#include <stdlib.h>
#include <stdio.h>
#include <vga.h>
#include <vgagl.h>

#define RGB(r,g,b) ((((int)(r) & 0x1f) << 11) | (((int)(g) & 0x2f) << 5) | ((int)(b) & 0x1f))

int main(int argc, char *argv[])
{
  GraphicsContext *context;

  int mode = G800x600x64K;
  int x,y;
  int xmax,ymax;
  int midx,midy;
  float r,g,b;
  float color;

  vga_init();
  vga_setmode(mode);

  gl_setcontextvga(mode);
  context = gl_allocatecontext();
  gl_getcontext(context);

  xmax = vga_getxdim();
  ymax = vga_getydim();

  midx = xmax / 2;
  midy = ymax / 2;

  r = (float)0x1f;
  g = b = 0.0;
  x = y = 0;

  for (b = 0.0; b < (float)0x1f; b += 1.0) {
    color = RGB(r,g,b);
    gl_line(midx,midy,x,0,color);
    x += 3;
  }
  for (; g < 0x2f; g += 1.5) {
    color = RGB(r,g,b);
    gl_line(midx,midy,x,0,color);
    x += 3;
  }
  for (; r > 0.0; r -= 1.0) {
    color = RGB(r,g,b);
    gl_line(midx,midy,x,0,color);
    x += 3;
  }
  for (; b > 0.0; b -= 1.0) {
    color = RGB(r,g,b);
    gl_line(midx,midy,x,0,color);
    x += 3;
  }
  for (; r < (float)0x1f; r += 1.0) {
    color = RGB(r,g,b);
    gl_line(midx,midy,x,0,color);
    x += 3;
  }
  for (; b < (float)0x1f; b += 1.0) {
    color = RGB(r,g,b);
    gl_line(midx,midy,x,0,color);
    x += 3;
  }
  for (; b > 0.0; b -= 1.0) {
    color = RGB(r,g,b);
    gl_line(midx,midy,x,0,color);
    x += 3;
  }
  for (; g > 0.0; g -= 1.5) {
    color = RGB(r,g,b);
    gl_line(midx,midy,x,0,color);
    x += 3;
  }


  getchar();
  printf("\n");

  vga_setmode(TEXT);
  return 0;
}