Unicode::LineBreak(3) User Contributed Perl DocumentationUnicode::LineBreak(3)
NAME
Unicode::LineBreak - UAX #14 Unicode Line Breaking Algorithm
SYNOPSIS
use Unicode::LineBreak;
$lb = Unicode::LineBreak->new();
$broken = $lb->break($string);
DESCRIPTION
Unicode::LineBreak performs Line Breaking Algorithm described in
Unicode Standard Annex #14 [UAX #14]. East_Asian_Width informative
property defined by Annex #11 [UAX #11] will be concerned to determine
breaking positions.
Terminology
Following terms are used for convenience.
Mandatory break is obligatory line breaking behavior defined by core
rules and performed regardless of surrounding characters. Arbitrary
break is line breaking behavior allowed by core rules and chosen by
user to perform it. Arbitrary break includes direct break and indirect
break defined by [UAX #14].
Alphabetic characters are characters usually no line breaks are allowed
between pairs of them, except that other characters provide break
oppotunities. Ideographic characters are characters that usually allow
line breaks both before and after themselves. [UAX #14] classifies
most of alphabetic to AL and most of ideographic to ID (These terms are
inaccurate from the point of view by grammatology). On several
scripts, breaking positions are not obvious by each characters
therefore heuristic based on dictionary is used.
Number of columns of a string is not always equal to the number of
characters it contains: Each of characters is either wide, narrow or
nonspacing; they occupy 2, 1 or 0 columns, respectively. Several
characters may be both wide and narrow by the contexts they are used.
Characters may have more various widths by customization.
PUBLIC INTERFACE
Line Breaking
new ([KEY => VALUE, ...])
Constructor. About KEY => VALUE pairs see "Options".
break (STRING)
Instance method. Break Unicode string STRING and returns it. In
array context, returns array of lines contained in the result.
break_partial (STRING)
Instance method. Same as break() but accepts incremental inputs.
Give "undef" as STRING argument to specify that input was
completed.
config (KEY)
config (KEY => VALUE, ...)
Instance method. Get or update configuration. About KEY => VALUE
pairs see "Options".
copy
Copy constructor. Create a copy of object instance.
Getting Informations
breakingRule (BEFORESTR, AFTERSTR)
Instance method. Get possible line breaking behavior between
strings BEFORESTR and AFTERSTR. See "Constants" for returned
value.
Note: This method gives just approximate description of line
breaking behavior. Use break() and so on to wrap actual texts.
context ([Charset => CHARSET], [Language => LANGUAGE])
Function. Get language/region context used by character set
CHARSET or language LANGUAGE.
Options
"new" and "config" methods accept following pairs. Some of them affect
number of columns ([E]), grapheme cluster segmentation ([G]) (see also
Unicode::GCString) or line breaking behavior ([L]).
BreakIndent => "YES" | "NO"
[L] Always allows break after SPACEs at beginning of line, a.k.a.
indent. [UAX #14] does not take account of such usage of SPACE.
Default is "YES".
Note: This option was introduced at release 1.011.
CharMax => NUMBER
[L] Possible maximum number of characters in one line, not counting
trailing SPACEs and newline sequence. Note that number of
characters generally doesn't represent length of line. Default is
998. 0 means unlimited (as of release 2012.01).
ColMin => NUMBER
[L] Minimum number of columns which line broken arbitrarily may
include, not counting trailing spaces and newline sequences.
Default is 0.
ColMax => NUMBER
[L] Maximum number of columns line may include not counting
trailing spaces and newline sequence. In other words, maximum
length of line. Default is 76.
See also "Urgent" option and "User-Defined Breaking Behaviors".
ComplexBreaking => "YES" | "NO"
[L] Performs heuristic breaking on South East Asian complex
context. Default is, if word segmentation for South East Asian
writing systems is enabled, "YES".
Context => CONTEXT
[E][L] Specify language/region context. Currently available
contexts are "EASTASIAN" and "NONEASTASIAN". Default context is
"NONEASTASIAN".
In "EASTASIAN" context, characters with East_Asian_Width property
ambiguous (A) are treated as "wide" and with Line Breaking Class AI
as ideographic (ID).
In "NONEASTASIAN" context, characters with East_Asian_Width
property ambiguous (A) are treated as "narrow" and with Line
Breaking Class AI as alphabetic (AL).
EAWidth => "[" ORD "=>" PROPERTY "]"
EAWidth => "undef"
[E] Tailor classification of East_Asian_Width property. ORD is UCS
scalar value of character or array reference of them. PROPERTY is
one of East_Asian_Width property values and extended values (See
"Constants"). This option may be specified multiple times. If
"undef" is specified, all tailoring assigned before will be
canceled.
By default, no tailorings are available. See also "Tailoring
Character Properties".
Format => METHOD
[L] Specify the method to format broken lines.
"SIMPLE"
Default method. Just only insert newline at arbitrary breaking
positions.
"NEWLINE"
Insert or replace newline sequences with that specified by
"Newline" option, remove SPACEs leading newline sequences or
end-of-text. Then append newline at end of text if it does not
exist.
"TRIM"
Insert newline at arbitrary breaking positions. Remove SPACEs
leading newline sequences.
"undef"
Do nothing, even inserting any newlines.
Subroutine reference
See "Formatting Lines".
HangulAsAL => "YES" | "NO"
[L] Treat hangul syllables and conjoining jamos as alphabetic
characters (AL). Default is "NO".
LBClass => "[" ORD "=>" CLASS "]"
LBClass => "undef"
[G][L] Tailor classification of line breaking property. ORD is UCS
scalar value of character or array reference of them. CLASS is one
of line breaking classes (See "Constants"). This option may be
specified multiple times. If "undef" is specified, all tailoring
assigned before will be canceled.
By default, no tailorings are available. See also "Tailoring
Character Properties".
LegacyCM => "YES" | "NO"
[G][L] Treat combining characters lead by a SPACE as an isolated
combining character (ID). As of Unicode 5.0, such use of SPACE is
not recommended. Default is "YES".
Newline => STRING
[L] Unicode string to be used for newline sequence. Default is
"\n".
Prep => METHOD
[L] Add user-defined line breaking behavior(s). This option may be
specified multiple times. Following methods are available.
"NONBREAKURI"
Won't break URIs.
"BREAKURI"
Break URIs according to a rule suitable for printed materials.
For more details see [CMOS], sections 6.17 and 17.11.
"[" REGEX, SUBREF "]"
The sequences matching regular expression REGEX will be broken
by subroutine referred by SUBREF. For more details see "User-
Defined Breaking Behaviors".
"undef"
Cancel all methods assigned before.
Sizing => METHOD
[L] Specify method to calculate size of string. Following options
are available.
"UAX11"
Default method. Sizes are computed by columns of each
characters accoring to built-in character database.
"undef"
Number of grapheme clusters (see Unicode::GCString) contained
in the string.
Subroutine reference
See "Calculating String Size".
See also "ColMax", "ColMin" and "EAWidth" options.
Urgent => METHOD
[L] Specify method to handle excessing lines. Following options
are available.
"CROAK"
Print error message and die.
"FORCE"
Force breaking excessing fragment.
"undef"
Default method. Won't break excessing fragment.
Subroutine reference
See "User-Defined Breaking Behaviors".
ViramaAsJoiner => "YES" | "NO"
[G] Virama sign ("halant" in Hindi, "coeng" in Khmer) and its
succeeding letter are not broken. Default is "YES". Note: This
option was introduced by release 2012.001_29. On previous
releases, it was fixed to "NO". "Default" grapheme cluster defined
by [UAX #29] does not include this feature.
Constants
"EA_Na", "EA_N", "EA_A", "EA_W", "EA_H", "EA_F"
Index values to specify six East_Asian_Width property values
defined by [UAX #11]: narrow (Na), neutral (N), ambiguous (A), wide
(W), halfwidth (H) and fullwidth (F).
"EA_Z"
Index value to specify nonspacing characters.
Note: This "nonspacing" value is extension by this module, not a
part of [UAX #11].
"LB_BK", "LB_CR", "LB_LF", "LB_NL", "LB_SP", "LB_OP", "LB_CL", "LB_CP",
"LB_QU", "LB_GL", "LB_NS", "LB_EX", "LB_SY", "LB_IS", "LB_PR", "LB_PO",
"LB_NU", "LB_AL", "LB_HL", "LB_ID", "LB_IN", "LB_HY", "LB_BA", "LB_BB",
"LB_B2", "LB_CB", "LB_ZW", "LB_CM", "LB_WJ", "LB_H2", "LB_H3", "LB_JL",
"LB_JV", "LB_JT", "LB_SG", "LB_AI", "LB_CJ", "LB_SA", "LB_XX", "LB_RI"
Index values to specify 40 line breaking property values (classes)
defined by [UAX #14].
Note: Property value CP was introduced by Unicode 5.2.0. Property
values HL and CJ were introduced by Unicode 6.1.0. Property value
RI was introduced by Unicode 6.2.0.
"MANDATORY", "DIRECT", "INDIRECT", "PROHIBITED"
Four values to specify line breaking behaviors: Mandatory break;
Both direct break and indirect break are allowed; Indirect break is
allowed but direct break is prohibited; Prohibited break.
"Unicode::LineBreak::SouthEastAsian::supported"
Flag to determin if word segmentation for South East Asian writing
systems is enabled. If this feature was enabled, a non-empty
string is set. Otherwise, "undef" is set.
N.B.: Current release supports Thai script of modern Thai language
only.
"UNICODE_VERSION"
A string to specify version of Unicode standard this module refers.
CUSTOMIZATION
Formatting Lines
If you specify subroutine reference as a value of "Format" option, it
should accept three arguments:
$MODIFIED = &subroutine(SELF, EVENT, STR);
SELF is a Unicode::LineBreak object, EVENT is a string to determine the
context that subroutine was called in, and STR is a fragment of Unicode
string leading or trailing breaking position.
EVENT |When Fired |Value of STR
-----------------------------------------------------------------
"sot" |Beginning of text |Fragment of first line
"sop" |After mandatory break|Fragment of next line
"sol" |After arbitrary break|Fragment on sequel of line
"" |Just before any |Complete line without trailing
|breaks |SPACEs
"eol" |Arbitrary break |SPACEs leading breaking position
"eop" |Mandatory break |Newline and its leading SPACEs
"eot" |End of text |SPACEs (and newline) at end of
| |text
-----------------------------------------------------------------
Subroutine should return modified text fragment or may return "undef"
to express that no modification occurred. Note that modification in
the context of "sot", "sop" or "sol" may affect decision of successive
breaking positions while in the others won't.
Note: String arguments are actually sequences of grapheme clusters.
See Unicode::GCString.
For example, following code folds lines removing trailing spaces:
sub fmt {
if ($_[1] =~ /^eo/) {
return "\n";
}
return undef;
}
my $lb = Unicode::LineBreak->new(Format => \&fmt);
$output = $lb->break($text);
User-Defined Breaking Behaviors
When a line generated by arbitrary break is expected to be beyond
measure of either CharMax, ColMax or ColMin, urgent break may be
performed on successive string. If you specify subroutine reference as
a value of "Urgent" option, it should accept two arguments:
@BROKEN = &subroutine(SELF, STR);
SELF is a Unicode::LineBreak object and STR is a Unicode string to be
broken.
Subroutine should return an array of broken string STR.
Note: String argument is actually a sequence of grapheme clusters. See
Unicode::GCString.
For example, following code inserts hyphen to the name of several
chemical substances (such as Titin) so that it may be folded:
sub hyphenize {
return map {$_ =~ s/yl$/yl-/; $_} split /(\w+?yl(?=\w))/, $_[1];
}
my $lb = Unicode::LineBreak->new(Urgent => \&hyphenize);
$output = $lb->break("Methionylthreonylthreonylglutaminylarginyl...");
If you specify [REGEX, SUBREF] array reference as any of "Prep" option,
subroutine should accept two arguments:
@BROKEN = &subroutine(SELF, STR);
SELF is a Unicode::LineBreak object and STR is a Unicode string matched
with REGEX.
Subroutine should return an array of broken string STR.
For example, following code will break HTTP URLs using [CMOS] rule.
my $url = qr{http://[\x21-\x7E]+}i;
sub breakurl {
my $self = shift;
my $str = shift;
return split m{(?<=[/]) (?=[^/]) |
(?<=[^-.]) (?=[-~.,_?\#%=&]) |
(?<=[=&]) (?=.)}x, $str;
}
my $lb = Unicode::LineBreak->new(Prep => [$url, \&breakurl]);
$output = $lb->break($string);
Preserving State
Unicode::LineBreak object can behave as hash reference. Any items may
be preserved throughout its life.
For example, following code will separate paragraphs with empty lines.
sub paraformat {
my $self = shift;
my $action = shift;
my $str = shift;
if ($action eq 'sot' or $action eq 'sop') {
$self->{'line'} = '';
} elsif ($action eq '') {
$self->{'line'} = $str;
} elsif ($action eq 'eol') {
return "\n";
} elsif ($action eq 'eop') {
if (length $self->{'line'}) {
return "\n\n";
} else {
return "\n";
}
} elsif ($action eq 'eot') {
return "\n";
}
return undef;
}
my $lb = Unicode::LineBreak->new(Format => \¶format);
$output = $lb->break($string);
Calculating String Size
If you specify subroutine reference as a value of "Sizing" option, it
will be called with five arguments:
$COLS = &subroutine(SELF, LEN, PRE, SPC, STR);
SELF is a Unicode::LineBreak object, LEN is size of preceding string,
PRE is preceding Unicode string, SPC is additional SPACEs and STR is a
Unicode string to be processed.
Subroutine should return calculated number of columns of "PRE.SPC.STR".
The number of columns may not be an integer: Unit of the number may be
freely chosen, however, it should be same as those of "ColMin" and
"ColMax" option.
Note: String arguments are actually sequences of grapheme clusters.
See Unicode::GCString.
For example, following code processes lines with tab stops by each
eight columns.
sub tabbedsizing {
my ($self, $cols, $pre, $spc, $str) = @_;
my $spcstr = $spc.$str;
while ($spcstr->lbc == LB_SP) {
my $c = $spcstr->item(0);
if ($c eq "\t") {
$cols += 8 - $cols % 8;
} else {
$cols += $c->columns;
}
$spcstr = $spcstr->substr(1);
}
$cols += $spcstr->columns;
return $cols;
};
my $lb = Unicode::LineBreak->new(LBClass => [ord("\t") => LB_SP],
Sizing => \&tabbedsizing);
$output = $lb->break($string);
Tailoring Character Properties
Character properties may be tailored by "LBClass" and "EAWidth"
options. Some constants are defined for convenience of tailoring.
Line Breaking Properties
Non-starters of Kana-like Characters
By default, several hiragana, katakana and characters corresponding to
kana are treated as non-starters (NS or CJ). When the following
pair(s) are specified for value of "LBClass" option, these characters
are treated as normal ideographic characters (ID).
"KANA_NONSTARTERS() => LB_ID"
All of characters below.
"IDEOGRAPHIC_ITERATION_MARKS() => LB_ID"
Ideographic iteration marks. U+3005 IDEOGRAPHIC ITERATION MARK,
U+303B VERTICAL IDEOGRAPHIC ITERATION MARK, U+309D HIRAGANA
ITERATION MARK, U+309E HIRAGANA VOICED ITERATION MARK, U+30FD
KATAKANA ITERATION MARK and U+30FE KATAKANA VOICED ITERATION MARK.
N.B. Some of them are neither hiragana nor katakana.
"KANA_SMALL_LETTERS() => LB_ID"
"KANA_PROLONGED_SOUND_MARKS() => LB_ID"
Hiragana or katakana small letters: Hiragana small letters U+3041
A, U+3043 I, U+3045 U, U+3047 E, U+3049 O, U+3063 TU, U+3083 YA,
U+3085 YU, U+3087 YO, U+308E WA, U+3095 KA, U+3096 KE. Katakana
small letters U+30A1 A, U+30A3 I, U+30A5 U, U+30A7 E, U+30A9 O,
U+30C3 TU, U+30E3 YA, U+30E5 YU, U+30E7 YO, U+30EE WA, U+30F5 KA,
U+30F6 KE. Katakana phonetic extensions U+31F0 KU - U+31FF RO.
Halfwidth katakana small letters U+FF67 A - U+FF6F TU.
Hiragana or katakana prolonged sound marks: U+30FC KATAKANA-
HIRAGANA PROLONGED SOUND MARK and U+FF70 HALFWIDTH KATAKANA-
HIRAGANA PROLONGED SOUND MARK.
N.B. These letters are optionally treated either as non-starter or
as normal ideographic. See [JIS X 4051] 6.1.1, [JLREQ] 3.1.7 or
[UAX14].
N.B. U+3095, U+3096, U+30F5, U+30F6 are considered to be neither
hiragana nor katakana.
"MASU_MARK() => LB_ID"
U+303C MASU MARK.
N.B. Although this character is not kana, it is usually regarded as
abbreviation to sequence of hiragana a3/4 a or katakana a a1, MA
and SU.
N.B. This character is classified as non-starter (NS) by [UAX #14]
and as the class corresponding to ID by [JIS X 4051] and [JLREQ].
Ambiguous Quotation Marks
By default, some punctuations are ambiguous quotation marks (QU).
"BACKWARD_QUOTES() => LB_OP, FORWARD_QUOTES() => LB_CL"
Some languages (Dutch, English, Italian, Portugese, Spanish,
Turkish and most East Asian) use rotated-9-style punctuations (a a)
as opening and 9-style punctuations (a a) as closing quotation
marks.
"FORWARD_QUOTES() => LB_OP, BACKWARD_QUOTES() => LB_CL"
Some others (Czech, German and Slovak) use 9-style punctuations (a
a) as opening and rotated-9-style punctuations (a a) as closing
quotation marks.
"BACKWARD_GUILLEMETS() => LB_OP, FORWARD_GUILLEMETS() => LB_CL"
French, Greek, Russian etc. use left-pointing guillemets (A<< a1)
as opening and right-pointing guillemets (A>> ao) as closing
quotation marks.
"FORWARD_GUILLEMETS() => LB_OP, BACKWARD_GUILLEMETS() => LB_CL"
German and Slovak use right-pointing guillemets (A>> ao) as opening
and left-pointing guillemets (A<< a1) as closing quotation marks.
Danish, Finnish, Norwegian and Swedish use 9-style or right-pointing
punctuations (a a A>> ao) as both opening and closing quotation marks.
IDEOGRAPHIC SPACE
"IDEOGRAPHIC_SPACE() => LB_BA"
U+3000 IDEOGRAPHIC SPACE won't be placed at beginning of line.
This is default behavior.
"IDEOGRAPHIC_SPACE() => LB_ID"
IDEOGRAPHIC SPACE can be placed at beginning of line. This was
default behavior by Unicode 6.2 and earlier.
"IDEOGRAPHIC_SPACE() => LB_SP"
IDEOGRAPHIC SPACE won't be placed at beginning of line, and will
protrude from end of line.
East_Asian_Width Properties
Some particular letters of Latin, Greek and Cyrillic scripts have
ambiguous (A) East_Asian_Width property. Thus, these characters are
treated as wide in "EASTASIAN" context. Specifying "EAWidth => [
AMBIGUOUS_"*"() => EA_N ]", those characters are always treated as
narrow.
"AMBIGUOUS_ALPHABETICS() => EA_N"
Treat all of characters below as East_Asian_Width neutral (N).
"AMBIGUOUS_CYRILLIC() => EA_N"
"AMBIGUOUS_GREEK() => EA_N"
"AMBIGUOUS_LATIN() => EA_N"
Treate letters having ambiguous (A) width of Cyrillic, Greek and
Latin scripts as neutral (N).
On the other hand, despite several characters were occasionally
rendered as wide characters by number of implementations for East Asian
character sets, they are given narrow (Na) East_Asian_Width property
just because they have fullwidth (F) compatibility characters.
Specifying "EAWidth" as below, those characters are treated as
ambiguous --- wide on "EASTASIAN" context.
"QUESTIONABLE_NARROW_SIGNS() => EA_A"
U+00A2 CENT SIGN, U+00A3 POUND SIGN, U+00A5 YEN SIGN (or yuan
sign), U+00A6 BROKEN BAR, U+00AC NOT SIGN, U+00AF MACRON.
Configuration File
Built-in defaults of option parameters for "new" and "config" method
can be overridden by configuration files:
Unicode/LineBreak/Defaults.pm. For more details read
Unicode/LineBreak/Defaults.pm.sample.
BUGS
Please report bugs or buggy behaviors to developer.
CPAN Request Tracker:
<http://rt.cpan.org/Public/Dist/Display.html?Name=Unicode-LineBreak>.
VERSION
Consult $VERSION variable.
Incompatible Changes
Release 2012.06
o eawidth() method was deprecated. "columns" in
Unicode::GCString may be used instead.
o lbclass() method was deprecated. Use "lbc" in
Unicode::GCString or "lbcext" in Unicode::GCString.
Conformance to Standards
Character properties this module is based on are defined by Unicode
Standard version 8.0.0.
This module is intended to implement UAX14-C2.
IMPLEMENTATION NOTES
o Some ideographic characters may be treated either as NS or as ID by
choice.
o Hangul syllables and conjoining jamos may be treated as either ID
or AL by choice.
o Characters assigned to AI may be resolved to either AL or ID by
choice.
o Character(s) assigned to CB are not resolved.
o Characters assigned to CJ are always resolved to NS. More flexible
tailoring mechanism is provided.
o When word segmentation for South East Asian writing systems is not
supported, characters assigned to SA are resolved to AL, except
that characters that have Grapheme_Cluster_Break property value
Extend or SpacingMark be resolved to CM.
o Characters assigned to SG or XX are resolved to AL.
o Code points of following UCS ranges are given fixed property values
even if they have not been assigned any characers.
Ranges | UAX #14 | UAX #11 | Description
-------------------------------------------------------------
U+20A0..U+20CF | PR [*1] | N [*2] | Currency symbols
U+3400..U+4DBF | ID | W | CJK ideographs
U+4E00..U+9FFF | ID | W | CJK ideographs
U+D800..U+DFFF | AL (SG) | N | Surrogates
U+E000..U+F8FF | AL (XX) | F or N (A) | Private use
U+F900..U+FAFF | ID | W | CJK ideographs
U+20000..U+2FFFD | ID | W | CJK ideographs
U+30000..U+3FFFD | ID | W | Old hanzi
U+F0000..U+FFFFD | AL (XX) | F or N (A) | Private use
U+100000..U+10FFFD | AL (XX) | F or N (A) | Private use
Other unassigned | AL (XX) | N | Unassigned,
| | | reserved or
| | | noncharacters
-------------------------------------------------------------
[*1] Except U+20A7 PESETA SIGN (PO),
U+20B6 LIVRE TOURNOIS SIGN (PO), U+20BB NORDIC MARK SIGN (PO)
and U+20BE LARI SIGN (PO).
[*2] Except U+20A9 WON SIGN (H) and U+20AC EURO SIGN
(F or N (A)).
o Characters belonging to General Category Mn, Me, Cc, Cf, Zl or Zp
are treated as nonspacing by this module.
REFERENCES
[CMOS]
The Chicago Manual of Style, 15th edition. University of Chicago
Press, 2003.
[JIS X 4051]
JIS X 4051:2004 ae=<i>Yae~`<i>e<i>aaeae,~<i>a(R),<i>c,<i>u,<i>cae1ae3 (Formatting Rules for
Japanese Documents). Japanese Standards Association, 2004.
[JLREQ]
Anan, Yasuhiro et al. Requirements for Japanese Text Layout, W3C
Working Group Note 3 April 2012.
<http://www.w3.org/TR/2012/NOTE-jlreq-20120403/>.
[UAX #11]
A. Freytag (ed.) (2008-2009). Unicode Standard Annex #11: East
Asian Width, Revisions 17-19. <http://unicode.org/reports/tr11/>.
[UAX #14]
A. Freytag and A. Heninger (eds.) (2008-2015). Unicode Standard
Annex #14: Unicode Line Breaking Algorithm, Revisions 22-35.
<http://unicode.org/reports/tr14/>.
[UAX #29]
Mark Davis (ed.) (2009-2013). Unicode Standard Annex #29: Unicode
Text Segmentation, Revisions 15-23.
<http://www.unicode.org/reports/tr29/>.
SEE ALSO
Text::LineFold(3), Text::Wrap(3), Unicode::GCString(3).
AUTHOR
Copyright (C) 2009-2018 Hatuka*nezumi - IKEDA Soji
<hatuka(at)nezumi.nu>.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.30.0 2018-03-29 Unicode::LineBreak(3)
unicode-linebreak 2019.1.0 - Generated Fri Jun 11 14:30:43 CDT 2021