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  1. /*!
  2.   \file Draw_Line.c
  3.   \author Mario Palomo <mpalomo@ihman.com>
  4.   \author Jose M. de la Huerga Fernández
  5.   \author Pepe González Mora
  6.   \date 05-2002
  7.  
  8.   This library is free software; you can redistribute it and/or
  9.   modify it under the terms of the GNU Library General Public
  10.   License as published by the Free Software Foundation; either
  11.   version 2 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.   Library General Public License for more details.
  17.  
  18.   You should have received a copy of the GNU Library General Public
  19.   License along with this library; if not, write to the Free Foundation,
  20.   Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  21. */
  22. #define SDL_DRAW_PUTPIXEL_BPP(A, B, C)  \
  23. *(##A##(##B##(Uint8*)super->pixels + y*super->pitch + x*SDL_DRAW_BPP))=##C##;
  24.  
  25. #if SDL_DRAW_BPP == 1
  26. #define SDL_DRAW_PUTPIXEL SDL_DRAW_PUTPIXEL_BPP(0+,0+,color)
  27.  
  28. #elif SDL_DRAW_BPP == 2
  29. #define SDL_DRAW_PUTPIXEL SDL_DRAW_PUTPIXEL_BPP((Uint16*),0+,color)
  30.  
  31. #elif SDL_DRAW_BPP == 3
  32. #define SDL_DRAW_PUTPIXEL \
  33.   SDL_DRAW_PUTPIXEL_BPP(0+,1+,(Uint8)colorbyte1)   \
  34.   if (SDL_BYTEORDER == SDL_BIG_ENDIAN) {         \
  35.     SDL_DRAW_PUTPIXEL_BPP(0+,0+,(Uint8)colorbyte2)   \
  36.     SDL_DRAW_PUTPIXEL_BPP(0+,2+,(Uint8)colorbyte0) \
  37.   }else{                                         \
  38.     SDL_DRAW_PUTPIXEL_BPP(0+,0+,(Uint8)colorbyte0)   \
  39.     SDL_DRAW_PUTPIXEL_BPP(0+,2+,(Uint8)colorbyte2) \
  40.   }
  41.  
  42. #elif SDL_DRAW_BPP == 4
  43. #define SDL_DRAW_PUTPIXEL SDL_DRAW_PUTPIXEL_BPP((Uint32*),0+,color)
  44.  
  45. #endif /*SDL_DRAW_BPP*/
  46.  
  47.  
  48. void SDL_DRAWFUNCTION(SDL_Surface *super,
  49.                       Sint16 x1, Sint16 y1, Sint16 x2, Sint16 y2,
  50.                       Uint32 color)
  51. {
  52. #if SDL_DRAW_BPP == 3
  53.   Uint8 colorbyte0 = (Uint8) (color & 0xff);
  54.   Uint8 colorbyte1 = (Uint8) ((color >> 8) & 0xff);
  55.   Uint8 colorbyte2 = (Uint8) ((color >> 16) & 0xff);
  56. #endif
  57.  
  58.   Sint16 x = x1;
  59.   Sint16 y = y1;
  60.   Sint16 dy = y2 - y1;
  61.   Sint16 dx = x2 - x1;
  62.  
  63.   Sint16 G, DeltaG1, DeltaG2, minG, maxG;
  64.   Sint16 swap;
  65.   Sint16 inc = 1;
  66.  
  67.   SDL_DRAW_PUTPIXEL
  68.  
  69.   if (abs(dy) < abs(dx)) { /* -1 < ramp < 1 */
  70.       if (dx < 0) {
  71.         dx = -dx;
  72.         dy = -dy;
  73.  
  74.         swap = y2;
  75.         y2 = y1;
  76.         y1 = swap;
  77.  
  78.         swap = x2;
  79.         x2 = x1;
  80.         x1 = swap;
  81.       }
  82.       if (dy < 0) {
  83.         dy = -dy;
  84.         inc = -1;
  85.       }
  86.  
  87.       G = 2 * dy - dx;
  88.       DeltaG1 = 2 * (dy - dx);
  89.       DeltaG2 = 2 * dy;
  90.  
  91.       while (x++ < x2) {
  92.         if (G > 0) { G += DeltaG1; y += inc; }
  93.         else  G += DeltaG2;
  94.  
  95.         SDL_DRAW_PUTPIXEL
  96.       }/*while*/
  97.  
  98.   } else { /* ramp < -1 or ramp > 1 */
  99.       if (dy < 0) {
  100.         dx = -dx;
  101.         dy = -dy;
  102.  
  103.         swap = y2;
  104.         y2 = y1;
  105.         y1 = swap;
  106.  
  107.         swap = x2;
  108.         x2 = x1;
  109.         x1 = swap;
  110.       }
  111.       if (dx < 0) {
  112.         dx = -dx;
  113.         inc = -1;
  114.       }
  115.  
  116.       G = 2 * dx - dy;
  117.       minG = maxG = G;
  118.       DeltaG1 = 2 * (dx - dy);
  119.       DeltaG2 = 2 * dx;
  120.  
  121.       while (y++ < y2) {
  122.         if (G > 0) { G += DeltaG1; x += inc; }
  123.         else  G += DeltaG2;
  124.  
  125.         SDL_DRAW_PUTPIXEL
  126.       }/*while*/
  127.  
  128.   }/*if*/
  129.  
  130. }/*Draw_Line*/
  131.  
  132.  
  133. #undef SDL_DRAW_PUTPIXEL
  134. #undef SDL_DRAW_PUTPIXEL_BPP
  135.  
  136.