Xprint(7)Xprint(7)NAMEXprint - The "X print service" - a portable, network-transparent print‐
ing system based on the X11 protocol
SYNOPSISXprint is a very flexible, extensible, scaleable, client/server print
system based on ISO 10175 (and some other specs) and the X11 rendering
protocol. Using Xprint an application can search, query and use
devices like printers, FAX machines or create documents in formats like
PDF. In particular, an application can seek a printer, query supported
attributes (like paper size, trays, fonts etc.), configure the printer
device to match it’s needs and print on it like on any other X device
reusing parts of the code which is used for the video card Xserver.
OVERVIEW
The "X Print Service" technology allows X rendering to devices such as
printers and fax. Most of the service is available in the X11 technol‐
ogy stack as Xp, with the remainder in single toolkit stacks (e.g.
DtPrint for CDE). Modifications have also been made to the Less‐
Tif/Motif/Qt technology stacks to support Xprint.
The Xp portion consists of:
· Xp Extension for the X-Server (included in the X-Server Xprt)
· Xp Extension API for the client side (libXp/libXprintUtils)
· PCL ddx driver that converts core X to native PCL
· PDF ddx driver that converts core X to native PDF
· PostScript ddx driver that converts core X to native PostScript
· Raster ddx driver that generates xwd rasters which can be converted
to PCL, PDF or PostScript rasters
From an X clients perspective, it can attach to one of two nearly iden‐
tical X-Servers, a "Video" X-Server, and a "Print" X-Server which has
the additional Xp capability but otherwise looks and behaves the same.
HOW THE X PRINT SERVICE WORKS
The X Print Service expands on the traditional X-Server and Xlib world
in four ways.
1. Most obvious is the use of "print ddx drivers" instead of "video
ddx drivers". While a video ddx driver modifies pixels in a video
frame buffer, a print ddx driver generates "page description lan‐
guage (PDL)" output (such as PCL, PDF or PostScript) or sends the
print rendering instructions to a platform-specific print API (like
Win32/GDI).
Once a print ddx driver generates PDL output, it can be sent to a
spooler such as lp(1) or retrieved by the client (to implement
functionality like "print-to-file").
Though not currently done, a single X-Server can support both print
and video ddx drivers.
2. Since printers support "paged" output, unlike video, a portion of
the Xp Extension supports APIs to delineate printed output. For
example, XpStartPage and XpEndPage tell the X-Server where a physi‐
cal page starts and ends in an otherwise continuous stream of X
rendering primitives. Likewise, XpStartJob and XpEndJob determine
when a collection of pages starts and ends. XpEndJob typically
causes the generated PDL to be submitted to a spooler, such as
lp(1).
3. Since printers have extensive capabilities, another portion of the
Xp Extension supports APIs to manipulate "print contexts".
Once a printer is selected using the Xp Extension API, a print con‐
text to represent it can be created. A print context embodies the
printer selected - it contains the printer's default capabilities,
selectable range of capabilities, printer state, and generated out‐
put. Some "attributes" within the print context can be modified by
the user, and the X-Server and print ddx driver will react accord‐
ingly. For example, the attribute "content-orientation" can be set
to "landscape" or "portrait" (if the printer supports these values
- which can be queried using the Xprint API as well).
4. Since printers can have "built in" fonts, the Xp Extension in the
X-Server works with the print ddx drivers to make available (for
printing only) additional fonts on a per print context basis.
When a print context is created and set for a given printer, the X
font calls may be able to access additional printer fonts. To do
this (typically), the X-Server must have access to "printer metric
files" (.pmf) that describe at minimum the metrics of the built in
fonts.
USAGE
There are three tasks to start the X Print Service:
1. configuring the X Print Server,
2. starting the X Print Service
3. configuring the user session so that clients can find the running X
Print Service
The tasks are described in detail below.
SERVER CONFIGURATION
The X Print Server (Xprt) can read a number of configuration files
which control its behavior and support for printers. Each vendor plat‐
form has a default location for this information. Xprt can also read
the environment variable XPCONFIGDIR to locate alternate configuration
directories. Common settings include:
export XPCONFIGDIR=/X11/lib/X11/XpConfig/
export XPCONFIGDIR=/proj/x11/xc/programs/Xserver/XpConfig/
Xprt has many built-in defaults, and lacking any configuration files,
will immediately try to support all printers visible via lpstat(1).
In order of importance for configuration by a system administrator, the
configuration files for a "C" locale are as follows (see Xprt(1) for
more details (including support for non-"C" locales)):
${XPCONFIGDIR}/C/print/Xprinters
'Xprinters' is the top most configuration file. It tells Xprt
which specific printer names (e.g. mylaser) should be supported,
and whether lpstat(1) or other commands should be used to auto‐
matically supplement the list of printers.
${XPCONFIGDIR}/C/print/attributes/printer
The 'printer' file maps printer names to model configurations
(see 'model-config' below). For example, "mylaser" could be
mapped to a "HPDJ1600C", and all other arbitrary printers could
be mapped to a default, such as "HPLJ4SI". When depending on
lpstat(1) in the Xprinters file, setting up defaults in
'printer' becomes all the more important.
${XPCONFIGDIR}/C/print/attributes/document
The 'document' file specifies the initial document values for
any print jobs. For example, which paper tray to use, what
default resolution, etc.
${XPCONFIGDIR}/C/print/attributes/job
The 'job' file specifies the initial job values for any print
jobs. For example, "notification-profile" can be set so that
when a print job is successfully sent to a printer, e-mail is
sent to the user.
${XPCONFIGDIR}/C/print/models/PSdefault/model-config, ${XPCON‐
FIGDIR}/C/print/models/PSdefault/fonts/fonts.dir, ${XPCON‐
FIGDIR}/C/print/models/PSdefault/fonts/9nb00051.pmf, ${XPCON‐
FIGDIR}/C/print/models/PSdefault/fonts/9nb00093.pmf
The 'model-config' file has attributes that describe the printer
model’s capabilities and default settings. Printer model fonts
may also be present. The model-config file also identifies the
print ddx driver to be used. For each printer model supported,
a complete hierarchy of files should exist. In most cases, these
files do not need to be modified.
${XPCONFIGDIR}/C/print/ddx-config/raster/pcl, ${XPCON‐
FIGDIR}/C/print/ddx-config/raster/pdf, ${XPCONFIGDIR}/C/print/ddx-con‐
fig/raster/postscript
The print ddx drivers can have highly specific configuration
files to control their behavior. In most cases, these files do
not need to be modified.
More information in how to configure and customize the X print server
can be found in the Xprt(1) manual page.
STARTING UP
The summary checklist for starting the X Print Service is as follows:
1. Choose an execution model for the X Print Service. The X Print Ser‐
vice can be run on a per-user session basis, per machine basis, or
can be run on a few machines globally available to a number of
users.
2. If print jobs are to be submitted to a spooler (almost always the
case), make sure all needed printers are available to the spooler
subsystem (most often lp(1)) on the same machine running the X
Print Service.
3. Configure the X Print Server. See ``X Print Server Configuration''.
4. Depending on #1, start the X Print Server process "Xprt", and then
the toolkit-specific Print Dialog Manager Daemon process (such as
CDEnext's "dtpdmd") at the appropriate times. Note that libX‐
printUtils-based applications/toolkits do not need a Print Dialog
Manager Daemon process to use Xprint.
The details are described below.
Because the X Print Service is based on X, it can be easily distrib‐
uted. The most significant factors in which execution model to choose
will be driven by:
· how many printers will be accessable through the printer subsystem on
any given machine. A system administrator may choose to cluster
printers on a few given machines, or scatter them across an organiza‐
tion and possibly make extensive use of remote spoolers to make them
globally available.
· how many machines will need a copy of the X Print Server configura‐
tion files. The files have been architected so that one super-set
version of them can be maintained and distributed (e.g. via NFS), and
a per-machine or per-user version of the `Xprinters' is all that is
needed to have the appropriate information in them utilized or
ignored.
· how many users can demand services from a given X Print Service.
With the above in mind, some obvious execution models include:
· Global - in this model, the system administrator is choosing to run
the X Print Service on a *few* select machines with appropriate
printers configured, and allow clients access to the global resource.
This can centralize the administration of printers and configuration
files, but may have to be monitored for performance loading.
Startup would likely be done by boot-up scripts (such as
/etc/init.d/xprint).
· Per-machine - every machine with potential X Print Service users
would run the service. Printer and configuration file administration
is decentralized, and usage would be limited to the users on the
machine.
Startup would likely be done by boot-up scripts (such as
/etc/init.d/xprint).
· Per-user session - every user would run an entire X Print Service for
themselves. In the future, the Video X Server normally started may
contain Print X Server capability, so this model becomes very natu‐
ral.
Startup would likely be done at session login or by launching actions
or processes manually once the user logs in. Note: Deamons like
"dtpdmd" must be started after Xprt.
Starting of the processes is straight forward. In strict order (example
is for manually starting the X print server for CDEnext usage):
1.
[machineA] % Xprt [-XpFile <Xprinters file>] [:dispNum] &
Note that Xprt will look for configuration files in either a
default location or where XPCONFIGDIR points.
-XpFile specifies an alternate `Xprinters' file, rather than the
default one or `${XPCONFIGDIR}/C/print/Xprinters'.
2.
[machineA] % dtpdmd -d machineA[:dispNum] [-l /tmp/dtpdmd.log] &
The dtpdmd will maintain an X-Selection on the X-Server, and will
start dtpdm's as required to service requests.
In all but the per-user session model, the machine running the dtpdmd
(thus dtpdm's) will need display authorization to the users video dis‐
play.
CLIENT CONFIGURATION
Once a X Print Server and dtpdmd have been started -- many of them in
some cases -- clients will need to find and use them. There are two
mechanisms that allow clients to discover X Print Servers and printers.
· "X Print Specifier" - assuming usage of the DtPrint/XprintUtils-based
print applications, the following notation is understood:
printer_name@machine[:dispNum]
For example:
colorlj7@printhub:2
In the above example, the X Print Server running at `printhub:2' is
assumed to support the printer named `colorlj7'.
· ${XPSERVERLIST} - assuming usage of the DtPrint print dialogs, the
environment variable ${XPSERVERLIST} can contain a list of X Print
Servers. For example:
XPSERVERLIST="printhub:2 printhub:3 otherdept:0"
Then in the dialogs, only a printer name needs to be entered. The
dialog will then search the X Print Servers in ${XPSERVERLIST} for a
server than supports the printer, and then establish contact.
END-USER SEQUENCE
From most CDEnext applications, printing is accomplished by bringing
down the <File> menu and selecting <Print...>. This will result in the
DtPrintSetupBox dialog, which will request the name of a printer, and
offer limited capability to configure print options (e.g. number of
copies). If the user wishes, they can select <Setup...>, which will
start a dtpdm capable of modifying additional print options. Finally,
the user should select <Print>.
ENVIRONMENT
${XPCONFIGDIR}
This environment variable points to the root of the Xprint
server configuration directory hierarchy. If the variable is
not defined, the default path is be assumed. The default path
may be /usr/X11R6/lib/X11/xserver/, /usr/lib/X11/xserver/,
/usr/share/Xprint/xserver/ or /usr/openwin/server/etc/XpConfig,
depending on the system, and may be configured in
/etc/init.d/xprint.
${LANG}
This environment variable selects the locale settings used by
the Xprint server. Xprt allows language-specific settings
(stored in ${XPCONFIGDIR}/${LANG}/print/) which will override
the default settings (stored in ${XPCONFIGDIR}/C/print/). If
${LANG} is not set "C" is assumed.
${XPSERVERLIST}
The environment variable ${XPSERVERLIST} contains a list of dis‐
play identifiers (separated by whitespace) which tell an appli‐
cation where it can find the Xprint servers. Usually
${XPSERVERLIST} is set by the profile startup scripts (e.g.
/etc/profile or /etc/profile.d/xprint.sh) using the output of
/etc/init.d/xprint get_xpserverlist.
Example:
export XPSERVERLIST="`/etc/init.d/xprint get_xpserverlist`"
Alternatively ${XPSERVERLIST} can be set manually. Example:
export XPSERVERLIST="littlecat:80 bitdog:72"
instructs an application to find an Xprint server at display 80
on the machine "littlecat" and at display 72 on the machine big‐
dog.
${XPRINTER}
The environment variable ${XPRINTER} defines the default printer
used by print applications. The syntax is either printername or
printername@display.
Examples:
XPRINTER=ps003
tells an application to look for the first printer named
"ps003" on all Xprint servers.
XPRINTER=hplaser19@littlecat:80
tells an application to use the printer "hplaser19" on
the Xprint server at display "littlecat:80".
If ${XPRINTER} is not set the applications will examine the values of
the ${PDPRINTER}, ${LPDEST}, and ${PRINTER} environment variables (in
that order).
SEE ALSOX11(7), xplsprinters(1), xprehashprinterlist(1), xphelloworld(1),
xpxmhelloworld(1), xpawhelloworld(1), xpxthelloworld(1), xpsimplehel‐
loworld(1), Xserver(1), Xprt(1), libXp(3), libXprintUtils(3), libX‐
printAppUtils(3), XmPrintShell(3), XawPrintShell(3), Xprint FAQ
(http://xprint.mozdev.org/docs/Xprint_FAQ.html), Xprint main site
(http://xprint.mozdev.org/)
AUTHORS
This manual page was written by Roland Mainz <roland.mainz@nrubsig.org>
based on the original X11R6.6 xc/programs/Xserver/XpConfig/README.
8 October 2004 Xprint(7)
