Update to PodParser 1.18, from Brad Appleton.

[perl5.git] / lib / Pod / Man.pm

# Pod::Man -- Convert POD data to formatted *roff input.
# $Id: Man.pm,v 1.4 2000/04/26 04:03:41 eagle Exp $
#
# Copyright 1999, 2000 by Russ Allbery <rra@stanford.edu>
#
# This program is free software; you can redistribute it and/or modify it
# under the same terms as Perl itself.
#
# This module is intended to be a replacement for the pod2man script
# distributed with versions of Perl prior to 5.6, and attempts to match its
# output except for some specific circumstances where other decisions seemed
# to produce better output.  It uses Pod::Parser and is designed to be easy
# to subclass.
#
# Perl core hackers, please note that this module is also separately
# maintained outside of the Perl core as part of the podlators.  Please send
# me any patches at the address above in addition to sending them to the
# standard Perl mailing lists.

############################################################################
# Modules and declarations
############################################################################

package Pod::Man;

require 5.004;

use Carp qw(carp croak);
use Pod::Parser ();

use strict;
use subs qw(makespace);
use vars qw(@ISA %ESCAPES $PREAMBLE $VERSION);

@ISA = qw(Pod::Parser);

# Don't use the CVS revision as the version, since this module is also in
# Perl core and too many things could munge CVS magic revision strings.
# This number should ideally be the same as the CVS revision in podlators,
# however.
$VERSION = 1.04;


############################################################################
# Preamble and *roff output tables
############################################################################

# The following is the static preamble which starts all *roff output we
# generate.  It's completely static except for the font to use as a
# fixed-width font, which is designed by @CFONT@.  $PREAMBLE should
# therefore be run through s/\@CFONT\@/<font>/g before output.
$PREAMBLE = <<'----END OF PREAMBLE----';
.de Sh \" Subsection heading
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Ip \" List item
.br
.ie \\n(.$>=3 .ne \\$3
.el .ne 3
.IP "\\$1" \\$2
..
.de Vb \" Begin verbatim text
.ft @CFONT@
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R

.fi
..
.\" Set up some character translations and predefined strings.  \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote.  | will give a
.\" real vertical bar.  \*(C+ will give a nicer C++.  Capital omega is used
.\" to do unbreakable dashes and therefore won't be available.  \*(C` and
.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<>
.tr \(*W-|\(bv\*(Tr
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
.    ds -- \(*W-
.    ds PI pi
.    if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.    if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\"  diablo 12 pitch
.    ds L" ""
.    ds R" ""
.    ds C` `
.    ds C' '
'br\}
.el\{\
.    ds -- \|\(em\|
.    ds PI \(*p
.    ds L" ``
.    ds R" ''
'br\}
.\"
.\" If the F register is turned on, we'll generate index entries on stderr
.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and
.\" index entries marked with X<> in POD.  Of course, you'll have to process
.\" the output yourself in some meaningful fashion.
.if \nF \{\
.    de IX
.    tm Index:\\$1\t\\n%\t"\\$2"
..
.    nr % 0
.    rr F
.\}
.\"
.\" For nroff, turn off justification.  Always turn off hyphenation; it
.\" makes way too many mistakes in technical documents.
.hy 0
.if n .na
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear.  Run.  Save yourself.  No user-serviceable parts.
.bd B 3
.    \" fudge factors for nroff and troff
.if n \{\
.    ds #H 0
.    ds #V .8m
.    ds #F .3m
.    ds #[ \f1
.    ds #] \fP
.\}
.if t \{\
.    ds #H ((1u-(\\\\n(.fu%2u))*.13m)
.    ds #V .6m
.    ds #F 0
.    ds #[ \&
.    ds #] \&
.\}
.    \" simple accents for nroff and troff
.if n \{\
.    ds ' \&
.    ds ` \&
.    ds ^ \&
.    ds , \&
.    ds ~ ~
.    ds /
.\}
.if t \{\
.    ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
.    ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
.    ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
.    ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
.    ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
.    ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
.    \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.    \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
.    \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
.    ds : e
.    ds 8 ss
.    ds o a
.    ds d- d\h'-1'\(ga
.    ds D- D\h'-1'\(hy
.    ds th \o'bp'
.    ds Th \o'LP'
.    ds ae ae
.    ds Ae AE
.\}
.rm #[ #] #H #V #F C
----END OF PREAMBLE----
                                   
# This table is taken nearly verbatim from Tom Christiansen's pod2man.  It
# assumes that the standard preamble has already been printed, since that's
# what defines all of the accent marks.  Note that some of these are quoted
# with double quotes since they contain embedded single quotes, so use \\
# uniformly for backslash for readability.
%ESCAPES = (
    'amp'       =>    '&',      # ampersand
    'lt'        =>    '<',      # left chevron, less-than
    'gt'        =>    '>',      # right chevron, greater-than
    'quot'      =>    '"',      # double quote
    'sol'       =>    '/',      # solidus
    'verbar'    =>    '|',      # vertical bar

    'Aacute'    =>    "A\\*'",  # capital A, acute accent
    'aacute'    =>    "a\\*'",  # small a, acute accent
    'Acirc'     =>    'A\\*^',  # capital A, circumflex accent
    'acirc'     =>    'a\\*^',  # small a, circumflex accent
    'AElig'     =>    '\*(AE',  # capital AE diphthong (ligature)
    'aelig'     =>    '\*(ae',  # small ae diphthong (ligature)
    'Agrave'    =>    "A\\*`",  # capital A, grave accent
    'agrave'    =>    "A\\*`",  # small a, grave accent
    'Aring'     =>    'A\\*o',  # capital A, ring
    'aring'     =>    'a\\*o',  # small a, ring
    'Atilde'    =>    'A\\*~',  # capital A, tilde
    'atilde'    =>    'a\\*~',  # small a, tilde
    'Auml'      =>    'A\\*:',  # capital A, dieresis or umlaut mark
    'auml'      =>    'a\\*:',  # small a, dieresis or umlaut mark
    'Ccedil'    =>    'C\\*,',  # capital C, cedilla
    'ccedil'    =>    'c\\*,',  # small c, cedilla
    'Eacute'    =>    "E\\*'",  # capital E, acute accent
    'eacute'    =>    "e\\*'",  # small e, acute accent
    'Ecirc'     =>    'E\\*^',  # capital E, circumflex accent
    'ecirc'     =>    'e\\*^',  # small e, circumflex accent
    'Egrave'    =>    'E\\*`',  # capital E, grave accent
    'egrave'    =>    'e\\*`',  # small e, grave accent
    'ETH'       =>    '\\*(D-', # capital Eth, Icelandic
    'eth'       =>    '\\*(d-', # small eth, Icelandic
    'Euml'      =>    'E\\*:',  # capital E, dieresis or umlaut mark
    'euml'      =>    'e\\*:',  # small e, dieresis or umlaut mark
    'Iacute'    =>    "I\\*'",  # capital I, acute accent
    'iacute'    =>    "i\\*'",  # small i, acute accent
    'Icirc'     =>    'I\\*^',  # capital I, circumflex accent
    'icirc'     =>    'i\\*^',  # small i, circumflex accent
    'Igrave'    =>    'I\\*`',  # capital I, grave accent
    'igrave'    =>    'i\\*`',  # small i, grave accent
    'Iuml'      =>    'I\\*:',  # capital I, dieresis or umlaut mark
    'iuml'      =>    'i\\*:',  # small i, dieresis or umlaut mark
    'Ntilde'    =>    'N\*~',   # capital N, tilde
    'ntilde'    =>    'n\*~',   # small n, tilde
    'Oacute'    =>    "O\\*'",  # capital O, acute accent
    'oacute'    =>    "o\\*'",  # small o, acute accent
    'Ocirc'     =>    'O\\*^',  # capital O, circumflex accent
    'ocirc'     =>    'o\\*^',  # small o, circumflex accent
    'Ograve'    =>    'O\\*`',  # capital O, grave accent
    'ograve'    =>    'o\\*`',  # small o, grave accent
    'Oslash'    =>    'O\\*/',  # capital O, slash
    'oslash'    =>    'o\\*/',  # small o, slash
    'Otilde'    =>    'O\\*~',  # capital O, tilde
    'otilde'    =>    'o\\*~',  # small o, tilde
    'Ouml'      =>    'O\\*:',  # capital O, dieresis or umlaut mark
    'ouml'      =>    'o\\*:',  # small o, dieresis or umlaut mark
    'szlig'     =>    '\*8',    # small sharp s, German (sz ligature)
    'THORN'     =>    '\\*(Th', # capital THORN, Icelandic
    'thorn'     =>    '\\*(th', # small thorn, Icelandic
    'Uacute'    =>    "U\\*'",  # capital U, acute accent
    'uacute'    =>    "u\\*'",  # small u, acute accent
    'Ucirc'     =>    'U\\*^',  # capital U, circumflex accent
    'ucirc'     =>    'u\\*^',  # small u, circumflex accent
    'Ugrave'    =>    'U\\*`',  # capital U, grave accent
    'ugrave'    =>    'u\\*`',  # small u, grave accent
    'Uuml'      =>    'U\\*:',  # capital U, dieresis or umlaut mark
    'uuml'      =>    'u\\*:',  # small u, dieresis or umlaut mark
    'Yacute'    =>    "Y\\*'",  # capital Y, acute accent
    'yacute'    =>    "y\\*'",  # small y, acute accent
    'yuml'      =>    'y\\*:',  # small y, dieresis or umlaut mark
);


############################################################################
# Static helper functions
############################################################################

# Protect leading quotes and periods against interpretation as commands.
# Also protect anything starting with a backslash, since it could expand
# or hide something that *roff would interpret as a command.  This is
# overkill, but it's much simpler than trying to parse *roff here.
sub protect {
    local $_ = shift;
    s/^([.\'\\])/\\&$1/mg;
    $_;
}
                    
# Given a command and a single argument that may or may not contain double
# quotes, handle double-quote formatting for it.  If there are no double
# quotes, just return the command followed by the argument in double quotes.
# If there are double quotes, use an if statement to test for nroff, and for
# nroff output the command followed by the argument in double quotes with
# embedded double quotes doubled.  For other formatters, remap paired double
# quotes to `` and ''.
sub switchquotes {
    my $command = shift;
    local $_ = shift;
    my $extra = shift;
    s/\\\*\([LR]\"/\"/g;
    if (/\"/) {
        s/\"/\"\"/g;
        my $troff = $_;
        $troff =~ s/\"\"([^\"]*)\"\"/\`\`$1\'\'/g;
        s/\"/\"\"/g if $extra;
        $troff =~ s/\"/\"\"/g if $extra;
        $_ = qq("$_") . ($extra ? " $extra" : '');
        $troff = qq("$troff") . ($extra ? " $extra" : '');
        return ".if n $command $_\n.el $command $troff\n";
    } else {
        $_ = qq("$_") . ($extra ? " $extra" : '');
        return "$command $_\n";
    }
}

# Translate a font string into an escape.
sub toescape { (length ($_[0]) > 1 ? '\f(' : '\f') . $_[0] }

                    
############################################################################
# Initialization
############################################################################

# Initialize the object.  Here, we also process any additional options
# passed to the constructor or set up defaults if none were given.  center
# is the centered title, release is the version number, and date is the date
# for the documentation.  Note that we can't know what file name we're
# processing due to the architecture of Pod::Parser, so that *has* to either
# be passed to the constructor or set separately with Pod::Man::name().
sub initialize {
    my $self = shift;

    # Figure out the fixed-width font.  If user-supplied, make sure that
    # they are the right length.
    for (qw/fixed fixedbold fixeditalic fixedbolditalic/) {
        if (defined $$self{$_}) {
            if (length ($$self{$_}) < 1 || length ($$self{$_}) > 2) {
                croak "roff font should be 1 or 2 chars, not `$$self{$_}'";
            }
        } else {
            $$self{$_} = '';
        }
    }

    # Set the default fonts.  We can't be sure what fixed bold-italic is
    # going to be called, so default to just bold.
    $$self{fixed}           ||= 'CW';
    $$self{fixedbold}       ||= 'CB';
    $$self{fixeditalic}     ||= 'CI';
    $$self{fixedbolditalic} ||= 'CB';

    # Set up a table of font escapes.  First number is fixed-width, second
    # is bold, third is italic.
    $$self{FONTS} = { '000' => '\fR', '001' => '\fI',
                      '010' => '\fB', '011' => '\f(BI',
                      '100' => toescape ($$self{fixed}),
                      '101' => toescape ($$self{fixeditalic}),
                      '110' => toescape ($$self{fixedbold}),
                      '111' => toescape ($$self{fixedbolditalic})};

    # Extra stuff for page titles.
    $$self{center} = 'User Contributed Perl Documentation'
        unless defined $$self{center};
    $$self{indent}  = 4 unless defined $$self{indent};

    # We used to try first to get the version number from a local binary,
    # but we shouldn't need that any more.  Get the version from the running
    # Perl.  Work a little magic to handle subversions correctly under both
    # the pre-5.6 and the post-5.6 version numbering schemes.
    if (!defined $$self{release}) {
        my @version = ($] =~ /^(\d+)\.(\d{3})(\d{0,3})$/);
        $version[2] ||= 0;
        $version[2] *= 10 ** (3 - length $version[2]);
        for (@version) { $_ += 0 }
        $$self{release} = 'perl v' . join ('.', @version);
    }

    # Double quotes in things that will be quoted.
    for (qw/center date release/) {
        $$self{$_} =~ s/\"/\"\"/g if $$self{$_};
    }

    $$self{INDENT}  = 0;        # Current indentation level.
    $$self{INDENTS} = [];       # Stack of indentations.
    $$self{INDEX}   = [];       # Index keys waiting to be printed.

    $self->SUPER::initialize;
}

# For each document we process, output the preamble first.  Note that the
# fixed width font is a global default; once we interpolate it into the
# PREAMBLE, it ain't ever changing.  Maybe fix this later.
sub begin_pod {
    my $self = shift;

    # Try to figure out the name and section from the file name.
    my $section = $$self{section} || 1;
    my $name = $$self{name};
    if (!defined $name) {
        $name = $self->input_file;
        $section = 3 if (!$$self{section} && $name =~ /\.pm\z/i);
        $name =~ s/\.p(od|[lm])\z//i;
        if ($section =~ /^1/) {
            require File::Basename;
            $name = uc File::Basename::basename ($name);
        } else {
            # Lose everything up to the first of
            #     */lib/*perl*      standard or site_perl module
            #     */*perl*/lib      from -D prefix=/opt/perl
            #     */*perl*/         random module hierarchy
            # which works.  Should be fixed to use File::Spec.  Also handle
            # a leading lib/ since that's what ExtUtils::MakeMaker creates.
            for ($name) {
                s%//+%/%g;
                if (     s%^.*?/lib/[^/]*perl[^/]*/%%si
                      or s%^.*?/[^/]*perl[^/]*/(?:lib/)?%%si) {
                    s%^site(_perl)?/%%s;      # site and site_perl
                    s%^(.*-$^O|$^O-.*)/%%so;  # arch
                    s%^\d+\.\d+%%s;           # version
                }
                s%^lib/%%;
                s%/%::%g;
            }
        }
    }

    # Modification date header.  Try to use the modification time of our
    # input.
    if (!defined $$self{date}) {
        my $time = (stat $self->input_file)[9] || time;
        my ($day, $month, $year) = (localtime $time)[3,4,5];
        $month++;
        $year += 1900;
        $$self{date} = sprintf ('%4d-%02d-%02d', $year, $month, $day);
    }

    # Now, print out the preamble and the title.
    $PREAMBLE =~ s/\@CFONT\@/$$self{fixed}/;
    chomp $PREAMBLE;
    print { $self->output_handle } <<"----END OF HEADER----";
.\\" Automatically generated by Pod::Man version $VERSION
.\\" @{[ scalar localtime ]}
.\\"
.\\" Standard preamble:
.\\" ======================================================================
$PREAMBLE
.\\" ======================================================================
.\\"
.IX Title "$name $section"
.TH $name $section "$$self{release}" "$$self{date}" "$$self{center}"
.UC
----END OF HEADER----
#"# for cperl-mode

    # Initialize a few per-file variables.
    $$self{INDENT} = 0;
    $$self{NEEDSPACE} = 0;
}


############################################################################
# Core overrides
############################################################################

# Called for each command paragraph.  Gets the command, the associated
# paragraph, the line number, and a Pod::Paragraph object.  Just dispatches
# the command to a method named the same as the command.  =cut is handled
# internally by Pod::Parser.
sub command {
    my $self = shift;
    my $command = shift;
    return if $command eq 'pod';
    return if ($$self{EXCLUDE} && $command ne 'end');
    $command = 'cmd_' . $command;
    unless ($self -> can ($command)) {
        my $com = substr $command => 4;
        my ($file, $line) = $_ [2] -> file_line;
       (my $text = $_ [0]) =~ s/\n+\z//g;
        $text = " $text" if $text =~ /^\S/;
        warn qq {$file: Unknown command paragraph "=$com${text}"},
             qq { on line $line.\n};
        return;
    }
    else {
        $self->$command (@_);
    }
}

# Called for a verbatim paragraph.  Gets the paragraph, the line number, and
# a Pod::Paragraph object.  Rofficate backslashes, untabify, put a
# zero-width character at the beginning of each line to protect against
# commands, and wrap in .Vb/.Ve.
sub verbatim {
    my $self = shift;
    return if $$self{EXCLUDE};
    local $_ = shift;
    return if /^\s+$/;
    s/\s+$/\n/;
    my $lines = tr/\n/\n/;
    1 while s/^(.*?)(\t+)/$1 . ' ' x (length ($2) * 8 - length ($1) % 8)/me;
    s/\\/\\e/g;
    s/^(\s*\S)/'\&' . $1/gme;
    $self->makespace if $$self{NEEDSPACE};
    $self->output (".Vb $lines\n$_.Ve\n");
    $$self{NEEDSPACE} = 0;
}

# Called for a regular text block.  Gets the paragraph, the line number, and
# a Pod::Paragraph object.  Perform interpolation and output the results.
sub textblock {
    my $self = shift;
    return if $$self{EXCLUDE};
    $self->output ($_[0]), return if $$self{VERBATIM};

    # Perform a little magic to collapse multiple L<> references.  We'll
    # just rewrite the whole thing into actual text at this part, bypassing
    # the whole internal sequence parsing thing.
    my $text = shift;
    $text =~ s{
        (L<                     # A link of the form L</something>.
              /
              (
                  [:\w]+        # The item has to be a simple word...
                  (\(\))?       # ...or simple function.
              )
          >
          (
              ,?\s+(and\s+)?    # Allow lots of them, conjuncted.
              L<  
                  /
                  ( [:\w]+ ( \(\) )? )
              >
          )+
        )
    } {
        local $_ = $1;
        s{ L< / ( [^>]+ ) > } {$1}xg;
        my @items = split /(?:,?\s+(?:and\s+)?)/;
        my $string = 'the ';
        my $i;
        for ($i = 0; $i < @items; $i++) {
            $string .= $items[$i];
            $string .= ', ' if @items > 2 && $i != $#items;
            $string .= ' ' if @items == 2 && $i == 2;
            $string .= 'and ' if ($i == $#items - 1);
        }
        $string .= ' entries elsewhere in this document';
        $string;
    }gex;

    # Parse the tree and output it.  collapse knows about references to
    # scalars as well as scalars and does the right thing with them.
    $text = $self->parse ($text, @_);
    $text =~ s/\n\s*$/\n/;
    $self->makespace if $$self{NEEDSPACE};
    $self->output (protect $self->mapfonts ($text));
    $self->outindex;
    $$self{NEEDSPACE} = 1;
}

# Called for an interior sequence.  Takes a Pod::InteriorSequence object and
# returns a reference to a scalar.  This scalar is the final formatted text.
# It's returned as a reference so that other interior sequences above us
# know that the text has already been processed.
sub sequence {
    my ($self, $seq) = @_;
    my $command = $seq->cmd_name;

    # Zero-width characters.
    if ($command eq 'Z') {
        # Workaround to generate a blessable reference, needed by 5.005.
        my $tmp = '\&';
        return bless \ "$tmp", 'Pod::Man::String';
    }

    # C<>, L<>, X<>, and E<> don't apply guesswork to their contents.  C<>
    # needs some additional special handling.
    my $literal = ($command =~ /^[CELX]$/);
    $literal++ if $command eq 'C';
    local $_ = $self->collapse ($seq->parse_tree, $literal);

    # Handle E<> escapes.
    if ($command eq 'E') {
        if (/^\d+$/) {
            return bless \ chr ($_), 'Pod::Man::String';
        } elsif (exists $ESCAPES{$_}) {
            return bless \ "$ESCAPES{$_}", 'Pod::Man::String';
        } else {
            carp "Unknown escape E<$1>";
            return bless \ "E<$_>", 'Pod::Man::String';
        }
    }

    # For all the other sequences, empty content produces no output.
    return '' if $_ eq '';

    # Handle formatting sequences.
    if ($command eq 'B') {
        return bless \ ('\f(BS' . $_ . '\f(BE'), 'Pod::Man::String';
    } elsif ($command eq 'F') {
        return bless \ ('\f(IS' . $_ . '\f(IE'), 'Pod::Man::String';
    } elsif ($command eq 'I') {
        return bless \ ('\f(IS' . $_ . '\f(IE'), 'Pod::Man::String';
    } elsif ($command eq 'C') {
        return bless \ ('\f(FS\*(C`' . $_ . "\\*(C'\\f(FE"),
            'Pod::Man::String';
    }

    # Handle links.
    if ($command eq 'L') {
        # A bug in lvalue subs in 5.6 requires the temporary variable.
        my $tmp = $self->buildlink ($_);
        return bless \ "$tmp", 'Pod::Man::String';
    }
                         
    # Whitespace protection replaces whitespace with "\ ".
    if ($command eq 'S') {
        s/\s+/\\ /g;
        return bless \ "$_", 'Pod::Man::String';
    }

    # Add an index entry to the list of ones waiting to be output.
    if ($command eq 'X') { push (@{ $$self{INDEX} }, $_); return '' }

    # Anything else is unknown.
    carp "Unknown sequence $command<$_>";
}


############################################################################
# Command paragraphs
############################################################################

# All command paragraphs take the paragraph and the line number.

# First level heading.  We can't output .IX in the NAME section due to a bug
# in some versions of catman, so don't output a .IX for that section.  .SH
# already uses small caps, so remove any E<> sequences that would cause
# them.
sub cmd_head1 {
    my $self = shift;
    local $_ = $self->parse (@_);
    s/\s+$//;
    s/\\s-?\d//g;
    $self->output (switchquotes ('.SH', $self->mapfonts ($_)));
    $self->outindex (($_ eq 'NAME') ? () : ('Header', $_));
    $$self{NEEDSPACE} = 0;
}

# Second level heading.
sub cmd_head2 {
    my $self = shift;
    local $_ = $self->parse (@_);
    s/\s+$//;
    $self->output (switchquotes ('.Sh', $self->mapfonts ($_)));
    $self->outindex ('Subsection', $_);
    $$self{NEEDSPACE} = 0;
}

# Start a list.  For indents after the first, wrap the outside indent in .RS
# so that hanging paragraph tags will be correct.
sub cmd_over {
    my $self = shift;
    local $_ = shift;
    unless (/^[-+]?\d+\s+$/) { $_ = $$self{indent} }
    if (@{ $$self{INDENTS} } > 0) {
        $self->output (".RS $$self{INDENT}\n");
    }
    push (@{ $$self{INDENTS} }, $$self{INDENT});
    $$self{INDENT} = ($_ + 0);
}

# End a list.  If we've closed an embedded indent, we've mangled the hanging
# paragraph indent, so temporarily replace it with .RS and set WEIRDINDENT.
# We'll close that .RS at the next =back or =item.
sub cmd_back {
    my $self = shift;
    $$self{INDENT} = pop @{ $$self{INDENTS} };
    unless (defined $$self{INDENT}) {
        carp "Unmatched =back";
        $$self{INDENT} = 0;
    }
    if ($$self{WEIRDINDENT}) {
        $self->output (".RE\n");
        $$self{WEIRDINDENT} = 0;
    }
    if (@{ $$self{INDENTS} } > 0) {
        $self->output (".RE\n");
        $self->output (".RS $$self{INDENT}\n");
        $$self{WEIRDINDENT} = 1;
    }
    $$self{NEEDSPACE} = 1;
}

# An individual list item.  Emit an index entry for anything that's
# interesting, but don't emit index entries for things like bullets and
# numbers.  rofficate bullets too while we're at it (so for nice output, use
# * for your lists rather than o or . or - or some other thing).  Newlines
# in an item title are turned into spaces since *roff can't handle them
# embedded.
sub cmd_item {
    my $self = shift;
    local $_ = $self->parse (@_);
    s/\s+$//;
    s/\s*\n\s*/ /g;
    my $index;
    if (/\w/ && !/^\w[.\)]\s*$/) {
        $index = $_;
        $index =~ s/^\s*[-*+o.]?(?:\s+|\Z)//;
    }
    s/^\*(\s|\Z)/\\\(bu$1/;
    if ($$self{WEIRDINDENT}) {
        $self->output (".RE\n");
        $$self{WEIRDINDENT} = 0;
    }
    $_ = $self->mapfonts ($_);
    $self->output (switchquotes ('.Ip', $_, $$self{INDENT}));
    $self->outindex ($index ? ('Item', $index) : ());
    $$self{NEEDSPACE} = 0;
}

# Begin a block for a particular translator.  Setting VERBATIM triggers
# special handling in textblock().
sub cmd_begin {
    my $self = shift;
    local $_ = shift;
    my ($kind) = /^(\S+)/ or return;
    if ($kind eq 'man' || $kind eq 'roff') {
        $$self{VERBATIM} = 1;
    } else {
        $$self{EXCLUDE} = 1;
    }
}

# End a block for a particular translator.  We assume that all =begin/=end
# pairs are properly closed.
sub cmd_end {
    my $self = shift;
    $$self{EXCLUDE} = 0;
    $$self{VERBATIM} = 0;
}

# One paragraph for a particular translator.  Ignore it unless it's intended
# for man or roff, in which case we output it verbatim.
sub cmd_for {
    my $self = shift;
    local $_ = shift;
    return unless s/^(?:man|roff)\b[ \t]*\n?//;
    $self->output ($_);
}


############################################################################
# Link handling
############################################################################

# Handle links.  We can't actually make real hyperlinks, so this is all to
# figure out what text and formatting we print out.
sub buildlink {
    my $self = shift;
    local $_ = shift;

    # Smash whitespace in case we were split across multiple lines.
    s/\s+/ /g;

    # If we were given any explicit text, just output it.
    if (m{ ^ ([^|]+) \| }x) { return $1 }

    # Okay, leading and trailing whitespace isn't important.
    s/^\s+//;
    s/\s+$//;

    # Default to using the whole content of the link entry as a section
    # name.  Note that L<manpage/> forces a manpage interpretation, as does
    # something looking like L<manpage(section)>.  Do the same thing to
    # L<manpage(section)> as we would to manpage(section) without the L<>;
    # see guesswork().  If we've added italics, don't add the "manpage"
    # text; markup is sufficient.
    my ($manpage, $section) = ('', $_);
    if (/^"\s*(.*?)\s*"$/) {
        $section = '"' . $1 . '"';
    } elsif (m{ ^ [-:.\w]+ (?: \( \S+ \) )? $ }x) {
        ($manpage, $section) = ($_, '');
        $manpage =~ s/^([^\(]+)\(/'\f(IS' . $1 . '\f(IE\|('/e;
    } elsif (m%/%) {
        ($manpage, $section) = split (/\s*\/\s*/, $_, 2);
        if ($manpage =~ /^[-:.\w]+(?:\(\S+\))?$/) {
            $manpage =~ s/^([^\(]+)\(/'\f(IS' . $1 . '\f(IE\|'/e;
        }
        $section =~ s/^\"\s*//;
        $section =~ s/\s*\"$//;
    }
    if ($manpage && $manpage !~ /\\f\(IS/) {
        $manpage = "the $manpage manpage";
    }

    # Now build the actual output text.
    my $text = '';
    if (!length ($section) && !length ($manpage)) {
        carp "Invalid link $_";
    } elsif (!length ($section)) {
        $text = $manpage;
    } elsif ($section =~ /^[:\w]+(?:\(\))?/) {
        $text .= 'the ' . $section . ' entry';
        $text .= (length $manpage) ? " in $manpage"
                                   : " elsewhere in this document";
    } else {
        if ($section !~ /^".*"$/) { $section = '"' . $section . '"' }
        $text .= 'the section on ' . $section;
        $text .= " in $manpage" if length $manpage;
    }
    $text;
}


############################################################################
# Escaping and fontification
############################################################################

# At this point, we'll have embedded font codes of the form \f(<font>[SE]
# where <font> is one of B, I, or F.  Turn those into the right font start
# or end codes.  B<someI<thing> else> should map to \fBsome\f(BIthing\fB
# else\fR.  The old pod2man didn't get this right; the second \fB was \fR,
# so nested sequences didn't work right.  We take care of this by using
# variables as a combined pointer to our current font sequence, and set each
# to the number of current nestings of start tags for that font.  Use them
# as a vector to look up what font sequence to use.
sub mapfonts {
    my $self = shift;
    local $_ = shift;

    my ($fixed, $bold, $italic) = (0, 0, 0);
    my %magic = (F => \$fixed, B => \$bold, I => \$italic);
    s { \\f\((.)(.) } {
        ${ $magic{$1} } += ($2 eq 'S') ? 1 : -1;
        $$self{FONTS}{($fixed && 1) . ($bold && 1) . ($italic && 1)};
    }gxe;
    $_;
}


############################################################################
# *roff-specific parsing
############################################################################

# Called instead of parse_text, calls parse_text with the right flags.
sub parse {
    my $self = shift;
    $self->parse_text ({ -expand_seq   => 'sequence',
                         -expand_ptree => 'collapse' }, @_);
}
    
# Takes a parse tree and a flag saying whether or not to treat it as literal
# text (not call guesswork on it), and returns the concatenation of all of
# the text strings in that parse tree.  If the literal flag isn't true,
# guesswork() will be called on all plain scalars in the parse tree.
# Otherwise, just escape backslashes in the normal case.  If collapse is
# being called on a C<> sequence, literal is set to 2, and we do some
# additional cleanup.  Assumes that everything in the parse tree is either a
# scalar or a reference to a scalar.
sub collapse {
    my ($self, $ptree, $literal) = @_;
    if ($literal) {
        return join ('', map {
            if (ref $_) {
                $$_;
            } else {
                s/\\/\\e/g;
                s/-/\\-/g    if $literal > 1;
                s/__/_\\|_/g if $literal > 1;
                $_;
            }
        } $ptree->children);
    } else {
        return join ('', map {
            ref ($_) ? $$_ : $self->guesswork ($_)
        } $ptree->children);
    }
}

# Takes a text block to perform guesswork on; this is guaranteed not to
# contain any interior sequences.  Returns the text block with remapping
# done.
sub guesswork {
    my $self = shift;
    local $_ = shift;

    # rofficate backslashes.
    s/\\/\\e/g;

    # Ensure double underbars have a tiny space between them.
    s/__/_\\|_/g;

    # Make all caps a little smaller.  Be careful here, since we don't want
    # to make @ARGV into small caps, nor do we want to fix the MIME in
    # MIME-Version, since it looks weird with the full-height V.
    s{
        ( ^ | [\s\(\"\'\`\[\{<>] )
        ( [A-Z] [A-Z] [/A-Z+:\d_\$&-]* )
        (?: (?= [\s>\}\]\)\'\".?!,;:] | -- ) | $ )
    } { $1 . '\s-1' . $2 . '\s0' }egx;

    # Turn PI into a pretty pi.
    s{ (?: \\s-1 | \b ) PI (?: \\s0 | \b ) } {\\*\(PI}gx;

    # Italize functions in the form func().
    s{
        \b
        (
            [:\w]+ (?:\\s-1)? \(\)
        )
    } { '\f(IS' . $1 . '\f(IE' }egx;

    # func(n) is a reference to a manual page.  Make it \fIfunc\fR\|(n).
    s{
        \b
        (\w[-:.\w]+ (?:\\s-1)?)
        (
            \( [^\)] \)
        )
    } { '\f(IS' . $1 . '\f(IE\|' . $2 }egx;

    # Convert simple Perl variable references to a fixed-width font.
    s{
        ( \s+ )
        ( [\$\@%] [\w:]+ )
        (?! \( )
    } { $1 . '\f(FS' . $2 . '\f(FE'}egx;

    # Translate -- into a real em dash if it's used like one and fix up
    # dashes, but keep hyphens hyphens.
    s{ (\G|^|.) (-+) (\b|.) } {
        my ($pre, $dash, $post) = ($1, $2, $3);
        if (length ($dash) == 1) {
            ($pre =~ /[a-zA-Z]/) ? "$pre-$post" : "$pre\\-$post";
        } elsif (length ($dash) == 2
                 && ((!$pre && !$post)
                     || ($pre =~ /\w/ && !$post)
                     || ($pre eq ' ' && $post eq ' ')
                     || ($pre eq '=' && $post ne '=')
                     || ($pre ne '=' && $post eq '='))) {
            "$pre\\*(--$post";
        } else {
            $pre . ('\-' x length $dash) . $post;
        }
    }egxs;

    # Fix up double quotes.
    s{ \" ([^\"]+) \" } { '\*(L"' . $1 . '\*(R"' }egx;

    # Make C++ into \*(C+, which is a squinched version.
    s{ \b C\+\+ } {\\*\(C+}gx;

    # All done.
    $_;
}


############################################################################
# Output formatting
############################################################################

# Make vertical whitespace.
sub makespace {
    my $self = shift;
    $self->output ($$self{INDENT} > 0 ? ".Sp\n" : ".PP\n");
}

# Output any pending index entries, and optionally an index entry given as
# an argument.  Support multiple index entries in X<> separated by slashes,
# and strip special escapes from index entries.
sub outindex {
    my ($self, $section, $index) = @_;
    my @entries = map { split m%\s*/\s*% } @{ $$self{INDEX} };
    return unless ($section || @entries);
    $$self{INDEX} = [];
    my $output;
    if (@entries) {
        my $output = '.IX Xref "'
            . join (' ', map { s/\"/\"\"/; $_ } @entries)
            . '"' . "\n";
    }
    if ($section) {
        $index =~ s/\"/\"\"/;
        $index =~ s/\\-/-/g;
        $index =~ s/\\(?:s-?\d|.\(..|.)//g;
        $output .= ".IX $section " . '"' . $index . '"' . "\n";
    }
    $self->output ($output);
}

# Output text to the output device.
sub output { print { $_[0]->output_handle } $_[1] }

__END__

.\" These are some extra bits of roff that I don't want to lose track of
.\" but that have been removed from the preamble to make it a bit shorter
.\" since they're not currently being used.  They're accents and special
.\" characters we don't currently have escapes for.
.if n \{\
.    ds ? ?
.    ds ! !
.    ds q
.\}
.if t \{\
.    ds ? \s-2c\h'-\w'c'u*7/10'\u\h'\*(#H'\zi\d\s+2\h'\w'c'u*8/10'
.    ds ! \s-2\(or\s+2\h'-\w'\(or'u'\v'-.8m'.\v'.8m'
.    ds q o\h'-\w'o'u*8/10'\s-4\v'.4m'\z\(*i\v'-.4m'\s+4\h'\w'o'u*8/10'
.\}
.ds v \\k:\h'-(\\n(.wu*9/10-\*(#H)'\v'-\*(#V'\*(#[\s-4v\s0\v'\*(#V'\h'|\\n:u'\*(#]
.ds _ \\k:\h'-(\\n(.wu*9/10-\*(#H+(\*(#F*2/3))'\v'-.4m'\z\(hy\v'.4m'\h'|\\n:u'
.ds . \\k:\h'-(\\n(.wu*8/10)'\v'\*(#V*4/10'\z.\v'-\*(#V*4/10'\h'|\\n:u'
.ds 3 \*(#[\v'.2m'\s-2\&3\s0\v'-.2m'\*(#]
.ds oe o\h'-(\w'o'u*4/10)'e
.ds Oe O\h'-(\w'O'u*4/10)'E
.if \n(.H>23 .if \n(.V>19 \
\{\
.    ds v \h'-1'\o'\(aa\(ga'
.    ds _ \h'-1'^
.    ds . \h'-1'.
.    ds 3 3
.    ds oe oe
.    ds Oe OE
.\}

############################################################################
# Documentation
############################################################################

=head1 NAME

Pod::Man - Convert POD data to formatted *roff input

=head1 SYNOPSIS

    use Pod::Man;
    my $parser = Pod::Man->new (release => $VERSION, section => 8);

    # Read POD from STDIN and write to STDOUT.
    $parser->parse_from_filehandle;

    # Read POD from file.pod and write to file.1.
    $parser->parse_from_file ('file.pod', 'file.1');

=head1 DESCRIPTION

Pod::Man is a module to convert documentation in the POD format (the
preferred language for documenting Perl) into *roff input using the man
macro set.  The resulting *roff code is suitable for display on a terminal
using nroff(1), normally via man(1), or printing using troff(1).  It is
conventionally invoked using the driver script B<pod2man>, but it can also
be used directly.

As a derived class from Pod::Parser, Pod::Man supports the same methods and
interfaces.  See L<Pod::Parser> for all the details; briefly, one creates a
new parser with C<Pod::Man-E<gt>new()> and then calls either
parse_from_filehandle() or parse_from_file().

new() can take options, in the form of key/value pairs that control the
behavior of the parser.  See below for details.

If no options are given, Pod::Man uses the name of the input file with any
trailing C<.pod>, C<.pm>, or C<.pl> stripped as the man page title, to
section 1 unless the file ended in C<.pm> in which case it defaults to
section 3, to a centered title of "User Contributed Perl Documentation", to
a centered footer of the Perl version it is run with, and to a left-hand
footer of the modification date of its input (or the current date if given
STDIN for input).

Pod::Man assumes that your *roff formatters have a fixed-width font named
CW.  If yours is called something else (like CR), use the C<fixed> option to
specify it.  This generally only matters for troff output for printing.
Similarly, you can set the fonts used for bold, italic, and bold italic
fixed-width output.

Besides the obvious pod conversions, Pod::Man also takes care of formatting
func(), func(n), and simple variable references like $foo or @bar so you
don't have to use code escapes for them; complex expressions like
C<$fred{'stuff'}> will still need to be escaped, though.  It also translates
dashes that aren't used as hyphens into en dashes, makes long dashes--like
this--into proper em dashes, fixes "paired quotes," makes C++ and PI look
right, puts a little space between double underbars, makes ALLCAPS a teeny
bit smaller in troff(1), and escapes stuff that *roff treats as special so
that you don't have to.

The recognized options to new() are as follows.  All options take a single
argument.

=over 4

=item center

Sets the centered page header to use instead of "User Contributed Perl
Documentation".

=item date

Sets the left-hand footer.  By default, the modification date of the input
file will be used, or the current date if stat() can't find that file (the
case if the input is from STDIN), and the date will be formatted as
YYYY-MM-DD.

=item fixed

The fixed-width font to use for vertabim text and code.  Defaults to CW.
Some systems may want CR instead.  Only matters for troff(1) output.

=item fixedbold

Bold version of the fixed-width font.  Defaults to CB.  Only matters for
troff(1) output.

=item fixeditalic

Italic version of the fixed-width font (actually, something of a misnomer,
since most fixed-width fonts only have an oblique version, not an italic
version).  Defaults to CI.  Only matters for troff(1) output.

=item fixedbolditalic

Bold italic (probably actually oblique) version of the fixed-width font.
Pod::Man doesn't assume you have this, and defaults to CB.  Some systems
(such as Solaris) have this font available as CX.  Only matters for troff(1)
output.

=item release

Set the centered footer.  By default, this is the version of Perl you run
Pod::Man under.  Note that some system an macro sets assume that the
centered footer will be a modification date and will prepend something like
"Last modified: "; if this is the case, you may want to set C<release> to
the last modified date and C<date> to the version number.

=item section

Set the section for the C<.TH> macro.  The standard section numbering
convention is to use 1 for user commands, 2 for system calls, 3 for
functions, 4 for devices, 5 for file formats, 6 for games, 7 for
miscellaneous information, and 8 for administrator commands.  There is a lot
of variation here, however; some systems (like Solaris) use 4 for file
formats, 5 for miscellaneous information, and 7 for devices.  Still others
use 1m instead of 8, or some mix of both.  About the only section numbers
that are reliably consistent are 1, 2, and 3.

By default, section 1 will be used unless the file ends in .pm in which case
section 3 will be selected.

=back

The standard Pod::Parser method parse_from_filehandle() takes up to two
arguments, the first being the file handle to read POD from and the second
being the file handle to write the formatted output to.  The first defaults
to STDIN if not given, and the second defaults to STDOUT.  The method
parse_from_file() is almost identical, except that its two arguments are the
input and output disk files instead.  See L<Pod::Parser> for the specific
details.

=head1 DIAGNOSTICS

=over 4

=item roff font should be 1 or 2 chars, not `%s'

(F) You specified a *roff font (using C<fixed>, C<fixedbold>, etc.) that
wasn't either one or two characters.  Pod::Man doesn't support *roff fonts
longer than two characters, although some *roff extensions do (the canonical
versions of nroff(1) and troff(1) don't either).

=item Invalid link %s

(W) The POD source contained a C<LE<lt>E<gt>> sequence that Pod::Man was
unable to parse.  You should never see this error message; it probably
indicates a bug in Pod::Man.

=item Unknown escape EE<lt>%sE<gt>

(W) The POD source contained an C<EE<lt>E<gt>> escape that Pod::Man didn't
know about.  C<EE<lt>%sE<gt>> was printed verbatim in the output.

=item Unknown sequence %s

(W) The POD source contained a non-standard interior sequence (something of
the form C<XE<lt>E<gt>>) that Pod::Man didn't know about.  It was ignored.

=item %s: Unknown command paragraph "%s" on line %d.

(W) The POD source contained a non-standard command paragraph (something of
the form C<=command args>) that Pod::Man didn't know about. It was ignored.

=item Unmatched =back

(W) Pod::Man encountered a C<=back> command that didn't correspond to an
C<=over> command.

=back

=head1 BUGS

The lint-like features and strict POD format checking done by B<pod2man> are
not yet implemented and should be, along with the corresponding C<lax>
option.

The NAME section should be recognized specially and index entries emitted
for everything in that section.  This would have to be deferred until the
next section, since extraneous things in NAME tends to confuse various man
page processors.

The handling of hyphens, en dashes, and em dashes is somewhat fragile, and
one may get the wrong one under some circumstances.  This should only matter
for troff(1) output.

When and whether to use small caps is somewhat tricky, and Pod::Man doesn't
necessarily get it right.

Pod::Man doesn't handle font names longer than two characters.  Neither do
most troff(1) implementations, but GNU troff does as an extension.  It would
be nice to support as an option for those who want to use it.

The preamble added to each output file is rather verbose, and most of it is
only necessary in the presence of EE<lt>E<gt> escapes for non-ASCII
characters.  It would ideally be nice if all of those definitions were only
output if needed, perhaps on the fly as the characters are used.

Some of the automagic applied to file names assumes Unix directory
separators.

Pod::Man is excessively slow.

=head1 SEE ALSO

L<Pod::Parser|Pod::Parser>, perlpod(1), pod2man(1), nroff(1), troff(1),
man(1), man(7)

Ossanna, Joseph F., and Brian W. Kernighan.  "Troff User's Manual,"
Computing Science Technical Report No. 54, AT&T Bell Laboratories.  This is
the best documentation of standard nroff(1) and troff(1).  At the time of
this writing, it's available at http://www.cs.bell-labs.com/cm/cs/cstr.html.

The man page documenting the man macro set may be man(5) instead of man(7)
on your system.  Also, please see pod2man(1) for extensive documentation on
writing manual pages if you've not done it before and aren't familiar with
the conventions.

=head1 AUTHOR

Russ Allbery E<lt>rra@stanford.eduE<gt>, based I<very> heavily on the
original B<pod2man> by Tom Christiansen E<lt>tchrist@mox.perl.comE<gt>.

=cut