Overview of X, Motif and Broadway

The X Window System is a network-transparent windowing system. Unlike most other windowing systems, such as Windows and Macintosh, X itself provides no inherenet look and feel. Instead, each application provides its own look and feel. Because this tends to be difficult, most X applications use the Motif look and feel, supported by the Motif programming API.

X includes a set of low-level programming APIs, called the X library or Xlib. X also provides a higher-level abstraction layer called the X Toolkit Intrinsics. On top of this come particular look and feel libraries, such as Motif.

For networking, X provides the neat ability to run an application on one machine and display the windows on another. This is very handy if you have powerful compute servers. It also led to the development of X terminals.

A very strange part about this is the terminology. In X, the server owns the desktop. The server draws the dots on the screen, reads the mouse and handles keyboard input. A client is simply a graphical application. The client connects to the server to create windows and draw data to the screen.

Because X can run over a network, a client can compute on any system on your network. The server is the machine in front of you at your desk. This usage is reversed from standard database terminology where the server is the big machine somewhere on the network and the client resides on your desktop.

The best thing about X has always been that it was the first standard windowing system for Unix workstations. While not limited to Unix, X has been most popular on that operating system. X also runs on a variety of other platforms, such as Windows and MacOS.

X is free and the source code is available over the Internet from the Open Group (formerly the X Consortium).W

Motif Backgrounder

Motif is a lot of things, which tends to confuse people. Motif is a window manager, a user interface style and also a programmer's library that sits on top of the X Window System.

If you program using the Motif programmer's libraries, then your applications will follow the Motif style guide (unless you do something truly bizarre).

One common point of confusion lies with the use of window managers. Yes, you can easily run a Motif application under an Open Look window manager. You can consider the resulting combination a Motif or an Open Look style--it doesn't really matter.

Motif was created by the Open Group (formerly the Open Software Foundation).

The Common Desktop Environment, or CDE, is the next wave in UNIX user interfaces. It's built on top of Motif (although not the latest version) and looks a lot like Hewlett-Packard's existing VUE interface, only cleaner.

The Common Desktop Environment provides a unified user environment on many UNIX systems. It presents a front panel at the bottom of your screen, a number of virtual desktops and a host of simple productivity applications, including a text editor, calendar and email program.

Motif Alternatives

Motif is a commercial product. There's also a freeware set of Motif-like APIs called LessTif.

Broadway: X and the Web

Broadway, available starting in X11R6.3, provides an attempt to marry X with the World Wide Web and provide what is called "universal access to interactive applications on the Web".

Broadway extends the X Window System with the following key features:

Remote Execution Providing Universal Access

With Broadway, you can run X applications on a remote machine and display the application from your Web browser, if equiped with the necessary plug-in.

Web Browser Plug-in

This plug-in allows you to embed X applications within Web pages.

Security

Broadway defines security around the concepts of trusted and untrusted systems. Any system outside your firewall is not trusted, limiting which X calls the application can make.

Protocol Compression

Because Broadway enables more applications running remotely and often over slow links, the LBX, or Low-Bandwidth X, system compresses the weighty X protocol resulting in less network traffic.

With Broadway support in Web browsers, Web pages will be able to launch X applications. These applications will either appear in separate windows on your X desktop or remain embedded within the Web page window.

The key feature of all this is that existing X applications will remain unchanged. You will be able to run these applications from Web browsers without porting your code to a new language like Java or dramatically altering your software.

The crux of this new technology is exceedingly simple. Web browsers already support the concept of "helper applications" for various document types. For example, few Web browsers can directly display MPEG videos, but virtually all will happily launch the helper application you have configured for this "document type" when you click on an MPEG URL (or Universal Resource Locator, the linga franca of the Web). The basic scheme for Broadway makes X applications a new type of "document". Thus, when you click on an X application URL, Web browsers will open a connection to your X server on your desktop. The Web server (at the other end of the Internet) will launch the X application.

For More Information On X

X Freeware

Source for most of the X freeware (in the contrib directory at ftp.x.org, the Open Group). Many useful applications are found in the contrib/applications directory.

XFree86

A version of X for Intel-based PCs running UNIX.

Power Programming Motif

A book covering how to create Motif applications.

MW3: Motif on the World Wide Web

A wide set of links to lots of Motif information. Not updated since 1997.

Frequently-Asked Questions (FAQ)

• X Window System FAQ
• X Toolkit Intrinsics FAQ
• Motif FAQ or another Motif FAQ
• Common Desktop Environment FAQ
• CDE FAQ
• X Freeware FAQ
• New Widgets FAQ
• Information on Imake, used to create platform-specific Makefiles for X programs.
• General FAQ Archive

Last updated: September 5, 2000