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: win32ss/gdi/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; 62 erradd = 2*dy - 2*dx; 63 for(cnt = 0; cnt < dx; cnt++) 64 { 65 callback(nXStart,nYStart,lParam); 66 if (err > 0) 67 { 68 nYStart += yadd; 69 err += erradd; 70 } 71 else err += 2*dy; 72 nXStart += xadd; 73 } 74 } 75 else /* line is "more vertical" */ 76 { 77 err = 2*dx - dy; 78 erradd = 2*dx - 2*dy; 79 for(cnt = 0; cnt < dy; cnt++) 80 { 81 callback(nXStart,nYStart,lParam); 82 if (err > 0) 83 { 84 nXStart += xadd; 85 err += erradd; 86 } 87 else err += 2*dx; 88 nYStart += yadd; 89 } 90 } 91 return TRUE; 92 } 93 94