https://invisible-island.net/xterm/xtoolkit/
XtParent - obtain widget's parent widget id
#include <X11/Intrinsic.h>
Widget XtParent(Widget w);
w Specifies the widget.
XtParent returns the widget's parent widget ID.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface
X Version 11 libXt 1.3.1 XtParent(3)