drafts: css3-exclusions/Overview.html@757d9e99cd55 (annotated)

css3-exclusions/Overview.html@757d9e99cd55 (annotated)

css3-exclusions/Overview.html

Thu, 12 Apr 2012 12:57:08 -0700

author: Vincent Hardy <vhardy@adobe.com>
date: Thu, 12 Apr 2012 12:57:08 -0700
changeset 5468: 757d9e99cd55
parent 5466: fb0270eb9aa2
child 5488: d3306d846020
permissions: -rw-r--r--

Added note about animated images, as per https://www.w3.org/Style/CSS/Tracker/actions/441

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    <h1 id=css-exclusions-module>CSS Exclusions and Shapes Module Level 3</h1>
    <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 12 April 2012</h2>
    <dl>
     <dt>This version:
     <dd><a
      href="http://dev.w3.org/csswg/css3-exclusions/">http://dev.w3.org/csswg/css3-exclusions/</a></dd>
     <!--<dd><a href="http://www.w3.org/TR/2012/ED-css3-exclusions-20120412/">http://www.w3.org/TR/2012/WD-css3-exclusions-20120412/</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/css3-exclusions/">http://dev.w3.org/csswg/css3-exclusions/</a>
     <dt>Previous version:
     <dd>None
     <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>
     <dt>Issues List:
     <dd><a
      href="https://www.w3.org/Bugs/Public/buglist.cgi?query_format=advanced&product=CSS&component=Exclusions&resolution=---&cmdtype=doit">in
      Bugzilla</a>
     <dt>Discussion:
     <dd><a
      href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a>
      with subject line "<code>[css3-exclusions] message topic</code>"
    </dl>
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     href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
     rel=license>Copyright</a> &copy; 2012 <a href="http://www.w3.org/"><abbr
     title="World Wide Web Consortium">W3C</abbr></a><sup>&reg;</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>,
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   </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>) content 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>CSS Shapes control the geometric shapes used for wrapping inline flow
    content outside or inside an element. CSS Shapes can be applied to any
    element. A circle shape on a float will cause inline content to wrap
    around the circle shape instead of the float's bounding box.
   <p>Combining CSS Exclusions and CSS Shapes allows sophisticated layouts,
    allowing interactions between shapes in complex positioning schemes.
   <h2 class="no-num no-toc" id=status>Status of this document</h2>
   <!--begin-status-->
   <p>This is a public copy of the editors' draft. It is provided for
    discussion only and may change at any moment. Its publication here does
    not imply endorsement of its contents by W3C. Don't cite this document
    other than as work in progress.
   <p>The (<a
    href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
    mailing list <a
    href="mailto:www-style@w3.org?Subject=%5Bcss3-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
    &#8220;css3-exclusions&#8221; in the subject, preferably like this:
    &#8220;[<!---->css3-exclusions<!---->] <em>&hellip;summary of
    comment&hellip;</em>&#8221;
   <p>This document was produced by the <a href="/Style/CSS/members">CSS
    Working Group</a> (part of the <a href="/Style/">Style Activity</a>).
   <p>This document was produced by a group operating under the <a
    href="/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent
    Policy</a>. W3C maintains a <a href="/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="/Consortium/Patent-Policy-20040205/#def-essential">Essential
    Claim(s)</a> must disclose the information in accordance with <a
    href="/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the
    W3C Patent Policy</a>.</p>
   <!--end-status-->
   <p>This is the First Public Working Draft of the CSS Exclusions and Shapes
    Level 3 Module.
   <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>Definitions</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
         &lsquo;<code class=property>wrap-flow</code>&rsquo; property</a>
       </ul>
      <li><a href="#scope-and-effect-of-exclusions"><span class=secno>3.2.
       </span>Scope and effect of exclusions</a>
       <ul class=toc>
        <li><a href="#wrap-margin-property"><span class=secno>3.2.1.
         </span>The &lsquo;<code class=property>wrap-margin</code>&rsquo;
         property</a>
        <li><a href="#wrap-padding-property"><span class=secno>3.2.2.
         </span>The &lsquo;<code class=property>wrap-padding</code>&rsquo;
         Property</a>
       </ul>
      <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 &lsquo;<code class=property>wrap-through</code>&rsquo;
         Property</a>
        <li><a href="#wrap-shorthand-property"><span class=secno>3.3.2.
         </span>The &lsquo;<code class=property>wrap</code>&rsquo; Shorthand
         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 wrapping context</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
         layout 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 exclusions position and
         size</a>
        <li><a
         href="#step-2-B-layout-containing-block-applying-wrapping"><span
         class=secno>3.5.5. </span>Step 2-B: layout 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 wrapping context</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
           layout 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="#shapes"><span class=secno>4. </span>Shapes</a>
     <ul class=toc>
      <li><a href="#relation-to-box-model-and-float-behavior"><span
       class=secno>4.1. </span>Relation to the box model and float
       behavior</a>
      <li><a href="#shapes-from-svg-syntax"><span class=secno>4.2.
       </span>Shapes from SVG Syntax</a>
       <ul class=toc>
        <li><a href="#supported-svg-shapes"><span class=secno>4.2.1.
         </span>Supported SVG Shapes</a>
        <li><a href="#referencing-svg-shapes"><span class=secno>4.2.2.
         </span>Referencing SVG shapes</a>
       </ul>
      <li><a href="#shapes-from-image"><span class=secno>4.3. </span>Shapes
       from Image</a>
      <li><a href="#declaring-shapes"><span class=secno>4.4. </span>Declaring
       Shapes</a>
       <ul class=toc>
        <li><a href="#shape-outside-property"><span class=secno>4.4.1.
         </span>The &lsquo;<code class=property>shape-outside</code>&rsquo;
         Property</a>
        <li><a href="#shape-inside-property"><span class=secno>4.4.2.
         </span>The &lsquo;<code class=property>shape-inside</code>&rsquo;
         Property</a>
        <li><a href="#shape-image-threshold-property"><span class=secno>4.4.3.
         </span>The &lsquo;<code
         class=property>shape-image-threshold</code>&rsquo; Property</a>
       </ul>
     </ul>
    <li><a href="#conformance"><span class=secno>5. </span>Conformance</a>
     <ul class=toc>
      <li><a href="#conventions"><span class=secno>5.1. </span>Document
       Conventions</a>
      <li><a href="#conformance-classes"><span class=secno>5.2.
       </span>Conformance Classes</a>
      <li><a href="#partial"><span class=secno>5.3. </span> Partial
       Implementations</a>
      <li><a href="#experimental"><span class=secno>5.4. </span> Experimental
       Implementations</a>
      <li><a href="#testing"><span class=secno>5.5. </span> Non-Experimental
       Implementations</a>
      <li><a href="#cr-exit-criteria"><span class=secno>5.6. </span> CR Exit
       Criteria</a>
     </ul>
    <li class=no-num><a href="#acknowledgments">Acknowledgments</a>
    <li class=no-num><a href="#references">References</a>
     <ul class=toc>
      <li class=no-num><a href="#normative-references">Normative
       references</a>
      <li class=no-num><a href="#other-references">Other references</a>
     </ul>
    <li class=no-num><a href="#index">Index</a>
    <li class=no-num><a href="#property-index">Property index</a>
    <li class=no-num><a href="#change-log">Change Log</a>
     <ul class=toc>
      <li><a href="#since-december-13th-2011"><span class=secno>5.7.
       </span>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> The exclusions section of this specification defines features that
    allow inline flow content to wrap around outside the <a
    href="#exclusion-area">exclusion area</a> of elements.
   <p> The shapes section of the specification defines properties to control
    the geometry of an element's <a href="#exclusion-area">exclusion area</a>
    as well as the geometry used for wrapping an element's inline flow
    content.
   <h2 id=definitions><span class=secno>2. </span>Definitions</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 &lsquo;<a
    href="#wrap-flow"><code class=property>wrap-flow</code></a>&rsquo;
    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 &lsquo;<code class=property>float</code>&rsquo; computed
    value other than &lsquo;<code class=property>none</code>&rsquo; does not
    become an exclusion.
   <p><dfn id=exclusion-area>Exclusion area</dfn>
   <div class=issue-marker data-bug_id=15087 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15087">Bug-15087</a>
    <div class=issue-details>
     <p class=short-desc>Interaction of floats and exclusions (Howcome's
      questions)</p>
    </div>
   </div>
   <p> The area used for excluding inline flow content around an exclusion
    element. The exclusion area is equivalent to the <a
    href="http://www.w3.org/TR/CSS2/box.html#box-dimensions"> border box</a>.
    This specification's &lsquo;<a href="#shape-outside"><code
    class=property>shape-outside</code></a>&rsquo; property can be used to
    define arbitrary, non-rectangular exclusion areas.
   <p><dfn id=float-area>Float area</dfn>
   <p> The area used for excluding inline flow content around a float element.
    By default, the float area is the <a
    href="http://www.w3.org/TR/CSS2/box.html#box-dimensions">margin box</a>.
    This specification's &lsquo;<a href="#shape-outside"><code
    class=property>shape-outside</code></a>&rsquo; property can be used to
    define arbitrary, non-rectangular float areas.
   <p><dfn id=wrapping-context>Wrapping context</dfn>
   <div class=issue-marker data-bug_id=15086 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15086">Bug-15086</a>
    <div class=issue-details>
     <p class=short-desc>should the wrapping context be generic and include
      floats?</p>
    </div>
   </div>
   <p> The wrapping context of a box is a collection of &lsquo;<a
    href="#exclusion-area"><code class=css>exclusion areas</code></a>&rsquo;.
    During layout, a box wraps its inline flow content in the area that
    corresponds to the subtraction of its wrapping context 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> wrapping context unless it specifically resets it using the
    &lsquo;<a href="#wrap-through"><code
    class=property>wrap-through</code></a>&rsquo; property.
   <p><dfn id=content-area>Content area</dfn>
   <p> The area used for layout of the inline flow content of a box. By
    default the area is equivalent to the <a
    href="http://www.w3.org/TR/CSS2/box.html#box-dimensions">content box</a>.
    This specification's &lsquo;<a href="#shape-inside"><code
    class=property>shape-inside</code></a>&rsquo; property can define
    arbitrary, non-rectangular content areas.
   <p><dfn id=outside-and-inside title=outside-inside>Outside and inside</dfn>
   <p> In this specification, &lsquo;<code
    class=property>outside</code>&rsquo; refers to DOM content that is not a
    descendant of an element while &lsquo;<code
    class=property>inside</code>&rsquo; refers to the element's descendants.
   <h2 id=exclusions><span class=secno>3. </span>Exclusions</h2>
   <p> Exclusion elements define exclusion areas 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 areas in their
    associated wrapping context. If the element is itself an exclusion, it
    does not wrap around its own exclusion shape and the impact of other
    exclusions on other exclusions is controlled by the &lsquo;<code
    class=property>z-index</code>&rsquo; property as explained in the <a
    href="#exclusions-order">exclusions order</a> section.
   <p> The <a href="#shapes">shape properties</a> can be used to change the
    shape of <a href="#exclusion-area">exclusion areas</a>.
   <h3 id=declaring-exclusions><span class=secno>3.1. </span>Declaring
    exclusions</h3>
   <p> An element becomes an exclusion when its &lsquo;<a
    href="#wrap-flow"><code class=property>wrap-flow</code></a>&rsquo;
    property has a computed value other than &lsquo;<code
    class=property>auto</code>&rsquo;.
   <h4 id=wrap-flow-property><span class=secno>3.1.1. </span>The &lsquo;<a
    href="#wrap-flow"><code class=property>wrap-flow</code></a>&rsquo;
    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>maximum</var> | <var>clear</var>
     <tr>
      <th>Initial:
      <td>auto
     <tr>
      <th>Applies to:
      <td>block-level elements. Does not apply to elements with a &lsquo;<code
       class=property>float</code>&rsquo; computed value other than <code
       class=css>none</code>
     <tr>
      <th>Inherited:
      <td>no
     <tr>
      <th>Percentages:
      <td>N/A
     <tr>
      <th>Media:
      <td>visual
     <tr>
      <th>Computed&nbsp;value:
      <td>as specified
   </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.
    <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 before the start edge of the exclusion
     area but must leave the area after the end edge of the exclusion empty.
    <dt><dfn id=end title="'wrap-flow'!!'end'">end</dfn>
    <dd> Inline flow content can flow after the end edge of the exclusion area
     but must leave the area before the start edge of the exclusion empty.
    <dt><dfn id=maximum title="'wrap-flow'!!'maximum'">maximum</dfn>
    <dd> Inline flow content can flow on the edge of the exclusion with the
     largest available space for the given line, 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 on top and bottom edges of the
     exclusion and must leave the areas before the start and after the end
     edges of the exclusion empty.
   </dl>
   <p> If the property's computed value is &lsquo;<code
    class=property>auto</code>&rsquo;, the element does not become an
    <span>exclusion</span>.
   <p> Otherwise, a computed &lsquo;<a href="#wrap-flow"><code
    class=property>wrap-flow</code></a>&rsquo; property value of &lsquo;<code
    class=property>both</code>&rsquo;, &lsquo;<code
    class=property>start</code>&rsquo;, &lsquo;<code
    class=property>end</code>&rsquo;, &lsquo;<code
    class=property>maximum</code>&rsquo; or &lsquo;<code
    class=property>clear</code>&rsquo; on an element makes that element an
    <span>exclusion element. It's <span>exclusion shape</span> is contributed
    to its containing block's <a href="#wrapping-context">wrapping
    context</a>, causing the containing block's descendants to wrap around its
    exclusion area. </span>
   <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 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 wrapping context. A, B, C and
    D have their respective &lsquo;<a href="#wrap-flow"><code
    class=property>wrap-flow</code></a>&rsquo; set to &lsquo;<code
    class=property>both</code>&rsquo;, &lsquo;<code
    class=property>start</code>&rsquo;, &lsquo;<code
    class=property>end</code>&rsquo; and &lsquo;<code
    class=property>clear</code>&rsquo; respectively. The lighter gray areas
    show the additional areas that are excluded for inline layout as a result
    of the &lsquo;<a href="#wrap-flow"><code
    class=property>wrap-flow</code></a>&rsquo; value. For example, the area to
    the right of &lsquo;<code class=property>B</code>&rsquo; cannot be used
    for inline layout because the &lsquo;<a href="#wrap-flow"><code
    class=property>wrap-flow</code></a>&rsquo; for &lsquo;<code
    class=property>B</code>&rsquo; is &lsquo;<code
    class=property>start</code>&rsquo;.
   <p> The background &lsquo;<code class=property>blue</code>&rsquo; area
    shows what areas are available for the element's inline content layout.
    All areas represented with a light or dark shade of gray are not available
    for inline content layout.
   <div class=issue-marker data-bug_id=15088 data-bug_status=FIXED> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15088">Bug-15088</a>
    <div class=issue-details>
     <p class=short-desc>Add an example with auto-height content and z-index
      for exclusions order.</p>
    </div>
   </div>
   <div class=issue-marker data-bug_id=15084 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15084">Bug-15084</a>
    <div class=issue-details>
     <p class=short-desc>Fluidity of the layout with respect to different
      amounts of content</p>
    </div>
   </div>
   <div class=example>
    <p> The &lsquo;<a href="#wrap-flow"><code
     class=property>wrap-flow</code></a>&rsquo; property values applied to an
     absolutely positioned element.</p>
    <code class=html></code>
    <pre>
 &lt;div id="grid"&gt;
     &lt;div id="exclusion"&gt;Donec metus …&lt;/div&gt;
     &lt;div id="content"&gt;Lorem ipsum…&lt;/div&gt;
 &lt;/div&gt;
 &lt;style type="text/css"&gt;
 #grid {
     width: 100em;
     height: 100em;
     display: grid;
     grid-columns: 50% 20% 20%;
     grid-rows: 40% 20% 40%;
 }
 #exclusion {
     grid-row: 2;
     grid-column: 2;
     wrap-flow: &lt;see below&gt;
 }
 #content {
     grid-row: 1;
     grid-row-span: 3;
     grid-column: 1;
     grid-column-span: 3;
 }
 &lt;/style&gt;
 </pre>
    <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: maximum; }</code>
       <td><code class=html>#exclusion{ wrap-flow: maximum; }</code>
      <tr>
       <td><img alt="Example rendering for wrap-side: maximum"
        src="images/exclusion_wrap_side_maximum_L.png">
       <td><img alt="Example rendering for wrap-side: maximum"
        src="images/exclusion_wrap_side_maximum_R.png">
      <tr>
       <td><code class=html>#exclusion{ wrap-flow: clear; }</code>
       <td><code class=html>&nbsp;</code>
      <tr>
       <td><img alt="Example rendering for wrap-side: clear"
        src="images/exclusion_wrap_side_clear.png">
       <td>&nbsp;
    </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 blocks (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 &lsquo;<a href="#wrap-through"><code
    class=property>wrap-through</code></a>&rsquo; property can be used (see
    the <a href="#propagation-of-exclusions">propagation of exclusions</a>
    section below).
   <p> For exclusions with &lsquo;<code
    class=css>position:fixed</code>&rsquo;, the containing block is that of
    the root element.
   <h4 id=wrap-margin-property><span class=secno>3.2.1. </span>The &lsquo;<a
    href="#wrap-margin"><code class=property>wrap-margin</code></a>&rsquo;
    property</h4>
   <p> The &lsquo;<a href="#wrap-margin"><code
    class=property>wrap-margin</code></a>&rsquo; property can be used to
    offset the inline flow content wrapping on the outside of exclusions.
    Offsets created by the &lsquo;<a href="#wrap-margin"><code
    class=property>wrap-margin</code></a>&rsquo; property are offset from the
    outside of the exclusion. This property takes on positive values only.
   <table class=propdef>
    <tbody>
     <tr>
      <th>Name:
      <td><dfn id=wrap-margin title="'wrap-margin'">wrap-margin</dfn>
     <tr>
      <th>Value:
      <td><var>&lt;length&gt;</var>
     <tr>
      <th>Initial:
      <td>0
     <tr>
      <th>Applies to:
      <td><span>exclusion</span> elements
     <tr>
      <th>Inherited:
      <td>no
     <tr>
      <th>Percentages:
      <td>N/A
     <tr>
      <th>Media:
      <td>visual
     <tr>
      <th>Computed&nbsp;value:
      <td>the absolute length
   </table>
   <!-- End secion "wrap-margin property" -->
   <h4 id=wrap-padding-property><span class=secno>3.2.2. </span>The &lsquo;<a
    href="#wrap-padding"><code class=property>wrap-padding</code></a>&rsquo;
    Property</h4>
   <p> The &lsquo;<a href="#wrap-padding"><code
    class=property>wrap-padding</code></a>&rsquo; property can be used to
    offset the inline flow content wrapping on the inside of elements. Offsets
    created by the &lsquo;<a href="#wrap-padding"><code
    class=property>wrap-padding</code></a>&rsquo; property are offset from the
    <a href="#content-area">content area</a> of the element. This property
    takes on positive values only.
   <table class=propdef>
    <tbody>
     <tr>
      <th>Name:
      <td><dfn id=wrap-padding title="'wrap-padding'">wrap-padding</dfn>
     <tr>
      <th>Value:
      <td><var>&lt;length&gt;</var>
     <tr>
      <th>Initial:
      <td>0
     <tr>
      <th>Applies to:
      <td><span>exclusion</span> elements
     <tr>
      <th>Inherited:
      <td>no
     <tr>
      <th>Percentages:
      <td>N/A
     <tr>
      <th>Media:
      <td>visual
     <tr>
      <th>Computed&nbsp;value:
      <td>the absolute length
   </table>
   <!-- End section "wrap-padding property" -->
   <div class=note>Note that the &lsquo;<a href="#wrap-padding"><code
    class=property>wrap-padding</code></a>&rsquo; property affects layout of
    content inside the element it applies to while the &lsquo;<a
    href="#wrap-margin"><code class=property>wrap-margin</code></a>&rsquo;
    property affects layout of content outside the element.</div>
   <!-- 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 the element. </a>
   <p>Setting the &lsquo;<a href="#wrap-through"><code
    class=property>wrap-through</code></a>&rsquo; property to &lsquo;<code
    class=property>none</code>&rsquo; prevents an element from inheriting its
    parent wrapping context. In other words, exclusions defined &lsquo;<code
    class=property>outside</code>&rsquo; 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 &lsquo;<a href="#wrap-through"><code
    class=property>wrap-through</code></a>&rsquo; set 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 &lsquo;<a
    href="#wrap-through"><code class=property>wrap-through</code></a>&rsquo;
    Property</h4>
   <div class=issue-marker data-bug_id=15085 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15085">Bug-15085</a>
    <div class=issue-details>
     <p class=short-desc>do we need wrap-through?</p>
    </div>
   </div>
   <table class=propdef>
    <tbody>
     <tr>
      <th>Name:
      <td><dfn id=wrap-through title="'wrap-through'">wrap-through</dfn>
     <tr>
      <th>Value:
      <td><a href="#wrap0"><var>wrap</var></a> | <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&nbsp;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 shapes defined <a href="#outside-and-inside"
     title=outside-inside>inside</a> the element.
   </dl>
   <div class=example>
    <p> Using the &lsquo;<a href="#wrap-through"><code
     class=property>wrap-through</code></a>&rsquo; property to control the
     effect of exclusions.</p>
    <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" -->
   <h4 id=wrap-shorthand-property><span class=secno>3.3.2. </span>The
    &lsquo;<a href="#wrap0"><code class=property>wrap</code></a>&rsquo;
    Shorthand Property</h4>
   <table class=propdef>
    <tbody>
     <tr>
      <th>Name:
      <td><dfn id=wrap0 title="'wrap'">wrap</dfn>
     <tr>
      <th>Value:
      <td><var>&lt;wrap-flow&gt;</var> || <var>&lt;wrap-margin&gt;</var> [ /
       <var>&lt;wrap-padding&gt;</var>]
     <tr>
      <th>Initial:
      <td>see individual properties
     <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&nbsp;value:
      <td>see individual properties
   </table>
   <p> The &lsquo;<a href="#wrap0"><code class=property>wrap</code></a>&rsquo;
    property is a shorthand property for setting the exclusions properties at
    the same place in the style sheet.</p>
   <!-- End section "wrap shorthand 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. To change the ordering of
    exclusions with &lsquo;<code class=property>position</code>&rsquo;
    property computed to a value other than &lsquo;<code
    class=property>static</code>&rsquo;, &lsquo;<code
    class=property>z-index</code>&rsquo; can be used. Exclusions with
    &lsquo;<code class=property>position</code>&rsquo; property computed to
    &lsquo;<code class=property>static</code>&rsquo; are not affected by the
    &lsquo;<code class=property>z-index</code>&rsquo; property, thus follow
    the painting order.
   <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: 50%;
     	height: auto;
     }
 &lt;/style&gt;
 &lt;div class=”exclusion” style=”top: 0px; left: 0px;”&gt;
     Lorem ipsum dolor sit amet...
 &lt;/div&gt;
 &lt;div id="orderedExclusion" class=”exclusion” style=”top: 25%; left: 25%;”&gt;
     Lorem ipsum dolor sit amet...
 &lt;/div&gt;
 &lt;div class=”exclusion” style=”top: 50%; left: 50%;”&gt;
     Lorem ipsum dolor sit amet...
 &lt;/div&gt;
 </code></pre>
    <table class=example-table>
     <tbody>
      <tr>
       <td style="width:50%"><code class=html>#orderedExclusion{ z-index:
        auto; }</code>
       <td style="width:50%"><code class=html>#orderedExclusion{ 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 data-bug_id=15183 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15183">Bug-15183</a>
    <div class=issue-details>
     <p class=short-desc>Is the CSS exclusions processing model incorrect?</p>
    </div>
   </div>
   <div class=issue-marker data-bug_id=15083 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15083">Bug-15083</a>
    <div class=issue-details>
     <p class=short-desc>Concerns over Error accumulation vs. performance</p>
    </div>
   </div>
   <p class=issue> The rules for exclusions order and exclusions on absolutely
    positioned elements (particularly those with static position) build this
    exclusions model on top of the absolute positioning model in CSS Level 2,
    rather than on top of floats, the existing exclusion model in CSS Level 1
    and 2. The CSS Working Group has not reached consensus on whether it
    intends to base the new exclusions features in this specification on top
    of absolute positioning (as these sections of this specification do) or on
    top of floats.
   <p class=note> This module does not depend on any particular positioning
    scheme.
   <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
     wrapping context
    <li><strong>Step 2</strong>: resolve wrapping contexts and layout each
     containing block in turn:
     <ul>
      <li><strong>Step 2-A</strong>: resolve the position and size of
       exclusions
      <li><strong>Step 2-B</strong>: layout containing block, wrapping around
       exclusion areas
     </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 wrapping context</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 &lsquo;<a href="#wrap-flow"><code
    class=property>wrap-flow</code></a>&rsquo; that is not <code
    class=css>none</code>.
   <h4 id="step-2-resolve wrapping-contexts-layout-containing-blocks"><span
    class=secno>3.5.3. </span>Step 2: resolve wrapping contexts and layout
    containing blocks</h4>
   <p>In this step, starting from the top of the rendering tree, 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 exclusions position and size</h4>
   <p>Resolving the position and size of exclusions in the wrapping context
    may or may not require a layout. For example, if an exclusion is
    absolutely positioned and sized, there is no need to perform a layout to
    resolve its position and size. In other situations, laying out the
    containing block's content is required.
   <p>When a layout is required, it is carried out without applying any
    exclusion area. In other words, the containing block is laid out without a
    wrapping context.
   <p>Step 2-A yields a position and size for all exclusion areas in the
    wrapping context.
   <p>Scrolling is ignored in this step when resolving the position and size
    of &lsquo;<code class=css>position:fixed</code>&rsquo;
    <span>exclusions</span>.
   <h4 id=step-2-B-layout-containing-block-applying-wrapping><span
    class=secno>3.5.5. </span>Step 2-B: layout containing block applying
    wrapping</h4>
   <p>Finally, the content of the containing block is laid out, with the
    inline content wrapping around the wrapping content's exclusion areas.
   <h4 id=exclusions-processing-model-example><span class=secno>3.5.6.
    </span>Example</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>The code snippet in the following example has two exclusions affecting
    the document's inline content.
   <div class=example>
    <pre class="code idl">
     &lt;html&gt;
         &lt;body&gt;
             &lt;div id="d1" style="width:100%;height:auto;position:relative"&gt;
                 Lorem ipsusm ...
                 &lt;p id="e1" style="wrap-flow: both;position:absolute; left:50%; top:50%;
                                   width:40%;height:40%; margin-left:-20%;" &gt;&lt/p&gt;
             &lt;/div&gt;
             &lt;div id="d2" style="width:100%;height:auto;position:static"&gt;
                 Lorem ipsusm ...
                 &lt;p id="e2" style="wrap-flow: both;position:absolute; right:5ex; top:1em;
                                   width:12ex;height:10em; margin-left:-20%;" &gt;&lt/p&gt;
             &lt;/div&gt;
         &lt;/body&gt;
     &lt;/html&gt;
         </pre>
   </div>
   <p>The following figures illustrate:
   <ul>
    <li>the document's DOM tree
    <li>the layout tree of generated block boxes
   </ul>
   <div class=figure> <img src="images/processing-model-example-dom.svg"
    width=200>
    <p class=caption>DOM tree</p>
   </div>
   <div class=figure> <img
    src="images/processing-model-example-layout-tree.svg" width=250>
    <p class=caption>Layout tree of generated block boxes</p>
   </div>
   <h5 id=step-1-resolve-exclusion-boxes-belonging><span class=secno>3.5.6.1.
    </span>Step 1: resolve exclusion boxes belonging to each wrapping context</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-block</code> box, 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 href="#CSS21"
    rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>) for details.
   <p>As a result of the computation of containing blocks for the tree, the
    boxes belonging to the wrapping contexts of all the elements can be
    determined:
   <ul>
    <li>The wrapping context for the html element contains the <code
     class=idl>e2</code> box: WC-1 (Wrapping Context 1)
    <li>The wrapping context for the body element inherits the html element's
     wrapping context: WC-1
    <li>The wrapping context for <code class=idl>d1</code> inherits the body
     element's wrapping context and adds the <code class=idl>e1</code> box to
     it. So the wrapping context is made of both the <code class=idl>e1</code>
     box and the <code class=idl>e2</code> box: WC-2
    <li>The wrapping context for <code class=idl>d2</code> inherits the body
     element's wrapping context: WC-1
   </ul>
   <h5 id=step-2-resolve-wrapping-contexts-and-lay><span class=secno>3.5.6.2.
    </span>Step 2: resolve wrapping contexts and layout containing blocks</h5>
   <p>In this step, each containing block is processed in turn. For each
    containing block, we (conceptually) go through two phases:
   <ol>
    <li>resolve the wrapping context: resolve the position and size of its
     exclusions
    <li>layout the containing block
   </ol>
   <p>In our example, this breaks down to:
   <ol>
    <li>resolve the position and size of the exclusions belonging to WC-1:
     RWC-1 (Resolved Wrapping Context 1).
    <li>layout the initial containing block (i.e., layout its content):
     <ol>
      <li>resolve the html element's wrapping context: RWC-1
      <li>layout the html element:
       <ol>
        <li>resolve the body element's wrapping context: RWC-1
        <li>layout the body element:
         <ol>
          <li>resolve the d1 element's wrapping context: RWC-2
          <li>layout the d1 element
          <li>resolve the d2 element's wrapping context: RWC-1
          <li>layout the d2 element
         </ol>
       </ol>
     </ol>
   </ol>
   <h6 id=resolving-rwc-1><span class=secno>3.5.6.2.1. </span>Resolving RWC-1</h6>
   <p>The top-most wrapping context 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 our 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.
   <h6 id=resolving-rwc-2><span class=secno>3.5.6.2.2. </span>Resolving RWC-2</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>&lsquo;<code class=css>s box. As a
    result, in order to resolve a size for <code
    class=idl>d1</code></code>&rsquo;s box, a first layout of <code
    class=idl>d1</code> is done without any wrapping context (i.e., no
    exclusions applied). The layout yields a position and size for <code
    class=idl>e1</code>&lsquo;<code class=css>s box. </code>
   <p>At this point, RWC-2 is resolved because the position and size of both
    e1 and e2 are resolved.
   <p class=note>The important aspect of the above processing example is that
    once an element&rsquo;s wrapping context 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 wrapping context (as for RWC-2) and
    the layout done with the resolved wrapping context. This is what breaks
    the possible circular dependency between the resolution of wrapping
    contexts and the layout of containing blocks.
   <h3 id=floats-and-exclusions><span class=secno>3.6. </span>Floats and
    exclusions</h3>
   <h4 id=floats-and-exclusions-similarities><span class=secno>3.6.1.
    </span>Similarities</h4>
   <p>This section is non-normative.
   <p>There are similarities between floats an exclusions in that inline
    content wraps around floats and also wraps around exclusion areas.
    However, there are very significant differences.
   <h4 id=floats-and-exclusions-differences><span class=secno>3.6.2.
    </span>Differences</h4>
   <p>This section is non-normative.
   <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
     &lsquo;<code class=property>float</code>&rsquo; 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 href="#CSS3-GRID-LAYOUT"
     rel=biblioentry>[CSS3-GRID-LAYOUT]<!--{{CSS3-GRID-LAYOUT}}--></a>),
     flexible box (<a href="#CSS3-FLEXBOX"
     rel=biblioentry>[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 id=floats-and-exclusions-interoperability><span class=secno>3.6.3.
    </span>Interoperability</h4>
   <h5 id=effect-of-floats-on-exclusions><span class=secno>3.6.3.1.
    </span>Effect of floats on exclusions</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-resolve-exclusions-position-and-size>Step 2-A</a> will be
    impacted by the float, as is any other inline content.
   <h5 id=effect-of-exclusions-on-floats><span class=secno>3.6.3.2.
    </span>Effect of exclusions on floats</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-layout-containing-block-applying-wrapping>Step 2-B</a>,
    floats will avoid <a href="#exclusion-area">exclusion areas</a>.</p>
   <!-- End section "Exclusions" -->
   <h2 id=shapes><span class=secno>4. </span>Shapes</h2>
   <div class=issue-marker data-bug_id=15091 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15091">Bug-15091</a><br>
    <div class=issue-details>
     <p class=short-desc>Simplify the syntax for shapes</p>
    </div>
   </div>
   <p> Shapes define arbitrary geometric contours around which or into which
    inline flow content flows. There are two different types of shapes –
    &lsquo;<code class=property>outside</code>&rsquo; and &lsquo;<code
    class=property>inside</code>&rsquo;. The outside shape defines the <a
    href="#exclusion-area">exclusion area</a> for an <span>exclusion
    element</span> or the <a href="#float-area">float area</a> for a float.
    The inside shape defines an element's <span>content shape</span> and the
    element's inline content will flow within that shape.
   <p class=note>It is important to note that while outside shapes only apply
    to <span>exclusions</span> and floats, inside shapes apply to all
    block-level elements.
   <h3 id=relation-to-box-model-and-float-behavior><span class=secno>4.1.
    </span>Relation to the box model and float behavior</h3>
   <p> While the boundaries used for wrapping inline flow content outside and
    inside an element can be defined using shapes, the actual box model does
    not change. If the element has specified margins, borders or paddings they
    will be computed and rendered according to the <a href="#CSS3BOX"
    rel=biblioentry>[CSS3BOX]<!--{{!CSS3BOX}}--></a> module.
   <p> However, floats are an exception. If a float has an outside shape, its
    positioning is resolved as <a
    href="http://www.w3.org/TR/CSS2/visuren.html#float-position">defined</a>
    in <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> but using
    the outside shape's bounding box is used in lieu of the float's margin
    box.
   <div class=example>
    <p>CSS &lsquo;<code class=property>shape</code>&rsquo; and CSS box model
     relation.</p>
    <pre><code class=html>
 &lt;style type="text/css"&gt;
     .exclusion  {
     	wrap-flow: both;
     	position: absolute;
     	shape-outside: circle(50%, 50%, 50%);
     	border: 1px solid red;
     }
 &lt;/style&gt;
 &lt;div style=”position: relative;”&gt;
     &lt;div class=”exclusion”&gt;&lt;/div&gt;
     Lorem ipsum dolor sit amet...
 &lt;/div&gt;
 </code></pre>
    <img alt="Example rendering of circle shape and box model."
    class=singleImgExample src="images/shapes_CSS2.1_MBP.png"
    style="max-width:40%"></div>
   <h3 id=shapes-from-svg-syntax><span class=secno>4.2. </span>Shapes from SVG
    Syntax</h3>
   <p> Shapes can be specified using <a
    href="http://www.w3.org/TR/SVG/shapes.html">SVG basic shapes</a>.
   <h4 id=supported-svg-shapes><span class=secno>4.2.1. </span>Supported SVG
    Shapes</h4>
   <p> The following SVG shapes are supported by the CSS shapes module.
   <dl>
    <dt>rectangle(&lt;length&gt;{4} [ curve &lt;length&gt;{1,2} ]? )
    <dd>
     <ul>
      <li>The four values represent <strong>x, y, width and height</strong> -
       define the bounding box of the rectangle
      <li> The two &lsquo;<code class=property>curve</code>&rsquo; values
       represent <strong> rx</strong> and <strong>ry</strong> - define the
       rounded rectangles, the <strong>x</strong> and <strong>y</strong> axis
       and radius of the ellipse used to round off the corners of the
       rectangle
     </ul>
    <dt>circle(&lt;length&gt;{3})
    <dd>
     <ul>
      <li> The three values values represent <strong>cx</strong>,
       <strong>cy</strong>, <strong>r</strong> - The <strong>x</strong> and
       <strong>y</strong> axis coordinate of the center of the circle and the
       radius of the circle
     </ul>
    <dt>ellipse(&lt;length&gt;{4})
    <dd>
     <ul>
      <li>The four values represent <strong>cx</strong>, <strong>cy</strong>,
       <strong>rx</strong> and <strong>ry</strong> - The <strong>x</strong>
       and <strong>y</strong> coordinate of the center of the ellipse and the
       <strong>x</strong> and <strong>y</strong> axis radius of the ellipse
     </ul>
    <dt>polygon([&lt;fill-rule&gt;,]? &lt;length&gt;{2}#)
    <dd>
     <ul>
      <li><strong>fillRule</strong> - The filling rule used to determine the
       interior of the polygon. See fill-rule property in SVG for details.
       Possible values are nonzero or evenodd. Default value when omitted is
       nonzero.
      <li> The two length values represent <strong>xi</strong> and
       <strong>yi</strong> - the <strong>x</strong> and <strong>y</strong>
       axis coordinates of the i-th vertex of the polygon.
     </ul>
     <p> If the polygon is not closed the user-agent will automatically add a
      new vertex at the end.</p>
     <br>
   </dl>
   <h4 id=referencing-svg-shapes><span class=secno>4.2.2. </span>Referencing
    SVG shapes</h4>
   <p>An SVG shape can be referenced using the <code>url()</code> syntax. The
    shape can be any of the <a href="http://www.w3.org/TR/SVG/shapes.html">SVG
    basic shapes</a> or a <a href="http://www.w3.org/TR/SVG/paths.html">path
    element</a>.
   <p>In all cases, percentages are resolved from the border box of the
    element.
   <div class=example> <code class=html></code>
    <pre>
 &lt;style&gt;
 .in-a-circle {
     shape-inside: url(#circle_shape);
 }
 .in-a-path {
     shape-inside: url(#path-shape);
 }
 &lt;/style&gt;
 &lt;svg ...&gt;
 &lt;circle id="circle_shape" cx="50%" cy="50%" r="50%" /&gt;
 &lt;path id="path-shape" d="..." /&gt;
 &lt;/svg&gt;
 &lt;div class="in-a-circle"&gt;...&lt;/div&gt;
 &lt;div class="in-a-path"&gt;...&lt;/div&gt;
           </pre>
   </div>
   <p> When using the SVG syntax or referencing SVG elements to define shapes,
    all the lengths expressed in percentages are resolved from the border box
    of the element. The coordinate system for the shape has its origin on the
    top-left corner of the border box with the x-axis running to the right and
    the y-axis running downwards. If the SVG element uses unitless coordinate
    values, they are equivalent to using &lsquo;<code
    class=property>px</code>&rsquo; units. If the border box of the element is
    dependent on auto sizing (i.e., the element's &lsquo;<code
    class=property>width</code>&rsquo; or &lsquo;<code
    class=property>height</code>&rsquo; property is &lsquo;<code
    class=property>auto</code>&rsquo;), then the percentage values resolve to
 .</p>
   <!-- End section "Shapes from SVG Syntax -->
   <h3 id=shapes-from-image><span class=secno>4.3. </span>Shapes from Image</h3>
   <div class=issue-marker data-bug_id=15093 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15093">Bug-15093</a><br>
    <div class=issue-details>
     <p class=short-desc> Do we need to provide properties to repeat exclusion
      images as for the background-image property?</p>
    </div>
   </div>
   <div class=issue-marker data-bug_id=15090 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15090">Bug-15090</a><br>
    <div class=issue-details>
     <p class=short-desc> Use the contour() keyword. &lt;img id=shape-me
      url=foo&gt;&lt;style&gt;#shape-me { shape-outside: contour;
      }&lt;/style&gt; //equal to &lsquo;<code class=css>shape-outside:
      url(foo)</code>&rsquo; shape-outside: attr(src as url);</p>
    </div>
   </div>
   <div class=issue-marker data-bug_id=15092 data-bug_status=NEW> <a
    href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15092">Bug-15092</a>
    <div class=issue-details>
     <p class=short-desc>Specify what happens with animated images</p>
    </div>
   </div>
   <p> Another way of defining shapes is by specifying a source image whose
    alpha channel is used to compute the inside or outside shape. The shape is
    computed to be the path that encloses the area where the opacity of the
    specified image is greater than the &lsquo;<a
    href="#shape-image-threshold"><code
    class=property>shape-image-threshold</code></a>&rsquo; value. If the
    &lsquo;<a href="#shape-image-threshold"><code
    class=property>shape-image-threshold</code></a>&rsquo; is not specified,
    the initial value to be considered is 0.5.
   <p class=note> Note, images can define cavities and inline flow content
    should wrap inside them. In order to avoid that, another exclusion element
    can be overlaid.
   <p>For animated raster image formats (such as <a
    href="http://www.w3.org/Graphics/GIF/spec-gif89a.txt">GIF</a>), the first
    frame of the animation sequence is used. For <a
    href="http://www.w3.org/TR/2002/WD-SVG2Reqs-20020422/">SVG</a> images (<a
    href="#SVG11" rel=biblioentry>[SVG11]<!--{{SVG11}}--></a>), the image is
    rendered without animations applied.</p>
   <!-- End section "Shapes from image" -->
   <h3 id=declaring-shapes><span class=secno>4.4. </span>Declaring Shapes</h3>
   <p> Shapes are declared with the &lsquo;<a href="#shape-outside"><code
    class=property>shape-outside</code></a>&rsquo; or &lsquo;<a
    href="#shape-inside"><code class=property>shape-inside</code></a>&rsquo;
    properties. The &lsquo;<a href="#shape-outside"><code
    class=property>shape-outside</code></a>&rsquo; property changes the
    geometry of an <span>exclusion element</span>&lsquo;<code class=css>s <a
    href="#exclusion-area">exclusion area</a> or or a float
    element</code>&rsquo;s <a href="#float-area">float area</a>. If the
    element is not an <span>exclusion element</span> (see the &lsquo;<a
    href="#wrap-flow"><code class=property>wrap-flow</code></a>&rsquo;
    property) or a float, then the &lsquo;<a href="#shape-outside"><code
    class=property>shape-outside</code></a>&rsquo; property has no effect.
   <p> The &lsquo;<a href="#shape-inside"><code
    class=property>shape-inside</code></a>&rsquo; property defines an
    element's <a href="#content-area">content area</a> and the element's
    inline flow content wraps into that shape. The &lsquo;<a
    href="#shape-inside"><code class=property>shape-inside</code></a>&rsquo;
    property applies to all block-level elements.
   <h4 id=shape-outside-property><span class=secno>4.4.1. </span>The &lsquo;<a
    href="#shape-outside"><code class=property>shape-outside</code></a>&rsquo;
    Property</h4>
   <table class=propdef>
    <tbody>
     <tr>
      <th>Name:
      <td><dfn id=shape-outside title="'shape-outside'">shape-outside</dfn>
     <tr>
      <th>Value:
      <td><var>auto</var> | <var>&lt;shape&gt;</var> | <var>&lt;uri&gt;</var>
     <tr>
      <th>Initial:
      <td>auto
     <tr>
      <th>Applies to:
      <td>exclusion elements and floats
     <tr>
      <th>Inherited:
      <td>no
     <tr>
      <th>Percentages:
      <td>N/A
     <tr>
      <th>Media:
      <td>visual
     <tr>
      <th>Computed&nbsp;value:
      <td>computed lengths for &lt;shape&gt;, the absolute URI for
       &lt;uri&gt;, otherwise as specified
   </table>
   <p>The values of this property have the following meanings:
   <dl>
    <dt><dfn id=auto0 title="'shape-outside'!!'auto'">auto</dfn>
    <dd>The shape is computed based on the border box of the element.
   </dl>
   <dl>
    <dt><dfn id=ltshapegt
     title="'shape-outside'!!'&lt;shape&gt;'">&lt;shape&gt;</dfn>
    <dd> The shape is computed based on the values of one of &lsquo;<code
     class=property>rectangle</code>&rsquo;, &lsquo;<code
     class=property>circle</code>&rsquo;, &lsquo;<code
     class=property>ellipse</code>&rsquo; or &lsquo;<code
     class=property>polygon</code>&rsquo;.
   </dl>
   <dl>
    <dt><dfn id=lturigt
     title="'shape-outside'!!'&lt;uri&gt;'">&lt;uri&gt;</dfn>
    <dd> If the &lt;uri&gt; references an SVG shape element, that element
     defines the shape. Otherwise, if the &lt;uri&gt; references an image, the
     shape is extracted and computed based on the alpha channel of the
     specified image. If the &lt;uri&gt; does not reference an SVG shape
     element or an image, the effect is as if the value &lsquo;<code
     class=property>auto</code>&rsquo; had been specified.
   </dl>
   <div class=figure> <img
    alt="arbitrary shapes for excluions. Illustrates how content flows around shapes"
    src="images/shapes-exclusions.png" width="70%">
    <p class=caption>Arbitrary shapes for exclusions</p>
   </div>
   <div>
    <p>The above figure shows how &lsquo;<a href="#shape-outside"><code
     class=property>shape-outside</code></a>&rsquo; shapes impact the
     exclusion areas. The red box represents an element's content box and
     &lsquo;<code class=property>A</code>&rsquo;, &lsquo;<code
     class=property>B</code>&rsquo;, &lsquo;<code
     class=property>C</code>&rsquo; and &lsquo;<code
     class=property>C</code>&rsquo; represent exclusions with a complex shape
     and their &lsquo;<a href="#wrap-flow"><code
     class=property>wrap-flow</code></a>&rsquo; property set to &lsquo;<code
     class=property>both</code>&rsquo;, &lsquo;<code
     class=property>start</code>&rsquo;, &lsquo;<code
     class=property>end</code>&rsquo; and &lsquo;<code
     class=property>clear</code>&rsquo;, respectively.</p>
    <p>As illustrated in the picture, when an exclusion allows wrapping on all
     sides, text can flow inside &lsquo;<code
     class=property>holes</code>&rsquo; in the exclusion (as for exclusion
     &lsquo;<code class=property>A</code>&rsquo;). Otherwise, the exclusion
     clears the area on the side(s) defined by wrap flow, as illustrated for
     &lsquo;<code class=property>B</code>&rsquo;, &lsquo;<code
     class=property>C</code>&rsquo; and &lsquo;<code
     class=property>D</code>&rsquo; above.</p>
   </div>
   <!-- End section "The shape-outside Property" -->
   <h4 id=shape-inside-property><span class=secno>4.4.2. </span>The &lsquo;<a
    href="#shape-inside"><code class=property>shape-inside</code></a>&rsquo;
    Property</h4>
   <p> The &lsquo;<a href="#shape-inside"><code
    class=property>shape-inside</code></a>&rsquo; modifies the shape of the
    inner inline flow content from rectangular content box to an arbitrary
    geometry.
   <table class=propdef>
    <tbody>
     <tr>
      <th>Name:
      <td><dfn id=shape-inside title="'shape-inside'">shape-inside</dfn>
     <tr>
      <th>Value:
      <td><var>outside-shape</var> | <var>auto</var> |
       <var>&lt;shape&gt;</var> | <var>&lt;uri&gt;</var>
     <tr>
      <th>Initial:
      <td>outside-shape
     <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&nbsp;value:
      <td>computed lengths for &lt;shape&gt;, the absolute URI for
       &lt;uri&gt;, otherwise as specified
   </table>
   <p>The values of this property have the following meanings:
   <dl>
    <dt><dfn id=outside-shape
     title="'shape-inside'!!'outside-shape'">outside-shape</dfn>
    <dd> The shape is computed based on the computed value of the &lsquo;<a
     href="#shape-outside"><code
     class=property>shape-outside</code></a>&rsquo; property.
   </dl>
   <dl>
    <dt><dfn id=auto1 title="'shape-inside'!!'auto'">auto</dfn>
    <dd> The shape is computed based on the content box of the element.
   </dl>
   <dl>
    <dt><dfn id=ltshapegt0
     title="'shape-inside'!!'&lt;shape&gt;'">&lt;shape&gt;</dfn>
    <dd> The shape is computed based on the values of one of &lsquo;<code
     class=property>rectangle</code>&rsquo;,&lsquo;<code class=css>
     circle</code>&rsquo;, &lsquo;<code class=property>ellipse</code>&rsquo;
     or &lsquo;<code class=property>polygon</code>&rsquo;.
   </dl>
   <dl>
    <dt><dfn id=lturigt0
     title="'shape-inside'!!'&lt;uri&gt;'">&lt;uri&gt;</dfn>
    <dd> If the &lt;uri&gt; references an SVG shape element, that element
     defines the shape. Otherwise, if the &lt;uri&gt; references an image, the
     shape is extracted and computed based on the alpha channel of the
     specified image. If the &lt;uri&gt; does not reference an SVG shape
     element or an image, the effect is as if the value &lsquo;<code
     class=property>auto</code>&rsquo; had been specified.
   </dl>
   <p>The &lsquo;<a href="#shape-inside"><code
    class=property>shape-inside</code></a>&rsquo; property applies to floats.
   <p>The &lsquo;<a href="#shape-inside"><code
    class=property>shape-inside</code></a>&rsquo; property may not apply on
    some elements such as elements with a computed &lsquo;<code
    class=property>display</code>&rsquo; value of &lsquo;<code
    class=property>table</code>&rsquo;.</p>
   <!-- End section "The shape-inside property" -->
   <h4 id=shape-image-threshold-property><span class=secno>4.4.3. </span>The
    &lsquo;<a href="#shape-image-threshold"><code
    class=property>shape-image-threshold</code></a>&rsquo; Property</h4>
   <p> The &lsquo;<a href="#shape-image-threshold"><code
    class=property>shape-image-threshold</code></a>&rsquo; defines the alpha
    channel threshold used to extract the shape using an image. A value of 0.5
    means that all the pixels that are more than 50% transparent define the
    path of the exclusion shape. The &lsquo;<a
    href="#shape-image-threshold"><code
    class=property>shape-image-threshold</code></a>&rsquo; applies to both
    &lsquo;<a href="#shape-outside"><code
    class=property>shape-outside</code></a>&rsquo; and &lsquo;<a
    href="#shape-inside"><code class=property>shape-inside</code></a>&rsquo;.
   <p class=note> The specified value of &lsquo;<a
    href="#shape-image-threshold"><code
    class=property>shape-image-threshold</code></a>&rsquo; is applied to both
    images used for &lsquo;<a href="#shape-outside"><code
    class=property>shape-outside</code></a>&rsquo; and &lsquo;<a
    href="#shape-inside"><code class=property>shape-inside</code></a>&rsquo;.
   <table class=propdef>
    <tbody>
     <tr>
      <th>Name:
      <td><dfn id=shape-image-threshold
       title="'shape-image-threshold'">shape-image-threshold</dfn>
     <tr>
      <th>Value:
      <td><var>&lt;alphavalue&gt;</var>
     <tr>
      <th>Initial:
      <td>0.5
     <tr>
      <th>Applies to:
      <td>block-level elements
     <tr>
      <th>Inherited:
      <td>no
     <tr>
      <th>Percentages:
      <td>alpha channel of the image specified by &lt;uri&gt;
     <tr>
      <th>Media:
      <td>visual
     <tr>
      <th>Computed&nbsp;value:
      <td>The same as the specified value after clipping the
       &lt;alphavalue&gt; to the range [0.0,1.0].
   </table>
   <p>The values of this property have the following meanings:
   <dl>
    <dt><dfn id=ltalphavaluegt
     title="'shape-image-threshold'!!'&lt;alphavalue&gt;'">&lt;alphavalue&gt;</dfn>
    <dd> A &lt;number&gt; value used to set the threshold used for extracting
     a shape from an image. Any values outside the range 0.0 (fully
     transparent) to 1.0 (fully opaque) will be clamped to this range.
   </dl>
   <!-- End section "The shape-image-threshold property" -->
   <!--
     <h4 id="shape-shorthand-property">The 'shape' Shorthand Property</h4>
     <table class="propdef">
         <tr>
             <th>Name:</th>
             <td><dfn title="'shape'">shape</dfn></td>
         </tr>
         <tr>
             <th>Value:</th>
             <td><var>&lt;shape-outside&gt;</var> [ / <var>&lt;shape-inside&gt;</var> ] || <var>&lt;shape-image-threshold&gt;</var></td>
         </tr>
         <tr>
             <th>Initial:</th>
             <td>see individual properties</td>
         </tr>
         <tr>
             <th>Applies to:</th>
             <td>block-level elements</td>
         </tr>
         <tr>
             <th>Inherited:</th>
             <td>no</td>
         </tr>
         <tr>
             <th>Percentages:</th>
             <td>N/A</td>
         </tr>
         <tr>
             <th>Media:</th>
             <td>visual</td>
         </tr>
         <tr>
             <th>Computed&nbsp;value:</th>
             <td>see individual properties</td>
         </tr>
     </table>
     <p>
         The 'shape' property is a shorthand property for setting the individual shape properties
         at the same place in a style sheet.
     </p>
     <div class="example">
         <p>Style declaration using the 'shape' shorthand property.</p>
 <pre><code class="html">
 &lt;style type="text/css"&gt;
     .shape {
         shape: rectangle(50px, 50px, 200px, 100px) / url("shape_image.png")  0.7;
     }
 &lt;/style&gt
 </code></pre>
     </div>
     <p class="issue">The example above must be finished.</p>
     -->
   <!-- End section "Shape Shorthand property -->
   <!-- End section "Declaring Shapes" -->
   <p>The shape properties apply to <!-- End section "Shapes" -->
   <h2 id=conformance><span class=secno>5. </span>Conformance</h2>
   <h3 id=conventions><span class=secno>5.1. </span>Document Conventions</h3>
   <p> Conformance requirements are expressed with a combination of
    descriptive assertions and RFC 2119 terminology. The key words “MUST”,
    “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”,
    “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and
    “OPTIONAL” in the normative parts of this document are to be
    interpreted as described in RFC 2119. However, for readability, these
    words do not appear in all uppercase letters in this specification.
   <p> All of the text of this specification is normative except sections
    explicitly marked as non-normative, examples, and notes. <a
    href="#RFC2119" rel=biblioentry>[RFC2119]<!--{{!RFC2119}}--></a>
   <p> Examples in this specification are introduced with the words “for
    example” or are set apart from the normative text with
    <code>class="example"</code>, like this:
   <div class=example>
    <p>This is an example of an informative example.</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.
   <h3 id=conformance-classes><span class=secno>5.2. </span>Conformance
    Classes</h3>
   <p>Conformance to CSS Exclusions and Shapes is defined for three
    conformance classes:
   <dl>
    <dt><dfn id=style-sheet title="style sheet!!as conformance class">style
     sheet</dfn>
    <dd> A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
     style sheet</a>.
    <dt><dfn id=renderer>renderer</dfn>
    <dd> A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
     that interprets the semantics of a style sheet and renders documents that
     use them.
    <dt><dfn id=authoring-tool>authoring tool</dfn>
    <dd> A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
     that writes a style sheet.
   </dl>
   <p> A style sheet is conformant to CSS Exclusions and Shapes if all of its
    declarations that use properties defined in this module have values that
    are valid according to the generic CSS grammar and the individual grammars
    of each property as given in this module.
   <p> A renderer is conformant to CSS Exclusions and Shapes if, in addition
    to interpreting the style sheet as defined by the appropriate
    specifications, it supports all the features defined by CSS Exclusions and
    Shapes by parsing them correctly and rendering the document accordingly.
    However, the inability of a UA to correctly render a document due to
    limitations of the device does not make the UA non-conformant. (For
    example, a UA is not required to render color on a monochrome monitor.)
   <p> An authoring tool is conformant to CSS Exclusions and Shapes if it
    writes style sheets that are syntactically correct according to the
    generic CSS grammar and the individual grammars of each feature in this
    module, and meet all other conformance requirements of style sheets as
    described in this module.
   <h3 id=partial><span class=secno>5.3. </span> Partial Implementations</h3>
   <p> So that authors can exploit the forward-compatible parsing rules to
    assign fallback values, CSS renderers <strong>must</strong> treat as
    invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">
    ignore as appropriate</a>) any at-rules, properties, property values,
    keywords, and other syntactic constructs for which they have no usable
    level of support. In particular, user agents <strong>must not</strong>
    selectively ignore unsupported component values and honor supported values
    in a single multi-value property declaration: if any value is considered
    invalid (as unsupported values must be), CSS requires that the entire
    declaration be ignored.
   <h3 id=experimental><span class=secno>5.4. </span> Experimental
    Implementations</h3>
   <p> To avoid clashes with future CSS features, the CSS2.1 specification
    reserves a <a
    href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
    syntax</a> for proprietary and experimental extensions to CSS.
   <p> Prior to a specification reaching the Candidate Recommendation stage in
    the W3C process, all implementations of a CSS feature are considered
    experimental. The CSS Working Group recommends that implementations use a
    vendor-prefixed syntax for such features, including those in W3C Working
    Drafts. This avoids incompatibilities with future changes in the draft.
   <h3 id=testing><span class=secno>5.5. </span> Non-Experimental
    Implementations</h3>
   <p> Once a specification reaches the Candidate Recommendation stage,
    non-experimental implementations are possible, and implementors should
    release an unprefixed implementation of any CR-level feature they can
    demonstrate to be correctly implemented according to spec.
   <p> To establish and maintain the interoperability of CSS across
    implementations, the CSS Working Group requests that non-experimental CSS
    renderers submit an implementation report (and, if necessary, the
    testcases used for that implementation report) to the W3C before releasing
    an unprefixed implementation of any CSS features. Testcases submitted to
    W3C are subject to review and correction by the CSS Working Group.
   <p> Further information on submitting testcases and implementation reports
    can be found from on the CSS Working Group's website at <a
    href="http://www.w3.org/Style/CSS/Test/">
    http://www.w3.org/Style/CSS/Test/</a>. Questions should be directed to the
    <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">
    public-css-testsuite@w3.org</a> mailing list.
   <h3 id=cr-exit-criteria><span class=secno>5.6. </span> CR Exit Criteria</h3>
   <p> For this specification to be advanced to Proposed Recommendation, there
    must be at least two independent, interoperable implementations of each
    feature. Each feature may be implemented by a different set of products,
    there is no requirement that all features be implemented by a single
    product. For the purposes of this criterion, we define the following
    terms:
   <dl>
    <dt>independent
    <dd> each implementation must be developed by a different party and cannot
     share, reuse, or derive from code used by another qualifying
     implementation. Sections of code that have no bearing on the
     implementation of this specification are exempt from this requirement.
    <dt>interoperable
    <dd> passing the respective test case(s) in the official CSS test suite,
     or, if the implementation is not a Web browser, an equivalent test. Every
     relevant test in the test suite should have an equivalent test created if
     such a user agent (UA) is to be used to claim interoperability. In
     addition if such a UA is to be used to claim interoperability, then there
     must one or more additional UAs which can also pass those equivalent
     tests in the same way for the purpose of interoperability. The equivalent
     tests must be made publicly available for the purposes of peer review.
    <dt>implementation
    <dd> a user agent which:
     <ol class=inline>
      <li>implements the specification.
      <li>is available to the general public. The implementation may be a
       shipping product or other publicly available version (i.e., beta
       version, preview release, or “nightly build”). Non-shipping product
       releases must have implemented the feature(s) for a period of at least
       one month in order to demonstrate stability.
      <li>is not experimental (i.e., a version specifically designed to pass
       the test suite and is not intended for normal usage going forward).
     </ol>
   </dl>
   <p> The specification will remain Candidate Recommendation for at least six
    months.
   <h2 class=no-num id=acknowledgments>Acknowledgments</h2>
   <p> This specification is made possible by input from Stephen Zilles,
    Alexandru Chiculita, Andrei Bucur, Mihnea Ovidenie, Peter Sorotokin,
    Virgil Palanciuc, Alan Stearns, Arno Gourdol, Eugene Veselov, Arron
    Eicholz, Alex Mogilevsky, Chris Jones, Marcus Mielke, and the CSS Working
    Group members.
   <h2 class=no-num id=references>References</h2>
   <h3 class=no-num id=normative-references>Normative references</h3>
   <!--begin-normative-->
   <!-- Sorted by label -->
   <dl class=bibliography>
    <dt style="display: none"><!-- keeps the doc valid if the DL is empty -->
     <!---->
    <dt id=CSS21>[CSS21]
    <dd>Bert Bos; et al. <a
     href="http://www.w3.org/TR/2011/REC-CSS2-20110607"><cite>Cascading Style
     Sheets Level 2 Revision 1 (CSS&#160;2.1) Specification.</cite></a> 7 June
 . W3C Recommendation. URL: <a
     href="http://www.w3.org/TR/2011/REC-CSS2-20110607">http://www.w3.org/TR/2011/REC-CSS2-20110607</a>
     </dd>
    <!---->
    <dt id=CSS3BOX>[CSS3BOX]
    <dd>Bert Bos. <a
     href="http://www.w3.org/TR/2007/WD-css3-box-20070809"><cite>CSS basic box
     model.</cite></a> 9 August 2007. W3C Working Draft. (Work in progress.)
     URL: <a
     href="http://www.w3.org/TR/2007/WD-css3-box-20070809">http://www.w3.org/TR/2007/WD-css3-box-20070809</a>
     </dd>
    <!---->
    <dt id=RFC2119>[RFC2119]
    <dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key
     words for use in RFCs to Indicate Requirement Levels.</cite></a> Internet
     RFC 2119. URL: <a
     href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a>
     </dd>
    <!---->
   </dl>
   <!--end-normative-->
   <h3 class=no-num id=other-references>Other references</h3>
   <!--begin-informative-->
   <!-- Sorted by label -->
   <dl class=bibliography>
    <dt style="display: none"><!-- keeps the doc valid if the DL is empty -->
     <!---->
    <dt id=CSS3-FLEXBOX>[CSS3-FLEXBOX]
    <dd>Tab Atkins Jr.; Alex Mogilevsky; L. David Baron. <a
     href="http://www.w3.org/TR/2011/WD-css3-flexbox-20111129/"><cite>CSS
     Flexible Box Layout Module.</cite></a> 29 November 2011. W3C Working
     Draft. (Work in progress.) URL: <a
     href="http://www.w3.org/TR/2011/WD-css3-flexbox-20111129/">http://www.w3.org/TR/2011/WD-css3-flexbox-20111129/</a>
     </dd>
    <!---->
    <dt id=CSS3-GRID-LAYOUT>[CSS3-GRID-LAYOUT]
    <dd>Alex Mogilevsky; et al. <a
     href="http://www.w3.org/TR/2011/WD-css3-grid-layout-20110407"><cite>Grid
     Layout.</cite></a> 7 April 2011. W3C Working Draft. (Work in progress.)
     URL: <a
     href="http://www.w3.org/TR/2011/WD-css3-grid-layout-20110407">http://www.w3.org/TR/2011/WD-css3-grid-layout-20110407</a>
     </dd>
    <!---->
    <dt id=SVG11>[SVG11]
    <dd>Erik Dahlstr&#246;m; et al. <a
     href="http://www.w3.org/TR/2011/REC-SVG11-20110816/"><cite>Scalable
     Vector Graphics (SVG) 1.1 (Second Edition).</cite></a> 16 August 2011.
     W3C Recommendation. URL: <a
     href="http://www.w3.org/TR/2011/REC-SVG11-20110816/">http://www.w3.org/TR/2011/REC-SVG11-20110816/</a>
     </dd>
    <!---->
   </dl>
   <!--end-informative-->
   <h2 class=no-num id=index>Index</h2>
   <!--begin-index-->
   <ul class=indexlist>
    <li>authoring tool, <a href="#authoring-tool"
     title="authoring tool"><strong>5.2.</strong></a>
    <li>Content area, <a href="#content-area"
     title="Content area"><strong>2.</strong></a>
    <li>Exclusion area, <a href="#exclusion-area"
     title="Exclusion area"><strong>2.</strong></a>
    <li>Exclusion box, <a href="#exclusion-box"
     title="Exclusion box"><strong>2.</strong></a>
    <li>Float area, <a href="#float-area"
     title="Float area"><strong>2.</strong></a>
    <li>outside-inside, <a href="#outside-and-inside"
     title=outside-inside><strong>2.</strong></a>
    <li>renderer, <a href="#renderer" title=renderer><strong>5.2.</strong></a>
    <li>&lsquo;<a href="#shape-image-threshold"><code
     class=property>shape-image-threshold</code></a>&rsquo;, <a
     href="#shape-image-threshold"
     title="'shape-image-threshold'"><strong>4.4.3.</strong></a>
     <ul>
      <li>&lsquo;<code class=css>&lt;alphavalue&gt;</code>&rsquo;, <a
       href="#ltalphavaluegt"
       title="'shape-image-threshold', '&lt;alphavalue&gt;'"><strong>4.4.3.</strong></a>
     </ul>
    <li>&lsquo;<a href="#shape-inside"><code
     class=property>shape-inside</code></a>&rsquo;, <a href="#shape-inside"
     title="'shape-inside'"><strong>4.4.2.</strong></a>
     <ul>
      <li>&lsquo;<code class=property>auto</code>&rsquo;, <a href="#auto1"
       title="'shape-inside', 'auto'"><strong>4.4.2.</strong></a>
      <li>&lsquo;<code class=property>outside-shape</code>&rsquo;, <a
       href="#outside-shape"
       title="'shape-inside', 'outside-shape'"><strong>4.4.2.</strong></a>
      <li>&lsquo;<code class=css>&lt;shape&gt;</code>&rsquo;, <a
       href="#ltshapegt0"
       title="'shape-inside', '&lt;shape&gt;'"><strong>4.4.2.</strong></a>
      <li>&lsquo;<code class=css>&lt;uri&gt;</code>&rsquo;, <a
       href="#lturigt0"
       title="'shape-inside', '&lt;uri&gt;'"><strong>4.4.2.</strong></a>
     </ul>
    <li>&lsquo;<a href="#shape-outside"><code
     class=property>shape-outside</code></a>&rsquo;, <a href="#shape-outside"
     title="'shape-outside'"><strong>4.4.1.</strong></a>
     <ul>
      <li>&lsquo;<code class=property>auto</code>&rsquo;, <a href="#auto0"
       title="'shape-outside', 'auto'"><strong>4.4.1.</strong></a>
      <li>&lsquo;<code class=css>&lt;shape&gt;</code>&rsquo;, <a
       href="#ltshapegt"
       title="'shape-outside', '&lt;shape&gt;'"><strong>4.4.1.</strong></a>
      <li>&lsquo;<code class=css>&lt;uri&gt;</code>&rsquo;, <a href="#lturigt"
       title="'shape-outside', '&lt;uri&gt;'"><strong>4.4.1.</strong></a>
     </ul>
    <li>style sheet
     <ul>
      <li>as conformance class, <a href="#style-sheet"
       title="style sheet, as conformance class"><strong>5.2.</strong></a>
     </ul>
    <li>&lsquo;<a href="#wrap0"><code class=property>wrap</code></a>&rsquo;,
     <a href="#wrap0" title="'wrap'"><strong>3.3.2.</strong></a>
    <li>&lsquo;<a href="#wrap-flow"><code
     class=property>wrap-flow</code></a>&rsquo;, <a href="#wrap-flow"
     title="'wrap-flow'"><strong>3.1.1.</strong></a>
     <ul>
      <li>&lsquo;<code class=property>auto</code>&rsquo;, <a href="#auto"
       title="'wrap-flow', 'auto'"><strong>3.1.1.</strong></a>
      <li>&lsquo;<code class=property>both</code>&rsquo;, <a href="#both"
       title="'wrap-flow', 'both'"><strong>3.1.1.</strong></a>
      <li>&lsquo;<code class=property>clear</code>&rsquo;, <a href="#clear"
       title="'wrap-flow', 'clear'"><strong>3.1.1.</strong></a>
      <li>&lsquo;<code class=property>end</code>&rsquo;, <a href="#end"
       title="'wrap-flow', 'end'"><strong>3.1.1.</strong></a>
      <li>&lsquo;<code class=property>maximum</code>&rsquo;, <a
       href="#maximum"
       title="'wrap-flow', 'maximum'"><strong>3.1.1.</strong></a>
      <li>&lsquo;<code class=property>start</code>&rsquo;, <a href="#start"
       title="'wrap-flow', 'start'"><strong>3.1.1.</strong></a>
     </ul>
    <li>&lsquo;<a href="#wrap-margin"><code
     class=property>wrap-margin</code></a>&rsquo;, <a href="#wrap-margin"
     title="'wrap-margin'"><strong>3.2.1.</strong></a>
    <li>&lsquo;<a href="#wrap-padding"><code
     class=property>wrap-padding</code></a>&rsquo;, <a href="#wrap-padding"
     title="'wrap-padding'"><strong>3.2.2.</strong></a>
    <li>Wrapping context, <a href="#wrapping-context"
     title="Wrapping context"><strong>2.</strong></a>
    <li>&lsquo;<a href="#wrap-through"><code
     class=property>wrap-through</code></a>&rsquo;, <a href="#wrap-through"
     title="'wrap-through'"><strong>3.3.1.</strong></a>
     <ul>
      <li>&lsquo;<code class=property>none</code>&rsquo;, <a href="#none"
       title="'wrap-through', 'none'"><strong>3.3.1.</strong></a>
      <li>&lsquo;<a href="#wrap0"><code class=property>wrap</code></a>&rsquo;,
       <a href="#wrap"
       title="'wrap-through', 'wrap'"><strong>3.3.1.</strong></a>
     </ul>
   </ul>
   <!--end-index-->
   <h2 class=no-num id=property-index>Property index</h2>
   <!--begin-properties-->
   <table class=proptable>
    <thead>
     <tr>
      <th>Property
      <th>Values
      <th>Initial
      <th>Applies&nbsp;to
      <th>Inh.
      <th>Percentages
      <th>Media
    <tbody>
     <tr>
      <th><a class=property
       href="#shape-image-threshold">shape-image-threshold</a>
      <td>&lt;alphavalue&gt;
      <td>0.5
      <td>block-level elements
      <td>no
      <td>alpha channel of the image specified by &lt;uri&gt;
      <td>visual
     <tr>
      <th><a class=property href="#shape-inside">shape-inside</a>
      <td>outside-shape | auto | &lt;shape&gt; | &lt;uri&gt;
      <td>outside-shape
      <td>block-level elements
      <td>no
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#shape-outside">shape-outside</a>
      <td>auto | &lt;shape&gt; | &lt;uri&gt;
      <td>auto
      <td>exclusion elements and floats
      <td>no
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#wrap0">wrap</a>
      <td>&lt;wrap-flow&gt; || &lt;wrap-margin&gt; [ / &lt;wrap-padding&gt;]
      <td>see individual properties
      <td>block-level elements
      <td>no
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#wrap-flow">wrap-flow</a>
      <td>auto | both | start | end | maximum | clear
      <td>auto
      <td>block-level elements. Does not apply to elements with a
       &lsquo;float&rsquo; computed value other than none
      <td>no
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#wrap-margin">wrap-margin</a>
      <td>&lt;length&gt;
      <td>0
      <td>exclusion elements
      <td>no
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#wrap-padding">wrap-padding</a>
      <td>&lt;length&gt;
      <td>0
      <td>exclusion elements
      <td>no
      <td>N/A
      <td>visual
     <tr>
      <th><a class=property href="#wrap-through">wrap-through</a>
      <td>wrap | none
      <td>wrap
      <td>block-level elements
      <td>no
      <td>N/A
      <td>visual
   </table>
   <!--end-properties-->
   <h2 class=no-num id=change-log>Change Log</h2>
   <h3 id=since-december-13th-2011><span class=secno>5.7. </span>Since <a
    href="http://www.w3.org/TR/2011/WD-css3-exclusions-20111213/">December
 th 2011</a></h3>
   <ul>
    <li>Clarified processing model
    <li>Clarified interaction with floats
   </ul>
 </html>
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