/*************************/
/* grabkey.c 1.00        */
/* by Adam M. Costello   */
/* <amc@cs.berkeley.edu> ***********************************/
/*                                                         */
/* grabkey [ -display <display> ] <keysym>                 */
/*                                                         */
/* Grabs the specified key, waits for it to be pressed     */
/* once, then ungrabs it and exits.  The <keysym> has the  */
/* form keysymname+modifier+modifier+...  Valid modifiers  */
/* are Shift, Lock, Control, Mod1, Mod2, Mod3, Mod4, Mod5. */
/***********************************************************/

/* This is ANSI C plus X11R6 code. */


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


#ifndef EXIT_FAILURE
#define EXIT_FAILURE 1
#endif

#ifndef EXIT_SUCCESS
#define EXIT_SUCCESS 1
#endif


void warn(char *msg)
{
  fputs(msg,stderr);
  fflush(stderr);
}

void fail(char *msg)
{
  warn(msg);
  exit(EXIT_FAILURE);
}


void usage(char **argv)
/* Prints a usage message to stderr, then exits unsuccessfully. */
{
  fprintf(stderr,
          "\n"
          "usage:\n"
          "%s [ -display <display> ] <keysym>\n"
          "\n"
          "<keysym> has the form keysymname+modifier+modifier+...\n"
          "Valid modifiers are"
            " Shift, Lock, Control, Mod1, Mod2, Mod3, Mod4, Mod5.\n"
          , argv[0]
         );

  exit(EXIT_FAILURE);
}


void parseargs(int argc, char **argv, char **displayname,
               char **keysymname, unsigned int *modifiers)

/* Parses the command line arguments and */
/* sets **displayname and **keysymname.  */
{
  char **argp, *mod;
  int keysymseen = 0;

  *modifiers = 0;

  argp = argv;

  while (*++argp) {
    if        (!strcmp(*argp, "-display")) {
      if (!*++argp) usage(argv);
      *displayname = *argp;
    } else if (**argp == '-') {
      usage(argv);
    }
    else {
      if (keysymseen) usage(argv);
      *keysymname = strtok(*argp, "+");
      for (;;) {
        mod = strtok(NULL, "+");
        if (!mod) break;
        if      (!strcmp(mod, "Shift"  )) *modifiers |= ShiftMask;
        else if (!strcmp(mod, "Lock"   )) *modifiers |= LockMask;
        else if (!strcmp(mod, "Control")) *modifiers |= ControlMask;
        else if (!strcmp(mod, "Mod1"   )) *modifiers |= Mod1Mask;
        else if (!strcmp(mod, "Mod2"   )) *modifiers |= Mod2Mask;
        else if (!strcmp(mod, "Mod3"   )) *modifiers |= Mod3Mask;
        else if (!strcmp(mod, "Mod4"   )) *modifiers |= Mod4Mask;
        else if (!strcmp(mod, "Mod5"   )) *modifiers |= Mod5Mask;
        else {
          warn("Unrecognized modifier.\n");
          usage(argv);
        }
      }
      keysymseen = 1;
    }
  }
}


int main(int argc, char **argv)
{
  char *displayname = NULL;
  Display *display;
  char *keysymname;
  unsigned int modifiers;
  KeySym keysym;
  KeyCode keycode;
  Window rootwindow;
  XEvent event;

  parseargs(argc, argv, &displayname, &keysymname, &modifiers);

  display = XOpenDisplay(displayname);
  if (!display) fail("Cannot open display.\n");

  keysym = XStringToKeysym(keysymname);
  if (keysym == NoSymbol) fail("Invalid keysym.\n");

  keycode = XKeysymToKeycode(display,keysym);
  if (!keycode) fail("Undefined keysym.\n");

  rootwindow = DefaultRootWindow(display);

  XGrabKey(display,keycode,modifiers,rootwindow,
           False,GrabModeAsync,GrabModeAsync    );

  do XNextEvent(display, &event);
  while (event.type != KeyPress || event.xkey.keycode != keycode);

  XUngrabKey(display,keycode,modifiers,rootwindow);

  XCloseDisplay(display);

  return EXIT_SUCCESS;
}