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 1.1.5.2 XtAppLock(3)