csswg-drafts/css-exclusions/Overview.html at 99f3ea751933f473f01bf386f5d414982d12ea75 · w3c/csswg-drafts · GitHub

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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">

<html lang=en>
 <head
  profile="http://dublincore.org/documents/2008/08/04/dc-html/ http://www.w3.org/2006/03/hcard">
  <meta content="text/html; charset=utf-8" http-equiv=Content-Type>
  <title>CSS Exclusions Module Level 1</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 Exclusions Module Level 1" name=dcterms.title>
  <meta content=text name=dcterms.type>
  <meta content=2013-10-01 name=dcterms.date>
  <meta content="Vincent Hardy" name=dcterms.creator>
  <meta content="Rossen Atanassov" name=dcterms.creator>
  <meta content="Alan Stearns" name=dcterms.creator>
  <meta content=W3C name=dcterms.publisher>
  <meta content="http://dev.w3.org/csswg/css-exclusions/"
   name=dcterms.identifier>
  <link href="../shared/style/default.css" rel=stylesheet type="text/css">
  <script defer=defer
   src="http://test.csswg.org/harness/annotate.js#css-exclusions-1_dev"
   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>
  <link href="../shared/style/issues.css" rel=stylesheet type="text/css">
  <link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
   type="text/css">
  <link href="../shared/style/alternate-spec-style.css" id=st rel=stylesheet
   title="alternate spec style" type="text/css">

 <body>
  <div class=head id=div-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 id=css-exclusions-module>CSS Exclusions Module Level 1</h1>

   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 1 October 2013</h2>

   <dl>
    <dt>This version:

    <dd><a
     href="http://dev.w3.org/csswg/css-exclusions/">http://dev.w3.org/csswg/css-exclusions/</a></dd>
    <!--<dd><a href="http://dev.w3.org/csswg/css-exclusions/">http://www.w3.org/TR/2013/WD-css-exclusions-20131001/</a></dd>-->

    <dt>Latest version:

    <dd><a
     href="http://www.w3.org/TR/css3-exclusions/">http://www.w3.org/TR/css3-exclusions/</a>

    <dt>Editor's Draft:

    <dd><a
     href="http://dev.w3.org/csswg/css-exclusions/">http://dev.w3.org/csswg/css-exclusions/</a>

    <dt>Previous version:

    <dd><a
     href="http://www.w3.org/TR/2013/WD-css3-exclusions-20130528/">http://www.w3.org/TR/2013/WD-css3-exclusions-20130528/</a>

    <dt>Editors:

    <dd class=vcard><span class=fn>Vincent Hardy</span>, <span
     class=org>Adobe Systems, Inc.</span>, <span
     class=email>vhardy@adobe.com</span>

    <dd class=vcard><span class=fn>Rossen Atanassov</span>, <span
     class=org>Microsoft Corporation</span>, <span
     class=email>ratan@microsoft.com</span>

    <dd class=vcard><span class=fn>Alan Stearns</span>, <span class=org>Adobe
     Systems, Inc.</span>, <span class=email>stearns@adobe.com</span>

    <dt>Issues List:

    <dd><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>

    <dt>Feedback:

    <dd><a
     href="mailto:www-style@w3.org?subject=%5B[css-exclusions]%5D%20feedback">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>)

    <dt>Test Suite:

    <dd><a
     href="http://test.csswg.org/suites/css3-exclusions/nightly-unstable/">http://test.csswg.org/suites/css3-exclusions/nightly-unstable/</a>
   </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>CSS Exclusions define arbitrary areas around which <a
   href="http://www.w3.org/TR/CSS2/visuren.html#inline-boxes">inline
   content</a> (<a href="#CSS21"
   rel=biblioentry>[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.

  <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=%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>
  <!--end-status-->

  <p>This specification was previously called “CSS Exclusions and
   Shapes.” The definitions for shapes are now in a separate specification,
   see <a href="#CSS-SHAPES"
   rel=biblioentry>[CSS-SHAPES]<!--{{CSS-SHAPES}}--></a>.

  <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>

   <li><a href="#definitions"><span class=secno>2. </span>Terminology</a>

   <li><a href="#exclusions"><span class=secno>3. </span>Exclusions</a>
    <ul class=toc>
     <li><a href="#declaring-exclusions"><span class=secno>3.1.
      </span>Declaring exclusions</a>
      <ul class=toc>
       <li><a href="#wrap-flow-property"><span class=secno>3.1.1. </span>The
        ‘<code class=property>wrap-flow</code>’ property</a>
      </ul>

     <li><a href="#scope-and-effect-of-exclusions"><span class=secno>3.2.
      </span>Scope and effect of exclusions</a>

     <li><a href="#propagation-of-exclusions"><span class=secno>3.3.
      </span>Propagation of Exclusions</a>
      <ul class=toc>
       <li><a href="#wrap-through-property"><span class=secno>3.3.1.
        </span>The ‘<code class=property>wrap-through</code>’
        Property</a>
      </ul>

     <li><a href="#exclusions-order"><span class=secno>3.4. </span>Exclusions
      order</a>

     <li><a href="#exclusions-processing-model"><span class=secno>3.5.
      </span>Processing model</a>
      <ul class=toc>
       <li><a href="#exclusions-processing-model-description"><span
        class=secno>3.5.1. </span>Description</a>

       <li><a
        href="#step-1-resolve-exclusion-boxes-belonging-to-each-wrapping-context"><span
        class=secno>3.5.2. </span>Step 1: resolve exclusion boxes belonging
        to each <span>wrapping context</span></a>

       <li><a
        href="#step-2-resolve-wrapping-contexts-layout-containing-blocks"><span
        class=secno>3.5.3. </span>Step 2: resolve wrapping contexts and lay
        out containing blocks</a>

       <li><a href="#step-2-A-resolve-exclusions-position-and-size"><span
        class=secno>3.5.4. </span>Step 2-A: resolve the position and size of
        exclusion boxes</a>

       <li><a
        href="#step-2-B-layout-containing-block-applying-wrapping"><span
        class=secno>3.5.5. </span>Step 2-B: lay out containing block applying
        wrapping</a>

       <li><a href="#exclusions-processing-model-example"><span
        class=secno>3.5.6. </span>Example</a>
        <ul class=toc>
         <li><a href="#step-1-resolve-exclusion-boxes-belonging"><span
          class=secno>3.5.6.1. </span>Step 1: resolve exclusion boxes
          belonging to each <span>wrapping context</span></a>

         <li><a href="#step-2-resolve-wrapping-contexts-and-lay"><span
          class=secno>3.5.6.2. </span>Step 2: resolve wrapping contexts and
          lay out containing blocks</a>
          <ul class=toc>
           <li><a href="#resolving-rwc-1"><span class=secno>3.5.6.2.1.
            </span>Resolving RWC-1</a>

           <li><a href="#resolving-rwc-2"><span class=secno>3.5.6.2.2.
            </span>Resolving RWC-2</a>
          </ul>
        </ul>
      </ul>

     <li><a href="#floats-and-exclusions"><span class=secno>3.6.
      </span>Floats and exclusions</a>
      <ul class=toc>
       <li><a href="#floats-and-exclusions-similarities"><span
        class=secno>3.6.1. </span>Similarities</a>

       <li><a href="#floats-and-exclusions-differences"><span
        class=secno>3.6.2. </span>Differences</a>

       <li><a href="#floats-and-exclusions-interoperability"><span
        class=secno>3.6.3. </span>Interoperability</a>
        <ul class=toc>
         <li><a href="#effect-of-floats-on-exclusions"><span
          class=secno>3.6.3.1. </span>Effect of floats on exclusions</a>

         <li><a href="#effect-of-exclusions-on-floats"><span
          class=secno>3.6.3.2. </span>Effect of exclusions on floats</a>
        </ul>
      </ul>
    </ul>

   <li><a href="#conformance"><span class=secno>4. </span>Conformance</a>

   <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>

   <li class=no-num><a href="#change-log">Change Log</a>
    <ul class=toc>
     <li class=no-num><a href="#since-may-3rd-2012">Since May 3rd 2012</a>

     <li class=no-num><a href="#since-december-13th-2011">Since December 13th
      2011</a>
    </ul>
  </ul>
  <!--end-toc-->

  <h2 id=intro><span class=secno>1. </span>Introduction</h2>

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

  <p> This specification defines features that allow inline flow content to
   wrap around outside the <a href="#exclusion-area">exclusion area</a> of
   elements.

  <h2 id=definitions><span class=secno>2. </span>Terminology</h2>

  <p><dfn id=exclusion-box>Exclusion box</dfn>

  <p> A <a href="http://www.w3.org/TR/css3-box/">box</a> (<a href="#CSS3BOX"
   rel=biblioentry>[CSS3BOX]<!--{{!CSS3BOX}}--></a>) that defines an <a
   href="#exclusion-area">exclusion area</a> for other boxes. The ‘<a
   href="#wrap-flow"><code class=property>wrap-flow</code></a>’ property is
   used to make an element's generated box an exclusion box. An exclusion box
   contributes its <a href="#exclusion-area">exclusion area</a> to its <a
   href="http://www.w3.org/TR/CSS2/visudet.html#containing-block-details">
   containing block's</a> <a href="#wrapping-context">wrapping context</a>.
   An element with a ‘<code class=property>float</code>’ computed value
   other than ‘<code class=property>none</code>’ does not become an
   exclusion.

  <p><dfn id=exclusion-area>Exclusion area</dfn>

  <p> The area used for excluding inline flow content around an exclusion
   box. The <a href="#exclusion-area">exclusion area</a> 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.

  <p><dfn id=exclusion-element>Exclusion element</dfn>

  <p> An <a href="#exclusion-element">exclusion element</a> is a block-level
   element which is not a float and generates an <a
   href="#exclusion-box">exclusion box</a>. An element generates an exclusion
   box when its ‘<a href="#wrap-flow"><code
   class=property>wrap-flow</code></a>’ property's computed value is not
   ‘<code class=property>auto</code>’.

  <p><dfn id=wrapping-context>Wrapping context</dfn>

  <p> The <a href="#wrapping-context">wrapping context</a> of a box is a
   collection of <a href="#exclusion-area">exclusion areas</a> contributed by
   its associated <a href="#exclusion-box">exclusion boxes</a>. During
   layout, a box wraps its inline flow content in the <a
   href="#wrapping-area"><code>wrapping area</code></a> that corresponds to
   the subtraction of its <a href="#wrapping-context">wrapping context</a>
   from its own <a href="#content-area">content area</a>.

  <p> A box inherits its <a
   href="http://www.w3.org/TR/CSS2/visudet.html#containing-block-details">containing
   block's</a> <a href="#wrapping-context">wrapping context</a> unless it
   specifically resets it using the ‘<a href="#wrap-through"><code
   class=property>wrap-through</code></a>’ property.

  <p><dfn id=content-area>Content area</dfn>

  <p> 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.

  <p><dfn id=wrapping-area>Wrapping area</dfn>

  <p> The area used for layout of inline flow content of a box affected by a
   <a href="#wrapping-context">wrapping context</a>, defined by subtracting
   the <a href="#wrapping-context">wrapping context</a> from its <a
   href="#content-area">content area</a>

  <p><dfn id=outside-and-inside title=outside-inside>Outside and inside</dfn>

  <p> In this specification, ‘<code class=property>outside</code>’ refers
   to DOM content that is not a descendant of an element while ‘<code
   class=property>inside</code>’ refers to the element's descendants.

  <h2 id=exclusions><span class=secno>3. </span>Exclusions</h2>

  <p> Exclusion elements define <a href="#exclusion-area">exclusion areas</a>
   that contribute to their containing block's <a
   href="#wrapping-context">wrapping context</a>. As a consequence,
   exclusions impact the layout of their containing block's descendants.

  <p>

  <p> Elements layout their inline content in their <a
   href="#content-area">content area</a> and wrap around the <a
   href="#exclusion-area">exclusion areas</a> in their associated <a
   href="#wrapping-context">wrapping context</a>. 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 ‘<code
   class=property>z-index</code>’ property as explained in the <a
   href="#exclusions-order">exclusions order</a> section.

  <h3 id=declaring-exclusions><span class=secno>3.1. </span>Declaring
   exclusions</h3>

  <p> An element becomes an exclusion when its ‘<a href="#wrap-flow"><code
   class=property>wrap-flow</code></a>’ property has a computed value other
   than ‘<code class=property>auto</code>’.

  <h4 id=wrap-flow-property><span class=secno>3.1.1. </span>The ‘<a
   href="#wrap-flow"><code class=property>wrap-flow</code></a>’ property</h4>

  <table class=propdef>
   <tbody>
    <tr>
     <th>Name:

     <td><dfn id=wrap-flow title="'wrap-flow'">wrap-flow</dfn>

    <tr>
     <th>Value:

     <td><var>auto</var> | <var>both</var> | <var>start</var> |
      <var>end</var> | <var>minimum</var> | <var>maximum</var> |
      <var>clear</var>

    <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 ‘<code
      class=property>float</code>’ computed value is not <code
      class=css>none</code>, in which case the computed value is ‘<code
      class=property>auto</code>’.
  </table>

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

  <dl>
   <dt><dfn id=auto title="'wrap-flow'!!'auto'">auto</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
    href="#CSS21" rel=biblioentry>[CSS21]<!--{{CSS21}}--></a>), the behavior
    is unchanged.

   <dt><dfn id=both title="'wrap-flow'!!'both'">both</dfn>

   <dd> Inline flow content can flow on all sides of the exclusion.

   <dt><dfn id=start title="'wrap-flow'!!'start'">start</dfn>

   <dd> Inline flow content can flow around the start edge of the <a
    href="#exclusion-area">exclusion area</a> but must leave the area next to
    the end edge of the exclusion empty.

   <dt><dfn id=end title="'wrap-flow'!!'end'">end</dfn>

   <dd> Inline flow content can flow around the end edge of the <a
    href="#exclusion-area">exclusion area</a> but must leave the area next to
    the start edge of the exclusion empty.

   <dt><dfn id=minimum title="'wrap-flow'!!'minimum'">minimum</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 id=maximum title="'wrap-flow'!!'maximum'">maximum</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 id=clear title="'wrap-flow'!!'clear'">clear</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 ‘<code
   class=property>auto</code>’, the element does not become an
   <span>exclusion</span>.

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

  <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 ‘<code class=css>wrap-flow:
    start</code>’ interacting with various writing modes.
  </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 href="#CSS3-WRITING-MODES"
   rel=biblioentry>[CSS3-WRITING-MODES]<!--{{!CSS3-WRITING-MODES}}--></a> of
   the content wrapping around the <a href="#exclusion-area">exclusion
   area</a>.

  <p>An <a href="#exclusion-element">exclusion element</a> establishes a new
   <a href="">block formatting context</a> (see <a href="#CSS21"
   rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>) for its content.

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

  <p> The above 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
   href="#wrapping-context">wrapping context</a>. A, B, C and D have their
   respective ‘<a href="#wrap-flow"><code
   class=property>wrap-flow</code></a>’ computed to ‘<code
   class=property>both</code>’, ‘<code class=property>start</code>’,
   ‘<code class=property>end</code>’ and ‘<code
   class=property>clear</code>’ respectively. The lighter gray areas show
   the additional areas that are excluded for inline layout as a result of
   the ‘<a href="#wrap-flow"><code
   class=property>wrap-flow</code></a>’value. For example, the area to the
   right of ‘<code class=property>B</code>’ cannot be used for inline
   layout of left-to-right writing mode content because the ‘<a
   href="#wrap-flow"><code class=property>wrap-flow</code></a>’ for
   ‘<code class=property>B</code>’ is ‘<code
   class=property>start</code>’.

  <p> The background ‘<code class=property>blue</code>’ 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.

  <div class=example>
   <p> The ‘<a href="#wrap-flow"><code
    class=property>wrap-flow</code></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 href="#wrap-flow"><code
    class=property>wrap-flow</code></a>’ property. The gray grid lines are
    marking the grid cells. and the blue area is the exclusion box
    (positioned by the grid).

   <table class=example-table>
    <tbody>
     <tr>
      <td><code class=html>.exclusion{ wrap-flow: auto; }</code>

      <td><code class=html>.exclusion{ wrap-flow: both; }</code>

     <tr>
      <td><img alt="Example rendering for wrap-side: auto"
       src="images/exclusion_wrap_side_auto.png">

      <td><img alt="Example rendering for wrap-side: both"
       src="images/exclusion_wrap_side_both.png">

     <tr>
      <td><code class=html>.exclusion{ wrap-flow: start; }</code>

      <td><code class=html>.exclusion{ wrap-flow: end; }</code>

     <tr>
      <td><img alt="Example rendering for wrap-side: start"
       src="images/exclusion_wrap_side_left.png">

      <td><img alt="Example rendering for wrap-side: end"
       src="images/exclusion_wrap_side_right.png">

     <tr>
      <td><code class=html>.exclusion{ wrap-flow: minimum; }</code>

      <td><code class=html>.exclusion{ wrap-flow: maximum; }</code>

     <tr>
      <td><img alt="Example rendering for wrap-side: minimum"
       src="images/exclusion_wrap_side_minimum.png">

      <td><img alt="Example rendering for wrap-side: maximum"
       src="images/exclusion_wrap_side_maximum.png">

     <tr>
      <td><code class=html>.exclusion{ wrap-flow: clear; }</code>

      <td>

     <tr>
      <td><img alt="Example rendering for wrap-side: clear"
       src="images/exclusion_wrap_side_clear.png">

      <td>
   </table>
  </div>
  <!-- End section "wrap-flow Property" -->
  <!-- End section "Declaring Exclusions" -->

  <h3 id=scope-and-effect-of-exclusions><span class=secno>3.2. </span>Scope
   and effect of exclusions</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 href="#wrap-through"><code
   class=property>wrap-through</code></a>’ property can be used (see the <a
   href="#propagation-of-exclusions">propagation of exclusions</a> section
   below).

  <p> As a reminder, for exclusions with ‘<code
   class=css>position:fixed</code>’, the containing block is that of the
   root element.</p>
  <!-- End section "Scope and Effect of Exclusions" -->

  <h3 id=propagation-of-exclusions><span class=secno>3.3. </span>Propagation
   of Exclusions</h3>

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

  <p>Setting the ‘<a href="#wrap-through"><code
   class=property>wrap-through</code></a>’ property to ‘<code
   class=property>none</code>’ prevents an element from inheriting its
   parent <a href="#wrapping-context">wrapping context</a>. In other words,
   exclusions defined ‘<code class=property>outside</code>’ the element,
   have not effect on the element's children layout.

  <div class=note> Exclusions defined by an element's descendants still
   contribute to their containing block's <a
   href="#wrapping-context">wrapping context</a>. If that containing block is
   a child of an element with ‘<a href="#wrap-through"><code
   class=property>wrap-through</code></a>’ computes to none, or the element
   itself, then exclusion still have an effect on the children of that
   containing block element.</div>

  <h4 id=wrap-through-property><span class=secno>3.3.1. </span>The ‘<a
   href="#wrap-through"><code class=property>wrap-through</code></a>’
   Property</h4>

  <table class=propdef>
   <tbody>
    <tr>
     <th>Name:

     <td><dfn id=wrap-through title="'wrap-through'">wrap-through</dfn>

    <tr>
     <th>Value:

     <td><var>wrap</var> | <var>none</var>

    <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
  </table>

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

  <dl>
   <dt><dfn id=wrap title="'wrap-through'!!'wrap'">wrap</dfn>

   <dd> The element inherits its parent node's <a
    href="#wrapping-context">wrapping context</a>. Its descendant inline
    content wraps around exclusions defined <a href="#outside-and-inside"
    title=outside-inside>outside</a> the element.
  </dl>

  <dl>
   <dt><dfn id=none title="'wrap-through'!!'none'">none</dfn>

   <dd> The element does not inherit its parent node's <a
    href="#wrapping-context">wrapping context</a>. Its descendants are only
    subject to exclusion areas defined <a href="#outside-and-inside"
    title=outside-inside>inside</a> the element.
  </dl>

  <div class=example>
   <p> Using the ‘<a href="#wrap-through"><code
    class=property>wrap-through</code></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>
   <img alt="Example rendering of wrap-through: wrap | none"
   class=singleImgExample src="images/exclusion_wrap_through.png"
   style="max-width:40%"></div>
  <!-- End section "wrap-through property" -->
  <!-- End section "Propagation of Exclusions" -->

  <h3 id=exclusions-order><span class=secno>3.4. </span>Exclusions order</h3>

  <p> Exclusions follow the painting order (See <a href="#CSS21"
   rel=biblioentry>[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 ‘<code
   class=property>z-index</code>’ 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 href="#CSS21"
   rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>). Statically positioned
   exclusions are not affected by the ‘<code
   class=property>z-index</code>’ property and thus follow the painting
   order.

  <div class=example>
   <p>Ordering of exclusions.

   <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 {
      top: 170px;
      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>
    <tbody>
     <tr>
      <td style="width:50%"><code class=html>.middle { z-index: auto;
       }</code>

      <td style="width:50%"><code class=html>.middle { z-index: 1; }</code>

     <tr>
      <td><img alt="Example rendering of default exclusion ordering."
       class=singleImgExample src="images/exclusion_ordering.png">

      <td><img alt="Example rendering of default exclusion ordering."
       class=singleImgExample src="images/exclusion_ordering_z_order.png">
   </table>
  </div>
  <!-- End section "Order of Exclusions" -->

  <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?
    </div>
   </div>
  </div>

  <div class=issue>
   <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>Disallow exclusions in positioning schemes with no collision
     avoidance.

    <li>Define collision-avoidance behavior for positioning schemes without
     it, and use this behavior by default with exclusions.
   </ol>
  </div>

  <h3 id=exclusions-processing-model><span class=secno>3.5. </span>Processing
   model</h3>

  <h4 id=exclusions-processing-model-description><span class=secno>3.5.1.
   </span>Description</h4>

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

  <ul>
   <li><strong>Step 1</strong>: resolve exclusion boxes belonging to each <a
    href="#wrapping-context">wrapping context</a>

   <li><strong>Step 2</strong>: resolve <a href="#wrapping-context">wrapping
    context</a>s 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
      <a href="#exclusion-area">exclusion areas</a>
    </ul>
  </ul>

  <h4
   id=step-1-resolve-exclusion-boxes-belonging-to-each-wrapping-context><span
   class=secno>3.5.2. </span>Step 1: resolve exclusion boxes belonging to
   each <a href="#wrapping-context">wrapping context</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 href="#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 href="#wrap-flow"><code
   class=property>wrap-flow</code></a>’ that is not <code
   class=css>auto</code>.

  <h4 id=step-2-resolve-wrapping-contexts-layout-containing-blocks><span
   class=secno>3.5.3. </span>Step 2: resolve wrapping contexts and lay out
   containing blocks</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 href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>), the
   the agent processes each containing block in two sub-steps.

  <h4 id=step-2-A-resolve-exclusions-position-and-size><span
   class=secno>3.5.4. </span>Step 2-A: resolve the position and size of
   exclusion boxes</h4>

  <p>Resolving the position and size of <a href="#exclusion-box">exclusion
   boxes</a> in the <a href="#wrapping-context">wrapping context</a> may or
   may not require a layout. For example, if an <a
   href="#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.