https://invisible-island.net/xterm/xtoolkit/
XtGetApplicationNameAndClass - retrieve application name and class
#include <X11/Intrinsic.h> void XtGetApplicationNameAndClass(Display* display, String* name_return, String* class_return);
display Specifies an open display connection that has been initial- ized with XtDisplayInitialize. name_return Returns the application name. class_return Returns the application class.
XtGetApplicationNameAndClass returns the application name and class passed to XtDisplayInitialize for the specified display. If the dis- play was never initialized or has been closed, the result is undefined. The returned strings are owned by the Intrinsics and must not be modi- fied or freed by the caller.
XtDisplayInitialize(3) X Toolkit Intrinsics – C Language Interface Xlib - C Language X Interface X Version 11 libXt 1.1.5.2 XtGetApplicationNameAndClass(3)