#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <unistd.h>
#include <stdio.h>

const unsigned int RED = 0xFFFF0000;
const unsigned int GREEN = 0xFF00FF00;
const unsigned int BLUE = 0xFF0000FF;
const unsigned int SECOND = 1000000;


// AARRGGBB
void clearFramebuffer(int fd, int width, int height, int bytespp, unsigned int color) {
	int row, col;
	unsigned int *data;

	data = (unsigned int*) mmap(0, width * height * bytespp, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

	for(row = 0; row < height; row++)
		for(col = 0; col < width; col++)
			data[row * width + col] = color;

	munmap(data, width * height * bytespp);
}

int main() {
	int width, height, bitspp, bytespp;

	int fd = open("/dev/fb0", O_RDWR);

	struct fb_var_screeninfo screeninfo;
	ioctl(fd, FBIOGET_VSCREENINFO, &screeninfo);

	bitspp = screeninfo.bits_per_pixel;
	if(bitspp != 32) {
		printf("Farbaufloesung = %i Bits pro Pixel\n", bitspp);
		printf("Bitte aendern Sie die Farbtiefe auf 32 Bits pro Pixel\n");
		close(fd);
		return 1;
	}

	width = screeninfo.xres;
	height = screeninfo.yres;
	bytespp = bitspp / 8;

	if(sizeof(unsigned int) != bytespp) {
		close(fd);
		return 1;
	}

	int counter = 0;

	while(true) {
		unsigned int color = (counter == 0) ? RED : ((counter == 1) ? GREEN : BLUE);
		clearFramebuffer(fd, width, height, bytespp, color);
		if(counter < 2)
			counter++;
		else
			counter = 0;
		usleep(SECOND);
	}

	close(fd);
	
	return 0;
}