This is groff, produced by makeinfo version 4.3d from ./groff.texinfo.

This manual documents GNU `troff' version 1.19.

   Copyright (C) 1994-2000, 2001, 2002, 2003 Free Software Foundation,
Inc.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.1 or any later version published by the Free Software
     Foundation; with no Invariant Sections, with the Front-Cover texts
     being `A GNU Manual," and with the Back-Cover Texts as in (a)
     below.  A copy of the license is included in the section entitled
     `GNU Free Documentation License."

     (a) The FSF's Back-Cover Text is: `You have freedom to copy and
     modify this GNU Manual, like GNU software.  Copies published by
     the Free Software Foundation raise funds for GNU development."
   
INFO-DIR-SECTION Typesetting
START-INFO-DIR-ENTRY
* Groff: (groff).               The GNU troff document formatting system.
END-INFO-DIR-ENTRY


File: groff,  Node: Warnings,  Prev: Debugging,  Up: Debugging

Warnings
--------

   The warnings that can be given to `gtroff' are divided into the
following categories.  The name associated with each warning is used by
the `-w' and `-W' options; the number is used by the `warn' request and
by the `.warn' register.

`char'
`1'
     Non-existent glyphs.(1) (*note Warnings-Footnote-1::)  This is
     enabled by default.

`number'
`2'
     Invalid numeric expressions.  This is enabled by default.  *Note
     Expressions::.

`break'
`4'
     In fill mode, lines which could not be broken so that their length
     was less than the line length.  This is enabled by default.

`delim'
`8'
     Missing or mismatched closing delimiters.

`el'
`16'
     Use of the `el' request with no matching `ie' request.  *Note
     if-else::.

`scale'
`32'
     Meaningless scaling indicators.

`range'
`64'
     Out of range arguments.

`syntax'
`128'
     Dubious syntax in numeric expressions.

`di'
`256'
     Use of `di' or `da' without an argument when there is no current
     diversion.

`mac'
`512'
     Use of undefined strings, macros and diversions.  When an undefined
     string, macro, or diversion is used, that string is automatically
     defined as empty.  So, in most cases, at most one warning is given
     for each name.

`reg'
`1024'
     Use of undefined number registers.  When an undefined number
     register is used, that register is automatically defined to have a
     value of 0.  So, in most cases, at most one warning is given for
     use of a particular name.

`tab'
`2048'
     Use of a tab character where a number was expected.

`right-brace'
`4096'
     Use of `\}' where a number was expected.

`missing'
`8192'
     Requests that are missing non-optional arguments.

`input'
`16384'
     Invalid input characters.

`escape'
`32768'
     Unrecognized escape sequences.  When an unrecognized escape
     sequence `\X' is encountered, the escape character is ignored, and
     X is printed.

`space'
`65536'
     Missing space between a request or macro and its argument.  This
     warning is given when an undefined name longer than two characters
     is encountered, and the first two characters of the name make a
     defined name.  The request or macro is not invoked.  When this
     warning is given, no macro is automatically defined.  This is
     enabled by default.  This warning never occurs in compatibility
     mode.

`font'
`131072'
     Non-existent fonts.  This is enabled by default.

`ig'
`262144'
     Invalid escapes in text ignored with the `ig' request.  These are
     conditions that are errors when they do not occur in ignored text.

`color'
`524288'
     Color related warnings.

`all'
     All warnings except `di', `mac' and `reg'.  It is intended that
     this covers all warnings that are useful with traditional macro
     packages.

`w'
     All warnings.


File: groff,  Node: Warnings-Footnotes,  Up: Warnings

   (1) `char' is a misnomer since it reports missing glyphs - there
aren't missing input characters, only invalid ones.


File: groff,  Node: Implementation Differences,  Prev: Debugging,  Up: gtroff Reference

Implementation Differences
==========================

   GNU `troff' has a number of features which cause incompatibilities
with documents written with old versions of `troff'.

   Long names cause some incompatibilities.  UNIX `troff' interprets


     .dsabcd

as defining a string `ab' with contents `cd'.  Normally, GNU `troff'
interprets this as a call of a macro named `dsabcd'.  Also UNIX `troff'
interprets `\*[' or `\n[' as references to a string or number register
called `['.  In GNU `troff', however, this is normally interpreted as
the start of a long name.  In compatibility mode GNU `troff' interprets
long names in the traditional way (which means that they are not
recognized as names).

 - Request: .cp [n]
 - Request: .do cmd
 - Register: \n[.C]
     If N is missing or non-zero, turn on compatibility mode;
     otherwise, turn it off.

     The read-only number register `.C' is 1 if compatibility mode is
     on, 0 otherwise.

     Compatibility mode can be also turned on with the `-C' command line
     option.

     The `do' request turns off compatibility mode while executing its
     arguments as a `gtroff' command.


          .do fam T

     executes the `fam' request when compatibility mode is enabled.

     `gtroff' restores the previous compatibility setting before
     interpreting any files sourced by the CMD.

   Two other features are controlled by `-C'.  If not in compatibility
mode, GNU `troff' preserves the input level in delimited arguments:


     .ds xx '
     \w'abc\*(xxdef'

In compatibility mode, the string `72def'' is returned; without `-C'
the resulting string is `168' (assuming a TTY output device).

   Finally, the escapes `\f', `\H', `\m', `\M', `\R', `\s', and `\S'
are transparent for recognizing the beginning of a line only in
compatibility mode (this is a rather obscure feature).  For example,
the code


     .de xx
     Hallo!
     ..
     \fB.xx\fP

prints `Hallo!' in bold face if in compatibility mode, and `.xx' in
bold face otherwise.

   GNU `troff' does not allow the use of the escape sequences `\|',
`\^', `\&', `\{', `\}', `\<SP>', `\'', `\`', `\-', `\_', `\!', `\%',
and `\c' in names of strings, macros, diversions, number registers,
fonts or environments; UNIX `troff' does.  The `\A' escape sequence
(*note Identifiers::) may be helpful in avoiding use of these escape
sequences in names.

   Fractional point sizes cause one noteworthy incompatibility.  In
UNIX `troff' the `ps' request ignores scale indicators and thus


     .ps 10u

sets the point size to 10 points, whereas in GNU `troff' it sets the
point size to 10 scaled points.  *Note Fractional Type Sizes::, for
more information.

   In GNU `troff' there is a fundamental difference between
(unformatted) input characters and (formatted) output glyphs.
Everything that affects how a glyph is output is stored with the glyph
node; once a glyph node has been constructed it is unaffected by any
subsequent requests that are executed, including `bd', `cs', `tkf',
`tr', or `fp' requests.  Normally glyphs are constructed from input
characters at the moment immediately before the glyph is added to the
current output line.  Macros, diversions and strings are all, in fact,
the same type of object; they contain lists of input characters and
glyph nodes in any combination.  A glyph node does not behave like an
input character for the purposes of macro processing; it does not
inherit any of the special properties that the input character from
which it was constructed might have had.  For example,


     .di x
     \\\\
     .br
     .di
     .x

prints `\\' in GNU `troff'; each pair of input backslashes is turned
into one output backslash and the resulting output backslashes are not
interpreted as escape characters when they are reread.  UNIX `troff'
would interpret them as escape characters when they were reread and
would end up printing one `\'.  The correct way to obtain a printable
backslash is to use the `\e' escape sequence: This always prints a
single instance of the current escape character, regardless of whether
or not it is used in a diversion; it also works in both GNU `troff' and
UNIX `troff'.(1) (*note Implementation Differences-Footnote-1::)  To
store, for some reason, an escape sequence in a diversion that will be
interpreted when the diversion is reread, either use the traditional
`\!' transparent output facility, or, if this is unsuitable, the new
`\?' escape sequence.

   *Note Diversions::, and *Note Gtroff Internals::, for more
information.


File: groff,  Node: Implementation Differences-Footnotes,  Up: Implementation Differences

   (1) To be completely independent of the current escape character,
use `\(rs' which represents a reverse solidus (backslash) glyph.


File: groff,  Node: Preprocessors,  Next: Output Devices,  Prev: gtroff Reference,  Up: Top

Preprocessors
*************

   This chapter describes all preprocessors that come with `groff' or
which are freely available.

* Menu:

* geqn::
* gtbl::
* gpic::
* ggrn::
* grap::
* grefer::
* gsoelim::


File: groff,  Node: geqn,  Next: gtbl,  Prev: Preprocessors,  Up: Preprocessors

`geqn'
======

* Menu:

* Invoking geqn::


File: groff,  Node: Invoking geqn,  Prev: geqn,  Up: geqn

Invoking `geqn'
---------------


File: groff,  Node: gtbl,  Next: gpic,  Prev: geqn,  Up: Preprocessors

`gtbl'
======

* Menu:

* Invoking gtbl::


File: groff,  Node: Invoking gtbl,  Prev: gtbl,  Up: gtbl

Invoking `gtbl'
---------------


File: groff,  Node: gpic,  Next: ggrn,  Prev: gtbl,  Up: Preprocessors

`gpic'
======

* Menu:

* Invoking gpic::


File: groff,  Node: Invoking gpic,  Prev: gpic,  Up: gpic

Invoking `gpic'
---------------


File: groff,  Node: ggrn,  Next: grap,  Prev: gpic,  Up: Preprocessors

`ggrn'
======

* Menu:

* Invoking ggrn::


File: groff,  Node: Invoking ggrn,  Prev: ggrn,  Up: ggrn

Invoking `ggrn'
---------------


File: groff,  Node: grap,  Next: grefer,  Prev: ggrn,  Up: Preprocessors

`grap'
======

   A free implementation of `grap', written by Ted Faber, is available
as an extra package from the following address:

     `http://www.lunabase.org/~faber/Vault/software/grap/'


File: groff,  Node: grefer,  Next: gsoelim,  Prev: grap,  Up: Preprocessors

`grefer'
========

* Menu:

* Invoking grefer::


File: groff,  Node: Invoking grefer,  Prev: grefer,  Up: grefer

Invoking `grefer'
-----------------


File: groff,  Node: gsoelim,  Prev: grefer,  Up: Preprocessors

`gsoelim'
=========

* Menu:

* Invoking gsoelim::


File: groff,  Node: Invoking gsoelim,  Prev: gsoelim,  Up: gsoelim

Invoking `gsoelim'
------------------


File: groff,  Node: Output Devices,  Next: File formats,  Prev: Preprocessors,  Up: Top

Output Devices
**************

* Menu:

* Special Characters::
* grotty::
* grops::
* grodvi::
* grolj4::
* grolbp::
* grohtml::
* gxditview::


File: groff,  Node: Special Characters,  Next: grotty,  Prev: Output Devices,  Up: Output Devices

Special Characters
==================

   *Note Font Files::.


File: groff,  Node: grotty,  Next: grops,  Prev: Special Characters,  Up: Output Devices

`grotty'
========

* Menu:

* Invoking grotty::


File: groff,  Node: Invoking grotty,  Prev: grotty,  Up: grotty

Invoking `grotty'
-----------------


File: groff,  Node: grops,  Next: grodvi,  Prev: grotty,  Up: Output Devices

`grops'
=======

* Menu:

* Invoking grops::
* Embedding PostScript::


File: groff,  Node: Invoking grops,  Next: Embedding PostScript,  Prev: grops,  Up: grops

Invoking `grops'
----------------


File: groff,  Node: Embedding PostScript,  Prev: Invoking grops,  Up: grops

Embedding POSTSCRIPT
--------------------


File: groff,  Node: grodvi,  Next: grolj4,  Prev: grops,  Up: Output Devices

`grodvi'
========

* Menu:

* Invoking grodvi::


File: groff,  Node: Invoking grodvi,  Prev: grodvi,  Up: grodvi

Invoking `grodvi'
-----------------


File: groff,  Node: grolj4,  Next: grolbp,  Prev: grodvi,  Up: Output Devices

`grolj4'
========

* Menu:

* Invoking grolj4::


File: groff,  Node: Invoking grolj4,  Prev: grolj4,  Up: grolj4

Invoking `grolj4'
-----------------


File: groff,  Node: grolbp,  Next: grohtml,  Prev: grolj4,  Up: Output Devices

`grolbp'
========

* Menu:

* Invoking grolbp::


File: groff,  Node: Invoking grolbp,  Prev: grolbp,  Up: grolbp

Invoking `grolbp'
-----------------


File: groff,  Node: grohtml,  Next: gxditview,  Prev: grolbp,  Up: Output Devices

`grohtml'
=========

* Menu:

* Invoking grohtml::
* grohtml specific registers and strings::


File: groff,  Node: Invoking grohtml,  Next: grohtml specific registers and strings,  Prev: grohtml,  Up: grohtml

Invoking `grohtml'
------------------


File: groff,  Node: grohtml specific registers and strings,  Prev: Invoking grohtml,  Up: grohtml

`grohtml' specific registers and strings
----------------------------------------

 - Register: \n[ps4html]
 - String: \*[www-image-template]
     The registers `ps4html' and `www-image-template' are defined by
     the `pre-grohtml' preprocessor.  `pre-grohtml' reads in the
     `troff' input, marks up the inline equations and passes the result
     firstly to


          troff -Tps -rps4html=1 -dwww-image-template=TEMPLATE

     and secondly to


          troff -Thtml

     The PostScript device is used to create all the image files, and
     the register `ps4html' enables the macro sets to ignore floating
     keeps, footers, and headings.

     The register `www-image-template' is set to the user specified
     template name or the default name.


File: groff,  Node: gxditview,  Prev: grohtml,  Up: Output Devices

`gxditview'
===========

* Menu:

* Invoking gxditview::


File: groff,  Node: Invoking gxditview,  Prev: gxditview,  Up: gxditview

Invoking `gxditview'
--------------------


File: groff,  Node: File formats,  Next: Installation,  Prev: Output Devices,  Up: Top

File formats
************

   All files read and written by `gtroff' are text files.  The
following two sections describe their format.

* Menu:

* gtroff Output::
* Font Files::


File: groff,  Node: gtroff Output,  Next: Font Files,  Prev: File formats,  Up: File formats

`gtroff' Output
===============

   This section describes the intermediate output format of GNU
`troff'.  This output is produced by a run of `gtroff' before it is fed
into a device postprocessor program.

   As `groff' is a wrapper program around `gtroff' that automatically
calls a postprocessor, this output does not show up normally.  This is
why it is called "intermediate".  `groff' provides the option `-Z' to
inhibit postprocessing, such that the produced intermediate output is
sent to standard output just like calling `gtroff' manually.

   Here, the term "troff output" describes what is output by `gtroff',
while "intermediate output" refers to the language that is accepted by
the parser that prepares this output for the postprocessors.  This
parser is smarter on whitespace and implements obsolete elements for
compatibility, otherwise both formats are the same.(1) (*note gtroff
Output-Footnote-1::)

   The main purpose of the intermediate output concept is to facilitate
the development of postprocessors by providing a common programming
interface for all devices.  It has a language of its own that is
completely different from the `gtroff' language.  While the `gtroff'
language is a high-level programming language for text processing, the
intermediate output language is a kind of low-level assembler language
by specifying all positions on the page for writing and drawing.

   The intermediate output produced by `gtroff' is fairly readable,
while output from AT&T `troff' is rather hard to understand because of
strange habits that are still supported, but not used any longer by
`gtroff'.

* Menu:

* Language Concepts::
* Command Reference::
* Intermediate Output Examples::
* Output Language Compatibility::


File: groff,  Node: gtroff Output-Footnotes,  Up: gtroff Output

   (1) The parser and postprocessor for intermediate output can be
found in the file
`GROFF-SOURCE-DIR/src/libs/libdriver/input.cpp'.


File: groff,  Node: Language Concepts,  Next: Command Reference,  Prev: gtroff Output,  Up: gtroff Output

Language Concepts
-----------------

   During the run of `gtroff', the input data is cracked down to the
information on what has to be printed at what position on the intended
device.  So the language of the intermediate output format can be quite
small.  Its only elements are commands with and without arguments.  In
this section, the term "command" always refers to the intermediate
output language, and never to the `gtroff' language used for document
formatting.  There are commands for positioning and text writing, for
drawing, and for device controlling.

* Menu:

* Separation::
* Argument Units::
* Document Parts::


File: groff,  Node: Separation,  Next: Argument Units,  Prev: Language Concepts,  Up: Language Concepts

Separation
..........

   AT&T `troff' output has strange requirements on whitespace.  The
`gtroff' output parser, however, is smart about whitespace by making it
maximally optional.  The whitespace characters, i.e., the tab, space,
and newline characters, always have a syntactical meaning.  They are
never printable because spacing within the output is always done by
positioning commands.

   Any sequence of space or tab characters is treated as a single
"syntactical space".  It separates commands and arguments, but is only
required when there would occur a clashing between the command code and
the arguments without the space.  Most often, this happens when
variable-length command names, arguments, argument lists, or command
clusters meet.  Commands and arguments with a known, fixed length need
not be separated by syntactical space.

   A line break is a syntactical element, too.  Every command argument
can be followed by whitespace, a comment, or a newline character.  Thus
a "syntactical line break" is defined to consist of optional
syntactical space that is optionally followed by a comment, and a
newline character.

   The normal commands, those for positioning and text, consist of a
single letter taking a fixed number of arguments.  For historical
reasons, the parser allows to stack such commands on the same line, but
fortunately, in `gtroff''s intermediate output, every command with at
least one argument is followed by a line break, thus providing
excellent readability.

   The other commands - those for drawing and device controlling - have
a more complicated structure; some recognize long command names, and
some take a variable number of arguments.  So all `D' and `x' commands
were designed to request a syntactical line break after their last
argument.  Only one command, `x X', has an argument that can stretch
over several lines; all other commands must have all of their arguments
on the same line as the command, i.e., the arguments may not be
splitted by a line break.

   Empty lines (these are lines containing only space and/or a
comment), can occur everywhere.  They are just ignored.


File: groff,  Node: Argument Units,  Next: Document Parts,  Prev: Separation,  Up: Language Concepts

Argument Units
..............

   Some commands take integer arguments that are assumed to represent
values in a measurement unit, but the letter for the corresponding
scale indicator is not written with the output command arguments.  Most
commands assume the scale indicator `u', the basic unit of the device,
some use `z', the scaled point unit of the device, while others, such
as the color commands, expect plain integers.

   Note that single characters can have the eighth bit set, as can the
names of fonts and special characters.  The names of characters and
fonts can be of arbitrary length.  A character that is to be printed
will always be in the current font.

   A string argument is always terminated by the next whitespace
character (space, tab, or newline); an embedded `#' character is
regarded as part of the argument, not as the beginning of a comment
command.  An integer argument is already terminated by the next
non-digit character, which then is regarded as the first character of
the next argument or command.


File: groff,  Node: Document Parts,  Prev: Argument Units,  Up: Language Concepts

Document Parts
..............

   A correct intermediate output document consists of two parts, the
"prologue" and the "body".

   The task of the prologue is to set the general device parameters
using three exactly specified commands.  `gtroff''s prologue is
guaranteed to consist of the following three lines (in that order):


     x T DEVICE
     x res N H V
     x init

with the arguments set as outlined in *Note Device Control Commands::.
Note that the parser for the intermediate output format is able to
swallow additional whitespace and comments as well even in the prologue.

   The body is the main section for processing the document data.
Syntactically, it is a sequence of any commands different from the ones
used in the prologue.  Processing is terminated as soon as the first
`x stop' command is encountered; the last line of any `gtroff'
intermediate output always contains such a command.

   Semantically, the body is page oriented.  A new page is started by a
`p' command.  Positioning, writing, and drawing commands are always
done within the current page, so they cannot occur before the first `p'
command.  Absolute positioning (by the `H' and `V' commands) is done
relative to the current page; all other positioning is done relative to
the current location within this page.


File: groff,  Node: Command Reference,  Next: Intermediate Output Examples,  Prev: Language Concepts,  Up: gtroff Output

Command Reference
-----------------

   This section describes all intermediate output commands, both from
AT&T `troff' as well as the `gtroff' extensions.

* Menu:

* Comment Command::
* Simple Commands::
* Graphics Commands::
* Device Control Commands::
* Obsolete Command::


File: groff,  Node: Comment Command,  Next: Simple Commands,  Prev: Command Reference,  Up: Command Reference

Comment Command
...............

`#ANYTHING<end of line>'
     A comment.  Ignore any characters from the `#' character up to the
     next newline character.

     This command is the only possibility for commenting in the
     intermediate output.  Each comment can be preceded by arbitrary
     syntactical space; every command can be terminated by a comment.


File: groff,  Node: Simple Commands,  Next: Graphics Commands,  Prev: Comment Command,  Up: Command Reference

Simple Commands
...............

   The commands in this subsection have a command code consisting of a
single character, taking a fixed number of arguments.  Most of them are
commands for positioning and text writing.  These commands are smart
about whitespace.  Optionally, syntactical space can be inserted
before, after, and between the command letter and its arguments.  All
of these commands are stackable, i.e., they can be preceded by other
simple commands or followed by arbitrary other commands on the same
line.  A separating syntactical space is only necessary when two
integer arguments would clash or if the preceding argument ends with a
string argument.

`C XXX<whitespace>'
     Print a special character named XXX.  The trailing syntactical
     space or line break is necessary to allow glyph names of arbitrary
     length.  The glyph is printed at the current print position; the
     glyph's size is read from the font file.  The print position is
     not changed.

`c G'
     Print glyph G at the current print position;(1) (*note Simple
     Commands-Footnote-1::) the glyph's size is read from the font
     file.  The print position is not changed.

`f N'
     Set font to font number N (a non-negative integer).

`H N'
     Move right to the absolute vertical position N (a non-negative
     integer in basic units `u' relative to left edge of current page.

`h N'
     Move N (a non-negative integer) basic units `u' horizontally to
     the right.  The original UNIX troff manual allows negative values
     for N also, but `gtroff' doesn't use this.

`m COLOR-SCHEME [COMPONENT ...]'
     Set the color for text (glyphs), line drawing, and the outline of
     graphic objects using different color schemes; the analoguous
     command for the filling color of graphic objects is `DF'.  The
     color components are specified as integer arguments between 0 and
     65536.  The number of color components and their meaning vary for
     the different color schemes.  These commands are generated by
     `gtroff''s escape sequence `\m'.  No position changing.  These
     commands are a `gtroff' extension.

    `mc CYAN MAGENTA YELLOW'
          Set color using the CMY color scheme, having the 3 color
          components CYAN, MAGENTA, and YELLOW.

    `md'
          Set color to the default color value (black in most cases).
          No component arguments.

    `mg GRAY'
          Set color to the shade of gray given by the argument, an
          integer between 0 (black) and 65536 (white).

    `mk CYAN MAGENTA YELLOW BLACK'
          Set color using the CMYK color scheme, having the 4 color
          components CYAN, MAGENTA, YELLOW, and BLACK.

    `mr RED GREEN BLUE'
          Set color using the RGB color scheme, having the 3 color
          components RED, GREEN, and BLUE.


`N N'
     Print glyph with index N (a non-negative integer) of the current
     font.  This command is a `gtroff' extension.

`n B A'
     Inform the device about a line break, but no positioning is done by
     this command.  In AT&T `troff', the integer arguments B and A
     informed about the space before and after the current line to make
     the intermediate output more human readable without performing any
     action.  In `groff', they are just ignored, but they must be
     provided for compatibility reasons.

`p N'
     Begin a new page in the outprint.  The page number is set to N.
     This page is completely independent of pages formerly processed
     even if those have the same page number.  The vertical position on
     the outprint is automatically set to 0.  All positioning, writing,
     and drawing is always done relative to a page, so a `p' command
     must be issued before any of these commands.

`s N'
     Set point size to N scaled points (this is unit `z').  AT&T
     `troff' used the unit points (`p') instead.  *Note Output Language
     Compatibility::.

`t XXX<whitespace>'
`t XXX DUMMY-ARG<whitespace>'
     Print a word, i.e., a sequence of characters XXX representing
     output glyphs which names are single characters, terminated by a
     space character or a line break; an optional second integer
     argument is ignored (this allows the formatter to generate an even
     number of arguments).  The first glyph should be printed at the
     current position, the current horizontal position should then be
     increased by the width of the first glyph, and so on for each
     glyph.  The widths of the glyphs are read from the font file,
     scaled for the current point size, and rounded to a multiple of
     the horizontal resolution.  Special characters cannot be printed
     using this command (use the `C' command for special characters).
     This command is a `gtroff' extension; it is only used for devices
     whose `DESC' file contains the `tcommand' keyword (*note DESC File
     Format::).

`u N XXX<whitespace>'
     Print word with track kerning.  This is the same as the `t'
     command except that after printing each glyph, the current
     horizontal position is increased by the sum of the width of that
     glyph and N (an integer in basic units `u').  This command is a
     `gtroff' extension; it is only used for devices whose `DESC' file
     contains the `tcommand' keyword (*note DESC File Format::).

`V N'
     Move down to the absolute vertical position N (a non-negative
     integer in basic units `u') relative to upper edge of current page.

`v N'
     Move N basic units `u' down (N is a non-negative integer).  The
     original UNIX troff manual allows negative values for N also, but
     `gtroff' doesn't use this.

`w'
     Informs about a paddable white space to increase readability.  The
     spacing itself must be performed explicitly by a move command.



File: groff,  Node: Simple Commands-Footnotes,  Up: Simple Commands

   (1) `c' is actually a misnomer since it outputs a glyph.


File: groff,  Node: Graphics Commands,  Next: Device Control Commands,  Prev: Simple Commands,  Up: Command Reference

Graphics Commands
.................

   Each graphics or drawing command in the intermediate output starts
with the letter `D', followed by one or two characters that specify a
subcommand; this is followed by a fixed or variable number of integer
arguments that are separated by a single space character.  A `D'
command may not be followed by another command on the same line (apart
from a comment), so each `D' command is terminated by a syntactical
line break.

   `gtroff' output follows the classical spacing rules (no space
between command and subcommand, all arguments are preceded by a single
space character), but the parser allows optional space between the
command letters and makes the space before the first argument optional.
As usual, each space can be any sequence of tab and space characters.

   Some graphics commands can take a variable number of arguments.  In
this case, they are integers representing a size measured in basic
units `u'.  The arguments called H1, H2, ..., HN stand for horizontal
distances where positive means right, negative left.  The arguments
called V1, V2, ..., VN stand for vertical distances where positive
means down, negative up.  All these distances are offsets relative to
the current location.

   Each graphics command directly corresponds to a similar `gtroff'
`\D' escape sequence.  *Note Drawing Requests::.

   Unknown `D' commands are assumed to be device-specific.  Its
arguments are parsed as strings; the whole information is then sent to
the postprocessor.

   In the following command reference, the syntax element <line break>
means a syntactical line break as defined above.

`D~ H1 V1 H2 V2 ... HN VN<line break>'
     Draw B-spline from current position to offset (H1,V1), then to
     offset (H2,V2), if given, etc. up to (HN,VN).  This command takes
     a variable number of argument pairs; the current position is moved
     to the terminal point of the drawn curve.

`Da H1 V1 H2 V2<line break>'
     Draw arc from current position to (H1,V1)+(H2,V2) with center at
     (H1,V1); then move the current position to the final point of the
     arc.

`DC D<line break>'
`DC D DUMMY-ARG<line break>'
     Draw a solid circle using the current fill color with diameter D
     (integer in basic units `u') with leftmost point at the current
     position; then move the current position to the rightmost point of
     the circle.  An optional second integer argument is ignored (this
     allows the formatter to generate an even number of arguments).
     This command is a `gtroff' extension.

`Dc D<line break>'
     Draw circle line with diameter D (integer in basic units `u') with
     leftmost point at the current position; then move the current
     position to the rightmost point of the circle.

`DE H V<line break>'
     Draw a solid ellipse in the current fill color with a horizontal
     diameter of H and a vertical diameter of V (both integers in basic
     units `u') with the leftmost point at the current position; then
     move to the rightmost point of the ellipse.  This command is a
     `gtroff' extension.

`De H V<line break>'
     Draw an outlined ellipse with a horizontal diameter of H and a
     vertical diameter of V (both integers in basic units `u') with the
     leftmost point at current position; then move to the rightmost
     point of the ellipse.

`DF COLOR-SCHEME [COMPONENT ...]<line break>'
     Set fill color for solid drawing objects using different color
     schemes; the analoguous command for setting the color of text, line
     graphics, and the outline of graphic objects is `m'.  The color
     components are specified as integer arguments between 0 and 65536.
     The number of color components and their meaning vary for the
     different color schemes.  These commands are generated by
     `gtroff''s escape sequences `\D'F ...'' and `\M' (with no other
     corresponding graphics commands).  No position changing.  This
     command is a `gtroff' extension.

    `DFc CYAN MAGENTA YELLOW<line break>'
          Set fill color for solid drawing objects using the CMY color
          scheme, having the 3 color components CYAN, MAGENTA, and
          YELLOW.

    `DFd<line break>'
          Set fill color for solid drawing objects to the default fill
          color value (black in most cases).  No component arguments.

    `DFg GRAY<line break>'
          Set fill color for solid drawing objects to the shade of gray
          given by the argument, an integer between 0 (black) and 65536
          (white).

    `DFk CYAN MAGENTA YELLOW BLACK<line break>'
          Set fill color for solid drawing objects using the CMYK color
          scheme, having the 4 color components CYAN, MAGENTA, YELLOW,
          and BLACK.

    `DFr RED GREEN BLUE<line break>'
          Set fill color for solid drawing objects using the RGB color
          scheme, having the 3 color components RED, GREEN, and BLUE.


`Df N<line break>'
     The argument N must be an integer in the range -32767 to 32767.

    0 <= N <= 1000
          Set the color for filling solid drawing objects to a shade of
          gray, where 0 corresponds to solid white, 1000 (the default)
          to solid black, and values in between to intermediate shades
          of gray; this is obsoleted by command `DFg'.

    N < 0 or N > 1000
          Set the filling color to the color that is currently being
          used for the text and the outline, see command `m'.  For
          example, the command sequence


               mg 0 0 65536
               Df -1

          sets all colors to blue.


     No position changing.  This command is a `gtroff' extension.

`Dl H V<line break>'
     Draw line from current position to offset (H,V) (integers in basic
     units `u'); then set current position to the end of the drawn line.

`Dp H1 V1 H2 V2 ... HN VN<line break>'
     Draw a polygon line from current position to offset (H1,V1), from
     there to offset (H2,V2), etc. up to offset (HN,VN), and from there
     back to the starting position.  For historical reasons, the
     position is changed by adding the sum of all arguments with odd
     index to the actual horizontal position and the even ones to the
     vertical position.  Although this doesn't make sense it is kept
     for compatibility.  This command is a `gtroff' extension.

`Dp H1 V1 H2 V2 ... HN VN<line break>'
     Draw a solid polygon in the current fill color rather than an
     outlined polygon, using the same arguments and positioning as the
     corresponding `Dp' command.  This command is a `gtroff' extension.

`Dt N<line break>'
     Set the current line thickness to N (an integer in basic units
     `u') if N>0; if N=0 select the smallest available line thickness;
     if N<0 set the line thickness proportional to the point size (this
     is the default before the first `Dt' command was specified).  For
     historical reasons, the horizontal position is changed by adding
     the argument to the actual horizontal position, while the vertical
     position is not changed.  Although this doesn't make sense it is
     kept for compatibility.  This command is a `gtroff' extension.



File: groff,  Node: Device Control Commands,  Next: Obsolete Command,  Prev: Graphics Commands,  Up: Command Reference

Device Control Commands
.......................

   Each device control command starts with the letter `x', followed by
a space character (optional or arbitrary space or tab in `gtroff') and
a subcommand letter or word; each argument (if any) must be preceded by
a syntactical space.  All `x' commands are terminated by a syntactical
line break; no device control command can be followed by another
command on the same line (except a comment).

   The subcommand is basically a single letter, but to increase
readability, it can be written as a word, i.e., an arbitrary sequence
of characters terminated by the next tab, space, or newline character.
All characters of the subcommand word but the first are simply ignored.
For example, `gtroff' outputs the initialization command `x i' as
`x init' and the resolution command `x r' as `x res'.

   In the following, the syntax element <line break> means a
syntactical line break (*note Separation::).

`xF NAME<line break>'
     The `F' stands for FILENAME.

     Use NAME as the intended name for the current file in error
     reports.  This is useful for remembering the original file name
     when `gtroff' uses an internal piping mechanism.  The input file is
     not changed by this command.  This command is a `gtroff' extension.

`xf N S<line break>'
     The `f' stands for FONT.

     Mount font position N (a non-negative integer) with font named S
     (a text word).  *Note Font Positions::.

`xH N<line break>'
     The `H' stands for HEIGHT.

     Set glyph height to N (a positive integer in scaled points `z').
     AT&T `troff' uses the unit points (`p') instead.  *Note Output
     Language Compatibility::.

`xi<line break>'
     The `i' stands for INIT.

     Initialize device.  This is the third command of the prologue.

`xp<line break>'
     The `p' stands for PAUSE.

     Parsed but ignored.  The original UNIX troff manual writes

          pause device, can be restarted

`xr N H V<line break>'
     The `r' stands for RESOLUTION.

     Resolution is N, while H is the minimal horizontal motion, and V
     the minimal vertical motion possible with this device; all
     arguments are positive integers in basic units `u' per inch.  This
     is the second command of the prologue.

`xS N<line break>'
     The `S' stands for SLANT.

     Set slant to N (an integer in basic units `u').

`xs<line break>'
     The `s' stands for STOP.

     Terminates the processing of the current file; issued as the last
     command of any intermediate troff output.

`xt<line break>'
     The `t' stands for TRAILER.

     Generate trailer information, if any.  In GTROFF, this is actually
     just ignored.

`xT XXX<line break>'
     The `T' stands for TYPESETTER.

     Set name of device to word XXX, a sequence of characters ended by
     the next white space character.  The possible device names coincide
     with those from the `groff' `-T' option.  This is the first
     command of the prologue.

`xu N<line break>'
     The `u' stands for UNDERLINE.

     Configure underlining of spaces.  If N is 1, start underlining of
     spaces; if N is 0, stop underlining of spaces.  This is needed for
     the `cu' request in nroff mode and is ignored otherwise.  This
     command is a `gtroff' extension.

`xX ANYTHING<line break>'
     The `x' stands for X-ESCAPE.

     Send string ANYTHING uninterpreted to the device.  If the line
     following this command starts with a `+' character this line is
     interpreted as a continuation line in the following sense.  The
     `+' is ignored, but a newline character is sent instead to the
     device, the rest of the line is sent uninterpreted.  The same
     applies to all following lines until the first character of a line
     is not a `+' character.  This command is generated by the `gtroff'
     escape sequence `\X'.  The line-continuing feature is a `gtroff'
     extension.



File: groff,  Node: Obsolete Command,  Prev: Device Control Commands,  Up: Command Reference

Obsolete Command
................

   In AT&T `troff' output, the writing of a single glyph is mostly done
by a very strange command that combines a horizontal move and a single
character giving the glyph name.  It doesn't have a command code, but
is represented by a 3-character argument consisting of exactly 2 digits
and a character.

DDG
     Move right DD (exactly two decimal digits) basic units `u', then
     print glyph G (represented as a single character).

     In `gtroff', arbitrary syntactical space around and within this
     command is allowed to be added.  Only when a preceding command on
     the same line ends with an argument of variable length a
     separating space is obligatory.  In AT&T `troff', large clusters
     of these and other commands are used, mostly without spaces; this
     made such output almost unreadable.


   For modern high-resolution devices, this command does not make sense
because the width of the glyphs can become much larger than two decimal
digits.  In `gtroff', this is only used for the devices `X75',
`X75-12', `X100', and `X100-12'.  For other devices, the commands `t'
and `u' provide a better functionality.


File: groff,  Node: Intermediate Output Examples,  Next: Output Language Compatibility,  Prev: Command Reference,  Up: gtroff Output

Intermediate Output Examples
----------------------------

   This section presents the intermediate output generated from the same
input for three different devices.  The input is the sentence `hell
world' fed into `gtroff' on the command line.

High-resolution device `ps'
     This is the standard output of `gtroff' if no `-T' option is given.

          shell> echo "hell world" | groff -Z -T ps
          
          x T ps
          x res 72000 1 1
          x init
          p1
          x font 5 TR
          f5
          s10000
          V12000
          H72000
          thell
          wh2500
          tw
          H96620
          torld
          n12000 0
          x trailer
          V792000
          x stop

     This output can be fed into `grops' to get its representation as a
     PostScript file.

Low-resolution device `latin1'
     This is similar to the high-resolution device except that the
     positioning is done at a minor scale.  Some comments (lines
     starting with `#') were added for clarification; they were not
     generated by the formatter.

          shell> echo "hell world" | groff -Z -T latin1
          
          # prologue
          x T latin1
          x res 240 24 40
          x init
          # begin a new page
          p1
          # font setup
          x font 1 R
          f1
          s10
          # initial positioning on the page
          V40
          H0
          # write text `hell'
          thell
          # inform about space, and issue a horizontal jump
          wh24
          # write text `world'
          tworld
          # announce line break, but do nothing because ...
          n40 0
          # ... the end of the document has been reached
          x trailer
          V2640
          x stop

     This output can be fed into `grotty' to get a formatted text
     document.

AT&T `troff' output
     Since a computer monitor has a very low resolution compared to
     modern printers the intermediate output for the X Window devices
     can use the jump-and-write command with its 2-digit displacements.

          shell> echo "hell world" | groff -Z -T X100
          
          x T X100
          x res 100 1 1
          x init
          p1
          x font 5 TR
          f5
          s10
          V16
          H100
          # write text with jump-and-write commands
          ch07e07l03lw06w11o07r05l03dh7
          n16 0
          x trailer
          V1100
          x stop

     This output can be fed into `xditview' or `gxditview' for
     displaying in X.

     Due to the obsolete jump-and-write command, the text clusters in
     the AT&T `troff' output are almost unreadable.



File: groff,  Node: Output Language Compatibility,  Prev: Intermediate Output Examples,  Up: gtroff Output

Output Language Compatibility
-----------------------------

   The intermediate output language of AT&T `troff' was first
documented in the UNIX troff manual, with later additions documented in
`A Typesetter-indenpendent TROFF', written by Brian Kernighan.

   The `gtroff' intermediate output format is compatible with this
specification except for the following features.

   * The classical quasi device independence is not yet implemented.

   * The old hardware was very different from what we use today.  So the
     `groff' devices are also fundamentally different from the ones in
     AT&T `troff'.  For example, the AT&T PostScript device is called
     `post' and has a resolution of only 720 units per inch, suitable
     for printers 20 years ago, while `groff''s `ps' device has a
     resolution of 72000 units per inch.  Maybe, by implementing some
     rescaling mechanism similar to the classical quasi device
     independence, `groff' could emulate AT&T's `post' device.

   * The B-spline command `D~' is correctly handled by the intermediate
     output parser, but the drawing routines aren't implemented in some
     of the postprocessor programs.

   * The argument of the commands `s' and `x H' has the implicit unit
     scaled point `z' in `gtroff', while AT&T `troff' has point (`p').
     This isn't an incompatibility but a compatible extension, for both
     units coincide for all devices without a `sizescale' parameter in
     the `DESC' file, including all postprocessors from AT&T and
     `groff''s text devices.  The few `groff' devices with a
     `sizescale' parameter either do not exist for AT&T `troff', have a
     different name, or seem to have a different resolution.  So
     conflicts are very unlikely.

   * The position changing after the commands `Dp', `DP', and `Dt' is
     illogical, but as old versions of `gtroff' used this feature it is
     kept for compatibility reasons.



File: groff,  Node: Font Files,  Prev: gtroff Output,  Up: File formats

Font Files
==========

   The `gtroff' font format is roughly a superset of the `ditroff' font
format (as used in later versions of AT&T `troff' and its descendants).
Unlike the `ditroff' font format, there is no associated binary
format; all files are text files.(1) (*note Font Files-Footnote-1::)
The font files for device NAME are stored in a directory `devNAME'.
There are two types of file: a device description file called `DESC'
and for each font F a font file called `F'.

* Menu:

* DESC File Format::
* Font File Format::


File: groff,  Node: Font Files-Footnotes,  Up: Font Files

   (1) Plan 9 `troff' has also abandoned the binary format.

