Mercurial > sdl-ios-xcode

annotate src/video/SDL_drawline.c @ 3473:7bdc10624cba

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This is terrible, but the OpenGL standard says that lines are half open, which means that one endpoint is not covered so adjoining lines don't overlap. It also doesn't define which end is open, and indeed Mac OS X and Linux differ. Mac OS X seems to leave the second endpoint open, but Linux uses the right-most endpoint for x major lines and the bottom-most endpoint for y major lines.
author Sam Lantinga <slouken@libsdl.org>
date Sat, 21 Nov 2009 07:14:21 +0000
parents 27d8b12e0e8e
children 0267b8b1595c
rev   line source
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1 /*
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2 SDL - Simple DirectMedia Layer
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3 Copyright (C) 1997-2009 Sam Lantinga
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4
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5 This library is free software; you can redistribute it and/or
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6 modify it under the terms of the GNU Lesser General Public
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7 License as published by the Free Software Foundation; either
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8 version 2.1 of the License, or (at your option) any later version.
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9
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10 This library is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 Lesser General Public License for more details.
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14
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15 You should have received a copy of the GNU Lesser General Public
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16 License along with this library; if not, write to the Free Software
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17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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18
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19 Sam Lantinga
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20 slouken@libsdl.org
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21 */
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22 #include "SDL_config.h"
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23
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24 #include "SDL_draw.h"
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25
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26
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27 int
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28 SDL_DrawLine(SDL_Surface * dst, int x1, int y1, int x2, int y2, Uint32 color)
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29 {
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30 /* This function doesn't work on surfaces < 8 bpp */
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31 if (dst->format->BitsPerPixel < 8) {
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32 SDL_SetError("SDL_DrawLine(): Unsupported surface format");
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33 return (-1);
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34 }
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35
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36 /* Perform clipping */
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37 if (!SDL_IntersectRectAndLine(&dst->clip_rect, &x1, &y1, &x2, &y2)) {
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38 return (0);
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39 }
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40
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41 switch (dst->format->BytesPerPixel) {
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42 case 1:
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43 DRAWLINE(x1, y1, x2, y2, DRAW_FASTSETPIXEL1);
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44 break;
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45 case 2:
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46 DRAWLINE(x1, y1, x2, y2, DRAW_FASTSETPIXEL2);
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47 break;
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48 case 3:
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49 SDL_Unsupported();
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50 return -1;
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51 case 4:
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52 DRAWLINE(x1, y1, x2, y2, DRAW_FASTSETPIXEL4);
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53 break;
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54 }
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55 return 0;
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56 }
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57
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58 /* vi: set ts=4 sw=4 expandtab: */