Page 5

X Version 11

Release 6.4

X Print Service Overview

The X Print Service allows X imaging to non-display devices, such as printers. It is called the X "Print"
Service because the technology will primarily be applied to printing. The technology can, however, be
applied to a range of non-display devices. To date, print rendering technologies have evolved separately
from display rendering technologies. The thrust of the X Print Service is to converge the evolution of these
print and display technologies by extending the use of the X imaging model.

For example, today's X environment provides a number of APIs and technologies for rendering to a display,
including:

Xlib

PEXlib

X Imaging Extension

OSF/Motif Toolkit

Scalable Fonts

By retaining and supplementing these (and many more) standard APIs with one small print-specific API,
libXp, the X Print Service will allow an existing X application to render against a printer in addition to tradi-
tional display devices with small changes.

1.1

X Print Service Core Components

The X Print Service is made up of the following core components:

X Print Extension - A new X-Server Extension and corresponding X Print Extension Protocol.

libXp - The X Print Extension Library which provides an API for applications to the X Print Exten-
sion Protocol.

X Print "DDX" Drivers - DDX-level drivers for the X Server that generate page description lan-
guages (PDL) such as PCL and Postscript.

Configuration Files and Defaults - Configuration files that describe the capabilities of several
printer models, and other X Print Server configuration files.

The X Print Service is enhanced by the addition of the following components that are not included in this
standard:

libDtPrint - A library of print-specific GUIs tuned to several reference page-description-languages
and printer models. See the Common Desktop Environment Specification, Version 2.

dtpdm - Also known as the Dt Print Dialog Manager, a daemon-like process that provides second-
ary printer-specific GUIs that handle specific printer and spooler setup tasks. See the Common
Desktop Environment Specification, Version 2.

Several keywords and concepts used in this specification were borrowed from the abstract standard ISO
10175, the subsetted standard and implementation represented by POSIX 1387.4, and the yet further subset-
ted implementation represented by OSF Palladium. The X Print Service does not attempt to duplicate the
functionality or APIs provided by any of these print subsystems, or by any other print subsystems such as
System V lp or BSD lp. It does, however, attempt to allow implementations to work with these print sub-
system, and its architecture is open enough to allow tighter binding to a specific print subsystem in the
future.