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         // optimized for vertical and horizontal lines so we avoid unnecessary math
  48         if(nXStart == nXEnd)
  49         {
  50           // vertical line - use dx,dy as temp variables so we don't waste stack space
  51           if(nYStart < nYEnd)
  52           {
  53             dx = nYStart;
  54             dy = nYEnd;
  55           } else {
  56             dx = nYEnd;
  57             dy = nYStart;
  58           }
  59           for(cnt = dx; cnt <= dy; cnt++)
  60           {
  61            lpLineFunc(nXStart,cnt,lpData);
  62           }
  63           return TRUE;
  64         }
  65
  66         if(nYStart == nYEnd)
  67         {
  68           // horizontal line - use dx,dy as temp variables so we don't waste stack space
  69           if(nXStart < nXEnd)
  70           {
  71             dx = nXStart;
  72             dy = nXEnd;
  73           } else {
  74             dx = nXEnd;
  75             dy = nXStart;
  76           }
  77           for(cnt = dx; cnt <= dy; cnt++)
  78           {
  79            lpLineFunc(cnt, nYStart,lpData);
  80           }
  81           return TRUE;
  82         }
  83         // end of H/V line code
  84     if (dx < 0)  {
  85       dx = -dx; xadd = -1;
  86     }
  87     if (dy < 0)  {
  88       dy = -dy; yadd = -1;
  89     }
  90     if (dx > dy) { /* line is "more horizontal" */
  91       err = 2*dy - dx; erradd = 2*dy - 2*dx;
  92       for(cnt = 0;cnt <= dx; cnt++) {
  93         lpLineFunc(nXStart,nYStart,lpData);
  94         if (err > 0) {
  95           nYStart += yadd;
  96           err += erradd;
  97         } else  {
  98           err += 2*dy;
  99         }
 100         nXStart += xadd;
 101       }
 102     } else  { /* line is "more vertical" */
 103       err = 2*dx - dy; erradd = 2*dx - 2*dy;
 104       for(cnt = 0;cnt <= dy; cnt++) {
 105         lpLineFunc(nXStart,nYStart,lpData);
 106         if (err > 0) {
 107           nXStart += xadd;
 108           err += erradd;
 109         } else  {
 110           err += 2*dx;
 111         }
 112         nYStart += yadd;
 113       }
 114     }
 115     return TRUE;
 116 }