https://invisible-island.net/xterm/xtoolkit/
       XtGetApplicationNameAndClass - retrieve application name and class
       #include <X11/Intrinsic.h>
       void XtGetApplicationNameAndClass(Display* display, String* name_re-
              turn, 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 1.3.1  XtGetApplicationNameAndClass(3)