Foomatic Database
=================


foomatic-db
-----------

The collected knowledge about printers, drivers, and driver options in
XML files, used by foomatic-db-engine to generate PPD files.


Grant Taylor <gtaylor@picante.com>
Till Kamppeter <till.kamppeter@gmx.net>

http://www.linuxprinting.org/

This README contains mainly info for developers. See the file USAGE if
you want to know how to use Foomatic.


Copying
-------

To most of this package the GPL applies (see http://www.gnu.org/),
exception are the PPD files in db/source/PPD, they can have different
licenses (mostlu MIT), see the comments in the beginning of the PPD
files.

If you spot a data error or any other bug, send mail describing the bug to
foomatic-devel@linuxprinting.org

General discussion happens in the foomatic-devel forum/list thing at
www.linuxprinting.org.


Intro
-----

This is the stable version of Foomatic. See

http://www.linuxprinting.org/contribute.html#programming
http://www.linuxprinting.org/pipermail/foomatic-devel/2002q3/thread.html
http://www.linuxprinting.org/pipermail/foomatic-devel/2002q4/thread.html
http://www.linuxprinting.org/kpfeifle/LinuxKongress2002/Tutorial/IV.Foomatic-Developer/IV.tutorial-handout-foomatic-development.html

to know more about its development.

Your suggestions, bug reports, patches, ... are welcome on

http://www.linuxprinting.org/newsportal/thread.php3?name=linuxprinting.foomatic.devel

This database is the base of our web site:

http://www.linuxprinting.org/


Programs and important files from this package
----------------------------------------------

configure.in

  The source from which GNU autoconf generates the "configure" script

acinclude.m4

  Additional macros for the "configure" script

make_configure

  Calls aclocal and autoconf to generate "configure" from "configure.ac" 
  and "acinclude.m4"

Makefile.in

  The template from which "configure" generates the Makefile

install-sh

  Helper script for "configure"

db/

  The XML database. See below.


Dependencies
------------

This package does not require anything else. It is needed by
foomatic-db-engine, the database engine of Foomatic. It is required to
use foomatic-db-engine 3.0.1 or newer, as it contains important bug
fixes and also support for nested composite options. Do not use this
database with Foomatic 3.0.0 or older, the nested composite options
will probably appear but they will not work.

Foomatic 3.0.0 or newer support also string, password, options, but
they are not used yet in the Foomatic database,

See the USAGE file for installation details.


About the database
------------------

The database is provided by the "foomatic-db" package, additional database
entries are in "foomatic-db-hpijs", other "foomatic-db-..." packages or are
supplied with the drivers. "foomatic-db" is required for using the programs
provided by this package.

There is a $libdir, somewhere.  Underneath $libdir there are (Install
"foomatic-db" at first and then this package. Then the $libdir will be
auto-detected):

 db/                             - the database
 db/oldprinterids                - translation table for old numerical
				   printer IDs
 db/kitload.log                  - list of third-party "kit" files
 db/source/                      - "source" data, provided by humans, etc
 db/source/printer/<poid>.xml    - printer-specific data, one per printer id
 db/source/driver/<driver>.xml   - driver-specific data, one per driver name
 db/source/opt/<idx>.xml         - option data, one file per option

You can edit the files whenever you want and regenerate the affected
printer queues with foomatic-configure, there is no on-disk cache (it
is not needed, the database handling is fast enough), the data is
always directly derived from the source files. So you changes will be
taken into account without any special steps.


Data
----

There are three main source datafiles; annotated examples:

source/opt/2.xml
================

# Every option exists independently from printers or drivers, because
# they might apply to arbitrary combinations of printers and/or
# drivers.  In practice, some drivers have wholly unique options
# (gimp-print/stp, for example), while others (lots of generic basic
# Ghostscript drivers, for example) share some options.

<option type="enum" id="opt/2">

# Options are of a type "enum", "bool", "int", "float", "string", or
# "password", options have an ID.  The id is also the filename.

# The shortname is a spaceless short name for the thing.  It must not
# contain / or : (otherwise it will not be handled correctly in PPD
# files). It should be one of the standard Adobe PPD option names if
# apropriate

  <arg_shortname>

# Various things here, and all <comments>, are internationalized.
# They take the usual posix locale codes in the form xx[_YY], where xx
# is a two-letter iso language code, and YY is two-letter country code
# to distinguise differing national dialects.
#
# Generally the national dialects won't be very common or necessary
# here.  The backends currently require that <en> content be provided.

   <en>PageSize</en><!-- backends only know <en> shortnames! -->
  </arg_shortname>

# The longname is a short phrase describing the thing in more detail
# GUI tools usually show longnames

  <arg_longname>
   <en>Page Size</en>
  </arg_longname>

# The comments are used to form documentation.  In theory these can
# become man pages or the like.

  <!-- A multilingual <comments> block can appear here, too;
       it should be treated as documentation for the user. -->

# The execution section describe how the backend should execute this
# option. The order and spot apply to the *driver*'s prototype for
# <arg_substitution /> (once called commandline) style options, or
# just the order applies for <arg_postscript /> and <arg_pjl />
# options. The order and the <arg_section> go into the "*OrderDependency"
# line of the appropriate option entry in the PPD file, for this example
# one would get

#    *OrderDependency: 100 DocumentSetup *PageSize

# When no <arg_section> is given, "AnySetup" is used as a default.

# For <arg_substitution /> options the <arg_proto> is inserted into
# the driver's command line, at the spot (e. g. "%A") whose letter is
# given between the <arg_spot>...</arg_spot> tags, the <arg_proto> of
# an <arg_postscript /> option is a snippet of PostScript code which
# is inserted into the PostScript data stream of the job, for
# DSC-conforming PostScript into the section specified with
# <arg_section>, otherwise in the beginning. The <arg_proto> lines of
# <arg_pjl /> options are PJL commands which are sent to the printer
# before the output of the driver's command line is sent. Because this
# only works reliably when the driver output does not have its own PJL
# command header, these options are ignored when the driver's XML file
# is marked with a <nopjl /> tag in its <execution> section. Drivers
# which produce their own PJL and therefore are marked with <nopjl />
# are for example "hpijs" and "hl1250". There is also the
# <arg_composite /> execution style for composite options, see the
# "Composite Options" section below. The user's value gets put into
# the <arg_proto>'s %s location. 

# The <arg_group>...</arg_group> tags put the option into the PPD
# option group named here. In many PPD-based GUIs ("kprinter", "xpp",
# OpenOffice.org, ...) every group is shown as a tab or a tree branch
# containing the member options of this group. You can also specify
# subgroups. Then you have to use a "group path" similar to directory
# paths, with the group and subgroup names separated by slashes
# (<arg_group>General/Paper</arg_group> is the "Paper" subgroup in the
# "General" group). Subgroups are not recommended as there is no GUI
# supporting them. If an option is member of a composite option (See
# "Composite Options" section below), the <arg_group>...</arg_group>
# tags will be ignored.

  <arg_execution>
   <arg_group>General</arg_group>
   <arg_order>100</arg_order>
   <arg_section>DocumentSetup</arg_section>
   <arg_spot>Z</arg_spot>
   <arg_postscript />
   <arg_proto>&lt;&lt;/PageSize[%s]/ImagingBBox null&gt;&gt;setpagedevice</arg_proto>
  </arg_execution>

# The constraints define what printer/driver combinations this option
# applies to.  The *most specific* constraint rules the day; it's
# "sense" says whether or not the option is "in".  The winning
# constraint also provides the default value used when this option
# applies to that printer and driver.

# Constraint elements are: driver, make, model.  The driver is the
# driver name, or not present to apply to any driver.  The make is the
# printer make, or not present to apply to any printer make.  The
# model is the driver model, or not present to apply to any printer.
# Instead of make/model, you can also specify <printer>id</printer>.

# IMPORTANT: The make and model must match the one in the printer xml
# definition, and everywhere else in the other options. One needs to
# write a utility to change printer names sensibly.

# It is illegal to have a model with no make.

# It is illegal to have none of make/model/driver.

# It is illegal to have *no* constraints, or at least such options are
# never used.

# For enum options, the defval is the id of the enum_val that is the
# default.  For other option types, it is the actual default value
# (ie, a number, or 1 or 0 for boolean, etc).

  <constraints>
     <constraint sense="true">
      <driver>sj48</driver>
      <arg_defval>ev/1</arg_defval>
     </constraint>
     <constraint sense="true">
      <driver>r4081</driver>
      <arg_defval>ev/1</arg_defval>
     </constraint>
# A gajillion constraings deleted
  </constraints>
  <enum_vals>
   <enum_val id="ev/1">
    <ev_longname>
     <en>US Letter</en>
    </ev_longname>
    <!-- A multilingual <comments> block can appear here, too;
         it should be treated as documentation for the user. -->
    <ev_shortname>
     <en>Letter</en>
     <!-- Until someone tells me how to learn the user locale in 
          backends, the shortname must be monolingual in <en>! -->
    </ev_shortname>

# If present, the driverval is what gets substituted in for the %s in
# the option's prototype.  This way the user-visible stuff can be
# anything.

    <ev_driverval>612 792</ev_driverval>

# This enum_val has no constraints.  It *is* OK for enum_vals to
# have no constraints; they are assumed to apply unless
# constrained otherwise.

   </enum_val>
   <enum_val id="ev/115">
    <ev_longname>
     <en>A3</en>
    </ev_longname>
    <!-- A multilingual <comments> block can appear here, too;
         it should be treated as documentation for the user. -->
    <ev_shortname>
     <en>A3</en>
     <!-- Until someone tells me how to learn the user locale in 
          backends, the shortname must be monolingual in <en>! -->
    </ev_shortname>
    <ev_driverval>842 1191</ev_driverval>

# Here are some example constraints for an enum_val.  The A3 size
# paper doesn't fit on lots of printers, so there are various
# constraints to make the right thing happen.

    <constraints>
     <constraint sense="true">
      <driver>ml85p</driver>
      <arg_defval>na</arg_defval>
     </constraint>
     <constraint sense="true">
      <make>HP</make>
      <model>DeskJet 1000C</model>
      <driver>pnm2ppa</driver>
      <arg_defval>na</arg_defval>
     </constraint>
     <constraint sense="false">
      <make>HP</make>
      <model>DeskJet 820C</model>
      <driver>pnm2ppa</driver>
      <arg_defval>na</arg_defval>
     </constraint>

     # lots more...

    </constraints>
   </enum_val>
  </enum_vals>
</option>

# To allow custom page sizes to be used one has add a choice with the
# "<ev_shortname>" being "Custom" to the "PageSize" option (example
# below). This choice will be treated as the custom page size. When
# the user selects this choice, he has to provide the width and the
# height of the page in addition. These values are converted into
# PostScript points (1/72 inches) and inserted into placeholders in
# the "<ev_driverval>" of this choice. The "<ev_driverval>" should
# contain a placeholder "%0" for the page width and "%1" for the page
# height. Alternatively the "<ev_driverval>" can contain two zeros
# ("0") from which the first will be replaced by the page width and
# the second by the page height. Then one gets Adobe-compliant entries
# for the custom page size in the PPD files and one can set a custom
# page size with the following commands:

# CUPS: lpr -P huge -o PageSize=Custom.500x750cm bigposter.ps
# LPRng: lpr -P huge -Z PageSize=Custom.500x750cm bigposter.ps
# GNUlpr: lpr -P huge -o PageSize=Custom.500x750cm bigposter.ps
# LPD: lpr -P huge -JPageSize=Custom.500x750cm bigposter.ps
# PPR (RIP): ppr -P huge -F "*PageSize Custom" --ripopts 500x750cm
#          bigposter.ps
# PPR (Int.): ppr -P huge -F "*PageSize Custom" -i 500x750cm bigposter.ps
# PDQ: pdq -P huge -oPageSize_Custom -aPageWidth=500
#          -aPageHeight=750 -oPageSizeUnit_cm bigposter.ps
# No spooler: foomatic-rip -P huge -o PageSize=Custom.500x750cm
#	   bigposter.ps

# Here is an example for a custom page size setting:

#   <enum_val id="ev/PageSize-Custom">
#    <ev_longname>
#     <en>Custom size</en>
#    </ev_longname>
#    <!-- A multilingual <comments> block can appear here, too;
#         it should be treated as documentation for the user. -->
#    <ev_shortname>
#     <en>Custom</en>
#     <!-- Until someone tells me how to learn the user locale in 
#          backends, the shortname must be monolingual in <en>! -->
#    </ev_shortname>
#    <ev_driverval>%0 %1</ev_driverval>
#   </enum_val>

# The entry

#    <ev_driverval>0 0</ev_driverval>

# would have the same effect as the <ev_driverval> of the example.

# For numerical (int, float) and bool options there is no <enum_vals>
# section. Instead of this section numerical options have tags to
# specify minimum and maximum value:

#  <arg_max>10.0</arg_max>
#  <arg_min>0.0</arg_min>

# For the %s in the <arg_proto> a number, either the user's choice
# when he has specified this option or the default value is
# inserted. Only numbers between the minimum and the maximum and in
# case of int options only integer numbers are allowed.

# Bool options can be set or not be set. There <arg_proto> will be
# inserted if they are set, nothing if they are not set. A %s in the
# <arg_proto> is not allowed, there is nothing to insert for it. As
# <arg_defval> in the option's constraints one can use 0 for not
# setting the option by default or 1 for setting it by default.

# Bool options need the specification of a name for the case when they
# are not set. This will be used by GUIs and in PPD files:

#  <arg_shortname_false>
#    <en>CorrectBlack</en><!-- Backends only know <en> shortnames! -->
#  </arg_shortname_false>

# This name should not contain spaces, ":", or "/".

# See below for string and password options.

printer/HP-LaserJet_4000.xml
============================

# The printer file contains information specific to a particular
# printer.

<printer id="printer/HP-LaserJet_4000">

# Make and model are not internationalized.  There will eventually be
# an "alias" mechanism, but the need is different.

  <make>HP</make>
  <model>LaserJet 4000</model>

# According to the Adobe specifications for PPD files every PPD file
# must contain a unique DOS-compatible file name (the "*PCFileName"),
# a file name with an up to 8 characters log base name and an up to 3
# characters long extension, and upper and lower case letters being
# considered as equal. As every PPD file is for a printer/driver
# combo, we let the first 6 characters being provided by the printer
# entry:

  <pcmodel>HPLJ4K</pcmodel>

# The first two characters should be the manufacturer prefix as listed
# in Appendix D of Adobe's "PostScript Printer Description (PPD) File
# Format Specification Version 4.3", available on

# http://partners.adobe.com/public/developer/en/ps/5003.PPD_Spec_v4.3.pdf

# Various stuff about the machine

  <mechanism>

# Printer types can be <laser />, <led />, <inkjet />, <dotmatrix />,
# <impact />, <sublimation />, <transfer />. Other types we have to
# add to the CGI script on linuxprinting.org to make the web interface
# displaying them properly.

    <laser/>

# At some point we can make color be less of a boolean flag and more
# of a section full of goodies.

    <!--not "color"-->
    <resolution>

# In theory this is a list.  In practice We've only got one per
# printer which is the maximum resolution the manufacturer claims
# for this printer.

      <dpi>
        <x>1200</x>
        <y>1200</y>
      </dpi>
    </resolution>

    <consumables>

# Information about ink, drums, etc.
# The comments are supposed to be qualitative ("Separate drum and
# toner cartridges")

      <comments>
        <en>toner</en>
      </comments>

# There should be <partno>12A1975</partno> elements with manufacturer
# part numbers for the various carts, etc it takes. Then one could
# have a price watcher thingy like there is now for the printers.

      <!--one or more "partno" elements.-->
    </consumables>
  </mechanism>

  <url>http://www.pandi.hp.com/pandi-db/prod_info.show?model=C4118A&amp;name=LaserJet4000</url>

# The lang section.  In practice this will be only minimally useful;
# 
#  - Backends can pstops the ps down a level if needed
#  - Backends know if pjl options apply
#  - Backends can know if "quick text" will work
#
# Commonly used language tags: <pcl level="x" />, <escp2 />, <proprietary />

  <lang>
    <postscript level="2">
    <!--unknown ppd filename "ppd"--></postscript>
    <pjl/>
    <text>
      <charset>us-ascii</charset>
    </text>
  </lang>

# The autodetection stuff

  <autodetect>

# There are three ways to auto-detect a printer, via the parallel port
# (<parallel>...</parallel>), the USB (<usb>...</usb>), or SNMP
# (TCP/Socket-connected printer, <snmp>...</snmp>). Through these
# interfaces the printers report back an IEEE-1284-complient ID string
# from which the fields "MFG" (<manufacturer>...</manufacturer>),
# "MDL" (<model>...</model>), "DES" (<description>...</description>),
# and "CMD" (<commandset>...</commandset>) are used. The string itself
# can be put between <ieee1284>...</ieee1284> tags, but all items
# which are not constant for all printers of this model, as the serial
# number ("SERN:...;") and the device status ("VSTATUS:...;") have to
# be removed here. As the ID string is usually the same for all
# detection methods, one can put the entries between
# <general>...</general> tags, then the <parallel>...</parallel>,
# <usb>...</usb>, and <snmp>...</snmp> are only used for
# differences to the data between the <general>...</general> tags. A
# complete entry could look like:
#
#  <autodetect>
#    <general>
#      <ieee1284>MFG:HEWLETT-PACKARD;MDL:DESKJET 600;CMD:MLC,PCL,PML;CLASS:PRINTER;DESCRIPTION:Hewlett-Packard DeskJet 600;</ieee1284>
#      <commandset>MLC,PCL,PML</commandset>
#      <description>Hewlett-Packard DeskJet 600</description>
#      <manufacturer>HEWLETT-PACKARD</manufacturer>
#      <model>DESKJET 600</model>
#    </general>
#  </autodetect>
#

# On Linux you find this info for the parallel ports (/dev/lp<N>, <N>
# = 0, 1, 2, ...) in the files
#
#   /proc/sys/dev/parport/parport0/autoprobe*
#
# for the USB under Linux it is more complicated, easiest is to use a little
# Perl script, called "getusbprinterid.pl":

# --------------------------------------------------------------------------

#!/usr/bin/perl

open FILE, "$ARGV[0]" or die;

my $result;
# Calculation of IOCTL function 0x84005001 (to get device ID string):
# len = 1024
# IOCNR_GET_DEVICE_ID = 1
# LPIOC_GET_DEVICE_ID(len) = _IOC(_IOC_READ, 'P', IOCNR_GET_DEVICE_ID, len)
# _IOC(), _IOC_READ as defined in /usr/include/asm/ioctl.h

ioctl(FILE, 0x84005001, $result) or die;
close FILE;

# Cut resulting string to its real length
my $length = ord(substr($result, 1, 1)) + (ord(substr($result, 0, 1)) << 8);
$result = substr($result, 2, $length-2);

# Remove non-printable characters
$result =~ tr/[\x0-\x1f]/\./;
print "$result\n";

# --------------------------------------------------------------------------

# Running the program with "./getusbprinterid.pl /dev/usb/lp0" returns the
# ID string of the device on /dev/usb/lp0.

    <!--no known parport probe information-->
  </autodetect>

# Our grading system.  It's US-style letter grades A, B, D, and F,
# which the website shows as "Perfectly", "Mostly", "Partially" and
# "Paperweight" .
# THERE IS NO `C'!!!

  <functionality>A</functionality>

# Arguably, the scores should live with the printer/driver association
# and not on the printer, but then it's a big hassle to figure out if
# a printer works... So the score is the one reached with the driver
# working best, the "recommended" driver.

# There's a spot for this "recommended" driver, usually the driver
# which gives the maximum output quality. It is for user information
# on the web site, but newbie-friendly printer setup GUIs should use
# it, too. Unfortunately, only "printerdrake" of Mandrake Linux makes
# use of it.

  <!--unknown preferred "driver"-->

# The <unverified /> tag was on all printer entries which were
# formerly entered by visitors using the web printer input interface
# as the database was still PostGreSQL-driven.

  <!--not "unverified"-->

# If there is a web site with additional interesting info about this
# printer, it can be mentioned in the entry by putting it between
# <contrib_url>...</contrib_url> tags,

  <!--no "contrib_url"-->

# The regular notes section.  The allowed tags are: <p>, <a
# href="foobar"> </a> and many other simple tags (<b>, <i>, <tt>,
# ...). Not that to distinguish what is XML and what is the embedded
# HTML, make the following replacements:
#
#   < --> &lt;
#   > --> &gt;
#   " --> &quot;
#   ' --> &apos;
#   & --> &amp;
#

  <comments>
    <en>
    I don&apos;t believe this:&lt;p&gt;

    &lt;i&gt;1200x1200 dpi only possible with Windows drivers,
    600x600 can be reached w/o particular software.
    The difference is visible, but only slightly, so
    the Functionality got &quot;Mostly&quot;&lt;p&gt;&lt;/i&gt;&lt;p&gt;

    Do the following:&lt;p&gt;

    Set the resolution on the front panel to &quot;Prores 1200&quot;, not
    to &quot;Fastres 1200&quot;. When you use CUPS with HPs PPD file, turn
    off &quot;Fastres 1200&quot; in the printer configuration
    options.&lt;p&gt;

    Try the generic PostScript PPD file which comes with KUPS 1.0 or newer.
    </en>
  </comments>
</printer>


driver/md2k.xml
===============

The driver files contain information about drivers.  There are a few
things, but the two biggies are the prototype and the printers list

<driver id="driver/md2k">
 <name>md2k</name>

# According to the Adobe specifications for PPD files every PPD file
# must contain a unique DOS-compatible file name (the "*PCFileName"),
# a file name with an up to 8 characters log base name and an up to 3
# characters long extension, and upper and lower case letters being
# considered as equal. As every PPD file is for a printer/driver combo,
# we let the last 2 characters being provided by the driver entry:

 <pcdriver>M2</pcdriver>
 <url>http://plaza26.mbn.or.jp/~higamasa/gdevmd2k/</url>
 <execution>

# Driver types are 
#
#  <ghostscript /> : The driver code is compiled into GhostScript
#
#  <filter /> :      The driver code is a separate executable, either a
#                    filter which converts generic bitmap output of
#                    GhostScript to the printer's language, a wrapper 
#                    around GhostScript, or an IJS plug-in.
#
#  <uniprint /> :    A uniprint driver, consisting of one or more .upp
#                    files for GhostScript.
#
#  <postscript /> :  A driver which has PostScript also as output (for 
#                    PostScript printers). It usually does not call
#                    GhostScript but only applies the user's option
#                    settings to the data stream. But GhostScript can
#                    be called here, too, as for downgrading to a lower
#                    PostScript level.
#
# The driver type only provides information for the web pages, it is not
# used when generating config files for a spooler.

# The driver's <execution> section can also contain a
#
# <nopjl />
#
# which suppresses the usage of PJL options (options which send PJL
# commands to the printer). This one does with drivers where the
# driver itself already produces a PJL header, the second one built
# by the PJL options would then be ignored by the printer, and so
# this kind of options does not make sense. Such driver are for
# example "hpijs" and "hl1250".

# The prototype defines what command the backends run to drive this
# printer.  It must take postscript on stdin and generate "printer
# stuff" on stdout.  Various %A, %B, etc substitution "spots" are
# specified; this is where substition options will be placed.

  <prototype>gs -q -dBATCH -dSAFER -dQUIET -dNOPAUSE -sDEVICE=md2k%A%Z -sOutputFile=- -</prototype>
 </execution>
 <comments>
  <en>
    Part of the gdevmd2k-0.2a package by Shinya Umino.  The web page and
    documentation are in Japanese.
    &lt;a href="/clippings/MD5000-translation.txt"&gt;Here&lt;/a&gt;
    is an English translation of the driver's web page, and &lt;a
    href="/clippings/alpsmd.txt"&gt;here&lt;/a&gt; is the README from the
    driver package.
  </en>
 </comments>

# The printer list is a simple list of printers that this driver works
# with.  Historically, these "bits" were on the printer cgi form page,
# but now they're put here.

 <printers>
  <printer>
   <id>printer/Alps-MD-1000</id><!-- Alps MD-1000 -->
  </printer>
  <printer>
   <id>printer/Alps-MD-1300</id><!-- Alps MD-1300 -->
  </printer>
  <printer>
   <id>printer/Alps-MD-2000</id><!-- Alps MD-2000 -->
  </printer>
  <printer>
   <id>printer/Alps-MD-4000</id><!-- Alps MD-4000 -->
  </printer>
 </printers>
</driver>

# In the printer list it is also possible to place comments specific to
# a certain printer/driver pair:
#
#  <printer>
#   <id>printer/HP-LaserJet_4050</id><!-- HP LaserJet 4050 -->
#   <comments>
#    <en>to 1200dpi</en>
#   </comments>
#  </printer>


Composite Options
-----------------

This is a new option type to make it easier for users to choose the
best settings for a certain printing task, even if the driver has very
many options. The idea is to have an enumerated choice option which
does not directly modify something in the driver's command line but
sets several of the other options.

One example is the "PrintoutMode" option which will be made available
for all printer/driver combos which have at least one option regarding
the printout quality or document type. 

The possible choices should be the same for every printer and driver,
so that users (especially newbies) can bring their printers in the
right mode by choosing one easy to understand item from a menu instead
of having to switch several cryptic driver options. For now the
choices are the following:

   Command line  GUI                Intention
   -----------------------------------------------------------------------
   Draft         Draft              Very fast, ink/toner-saving printout
   Normal        Normal             Quick standard quality printout
   High          High Quality       High quality for plain paper
   VeryHigh      Very High Quality  Highest quality for plain/inkjet paper
   Photo         Photo              Highest quality for photo paper

These choices can also have one of the following modifiers:

   Modifier      Intention
   -----------------------------------------------------------------------
   .Gray         Grayscale printing on a color printer
   .Mono         Monochrome printing (no grayscales, black or white)

Examples:

   Command line   GUI                      Comment
   ---------------------------------------------------------------------
   High.Gray      High Quality Grayscale
   Photo          Photo                    Color photos on color printer
   VeryHigh.Mono  Very High Quality Monochrome  Really black text in
                                           highest quality on inkjet
                                           printer, not suitable for
                                           halftone images.
   Normal         Normal                   Standard color in 300/360 dpi
                                           on normal paper, grayscale
                                           on black-and-white printers

Not all choices/combinations of basic choices and modifiers must be
present. Often modes are simply not available on certain
printer/driver combos, as "Photo" on most lasers. It is highly
recommended to have "Normal" available, though (and having this the
default).

The GUI names can have additional remarks in parantheses, for example
when manual intervention (other cartridge, photo paper) is needed.

To add such an option to the database, one only needs to add an option
XML file like the one below into the db/source/opt directory of the
database. The file db/source/opt/pcl3-PrintoutMode.xml could look
like this:

--------------------------------------------------------------------------
<option type="enum" id="opt/pcl3-PrintoutMode">
  <!-- A multilingual <comments> block can appear here, too;
       it should be treated as documentation for the user. -->
  <arg_longname>
   <en>Printout Mode</en>
  </arg_longname>
  <arg_shortname>
   <en>PrintoutMode</en><!-- backends only know <en> shortnames! -->
  </arg_shortname>
  <arg_execution>
   <arg_order>10</arg_order>
   <arg_section>AnySetup</arg_section>
   <arg_spot>A</arg_spot>
   <arg_composite />
   <!-- <arg_proto></arg_proto> -->
  </arg_execution>
  <constraints>
     <constraint sense="true">
      <driver>pcl3</driver>
      <arg_defval>ev/pcl3-PrintoutMode-Normal</arg_defval>
     </constraint>
  </constraints>
  <enum_vals>
   <enum_val id="ev/pcl3-PrintoutMode-Draft">
    <ev_longname>
     <en>Draft</en>
    </ev_longname>
    <!-- A multilingual <comments> block can appear here, too;
         it should be treated as documentation for the user. -->
    <ev_shortname>
     <en>Draft</en>
     <!-- Until someone tells me how to learn the user locale in
          backends, the shortname must be monolingual in <en>! -->
    </ev_shortname>
    <ev_driverval>MediaType=Plain Resolution=150 Quality=Draft IntensityRendering=Halftones Passes=1</ev_driverval>
   </enum_val>
   <enum_val id="ev/pcl3-PrintoutMode-Normal">
    <ev_longname>
     <en>Normal</en>
    </ev_longname>
    <!-- A multilingual <comments> block can appear here, too;
         it should be treated as documentation for the user. -->
    <ev_shortname>
     <en>Normal</en>
     <!-- Until someone tells me how to learn the user locale in
          backends, the shortname must be monolingual in <en>! -->
    </ev_shortname>
    <ev_driverval>MediaType=Plain Resolution=300 Quality=Normal IntensityRendering=Halftones Passes=1</ev_driverval>
   </enum_val>
   <enum_val id="ev/pcl3-PrintoutMode-High">
    <ev_longname>
     <en>High</en>
    </ev_longname>
    <!-- A multilingual <comments> block can appear here, too;
         it should be treated as documentation for the user. -->
    <ev_shortname>
     <en>High</en>
     <!-- Until someone tells me how to learn the user locale in
          backends, the shortname must be monolingual in <en>! -->
    </ev_shortname>
    <ev_driverval>MediaType=Plain Resolution=600 Quality=Presentation IntensityRendering=FloydSteinberg Passes=4</ev_driverval>
   </enum_val>
   <enum_val id="ev/pcl3-PrintoutMode-Photo">
    <ev_longname>
     <en>Photo (on photo paper)</en>
    </ev_longname>
    <!-- A multilingual <comments> block can appear here, too;
         it should be treated as documentation for the user. -->
    <ev_shortname>
     <en>Photo</en>
     <!-- Until someone tells me how to learn the user locale in
          backends, the shortname must be monolingual in <en>! -->
    </ev_shortname>
    <ev_driverval>MediaType=Premium Resolution=600 Quality=Presentation IntensityRendering=FloydSteinberg Passes=4</ev_driverval>
   </enum_val>
  </enum_vals>
</option>
--------------------------------------------------------------------------

The shown option is only an example, it is neither in the CVS nore
will it work with all printers which use the "pcl3" driver. You can
paste it into a file (make the <ev_driverval>"s being one line, the
items separated by spaces) and copy it to db/source/opt/ to try it
out.

The "<arg_composite />" tag for the execution style specifies it as a
composite option. The <arg_spot> and <arg_proto> are meaningless in a
composite option and the "<ev_driverval>"s contain a space-separated
list of all settings of which the pre-made configuration represented
by this choice consists. Every choice of the composite option must set
EXACTLY THE SAME individual options. In no choice it is allowed to
leave out one of them. These individual options are the member options
of the composite option. Not all options of a driver/printer combo
need to be member options of the composite option. It is not allowed
to have one option being member of more than one composite option. The
composite option must be an enumerated choice options, the member
options must be enumerated choice or boolean options. Member options
can even be composite options, so composite options can be nested.

It is enough to add a composite option as shown. The PPD generator
(getppd() in lib/Foomatic/DB.pm, package "foomatic-db-engine") will
take care of the rest. It will

   - Order all member options into a group (PPD group, see "Option
     Grouping" below) named after the composite option.

   - Add to every member option the choice "Controlled by '<name of
     the composite option>'" and make this choice the default. If this
     is chosen, the composite option will set the value for this
     member, depending on what value is chosen for the composite
     option. If the user chooses something else than "Controlled by
     '<name of the composite option>'" the member option does not obey
     the setting given by the composite option. So the advanced user
     can also set the member options individually.

   - If necessary the <arg_order> and <arg_section> of the composite
     option is replaced by other values in the PPD file, so that the
     composite option will be stuffed into the PostScript data stream
     always before all its member options. Do not give "0" as the
     order number to any of the member options.

A composite option can also span only one (but not zero) member
option. This is for example done with the "PrintoutMode" option of the
HPIJS driver ("foomatic-db-hpijs" package). This driver has only one
option for setting resolution and quality, but this options has
sometimes many choices with rather cryptic names. The "PrintoutMode"
maps to the most important choices with the above-mentioned names, and
in addition, these names are the same as of the "PrintoutMode" options
of other drivers, so the user finds the important printing modes more
easily.

The facility of composite options can also be used for other things
than for a "PrintoutMode" option, for example a finisher could be
controlled by a composite option (to have the most common finishing
tasks as "Bound booklet", "Stapled booklet", "Letter in envelope",
...).


Forced Composite Options
------------------------

Forced composite options are very similar to composite options, but the
user cannot set the individual member options, but only the composite
option (the user is forced to use the composite option). This allows
options acting at two or more places.

Example: A printer driver is a filter which converts a generic bitmap
produced by GhostScript to the printer's native format. The command
line for converting PostScript to the printer's language could look like this

gs -q -dBATCH -dSAFER -dNOPAUSE -sDEVICE=bitcmyk -r600 -sOutputFile=-
- | filter -size=<width>x<height>

where <width> and <height> is the page size in points (1/72
inches). In addition, GhostScript needs to know the page size. For
this one usually puts the following PostScript code into the
PostScript input file:

<</PageSize[<width> <height>]/ImagingBBox null>>setpagedevice

where <width> and <height> is again the page size in points. So we
need two options for setting the page size, one PostScript option to
set the page size for GhostScript and one command line option to set
the page size for the filter. The user would have to change both when
he wants to print on another paper size, and it does not make sense to
have different settings for the two. So one could make the "PageSize"
option a composite option of the two, but then the GUI exposes an ugly
"PageSize" group with the two individual options. To avoid this, one
uses a forced composite option ("Forced" because the user is forced to
use the composite option, the individual member options are not
accessible).

Assuming that the name of the PostScript option for the page size is
"GSPageSize", the name of the page size option for the filter is
"filterPageSize" and both have the choices "A4", "Letter", and
"Legal", the forced composite option named "PageSize" would look as
follows:

--------------------------------------------------------------------------
<option type="enum" id="opt/filter-PageSize">
  <!-- A multilingual <comments> block can appear here, too;
       it should be treated as documentation for the user. -->
  <arg_longname>
   <en>Page Size</en>
  </arg_longname>
  <arg_shortname>
   <en>PageSize</en><!-- backends only know <en> shortnames! -->
  </arg_shortname>
  <arg_execution>
   <arg_order>10</arg_order>
   <arg_section>AnySetup</arg_section>
   <arg_spot>A</arg_spot>
   <arg_forced_composite />
  </arg_execution>
  <constraints>
     <constraint sense="true">
      <driver>filter</driver>
      <arg_defval>ev/filter-PageSize-Letter</arg_defval>
     </constraint>
  </constraints>
  <enum_vals>
   <enum_val id="ev/filter-PageSize-Letter">
    <ev_longname>
     <en>Letter</en>
    </ev_longname>
    <!-- A multilingual <comments> block can appear here, too;
         it should be treated as documentation for the user. -->
    <ev_shortname>
     <en>Letter</en>
     <!-- Until someone tells me how to learn the user locale in
          backends, the shortname must be monolingual in <en>! -->
    </ev_shortname>
    <ev_driverval>GSPageSize=Letter filterPageSize=Letter</ev_driverval>
   </enum_val>
   <enum_val id="ev/filter-PageSize-Legal">
    <ev_longname>
     <en>Legal</en>
    </ev_longname>
    <!-- A multilingual <comments> block can appear here, too;
         it should be treated as documentation for the user. -->
    <ev_shortname>
     <en>Legal</en>
     <!-- Until someone tells me how to learn the user locale in
          backends, the shortname must be monolingual in <en>! -->
    </ev_shortname>
    <ev_driverval>GSPageSize=Legal filterPageSize=Legal</ev_driverval>
   </enum_val>
   <enum_val id="ev/filter-PageSize-A4">
    <ev_longname>
     <en>A4</en>
    </ev_longname>
    <!-- A multilingual <comments> block can appear here, too;
         it should be treated as documentation for the user. -->
    <ev_shortname>
     <en>A4</en>
     <!-- Until someone tells me how to learn the user locale in
          backends, the shortname must be monolingual in <en>! -->
    </ev_shortname>
    <ev_driverval>GSPageSize=A4 filterPageSize=A4</ev_driverval>
   </enum_val>
  </enum_vals>
</option>
--------------------------------------------------------------------------

This looks exactly like a usual composite option and works also the
same way. The only difference is that instead of an "<arg_composite
/>" tag "<arg_forced_composite />" is used. If the PPD generator finds
such an option, it hides the member options by only using
"*Foomatic..." keywords to describe them, not any standard PPD
keywords as "*OpenUI...", "*OrderDependency...", ... This way
PPD-aware graphical frontends do not see the member options but
foomatic-rip has all information from them to run the driver
correctly.


String and Password Options
---------------------------

These options allow the user to supply nearly arbitrary strings
(within limits of length, characters and structure) to the printer
driver, for example names of color calibration files, fax numbers,
passwords for confidential jobs, ... Frequently needed strings can be
added as enumerated choices, so a frontend can show the option as a
combo-box. The enumerated choices are also used for frontends which
only support options as defined by the PPD spec. So having enumerated
choices is highly recommended for most of these options.

In the XML database string and password options look similar to
enumerated choice options. The differences are the option types
"string" or "password" and the additional tags to restrict the
possible strings.

The "<arg_maxlength>" tags give a length limit, it should once not
allow strings longer than around 100 characters, as otherwise
foomatic-configure could generate a line longer than the allowed 255
characters in the PPD file when setting the default value, and second,
which is very important, it should not allow strings which are too
long for the printer filter or driver so that buffer overflows cannot
occur. Not using the "<arg_maxlength>" tags makes arbitrary long
strings to be accepted, this is not recommended.

With "<arg_allowedchars>" the accepted strings can be restricted to
contain only the characters given in the list. This restrictions does
not only avoid that the filter chokes on a wrong option, it serves
mainly for security reasons, for example to avoid a string like "|| rm
-rf * ||" for a command line option. So if the option prototype does
not quote the string, command delimiter characters, I/O re-directors,
and shell special characters (";", "|", "&", "<", ">", "*", "?", "[",
"]", "{", "}", "(", ")", "$", "\", "'", """) should not be allowed. If
the string is quoted by the option prototype, the closing quote
character and the backslash should not be allowed, so that one cannot
escape from the quoting. The allowed characters are checked by a
"/^[...]*$/" expression in the Perl scripts, so ranges with "-", a
list of forbidden characters with a leading "^", or special characters
as "\w", "\d", "\x07", ...  are allowed. To allow a backslash, one has
to escape it by using two backslashes ("\\"). To allow a "-" it must
be in the end of the list to not make it defining a range and for a
"^" must be placed at any other place than the beginning of the string
if it should be explicitly allowed.

"<arg_allowedregexp>" allows also to restrict the structure of the
string, as it defines an arbitrary Perl regular expression (see "man
perlre") which has to be matched by the string. This serves also for
having only strings which are usable by the filter and which do not
destroy the command line structure. With this one can for example
forbid a backslash as the last character to avoid escaping the closing
quote of the option prototype. Regular expressions are applied via a
'/.../' expression in the Perl scripts. To apply the pattern matching
modifiers "i", "m", "s", or "x" (as "/.../i" for case-insensitive
matching) begin the regular expression with "(?<modifiers>)" (as
"(?i)..." for case-insensitive matching).

It is highly recommended to use at least one of "<arg_allowedchars>"
and "<arg_allowedregexp>", as otherwise all characters are allowed in
the user-supplied string and so a malicious user can execute arbitrary
shell or PostScript commands. If both tags are used, both conditions
have to be fulfilled.

Note that for the character lists and regular expressions in the XML
files the following character substitutions have to be done:

   < --> &lt;
   > --> &gt;
   " --> &quot;
   ' --> &apos;
   & --> &amp;

Here is an example for an option to supply the file name for an ICC
profile for the "foo2zjs" driver (this option is neither in the CVS
for the Foomatic database nor tested with this driver):

--------------------------------------------------------------------------
<option type="string" id="opt/foo2zjs-ICM">
    <comments>
	<en>
	This option controls which .ICM file to use for color correction.
	ICM files are stored in the directory /usr/share/foo2zjs/icm/.
	</en>
    </comments>
    <arg_longname> <en>ICM Color Profile</en> </arg_longname>
    <arg_shortname> <en>ICM</en> </arg_shortname>
    <arg_execution>
	<arg_group>Adjustment</arg_group>
	<arg_order>300</arg_order>
	<arg_spot>A</arg_spot>
	<arg_required />
	<arg_substitution />
	<arg_proto>-G%s </arg_proto>
    </arg_execution>
    <arg_maxlength>127</arg_maxlength>
    <arg_allowedchars>A-Za-z0-9\._/-</arg_allowedchars>
    <arg_allowedregexp>(?&lt;!\/)$</arg_allowedregexp>
    <constraints>
	<constraint sense="true">
	    <driver>foo2zjs</driver>
	    <arg_defval>ev/foo2zjs-ICM-none</arg_defval>
	</constraint>
	<constraint sense="true">
	    <make>Minolta</make>
	    <model>magicolor 2300 DL</model>
	    <driver>foo2zjs</driver>
	    <arg_defval>ev/foo2zjs-ICM-DL2312</arg_defval>
	</constraint>
	<constraint sense="true">
	    <make>Minolta</make>
	    <model>magicolor 2200 DL</model>
	    <driver>foo2zjs</driver>
	    <arg_defval>ev/foo2zjs-ICM-DL2200RGB</arg_defval>
	</constraint>
    </constraints>
    <enum_vals>
	<enum_val id="ev/foo2zjs-ICM-none">
	    <ev_longname> <en>No ICM color correction</en> </ev_longname>
	    <ev_shortname> <en>None</en> </ev_shortname>
	    <ev_driverval></ev_driverval>
	</enum_val>
	<enum_val id="ev/foo2zjs-ICM-DL2312">
	    <ev_longname> <en>File DL2312.icm</en> </ev_longname>
	    <ev_shortname> <en>DL2312</en> </ev_shortname>
	    <ev_driverval>DL2312.icm</ev_driverval>
	    <constraints>
	        <constraint sense="false">
	    	    <make>HP</make> <model>LaserJet 1000</model>
	        </constraint>
	    </constraints>
	</enum_val>
	<enum_val id="ev/foo2zjs-ICM-DL2324">
	    <ev_longname> <en>File DL2324.icm</en> </ev_longname>
	    <ev_shortname> <en>DL2324</en> </ev_shortname>
	    <ev_driverval>DL2324.icm</ev_driverval>
	    <constraints>
	        <constraint sense="false">
	    	    <make>HP</make> <model>LaserJet 1000</model>
	        </constraint>
	    </constraints>
	</enum_val>

	...

    </enum_vals>
</option>
--------------------------------------------------------------------------

This option allows to choose either one of the given file names,
either by using the "<ev_shortname>"s or the "<ev_driverval>"s, or one
can give every arbitrary other file name with a maximum length of 127
characters, only containing letters, digits, periods, underscores,
dashes, and slashes, and not having a slash in the end (no
directories). Note that in Perl the period must be escaped by a
backslash to be taken literally, otherwise it stands for an arbitrary
character. The regukar expression for blocking out strings ending with
a slash is "(?<!\/)$" (see "man perlre", search for "(?"). Here the
slash is quoted by a backslash. In the XML file the "<" is replaced by
"&lt;" so that the XML structure does not get broken. foomatic-rip
translates this back before applying the regular expression.

To be able to offer strings as an enumerated choice which are not
allowed as an option name in a PPD file, the "<ev_shortname>" may
differ from the "<ev_driverval>", the string inserted at the "%s"
place holder in the "<arg_proto>" is always the "<ev_driverval>",
independent whether the user supplies the "<ev_driverval>" directly or
the "<ev_shortname>". In this example both

   lpr -o ICM= file.ps

and

   lpr -o ICM=None file.ps

supply an empty string as the value of the ICM option.

For the default value there must be an enumerated choice, if there is
none, the PPD generator will create one. So this entry is allowed
(this option is only an example, it is not in the CVS of the Foomatic
database):

--------------------------------------------------------------------------
<option type="password" id="opt/Password">
  <!-- A multilingual <comments> block can appear here, too;
       it should be treated as documentation for the user. -->
  <arg_longname>
   <en>Password (for confidential jobs)</en>
  </arg_longname>
  <arg_shortname>
   <en>Password</en><!-- backends only know <en> shortnames! -->
  </arg_shortname>
  <arg_execution>
   <arg_group>General</arg_group>
   <arg_order>100</arg_order>
   <arg_spot>B</arg_spot>
   <arg_substitution />
   <arg_proto> --pass=%s</arg_proto>
  </arg_execution>
  <arg_maxlength>30</arg_maxlength>
  <arg_allowedchars>A-Za-z0-9\.,_\+\=\:-/</arg_allowedchars>
  <constraints>
     <constraint sense='true'>
      <driver>mydriver</driver>
      <arg_defval></arg_defval>
     </constraint>
  </constraints>
</option>
--------------------------------------------------------------------------

The default value is an empty string here. So the PPD generator will
add a choice for the empty string.

Normally, automatically added choices get the same "<ev_shortname>" as
the string itself, but if the string is not allowed as an option name
in a PPD file, the "<ev_shortname>" will be modified. For an empty
string (as in the example above) "None" will be used and all
characters except numbers, letters, and underscores ("_") will be
replaced by underscores.

The option types "string" and "password" are treated exactly the same
way by the PPD generator and by foomatic-rip, the different names
are only for frontends to know whether the input field should display
the typed characters or asterisks on the screen.


Option Grouping
---------------

All options should be put in groups (with the tags
"<arg_group>...</arg_group>" in the "<arg_execution>" section of the
option XML files, see above). This way many GUIs sort the options into
tabs or tree branches according to the groups. This way one gets only
the most important options on the first tab and not so often needed
ones on additional tabs. This also overrides the automatic option
grouping of CUPS (Groups "General" and "Extra").

It is recommended to have the options in groups as follows (plus
perhaps special groups, but not one group for every option):

General

  Here go options which are most used on a job-by-job basis, as the
  options for paper type, size, and tray, ink type, duplex, ... and
  all options affecting the printout quality, as resolution,
  dithering, ... and especially "PrintoutMode". If a "PrintoutMode"
  option is present, all quality-related options covered by the
  "PrintoutMode" option go into the automatically created
  "PrintoutMode" group (see above). And this is intended, these
  options are now usually controlled by "PrintoutMode" and so they are
  not the most important options for the first tab any more.

  Do not put color/brightness/gamma, ... options here, they go to
  "Adjustment".

  Options typically to go here are:

    o PageSize
    o InputSlot
    o MediaType
    o InkType
    o Duplex
    o PrintoutMode
    o Resolution
    o REt
    o Dither
    o FastRes
    o Economode
    o ...

  All options mentioned after "PrintoutMode" will usually be used as
  member options for "PrintoutMode", they are only in this group when
  there is no "PrintoutMode" option.

PrintoutMode

  This group only exists if there is a "PrintoutMode" option, because
  it is generated by this option. It contains the member options of
  "PrintoutMode". Typical candidates are

    o Resolution
    o REt
    o Dither
    o FastRes
    o Economode
    o ...

  They do not need an "<arg_group>PrintoutMode</arg_group>" line, they
  are put into this group automatically. You should better put an
  "<arg_group>General</arg_group>" line into these options, so that
  they go into the "General" group when there is a printer/driver
  combo for which no "PrintoutMode" option applies.

Adjustment

  Options for correcting the appearance of colors, contrast, ..., for
  head alignment, ... etc. Here most numerical options will go, but
  also things like "Density", also if it is an enumerated choice
  option. Typical candidates are:

    o Gamma
    o Brightness
    o Contrast
    o Density
    o Saturation
    o Cyan
    o Magenta
    o Yellow
    o ...

Finishing

  If a printer has a stapler, folder, cutter, envelope packer, or
  similar devices to do additional processing on the ready printout,
  the options to control this stuff go into this group. Examples:

    o Stapling
    o Binding
    o Cutting
    o Booklet
    o ...

Miscellaneous

  Options which do not fit into the mentioned groups and for which it
  is not worth to make a special group.


Unprintable margins
-------------------

On most printers you cannot print arbitrarily close to the borders of
the paper. You usually will have margins of certain width on which you
cannot print. For filters and applkication programs to know about
these margins PPD file have "*ImageableArea" lines which define the
positions of the lower, the upper, the left, and the right borders of
the area on which the printer can print. There is one line for each
paper size listed in the "*PageSize" option.

To conveniently generating these lines one can use the following XML
structure in the Foomatic database entries:

--------------------------------------------------------------------------
<margins>
     <general>
       <!-- The margins here are valid for every paper size for -->
       <!-- which there is no "exception" section -->
       <!-- ---------- -->
       <!-- possible units: -->
       <!-- pt, inches, mm, cm,
       <!-- dotsNNNdpi (NNN: resolution in which dots are counted) -->
       <!-- if "unit" not present, default unit is pt -->
       <!-- ---------- -->
       <!-- if a margin is not present, default width is 0 -->
       <!-- ---------- -->
       <!-- a missing "general" section assumes zero borders as the -->
       <!-- general borders and "pt" as the default unit for -->
       <!-- "exceptions". -->
       <unit>pt</unit>
       <top>9</top>
       <bottom>36</bottom>
       <left>18</left>
       <right>18</right>
     </general>
     <exception PageSize="Photo4x6TearoffTab">
       <!-- if one or more of "unit", "top", "bottom", "left", -->
       <!-- "right" is missing, the appropriate item of the "general" -->
       <!-- section is used -->
       <top>0</top>
       <left>0</left>
       <right>0</right>
     </exception>
     <exception PageSize="A4">
       <!-- It is also possible to give absolute values in PostScript -->
       <!-- coordinates where the origin is the lower left corner. To -->
       <!-- do so, the <absolute /> tag has to be added, otherwise -->
       <!-- the values are the widths of the unprintable margins -->
       <absolute />
       <left>10</left>
       <right>585</right>
     </exception>
     <exception PageSize="...">
       ...
     </exception>
     ...
<margins>
--------------------------------------------------------------------------

This structure is allowed in printer entries in the "<mechanism>" 
section and in driver entries in the "<execution>" section or inside a 
"<printer>" entry of the driver's printer list. In the "<execution>" 
section of a driver entry the margins are valid for all printers used 
with this driver, in a "<printer>" entry they apply only to the given 
printer/driver combo.

The shown example could be for the HP PhotoSmart 7150/7350, which does 
full-bleed only on HP's special photo paper with an 0.5 inch wide 
tear-off tab on the lower border (and some other paper sizes used in the 
photo tray). On all other paper sizes the printer leaves white borders 
of half an inch at the top and at the bottom and a quarter of an inch on 
the left and right hand side (1 inch are 72 pt). In addition, the page 
size "A4" allows to print up to 10 points to the left and the right borders.

At first we give the general borders ("<general>" section) where we 
choose the unit "pt" (PostScript points) for the numbers. These borders 
are valid for all paper sizes which are not explicitly mentioned with an 
"<exception ...>" section. For our printers one of the exceptions is the 
4x6 photo paper with the tear-off tab (including the tab the paper is 
4x6.5 inches large). here the printer prints up to the left, right, and 
top borders. Therefore we have margins of zero here. At the lower border 
the printer still leaves half an inch white (therefore probably HP 
introduced the tear-off tab), so we keep the 36 pt of the "<general>" 
section by not mentioning a new lower border. For A4 we redefine the 
left and the right border. This is also possible in absolute PostScript 
coordinates measured from the lower left corner, as we do here. We 
indicate this with the "<absolute />" tag. The left border is at 10 pt 
from the left, and as A4 paper is 595 pt wide, the right border is at 
585 points from the left.

One hint for the choice of the units: Float numbers as border widths are 
allowed, but it is recommended for having exact info to choose a unit 
which gives integer numbers for the widths (which is always possible 
with the "dotsNNNdpi" unit with NNN being the maximum resolution of the 
printer).

A "<margins>" section in a printer entry should represent the printer's 
hardware capabilities. Such a section in a driver entry should represent 
how the driver's limitations are. If there are margins defined in both 
the printer and the driver entry of the desired printer/driver combo, 
the more restrictive (wider) borders count. If there are no border 
definitions in both the printer and the driver entry, the borders are 
assumed to be of zero width (full-bleed).


Adding arbitrary extra entries to the PPD file
----------------------------------------------

The "<ppdentry>" tags allow to add extra lines to the PPD file. The 
tags can be put into the top level ("<printer>") of a printer XML entry, 
into the "<execution>" section of a driver XML entry, or into the 
"<printer>" entries of the printer list in a driver XML file. They serve 
mainly to put a default resolution into PPD files for drivers without 
"Resolution" option. Examples:

"hpijs"  driver, default resolution for HP DeskJet 350. For this driver 
the default resolution depends on the printer class. Therefore the 
appropriate "<ppdentry>"s have to be in the printer entries of the 
printer list:

--------------------------------------------------------------------------
<driver id="driver/hpijs">
  <name>hpijs</name>
  ...
  <printers>
   <printer>
    <id>printer/HP-DeskJet_350C</id><!-- HP DeskJet 350C -->
    <ppdentry>
      *DefaultResolution: 600dpi
    </ppdentry>
    <margins>
     <general>
      <unit>in</unit>
      <relative />
      <left>0.25</left>
      <right>0.25</right>
      <top>0.125</top>
      <bottom>0.67</bottom>
     </general>
     <exception PageSize="A4">
      <left>0.135</left>
      <right>0.135</right>
     </exception>
    </margins>
   </printer>
   ...
  </printers>
</driver>
--------------------------------------------------------------------------

"pnm2ppa" driver: This driver has no "Resolution" option, and all 
printers print in 600 dpi with it. So we put the "<ppdentry>" into the 
"<execution>" section:

--------------------------------------------------------------------------
<driver id="driver/pnm2ppa">
  <name>pnm2ppa</name>
  <url>http://sourceforge.net/projects/pnm2ppa/</url>
  <execution>
   <filter />
   <prototype>gs -q -dNOPAUSE -dPARANOIDSAFER -dBATCH -r600%A%Z 
-sOutputFile=- - | pnm2ppa%C%B -i - -o -</prototype>
   <ppdentry>
    *DefaultResolution: 600dpi
   </ppdentry>
  </execution>
  ...
</driver>
--------------------------------------------------------------------------

Note that leading spaces are removed from the lines between the
"<ppdentry>" tags before they get inserted into the PPD file.

The lines are added at the end of the PPD file header, right after the
lines for the basic hardware capabilities of the printer.