// gcc test.c -lX11 -o test
#include <X11/Xlib.h>
#include <stdio.h>

#define TIMEDIFF(t1, t2) ((t1.tv_sec-t2.tv_sec)*1000 + (t1.tv_usec-t2.tv_usec)/1000)

static void wait_for_rendering(Display *dpy, Window win)
{
	XImage *ximage = XGetImage(dpy, win, 0, 0, 1, 1, AllPlanes, ZPixmap);
	if (ximage != NULL)
		XDestroyImage(ximage);
}

int main()
{
	Display *dpy;
	Window win;
	GC gc;
	XSetWindowAttributes attr;
	int width = 1000;
	int height = 800;
	int black, white, x, y, i, len;
	struct timeval t1, t2;
	char string[300];
	char buf[256];
	double time = -1;
	dpy = XOpenDisplay(NULL);


	black = BlackPixel(dpy, DefaultScreen(dpy));
	white = WhitePixel(dpy, DefaultScreen(dpy));

	attr.override_redirect = True;
	win = XCreateWindow(dpy, DefaultRootWindow(dpy),
			    0, 0, width, height, 0,
			    DefaultDepth(dpy, DefaultScreen(dpy)),
			    InputOutput,
			    DefaultVisual(dpy, DefaultScreen(dpy)),
			    CWOverrideRedirect, &attr);
	XMapWindow(dpy, win);
	XSync(dpy, True);

	gc = XCreateGC(dpy, win, 0, NULL);

	for (i = 0; i < 95; i++) {
		string[i] = i + 32;
		string[i+95] = i + 32;
		string[i+95*2] = i + 32;
	}

	while (1) {
		gettimeofday(&t1, NULL);
		for (i = 0; i < 5; i++) {
			XSetForeground(dpy, gc, white);
			XFillRectangle(dpy, win, gc, 0, 0, width, height);
			XSetForeground(dpy, gc, black);
			XSetBackground(dpy, gc, white);
			len = sprintf(buf, "%.1f ms", time);
			XDrawImageString(dpy, win, gc, 5, 15, buf, len);
			for(y = 0; y < height/15; y ++)
				for(x = 0; x < width/30; x ++)
					XDrawImageString(dpy, win, gc, 5 + x*30 , 30 + y*15, "Test", 4);
		}
		wait_for_rendering(dpy, win);
		gettimeofday(&t2, NULL);
		/* decaying average over ~1s! */
		if (time < 0)
			time = TIMEDIFF(t2, t1);
		else
			time = (49*time + TIMEDIFF(t2, t1))/50;
//		printf("%i ms\n", time);
	}

	return 0;
}