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 1.1.5.2 XtParent(3)