歌代 和正 (Kaz Utashiro)
and 2 contributors

NAME

Text::ANSI::Fold - Text folding library supporting ANSI terminal sequence and Asian wide characters with prohibition character handling.

SYNOPSIS

    use Text::ANSI::Fold qw(ansi_fold);
    ($folded, $remain) = ansi_fold($text, $width, [ option ]);

    use Text::ANSI::Fold;
    my $f = new Text::ANSI::Fold width => 80, boundary => 'word';
    $f->configure(ambiguous => 'wide');
    ($folded, $remain) = $f->fold($text);

    use Text::ANSI::Fold;
    while (<>) {
        print join "\n",
            Text::ANSI::Fold->new(width => 40, text => $_)->chops;
    }

    use Text::ANSI::Fold qw(:constants);
    my $fold = new Text::ANSI::Fold
        width     => 70,
        boundary  => 'word',
        linebreak => LINEBREAK_ALL,
        runin     => 4,
        runout    => 4,
        ;

DESCRIPTION

Text::ANSI::Fold provides capability to fold a text into two strings by given width. Text can include ANSI terminal sequences. If the text is divided in the middle of ANSI-effect region, reset sequence is appended to folded text, and recover sequence is prepended to trimmed string.

This module also support Unicode Asian full-width and non-spacing combining characters properly. Japanese text formatting with head-or-end of line prohibition character is also supported. Set the linebreak mode to enable it.

Use exported ansi_fold function to fold original text, with number of visual columns you want to cut off the text. Width parameter have to be a number greater than zero.

    ($folded, $remain, $w) = ansi_fold($text, $width);

It returns a pair of strings; first one is folded text, and second is the rest.

Additional third result is the visual width of folded text. You may want to know how many columns returned string takes for further processing.

This function returns at least one character in any situation. If you provide Asian wide string and just one column as width, it trims off the first wide character even if it does not fit to given width.

Default parameter can be set by configure class method:

    Text::ANSI::Fold->configure(width => 80, padding => 1);

Then you don't have to pass second argument.

    ($folded, $remain) = ansi_fold($text);

Because second argument is always taken as width, use undef when using default width with additional parameter:

    ($folded, $remain) = ansi_fold($text, undef, padding => 1);

OBJECT INTERFACE

You can create an object to hold parameters, which is effective during object life time. For example,

    my $f = new Text::ANSI::Fold
        width => 80,
        boundary => 'word';

makes an object folding on word boundaries with 80 columns width. Then you can use this without parameters.

    $f->fold($text);

Use configure method to update parameters:

    $f->configure(padding => 1);

Additional parameter can be specified on each call, and they precede saved value.

    $f->fold($text, width => 40);

STRING OBJECT INTERFACE

Fold object can hold string inside by text method.

    $f->text("text");

And folded string can be taken by retrieve method. It returns empty string if nothing remained.

    while ((my $folded = $f->retrieve) ne '') {
        print $folded;
        print "\n" if $folded !~ /\n\z/;
    }

Method chops returns chopped string list. Because text method returns the object itself, you can use text and chops like this:

    print join "\n", $f->text($text)->chops;

Actually, text can be set by new or configure method through text option. Next program just works.

    use Text::ANSI::Fold;
    while (<>) {
        print join "\n",
            Text::ANSI::Fold->new(width => 40, text => $_)->chops;
    }

When using chops method, width parameter can take array reference, and chops text into given width list.

    my $fold = new Text::ANSI::Fold;
    my @list = $fold->text("1223334444")->chops(width => [ 1, 2, 3 ]);
    # return ("1", "22", "333") and keep "4444"

OPTIONS

Option parameter can be specified as name-value list for ansi_fold function as well as new and configure method.

    ansi_fold($text, $width, boundary => 'word', ...);

    Text::ANSI::Fold->configure(boundary => 'word');

    my $f = new Text::ANSI::Fold boundary => 'word';

    $f->configure(boundary => 'word');
width => n, [ n, m, ... ]

Specify folding width. Array reference can be specified but works only with chops method.

boundary => "word"

boundary option currently takes only "word" as a valid value. In this case, text is folded on word boundary. This occurs only when enough space will be provided to hold the word on next call with same width.

padding => bool

If padding option is given with true value, margin space is filled up with space character. Next code fills spaces if the given text is shorter than 80.

    ansi_fold($text, 80, padding => 1);
padchar => char

padchar option specifies character used to fill up the remainder of given width.

    ansi_fold($text, 80, padding => 1, padchar => '_');
ambiguous => "narrow" or "wide"

Tells how to treat Unicode East Asian ambiguous characters. Default is "narrow" which means single column. Set "wide" to tell the module to treat them as wide character.

linebreak => mode
runin => width
runout => width

These options specify the behavior of line break handling for Asian multi byte characters. Only Japanese is supported currently.

If the cut-off text start with space or prohibited characters (e.g. closing parenthesis), they are ran-in at the end of current line as much as possible.

If the trimmed text end with prohibited characters (e.g. opening parenthesis), they are ran-out to the head of next line, if it fits to maximum width.

Default linebreak mode is LINEBREAK_NONE and can be set one of those:

    LINEBREAK_NONE
    LINEBREAK_RUNIN
    LINEBREAK_RUNOUT
    LINEBREAK_ALL

Import-tag :constants can be used to access these constants.

Option runin and runout is used to set maximum width of moving characters. Default values are both 2.

EXAMPLE

Next code implements almost perfect fold command for multi byte characters with prohibited character handling.

    #!/usr/bin/env perl
    
    use strict;
    use warnings;
    use open IO => 'utf8', ':std';
    
    use Text::ANSI::Fold qw(:constants);
    my $fold = new Text::ANSI::Fold
        width     => 70,
        boundary  => 'word',
        linebreak => LINEBREAK_ALL,
        runin     => 4,
        runout    => 4,
        ;
    
    $, = "\n";
    while (<>) {
        print $fold->text($_)->chops;
    }

SEE ALSO

App::ansifold

Command line utility using Text::ANSI::Fold.

App::sdif

Text::ANSI::Fold was originally implemented in sdif command for long time, which provide side-by-side view for diff output. It is necessary to process output from cdif command which highlight diff output using ANSI escape sequences.

Text::ANSI::Util, Text::ANSI::WideUtil

These modules provide a rich set of functions to handle string contains ANSI color terminal sequences. In contrast, Text::ANSI::Fold provides simple folding mechanism with minimum overhead. Also sdif need to process other than SGR (Select Graphic Rendition) color sequence, and non-spacing combining characters, those are not supported by these modules.

https://en.wikipedia.org/wiki/ANSI_escape_code

ANSI escape code definition.

https://www.w3.org/TR/2012/NOTE-jlreq-20120403/

Requirements for Japanese Text Layout, W3C Working Group Note 3 April 2012

LICENSE

Copyright (C) 2018- Kazumasa Utashiro.

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

AUTHOR

Kazumasa Utashiro
https://github.com/kaz-utashiro/Text-ANSI-Fold