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annotate src/video/SDL_drawline.c @ 2893:e67f3f3bf221

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Turn on line antialiasing (requires blending to be enabled)
author Sam Lantinga <slouken@libsdl.org>
date Sat, 20 Dec 2008 18:40:30 +0000
parents 1863c8b59658
children 1ef2f1e75ff7
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_video.h"
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25 #include "SDL_blit.h"
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26
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27 #define ABS(x) (x < 0 ? -x : x)
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28
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29 #define SWAP(x, y) (x ^= y ^= x ^= y)
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30
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31 #define BRESENHAM(x0, y0, x1, y1, op, color) \
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32 { \
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33 int deltax, deltay, steep, error, xstep, ystep, x, y; \
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34 \
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35 deltax = ABS(x1 - x0); \
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36 deltay = ABS(y1 - y0); \
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37 steep = deltay > deltax; \
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38 error = deltax / 2; \
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39 if (steep) { \
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40 SWAP(x0, y0); \
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41 SWAP(x1, y1); \
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42 } \
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43 y = y0; \
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44 if (x0 > x1) { \
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45 xstep = -1; \
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46 deltax = -deltax; \
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47 } else { \
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48 xstep = 1; \
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49 } \
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50 if (y0 < y1) { \
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51 ystep = 1; \
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52 } else { \
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53 ystep = -1; \
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54 } \
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55 if (!steep) { \
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56 for (x = x0; x != x1; x += xstep) { \
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57 op(x, y, color); \
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58 error -= deltay; \
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59 if (error < 0) { \
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60 y = y + ystep; \
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61 error += deltax; \
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62 } \
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63 } \
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64 } else { \
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65 for (x = x0; x != x1; x += xstep) { \
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66 op(y, x, color); \
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67 error -= deltay; \
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68 if (error < 0) { \
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69 y = y + ystep; \
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70 error += deltax; \
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71 } \
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72 } \
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73 } \
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74 }
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75
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76 #define SETPIXEL(x, y, type, bpp, color) \
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77 *(type *)(dst->pixels + y * dst->pitch + x * bpp) = (type) color
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78
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79 #define SETPIXEL1(x, y, color) SETPIXEL(x, y, Uint8, 1, color);
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80 #define SETPIXEL2(x, y, color) SETPIXEL(x, y, Uint16, 2, color);
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81 #define SETPIXEL4(x, y, color) SETPIXEL(x, y, Uint32, 4, color);
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82
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83 SDL_DrawLine(SDL_Surface * dst, int x1, int y1, int x2, int y2, Uint32 color)
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84 {
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85 /* This function doesn't work on surfaces < 8 bpp */
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86 if (dst->format->BitsPerPixel < 8) {
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87 SDL_SetError("SDL_DrawLine(): Unsupported surface format");
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88 return (-1);
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89 }
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90
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91 /* Perform clipping */
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92 /* FIXME
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93 if (!SDL_IntersectRect(dstrect, &dst->clip_rect, dstrect)) {
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94 return (0);
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95 }
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96 */
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97
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98 switch (dst->format->BytesPerPixel) {
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99 case 1:
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100 BRESENHAM(x1, y1, x2, y2, SETPIXEL1, color);
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101 break;
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102 case 2:
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103 BRESENHAM(x1, y1, x2, y2, SETPIXEL2, color);
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104 break;
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105 case 3:
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106 SDL_Unsupported();
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107 return -1;
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108 case 4:
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109 BRESENHAM(x1, y1, x2, y2, SETPIXEL4, color);
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110 break;
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111 }
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112 return 0;
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113 }
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114
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115 /* vi: set ts=4 sw=4 expandtab: */