A majority of the LUCAS modules were developed on UNIX-based workstations (e.g., Sun SPARCstation 10) running X Windows (X11 Release 5) with the OSF/Motif library toolkit (version 1.2.1). It is expected that most LUCAS end-users will have such a UNIX-based system available. OSF/Motif provides a standard for user interface behavior which allows users of other Motif, Microsoft Windows, and Presentation Manager applications to use Motif-compliant applications without the need to learn a new graphical user interface. The OSF/Motif run-time libraries are available on most platforms, including HP, DEC, IBM, SUN, and Silicon Graphics. This availability was an important factor in our selection of OSF/Motif for the LUCAS GUI development. In order to develop an application which is not only portable to various hardware platforms, but which also provides a familiar look and feel to windowing system users, the principles in the OSF/Motif Style Guide were applied to the LUCAS GUI where appropriate.
The OSF/Motif library is a toolkit which contains a pre-defined set of components called widgets. A widget consists of a complex data structure (an object) and a set of procedures (methods). Widgets are organized into classes which are groups of widgets with similar characteristics. Each widget class has a set of associated resources and actions. A resource is an attribute of a widget class such as foreground color, background color, or font. An action is triggered in response to the occurrence of certain types of events. Widget classes are organized into a hierarchy whereby a widget class inherits resources from its superclass. All resources are inherited by a subclass from its superclass so that the inheritance of resources extends all the way back to the root widget class in the inheritance hierarchy.
Since the Sun SPARCstation 10 does not come pre-configured with OSF/Motif, the IXI Motif developers kit and run-time libraries were purchased and installed for LUCAS GUI development. The IXI Motif software provides a standard implementation of OSF/Motif for Sun workstations running the SunOS operating system.