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<pre class='metadata'>
Title: CSS Text Module Level 4
Shortname: css-text
Level: 4
Status: ED
Work Status: Exploring
Group: csswg
ED: https://drafts.csswg.org/css-text-4/
TR: https://www.w3.org/TR/css-text-4/
Previous Version: https://www.w3.org/TR/2015/WD-css-text-4-20150922/
Editor: Elika J. Etemad / fantasai, Invited Expert, http://fantasai.inkedblade.net/contact, w3cid 35400
Editor: Koji Ishii, Google, kojiishi@gmail.com, w3cid 45369
Editor: Alan Stearns, Adobe Systems, stearns@adobe.com, w3cid 46659
Abstract: This module defines properties for text manipulation and specifies their processing model. It covers line breaking, justification and alignment, white space handling, and text transformation.
Ignored terms: segment break, segment breaks
</pre>
<pre class='link-defaults'>
spec: css-text-3; type: property
text: text-align
text: letter-spacing
text: word-spacing
</pre>
<h2 id="intro">
Introduction</h2>
Issue: Add final level 3 content
<h2 id="transforming">
Transforming Text</h2>
Issue: Add final level 3 content
<h2 id="white-space-processing">
White Space Processing</h2>
Issue: Add final level 3 tab-size and processing details
<h3 id="white-space-collapsing">
White Space Collapsing: the 'text-space-collapse' property</h3>
ISSUE: This section is still under discussion and may change in future drafts.
<pre class="propdef">
Name: text-space-collapse
Value: collapse | discard | preserve | preserve-breaks | preserve-spaces
Initial: collapse
Applies to: all elements
Inherited: yes
Percentages: n/a
Computed value: specified keyword
Animation type: discrete
</pre>
This property declares whether and how
<a href="#white-space-processing">white space</a> inside the element is
collapsed. Values have the following meanings, which must be interpreted
according to the white space processing rules:
<dl dfn-for=text-space-collapse dfn-type=value>
<dt><dfn>collapse</dfn>
<dd>
This value directs user agents to collapse sequences of white space
into a single character
(or <a href="https://www.w3.org/TR/css-text/#line-break-transform">in some cases</a>, no character).
<dt><dfn>preserve</dfn>
<dd>
This value prevents user agents
from collapsing sequences of white space.
<a>Segment breaks</a> are preserved as forced line breaks.
<dt><dfn>preserve-breaks</dfn>
<dd>
This value collapses white space as for ''collapse'', but preserves
<a>segment breaks</a> as forced line breaks.
<dt><dfn>preserve-spaces</dfn>
<dd>
This value prevents user agents
from collapsing sequences of white space,
and converts tabs and <a>segment breaks</a> to spaces.
(This value is intended to match the behavior
of <code>xml:space="preserve"</code> in SVG.)
<dt><dfn>discard</dfn>
<dd>
This value directs user agents to “discard”
all white space in the element.
Issue: Does this preserve line break opportunities or no? Do we need a "hide" value?
</dl>
<div class="example">
The following style rules implement MathML's white space processing:
<pre>
@namespace m "http://www.w3.org/1998/Math/MathML";
m|* {
text-space-collapse: discard;
}
m|mi, m|mn, m|mo, m|ms, m|mtext {
text-space-trim: trim-inner;
}
</pre>
</div>
<h3 id="white-space-trim">
White Space Trimming: the 'text-space-trim' property</h3>
<pre class="propdef">
Name: text-space-trim
Value: none | trim-inner || discard-before || discard-after
Initial: none
Applies to: all elements
Inherited: no
Percentages: n/a
Computed value: specified keyword(s)
Animation type: discrete
</pre>
This property allows authors to specify trimming behavior
at the beginning and end of a box.
Values have the following meanings,
which must be interpreted according to the white space processing rules:
<dl dfn-for=text-space-trim dfn-type=value>
<dt><dfn>trim-inner</dfn>
<dd>
For block containers this value directs UAs to discard all whitespace
at the beginning of the element up to and including the last <a>segment break</a>
before the first non-white-space character in the element as well as
to discard all white space at the end of the element starting with the
first <a>segment break</a> after the last non-white-space character in the element.
For other elements this value directs UAs to discard all whitespace
at the beginning and end of the element.
<dt><dfn>discard-before</dfn>
<dd>
This value directs the UA to collapse all collapsible whitespace
immediately before the start of the element.
<dt><dfn>discard-after</dfn>
<dd>
This value directs the UA to collapse all collapsible whitespace
immediately after the end of the element.
</dl>
<div class="example">
<p>The following style rules render DT elements as a comma-separated list:
<pre>
dt { display: inline; }
dt + dt:before { content: ", "; text-space-trim: discard-before; }
</pre>
</div>
<h2 id="line-breaking">
Line Breaking and Word Boundaries</h2>
Issue: Add final level 3 content
<h2 id="wrapping">
Text Wrapping</h2>
Text wrapping is controlled by the 'text-wrap',
'wrap-before',
'wrap-after',
'wrap-inside',
and overflow-wrap properties:
Issue: Add final level 3 overflow-wrap
<h3 id="text-wrap">
Text Wrap Settings: the 'text-wrap' property</h3>
<pre class="propdef">
Name: text-wrap
Value: wrap | nowrap | balance
Initial: wrap
Applies to: <a>inline boxes</a> and <a>block containers</a>
Inherited: yes
Percentages: n/a
Computed value: specified keyword
Animation type: discrete
</pre>
This property specifies the mode for text wrapping.
Possible values:
<dl dfn-for=text-wrap dfn-type=value>
<dt><dfn>wrap</dfn>
<dd>
Inline-level content may break across lines
at allowed <a>soft wrap opportunities</a>,
as determined by the line-breaking rules in effect
in order to minimize <a>inline-axis</a> overflow.
The exact algorithm is UA-defined.
The algorithm may consider multiple lines when making break decisions.
The UA may bias for speed over best layout.
<dt><dfn>nowrap</dfn>
<dd>
Inline-level content does not break across lines;
content that does not fit within the block container overflows it.
<dt><dfn>balance</dfn>
<dd>
Same as ''text-wrap/wrap'' for <a>inline boxes</a>.
For <a>block containers</a> that
establish an <a>inline formatting context</a>,
line breaks are chosen to balance
the remaining (empty) space in each line box,
if better balance than ''text-wrap/wrap'' is possible.
This must not change the number of line boxes
the block would contain
if 'text-wrap' were set to ''text-wrap/wrap''.
The remaining space to consider
is that which remains after placing floats and inline content,
but before any adjustments due to text justification.
Line boxes are balanced when the standard deviation
from the average <a>inline-size</a> of the remaining space in each line box
is reduced over the block
(including lines that end in a forced break).
The exact algorithm is UA-defined.
UAs may treat this value as ''text-wrap/wrap'' if there are more than ten lines to balance.
</dl>
ISSUE: There's some discussion about whether different wrapping algorithms (higher quality vs faster) need special keywords, see <a href="https://github.com/w3c/csswg-drafts/issues/672#issuecomment-379723243">Issue 672</a>.
Regardless of the 'text-wrap' value,
lines always break at forced breaks:
for all values,
line-breaking behavior defined
for the BK, CR, LF, CM, NL, and SG line breaking classes
in [[!UAX14]] must be honored.
Additionally, if wrapping is allowed (i.e. 'text-wrap' is not ''text-wrap/none''),
line breaking behavior defined
for the WJ, ZW, and GL line-breaking classes
in [[!UAX14]] must be honored.
UAs that allow breaks at punctuation other than spaces
should prioritize breakpoints.
For example,
if breaks after slashes have 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.
<!-- add a sample prioritization algorithm -->
Note: The ''text-wrap/wrap'' value is intended
for speedy legacy line breaking,
which has so far used first-fit/greedy algorithms
that can often give sub-optimal results.
UAs could experiment with better line breaking algorithms
with this default value,
but optimal results will probably take more time.
The ''text-wrap/multi-line'' and ''text-wrap/balance'' values
are intended as opt-in choices to take more time for better results.
The ''text-wrap/balance'' value is intended for titles and captions,
and the ''text-wrap/multi-line'' is intended for body text.
Note: Some line breaking algorithms can interact unexpectedly with editing.
Changing upstream line breaks on user edits can be unsettling.
As UAs experiment with better line breaking algorithms,
we will likely need to add a property
to constrain upstream changes while editing.
<h3 id="wrap-before">
Inline breaks between boxes: the 'wrap-before'/'wrap-after' properties</h3>
<pre class="propdef">
Name: wrap-before, wrap-after
Value: auto | avoid | avoid-line | avoid-flex | line | flex
Initial: auto
Applies to: <a>inline-level</a> boxes and <a>flex items</a>
Inherited: no
Percentages: n/a
Computed value: specified keyword
Animation type: discrete
</pre>
These properties specify modifications to break opportunities
in line breaking (and <a>flex line</a> breaking [[CSS3-FLEXBOX]]).
Possible values:
<dl dfn-for="wrap-before, wrap-after" dfn-type=value>
<dt><dfn>auto</dfn>
<dd>
Lines may break at allowed break points
before and after the box,
as determined by the line-breaking rules in effect.
<dt><dfn>avoid</dfn>
<dd>
Line breaking is suppressed immediately before/after the box:
the UA may only break there
if there are no other valid break points
in the line.
If the text breaks,
line-breaking restrictions are honored as for
''wrap-before/auto''.
<dt><dfn>avoid-line</dfn>
<dd>
Same as ''wrap-before/avoid'',
but only for line breaks.
<dt><dfn>avoid-flex</dfn>
<dd>
Same as ''wrap-before/avoid'',
but only for flex line breaks.
<dt><dfn>line</dfn>
<dd>
Force a line break immediately before/after the box
if the box is an <a>inline-level</a> box.
<dt><dfn>flex</dfn>
<dd>
Force a <a>flex line</a> break immediately before/after the box
if the box is a <a>flex item</a>
in a <a>multi-line flex container</a>.
</dl>
Forced line breaks on <a>inline-level</a> boxes propagate upward
through any parent <a>inline boxes</a>
the same way forced breaks on <a>block-level</a> boxes propagate upward
through any parent <a>block boxes</a>
in the same <a>fragmentation context</a>.
[[!CSS3-BREAK]]
<h3 id="wrap-inside">
Line breaks within boxes: the 'wrap-inside' property</h3>
<pre class="propdef">
Name: wrap-inside
Value: auto | avoid
Initial: auto
Applies to: <a>inline boxes</a>
Inherited: no
Percentages: n/a
Computed value: specified keyword
Animation type: discrete
</pre>
<dl dfn-for=wrap-inside dfn-type=value>
<dt><dfn>auto</dfn>
<dd>
Lines may break at allowed break points
within the box,
as determined by the line-breaking rules in effect.
<dt><dfn>avoid</dfn>
<dd>
Line breaking is suppressed within the box:
the UA may only break within the box
if there are no other valid break points in the line.
If the text breaks,
line-breaking restrictions are honored as for
''wrap-inside/auto''.
If boxes with ''wrap-inside/avoid'' are nested
and the UA must break within these boxes,
a break in an outer box must be used
before a break within an inner box may be used.
</dl>
<h4 id="example-avoid">
Example of using 'wrap-inside: avoid' in presenting a footer</h4>
<div class="example">
The priority of breakpoints can be set
to reflect the intended grouping of text.
Given the rules
<pre>
footer { wrap-inside: avoid; }
venue { wrap-inside: avoid; }
date { wrap-inside: avoid; }
place { wrap-inside: avoid; }
</pre>
and the following markup:
<pre>
<footer>
<venue>27th Internationalization and Unicode Conference</venue>
&#8226; <date>April 7, 2005</date> &#8226;
<place>Berlin, Germany</place>
</footer>
</pre>
In a narrow window the footer could be broken as
<pre>
27th Internationalization and Unicode Conference •
April 7, 2005 • Berlin, Germany
</pre>
or in a narrower window as
<pre>
27th Internationalization and Unicode
Conference • April 7, 2005 •
Berlin, Germany
</pre>
but not as
<pre>
27th Internationalization and Unicode Conference • April
7, 2005 • Berlin, Germany
</pre>
</div>
<h2 id="last-line-limits">
Last Line Minimum Length</h2>
<div class="issue">
See <a href="http://www.w3.org/mid/0BD85DFF-A147-44EF-B18A-FF03C3D67EF0@verou.me">thread</a>.
Issue is about requiring a minimum length for lines.
Common measures seem to be
<ul>
<li>At least as long as the text-indent.
<li>At least X characters.
<li>Percentage-based.
</ul>
Suggestion for value space is ''match-indent | <<length>> | <<percentage>>''
(with ''Xch'' given as an example to make that use case clear).
Alternately <<integer>> could actually count the characters.
It's unclear how this would interact with text balancing (above);
one earlier proposal had them be the same property
(with ''100%'' meaning full balancing).
People have requested word-based limits, but since this is really
dependent on the length of the word, character-based is better.
</div>
<h2 id="white-space-property">
Shorthand for White Space and Wrapping: the 'white-space' property</h2>
<pre class="propdef shorthand">
Name: white-space
Value: normal | pre | nowrap | pre-wrap | pre-line
Initial: auto
Applies to: all elements
Inherited: yes
Percentages: n/a
Animation type: discrete
</pre>
This property is a shorthand for 'text-space-collapse', 'text-wrap', and 'text-space-trim'.
Note: This shorthand combines both inheritable and non-inheritable properties.
If this is a problem, please inform the CSSWG.
The following table gives the mapping of the values of the shorthand to its longhands.
<table class="data">
<colgroup class="header"></colgroup>
<colgroup span=3></colgroup>
<thead>
<tr>
<th>'white-space'
<th>'text-space-collapse'
<th>'text-wrap'
<th>'text-space-trim'
</thead>
<tbody>
<tr>
<th>''white-space/normal''
<td>''text-space-collapse/collapse''
<td>''text-wrap/wrap''
<td>''text-space-trim/none''
<tr>
<th>''pre''
<td>''text-space-collapse/preserve''
<td>''text-wrap/nowrap''
<td>''text-space-trim/none''
<tr>
<th>''nowrap''
<td>''text-space-collapse/collapse''
<td>''text-wrap/nowrap''
<td>''text-space-trim/none''
<tr>
<th>''pre-wrap''
<td>''text-space-collapse/preserve''
<td>''text-wrap/wrap''
<td>''text-space-trim/none''
<tr>
<th>''pre-line''
<td>''text-space-collapse/preserve-breaks''
<td>''text-wrap/wrap''
<td>''text-space-trim/none''
</tbody>
</table>
Issue: Add details from level 3
<h2 id="hyphenation">
Breaking Within Words</h2>
Issue: Add final level 3 content
<h3 id="hyphenate-character">
Hyphens: the 'hyphenate-character' property</h3>
<pre class="propdef">
Name: hyphenate-character
Value: auto | <<string>>
Initial: auto
Applies to: all elements
Inherited: yes
Percentages: n/a
Computed value: specified keyword
Animation type: discrete
</pre>
This property specifies the string that is shown
between parts of hyphenated words.
Values have the following meanings:
<dl dfn-for=hyphenate-character dfn-type=value>
<dt><dfn>auto</dfn>
<dd>
Specifies that the user agent should find an appropriate string
based on the <a>content language</a>’s typographic conventions,
possibly from the same source as the hyphenation dictionary.
<dt><dfn><<string>></dfn>
<dd>
Specifies the string that appears
at the end of the line before a hyphenation break.
The UA <em>may</em> truncate the <a>used value</a>
to a limited number of <a>typographic character units</a>.
(It must not truncate only part of a <a>typographic character unit</a>.)
</dl>
<div class="example">
The hyphen character (U+2010) is most typically used
to indicate that a word has been split.
However, 'hyphenate-character' can be used
to specify a different type of hyphen when necessary.
<pre>
article { hyphenate-character: "᐀" /* CANADIAN SYLLABICS HYPHEN (U+1400) */ }
</pre>
</div>
Note: Both hyphens triggered by automatic hyphenation
and hyphens triggered by soft hyphens
are rendered according to 'hyphenate-character'.
<h3 id="hyphenate-size-limits">
Hyphenation Size Limit: the 'hyphenate-limit-zone' property</h3>
<pre class="propdef">
Name: hyphenate-limit-zone
Value: <<length-percentage>>
Initial: 0
Applies to: block containers
Inherited: yes
Percentages: refers to length of the line box
Computed value: computed <<length-percentage>> value
Animation type: by computed value type
</pre>
<p class="issue">Is 'hyphenate-limit-zone' a good name? Comments/suggestions?
This property specifies the maximum amount of unfilled space (before
justification) that may be left in the line box before hyphenation is
triggered to pull part of a word from the next line back up into the
current line.
<h3 id="hyphenate-char-limits">
Hyphenation Character Limits: the 'hyphenate-limit-chars' property</h3>
<pre class="propdef">
Name: hyphenate-limit-chars
Value: [ auto | <<integer>> ]{1,3}
Initial: auto
Applies to: all elements
Inherited: yes
Percentages: n/a
Computed value: three values, each either the ''hyphenate-limit-chars/auto'' keyword or an integer
Animation type: by computed value type
</pre>
This property specifies the minimum number of characters in a
hyphenated word. If the word does not meet the required minimum
number of characters in the word / before the hyphen / after the
hyphen, then the word must not be hyphenated. Nonspacing combining
marks (<span class="issue">Unicode class</span>) and intra-word
punctuation (Unicode classes P*) do not count towards the minimum.
If three values are specified, the first value is the required
minimum for the total characters in a word, the second value is
the minimum for characters before the hyphenation point, and
the third value is the minimum for characters after the hyphenation
point. If the third value is missing, it is the same as the second.
If the second value is missing,
then it is ''hyphenate-limit-chars/auto''.
The ''hyphenate-limit-chars/auto''
value means that the UA chooses a value that adapts to the current
layout.
Note: Unless the UA is able to calculate a better value, it
is suggested that ''hyphenate-limit-chars/auto'' means 2 for before and after, and 5 for
the word total.
<div class="example">
In the example below, the minimum size of a hyphenated word is
left to the UA (which means it may vary depending on the language,
the length of the line, or other factors), but the minimum number
of characters before and after the hyphenation point is set to 3.
<pre>
p { hyphenate-limit-chars: auto 3; }
</pre>
</div>
<h3 id="hyphenate-line-limits">
Hyphenation Line Limits: the 'hyphenate-limit-lines' and 'hyphenate-limit-last' properties</h3>
<pre class="propdef">
Name: hyphenate-limit-lines
Value: no-limit | <integer>
Initial: no-limit
Applies to: block containers
Inherited: yes
Percentages: n/a
Computed value: specified keyword or integer
Animation type: by computed value type
</pre>
This property indicates the maximum number of successive hyphenated
lines in an element. The ''no-limit'' value means that there is no limit.
In some cases, user agents may not be able to honor the specified value.
(See overflow-wrap.) It is not defined whether hyphenation introduced by
such emergency breaking influences nearby hyphenation points.
<pre class="propdef">
Name: hyphenate-limit-last
Value: none | always | column | page | spread
Initial: none
Applies to: block containers
Inherited: yes
Percentages: n/a
Computed value: specified keyword
Animation type: discrete
</pre>
This property indicates hyphenation behavior at the end of elements,
column, pages, and spreads. A spread is a set of two pages that are
visible to the reader at the same time. Values are:
<dl dfn-for=hyphenate-limit-lines dfn-type=value>
<dt><dfn>none</dfn>
<dd>
No restrictions imposed.
<dt><dfn>always</dfn>
<dd>
The last full line of the element, or the last line before any
column, page, or spread break inside the element should not be
hyphenated.
<dt><dfn>column</dfn>
<dd>
The last line before any column, page, or spread break inside
the element should not be hyphenated.
<dt><dfn>page</dfn>
<dd>
The last line before page or spread break inside the element
should not be hyphenated.
<dt><dfn>spread</dfn>
<dd>
The last line before any spread break inside the element should
not be hyphenated.
</dl>
<div class=example>
<pre>
p { hyphenate-limit-last: always }
div.chapter { hyphenate-limit-last: spread }
</pre>
</div>
<div class=example>
A paragraph may be formatted like this when 'hyphenate-limit-last: none' is set:
<pre>
This is just a
simple example
to show Antarc-
tica.
</pre>
With 'hyphenate-limit-last: always' one would get:
<pre>
This is just a
simple example
to show
Antarctica.
</pre>
</div>
<h2 id="alignment">
Alignment and Justification</h2>
<h3 id="text-align-property">
Text Alignment: the 'text-align' shorthand</h3>
Issue: Add final level 3 content
Add this value to 'text-align'
<dl dfn-for=text-align dfn-type=value>
<dt><dfn><string></dfn></dt>
<dd>
The string must be a single character; otherwise the declaration must
be <a href="https://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>.
When applied to a table cell, specifies the <dfn>alignment character</dfn>
around which the cell's contents will align. See
<a href="#character-alignment">below</a> for further details and
how this value combines with keywords.
</dl>
<h3 id="character-alignment">
Character-based Alignment in a Table Column</h3>
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.)
<p class="issue">Is this intended to say that it's the centers
of the alignment characters that should be aligned?
It's not clear that's what it says,
but that (or a different behavior) needs to be specified,
to describe what happens
when different occurrences of the alignment character
are in different fonts.
(Further, is that the intended behavior? Probably the most
significant use case to consider is bold vs. non-bold text,
which only varies slightly in width.)
[<a href="https://lists.w3.org/Archives/Public/www-style/2016Jan/0233.html">feedback</a>]
[minutes face-to-face 2016-02-02 10:00 AM]
</p>
<div class="example">
97F3
The following style sheet:
<pre>
TD { text-align: "." center }
</pre>
will cause the column of dollar figures in the following HTML table:
<pre class="html-example">
<TABLE>
<COL width="40">
<TR> <TH>Long distance calls
<TR> <TD> $1.30
<TR> <TD> $2.50
<TR> <TD> $10.80
<TR> <TD> $111.01
<TR> <TD> $85.
<TR> <TD> N/A
<TR> <TD> $.05
<TR> <TD> $.06
</TABLE>
</pre>
to align along the decimal point. The table might be rendered as
follows:
<pre>
+---------------------+
| Long distance calls |
+---------------------+
| $1.30 |
| $2.50 |
| $10.80 |
| $111.01 |
| $85. |
| N/A |
| $.05 |
| $.06 |
+---------------------+
</pre>
</div>
A keyword value may be specified in conjunction with the <string>
value; if it is not given, it defaults to ''text-align/right''. This value is used:
<ul>
<li>
when character-based alignment is applied to boxes that are not table
cells.
<li>
when the text wraps to multiple lines (at unforced break points).
<li>
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 ''text-align/left'', the rightmost
column for ''text-align/right'' and ''text-align/center'', the startmost column for ''text-align/start'',
the endmost column for ''text-align/end''.
<li>
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 ''text-align/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).
</ul>
Note: 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.
<p class="issue">This needs to specify what text is searched
for the alignment character.
Is it only in-flow text whose containing block is the cell?
Or is text within any in-flow descendants
in the block formatting context established by the cell considered?
If so, is it considered only as long as its 'text-align' property
is consistent with the cell's?
(Consistent in the alignment character, or fully consistent?)</p>
<p class="issue">This behavior of aligning as though
the alignment character had been inserted at the end of
the contents of the cell,
combined with center-of-character alignment,
will produce gaps on the end-side of lines
that are alone on a line with <string> text-alignment,
when none of the lines of the column has the alignment character,
or, more importantly, when some of the lines
do have the alignment character,
but the column is not laid out at its max-content width.
This is probably undesirable.</p>
<p class="issue">When the alignment character is inserted at
the end of the contents, which font is used?
(In particular, if the alignment character might be within
a descendant block, is it the font of the block or
the font of the table cell?
Or if the insertion is at a forced break within an inline,
does it use the font of the inline or the font of the block or cell?)
</p>
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.
<p class="issue">This should have a formal definition
of how character alignment affects
the min-content and max-content intrinsic widths
(of table columns and all content that can be inside table columns).
Max-content intrinsic widths need to be split
into three numbers (assuming that it's the centers of the
alignment character that are aligned):
one for widths without alignment characters,
one for widths on the inline-start side
of the center of the alignment character,
one for widths on the inline-end side
of the center of the alignment character.
This operates based on all segments of text
between forced breaks for max-content widths.
For min-content widths, segments of text between forced breaks
that contain optional breaks within them should clearly contribute
only to the without-alignment-character width.
However, it's less clear
whether all min-content widths should work this way,
or whether segments between forced breaks
that do not have optional breaks
(and perhaps only those that actually contain the alignment character)
should contribute to start-side-of-alignment-character
and end-side-of-alignment-character min-content widths instead;
this choice is a tradeoff between the meaning of min-content
sizing of a table meaning the narrowest reasonable size versus
honoring alignment characters in more cases.
Another option might be to use whether line-breaking of optional breaks
is allowed as a control for which behavior to use.</p>
<p class="issue">Formally defining the intrinsic width contributions
of column-spanning cells with <string> values of
'text-align' is a complicated (although straightforward) extension
of the decisions made for intrinsic width contributions
of non-column-spanning cells;
this should also be formally defined.
Contributions end up being made to the split intrinsic widths
of the startmost or endmost column (whichever is used for alignment),
and to the without-alignment-character intrinsic widths
of the other spanned columns.</p>
<h3 id="text-group-align-property">
Aligning a block of text within its container: the 'text-group-align' property</h3>
<pre class="propdef">
Name: text-group-align
Value: none | start | end | left | right | center
Initial: none
Applies to: <a>block containers</a>
Inherited: no
Percentages: N/A
Computed value: specified keyword
Animation type: discrete
</pre>
This property aligns the contents of the line boxes as a group while maintaining their text alignment.
<dfn lt="group alignment | group-align | group-aligned">Group alignment</dfn> is performed by finding the line box with the shortest remaining space
and adding that amount of space as padding to one or both sides of the line box,
reducing the amount of space available for its contents;
<a href="#text-align-property">text alignment</a> is then applied to its contents within the remaining space.
All descendant [=in-flow=] line boxes within the same [=block formatting context=] are considered
both when searching for the shortest remaining space
and when adding the padding;
the contents of descendants that establish [=independent formatting contexts=] are skipped.
Issue: A variant of this property is inherited,
and applies on each block container individually,
only affecting the line boxes that are direct children of that block.
This is less useful, but probably easier to implement.
Issue: Somehow also moving the floats that originate in the same block container
by the same amount
would make things line up more nicely,
which would be especially valuable in CJK layout.
Exactly how that works, and how it interacts with intruding floats
from ancestor elements is left as an exercise for the reader.
Values have the following meanings:
<dl dfn-for=text-group-align dfn-type=value>
<dt><dfn>none</dfn>
<dd>Text alignment happens normally: [=group alignment=] is not performed.
<dt><dfn>start</dfn>
<dd>Inline-level content is [=group-aligned=] to the [=inline start=] side,
by padding the [=inline end=] side of each line box.
<dt><dfn>end</dfn>
<dd>Inline-level content is [=group-aligned=] to the [=inline end=] side,
by padding the [=inline start=] side of each line box.
<dt><dfn>left</dfn>
<dd>Inline-level content is [=group-aligned=] to the [=line-left=] side,
by padding the [=line-right=] side of each line box.
<dt><dfn>right</dfn>
<dd>Inline-level content is [=group-aligned=] to the [=line-right=] side,
by padding the [=line-left=] side of each line box.
<dt><dfn>center</dfn>
<dd>Inline-level content is [=group-aligned=] to the center,
by padding both sides of each line box,
half the spacing to each side.
</dl>
<h2 id="spacing">
Spacing</h2>