https://invisible-island.net/xterm/xtoolkit/
XtSessionGetToken, XtSessionReturnToken - token management for check-
pointing
#include <X11/Intrinsic.h>
XtCheckpointToken XtSessionGetToken(Widget w);
void XtSessionReturnToken(XtCheckpointToken token);
w Specifies the session widget.
token Specifies the token to be returned.
The XtSessionGetToken function will return NULL if the checkpoint oper-
ation instigated by the session manager is not currently under way.
To indicate the completion of a deferred save operation and to return
the checkpoint token use XtSessionReturnToken.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface
X Version 11 libXt 1.3.1 XtSessionGetToken(3)