XtToolkitThreadInitialize - initialize the toolkit for multiple threads
Boolean XtToolkitThreadInitialize(void);
If XtToolkitThreadInitialize was previously called, it returns. The
application programmer must ensure that two or more threads do not
simultaneously attempt to call XtToolkitThreadInitialize; the effect of
this is undefined. XtToolkitThreadInitialize returns True if the
host operating system has threads and the Intrinsics are thread safe.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface