#include <stdio.h>
#include <X11/Xlib.h>

int
main (int argc, char **argv)
{
	Display			*dpy;
	Window			parent, child;
	GC			gc;
	XSetWindowAttributes	attr;
	unsigned long		bits;
	XEvent			ev;

	dpy = XOpenDisplay(NULL);
	if (!dpy) {
		fprintf(stderr, "Failed to open display\n");
		return 1;
	}
	attr.background_pixel = WhitePixel(dpy,0);
	attr.event_mask = ExposureMask|KeyPressMask;
	bits = CWBackPixel|CWEventMask;
	parent = XCreateWindow(dpy, RootWindow(dpy,0), 0, 0, 200, 200, 0, DefaultDepth(dpy, 0),
			       CopyFromParent, CopyFromParent, bits, &attr);
	child = XCreateWindow(dpy, parent, 0, -32760, 200, 32760 + 200, 0, DefaultDepth(dpy, 0),
			       CopyFromParent, CopyFromParent, bits, &attr);
	gc = XCreateGC(dpy, child, 0, NULL);
	XSetForeground(dpy, gc, BlackPixel(dpy,0));
	XMapWindow(dpy, child);
	XMapWindow(dpy, parent);
	for (;;) {
		XNextEvent(dpy, &ev);
		switch (ev.type) {
		case Expose:
			if (ev.xexpose.window == child) {
				XDrawLine(dpy, child, gc, 0, 32760, 100, 32760 + 100);
			}
		default:
			continue;
		case KeyPress:
			break;
		}
		break;
	}
	return 0;
}