ss_        Ss ;
  typedef Traits_    Traits ;
  typedef Container_ Container ;
  typedef Visitor_   Visitor ;

  typedef typename Traits::Kernel K ;

  typedef typename Traits::FT      FT ;
  typedef typename Traits::Point_2 Point_2 ;

  typedef std::optional<Point_2> OptionalPoint_2 ;

  typedef std::shared_ptr<Container> ContainerPtr ;

  Polygon_offset_builder_2( Ss const& aSs, Traits const& aTraits = Traits(), Visitor const& aVisitor = Visitor() )  ;

  template<class OutputIterator>
  OutputIterator construct_offset_contours( FT aTime, OutputIterator aOut ) ;

  struct Bisector_data
  {
    Bisector_data() : IsVisited(false), IsUsedSeed(false) {}

    bool IsVisited ;
    bool IsUsedSeed ;
  } ;

private:

  typedef typename Ss::Vertex                Vertex ;
  typedef typename Ss::Halfedge_handle       Halfedge_handle  ;
  typedef typename Ss::Halfedge_const_handle Halfedge_const_handle  ;
  typedef typename Ss::Vertex_const_handle   Vertex_const_handle  ;

  typedef std::vector<Halfedge_const_handle> Halfedge_vector ;

  typedef typename Traits::Segment_2        Segment_2 ;
  typedef typename Traits::Trisegment_2     Trisegment_2 ;
  typedef typename Traits::Trisegment_2_ptr Trisegment_2_ptr ;

  typedef CGAL_SS_i::Triedge<Halfedge_handle> Triedge ;

  enum Hook_position { SOURCE, TARGET, INSIDE } ;

  static char const* Hook_position2Str( Hook_position aPos )
  {
    return aPos == SOURCE ? "source" : ( aPos == TARGET ? "target" : "inside" ) ;
  }

  Halfedge_const_handle LocateHook( FT aTime, Halfedge_const_handle aBisector, bool aIncludeLastBisector, Hook_position& rPos ) ;

  void AddOffsetVertex( FT aTime, Halfedge_const_handle aHook, ContainerPtr aPoly ) ;

  template<class OutputIterator>
  OutputIterator TraceOffsetPolygon( FT aTime, Halfedge_const_handle aHook, OutputIterator aOut ) ;

  Halfedge_const_handle LocateSeed( FT aTime, Halfedge_const_handle aBorder ) ;

  Halfedge_const_handle LocateSeed( FT aTime ) ;

  Bisector_data const& GetBisectorData ( Halfedge_const_handle aBisector ) const { return mBisectorData[aBisector->id()] ; }
  Bisector_data&       GetBisectorData ( Halfedge_const_handle aBisector )       { return mBisectorData[aBisector->id()] ; }

  bool IsVisited( Halfedge_const_handle aBisector ) { return GetBisectorData(aBisector).IsVisited ; }

  bool IsUsedSeed( Halfedge_const_handle aBisector ) { return GetBisectorData(aBisector).IsUsedSeed ; }

  void Visit( Halfedge_const_handle aBisector ) { GetBisectorData(aBisector).IsVisited = true ; }

  void SetIsUsedSeed( Halfedge_const_handle aBisector ) { GetBisectorData(aBisector).IsUsedSeed = true ; }

  inline Segment_2 CreateSegment ( Halfedge_const_handle aH ) const
  {
    Point_2 s = aH->opposite()->vertex()->point() ;
    Point_2 t = aH->vertex()->point() ;
    return K().construct_segment_2_object()(s,t);
  }

  Trisegment_2_ptr GetTrisegment ( Vertex_const_handle aNode ) const ;

public:
  Comparison_result Compare_offset_against_event_time( FT aT, Vertex_const_handle aNode ) const
  {
    CGAL_precondition( aNode->is_skeleton() ) ;

    Comparison_result r = aNode->has_infinite_time() ? SMALLER
                                                     : static_cast<Comparison_result>(mTraits.compare_offset_against_event_time_2_object()(aT,GetTrisegment(aNode)));

    return r ;
  }

  std::optional<Point_2> Construct_offset_point( FT aT, Halfedge_const_handle aBisector ) const
  {
    CGAL_assertion(aBisector->is_bisector());
    CGAL_assertion(handle_assigned(aBisector->opposite()));
    CGAL_assertion(aBisector->opposite()->is_bisector());

    Halfedge_const_handle lBorderA = aBisector->defining_contour_edge();
    Halfedge_const_handle lBorderB = aBisector->opposite()->defining_contour_edge();

    Vertex_const_handle lNodeS = aBisector->opposite()->vertex();
    Vertex_const_handle lNodeT = aBisector->vertex();


    // If aBisector is not a border bisector the offset point construction needs to get to seed event
    Trisegment_2_ptr lSeedEvent ;
    if ( aBisector->is_inner_bisector() )
    {
      CGAL_assertion ( lNodeS->is_skeleton() ) ;
      CGAL_assertion ( lNodeT->is_skeleton() ) ;

      Vertex_const_handle lSeedNode = aBisector->slope() == POSITIVE ? lNodeS : lNodeT ;
      lSeedEvent = GetTrisegment(lSeedNode) ;

      CGAL_POLYOFFSET_TRACE(3,"Seed node for " << e2str(*aBisector) << " is " << v2str(*lSeedNode) << " event=" << lSeedEvent ) ;
    }

    OptionalPoint_2 p = mTraits.construct_offset_point_2_object()( aT,
                                                                   CreateSegment(lBorderA),
                                                                   lBorderA->weight(),
                                                                   CreateSegment(lBorderB),
                                                                   lBorderB->weight(),
                                                                   lSeedEvent );

    return p ;
  }
private:
  void ResetBisectorData();

  Traits const&              mTraits ;
  Visitor const&             mVisitor ;
  Halfedge_vector            mBorders ;
  std::vector<Bisector_data> mBisectorData;
  OptionalPoint_2            mLastPoint ;
  CGAL_POLYOFFSET_DEBUG_CODE( int mStepID ; )
};

} // end namespace CGAL

#include <CGAL/Straight_skeleton_2/Polygon_offset_builder_2_impl.h>

#endif // CGAL_POLYGON_OFFSET_BUILDER_2_H //
// EOF //