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annotate dmdrawline.h @ 234:a2abd0b991b6

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Modularize line drawing related templates and functions, add clipping functions to dmlib.h.
author Matti Hamalainen <ccr@tnsp.org>
date Mon, 08 Oct 2012 15:21:59 +0300
parents 79dac918c81e
children 51ba74f7668c
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1 /*
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2 * DMLib
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3 * -- Simple Bresenham's style line drawing
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4 * Programmed and designed by Matti 'ccr' Hamalainen
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5 * (C) Copyright 2011-2012 Tecnic Software productions (TNSP)
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6 */
0
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7
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8 int DM_DRAWLINE_NAME (SDL_Surface *screen, int x0, int y0, int x1, int y1, const Uint32 col
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9 #ifdef DM_DRAWLINE_ARGS
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10 DM_DRAWLINE_ARGS
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11 #endif
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12 )
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13 #ifdef DM_HEADER
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14 ;
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15 #else
0
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16 {
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17 int dx, dy, xstep, ystep;
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18 const int qpitch = screen->pitch / DM_DRAWLINE_DST_BYTES;
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19
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20 // Clipping
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21 if (dmClipLineCoordsInt(screen, &x0, &y0, &x1, &y1) < 0)
0
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22 return -1;
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23
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24 // Compute initial deltas
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25 dx = (x1 - x0) * 2;
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26 dy = (y1 - y0) * 2;
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0
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29 if (dx < 0)
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30 {
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31 dx = -dx;
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32 xstep = -1;
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33 }
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34 else
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35 xstep = 1;
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36
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37 if (dy < 0)
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38 {
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39 dy = -dy;
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40 ystep = -1;
0
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41 }
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42 else
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43 ystep = 1;
0
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44
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45 #ifndef DM_DRAWLINE_SPEC
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46 // Compute offsets
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47 y0 *= qpitch;
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48 y1 *= qpitch;
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49 ystep *= qpitch;
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50 #endif
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51
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52 #ifdef DM_DRAWLINE_INIT
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53 DM_DRAWLINE_INIT
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54 #endif
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55
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56 DM_DRAWLINE_DST_TYPE *pix = (DM_DRAWLINE_DST_TYPE *) screen->pixels;
0
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57
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58 // Continue based on which delta is larger
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59 if (dx > dy)
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60 {
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61 int afrac = dy - (dx / 2);
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62 while (x0 != x1)
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63 {
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64 if (afrac >= 0)
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65 {
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66 y0 += ystep;
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67 afrac -= dx;
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68 }
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69
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70 x0 += xstep;
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71 afrac += dy;
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72
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73 DM_DRAWLINE_INNER
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74 }
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75 }
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76 else
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77 {
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78 int afrac = dx - (dy / 2);
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79 while (y0 != y1)
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80 {
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81 if (afrac >= 0)
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82 {
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83 x0 += xstep;
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84 afrac -= dy;
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85 }
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86
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87 y0 += ystep;
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88 afrac += dx;
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89
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90 DM_DRAWLINE_INNER
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91 }
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92 }
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93
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94 return 0;
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95 }
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96 #endif
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97
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98 #undef DM_DRAWLINE_NAME
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99 #undef DM_DRAWLINE_ARGS
0
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100 #undef DM_DRAWLINE_DST_BYTES
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101 #undef DM_DRAWLINE_DST_TYPE
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102 #undef DM_DRAWLINE_INIT
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103 #undef DM_DRAWLINE_INNER