circle and squares fractal with Quadrance

// study in quadrance / Wildberger's chromogeometry
// 	https://www.flickr.com/photos/140786894@N03/albums/72157670200898221/with/28173892446/
//  https://www.youtube.com/watch?v=xgS9JBs5RV0

#include <SDL.h>
#include <stdio.h>

#define pixelsize 4
Uint32 pixels[256*256*pixelsize];
struct pixl8_t {
	Uint8 blue,green,red,alpha;
};

void quitf() {
	printf("%s\n",SDL_GetError() );
	exit(0);
}

int main( int argc, char* args[] )
{
	if( SDL_Init( SDL_INIT_VIDEO ) < 0 ) quitf();
	if( !SDL_SetHint( SDL_HINT_RENDER_SCALE_QUALITY, "1" ) ) quitf();
	SDL_Window *window = SDL_CreateWindow( "mpixel",
		SDL_WINDOWPOS_UNDEFINED,
		SDL_WINDOWPOS_UNDEFINED,
		256,256,
		SDL_WINDOW_SHOWN );
	if (!window) quitf();
	SDL_Renderer* renderer = SDL_CreateRenderer( window, -1, SDL_RENDERER_ACCELERATED );
	if (!renderer) quitf();
	SDL_SetRenderDrawColor( renderer, 0, 0, 0, 255 );
	SDL_RenderClear( renderer );
	// http://gamedev.stackexchange.com/questions/87727/sdl-updatetexture-is-slow
	SDL_Texture* texture = SDL_CreateTexture(renderer,
                               SDL_PIXELFORMAT_ARGB8888,
                               SDL_TEXTUREACCESS_STREAMING,
                               256, 256);
	if( !texture ) quitf();
	bool quit = false;
	while (!quit)
	{
		SDL_Event event;
		while( SDL_PollEvent( &event ) )
		{
			if( event.type == SDL_QUIT ) quit = true;
			if( event.type == SDL_KEYDOWN ) {
				if ( event.key.keysym.sym == SDLK_ESCAPE ) quit = true;
			}
		}
		for (Uint32 i=0;i<256;i++) {
			for (Uint32 j=0;j<256;j++) {
				struct pixl8_t *p;
				p = (struct pixl8_t *)&pixels[j*256+i];
				p->red = p->green = p->blue = i*i+j*j;
			}
		}
		SDL_Delay(400);
		SDL_UpdateTexture( texture, NULL, pixels, 256 * pixelsize);
		SDL_RenderCopy( renderer, texture, NULL, NULL );
		SDL_RenderPresent( renderer );
	}
	SDL_DestroyTexture( texture );
	SDL_DestroyRenderer( renderer );
	SDL_DestroyWindow( window );
	SDL_Quit();
	return 0;
}