#include <X11/Xlib.h>
#include <X11/Xmu/WinUtil.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
  Display *display;
  Window root;
  XEvent event;
  Window from, to;
  int x0, y0, x1, y1;

  if (argc != 1) {
    char *name;
    name = strrchr(argv[0], '/');
    name = name ? name+1 : argv[0];
    fprintf(stderr, "usage: %s\n", name);
    exit(1);
  }

  if ((display = XOpenDisplay(NULL)) == NULL) {
    fprintf(stderr, "cannot open display\n");
    exit(1);
  }

  root = DefaultRootWindow(display);

  if (XGrabPointer(
        display, root, False, ButtonPressMask|ButtonReleaseMask,
        GrabModeAsync, GrabModeAsync, None, None, CurrentTime)
      != GrabSuccess) {
    fprintf(stderr, "cannot grab pointer\n");
    exit(1);
  }

  XNextEvent(display, &event);
  if (event.type == ButtonPress && event.xbutton.button == 1) {
    from = event.xbutton.subwindow;
    x0 = event.xbutton.x_root;
    y0 = event.xbutton.y_root;
    if (from == None)
      from = event.xbutton.window;
    else
      from = XmuClientWindow(display, from);
    if (from != None) {
      XNextEvent(display, &event);
      if (event.type == ButtonRelease && event.xbutton.button == 1) {
        to = event.xbutton.subwindow;
        x1 = event.xbutton.x_root;
        y1 = event.xbutton.y_root;
        if (to == None)
          to = event.xbutton.window;
        else
          to = XmuClientWindow(display, to);
        if (to != None) {
          printf("%ld %d %d\n", from, x0, y0);
          printf("%ld %d %d\n", to, x1, y1);
        }
      }
    }
  }

  XCloseDisplay(display);
  exit(0);
}