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

char *get_name(Window window);
void set_name(Window window, char *name);

Display *display;

int main(int argc, char **argv)
{
  Window target;
  char *name;
  char buf[4096];
  if (argc == 2 && snprintf(buf, sizeof(buf), "\"%s\" `xselect` \"%s\"", argv[0], argv[1]) < sizeof(buf))
    execlp("sh", "sh", "-c", buf, NULL);

  if (argc != 3) {
    char *name;
    name = strrchr(argv[0], '/');
    name = name ? name+1 : argv[0];
    fprintf(stderr, "usage: %s --get [window-id]\n       %s [window-id] name\n", name, name);
    exit(1);
  }

  if (!strcmp(argv[1], "--get")) {
    argv[1] = argv[2];
    --argc;
  } else if (!strcmp(argv[2], "--get")) {
    --argc;
  }

  target = strtol(argv[1], NULL, 10);

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

  if (argc == 2) {
    name = get_name(target);
    if (name) {
      printf("%s\n", name);
      XFree(name);
    }
  } else {
    name = argv[2];
    set_name(target, name);
  }

  XCloseDisplay(display);
  exit(0);
}

char *get_name(Window window)
/* need to XFree the returned name if not NULL */
{
  unsigned long n, extra;
  char *name;
  Atom real_type;
  int format;

  if (XGetWindowProperty(
        display, window, XA_WM_NAME, 0L, 256L, False, XA_STRING,
        &real_type, &format, &n, &extra, (unsigned char **)&name)
      != Success) {
    return False;
  }

  return name;
}

void set_name(Window window, char *name)
{
  XChangeProperty(display, window, XA_WM_NAME, XA_STRING, 8,
      PropModeReplace, (unsigned char *)name, strlen(name));
  XChangeProperty(display, window, XA_WM_ICON_NAME, XA_STRING, 8,
      PropModeReplace, (unsigned char *)name, strlen(name));
}