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October 1989

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Document:	ULTRIX Worksystem Software Display PostScript® Perspective for Software Developers
Order Number:	AA-PAN7A-TE
Revision:	000
Pages:	19
Original Filename:

OCR Text

VL TRIX W orksystem Software

Display PostScript® Perspective
for Software Developers

Order Number: AA- PAN7 A - TE

Perspective
for Software Developers
Order No. AA-PAN7A-TE

ADOBE SYSTEMS
INCORPORATED

Perspective for Software Developers

Writer: Amy Davidson
October 25, 1989
Copyright © 1988, 1989 Adobe Systems Incorporated.
All rights reserved.
POSTSCRIPT and DISPLAY POSTSCRIPT are registered
trademarks of Adobe Systems Incorporated.
X and X Window System are trademarks of the Massachusetts
Institute of Technology.
The information in this document is furnished for informational use
only, is subject to change without notice, and should not be construed
as a commitment by Adobe Systems Incorporated. Adobe Systems
Incorporated assumes no responsibility or liability for any errors or
inaccuracies that may appear in this document. The software described
in this document is furnished under license and may only be used or
copied in accordance with the terms of such license.
No part of this publication may be reproduced, stored in a retrieval
system, or transmitted in any form or by any means, electronic,
mechanical, recording, or otherwise, without the prior written
permission of Adobe Systems Incorporated.

This document replaces the previous version dated October 10,
1988.

:mf"lTcnts

1
2
3
4
5
6

About This Document 1
About the DISPLAY POSTSCRIPT System
Application Building Blocks 2
Using pswrap 3
The Client Library Interface 5
Manuals for Application Developers 5

Index 9

iii

Figure 1:

The DISPLAY POSTSCRIPT System 2

Figure 2:

Creating a DISPLAY POSTSCRIPT Application 4

1 ABOUT THIS DOCUMENT
This document is your introduction to application development
using the text and graphics imaging resources of the DISPLAY
POSTSCRIPT@ system.
This introduction for the application programmer describes:
• The DISPLAY POSTSCRIPT system environment you'll be
interacting with.
• The Client Library interface you'll be programming for.
o The

use of the pswrap translator to prepare C-callable
procedures containing POSTSCRIPT@ language programs.

• The manuals you'll need.

2 ABOUT THE DISPLAY POSTSCRIPT SYSTEM
The DISPLAY POSTSCRIPT system provides a device-independent
imaging model for displaying information on a screen. This imaging model is fully compatible with the imaging model used in
POSTSCRIPT printers. By allowing you to use the POSTSCRIPT
language to display text, graphics, and sampled images, it frees
you from display-specific details such as screen resolution and
number of available colors.
You can look at the DISPLAY POSTSCRIPT system as part of the
window system. Your application will use window system features for window placement and sizing, menu creation, and event
handling, while using DISPLAY POSTSCRIPT features to take care
of imaging inside the window.
DISPLAY POSTSCRIPT system components include the Client
Library, the POSTSCRIPT interpreter, and the pswrap translator.
These components are described in the accompanying set of
manuals. If you are a new POSTSCRIPT language programmer,
you'll also need copies of the POSTSCRIPT language manuals.
See Section 6 for a discussion of documentation required by application developers.
Figure 1 shows the relationship between your application and the

2 ABOUT THE DISPLAY POSTSCRIPT SYSTEM

DISPLAY POSTSCRIPT system. The Client Library contains data

structures and procedures your application will use to send requests to the POSTSCRIPT interpreter. No matter what operating
system you're dealing with, you can send POSTSCRIPT language
programs to the interpreter in the same way, using the same procedure calls. Therefore portability issues are minimized if you're
developing an application for more than one environment.
Figure 1 The DISPLA Y POSTSCRIPT System

Application

Window

t
il1 L

•••••••

PostScript
Language

I>
P"

1)< Itl

x,> .',.,., '>':; <.< :>

.. ,.

'"
Display

IttI~ ,}\;:I

Ii) (> \»

i ...

System
..... Data & Events ...
.....

...

\..

\·"·<

Keyboard

.....
.....

Mouse

I
Operating System

3 APPLICATION BUILDING BLOCKS
Most of your application will be written in C or another highlevel languge. You'll call Client Library procedures to start a
POSTSCRIPT execution context, send programs and data to the
POSTSCRIPT interpreter, and get results from the the interpreter.
The Client Library is the application's primary interface to the
DISPLAY POSTSCRIPT system.
In addition, you'll call wraps POSTSCRIPT language
procedures developed specifically for your application. Wraps,
short for wrapped procedures, are created by the pswrap translator from POSTSCRIPT language programs written to meet application needs. Figure 2 on page 4 shows how an application
program is built.

Perspective for Software Developers

4 USING PSWRAP
Your application will perform calculations, communicate with
the window system, read and write files, and do other application
processing in C or another high-level language. It will perform
imaging tasks by calling wrapped procedures to send
POSTSCRIPT language programs to the interpreter. The pswrap
translator creates these wraps from POSTSCRIPT language input.
Figure 2 shows how an application is built of C source code and
POSTSCRIPT language code translated into C-callable procedures
by pswrap.

4 USING PSWRAP

Figure 2 Creating a DISPLAY POSTSCRIPT Application

pswrap
Translator

COMPILE

Display PostScript
Client Library

LINK

Application

Consider a wrap, PWDisplayText, that places text on the screen
at a particular x,y coordinate. A call to PWDisplayText from the
application program might look something like this:
PWDisplayText(72.0, 100.0, "Hello World");

The body of the PWDisplayText procedure, is actually written in
the POSTSCRIPT language. It was defined to pswrap as follows:

Perspective for Software Developers

defineps PWDisplayText(f1oat X,V; char *text)
X Y moveto
(text) show
endps

In the wrap definition, the 'defineps' and 'endps' keywords tell
pswrap where a given POSTSCRIPT language program begins and
ends. The 'defineps' statement defines the resulting procedure
call. The pswrap translator processes this input and produces a C
language source-code file. When compiled and linked with the
application, the PWDisplayText procedure sends a POSTSCRIPT
language program to the interpreter (binary-encoded for more efficient processing), causing the specified text to be displayed.

To summarize, pswrap takes a POSTSCRIPT language program as
input and gives you back a C language program. After you compile the resulting C program and link it into your application,
calling the wrap will transmit a stream of POSTSCRIPT language
binary objects to the interpreter.

5 THE CLIENT LIBRARY INTERFACE
The Client Library is a linkable library of compiled C procedures
that provides an interface between the application and the
DISPLAY POSTSCRIPT system. It creates an environment for handling imaging calls to specific Client Library procedures like
DPSmoveto and custom wraps written for the application.
The Client Library is tailored by the DISPLAY POSTSCRIPT system vendor for your particular operating environment. The
Client Library Reference Manual describes a generic interface;
your system vendor may add additional features or slightly
modify the interface to suit your hardware and software. See
your vendor's system-specific documentation for details.

6 MANUALS FOR APPLICATION DEVELOPERS
The accompanying set of manuals contains information needed
by a POSTSCRIPT programmer developing an application for the
DISPLAY POSTSCRIPT system. If you're new to the POSTSCRIPT
language, you should first read the following manuals (published

6 MANUALS FOR APPLICATION DEVELOPERS

for Adobe by Addison-Wesley and available by calling
1-800-344-8335 or through your technical bookstore):
POSTSCRIPT Language Reference Manual

The standard reference for the POSTSCRIPT language. Describes the POSTSCRIPT imaging
model and the concepts and facilities of the
POSTSCRIPT
interpreter.
Documents
the
POSTSCRIPT language. Required reading.
POSTSCRIPT Language Tutorial and Cookbook

Provides an infonnal, interactive introduction to
the POSTSCRIPT language and a collection of
programs that offer examples of POSTSCRIPT
usage.
POSTSCRIPT Language Program Design

Gives guidelines for designing and debugging
POSTSCRIPT language programs. Printeroriented, but some of the infonnation is relevant
to writing for a DISPLAY POSTSCRIPT application.
Once you're up to speed in the POSTSCRIPT language, read the
following manuals:
POSTSCRIPT Language Extensions for the DISPLAY POSTSCRIPT
System

Describes the extensions to the POSTSCRIPT language that were made for the DISPLA Y
POSTSCRIPT system, such as alternative
POSTSCRIPT language encodings, multiple execution contexts, user paths, window system
support, and memory management. Introduces
important system concepts and documents additional POSTSCRIPT operators.
Client Library Reference Manual

Describes the procedural interface to the
DISPLA Y POSTSCRIPT system. Tells how to send
programs and data to a POSTSCRIPT execution
context, how to handle context output, how to
create and tenninate a context. Contains procedure definitions, programming tips, and a
sample application program.

Perspective for Software Developers

pswrap Reference Manual
Describes how to define C-callable procedures
that contain POSTSCRIPT language programs.
Tells how to declare input arguments and output
to be received from the interpreter. Documents
the pswrap command line options.
POSTSCRIPT Language Color Extensions
Describes color extensions to the POSTSCRIPT
language, including multiple color images, color
halftone screen definitions, color correction, and
CMYK color specification.

Because of the nature of DISPLAY POSTSCRIPT, some of the information you need to write programs is necessarily systemspecific. Therefore, in addition to the manuals listed above,
you'll need to consult the documentation provided by your system software vendor. The following system-specific documentation is available from Adobe:
X Window System Programmer's Supplement to the Client
Library Reference Manual

Describes information about the Client Library
interface that is specific to the X Window
System™, such as context creation and additional error codes.

6 MANUALS FOR APPLICATION DEVELOPERS

ex
Client Library 5
device independence
Display PostScript components
DPSmoveto 5
imaging modell, 6
manuals 5
portability 2
PostScript imaging modell, 6
pswrap translator 3
PWDisplayText 4
window system
wraps 2,3

How to Order Additional Documentation

Technical Support
If you need help deciding which documentation best meets your needs, call SOO-343-4040
before placing your electronic, telephone, or direct mail order.

Electronic Orders
To place an order at the Electronic Store, dial SOO-DEC-DEMO (SOO-332-3366) using
a 1200- or 2400-baud modem. If you need assistance using the Electronic Store,
call SOO-DIGITAL (SOO-344-4S25).

Telephone and Direct Mail Orders
Your Location

Call

Contact

Continental USA,
Alaska, or Hawaii

SOO-DIGITAL

Digital Equipment Corporation
P.O. Box CS200S
Nashua, New Hampshire 03061

Puerto Rico

S09-754-7575

Local DIGITAL subsidiary

Canada

SOO-267-6215

Digital Equipment of Canada
Attn: DECdirect Operations KA02j2
P.O. Box 13000
100 Herzberg Road
Kanata, Ontario, Canada K2K 2A6

In terna tional
Internal)

Local DIGITAL subsidiary or
approved distributor
SOC Order Processing - WMO jE 15

or
Software Distribution Center
Digital Equipment Corporation
Westminster, Massachusetts 01473

) For internal orders, you must submit an Internal Software Order Form (EN-01740-07).