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Filename : Termcap.pm
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# Convert POD data to ASCII text with format escapes.
#
# This is a simple subclass of Pod::Text that overrides a few key methods to
# output the right termcap escape sequences for formatted text on the current
# terminal type.
#
# SPDX-License-Identifier: GPL-1.0-or-later OR Artistic-1.0-Perl

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

package Pod::Text::Termcap;

use 5.006;
use strict;
use warnings;

use Pod::Text ();
use POSIX ();
use Term::Cap;

use vars qw(@ISA $VERSION);

@ISA = qw(Pod::Text);

$VERSION = '4.11';

##############################################################################
# Overrides
##############################################################################

# In the initialization method, grab our terminal characteristics as well as
# do all the stuff we normally do.
sub new {
    my ($self, %args) = @_;
    my ($ospeed, $term, $termios);

    # $ENV{HOME} is usually not set on Windows.  The default Term::Cap path
    # may not work on Solaris.
    unless (exists $ENV{TERMPATH}) {
        my $home = exists $ENV{HOME} ? "$ENV{HOME}/.termcap:" : '';
        $ENV{TERMPATH} =
          "${home}/etc/termcap:/usr/share/misc/termcap:/usr/share/lib/termcap";
    }

    # Fall back on a hard-coded terminal speed if POSIX::Termios isn't
    # available (such as on VMS).
    eval { $termios = POSIX::Termios->new };
    if ($@) {
        $ospeed = 9600;
    } else {
        $termios->getattr;
        $ospeed = $termios->getospeed || 9600;
    }

    # Get data from Term::Cap if possible.
    my ($bold, $undl, $norm, $width);
    eval {
        my $term = Tgetent Term::Cap { TERM => undef, OSPEED => $ospeed };
        $bold = $term->Tputs('md');
        $undl = $term->Tputs('us');
        $norm = $term->Tputs('me');
        if (defined $$term{_co}) {
            $width = $$term{_co};
            $width =~ s/^\#//;
        }
    };

    # Figure out the terminal width before calling the Pod::Text constructor,
    # since it will otherwise force 76 characters.  Pod::Text::Termcap has
    # historically used 2 characters less than the width of the screen, while
    # the other Pod::Text classes have used 76.  This is weirdly inconsistent,
    # but there's probably no good reason to change it now.
    unless (defined $args{width}) {
        $args{width} = $ENV{COLUMNS} || $width || 80;
        $args{width} -= 2;
    }

    # Initialize Pod::Text.
    $self = $self->SUPER::new (%args);

    # Fall back on the ANSI escape sequences if Term::Cap doesn't work.
    $$self{BOLD} = $bold || "\e[1m";
    $$self{UNDL} = $undl || "\e[4m";
    $$self{NORM} = $norm || "\e[m";

    return $self;
}

# Make level one headings bold.
sub cmd_head1 {
    my ($self, $attrs, $text) = @_;
    $text =~ s/\s+$//;
    $self->SUPER::cmd_head1 ($attrs, "$$self{BOLD}$text$$self{NORM}");
}

# Make level two headings bold.
sub cmd_head2 {
    my ($self, $attrs, $text) = @_;
    $text =~ s/\s+$//;
    $self->SUPER::cmd_head2 ($attrs, "$$self{BOLD}$text$$self{NORM}");
}

# Fix up B<> and I<>.  Note that we intentionally don't do F<>.
sub cmd_b { my $self = shift; return "$$self{BOLD}$_[1]$$self{NORM}" }
sub cmd_i { my $self = shift; return "$$self{UNDL}$_[1]$$self{NORM}" }

# Analyze a single line and return any formatting codes in effect at the end
# of that line.
sub end_format {
    my ($self, $line) = @_;
    my $pattern = "(\Q$$self{BOLD}\E|\Q$$self{UNDL}\E|\Q$$self{NORM}\E)";
    my $current;
    while ($line =~ /$pattern/g) {
        my $code = $1;
        if ($code eq $$self{NORM}) {
            undef $current;
        } else {
            $current .= $code;
        }
    }
    return $current;
}

# Output any included code in bold.
sub output_code {
    my ($self, $code) = @_;
    $self->output ($$self{BOLD} . $code . $$self{NORM});
}

# Strip all of the formatting from a provided string, returning the stripped
# version.
sub strip_format {
    my ($self, $text) = @_;
    $text =~ s/\Q$$self{BOLD}//g;
    $text =~ s/\Q$$self{UNDL}//g;
    $text =~ s/\Q$$self{NORM}//g;
    return $text;
}

# Override the wrapping code to ignore the special sequences.
sub wrap {
    my $self = shift;
    local $_ = shift;
    my $output = '';
    my $spaces = ' ' x $$self{MARGIN};
    my $width = $$self{opt_width} - $$self{MARGIN};

    # $code matches a single special sequence.  $char matches any number of
    # special sequences preceding a single character other than a newline.
    # $shortchar matches some sequence of $char ending in codes followed by
    # whitespace or the end of the string.  $longchar matches exactly $width
    # $chars, used when we have to truncate and hard wrap.
    #
    # $shortchar and $longchar are created in a slightly odd way because the
    # construct ${char}{0,$width} didn't do the right thing until Perl 5.8.x.
    my $code = "(?:\Q$$self{BOLD}\E|\Q$$self{UNDL}\E|\Q$$self{NORM}\E)";
    my $char = "(?>$code*[^\\n])";
    my $shortchar = '^(' . $char . "{0,$width}(?>$code*)" . ')(?:\s+|\z)';
    my $longchar = '^(' . $char . "{$width})";
    while (length > $width) {
        if (s/$shortchar// || s/$longchar//) {
            $output .= $spaces . $1 . "\n";
        } else {
            last;
        }
    }
    $output .= $spaces . $_;

    # less -R always resets terminal attributes at the end of each line, so we
    # need to clear attributes at the end of lines and then set them again at
    # the start of the next line.  This requires a second pass through the
    # wrapped string, accumulating any attributes we see, remembering them,
    # and then inserting the appropriate sequences at the newline.
    if ($output =~ /\n/) {
        my @lines = split (/\n/, $output);
        my $start_format;
        for my $line (@lines) {
            if ($start_format && $line =~ /\S/) {
                $line =~ s/^(\s*)(\S)/$1$start_format$2/;
            }
            $start_format = $self->end_format ($line);
            if ($start_format) {
                $line .= $$self{NORM};
            }
        }
        $output = join ("\n", @lines);
    }

    # Fix up trailing whitespace and return the results.
    $output =~ s/\s+$/\n\n/;
    return $output;
}

##############################################################################
# Module return value and documentation
##############################################################################

1;
__END__

=head1 NAME

Pod::Text::Termcap - Convert POD data to ASCII text with format escapes

=for stopwords
ECMA-48 VT100 Allbery Solaris TERMPATH

=head1 SYNOPSIS

    use Pod::Text::Termcap;
    my $parser = Pod::Text::Termcap->new (sentence => 0, width => 78);

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

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

=head1 DESCRIPTION

Pod::Text::Termcap is a simple subclass of Pod::Text that highlights output
text using the correct termcap escape sequences for the current terminal.
Apart from the format codes, it in all ways functions like Pod::Text.  See
L<Pod::Text> for details and available options.

=head1 ENVIRONMENT

This module sets the TERMPATH environment variable globally to:

    $HOME/.termcap:/etc/termcap:/usr/share/misc/termcap:/usr/share/lib/termcap

if it isn't already set.  (The first entry is omitted if the HOME
environment variable isn't set.)  This is a (very old) workaround for
problems finding termcap information on older versions of Solaris, and is
not good module behavior.  Please do not rely on this behavior; it may be
dropped in a future release.

=head1 NOTES

This module uses Term::Cap to retrieve the formatting escape sequences for
the current terminal, and falls back on the ECMA-48 (the same in this
regard as ANSI X3.64 and ISO 6429, the escape codes also used by DEC VT100
terminals) if the bold, underline, and reset codes aren't set in the
termcap information.

=head1 AUTHOR

Russ Allbery <rra@cpan.org>.

=head1 COPYRIGHT AND LICENSE

Copyright 1999, 2001-2002, 2004, 2006, 2008-2009, 2014-2015, 2018 Russ Allbery
<rra@cpan.org>

This program is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.

=head1 SEE ALSO

L<Pod::Text>, L<Pod::Simple>, L<Term::Cap>

The current version of this module is always available from its web site at
L<https://www.eyrie.org/~eagle/software/podlators/>.  It is also part of the
Perl core distribution as of 5.6.0.

=cut

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