linedda.c

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/*
 * 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;
}