Motif/Lesstif Application Development

This article is directed toward those who have spent their time in the pleasant arena of development and are finding it harder and harder to ignore the growth of graphical front-ends. My perspective is that of a developer of commercial UNIX applications distributed largely on commercial versions of UNIX. I have an interest in making these applications easily portable to Linux and developing skills that are useful across OS boundaries. Given a choice, I prefer to use technologies which can be readily applied in both the commercial and open-source worlds.

My goal is to give you a basic understanding of the essential components of an X/Motif application—enough to begin developing your own applications. Development of server-side programs or command-line interfaces (CLIs) tends to be more cut-and-dried than that of graphical user interfaces (GUIs). Human beings are notoriously unpredictable, especially when one is used to developing according to strict protocols and well-defined boundaries. The complicated interaction with a GUI is usually best handled by a toolkit or library—someone else can worry about the details of where the mouse pointer happened to be when the left button was pressed, and how to render those beautiful 3-D effects on the components on the screen. Although every UNIX ships with libraries to take care of these details (X, Xt), they are still quite tedious and time-consuming. Motif is a library that provides enough insulation from the underlying primitives to make development of GUIs realistic, while still allowing easy access to those primitives should you need them.

Strictly speaking, Motif is a standard put forward by the Open Software Foundation (OSF) that describes expected behavior and the look and feel of an application. An application can be described as Motif-compliant; OSF even provides for branding of applications that adhere to the Motif standard. The practical utility of the standard is arguable; however, the benefits of the framework provided by the Motif libraries is unquestionable. You can build a Motif application that uses the libraries but is not compliant with the standard; in fact, most programmers simply use the library and ignore the more Byzantine dictums of the standards.

Henceforth, when I say Motif, I mean the Motif library or any one of the various API-compatible libraries (Lesstif, Mootif, Moteeth, etc.). Differences between Motif (v. 1.2) and Lesstif will be pointed out. Although Motif 2.1 has been released, I will focus on version 1.2 since this is the revision level of most installed clients and the most common open-source alternative, Lesstif. The newer releases of Motif are generally backward compatible, although some techniques and elements of the API may be deprecated. The biggest differences between versions 1.2 and 2.1 include thread-safe libraries and some additional widgets, such as the Notebook.

My decision to use Motif is motivated by several very specific concerns, some of which will strike a chord in those of you involved with commercial software development. The tools I use in commercial efforts must:

The Motif library is a toolkit that meets my requirements. Virtually every commercial UNIX ships with a run-time license for Motif. Free UNIX variants (including Linux and BSD) also have access to Motif libraries (although at a fee); however, a Motif “clone” called Lesstif is now stable and mature enough to use in place of a “real” Motif library. Alternative GUI toolkits exist (GTK, Qt, etc.) and may be a good choice for projects which dodge the commercial world—for those of us who make a living writing software for commercial distributions, I think Motif is still a good choice.

The Common Desktop Environment (CDE) that ships with most commercial UNIX operating systems is built on Motif 2.1, which was intended to provide a backward-compatible API for applications built on version 1.2. I have found I can work on the same project on Solaris (using Motif) and Linux (using Lesstif), moving the source back and forth regularly with surprisingly few hiccups.

Finally, the end product looks sharp. Motif makes it easy to get a professional-looking GUI without any extra effort. 3-D effects, text clipboard operations (cut, copy and paste) and other trappings users have come to expect from even small applications are taken care of automatically, so you can focus on your application's problem domain.