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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html lang=en>
<head profile="http://www.w3.org/2006/03/hcard"><meta
content="text/html; charset=utf-8" http-equiv=Content-Type>
<title>CSS Regions Module Level 3</title>
<link href="../default.css" rel=stylesheet type="text/css">
<style type="text/css">
/* Alternate stylesheet fonts are here because in some browsers (Opera 11.5) */
/* The fonts are not applied if only loaded from the alternate stylesheet */
/* License font the following two fonts: fonts/Droid-Serif-fontfacekit/Google Android License.txt */
@import url(fonts/Droid-Serif-fontfacekit/stylesheet.css);
@import url(fonts/Droid-Sans-Mono-fontfacekit/stylesheet.css);
a.toggle {
position: fixed;
top: 0.5em;
right: 0.5em;
font-size: smaller;
color: gray;
opacity: 0.2;
}
a.toggle:hover {
opacity: 1;
color: #46A4E9;
}
.issue.resolved, .issue.stale, .issue.moved {
display: none;
}
#region-style-example p, #region-style-example pre {
clear: both;
}
#region_styling_illustration {
margin: 0px auto;
width: 70ex;
}
.big.note {
font-size: 1.2em;
line-height: 1.3em;
color: #2f2f2f;
}
#mobile-logo {
display: none;
}
@media screen and (min-width: 68em){
.issue-marker {
position: absolute;
width: 20ex;
margin-left: -22ex;
text-align: right;
margin-bottom: 1em;
}
div.issue-marker .issue-marker {
position: static;
width: auto;
margin-left: 0;
text-align: right;
}
div.issue-marker {
position: absolute;
width: 20ex;
margin-left: -22ex;
}
}
@media screen and (max-width: 68em){
.issue-marker {
margin-bottom: 1em;
}
.issue-marker a:link {
padding-left: 0.5em;
}
}
#issue-manager form{
background: #eee;
padding:10px 1em;
}
/* hide all non-"updated" issues */
#issue-manager[data-view_state="updated"] #issue-list>div:not([data-issue_state="updated"]){
display:none;
}
/* hide all non-"new" issues */
#issue-manager[data-view_state="new"] #issue-list>div:not([data-issue_state="new"]){
display:none;
}
#issue-manager .issue-marker{
background: none;
position: relative;
margin:0;
width:auto;
text-align:left;
padding:0.5em 0;
}
#issue-manager .issue-marker a:link{
padding:0.5em;
}
#issue-list div[data-issue_state="new"]{
background:#C1FFC1;
}
#issue-list div[data-issue_state="resolved"]{
background:white;
color: #a0a0a0;
}
#issue-list div[data-issue_state="updated"]{
background:papayawhip;
}
#issue-list{
margin-top:20px;
}
#issue-list pre{
padding:1em;
margin:0;
}
#issue-list>div{
position:relative;
}
#issue-list a.issue-markup-trigger{
font-size: 0.8em;
padding: 0.2em 0.5em;
background: #eee;
text-decoration: none;
color: #444;
position: absolute;
right: 10px;
top: 10px;
z-index: 1;
}
#issue-list a.issue-markup-trigger:hover{
background: #ddd;
color: #000;
}
#issue-list .showMarkup pre{
display: block;
}
#issue-list .showMarkup .issue-marker,
#issue-list pre{
display: none;
}
.issue-marker {
background:#eee;
border:1px solid #ddd;
font-size: 1em;
}
.issue-marker.wrapper {
background: none;
border: none;
}
.issue-marker a:link {
color: #c00;
background: none;
font-weight: normal;
padding-right: 0.5em;
}
.issue-details {
padding:0.5em;
font-size: 0.8em;
line-height: 1.5;
}
.issue-details p{
padding:0;
margin:0;
}
.issue-details .status{
background:#333;
color:white;
float:left;
padding:0.15em 0.8em;
font-size:0.8em;
margin-right:0.8em;
text-transform:uppercase;
}
</style>
<link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel=stylesheet
type="text/css">
<link href="../alternate-spec-style.css" id=st rel=stylesheet
title="alternate spec style" type="text/css">
<body>
<div class=head id=div-head>
<p><a href="http://www.w3.org/"><img alt=W3C height=53 id=mobile-logo
src="http://www.w3.org/2008/site/images/logo-w3c-mobile-lg" width=90></a>
<!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt=W3C height=48
src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo--></p>
<h1 id=css-regions-module>CSS Regions Module Level 3</h1>
<h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 27 March 2012</h2>
<dl>
<dt>This version:
<dd><a
href="http://www.w3.org/TR/2012/ED-css3-regions-20120327/">http://www.w3.org/csswg/css3-regions</a>
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-regions/">http://www.w3.org/TR/css3-regions/</a>
<dt>Previous version:
<dd><a
href="http://www.w3.org/TR/2011/WD-css3-regions-20111129/">http://www.w3.org/TR/2011/WD-css3-regions-20111129/</a>
<dt>Editors:
<dd class=vcard><span class=fn>Vincent Hardy</span>, <span
class=org>Adobe Systems, Inc.</span>, <span
class=email>vhardy@adobe.com</span>
<dd class=vcard><span class=fn>Alex Mogilevsky</span>, <span
class=org>Microsoft</span>, <span
class=email>alexmog@microsoft.com</span>
<dt>Issues List:
<dd><a
href="https://www.w3.org/Bugs/Public/buglist.cgi?product=CSS&component=CSS%20Regions&resolution=---">Bugzilla
Bugs for CSS regions</a>
<dt>Discussion:
<dd><a
href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a>
with subject line "<code>[css3-regions] message topic</code>"
</dl>
<!--begin-copyright-->
<p class=copyright><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=license>Copyright</a> © 2012 <a href="http://www.w3.org/"><abbr
title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a
href="http://www.csail.mit.edu/"><abbr
title="Massachusetts Institute of Technology">MIT</abbr></a>, <a
href="http://www.ercim.eu/"><abbr
title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
<a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a
href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
and <a
href="http://www.w3.org/Consortium/Legal/copyright-documents">document
use</a> rules apply.</p>
<!--end-copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id=abstract>Abstract</h2>
<p>The CSS regions module allows content to flow across multiple areas
called regions. The regions are not necessarily contiguous in the document
order. The CSS regions module provides an advanced content flow mechanism,
which can be combined with positioning schemes as defined by other CSS
modules such as the Multi-Column Module <a href="#CSS3COL"
rel=biblioentry>[CSS3COL]<!--{{CSS3COL}}--></a> or the Grid Layout Module
<a href="#CSS3-GRID-LAYOUT"
rel=biblioentry>[CSS3-GRID-LAYOUT]<!--{{CSS3-GRID-LAYOUT}}--></a> to
position the regions where content flows.
<h2 class="no-num no-toc" id=status-of-this-document>Status of this
document</h2>
<p class="big note"><span class=note-prefix>Note </span>This document uses
an experimental style sheet. We welcome your feedback on the styles at <a
href="mailto:site-comments@w3.org">site-comments@w3.org</a>.</p>
<!--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-regions%5D%20PUT%20SUBJECT%20HERE">
www-style@w3.org</a> (see <a
href="http://www.w3.org/Mail/Request">instructions</a>) is preferred for
discussion of this specification. When sending e-mail, please put the text
“css3-regions” in the subject, preferably like this:
“[<!---->css3-regions<!---->] <em>…summary of
comment…</em>”
<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 draft is related to the drafts about Multi-column Layout <a
href="#CSS3COL" rel=biblioentry>[CSS3COL]<!--{{CSS3COL}}--></a>, Grid
Layout <a href="#CSS3GRID"
rel=biblioentry>[CSS3GRID]<!--{{CSS3GRID}}--></a>, Flexible Box Layout <a
href="#CSS3-FLEXBOX"
rel=biblioentry>[CSS3-FLEXBOX]<!--{{CSS3-FLEXBOX}}--></a>, and Template
Layout <a href="#CSS3LAYOUT"
rel=biblioentry>[CSS3LAYOUT]<!--{{CSS3LAYOUT}}--></a>.
<h2 class="no-num no-toc" id=table-of-contents>Table of contents</h2>
<!--begin-toc-->
<ul class=toc>
<li><a href="#introduction"><span class=secno>1. </span>Introduction</a>
<ul class=toc>
<li><a href="#named-flows-and-regions"><span class=secno>1.1.
</span>Named flows and regions</a>
<li><a href="#region-styling"><span class=secno>1.2. </span>Regions
styling</a>
</ul>
<li><a href="#css-regions-concepts"><span class=secno>2. </span>CSS
regions concepts</a>
<ul class=toc>
<li><a href="#regions"><span class=secno>2.1. </span>Regions</a>
<li><a href="#named-flow"><span class=secno>2.2. </span>Named flow</a>
<li><a href="#regions-flow-breaking-rules"><span class=secno>2.3.
</span>Regions flow breaking rules</a>
</ul>
<li><a href="#relation-to-document-events"><span class=secno>3.
</span>Relation to document events</a>
<li><a href="#properties-and-rules"><span class=secno>4. </span>Properties
and rules</a>
<ul class=toc>
<li><a href="#the-flow-into-property"><span class=secno>4.1. </span>The
‘<code class=property>flow-into</code>’ property</a>
<li><a href="#the-flow-from-property"><span class=secno>4.2. </span>The
‘<code class=property>flow-from</code>’ property</a>
<ul class=toc>
<li><a href="#intrinsic-width-of-regions"><span class=secno>4.2.1.
</span>Intrinsic width of regions</a>
<li><a href="#intrinsic-height-of-regions"><span class=secno>4.2.2.
</span>Intrinsic height of regions</a>
</ul>
<li><a href="#region-flow-break"><span class=secno>4.3. </span>Region
flow break properties: ‘<code
class=property>break-before</code>’, ‘<code
class=property>break-after</code>’, ‘<code
class=property>break-inside</code>’</a>
<li><a href="#the-region-overflow-property"><span class=secno>4.4.
</span>The region-overflow property</a>
<li><a href="#the-at-region-style-rule"><span class=secno>4.5.
</span>The @region rule</a>
</ul>
<li><a href="#multi-column-regions"><span class=secno>5.
</span>Multi-column regions</a>
<ul class=toc>
<li><a href="#regions"><span class=secno>5.1. </span> </a>
</ul>
<li><a href="#pseudo_elements"><span class=secno>6.
</span>Pseudo-elements</a>
<ul class=toc>
<li><a href="#processing-model"><span class=secno>6.1. </span>Processing
model</a>
</ul>
<li><a href="#cssom_view_and_css_regions"><span class=secno>7.
</span>CSSOM view and CSS regions</a>
<ul class=toc>
<li><a href="#the-namedflow-interface"><span class=secno>7.1. </span>The
NamedFlow interface</a>
<li><a href="#the-region-interface"><span class=secno>7.2. </span>The
Region interface</a>
<li><a href="#region-flow-layout-events"><span class=secno>7.3.
</span>Region flow layout events</a>
<li><a href="#cssomview-and-regions"><span class=secno>7.4. </span>CSS
OM View and CSS Regions</a>
<ul class=toc>
<li><a
href="#cssomview-getclientrects-and-getboundingclientrect"><span
class=secno>7.4.1. </span><code class=idl>getClientRects()</code> and
<code>getBoundingClientRects()</code></a>
<li><a href="#cssomview-offset-attributes"><span class=secno>7.4.2.
</span><code class=idl>offsetTop</code>, <code
class=idl>offsetLeft</code>, <code class=idl>offsetWidth</code> and
<code class=idl>offsetWidth</code></a>
</ul>
</ul>
<li><a href="#relation-to-other-specifications"><span class=secno>8.
</span>Relation to other specifications</a>
<li><a href="#usecases"><span class=secno>9. </span>Use Cases</a>
<li><a href="#conformance"><span class=secno>10. </span>Conformance</a>
<li><a href="#changes"><span class=secno>11. </span>Changes</a>
<ul class=toc>
<li><a href="#changes_from_June_09_2011"><span class=secno>11.1.
</span>Changes from November 29<sup>th</sup> 2011 version</a>
<li><a href="#changes_from_June_09_2011"><span class=secno>11.2.
</span>Changes from June 09<sup>th</sup> 2011 version</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><a href="#issue-manager0"><span class=secno>12. </span>Issue
manager</a>
</ul>
<!--end-toc-->
<h2 id=introduction><span class=secno>1. </span>Introduction</h2>
<p><em>This section is non-normative.</em>
<div class=issue-marker data-bug_id=15159 data-bug_status=NEW> <a
href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15159">Bug-15159</a>
<div class=issue-details>
<p class=short-desc>Add code samples to the CSS regions use cases page</p>
</div>
</div>
<p>Capturing the complex layouts of a typical magazine, newspaper, or
textbook requires capabilities beyond those available in existing CSS
modules. This is the purpose of the CSS regions module.
<p>The CSS regions module can be seen as an extension of the concept of
multi-column elements. With CSS Multi-column layout <a href="#CSS3COL"
rel=biblioentry>[CSS3COL]<!--{{CSS3COL}}--></a>, columns share the same
dimensions and define column boxes organized in rows. Content flows from
one column to the next.
<p>The multi-column model is an example of flowing content from one area to
another, where the areas are the multi-column element's column boxes and
the flow is made of the multi-column element's children.
<div class=issue-marker data-bug_id=15733 data-bug_status=NEW> <a
href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15733">Bug-15733</a>
<div class=issue-details>
<p class=short-desc>Should the region specification define a mechanism to
create blocks that can be regions with CSS syntax?</p>
</div>
</div>
<p>However, for more complex layouts, content needs to flow from one area
of the page to the next without limitation of the areas' sizes and
positions. These arbitrary areas are the target of specific content flows.
In this document these areas are called regions, and the content flows are
called named flows. Regions are based on the rectangular geometry of the
CSS box model. Elements in a named flow are taken out of the normal visual
formatting and rendered in a chain of regions.
<h3 id=named-flows-and-regions><span class=secno>1.1. </span>Named flows
and regions</h3>
<p>Consider the layout illustrated in figure 1.
<div class=figure> <img
alt="multiple chained regions which should receive content from a flow"
src="images/regions-intro.svg" width=400>
<p class=caption>Layout requiring sophisticated content flow</p>
</div>
<div class=issue-marker data-bug_id=15131 data-bug_status=NEW> <a
href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15131">Bug-15131</a>
<div class=issue-details>
<p class=short-desc>Add layout to initial example</p>
</div>
</div>
<p>The designer's intent is to position an image in region ‘<code
class=property>A</code>’ and to flow an article's text from region
‘<code class=css>1</code>’, to region ‘<code
class=css>2</code>’, ‘<code class=css>3</code>’ and
‘<code class=css>4</code>’.
<p>The following code snippet shows the content to flow between the regions
1, 2, 3 and 4.
<pre>
<div <em>id="article"</em>>
<h1>Introduction</h1>
<p>This is an example ...</p>
<h1>More Details</h1>
<p>This illustrates ...</p>
<p>Then, the example ...</p>
<p>Finally, this ...</p>
</div>
</pre>
<p>And the following snippet shows an example using grid cells to define
the region areas:
<pre>
<style>
#page {
width: 800px;
height: 600px;
grid-template: "aaa.e"
"....e"
"bbb.e"
"....e"
"c.d.e";
grid-rows: 52% 4% 20% 4% 20%;
grid-columns: 30% 5% 30% 5% 30%;
}
#regionA { grid-cell: a; }
#region1 { grid-cell: b; }
#region2 { grid-cell: c; }
#region3 { grid-cell: d; }
#region4 { grid-cell: e; }
</style>
<div id="page">
<div id="region1"></div>
<div id="region2"></div>
<div id="region3"></div>
<div id="region4"></div>
</div>
</pre>
<p>Any of the CSS layout facilities can be used to create, position and
size regions as needed.
<div class=note>
<p>Using a grid layout (see <a href="#CSS3-GRID-LAYOUT"
rel=biblioentry>[CSS3-GRID-LAYOUT]<!--{{CSS3-GRID-LAYOUT}}--></a> is just
an example. The example could use a flexible box layout as well, see <a
href="#CSS3-FLEXBOX"
rel=biblioentry>[CSS3-FLEXBOX]<!--{{CSS3-FLEXBOX}}--></a>.</p>
<p>The CSS regions specification does not define a layout mechanism and is
meant to integrate with existing and future CSS layout facilities.</p>
</div>
<p>However, there is no existing mechanism to associate the content with
the regions so that content flows as intended. Figure 2 shows an example
of the intended visual rendering of the content.
<div class=figure> <img
alt="Sample rendering showing a single thread of text flowing through a chain of regions"
src="images/regions-intro-rendering.png" width=450>
<p class=caption>Sample rendering for desired layout</p>
</div>
<p>The CSS regions module is independent of the layout of regions and the
mechanism used to create them. For simplicity, our example uses elements
as regions as shown in the previous code snippet.
<div class=note>
<p>While the example uses elements as regions (since [CSS3-GRID-LAYOUT]
requires elements to create grid items) it is important to note that this
is not required for regions. Regions can be pseudo-elements, such as
‘<code class=css>::before</code>’ and ‘<code
class=css>::after</code>’. The only requirement for an element or
pseudo-element to become a region is that it needs to be subject to CSS
styling to receive the ‘<a href="#flow-from"><code
class=property>flow-from</code></a>’ property.</p>
</div>
<p>The following code example illustrates how the content of the
<code>article</code> element becomes a flow and how the areas ‘<code
class=css>region1</code>’, ‘<code
class=css>region2</code>’, ‘<code
class=css>region3</code>’ and ‘<code
class=css>region4</code>’ become regions that consume the
‘<code class=css>article_flow</code>’ content.
<div class=example>
<pre>
<style>
#article {
<strong>flow-into: article_flow;</strong>
}
#region1, #region2, #region3, #region4 {
<strong>flow-from: article_flow;</strong>
}
</style>
</pre>
</div>
<p>The ‘<code class=css>article_flow</code>’ value on the
‘<a href="#flow-into"><code
class=property>flow-into</code></a>’ property directs the
‘<code class=css>#article</code>’ element to the ‘<code
class=css>article_flow</code>’ named flow. Setting the elements'
‘<a href="#flow-from"><code
class=property>flow-from</code></a>’ property to ‘<code
class=css>article_flow</code>’ on elements makes them regions and
associates these regions with the named flow: the flow is ‘<code
class=css>poured</code>’ into the desired regions.
<h3 id=region-styling><span class=secno>1.2. </span>Regions styling</h3>
<p>Region styling allows content to be styled depending on the region it
flows into. It is a form of context-based styling, similar to Media
Queries <a href="#MEDIAQ" rel=biblioentry>[MEDIAQ]<!--{{MEDIAQ}}--></a>
which enable or disable selectors depending on the rendering context. With
region styling, additional selectors may apply depending on the region
into which content flows.
<p>In our example, the designer wants to make text flowing into region 1
larger, bold and dark blue. In addition, <code
class=html><h1></code> headers should be crimson.
<p>This design can be expressed with region styling as shown below.
<div class=example>
<pre>
<style>
/*
* Default article styling.
*/
#article {
color:#777;
text-align: justify;
}
#article h1 {
border-left: 1px solid #777;
padding-left: 2ex;
display: run-in;
}
/*
* Additional styling to apply to content when it falls into
* region1
*/
<strong>@region #region1 {</strong>
#article {
font-weight: bold;
color: #0C3D5F;
font-size: larger;
}
#article h1 {
color: crimson;
border: none;
padding: 0px;
}
<strong>}</strong>
/*
* Style that would apply to region1's normal content but
* will not apply to its named flow content.
*/
#region1 p {
color: red;
}
</style>
</pre>
</div>
<p>The ‘<code class=css>@region</code>’ rule for region 1
limits its selectors to content flowing into region 1. The following
figure shows how the rendering changes if we do not increase the font size
nor make it bold for content flowing into region 1. As more content can be
fitted, more content is subject to the contextual selectors, resulting in
more dark blue text into region 1.
<div class=figure> <img
alt="Illustrate how changing region styling affects the flow of content."
src="images/region-styling.png" width=450>
<p class=caption>Different rendering with a different region styling</p>
</div>
<p>Finally, note how the ‘<code class=property>red</code>’
color specified for <code><p></code> elements under
<code>#region1</code> does not apply to content that flows into the
region. This specified style does not apply to the named flow content
because the <code><p></code> elements in the ‘<code
class=property>article</code>’ named flow are not descendants of the
<code>#region1</code> element and, consequently, the <code>"#region1
p"</code> selector does not apply to these elements.
<h2 id=css-regions-concepts><span class=secno>2. </span>CSS regions
concepts</h2>
<h3 id=regions><span class=secno>2.1. </span>Regions</h3>
<div class="issue-marker wrapper">
<div class=issue-marker data-bug_id=15186 data-bug_status=NEW> <a
href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15186">Bug-15186</a>
<div class=issue-details>
<p class=short-desc>Is a mechanism to auto-generate regions necessary in
order to support reusable style sheets?</p>
</div>
</div>
<div class=issue-marker data-bug_id=15187 data-bug_status=NEW> <a
href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15187">Bug-15187</a>
<div class=issue-details>
<p class=short-desc>Explain how regions and pages interact. How can
regions be placed onto certain pages, and how can they be positiond
wrt. pages.</p>
</div>
</div>
</div>
<p class=index id=region title=region>A region is an element that generates
a <a href="http://www.w3.org/TR/CSS21/visuren.html#block-boxes">block
container box</a> and has an associated <a href="#named-flow0"><em>named
flow</em></a> (see the ‘<a href="#flow-from"><code
class=property>flow-from</code></a>’ property). The <a
href="http://dev.w3.org/csswg/css3-multicol/#column-box">column boxes</a>
of multi-column elements which have an associated <a
href="#named-flow0"><em>named flow</em></a> are also regions.
<h3 id=named-flow><span class=secno>2.2. </span>Named flow</h3>
<p>A <dfn id=named-flow0>named flow</dfn> is the ordered sequence of
elements associated with a flow with a given identifier. Elements in a
named flow are ordered according to the document order.
<p>Elements are placed into a named flow with the ‘<a
href="#flow-into"><code class=property>flow-into</code></a>’
property. The elements in a named flow are laid out in the chain of
regions that are associated with this named flow. <span
title=region>Regions</span> are organized in to a <span
title=region-chain>region chain</span> according to the document order.
<p>Content from a named flow is broken up between regions according to the
regions flow breaking rules.
<h3 id=regions-flow-breaking-rules><span class=secno>2.3. </span>Regions
flow breaking rules</h3>
<p>Breaking a named flow across multiple regions is similar to breaking a
document's content across multiple pages (see <a href="#CSS3PAGE"
rel=biblioentry>[CSS3PAGE]<!--{{CSS3PAGE}}--></a>) or a multi-column
element's content across column boxes (see <a href="#CSS3COL"
rel=biblioentry>[CSS3COL]<!--{{CSS3COL}}--></a>). One difference is that
page boxes are generated based on the available content whereas regions
are a set of recipient boxes for the named flow content whose dynamic
generation is not in the scope of this specification.
<p><span title=region>Regions</span> are organized in to a <span
title=region-chain>region chain</span>.
<p>Each region in turn consumes content from its associated <a
href="#named-flow0">named flow</a>. The named flow content is positioned
in the <dfn id=current-region title=current-region>current region</dfn>
until a natural or forced region break occurs, at which point the <a
href="#current-region" title=current-region>current region</a> becomes the
next one in the <span title=region-chain>region chain</span>. If there are
no more <span>region</span>s in the region chain and there is still
content in the flow, the positioning of the remaining content is
controlled by the ‘<a href="#region-overflow"><code
class=property>region-overflow</code></a>’ property on the last
<span>region</span> in the chain.
<h2 id=relation-to-document-events><span class=secno>3. </span>Relation to
document events</h2>
<p>The CSS regions module does not alter the normal processing of events in
the document tree. In particular, if an event occurs on an element that is
part of a named flow, the <a
href="http://www.w3.org/TR/dom/#events">event's bubble and capture
phases</a> happen following the document tree order.
<h2 id=properties-and-rules><span class=secno>4. </span>Properties and
rules</h2>
<p><em>This section is normative.</em>
<h3 id=the-flow-into-property><span class=secno>4.1. </span>The ‘<a
href="#flow-into"><code class=property>flow-into</code></a>’
property</h3>
<div class=issue-marker data-bug_id=15811 data-bug_status=NEW> <a
href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15811">Bug-15811</a>
<div class=issue-details>
<p class=short-desc>Creating a named flow from external resource</p>
</div>
</div>
<p>The ‘flow-into’ property can place an element into a named flow.
Elements that belong to the same flow are laid out in the regions
associated with that flow.
<table class=propdef summary="flow property definition">
<tbody>
<tr>
<th>Name:
<td><dfn id=flow-into>flow-into</dfn>
<tr>
<th>Value:
<td><ident> | none | inherit
<tr>
<th>Initial:
<td>none
<tr>
<th>Applies to:
<td>any element.
<p>The ‘<a href="#flow-into"><code
class=property>flow-into</code></a>’ property does not apply to
any <a
href="http://www.w3.org/TR/selectors/#pseudo-elements">pseudo-element</a>
such as <code class=css>::first-line</code>, <code
class=css>::first-letter</code>, <code class=css>::before</code> or
<code class=css>::after</code>.
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed value:
<td>as specified
</table>
<dl>
<dt>none
<dd>The element is not moved to a named flow and normal CSS processing
takes place.
<dt><a
href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier"><ident></a>
<dd>The element is taken out of its parent's flow and placed into the flow
with the name ‘<code class=css><ident></code>’. The
element is said to have a <dfn id=specified-flow>specified flow</dfn>.
The values ‘<code class=property>none</code>’, ‘<code
class=property>inherit</code>’, ‘<code
class=property>default</code>’, ‘<code
class=property>auto</code>’ and ‘<code
class=property>initial</code>’ are invalid flow names.
</dl>
<p>A named flow needs to be associated with one or more regions for its
elements to be visually formatted. If no region is associated with a given
named flow, the elements in the named flow are not rendered: they do not
generate boxes and are not displayed.
<p>The children of an element with a specified flow may themselves have a
specified flow.
<p>If an element has the same specified flow as one of its ancestors, it
becomes a sibling of it's ancestor for the purpose of layout in the
regions laying out content from that flow.
<p>The ‘<a href="#flow-into"><code
class=property>flow-into</code></a>’ property does not affect the
CSS cascade and inheritance for the elements on which it is specified. The
‘<a href="#flow-into"><code
class=property>flow-into</code></a>’ property affects the visual
formatting of elements placed into a named flow and of regions laying out
content from a named flow.
<div class="issue-marker wrapper">
<div class=issue-marker data-bug_id=15858 data-bug_status=NEW> <a
href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15858">Bug-15858</a>
<div class=issue-details>
<p class=short-desc>Should first region be ICB for flow content?</p>
</div>
</div>
<div class=issue-marker data-bug_id=15870 data-bug_status=NEW> <a
href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15870">Bug-15870</a>
<div class=issue-details>
<p class=short-desc>Describe how containing blocks are used for element
fragments</p>
</div>
</div>
</div>
<p>The edges of the first region in a region chain associated with a named
flow establish the rectangle that is the <a
href="http://www.w3.org/TR/CSS2/visudet.html#containing-block-details">containing
block</a> used for absolutely positioned elements in the name named flow
which do not have an ancestor with a ‘<code
class=property>position</code>’ of ‘<code
class=property>absolute</code>’, ‘<code
class=property>relative</code>’ or ‘<code
class=property>fixed</code>’ (see <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>). That first region rectangle
is used as the containing block instead of the initial containing block.
<p>The first region defines the <a
href="http://www.w3.org/TR/css3-writing-modes/#writing-mode">writing
mode</a> for the entire flow. The writing mode on subsequent regions is
ignored.
<p>Elements in a named flow are sequenced in document order.
<div class=note><span class=note-prefix>Note </span>
<p>The ‘<a href="#flow-into"><code
class=property>flow-into</code></a>’ property moves an element into
the flow and the interplay with selectors should be considered carefully.</p>
<p>For example,</p>
<pre>table {flow-into: table-content}</pre>
<p>will move all tables in the ‘<code
class=property>table-content</code>’ named flow. However, the</p>
<pre>table > * {flow-into: table-content} ...</pre>
<p>selector will move all immediate children of all table elements into
the ‘table-content’ named flow (which may be useful as it will
usually result, if the immediate children are rows, in merging rows of
multiple tables), but the</p>