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<!DOCTYPE html>
<html lang=en>
<head>
<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
<title>CSS Intrinsic & Extrinsic Sizing Module Level 3</title>
<!--
<link href="http://purl.org/dc/terms/" rel="schema.dcterms">
<link href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright" rel="dcterms.rights">
-->
<meta content="CSS Intrinsic & Extrinsic Sizing Module Level 3"
name=dcterms.title>
<meta content=text name=dcterms.type>
<meta content=2013-08-20 name=dcterms.date>
<meta content="Tab Atkins Jr." name=dcterms.creator>
<meta content="Elika J. Etemad" name=dcterms.creator>
<meta content=W3C name=dcterms.publisher>
<meta content="http://dev.w3.org/csswg/css3-sizing/"
name=dcterms.identifier>
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<body>
<div class=head> <!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt=W3C height=48
src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
<h1>CSS Intrinsic & Extrinsic Sizing Module Level 3</h1>
<h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 20 August 2013</h2>
<dl><!--
<dt>This version:
<dd><a href="http://dev.w3.org/csswg/css3-sizing/">http://www.w3.org/TR/2013/ED-css3-sizing-20130820/</a>
-->
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-sizing/">http://www.w3.org/TR/css3-sizing/</a>
<dt>Editor's draft:
<dd><a
href="http://dev.w3.org/csswg/css3-sizing/">http://dev.w3.org/csswg/css3-sizing/</a>
<dt>Previous Versions:
<dd><a
href="http://www.w3.org/TR/2012/WD-css3-sizing-20120927/">http://www.w3.org/TR/2012/WD-css3-sizing-20120927/</a>
<dt>Issue Tracking:
<dd><a
href="https://www.w3.org/Bugs/Public/buglist.cgi?product=CSS&component=Sizing&resolution=---">W3C
Bugzilla</a>
<dt>Feedback:
<dd><a
href="mailto:www-style@w3.org?subject=%5Bcss-sizing%5D%20feedback">www-style@w3.org</a>
with subject line “<kbd>[css-sizing] <var>… message topic
…</var></kbd>” (<a
href="http://lists.w3.org/Archives/Public/www-style/"
rel=discussion>archives</a>)
<dt>Editors:
<dd class=hcard><a class="fn url"
href="http://www.xanthir.com/contact">Tab Atkins Jr.</a>, <span
class=org>Google Inc.</span>
<dd class=hcard><a class="fn url"
href="http://fantasai.inkedblade.net/contact">Elika J. Etemad</a>, <span
class=org>Mozilla</span>
</dl>
<!--begin-copyright-->
<p class=copyright><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=license>Copyright</a> © 2013 <a href="http://www.w3.org/"><abbr
title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a
href="http://www.csail.mit.edu/"><abbr
title="Massachusetts Institute of Technology">MIT</abbr></a>, <a
href="http://www.ercim.eu/"><abbr
title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
<a href="http://www.keio.ac.jp/">Keio</a>, <a
href="http://ev.buaa.edu.cn/">Beihang</a>), All Rights Reserved. W3C <a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a
href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
and <a
href="http://www.w3.org/Consortium/Legal/copyright-documents">document
use</a> rules apply.</p>
<!--end-copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id=abstract>Abstract</h2>
<p>This module extends the CSS sizing properties with keywords that
represent content-based "intrinsic" sizes and context-based "extrinsic"
sizes, allowing CSS to more easily describe boxes that fit their content
or fit into a particular layout context. <a
href="http://www.w3.org/TR/CSS/">CSS</a> is a language for describing the
rendering of structured documents (such as HTML and XML) on screen, on
paper, in speech, etc.
<h2 class="no-num no-toc" id=status>Status of this document</h2>
<!--begin-status-->
<p>This is a public copy of the editors' draft. It is provided for
discussion only and may change at any moment. Its publication here does
not imply endorsement of its contents by W3C. Don't cite this document
other than as work in progress.
<p>The (<a
href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
mailing list <a
href="mailto:www-style@w3.org?Subject=%5Bcss3-sizing%5D%20PUT%20SUBJECT%20HERE">
www-style@w3.org</a> (see <a
href="http://www.w3.org/Mail/Request">instructions</a>) is preferred for
discussion of this specification. When sending e-mail, please put the text
“css3-sizing” in the subject, preferably like this:
“[<!---->css3-sizing<!---->] <em>…summary of comment…</em>”
<p>This document was produced by the <a
href="http://www.w3.org/Style/CSS/members">CSS Working Group</a> (part of
the <a href="http://www.w3.org/Style/">Style Activity</a>).
<p>This document was produced by a group operating under the <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February
2004 W3C Patent Policy</a>. W3C maintains a <a
href="http://www.w3.org/2004/01/pp-impl/32061/status"
rel=disclosure>public list of any patent disclosures</a> 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 <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
Claim(s)</a> must disclose the information in accordance with <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
6 of the W3C Patent Policy</a>.</p>
<!--end-status-->
<p>The following features are at risk: …
<h2 class="no-num no-toc" id=contents> Table of contents</h2>
<!--begin-toc-->
<ul class=toc>
<li><a href="#intro"><span class=secno>1. </span> Introduction</a>
<ul class=toc>
<li><a href="#placement"><span class=secno>1.1. </span> Module
interactions</a>
<li><a href="#values"><span class=secno>1.2. </span> Values</a>
</ul>
<li><a href="#terms"><span class=secno>2. </span> Terminology</a>
<li><a href="#size-keywords"><span class=secno>3. </span> New Sizing
Keywords</a>
<ul class=toc>
<li><a href="#width-height-keywords"><span class=secno>3.1. </span> New
Keywords for ‘<code class=property>width</code>’ and ‘<code
class=property>height</code>’</a>
<li><a href="#the-contain-floats-value"><span class=secno>3.2. </span>
Containing Floats</a>
<li><a href="#column-sizing"><span class=secno>3.3. </span> Column
Sizing Keywords</a>
</ul>
<li><a href="#intrinsic-sizing"><span class=secno>4. </span> Intrinsic
Size Determination</a>
<ul class=toc>
<li><a href="#replaced-intrinsic"><span class=secno>4.1. </span>
Intrinsic Sizes of Replaced Elements</a>
<li><a href="#inline-intrinsic"><span class=secno>4.2. </span> Intrinsic
Sizes of Non-Replaced Inlines</a>
<li><a href="#block-intrinsic"><span class=secno>4.3. </span> Intrinsic
Sizes of Non-Replaced Blocks</a>
<li><a href="#table-intrinsic"><span class=secno>4.4. </span> Intrinsic
Sizes in Table Layout</a>
<li><a href="#multicol-intrinsic"><span class=secno>4.5. </span>
Intrinsic Sizes in Multi-column Layout</a>
</ul>
<li><a href="#extrinsic-sizing"><span class=secno>5. </span> Extrinsic
Size Determination</a>
<li><a href="#conformance"><span class=secno>6. </span> Conformance</a>
<ul class=toc>
<li><a href="#conventions"><span class=secno>6.1. </span> Document
conventions</a>
<li><a href="#conformance-classes"><span class=secno>6.2. </span>
Conformance classes</a>
<li><a href="#partial"><span class=secno>6.3. </span> Partial
implementations</a>
<li><a href="#experimental"><span class=secno>6.4. </span> Experimental
implementations</a>
<li><a href="#testing"><span class=secno>6.5. </span> Non-experimental
implementations</a>
<li><a href="#cr-exit-criteria"><span class=secno>6.6. </span> CR exit
criteria</a>
</ul>
<li class=no-num><a href="#acknowledgments"> Acknowledgments</a>
<li class=no-num><a href="#references"> References</a>
<ul class=toc>
<li class=no-num><a href="#normative-references"> Normative
references</a>
<li class=no-num><a href="#other-references"> Other references</a>
</ul>
<li class=no-num><a href="#index"> Index</a>
<li class=no-num><a href="#property-index"> Property index</a>
</ul>
<!--end-toc-->
<h2 id=intro><span class=secno>1. </span> Introduction</h2>
<p><em>This section is not normative.</em>
<p> 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
‘<code class=property>width</code>’ and ‘<code
class=property>height</code>’ properties to allow authors to assign
elements the dimensions resulting from these size calculations.
<h3 id=placement><span class=secno>1.1. </span> Module interactions</h3>
<p>This module extends the ‘<code class=property>width</code>’,
‘<code class=property>height</code>’, ‘<code
class=property>min-width</code>’, ‘<code
class=property>min-height</code>’, ‘<code
class=property>max-width</code>’, ‘<code
class=property>max-height</code>’, and ‘<code
class=property>column-width</code>’ features defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> chapter 10 and in <a
href="#CSS3COL" rel=biblioentry>[CSS3COL]<!--{{!CSS3COL}}--></a>
<h3 id=values><span class=secno>1.2. </span> Values</h3>
<p>This specification follows the <a
href="http://www.w3.org/TR/CSS21/about.html#property-defs">CSS property
definition conventions</a> from <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. Value types not defined in
this specification are defined in CSS Level 2 Revision 1 <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. Other CSS
modules may expand the definitions of these value types: for example <a
href="#CSS3COLOR" rel=biblioentry>[CSS3COLOR]<!--{{CSS3COLOR}}--></a>,
when combined with this module, expands the definition of the
<color> value type as used in this specification.
<p>In addition to the property-specific values listed in their definitions,
all properties defined in this specification also accept the <a
href="http://www.w3.org/TR/CSS21/cascade.html#value-def-inherit">inherit</a>
keyword as their property value. For readability it has not been repeated
explicitly.
<h2 id=terms><span class=secno>2. </span> Terminology</h2>
<dl data-export=data-export>
<dt><dfn id=size>size</dfn>
<dd> A one- or two-dimensional measurement: a <a
href="http://www.w3.org/TR/css3-writing-modes/#measure"><i>measure</i></a>
and/or <a
href="http://www.w3.org/TR/css3-writing-modes/#extent"><i>extent</i></a>;
alternatively a width and/or height.
<dt><dfn id=definite title="definite|definite size">definite size</dfn>
<dd> A size that can be determined without measuring content; that is, a
<var><length></var>, a size of the <i>initial containing block</i>, or
a <var><percentage></var> that is resolved against a <a
href="#definite"><i>definite</i></a> size. Additionally, the size of the
<i>containing block</i> of an absolutely positioned element is always <a
href="#definite"><i>definite</i></a> with respect to that element.
<dt><dfn id=indefinite title="indefinite|indefinite size">indefinite
size</dfn>
<dd> A size that is not <a href="#definite"><i>definite</i></a>. An <a
href="#indefinite"><i>indefinite</i></a> <a
href="#available"><i>available size</i></a> is essentially infinite.
<dt><dfn id=available
title="available|available size|available measure|available extent|available space">available
size</dfn>
<dd> The space into which a box is laid out. Unless otherwise specified,
this is either a measurement of its <i>containing block</i> (if that is
<a href="#definite"><i>definite</i></a>) or an infinite size (when it is
<a href="#indefinite"><i>indefinite</i></a>). An <a
href="#available"><i>available size</i></a> can alternatively be either a
<dfn id=min-content-constraint>min-content constraint</dfn> or a <dfn
id=max-content-constraint>max-content constraint</dfn>. <!--
<p>
The space <i>available</i> to a box is determined by the formatting context in which it participates.
In block, table, and inline formatting contexts [[!CSS21]],
the <i>available size</i> is infinite in the block-axis dimension.
<span class="issue">What, exactly, is the available size in the inline axis??? What about other formatting models?</span>
-->
<dt><dfn id=fill-available-fit>fill-available fit</dfn>
<dd> The <a href="#fill-available-fit"><i>fill-available fit</i></a> into
a given size is that size, minus the element's computed margins (not
collapsed, treating ‘<code class=css>auto</code>’ as zero), border,
and padding in the given dimension.
<p class=note> Note: This is the formula used to calculate the ‘<code
class=css>auto</code>’ widths of non-replaced blocks in normal flow in
<a
href="http://www.w3.org/TR/CSS21/visudet.html#blockwidth">CSS2.1§10.3.3</a>.
<dt><dfn id=fallback-size title="fallback|fallback size">fallback
size</dfn>
<dd> Some sizing algorithms do not work well with an infinite size. In
these cases, the <a href="#fallback-size"><i>fallback size</i></a> is
used instead. Unless otherwise specified, this is the size of the
<i>initial containing block</i>.
<dt><dfn id=fill-available-measure>fill-available measure</dfn>
<dd> Roughly, the <i>measure<i> a box would take if it filled its <a
href="#available"><i>available measure</i></a>. (See <a
href="http://dev.w3.org/csswg/css3-sizing/#extrinsic-sizing">Extrinsic
Size Determination</a>.) </i></i>
<p class=note> Note: This is called the <i>available width</i> in <a
href="http://www.w3.org/TR/CSS21/visudet.html#float-width">CSS2.1§10.3.5</a>
and computed by the rules in <a
href="http://www.w3.org/TR/CSS21/visudet.html#blockwidth">CSS2.1§10.3.3</a>.
<dt><dfn id=max-content-measure>max-content measure</dfn>
<dd> Roughly, the narrowest <i>measure</i> a box could take while fitting
around its contents if <em>none</em> of the soft wrap opportunities
within the box were taken. (See <a
href="http://dev.w3.org/csswg/css3-sizing/#intrinsic-sizing">Intrinsic
Size Determination</a>.)
<p class=note> Note: This is called the <i>preferred width</i> in <a
href="http://www.w3.org/TR/CSS21/visudet.html#float-width">CSS2.1§10.3.5</a>
and the <i>maximum cell width</i> in <a
href="http://www.w3.org/TR/CSS21/tables.html#auto-table-layout">CSS2.1§17.5.2.2</a>.
<dt><dfn id=min-content-measure>min-content measure</dfn>
<dd> The narrowest <i>measure</i> a box could take that doesn't lead to
inline-dimension overflow that could be avoided by choosing a larger
<i>measure</i>. Roughly, the <i>measure</i> that would fit around its
contents if <em>all</em> soft wrap opportunities within the box were
taken. (See <a
href="http://dev.w3.org/csswg/css3-sizing/#intrinsic-sizing">Intrinsic
Size Determination</a>.)
<p class=note> Note: This is called the <i>preferred minimum width</i> in
<a
href="http://www.w3.org/TR/CSS21/visudet.html#float-width">CSS2.1§10.3.5</a>
and the <i>minimum content width</i> in <a
href="http://www.w3.org/TR/CSS21/tables.html#auto-table-layout">CSS2.1§17.5.2.2</a>.
<dt><dfn id=fit-content-measure>fit-content measure</dfn>
<dd> If the <a href="#available"><i>available</i></a> measure is finite,
equal to <code>min(<a href="#preferred-measure"><i>preferred
measure</i></a>, max(<a href="#min-content-measure"><i>min-content
measure</i></a>, <a href="#fill-available-measure"><i>fill-available
measure</i></a>))</code>. Otherwise, equal to the <a
href="#max-content-measure"><i>max-content measure</i></a>.
<p class=note> Note: This is called the <i>shrink-to-fit</i> width in <a
href="http://www.w3.org/TR/CSS21/visudet.html#float-width">CSS2.1§10.3.5</a>
and <a href="http://www.w3.org/TR/css3-multicol/#pseudo-algorithm">CSS
Multi-column Layout § 3.4</a>.
<dt><dfn id=preferred-measure>preferred measure</dfn>
<dd> A box’s “ideal” <i>measure</i>. Unless otherwise specified,
this is the <a href="#max-content-measure"><i>max-content
measure</i></a>.
<dt><dfn id=fill-available-extent>fill-available extent</dfn>
<dd> Roughly, the <i>extent</i> a box would take if it filled its <a
href="#available"><i>available extent</i></a>. (See <a
href="http://dev.w3.org/csswg/css3-sizing/#intrinsic-sizing">Intrinsic
Size Determination</a>.)
<dt><dfn id=max-content-extent>max-content extent</dfn>
<dd> Roughly, the <i>extent</i> of the content after layout.
<dt><dfn id=min-content-extent>min-content extent</dfn>
<dd> Equivalent to the <a href="#max-content-extent"><i>max-content
extent</i></a>.
<p class=issue> Or should this be the minimum between allowed break
points? It might make sense in multi-col contexts to have min-content
and max-content extents be different, even if they are the same
elsewhere.
<dt><dfn id=fit-content-extent>fit-content extent</dfn>
<dd> Analogous to the <a href="#fit-content-measure"><i>fit-content
measure</i></a>.
<dt><dfn id=preferred-extent>preferred extent</dfn>
<dd> Equivalent to the <a href="#max-content-extent"><i>max-content
extent</i></a>.
<p class=issue> Same issue as <a
href="#min-content-extent"><i>min-content extent</i></a>.
<dt><dfn id=max-size-contribution>max-size contribution</dfn>
<dd> The size that a box contributes to its <i>containing
block</i>‘<code class=css>s <i>max-content size</i>. </code>
<dt><dfn id=min-size-contribution>min-size contribution</dfn>
<dd> The size that a box contributes to its <i>containing block</i>’s
<i>min-content size</i>.
<dt><dfn id=preferred-size-contribution>preferred-size contribution</dfn>
<dd> If the box's layout mode has a defined <a
href="#preferred-size-contribution"><i>preferred-size
contribution</i></a>, that. Otherwise, the box's <a
href="#max-size-contribution"><i>max-size contribution</i></a>.
<dt><dfn id=max-size-constraint>max-size constraint</dfn>
<dd> A sizing constraint imposed by the box's <i>containing block</i> that
causes it to produce its <a href="#max-size-contribution"><i>max-size
contribution</i></a>.
<dt><dfn id=min-size-constraint>min-size constraint</dfn>
<dd> A sizing constraint imposed by the box's <i>containing block</i> that
causes it to produce its <a href="#min-size-contribution"><i>min-size
contribution</i></a>.
<dt><dfn id=preferred-size-constraint>preferred-size constraint</dfn>
<dd> A sizing constraint imposed by the box's <i>containing block</i> that
causes it to produce its <a
href="#preferred-size-contribution"><i>preferred-size
contribution</i></a>.
</dl>
<h2 id=size-keywords><span class=secno>3. </span> New Sizing Keywords</h2>
<h3 id=width-height-keywords><span class=secno>3.1. </span> New Keywords
for ‘<code class=property>width</code>’ and ‘<code
class=property>height</code>’</h3>
<table class=propdef>
<tbody>
<tr>
<th>Properties:
<td>‘<code class=property>width</code>’, ‘<code
class=property>min-width</code>’, ‘<code
class=property>max-width</code>’, ‘<code
class=property>height</code>’, ‘<code
class=property>min-height</code>’, ‘<code
class=property>max-height</code>’
<tr>
<th>New Values:
<td>fill | max-content | min-content | fit-content
<tr>
<th>Initial:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> and <a
href="#CSS3-FLEXBOX"
rel=biblioentry>[CSS3-FLEXBOX]<!--{{!CSS3-FLEXBOX}}--></a>
<tr>
<th>Applies to:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<tr>
<th>Inherited:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<tr>
<th>Percentages:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<tr>
<th>Media:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<tr>
<th>Computed value:
<td>specified value if keyword specified, else as defined in <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
</table>
<p>There are four types of automatically-determined sizes in CSS (which are
represented in the width and height properties by the keywords defined
above):
<dl>
<dt><dfn id=fill>‘<code class=css>fill</code>’</dfn>
<dd> Use the <a href="#fill-available-measure"><i>fill-available
measure</i></a> or <a href="#fill-available-extent"><i>fill-available
extent</i></a>, as appropriate to the writing mode.
<dt><dfn id=max-content>‘<code class=css>max-content</code>’</dfn>
<dd> Use the <a href="#max-content-measure"><i>max-content measure</i></a>
or <a href="#max-content-extent"><i>max-content extent</i></a>, as
appropriate to the writing mode.
<dt><dfn id=min-content>‘<code class=css>min-content</code>’</dfn>
<dd> Use the <a href="#min-content-measure"><i>min-content measure</i></a>
or <a href="#min-content-extent"><i>min-content extent</i></a>, as
appropriate to the writing mode.
<dt><dfn id=fit-content>‘<code class=css>fit-content</code>’</dfn>
<dd> Use the <a href="#fit-content-measure"><i>fit-content measure</i></a>
or <a href="#fit-content-extent"><i>fit-content extent</i></a>, as
appropriate to the writing mode.
<dt><dfn id=repudiate-floats>‘<code
class=css>repudiate-floats</code>’</dfn> <span class=issue>Less stupid
name?</span>
<dd> In the inline axis, use the larger of the min-content measure, and
the fill-available measure minus the size of any non-descendant floats in
the same formatting context. (This is similar to the behavior of a box
that establishes a formatting context next to a float.) In the block
axis, this is identical to ‘<code class=css>auto</code>’.
<p class=issue> Does this value work? Is it needed?
</dl>
<p class=issue> Right now all of these except ‘<a href="#fill"><code
class=css>fill</code></a>’ mean the same thing for extents. This may or
may not be ideal.
<p class=issue> If the measure is ‘<code class=css>auto</code>’, we
could have min-content extent imply a max-content measure, and vice versa.
<p class=note> Note that percentages resolved against the intrinsic sizes
(‘<a href="#max-content"><code class=css>max-content</code></a>’,
‘<a href="#min-content"><code class=css>min-content</code></a>’, ‘<a
href="#fit-content"><code class=css>fit-content</code></a>’, ‘<a
href="#repudiate-floats"><code class=css>repudiate-floats</code></a>’)
will compute to ‘<code class=css>auto</code>’, <a
href="http://www.w3.org/TR/CSS21/visudet.html#the-height-property">as
defined by CSS 2.1</a>. <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<h3 id=the-contain-floats-value><span class=secno>3.2. </span> Containing
Floats</h3>
<table class=propdef>
<tbody>
<tr>
<th>Properties:
<td>‘<code class=property>min-width</code>’, ‘<code
class=property>min-height</code>’
<tr>
<th>New Value:
<td>‘<a href="#contain-floats"><code
class=css>contain-floats</code></a>’
<tr>
<th>Initial:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> and <a
href="#CSS3-FLEXBOX"
rel=biblioentry>[CSS3-FLEXBOX]<!--{{!CSS3-FLEXBOX}}--></a>
<tr>
<th>Applies to:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<tr>
<th>Inherited:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<tr>
<th>Percentages:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<tr>
<th>Media:
<td>as defined in <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<tr>
<th>Computed value:
<td>specified value if keyword specified, else as defined in <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
</table>
<dl>
<dt><dfn id=contain-floats>‘<code
class=css>contain-floats</code>’</dfn>
<dd> Equivalent to ‘<a href="#min-content"><code
class=css>min-content</code></a>’ except that when applied to the
extent of a block box it forces the inner extent to be large enough to
contain the margin boxes of any floats that originate inside the block
and that participate in the same block formatting context as the block's
immediate contents.
</dl>
<h3 id=column-sizing><span class=secno>3.3. </span> Column Sizing Keywords</h3>
<table class=propdef>
<tbody>
<tr>
<th>Property:
<td>‘<code class=property>column-width</code>’
<tr>
<th>New Values:
<td>fill | max-content | min-content | fit-content
<tr>
<th>Initial:
<td>as defined in <a href="#CSS3COL"
rel=biblioentry>[CSS3COL]<!--{{!CSS3COL}}--></a>
<tr>
<th>Applies to:
<td>as defined in <a href="#CSS3COL"
rel=biblioentry>[CSS3COL]<!--{{!CSS3COL}}--></a>
<tr>
<th>Inherited:
<td>as defined in <a href="#CSS3COL"
rel=biblioentry>[CSS3COL]<!--{{!CSS3COL}}--></a>
<tr>
<th>Percentages:
<td>as defined in <a href="#CSS3COL"
rel=biblioentry>[CSS3COL]<!--{{!CSS3COL}}--></a>
<tr>
<th>Media:
<td>as defined in <a href="#CSS3COL"
rel=biblioentry>[CSS3COL]<!--{{!CSS3COL}}--></a>
<tr>
<th>Computed value:
<td>specified value if keyword specified, else as defined in <a
href="#CSS3COL" rel=biblioentry>[CSS3COL]<!--{{!CSS3COL}}--></a>
</table>
<p>When used as values for <a
href="http://www.w3.org/TR/css3-multicol/#cw">‘<code
class=property>column-width</code>’</a>, the new keywords specify the
optimal column width:
<dl>
<dt>‘<a href="#fill"><code class=css>fill</code></a>’
<dd>Specifies the optimal column width as the <a
href="#fill-available-measure"><i>fill-available measure</i></a> of the
multi-column element.
<dt>‘<a href="#max-content"><code class=css>max-content</code></a>’
<dd>Specifies the optimal column width as the <a
href="#max-content-measure"><i>max-content measure</i></a> of the
multi-column element's contents.
<dt>‘<a href="#min-content"><code class=css>min-content</code></a>’
<dd>Specifies the optimal column width as the <a
href="#min-content-measure"><i>min-content measure</i></a> of the
multi-column element's contents.
<dt>‘<a href="#fit-content"><code class=css>fit-content</code></a>’
<dd>Specifies the optimal column width as <code>min(<a
href="#max-content"><i>max-content</i></a>, max(<a
href="#min-content"><i>min-content</i></a>,
<i>fill-available</i>))</code>.
</dl>
<h2 id=intrinsic-sizing><span class=secno>4. </span> Intrinsic Size
Determination</h2>
<p> <dfn data-export=data-export id=intrinsic-sizing0>Intrinsic
sizing</dfn> determines sizes based on the contents of an element, without
regard for its context.
<h3 id=replaced-intrinsic><span class=secno>4.1. </span> Intrinsic Sizes of
Replaced Elements</h3>
<p> For replaced elements, the <a
href="#min-content"><i>min-content</i></a> and <a
href="#max-content"><i>max-content</i></a> sizes are equivalent and
correspond to the appropriate dimension of the concrete object size
returned by the <a
href="http://www.w3.org/TR/css3-images/#default-sizing">default sizing
algorithm</a> <a href="#CSS3-IMAGES"
rel=biblioentry>[CSS3-IMAGES]<!--{{!CSS3-IMAGES}}--></a> of the element,
calculated with an unconstrained specified size.
<h3 id=inline-intrinsic><span class=secno>4.2. </span> Intrinsic Sizes of
Non-Replaced Inlines</h3>
<p> The <a href="#min-content-measure"><i>min-content measure</i></a> of an
inline box is the length of the largest unbreakable sequence of inline
content. The <i>min-measure contribution</i> of an inline box is its <a
href="#min-content-measure"><i>min-content measure</i></a>, plus any
inline-axis margin, border, and padding adjacent to that sequence.
<p> The <a href="#max-content-measure"><i>max-content measure</i></a> of an
inline box is the length of the largest sequence of inline content on a
single line when only forced line breaks are taken. The <i>max-measure
contribution</i> of an inline box is its <a
href="#max-content-measure"><i>max-content measure</i></a>, plus any
inline-axis margin, border, and padding adjacent to that sequence.
<p> The <a href="#min-content-extent"><i>min-content extent</i></a>, <a
href="#max-content-extent"><i>max-content extent</i></a>, <i>min-extent
contribution</i>, and <i>max-content contribution</i> of an inline box are
the distance from the head edge of the first line box to the foot edge of
the last line box on which the inline appears.
<h3 id=block-intrinsic><span class=secno>4.3. </span> Intrinsic Sizes of
Non-Replaced Blocks</h3>
<p> The <a href="#min-content-measure"><i>min-content measure</i></a> of a
<i>block container box</i> is the largest <i>min-measure contribution</i>
of its in-flow or floated children.
<p> The <a href="#max-content-measure"><i>max-content measure</i></a> of a
<i>block container box</i> is the measure of the box after layout, if all
children are sized under a <a href="#max-size-constraint"><i>max-size
constraint</i></a>.
<p> If the computed measure of a <i>block-level box</i> is ‘<a
href="#min-content"><code class=css>min-content</code></a>’, ‘<a
href="#max-content"><code class=css>max-content</code></a>’, or a <a
href="#definite"><i>definite size</i></a>, its <i>min-measure
contribution</i> is that size plus any inline-axis margin, border, and
padding. Otherwise, if the computed measure of the block is ‘<a
href="#fit-content"><code class=css>fit-content</code></a>’, ‘<code
class=css>auto</code>’, or ‘<a href="#fill"><code
class=css>fill</code></a>’, its <i>min-measure contribution</i> is its
<a href="#min-content-measure"><i>min-content measure</i></a> plus any
inline-axis margin, border, and padding.
<p> If the computed measure of a <i>block-level box</i> is ‘<a
href="#min-content"><code class=css>min-content</code></a>’, ‘<a
href="#max-content"><code class=css>max-content</code></a>’, or a <a
href="#definite"><i>definite size</i></a>, its <i>max-measure
contribution</i> is that size plus any inline-axis margin, border, and
padding. Otherwise, if the computed measure of the block is ‘<a
href="#fit-content"><code class=css>fit-content</code></a>’, ‘<code
class=css>auto</code>’, or ‘<a href="#fill"><code
class=css>fill</code></a>’, its <i>max-measure contribution</i> is its
<a href="#max-content-measure"><i>max-content measure</i></a> plus any
inline-axis margin, border, and padding.
<p> The <a href="#min-content-extent"><i>min-content extent</i></a> and <a
href="#max-content-extent"><i>max-content extent</i></a> of a <i>block
container box</i> is the content extent as defined (for horizontal writing
modes) in <a
href="http://www.w3.org/TR/CSS21/visudet.html#normal-block">CSS2.1§10.6.3</a>
and <a
href="http://www.w3.org/TR/CSS21/tables.html#height-layout">CSS2.1§17.5.3</a>
for elements with ‘<code class=css>height: auto</code>’, and
analogously for vertical writing modes.
<p> The <i>min-extent contribution</i> and <i>max-extent contribution</i>
of a <i>block-level box</i> is the extent of the block after layout, plus
any block-axis margin, border, and padding.
<h3 id=table-intrinsic><span class=secno>4.4. </span> Intrinsic Sizes in
Table Layout</h3>
<p class=issue> ???
<h3 id=multicol-intrinsic><span class=secno>4.5. </span> Intrinsic Sizes in
Multi-column Layout</h3>
<p> The <a href="#min-content-measure"><i>min-content measure</i></a> of a
multi-column element with a computed ‘<code
class=property>column-width</code>’ not ‘<code
class=css>auto</code>’ is the smaller of its ‘<code
class=property>column-width</code>’ and the largest <i>min-measure
contribution</i> of its contents.
<p> The <a href="#min-content-measure"><i>min-content measure</i></a> of a
multi-column element with a computed ‘<code
class=property>column-width</code>’ of ‘<code class=css>auto</code>’
is the largest <i>min-measure contribution</i> of its contents multiplied
by its ‘<code class=property>column-count</code>’ (treating ‘<code
class=css>auto</code>’ as ‘<code class=css>1</code>’).
<p> The <a href="#max-content-measure"><i>max-content measure</i></a> of a
multi-column element with unrestrained column heights and a computed
‘<code class=property>column-count</code>’ not ‘<code
class=css>auto</code>’ is its ‘<code
class=property>column-count</code>’ multiplied by the larger of its
‘<code class=property>column-width</code>’ (treating ‘<code
class=css>auto</code>’ as 0) and the largest <i>max-measure
contribution</i> of its contents.
<p> The <a href="#max-content-measure"><i>max-content measure</i></a> of a
multi-column element with unrestrained column heights and a computed
‘<code class=property>column-count</code>’ of ‘<code
class=css>auto</code>’ is its ‘<code
class=property>column-width</code>’ multiplied by the number of columns
obtained by taking all allowed column breaks <a href="#CSS3-BREAK"
rel=biblioentry>[CSS3-BREAK]<!--{{CSS3-BREAK}}--></a>. <!--
The above was decided based on dholbert's example in http://lists.w3.org/Archives/Public/www-style/2012Oct/0017.html .
These definitions make multicols work well in flexbox,
both in 'stretch' and non-'stretch' cases,
without wasted space or needless overflow.
-->
<p> The <a href="#max-content-measure"><i>max-content measure</i></a> of a
multi-column element with restrained-height columns (i.e. a specified
‘<code class=property>extent</code>’ or ‘<code
class=property>max-extent</code>’) is the <i>measure</i> that would
exactly include all of its columns. It may be approximated by:
<ul>
<li> Laying out the element with column-spanning elements given ‘<code
class=css>display: none</code>’, and taking a measure that includes all
the columns.
<li> Laying out all of the column-spanning elements into that resulting
measure, and taking the resulting extent.
<li> Subtracting that resulting extent from the specified restraint,
laying out the element without column-spanning elements again into this
adjusted extent, and taking the measure of all its columns as its <a
href="#max-content-measure"><i>max-content measure</i></a>.
</ul>
<p> or by some more accurate method.
<p class=note> This approximation can result in some slack, but avoids
overflow in the most common cases, where the balanced height of the
columns above spanning elements are approximately equal.
<p class=note> In the common case of no column-spanning elements, this
approximation collapses to simply doing a layout, and measuring the
resulting columns.
<h2 id=extrinsic-sizing><span class=secno>5. </span> Extrinsic Size
Determination</h2>
<p> <dfn data-export=data-export id=extrinsic-sizing0>Extrinsic
sizing</dfn> determines sizes based on the context of an element, without
regard for its contents.
<p> The inner <a href="#fill-available-measure"><i>fill-available
measure</i></a> of a box is…
<ul>
<li> If the box is the root or is absolutely-positioned, the measure of
its containing block, else
<li> <code>max(<i>min-measure</i>|0, min(<i>max-measure</i>|infinity,
<i>measure</i>|<i>fill-available</i>))</code> where the sizes are inner
measures of the element establishing the box's <i>containing block</i>,
and where the first value is used if it is <a
href="#definite"><i>definite</i></a> and the second value otherwise.
</ul>
<p> …less the box's inline-axis margins (after any <a
href="http://www.w3.org/TR/CSS21/box.html#collapsing-margins">margin
collapsing</a>, and treating ‘<code class=css>auto</code>’ margins as
zero), borders, and padding.
<p> The <a href="#fill-available-extent"><i>fill-available extent</i></a>
of a box is defined analogously, but in the other dimension.
<p class=issue> This definition might end up skipping further up the
ancestor chain than we'd like in some cases. <a
href="http://lists.w3.org/Archives/Public/www-style/2012Oct/0204.html">Example.</a>
Maybe it should stop at each formatting root, or something similar? <!--
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T:::::::::::::::::::::Th:::::h E::::::::::::::::::::E d::::::d
T:::::::::::::::::::::Th:::::h E::::::::::::::::::::E d::::::d
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-->
<h2 id=conformance><span class=secno>6. </span> Conformance</h2>
<h3 id=conventions><span class=secno>6.1. </span> Document conventions</h3>
<p>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.
<p>All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes. <a
href="#RFC2119" rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a>
<p>Examples in this specification are introduced with the words “for
example” or are set apart from the normative text with
<code>class="example"</code>, like this:
<div class=example>
<p>This is an example of an informative example.
</div>
<p>Informative notes begin with the word “Note” and are set apart from
the normative text with <code>class="note"</code>, like this:
<p class=note>Note, this is an informative note.
<h3 id=conformance-classes><span class=secno>6.2. </span> Conformance
classes</h3>
<p>Conformance to CSS Intrinsic & Extrinsic Sizing Level 3 is defined
for three conformance classes:
<dl>
<dt><dfn data-noexport=data-noexport id=style-sheet
title="style sheet!!as conformance class">style sheet</dfn>
<dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
style sheet</a>.