===================================================================
RCS file: /cvs/mandoc/roff.7,v
retrieving revision 1.56
retrieving revision 1.115
diff -u -p -r1.56 -r1.115
--- mandoc/roff.7	2014/08/13 20:34:29	1.56
+++ mandoc/roff.7	2020/10/28 21:07:47	1.115
@@ -1,7 +1,7 @@
-.\"	$Id: roff.7,v 1.56 2014/08/13 20:34:29 kristaps Exp $
+.\"	$Id: roff.7,v 1.115 2020/10/28 21:07:47 schwarze Exp $
 .\"
 .\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
-.\" Copyright (c) 2010, 2011, 2013, 2014 Ingo Schwarze <schwarze@openbsd.org>
+.\" Copyright (c) 2010-2019 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
@@ -15,7 +15,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: August 13 2014 $
+.Dd $Mdocdate: October 28 2020 $
 .Dt ROFF 7
 .Os
 .Sh NAME
@@ -39,17 +39,15 @@ or
 code.
 To properly format such manuals, the
 .Xr mandoc 1
-utility supports a tiny subset of
+utility supports a subset of
 .Nm
 requests and escapes.
-Only these requests and escapes supported by
+Even though this manual page lists all
+.Nm
+requests and escape sequences, it only contains partial information
+about requests not supported by
 .Xr mandoc 1
-are documented in the present manual,
-together with the basic language syntax shared by
-.Nm ,
-.Xr mdoc 7 ,
-and
-.Xr man 7 .
+and about language features that do not matter for manual pages.
 For complete
 .Nm
 manuals, consult the
@@ -86,14 +84,10 @@ character, and, in certain circumstances, the tab char
 The backslash character
 .Sq \e
 indicates the start of an escape sequence, used for example for
-.Sx Comments ,
-.Sx Special Characters ,
-.Sx Predefined Strings ,
+.Sx Comments
 and
-user-defined strings defined using the
-.Sx ds
-request.
-For a listing of escape sequences, consult the
+.Sx Special Characters .
+For a complete listing of escape sequences, consult the
 .Sx ESCAPE SEQUENCE REFERENCE
 below.
 .Ss Comments
@@ -139,21 +133,74 @@ One-letter backslash escape.
 See
 .Xr mandoc_char 7
 for a complete list.
-.Ss Text Decoration
-Terms may be text-decorated using the
-.Sq \ef
-escape followed by an indicator: B (bold), I (italic), R (regular), or P
-(revert to previous mode).
-A numerical representation 3, 2, or 1 (bold, italic, and regular,
-respectively) may be used instead.
-The indicator or numerical representative may be preceded by C
-(constant-width), which is ignored.
+.Ss Font Selection
+In
+.Xr mdoc 7
+and
+.Xr man 7
+documents, fonts are usually selected with macros.
+The
+.Ic \ef
+escape sequence and the
+.Ic \&ft
+request can be used to manually change the font,
+but this is not recommended in
+.Xr mdoc 7
+documents.
+Such manual font changes are overridden by many subsequent macros.
 .Pp
-The two-character indicator
-.Sq BI
-requests a font that is both bold and italic.
-It may not be portable to old roff implementations.
+The following fonts are supported:
 .Pp
+.Bl -tag -width CW -offset indent -compact
+.It Cm B
+Bold font.
+.It Cm BI
+A font that is both bold and italic.
+.It Cm CB
+Bold constant width font.
+Same as
+.Cm B
+in terminal output.
+.It Cm CI
+Italic constant width font.
+Same as
+.Cm I
+in terminal output.
+.It Cm CR
+Regular constant width font.
+Same as
+.Cm R
+in terminal output.
+.It Cm CW
+An alias for
+.Cm CR .
+.It Cm I
+Italic font.
+.It Cm P
+Return to the previous font.
+If a macro caused a font change since the last
+.Ic \ef
+eascape sequence or
+.Ic \&ft
+request, this returns to the font before the last font change in
+the macro rather than to the font before the last manual font change.
+.It Cm R
+Roman font.
+This is the default font.
+.It Cm 1
+An alias for
+.Cm R .
+.It Cm 2
+An alias for
+.Cm I .
+.It Cm 3
+An alias for
+.Cm B .
+.It Cm 4
+An alias for
+.Cm BI .
+.El
+.Pp
 Examples:
 .Bl -tag -width Ds -offset indent -compact
 .It Li \efBbold\efR
@@ -163,40 +210,6 @@ Write in \fIitalic\fP, then return to previous font mo
 .It Li \ef(BIbold italic\efP
 Write in \f(BIbold italic\fP, then return to previous font mode.
 .El
-.Pp
-Text decoration is
-.Em not
-recommended for
-.Xr mdoc 7 ,
-which encourages semantic annotation.
-.Ss Predefined Strings
-Predefined strings, like
-.Sx Special Characters ,
-mark special output glyphs.
-Predefined strings are escaped with the slash-asterisk,
-.Sq \e* :
-single-character
-.Sq \e*X ,
-two-character
-.Sq \e*(XX ,
-and N-character
-.Sq \e*[N] .
-.Pp
-Examples:
-.Bl -tag -width Ds -offset indent -compact
-.It Li \e*(Am
-Two-letter ampersand predefined string.
-.It Li \e*q
-One-letter double-quote predefined string.
-.El
-.Pp
-Predefined strings are not recommended for use,
-as they differ across implementations.
-Those supported by
-.Xr mandoc 1
-are listed in
-.Xr mandoc_char 7 .
-Manuals using these predefined strings are almost certainly not portable.
 .Ss Whitespace
 Whitespace consists of the space character.
 In text lines, whitespace is preserved within a line.
@@ -206,7 +219,7 @@ Unescaped trailing spaces are stripped from text line 
 literal context.
 In general, trailing whitespace on any input line is discouraged for
 reasons of portability.
-In the rare case that a blank character is needed at the end of an
+In the rare case that a space character is needed at the end of an
 input line, it may be forced by
 .Sq \e\ \e& .
 .Pp
@@ -225,7 +238,6 @@ Many requests and macros support scaled widths for the
 The syntax for a scaled width is
 .Sq Li [+-]?[0-9]*.[0-9]*[:unit:] ,
 where a decimal must be preceded or followed by at least one digit.
-Negative numbers, while accepted, are truncated to zero.
 .Pp
 The following scaling units are accepted:
 .Pp
@@ -235,9 +247,9 @@ centimetre
 .It i
 inch
 .It P
-pica (~1/6 inch)
+pica (1/6 inch)
 .It p
-point (~1/72 inch)
+point (1/72 inch)
 .It f
 scale
 .Sq u
@@ -257,7 +269,7 @@ character
 .It u
 default horizontal span for the terminal
 .It M
-mini-em (~1/100 em)
+mini-em (1/100 em)
 .El
 .Pp
 Using anything other than
@@ -303,12 +315,18 @@ delimiters
 The proper spacing is also intelligently preserved if a sentence ends at
 the boundary of a macro line.
 .Pp
+If an input line happens to end with a period, exclamation or question
+mark that isn't the end of a sentence, append a zero-width space
+.Pq Sq \e& .
+.Pp
 Examples:
 .Bd -literal -offset indent -compact
 Do not end sentences mid-line like this.  Instead,
 end a sentence like this.
 A macro would end like this:
 \&.Xr mandoc 1 \&.
+An abbreviation at the end of an input line needs escaping, e.g.\e&
+like this.
 .Ed
 .Sh REQUEST SYNTAX
 A request or macro line consists of:
@@ -341,7 +359,7 @@ Macros are provided by the
 and
 .Xr man 7
 languages and can be defined by the
-.Sx \&de
+.Ic \&de
 request.
 When called, they follow the same syntax as requests, except that
 macro arguments may optionally be quoted by enclosing them
@@ -395,81 +413,226 @@ The
 .Xr mandoc 1
 .Nm
 parser recognises the following requests.
-Note that the
-.Nm
-language defines many more requests not implemented in
-.Xr mandoc 1 .
-.Ss \&ad
-Set line adjustment mode.
-This line-scoped request is intended to have one argument to select
-normal, left, right, or centre adjustment for subsequent text.
-Currently, it is ignored including its arguments,
-and the number of arguments is not checked.
-.Ss \&am
+For requests marked as "ignored" or "unsupported", any arguments are
+ignored, and the number of arguments is not checked.
+.Bl -tag -width Ds
+.It Ic \&ab Op Ar message
+Abort processing.
+Currently unsupported.
+.It Ic \&ad Op Cm b | c | l | n | r
+Set line adjustment mode for subsequent text.
+Currently ignored.
+.It Ic \&af Ar registername format
+Assign an output format to a number register.
+Currently ignored.
+.It Ic \&aln Ar newname oldname
+Create an alias for a number register.
+Currently unsupported.
+.It Ic \&als Ar newname oldname
+Create an alias for a request, string, macro, or diversion.
+.It Ic \&am Ar macroname Op Ar endmacro
 Append to a macro definition.
 The syntax of this request is the same as that of
-.Sx \&de .
-.Ss \&ami
-Append to a macro definition, specifying the macro name indirectly.
-The syntax of this request is the same as that of
-.Sx \&dei .
-.Ss \&am1
+.Ic \&de .
+.It Ic \&am1 Ar macroname Op Ar endmacro
 Append to a macro definition, switching roff compatibility mode off
-during macro execution.
+during macro execution (groff extension).
 The syntax of this request is the same as that of
-.Sx \&de1 .
+.Ic \&de1 .
 Since
 .Xr mandoc 1
 does not implement
 .Nm
 compatibility mode at all, it handles this request as an alias for
-.Sx \&am .
-.Ss \&as
+.Ic \&am .
+.It Ic \&ami Ar macrostring Op Ar endstring
+Append to a macro definition, specifying the macro name indirectly
+(groff extension).
+The syntax of this request is the same as that of
+.Ic \&dei .
+.It Ic \&ami1 Ar macrostring Op Ar endstring
+Append to a macro definition, specifying the macro name indirectly
+and switching roff compatibility mode off during macro execution
+(groff extension).
+The syntax of this request is the same as that of
+.Ic \&dei1 .
+Since
+.Xr mandoc 1
+does not implement
+.Nm
+compatibility mode at all, it handles this request as an alias for
+.Ic \&ami .
+.It Ic \&as Ar stringname Op Ar string
 Append to a user-defined string.
 The syntax of this request is the same as that of
-.Sx \&ds .
+.Ic \&ds .
 If a user-defined string with the specified name does not yet exist,
 it is set to the empty string before appending.
-.Ss \&cc
-Changes the control character.
-Its syntax is as follows:
-.Bd -literal -offset indent
-.Pf . Cm \&cc Op Ar c
-.Ed
-.Pp
+.It Ic \&as1 Ar stringname Op Ar string
+Append to a user-defined string, switching roff compatibility mode off
+during macro execution (groff extension).
+The syntax of this request is the same as that of
+.Ic \&ds1 .
+Since
+.Xr mandoc 1
+does not implement
+.Nm
+compatibility mode at all, it handles this request as an alias for
+.Ic \&as .
+.It Ic \&asciify Ar divname
+Fully unformat a diversion.
+Currently unsupported.
+.It Ic \&backtrace
+Print a backtrace of the input stack.
+This is a groff extension and currently ignored.
+.It Ic \&bd Ar font Oo Ar curfont Oc Op Ar offset
+Artificially embolden by repeated printing with small shifts.
+Currently ignored.
+.It Ic \&bleedat Ar left top width height
+Set the BleedBox page parameter for PDF generation.
+This is a Heirloom extension and currently ignored.
+.It Ic \&blm Ar macroname
+Set a blank line trap.
+Currently unsupported.
+.It Ic \&box Ar divname
+Begin a diversion without including a partially filled line.
+Currently unsupported.
+.It Ic \&boxa Ar divname
+Add to a diversion without including a partially filled line.
+Currently unsupported.
+.It Ic \&bp Oo Cm + Ns | Ns Cm - Oc Ns Ar pagenumber
+Begin a new page.
+Currently ignored.
+.It Ic \&BP Ar source height width position offset flags label
+Define a frame and place a picture in it.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&br
+Break the output line.
+.It Ic \&break
+Break out of the innermost
+.Ic \&while
+loop.
+.It Ic \&breakchar Ar char ...
+Optional line break characters.
+This is a Heirloom extension and currently ignored.
+.It Ic \&brnl Ar N
+Break output line after the next
+.Ar N
+input lines.
+This is a Heirloom extension and currently ignored.
+.It Ic \&brp
+Break and spread output line.
+Currently, this is implemented as an alias for
+.Ic \&br .
+.It Ic \&brpnl Ar N
+Break and spread output line after the next
+.Ar N
+input lines.
+This is a Heirloom extension and currently ignored.
+.It Ic \&c2 Op Ar char
+Change the no-break control character.
+Currently unsupported.
+.It Ic \&cc Op Ar char
+Change the control character.
 If
-.Ar c
+.Ar char
 is not specified, the control character is reset to
 .Sq \&. .
 Trailing characters are ignored.
-.Ss \&ce
-Center some lines.
-This line-scoped request is intended to take one integer argument,
-specifying how many lines to center.
-Currently, it is ignored including its arguments, and the number
-of arguments is not checked.
-.Ss \&de
+.It Ic \&ce Op Ar N
+Center the next
+.Ar N
+input lines without filling.
+.Ar N
+defaults to 1.
+An argument of 0 or less ends centering.
+Currently, high level macros abort centering.
+.It Ic \&cf Ar filename
+Output the contents of a file.
+Ignored because insecure.
+.It Ic \&cflags Ar flags char ...
+Set character flags.
+This is a groff extension and currently ignored.
+.It Ic \&ch Ar macroname Op Ar dist
+Change a trap location.
+Currently ignored.
+.It Ic \&char Ar glyph Op Ar string
+Define or redefine the ASCII character or character escape sequence
+.Ar glyph
+to be rendered as
+.Ar string ,
+which can be empty.
+Only partially supported in
+.Xr mandoc 1 ;
+may interact incorrectly with
+.Ic \&tr .
+.It Ic \&chop Ar stringname
+Remove the last character from a macro, string, or diversion.
+Currently unsupported.
+.It Ic \&class Ar classname char ...
+Define a character class.
+This is a groff extension and currently ignored.
+.It Ic \&close Ar streamname
+Close an open file.
+Ignored because insecure.
+.It Ic \&CL Ar color text
+Print text in color.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&color Op Cm 1 | 0
+Activate or deactivate colors.
+This is a groff extension and currently ignored.
+.It Ic \&composite Ar from to
+Define a name component for composite glyph names.
+This is a groff extension and currently unsupported.
+.It Ic \&continue
+Immediately start the next iteration of a
+.Ic \&while
+loop.
+Currently unsupported.
+.It Ic \&cp Op Cm 1 | 0
+Switch
+.Nm
+compatibility mode on or off.
+Currently ignored.
+.It Ic \&cropat Ar left top width height
+Set the CropBox page parameter for PDF generation.
+This is a Heirloom extension and currently ignored.
+.It Ic \&cs Ar font Op Ar width Op Ar emsize
+Constant character spacing mode.
+Currently ignored.
+.It Ic \&cu Op Ar N
+Underline next
+.Ar N
+input lines including whitespace.
+Currently ignored.
+.It Ic \&da Ar divname
+Append to a diversion.
+Currently unsupported.
+.It Ic \&dch Ar macroname Op Ar dist
+Change a trap location in the current diversion.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&de Ar macroname Op Ar endmacro
 Define a
 .Nm
 macro.
 Its syntax can be either
 .Bd -literal -offset indent
-.Pf . Cm \&de Ar name
-.Ar macro definition
+.Pf . Ic \&de Ar macroname
+.Ar definition
 \&..
 .Ed
 .Pp
 or
 .Bd -literal -offset indent
-.Pf . Cm \&de Ar name Ar end
-.Ar macro definition
-.Pf . Ar end
+.Pf . Ic \&de Ar macroname Ar endmacro
+.Ar definition
+.Pf . Ar endmacro
 .Ed
 .Pp
 Both forms define or redefine the macro
-.Ar name
+.Ar macroname
 to represent the
-.Ar macro definition ,
+.Ar definition ,
 which may consist of one or more input lines, including the newline
 characters terminating each line, optionally containing calls to
 .Nm
@@ -482,13 +645,13 @@ or
 macros, whichever applies to the document in question.
 .Pp
 Specifying a custom
-.Ar end
-macro works in the same way as for
-.Sx \&ig ;
+.Ar endmacro
+works in the same way as for
+.Ic \&ig ;
 namely, the call to
-.Sq Pf . Ar end
+.Sq Pf . Ar endmacro
 first ends the
-.Ar macro definition ,
+.Ar definition ,
 and after that, it is also evaluated as a
 .Nm
 request or
@@ -497,7 +660,7 @@ macro, but not as a high-level macro.
 .Pp
 The macro can be invoked later using the syntax
 .Pp
-.D1 Pf . Ar name Op Ar argument Op Ar argument ...
+.D1 Pf . Ar macroname Op Ar argument Op Ar argument ...
 .Pp
 Regarding argument parsing, see
 .Sx MACRO SYNTAX
@@ -505,7 +668,7 @@ above.
 .Pp
 The line invoking the macro will be replaced
 in the input stream by the
-.Ar macro definition ,
+.Ar definition ,
 replacing all occurrences of
 .No \e\e$ Ns Ar N ,
 where
@@ -525,62 +688,86 @@ produces
 .D1 \efI\e^XtFree\e^\efP.
 .Pp
 in the input stream, and thus in the output: \fI\^XtFree\^\fP.
+Each occurrence of \e\e$* is replaced with all the arguments,
+joined together with single space characters.
+The variant \e\e$@ is similar, except that each argument is
+individually quoted.
 .Pp
 Since macros and user-defined strings share a common string table,
 defining a macro
-.Ar name
+.Ar macroname
 clobbers the user-defined string
-.Ar name ,
+.Ar macroname ,
 and the
-.Ar macro definition
+.Ar definition
 can also be printed using the
 .Sq \e*
 string interpolation syntax described below
-.Sx ds ,
+.Ic ds ,
 but this is rarely useful because every macro definition contains at least
 one explicit newline character.
 .Pp
 In order to prevent endless recursion, both groff and
 .Xr mandoc 1
 limit the stack depth for expanding macros and strings
-to a large, but finite number.
-Do not rely on the exact value of this limit.
-.Ss \&dei
+to a large, but finite number, and
+.Xr mandoc 1
+also limits the length of the expanded input line.
+Do not rely on the exact values of these limits.
+.It Ic \&de1 Ar macroname Op Ar endmacro
 Define a
 .Nm
-macro, specifying the macro name indirectly.
+macro that will be executed with
+.Nm
+compatibility mode switched off during macro execution.
+This is a groff extension.
+Since
+.Xr mandoc 1
+does not implement
+.Nm
+compatibility mode at all, it handles this request as an alias for
+.Ic \&de .
+.It Ic \&defcolor Ar newname scheme component ...
+Define a color name.
+This is a groff extension and currently ignored.
+.It Ic \&dei Ar macrostring Op Ar endstring
+Define a
+.Nm
+macro, specifying the macro name indirectly (groff extension).
 The syntax of this request is the same as that of
-.Sx \&de .
-The request
+.Ic \&de .
+The effect is the same as:
 .Pp
-.D1 Pf . Cm \&dei Ar name Op Ar end
-.Pp
-has the same effect as:
-.Pp
-.D1 Pf . Cm \&de No \e* Ns Bo Ar name Bc Op \e* Ns Bq Ar end
-.Ss \&de1
+.D1 Pf . Cm \&de No \e* Ns Bo Ar macrostring Bc Op \e* Ns Bq Ar endstring
+.It Ic \&dei1 Ar macrostring Op Ar endstring
 Define a
 .Nm
 macro that will be executed with
 .Nm
-compatibility mode switched off during macro execution.
-This is a GNU extension not available in traditional
-.Nm
-implementations and not even in older versions of groff.
+compatibility mode switched off during macro execution,
+specifying the macro name indirectly (groff extension).
 Since
 .Xr mandoc 1
 does not implement
 .Nm
 compatibility mode at all, it handles this request as an alias for
-.Sx \&de .
-.Ss \&ds
+.Ic \&dei .
+.It Ic \&device Ar string ...
+.It Ic \&devicem Ar stringname
+These two requests only make sense with the groff-specific intermediate
+output format and are unsupported.
+.It Ic \&di Ar divname
+Begin a diversion.
+Currently unsupported.
+.It Ic \&do Ar command Op Ar argument ...
+Execute
+.Nm
+request or macro line with compatibility mode disabled.
+Currently unsupported.
+.It Ic \&ds Ar stringname Op Oo \(dq Oc Ns Ar string
 Define a user-defined string.
-Its syntax is as follows:
-.Pp
-.D1 Pf . Cm \&ds Ar name Oo \(dq Oc Ns Ar string
-.Pp
 The
-.Ar name
+.Ar stringname
 and
 .Ar string
 arguments are space-separated.
@@ -595,11 +782,11 @@ including whitespace and double-quote characters, even
 The
 .Ar string
 can be interpolated into subsequent text by using
-.No \e* Ns Bq Ar name
+.No \e* Ns Bq Ar stringname
 for a
-.Ar name
+.Ar stringname
 of arbitrary length, or \e*(NN or \e*N if the length of
-.Ar name
+.Ar stringname
 is two or one characters, respectively.
 Interpolation can be prevented by escaping the leading backslash;
 that is, an asterisk preceded by an even number of backslashes
@@ -607,11 +794,11 @@ does not trigger string interpolation.
 .Pp
 Since user-defined strings and macros share a common string table,
 defining a string
-.Ar name
+.Ar stringname
 clobbers the macro
-.Ar name ,
+.Ar stringname ,
 and the
-.Ar name
+.Ar stringname
 used for defining a string can also be invoked as a macro,
 in which case the following input line will be appended to the
 .Ar string ,
@@ -626,101 +813,234 @@ H SYNOPSIS
 .Ed
 .Pp
 invokes the
-.Cm SH
+.Ic SH
 macro when used in a
 .Xr man 7
 document.
 Such abuse is of course strongly discouraged.
-.Ss \&el
+.It Ic \&ds1 Ar stringname Op Oo \(dq Oc Ns Ar string
+Define a user-defined string that will be expanded with
+.Nm
+compatibility mode switched off during string expansion.
+This is a groff extension.
+Since
+.Xr mandoc 1
+does not implement
+.Nm
+compatibility mode at all, it handles this request as an alias for
+.Ic \&ds .
+.It Ic \&dwh Ar dist macroname
+Set a location trap in the current diversion.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&dt Op Ar dist macroname
+Set a trap within a diversion.
+Currently unsupported.
+.It Ic \&ec Op Ar char
+Enable the escape mechanism and change the escape character.
 The
-.Qq else
+.Ar char
+argument defaults to the backslash
+.Pq Sq \e .
+.It Ic \&ecr
+Restore the escape character.
+Currently unsupported.
+.It Ic \&ecs
+Save the escape character.
+Currently unsupported.
+.It Ic \&el Ar body
+The
+.Dq else
 half of an if/else conditional.
 Pops a result off the stack of conditional evaluations pushed by
-.Sx \&ie
+.Ic \&ie
 and uses it as its conditional.
 If no stack entries are present (e.g., due to no prior
-.Sx \&ie
+.Ic \&ie
 calls)
 then false is assumed.
 The syntax of this request is similar to
-.Sx \&if
+.Ic \&if
 except that the conditional is missing.
-.Ss \&EN
+.It Ic \&em Ar macroname
+Set a trap at the end of input.
+Currently unsupported.
+.It Ic \&EN
 End an equation block.
 See
-.Sx \&EQ .
-.Ss \&EQ
+.Ic \&EQ .
+.It Ic \&eo
+Disable the escape mechanism completely.
+.It Ic \&EP
+End a picture started by
+.Ic \&BP .
+This is a Heirloom extension and currently unsupported.
+.It Ic \&EQ
 Begin an equation block.
 See
 .Xr eqn 7
 for a description of the equation language.
-.Ss \&fam
+.It Ic \&errprint Ar message
+Print a string like an error message.
+This is a Heirloom extension and currently ignored.
+.It Ic \&ev Op Ar envname
+Switch to another environment.
+Currently unsupported.
+.It Ic \&evc Op Ar envname
+Copy an environment into the current environment.
+Currently unsupported.
+.It Ic \&ex
+Abort processing and exit.
+Currently unsupported.
+.It Ic \&fallback Ar curfont font ...
+Select the fallback sequence for a font.
+This is a Heirloom extension and currently ignored.
+.It Ic \&fam Op Ar familyname
 Change the font family.
-This line-scoped request is intended to have one argument specifying
-the font family to be selected.
-It is a groff extension, and currently, it is ignored including its
-arguments, and the number of arguments is not checked.
-.Ss \&ft
-Change the font.
-Its syntax is as follows:
-.Pp
-.D1 Pf . Cm \&ft Op Ar font
-.Pp
-The following
-.Ar font
-arguments are supported:
-.Bl -tag -width 4n -offset indent
-.It Cm B , BI , 3 , 4
-switches to
-.Sy bold
-font
-.It Cm I , 2
-switches to
-.Em underlined
-font
-.It Cm R , CW , 1
-switches to normal font
-.It Cm P No "or no argument"
-switches back to the previous font
-.El
-.Pp
-This request takes effect only locally, may be overridden by macros
-and escape sequences, and is only supported in
+This is a groff extension and currently ignored.
+.It Ic \&fc Op Ar delimchar Op Ar padchar
+Define a delimiting and a padding character for fields.
+Currently unsupported.
+.It Ic \&fchar Ar glyphname Op Ar string
+Define a fallback glyph.
+Currently unsupported.
+.It Ic \&fcolor Ar colorname
+Set the fill color for \eD objects.
+This is a groff extension and currently ignored.
+.It Ic \&fdeferlig Ar font string ...
+Defer ligature building.
+This is a Heirloom extension and currently ignored.
+.It Ic \&feature Cm + Ns | Ns Cm - Ns Ar name
+Enable or disable an OpenType feature.
+This is a Heirloom extension and currently ignored.
+.It Ic \&fi
+Break the output line and switch to fill mode,
+which is active by default but can be ended with the
+.Ic \&nf
+request.
+In fill mode, input from subsequent input lines is added to
+the same output line until the next word no longer fits,
+at which point the output line is broken.
+This request is implied by the
+.Xr mdoc 7
+.Ic \&Sh
+macro and by the
 .Xr man 7
-for now.
-.Ss \&hw
+.Ic \&SH ,
+.Ic \&SS ,
+and
+.Ic \&EE
+macros.
+.It Ic \&fkern Ar font minkern
+Control the use of kerning tables for a font.
+This is a Heirloom extension and currently ignored.
+.It Ic \&fl
+Flush output.
+Currently ignored.
+.It Ic \&flig Ar font string char ...
+Define ligatures.
+This is a Heirloom extension and currently ignored.
+.It Ic \&fp Ar position font Op Ar filename
+Assign font position.
+Currently ignored.
+.It Ic \&fps Ar mapname ...
+Mount a font with a special character map.
+This is a Heirloom extension and currently ignored.
+.It Ic \&fschar Ar font glyphname Op Ar string
+Define a font-specific fallback glyph.
+This is a groff extension and currently unsupported.
+.It Ic \&fspacewidth Ar font Op Ar afmunits
+Set a font-specific width for the space character.
+This is a Heirloom extension and currently ignored.
+.It Ic \&fspecial Ar curfont Op Ar font ...
+Conditionally define a special font.
+This is a groff extension and currently ignored.
+.It Ic \&ft Op Ar font
+Change the font; see
+.Sx Font Selection .
+The
+.Ar font
+argument defaults to
+.Cm P .
+.It Ic \&ftr Ar newname Op Ar oldname
+Translate font name.
+This is a groff extension and currently ignored.
+.It Ic \&fzoom Ar font Op Ar permille
+Zoom font size.
+Currently ignored.
+.It Ic \&gcolor Op Ar colorname
+Set glyph color.
+This is a groff extension and currently ignored.
+.It Ic \&hc Op Ar char
+Set the hyphenation character.
+Currently ignored.
+.It Ic \&hcode Ar char code ...
+Set hyphenation codes of characters.
+Currently ignored.
+.It Ic \&hidechar Ar font char ...
+Hide characters in a font.
+This is a Heirloom extension and currently ignored.
+.It Ic \&hla Ar language
+Set hyphenation language.
+This is a groff extension and currently ignored.
+.It Ic \&hlm Op Ar number
+Set maximum number of consecutive hyphenated lines.
+Currently ignored.
+.It Ic \&hpf Ar filename
+Load hyphenation pattern file.
+This is a groff extension and currently ignored.
+.It Ic \&hpfa Ar filename
+Load hyphenation pattern file, appending to the current patterns.
+This is a groff extension and currently ignored.
+.It Ic \&hpfcode Ar code code ...
+Define mapping values for character codes in hyphenation patterns.
+This is a groff extension and currently ignored.
+.It Ic \&hw Ar word ...
 Specify hyphenation points in words.
-This line-scoped request is currently ignored.
-.Ss \&hy
+Currently ignored.
+.It Ic \&hy Op Ar mode
 Set automatic hyphenation mode.
-This line-scoped request is currently ignored.
-.Ss \&ie
+Currently ignored.
+.It Ic \&hylang Ar language
+Set hyphenation language.
+This is a Heirloom extension and currently ignored.
+.It Ic \&hylen Ar nchar
+Minimum word length for hyphenation.
+This is a Heirloom extension and currently ignored.
+.It Ic \&hym Op Ar length
+Set hyphenation margin.
+This is a groff extension and currently ignored.
+.It Ic \&hypp Ar penalty ...
+Define hyphenation penalties.
+This is a Heirloom extension and currently ignored.
+.It Ic \&hys Op Ar length
+Set hyphenation space.
+This is a groff extension and currently ignored.
+.It Ic \&ie Ar condition body
 The
-.Qq if
+.Dq if
 half of an if/else conditional.
 The result of the conditional is pushed into a stack used by subsequent
 invocations of
-.Sx \&el ,
+.Ic \&el ,
 which may be separated by any intervening input (or not exist at all).
 Its syntax is equivalent to
-.Sx \&if .
-.Ss \&if
-Begins a conditional.
-This request has the following syntax:
-.Bd -literal -offset indent
-\&.if COND BODY
+.Ic \&if .
+.It Ic \&if Ar condition body
+Begin a conditional.
+This request can also be written as follows:
+.Bd -unfilled -offset indent
+.Pf . Ic \&if Ar condition No \e{ Ns Ar body
+.Ar body ... Ns \e}
 .Ed
-.Bd -literal -offset indent
-\&.if COND \e{BODY
-BODY...\e}
+.Bd -unfilled -offset indent
+.Pf . Ic \&if Ar condition No \e{\e
+.Ar body ...
+.Pf . No \e}
 .Ed
-.Bd -literal -offset indent
-\&.if COND \e{\e
-BODY...
-\&.\e}
-.Ed
 .Pp
-COND is a conditional statement.
+The
+.Ar condition
+is a boolean expression.
 Currently,
 .Xr mandoc 1
 supports the following subset of roff conditionals:
@@ -728,43 +1048,83 @@ supports the following subset of roff conditionals:
 .It
 If
 .Sq \&!
-is prefixed to COND, the condition is logically inverted.
+is prefixed to
+.Ar condition ,
+it is logically inverted.
 .It
-If the first character of COND is
+If the first character of
+.Ar condition
+is
 .Sq n
 .Pq nroff mode
 or
 .Sq o
 .Pq odd page ,
-COND evaluates to true.
+it evaluates to true, and the
+.Ar body
+starts with the next character.
 .It
-If the first character of COND is
-.Sq c
-.Pq character available ,
-.Sq d
-.Pq string defined ,
+If the first character of
+.Ar condition
+is
 .Sq e
 .Pq even page ,
-.Sq r
-.Pq register accessed ,
-or
 .Sq t
 .Pq troff mode ,
-COND evaluates to false.
+or
+.Sq v
+.Pq vroff mode ,
+it evaluates to false, and the
+.Ar body
+starts with the next character.
 .It
-If COND starts with a parenthesis or with an optionally signed
+If the first character of
+.Ar condition
+is
+.Sq c
+.Pq character available ,
+it evaluates to true if the following character is an ASCII character
+or a valid character escape sequence, or to false otherwise.
+The
+.Ar body
+starts with the character following that next character.
+.It
+If the first character of
+.Ar condition
+is
+.Sq d ,
+it evaluates to true if the rest of
+.Ar condition
+is the name of an existing user defined macro or string;
+otherwise, it evaluates to false.
+.It
+If the first character of
+.Ar condition
+is
+.Sq r ,
+it evaluates to true if the rest of
+.Ar condition
+is the name of an existing number register;
+otherwise, it evaluates to false.
+.It
+If the
+.Ar condition
+starts with a parenthesis or with an optionally signed
 integer number, it is evaluated according to the rules of
 .Sx Numerical expressions
 explained below.
-It evaluates to true if the the result is positive,
+It evaluates to true if the result is positive,
 or to false if the result is zero or negative.
 .It
-Otherwise, the first character of COND is regarded as a delimiter
-and COND evaluates to true if the string extending from its first
-to its second occurrence is equal to the string extending from its
-second to its third occurrence.
+Otherwise, the first character of
+.Ar condition
+is regarded as a delimiter and it evaluates to true if the string
+extending from its first to its second occurrence is equal to the
+string extending from its second to its third occurrence.
 .It
-If COND cannot be parsed, it evaluates to false.
+If
+.Ar condition
+cannot be parsed, it evaluates to false.
 .El
 .Pp
 If a conditional is false, its children are not processed, but are
@@ -785,28 +1145,33 @@ conditional.
 Sub-conditionals, in this case, obviously inherit the truth value of
 the parent.
 .Pp
-If the BODY section is begun by an escaped brace
+If the
+.Ar body
+section is begun by an escaped brace
 .Sq \e{ ,
 scope continues until the end of the input line containing the
 matching closing-brace escape sequence
 .Sq \e} .
-If the BODY is not enclosed in braces, scope continues until
-the end of the line.
-If the COND is followed by a BODY on the same line, whether after a
-brace or not, then requests and macros
+If the
+.Ar body
+is not enclosed in braces, scope continues until the end of the line.
+If the
+.Ar condition
+is followed by a
+.Ar body
+on the same line, whether after a brace or not, then requests and macros
 .Em must
 begin with a control character.
 It is generally more intuitive, in this case, to write
-.Bd -literal -offset indent
-\&.if COND \e{\e
-\&.foo
-bar
-\&.\e}
+.Bd -unfilled -offset indent
+.Pf . Ic \&if Ar condition No \e{\e
+.Pf . Ar request
+.Pf . No \e}
 .Ed
 .Pp
 than having the request or macro follow as
 .Pp
-.D1 \&.if COND \e{ .foo
+.D1 Pf . Ic \&if Ar condition Pf \e{. Ar request
 .Pp
 The scope of a conditional is always parsed, but only executed if the
 conditional evaluates to true.
@@ -825,7 +1190,7 @@ will result in
 being considered an argument of the
 .Sq \&Fl
 macro.
-.Ss \&ig
+.It Ic \&ig Op Ar endmacro
 Ignore input.
 Its syntax can be either
 .Bd -literal -offset indent
@@ -836,31 +1201,31 @@ Its syntax can be either
 .Pp
 or
 .Bd -literal -offset indent
-.Pf . Cm \&ig Ar end
+.Pf . Cm \&ig Ar endmacro
 .Ar ignored text
-.Pf . Ar end
+.Pf . Ar endmacro
 .Ed
 .Pp
 In the first case, input is ignored until a
 .Sq \&..
 request is encountered on its own line.
 In the second case, input is ignored until the specified
-.Sq Pf . Ar end
-macro is encountered.
+.Sq Pf . Ar endmacro
+is encountered.
 Do not use the escape character
 .Sq \e
 anywhere in the definition of
-.Ar end ;
+.Ar endmacro ;
 it would cause very strange behaviour.
 .Pp
 When the
-.Ar end
-macro is a roff request or a roff macro, like in
+.Ar endmacro
+is a roff request or a roff macro, like in
 .Pp
 .D1 \&.ig if
 .Pp
 the subsequent invocation of
-.Sx \&if
+.Ic \&if
 will first terminate the
 .Ar ignored text ,
 then be invoked as usual.
@@ -869,12 +1234,80 @@ Otherwise, it only terminates the
 and arguments following it or the
 .Sq \&..
 request are discarded.
-.Ss \&ll
+.It Ic \&in Op Oo Cm + Ns | Ns Cm - Oc Ns Ar width
+Change indentation.
+See
+.Xr man 7 .
+Ignored in
+.Xr mdoc 7 .
+.It Ic \&index Ar register stringname substring
+Find a substring in a string.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&it Ar expression macro
+Set an input line trap.
+The named
+.Ar macro
+will be invoked after processing the number of input text lines
+specified by the numerical
+.Ar expression .
+While evaluating the
+.Ar expression ,
+the unit suffixes described below
+.Sx Scaling Widths
+are ignored.
+.It Ic \&itc Ar expression macro
+Set an input line trap, not counting lines ending with \ec.
+Currently unsupported.
+.It Ic \&IX Ar class keystring
+To support the generation of a table of contents,
+.Xr pod2man 1
+emits this user-defined macro, usually without defining it.
+To avoid reporting large numbers of spurious errors,
+.Xr mandoc 1
+ignores it.
+.It Ic \&kern Op Cm 1 | 0
+Switch kerning on or off.
+Currently ignored.
+.It Ic \&kernafter Ar font char ... afmunits ...
+Increase kerning after some characters.
+This is a Heirloom extension and currently ignored.
+.It Ic \&kernbefore Ar font char ... afmunits ...
+Increase kerning before some characters.
+This is a Heirloom extension and currently ignored.
+.It Ic \&kernpair Ar font char ... font char ... afmunits
+Add a kerning pair to the kerning table.
+This is a Heirloom extension and currently ignored.
+.It Ic \&lc Op Ar glyph
+Define a leader repetition character.
+Currently unsupported.
+.It Ic \&lc_ctype Ar localename
+Set the
+.Dv LC_CTYPE
+locale.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&lds Ar macroname string
+Define a local string.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&length Ar register string
+Count the number of input characters in a string.
+Currently unsupported.
+.It Ic \&letadj Ar lspmin lshmin letss lspmax lshmax
+Dynamic letter spacing and reshaping.
+This is a Heirloom extension and currently ignored.
+.It Ic \&lf Ar lineno Op Ar filename
+Change the line number for error messages.
+Ignored because insecure.
+.It Ic \&lg Op Cm 1 | 0
+Switch the ligature mechanism on or off.
+Currently ignored.
+.It Ic \&lhang Ar font char ... afmunits
+Hang characters at left margin.
+This is a Heirloom extension and currently ignored.
+.It Ic \&linetabs Op Cm 1 | 0
+Enable or disable line-tabs mode.
+This is a groff extension and currently unsupported.
+.It Ic \&ll Op Oo Cm + Ns | Ns Cm - Oc Ns Ar width
 Change the output line length.
-Its syntax is as follows:
-.Pp
-.D1 Pf . Cm \&ll Op Oo +|- Oc Ns Ar width
-.Pp
 If the
 .Ar width
 argument is omitted, the line length is reset to its previous value.
@@ -886,21 +1319,89 @@ among others because it overrides the
 .Xr mandoc 1
 .Fl O Cm width
 command line option.
-.Ss \&ne
+.It Ic \&lnr Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar value Op Ar increment
+Set local number register.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&lnrf Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar value Op Ar increment
+Set local floating-point register.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&lpfx Ar string
+Set a line prefix.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&ls Op Ar factor
+Set line spacing.
+It takes one integer argument specifying the vertical distance of
+subsequent output text lines measured in v units.
+Currently ignored.
+.It Ic \&lsm Ar macroname
+Set a leading spaces trap.
+This is a groff extension and currently unsupported.
+.It Ic \&lt Op Oo Cm + Ns | Ns Cm - Oc Ns Ar width
+Set title line length.
+Currently ignored.
+.It Ic \&mc Ar glyph Op Ar dist
+Print margin character in the right margin.
+The
+.Ar dist
+is currently ignored; instead, 1n is used.
+.It Ic \&mediasize Ar media
+Set the device media size.
+This is a Heirloom extension and currently ignored.
+.It Ic \&minss Ar width
+Set minimum word space.
+This is a Heirloom extension and currently ignored.
+.It Ic \&mk Op Ar register
+Mark vertical position.
+Currently ignored.
+.It Ic \&mso Ar filename
+Load a macro file using the search path.
+Ignored because insecure.
+.It Ic \&na
+Disable adjusting without changing the adjustment mode.
+Currently ignored.
+.It Ic \&ne Op Ar height
 Declare the need for the specified minimum vertical space
 before the next trap or the bottom of the page.
-This line-scoped request is currently ignored.
-.Ss \&nh
+Currently ignored.
+.It Ic \&nf
+Break the output line and switch to no-fill mode.
+Subsequent input lines are kept together on the same output line
+even when exceeding the right margin,
+and line breaks in subsequent input cause output line breaks.
+This request is implied by the
+.Xr mdoc 7
+.Ic \&Bd Fl unfilled
+and
+.Ic \&Bd Fl literal
+macros and by the
+.Xr man 7
+.Ic \&EX
+macro.
+The
+.Ic \&fi
+request switches back to the default fill mode.
+.It Ic \&nh
 Turn off automatic hyphenation mode.
-This line-scoped request is currently ignored.
-.Ss \&nr
+Currently ignored.
+.It Ic \&nhychar Ar char ...
+Define hyphenation-inhibiting characters.
+This is a Heirloom extension and currently ignored.
+.It Ic \&nm Op Ar start Op Ar inc Op Ar space Op Ar indent
+Print line numbers.
+Currently unsupported.
+.It Ic \&nn Op Ar number
+Temporarily turn off line numbering.
+Currently unsupported.
+.It Ic \&nop Ar body
+Execute the rest of the input line as a request, macro, or text line,
+skipping the
+.Ic \&nop
+request and any space characters immediately following it.
+This is mostly used to indent text lines inside macro definitions.
+.It Ic \&nr Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar expression Op Ar stepsize
 Define or change a register.
 A register is an arbitrary string value that defines some sort of state,
 which influences parsing and/or formatting.
-Its syntax is as follows:
-.Pp
-.D1 Pf \. Cm \&nr Ar name Oo +|- Oc Ns Ar expression
-.Pp
 For the syntax of
 .Ar expression ,
 see
@@ -909,8 +1410,16 @@ below.
 If it is prefixed by a sign, the register will be
 incremented or decremented instead of assigned to.
 .Pp
-The following register
-.Ar name
+The
+.Ar stepsize
+is used by the
+.Ic \en+
+auto-increment feature.
+It remains unchanged when omitted while changing an existing register,
+and it defaults to 0 when defining a new register.
+.Pp
+The following
+.Ar register
 is handled specially:
 .Bl -tag -width Ds
 .It Cm nS
@@ -927,39 +1436,168 @@ section itself.
 Note that starting a new
 .Xr mdoc 7
 section with the
-.Cm \&Sh
+.Ic \&Sh
 macro will reset this register.
 .El
-.Ss \&ns
+.It Xo
+.Ic \&nrf Ar register Oo Cm + Ns | Ns Cm - Oc Ns Ar expression
+.Op Ar increment
+.Xc
+Define or change a floating-point register.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&nroff
+Force nroff mode.
+This is a groff extension and currently ignored.
+.It Ic \&ns
 Turn on no-space mode.
-This line-scoped request is intended to take no arguments.
-Currently, it is ignored including its arguments,
-and the number of arguments is not checked.
-.Ss \&ps
+Currently ignored.
+.It Ic \&nx Op Ar filename
+Abort processing of the current input file and process another one.
+Ignored because insecure.
+.It Ic \&open Ar stream file
+Open a file for writing.
+Ignored because insecure.
+.It Ic \&opena Ar stream file
+Open a file for appending.
+Ignored because insecure.
+.It Ic \&os
+Output saved vertical space.
+Currently ignored.
+.It Ic \&output Ar string
+Output directly to intermediate output.
+Not supported.
+.It Ic \&padj Op Cm 1 | 0
+Globally control paragraph-at-once adjustment.
+This is a Heirloom extension and currently ignored.
+.It Ic \&papersize Ar media
+Set the paper size.
+This is a Heirloom extension and currently ignored.
+.It Ic \&pc Op Ar char
+Change the page number character.
+Currently ignored.
+.It Ic \&pev
+Print environments.
+This is a groff extension and currently ignored.
+.It Ic \&pi Ar command
+Pipe output to a shell command.
+Ignored because insecure.
+.It Ic \&PI
+Low-level request used by
+.Ic \&BP .
+This is a Heirloom extension and currently unsupported.
+.It Ic \&pl Op Oo Cm + Ns | Ns Cm - Oc Ns Ar height
+Change page length.
+Currently ignored.
+.It Ic \&pm
+Print names and sizes of macros, strings, and diversions
+to standard error output.
+Currently ignored.
+.It Ic \&pn Oo Cm + Ns | Ns Cm - Oc Ns Ar number
+Change the page number of the next page.
+Currently ignored.
+.It Ic \&pnr
+Print all number registers on standard error output.
+Currently ignored.
+.It Ic \&po Op Oo Cm + Ns | Ns Cm - Oc Ns Ar offset
+Set a horizontal page offset.
+If no argument is specified, the page offset is reverted to its
+previous value.
+If a sign is specified, the new page offset is calculated relative
+to the current one; otherwise, it is absolute.
+The argument follows the syntax of
+.Sx Scaling Widths
+and the default scaling unit is
+.Cm m .
+.It Ic \&ps Op Oo Cm + Ns | Ns Cm - Oc Ns size
 Change point size.
-This line-scoped request is intended to take one numerical argument.
-Currently, it is ignored including its arguments,
-and the number of arguments is not checked.
-.Ss \&rm
+Currently ignored.
+.It Ic \&psbb Ar filename
+Retrieve the bounding box of a PostScript file.
+Currently unsupported.
+.It Ic \&pshape Ar indent length ...
+Set a special shape for the current paragraph.
+This is a Heirloom extension and currently unsupported.
+.It Ic \&pso Ar command
+Include output of a shell command.
+Ignored because insecure.
+.It Ic \&ptr
+Print the names and positions of all traps on standard error output.
+This is a groff extension and currently ignored.
+.It Ic \&pvs Op Oo Cm + Ns | Ns Cm - Oc Ns Ar height
+Change post-vertical spacing.
+This is a groff extension and currently ignored.
+.It Ic \&rchar Ar glyph ...
+Remove glyph definitions.
+Currently unsupported.
+.It Ic \&rd Op Ar prompt Op Ar argument ...
+Read from standard input.
+Currently ignored.
+.It Ic \&recursionlimit Ar maxrec maxtail
+Set the maximum stack depth for recursive macros.
+This is a Heirloom extension and currently ignored.
+.It Ic \&return Op Ar twice
+Exit the presently executed macro and return to the caller.
+The argument is currently ignored.
+.It Ic \&rfschar Ar font glyph ...
+Remove font-specific fallback glyph definitions.
+Currently unsupported.
+.It Ic \&rhang Ar font char ... afmunits
+Hang characters at right margin.
+This is a Heirloom extension and currently ignored.
+.It Ic \&rj Op Ar N
+Justify the next
+.Ar N
+input lines to the right margin without filling.
+.Ar N
+defaults to 1.
+An argument of 0 or less ends right adjustment.
+.It Ic \&rm Ar macroname
 Remove a request, macro or string.
-Its syntax is as follows:
-.Pp
-.D1 Pf \. Cm \&rm Ar name
-.Ss \&rr
+.It Ic \&rn Ar oldname newname
+Rename a request, macro, diversion, or string.
+In
+.Xr mandoc 1 ,
+user-defined macros,
+.Xr mdoc 7
+and
+.Xr man 7
+macros, and user-defined strings can be renamed, but renaming of
+predefined strings and of
+.Nm
+requests is not supported, and diversions are not implemented at all.
+.It Ic \&rnn Ar oldname newname
+Rename a number register.
+Currently unsupported.
+.It Ic \&rr Ar register
 Remove a register.
-Its syntax is as follows:
-.Pp
-.D1 Pf \. Cm \&rr Ar name
-.Ss \&so
+.It Ic \&rs
+End no-space mode.
+Currently ignored.
+.It Ic \&rt Op Ar dist
+Return to marked vertical position.
+Currently ignored.
+.It Ic \&schar Ar glyph Op Ar string
+Define global fallback glyph.
+This is a groff extension and currently unsupported.
+.It Ic \&sentchar Ar char ...
+Define sentence-ending characters.
+This is a Heirloom extension and currently ignored.
+.It Ic \&shc Op Ar glyph
+Change the soft hyphen character.
+Currently ignored.
+.It Ic \&shift Op Ar number
+Shift macro arguments
+.Ar number
+times, by default once: \e\e$i becomes what \e\e$i+number was.
+Also decrement \en(.$ by
+.Ar number .
+.It Ic \&sizes Ar size ...
+Define permissible point sizes.
+This is a groff extension and currently ignored.
+.It Ic \&so Ar filename
 Include a source file.
-Its syntax is as follows:
-.Pp
-.D1 Pf \. Cm \&so Ar file
-.Pp
-The
-.Ar file
-will be read and its contents processed as input in place of the
-.Sq \&.so
+The file is read and its contents processed as input in place of the
+.Ic \&so
 request line.
 To avoid inadvertent inclusion of unrelated files,
 .Xr mandoc 1
@@ -978,52 +1616,194 @@ Typical usage looks like:
 .Dl \&.so man3/Xcursor.3
 .Pp
 As the whole concept is rather fragile, the use of
-.Sx \&so
+.Ic \&so
 is discouraged.
 Use
 .Xr ln 1
 instead.
-.Ss \&ta
+.It Ic \&sp Op Ar height
+Break the output line and emit vertical space.
+The argument follows the syntax of
+.Sx Scaling Widths
+and defaults to one blank line
+.Pq Li 1v .
+.It Ic \&spacewidth Op Cm 1 | 0
+Set the space width from the font metrics file.
+This is a Heirloom extension and currently ignored.
+.It Ic \&special Op Ar font ...
+Define a special font.
+This is a groff extension and currently ignored.
+.It Ic \&spreadwarn Op Ar width
+Warn about wide spacing between words.
+Currently ignored.
+.It Ic \&ss Ar wordspace Op Ar sentencespace
+Set space character size.
+Currently ignored.
+.It Ic \&sty Ar position style
+Associate style with a font position.
+This is a groff extension and currently ignored.
+.It Ic \&substring Ar stringname startpos Op Ar endpos
+Replace a user-defined string with a substring.
+Currently unsupported.
+.It Ic \&sv Op Ar height
+Save vertical space.
+Currently ignored.
+.It Ic \&sy Ar command
+Execute shell command.
+Ignored because insecure.
+.It Ic \&T&
+Re-start a table layout, retaining the options of the prior table
+invocation.
+See
+.Ic \&TS .
+.It Ic \&ta Op Ar width ... Op Cm T Ar width ...
 Set tab stops.
-This line-scoped request can take an arbitrary number of arguments.
-Currently, it is ignored including its arguments.
-.Ss \&tr
+Each
+.Ar width
+argument follows the syntax of
+.Sx Scaling Widths .
+If prefixed by a plus sign, it is relative to the previous tab stop.
+The arguments after the
+.Cm T
+marker are used repeatedly as often as needed; for each reuse,
+they are taken relative to the last previously established tab stop.
+When
+.Ic \&ta
+is called without arguments, all tab stops are cleared.
+.It Ic \&tc Op Ar glyph
+Change tab repetition character.
+Currently unsupported.
+.It Ic \&TE
+End a table context.
+See
+.Ic \&TS .
+.It Ic \&ti Oo Cm + Ns | Ns Cm - Oc Ns Ar width
+Break the output line and indent the next output line by
+.Ar width .
+If a sign is specified, the temporary indentation is calculated
+relative to the current indentation; otherwise, it is absolute.
+The argument follows the syntax of
+.Sx Scaling Widths
+and the default scaling unit is
+.Cm m .
+.It Ic \&tkf Ar font minps width1 maxps width2
+Enable track kerning for a font.
+Currently ignored.
+.It Ic \&tl No \& Ap Ar left Ap Ar center Ap Ar right Ap
+Print a title line.
+Currently unsupported.
+.It Ic \&tm Ar string
+Print to standard error output.
+Currently ignored.
+.It Ic \&tm1 Ar string
+Print to standard error output, allowing leading blanks.
+This is a groff extension and currently ignored.
+.It Ic \&tmc Ar string
+Print to standard error output without a trailing newline.
+This is a groff extension and currently ignored.
+.It Ic \&tr Ar glyph glyph ...
 Output character translation.
-Its syntax is as follows:
+The first glyph in each pair is replaced by the second one.
+Character escapes can be used; for example,
 .Pp
-.D1 Pf \. Cm \&tr Ar [ab]+
-.Pp
-Pairs of
-.Ar ab
-characters are replaced
-.Ar ( a
-for
-.Ar b ) .
-Replacement (or origin) characters may also be character escapes; thus,
-.Pp
 .Dl tr \e(xx\e(yy
 .Pp
 replaces all invocations of \e(xx with \e(yy.
-.Ss \&T&
-Re-start a table layout, retaining the options of the prior table
-invocation.
-See
-.Sx \&TS .
-.Ss \&TE
-End a table context.
-See
-.Sx \&TS .
-.Ss \&TS
+.It Ic \&track Ar font minps width1 maxps width2
+Static letter space tracking.
+This is a Heirloom extension and currently ignored.
+.It Ic \&transchar Ar char ...
+Define transparent characters for sentence-ending.
+This is a Heirloom extension and currently ignored.
+.It Ic \&trf Ar filename
+Output the contents of a file, disallowing invalid characters.
+This is a groff extension and ignored because insecure.
+.It Ic \&trimat Ar left top width height
+Set the TrimBox page parameter for PDF generation.
+This is a Heirloom extension and currently ignored.
+.It Ic \&trin Ar glyph glyph ...
+Output character translation, ignored by
+.Ic \&asciify .
+Currently unsupported.
+.It Ic \&trnt Ar glyph glyph ...
+Output character translation, ignored by \e!.
+Currently unsupported.
+.It Ic \&troff
+Force troff mode.
+This is a groff extension and currently ignored.
+.It Ic \&TS
 Begin a table, which formats input in aligned rows and columns.
 See
 .Xr tbl 7
 for a description of the tbl language.
+.It Ic \&uf Ar font
+Globally set the underline font.
+Currently ignored.
+.It Ic \&ul Op Ar N
+Underline next
+.Ar N
+input lines.
+Currently ignored.
+.It Ic \&unformat Ar divname
+Unformat spaces and tabs in a diversion.
+Currently unsupported.
+.It Ic \&unwatch Ar macroname
+Disable notification for string or macro.
+This is a Heirloom extension and currently ignored.
+.It Ic \&unwatchn Ar register
+Disable notification for register.
+This is a Heirloom extension and currently ignored.
+.It Ic \&vpt Op Cm 1 | 0
+Enable or disable vertical position traps.
+This is a groff extension and currently ignored.
+.It Ic \&vs Op Oo Cm + Ns | Ns Cm - Oc Ns Ar height
+Change vertical spacing.
+Currently ignored.
+.It Ic \&warn Ar flags
+Set warning level.
+Currently ignored.
+.It Ic \&warnscale Ar si
+Set the scaling indicator used in warnings.
+This is a groff extension and currently ignored.
+.It Ic \&watch Ar macroname
+Notify on change of string or macro.
+This is a Heirloom extension and currently ignored.
+.It Ic \&watchlength Ar maxlength
+On change, report the contents of macros and strings
+up to the specified length.
+This is a Heirloom extension and currently ignored.
+.It Ic \&watchn Ar register
+Notify on change of register.
+This is a Heirloom extension and currently ignored.
+.It Ic \&wh Ar dist Op Ar macroname
+Set a page location trap.
+Currently unsupported.
+.It Ic \&while Ar condition body
+Repeated execution while a
+.Ar condition
+is true, with syntax similar to
+.Ic \&if .
+Currently implemented with two restrictions: cannot nest,
+and each loop must start and end in the same scope.
+.It Ic \&write Oo \(dq Oc Ns Ar string
+Write to an open file.
+Ignored because insecure.
+.It Ic \&writec Oo \(dq Oc Ns Ar string
+Write to an open file without appending a newline.
+Ignored because insecure.
+.It Ic \&writem Ar macroname
+Write macro or string to an open file.
+Ignored because insecure.
+.It Ic \&xflag Ar level
+Set the extension level.
+This is a Heirloom extension and currently ignored.
+.El
 .Ss Numerical expressions
 The
-.Sx \&nr ,
-.Sx \&if ,
+.Ic \&nr ,
+.Ic \&if ,
 and
-.Sx \&ie
+.Ic \&ie
 requests accept integer numerical expressions as arguments.
 These are always evaluated using the C
 .Vt int
@@ -1036,6 +1816,14 @@ prefixed by an optional sign
 .Sq +
 or
 .Sq - .
+Each number may be followed by one optional scaling unit described below
+.Sx Scaling Widths .
+The following equations hold:
+.Bd -literal -offset indent
+1i = 6v = 6P = 10m = 10n = 72p = 1000M = 240u = 240
+254c = 100i = 24000u = 24000
+1f = 65536u = 65536
+.Ed
 .Pp
 The following binary operators are implemented.
 Unless otherwise stated, they behave as in the C language:
@@ -1075,25 +1863,21 @@ logical and (corresponds to C
 .Ic && )
 .It Ic \&:
 logical or (corresponds to C
-.Ic \&|| )
+.Ic || )
 .It Ic <?
 minimum (not available in C)
 .It Ic >?
 maximum (not available in C)
 .El
 .Pp
-There is no concept of precendence; evaluation proceeds from left to right,
-except when subexpressions are enclosed in parantheses.
+There is no concept of precedence; evaluation proceeds from left to right,
+except when subexpressions are enclosed in parentheses.
 Inside parentheses, whitespace is ignored.
 .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
@@ -1105,205 +1889,315 @@ section above.
 .Pp
 A backslash followed by any character not listed here
 simply prints that character itself.
-.Ss \e<newline>
+.Bl -tag -width Ds
+.It Ic \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>
+.It Ic \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
+.Sx Whitespace
+and
+.Xr mandoc_char 7 .
+.It Ic \e!
+Embed text up to and including the end of the input line into the
+current diversion or into intermediate output without interpreting
+requests, macros, and escapes.
+Currently unsupported.
+.It Ic \e\(dq
 The rest of the input line is treated as
 .Sx Comments .
-.Ss \e%
+.It Ic \e#
+Line continuation with comment.
+Discard the rest of the physical input line and 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.
+This is a groff extension.
+.It Ic \e$ Ns Ar arg
+Macro argument expansion, see
+.Ic \&de .
+.It Ic \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
+.It Ic \e&
+Non-printing zero-width character,
+often used for various kinds of escaping; see
+.Sx Whitespace ,
+.Xr mandoc_char 7 ,
+and the
+.Dq MACRO SYNTAX
+and
+.Dq Delimiters
+sections in
+.Xr mdoc 7 .
+.It Ic \e\(aq
 Acute accent special character; use
-.Sq \e(aa
+.Ic \e(aa
 instead.
-.Ss \e( Ns Ar cc
+.It Ic \e( Ns Ar cc
 .Sx Special Characters
 with two-letter names, see
 .Xr mandoc_char 7 .
-.Ss \e*[ Ns Ar name ]
+.It Ic \e)
+Zero-width space transparent to end-of-sentence detection;
+ignored by
+.Xr mandoc 1 .
+.It Ic \e*[ Ns Ar name Ns Ic \&]
 Interpolate the string with the
-.Ar name ;
-see
-.Sx Predefined Strings
-and
-.Sx ds .
+.Ar name .
 For short names, there are variants
-.No \e* Ns Ar c
+.Ic \e* Ns Ar c
 and
-.No \e*( Ns Ar cc .
-.Ss \e-
+.Ic \e*( Ns Ar cc .
+.Pp
+One string is predefined on the
+.Nm
+language level:
+.Ic \e*(.T
+expands to the name of the output device,
+for example ascii, utf8, ps, pdf, html, or markdown.
+.Pp
+Macro sets traditionally predefine additional strings which are not
+portable and differ across implementations.
+Those supported by
+.Xr mandoc 1
+are listed in
+.Xr mandoc_char 7 .
+.Pp
+Strings can be defined, changed, and deleted with the
+.Ic \&ds ,
+.Ic \&as ,
+and
+.Ic \&rm
+requests.
+.It Ic \e,
+Left italic correction (groff extension); ignored by
+.Xr mandoc 1 .
+.It Ic \e-
 Special character
-.Dq mathematical minus sign .
-.Ss \e[ Ns Ar name ]
+.Dq mathematical minus sign ;
+see
+.Xr mandoc_char 7
+for details.
+.It Ic \e/
+Right italic correction (groff extension); ignored by
+.Xr mandoc 1 .
+.It Ic \e:
+Breaking the line is allowed at this point of the word
+without inserting a hyphen.
+.It Ic \e?
+Embed the text up to the next
+.Ic \e?
+into the current diversion without interpreting requests, macros,
+and escapes.
+This is a groff extension and currently unsupported.
+.It Ic \e[ Ns Ar name Ns Ic \&]
 .Sx Special Characters
 with names of arbitrary length, see
 .Xr mandoc_char 7 .
-.Ss \e^
+.It Ic \e^
 One-twelfth em half-narrow space character, effectively zero-width in
 .Xr mandoc 1 .
-.Ss \e`
+.It Ic \e_
+Underline special character; use
+.Ic \e(ul
+instead.
+.It Ic \e`
 Grave accent special character; use
-.Sq \e(ga
+.Ic \e(ga
 instead.
-.Ss \e{
+.It Ic \e{
 Begin conditional input; see
-.Sx if .
-.Ss \e\(ba
+.Ic \&if .
+.It Ic \e\(ba
 One-sixth em narrow space character, effectively zero-width in
 .Xr mandoc 1 .
-.Ss \e}
+.It Ic \e}
 End conditional input; see
-.Sx if .
-.Ss \e~
+.Ic \&if .
+.It Ic \e~
 Paddable non-breaking space character.
-.Ss \e0
+.It Ic \e0
 Digit width space character.
-.Ss \eA\(aq Ns Ar string Ns \(aq
+.It Ic \eA\(aq Ns Ar string Ns Ic \(aq
 Anchor definition; ignored by
 .Xr mandoc 1 .
-.Ss \eB\(aq Ns Ar string Ns \(aq
+.It Ic \ea
+Leader character; ignored by
+.Xr mandoc 1 .
+.It Ic \eB\(aq Ns Ar string Ns Ic \(aq
 Interpolate
 .Sq 1
 if
 .Ar string
 conforms to the syntax of
 .Sx Numerical expressions
-explained above and
+explained above or
 .Sq 0
 otherwise.
-.Ss \eb\(aq Ns Ar string Ns \(aq
+.It Ic \eb\(aq Ns Ar string Ns Ic \(aq
 Bracket building function; ignored by
 .Xr mandoc 1 .
-.Ss \eC\(aq Ns Ar name Ns \(aq
+.It Ic \eC\(aq Ns Ar name Ns Ic \(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
+.It Ic \ec
+When encountered at the end of an input text line,
+the next input text line is considered to continue that line,
+even if there are request or macro lines in between.
+No whitespace is inserted.
+.It Ic \eD\(aq Ns Ar string Ns Ic \(aq
 Draw graphics function; ignored by
 .Xr mandoc 1 .
-.Ss \ed
+.It Ic \ed
 Move down by half a line; ignored by
 .Xr mandoc 1 .
-.Ss \ee
+.It Ic \eE
+Escape character intended to not be interpreted in copy mode.
+In
+.Xr mandoc 1 ,
+it currently does the same as
+.Ic \e
+itself.
+.It Ic \ee
 Backslash special character.
-.Ss \eF[ Ns Ar name ]
+.It Ic \eF[ Ns Ar name Ns Ic \&]
 Switch font family (groff extension); ignored by
 .Xr mandoc 1 .
 For short names, there are variants
-.No \eF Ns Ar c
+.Ic \eF Ns Ar c
 and
-.No \eF( Ns Ar cc .
-.Ss \ef[ Ns Ar name ]
+.Ic \eF( Ns Ar cc .
+.It Ic \ef[ Ns Ar name Ns Ic \&]
 Switch to the font
 .Ar name ,
 see
-.Sx Text Decoration .
+.Sx Font Selection .
 For short names, there are variants
-.No \ef Ns Ar c
+.Ic \ef Ns Ar c
 and
-.No \ef( Ns Ar cc .
-.Ss \eg[ Ns Ar name ]
+.Ic \ef( Ns Ar cc .
+An empty name
+.Ic \ef[]
+defaults to
+.Ic \efP .
+.It Ic \eg[ Ns Ar name Ns Ic \&]
 Interpolate the format of a number register; ignored by
 .Xr mandoc 1 .
 For short names, there are variants
-.No \eg Ns Ar c
+.Ic \eg Ns Ar c
 and
-.No \eg( Ns Ar cc .
-.Ss \eH\(aq Ns Oo +|- Oc Ns Ar number Ns \(aq
+.Ic \eg( Ns Ar cc .
+.It Ic \eH\(aq Ns Oo +|- Oc Ns Ar number Ns Ic \(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 ]
+.It Ic \eh\(aq Ns Oo Cm \&| Oc Ns Ar width Ns Ic \(aq
+Horizontal motion.
+If the vertical bar is given, the motion is relative to the current
+indentation.
+Otherwise, it is relative to the current position.
+The default scaling unit is
+.Cm m .
+.It Ic \ek[ Ns Ar name Ns Ic \&]
 Mark horizontal input place in register; ignored by
 .Xr mandoc 1 .
 For short names, there are variants
-.No \ek Ns Ar c
+.Ic \ek Ns Ar c
 and
-.No \ek( Ns Ar cc .
-.Ss \eL\(aq Ns Ar number Ns Oo Ar c Oc Ns \(aq
+.Ic \ek( Ns Ar cc .
+.It Ic \eL\(aq Ns Ar number Ns Oo Ar c Oc Ns Ic \(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 ]
+.It Ic \el\(aq Ns Ar width Ns Oo Ar c Oc Ns Ic \(aq
+Draw a horizontal line of
+.Ar width
+using the glyph
+.Ar c .
+.It Ic \eM[ Ns Ar name Ns Ic \&]
 Set fill (background) color (groff extension); ignored by
 .Xr mandoc 1 .
 For short names, there are variants
-.No \eM Ns Ar c
+.Ic \eM Ns Ar c
 and
-.No \eM( Ns Ar cc .
-.Ss \em[ Ns Ar name ]
+.Ic \eM( Ns Ar cc .
+.It Ic \em[ Ns Ar name Ns Ic \&]
 Set glyph drawing color (groff extension); ignored by
 .Xr mandoc 1 .
 For short names, there are variants
-.No \em Ns Ar c
+.Ic \em Ns Ar c
 and
-.No \em( Ns Ar cc .
-.Ss \eN\(aq Ns Ar number Ns \(aq
+.Ic \em( Ns Ar cc .
+.It Ic \eN\(aq Ns Ar number Ns Ic \(aq
 Character
 .Ar number
 on the current font.
-.Ss \en[ Ns Ar name ]
+.It Ic \en Ns Oo +|- Oc Ns Ic \&[ Ns Ar name Ns Ic \&]
 Interpolate the number register
 .Ar name .
 For short names, there are variants
-.No \en Ns Ar c
+.Ic \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
+.Ic \en( Ns Ar cc .
+If the optional sign is specified,
+the register is first incremented or decremented by the
+.Ar stepsize
+that was specified in the relevant
+.Ic \&nr
+request, and the changed value is interpolated.
+.It Ic \eO Ns Ar digit , Ic \eO[5 Ns arguments Ns Ic \&]
+Suppress output.
+This is a groff extension and currently unsupported.
+With an argument of
+.Ic 1 , 2 , 3 ,
+or
+.Ic 4 ,
+it is ignored.
+.It Ic \eo\(aq Ns Ar string Ns Ic \(aq
+Overstrike, writing all the characters contained in the
+.Ar string
+to the same output position.
+In terminal and HTML output modes,
+only the last one of the characters is visible.
+.It Ic \ep
+Break the output line at the end of the current word.
+.It Ic \eR\(aq Ns Ar name Oo +|- Oc Ns Ar number Ns Ic \(aq
 Set number register; ignored by
 .Xr mandoc 1 .
-.Ss \eS\(aq Ns Ar number Ns \(aq
+.It Ic \er
+Move up by one line; ignored by
+.Xr mandoc 1 .
+.It Ic \eS\(aq Ns Ar number Ns Ic \(aq
 Slant output; ignored by
 .Xr mandoc 1 .
-.Ss \es\(aq Ns Oo +|- Oc Ns Ar number Ns \(aq
+.It Ic \es\(aq Ns Oo +|- Oc Ns Ar number Ns Ic \(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 ] ,
+.Ic \es Ns Oo +|- Oc Ns Ar n ,
+.Ic \es Ns Oo +|- Oc Ns Ic \(aq Ns Ar number Ns Ic \(aq ,
+.Ic \es[ Ns Oo +|- Oc Ns Ar number Ns Ic \&] ,
 and
-.No \es Ns Oo +|- Oc Ns [ Ar number Ns ]
+.Ic \es Ns Oo +|- Oc Ns Ic \&[ Ns Ar number Ns Ic \&]
 are also parsed and ignored.
-.Ss \et
+.It Ic \et
 Horizontal tab; ignored by
 .Xr mandoc 1 .
-.Ss \eu
+.It Ic \eu
 Move up by half a line; ignored by
 .Xr mandoc 1 .
-.Ss \eV[ Ns Ar name ]
+.It Ic \eV[ Ns Ar name Ns Ic \&]
 Interpolate an environment variable; ignored by
 .Xr mandoc 1 .
 For short names, there are variants
-.No \eV Ns Ar c
+.Ic \eV Ns Ar c
 and
-.No \eV( Ns Ar cc .
-.Ss \ev\(aq Ns Ar number Ns \(aq
+.Ic \eV( Ns Ar cc .
+.It Ic \ev\(aq Ns Ar number Ns Ic \(aq
 Vertical motion; ignored by
 .Xr mandoc 1 .
-.Ss \ew\(aq Ns Ar string Ns \(aq
+.It Ic \ew\(aq Ns Ar string Ns Ic \(aq
 Interpolate the width of the
 .Ar string .
 The
@@ -1312,76 +2206,89 @@ implementation assumes that after expansion of user-de
 .Ar string
 only contains normal characters, no escape sequences, and that each
 character has a width of 24 basic units.
-.Ss \eX\(aq Ns Ar string Ns \(aq
+.It Ic \eX\(aq Ns Ar string Ns Ic \(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
+.It Ic \ex\(aq Ns Ar number Ns Ic \(aq
 Extra line space function; ignored by
 .Xr mandoc 1 .
-.Ss \eY[ Ns Ar name ]
+.It Ic \eY[ Ns Ar name Ns Ic \&]
 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
+.Ic \eY Ns Ar c
 and
-.No \eY( Ns Ar cc .
-.Ss \eZ\(aq Ns Ar string Ns \(aq
+.Ic \eY( Ns Ar cc .
+.It Ic \eZ\(aq Ns Ar string Ns Ic \(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.
+.It Ic \ez
+Output the next character without advancing the cursor position.
+.El
 .Sh COMPATIBILITY
-This section documents compatibility between mandoc and other
+The
+.Xr mandoc 1
+implementation of the
 .Nm
-implementations, at this time limited to GNU troff
-.Pq Qq groff .
-The term
-.Qq historic groff
-refers to groff version 1.15.
+language is incomplete.
+Major unimplemented features include:
 .Pp
 .Bl -dash -compact
 .It
+For security reasons,
+.Xr mandoc 1
+never reads or writes external files except via
+.Ic \&so
+requests with safe relative paths.
+.It
+There is no automatic hyphenation, no adjustment to the right margin,
+and very limited support for centering; the output is always set flush-left.
+.It
+Support for setting tabulator and leader characters is missing,
+and support for manually changing indentation is limited.
+.It
 The
 .Sq u
 scaling unit is the default terminal unit.
-In traditional troff systems, this unit would change depending on the
+In traditional troff systems, this unit changes depending on the
 output media.
 .It
-In mandoc, the
-.Sx \&EQ ,
-.Sx \&TE ,
-.Sx \&TS ,
-and
-.Sx \&T& ,
-macros are considered regular macros.
-In all other
-.Nm
-implementations, these are special macros that must be specified without
-spacing between the control character (which must be a period) and the
-macro name.
+Width measurements are implemented in a crude way
+and often yield wrong results.
+Support for explicit movement requests and escapes is limited.
 .It
-The
-.Cm nS
-register is only compatible with OpenBSD's groff-1.15.
+There is no concept of output pages, no support for floats,
+graphics drawing, and picture inclusion;
+terminal output is always continuous.
 .It
-Historic groff did not accept white-space before a custom
-.Ar end
-macro for the
-.Sx \&ig
-request.
+Requests regarding color, font families, font sizes,
+and glyph manipulation are ignored.
+Font support is very limited.
+Kerning is not implemented, and no ligatures are produced.
 .It
 The
-.Sx \&if
-and family would print funny white-spaces with historic groff when
-using the next-line syntax.
+.Qq \(aq
+macro control character does not suppress output line breaks.
+.It
+Diversions and environments are not implemented,
+and support for traps is very incomplete.
+.It
+Use of macros is not supported inside
+.Xr tbl 7
+code.
 .El
+.Pp
+The special semantics of the
+.Cm nS
+number register is an idiosyncrasy of
+.Ox
+manuals and not supported by other
+.Xr mdoc 7
+implementations.
 .Sh SEE ALSO
 .Xr mandoc 1 ,
 .Xr eqn 7 ,
@@ -1424,7 +2331,7 @@ for
 .At v2 ,
 then ported nroff to C as troff, which Brian W. Kernighan released with
 .At v7 .
-In 1989, James Clarke re-implemented troff in C++, naming it groff.
+In 1989, James Clark re-implemented troff in C++, naming it groff.
 .Sh AUTHORS
 .An -nosplit
 This