danielchatfield/shreddi.es — pull request #2 by alexbate (2014-12-04 11:45:09+00:00)
Title: Create DOM template

Such that, in the future, one may easily create a sheet of styles for
the application using the Cascading Style Sheet model [1]

[1] - Appendix
------------------------
W3C
CSS Text Module Level 3
W3C Last Call Working Draft 10 October 2013
Copyright © 2013 W3C® (MIT, ERCIM, Keio, Beihang), All Rights Reserved.
W3C liability, trademark and document use rules apply.

Abstract

This CSS3 module defines properties for text manipulation and specifies
their processing model. It covers line breaking, justification and
alignment, white space handling, and text transformation.

Status of This Document

This section describes the status of this document at the time of its
publication. Other documents may supersede this document. A list of
current W3C publications and the latest revision of this technical
report can be found in the W3C technical reports index at
http://www.w3.org/TR/.

Publication as a Last Call Working Draft does not imply endorsement by
the W3C Membership. This is a draft document and may be updated,
replaced or obsoleted by other documents at any time. It is
inappropriate to cite this document as other than work in progress.

This CSS module has been produced as a combined effort of the W3C
Internationalization Activity, and the Style Activity and is maintained
by the CSS Working Group. It also includes contributions made by
participants in the XSL Working Group (members only).

This document was produced by a group operating under the 5 February
2004 W3C Patent Policy. W3C maintains a public list of any patent
disclosures made in connection with the deliverables of the group; that
page also includes instructions for disclosing a patent. An individual
who has actual knowledge of a patent which the individual believes
contains Essential Claim(s) must disclose the information in accordance
with section 6 of the W3C Patent Policy.

The following features are at risk and may be cut from the spec during
its CR period if there are no (correct) implementations:

the ‘full-width’ value of ‘text-transform’
the values of the ‘tab-size’ property
the ‘start end’ value of ‘text-align’
the ‘text-justify’ property
the percentage values of ‘word-spacing’
the ‘hanging-punctuation’ property
This specification is a Last Call Working Draft. All persons are
encouraged to review this document and send comments to the www-style
mailing list as described below. The deadline for comments is 7 November
2013.

Feedback on this draft should be posted to the (archived) public mailing
list www-style@w3.org (see instructions) with [css-text] in the subject
line. You are strongly encouraged to complain if you see something
stupid in this draft. The editors will do their best to respond to all
feedback.

Table of Contents

1. Introduction
1.1. Module Interactions
1.2. Values
1.3. Terminology
2. Transforming Text
2.1. Case Transforms: the ‘text-transform’ property
3. White Space and Wrapping: the ‘white-space’ property
4. White Space Processing Details
4.1. The White Space Processing Rules
4.1.1. Phase I: Collapsing and Transformation
4.1.2. Segment Break Transformation Rules
4.1.3. Phase II: Trimming and Positioning
4.2. Tab Character Size: the ‘tab-size’ property
5. Line Breaking and Word Boundaries
5.1. Line Breaking Details
5.2. Breaking Rules for Punctuation: the ‘line-break’ property
5.3. Breaking Rules for Letters: the ‘word-break’ property
6. Breaking Within Words
6.1. Hyphenation Control: the ‘hyphens’ property
6.2. Overflow Wrapping: the ‘word-wrap’/‘overflow-wrap’ property
7. Alignment and Justification
7.1. Text Alignment: the ‘text-align’ property
7.2. Last Line Alignment: the ‘text-align-last’ property
7.3. Justification Method: the ‘text-justify’ property
7.3.1. Expanding and Compressing Text
7.3.2. Handling Symbols and Punctuation
7.3.3. Unexpandable Text
7.3.4. Cursive Scripts
7.3.5. Possible Algorithms
8. Spacing
8.1. Word Spacing: the ‘word-spacing’ property
8.2. Tracking: the ‘letter-spacing’ property
9. Edge Effects
9.1. First Line Indentation: the ‘text-indent’ property
9.2. Hanging Punctuation: the ‘hanging-punctuation’ property
9.3. Bidirectionality and Line Boxes
Appendix A: Text Processing Order of Operations
Appendix B: Default UA Stylesheet
Appendix C: Cursive Scripts
Acknowledgements
Changes
Changes from the November 2012 CSS3 Text WD
Conformance
Document Conventions
Conformance Classes
Partial Implementations
Experimental Implementations
Non-Experimental Implementations
CR Exit Criteria
References
Normative references
Informative references
Index
Property Index
1. Introduction

This module describes the typesetting controls of CSS; that is, the
features of CSS that control the translation of source text to
formatted, line-wrapped text. Various CSS properties provide control
over case transformation, white space collapsing, text wrapping, line
breaking rules and hyphenation, alignment and justification, spacing,
and indentation.

Font selection is covered in CSS Fonts Level 3 [CSS3-FONTS].

Features for decorating text, such as underlines, emphasis marks, and
shadows, (previously part of this module) are covered in CSS Text
Decoration Level 3 [CSS3-TEXT-DECOR].

Bidirectional and vertical text are addressed in CSS Writing Modes Level
3 [CSS3-WRITING-MODES].

1.1. Module Interactions

This module, together with [CSS3-TEXT-DECOR], replaces and extends the
text-level features defined in [CSS21] chapter 16.

1.2. Values

This specification follows the CSS property definition conventions from
[CSS21]. Value types not defined in this specification are defined in
CSS Level 2 Revision 1 [CSS21]. Other CSS modules may expand the
definitions of these value types: for example [CSS3VAL], when combined
with this module, expands the definition of the value type as
used in this specification.

In addition to the property-specific values listed in their definitions,
all properties defined in this specification also accept the inherit
keyword as their property value. For readability it has not been
repeated explicitly.

1.3. Terminology

A grapheme cluster is what a language user considers to be a character
or a basic unit of the script. The term is described in detail in the
Unicode Technical Report: Text Boundaries [UAX29]. This specification
uses the extended grapheme cluster definition in [UAX29] (not the legacy
grapheme cluster definition). The UA may further tailor the definition
as required by typographical tradition.

For example, to properly letter-space the Thai word คำ (U+0E04 +
U+0E33), the U+0E33 needs to be decomposed into U+0E4D + U+0E32, and
then the extra letter-space inserted before the U+0E32: คํ า.

A slightly more complex example is น้ำ (U+0E19 + U+0E49 + U+0E33). In
this case, normal Thai shaping will first decompose the U+0E33 into
U+0E4D + U+0E32 and then swap the U+0E4D with the U+0E49, giving U+0E19
+ U+0E4D + U+0E49 + U+0E32. As before the extra letter-space is then
inserted before the U+0E32: นํ้ า.

Within this specification, the ambiguous term character is used as a
friendlier synonym for grapheme cluster. See Characters and Properties
for how to determine the Unicode properties of a character.

A letter for the purpose of this specification is a character belonging
to one of the Letter or Number general categories in Unicode. [UAX44]

The rendering characteristics of a character divided by an element
boundary is undefined: it may be rendered as belonging to either side of
the boundary, or as some approximation of belonging to both. Authors are
forewarned that dividing grapheme clusters by element boundaries may
give inconsistent or undesired results.

The content language of an element is the (human) language the element
is declared to be in, according to the rules of the document language.
For example, the rules for determining the content language of an HTML
element use the lang attribute and are defined in [HTML5], and the rules
for determining the content language of an XML element use the xml:lang
attribute and are defined in [XML10]. Note that it is possible for the
content language of an element to be unknown.

Other terminology and concepts used in this specification are defined in
[CSS21] and [CSS3-WRITING-MODES].

2. Transforming Text

2.1. Case Transforms: the ‘text-transform’ property

Name: text-transform
Value: none | capitalize | uppercase | lowercase | full-width
Initial: none
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: as specified
Animatable: no
Canonical order: N/A
This property transforms text for styling purposes. (It has no effect on
the underlying content.) Values have the following meanings:

‘none’
No effects.
‘capitalize’
Puts the first letter of each word in titlecase; other characters are
unaffected.
‘uppercase’
Puts all letters in uppercase.
‘lowercase’
Puts all letters in lowercase.
‘full-width’
Puts all characters in fullwidth form. If the character does not have a
corresponding fullwidth form, it is left as is. This value is typically
used to typeset Latin characters and digits like ideographic characters.
The definition of “word“ used for ‘capitalize’ is UA-dependent; [UAX29]
is suggested (but not required) for determining such word boundaries.
Authors should not expect ‘capitalize’ to follow language-specific
titlecasing conventions (such as skipping articles in English).

The following example converts the ASCII characters used in
abbreviations in Japanese text to their fullwidth variants so that they
lay out and line break like ideographs:

abbr:lang(ja) { text-transform: full-width; }
The case mapping rules for the character repertoire specified by the
Unicode Standard can be found on the Unicode Consortium Web site
[UNICODE]. The UA must use the full case mappings for Unicode
characters, including any conditional casing rules, as defined in
Default Case Algorithm section. If (and only if) the content language of
the element is, according to the rules of the document language, known,
then any appropriate language-specific rules must be applied as well.
These minimally include, but are not limited to, the language-specific
rules in Unicode's SpecialCasing.txt.

For example, in Turkish there are two “i”s, one with a dot—“İ” and “i”—
and one without—“I” and “ı”. Thus the usual case mappings between “I”
and “i” are replaced with a different set of mappings to their
respective undotted/dotted counterparts, which do not exist in English.
This mapping must only take effect if the content language is Turkish
(or another Turkic language that uses Turkish casing rules); in other
languages, the usual mapping of “I” and “i” is required. This rule is
thus conditionally defined in Unicode's SpecialCasing.txt file.

The definition of fullwidth and halfwidth forms can be found on the
Unicode consortium web site at [UAX11]. The mapping to fullwidth form is
defined by taking code points with the or the tag in
their Decomposition_Mapping in [UAX44]. For the tag, the
mapping is from the code point to the decomposition (minus
tag), and for the tag, the mapping is from the decomposition
(minus the tag) back to the original code point.

Text transformation happens after white space processing, which means
that ‘full-width’ transforms only preserved U+0020 spaces to U+3000.

A future level of CSS may introduce the ability to create custom mapping
tables for less common text transforms, such as by an ‘@text-transform’
rule similar to ‘@counter-style’ from [CSS-COUNTER-STYLES-3].

3. White Space and Wrapping: the ‘white-space’ property

Name: white-space
Value: normal | pre | nowrap | pre-wrap | pre-line
Initial: normal
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: as specified
Animatable: no
Canonical order: N/A
This property specifies two things:

whether and how white space inside the element is collapsed
whether lines may wrap at unforced soft wrap opportunities
Values have the following meanings, which must be interpreted according
to the White Space Processing and Line Breaking rules:

‘normal’
This value directs user agents to collapse sequences of white space into
a single character (or in some cases, no character). Lines may wrap at
allowed soft wrap opportunities, as determined by the line-breaking
rules in effect, in order to minimize inline-axis overflow.
‘pre’
This value prevents user agents from collapsing sequences of white
space. Segment breaks such as line feeds and carriage returns are
preserved as forced line breaks. Lines only break at forced line breaks;
content that does not fit within the block container overflows it.
‘nowrap’
Like ‘normal’, this value collapses white space; but like ‘pre’, it does
not allow wrapping.
‘pre-wrap’
Like ‘pre’, this value preserves white space; but like ‘normal’, it
allows wrapping.
‘pre-line’
Like ‘normal’, this value collapses consecutive spaces and allows
wrapping, but preserves segment breaks in the source as forced line
breaks.
The following informative table summarizes the behavior of various
‘white-space’ values:

New Lines Spaces and Tabs Text Wrapping
‘normal’ Collapse Collapse Wrap
‘pre’ Preserve Preserve No wrap
‘nowrap’ Collapse Collapse No wrap
‘pre-wrap’ Preserve Preserve Wrap
‘pre-line’ Preserve Collapse Wrap
See White Space Processing Rules for details on how white space
collapses. An informative summary of collapsing (‘normal’ and ‘nowrap’)
is presented below:

A sequence of segment breaks and other white space between two Chinese,
Japanese, or Yi characters collapses into nothing.
A zero width space before or after a white space sequence containing a
segment break causes the entire sequence of white space to collapse into
a zero width space.
Otherwise, consecutive white space collapses into a single space.
See Line Breaking for details on wrapping behavior.

4. White Space Processing Details

The source text of a document often contains formatting that is not
relevant to the final rendering: for example, breaking the source into
segments (lines) for ease of editing or adding white space characters
such as tabs and spaces to indent the source code. CSS white space
processing allows the author to control interpretation of such
formatting: to preserve or collapse it away when rendering the document.
White space processing in CSS interprets white space characters only for
rendering: it has no effect on the underlying document data.

White space processing in CSS is controlled with the ‘white-space’
property.

CSS does not define document segmentation rules. Segments could be
separated by a particular newline seqence (such as a line feed or CRLF
pair), or delimited by some other mechanism, such as the SGML
RECORD-START and RECORD-END tokens. For CSS processing, each document
language–defined segment break, CRLF sequence (U+000D U+000A), carriage
return (U+000D), and line feed (U+000A) in the text is treated as a
segment break, which is then interpreted for rendering as specified by
the ‘white-space’ property.

Note that the document parser may have not only normalized any segment
breaks, but also collapsed other space characters or otherwise processed
white space according to markup rules. Because CSS processing occurs
after the parsing stage, it is not possible to restore these characters
for styling. Therefore, some of the behavior specified below can be
affected by these limitations and may be user agent dependent.

Note that anonymous inlines consisting entirely of collapsible white
space are removed from the rendering tree. See [CSS21] section 9.2.2.1

Control characters (Unicode class Cc) other than tab (U+0009), line feed
(U+000A), and carriage return (U+000D) are ignored for the purpose of
rendering.

4.1. The White Space Processing Rules

White space processing affects only spaces (U+0020), tabs (U+0009), and
segment breaks.

4.1.1. Phase I: Collapsing and Transformation

For each inline (including anonymous inlines) within an inline
formatting context, white space characters are handled as follows,
ignoring bidi formatting characters as if they were not there:

If ‘white-space’ is set to ‘normal’, ‘nowrap’, or ‘pre-line’, white
space characters are considered collapsible and are processed by
performing the following steps:

All spaces and tabs immediately preceding or following a segment break
are removed.
Segment breaks are transformed for rendering according to the segment
break transformation rules.
Every tab is converted to a space (U+0020).
Any space immediately following another collapsible space—even one
outside the boundary of the inline containing that space, provided they
are both within the same inline formatting context—is collapsed to have
zero advance width. (It is invisible, but retains its soft wrap
opportunity, if any.)
If ‘white-space’ is set to ‘pre-wrap’, any sequence of spaces is treated
as a sequence of non-breaking spaces. However, a soft wrap opportunity
exists at the end of the sequence.

Then, the entire block is rendered. Inlines are laid out, taking bidi
reordering into account, and wrapping as specified by the ‘white-space’
property.

The following example illustrates the interaction of white-space
collapsing and bidirectionality. Consider the following markup fragment,
taking special note of spaces (with varied backgrounds and borders for
emphasis and identification):

A B C
where the element represents a left-to-right embedding and the
element represents a right-to-left embedding. If the ‘white-space’
property is set to ‘normal’, the white-space processing model would
result in the following:

The space before the B ( ) would collapse with the space after the A (
).
The space before the C ( ) would collapse with the space after the B (
).
This would leave two spaces, one after the A in the left-to-right
embedding level, and one after the B in the right-to-left embedding
level. This is then ordered according to the Unicode bidirectional
algorithm, with the end result being:

A BC
Note that there are two spaces between A and B, and none between B and
C. This is best avoided by putting spaces outside the element instead of
just inside the opening and closing tags and, where practical, by
relying on implicit bidirectionality instead of explicit embedding
levels.

4.1.2. Segment Break Transformation Rules

When ‘white-space’ is ‘pre’, ‘pre-wrap’, or ‘pre-line’, segment breaks
are not collapsible and are instead transformed into a preserved line
feed (U+000A).

For other values of ‘white-space’, segment breaks are collapsible, and
are either transformed into a space (U+0020) or removed depending on the
context before and after the break:

If the character immediately before or immediately after the segment
break is the zero-width space character (U+200B), then the break is
removed, leaving behind the zero-width space.
Otherwise, if the East Asian Width property [UAX11] of both the
character before and after the line feed is F, W, or H (not A), and
neither side is Hangul, then the segment break is removed.
Otherwise, the segment break is converted to a space (U+0020).
Note that the white space processing rules have already removed any tabs
and spaces after the segment break before these checks take place.

Comments on how well this would work in practice would be very much
appreciated, particularly from people who work with Thai and similar
scripts. Note that browser implementations do not currently follow these
rules (although IE does in some cases transform the break).

4.1.3. Phase II: Trimming and Positioning

As each line is laid out,

A sequence of collapsible spaces at the beginning of a line is removed.
Each tab is rendered as a horizontal shift that lines up the start edge
of the next glyph with the next tab stop. Tab stops occur at points that
are multiples of the tab size from the block's starting content edge.
The tab size is given by the ‘tab-size’ property.
A sequence of collapsible spaces at the end of a line is removed.
If spaces or tabs at the end of a line are non-collapsible but have
‘white-space’ set to ‘pre-wrap’ the UA may visually collapse their
character advance widths.
White space that was not removed or collapsed during the white space
processing steps is called preserved white space.

4.2. Tab Character Size: the ‘tab-size’ property

Name: tab-size
Value: |
Initial: 8
Applies to: block containers
Inherited: yes
Percentages: N/A
Media: visual
Computed value: the specified integer or length made absolute
Animatable: as length
Canonical order: N/A
This property determines the tab size used to render preserved tab
characters (U+0009). Integers represent the measure as multiples of the
space character's advance width (U+0020). Negative values are not
allowed.

5. Line Breaking and Word Boundaries

When inline-level content is laid out into lines, it is broken across
line boxes. Such a break is called a line break. When a line is broken
due to explicit line-breaking controls, or due to the start or end of a
block, it is a forced line break. When a line is broken due to content
wrapping (i.e. when the UA creates unforced line breaks in order to fit
the content within the measure), it is a soft wrap break. The process of
breaking inline-level content into lines is called line breaking.

Wrapping is only performed at an allowed break point, called a soft wrap
opportunity.

In most writing systems, in the absence of hyphenation a soft wrap
opportunity occurs only at word boundaries. Many such systems use spaces
or punctuation to explicitly separate words, and soft wrap opportunities
can be identified by these characters. Scripts such as Thai, Lao, and
Khmer, however, do not use spaces or punctuation to separate words.
Although the zero width space (U+200B) can be used as an explicit word
delimiter in these scripts, this practice is not common. As a result, a
lexical resource is needed to correctly identify soft wrap opportunities
in such texts.

In several other writing systems, (including Chinese, Japanese, Yi, and
sometimes also Korean) a soft wrap opportunity is based on syllable
boundaries, not word boundaries. In these systems a line can break
anywhere except between certain character combinations. Additionally the
level of strictness in these restrictions can vary with the typesetting
style.

CSS does not fully define where soft wrap opportunities occur, however
some controls are provided to distinguish common variations.

Further information on line breaking conventions can be found in [JLREQ]
and [JIS4051] for Japanese, [ZHMARK] for Chinese, and in [UAX14] for all
scripts in Unicode.

Any guidance for appropriate references here would be much appreciated.

5.1. Line Breaking Details

When determining line breaks:

Regardless of the ‘white-space’ value, lines always break at each
preserved forced break character: for all values, line-breaking behavior
defined for the BK, CR, LF, CM, NL, and SG line breaking classes in
[UAX14] must be honored.
When ‘white-space’ allows wrapping, line breaking behavior defined for
the WJ, ZW, and GL line-breaking classes in [UAX14] must be honored.
UAs that allow wrapping at punctuation other than spaces should
prioritize breakpoints. For example, if breaks after slashes are given a
lower priority than spaces, the sequence "check /etc" will never break
between the ‘/’ and the ‘e’. The UA may use the width of the containing
block, the text's language, and other factors in assigning priorities.
As long as care is taken to avoid such awkward breaks, allowing breaks
at appropriate punctuation other than spaces is recommended, as it
results in more even-looking margins, particularly in narrow measures.
Out-of-flow elements do not introduce a forced line break or soft wrap
opportunity in the flow.
The line breaking behavior of a replaced element or other atomic inline
is equivalent to that of the Object Replacement Character (U+FFFC).
For soft wrap opportunities created by characters that disappear at the
line break (e.g. U+0020 SPACE), properties on the element containing
that character control the line breaking at that opportunity. For soft
wrap opportunities defined by the boundary between two characters, the
properties on the element containing the boundary control breaking.
For soft wrap opportunities before the first or after the last character
of a box, the break occurs immediately before/after the box (at its
margin edge) rather than breaking the box between its content edge and
the content.
For line breaking in/around ruby, the base text is considered part of
the same inline formatting context as its surrouding content, but the
ruby text is not: i.e. line breaking opportunities between the ruby
element and its surrounding content are determined as if the ruby base
were inline and the ruby text were not there.
5.2. Breaking Rules for Punctuation: the ‘line-break’ property

Name: line-break
Value: auto | loose | normal | strict
Initial: auto
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value
Animatable: no
Canonical order: N/A
This property specifies the strictness of line-breaking rules applied
within an element: particularly how wrapping interacts with punctuation
and symbols. Values have the following meanings:

‘auto’
The UA determines the set of line-breaking restrictions to use, and it
may vary the restrictions based on the length of the line; e.g., use a
less restrictive set of line-break rules for short lines.
‘loose’
Breaks text using the least restrictive set of line-breaking rules.
Typically used for short lines, such as in newspapers.
‘normal’
Breaks text using the most common set of line-breaking rules.
‘strict’
Breaks text using the most stringent set of line-breaking rules.
The rules here are following guidelines from KLREQ for Korean, which
don't allow the Chinese/Japanese-specific breaks. However, the resulting
behavior could use some review and feedback to make sure they are
correct, particularly when “word basis” breaking is used (‘word-break:
keep-all’) in Korean.

CSS distinguishes between three levels of strictness in the rules for
text wrapping. The precise set of rules in effect for each level is up
to the UA and should follow language conventions. However, this
specification does require that:

Following breaks be forbidden in ‘strict’ line breaking and allowed in
‘normal’ and ‘loose’:
breaks before Japanese small kana or the Katakana-Hiragana prolonged
sound mark: i.e. characters with the Unicode Line Break property CJ.
(See LineBreak.txt in [UNICODE].)
If the content language is Chinese or Japanese, then additionally allow
(but otherwise forbid) for ‘normal’ and ‘loose’:
breaks before hyphens:
‐ U+2010, – U+2013, 〜 U+301C, ゠ U+30A0
Following breaks be forbidden in ‘normal’ and ‘strict’ line breaking and
allowed in ‘loose’:
breaks before iteration marks:
々 U+3005, 〻 U+303B, ゝ U+309D, ゞ U+309E, ヽ U+30FD, ヾ U+30FE
breaks between inseparable characters such as ‥ U+2025, … U+2026 i.e.
characters with the Unicode Line Break property IN. (See LineBreak.txt
in [UNICODE].)
If the content language is Chinese or Japanese, then additionally allow
(but otherwise forbid) for ‘loose’:
breaks before certain centered punctuation marks:
: U+003A, ; U+003B, ・ U+30FB, ： U+FF1A, ； U+FF1B, ･ U+FF65, ! U+0021, ?
U+003F, ‼ U+203C, ⁇ U+2047, ⁈ U+2048, ⁉ U+2049, ！ U+FF01, ？ U+FF1F
breaks before suffixes:
% U+0025, ¢ U+00A2, ° U+00B0, ‰ U+2030, ′ U+2032, ″ U+2033, ℃ U+2103, �
U+FF05, ￠ U+FFE0
breaks after prefixes:
№ U+2116 and all currency symbols (Unicode general category Sc) other
than ¢ U+00A2 and ￠ U+FFE0
In the recommended list above, no distinction is made among the levels
of strictness in non-CJK text: only CJK codepoints are affected, unless
the text is marked as Chinese or Japanese, in which case some additional
common codepoints are affected. However a future level of CSS may add
behaviors affecting non-CJK text.

The CSSWG recognizes that in a future edition of the specification finer
control over line breaking may be necessary to satisfy high-end
publishing requirements.

5.3. Breaking Rules for Letters: the ‘word-break’ property

Name: word-break
Value: normal | keep-all | break-all
Initial: normal
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value
Animatable: no
Canonical order: N/A
This property specifies soft wrap opportunities between letters, i.e.
where it is “normal” and permissible to break lines of text.

For example, in some styles of CJK typesetting, English words are
allowed to break between any two letters, rather than only at spaces or
hyphenation points; this can be enabled with ‘word-break:break-all’.

A snippet of Japanese text with English in it. The word 'caption' is
broken into 'capt' and 'ion' across two lines.
An example of English text embedded in Japanese being broken at an
arbitrary point in the word.

As another example, Korean has two styles of line-breaking: between any
two Korean syllables (‘word-break: normal’) or, like English, mainly at
spaces (‘word-break: keep-all’).

각 줄의 마지막에 한글이 올 때 줄 나눔 기 /* break between syllables */
준을 “글자” 또는 “어절” 단위로 한다.
각 줄의 마지막에 한글이 올 때 줄 나눔 /* break only at spaces */
기준을 “글자” 또는 “어절” 단위로 한다.
To enable additional break opportunities only in the case of overflow,
see ‘overflow-wrap’.

Values have the following meanings:

‘normal’
Words break according to their usual rules.
‘break-all’
In addition to ‘normal’ soft wrap opportunities, lines may break between
any two letters (except where forbidden by the ‘line-break’ property).
Hyphenation is not applied. This option is used mostly in a context
where the text is predominantly using CJK characters with few non-CJK
excerpts and it is desired that the text be better distributed on each
line.
‘keep-all’
Implicit soft wrap opportunities between letters are suppressed, i.e.
breaks are prohibited between pairs of letters (including those
explicitly allowed by ‘line-break’) except where opportunities exist due
to dictionary-based breaking. Otherwise this option is equivalent to
‘normal’. In this style, sequences of CJK characters do not break.
This is sometimes seen in Korean (which uses spaces between words), and
is also useful for mixed-script text where CJK snippets are mixed into
another language that uses spaces for separation.

Symbols that line-break the same way as letters of a particular category
are affected the same way as those letters.

Here's a mixed-script sample text:

这是一些汉字, and some Latin, و کمی نوشتنن عربی, และตัวอย่างการเขียนภาษาไทย.
The break-points are determined as follows (indicated by ‘·’):

‘word-break: normal’

这·是·一·些·汉·字,·and·some·Latin,·و·کمی·نوشتنن·عربی·และ·ตัวอย่าง·การเขียน·ภาษาไทย.
‘word-break: break-all’

这·是·一·些·汉·字,·a·n·d·s·o·m·e·L·a·t·i·n,·و·ﮐ·ﻤ·ﻰ·ﻧ·ﻮ·ﺷ·ﺘ·ﻦ·ﻋ·ﺮ·ﺑ·ﻰ,·แ·ล·ะ·ตั·ว·อ·ย่·า·ง·ก·า·ร·เ·ขี·ย·น·ภ·า·ษ·า·ไ·ท·ย.
‘word-break: keep-all’
这是一些汉字,·and·some·Latin,·و·کمی·نوشتنن·عربی,·และตัวอย่างการเขียนภาษาไทย.
When shaping scripts such as Arabic are allowed to break within words
due to ‘break-all’, the characters must still be shaped as if the word
were not broken.

6. Breaking Within Words

Hyphenation allows the controlled splitting of words to improve the
layout of paragraphs, typically splitting words at syllabic or morphemic
boundaries and visually indicating the split (usually by inserting a
hyphen, U+2010). In some cases, hyphenation may also alter the spelling
of a word. Regardless, hyphenation is a rendering effect only: it must
have no effect on the underlying document content or on text selection
or searching.

Hyphenation occurs when the line breaks at a valid hyphenation
opportunity, which creates a soft wrap opportunity within the word. In
CSS it is controlled with the ‘hyphens’ property. CSS Text Level 3 does
not define the exact rules for hyphenation, however UAs are strongly
encouraged to optimize their line-breaking implementation to choose good
break points and appropriate hyphenation points. Hyphenation
opportunities are considered when calculating ‘min-content’ intrinsic
sizes.

CSS also provides the ‘overflow-wrap’ property, which can allow
arbitrary breaking within words when the text would otherwise overflow
its container.

6.1. Hyphenation Control: the ‘hyphens’ property

Name: hyphens
Value: none | manual | auto
Initial: manual
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value
Animatable: no
Canonical order: N/A
This property controls whether hyphenation is allowed to create more
soft wrap opportunities within a line of text. Values have the following
meanings:

‘none’
Words are not hyphenated, even if characters inside the word explicitly
define hyphenation opportunities.
‘manual’
Words are only hyphenated where there are characters inside the word
that explicitly suggest hyphenation opportunities.
In Unicode, U+00AD is a conditional "soft hyphen" and U+2010 is an
unconditional hyphen. Unicode Standard Annex #14 describes the role of
soft hyphens in Unicode line breaking. [UAX14] In HTML, ­ represents
the soft hyphen character which suggests a hyphenation opportunity.

ex­ample
‘auto’
Words may be broken at appropriate hyphenation points either as
determined by hyphenation characters inside the word or as determined
automatically by a language-appropriate hyphenation resource.
Conditional hyphenation characters inside a word, if present, take
priority over automatic resources when determining hyphenation
opportunities within the word.
Correct automatic hyphenation requires a hyphenation resource
appropriate to the language of the text being broken. The UA is
therefore only required to automatically hyphenate text for which the
author has declared a language (e.g. via HTML lang or XML xml:lang) and
for which it has an appropriate hyphenation resource.

When shaping scripts such as Arabic are allowed to break within words
due to hyphenation, the characters must still be shaped as if the word
were not broken.

For example, if the word “نوشتنن” were hyphenated, it would appear as
“ﻧﻮﺷ-ﺘﻦ” not as “ﻧﻮﺵ-ﺗﻦ”.

6.2. Overflow Wrapping: the ‘word-wrap’/‘overflow-wrap’ property

Name: overflow-wrap/word-wrap
Value: normal | break-word
Initial: normal
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value
Animatable: no
Canonical order: N/A
This property specifies whether the UA may arbitrarily break within a
word to prevent overflow when an otherwise-unbreakable string is too
long to fit within the line box. It only has an effect when
‘white-space’ allows wrapping. Possible values:

‘normal’
Lines may break only at allowed break points. However, the restrictions
introduced by ‘word-break: keep-all’ may be relaxed to match
‘word-break: normal’ if there are no otherwise-acceptable break points
in the line.
‘break-word’
An unbreakable "word" may be broken at an arbitrary point if there are
no otherwise-acceptable break points in the line. Shaping characters are
still shaped as if the word were not broken, and grapheme clusters must
together stay as one unit. No hyphenation character is inserted at the
break point.
Soft wrap opportunities introduced by ‘overflow-wrap: break-word’ are
not considered when calculating ‘min-content’ intrinsic sizes.

For legacy reasons, UAs must treat ‘word-wrap’ as an alternate name for
the ‘overflow-wrap’ property, as if it were a shorthand of
‘overflow-wrap’.

7. Alignment and Justification

Alignment and justification controls how inline content is distributed
within a line box.

There's a proposal for ‘text-align’ to become a shorthand for
‘text-align-last’ and ‘text-align-all’. This has the advantage that
‘text-align-last’ can be set in a single declaration with ‘text-align’,
e.g. ‘text-align: justify-all’ (justify align all lines) or ‘text-align:
justify center’ (justify all lines except center last line). It has the
disadvantage of creating the ‘text-align-all’ property. There are also
some cascading considerations: if ‘text-align-last’ is part of the
shorthand, then any declaration of ‘text-align’ will reset it; it's
unclear if this is an advantage or a disadvantage.

The CSSWG has no strong opinion on this issue, and solicits feedback
from others. We unfortunately can't drop ‘text-align-last’ in favor of
an expanded value set in ‘text-align’ because of existing content and
implementations. However, because authors have a pattern of typing
‘text-align-last’ after ‘text-align’, we can change their interaction
without breaking content.

7.1. Text Alignment: the ‘text-align’ property

Name: text-align
Value: start | end | left | right | center | justify | match-parent |
start end
Initial: start
Applies to: block containers
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value, except for ‘match-parent’ which
computes as defined below
Animatable: no
Canonical order: N/A
This property describes how the inline-level content of a block is
aligned along the inline axis if the content does not completely fill
the line box. Values have the following meanings:

‘start’
Inline-level content is aligned to the start edge of the line box.
‘end’
Inline-level content is aligned to the end edge of the line box.
‘left’
Inline-level content is aligned to the line left edge of the line box.
(In vertical writing modes, this will be either the physical top or
bottom, depending on ‘text-orientation’.) [CSS3-WRITING-MODES]
‘right’
Inline-level content is aligned to the line right edge of the line box.
(In vertical writing modes, this will be either the physical top or
bottom, depending on ‘text-orientation’.) [CSS3-WRITING-MODES]
‘center’
Inline-level content is centered within the line box.
‘justify’
Text is justified according to the method specified by the
‘text-justify’ property, in order to exactly fill the line box.
‘match-parent’
This value behaves the same as ‘inherit’ (computes to its parent's
computed value) except that an inherited ‘start’ or ‘end’ keyword is
interpreted against its parent's ‘direction’ value and results in a
computed value of either ‘left’ or ‘right’.
‘start end’
Specifies ‘start’ alignment of the first line and any line immediately
after a forced line break; and ‘end’ alignment of any remaining lines.
This value will be removed at the end of the LC period unless someone
comes up with a more understandable keyword to replace it with.

A block of text is a stack of line boxes. This property specifies how
the inline-level boxes within each line box align with respect to the
start and end sides of the line box. Alignment is not with respect to
the viewport or containing block.

In the case of ‘justify’, the UA may stretch or shrink any inline boxes
by adjusting their text. (See ‘text-justify’.) If an element's white
space is not collapsible, then the UA is not required to adjust its text
for the purpose of justification and may instead treat the text as
having no expansion opportunities. If the UA chooses to adjust the text,
then it must ensure that tab stops continue to line up as required by
the white space processing rules.

If (after justification, if any) the inline contents of a line box are
too long to fit within it, then the contents are start-aligned: any
content that doesn't fit overflows the line box's end edge.

See Bidirectionality and line boxes for details on how to determine the
start and end edges of a line box.

7.2. Last Line Alignment: the ‘text-align-last’ property

Name: text-align-last
Value: auto | start | end | left | right | center | justify
Initial: auto
Applies to: block containers
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value
Animatable: no
Canonical order: N/A
This property describes how the last line of a block or a line right
before a forced line break is aligned when ‘text-align’ is ‘justify’. If
a line is also the first line of the block or the first line after a
forced line break, then, unless ‘text-align’ assigns an explicit first
line alignment (via ‘start end’), ‘text-align-last’ takes precedence
over ‘text-align’.

If ‘auto’ is specified, content on the affected line is aligned per
‘text-align’ unless ‘text-align’ is set to ‘justify’. In this case,
content is justified if ‘text-justify’ is ‘distribute’ and start-aligned
otherwise. All other values have the same meanings as in ‘text-align’.

7.3. Justification Method: the ‘text-justify’ property

Name: text-justify
Value: auto | none | inter-word | distribute
Initial: auto
Applies to: block containers and, optionally, inline elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: specified value
Animatable: no
Canonical order: N/A
This property selects the justification method used when a line's
alignment is set to ‘justify’ (see ‘text-align’). The property applies
to block containers, but the UA may (but is not required to) also
support it on inline elements. It takes the following values:

‘auto’
The UA determines the justification algorithm to follow, based on a
balance between performance and adequate presentation quality.
One possible algorithm is to choose the appropriate justification
behavior based on the language of the paragraph e.g. following [JLREQ]
for Japanese, using cursive elongation for Arabic, using ‘inter-word’
for English, etc. Another possibility is to use a justification method
that is a simple universal compromise for all writing systems, such as
primarily expanding word separators along with secondarily expanding
between CJK and Southeast Asian letters.

Two lines of calligraphic Arabic end together due to a mix of compressed
and swash forms.
An example of cursively-justified Arabic text rendered by Tasmeem.

Extra space is partly to spaces and partly among CJK and Thai letters.
Mixed-script text with ‘text-justify: auto’: this interpretation uses a
universal-compromise justification method, expanding at spaces as well
as between CJK and Southeast Asian letters.

‘none’
Justification is disabled: there are no expansion opportunities within
the text.
This value is intended for use in user stylesheets to improve
readability or for accessibility purposes.

‘inter-word’
Justification adjusts spacing at word separators only (effectively
varying the used ‘word-spacing’ on the line). This behavior is typical
for languages that separate words using spaces, like English or Korean.
Extra space is equally distributed mainly to spaces.
Mixed-script text with ‘text-justify: inter-word’

‘distribute’
Justification adjusts spacing between each pair of adjacent characters
(effectively varying the used ‘letter-spacing’ on the line). This value
is sometimes used in e.g. Japanese.
Extra space is equally distributed at points between spaces and letters
of all writing systems.
Mixed-script text with ‘text-justify: distribute’

The exact justification algorithm is UA-dependent; however, CSS provides
some general guidelines.

7.3.1. Expanding and Compressing Text

When justifying text, the user agent takes the remaining space between
the ends of a line's contents and the edges of its line box, and
distributes that space throughout its contents so that the contents
exactly fill the line box. The user agent may alternatively distribute
negative space, putting more content on the line than would otherwise
fit under normal spacing conditions.

An expansion opportunity is a point where the justification algorithm
may alter spacing within the text. An expansion opportunity can be
provided by a single character (such as a word separator), or by the
juxtaposition of two characters. Space distributed by justification is
in addition to the spacing defined by the ‘letter-spacing’ or
‘word-spacing’ properties. However, when space is distributed to a word
separator expansion opportunity, it is applied under the same rules as
for ‘word-spacing’. Similarly, when space is distributed an expansion
opportunity between two characters, it is applied under the same rules
as for ‘letter-spacing’.

A justification algorithm may divide expansion opportunities into
different priority levels. All expansion opportunities within a given
level are expanded or compressed at the same priority, regardless of
which characters created that opportunity. For example, if expansion
opportunities between two Han characters and between two Latin letters
are defined to be at the same level (as they are in the ‘distribute’
justification style), they are not treated differently because they
originate from different characters. It is not defined in this level
whether or how other factors (such as font size, letter-spacing, glyph
shape, position within the line, etc.) may influence the distribution of
space to expansion opportunities within the line.

7.3.2. Handling Symbols and Punctuation

When determining expansion opportunities, characters from the Unicode
Symbols (S*) and Punctuation (P*) classes are generally treated the same
as a letter: in the case of ‘inter-word’, as a Latin letter; in the case
of ‘distribute’, as a Han letter; and in the case of ‘auto’, as a letter
of the dominant script.

However, by typographic tradition there may be additional rules
controlling the justification of symbols and punctuation. Therefore, the
UA may reassign specific characters or introduce additional levels of
prioritization to handle expansion opportunities involving symbols and
punctuation.

For example, there are traditionally no expansion opportunities between
consecutive EM DASH U+2014, HORIZONTAL BAR U+2015, HORIZONTAL ELLIPSIS
U+2026, or TWO DOT LEADER U+2025 characters [JLREQ]; thus a UA might
assign these characters to a “never” prioritization level. As another
example, certain fullwidth punctuation characters are considered to
contain an expansion opportunity in Japanese. The UA might therefore
assign these characters to a higher prioritization level than the
opportunities between ideographic characters.

7.3.3. Unexpandable Text

If the inline contents of a line cannot be stretched to the full width
of the line box, then they must be aligned as specified by the
‘text-align-last’ property. (If ‘text-align-last’ is ‘justify’, then
they must be aligned as for ‘center’ if ‘text-justify’ is ‘distribute’,
and as ‘start’ otherwise.)

7.3.4. Cursive Scripts

Justification must not introduce gaps between letters of cursive scripts
such as Arabic. If it is able, the UA may translate space distributed to
expansion opportunities within a run of such letters into some form of
cursive elongation for that run. It otherwise must assume that no
expansion opportunity exists between any pair of cursive script letters.

7.3.5. Possible Algorithms

The guidelines in this level of CSS do not describe a complete
justification algorithm. They are merely a minimum set of requirements
that a complete algorithm should meet. Limiting the set of requirements
gives UAs some latitude in choosing a justification algorithm that meets
their needs and desired balance of quality, speed, and complexity.

For instance, a basic but fast justification algorithm might use a
simple greedy method for determining line breaks, then distribute
leftover space. This algorithm could follow the guidelines by expanding
word spaces first, expanding between letters only if the spaces between
words hit a limit defined by the UA.

A more sophisticated but slower justification algorithm might use a
Knuth/Plass method where expansion opportunities and limits were
assigned weights and assessed with other line breaking considerations.
This algorithm could follow the guidelines by giving more weight to word
separators than letter spacing.

A UA can also tailor its justification rules by language, to produce
results more closely aligned to the typography of that language. For
example, it's not defined whether expansion or compression is preferred,
so a UA may, for example, bias towards compression for CJK languages but
towards expansion for Western alphabetic languages.

As another example, 3.8 Line Adjustment in [JLREQ] gives an example of a
set of rules for how a text formatter can justify Japanese text. A UA
could use this algorithm when the ‘text-justify’ property is ‘auto’.
However, since the rules described in the document specifically target
Japanese, they may produce non-optimal results when used to justify
other languages such as English. The UA could adapt the rules to
accommodate other scripts by, for instance, omitting the rule to
compress half-width spaces (rule a. of 3.8.3). Or it could keep the
rule, but only enable it when the content language is known to be
Japanese.

The UA may enable or break optional ligatures or use other font features
such as alternate glyphs or glyph compression to help justify the text
under any method. This behavior is not controlled by this level of CSS.
However, UAs must not break required ligatures or otherwise disable
features required to correctly shape complex scripts.

8. Spacing

CSS offers control over text spacing via the ‘word-spacing’ and
‘letter-spacing’ properties, which specify additional space around word
separators or between characters, respectively. The ‘word-spacing’
property can now be specified in percentages, making it possible to, for
example, double or eliminate word spacing.

In the following example, word spacing is halved, but may expand if
needed for text justification.

p { word-spacing: -50%; }
8.1. Word Spacing: the ‘word-spacing’ property

Name: word-spacing
Value: [ normal | | ]
Initial: normal
Applies to: all elements
Inherited: yes
Percentages: refers to width of the affected glyph
Media: visual
Computed value: an absolute length
Animatable: as length, percentage, or calc
Canonical order: N/A
This property specifies additional spacing between “words”. Missing
values are assumed to be ‘normal’. Values are interpreted as defined
below:

‘normal’
No additional spacing is applied. Computes to zero.
‘’
Specifies extra spacing in addition to the intrinsic inter-word spacing
defined by the font. Values may be negative, but there may be
implementation-dependent limits.
‘’
Specifies the additional spacing as a percentage of the affected
character's advance measure.
Additional spacing is applied to each word separator left in the text
after the white space processing rules have been applied, and should be
applied half on each side of the character unless otherwise dictated by
typographic tradition.

The following example will make all the spaces between words in Arabic
be rendered as zero-width, and double the width of each space in
English:

:lang(ar) { word-spacing: -100%; }
:lang(en) { word-spacing: 100%; }
The following example will add half the the width of the “0” glyph to
word spacing character [CSS3VAL]:

p { word-spacing: 0.5ch; }
Word-separator characters include the space (U+0020), the no-break space
(U+00A0), the Ethiopic word space (U+1361), the Aegean word separators
(U+10100,U+10101), the Ugaritic word divider (U+1039F), and the
Phoenician Word Separator (U+1091F). If there are no word-separator
characters, or if a word-separating character has a zero advance width
(such as the zero width space U+200B) then the user agent must not
create an additional spacing between words. General punctuation and
fixed-width spaces (such as U+3000 and U+2000 through U+200A) are not
considered word-separator characters.

8.2. Tracking: the ‘letter-spacing’ property

Name: letter-spacing
Value: normal |
Initial: normal
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: an absolute length
Animatable: as length
Canonical order: N/A
This property specifies additional spacing between adjacent characters
(commonly called tracking). Letter-spacing is applied after bidi
reordering and is in addition to any ‘word-spacing’. Depending on the
justification rules in effect, user agents may further increase or
decrease the space between characters in order to justify text.

Values have the following meanings:

‘normal’
No additional spacing is applied. Computes to zero.
‘’
Specifies additional spacing between characters. Values may be negative,
but there may be implementation-dependent limits.
For the purpose of ‘letter-spacing’, each consecutive run of atomic
inlines (such as images and inline blocks) is treated as a single
character.

Letter-spacing must not be applied at the beginning or at the end of a
line.

Because letter-spacing is not applied at the beginning or end of a line,
text always fits flush with the edge of the block.

p { letter-spacing: 1em; }

abc

a b c

a b c

UAs therefore must not append letter spacing to the right or trailing
edge of a line:

a b c

Letter spacing between two characters effectively “belongs” to the
innermost element element that contains the two characters: the total
letter spacing between two adjacent characters (after bidi reordering)
is specified by and rendered within the innermost element that contains
the boundary between the two characters.

A given value of ‘letter-spacing’ only affects the spacing between
characters completely contained within the element for which it is
specified:

p { letter-spacing: 1em; }
span { letter-spacing: 2em; }

abbc

a b  b c

This also means that applying ‘letter-spacing’ to an element containing
only a single character has no effect on the rendered result:

p { letter-spacing: 1em; }
span { letter-spacing: 2em; }

abc

a b c

An inline box only includes letter spacing between characters completely
contained within that element:

p { letter-spacing: 1em; }

abbc

a b b c

It is incorrect to include the letter spacing on the right or trailing
edge of the element:

a b b c

Letter spacing is inserted after RTL reordering, so the letter spacing
applied to the inner span below has no effect, since after reordering
the ‘c’ doesn't end up next to ‘א’:

p { letter-spacing: 1em; }
span { letter-spacing: 2em; }

abcאבג

a b c א ב ג

Letter-spacing ignores zero-width characters (such as those from the
Unicode Cf category).

For example, ‘letter-spacing’ applied to A&zwsp;B is identical to AB,
regardless of where any element boundaries might fall.

When the effective letter-spacing between two characters is not zero
(due to either justification or non-zero computed ‘letter-spacing’),
user agents should not apply optional ligatures.

For example, if the word “filial” is letter-spaced, an “fi” ligature
should not be used as it will prevent even spacing of the text.

If it is able, the UA may apply letter-spacing to cursive scripts by
translating the total spacing distributed to a run of such letters into
some form of cursive elongation for that run. Otherwise, if the UA
cannot expand text from a cursive script without breaking its cursive
connections, it must not apply spacing between any pair of that script's
letters at all.

9. Edge Effects

Edge effects control the indentation of lines with respect to other
lines in the block (‘text-indent’) and how content is measured at the
start and end edges of a line (‘hanging-punctuation’).

9.1. First Line Indentation: the ‘text-indent’ property

Name: text-indent
Value: [ | ] && hanging? && each-line?
Initial: 0
Applies to: block containers
Inherited: yes
Percentages: refers to width of containing block
Media: visual
Computed value: the percentage as specified or the absolute length, plus
any keywords as specified
Animatable: as length, percentage, or calc, but only if keywords match
Canonical order: per grammar
This property specifies the indentation applied to lines of inline
content in a block. The indent is treated as a margin applied to the
start edge of the line box. Unless otherwise specified via the
‘each-line’ and/or ‘hanging’ keywords, only lines that are the first
formatted line of an element are affected. For example, the first line
of an anonymous block box is only affected if it is the first child of
its parent element.

Values have the following meanings:

‘’
Gives the amount of the indent as an absolute length.
‘’
Gives the amount of the indent as a percentage of the containing block's
logical width.
‘each-line’
Indentation affects the first line of the block container as well as
each line after a forced line break, but does not affect lines after a
soft wrap break.
‘hanging’
Inverts which lines are affected.
If ‘text-align’ is ‘start’ and ‘text-indent’ is ‘5em’ in left-to-right
text with no floats present, then first line of text will start 5em into
the block:

Since CSS1 it has been possible
to indent the first line of a block
element using the 'text-indent'
property.
Note that since the ‘text-indent’ property inherits, when specified on a
block element, it will affect descendant inline-block elements. For this
reason, it is often wise to specify ‘text-indent: 0’ on elements that
are specified ‘display: inline-block’.

9.2. Hanging Punctuation: the ‘hanging-punctuation’ property

Name: hanging-punctuation
Value: none | [ first || [ force-end | allow-end ] || last ]
Initial: none
Applies to: inline elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: as specified
Animatable:> no
Canonical order: per grammar
This property determines whether a punctuation mark, if one is present,
hangs and may be placed outside the line box (or in the indent) at the
start or at the end of a line of text.

Note that if there is not sufficient padding on the block container,
‘hanging-punctuation’ can trigger overflow.

When a punctuation mark hangs, it is not considered when measuring the
line's contents for fit, alignment, or justification. Depending on the
line's alignment, this may (or may not) result in the mark being placed
outside the line box.

Values have the following meanings:

‘none’
No character hangs.
‘first’
An opening bracket or quote at the start of the first formatted line of
an element hangs. This applies to all characters in the Unicode
categories Ps, Pf, Pi.
‘last’
A closing bracket or quote at the end of the last formatted line of an
element hangs. This applies to all characters in the Unicode categories
Pe, Pf, Pi.
‘force-end’
A stop or comma at the end of a line hangs.
‘allow-end’
A stop or comma at the end of a line hangs if it does not otherwise fit
prior to justification.
Non-zero start and end borders/padding between a hangeable mark and the
edge of the line prevent the mark from hanging. For example, a period at
the end of an inline box with end padding does not hang at the end edge
of a line. At most one punctuation character may hang at each edge of
the line.

A hanging punctuation mark is still enclosed inside its inline box and
participates in text justification: its character advance width is just
not measured when determining how much content fits on the line, how
much the line's contents need to be expanded or compressed for
justification, or how to position the content within the line box for
text alignment.

Stops and commas allowed to hang include:

U+002C , COMMA
U+002E . FULL STOP
U+060C ، ARABIC COMMA
U+06D4 ۔ ARABIC FULL STOP
U+3001 、 IDEOGRAPHIC COMMA
U+3002 。 IDEOGRAPHIC FULL STOP
U+FF0C ， FULLWIDTH COMMA
U+FF0E ． FULLWIDTH FULL STOP
U+FE50 ﹐ SMALL COMMA
U+FE51 ﹑ SMALL IDEOGRAPHIC COMMA
U+FE52 ﹒ SMALL FULL STOP
U+FF61 ｡ HALFWIDTH IDEOGRAPHIC FULL STOP
U+FF64 ､ HALFWIDTH IDEOGRAPHIC COMMA
The UA may include other characters as appropriate.

The CSS Working Group would appreciate if UAs including other characters
would inform the working group of such additions.

The ‘allow-end’ and ‘force-end’ are two variations of hanging
punctuation used in East Asia.

hanging-punctuation: allow-end
p {
text-align: justify;
hanging-punctuation: allow-end;
}
hanging-punctuation: force-end
p {
text-align: justify;
hanging-punctuation: force-end;
}
The punctuation at the end of the first line for ‘allow-end’ does not
hang, because it fits without hanging. However, if ‘force-end’ is used,
it is forced to hang. The justification measures the line without the
hanging punctuation. Therefore when the line is expanded, the
punctuation is pushed outside the line.

9.3. Bidirectionality and Line Boxes

The start and end edges of a line box are determined by the inline base
direction of the line box. In most cases, this is given by its
containing block's computed ‘direction’.

However if its containing block has ‘unicode-bidi: plaintext’
[CSS3-WRITING-MODES], the line box's inline base direction must be
determined by the base direction of the bidi paragraph to which it
belongs: that is, the bidi paragraph for which the line box holds
content. An empty line box (i.e. one that contains no atomic inlines or
characters other than the line-breaking character, if any), takes its
inline base direction from the preceding line box (if any), or, if this
is the first line box in the containing block, then from the ‘direction’
property of the containing block.

In the following example, assuming the is a preformatted block
(‘display: block; white-space: pre’) inheriting ‘text-align: start’,
every other line is right-aligned:

Latin
و·کمی
Latin
و·کمی
Latin
و·کمی

Note that the inline base direction determined here applies to the line
box itself, and not to its contents. It affects ‘text-align’,
‘text-align-last’, ‘text-indent’, and ‘hanging-punctuation’, i.e. the
position and alignment of its contents with respect to its edges. It
does not affect the formatting or ordering of its content.

In the following example:

שלום!

", he said.

The result should be a left-aligned line looking like this:

"!שלום", he said.
The line is left-aligned (despite the containing block having
‘direction: rtl’) because the containing block (the ) has
‘unicode-bidi:plaintext’, and the line box belongs to a bidi paragraph
that is LTR. This is because that paragraph's first character with a
strong direction is the LTR "h" from "he". The RTL "שלום!" does precede
the "he", but it sits in its own bidi-isolated paragraph that is not
immediately contained by the , and is thus irrelevent to the line
box's alignment. From from the standpoint of the bidi paragraph
immediately contained by the containing block, the

’s
bidi-isolated paragraph inside it is, by definition, just a neutral
U+FFFC character, so the immediately-contained paragraph becomes LTR by
virtue of the "he" following it.

Hello!

As expected, the "Hello!" should be displayed LTR (i.e. with the
exclamation mark on the right end, despite the ’s
‘direction:rtl’) and left-aligned. This makes the empty line following
it left-aligned as well, which means that the caret on that line should
appear at its left edge. The first empty line, on the other hand, should
be right-aligned, due to the RTL direction of its containing paragraph,
the <textarea>.

Appendix A: Text Processing Order of Operations

The following list defines the order of text operations.
(Implementations are not bound to this order as long as the resulting
layout is the same.)

white space processing part I (pre-wrapping)
text transformation
text combination
text orientation [CSS3-WRITING-MODES]
text wrapping while applying per line:
indentation
bidirectional reordering [CSS21] / [CSS3-WRITING-MODES]
white space processing part II
‘letter-spacing’ and ‘word-spacing’
font/glyph selection and positioning [CSS21] / [CSS3-FONTS]
hanging punctuation
justification (which may affect glyph selection and/or text wrapping,
looping back into that step)
text alignment
Appendix B: Default UA Stylesheet

This appendix is informative, and is to help UA developers to implement
default stylesheet, but UA developers are free to ignore or change.

/* make list items and option elements align together */
li, option { text-align: match-parent; }
If you find any issues, recommendations to add, or corrections, please
send the information to www-style@w3.org with [css3-text] in the subject
line.

Appendix C: Cursive Scripts

This appendix is normative.

The following scripts in Unicode 6 are considered to be cursive scripts,
and do not admit expansion opportunities between their letters: Arabic,
Mandaic, Mongolian, N'Ko, Phags Pa, Syriac

User agents should update this list as they update their Unicode support
to handle as-yet-unencoded cursive scripts in future versions of
Unicode, and are encourage to request the CSSWG to update this spec
accordingly.

Acknowledgements

This specification would not have been possible without the help from:
Ayman Aldahleh, Bert Bos, Tantek Çelik, James Clark, Stephen Deach, John
Daggett, Martin Dürst, Laurie Anna Edlund, Ben Errez, Yaniv Feinberg,
Arye Gittelman, Ian Hickson, Martin Heijdra, Richard Ishida, Masayasu
Ishikawa, Michael Jochimsen, Eric LeVine, Ambrose Li, Håkon Wium Lie,
Chris Lilley, Ken Lunde, Nat McCully, Shinyu Murakami, Paul Nelson,
Chris Pratley, Marcin Sawicki, Arnold Schrijver, Rahul Sonnad, Alan
Stearns, Michel Suignard, Takao Suzuki, Frank Tang, Chris Thrasher, Etan
Wexler, Chris Wilson, Masafumi Yabe and Steve Zilles.

Changes

Changes from the November 2012 CSS3 Text WD

Major changes include:

Changed ‘text-align-last’ to depend on ‘text-align: justify’.
Removed ‘inter-ideograph’, ‘inter-cluster’, and ‘kashida’ values of
‘text-justify’.
Changed ‘text-justify: inter-word’ to prohibit justification between
letters.
Dropped minimum and maximum values in ‘letter-spacing’ and
‘word-spacing’.
Removed <string> value of ‘text-align’.
Changed the character list of ‘line-break’.
Changed orders of white space processing, text combination and text
orientation, ‘letter-spacing’, and ‘word-spacing’ of the Text Processing
Order of Operations.
Changed the definition of word separator characters.
Changed to allow ‘letter-spacing’ to justify.
Changed the computed value of ‘normal’ value of ‘letter-spacing’ and
‘word-spacing’.
Changed the grammer rule of ‘text-indent’.
Significant details updated:

Clarified ‘start end’ and ‘match-parent’ value of ‘text-align’.
Clarified ‘none’ value of ‘text-justify’.
Clarified expanding and compressing text for ‘text-justify’.
Clarified the behavior of ‘letter-spacing’.
Clarified the behavior of ‘text-align’ for too long lines.
Clarified the interaction of ‘word-break’ and ‘line-break’.
Conformance

Document Conventions

Conformance requirements are expressed with a combination of descriptive
assertions and RFC 2119 terminology. The key words “MUST”, “MUST NOT”,
“REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”,
“MAY”, and “OPTIONAL” in the normative parts of this document are to be
interpreted as described in RFC 2119. However, for readability, these
words do not appear in all uppercase letters in this specification.

All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes. [RFC2119]

Examples in this specification are introduced with the words “for
example” or are set apart from the normative text with class="example",
like this:

This is an example of an informative example.

Informative notes begin with the word “Note” and are set apart from the
normative text with class="note", like this:

Note, this is an informative note.

Conformance Classes

Conformance to CSS Text Level 3 is defined for three conformance
classes:

style sheet
A CSS style sheet.
renderer
A UA that interprets the semantics of a style sheet and renders
documents that use them.
authoring tool
A UA that writes a style sheet.
A style sheet is conformant to CSS Text Level 3 if all of its
declarations that use properties defined in this module have values that
are valid according to the generic CSS grammar and the individual
grammars of each property as given in this module.

A renderer is conformant to CSS Text Level 3 if, in addition to
interpreting the style sheet as defined by the appropriate
specifications, it supports all the features defined by CSS Text Level 3
by parsing them correctly and rendering the document accordingly.
However, the inability of a UA to correctly render a document due to
limitations of the device does not make the UA non-conformant. (For
example, a UA is not required to render color on a monochrome monitor.)

An authoring tool is conformant to CSS Text Level 3 if it writes style
sheets that are syntactically correct according to the generic CSS
grammar and the individual grammars of each feature in this module, and
meet all other conformance requirements of style sheets as described in
this module.

Partial Implementations

So that authors can exploit the forward-compatible parsing rules to
assign fallback values, CSS renderers must treat as invalid (and ignore
as appropriate) any at-rules, properties, property values, keywords, and
other syntactic constructs for which they have no usable level of
support. In particular, user agents must not selectively ignore
unsupported component values and honor supported values in a single
multi-value property declaration: if any value is considered invalid (as
unsupported values must be), CSS requires that the entire declaration be
ignored.

Experimental Implementations

To avoid clashes with future CSS features, the CSS2.1 specification
reserves a prefixed syntax for proprietary and experimental extensions
to CSS.

Prior to a specification reaching the Candidate Recommendation stage in
the W3C process, all implementations of a CSS feature are considered
experimental. The CSS Working Group recommends that implementations use
a vendor-prefixed syntax for such features, including those in W3C
Working Drafts. This avoids incompatibilities with future changes in the
draft.

Non-Experimental Implementations

Once a specification reaches the Candidate Recommendation stage,
non-experimental implementations are possible, and implementors should
release an unprefixed implementation of any CR-level feature they can
demonstrate to be correctly implemented according to spec.

To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS Working
Group.

Further information on submitting testcases and implementation reports
can be found from on the CSS Working Group's website at
http://www.w3.org/Style/CSS/Test/. Questions should be directed to the
public-css-testsuite@w3.org mailing list.

CR Exit Criteria

For this specification to be advanced to Proposed Recommendation, there
must be at least two independent, interoperable implementations of each
feature. Each feature may be implemented by a different set of products,
there is no requirement that all features be implemented by a single
product. For the purposes of this criterion, we define the following
terms:

independent
each implementation must be developed by a different party and cannot
share, reuse, or derive from code used by another qualifying
implementation. Sections of code that have no bearing on the
implementation of this specification are exempt from this requirement.
interoperable
passing the respective test case(s) in the official CSS test suite, or,
if the implementation is not a Web browser, an equivalent test. Every
relevant test in the test suite should have an equivalent test created
if such a user agent (UA) is to be used to claim interoperability. In
addition if such a UA is to be used to claim interoperability, then
there must one or more additional UAs which can also pass those
equivalent tests in the same way for the purpose of interoperability.
The equivalent tests must be made publicly available for the purposes of
peer review.
implementation
a user agent which: implements the specification. is available to the
general public. The implementation may be a shipping product or other
publicly available version (i.e., beta version, preview release, or
“nightly build”). Non-shipping product releases must have implemented
the feature(s) for a period of at least one month in order to
demonstrate stability. is not experimental (i.e., a version specifically
designed to pass the test suite and is not intended for normal usage
going forward).
The specification will remain Candidate Recommendation for at least six
months.

References

Normative references

[CSS21]
Bert Bos; et al. Cascading Style Sheets Level 2 Revision 1 (CSS 2.1)
Specification. 7 June 2011. W3C Recommendation. URL:
http://www.w3.org/TR/2011/REC-CSS2-20110607
[CSS3-FONTS]
John Daggett. CSS Fonts Module Level 3. 3 October 2013. W3C Candidate
Recommendation. (Work in progress.) URL:
http://www.w3.org/TR/2013/CR-css-fonts-3-20131003/
[CSS3-WRITING-MODES]
Elika J. Etemad; Koji Ishii. CSS Writing Modes Module Level 3. 15
November 2012. W3C Working Draft. (Work in progress.) URL:
http://www.w3.org/TR/2012/WD-css3-writing-modes-20121115/
[RFC2119]
S. Bradner. Key words for use in RFCs to Indicate Requirement Levels.
Internet RFC 2119. URL: http://www.ietf.org/rfc/rfc2119.txt
[UAX11]
Asmus Freytag. East Asian Width. 17 January 2012. Unicode Standard Annex
#11. URL: http://www.unicode.org/reports/tr11/
[UAX14]
Asmus Freytag. Line Breaking Properties. 17 January 2012. Unicode
Standard Annex #14. URL: http://www.unicode.org/unicode/reports/tr14/
[UAX29]
Mark Davis. Unicode Text Segmentation. 12 September 2012. Unicode
Standard Annex #29. URL: http://www.unicode.org/reports/tr29/
[UAX44]
Mark Davis; Ken Whistler. Unicode Character Database. 23 January 2012.
Unicode Standard Annex #44. URL: http://www.unicode.org/reports/tr44/
[UNICODE]
The Unicode Consortium. The Unicode Standard. 2012. Defined by: The
Unicode Standard, Version 6.2.0 (Mountain View, CA: The Unicode
Consortium, 2012. ISBN 978-1-936213-07-8), as updated from time to time
by the publication of new versions URL:
http://www.unicode.org/standard/versions/enumeratedversions.html
Informative references

[CSS-COUNTER-STYLES-3]
Tab Atkins Jr. CSS Counter Styles Level 3. 21 February 2013. W3C Working
Draft. (Work in progress.) URL:
http://www.w3.org/TR/2013/WD-css-counter-styles-3-20130221/
[CSS3-TEXT-DECOR]
Elika J. Etemad; Koji Ishii. CSS Text Decoration Module Level 3. 1
August 2013. W3C Candidate Recommendation. (Work in progress.) URL:
http://www.w3.org/TR/2013/CR-css-text-decor-3-20130801/
[CSS3VAL]
Håkon Wium Lie; Tab Atkins; Elika J. Etemad. CSS Values and Units Module
Level 3. 30 July 2013. W3C Candidate Recommendation. (Work in progress.)
URL: http://www.w3.org/TR/2013/CR-css3-values-20130730/
[HTML5]
Robin Berjon; et al. HTML5. 6 August 2013. W3C Candidate Recommendation.
(Work in progress.) URL: http://www.w3.org/TR/2013/CR-html5-20130806/
[JIS4051]
Formatting rules for Japanese documents (『日本語文書の組版方法』). Japanese
Standards Association. 2004. JIS X 4051:2004. In Japanese
[JLREQ]
Yasuhiro Anan; et al. Requirements for Japanese Text Layout. 3 April
2012. W3C Working Group Note. URL:
http://www.w3.org/TR/2012/NOTE-jlreq-20120403/
[XML10]
C. M. Sperberg-McQueen; et al. Extensible Markup Language (XML) 1.0
(Fifth Edition). 26 November 2008. W3C Recommendation. URL:
http://www.w3.org/TR/2008/REC-xml-20081126/
[ZHMARK]
标点符号用法 (Punctuation Mark Usage). 1995. 中华人民共和国国家标准
Index

allow-end
hanging-punctuation, 9.2.
authoring tool, ??
auto
hyphens, 6.1.
line-break, 5.2.
text-align-last, 7.2.
text-justify, 7.3.
break-all
word-break, 5.3.
break-word
overflow-wrap, 6.2.
capitalize
text-transform, 2.1.
center
text-align, 7.1.
character, 1.3.
collapsible, 4.1.1.
content language, 1.3.
cursive script, ??
distribute
text-justify, 7.3.
each-line
text-indent, 9.1.
end
text-align, 7.1.
expansion opportunity, 7.3.1.
first
hanging-punctuation, 9.2.
forced line break, 5.
force-end
hanging-punctuation, 9.2.
full-width
text-transform, 2.1.
grapheme cluster, 1.3.
hang, 9.2.
hanging
text-indent, 9.1.
hanging-punctuation, 9.2.
hyphenate, 6.
hyphenation, 6.
hyphenation opportunity, 6.
hyphens, 6.1.
inter-word
text-justify, 7.3.
justify
text-align, 7.1.
keep-all
word-break, 5.3.
last
hanging-punctuation, 9.2.
left
text-align, 7.1.
<length>
text-indent, 9.1., 9.1.
word-spacing, 8.1., 8.2.
letter, 1.3.
letter-spacing, 8.2.
line break, 5.
line-break, 5.2.
line breaking, 5.
loose
line-break, 5.2.
lowercase
text-transform, 2.1.
manual
hyphens, 6.1.
match-parent
text-align, 7.1.
none
hanging-punctuation, 9.2.
hyphens, 6.1.
text-justify, 7.3.
text-transform, 2.1.
normal
line-break, 5.2.
overflow-wrap, 6.2.
white-space, 3.
word-break, 5.3.
word-spacing, 8.1., 8.2.
nowrap
white-space, 3.
overflow-wrap, 6.2.
<percentage>
word-spacing, 8.1.
pre
white-space, 3.
pre-line
white-space, 3.
preserved, 4.1.3.
pre-wrap
white-space, 3.
renderer, ??
right
text-align, 7.1.
segment break, 4.
soft wrap break, 5.
soft wrap opportunity, 5.
start
text-align, 7.1.
start end
text-align, 7.1.
stop or comma, 9.2.
strict
line-break, 5.2.
style sheet
as conformance class, ??
tab-size, 4.2.
tab stop, 4.1.3.
text-align, 7.1.
text-align-last, 7.2.
text-indent, 9.1.
text-justify, 7.3.
text-transform, 2.1.
tracking, 8.2.
uppercase
text-transform, 2.1.
white-space, 3.
word-break, 5.3.
word separator, 8.1.
word-separator character, 8.1.
word-spacing, 8.1.
word-wrap, 6.2.
wrap, 5.
wrapping, 5.
Property Index

Property Values Initial Applies to Inh. Percentages Media
hanging-punctuation none | [ first || [ force-end | allow-end ] || last
] none inline elements yes N/A visual
hyphens none | manual | auto manual all elements yes N/A visual
letter-spacing normal | <length> normal all elements yes N/A visual
line-break auto | loose | normal | strict auto all elements yes N/A
visual
overflow-wrap normal | break-word normal all elements yes N/A visual
tab-size <integer> | <length> 8 block containers yes N/A visual
text-align start | end | left | right | center | justify | match-parent
| start end start block containers yes N/A visual
text-align-last auto | start | end | left | right | center | justify
auto block containers yes N/A visual
text-indent [ <length> | <percentage> ] && hanging? && each-line? 0
block containers yes refers to width of containing block visual
text-justify auto | none | inter-word | distribute auto block containers
and, optionally, inline elements yes N/A visual
text-transform none | capitalize | uppercase | lowercase | full-width
none all elements yes N/A visual
white-space normal | pre | nowrap | pre-wrap | pre-line normal all
elements yes N/A visual
word-break normal | keep-all | break-all normal all elements yes N/A
visual
word-spacing [ normal | <length> | <percentage>] normal all elements yes
refers to width of the affected glyph visual
word-wrap normal | break-word normal all elements yes N/A visual