https://invisible-island.net/xterm/xtoolkit/
XtAppLock, XtAppUnlock - lock and unlock application context
#include <X11/Intrinsic.h>
void XtAppLock(XtAppContext app_context);
void XtAppUnlock(XtAppContext app_context);
app_context
Specifies the application context.
XtAppLock locks the application context including all its related dis-
plays and widgets.
XtAppUnlock unlocks the application context.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface
X Version 11 libXt 1.3.1 XtAppLock(3)