Why doesn XtAppAddInput() work on OpenVMS?
Yes, XtAppAddInput() does work on OpenVMS. The MIT definition of the X Windows call XtAppAddInput() includes platform-specific arguments. On platforms where C is the typically the primary programming language for the platform, the file descriptor mask is one of the arguments to the XtAppAddInput() call. On OpenVMS, the platform-specific arguments to this call include an event flag and an IOSB, as these are the traditional OpenVMS constructs used to synchronize the completion of asynchronous operations. While it would be easier to port non-OpenVMS C code that calls XtAppAddInput() over to OpenVMS if the arguments included the C file descriptor, this would make the call unusable from other OpenVMS languages, and would make it extremely difficult to use OpenVMS features such as ASTs and sys$qio calls. One restriction on the event flag: the event flag chosen must be from event flag cluster zero. When using the traditional lib$get_ef and lib$free_ef calls to allocate and deallocate event fl
