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 <stdarg.h>
  22 #include <stdlib.h>
  23 #include "windef.h"
  24 #include "winbase.h"
  25 #include "wingdi.h"
  26
  27 /**********************************************************************
  28  *           LineDDA   (GDI32.@)
  29  */
  30 BOOL WINAPI LineDDA(INT nXStart, INT nYStart, INT nXEnd, INT nYEnd,
  31                         LINEDDAPROC callback, LPARAM lParam )
  32 {
  33     INT xadd = 1, yadd = 1;
  34     INT err,erradd;
  35     INT cnt;
  36     INT dx = nXEnd - nXStart;
  37     INT dy = nYEnd - nYStart;
  38
  39     if (dx < 0)  {
  40       dx = -dx; xadd = -1;
  41     }
  42     if (dy < 0)  {
  43       dy = -dy; yadd = -1;
  44     }
  45     if (dx > dy) { /* line is "more horizontal" */
  46       err = 2*dy - dx; erradd = 2*dy - 2*dx;
  47       for(cnt = 0;cnt <= dx; cnt++) {
  48         callback(nXStart,nYStart,lParam);
  49         if (err > 0) {
  50           nYStart += yadd;
  51           err += erradd;
  52         } else  {
  53           err += 2*dy;
  54         }
  55         nXStart += xadd;
  56       }
  57     } else  { /* line is "more vertical" */
  58       err = 2*dx - dy; erradd = 2*dx - 2*dy;
  59       for(cnt = 0;cnt <= dy; cnt++) {
  60         callback(nXStart,nYStart,lParam);
  61         if (err > 0) {
  62           nXStart += xadd;
  63           err += erradd;
  64         } else  {
  65           err += 2*dx;
  66         }
  67         nYStart += yadd;
  68       }
  69     }
  70     return TRUE;
  71 }