--- ./nx-X11/lib/X11/ChkIfEv.c.X.original	2015-02-13 14:03:44.620443950 +0100
+++ ./nx-X11/lib/X11/ChkIfEv.c	2015-02-10 19:13:13.120711494 +0100
@@ -83,3 +83,56 @@
 	UnlockDisplay(dpy);
 	return False;
 }
+
+#ifdef NX_TRANS_SOCKET
+
+/*
+ * This is just like XCheckIfEvent() but doesn't
+ * flush the output buffer if it can't read new
+ * events.
+ */
+
+Bool XCheckIfEventNoFlush (dpy, event, predicate, arg)
+        register Display *dpy;
+	Bool (*predicate)(
+			  Display*			/* display */,
+			  XEvent*			/* event */,
+			  char*				/* arg */
+			  );		/* function to call */
+	register XEvent *event;		/* XEvent to be filled in. */
+	char *arg;
+{
+	register _XQEvent *prev, *qelt;
+	unsigned long qe_serial = 0;
+	int n;			/* time through count */
+
+        LockDisplay(dpy);
+	prev = NULL;
+	for (n = 2; --n >= 0;) {
+	    for (qelt = prev ? prev->next : dpy->head;
+		 qelt;
+		 prev = qelt, qelt = qelt->next) {
+		if(qelt->qserial_num > qe_serial
+		   && (*predicate)(dpy, &qelt->event, arg)) {
+		    *event = qelt->event;
+		    _XDeq(dpy, prev, qelt);
+		    UnlockDisplay(dpy);
+		    return True;
+		}
+	    }
+	    if (prev)
+		qe_serial = prev->qserial_num;
+	    switch (n) {
+	      case 1:
+		_XEventsQueued(dpy, QueuedAfterReading);
+		break;
+	    }
+	    if (prev && prev->qserial_num != qe_serial)
+		/* another thread has snatched this event */
+		prev = NULL;
+	}
+	UnlockDisplay(dpy);
+	return False;
+}
+
+#endif