reactos/dll/win32/gdi32/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  * COPYRIGHT:        See COPYING in the top level directory
  22  * PROJECT:          ReactOS GDI32
  23  * PURPOSE:          LineDDA Function
  24  * FILE:             lib/gdi32/objects/linedda.c
  25  * PROGRAMER:        Steven Edwards
  26  * REVISION HISTORY: 2003/11/15 sedwards Created
  27  * NOTES:            Adapted from Wine
  28  */
  29
  30 #include "precomp.h"
  31
  32 #include <debug.h>
  33
  34 /**********************************************************************
  35  *           LineDDA   (GDI32.@)
  36  * @implemented
  37  */
  38 BOOL STDCALL LineDDA(INT nXStart, INT nYStart, INT nXEnd, INT nYEnd,
  39                         LINEDDAPROC lpLineFunc, LPARAM lpData )
  40 {
  41     INT xadd = 1, yadd = 1;
  42     INT err,erradd;
  43     INT cnt;
  44     INT dx = nXEnd - nXStart;
  45     INT dy = nYEnd - nYStart;
  46
  47     if (dx < 0)  {
  48       dx = -dx; xadd = -1;
  49     }
  50     if (dy < 0)  {
  51       dy = -dy; yadd = -1;
  52     }
  53     if (dx > dy) { /* line is "more horizontal" */
  54       err = 2*dy - dx; erradd = 2*dy - 2*dx;
  55       for(cnt = 0;cnt <= dx; cnt++) {
  56         lpLineFunc(nXStart,nYStart,lpData);
  57         if (err > 0) {
  58           nYStart += yadd;
  59           err += erradd;
  60         } else  {
  61           err += 2*dy;
  62         }
  63         nXStart += xadd;
  64       }
  65     } else  { /* line is "more vertical" */
  66       err = 2*dx - dy; erradd = 2*dx - 2*dy;
  67       for(cnt = 0;cnt <= dy; cnt++) {
  68         lpLineFunc(nXStart,nYStart,lpData);
  69         if (err > 0) {
  70           nXStart += xadd;
  71           err += erradd;
  72         } else  {
  73           err += 2*dx;
  74         }
  75         nYStart += yadd;
  76       }
  77     }
  78     return TRUE;
  79 }