path: root/example.t

.so g.tmac
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.\" configure environments
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. vs +1p
.@e n
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.eo
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.\" start document
.t
.x Mg ,
a simple macro package for troff
.d
John Ankarstr\(:om
.d e
.
.
.h
Introduction
.p
.i Mg
is a simple macro package for troff with the following features:
.n 1
It is designed to be easy to understand and to customize
by editing the source code.
.n
It makes use of the extended support for environments
offered by many modern troff implementations.
.n
It is designed to be practically easy to use.
Macros are consistently one letter long and written in lowercase.
.p
While
.i mg
does provide macros for many common tasks,
including footnotes,
it is at the end of the day an idiosyncratic macro package,
written to serve the author's personal needs.
Users of
.i mg
are encouraged to
.n 1 a )
modify the source code
according to their own needs, as well as
.n
use built-in troff requests for some things
that other packages might provide custom macros for.
.p
All in all,
.i mg
aspires to abstract as little as possible
from the underlying troff requests and registers.
In its author's humble opinion,
it is the ideal macro package for learning troff.
.p
In this document, the fundamental concepts of
.i mg
are explained.
The reader is encouraged to inspect the document's source code
in order to see how the macro package is used in practice.
.
.
.h
Environments
.p
.i Mg
makes heavy use of named environments,
supported by implementations such as GNU troff and Neatroff.
Environments obliviate the need for many special registers
that a macro package (and its user) would otherwise need to keep track of.
For example,
.i ms
keeps track of the document's font size in the
.c PS
register.
For the font size of headings,
it has yet another register.
.i Mg
has no such registers.
If the user wishes to modify the default font size,
he or she can simply switch to the relevant environment
and set the font size as desired
using regular troff requests:
.l
\&.\\" set heading font
\&.h
\&.fam H
\&.ps +1p
.p
Troff saves the font settings in the environment,
so that the next time the environment is invoked,
the desired font family and point size are automatically restored.
.p
The environments are initialized
as soon as the first
.q block-level
macro is called.
At the initialization of each environment,
the default environment (0) is copied,
meaning that all environment-relevant settings
defined before the first macro call
are applied to all
.i mg
environments.
It is thus remarkably simple and intuitive to set,
for example, the default font of a document:
.l
\&.fam N
\&.t
Document title
\&.p
First paragraph.
.p
In addition to the normal environment-relevant settings,
.i mg
manually associates a few special registers with the current environment:
.n 1
.c sp ,
the amount of vertical space to add before an environment
.n
.c sq ,
the amount of vertical space to add before a different type of environment
.n
.c ti ,
the indentation of the first line in some environments
(currently only
.c p )
.p
These can be set inside a given environment
to control its behavior when invoked.
The only exception are the margin and footnote environments
.c @m , (
.c @f ),
which are treated specially
and do not support these registers.
.
.
.h
External macros
.p
.i Mg
defines a number of macros.
Some of them are used internally by
.i mg
itself;
these carry an at
.c @ ) (
prefix
and are going to be explored later.
For now, we will focus on the external macros provided by
.i mg .
.s
Inline macros
.p
There is a group of macros that provide
convenient inline formatting.
All take three arguments:
the text to be formatted,
the text to be placed immediately after
and the text to be placed immediately before.
The inline macros are the following:
.n 1
.c b ,
bold font
.n
.c c ,
constant-width font
.n
.c i ,
italic font
.n
.c i ,
bold italic font
.p
For example, the following request outputs
.i mg .\(rq: \(lq
.l
\&.i mg .
.
.p
Note that
.c c
uses the font family and point size
set in the
.c l
environment (see below).
.s
Block-level macros
.p
There is a large group of macros that provide
block-level formatting:
.n 1
.c d ,
centered date or text
.n
.c h ,
heading
.n
.c l ,
literal display (for source code)
.n
.c p ,
paragraph
.n
.c s ,
subheading
.n
.c t ,
centered title
.p
The
.c t
and
.c d
macros can be used at the beginning of a document
to create a centered header:
.l
\&.t
Document title
\&.d
First author
\&.br
Second author
\&.d i \\" current date formatted as YYYY-MM-DD
.p
In the example above, you can see that the
.c d
macro may be used for other things than just dates.
This works because
.c d
displays the date only if given
an argument describing the desired date format:
.n 1 a )
.c i :
international date, like
.q 2021-06-21
.n
.c e :
English date, like
.q "21 June 2021"
.p
The formatted dates are defined in strings prefixed with a hash symbol
.c # ): (
.c #i
and
.c #e
are provided by default,
but more may be added by the user.
.
.s
Other macros
.p
Finally, there are a few macros
that belong to neither category:
.n 1
.ne 2
.c ( ,
begin footnote
.n
.c ) ,
end footnote
.n
.ne 2
.c q ,
quotation
.n
.c w ,
want space
.p
The macros
.c (
and
.c )
create footnotes,
placing a numerical reference at the place of their invocation.
Both
.c (
and
.c )
take an optional argument,
which is output either immediately before or immediately after
the inline reference.
For example, the following code
.l
\&.q
This is a quotation\\c
\&.(
.ne 1
This is a footnote.
\&.) .
.p
creates the following reference:
.q
This is a quotation\c
.(
This is a footnote.
.) .
.p
If
.c (
and
.c )
are called at such a position that the collected footnotes
cannot fit on the current page,
.i mg
will print the footnotes on the next page instead.
.p
The
.c q
behaves like an inline macro by default,
surrounding text in quotation marks,
but if no arguments are given to it,
it starts an indented block quotation instead:
.l
.ne 2
\&.q
This is an indented quotation.
\&.p
This is an inline
\&.q quotation .
.p
The
.c w
macro is an alternative to troff's
.c ne
request,
which ensures that a given amount of space is available on the page
\(en otherwise, a line break is issued \(en
but unlike
.c ne ,
which takes an exact amount of space as its argument,
.c w
takes a declarative specification
describing the amount of desired space
in terms of
.i mg
environments.
For example:
.l
\&.\\" want space for...
\&.w s p \\" a subheading of one line + a paragraph of one line
\&.w s pp \\" a subheading of one line + a paragraph of two lines
\&.w ss p \\" a subheading of two lines + a paragraph of one line
.
.
.h
Internal macros
.p
.i Mg 's
internal macros are generally not meant to be used outside of
.i g.tmac .
Documented in this section are the exceptions to this rule.
For examples of how these macros are used in practice,
see the FAQ section below.
.
.s
Margin macros
.p
The
.c @h ,
.c @f ,
.c @th
and
.c @tf
macros control the page header and footer.
.p
At document initialization,
.i mg
automatically creates traps for
.c @th
and
.c @tf .
When sprung,
.c @th
and
.c @tf
call
.c @h
and
.c @t ,
which control the text and spacing of the header and footer.
.p
.i Mg
will avoid creating a trap for
.c @tf
if any trap has already been set before document initialization.
This means that users can override the position of the
.c @tf
trap by setting it themselves.
Likewise, users can redefine
.c @h
and
.c @f
to change the content of the header and footer.
.
.s
Environment macros
.p
The environment-related macros
.c (e ,
.c @e
and
.c @c
may be used in advanced documents to define custom environments.
.p
At the present,
.c (e
is nothing more than a wrapper around troff's built-in
.c ev ,
but it may eventually be redefined in order to offer
compatibility with implementations of troff
without support for named environments.
.p
.c @e
and
.c @c
are equivalent to troff's
.c ev
and
.c evc ,
but perform some extra work to keep track of
.i mg 's
special environment variables
(see
.i Environments
above).
.
.
.h
Frequently anticipated questions
.
.s
How do I customize the default appearance of a document?
.p
All environment settings,
like point size, font family and indentation\c
.(
For a complete list of settings that are associated with the environment,
see 5.26\~\c
.i Environments
in the full GNU troff manual
.nh
.c "info '(groff.\:info)Environments'" ). (
.hy
.) ,
are configured with the standard troff requests.
If you set the point size at the beginning of the document,
before any
.i mg
macros have been called,
it will be correctly set for the entire document.
This works because
.i mg 's
environments initially copy all their settings from 0,
the default environment.
.p
For example, if you wanted to write a document
with the New Century Schoolbook font
at 9 points
and a vertical spacing of 12 points,
you would start the document like this
(before you call any
.i mg
macros):
.l
\&.fam N
\&.ps 9p
\&.vs 12p
.
.s
How do I customize the default appearance of a given environment?
.p
To configure the layout and font settings of a specific environment,
you can switch to that environment and use the relevant troff requests:
.l
.ne 1
\&.q
\&.ps +1p
.p
If you are merely configuring the environment
without printing anything in it,
you can also use the
.c @e
macro:
.l
\&.@e q
\&.ps +1p
.
.w s ll
.s
How do I customize the default appearance of the margin text?
.l
\&.(e @m \\" margin environment
\&.ps +1p
.p
You can also set such settings in your redefinition of
.c @h
or
.c @f .
.
.w s ll
.s
How do I customize the default appearance of footnotes?
.l
\&.(e @f \\" footnote environment
\&.ps +1p
.
.s
How do I redefine the page header?
.l
\&.de @h
\&. \\" set position of header text
\&. sp |36p
\&. \\" set header text
\&. tl 'left'center'right'
\&. \\" set position of page text
\&. sp |1i
\&..
.
.s
How do I redefine the page footer?
.l
\&.\\" set position of footer trap
\&.\\" (must be done before any macros have been called)
\&.wh -1i @tf
\&.
\&.de @f
\&. \\" set position of footer text
\&. \\" (must be below the footer trap)
\&. sp |\\\\n(.pu-48p
\&. tl 'left'center'right'
\&..
.
.s
How do I prevent a section from being broken up by a page break?
.p
Some macro packages have a concept of
.q keeps ,
sections that are kept together across page breaks.
.i Mg
does not define any such macros by default.
The simplest way to achieve the same is to use troff's
.c ne
request:
.l
\&.ne 7 \\" break page if seven lines won't fit on this page
\&.\\" ... some text ...
.p
If you want to keep text of various styles together,
you can use
.i mg 's
own
.c w
macro:
.l
\&.w s qq \\" break page if a subheading and two lines of a quotation won't fit
\&.\\" ... some text ...
.ig
.p
For a more general solution, you can use a diversion:
.l
\&.di keep
\&.\\" ... some text ...
\&.br
\&.di
\&.ne \\n(dnu
\&.keep
..
.
.s
How do I define my own environments?
.p
Environments are a feature built into troff,
accessed via the
.c ev
request, but because
.i mg
extends environments with additional functionality,
it provides special macros to be used instead of
.c ev :
.n 1
.c (e ,
set environment (same as
.c ev )
.n
.c @e ,
set extended environment
.n
.c @c ,
copy environment (same as
.c evc )
.p
The
.c @e
macro
can be used to activate any environment that supports
.i mg 's
extensions (see
.i Environments
above).
The following code configures an environment called
.c n
and defines a corresponding macro:
.l
\&.@e n
\&. @c 0 \\" copy default environment
\&. ps -1p
\&.@e
\&.
\&.de n
\&. br \\" finish current environment
\&. @e n \\" activate new environment
\&..