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[css-regions] circular dependency section
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‎css3-regions/Overview.html‎

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@@ -50,13 +50,14 @@
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rel=dcterms.rights>
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<meta content="CSS Regions Module Level 3" name=dcterms.title>
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<meta content=text name=dcterms.type>
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<meta content=2012-10-09 name=dcterms.issued>
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<meta content=2012-10-11 name=dcterms.issued>
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<meta content="Vincent Hardy" name=dcterms.creator>
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<meta content="Alex Mogilevsky" name=dcterms.creator>
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<meta content="Alan Stearns" name=dcterms.creator>
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<meta content=W3C name=dcterms.publisher>
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<meta content="http://www.w3.org/TR/2012/ED-css3-regions-20121009/"
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<meta content="http://www.w3.org/TR/2012/ED-css3-regions-20121011/"
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name=dcterms.identifier>
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<link href="../shared/style/default.css" rel=stylesheet type="text/css">
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<script defer=defer
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<h1 id=css-regions-module>CSS Regions Module Level 3</h1>
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<h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 9 October 2012</h2>
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<h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 11 October
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2012</h2>
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<dl>
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<dt>This version:
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<dd><a
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href="http://www.w3.org/TR/2012/ED-css3-regions-20121009/">http://www.w3.org/csswg/css3-regions</a>
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href="http://www.w3.org/TR/2012/ED-css3-regions-20121011/">http://www.w3.org/csswg/css3-regions</a>
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<dt>Latest version:
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@@ -208,6 +209,10 @@ <h2 class="no-num no-toc" id=table-of-contents>Table of contents</h2>
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<li><a href="#the-flow-from-property"><span class=secno>3.2. </span>The
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‘<code class=property>flow-from</code>’ property</a>
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<ul class=toc>
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<li><a href="#circular-dependencies"><span class=secno>3.2.1.
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</span>Cycle Detection</a>
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</ul>
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<li><a href="#region-flow-break"><span class=secno>3.3. </span>Region
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flow break properties: ‘<code class=property>break-before</code>’,
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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<dd>The element is taken out of its parent's flow and placed into the flow
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with the name ‘<code class=css>&lt;ident&gt;</code>’. The element is
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said to have a <dfn id=specified-flow>specified flow</dfn>. The values
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‘<code class=property>none</code>’, ‘<code
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with the name ‘<code class=css><a
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a></code>’.
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The element is said to have a <dfn id=specified-flow>specified
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flow</dfn>. The values ‘<code class=property>none</code>’, ‘<code
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class=property>inherit</code>’, ‘<code
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class=property>default</code>’, ‘<code class=property>auto</code>’
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and ‘<code class=property>initial</code>’ are invalid flow names.
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<dd>The block container is not a <a href="#css-region"
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title=region>region</a>.
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<dt><strong>&lt;ident&gt;</strong>
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<dt><strong><a
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a></strong>
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<dd> If the ‘<code class=property>content</code>’ property computes to
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something else than ‘<code class=property>normal</code>’ (or ‘<code
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href="http://www.w3.org/TR/CSS21/visuren.html#principal-box">principal
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boxes</a> of the <a href="#css-region">regions</a> in the <a
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href="#region-chain0">region chain</a>. <br>
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If there is no flow with name &lt;ident&gt;, then the block container
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does not format any content visually. <br>
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Likewise, if the block container is part of the flow with name
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&lt;ident&gt;, then the block container does not format any content
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visually.
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If there is no flow with name <a
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>,
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then the block container does not format any content visually.
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</dl>
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<div class=issue-marker data-bug_id=16819 data-bug_status=ASSIGNED> <a
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href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=16819">Issue-16819</a>
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<div class=issue-details>
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<p class=short-desc>No display when combining flow-from and flow-into is
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bad
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</div>
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</div>
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<p>A <span>CSS Region</span>‘<code class=css>s document children are not
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visually formatted unless they are directed to a <a
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href="#named-flow0">named flow</a> with an associated <a
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href="#region-chain0">region chain</a>.</code>
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<div class=note><span class=note-prefix>Note </span>
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<p>An block container becomes a <span>CSS Region</span> when its
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’flow-from' property is set to a valid &lt;ident&gt; value, even if
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there is no content contributing to the referenced flow. For example:
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’flow-from' property is set to a valid <a
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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value, even if there is no content contributing to the referenced flow.
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For example:
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<pre>
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&lt;style&gt;
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class=property>height</code>’ values are resolved for <span>CSS
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Region</span> boxes.
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<h4 id=circular-dependencies><span class=secno>3.2.1. </span>Cycle
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Detection</h4>
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<p><a href="#named-flow0">Named flows</a> containing elements where the
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value of ‘<a href="#flow-from"><code
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class=property>flow-from</code></a>’ computes to an <a
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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can produce nonsensical circular relationships, such as a <a
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href="#named-flow0">named flow</a> containing <span>CSS Regions</span> in
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its own <a href="#region-chain0">region chain</a>. These relationships can
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be easily and reliably detected and resolved, however, by keeping track of
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a dependency graph and using common cycle-detection algorithms.
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<p>The dependency graph consists of edges such that:
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<ul>
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<li>Every <a href="#named-flow0">named flow</a> depends on its elements
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where the value of ‘<a href="#flow-from"><code
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class=property>flow-from</code></a>’ computes to an <a
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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.
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<li>Every element in a <a href="#named-flow0">named flow</a> where the
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value of ‘<a href="#flow-from"><code
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class=property>flow-from</code></a>’ computes to an <a
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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depends on the <a href="#named-flow0">named flow</a> with the <a
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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name.
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</ul>
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<p>If the graph contains a cycle, any elements where the value of ‘<a
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href="#flow-from"><code class=property>flow-from</code></a>’ computes to
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an <a
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href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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participating in the cycle do not become <span>CSS Regions</span>.
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<h3 id=region-flow-break><span class=secno>3.3. </span>Region flow break
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properties: ‘<a href="#break-before"><code
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class=property>break-before</code></a>’, ‘<a href="#break-after"><code
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28<sup>th</sup> 2012</a> version</h3>
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<ul>
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<li>Added section on handling circular flow-from and flow-into situations
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<li>Added alignment and justification to region styling properties
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<li>Added timing for regionLayoutUpdate event
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<h2 class=no-num id=references>References</h2>
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<div class="issue-marker wrapper">
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<div class=issue-marker data-bug_id=16404 data-bug_status=ASSIGNED> <a
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href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=16404">Issue-16404</a>
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<div class=issue-details>
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<p class=short-desc>Fix specification dependencies
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</div>
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</div>
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<div class=issue-marker data-bug_id=18767 data-bug_status=NEW> <a
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href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=18767">Issue-18767</a>
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‎css3-regions/Overview.src.html‎

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@@ -502,7 +502,7 @@ <h3 id="the-flow-into-property">The 'flow-into' property</h3>
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<dd>The element is taken out
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of its parent's flow
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and placed into the flow
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with the name '&lt;ident&gt;'.
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with the name '<a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>'.
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The element is said to have
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a <dfn id="specified-flow">specified flow</dfn>.
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The values 'none', 'inherit', 'default', 'auto' and 'initial'
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<dd>The block container is not a <span title="region">region</span>.</dd>
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<dt><strong>&lt;ident&gt;</strong></dt>
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<dt><strong><a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a></strong></dt>
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<dd>
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If the 'content' property computes
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of the <span>regions</span>
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in the <span>region chain</span>.
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<br/>
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If there is no flow with name &lt;ident&gt;,
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If there is no flow with name
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<a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>,
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then the block container does not
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format any content visually.
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<br/>
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Likewise, if the block container is part
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of the flow with name &lt;ident&gt;,
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then the block container does not
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format any content visually.
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</dd>
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</dl>
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<div class="issue-marker" data-bug_id="16819" data-bug_status="ASSIGNED">
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<a href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=16819">Issue-16819</a>
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<div class="issue-details">
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<p class="short-desc">No display when combining flow-from and flow-into is bad</p>
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</div>
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</div>
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<p>A <span>CSS Region</span>'s document children
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are not visually formatted
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unless they are directed
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<div class="note"><span class="note-prefix">Note </span>
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<p>An block container becomes a <span>CSS Region</span>
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when its 'flow-from' property is set
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to a valid &lt;ident&gt; value,
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to a valid <a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a> value,
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even if there is no content contributing
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to the referenced flow.
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For example:</p>
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'width' and 'height' values are resolved
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for <span>CSS Region</span> boxes.</p>
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<h4 id="circular-dependencies">Cycle Detection</h4>
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<p><span>Named flows</span> containing elements
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where the value of 'flow-from' computes to an
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<a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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can produce nonsensical circular relationships,
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such as a <span>named flow</span> containing <span>CSS Regions</span>
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in its own <span>region chain</span>.
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These relationships can be easily
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and reliably detected and resolved, however,
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by keeping track of a dependency graph
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and using common cycle-detection algorithms.</p>
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<p>The dependency graph consists of edges such that:</p>
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<ul>
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<li>Every <span>named flow</span> depends on its elements
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where the value of 'flow-from' computes to an
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<a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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.</li>
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<li>Every element in a <span>named flow</span>
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where the value of 'flow-from' computes to an
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<a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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depends on the <span>named flow</span> with the
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<a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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name.</li>
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</ul>
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<p>If the graph contains a cycle,
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any elements where the value of 'flow-from'
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computes to an
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<a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier">&lt;ident&gt;</a>
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participating in the cycle
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do not become <span>CSS Regions</span>.</p>
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<h3 id=
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"region-flow-break">Region
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flow break properties: 'break-before', 'break-after', 'break-inside'</h3>
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<h3 id="changes_from_Aug_28_2012">Changes from <a href="http://www.w3.org/TR/2012/WD-css3-regions-20120823/">August 28<sup>th</sup> 2012</a> version</h3>
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<ul>
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<li>Added section on handling circular flow-from and flow-into situations</li>
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<li>Added alignment and justification to region styling properties</li>
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<li>Added timing for regionLayoutUpdate event</li>
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<li>Clarified interaction between content and flow-from for pseudo-elements</li>
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<h2 class="no-num" id="references">References</h2>
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<div class="issue-marker wrapper">
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<div class="issue-marker" data-bug_id="16404" data-bug_status="ASSIGNED">
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<a href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=16404">Issue-16404</a>
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<div class="issue-details">
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<p class="short-desc">Fix specification dependencies</p>
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</div>
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</div>
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<div class="issue-marker" data-bug_id="18767" data-bug_status="NEW">
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<a href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=18767">Issue-18767</a>
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<div class="issue-details">

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