Michelle J. Arden

Network applications and NeWS

Sun’s Network/extensible Window System (NeWS) was designed for use within a distributed network environment. A NeWS network can be heterogeneous, composed of many different systems. More than 50 companies have licensed NeWS, and it has been ported to more than ten different platforms. Developers are already building applications for NeWS that span a network of machines.

Porting NeWS to Other Platforms

“NeWS was designed to be portable.” What exactly does this mean? It means that it should be possible, with relatively little effort, to adapt the NeWS server to run on a variety of different: CPU architectures. Operating systems. Display hardware types.

NeWS Applications and the Network

Up to this point we have talked about the NeWS server and about writing PostScript programs that execute in the server. However, NeWS is a network-based window system. Network-based window servers allow the clients to make use of window system and display resources on the network, much as a distributed file system such as NFS allows programs to make use of file system and disk resources over the network. End-users or NeWS clients can connect to remote NeWS servers to display output inside a window on the screen or receive input from the keyboard mouse or other input device.

A Tour through a NeWS Application

This chapter reviews a relatively large NeWS application and explains some of the ways that it uses NeWS to advantage. The application is ched, a cheap editor built as a demonstration of how to build a WYSIWYG editor in NeWS. The source for this application is in the public domain and available from Sun Microsystems. The last section in this chapter explains how to obtain the ched program.

Introduction to the PostScript Language

This chapter gives a brief introduction to the standard PostScript language, as implemented in NeWS and many thousands of PostScript printers. This introduction is not particularly rigorous, but it should offer enough information for understanding the rest of the book. For a full description, see the PostScript Language Reference Manual[ADOBS5a].

Window System Architecture: History, Terms and Concepts

This chapter defines and explains the terms that commonly describe window systems. It establishes a general level of understanding for future chapters. The four parts of this chapter offer: a layered model of window systems; a historical survey of window systems, illustrating how a number of systems fit into the model; a detailed review of the components of the layered model; an examination of the relationship between window system architectures and their environments.

Object-Oriented PostScript

The previous chapter introduced the extensions that NeWS makes to the PostScript language in order to support interaction with a window system. This chapter shows how these extensions are combined with a stylized way of writing PostScript programs to make developing interactive programs easy. We do this by following the gradual construction of a simple example NeWS client.

NeWS Facilities for an Interactive World

The previous chapter described the PostScript language as defined by Adobe Systems, originally designed to drive printers. With printers, only one PostScript program is being executed at a time and output can only take place to a single page at a time. In contrast, NeWS is a window system. It requires that multiple application programs be able to concurrently access the display, which is partitioned into separate regions for each application. And it needs to handle input from a keyboard, a mouse, and the network.

X11/NeWS Design Overview

The X window system development at MIT defined an important standard protocol for window system development: the Version 11 protocol. (The evolution and structure of the X window system are described in Chapter 3.) The industry interest in X11, the PostScript language, and NeWS resulted in the definition of a combined window server architecture: the X11/NeWS merge. Combining the X11 fixed protocol with an enhanced PostScript language, together with the dynamic development environment of NeWS, gives the applications developer a synthesis of standards, functionality, and flexibility [ROBE88].