csswg-drafts/css-exclusions/Overview.html at d7e717662ca9ba1d54a41d62cd097fe3b96ad79d · w3c/csswg-drafts · GitHub

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<!DOCTYPE html><html lang=en><head>
  <meta content="text/html; charset=utf-8" http-equiv=Content-Type>
  <title>CSS Exclusions Module Level 1</title>
  <link href=../default.css rel=stylesheet type=text/css>
  <link href=../csslogo.ico rel="shortcut icon" type=image/x-icon>
  <style>
  body {
    background: url("https://www.w3.org/StyleSheets/TR/logo-ED") top left no-repeat white;
    background-attachment: fixed;
    color: black;
    font-family: sans-serif;
    margin: 0 auto;
    max-width: 50em;
    padding: 2em 1em 2em 70px;
  }
  :link { color: #00C; background: transparent }
  :visited { color: #609; background: transparent }
  a[href]:active { color: #C00; background: transparent }
  a[href]:hover { background: #ffa }

  a[href] img { border-style: none }

  h1, h2, h3, h4, h5, h6 { text-align: left }
  h1, h2, h3 { color: #005A9C; }
  h1 { font: 170% sans-serif }
  h2 { font: 140% sans-serif }
  h3 { font: 120% sans-serif }
  h4 { font: bold 100% sans-serif }
  h5 { font: italic 100% sans-serif }
  h6 { font: small-caps 100% sans-serif }

  .hide { display: none }

  div.head { margin-bottom: 1em }
  div.head h1 { margin-top: 2em; clear: both }
  div.head table { margin-left: 2em; margin-top: 2em }

  p.copyright { font-size: small }
  p.copyright small { font-size: small }

  pre { margin-left: 2em }
  dt { font-weight: bold }

  ul.toc, ol.toc {
    list-style: none;
  }
  </style>

  <script defer src=//test.csswg.org/harness/annotate.js#css-exclusions-1_dev/css-exclusions-1 type=text/javascript></script>
<style type=text/css>
  .singleImgExample {
    display: block;
    margin: auto;
  }

  .example-table {
    table-layout: fixed;
    width: 100%;
  }

  .example-table tr td img {
    width: 90%;
  }
</style>

</head>
<body class=h-entry>
<div class=head>
  <p data-fill-with=logo><a class=logo href=http://www.w3.org/>
    <img alt=W3C height=48 src=https://www.w3.org/Icons/w3c_home width=72>
</a>
</p>
  <h1 class="p-name no-ref" id=title>CSS Exclusions Module Level 1</h1>
  <h2 class="no-num no-toc no-ref heading settled" id=subtitle><span class=content>Editor’s Draft,
    <span class=dt-updated><span class=value-title title=20141030>30 October 2014</span></span></span></h2>
  <div data-fill-with=spec-metadata><dl><dt>This version:<dd><a class=u-url href=http://dev.w3.org/csswg/css-exclusions/>http://dev.w3.org/csswg/css-exclusions/</a><dt>Latest version:<dd><a href=http://www.w3.org/TR/css3-exclusions/>http://www.w3.org/TR/css3-exclusions/</a><dt>Previous Versions:<dd><a href=http://www.w3.org/TR/2013/WD-css3-exclusions-20130528/ rel=previous>http://www.w3.org/TR/2013/WD-css3-exclusions-20130528/</a><dt>Feedback:<dd><span><a href="mailto:www-style@w3.org?subject=[css-exclusions] feedback">www-style@w3.org</a> with subject line “<kbd>[css-exclusions] <var>… message topic …</var></kbd>” (<a href=http://lists.w3.org/Archives/Public/www-style/ rel=discussion>archives</a>)</span><dt>Test Suite:<dd><a href=http://test.csswg.org/suites/css-exclusions-1_dev/nightly-unstable/>http://test.csswg.org/suites/css-exclusions-1_dev/nightly-unstable/</a><dd><span><a href=http://test.csswg.org/suites/css3-exclusions/nightly-unstable/>http://test.csswg.org/suites/css3-exclusions/nightly-unstable/</a></span><dt class=editor>Editors:<dd class=editor><div class="p-author h-card vcard"><a class="p-name fn u-email email" href=mailto:ratan@microsoft.com>Rossen Atanassov</a> (<span class="p-org org">Microsoft</span>)</div><dd class=editor><div class="p-author h-card vcard"><a class="p-name fn u-email email" href=mailto:vhardy@adobe.com>Vincent Hardy</a> (<span class="p-org org">Adobe</span>)</div><dd class=editor><div class="p-author h-card vcard"><a class="p-name fn u-email email" href=mailto:astearns@adobe.com>Alan Stearns</a> (<span class="p-org org">Adobe</span>)</div><dt>Issues list:<dd><span><a href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&amp;product=CSS&amp;component=Exclusions&amp;resolution=---&amp;cmdtype=doit">in Bugzilla</a></span></dl></div>
  <div data-fill-with=warning></div>
  <p class=copyright data-fill-with=copyright><a href=http://www.w3.org/Consortium/Legal/ipr-notice#Copyright>Copyright</a> © 2014 <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>
  <hr title="Separator for header">
</div>

<h2 class="no-num no-toc no-ref heading settled" id=abstract><span class=content>Abstract</span></h2>
<div class=p-summary data-fill-with=abstract><p>CSS Exclusions define arbitrary areas around which inline content (<a data-biblio-type=normative data-link-type=biblio href=#biblio-css21 title=CSS21>[CSS21]</a>) can flow. CSS Exclusions can be defined on any CSS block-level elements. CSS Exclusions extend the notion of content wrapping previously limited to floats.</p>

<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.</div>

<h2 class="no-num no-toc no-ref heading settled" id=status><span class=content>Status of this document</span></h2>
<div data-fill-with=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=%5Bcss-exclusions%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 “css-exclusions” in the subject,
	preferably like this:
	“[css-exclusions] <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>
	This document is governed by the <a href=http://www.w3.org/2014/Process-20140801/>1 August 2014 W3C Process Document</a>.
</div>
<div data-fill-with=at-risk></div>

<h2 class="no-num no-toc no-ref heading settled" id=contents><span class=content>Table of Contents</span></h2>
<div data-fill-with=table-of-contents><ul class=toc><li><a href=#intro><span class=secno>1</span> <span class=content>
Introduction</span></a><li><a href=#terms><span class=secno>2</span> <span class=content>
Terminology</span></a><li><a href=#exclusions><span class=secno>3</span> <span class=content>
Exclusions</span></a><ul class=toc><li><a href=#declaring-exclusions><span class=secno>3.1</span> <span class=content>
Declaring exclusions</span></a><ul class=toc><li><a href=#wrap-flow-property><span class=secno>3.1.1</span> <span class=content>
The <span class=property data-link-type=propdesc title=wrap-flow>wrap-flow</span> property</span></a></ul><li><a href=#scope-and-effect-of-exclusions><span class=secno>3.2</span> <span class=content>
Scope and effect of exclusions</span></a><li><a href=#propagation-of-exclusions><span class=secno>3.3</span> <span class=content>
Propagation of Exclusions</span></a><ul class=toc><li><a href=#wrap-through-property><span class=secno>3.3.1</span> <span class=content>
The <span class=property data-link-type=propdesc title=wrap-through>wrap-through</span> Property</span></a></ul><li><a href=#exclusions-order><span class=secno>3.4</span> <span class=content>
Exclusions order</span></a><li><a href=#exclusions-processing-model><span class=secno>3.5</span> <span class=content>
Processing model</span></a><ul class=toc><li><a href=#exclusions-processing-model-description><span class=secno>3.5.1</span> <span class=content>
Description</span></a><li><a href=#step-1><span class=secno>3.5.2</span> <span class=content>
Step 1: resolve exclusion boxes belonging to each <span data-link-type=dfn title="wrapping context">wrapping context</span></span></a><li><a href=#step-2><span class=secno>3.5.3</span> <span class=content>
Step 2: resolve wrapping contexts and lay out containing blocks</span></a><li><a href=#step-2-A><span class=secno>3.5.4</span> <span class=content>
Step 2-A: resolve the position and size of exclusion boxes</span></a><li><a href=#step-2-B><span class=secno>3.5.5</span> <span class=content>
Step 2-B: lay out containing block applying wrapping</span></a><li><a href=#processing-model-example><span class=secno>3.5.6</span> <span class=content>
Processing Model Example</span></a><ul class=toc><li><a href=#example-step-1><span class=secno>3.5.6.1</span> <span class=content>
Step 1: resolve exclusion boxes belonging to each <span data-link-type=dfn title="wrapping context">wrapping context</span></span></a><li><a href=#example-step-2><span class=secno>3.5.6.2</span> <span class=content>
Step 2: resolve wrapping contexts and lay out containing blocks</span></a><ul class=toc><li><a href=#example-resolving-rwc-1><span class=secno>3.5.6.2.1</span> <span class=content>
Resolving RWC-1</span></a><li><a href=#example-resolving-rwc-2><span class=secno>3.5.6.2.2</span> <span class=content>
Resolving RWC-2</span></a></ul></ul></ul><li><a href=#floats-and-exclusions><span class=secno>3.6</span> <span class=content>
Floats and exclusions</span></a><ul class=toc><li><a href=#floats-and-exclusions-similarities><span class=secno>3.6.1</span> <span class=content>
Similarities</span></a><li><a href=#floats-and-exclusions-differences><span class=secno>3.6.2</span> <span class=content>
Differences</span></a><li><a href=#floats-interop><span class=secno>3.6.3</span> <span class=content>
Interoperability</span></a><ul class=toc><li><a href=#effect-of-floats-on-exclusions><span class=secno>3.6.3.1</span> <span class=content>
Effect of floats on exclusions</span></a><li><a href=#effect-of-exclusions-on-floats><span class=secno>3.6.3.2</span> <span class=content>
Effect of exclusions on floats</span></a></ul></ul></ul><li><a href=#acks><span class=secno></span> <span class=content>
Acknowledgments</span></a><li><a href=#conformance><span class=secno></span> <span class=content>
Conformance</span></a><ul class=toc><li><a href=#conventions><span class=secno></span> <span class=content>
Document conventions</span></a><li><a href=#conformance-classes><span class=secno></span> <span class=content>
Conformance classes</span></a><li><a href=#partial><span class=secno></span> <span class=content>
Partial implementations</span></a><li><a href=#experimental><span class=secno></span> <span class=content>
Experimental implementations</span></a><li><a href=#testing><span class=secno></span> <span class=content>
Non-experimental implementations</span></a></ul><li><a href=#references><span class=secno></span> <span class=content>References</span></a><ul class=toc><li><a href=#normative><span class=secno></span> <span class=content>Normative References</span></a><li><a href=#informative><span class=secno></span> <span class=content>Informative References</span></a></ul><li><a href=#index><span class=secno></span> <span class=content>Index</span></a><li><a href=#property-index><span class=secno></span> <span class=content>Property Index</span></a><li><a href=#issues-index><span class=secno></span> <span class=content>Issues Index</span></a></ul></div>


<h2 class="heading settled" data-level=1 id=intro><span class=secno>1. </span><span class=content>
Introduction</span><a class=self-link href=#intro></a></h2>

<p><em>This section is not normative.</em></p>

<p>This specification defines features that allow inline flow
  content to wrap around outside the <span>exclusion area</span> of elements.</p>

<h2 class="heading settled" data-level=2 id=terms><span class=secno>2. </span><span class=content>
Terminology</span><a class=self-link href=#terms></a></h2>

  <dl data-export="">
    <dt><dfn data-dfn-type=dfn data-export="" id=exclusion-box title="exclusion box">Exclusion box<a class=self-link href=#exclusion-box></a></dfn>
    <dd>
      A <a href=http://www.w3.org/TR/css3-box/>box</a> (<a data-biblio-type=normative data-link-type=biblio href=#biblio-css3box title=CSS3BOX>[CSS3BOX]</a>) that defines
      an <span>exclusion area</span> for other boxes. The <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a> property is
      used to make an element’s generated box an exclusion box. An exclusion box
      contributes its <span>exclusion area</span> to its <a href=http://www.w3.org/TR/CSS2/visudet.html#containing-block-details>containing block’s</a>
      <span>wrapping context</span>. An element with a <span class=css>float</span> computed value other
      than <span class=css>none</span> does not become an exclusion.

    <dt><dfn data-dfn-type=dfn data-export="" id=exclusion-area title="exclusion area">Exclusion area<a class=self-link href=#exclusion-area></a></dfn>
    <dd>
      The area used for excluding inline flow content around an exclusion box. The
      <span>exclusion area</span> is equivalent to the
      <a href=http://www.w3.org/TR/CSS2/box.html#box-dimensions>border box</a>
      for an exclusion box.

      <p class=note>
        If a user agent implements both CSS Exclusions and CSS Shapes, the
        shape-outside property defines the exclusion area instead of the border box.

    <dt><dfn data-dfn-type=dfn data-export="" id=exclusion-element title="exclusion element">Exclusion element<a class=self-link href=#exclusion-element></a></dfn>
    <dd>
      An <span>exclusion element</span> is a block-level element which is not a float
      and generates an <span>exclusion box</span>. An element generates an exclusion
      box when its <span class=css>wrap-flow</span> property’s computed value is not <span class=css>auto</span>.

    <dt><dfn data-dfn-type=dfn data-export="" id=wrapping-context title="wrapping context">Wrapping context<a class=self-link href=#wrapping-context></a></dfn>
    <dd>
      The <span>wrapping context</span> of a box is a collection of <span>exclusion
      areas</span> contributed by its associated <span>exclusion boxes</span>.
      During layout, a box wraps its inline flow content in the <code>wrapping area</code>
      that corresponds to the subtraction of its <span>wrapping context</span> from
      its own <span>content area</span>.

<p>A box inherits its <a href=http://www.w3.org/TR/CSS2/visudet.html#containing-block-details>containing block’s</a> <span>wrapping context</span> unless it specifically
      resets it using the <a class=property data-link-type=propdesc href=#propdef-wrap-through title=wrap-through>wrap-through</a> property.</p>

    <dt><dfn data-dfn-type=dfn data-export="" id=content-area title="content area">Content area<a class=self-link href=#content-area></a></dfn>
    <dd>
      The <a href=http://www.w3.org/TR/CSS2/box.html#box-dimensions>content area</a>
      is normally used for layout of the inline flow content of a box.

    <dt><dfn data-dfn-type=dfn data-export="" id=wrapping-area title="wrapping area">Wrapping area<a class=self-link href=#wrapping-area></a></dfn>
    <dd>
      The area used for layout of inline flow content of a box affected by a
      <span>wrapping context</span>, defined by subtracting the <span>wrapping
      context</span> from its <span>content area</span>.

    <dt><dfn data-dfn-type=dfn data-export="" id=outside-inside title=outside-inside>Outside and inside<a class=self-link href=#outside-inside></a></dfn>
    <dd>
      In this specification, <span class=css>outside</span> refers to DOM content that is not a descendant
      of an element while <span class=css>inside</span> refers to the element’s descendants.
  </dl>

<h2 class="heading settled" data-level=3 id=exclusions><span class=secno>3. </span><span class=content>
Exclusions</span><a class=self-link href=#exclusions></a></h2>

<p>Exclusion elements define <span>exclusion areas</span> that contribute to their
  containing block’s <span>wrapping context</span>. As a consequence, exclusions
  impact the layout of their containing block’s descendants.</p>

<p>Elements lay out their inline content in their <span>content area</span> and wrap
  around the <span>exclusion areas</span> in their associated <span>wrapping
  context</span>. If the element is itself an exclusion, it does not wrap around
  its own exclusion area and the impact of other exclusions on other exclusions
  is controlled by the <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-position-3/#propdef-z-index title=z-index>z-index</a> property as explained in the
  'exclusions order' section.</p>

<h3 class="heading settled" data-level=3.1 id=declaring-exclusions><span class=secno>3.1. </span><span class=content>
Declaring exclusions</span><a class=self-link href=#declaring-exclusions></a></h3>

<p>An element becomes an exclusion when its <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a> property has a computed
  value other than <span class=css>auto</span>.</p>

<h4 class="heading settled" data-level=3.1.1 id=wrap-flow-property><span class=secno>3.1.1. </span><span class=content>
The <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a> property</span><a class=self-link href=#wrap-flow-property></a></h4>

<table class="definition propdef"><tr><th>Name:<td><dfn class=css data-dfn-type=property data-export="" id=propdef-wrap-flow>wrap-flow<a class=self-link href=#propdef-wrap-flow></a></dfn><tr><th>Value:<td class=prod>auto <a data-link-for="" data-link-type=grammar href=http://dev.w3.org/csswg/css-values-3/#comb-one title=|>|</a> both <a data-link-for="" data-link-type=grammar href=http://dev.w3.org/csswg/css-values-3/#comb-one title=|>|</a> start <a data-link-for="" data-link-type=grammar href=http://dev.w3.org/csswg/css-values-3/#comb-one title=|>|</a> end <a data-link-for="" data-link-type=grammar href=http://dev.w3.org/csswg/css-values-3/#comb-one title=|>|</a> minimum <a data-link-for="" data-link-type=grammar href=http://dev.w3.org/csswg/css-values-3/#comb-one title=|>|</a> maximum <a data-link-for="" data-link-type=grammar href=http://dev.w3.org/csswg/css-values-3/#comb-one title=|>|</a> clear<tr><th>Initial:<td>auto<tr><th>Applies to:<td>block-level elements.<tr><th>Inherited:<td>no<tr><th>Percentages:<td>N/A<tr><th>Media:<td>visual<tr><th>Computed value:<td>as specified except for element’s whose <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css2/visuren.html#propdef-float title=float>float</a> computed value is not <span class=css>none</span>, in which case the computed value is <span class=css>auto</span>.<tr><th>Animatable:<td>no</table>

<p>The values of this property have the following meanings:</p>

  <dl data-dfn-for=wrap-flow data-dfn-type=value>
    <dt><dfn class=css data-dfn-for=wrap-flow data-dfn-type=value data-export="" id=valdef-wrap-flow-wrap-flowauto title="'wrap-flow'!!'auto'">auto<a class=self-link href=#valdef-wrap-flow-wrap-flowauto></a></dfn>
    <dd>
        No exclusion is created. Inline flow content interacts with the element
        as usual. In particular, if the element is a
        <a href=http://www.w3.org/TR/CSS2/visuren.html#floats>float</a>
        (see <a data-biblio-type=normative data-link-type=biblio href=#biblio-css21 title=CSS21>[CSS21]</a>), the behavior is unchanged.

    <dt><dfn class=css data-dfn-for=wrap-flow data-dfn-type=value data-export="" id=valdef-wrap-flow-wrap-flowboth title="'wrap-flow'!!'both'">both<a class=self-link href=#valdef-wrap-flow-wrap-flowboth></a></dfn>
    <dd>
        Inline flow content can flow on all sides of the exclusion.

    <dt><dfn class=css data-dfn-for=wrap-flow data-dfn-type=value data-export="" id=valdef-wrap-flow-wrap-flowstart title="'wrap-flow'!!'start'">start<a class=self-link href=#valdef-wrap-flow-wrap-flowstart></a></dfn>
    <dd>
        Inline flow content can flow around the start edge of the <span>exclusion
        area</span> but must leave the area next to the end edge of the exclusion
        empty.

    <dt><dfn class=css data-dfn-for=wrap-flow data-dfn-type=value data-export="" id=valdef-wrap-flow-wrap-flowend title="'wrap-flow'!!'end'">end<a class=self-link href=#valdef-wrap-flow-wrap-flowend></a></dfn>
    <dd>
        Inline flow content can flow around the end edge of the
        <span>exclusion area</span> but must leave the area next to the start edge
        of the exclusion empty.

    <dt><dfn class=css data-dfn-for=wrap-flow data-dfn-type=value data-export="" id=valdef-wrap-flow-wrap-flowminimum title="'wrap-flow'!!'minimum'">minimum<a class=self-link href=#valdef-wrap-flow-wrap-flowminimum></a></dfn>
    <dd>
        Inline flow content can flow around the edge of the exclusion with the
        smallest available space within the flow content’s containing block, and
        must leave the other edge of the exclusion empty.

    <dt><dfn class=css data-dfn-for=wrap-flow data-dfn-type=value data-export="" id=valdef-wrap-flow-wrap-flowmaximum title="'wrap-flow'!!'maximum'">maximum<a class=self-link href=#valdef-wrap-flow-wrap-flowmaximum></a></dfn>
    <dd>
        Inline flow content can flow around the edge of the exclusion with the
        largest available space within the flow content’s containing block, and
        must leave the other edge of the exclusion empty.

    <dt><dfn class=css data-dfn-for=wrap-flow data-dfn-type=value data-export="" id=valdef-wrap-flow-wrap-flowclear title="'wrap-flow'!!'clear'">clear<a class=self-link href=#valdef-wrap-flow-wrap-flowclear></a></dfn>
    <dd>
        Inline flow content can only flow before and after the exclusion in the
        flow content’s block direction and must leave the areas next to the start
        and end edges of the exclusion empty.
  </dl>

<p>If the property’s computed value is <span class=css>auto</span>, the element does not become an
  <span>exclusion</span>.</p>

<p>Otherwise, a computed <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a> property value of <span class=css>both</span>, <span class=css>start</span>, <span class=css>end</span>,
  <span class=css>minimum</span>, <span class=css>maximum</span> or <span class=css>clear</span> on an  element makes that element an
  <a data-link-type=dfn href=#exclusion-element title="exclusion element">exclusion element</a>. It’s <a data-link-type=dfn href=#exclusion-area title="exclusion area">exclusion area</a> is contributed
  to its containing block’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>, causing the containing
  block’s descendants to wrap around its <a data-link-type=dfn href=#exclusion-area title="exclusion area">exclusion area</a>.</p>

  <div class=figure>
    <img alt="LTR text wrapping on left edge, RTL text wrapping on right edge, and vertical text wrapping on top edge." src=images/exclusion-writing-modes.png width=70%>
    <p class=caption>Exclusion with <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a>: <span class=css>start</span> interacting with various
    writing modes.</p>
  </div>

<p>Determining the relevant edges of the exclusion depends on the
  <a href=http://www.w3.org/TR/css3-writing-modes/#text-flow>writing mode</a> <a data-biblio-type=normative data-link-type=biblio href=#biblio-css3-writing-modes title=CSS3-WRITING-MODES>[CSS3-WRITING-MODES]</a> of the content wrapping around the 'exclusion area'.</p>

<p>An <a data-link-type=dfn href=#exclusion-element title="exclusion element">exclusion element</a> establishes a new <a href="">block formatting
  context</a> (see <a data-biblio-type=normative data-link-type=biblio href=#biblio-css21 title=CSS21>[CSS21]</a>) for its content.</p>

  <div class=figure>
      <img alt="General illustration showing how exclusions combine" src=images/exclusions-illustration.png width=70%>
      <p class=caption>Combining exclusions</p>
  </div>

<p>The abo
77C
ve figure illustrates how exclusions are combined. The outermost box
  represents an element’s content box. The A, B, C and D darker gray boxes
  represent exclusions in the element’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>.
  A, B, C and D have their respective <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a> computed to <span class=css>both</span>, <span class=css>start</span>,
  <span class=css>end</span> and <span class=css>clear</span> respectively. The lighter gray areas show the additional areas
  that are excluded for inline layout as a result of the 'wrap-flow’value.
  of left-to-right writing mode content because the <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a> for B is <span class=css>start</span>.</p>

<p>The background blue area shows what areas are available for a left-to-right
  writing mode element’s inline content layout.
  All areas represented with a light or dark shade of gray are not available for
  (left-to-right writing mode) inline content layout.</p>

<div class=example>
  The <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a> property values applied to exclusions as grid items.

<pre>&lt;div id="grid"&gt;
    &lt;div id="top-right" class="exclusion"&gt;&lt;/div&gt;
    &lt;div id="bottom-left" class="exclusion"&gt;&lt;/div&gt;
    &lt;div id="content"&gt;Lorem ipsum…&lt;/div&gt;
&lt;/div&gt;

&lt;style type="text/css"&gt;
#grid {
    width: 30em;
    height: 30em;
    display: grid;
    grid-columns: 25% 25% 25% 25%;
    grid-rows: 25% 25% 25% 25%;

#top-right {
    grid-column: 3;
    grid-row: 2;
}

#bottom-left {
    grid-column: 2;
    grid-row: 3;
}

.exclusion {
    wrap-flow: &lt;see below&gt;
}

#content {
    grid-row: 1;
    grid-row-span: 4;
    grid-column: 1;
    grid-column-span: 4;
}
&lt;/style&gt;
</pre>

<p>The following figures illustrate the visual rendering for different values
  of the <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a> property. The gray grid lines are marking the grid cells
  and the blue area is the exclusion box (positioned by the grid).</p>

  <table class=example-table>
      <tr>
          <td><code class=html>.exclusion{ wrap-flow: auto; }</code></td>
          <td><code class=html>.exclusion{ wrap-flow: both; }</code></td>
      </tr>
      <tr>
          <td><img alt="Example rendering for wrap-side: auto" src=images/exclusion_wrap_side_auto.png></td>
          <td><img alt="Example rendering for wrap-side: both" src=images/exclusion_wrap_side_both.png></td>
      </tr>
      <tr>
          <td><code class=html>.exclusion{ wrap-flow: start; }</code></td>
          <td><code class=html>.exclusion{ wrap-flow: end; }</code></td>
      </tr>
      <tr>
          <td><img alt="Example rendering for wrap-side: start" src=images/exclusion_wrap_side_left.png></td>
          <td><img alt="Example rendering for wrap-side: end" src=images/exclusion_wrap_side_right.png></td>
      </tr>
      <tr>
          <td><code class=html>.exclusion{ wrap-flow: minimum; }</code></td>
          <td><code class=html>.exclusion{ wrap-flow: maximum; }</code></td>
      </tr>
      <tr>
          <td><img alt="Example rendering for wrap-side: minimum" src=images/exclusion_wrap_side_minimum.png></td>
          <td><img alt="Example rendering for wrap-side: maximum" src=images/exclusion_wrap_side_maximum.png></td>
      </tr>
      <tr>
          <td><code class=html>.exclusion{ wrap-flow: clear; }</code></td>
          <td></td>
      </tr>
      <tr>
          <td><img alt="Example rendering for wrap-side: clear" src=images/exclusion_wrap_side_clear.png></td>
          <td></td>
      </tr>
  </table>
</div>


<h3 class="heading settled" data-level=3.2 id=scope-and-effect-of-exclusions><span class=secno>3.2. </span><span class=content>
Scope and effect of exclusions</span><a class=self-link href=#scope-and-effect-of-exclusions></a></h3>

<p>An <span>exclusion</span> affects the inline flow content descended from the
  exclusion’s containing block (defined in <a href=http://www.w3.org/TR/CSS2/visudet.html#containing-block-details>CSS 2.1 10.1</a>) and that of all descendant
  elements of the same containing block. All inline flow content inside the
  containing block of the exclusions is affected. To stop the effect of exclusions
  defined outside an element, the <a class=property data-link-type=propdesc href=#propdef-wrap-through title=wrap-through>wrap-through</a> property can be used
  (see the <a href=#propagation-of-exclusions>propagation of exclusions</a>
  section below).</p>

<p>As a reminder, for exclusions with <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-position-3/#propdef-position title=position>position</a>:<span class=css>fixed</span>, the containing block
  is established by the root element.</p>


<h3 class="heading settled" data-level=3.3 id=propagation-of-exclusions><span class=secno>3.3. </span><span class=content>
Propagation of Exclusions</span><a class=self-link href=#propagation-of-exclusions></a></h3>

<p>By default, an element inherits its parent <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>. In other
  words it is subject to the exclusions defined <span title=outside-inside>outside</span>
  the element.</p>

<p>Setting the <a class=property data-link-type=propdesc href=#propdef-wrap-through title=wrap-through>wrap-through</a> property to <span class=css>none</span> prevents an element from
  inheriting its parent <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>. In other words, exclusions
  defined <span class=css>outside</span> the element, have not effect on the element’s children layout.</p>

  <p class=note>
    Exclusions defined by an element’s descendants still contribute to their
    containing block’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>. If that containing block is a
    child of an element with <a class=property data-link-type=propdesc href=#propdef-wrap-through title=wrap-through>wrap-through</a> computes to <span class=css>none</span>, or the element
    itself, then exclusion still have an effect on the children of that
    containing block element.
  </p>

<h4 class="heading settled" data-level=3.3.1 id=wrap-through-property><span class=secno>3.3.1. </span><span class=content>
The <a class=property data-link-type=propdesc href=#propdef-wrap-through title=wrap-through>wrap-through</a> Property</span><a class=self-link href=#wrap-through-property></a></h4>

<table class="definition propdef"><tr><th>Name:<td><dfn class=css data-dfn-type=property data-export="" id=propdef-wrap-through>wrap-through<a class=self-link href=#propdef-wrap-through></a></dfn><tr><th>Value:<td class=prod>wrap <a data-link-for="" data-link-type=grammar href=http://dev.w3.org/csswg/css-values-3/#comb-one title=|>|</a> none<tr><th>Initial:<td>wrap<tr><th>Applies to:<td>block-level elements<tr><th>Inherited:<td>no<tr><th>Percentages:<td>N/A<tr><th>Media:<td>visual<tr><th>Computed value:<td>as specified<tr><th>Animatable:<td>no</table>

<p>The values of this property have the following meanings:</p>

<dl data-dfn-for=wrap-through data-dfn-type=value>
  <dt><dfn class=css data-dfn-for=wrap-through data-dfn-type=value data-export="" id=valdef-wrap-through-wrap-throughwrap title="'wrap-through'!!'wrap'">wrap<a class=self-link href=#valdef-wrap-through-wrap-throughwrap></a></dfn></dt>
  <dd>
    The element inherits its parent node’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>. Its descendant
    inline content wraps around exclusions defined <a data-link-type=dfn href=#outside-inside title=outside-inside>outside</a>
    the element.

  <dt><dfn class=css data-dfn-for=wrap-through data-dfn-type=value data-export="" id=valdef-wrap-through-wrap-throughnone title="'wrap-through'!!'none'">none<a class=self-link href=#valdef-wrap-through-wrap-throughnone></a></dfn></dt>
  <dd>
    The element does not inherit its parent node’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>. Its
    descendants are only subject to exclusion areas defined <a data-link-type=dfn href=#outside-inside title=outside-inside>inside</a>
    the element.
</dl>

<div class=example>
  Using the <a class=property data-link-type=propdesc href=#propdef-wrap-through title=wrap-through>wrap-through</a> property to control the effect of exclusions.

<pre><code class=html>

&lt;style type="text/css"&gt;
    #grid {
        display: grid;
        grid-columns: 25% 50% 25%;
        grid-rows: 25% 25% 25% 25%;
    }

    #exclusion {
        grid-row: 2;
        grid-row-span: 2;
        grid-column: 2;
        wrap-flow: &lt;see below&gt;
    }

    #rowA, #rowB {
        grid-row-span: 2;
        grid-column: 1;
        grid-column-span: 3;
    }

    #rowA {
        grid-row: 1;
    }

    #rowB {
        grid-row: 3;
    }
    &lt;/style&gt;

&lt;style type="text/css"&gt;
    .exclusion  {
      wrap-flow: both;
      position: absolute;
      left: 20%;
      top: 20%;
      width: 50%;
      height: 50%;
      background-color: rgba(220, 230, 242, 0.5);
    }
&lt;/style&gt;

&lt;div id="grid"&gt;
    &lt;div class=”exclusion”&gt;&lt;/div&gt;
    &lt;div id="rowA" style=”wrap-through: wrap;”&gt; Lorem ipsum dolor sit amet...&lt;/div&gt;
    &lt;div id="rowB" style=”wrap-through: none;”&gt; Lorem ipsum dolor sit amet...&lt;/div&gt;
&lt;/div&gt;
</code></pre>

<p><img alt="Example rendering of wrap-through: wrap | none" class=singleImgExample src=images/exclusion_wrap_through.png style=max-width:40%></p>
</div>


<h3 class="heading settled" data-level=3.4 id=exclusions-order><span class=secno>3.4. </span><span class=content>
Exclusions order</span><a class=self-link href=#exclusions-order></a></h3>

<p>Exclusions follow the painting order (See <a data-biblio-type=normative data-link-type=biblio href=#biblio-css21 title=CSS21>[CSS21]</a> Appendix E). Exclusions are
  applied in reverse to the document order in which they are defined. The last exclusion
  appears on top of all other exclusion, thus it affects the inline flow content of
  all other preceding exclusions or elements descendant of the same containing block.
  The <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-position-3/#propdef-z-index title=z-index>z-index</a> property can be used to change the ordering of
  <a href=http://www.w3.org/TR/CSS2/visuren.html#choose-position>positioned</a> exclusion
  boxes (see <a data-biblio-type=normative data-link-type=biblio href=#biblio-css21 title=CSS21>[CSS21]</a>). Statically positioned exclusions are not affected by the
  <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-position-3/#propdef-z-index title=z-index>z-index</a> property and thus follow the painting order.</p>

<div class=example>

<p>Ordering of exclusions.</p>

<pre><code class=html>
&lt;style type="text/css"&gt;
    .exclusion  {
      wrap-flow: both;
      position: absolute;
      width: 200px;
    }
    .topleft {
      top: 10px;
      left: 10px;
      background-color: lightblue;
    }
    .middle {
      top: 90px;
      left: 90px;
      background-color: lightgreen;
    }
    .bottomright {
      left: 170px;
      background-color: pink;
    }
&lt;/style&gt;

&lt;div class="exclusion topleft"&gt;
    The top left div...
&lt;/div&gt;
&lt;div class="exclusion middle"&gt;
    The middle div...
&lt;/div&gt;
&lt;div class="exclusion bottomright"&gt;
    The bottom right div...
&lt;/div&gt;
</code></pre>

<table class=example-table>
  <tr>
    <td style=width:50%><code class=html>.middle { z-index: auto; }</code></td>
    <td style=width:50%><code class=html>.middle { z-index: 1; }</code></td>
  </tr>
  <tr>
    <td><img alt="Example rendering of default exclusion ordering." class=singleImgExample src=images/exclusion_ordering.png></td>
    <td><img alt="Example rendering of default exclusion ordering." class=singleImgExample src=images/exclusion_ordering_z_order.png></td>
  </tr>
</table>
</div>


<div class="issue-marker wrapper">
  <div class=issue-marker>
    <a href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15183">Issue-15183</a>
    <div class=issue-details>
      <p class=short-desc>Is the CSS exclusions processing model incorrect?</p>
    </div>
  </div>
</div>

<div class=issue id=issue-53942a83><a class=self-link href=#issue-53942a83></a>

<p>The current draft provides a model for exclusions
  without a collision-avoidance model.
  The existing exclusion model in CSS uses floats,
  which have both exclusion and collision-avoidance behavior.
  Concerns have been raised that allowing exclusions
  without collision avoidance could be harmful,
  particularly with absolutely-positioned elements.
  Three options should be considered:</p>

  <ol>
  <li>Allow exclusions in positioning schemes
      with no collision avoidance.</li>
  <li>Disallow exclusions in positioning schemes
      with no collision avoidance.</li>
  <li>Define collision-avoidance behavior
      for positioning schemes without it,
      and use this behavior by default with exclusions.</li>
  </ol>
</div>

<h3 class="heading settled" data-level=3.5 id=exclusions-processing-model><span class=secno>3.5. </span><span class=content>
Processing model</span><a class=self-link href=#exclusions-processing-model></a></h3>

<h4 class="heading settled" data-level=3.5.1 id=exclusions-processing-model-description><span class=secno>3.5.1. </span><span class=content>
Description</span><a class=self-link href=#exclusions-processing-model-description></a></h4>

<p>Applying exclusions is a two-step process:</p>

<ul>
  <li><strong>Step 1</strong>: resolve exclusion boxes belonging to each
  <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>
  <li><strong>Step 2</strong>: resolve each <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> and lay out
  each containing block in turn:
  <ul>
    <li><strong>Step 2-A</strong>: resolve the position and size of exclusion
    boxes
    <li><strong>Step 2-B</strong>: lay out containing block, wrapping around
    each <a data-link-type=dfn href=#exclusion-area title="exclusion area">exclusion area</a>
  </ul>
</ul>

<h4 class="heading settled" data-level=3.5.2 id=step-1><span class=secno>3.5.2. </span><span class=content>
Step 1: resolve exclusion boxes belonging to each <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a></span><a class=self-link href=#step-1></a></h4>

<p>In this step, the user agent determines which <a href=http://www.w3.org/TR/CSS2/visudet.html#containing-block-details>containing block</a> each <a data-link-type=dfn href=#exclusion-area title="exclusion area">exclusion area</a>
  belongs to. This is a simple step, based on the definition of containing
  blocks and elements with a computed value for <a class=property data-link-type=propdesc href=#propdef-wrap-flow title=wrap-flow>wrap-flow</a> that is not
  <code class=css>auto</code>.</p>

<h4 class="heading settled" data-level=3.5.3 id=step-2><span class=secno>3.5.3. </span><span class=content>
Step 2: resolve wrapping contexts and lay out containing blocks</span><a class=self-link href=#step-2></a></h4>

<p>In this step, starting from the top of the <a href=http://www.w3.org/TR/CSS2/visuren.html#z-index>rendering tree</a> (see <a data-biblio-type=normative data-link-type=biblio href=#biblio-css21 title=CSS21>[CSS21]</a>), the the agent processes each
  containing block in two sub-steps.</p>

<h4 class="heading settled" data-level=3.5.4 id=step-2-A><span class=secno>3.5.4. </span><span class=content>
Step 2-A: resolve the position and size of exclusion boxes</span><a class=self-link href=#step-2-A></a></h4>

<p>Resolving the position and size of <a data-link-type=dfn href=#exclusion-box title="exclusion boxes">exclusion boxes</a> in the <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping
  context</a> may or may not require a layout. For example, if an <a data-link-type=dfn href=#exclusion-box title="exclusion box">exclusion
  box</a> is absolutely positioned and sized, a layout may not be needed to
  resolve its position and size. In other situations, laying out the containing
  block’s content is required.</p>

<p>When a layout is required, it is carried out without applying any <a data-link-type=dfn href=#exclusion-area title="exclusion area">exclusion
  area</a>. In other words, the containing block is laid out without a
  <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>.</p>

<p>Step 2-A yields a position and size for all <a data-link-type=dfn href=#exclusion-box title="exclusion boxes">exclusion boxes</a> in the
  <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>. Each exclusion box is processed in turn, starting from
  the top-most, and each <a data-link-type=dfn href=#exclusion-area title="exclusion area">exclusion area</a> is computed and contributed to the
  <a href=http://www.w3.org/TR/CSS2/visudet.html#containing-block-details>containing
  block’s</a> <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>.</p>

<p>Scrolling is ignored in this step when resolving the position and size of
  <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css-position-3/#propdef-position title=position>position</a>: <span class=css>fixed</span> <a data-link-type=dfn href=#exclusion-box title="exclusion boxes">exclusion boxes</a>.</p>

<p>Once the <a href=http://www.w3.org/TR/CSS2/visudet.html#containing-block-details>containing block’s</a> <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> is computed, all <a data-link-type=dfn href=#exclusion-box title="exclusion boxes">exclusion boxes</a> in
  that <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> are removed from the normal flow.</p>

<h4 class="heading settled" data-level=3.5.5 id=step-2-B><span class=secno>3.5.5. </span><span class=content>
Step 2-B: lay out containing block applying wrapping</span><a class=self-link href=#step-2-B></a></h4>

<p>Finally, the content of the containing block is laid out, with the inline content
wrapping around the <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>’s <a data-link-type=dfn href=#exclusion-area title="exclusion area">exclusion area</a>.</p>


<p>When the containing block itself is an <a data-link-type=dfn href=#exclusion-box title="exclusion box">exclusion box</a>, then rules on
  <a href=#exclusions-order>exclusions order</a> define which exclusions affect
  the inline and descendant content of the box.</p>

<h4 class="heading settled" data-level=3.5.6 id=processing-model-example><span class=secno>3.5.6. </span><span class=content>
Processing Model Example</span><a class=self-link href=#processing-model-example></a></h4>

<p>This section illustrates the exclusions processing model with an example.
  It is meant to be simple. Yet, it contains enough complexity to address the
  issues of layout dependencies and re-layout.</p>


<p>The code snippet in the following example has two exclusions affecting the
  document’s inline content.</p>

<div class=example>
<pre class=html>&lt;html&gt;
&lt;style&gt;
#d1 {
    position:relative;
    height: auto;<
6392
/div>    color: #46A4E9;
    border: 1px solid gray;
}

#e1 {
    wrap-flow: both;
    position: absolute;
    left: 50%;
    top: 50%;
    width: 40%;
    height: 40%;
    border: 1px solid red;
    margin-left: -20%;
    margin-top: -20%;
}

#d2 {
    position: static;
    width: 100%;
    height: auto;
    color: #808080;
}

#e2 {
    wrap-flow: both;
    position: absolute;
    right: 5ex;
    top: 1em;
    width: 12ex;
    height: 10em;
    border: 1px solid lime;
}
&lt;/style&gt;
&lt;body&gt;
    &lt;div id="d1"&gt;
        Lorem ipsusm ...
        &lt;p id="e1"&gt;&lt;/p&gt;
    &lt;/div&gt;
    &lt;div id="d2"&gt;
        Lorem ipsusm ...
        &lt;p id="e2" &gt;&lt;/p&gt;
    &lt;/div&gt;
&lt;/body&gt;
&lt;/html&gt;</pre>
</div>

<p>The following figures illustrate:</p>
  <ul>
    <li>the document’s DOM tree
    <li>the layout tree of generated block boxes
  </ul>

  <div class=figure>
    <img alt="DOM tree nodes" src=images/processing-model-example-dom.svg width=200>
    <p class=caption>DOM tree
  </div>

  <div class=figure>
    <img alt="Layout tree boxes" src=images/processing-model-example-layout-tree.svg width=350>
    <p class=caption>Layout tree of generated block boxes
  </div>

<h5 class="heading settled" data-level=3.5.6.1 id=example-step-1><span class=secno>3.5.6.1. </span><span class=content>
Step 1: resolve exclusion boxes belonging to each <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a></span><a class=self-link href=#example-step-1></a></h5>

<p>The figures illustrate how the boxes corresponding to the element sometimes
  have a different containment hierarchy in the layout tree than in the DOM tree.
  For example, the box generated by <code class=idl>e1</code> is positioned in
  its containing block’s box, which is the <code class=idl>d1-box</code>, because
  <code class=idl>e1</code> is absolutely positioned and <code class=idl>d1</code>
  is relatively positioned. However, while <code class=idl>e2</code> is also absolutely
  positioned, its containing block is the initial containing block (ICB). See the
  section 10.1 of the CSS 2.1 specification (<a data-biblio-type=normative data-link-type=biblio href=#biblio-css21 title=CSS21>[CSS21]</a>) for details.</p>

<p>As a result of the computation of containing blocks for the tree, the boxes
  belonging to the <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>s of all the elements can be determined:</p>

  <ul>
    <li>The <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> for the html element contains the
    <code class=idl>e2</code> box: WC-1 (Wrapping Context 1)

    <li>The <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> for the body element inherits the html
    element’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>: WC-1

    <li>The <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> for <code class=idl>d1</code> inherits the
    body element’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> and adds the <code class=idl>e1-box</code>
    to it. So the wrapping context is made of both the
    <code class=idl>e1-box</code> and the <code class=idl>e2-box</code>:
    WC-2</li>

    <li>The <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> for <code class=idl>d2</code> inherits the
    body element’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>: WC-1
  </ul>

<h5 class="heading settled" data-level=3.5.6.2 id=example-step-2><span class=secno>3.5.6.2. </span><span class=content>
Step 2: resolve wrapping contexts and lay out containing blocks</span><a class=self-link href=#example-step-2></a></h5>

<p>In this step, each containing block is processed in turn. For each containing
  block, we (conceptually) go through two phases:</p>

<ol>
  <li>resolve the <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>: resolve the position and size of its
  exclusions

  <li>lay out the containing block
</ol>

<p>In our example, this breaks down to:</p>

  <ol>
    <li>resolve the position and size of the exclusions belonging to WC-1:
    RWC-1 (Resolved Wrapping Context 1).

    <li>lay out the initial containing block (i.e., lay out its content):
    <ol>
      <li>resolve the html element’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>: RWC-1
      <li>lay out the html element:
        <ol>
          <li>resolve the body element’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>: RWC-1
          <li>lay out the body element:
            <ol>
              <li>resolve the <code class=idl>d1</code> element’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping
              context</a>: RWC-2

              <li>lay out the <code class=idl>d1</code> element

              <li>resolve the <code class=idl>d2</code> element’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping
              context</a>: RWC-1

              <li>lay out the <code class=idl>d2</code> element
            </ol>
          </li>
        </ol>
      </li>
    </ol>
  </li>
</ol>

<h6 class="heading settled" data-level=3.5.6.2.1 id=example-resolving-rwc-1><span class=secno>3.5.6.2.1. </span><span class=content>
Resolving RWC-1</span><a class=self-link href=#example-resolving-rwc-1></a></h6>

<p>The top-most <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> in the layout tree contains the
  <code class=idl>e2</code> exclusion. Its position and size needs to be
  resolved. In general, computing an exclusion’s position and size may or may
  not require laying out other content. In this example, no content needs to be
  laid out to resolve the <code class=idl>e2</code> exclusion’s position
  because it is absolutely positioned and its size can be resolved without
  layout either. At this point, RWC-1 is resolved and can be used when laying
  inline content out.<p></p>

<h6 class="heading settled" data-level=3.5.6.2.2 id=example-resolving-rwc-2><span class=secno>3.5.6.2.2. </span><span class=content>
Resolving RWC-2</span><a class=self-link href=#example-resolving-rwc-2></a></h6>

<p>The process is similar: the position of the <code class=idl>e1</code>
  exclusion needs to be resolved. Again, resolving the exclusion’s position and
  size may require processing the containing block (d1 here). It is the case here
  because the size and position of <code class=idl>e1</code> depend on
  resolving the percentage lengths. The percentages are relative to the size of
  <code class=idl>d1</code>’s box. As a result, in order to resolve a size for
  <code class=idl>d1</code>’s box, a first layout of <code class=idl>d1</code>
  is done without any <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> (i.e., no exclusions applied).
  The layout yields a position and size for <code class=idl>e1</code>’s box.</p>

<p>At this point, RWC-2 is resolved because the position and size of both e1 and
  e2 are resolved.</p>

  <p class=note>The important aspect of the above processing example is that
  once an element’s <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> is resolved (by resolving its
  exclusions' position and size), the position and size of the exclusions are
  not re-processed if the element’s size changes between the layout that may be
  done without considering any <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a> (as for RWC-2) and the
  layout done with the resolved <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>. This is what breaks the
  possible circular dependency between the resolution of <a data-link-type=dfn href=#wrapping-context title="wrapping context">wrapping context</a>s
  and the layout of containing blocks.</p>

<h3 class="heading settled" data-level=3.6 id=floats-and-exclusions><span class=secno>3.6. </span><span class=content>
Floats and exclusions</span><a class=self-link href=#floats-and-exclusions></a></h3>

<h4 class="heading settled" data-level=3.6.1 id=floats-and-exclusions-similarities><span class=secno>3.6.1. </span><span class=content>
Similarities</span><a class=self-link href=#floats-and-exclusions-similarities></a></h4>

<p>There are similarities between floats and exclusions in that inline content
  wraps around floats and also wraps around <span>exclusion areas</span>. However,
  there are very significant differences.</p>

<h4 class="heading settled" data-level=3.6.2 id=floats-and-exclusions-differences><span class=secno>3.6.2. </span><span class=content>
Differences</span><a class=self-link href=#floats-and-exclusions-differences></a></h4>

  <ul>
    <li><strong>scope</strong>. While floats apply to content that follows in the
    document, exclusions apply to content in their containing block.

    <li><strong>positioning</strong>. Floats are part of the inline flow and
    <a class=property data-link-type=propdesc href=http://dev.w3.org/csswg/css2/visuren.html#propdef-float title=float>float</a> on the line box. Authors can control how the floats move on the line
    box, to the right or to the left. By contrast, exclusions can be positioned
    using any positioning scheme such as grid layout (<a data-biblio-type=informative data-link-type=biblio href=#biblio-css3-grid-layout title=CSS3-GRID-LAYOUT>[CSS3-GRID-LAYOUT]</a>),
    flexible box (<a data-biblio-type=informative data-link-type=biblio href=#biblio-css3-flexbox title=CSS3-FLEXBOX>[CSS3-FLEXBOX]</a>) or any other CSS positioning scheme.

    <li><strong>separation of concerns</strong>. Making an element a float
    determines both its positioning scheme and its effect on inline content.
    Making an element an exclusion only determines its impact on inline content
    and does not impose constraints on its positioning method.
  </ul>

<h4 class="heading settled" data-level=3.6.3 id=floats-interop><span class=secno>3.6.3. </span><span class=content>
Interoperability</span><a class=self-link href=#floats-interop></a></h4>

<h5 class="heading settled" data-level=3.6.3.1 id=effect-of-floats-on-exclusions><span class=secno>3.6.3.1. </span><span class=content>
Effect of floats on exclusions</span><a class=self-link href=#effect-of-floats-on-exclusions></a></h5>

<p>Floats have an effect on the positioning of exclusions and the layout of their
  inline content. For example, if an exclusion is an inline-box which happens to
  be on the same line as a float, its position, as computed in
  <a href=#step-2-A>Step 2-A</a> will be impacted by the float, as is any other
  inline content.</p>

<h5 class="heading settled" data-level=3.6.3.2 id=effect-of-exclusions-on-floats><span class=secno>3.6.3.2. </span><span class=content>
Effect of exclusions on floats</span><a class=self-link href=#effect-of-exclusions-on-floats></a></h5>

<p>Exclusions have an effect on the positioning of floats as they have an effect
  on inline content. Therefore, in <a href=#step-2-B>Step 2-B</a>, floats will
  avoid <a data-link-type=dfn href=#exclusion-area title="exclusion areas">exclusion areas</a>.</p>

<h2 class="no-num heading settled" id=acks><span class=content>
Acknowledgments</span><a class=self-link href=#acks></a></h2>

<p>This specification is made possible by input from
  Andrei Bucur,
  Alexandru Chiculita,
  Arron Eicholz,
  Daniel Glazman,
  Arno Gourdol,
  Chris Jones,
  Bem Jones-Bey,
  Marcus Mielke,
  Alex Mogilevsky,
  Hans Muller,
  Mihnea Ovidenie,
  Virgil Palanciuc,
  Florian Rivoal,
  Peter Sorotokin,
  Bear Travis,
  Eugene Veselov,
  Stephen Zilles
  and the CSS Working Group members.</p>

<h2 class="no-ref no-num heading settled" id=conformance><span class=content>
Conformance</span><a class=self-link href=#conformance></a></h2>

<h3 class="no-ref heading settled" id=conventions><span class=content>
Document conventions</span><a class=self-link href=#conventions></a></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 data-biblio-type=normative data-link-type=biblio href=#biblio-rfc2119 title=RFC2119>[RFC2119]</a></p>

    <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.</p>
    </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.</p>

    <p>Advisements are normative sections styled to evoke special attention and are
    set apart from other normative text with <code>&lt;strong class="advisement"&gt;</code>, like
    this: