334 lines
9.4 KiB
C
334 lines
9.4 KiB
C
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//----------------------------------------------------------------------------
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// Anti-Grain Geometry - Version 2.4
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// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
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//
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// Permission to copy, use, modify, sell and distribute this software
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// is granted provided this copyright notice appears in all copies.
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// This software is provided "as is" without express or implied
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// warranty, and with no claim as to its suitability for any purpose.
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//
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//----------------------------------------------------------------------------
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// Contact: mcseem@antigrain.com
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// mcseemagg@yahoo.com
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// http://www.antigrain.com
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//----------------------------------------------------------------------------
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//
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// Liang-Barsky clipping
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//
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//----------------------------------------------------------------------------
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#ifndef AGG_CLIP_LIANG_BARSKY_INCLUDED
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#define AGG_CLIP_LIANG_BARSKY_INCLUDED
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#include "agg_basics.h"
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namespace agg
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{
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//------------------------------------------------------------------------
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enum clipping_flags_e
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{
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clipping_flags_x1_clipped = 4,
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clipping_flags_x2_clipped = 1,
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clipping_flags_y1_clipped = 8,
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clipping_flags_y2_clipped = 2,
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clipping_flags_x_clipped = clipping_flags_x1_clipped | clipping_flags_x2_clipped,
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clipping_flags_y_clipped = clipping_flags_y1_clipped | clipping_flags_y2_clipped
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};
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//----------------------------------------------------------clipping_flags
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// Determine the clipping code of the vertex according to the
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// Cyrus-Beck line clipping algorithm
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//
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// | |
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// 0110 | 0010 | 0011
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// | |
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// -------+--------+-------- clip_box.y2
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// | |
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// 0100 | 0000 | 0001
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// | |
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// -------+--------+-------- clip_box.y1
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// | |
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// 1100 | 1000 | 1001
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// | |
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// clip_box.x1 clip_box.x2
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//
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//
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template<class T>
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inline unsigned clipping_flags(T x, T y, const rect_base<T>& clip_box)
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{
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return (x > clip_box.x2) |
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((y > clip_box.y2) << 1) |
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((x < clip_box.x1) << 2) |
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((y < clip_box.y1) << 3);
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}
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//--------------------------------------------------------clipping_flags_x
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template<class T>
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inline unsigned clipping_flags_x(T x, const rect_base<T>& clip_box)
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{
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return (x > clip_box.x2) | ((x < clip_box.x1) << 2);
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}
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//--------------------------------------------------------clipping_flags_y
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template<class T>
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inline unsigned clipping_flags_y(T y, const rect_base<T>& clip_box)
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{
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return ((y > clip_box.y2) << 1) | ((y < clip_box.y1) << 3);
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}
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//-------------------------------------------------------clip_liang_barsky
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template<class T>
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inline unsigned clip_liang_barsky(T x1, T y1, T x2, T y2,
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const rect_base<T>& clip_box,
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T* x, T* y)
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{
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const double nearzero = 1e-30;
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double deltax = x2 - x1;
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double deltay = y2 - y1;
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double xin;
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double xout;
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double yin;
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double yout;
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double tinx;
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double tiny;
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double toutx;
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double touty;
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double tin1;
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double tin2;
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double tout1;
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unsigned np = 0;
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if(deltax == 0.0)
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{
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// bump off of the vertical
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deltax = (x1 > clip_box.x1) ? -nearzero : nearzero;
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}
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if(deltay == 0.0)
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{
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// bump off of the horizontal
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deltay = (y1 > clip_box.y1) ? -nearzero : nearzero;
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}
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if(deltax > 0.0)
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{
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// points to right
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xin = clip_box.x1;
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xout = clip_box.x2;
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}
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else
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{
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xin = clip_box.x2;
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xout = clip_box.x1;
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}
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if(deltay > 0.0)
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{
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// points up
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yin = clip_box.y1;
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yout = clip_box.y2;
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}
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else
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{
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yin = clip_box.y2;
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yout = clip_box.y1;
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}
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tinx = (xin - x1) / deltax;
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tiny = (yin - y1) / deltay;
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if (tinx < tiny)
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{
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// hits x first
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tin1 = tinx;
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tin2 = tiny;
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}
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else
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{
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// hits y first
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tin1 = tiny;
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tin2 = tinx;
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}
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if(tin1 <= 1.0)
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{
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if(0.0 < tin1)
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{
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*x++ = (T)xin;
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*y++ = (T)yin;
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++np;
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}
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if(tin2 <= 1.0)
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{
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toutx = (xout - x1) / deltax;
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touty = (yout - y1) / deltay;
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tout1 = (toutx < touty) ? toutx : touty;
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if(tin2 > 0.0 || tout1 > 0.0)
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{
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if(tin2 <= tout1)
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{
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if(tin2 > 0.0)
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{
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if(tinx > tiny)
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{
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*x++ = (T)xin;
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*y++ = (T)(y1 + tinx * deltay);
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}
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else
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{
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*x++ = (T)(x1 + tiny * deltax);
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*y++ = (T)yin;
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}
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++np;
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}
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if(tout1 < 1.0)
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{
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if(toutx < touty)
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{
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*x++ = (T)xout;
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*y++ = (T)(y1 + toutx * deltay);
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}
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else
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{
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*x++ = (T)(x1 + touty * deltax);
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*y++ = (T)yout;
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}
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}
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else
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{
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*x++ = x2;
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*y++ = y2;
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}
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++np;
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}
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else
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{
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if(tinx > tiny)
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{
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*x++ = (T)xin;
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*y++ = (T)yout;
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}
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else
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{
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*x++ = (T)xout;
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*y++ = (T)yin;
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}
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++np;
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}
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}
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}
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}
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return np;
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}
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//----------------------------------------------------------------------------
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template<class T>
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bool clip_move_point(T x1, T y1, T x2, T y2,
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const rect_base<T>& clip_box,
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T* x, T* y, unsigned flags)
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{
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T bound;
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if(flags & clipping_flags_x_clipped)
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{
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if(x1 == x2)
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{
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return false;
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}
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bound = (flags & clipping_flags_x1_clipped) ? clip_box.x1 : clip_box.x2;
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*y = (T)(double(bound - x1) * (y2 - y1) / (x2 - x1) + y1);
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*x = bound;
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}
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flags = clipping_flags_y(*y, clip_box);
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if(flags & clipping_flags_y_clipped)
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{
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if(y1 == y2)
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{
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return false;
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}
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bound = (flags & clipping_flags_y1_clipped) ? clip_box.y1 : clip_box.y2;
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*x = (T)(double(bound - y1) * (x2 - x1) / (y2 - y1) + x1);
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*y = bound;
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}
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return true;
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}
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//-------------------------------------------------------clip_line_segment
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// Returns: ret >= 4 - Fully clipped
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// (ret & 1) != 0 - First point has been moved
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// (ret & 2) != 0 - Second point has been moved
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//
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template<class T>
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unsigned clip_line_segment(T* x1, T* y1, T* x2, T* y2,
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const rect_base<T>& clip_box)
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{
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unsigned f1 = clipping_flags(*x1, *y1, clip_box);
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unsigned f2 = clipping_flags(*x2, *y2, clip_box);
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unsigned ret = 0;
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if((f2 | f1) == 0)
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{
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// Fully visible
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return 0;
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}
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if((f1 & clipping_flags_x_clipped) != 0 &&
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(f1 & clipping_flags_x_clipped) == (f2 & clipping_flags_x_clipped))
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{
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// Fully clipped
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return 4;
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}
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if((f1 & clipping_flags_y_clipped) != 0 &&
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(f1 & clipping_flags_y_clipped) == (f2 & clipping_flags_y_clipped))
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{
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// Fully clipped
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return 4;
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}
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T tx1 = *x1;
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T ty1 = *y1;
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T tx2 = *x2;
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T ty2 = *y2;
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if(f1)
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{
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if(!clip_move_point(tx1, ty1, tx2, ty2, clip_box, x1, y1, f1))
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{
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return 4;
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}
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if(*x1 == *x2 && *y1 == *y2)
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{
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return 4;
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}
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ret |= 1;
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}
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if(f2)
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{
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if(!clip_move_point(tx1, ty1, tx2, ty2, clip_box, x2, y2, f2))
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{
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return 4;
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}
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if(*x1 == *x2 && *y1 == *y2)
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{
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return 4;
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}
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ret |= 2;
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}
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return ret;
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}
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}
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#endif
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