The roff language really has two groups of basic building blocks:

Requests and escape sequences.  Consequently, supplement the
REQUEST REFERENCE by an ESCAPE SEQUENCE REFERENCE, such that people
no longer need to guess or experiment what mandoc(1) implements,
what it parses and ignores, and what it doesn't handle at all.

1 files changed, 253 insertions, 7 deletions

diff --git a/roff.7 b/roff.7
index 8b0592f3..fcfb815e 100644
--- a/roff.7
+++ b/roff.7
@@ -1,7 +1,7 @@
 .\"	$Id$
 .\"
-.\" Copyright (c) 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
-.\" Copyright (c) 2010, 2011 Ingo Schwarze <schwarze@openbsd.org>
+.\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
+.\" Copyright (c) 2010, 2011, 2013 Ingo Schwarze <schwarze@openbsd.org>
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
 .\" purpose with or without fee is hereby granted, provided that the above
@@ -32,7 +32,7 @@ and
 manual formatting languages are based on it,
 many real-world manuals use small numbers of
 .Nm
-requests intermixed with their
+requests and escape sequences intermixed with their
 .Xr mdoc 7
 or
 .Xr man 7
@@ -41,8 +41,8 @@ To properly format such manuals, the
 .Xr mandoc 1
 utility supports a tiny subset of
 .Nm
-requests.
-Only these requests supported by
+requests and escapes.
+Only these requests and escapes supported by
 .Xr mandoc 1
 are documented in the present manual,
 together with the basic language syntax shared by
@@ -85,7 +85,7 @@ documents may contain only graphable 7-bit ASCII characters, the space
 character, and, in certain circumstances, the tab character.
 The backslash character
 .Sq \e
-indicates the start of an escape sequence for
+indicates the start of an escape sequence, used for example for
 .Sx Comments ,
 .Sx Special Characters ,
 .Sx Predefined Strings ,
@@ -93,6 +93,9 @@ and
 user-defined strings defined using the
 .Sx ds
 request.
+For a listing of escape sequences, consult the
+.Sx ESCAPE SEQUENCE REFERENCE
+below.
 .Ss Comments
 Text following an escaped double-quote
 .Sq \e\(dq ,
@@ -824,7 +827,7 @@ Its syntax is as follows:
 The
 .Ar value
 may, at the moment, only be an integer.
-If it is prefixed by a sign, the register will be 
+If it is prefixed by a sign, the register will be
 incremented or decremented instead of assigned to.
 .Pp
 The following register
@@ -926,6 +929,249 @@ Begin a table, which formats input in aligned rows and columns.
 See
 .Xr tbl 7
 for a description of the tbl language.
+.Sh ESCAPE SEQUENCE REFERENCE
+The
+.Xr mandoc 1
+.Nm
+parser recognises the following escape sequences.
+Note that the
+.Nm
+language defines more escape sequences not implemented in
+.Xr mandoc 1 .
+In
+.Xr mdoc 7
+and
+.Xr man 7
+documents, using escape sequences is discouraged except for those
+described in the
+.Sx LANGUAGE SYNTAX
+section above.
+.Pp
+A backslash followed by any character not listed here
+simply prints that character itself.
+.Ss \e<newline>
+A backslash at the end of an input line can be used to continue the
+logical input line on the next physical input line, joining the text
+on both lines together as if it were on a single input line.
+.Ss \e<space>
+The escape sequence backslash-space
+.Pq Sq \e\ \&
+is an unpaddable space-sized non-breaking space character; see
+.Sx Whitespace .
+.Ss \e\(dq
+The rest of the input line is treated as
+.Sx Comments .
+.Ss \e%
+Hyphenation allowed at this point of the word; ignored by
+.Xr mandoc 1 .
+.Ss \e&
+Non-printing zero-width character; see
+.Sx Whitespace .
+.Ss \e\(aq
+Acute accent special character; use
+.Sq \e(aa
+instead.
+.Ss \e( Ns Ar cc
+.Sx Special Characters
+with two-letter names, see
+.Xr mandoc_char 7 .
+.Ss \e*[ Ns Ar name ]
+Interpolate the string with the
+.Ar name ;
+see
+.Sx Predefined Strings
+and
+.Sx ds .
+For short names, there are variants
+.No \e* Ns Ar c
+and
+.No \e*( Ns Ar cc .
+.Ss \e-
+Special character
+.Dq mathematical minus sign .
+.Ss \e[ Ns Ar name ]
+.Sx Special Characters
+with names of arbitrary length, see
+.Xr mandoc_char 7 .
+.Ss \e^
+One-twelfth em half-narrow space character, effectively zero-width in
+.Xr mandoc 1 .
+.Ss \e`
+Grave accent special character; use
+.Sq \e(ga
+instead.
+.Ss \e{
+Begin conditional input; see
+.Sx if .
+.Ss \e\(ba
+One-sixth em narrow space character, effectively zero-width in
+.Xr mandoc 1 .
+.Ss \e}
+End conditional input; see
+.Sx if .
+.Ss \e~
+Paddable non-breaking space character.
+.Ss \e0
+Digit width space character.
+.Ss \eA\(aq Ns Ar string Ns \(aq
+Anchor definition; ignored by
+.Xr mandoc 1 .
+.Ss \eB\(aq Ns Ar string Ns \(aq
+Test whether
+.Ar string
+is a numerical expession; ignored by
+.Xr mandoc 1 .
+.Ss \eb\(aq Ns Ar string Ns \(aq
+Bracket building function; ignored by
+.Xr mandoc 1 .
+.Ss \eC\(aq Ns Ar name Ns \(aq
+.Sx Special Characters
+with names of arbitrary length.
+.Ss \ec
+Interrupt text processing to insert requests or macros; ignored by
+.Xr mandoc 1 .
+.Ss \eD\(aq Ns Ar string Ns \(aq
+Draw graphics function; ignored by
+.Xr mandoc 1 .
+.Ss \ed
+Move down by half a line; ignored by
+.Xr mandoc 1 .
+.Ss \ee
+Backslash special character.
+.Ss \eF[ Ns Ar name ]
+Switch font family (groff extension); ignored by
+.Xr mandoc 1 .
+For short names, there are variants
+.No \eF Ns Ar c
+and
+.No \eF( Ns Ar cc .
+.Ss \ef[ Ns Ar name ]
+Switch to the font
+.Ar name ,
+see
+.Sx Text Decoration .
+For short names, there are variants
+.No \ef Ns Ar c
+and
+.No \ef( Ns Ar cc .
+.Ss \eg[ Ns Ar name ]
+Interpolate the format of a number register; ignored by
+.Xr mandoc 1 .
+For short names, there are variants
+.No \eg Ns Ar c
+and
+.No \eg( Ns Ar cc .
+.Ss \eH\(aq Ns Oo +|- Oc Ns Ar number Ns \(aq
+Set the height of the current font; ignored by
+.Xr mandoc 1 .
+.Ss \eh\(aq Ns Ar number Ns \(aq
+Horizontal motion; ignored by
+.Xr mandoc 1 .
+.Ss \ek[ Ns Ar name ]
+Mark horizontal input place in register; ignored by
+.Xr mandoc 1 .
+For short names, there are variants
+.No \ek Ns Ar c
+and
+.No \ek( Ns Ar cc .
+.Ss \eL\(aq Ns Ar number Ns Oo Ar c Oc Ns \(aq
+Vertical line drawing function; ignored by
+.Xr mandoc 1 .
+.Ss \el\(aq Ns Ar number Ns Oo Ar c Oc Ns \(aq
+Horizontal line drawing function; ignored by
+.Xr mandoc 1 .
+.Ss \eM[ Ns Ar name ]
+Set fill (background) color (groff extension); ignored by
+.Xr mandoc 1 .
+For short names, there are variants
+.No \eM Ns Ar c
+and
+.No \eM( Ns Ar cc .
+.Ss \em[ Ns Ar name ]
+Set glyph drawing color (groff extension); ignored by
+.Xr mandoc 1 .
+For short names, there are variants
+.No \em Ns Ar c
+and
+.No \em( Ns Ar cc .
+.Ss \eN\(aq Ns Ar number Ns \(aq
+Character
+.Ar number
+on the current font.
+.Ss \en[ Ns Ar name ]
+Interpolate the number register
+.Ar name .
+For short names, there are variants
+.No \en Ns Ar c
+and
+.No \en( Ns Ar cc .
+.Ss \eo\(aq Ns Ar string Ns \(aq
+Overstrike
+.Ar string ;
+ignored by
+.Xr mandoc 1 .
+.Ss \eR\(aq Ns Ar name Oo +|- Oc Ns Ar number Ns \(aq
+Set number register; ignored by
+.Xr mandoc 1 .
+.Ss \eS\(aq Ns Ar number Ns \(aq
+Slant output; ignored by
+.Xr mandoc 1 .
+.Ss \es\(aq Ns Oo +|- Oc Ns Ar number Ns \(aq
+Change point size; ignored by
+.Xr mandoc 1 .
+Alternative forms
+.No \es Ns Oo +|- Oc Ns Ar n ,
+.No \es Ns Oo +|- Oc Ns \(aq Ns Ar number Ns \(aq ,
+.No \es Ns [ Oo +|- Oc Ns Ar number ] ,
+and
+.No \es Ns Oo +|- Oc Ns [ Ar number Ns ]
+are also parsed and ignored.
+.Ss \et
+Horizontal tab; ignored by
+.Xr mandoc 1 .
+.Ss \eu
+Move up by half a line; ignored by
+.Xr mandoc 1 .
+.Ss \eV[ Ns Ar name ]
+Interpolate an environment variable; ignored by
+.Xr mandoc 1 .
+For short names, there are variants
+.No \eV Ns Ar c
+and
+.No \eV( Ns Ar cc .
+.Ss \ev\(aq Ns Ar number Ns \(aq
+Vertical motion; ignored by
+.Xr mandoc 1 .
+.Ss \ew\(aq Ns Ar string Ns \(aq
+Interpolate the width of the
+.Ar string ;
+ignored by
+.Xr mandoc 1 .
+.Ss \eX\(aq Ns Ar string Ns \(aq
+Output
+.Ar string
+as device control function; ignored in nroff mode and by
+.Xr mandoc 1 .
+.Ss \ex\(aq Ns Ar number Ns \(aq
+Extra line space function; ignored by
+.Xr mandoc 1 .
+.Ss \eY[ Ns Ar name ]
+Output a string as a device control function; ignored in nroff mode and by
+.Xr mandoc 1 .
+For short names, there are variants
+.No \eY Ns Ar c
+and
+.No \eY( Ns Ar cc .
+.Ss \eZ\(aq Ns Ar string Ns \(aq
+Print
+.Ar string
+with zero width and height; ignored by
+.Xr mandoc 1 .
+.Ss \ez
+Output the next character without advancing the cursor position;
+approximated in
+.Xr mandoc 1
+by simply skipping the next character.
 .Sh COMPATIBILITY
 This section documents compatibility between mandoc and other
 .Nm