objects/linedda.c

   1 /*
   2  * LineDDA
   3  *
   4  * Copyright 1993 Bob Amstadt
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 #include <stdlib.h>
  22 #include "windef.h"
  23 #include "wingdi.h"
  24
  25 /**********************************************************************
  26  *           LineDDA   (GDI32.@)
  27  */
  28 BOOL WINAPI LineDDA(INT nXStart, INT nYStart, INT nXEnd, INT nYEnd,
  29                         LINEDDAPROC callback, LPARAM lParam )
  30 {
  31     INT xadd = 1, yadd = 1;
  32     INT err,erradd;
  33     INT cnt;
  34     INT dx = nXEnd - nXStart;
  35     INT dy = nYEnd - nYStart;
  36
  37     if (dx < 0)  {
  38       dx = -dx; xadd = -1;
  39     }
  40     if (dy < 0)  {
  41       dy = -dy; yadd = -1;
  42     }
  43     if (dx > dy) { /* line is "more horizontal" */
  44       err = 2*dy - dx; erradd = 2*dy - 2*dx;
  45       for(cnt = 0;cnt <= dx; cnt++) {
  46         callback(nXStart,nYStart,lParam);
  47         if (err > 0) {
  48           nYStart += yadd;
  49           err += erradd;
  50         } else  {
  51           err += 2*dy;
  52         }
  53         nXStart += xadd;
  54       }
  55     } else  { /* line is "more vertical" */
  56       err = 2*dx - dy; erradd = 2*dx - 2*dy;
  57       for(cnt = 0;cnt <= dy; cnt++) {
  58         callback(nXStart,nYStart,lParam);
  59         if (err > 0) {
  60           nXStart += xadd;
  61           err += erradd;
  62         } else  {
  63           err += 2*dx;
  64         }
  65         nYStart += yadd;
  66       }
  67     }
  68     return TRUE;
  69 }