Wrap mouse pointer at screen edges

mouse_wrap.c

/*
 * Wrap mouse pointer at screen edges.
 *
 * Compile:
 * $ cc -o mousewrap mouse_wrap.c -lX11 -lXi
 *
 * Usage:
 * $ ./mwrap
 *
 * Copyright (C) 2012 Alessandro Ghedini <alessandro@ghedini.me>
 * --------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * Alessandro Ghedini wrote this file. As long as you retain this
 * notice you can do whatever you want with this stuff. If we
 * meet some day, and you think this stuff is worth it, you can
 * buy me a beer in return.
 * --------------------------------------------------------------
 */

#include <X11/Xlib.h>
#include <X11/extensions/XInput2.h>

#define P_WARP(COND, X, Y)		\
	if (COND) {			\
		p_new_x = X;		\
		p_new_y = Y;		\
		goto warp;		\
	}

int main(int argc, char **argv) {
	Display *dpy = XOpenDisplay(NULL);
	Window root  = DefaultRootWindow(dpy);

	int screen   = DefaultScreen(dpy);
	int s_width  = DisplayWidth(dpy, screen);
	int s_height = DisplayHeight(dpy, screen);
	int xi_op, first, error;

	XQueryExtension(dpy, "XInputExtension", &xi_op, &first, &error);

	unsigned char mask_bytes[XIMaskLen(XI_RawMotion)];
	XISetMask(mask_bytes, XI_RawMotion);

	XIEventMask mask;

	mask.deviceid = XIAllMasterDevices;
	mask.mask_len = sizeof(mask_bytes);
	mask.mask     = mask_bytes;

	XISelectEvents(dpy, root, &mask, 1);

	while (1) {
		XEvent event;
		XNextEvent(dpy, &event);

		if ((event.xcookie.type == GenericEvent) &&
		    (event.xcookie.extension == xi_op)) {
			XGetEventData(dpy, &event.xcookie);

			if (event.xcookie.evtype == XI_RawMotion) {
				unsigned int p_mask;
				Window p_root, p_child;
				int p_x, p_y, p_new_x, p_new_y,
				    p_win_x, p_win_y;

				XQueryPointer(
					dpy, root, &p_root, &p_child,
					&p_x, &p_y, &p_win_x, &p_win_y, &p_mask
				);

				P_WARP((p_x == 0), s_width, p_y)
				P_WARP((p_x == (s_width - 1)), 0, p_y)
				P_WARP((p_y == 0), p_x, s_height);
				P_WARP((p_y == (s_height - 1)), p_x, 0);

				p_new_x = p_x;
				p_new_y = p_y;

warp:
				XWarpPointer(
					dpy, None, root, 0, 0, 0, 0,
					p_new_x, p_new_y
				);
			}

			XFreeEventData(dpy, &event.xcookie);
		}
	}

	XCloseDisplay(dpy);
	return 0;
}