Copyright © 2011 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.
CSS3 Writing Modes defines CSS features to support for various international writing modes, such as left-to-right (e.g. Latin or Indic), right-to-left (e.g. Hebrew or Arabic), bidirectional (e.g. mixed Latin and Arabic) and vertical (e.g. Asian scripts).
Inherently bottom-to-top scripts are not handled in this version. See [UTN22] for an explanation of relevant issues.
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.
The (archived) public mailing list www-style@w3.org (see instructions) is preferred for discussion of this specification. When sending e-mail, please put the text “css3-writing-modes” in the subject, preferably like this: “[css3-writing-modes] …summary of comment…”
This document was produced by the CSS Working Group (part of the Style Activity).
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.
text-combine
’
property
CSS3 Writing Modes defines CSS features to support for various international writing modes, such as left-to-right (e.g. Latin or Indic), right-to-left (e.g. Hebrew or Arabic), bidirectional (e.g. mixed Latin and Arabic) and vertical (e.g. Asian scripts).
A writing mode in CSS is determined by the
‘writing-mode
’, ‘direction
’, and
‘text-orientation
’ properties. It is
defined primarily in terms of its inline base direction and block flow direction:
The inline base direction is the
primary direction in which content is ordered on a line and defines on
which sides the "start" and "end" of a line are. The ‘direction
’
property specifies the inline base direction of an element and, together
with the ‘unicode-bidi
’ property and the inherent
directionality of any text content, determines the ordering of
inline-level content within a line.
The block flow direction is the
direction in which block-level boxes stack and the direction in which line
boxes stack within a block container. The ‘writing-mode
’
property determines the block flow direction.
A horizontal writing mode is one with horizontal lines of text, i.e. a downward or upward block flow. A vertical writing mode is one with vertical lines of text, i.e. a leftward or rightward block flow.
These terms should not be confused with vertical block flow (which is a downward or upward block flow) and horizontal block flow (which is leftward or rightward block flow). To avoid confusion, the CSS specifications avoid this latter set of terms.
Writing systems typically have one or two native writing modes. Some examples are:
The ‘text-orientation
’ component of the writing
mode determines the line
orientation and the typesetting mode, and controls details
of text layout such as the glyph orientation.
See Unicode Technical Note #22 [UTN22] (HTML version) for a more in-depth introduction to writing modes and vertical text.
This module replaces and extends the ‘unicode-bidi
’
and ‘direction
’ features defined in [CSS21] sections 8.6
and 9.10.
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.
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.
While the characters in most scripts are written from left to right, certain scripts are written from right to left. In some documents, in particular those written with the Arabic or Hebrew script, and in some mixed-language contexts, text in a single (visually displayed) block may appear with mixed directionality. This phenomenon is called bidirectionality, or "bidi" for short.
با Unicode بنویس.
<----- ------> <-
<================
Bidirectionality
The Unicode standard (Unicode Standard Annex #9)
defines a complex algorithm for determining the proper ordering of
bidirectional text. The algorithm consists of an implicit part based on
character properties, as well as explicit controls for embeddings and
overrides. CSS relies on this algorithm to achieve proper bidirectional
rendering. The ‘direction
’
and ‘unicode-bidi
’ properties allow
authors to specify how the elements and attributes of a document language
map to this algorithm.
User agents that support bidirectional text must apply the Unicode bidirectional algorithm to every sequence of inline boxes uninterrupted by a forced (bidi class B) paragraph break or block boundary. This sequence forms the paragraph unit in the bidirectional algorithm.
Except when the ‘plaintext
’ value of ‘unicode-bidi
’
is in effect, the paragraph embedding level is set according to the value
of the ‘direction
’ property of the paragraph's
element rather than by the heuristic given in steps P2 and P3 of the
Unicode algorithm. The paragraph's element is usually the containing
block, but in the case of a paragraph contained by bidi isolation it is the isolating inline element instead.
Because the base directionality of a text depends on the structure and
semantics of the document, the ‘direction
’ and ‘unicode-bidi
’
properties should in most cases be used only to map bidi information in
the markup to its corresponding CSS styles. If a document language
provides markup features to control bidi, authors and users should use
those features and not specify CSS rules to override them.
The HTML 4 specification ([HTML401], section 8.2) defines bidirectionality behavior for HTML elements. The HTML 4 specification also contains more information on bidirectionality issues.
Because HTML UAs can turn off CSS styling, we advise HTML
authors to use the HTML ‘dir
’
attribute and <bdo> element to ensure correct bidirectional layout
in the absence of a style sheet.
direction
’ propertyName: | direction |
---|---|
Value: | ltr | rtl |
Initial: | ltr |
Applies to: | all elements |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property specifies the base directionality of text and elements on
a line, and the directionality of embeddings and overrides (see ‘unicode-bidi
’)
for the Unicode bidirectional algorithm. In addition, it affects the
ordering of table
column layout, the direction of horizontal overflow, and
the default alignment of text within a line, and other things that depend
on the base inline base direction.
Values for this property have the following meanings:
The ‘direction
’ property has no effect on bidi
reordering when specified on inline elements whose ‘unicode-bidi
’
property's value is ‘normal
’.
The value of the ‘direction
’ property on the root element is
also propagated to the initial containing block and, together with the
‘writing-mode
’ property, determines the
document's principal writing mode. (See below.)
Note that the ‘direction
’ property of the HTML BODY
element is not propagated to the viewport. That special behavior
only applies to the background and overflow properties.
The ‘direction
’ property, when specified for
table column elements, is not inherited by cells in the column since
columns are not the ancestors of the cells in the document tree. Thus, CSS
cannot easily capture the "dir" attribute inheritance rules described in
[HTML401],
section 11.3.2.1.
unicode-bidi
’ propertyName: | unicode-bidi |
---|---|
Value: | normal | embed | [ isolate || [ plaintext | bidi-override ] ] |
Initial: | normal |
Applies to: | all elements, but see prose |
Inherited: | no |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
Values for this property have the following meanings:
direction
’ property. Inside the element,
reordering is done implicitly. This corresponds to adding a LRE (U+202A),
for ‘direction: ltr
’, or RLE (U+202B),
for ‘direction: rtl
’, at the start of
the element and a PDF (U+202C) at the end of the element. This value has no effect on elements that are not
inline.
For the purposes of the Unicode bidirectional algorithm, the base
directionality of each bidi paragraph for which the element forms the
containing block is determined not by the element's computed ‘direction
’ as
usual, but by following rules P2 and P3 of the Unicode bidirectional
algorithm. For inline elements, this value is equivalent to ‘isolate
’.
direction
’
property; the implicit part of the bidirectional algorithm is ignored.
This corresponds to adding a LRO (U+202D), for ‘direction: ltr
’, or RLO (U+202E), for ‘direction: rtl
’, at the start of the element and a
PDF (U+202C) at the end of the element.
The final order of characters within in each bidi paragraph is the same as if the bidi control codes had been added as described above, markup had been stripped, and the resulting character sequence had been passed to an implementation of the Unicode bidirectional algorithm for plain text that produced the same line-breaks as the styled text.
In this process, replaced elements with ‘display:
inline
’ are treated as neutral characters, unless their
‘unicode-bidi
’ property has a value other
than ‘normal
’, in which case they are treated as
strong characters in the ‘direction
’ specified for the element. All
other atomic inline-level boxes are treated as neutral characters always.
If an inline element is broken around a bidi paragraph boundary (e.g. if split by a block or forced paragraph break), then the bidi control codes corresponding to the end of the element are added before the interruption and the codes corresponding to the start of the element are added after it. (In other words, any embedding levels or overrides started by the element are closed at the paragraph break and reopened on the other side of it.)
Because the Unicode algorithm has a limit of 61 levels of
embedding, care should be taken not to use ‘unicode-bidi
’ with a value other
than ‘normal
’ unless appropriate. In particular,
a value of ‘inherit
’ should be
used with extreme caution. However, for elements that are, in general,
intended to be displayed as blocks, a setting of ‘unicode-bidi: isolate
’ is preferred to keep the
element together in case display is changed to inline (see example below).
The following example shows an XML document with bidirectional text. It illustrates an important design principle: document language designers should take bidi into account both in the language proper (elements and attributes) and in any accompanying style sheets. The style sheets should be designed so that bidi rules are separate from other style rules, and such rules should not be overridden by other style sheets so that the document language's bidi behavior is preserved.
In this example, lowercase letters stand for inherently left-to-right characters and uppercase letters represent inherently right-to-left characters. The text stream is shown in logical backing store order.
<HEBREW>
<PAR>HEBREW1 HEBREW2 english3 HEBREW4 HEBREW5</PAR>
<PAR>HEBREW6 <EMPH>HEBREW7</EMPH> HEBREW8</PAR>
</HEBREW>
<ENGLISH>
<PAR>english9 english10 english11 HEBREW12 HEBREW13</PAR>
<PAR>english14 english15 english16</PAR>
<PAR>english17 <HE-QUO>HEBREW18 english19 HEBREW20</HE-QUO></PAR>
</ENGLISH>
Since this is arbitrary XML, the style sheet is responsible for setting the writing direction. This is the style sheet:
/* Rules for bidi */ HEBREW, HE-QUO {direction: rtl; unicode-bidi: embed;} ENGLISH {direction: ltr; unicode-bidi: embed;} /* Rules for presentation */ HEBREW, ENGLISH, PAR {display: block;} EMPH {font-weight: bold;}
The HEBREW element is a block with a right-to-left base direction, the ENGLISH element is a block with a left-to-right base direction. The PARs are blocks that inherit the base direction from their parents. Thus, the first two PARs are read starting at the top right, the final three are read starting at the top left. Please note that HEBREW and ENGLISH are chosen as element names for explicitness only; in general, element names should convey structure without reference to language.
The EMPH element is inline-level, and since its value for ‘unicode-bidi
’ is ‘normal
’ (the initial
value), it has no effect on the ordering of the text. The HE-QUO element,
on the other hand, creates an embedding.
The formatting of this text might look like this if the line length is long:
5WERBEH 4WERBEH english3 2WERBEH 1WERBEH 8WERBEH 7WERBEH 6WERBEH english9 english10 english11 13WERBEH 12WERBEH english14 english15 english16 english17 20WERBEH english19 18WERBEH
Note that the HE-QUO embedding causes HEBREW18 to be to the right of english19.
If lines have to be broken, it might be more like this:
2WERBEH 1WERBEH -EH 4WERBEH english3 5WERB -EH 7WERBEH 6WERBEH 8WERB english9 english10 en- glish11 12WERBEH 13WERBEH english14 english15 english16 english17 18WERBEH 20WERBEH english19
Because HEBREW18 must be read before english19, it is on the line above english19. Just breaking the long line from the earlier formatting would not have worked. Note also that the first syllable from english19 might have fit on the previous line, but hyphenation of left-to-right words in a right-to-left context, and vice versa, is usually suppressed to avoid having to display a hyphen in the middle of a line.
Since bidi reordering can split apart and reorder text that is logically contiguous, bidirectional text can cause an inline boxes to be split and reordered within a line.
Note that in order to be able to flow inline boxes in a uniform direction (either entirely left-to-right or entirely right-to-left), anonymous inline boxes may have to be created.
For each line box, UAs must take the inline boxes generated for each
element and render the margins, borders and padding in visual order (not
logical order). The start-most box on the
first line box in which the element appears has the start edge's margin, border, and padding; and the
end-most box on the last line box in which the element appears has the end edge's margin, border, and padding. For
example, in the ‘horizontal-tb
’ writing mode:
direction
’ property is ‘ltr
’, the left-most
generated box of the first line box in which the element appears has the
left margin, left border and left padding, and the right-most generated
box of the last line box in which the element appears has the right
padding, right border and right margin.
direction
’ property is ‘rtl
’, the right-most
generated box of the first line box in which the element appears has the
right padding, right border and right margin, and the left-most generated
box of the last line box in which the element appears has the left
margin, left border and left padding.
Analogous rules hold for vertical writing modes.
The box model here seems backwards when the element breaks across lines...
The ‘box-decoration-break
’ property can override
this behavior to draw box decorations on both sides of each box. [CSS3BG]
In addition to extensions to CSS2.1’s support for bidirectional text, this module introduces the rules and properties needed to support vertical text layout in CSS.
Unlike languages that use the Latin script which are primarily laid out horizontally, Asian languages such as Chinese and Japanese can be laid out vertically. The Japanese example below shows the same text laid out horizontally and vertically. In the horizontal case, text is read from left to right, top to bottom. For the vertical case, the text is read top to bottom, right to left. Indentation from the left edge in the left-to-right horizontal case translates to indentation from the top edge in the top-to-bottom vertical case.
Comparison of vertical and horizontal Japanese: iBunko application (iOS)
For Chinese and Japanese lines are ordered either right to left or top to bottom, while for Mongolian and Manchu lines are ordered left to right.
The change from horizontal to vertical writing can affect not just the layout, but also the typesetting. For example, the position of a punctuation mark within its spacing box can change from the horizontal to the vertical case, and in some cases alternate glyphs are used.
Vertical text that includes Latin script text or text from other scripts normally displayed horizontally can display that text in a number of ways. For example, Latin words can be rotated sideways, or each letter can be oriented upright:
Examples of Latin in vertical Japanese: Daijirin Viewer 1.4 (iOS)
In some special cases such as two-digit numbers in dates, text is fit compactly into a single vertical character box:
Mac Fan, December 2010, p.49
Layouts often involve a mixture of vertical and horizontal elements:
Mixture of vertical and horizontal elements
Vertical text layouts also need to handle bidirectional text layout; clockwise-rotated Arabic, for example, is laid out bottom-to-top.
writing-mode
’ propertyName: | writing-mode |
---|---|
Value: | horizontal-tb | vertical-rl | vertical-lr |
Initial: | horizontal-tb |
Applies to: | All elements except table row groups, table column groups, table rows, and table columns |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property sets the block flow direction. Possible values:
SVG1.1 [SVG11]
defines some additional values: ‘lr
’,
‘lr-tb
’, ‘rl
’, ‘rl-tb
’,
‘tb
’, and ‘tb-rl
’. These values are deprecated in any
context except SVG1 documents. Implementations that wish to support them
in the context of CSS must treat these values as follows:
SVG1 | CSS |
---|---|
lr | horizontal-tb |
lr-tb | |
rl | |
tb | vertical-rl |
tb-rl |
In SVG1.1, these values set the inline progression direction, in
other words, the direction the current text position advances each time a
glyph is added. This is a geometric process that happens after bidi reordering, and thus has no effect
on the interpretation of the ‘direction
’ property (which is independent
of ‘writing-mode
’). (See Relationship
with bidirectionality. [SVG11]) There are varying
interpretations on whether this process causes "writing-mode: rl" to
merely shift the text string or reverse the order of all glyphs in the
text.
The ‘writing-mode
’ property determines the
direction of block flow. This determines the progression of block-level
boxes in a block formatting context; the progression of line boxes in a
block container that contains inlines; and the progression of rows in a
table. By virtue of determining the stacking direction of line boxes, the
‘writing-mode
’ property also determines
whether line boxes and thus the writing mode is horizontal or vertical.
When set on the root element, the ‘writing-mode
’ property together with the
‘direction
’ property determines the principal writing mode of the document.
This writing mode is used, for example, to determine the default page
progression direction. (See [CSS3PAGE].) The ‘writing-mode
’
value of the root element is also propagated to the initial containing
block and sets the block flow direction of the initial block formatting
context.
Note that the ‘writing-mode
’ property of the HTML BODY
element is not propagated to the viewport. That special behavior
only applies to the background and overflow properties.
If an element has a different block flow direction than its containing block:
display
’ of ‘inline
’, its ‘display
’ computes to ‘inline-block
’. [CSS21]
display
’ of ‘run-in
’, its ‘display
’ computes to ‘block
’. [CSS21]
If such an element is a block container, then it establishes a new block formatting context.
The content of replaced elements do not rotate due to the writing mode: images, for example, remain upright. However replaced content involving text (such as MathML content or form elements) should match the replaced element's writing mode and line orientation if the UA supports such a vertical writing mode for the replaced content.
In the following example, two block elements (1 and 3) separated by an image (2) are presented in various flow writing modes.
Here is a diagram of horizontal writing mode (writing-mode:
horizontal-tb
):
Here is a diagram for the right-to-left vertical writing mode commonly
used in East Asia (writing-mode: vertical-rl
):
And finally, here is a diagram for the left-to-right vertical writing
mode used for Manchu and Mongolian (writing-mode:
vertical-lr
):
When different kinds of inline-level content are placed together on a
line, the baselines of the content and the settings of the ‘vertical-align
’ property control how they are
aligned in the transverse direction of the line box. This section
discusses what baselines are, how to find them, and how they are used
together with the ‘vertical-align
’
property to determine the alignment of inline-level content.
This section is non-normative.
A baseline is a line along the inline axis of a line box along which individual glyphs of text are aligned. Baselines guide the design of glyphs in a font (for example, the bottom of most alphabetic glyphs typically align with the alphabetic baseline), and they guide the alignment of glyphs from different fonts or font sizes when typesetting.
Different writing systems prefer different baseline tables.
Preferred baselines in various writing systems
A well-constructed font contains a baseline table, which indicates the position of one or more baselines within the font's design coordinate space. (The design coordinate space is scaled with the font size.)
In a well-designed mixed-script font, the glyphs are positioned in the coordinate space to harmonize with one another when typeset together. The baseline table is then constructed to match the shape of the glyphs, each baseline positioned to match the glyphs from its preferred scripts.
The baseline table is a property of the font, and the positions of the various baselines apply to all glyphs in the font.
Different baseline tables can be provided for alignment in horizontal and vertical text.
In this specification, only the following baselines are considered:
A future CSS module will deal with baselines in more detail and allow the choice of other dominant baselines and alignment options.
This section is non-normative.
The alphabetic baseline is listed as the romn baseline in TrueType/OpenType baseline tables. If missing, it can sometimes be computed from the ascender and descender metrics. If it cannot be computed from other metrics, it may be assumed to correspond to the zero coordinate.
For the ascender and descender metrics, it is recommended to use the sTypoAscender and sTypoDescender metrics from the font's OS/2 table. These should match the idtp and ideo baselines (respectively), which, if present, may be used instead. In the absence of these metrics, the Ascent and Descent metrics from the HHEA/VHEA table should be used. The Win metrics can be used as a fallback; however these are intended as clipping bounds and are not always appropriate for use as em box measurements.
If an atomic inline (such as an inline-block, inline-table, or replaced inline element) is not capable of providing its own baseline information, then the UA synthesizes a baseline table thus:
The dominant baseline is used in CSS for alignment in two cases:
Given following sample markup:
<p><span class="outer">Ap <span class="inner">ji</span></span></p>
And the following style rule:
span.inner { font-size: .75em; }
The baseline tables of the parent (.outer
) and the child
(.inner
) will not match up due to the font size
difference. Since the dominant baseline is the alphabetic baseline, the
child box is aligned to its parent by matching up their alphabetic
baselines.
Baseline alignment in this fashion is used with the following values
of ‘vertical-align
’: ‘baseline
’,
‘sub
’, ‘super
’, <length>, <percentage>. In
the latter cases, the baselines are aligned as for ‘baseline
’, but the
child is shifted according to the offset given by its ‘vertical-align
’ value.
If we assign ‘vertical-align:
super
’ to the .inner
element from the example
above, the same rules are used to align the .inner
child
to its parent; the only difference is in addition to the baseline
alignment, the child is shifted to the superscript position.
span.inner { vertical-align: super; font-size: .75em; }
Each writing system has one or more native orientations. Modern scripts can therefore be classified into three orientational categories:
In modern typographic systems, all glyphs are assigned a horizontal orientation, which is used when laying out text horizontally. To lay out vertical text, the UA needs to transform the text from its horizontal orientation. This transformation is the bi-orientational transform, and there are two types:
Scripts with a native vertical orientation have an intrinsic bi-orientational transform, which orients them correctly in vertical text: CJK (Chinese/Japanese/Korean) characters translate, that is, they are always upright. Other scripts, such as Mongolian, rotate. (See Appendix B for a list of intrinsic bi-orientational transforms.)
Scripts without a native vertical orientation can be either rotated (set
sideways) or translated (set upright): the transform used is a stylistic
preference depending on the text's usage, rather than a matter of
correctness. The ‘text-orientation
’ property's ‘vertical-right
’
and ‘upright
’
values are provided to specify rotation vs. translation of horizontal-only
text.
The ‘rotate-left
’, ‘rotate-right
’, and
‘rotate-normal
’ values of ‘text-orientation
’ are provided for
decorative layout effects and to work around limitations in CSS support
for bottom-to-top scripts.
Ideally, punctuation should be either sideways or upright
depending on whether the primary script is horizontal-only or vertical.
However, this information (which, like the base directionality, is a
property of the content) is not available to us. (UTN 22 used the concept
of a vertical directionality, given via ‘direction
’ or the HTML dir
attribute to handle this issue.) The current spec works around this by
using the East Asian Width property; but this approach only works if
vertical scripts do not share punctuation with horizontal-only scripts.
text-orientation
’ propertyName: | text-orientation |
---|---|
Value: | vertical-right | upright | rotate-right | rotate-left | rotate-normal | auto |
Initial: | vertical-right |
Applies to: | all elements except table row groups, rows, column groups, and columns |
Inherited: | yes |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property specifies the orientation of characters within a line and sets the orientation of the line. Current values only have an effect in vertical writing modes.
In this section only, the term character is defined as extended grapheme cluster per [UAX29]. It is roughly equivalent to what a language user considers to be a character or a basic unit of the script (which might not be a single Unicode codepoint). The UA may further tailor the definition as allowed by Unicode. The properties of a grapheme cluster are given by its base.
Values have the following meanings:
In vertical writing modes, characters from horizontal-only scripts are set sideways, i.e. 90° clockwise from their standard orientation in horizontal text. Characters from vertical scripts are set with their intrinsic orientation.
In vertical writing modes, this value puts the element in a vertical typographic mode and is typical for layout of primarily vertical-script text.
In vertical writing modes, characters from horizonal-only scripts are rendered upright, i.e. in their standard horizontal orientation. Shaping characters from such scripts are shaped in their isolated forms. Characters from vertical scripts are set with their intrinsic orientation and shaped normally. When available, vertical glyph variants and vertical font metrics are used to set the text. The UA must synthesize vertical font metrics for grapheme clusters that do not have any.
For the purposes of bidi reordering, this value causes all characters
to be treated as strong LTR. This value causes the used value of
‘direction
’ to be ‘ltr
’.
In vertical writing modes, this value puts the element in a vertical typographic mode.
In vertical writing modes, this causes text to be set as if in a horizontal layout (using horizontal glyph variants and metrics), but rotated 90° clockwise. This value puts the element in a horizontal typographic mode.
In vertical writing modes, this causes text to be set as if in a horizontal layout (using horizontal glyph variants and metrics), but rotated 90° counter-clockwise. This value puts the element in a horizontal typographic mode.
If set on a non-replaced inline whose parent is not ‘rotate-left
’, this
forces ‘isolate
’ to be added to the computed value of
‘unicode-bidi
’. Layout of text is exactly
as for ‘rotate-right
’ except that the text content
and baseline table of each of the element's inline boxes is mirrored
around a vertical axis along the center of its content box. The
positions of text decorations propagated from an ancestor inline
(including the block container's root inline) are not mirrored, but any
text decorations introduced by the element are positioned using the
mirrored baseline table.
Similarly, if an inline child of the element has a ‘text-orientation
’ value other than
‘rotate-left
’, an analogous transformation is
applied.
This value is equivalent to ‘rotate-right
’ in ‘vertical-rl
’
writing mode and equivalent to ‘rotate-left
’ in ‘vertical-lr
’
writing mode. It can be useful when setting horizontal script text
vertically in a primarily horizontal-only document.
[SVG11] defines
‘glyph-orientation-vertical
’ and
‘glyph-orientation-horizontal
’
properties that were intended to control text orientation. These
properties are deprecated and do not apply to non-SVG elements.
If an implementation supports these properties, the ‘auto
’ value when set on
SVG elements indicates that the SVG ‘glyph-orientation-vertical
’ and ‘glyph-orientation-horizontal
’ behavior
control the layout of text. Such UAs must set ‘text-orientation: auto
’ on all SVG
text content elements in their default UA style sheet for SVG.
In all other contexts, and for implementations that do not support the
glyph orientation properties, the ‘auto
’ behavior is the same as for ‘vertical-right
’.
text-orientation: vertical-right, upright, rotate-left, and rotate-right (writing-mode is vertical-rl)
In the following example, the root element of a horizontal-only
document is set to use ‘rotate-normal
’. In the rest of the document,
the author can just set ‘writing-mode
’ without worrying about
whether the text is ‘vertical-rl
’ or ‘vertical-lr
’.
:root { text-orientation: rotate-normal; } caption { caption-side: left; writing-mode: vertical-lr; } thead th { writing-mode: vertical-lr; } h1.banner { position: absolute; top: 0; right: 0; writing-mode: vertical-rl; }
In vertical typographic modes, any characters belonging to a vertical
script must be set using its base character's intrinsic
orientation. (See Appendix B.)
Characters belonging to horizontal-only scripts must set sideways (for
‘vertical-right
’) or set upright (for ‘upright
’) depending on
the ‘text-orientation
’ property.
The orientation of characters belonging to the Common, Inherited, and Unknown script categories may be UA- or font-dependent in vertical typographic modes:
If the font and font system support mixed-orientation typesetting, the
UA should rely on that feature to set ‘vertical-right
’
text. Similarly if the font and font system support upright typesetting
then the UA should rely on that feature to set ‘upright
’ text.
If the UA needs to synthesize such features (e.g. if an OpenType font
has only the vert
but not the vrt2
feature),
then the settings in Appendix
C are recommended.
[CSS21] defines
the box layout model of CSS in detail. However, it only defines the box
model for the ‘horizontal-tb
’ writing mode. CSS box layout in
writing modes other than ‘horizontal-tb
’ is analogous to the box layout
defined in CSS2.1 if directions and dimensions are abstracted and remapped
appropriately. This section defines abstract directional and dimensional
terms and their mappings in order to define box layout for other writing
modes, and to provide terminology for future specs to define their layout
concepts abstractly.
The terms left, right, top, and bottom are always interpreted physically, i.e. with respect to the page independent of writing mode. Two abstract mappings are possible for these directions: line-relative and flow-relative, which are defined below.
Although they derive from the behavior of text, these directional terms
exist even for boxes that do not contain any line boxes: they are
calculated directly from the values of the ‘writing-mode
’,
‘text-orientation
’, and ‘direction
’
properties.
Although the block flow direction given by ‘writing-mode
’
determines whether the line is oriented horizontally or vertically, it
doesn't say anything about how the contents within the line are arranged.
The line-relative directions are
over, under,
line-left, and line-right. The line orientation, which is given by a
combination of ‘text-orientation
’ and ‘writing-mode
’,
determines which side of the line is the "top" and thus which sides are
under (ascender side) and over
(descender side) the line. The line orientation also affects the
interpretation of alignment (‘vertical-align
’) in the transverse dimension
of the line.
In addition to its over and under sides, a line box, even a
vertically-oriented one, also has a "left" and "right" side, which we will
call the line-left and line-right sides of the box (as distinct
from the physical left and physical right sides of the box). The line-left edge of a box is nominally the edge from
which LTR text would start. The line-right edge of a box is nominally the edge from
which RTL text would start. Depending on
the ‘writing-mode
’ and ‘text-orientation
’ properties, the
line-left side of a box could be on the physical left, top, or bottom.
Note also that while the over and
under directions often map to the same
directions as before and after
respectively, this mapping is reversed for some combinations of ‘writing-mode
’
and ‘text-orientation
’.
The flow-relative directions are
before, after, start, and end. In an LTR ‘horizontal-tb
’ writing mode, they correspond to
the top, bottom, left, and right directions, respectively.
The before edge of a box is nominally the edge that
comes earlier in the block progression, as determined by the ‘writing-mode
’
property. Similarly the after edge is the edge that
comes later in the progression.
The start edge of a box is nominally the edge from
which text of its inline base direction will start. For boxes with a used
‘direction
’ value of ‘ltr
’, this means the line-left edge. For boxes with a used
‘direction
’ value of ‘rtl
’, this means the line-right edge. The edge opposite the start
edge is the end edge.
Note that while determining the before and after
edges of a box depends only on the ‘writing-mode
’ property, determining the start and end edges of
a box depends not only on the ‘writing-mode
’ property but also the
‘direction
’ and ‘text-orientation
’ properties.
An English (LTR-TB) block:
<----- width / measure -----> top side/ before side +------------------------------+ A left side/ | ---inline direction ---> | right side/ | start side | | | end side | | | block * horizontal * | height/ | | direction *writing mode* | extent | V | | +------------------------------+ V bottom side/ after side
A vertical Japanese block (TTB-RL):
<----- width / extent ------> top side/ start side +------------------------------+ A left side/ | <---block direction--- | right side/ | after side | | | before side | | * vertical * inline| | height/ | *writing mode* direction| | measure | V | | +------------------------------+ V bottom side/ end side
The following table summarizes the abstract-to-physical mappings:
‘writing-mode ’
| ‘horizontal-tb ’
| ‘vertical-rl ’
| ‘vertical-lr ’
| |||||||
---|---|---|---|---|---|---|---|---|---|---|
‘text-orientation ’
| — | ‘rotate-left ’
| *right | ‘rotate-left ’
| *right | |||||
‘direction ’
| ‘ltr ’
| ‘rtl ’
| ‘ltr ’
| ‘rtl ’
| ‘ltr ’
| ‘rtl ’
| ‘ltr ’
| ‘rtl ’
| ‘ltr ’
| ‘rtl ’
|
extent | height | width | ||||||||
measure | width | height | ||||||||
before | top | right | left | |||||||
after | bottom | left | right | |||||||
start | left | right | bottom | top | top | bottom | bottom | top | top | bottom |
end | right | left | top | bottom | bottom | top | top | bottom | bottom | top |
over | top | left | right | left | right | |||||
under | bottom | right | left | right | left | |||||
line-left | left | bottom | top | bottom | top | |||||
line-right | right | top | bottom | top | bottom |
CSS box layout in vertical writing modes is analogous to layout in the horizontal writing modes, following the principles outlined below:
Layout calculation rules (such as those in CSS2.1, Section 10.3) that apply to the horizontal dimension in horizontal writing modes instead apply to the vertical dimension in vertical writing modes. Likewise, layout calculation rules (such as those in CSS2.1, Section 10.6) that apply to the vertical dimension in horizontal writing modes instead apply to the horizontal dimension in vertical writing modes. Thus:
Layout rules that refer to the width use the height instead, and vice versa.
Layout rules that refer to the ‘*-left
’ and ‘*-right
’ box properties (border, margin, padding)
use ‘*-top
’ and ‘*-bottom
’ instead, and vice versa.
Which side of the box the property applies to doesn't
change: only which values are inputs to which layout calculations
changes. The ‘margin-left
’
property still affects the lefthand margin, for example; however in a
‘vertical-rl
’ writing mode it takes part in
margin collapsing in place of ‘margin-bottom
’.
Layout rules that depend on the ‘direction
’ property to choose between
left and right (e.g. overflow, overconstraint resolution, the initial
value for ‘text-align
’, table
column ordering) are abstracted to the start and end sides and applied appropriately.
For example, in vertical writing modes, table rows are vertical and
table columns are horizontal. In a ‘vertical-rl
’ ‘vertical-right
’
‘rtl
’ table, the
first column would be on the bottom (the start side), and the first row
on the right (the before side). The table's ‘margin-left
’ and ‘margin-right
’ would collapse with margins
before (on the left) and after (on the right) the table, respectively,
and if the table had ‘auto
’ values for ‘margin-top
’ and ‘margin-bottom
’ it would be centered
vertically within its block flow.
Table in ‘vertical-rl
’ RTL writing mode
For features such as text alignment, floating, and list marker positioning, that primarily reference the left or right sides of the line box or its longitudinal parallels and therefore have no top or bottom equivalent, the line left and line right sides are used as the reference for the left and right sides respectively.
Likewise for features such as underlining, overlining, and baseline
alignment (the unfortunately-named ‘vertical-align
’), that primarily reference the
top or bottom sides of the linebox or its transversal parallels and
therefore have no left or right equivalent, the over
and under sides are used as the reference for the top
and bottom sides respectively.
The details of these mappings are provided below.
Certain properties behave logically as follows:
border-spacing
’ property represent spacing
between columns and rows respectively, not necessarily the horizontal and
vertical spacing respectively. [CSS21]
line-height
’ property
always refers to the logical height. [CSS21]
The height properties (‘height
’,
‘min-height
’, and ‘max-height
’) refer to the physical height, and
the width properties (‘width
’,
‘min-width
’, and ‘max-width
’) refer to the physical width.
However, the rules used to calculate box dimensions and positions are
logical.
For example, the calculation rules in CSS2.1 Section 10.3 are used for the inline dimension measurements: they apply to the measure (which could be either the physical width or physical height) and to the the start and end margins, padding, and border. Likewise the calculation rules in CSS2.1 Section 10.6 are used in the block dimension: they apply to the extent and to the before and after margins, padding, and border. [CSS21]
As a corollary, percentages on the margin and padding properties, which are always calculated with respect to the containing block width in CSS2.1, are calculated with respect to the measure of the containing block in CSS3.
When an element has a different ‘writing-mode
’ from its containing block
two cases are possible:
vertical-rl
’ and ‘vertical-lr
’).
horizontal-tb
’ and ‘vertical-rl
’).
To handle the second case, CSS layout calculations are divided into two phases: sizing a box, and positioning the box within its flow. In the sizing phase—calculating the width and height of the box—the dimensions of the box and the containing block are mapped to the measure and extent and calculations performed accordingly using the writing mode of the element. In the positioning phase—calculating the positioning offsets, margins, borders, and padding—the dimensions of the box and its containing block are mapped to the measure and extent and calculations performed according to the writing mode of the containing block.
For example, if a vertical block is placed inside a horizontal block, then when calculating the physical height (which is the measure) of the child block the physical height of the parent block is used to calculate the measure of the child's containing block, even though the physical height is the extent, not the measure, of the parent block.
Since auto margins are resolved consistent with the containing block's writing mode, a box establishing an orthogonal flow, can, once sized, be aligned or centered within its containing block just like other block-level elements by using auto margins.
It is common in CSS for a containing block to have a defined measure,
but not a defined extent. This typically happens in CSS2.1 when a
containing block has an ‘auto
’ height, for example: its width is given
by the calculations in 10.3.3, but
its extent depends on its contents. In such cases the available measure is defined as the measure of
the containing block; but the available
extent, which would otherwise be the extent of the containing block,
is infinite.
Orthogonal flows allow the opposite to happen: for the available extent to be defined, but the available measure to be infinite. In such cases a percentage of the containing block measure cannot be defined, and thus the initial containing block's size is used instead as a fallback measure to calculate such percentages.
If the computed measure of an element establishing an orthogonal flow is
‘auto
’, then the
used measure is calculated as the fit-content (shrink-to-fit) size using the
initial containing block's size as the available measure.
If the UA supports CSS Multi-column Layout [CSS3COL], then for the case where
the element's extent or available extent is defined but the element's
measure is ‘auto
’:
column-count
’ and
‘column-width
’ are both ‘auto
’, a used ‘column-width
’ is calculated for the element
as the fill-available
measure using the fallback
measure as the available
measure.
The used measure of the resulting multi-column element is then calculated: if the content neither wraps nor paginates within the multi-column element, then the used measure is the max-content measure of the element's contents; else it is calculated from the used column width, column count, and column gap.
The used extent of the element is either the used column extent (if multiple columns were used) or the max-content extent of the content.
This should behave the same as the auto-sizing algorithm defined in the previous section, except overflowing content, instead of continuing off the side of the containing block, is wrapped into columns in the flow direction of the containing block, thus avoiding T-shaped documents.
This section is informative.
With regards to pagination, the rules in CSS2.1 still hold in vertical writing modes and orthogonal flows: page break opportunities do not occur inside line boxes, only between them. UAs that support [CSS3COL] may break in the (potentially zero-width) gap between columns, however.
Note that if content spills outside the pagination stream established by the root element, the UA is not required to print such content. Authors wishing to mix writing modes with long streams of text are thus encouraged to use CSS columns to keep all content flowing in the document's pagination direction.
In other words, if your document would require two scrollbars on the screen it probably won't all print. Fix your layout, e.g. by using columns so that it all scrolls (and therefore paginates) in one direction if you want to make sure it'll all print. T-shaped documents tend not to print well.
Flow-relative directions are calculated with respect to the writing mode
of the containing block of the element and used to abstract
layout rules related to the box properties (margins, borders, padding) and
any properties related to positioning the box within its containing block
(‘float
’, ‘clear
’, ‘top
’, ‘bottom
’, ‘left
’, ‘right
’) For inline-level elements, the
writing mode of the parent element is used instead.
For example, the margin that is dropped when a box's inline dimension is over-constrained is the end margin as determined by the writing mode of the containing block.
The margin collapsing rules apply exactly with the before margin substituted for the top margin and the after margin substituted for the bottom margin. Similarly the before padding and border are substituted for the top padding and border, and the after padding and border substituted for the bottom padding and border. Note this means only before and after margins ever collapse.
Flow-relative directions are calculated with respect to the writing mode of the element and used to abstract layout related to the element's contents:
text-align
’ property aligns to the start edge
of the line box.
text-indent
’ property
indents from the start edge of the line box.
The line-relative directions are
over, under, line-left, and line-right.
In an LTR ‘horizontal-tb
’
writing mode, they correspond to the top, bottom, left, and right
directions, respectively.
The line-right and line-left directions are calculated with respect to
the writing mode of the element and used to interpret the ‘left
’ and ‘right
’ values of the
following properties:
text-align
’ property [CSS21]
The line-right and line-left directions are calculated with respect to
the writing mode of the containing block of the element and used
to interpret the ‘left
’ and ‘right
’ values of the following properties:
The over and under directions are calculated with respect to the writing mode of the element and used to define the interpretation of the "top" (over edge) and "bottom" (under edge) of the line box as follows:
vertical-align
’
property, the "top" of the line box is the over edge; the "bottom" of the
line box is the under edge. Positive length and percentage values shift
the baseline towards the over edge. [CSS21]
text-decoration
’
property, the underline is drawn on the under side of the text; the
overline is drawn on the over side of the text. [CSS21] Note that
the CSS Text Module defines this in more detail and provides additional
controls for controlling the position of underlines and overlines. [CSS3TEXT]
The following values are purely physical in their definitions and do not respond to changes in writing mode:
rect()
’ notation of the
‘clip
’ property [CSS21]
box-shadow
’ and ‘text-shadow
’ properties
caption-side
’ keywordsProperty: | ‘caption-side ’
|
---|---|
New Values: | ‘before ’ |
‘after ’
|
Initial: | before |
Applies to: | same as CSS2.1 |
Inherited: | same as CSS2.1 |
Percentages: | same as CSS2.1 |
Media: | same as CSS2.1 |
Computed value: | specified value |
This module introduces two new values to the ‘caption-side
’ property: ‘before
’ and ‘after
’, which position the
caption before and after the table box, respectively. For tables with
‘horizontal-tb
’ writing mode, they are
equivalent to the existing ‘top
’ and ‘bottom
’ values, respectively. [CSS21]
For implementations that support the ‘top-outside
’ and ‘bottom-outside
’ model, corresponding
‘before-outside
’ and ‘after-outside
’ will be similarly introduced.
Implementations that support the ‘top
’ and ‘bottom
’ values of the ‘caption-side
’ property but do not support side
captions (i.e. ‘left
’ and ‘right
’ captions in horizontal writing modes)
must treat ‘top
’ and
‘bottom
’ as
‘before
’, when
the table is in a vertical writing mode.
For implementations that do support side captions (i.e. the ‘left
’ and ‘right
’ values from the
obsolete CSS 2.0 specification [CSS2]), this module also introduces
the ‘start
’ and
‘end
’ values, which
behave similarly and which position the caption on the start and end sides
of the table box, calculated with respect to the writing mode of the table
element. For such implementations, the ‘top
’ and ‘bottom
’ values must place the caption on the
top and bottom sides of the table box, respectively.
The CSS2.0 side caption model had some problems and will likely have a different definition in CSS3.
In paged media CSS2.1 classifies all pages as either left or right pages. The page progression direction, which determines whether the left or right page in a spread is first in the flow and whether the first page is by default a left or right page, depends on the writing direction as follows:
writing-mode
’
is ‘vertical-rl
’ or if the root element's
‘writing-mode
’ is ‘horizontal-tb
’ and
its ‘direction
’ is ‘rtl
’.
writing-mode
’
is ‘vertical-lr
’ or if the root element's
‘writing-mode
’ is ‘horizontal-tb
’ and
its ‘direction
’ is ‘ltr
’.
(Unless otherwise overridden, the first page of a document begins on the second half of a spread, e.g. on the right page in a left-to-right page progression.)
text-combine
’ propertyName: | text-combine |
---|---|
Value: | none | [ horizontal <number>? ] |
Initial: | none |
Applies to: | non-replaced inline elements |
Inherited: | no |
Percentages: | N/A |
Media: | visual |
Computed value: | specified value |
This property allows the combination of multiple characters into the space of a single character. For text layout purposes, e.g. bidi ordering, line-breaking, emphasis marks, text-decoration, etc. the resulting composition is treated as a single glyph representing the Object Replacement Character U+FFFC. Values have the following meanings:
In vertical writing mode, attempt to display the text contents of the element horizontally within the vertical line box, ideally within the space of one ideographic character (1em square).
The glyphs are stacked horizontally (similar to the contents of an inline-box with a horizontal writing mode and a line-height of 1em) and the baseline of the resulting composition chosen such that it is centered between the content edges of its parent inline box.
The UA should determine how to render the composed glyph into the space. If the UA has compressed glyphs available for the contents of the element, then it may use those glyphs to attempt sizing the contents to 1em square. For example, a two digit number may use halfwidth or proportional glyphs, a three-digit number may use 1/3-em glyphs (if available, else halfwidth glyphs), etc.
The UA may scale the contents to fit instead, or in addition to the method above.
In horizontal mode, or if the number of grapheme clusters in
the element exceeds the number specified (if any), this value is
equivalent to ‘none
’.
In East Asian documents, the ‘text-combine:
horizontal
’ effect is often used to display Latin-based
strings such as components of a date or letters of an initialism, always
in a horizontal writing mode regardless of the writing mode of the line:
Example of horizontal-in-vertical tate-chu-yoko
The figure is the result of the rules
.num { text-combine: horizontal; }
and the following markup:
平成<span class="num">20</span>年 <span class="num">4</span>月 <span class="num">16</span>日に
In Japanese, this effect is known as tate-chu-yoko.
Major changes include:
unicode-bidi
’ syntax to disallow
questionable combinations.
before
’ value as the initial value of
‘caption-side
’ and added note
about ‘before-outside
’ and
‘after-outside
’ to parallel note in
CSS2.1.
width
’, ‘height
’, ‘min-width
’, ‘min-height
’, ‘max-width
’, ‘max-height
’, and ‘column-width
’ properties.
John Daggett, Martin Heijdra, Ken Lunde, Paul Nelson, Michel Suignard, Steve Zilles
The style sheet rules that would achieve the bidi behaviors specified in [HTML401] for the HTML Strict doctype are given below:
/* HTML dir attribute creates an embedding */ *[dir="ltr"] { direction: ltr; unicode-bidi: embed; } *[dir="rtl"] { direction: rtl; unicode-bidi: embed; } /* BDO element creates an override */ bdo[dir="ltr"] { direction: ltr; unicode-bidi: bidi-override; } bdo[dir="rtl"] { direction: rtl; unicode-bidi: bidi-override; } /* HTML4.01:8.2.6 - preserve bidi behavior if 'display' is changed */ html, body, div, address, blockquote, p, ul, ol, li, dl, dt, dd, fieldset, form, h1, h2, h3, h4, h5, h6, { unicode-bidi: isolate; }
This section is normative.
This appendix gives the orientational properties of scripts in Unicode 6.0 [UNICODE]. Any script not listed explicitly is assumed to be horizontal-only. The script classification of Unicode characters is given by [UAX24].
Code | Name | Transform |
---|---|---|
Bopo | Bopomofo | translate |
Egyp | Egyptian Hieroglyphs | translate |
Hira | Hiragana | translate |
Kana | Katakana | translate |
Hani | Han | translate |
Hang | Hangul | translate |
Mong | Mongolian | rotate |
Phag | Phags Pa | rotate |
Yiii | Yi | translate |
Exceptions: For the purposes of this specification, all fullwidth (F) and wide (W) characters are treated as belonging to a vertical script with a translate bi-orientational transform. All halfwidth (H) characters are treated as belonging to a vertical script with a rotate bi-orientational transform. [UAX11] Neutral (N), narrow (Na) and ambiguous (A) Letters (L*) belonging to the Common script are treated as belonging to a horizontal-only script.
Ogham is also a rotating bi-orientational script, but because
it is a bottom-to-top script, for the purposes of this specification it is
treated as left-to-right horizontal. A future version of CSS may define
proper handling of bottom-to-top scripts. Authors can work around this
lack of support with the ‘rotate-left
’ value of ‘text-orientation
’.
This appendix is non-normative.
This section needs careful review.
When ‘text-orientation
’ is either ‘vertical-right
’ or
‘upright
’, the
following settings are recommended:
text-orientation
’.
Thus a THREE-PER-EM SPACE (U+2004) can be expected to provide a 1/3-em advance in the inline dimension, and brackets can be expected to encase their contents.
When ‘text-orientation
’ is ‘vertical-right
’,
the following settings are recommended for characters not
otherwise-specified above.
When ‘text-orientation
’ is ‘vertical-right
’,
set all characters upright (using vertical font settings if available)
unless otherwise specified above.
In OpenType, vertical font settings are provided by the
vhea
, vmtx
, and VORG
tables, as
well as the vert
and vrt2
GSUB features. If any
of these are present, the font is considered to have vertical font
settings available.
This section is normative.
CSS layout has several different concepts of automatic sizing that are used in various layout calculations. This section defines some more precise terminology to help connect the layout behaviors of this spec to the calculations used in other modules, and some new keywords for the width and height properties to allow authors to assign elements the dimensions resulting from these size calculations.
Properties: | ‘width ’, ‘min-width ’, ‘max-width ’, ‘height ’, ‘min-height ’, ‘max-height ’
|
---|---|
New Values: | ‘min-content ’ | ‘max-content ’ |
‘fill-available ’ | ‘fit-content ’
|
Initial: | as defined in [CSS21] |
Applies to: | as defined in [CSS21] |
Inherited: | as defined in [CSS21] |
Percentages: | as defined in [CSS21] |
Media: | as defined in [CSS21] |
Computed value: | specified value if keyword specified, else as defined in [CSS21] |
There are four types of automatically-determined sizes in CSS (which are represented in the width and height properties by the keywords defined above):
max(min-content, min(max-content, fill-available))
if the
available measure is finite, and as the max-content measure otherwise. The fit-content extent is calculated from the
same expression applied to the block dimension.
For the layout models in CSS2.1, both the min-content extent and max-content extent of non-replaced elements
are defined as the content extent as defined (for horizontal writing
modes) in CSS2.1§10.6.3
and CSS2.1§17.5.3
for elements with ‘height: auto
’.
For replaced elements, the min-content
and max-content sizes are the same and
correspond used size of the replaced element according to the ‘auto
’ width and height
calculations.
The min-content and max-content sizes of a multi-column element are undefined per [CSS3COL]. A future specification may define them.
Property: | ‘column-width ’
|
---|---|
New Values: | ‘min-content ’ | ‘max-content ’ |
‘fill-available ’ | ‘fit-content ’
|
Initial: | as defined in [CSS3COL] |
Applies to: | as defined in [CSS3COL] |
Inherited: | as defined in [CSS3COL] |
Percentages: | as defined in [CSS3COL] |
Media: | as defined in [CSS3COL] |
Computed value: | specified value if keyword specified, else as defined in [CSS3COL] |
When used as values for ‘column-width
’, the new keywords specify
the optimal column width:
min-content
’
max-content
’
fill-available
’
fit-content
’
max(min-content, min(max-content, fill-available))
.
Property | Values | Initial | Applies to | Inh. | Percentages | Media |
---|---|---|---|---|---|---|
direction | ltr | rtl | ltr | all elements | yes | N/A | visual |
‘caption-side’ | ‘before’ | ‘after’ | before | same as CSS2.1 | same as CSS2.1 | same as CSS2.1 | same as CSS2.1 |
‘column-width’ | ‘min-content’ | ‘max-content’ | ‘fill-available’ | ‘fit-content’ | as defined in [CSS3COL] | as defined in [CSS3COL] | as defined in [CSS3COL] | as defined in [CSS3COL] | as defined in [CSS3COL] |
‘width’, ‘min-width’, ‘max-width’, ‘height’, ‘min-height’, ‘max-height’ | ‘min-content’ | ‘max-content’ | ‘fill-available’ | ‘fit-content’ | as defined in [CSS21] | as defined in [CSS21] | as defined in [CSS21] | as defined in [CSS21] | as defined in [CSS21] |
text-combine | none | [ horizontal <number>? ] | none | non-replaced inline elements | no | N/A | visual |
text-orientation | vertical-right | upright | rotate-right | rotate-left | rotate-normal | auto | vertical-right | all elements except table row groups, rows, column groups, and columns | yes | N/A | visual |
unicode-bidi | normal | embed | [ isolate || [ plaintext | bidi-override ] ] | normal | all elements, but see prose | no | N/A | visual |
writing-mode | horizontal-tb | vertical-rl | vertical-lr | horizontal-tb | All elements except table row groups, table column groups, table rows, and table columns | yes | N/A | visual |