src/clip.c

   1 /* $Id$ */
   2
   3 /*
   4  *                            COPYRIGHT
   5  *
   6  *  PCB, interactive printed circuit board design
   7  *  Copyright (C) 1994,1995,1996 Thomas Nau
   8  *  Copyright (C) 2004 harry eaton
   9  *
  10  *  This program is free software; you can redistribute it and/or modify
  11  *  it under the terms of the GNU General Public License as published by
  12  *  the Free Software Foundation; either version 2 of the License, or
  13  *  (at your option) any later version.
  14  *
  15  *  This program is distributed in the hope that it will be useful,
  16  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  *  GNU General Public License for more details.
  19  *
  20  *  You should have received a copy of the GNU General Public License
  21  *  along with this program; if not, write to the Free Software
  22  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  23  *
  24  *  Contact addresses for paper mail and Email:
  25  *  Thomas Nau, Schlehenweg 15, 88471 Baustetten, Germany
  26  *  Thomas.Nau@rz.uni-ulm.de
  27  *
  28  */
  29
  30
  31 #ifdef HAVE_CONFIG_H
  32 #include "config.h"
  33 #endif
  34
  35 #include <assert.h>
  36 #include <math.h>
  37 #include <stdlib.h>
  38
  39 #include "global.h"
  40 #include "data.h"
  41 #include "draw.h"
  42 #include "mymem.h"
  43
  44 #ifdef HAVE_LIBDMALLOC
  45 #include <dmalloc.h>
  46 #endif
  47
  48 RCSID ("$Id$");
  49
  50 /* Clip the line to the clipBox
  51  * return True if something to be drawn
  52  * false if the whole thing is clipped
  53  */
  54 Boolean
  55 ClipLine (double minx, double miny, double maxx, double maxy,
  56           double *x1, double *y1,
  57           double *x2, double *y2,
  58           double margin)
  59 {
  60   double d, r;
  61
  62   minx -= margin;
  63   miny -= margin;
  64   maxx += margin;
  65   maxy += margin;
  66
  67   /* clip first point on left side */
  68   if (*x1 < minx)
  69     {
  70       if (*x2 < minx)
  71         return False;
  72       d = *x2 - *x1;
  73       r = (minx - *x1) / d;
  74       *x1 = minx;
  75       *y1 += r * (*y2 - *y1);
  76     }
  77   /* clip second point on left side */
  78   if (*x2 < minx)
  79     {
  80       d = *x1 - *x2;
  81       r = (minx - *x2) / d;
  82       *x2 = minx;
  83       *y2 += r * (*y1 - *y2);
  84     }
  85   /* clip first point on right side */
  86   if (*x1 > maxx)
  87     {
  88       if (*x2 > maxx)
  89         return False;
  90       d = *x2 - *x1;
  91       r = (maxx - *x1) / d;
  92       *x1 = maxx;
  93       *y1 += r * (*y2 - *y1);
  94     }
  95   /* clip second point on right side */
  96   if (*x2 > maxx)
  97     {
  98       d = *x1 - *x2;
  99       r = (maxx - *x2) / d;
 100       *x2 = maxx;
 101       *y2 += r * (*y1 - *y2);
 102     }
 103
 104   /* clip first point on top */
 105   if (*y1 < miny)
 106     {
 107       if (*y2 < miny)
 108         return False;
 109       d = *y2 - *y1;
 110       r = (miny - *y1) / d;
 111       *y1 = miny;
 112       *x1 += r * (*x2 - *x1);
 113     }
 114   /* clip second point on top */
 115   if (*y2 < miny)
 116     {
 117       d = *y1 - *y2;
 118       r = (miny - *y2) / d;
 119       *y2 = miny;
 120       *x2 += r * (*x1 - *x2);
 121     }
 122   /* clip first point on bottom */
 123   if (*y1 > maxy)
 124     {
 125       if (*y2 > maxy)
 126         return False;
 127       d = *y2 - *y1;
 128       r = (maxy - *y1) / d;
 129       *y1 = maxy;
 130       *x1 += r * (*x2 - *x1);
 131     }
 132   /* clip second point on top */
 133   if (*y2 > maxy)
 134     {
 135       d = *y1 - *y2;
 136       r = (maxy - *y2) / d;
 137       *y2 = maxy;
 138       *x2 += r * (*x1 - *x2);
 139     }
 140   return True;
 141 }