src/clip.c

   1 /*
   2  *                            COPYRIGHT
   3  *
   4  *  PCB, interactive printed circuit board design
   5  *  Copyright (C) 1994,1995,1996 Thomas Nau
   6  *  Copyright (C) 2004 harry eaton
   7  *
   8  *  This program is free software; you can redistribute it and/or modify
   9  *  it under the terms of the GNU General Public License as published by
  10  *  the Free Software Foundation; either version 2 of the License, or
  11  *  (at your option) any later version.
  12  *
  13  *  This program is distributed in the hope that it will be useful,
  14  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  *  GNU General Public License for more details.
  17  *
  18  *  You should have received a copy of the GNU General Public License
  19  *  along with this program; if not, write to the Free Software
  20  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21  *
  22  *  Contact addresses for paper mail and Email:
  23  *  Thomas Nau, Schlehenweg 15, 88471 Baustetten, Germany
  24  *  Thomas.Nau@rz.uni-ulm.de
  25  *
  26  */
  27
  28
  29 #ifdef HAVE_CONFIG_H
  30 #include "config.h"
  31 #endif
  32
  33 #include <assert.h>
  34 #include <math.h>
  35 #include <stdlib.h>
  36
  37 #include "global.h"
  38 #include "data.h"
  39 #include "draw.h"
  40 #include "mymem.h"
  41
  42 #ifdef HAVE_LIBDMALLOC
  43 #include <dmalloc.h>
  44 #endif
  45
  46 /* Clip the line to the clipBox
  47  * return true if something to be drawn
  48  * false if the whole thing is clipped
  49  */
  50 bool
  51 ClipLine (double minx, double miny, double maxx, double maxy,
  52           double *x1, double *y1,
  53           double *x2, double *y2,
  54           double margin)
  55 {
  56   double d, r;
  57
  58   minx -= margin;
  59   miny -= margin;
  60   maxx += margin;
  61   maxy += margin;
  62
  63   /* clip first point on left side */
  64   if (*x1 < minx)
  65     {
  66       if (*x2 < minx)
  67         return false;
  68       d = *x2 - *x1;
  69       r = (minx - *x1) / d;
  70       *x1 = minx;
  71       *y1 += r * (*y2 - *y1);
  72     }
  73   /* clip second point on left side */
  74   if (*x2 < minx)
  75     {
  76       d = *x1 - *x2;
  77       r = (minx - *x2) / d;
  78       *x2 = minx;
  79       *y2 += r * (*y1 - *y2);
  80     }
  81   /* clip first point on right side */
  82   if (*x1 > maxx)
  83     {
  84       if (*x2 > maxx)
  85         return false;
  86       d = *x2 - *x1;
  87       r = (maxx - *x1) / d;
  88       *x1 = maxx;
  89       *y1 += r * (*y2 - *y1);
  90     }
  91   /* clip second point on right side */
  92   if (*x2 > maxx)
  93     {
  94       d = *x1 - *x2;
  95       r = (maxx - *x2) / d;
  96       *x2 = maxx;
  97       *y2 += r * (*y1 - *y2);
  98     }
  99
 100   /* clip first point on top */
 101   if (*y1 < miny)
 102     {
 103       if (*y2 < miny)
 104         return false;
 105       d = *y2 - *y1;
 106       r = (miny - *y1) / d;
 107       *y1 = miny;
 108       *x1 += r * (*x2 - *x1);
 109     }
 110   /* clip second point on top */
 111   if (*y2 < miny)
 112     {
 113       d = *y1 - *y2;
 114       r = (miny - *y2) / d;
 115       *y2 = miny;
 116       *x2 += r * (*x1 - *x2);
 117     }
 118   /* clip first point on bottom */
 119   if (*y1 > maxy)
 120     {
 121       if (*y2 > maxy)
 122         return false;
 123       d = *y2 - *y1;
 124       r = (maxy - *y1) / d;
 125       *y1 = maxy;
 126       *x1 += r * (*x2 - *x1);
 127     }
 128   /* clip second point on top */
 129   if (*y2 > maxy)
 130     {
 131       d = *y1 - *y2;
 132       r = (maxy - *y2) / d;
 133       *y2 = maxy;
 134       *x2 += r * (*x1 - *x2);
 135     }
 136   return true;
 137 }