#include <X11/Xlib.h>
#include <X11/extensions/Xrandr.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <err.h>

void test_and_fail(void *ptr, char *msg) {
	if (ptr == NULL) {
		fprintf(stderr, "Fatal error: %s\n", msg);
		exit(2);
	}
}

int rol4 (int x) {
	// Just rotate left by 1 bit
	int num = x & 0xf;
	int sh = num << 1;
	int overflow = (sh & 0x10) >> 4;
	return (sh & 0xf) | overflow;
}

int main (void) {
	Display *dpy = XOpenDisplay(NULL);
	test_and_fail(dpy, "Could not open display");

	int screen_number = XDefaultScreen(dpy);
	Screen *screen = XDefaultScreenOfDisplay(dpy);
	Window root = XRootWindow(dpy, screen_number);

	// TODO: Early check that RandR is supported by dpy

	Rotation current;
	Rotation all;
	all = XRRRotations(dpy, screen_number, &current);

	Rotation new = rol4(current);

	Time cfg_ts;
	Rotation cfg_rot;
	XRRScreenConfiguration *cfg = XRRGetScreenInfo(dpy, root);
	XRRSetScreenConfig(dpy, cfg, root, XRRConfigCurrentConfiguration(cfg, &cfg_rot), new, XRRConfigTimes(cfg, &cfg_ts));
	
	XRRFreeScreenConfigInfo(cfg);
	return 0;
}