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 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.
Feedback on this draft should be posted to the (archived) public
mailing list [email protected] (see instructions) with
[css3-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.
The following features are at risk and may be cut from the spec during
its CR period if there are no (correct) implementations:
This draft describes features that are specific to certain
scripts. There is an ongoing discussion about where these features belong:
in existing CSS properties, in new CSS properties, or perhaps in other
specifications.
Text decoration
has moved to CSS Text Decoration Module Level 3 [CSS3-TEXT-DECOR].
1.1. Module Interactions
This module 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 [CSS3COLOR],
when combined with this module, expands the definition of the
<color> 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
allowed by Unicode. 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.
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 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 "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 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 <wide> or the
<narrow> tag in their Decomposition_Mapping in [UAX44]. For the <narrow> tag,
the mapping is from the code point to the decomposition (minus
<narrow> tag), and for the <wide> tag, the mapping is from the
decomposition (minus the <wide> 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.
The following example converts the ASCII characters in abbreviations in
Japanese to their fullwidth variants so that they lay out and line break
like ideographs:
abbr:lang(ja) { text-transform: full-width; }
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 [CSS3LIST].
3. White Space and
Wrapping: the ‘white-space’ property
This property specifies two things:
whether and how white space
inside the element is collapsed
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
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.
There have been requests for the ability to "discard" white
space; the current definition has no facility for this.
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.
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.
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.
Any space immediately following another collapsible space —even
one outside the boundary of the inline containing the space, provided
they are 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.
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
‘text-wrap’ set to ‘normal’ 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.
4.1.1. Example of
bidirectionality with white space collapsing
Consider the following markup fragment, taking special note of spaces
(with varied backgrounds and borders for emphasis and identification):
<ltr>A<rtl>B</rtl>C</ltr>
where the <ltr> element represents a left-to-right
embedding and the <rtl> element represents a
right-to-left embedding. If the ‘text-space-collapse’ property is set to ‘collapse’, the above 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:
ABC
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. Line 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).
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.
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.
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
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.
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 recommend that:
Following breaks be forbidden in ‘strict’
line breaking and allowed in ‘normal’ and
‘loose’:
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.
Support for this property is optional. It is recommended for
UAs that wish to support CJK typography and strongly recommended for UAs
in the Japanese market.
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
This property specifies soft wrap
opportunities between letters. 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 (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 ‘·’):
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. Hyphenation
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 with a hyphen). Hyphenation
occurs when the line breaks at a valid hyphenation opportunity, which creates a
soft wrap opportunity within
the word.
Hyphenation in CSS 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.
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”.
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 not
part of ‘overflow-wrap: normal’ line breaking
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’.
[ [ start | end | left | right | center ] || <string> ] |
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’ (see prose)
This property describes how inline contents of a block are aligned along
the inline axis if the contents do not completely fill the line box.
Values have the following meanings:
‘start’
The inline contents are aligned to the start edge of the line box.
‘end’
The inline contents are aligned to the end edge of the line box.
‘left’
The inline contents are aligned to the line left
edge of the line box. (Note that in vertical writing modes, this will be
either the physical top or bottom.) [CSS3-WRITING-MODES]
‘right’
The inline contents are aligned to the line right
edge of the line box. (Note that in vertical writing modes, this will be
either the physical top or bottom.) [CSS3-WRITING-MODES]
‘center’
The inline contents are centered within the line box.
‘justify’
The text is justified according to the method specified by the ‘text-justify’ property.
The string must be a single character;
otherwise the declaration must be ignored. When
applied to a table cell, specifies the alignment character around which the cell's
contents will align. See below for
further details and how this value combines with keywords.
‘match-parent’
This value behaves the same as ‘inherit’ except that an inherited ‘start’ or ‘end’
keyword is calculated 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 not affected by
‘text-align-last’.
A block of text is a stack of line boxes. In
the case of ‘start’, ‘end’, ‘left’,
‘right’ and ‘center’, 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 in addition to shifting
their positions. (See also ‘text-justify’, ‘letter-spacing’,
and ‘word-spacing’.) 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.
7.1.1. 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 inline base direction the line box 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 <block> is a
preformatted block (‘display: block; white-space:
pre’) inheriting ‘text-align: start’,
every other line is right-aligned:
<block style="unicode-bidi: plaintext">
Latin
و·کمی
Latin
و·کمی
Latin
و·کمی
</block>
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.
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
<para>) 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
<para>, and is thus irrelevent to the line box's
alignment. From from the standpoint of the bidi paragraph immediately
contained by the <para> containing block, the
<quote>’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.
As expected, the "Hello!" should be displayed LTR (i.e. with the
exclamation mark on the right end, despite the
<textarea>‘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>.
7.1.2. Character-based
Alignment in a Table Column
When multiple cells in a column have an alignment character specified, the
alignment character of each such cell in the column is centered along a
single column-parallel axis and the rest of the text in the column shifted
accordingly. (Note that the strings do not have to be the same for each
cell, although they usually are.)
The following style sheet:
TD { text-align: "." center }
will cause the column of dollar figures in the following HTML table:
A keyword value may be specified in conjunction with the <string>
value; if it is not given, it defaults to ’‘right’‘. This value is used:
when character-based alignment is applied to boxes that are not table
cells.
when the text wraps to multiple lines (at unforced break points).
when a character-aligned cell spans more than one column. In this case
the keyword alignment value is used to determine which column’s axis to
align with: the leftmost column for ‘left’,
the rightmost column for ‘right’ and ‘center’, the startmost column for ‘start’, the endmost column for ‘end’.
when the column is wide enough that the character alignment alone does
not determine the positions of its character-aligned contents. In this
case the keyword alignment of the first cell in the column with a
specified alignment character is used to slide the position of the
character-aligned contents to match the keyword alignment insofar as
possible without changing the width of the column. For ‘center’, the UA may center the aligned contents using
its extremes, center the alignment axis itself (insofar as possible), or
optically center the aligned contents some other way (such as by taking a
weighted average of the extent of the cells' contents to either side of
the axis).
Right alignment is used by default for character-based
alignment because numbering systems are almost all left-to-right even in
right-to-left writing systems, and the primary use case of character-based
alignment is for numerical alignment.
If the alignment character appears more than once in the text, the first
instance is used for alignment. If the alignment character does not appear
in a cell at all, the string is aligned as if the alignment character had
been inserted at the end of its contents.
Character-based alignment occurs before table cell width computation so
that auto width computations can leave enough space for alignment. Whether
column-spanning cells participate in the alignment prior to or after width
computation is undefined. If width constraints on the cell contents
prevent full alignment throughout the column, the resulting alignment is
undefined.
auto | start | end | left | right | center | justify
Initial:
auto
Applies to:
block containers
Inherited:
yes
Percentages:
N/A
Media:
visual
Computed value:
specified value
This property describes how the last line of a block or a line right
before a forced line break is
aligned. 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
This property selects the justification method used when a line's
alignment is set to ‘justify’ (see ‘text-align’),
primarily by controlling which scripts' characters are adjusted together
or separately. 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:
Values of ‘text-justify’: ‘inter-word’, ‘inter-cluster’, ‘inter-ideograph’, and ‘distribute’
One possible example of rendering for ‘text-justify’:
‘kashida’
‘auto’
The UA determines the justification algorithm to follow, based on a
balance between performance and adequate presentation quality.
One possible algorithm is to determine the behavior based
on the language of the paragraph: the UA can then choose appropriate
value for the language, like ‘inter-ideograph’ for CJK, or ‘inter-word’ for English. Another possibility is to
use a justification method that is a universal compromise for all
scripts, e.g. the ‘inter-cluster’ method with
block scripts raised to first priority.
‘none’
Justification is disabled. This value is intended for
use in user stylesheets to improve readability or for accessibility
purposes.
‘inter-word’
Justification primarily changes spacing at word separators. This value
is typically used for languages that separate words using spaces, like
English or Korean.
‘inter-ideograph’
Justification primarily changes spacing at word separators and between
characters in block scripts. This value is
typically used for CJK
languages.
‘inter-cluster’
Justification primarily changes spacing at word separators and between
characters in clustered scripts. This
value is typically used for Southeast Asian scripts such as Thai.
‘distribute’
Justification primarily changes spacing both at word separators and
between characters in all scripts equally (except those in the connected
and cursive categories). This value is sometimes used in e.g. Japanese.
‘kashida’
Justification primarily stretches cursive
scripts through the use of kashida or other calligraphic elongation.
This value is optional for conformance to CSS3 Text. (UAs that
do not support cursive elongation must treat the value as
invalid.)
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. If the ‘letter-spacing’ and ‘word-spacing’
property values allow it, the user agent may also distribute negative
space, putting more content on the line than would otherwise fit under
normal spacing conditions. The exact justification algorithm is
UA-dependent; however, CSS provides some general guidelines which should
be followed when any justification method other than ‘auto’ is specified.
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.
For instance, a basic but fast ‘inter-word’
justification algorithm might use a simple greedy method for determining
line breaks, then distribute leftover space using the spacing limits provided. This algorithm could follow
the guidelines by expanding word spaces first, expanding between letters
only if ‘word-spacing’ hit a limit.
A more sophisticated but slower ‘inter-word’
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 spaces than letter spacing.
CSS defines expansion opportunities as points
where the justification algorithm may alter spacing within the text. These
expansion opportunities fall
into priority levels as defined by the justification method. Within a
line, expansion and compression should primarily target the first-priority
expansion opportunities; lower priority expansion opportunities are
adjusted at a lower priority as needed.
Expansion and compression limits are given by the letter-spacing and word-spacing properties. How any remaining space
is distributed once all expansion
opportunities reach their limits is up to the UA. 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.)
The expansion opportunity
priorities for values of ‘text-justify’ are given in the table below.
Since justification behavior varies by writing system, expansion opportunities are
organized by script categories. An expansion opportunity exists
between two letters at a priority level when
at least one of them belongs to a script category at that level and the
other does not belong to a higher priority level. All scripts in the same
priority level must be treated exactly the same. Word separators (spaces)
and other symbols and punctuation are treated specially, see below.
* The ‘auto’ column defined above is informative; it
suggests a prioritization that presents a universal compromise among
justification methods.
The spaces
category represents expansion
opportunities at word separators.
(See ‘word-spacing’.) Except when ‘text-justify’ is
‘distribute’, the UA may treat spaces
differently than other expansion
opportunities in the same priority, but must not change their
priority with respect to expansion
opportunities in other priority levels. For example, in Japanese
‘inter-ideograph’ justification (which treats
CJK characters at a higher priority than Latin characters), word spaces
traditionally have a higher priority than inter-CJK spacing, and the UA
may split the 1st-priority level to implement that. However the UA is not
allowed to drop either spaces or CJK characters to the same priority as
Latin characters.
The symbols
category represents the expansion
opportunity existing at or between any pair of characters from the
Unicode Symbols (S*) and Punctuation (P*) classes. The default
justification priority of these expansion opportunities is given
above. However, there may be additional rules controlling their
justification behavior due to typographic tradition. 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 the "never" prioritization level. As another
example, certain fullwidth punctuation characters are considered to
contain an expansion
opportunity (see ‘text-spacing’).
The UA might therefore assign these characters to a higher prioritization
level than the opportunities between ideographic characters.
For justification of cursive scripts, words may be expanded
through kashida elongation or other cursive expansion processes. Kashida
may be applied in discrete units or continuously, and the prioritization
of kashida opportunities is UA-dependent: for example, the UA may apply
more at the end of the line. The UA should not apply kashida to fonts for
which it is inappropriate. It may instead rely on other justification
methods that lengthen or shorten Arabic segments (e.g. by substituting in
swash forms or optional ligatures). Because elongation rules depend on the
typeface style, the UA should rely on on the font whenever possible rather
than inserting kashida based on a font-independent ruleset. The UA should
limit elongation so that, e.g. in multi-script lines a short stretch of
Arabic will not be forced to soak up too much of the extra space by
itself. If the UA does not support cursive elongation, then, as with
connected scripts, no expansion
opportunities exist between characters of these scripts.
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.
3.8 Line Adjustment in [JLREQ] gives an example of a set of
rules for how a text formatter can justify Japanese text. It describes
rules for cases where the ‘text-justify’ property is ‘inter-ideograph’ and the ‘text-spacing’ property does not specify ‘no-compress’.
It produces an effect similar to cases where the computed value of
‘text-spacing’ property does not specify
‘trim-end’ or ‘space-end’. If the UA wants to prohibit this behavior,
rule b. of 3.8.3 should be omitted.
Note that the rules described in the document specifically target
Japanese. Therefore they may produce non-optimal results when used to
justify other languages such as English. To make the rules more
applicable to other scripts, the UA could, for instance, omit the rule to
compress half-width spaces (rule a. of 3.8.3).
8. Spacing
CSS offers control over text spacing via the ‘word-spacing’ and
‘letter-spacing’ properties. While in CSS1 and
CSS2 these could only be ‘normal’ (justifiable)
or a fixed length, CSS3 can indicate range constraints to control
flexibility in justification. In addition 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 up to
its full amount if needed for text justification.
p { word-spacing: -50% 0%; }
The <spacing-limits> value type, which
represents optimum, minimum, and maximum spacing in ‘word-spacing’ and
‘letter-spacing’, is defined as
<spacing-limits> = [ normal | <length> | <percentage>]{1,3}
If three values are specified, they represent the optimum, minimum, and
maximum in that order. If only two values are specified, then the first
represents both the optimum and the minimum, and the second represents the
maximum. If just one value is specified, then it represents the optimum,
minimum, and maximum. The values are interpreted as defined below:
‘normal’
Specifies normal spacing as defined by the current font and/or the
user agent; see below. A ‘normal’ optimum spacing value computes to zero.
‘<length>’
Specifies extra spacing in addition to the intrinsic
inter-character/inter-word spacing defined by the font. Values may be
negative, but there may be implementation-dependent limits.
‘<percentage>’
Specifies the additional spacing as a percentage of the affected
character's advance measure. Only valid on ‘word-spacing’.
In the absence of justification the optimum spacing is be used. The text
justification process may alter the spacing from its optimum (see the ‘text-justify’
property, above) but must not violate the minimum spacing limit and should
also avoid exceeding the maximum. The UA may also use the difference
between the minimum/maximum limits and the optimum as input into a
weighting algorithm for justification.
The minimum is treated as a hard constraint: if the maximum is less than
the minimum, then the used it is set to the minimum. Likewise for the
optimum. Similarly if the maximum is less than the optimum, then the used
optimum is set to the used maximum.
Normal spacing: Although ‘normal’ minimum and maximum spacing limits are
UA-defined, they must be defined relative to the optimum so that the
limits increase and decrease with changes to the optimum spacing. Normal
limits may also vary according to the value of the ‘text-justify’
property, the element's language, some measure of the amount of text on a
line (e.g. block width divided by font size), and/or other factors.
an optimum, minimum, and maximum value, each consisting of either an
absolute length, a percentage, or the keyword ‘normal’
This property specifies the minimum, maximum, and optimal spacing
between “words”.
Additional spacing is applied to each word-separator character 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:
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), the Phoenician Word Separator (U+1091F), and the Tibetan tsek
(U+0F0B, U+0F0C). If there are no word-separator characters, or if the
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.
an optimum, minimum, and maximum value, each consisting of either an
absolute length or the keyword ‘normal’
This property specifies the minimum, maximum, and optimal spacing
between characters. Letter-spacing is
applied in addition to any word-spacing.
Letter-spacing must not be applied at the beginning or at the end of a
line. At element boundaries, the total letter spacing between two
characters is given by and rendered within the innermost element that
contains the boundary.
For the purpose of letter-spacing, each consecutive run of atomic
inlines (such as image and/or inline blocks) is treated as a single character.
For example, given the markup
<P>a<LS>b<Z>cd</Z><Y>ef</Y></LS>g</P>
and the style sheet
LS { letter-spacing: 1em; }
Z { letter-spacing: 0.3em; }
Y { letter-spacing: 0.4em; }
the spacing would be
a[0]b[1em]c[0.3em]d[1em]e[0.4em]f[0]g
UAs may apply letter-spacing to cursive scripts. In this case, UAs
should extend the space between disjoint characters as specified above
and extend the visible connection between cursively connected
characters by the same amount (rather than leaving a gap). The UA may use
glyph substitution or other font capabilities to spread out the letters.
If the UA cannot expand a cursive script without breaking the cursive
connections, it should not apply letter-spacing between characters of that
script at all.
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.
When the effective letter-spacing between two characters is not zero
(due to either justification or a non-zero
specified optimum), user agents should not apply optional ligatures.
9. Edge Effects
Edge effects control the indentation of lines with respect to other
lines in the block (‘text-indent’) and how content is aligned to
the start and end edges of a line (‘hanging-punctuation’).
9.1. First Line Indentation:
the ‘text-indent’ property
the percentage as specified or the absolute length, plus any
keywords as specified
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:
‘<length>’
Gives the amount of the indent as an absolute length.
‘<percentage>’
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’.
none | [ first || [ force-end | allow-end ] || last ]
Initial:
none
Applies to:
inline elements
Inherited:
yes
Percentages:
N/A
Media:
visual
Computed value:
as specified
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.
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.
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.
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.
Support for this property is optional. It is recommended for
UAs that wish to support CJK typography, particularly those in the
Japanese market.
The ‘allow-end’ and ‘force-end’ are two variations of hanging punctuation
used in East Asia.
p {
text-align: justify;
hanging-punctuation: allow-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.
10. Conformance
10.1. 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.
10.2. Conformance
Classes
Conformance to CSS Text Level 3 is defined for three conformance
classes:
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.
10.3. 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.
10.4. 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.
10.5. 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 [email protected]
mailing list.
10.6. 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.
Appendix A: Acknowledgements
This specification would not have been possible without the help from:
Ayman Aldahleh, Bert Bos, Tantek Çelik, 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, Michel Suignard, Takao
Suzuki, Frank Tang, Chris Thrasher, Etan Wexler, Chris Wilson, Masafumi
Yabe and Steve Zilles.
Shifted text decoration chapter to a separate Text Decoration module
[CSS3-TEXT-DECOR]
Significant details updated:
Shifted spaces higher in priority than clustered scripts for ‘inter-cluster’ value of ‘text-justify’.
Defined line breaking behavior for ruby and atomic inlines.
Added Korean to Chinese and Japanese in ‘line-break’ special
rules.
Added missing halfwidth codepoint to ‘line-break’ rules.
Appendix D: 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 [email protected] with
[css3-text] in the subject line.
Appendix E: Scripts and Spacing
This appendix is informative (non-normative).
Typographic behavior varies somewhat by language, but varies drastically
by writing system. This appendix categorizes some common scripts in
Unicode 6.0 according to their justification and spacing behavior.
Category descriptions are descriptive, not prescriptive; the determining
factor is the prioritization of expansion opportunities.
block scripts
CJK and by extension all Wide characters. (See [UAX11]) The following scripts are
included: Bopomofo, Han, Hangul, Hiragana, Katakana, Yi
clustered
scripts
Scripts that have discrete units but do not use spaces between words,
such as many Southeast Asian systems. The following scripts are included:
Javanese, Khmer, Lao, Myanmar, Thai, This list is
likely incomplete. What else fits here?
connected
scripts
Devanagari, Ogham, and other scripts that use spaces between words and
baseline connectors within words. By extension this category also
includes any other Indic scripts whose typographic behavior is similar to
Devanagari. The following scripts are included: Bengali, Brahmi,
Devanagari, Gujarati, Gurmukhi, Kannada, Malayalam, Oriya?, Ogham,
Tamil?, Telugu
cursive scripts
Arabic and similar inherently cursive scripts. The following scripts
are included: Arabic, Mongolian, N'Ko, Phags Pa, Syriac
discrete scripts
Scripts that use spaces or visible word-separating punctuation between
words and have discrete, unconnected (in print) units within words. The
following scripts are included: Armenian, Bamum?, Braille, Canadian
Aboriginal, Cherokee, Coptic, Cyrillic, Deseret, Ethiopic Greek, Hebrew,
Kharoshthi, Latin, Lisu, Osmanya, Shavian, Tifinagh, Vai?
UAs should treat unrecognized scripts as discrete.
This listing should ideally be exhaustive wrt Unicode.
Please send suggestions and corrections to the CSS
Working Group.
Guidelines for classification consider letter-spacing and
justification:
If the script is cursive and may expand cursively but must not space
between letters, it is cursive.
If the script primarily flexes word separators, it is either
discrete or connected. Discrete scripts can space
between letters. Connected scripts must not space between letters
(typically because that would break the connections or otherwise look
bad).
If the script primarily expands equally between its "letters" in
native typesettings, it is either block or clustered. The
exact classification depends on whether it always spaces when mixed with
CJK and sometimes stays together when mixed with Thai and related
scripts (block) or sometimes spaces when mixed with CJK and
always spaces with Thai (clustered).
Appendix F: Small Kana
Small Kana
A
I
U
E
O
ぁ U+3041
ぃ U+3043
ぅ U+3045
ぇ U+3047
ぉ U+3049
ゕ U+3095
ゖ U+3096
っ U+3063
ゃ U+3083
ゅ U+3085
ょ U+3087
ゎ U+308E
ァ U+30A1
ィ U+30A3
ゥ U+30A5
ェ U+30A7
ォ U+30A9
ヵ U+30F5
ㇰ U+31F0
ヶ U+30F6
ㇱ U+31F1
ㇲ U+31F2
ッ U+30C3
ㇳ U+31F3
ㇴ U+31F4
ㇵ U+31F5
ㇶ U+31F6
ㇷ U+31F7
ㇸ U+31F8
ㇹ U+31F9
ㇺ U+31FA
ャ U+30E3
ュ U+30E5
ョ U+30E7
ㇻ U+31FB
ㇼ U+31FC
ㇽ U+31FD
ㇾ U+31FE
ㇿ U+31FF
ヮ U+30EE
ｧ U+FF67
ｨ U+FF68
ｩ U+FF69
ｪ U+FF6A
ｫ U+FF6B
ｯ U+FF6F
ｬ U+FF6C
ｭ U+FF6D
ｮ U+FF6E
Appendix G:
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.)
