x윈도우상에서 마우스의 좌표를 어떻게 구하는지.. ㅜㅜ

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

int
main(void)
{
  Display *disp = XOpenDisplay(NULL);
  Window rootwin, childwin;
  int rootx, rooty;
  int winx, winy;
  unsigned mask;

  if (!disp) {
    fprintf(stderr, "can't open the display %s\n",
            getenv("DISPLAY") != 0 ? getenv("DISPLAY") : "NULL");
    return 1;
  }

  if (XQueryPointer(disp, DefaultRootWindow(disp), &rootwin, &childwin,
                    &rootx, &rooty, &winx, &winy, &mask) != True) {
    fprintf(stderr, "error: XQueryPointer(3X) failed\n");
    XCloseDisplay(disp);
    return 1;
  }

  printf("Mouse Position = (%d, %d)\n", rootx, rooty);

  return 0;
}