The new Widget Server being developed for IRAF means that existing packages such as RV no longer have to be entirely re-written to have a sophisticated graphical user interface. The GUI for this application is written as a Tcl script that is downloaded to the widget server who controls the windows operations. GUIs can be written with any number of graphics windows, menus, buttons, and forms. As new widgets are added to the server, the application can be changed to take advantage of the new features in a very short time.
A sample screen for the FXCOR GUI: