reactos/win32ss/gdi/gdi32/objects/linedda.c

94 lines
2.5 KiB
C

/*
* GDI drawing functions.
*
* Copyright 1993, 1994 Alexandre Julliard
* Copyright 1997 Bertho A. Stultiens
* 1999 Huw D M Davies
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
*/
/*
* COPYRIGHT: See COPYING in the top level directory
* PROJECT: ReactOS GDI32
* PURPOSE: LineDDA Function
* FILE: win32ss/gdi/gdi32/objects/linedda.c
* PROGRAMER: Steven Edwards
* REVISION HISTORY: 2003/11/15 sedwards Created, 2009/04 gschneider Updated
* NOTES: Adapted from Wine
*/
#include <precomp.h>
#include <debug.h>
/**********************************************************************
* LineDDA (GDI32.@)
* @implemented
*/
BOOL WINAPI LineDDA(INT nXStart, INT nYStart, INT nXEnd, INT nYEnd,
LINEDDAPROC callback, LPARAM lParam )
{
INT xadd = 1, yadd = 1;
INT err,erradd;
INT cnt;
INT dx = nXEnd - nXStart;
INT dy = nYEnd - nYStart;
if (dx < 0)
{
dx = -dx;
xadd = -1;
}
if (dy < 0)
{
dy = -dy;
yadd = -1;
}
if (dx > dy) /* line is "more horizontal" */
{
err = 2*dy - dx;
erradd = 2*dy - 2*dx;
for(cnt = 0; cnt < dx; cnt++)
{
callback(nXStart,nYStart,lParam);
if (err > 0)
{
nYStart += yadd;
err += erradd;
}
else err += 2*dy;
nXStart += xadd;
}
}
else /* line is "more vertical" */
{
err = 2*dx - dy;
erradd = 2*dx - 2*dy;
for(cnt = 0; cnt < dy; cnt++)
{
callback(nXStart,nYStart,lParam);
if (err > 0)
{
nXStart += xadd;
err += erradd;
}
else err += 2*dx;
nYStart += yadd;
}
}
return TRUE;
}