"Groff allows the initial macro on a line to be delimited by a space of

[mandoc.git] / mandoc.1

diff --git a/mandoc.1 b/mandoc.1
index df935e358e530797ab24925f601cae1d49cabc7a..187d7d40f3c61abf112c18a04bdabae891d14c5e 100644 (file)
--- a/mandoc.1
+++ b/mandoc.1
@@ -1,6 +1,6 @@
-.\"    $Id: mandoc.1,v 1.46 2009/11/05 10:16:01 kristaps Exp $
+.\"    $Id: mandoc.1,v 1.74 2010/08/07 17:46:39 kristaps Exp $

 .\"
 .\"

-.\" Copyright (c) 2009 Kristaps Dzonsons <kristaps@kth.se>
+.\" Copyright (c) 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>

 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
 .\" purpose with or without fee is hereby granted, provided that the above
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
 .\" purpose with or without fee is hereby granted, provided that the above


@@ -14,79 +14,71 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"

-.Dd $Mdocdate: November 5 2009 $
+.Dd $Mdocdate: August 7 2010 $

 .Dt MANDOC 1
 .Os
 .Dt MANDOC 1
 .Os

-.
-.

 .Sh NAME
 .Nm mandoc
 .Nd format and display UNIX manuals
 .Sh NAME
 .Nm mandoc
 .Nd format and display UNIX manuals

-.
-.

 .Sh SYNOPSIS
 .Nm mandoc
 .Sh SYNOPSIS
 .Nm mandoc

-.Op Fl f Ns Ar option...
+.Op Fl V
+.Op Fl f Ns Ar option

 .Op Fl m Ns Ar format
 .Op Fl m Ns Ar format

-.Op Fl O Ns Ar option...
+.Op Fl O Ns Ar option

 .Op Fl T Ns Ar output
 .Op Fl T Ns Ar output

-.Op Fl V
-.Op Fl W Ns Ar err...
-.Op Ar infile...
-.
-.
+.Op Fl W Ns Ar err
+.Op Ar file...

 .Sh DESCRIPTION
 The
 .Nm
 utility formats
 .Ux
 .Sh DESCRIPTION
 The
 .Nm
 utility formats
 .Ux

-manual pages for display.  The arguments are as follows:
-.
+manual pages for display.
+The arguments are as follows:

 .Bl -tag -width Ds
 .Bl -tag -width Ds

-.It Fl f Ns Ar option...
-Comma-separated compiler options.  See
+.It Fl f Ns Ar option
+Comma-separated compiler options.
+See

 .Sx Compiler Options
 for details.
 .Sx Compiler Options
 for details.

-.

 .It Fl m Ns Ar format
 .It Fl m Ns Ar format

-Input format.  See
+Input format.
+See

 .Sx Input Formats
 .Sx Input Formats

-for available formats.  Defaults to
-.Fl m Ns Ar andoc .
-.
-.It Fl O Ns Ar option...
-Comma-separated output options.  See
-.Sx Output Options
-for details.
-.
+for available formats.
+Defaults to
+.Fl m Ns Cm andoc .
+.It Fl O Ns Ar option
+Comma-separated output options.

 .It Fl T Ns Ar output
 .It Fl T Ns Ar output

-Output format.  See
+Output format.
+See

 .Sx Output Formats
 .Sx Output Formats

-for available formats.  Defaults to
-.Fl T Ns Ar ascii .
-.
+for available formats.
+Defaults to
+.Fl T Ns Cm ascii .

 .It Fl V
 Print version and exit.
 .It Fl V
 Print version and exit.

-.
-.It Fl W Ns Ar err...
-Comma-separated warning options.  Use
-.Fl W Ns Ar all
+.It Fl W Ns Ar err
+Comma-separated warning options.
+Use
+.Fl W Ns Cm all

 to print warnings,
 to print warnings,

-.Fl W Ns Ar error
+.Fl W Ns Cm error

 for warnings to be considered errors and cause utility
 for warnings to be considered errors and cause utility

-termination.  Multiple
+termination.
+Multiple

 .Fl W
 arguments may be comma-separated, such as
 .Fl W
 arguments may be comma-separated, such as

-.Fl W Ns Ar error,all .
-.
-.It Ar infile...
-Read input from zero or more
-.Ar infile .
-If unspecified, reads from stdin.  If multiple files are specified,
+.Fl W Ns Cm error , Ns Cm all .
+.It Ar file
+Read input from zero or more files.
+If unspecified, reads from stdin.
+If multiple files are specified,

 .Nm
 will halt with the first failed parse.
 .El
 .Nm
 will halt with the first failed parse.
 .El

-.

 .Pp
 By default,
 .Nm
 .Pp
 By default,
 .Nm


@@ -95,56 +87,12 @@ reads
 or
 .Xr man 7
 text from stdin, implying
 or
 .Xr man 7
 text from stdin, implying

-.Fl m Ns Ar andoc ,
-and prints 78-column backspace-encoded output to stdout as if
-.Fl T Ns Ar ascii
-were provided.
-.
+.Fl m Ns Cm andoc ,
+and produces
+.Fl T Ns Cm ascii
+output.

 .Pp
 .Ex -std mandoc
 .Pp
 .Ex -std mandoc

-.
-.
-.Ss Punctuation and Spacing
-If punctuation is set apart from words, such as in the phrase
-.Dq to be \&, or not to be ,
-it's processed by
-.Nm
-according to the following rules:  opening punctuation
-.Po
-.Sq \&( ,
-.Sq \&[ ,
-and
-.Sq \&{
-.Pc
-is not followed by a space; closing punctuation
-.Po
-.Sq \&. ,
-.Sq \&, ,
-.Sq \&; ,
-.Sq \&: ,
-.Sq \&? ,
-.Sq \&! ,
-.Sq \&) ,
-.Sq \&]
-and
-.Sq \&}
-.Pc
-is not preceded by whitespace.
-.
-.Pp
-If the input is
-.Xr mdoc 7 ,
-these rules are also applied to macro arguments when appropriate.
-.
-.Pp
-White-space, in non-literal (normal) mode, is stripped from input and
-replaced on output by a single space.  Thus, if you wish to preserve multiple
-spaces, they must be space-escaped or used in a literal display mode, e.g.,
-.Sq \&Bd \-literal
-in
-.Xr mdoc 7 .
-.
-.

 .Ss Input Formats
 The
 .Nm
 .Ss Input Formats
 The
 .Nm


@@ -153,20 +101,20 @@ utility accepts
 and
 .Xr man 7
 input with
 and
 .Xr man 7
 input with

-.Fl m Ns Ar doc
+.Fl m Ns Cm doc

 and
 and

-.Fl m Ns Ar an ,
-respectively.  The
+.Fl m Ns Cm an ,
+respectively.
+The

 .Xr mdoc 7
 format is
 .Em strongly
 recommended;
 .Xr man 7
 should only be used for legacy manuals.
 .Xr mdoc 7
 format is
 .Em strongly
 recommended;
 .Xr man 7
 should only be used for legacy manuals.

-.

 .Pp
 A third option,
 .Pp
 A third option,

-.Fl m Ns Ar andoc ,
+.Fl m Ns Cm andoc ,

 which is also the default, determines encoding on-the-fly: if the first
 non-comment macro is
 .Sq \&Dd
 which is also the default, determines encoding on-the-fly: if the first
 non-comment macro is
 .Sq \&Dd


@@ -177,220 +125,323 @@ the
 parser is used; otherwise, the
 .Xr man 7
 parser is used.
 parser is used; otherwise, the
 .Xr man 7
 parser is used.

-.

 .Pp
 If multiple
 files are specified with
 .Pp
 If multiple
 files are specified with

-.Fl m Ns Ar andoc ,
-each has its file-type determined this way.  If multiple files are
+.Fl m Ns Cm andoc ,
+each has its file-type determined this way.
+If multiple files are

 specified and
 specified and

-.Fl m Ns Ar doc
+.Fl m Ns Cm doc

 or
 or

-.Fl m Ns Ar an
+.Fl m Ns Cm an

 is specified, then this format is used exclusively.
 is specified, then this format is used exclusively.

-.
-.
+.Ss Compiler Options
+Default
+.Xr mdoc 7
+and
+.Xr man 7
+compilation behaviour may be overridden with the
+.Fl f
+flag.
+.Bl -tag -width Ds
+.It Fl f Ns Cm ign-errors
+When parsing multiple files, don't halt when one errors out.
+Useful with
+.Fl T Ns Cm lint
+over a large set of manuals passed on the command line.
+.It Fl f Ns Cm ign-escape
+Ignore invalid escape sequences.
+This is the default, but the option can be used to override an earlier
+.Fl f Ns Cm strict .
+.It Fl f Ns Cm ign-scope
+When rewinding the scope of a block macro, forces the compiler to ignore
+scope violations.
+This can seriously mangle the resulting tree.
+.Pq mdoc only
+.It Fl f Ns Cm no-ign-escape
+Do not ignore invalid escape sequences.
+.It Fl f Ns Cm no-ign-macro
+Do not ignore unknown macros at the start of input lines.
+.It Fl f Ns Cm strict
+Implies
+.Fl f Ns Cm no-ign-escape
+and
+.Fl f Ns Cm no-ign-macro .
+.El

 .Ss Output Formats
 The
 .Nm
 utility accepts the following
 .Fl T
 .Ss Output Formats
 The
 .Nm
 utility accepts the following
 .Fl T

-arguments:
-.
+arguments, which correspond to output modes:

 .Bl -tag -width Ds
 .Bl -tag -width Ds

-.It Fl T Ns Ar ascii
+.It Fl T Ns Cm ascii

 Produce 7-bit ASCII output, backspace-encoded for bold and underline
 Produce 7-bit ASCII output, backspace-encoded for bold and underline

-styles.  This is the default.
-.
-.It Fl T Ns Ar html
+styles.
+This is the default.
+See
+.Sx ASCII Output .
+.It Fl T Ns Cm html

 Produce strict HTML-4.01 output, with a sane default style.
 Produce strict HTML-4.01 output, with a sane default style.

-.
-.It Fl T Ns Ar tree
-Produce an indented parse tree.
-.
-.It Fl T Ns Ar lint
+See
+.Sx HTML Output .
+.It Fl T Ns Cm lint

 Parse only: produce no output.
 Parse only: produce no output.

+Implies
+.Fl W Ns Cm all
+and
+.Fl f Ns Cm strict .
+.It Fl T Ns Cm pdf
+Produce PDF output.
+See
+.Sx PDF Output .
+.It Fl T Ns Cm ps
+Produce PostScript output.
+See
+.Sx PostScript Output .
+.It Fl T Ns Cm tree
+Produce an indented parse tree.
+.It Fl T Ns Cm xhtml
+Produce strict XHTML-1.0 output, with a sane default style.
+See
+.Sx XHTML Output .

 .El
 .El

-.

 .Pp
 If multiple input files are specified, these will be processed by the
 corresponding filter in-order.
 .Pp
 If multiple input files are specified, these will be processed by the
 corresponding filter in-order.

-.
-.
-.Ss Compiler Options
-Default compiler behaviour may be overridden with the
-.Fl f
-flag.
-.
+.Ss ASCII Output
+Output produced by
+.Fl T Ns Cm ascii ,
+which is the default, is rendered in standard 7-bit ASCII documented in
+.Xr ascii 7 .
+.Pp
+Font styles are applied by using back-spaced encoding such that an
+underlined character
+.Sq c
+is rendered as
+.Sq _ Ns \e[bs] Ns c ,
+where
+.Sq \e[bs]
+is the back-space character number 8.
+Emboldened characters are rendered as
+.Sq c Ns \e[bs] Ns c .
+.Pp
+The special characters documented in
+.Xr mandoc_char 7
+are rendered best-effort in an ASCII equivalent.
+.Pp
+Output width is limited to 78 visible columns unless literal input lines
+exceed this limit.
+.Pp
+The following
+.Fl O
+arguments are accepted:

 .Bl -tag -width Ds
 .Bl -tag -width Ds

-.It Fl f Ns Ar ign-scope
-When rewinding the scope of a block macro, forces the compiler to ignore
-scope violations.  This can seriously mangle the resulting tree.
-.Pq mdoc only
-.
-.It Fl f Ns Ar ign-escape
-Ignore invalid escape sequences.
-This is the default, but the option can be used to override an earlier
-.Fl f Ns Ar strict .
-.
-.It Fl f Ns Ar no-ign-escape
-Don't ignore invalid escape sequences.
-.
-.It Fl f Ns Ar no-ign-macro
-Do not ignore unknown macros at the start of input lines.
-.
-.It Fl f Ns Ar no-ign-chars
-Do not ignore disallowed characters.
-.
-.It Fl f Ns Ar strict
-Implies
-.Fl f Ns Ar no-ign-escape ,
-.Fl f Ns Ar no-ign-macro
-and
-.Fl f Ns Ar no-ign-chars .
-.
-.It Fl f Ns Ar ign-errors
-Don't halt when encountering parse errors.  Useful with
-.Fl T Ns Ar lint
-over a large set of manuals passed on the command line.
+.It Cm width Ns = Ns Ar width
+The output width is set to
+.Ar width ,
+which will normalise to \(>=60.

 .El
 .El

-.
-.Ss Output Options
-For the time being, only
-.Fl T Ns Ar html
-is the only mode with output options:
+.Ss HTML Output
+Output produced by
+.Fl T Ns Cm html
+conforms to HTML-4.01 strict.
+.Pp
+Font styles and page structure are applied using CSS2.
+By default, no font style is applied to any text,
+although CSS2 is hard-coded to format
+the basic structure of output.
+.Pp
+The
+.Pa example.style.css
+file documents the range of styles applied to output and, if used, will
+cause rendered documents to appear as they do in
+.Fl T Ns Cm ascii .
+.Pp
+Special characters are rendered in decimal-encoded UTF-8.
+.Pp
+The following
+.Fl O
+arguments are accepted:

 .Bl -tag -width Ds
 .Bl -tag -width Ds

-.It Fl O Ns Ar style=style.css
-The file
-.Ar style.css
-is used for an external style-sheet.  This must be a valid absolute or
-relative URI.
-.It Fl O Ns Ar includes=fmt
+.It Cm includes Ns = Ns Ar fmt

 The string
 .Ar fmt ,
 The string
 .Ar fmt ,

-for example, 
+for example,

 .Ar ../src/%I.html ,
 is used as a template for linked header files (usually via the
 .Sq \&In
 .Ar ../src/%I.html ,
 is used as a template for linked header files (usually via the
 .Sq \&In

-macro).  Instances of
+macro).
+Instances of

 .Sq \&%I
 .Sq \&%I

-are replaced with the include filename.  The default is not to present a
+are replaced with the include filename.
+The default is not to present a

 hyperlink.
 hyperlink.

-.It Fl O Ns Ar man=fmt
+.It Cm man Ns = Ns Ar fmt

 The string
 .Ar fmt ,
 The string
 .Ar fmt ,

-for example, 
+for example,

 .Ar ../html%S/%N.%S.html ,
 is used as a template for linked manuals (usually via the
 .Sq \&Xr
 .Ar ../html%S/%N.%S.html ,
 is used as a template for linked manuals (usually via the
 .Sq \&Xr

-macro).  Instances of
+macro).
+Instances of

 .Sq \&%N
 and
 .Sq %S
 are replaced with the linked manual's name and section, respectively.
 .Sq \&%N
 and
 .Sq %S
 are replaced with the linked manual's name and section, respectively.

-If no section is included, section 1 is assumed.  The default is not to
+If no section is included, section 1 is assumed.
+The default is not to

 present a hyperlink.
 present a hyperlink.

+.It Cm style Ns = Ns Ar style.css
+The file
+.Ar style.css
+is used for an external style-sheet.
+This must be a valid absolute or
+relative URI.

 .El
 .El

-.
+.Ss PostScript Output
+PostScript
+.Qq Adobe-3.0
+Level-2 pages may be generated by
+.Fl T Ns Cm ps .
+Output pages default to letter sized and are rendered in the Times font
+family, 11-point.
+Margins are calculated as 1/9 the page length and width.
+Line-height is 1.4m.
+.Pp
+Special characters are rendered as in
+.Sx ASCII Output .
+.Pp
+The following
+.Fl O
+arguments are accepted:
+.Bl -tag -width Ds
+.It Cm paper Ns = Ns Ar name
+The paper size
+.Ar name
+may be one of
+.Ar a3 ,
+.Ar a4 ,
+.Ar a5 ,
+.Ar legal ,
+or
+.Ar letter .
+You may also manually specify dimensions as
+.Ar NNxNN ,
+width by height in millimetres.
+If an unknown value is encountered,
+.Ar letter
+is used.
+.El
+.Ss PDF Output
+PDF-1.1 output may be generated by
+.Fl T Ns Cm pdf .
+See
+.Sx PostScript Output
+for
+.Fl O
+arguments and defaults.
+.Ss XHTML Output
+Output produced by
+.Fl T Ns Cm xhtml
+conforms to XHTML-1.0 strict.
+.Pp
+See
+.Sx HTML Output
+for details; beyond generating XHTML tags instead of HTML tags, these
+output modes are identical.

 .Sh EXAMPLES
 To page manuals to the terminal:
 .Sh EXAMPLES
 To page manuals to the terminal:

-.

 .Pp
 .Pp

-.D1 % mandoc \-Wall,error \-fstrict mandoc.1 2>&1 | less
-.D1 % mandoc mandoc.1 mdoc.3 mdoc.7 | less
-.
+.D1 $ mandoc \-Wall,error \-fstrict mandoc.1 2\*(Gt&1 | less
+.D1 $ mandoc mandoc.1 mdoc.3 mdoc.7 | less

 .Pp
 To produce HTML manuals with
 .Ar style.css
 as the style-sheet:
 .Pp
 .Pp
 To produce HTML manuals with
 .Ar style.css
 as the style-sheet:
 .Pp

-.D1 % mandoc \-Thtml -ostyle=style.css mdoc.7 > mdoc.7.html
+.D1 $ mandoc \-Thtml -Ostyle=style.css mdoc.7 \*(Gt mdoc.7.html

 .Pp
 To check over a large set of manuals:
 .Pp
 To check over a large set of manuals:

-.

 .Pp
 .Pp

-.Dl % mandoc \-Tlint \-fign-errors `find /usr/src -name \e*\e.[1-9]`
-.
-.
+.Dl $ mandoc \-Tlint \-fign-errors `find /usr/src -name \e*\e.[1-9]`
+.Pp
+To produce a series of PostScript manuals for A4 paper:
+.Pp
+.D1 $ mandoc \-Tps \-Opaper=a4 mdoc.7 man.7 \*(Gt manuals.ps

 .Sh COMPATIBILITY
 This section summarises
 .Nm
 compatibility with
 .Xr groff 1 .
 Each input and output format is separately noted.
 .Sh COMPATIBILITY
 This section summarises
 .Nm
 compatibility with
 .Xr groff 1 .
 Each input and output format is separately noted.

-.
-.
-.Ss ASCII output
+.Ss ASCII Compatibility

 .Bl -bullet -compact
 .It
 .Bl -bullet -compact
 .It

-The 
-.Sq \e~
-special character doesn't produce expected behaviour in 
-.Fl T Ns Ar ascii .
-.
-.It
-The 
+The

 .Sq \&Bd \-literal
 .Sq \&Bd \-literal

-and 
+and

 .Sq \&Bd \-unfilled
 macros of
 .Xr mdoc 7
 in
 .Sq \&Bd \-unfilled
 macros of
 .Xr mdoc 7
 in

-.Fl T Ns Ar ascii
+.Fl T Ns Cm ascii

 are synonyms, as are \-filled and \-ragged.
 are synonyms, as are \-filled and \-ragged.

-.

 .It
 .It

-In 
+In

 .Xr groff 1 ,
 the
 .Sq \&Pa
 .Xr mdoc 7
 macro does not underline when scoped under an
 .Sq \&It
 .Xr groff 1 ,
 the
 .Sq \&Pa
 .Xr mdoc 7
 macro does not underline when scoped under an
 .Sq \&It

-in the FILES section.  This behaves correctly in
+in the FILES section.
+This behaves correctly in

 .Nm .
 .Nm .

-.

 .It
 .It

-A list or display following
+A list or display following the

 .Sq \&Ss
 .Xr mdoc 7
 macro in
 .Sq \&Ss
 .Xr mdoc 7
 macro in

-.Fl T Ns Ar ascii
+.Fl T Ns Cm ascii

 does not assert a prior vertical break, just as it doesn't with
 .Sq \&Sh .
 does not assert a prior vertical break, just as it doesn't with
 .Sq \&Sh .

-.

 .It
 The
 .Sq \&na
 .Xr man 7
 macro in
 .It
 The
 .Sq \&na
 .Xr man 7
 macro in

-.Fl T Ns Ar ascii
+.Fl T Ns Cm ascii

 has no effect.
 has no effect.

-.

 .It
 Words aren't hyphenated.
 .It
 Words aren't hyphenated.

-.
-.It
-In normal mode (not a literal block), blocks of spaces aren't preserved,
-so double spaces following sentence closure are reduced to a single space;
-.Xr groff 1
-retains spaces.
-.

 .It
 Sentences are unilaterally monospaced.
 .El
 .It
 Sentences are unilaterally monospaced.
 .El

-.
-.Ss HTML output
+.Ss HTML/XHTML Compatibility

 .Bl -bullet -compact
 .It
 The
 .Bl -bullet -compact
 .It
 The

+.Sq \efP
+escape will revert the font to the previous
+.Sq \ef
+escape, not to the last rendered decoration, which is now dictated by
+CSS instead of hard-coded.
+It also will not span past the current scope,
+for the same reason.
+Note that in
+.Sx ASCII Output
+mode, this will work fine.
+.It
+The

 .Xr mdoc 7
 .Sq \&Bl \-hang
 and
 .Sq \&Bl \-tag
 list types render similarly (no break following overreached left-hand
 side) due to the expressive constraints of HTML.
 .Xr mdoc 7
 .Sq \&Bl \-hang
 and
 .Sq \&Bl \-tag
 list types render similarly (no break following overreached left-hand
 side) due to the expressive constraints of HTML.

-.

 .It
 The
 .Xr man 7
 .It
 The
 .Xr man 7


@@ -399,34 +450,66 @@ and
 .Sq TP
 lists render similarly.
 .El
 .Sq TP
 lists render similarly.
 .El

-.\" SECTION

 .Sh SEE ALSO
 .Sh SEE ALSO

+.Xr man 7 ,

 .Xr mandoc_char 7 ,
 .Xr mandoc_char 7 ,

-.Xr mdoc 7 ,
-.Xr man 7
-.
+.Xr mdoc 7

 .Sh AUTHORS
 The
 .Nm
 utility was written by
 .Sh AUTHORS
 The
 .Nm
 utility was written by

-.An Kristaps Dzonsons Aq kristaps@kth.se .
-.
+.An Kristaps Dzonsons Aq kristaps@bsd.lv .

 .Sh CAVEATS
 .Sh CAVEATS

+The
+.Fl T Ns Cm html
+and
+.Fl T Ns Cm xhtml
+CSS2 styling used for
+.Fl m Ns Cm doc
+input lists does not render properly in older browsers, such as Internet
+Explorer 6 and earlier.
+.Pp

 In
 In

-.Fl T Ns Ar html ,
+.Fl T Ns Cm html
+and
+.Fl T Ns Cm xhtml ,

 the maximum size of an element attribute is determined by
 .Dv BUFSIZ ,
 the maximum size of an element attribute is determined by
 .Dv BUFSIZ ,

-which is usually 1024 bytes.  Be aware of this when setting long link
-formats with
-.Fl O Ns Ar man=fmt .
+which is usually 1024 bytes.
+Be aware of this when setting long link
+formats such as
+.Fl O Ns Cm style Ns = Ns Ar really/long/link .

 .Pp
 The
 .Pp
 The

-.Fl T Ns Ar html
-utility doesn't support the
-.Sq \ef
+.Fl T Ns Cm html

 and
 and

+.Fl T Ns Cm xhtml
+output modes don't render the

 .Sq \es
 .Sq \es

-text decorations documented in
+font size escape documented in

 .Xr mdoc 7
 and
 .Xr man 7 .
 .Xr mdoc 7
 and
 .Xr man 7 .

+.Pp
+Nesting elements within next-line element scopes of
+.Fl m Ns Cm an ,
+such as
+.Sq br
+within an empty
+.Sq B ,
+will confuse
+.Fl T Ns Cm html
+and
+.Fl T Ns Cm xhtml
+and cause them to forget the formatting of the prior next-line scope.
+.Pp
+The
+.Sq i
+macro in
+.Fl m Ns Cm an
+should italicise all subsequent text if a line argument is not provided.
+This behaviour is not implemented.
+The
+.Sq \(aq
+control character is an alias for the standard macro control character
+and does not emit a line-break as stipulated in GNU troff.