#include "copyright.h"

/* $XConsortium: XIfEvent.c,v 11.10 88/09/06 16:08:37 jim Exp $ */
/* Copyright    Massachusetts Institute of Technology    1986	 */

#define NEED_EVENTS
#include "Xlibint.h"

extern _XQEvent *_qfree;

/*
 * Flush output and (wait for and) return the next event matching the
 * predicate in the queue.
 */

XIfEvent (dpy, event, predicate, arg)
  register Display *dpy;
Bool (*predicate) ();		/* function to call */
  register XEvent *event;
  char *arg;
{
  register _XQEvent *qelt, *prev;

  LockDisplay (dpy);
  prev = NULL;
  while (1) {
    for (qelt = prev ? prev->next : dpy->head;
	 qelt;
	 prev = qelt, qelt = qelt->next) {
      if ((*predicate) (dpy, &qelt->event, arg)) {
	*event = qelt->event;
	if (prev) {
	  if ((prev->next = qelt->next) == NULL)
	    dpy->tail = prev;
	}
	else {
	  if ((dpy->head = qelt->next) == NULL)
	    dpy->tail = NULL;
	}
	qelt->next = _qfree;
	_qfree = qelt;
	dpy->qlen--;
	UnlockDisplay (dpy);
	return;
      }
    }
    _XReadEvents (dpy);
  }
}