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# NAME

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

# VERSION

Version 2.25

# SYNOPSIS

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

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

# DESCRIPTION

[Text::ANSI::Fold](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AFold) provides capability to divide a text into two
parts by given width.  Text can include ANSI terminal sequences and
the width is calculated by its visible representation.  If the text is
divided in the middle of colored region, reset sequence is appended to
the former text, and color recover sequence is inserted before the
latter 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.

Since the overhead of ANSI escape sequence handling is not significant
when the data does not include them, this module can be used for
normal text processing with small penalty.

## **ansi\_fold**

Use exported **ansi\_fold** function to fold original text, with number
of visual columns you want to cut off the text.

    ($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 visual width of the folded text.  It is not
always same as given width, and you may want to know how many columns
returned string takes for further processing.

Negative width value is taken as unlimited.  So the string is never
folded, but you can use this to expand tabs and to get visual string
width.

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.

## **configure**

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);

Some other easy-to-use interfaces are provided by sister module
[Text::ANSI::Fold::Util](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AFold%3A%3AUtil).

# OBJECT INTERFACE

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

## **new**

Use `new` method to make a fold object.

    my $obj = Text::ANSI::Fold->new(
        width => 80,
        boundary => 'word',
    );

This makes an object folding on word boundaries with 80 columns width.

## **fold**

Then you can call `fold` method without parameters because the object
keeps necessary information.

    $obj->fold($text);

## **configure**

Use **configure** method to update parameters:

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

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

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

# STRING OBJECT INTERFACE

You can use a fold object to hold string inside, and take out folded
strings from it.  Use `text` method to store data in the object, and
`retrieve` or `chops` method to take out folded string from it.

## **text**

A fold object can hold string inside by **text** method.

    $obj->text("text");

Method **text** has an lvalue attribute, so it can be assigned to, as
well as can be a subject of mutating operator such as `s///`.

    $obj->text = "text";

## **retrieve**

Folded string can be taken out by `retrieve` method.  It returns
empty string if nothing remained.

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

## **chops**

Method `chops` returns chopped string list.  Because the `text`
method returns the object itself when called with a parameter, you can
use `text` and `chops` in series:

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

Actually, text can be set by c&lt;new> or `configure` method through
`text` parameter.  Next program just works.

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

## **chops** with multiple width

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

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

If the width value is 0, it returns empty string.  Negative width
value takes all the rest of stored string.  In the following code, the
fourth width (3) is ignored because the -2 immediately preceding it
consumes all remaining strings.

    my $fold = Text::ANSI::Fold->new;
    my @list = $fold->text("1223334444")->chops(width => [ 1, 0, -2, 3 ]);
    # return ("1", "", "223334444")

# 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 $obj = Text::ANSI::Fold->new(boundary => 'word');

    $obj->configure(boundary => 'word');

- **width** => _n_ | _\[ n, m, ... \]_

    Specify folding width by integer.  Negative value means all the rest.

    Array reference can be specified but works only with **chops** method,
    and retunrs empty string for zero width.

- **boundary** => `word` | `space`

    Option **boundary** takes `word` and `space` as a valid value.  These
    prohibit to fold a line in the middle of ASCII/Latin sequence.  Value
    `word` means a sequence of alpha-numeric characters, and `space`
    means simply non-space printables.

    This operation takes place only when enough space will be provided to
    hold the word on next call with same width.

    If the color of text is altered within a word, that position is also
    taken as an boundary.

- **padding** => _bool_

    If **padding** option is given with true value, margin space is filled
    up with space character.  Default is 0.  Next code fills spaces if the
    given text is shorter than 80.

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

    If an ANSI **Erase Line** sequence is found in the string, color status
    at the position is remembered, and padding string is produced in that
    color.

- **padchar** => _char_

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

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

- **prefix** => _string_ | _coderef_

    **prefix** string is inserted before remained string if it is not
    empty.  This is convenient to produce indented series of text by
    **chops** interface.

    If the value is reference to subroutine, its result is used as a
    prefix string.

    The **fold** function does not complain if the result of adding a
    prefix string is longer than the original text.  The caller must be
    very careful because of the possibility of an infinite loop.

- **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.

- **discard** => \[ `EL`, `OSC` \]

    Specify the list reference of control sequence name to be discarded.
    **EL** means Erase Line; **OSC** means Operating System Command, defined
    in ECMA-48.  Erase Line right after RESET sequence is always kept.

- **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.

- **expand** => _bool_
- **tabstop** => _n_
- **tabhead** => _char_
- **tabspace** => _char_

    Enable tab character expansion.

    Default tabstop is 8 and can be set by **tabstop** option.

    Tab character is converted to **tabhead** and following **tabspace**
    characters.  Both are white space by default.

- **tabstyle** => _style_

    Set tab expansion style.  This parameter set both **tabhead** and
    **tabspace** at once according to the given style name.  Each style has
    two values for tabhead and tabspace.

    If two style names are combined, like `symbol,space`, use
    `symbols`'s tabhead and `space`'s tabspace.

    Currently these names are available.

        symbol   => [ "\N{SYMBOL FOR HORIZONTAL TABULATION}",
                      "\N{SYMBOL FOR SPACE}" ],
        shade    => [ "\N{MEDIUM SHADE}",
                      "\N{LIGHT SHADE}" ],
        block    => [ "\N{LOWER ONE QUARTER BLOCK}",
                      "\N{LOWER ONE EIGHTH BLOCK}" ],
        needle   => [ "\N{BOX DRAWINGS HEAVY RIGHT}",
                      "\N{BOX DRAWINGS LIGHT HORIZONTAL}" ],
        dash     => [ "\N{BOX DRAWINGS HEAVY RIGHT}",
                      "\N{BOX DRAWINGS LIGHT DOUBLE DASH HORIZONTAL}" ],
        triangle => [ "\N{BLACK RIGHT-POINTING SMALL TRIANGLE}",
                      "\N{WHITE RIGHT-POINTING SMALL TRIANGLE}" ],

    Below are styles providing same character for both tabhead and
    tabspace.

        dot          => '.',
        space        => ' ',
        emspace      => "\N{EM SPACE}",
        blank        => "\N{OPEN BOX}",
        middle-dot   => "\N{MIDDLE DOT}",
        arrow        => "\N{RIGHTWARDS ARROW}",
        double-arrow => "\N{RIGHTWARDS DOUBLE ARROW}",
        triple-arrow => "\N{RIGHTWARDS TRIPLE ARROW}",
        white-arrow  => "\N{RIGHTWARDS WHITE ARROW}",
        wave-arrow   => "\N{RIGHTWARDS WAVE ARROW}",
        circle-arrow => "\N{CIRCLED HEAVY WHITE RIGHTWARDS ARROW}",
        curved-arrow => "\N{HEAVY BLACK CURVED DOWNWARDS AND RIGHTWARDS ARROW}",
        shadow-arrow => "\N{HEAVY UPPER RIGHT-SHADOWED WHITE RIGHTWARDS ARROW}",
        squat-arrow  => "\N{SQUAT BLACK RIGHTWARDS ARROW}",
        squiggle     => "\N{RIGHTWARDS SQUIGGLE ARROW}",
        harpoon      => "\N{RIGHTWARDS HARPOON WITH BARB UPWARDS}",
        cuneiform    => "\N{CUNEIFORM SIGN TAB}",

# EXAMPLE

Next code implements almost fully-equipped fold command for multi byte
text with Japanese prohibited character handling.

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

# CONTROL CHARACTERS

Text::ANSI::Fold handles the following line break related codes
specially:

    Newline (\n)
    Form feed (\f)
    Carriage return (\r)
    Null (\0)
    Line separator (U+2028)
    Paragraph separator (U+2029)

These characters are handled as follows:

- NEWLINE (`\n`), CRNL (`\r\n`)
- NULL (`\0`)
- LINE SEPARATOR (`U+2028`)
- PARAGRAPH SEPARATOR (`U+2029`)

    If any of these characters are found, the folding process terminates
    immediately and the portion up to that character is returned as folded
    text.  These character itself is included at the end of the folded
    text.

- CARRIAGE RETURN (`\r`)

    When a carriage return is found, it is added to the folded text and
    the fold width is reset.

- FORM FEED (`\f`)

    If a form feed character is found in the middle of a string,
    processing stops and the string up to the point immediately before is
    returned.  If it is found at the beginning of a string, it is added to
    the folded text and processing continues.

# SEE ALSO

- [https://github.com/tecolicom/ANSI-Tools](https://github.com/tecolicom/ANSI-Tools)

    Collection of ANSI related tools.

- [Text::ANSI::Fold](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AFold)
- [https://github.com/tecolicom/Text-ANSI-Fold](https://github.com/tecolicom/Text-ANSI-Fold)

    Distribution and repository.

- [App::ansifold](https://metacpan.org/pod/App%3A%3Aansifold)

    Command line utility using [Text::ANSI::Fold](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AFold).

- [Text::ANSI::Fold::Util](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AFold%3A%3AUtil)

    Collection of utilities using [Text::ANSI::Fold](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AFold) module.

- [Text::ANSI::Tabs](https://metacpan.org/pod/Text%3A%3AANSI%3A%3ATabs)

    [Text::Tabs](https://metacpan.org/pod/Text%3A%3ATabs) compatible tab expand/unexpand module using
    [Text::ANSI::Fold](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AFold) as a backend processor.

- [App::sdif](https://metacpan.org/pod/App%3A%3Asdif)

    [Text::ANSI::Fold](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AFold) 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](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AUtil), [Text::ANSI::WideUtil](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AWideUtil)

    These modules provide a rich set of functions to handle string
    contains ANSI color terminal sequences.  In contrast,
    [Text::ANSI::Fold](https://metacpan.org/pod/Text%3A%3AANSI%3A%3AFold) 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](https://en.wikipedia.org/wiki/ANSI_escape_code)

    ANSI escape code definition.

- [https://www.w3.org/TR/jlreq/](https://www.w3.org/TR/jlreq/)

    Requirements for Japanese Text Layout,
    W3C Working Group Note 11 August 2020

- [ECMA-48](https://www.ecma-international.org/wp-content/uploads/ECMA-48_5th_edition_june_1991.pdf)

    ECMA-48: Control Functions for Coded Character Sets

# AUTHOR

Kazumasa Utashiro

# LICENSE

Copyright ©︎ 2018-2024 Kazumasa Utashiro.

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