Example D-6 is an example for the Xt input handler function.
int myTtFd;
char *myProcID;
myProcID = ttdt_open( &myTtFd, "WhizzyCalc", "Acme", "1.0", 1 );
/* ... */
/* Process the message that started us, if any */
tttk_Xt_input_handler( myProcID, 0, 0 );
/* ... */
XtAppAddInput( myContext, myTtFd, (XtPointer)XtInputReadMask,
tttk_Xt_input_handler, myProcID );