conic_arc_2_window_stream.h

来自「CGAL is a collaborative effort of severa」· C头文件 代码 · 共 107 行

// Copyright (c) 2001  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.
//
// $Source: /CVSROOT/CGAL/Packages/Arrangement/include/CGAL/IO/Conic_arc_2_Window_stream.h,v $
// $Revision: 1.8 $ $Date: 2004/07/21 08:48:29 $
// $Name:  $
//
// Author(s)     : Ron Wein <[e-mail]>
#ifndef CGAL_CONIC_ARC_2_WINDOW_STREAM_H
#define CGAL_CONIC_ARC_2_WINDOW_STREAM_H

#include <CGAL/IO/Window_stream.h>
#include <CGAL/Arrangement_2/Conic_arc_2.h>

CGAL_BEGIN_NAMESPACE

template <class Int_kernel, class Alg_kernel>
Window_stream& operator<<(Window_stream& ws,
                          const Conic_arc_2<Int_kernel, Alg_kernel>& cv)
{
  typedef typename Alg_kernel::FT                               CoNT;
  typedef typename Conic_arc_2<Int_kernel, Alg_kernel>::Point_2 Point_2;

  // Get the co-ordinates of the curve's source and target.
  double sx = CGAL::to_double(cv.source().x()),
         sy = CGAL::to_double(cv.source().y()),
         tx = CGAL::to_double(cv.target().x()),
         ty = CGAL::to_double(cv.target().y());

  if (cv.is_segment())
  {
    // The curve is a segment - simply draw it.
    ws << leda_segment(sx, sy, tx, ty);
  }
  else
  {
    // Draw a conic arc of degree 2.
    if (cv.is_x_monotone())
    {
      // If the curve is monotone, than its source and its target has the
      // extreme x co-ordinates on this curve.
      bool     is_source_left = (sx < tx);
      int      x_min = is_source_left ? ws.real_to_pix(sx) : 
	                                ws.real_to_pix(tx);
      int      x_max = is_source_left ? ws.real_to_pix(tx) :
                                        ws.real_to_pix(sx);
      double   prev_x = ws.pix_to_real(x_min);
      double   prev_y = is_source_left ? sy : ty;
      double   end_x = is_source_left ? tx : sx;
      double   end_y = is_source_left ? ty : sy;
      double   curr_x, curr_y;
      int      x;

      Point_2  q;
      Point_2  ps[2];
      int      nps;

      for (x = x_min + 1; x < x_max; x++)
      {
	curr_x = ws.pix_to_real(x);
	q = Point_2 (CoNT(curr_x), 0);
	nps = cv.get_points_at_x (q, ps);

	if (nps == 1)
	{
	  curr_y = CGAL::to_double(ps[0].y());
	  ws << leda_segment(prev_x, prev_y, curr_x, curr_y);
	  prev_x = curr_x;
	  prev_y = curr_y;
	  
	}
      }

      ws << leda_segment(prev_x, prev_y, end_x, end_y);
    }
    else
    {
      // Break the arc into x-monotone sub-curves and draw each one separately.
      Arr_conic_traits_2<Int_kernel, Alg_kernel>       traits; 
      std::list<Conic_arc_2<Int_kernel, Alg_kernel> >  x_mon_curves;
      typename std::list<Conic_arc_2<Int_kernel, Alg_kernel> >::iterator xit;

      traits.curve_make_x_monotone (cv,
				    std::back_inserter (x_mon_curves));

      for (xit = x_mon_curves.begin(); xit != x_mon_curves.end(); xit++)
	ws << *xit;
    }
  }

  return (ws); 
}

CGAL_END_NAMESPACE

#endif