SCREENSAVER HYPNOTISEUR

#define WW 800
#define HH 600
#include <stdio.h>
#include <stdlib.h>
#include <SDL/SDL.h>
#include <math.h>

static SDL_Surface * init(int w, int h, int bpp);
static void          loop(SDL_Surface * s);
static void          manageEvents(SDL_Surface * s);
static void          draw(SDL_Surface * s);
static void SDL_Rotate(SDL_Surface *src,SDL_Surface *dst, double rotation, int x, int y);


int main(int argc, char ** argv) {
  SDL_Surface * s;
  s = init(WW, HH, 32);
  loop(s);
  return 0;
}

static SDL_Surface * init(int w, int h, int bpp) {
  SDL_Surface * s;
  if ( SDL_Init(SDL_INIT_VIDEO) < 0 ) {
    exit(1);
  }
  if ( (s = SDL_SetVideoMode(w, h, bpp, SDL_SWSURFACE | SDL_HWSURFACE |SDL_FULLSCREEN )) == NULL ) {
    exit(1);
  }
  int i; Uint32 *t = s->pixels; for (i=0; i < WW*HH; i++) t[i] = 0xFFFFFFFF;
  atexit(SDL_Quit);
  return s;
}


static void loop(SDL_Surface * s) {
  SDL_Surface *s2 = SDL_CreateRGBSurface(SDL_HWSURFACE, WW*2, HH*2, 32, 0, 0, 0, 0);
  static int i,j;
  Uint32 *t = s2->pixels;
  static int count = 0;
  static int yesorno = 0;
  static double rotation3 = M_PI/2000;
  static SDL_Event event;
  static double rotation2 = 2.1543;
  for (i=0; i < WW*2; i++) for (j=0; j < HH*2; j++) t[j*WW+i] = 0;
  for(;;) {
    if (yesorno) rotation3 /= 1.3;
    else rotation3 *= 1.2;
    if (rotation3 < M_PI/500000) { yesorno = !yesorno; rotation3 = M_PI/500000; }
    if (rotation3 > M_PI/1000) { yesorno = !yesorno; rotation3 = M_PI/1000; }
    rotation2 += rotation3;
    while (rotation2 >= 2*M_PI) rotation2 -= 2*M_PI;
    SDL_Rotate(s2,s,rotation2,WW,HH);
    SDL_UpdateRect(s, 0, 0, WW, HH);
    SDL_Delay(1);
    if(SDL_PollEvent(&event) && event.type == SDL_KEYDOWN) exit(0);
  }
}

static void SDL_Rotate(SDL_Surface *src,SDL_Surface *dst, double rotation, int x, int y) {
    Uint32 *t1 = src->pixels, *t2 = dst->pixels;
    static int i,j,i2,j2,i3,j3;
    static double vi, vj;
    vi = cos(rotation); vj = sin(rotation);
    for (i=0; i < WW*HH; i++) t2[i] = 0xFFFFFFFF;
    for (i=0; i < WW*2; i++)
        for (j=0; j < HH*2; j++) {
            i3 = i - x; j3 = j - y;
            i2 = (double)i3*vi - (double)j3*vj + x - WW/2; j2 = (double)i3*vj + (double)j3*vi + y - HH/2;
            if (i2 >=0 && j2 >= 0 && i2 < WW && j2 < HH)
                t2[j2 * WW + i2] = t1[j * WW + i];
        }
}