reactos/dll/win32/gdi32/objects/linedda.c

   1 /*
   2  * GDI drawing functions.
   3  *
   4  * Copyright 1993, 1994 Alexandre Julliard
   5  * Copyright 1997 Bertho A. Stultiens
   6  *           1999 Huw D M Davies
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * This library 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 GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  21  */
  22 /*
  23  * COPYRIGHT:        See COPYING in the top level directory
  24  * PROJECT:          ReactOS GDI32
  25  * PURPOSE:          LineDDA Function
  26  * FILE:             dll/win32/gdi32/objects/linedda.c
  27  * PROGRAMER:        Steven Edwards
  28  * REVISION HISTORY: 2003/11/15 sedwards Created, 2009/04 gschneider Updated
  29  * NOTES:            Adapted from Wine
  30  */
  31
  32 #include "precomp.h"
  33
  34 #include <debug.h>
  35
  36 /**********************************************************************
  37  *           LineDDA   (GDI32.@)
  38  * @implemented
  39  */
  40 BOOL WINAPI LineDDA(INT nXStart, INT nYStart, INT nXEnd, INT nYEnd,
  41                     LINEDDAPROC callback, LPARAM lParam )
  42 {
  43     INT xadd = 1, yadd = 1;
  44     INT err,erradd;
  45     INT cnt;
  46     INT dx = nXEnd - nXStart;
  47     INT dy = nYEnd - nYStart;
  48
  49     if (dx < 0)
  50     {
  51         dx = -dx;
  52         xadd = -1;
  53     }
  54     if (dy < 0)
  55     {
  56         dy = -dy;
  57         yadd = -1;
  58     }
  59     if (dx > dy)  /* line is "more horizontal" */
  60     {
  61         err = 2*dy - dx; erradd = 2*dy - 2*dx;
  62         for(cnt = 0;cnt < dx; cnt++)
  63         {
  64             callback(nXStart,nYStart,lParam);
  65             if (err > 0)
  66             {
  67                 nYStart += yadd;
  68                 err += erradd;
  69             }
  70             else err += 2*dy;
  71             nXStart += xadd;
  72         }
  73     }
  74     else   /* line is "more vertical" */
  75     {
  76         err = 2*dx - dy; erradd = 2*dx - 2*dy;
  77         for(cnt = 0;cnt < dy; cnt++)
  78         {
  79             callback(nXStart,nYStart,lParam);
  80             if (err > 0)
  81             {
  82                 nXStart += xadd;
  83                 err += erradd;
  84             }
  85             else err += 2*dx;
  86             nYStart += yadd;
  87         }
  88     }
  89     return TRUE;
  90 }
  91