An embeddable language. Prepares suitable X event and other parameters. This puts all actions into the queue, and does no processing of events till the end. Won't allow for the delays required for demonstrations. Can't easily penetrate toplevel of the parse tree, e.g. into loops and procedures.
Gadgets are hacks to place load on the application side instead of on the server.
Proper handling of them requires regularities not specified by Xt. Send A communication method between X applications. Ported to Xt. Builtin to replay library.