1 /***

     2  *

     3  * $Id: sdl.cc,v 1.1.1.1 2008-04-28 17:33:22 mbroeker Exp $

     4  * $Source: /development/cpp/pmc/sdl.cc,v $

     5  *

     6  */

     7 

     8 #include <SDL/SDL.h>

     9 

    10 #define max(a,b) (((a) > (b)) ? (a) : (b))

    11 #define min(a,b) (((a) < (b)) ? (a) : (b))

    12 #define abs(a) (((a)<0) ? -(a) : (a))

    13 #define sign(a) (((a)<0) ? -1 : (a)>0 ? 1 : 0)

    14 

    15 void drawLine (SDL_Surface * s, int x1, int y1, int x2, int y2, Uint32 color)

    16 {

    17     int d;

    18     int x;

    19     int y;

    20     int ax;

    21     int ay;

    22     int sx;

    23     int sy;

    24     int dx;

    25     int dy;

    26 

    27     Uint8 *lineAddr;

    28     Sint32 yOffset;

    29 

    30     dx = x2 - x1;

    31     ax = abs (dx) << 1;

    32     sx = sign (dx);

    33 

    34     dy = y2 - y1;

    35     ay = abs (dy) << 1;

    36     sy = sign (dy);

    37     yOffset = sy * s->pitch;

    38 

    39     x = x1;

    40     y = y1;

    41 

    42     lineAddr = ((Uint8 *) s->pixels) + (y * s->pitch);

    43     if (ax > ay) {              /* x dominant */

    44         d = ay - (ax >> 1);

    45         for (;;) {

    46             *((Uint16 *) (lineAddr + (x << 1))) = (Uint16) color;

    47 

    48             if (x == x2) {

    49                 return;

    50             }

    51             if (d >= 0) {

    52                 y += sy;

    53                 lineAddr += yOffset;

    54                 d -= ax;

    55             }

    56             x += sx;

    57             d += ay;

    58         }

    59     } else {                    /* y dominant */

    60         d = ax - (ay >> 1);

    61         for (;;) {

    62             *((Uint16 *) (lineAddr + (x << 1))) = (Uint16) color;

    63 

    64             if (y == y2) {

    65                 return;

    66             }

    67             if (d >= 0) {

    68                 x += sx;

    69                 d -= ay;

    70             }

    71             y += sy;

    72             lineAddr += yOffset;

    73             d += ax;

    74         }

    75     }

    76 }