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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html dir="ltr" lang="en">
<head profile="http://www.w3.org/2006/03/hcard">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>CSS regions Module</title>
<link href="http://dev.w3.org/csswg/default.css" rel="stylesheet" type=
"text/css">
<link href="http://www.w3.org/StyleSheets/TR/W3C-ED.css" rel="Stylesheet"
type="text/css">
<link id="st" href="alternate-spec-style.css" rel="stylesheet" type=
"text/css" title="additional spec styles">
<script type="text/javascript" src="style-toggle.js">
</script>
<!-- <script src='http://test.csswg.org/harness/annotate.js#CSS3-REGIONS_DEV' type=
'text/javascript'> -->
</script>
</head>
<body>
<div class="head" id="div-head">
<!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt="W3C" height="48" src=
"http://www.w3.org/Icons/w3c_home" width="72"></a> <!--end-logo--></p>
<h1 id="css-regions-module">CSS regions Module</h1>
<h2 class="no-num no-toc" id="longstatus-date">Editor's Draft
[DATE]</h2>
<dl>
<dt>This version:</dt>
<dd><a href=
"[VERSION]">http://www.w3.org/csswg/css3-regions</a></dd>
<dt>Latest version:</dt>
<dd><a href=
"http://www.w3.org/TR/css3-regions">http://www.w3.org/csswg/css3-regions</a></dd>
<dt>Previous version:</dt>
<dd>none</dd>
<dt>Editors:</dt>
<dd class="vcard"><span class="fn">Vincent Hardy</span>,
<span class="org">Adobe Systems, Inc.</span>, <span class=
"email">vhardy@adobe.com</span></dd>
<dd class="vcard"><span class="fn">Alex Mogilevsky</span>,
<span class="org">Microsoft</span>, <span class=
"email">alexmog@microsoft.com</span></dd>
<dt>Authors and Former Editors:</dt>
<dd class="vcard"><span class="fn">Stephen Zilles</span>,
<span class="org">Adobe Systems, Inc.</span>, <span class=
"email">szilles@adobe.com</span></dd>
<dd class="vcard"><span class="fn">Alexandru Chiculita</span>,
<span class="org">Adobe Systems, Inc.</span>, <span class=
"email">achicu@adobe.com</span></dd>
<dd class="vcard"><span class="fn">Andrei Bucur</span>,
<span class="org">Adobe Systems, Inc.</span>, <span class=
"email">abucur@adobe.com</span></dd>
<dd class="vcard"><span class="fn">Mihnea Ovidenie</span>,
<span class="org">Adobe Systems, Inc.</span>, <span class=
"email">mihnea@adobe.com</span></dd>
<dd class="vcard"><span class="fn">Peter Sorotokin</span>,
<span class="org">Adobe Systems, Inc.</span>, <span class=
"email">psorotok@adobe.com</span></dd>
<dd class="vcard"><span class="fn">Virgil Palanciuc</span>,
<span class="org">Adobe Systems, Inc.</span>, <span class=
"email">virgilp@adobe.com</span></dd>
<dd class="vcard"><span class="fn">Arno Gourdol</span>,
<span class="org">Adobe Systems, Inc.</span>, <span class=
"email">agourdol@adobe.com</span></dd>
</dl><!--begin-copyright--><!--end-copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id="abstract">Abstract</h2>
<strong>CHANGES IN PROGRESS, NOT READY FOR REVIEW</strong>
<p>The CSS regions module allows content to flow across multiple areas
called regions. The regions do not necessarily follow 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 [[CSS3COL]] or the Grid Layout Module
[[CSS3-GRID-LAYOUT]] to position the regions where content flows.</p>
<h2 class="no-num no-toc" id="status-of-this-document">Status of this
document</h2><!--begin-status-->
<p><em>This section describes the status of this document at the time of
its publication. Other documents may supersede this document. A list of
current W3C publications and the latest revision of this technical report
can be found in the <a href="http://www.w3.org/TR/">W3C technical reports
index at http://www.w3.org/TR/.</a></em></p>
<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>
<p>The archived public mailing list www-style@w3.org 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]
…summary of comment…"</p>
<p>This draft is related to the drafts about Multi-column Layout <a href=
'#CSSMULTICOL'>[CSSMULTICOL]</a>, Grid Layout <a href=
'#CSS3GRID'>[CSS3GRID]</a>, Flexible Box Layout <a href=
'#CSS3FLEXBOX'>[CSS3FLEXBOX]</a>, and Template Layout <a href=
'#CSSTEMPLATELAYOUT'>[CSSTEMPLATELAYOUT]</a>.</p><!--end-status-->
<h2 class="no-num no-toc" id="table-of-contents">Table of contents</h2>
<!--begin-toc--><!--end-toc-->
<h2 id="introduction">Introduction</h2>
<p><em>This section is non-normative.</em></p>
<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>
<p> </p>
<p>The CSS regions module can be seen as an extension of the concept of
multi-column elements. With CSS Multi-column layout [[CSS3COL]], columns
share the same dimensions and define column boxes organized in rows.
Content flows from one column to the next.</p>
<p> </p>
<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.</p>
<p> </p>
<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.</p>
<h3 id="named-flows-and-regions">Named flows and regions</h3>
<p>Consider the layout illustrated in figure 1.</p>
<div class="figure">
<img src="images/regions-intro.svg" width="400" alt=
"multiple chained regions which should receive content from a flow">
<p class="caption">Layout requiring sophisticated content flow</p>
</div>
<p>The designer's intent is to position an image in region 'A' and to flow
an article's text from region '1', to region '2', '3' and '4'.</p>
<p>The following code snippet shows the content to flow between the regions
1, 2, 3 and 4.</p>
<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>CSS layout facilities can position and size regions as needed. 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.</p>
<div class="figure">
<img src="images/regions-intro-rendering.png" width="450" alt=
"Sample rendering showing a single thread of text flowing through a chain of regions">
<p class="caption">Sample rendering for desired layout</p>
</div>
<p>Since the CSS regions module is independent of the layout of regions and
the mechanism used to create them, the following assumes there is a CSS
selector for the regions and, for the purpose of the example, the selectors
for regions 1, 2, 3 and 4 show as ''<region1_sel>'',
''<region2_sel>'', ''<region3_sel>'' and
''<region4_sel>'' respectively.</p>
<div class="example">
<pre>
<style>
#article {
<strong>flow-into: article_flow;</strong>
}
<region1_sel>, <region2_sel>,
<region3_sel>, <region4_sel> {
<strong>content: flow-from(article_flow);</strong>
}
</style>
</pre>
</div>
<p>The 'article_flow' value on the 'flow-into' property directs the ''#article''
element to the 'article_flow' named flow. Setting the regions' content property
to 'flow-from(article_flow)' associates these regions with the named flow: the flow is
''poured'' into the desired regions.</p>
<h3 id="region-styling">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 <a href=
"#CSSMEDIAQUERIES">Media Queries</a> [[MEDIAQ]] 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>
<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 run-ins and crimson.</p>
<p>This design can be expressed with region styling as shown below.</p>
<div class="example">
<pre>
<style>
/*
* Default article styling.
*/
#article {
color:#777;
text-align: justify;
}
#article h1 {
border-left: 1px solid #777;
padding-left: 2ex;
}
/*
* Additional styling to apply to content when it falls into
* region1
*/
<strong>@region <region1_sel> {</strong>
#article::region-lines {
font-weight: bold;
color: #0C3D5F;
font-size: larger;
}
#article h1 {
color: crimson;
display: run-in;
border: none;
padding: 0px;
}
<strong>}</strong>
</style>
</pre>
</div>
<p>The '@region' 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.</p>
<p>The ''::region-lines'' pseudo-element is described later in this
specification.</p>
<div class="figure">
<img src="images/region-styling.png" width="450" alt=
"Illustrate how changing region styling affects the flow of content.">
<p class="caption">Different rendering with a different region
styling</p>
</div>
<h2 id="css-regions-concepts">CSS regions concepts</h2>
<p><em>This section is non-normative.</em></p>
<h3 id="regions">Regions</h3>
<p class="index" title="region" id="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
109B3
an associated <em>named flow</em> (see the 'content'
property).</p>
<p>A <span title="region">region</span>'s intrinsic width is zero.</p>
<div class="issue moved">
<p>See <a href="http://wiki.csswg.org/spec/css3-regions#issue-2-auto-sizing-of-regions"></a></p>.
<p>There was a recent discussion on intrinsic sizing of regions which
<a href="http://lists.w3.org/Archives/Public/www-style/2011Jun/0629.html">has not been resolved</a></p>.
</div>
<h3 id="named-flow">Named flow</h3>
<p>A <def name="named-flow">named flow</def> 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>
<p>Elements are placed into a named flow with the 'flow-into' property.
The elements in a named flow are laid out in the chain of regions that
are associated with this named flow. The 'region-order' property defines how <span title=
"region">regions</span> are organized in to a <span title=
"region-chain">region chain</span>.</p>
<p>Content from a named flow is broken up between regions according to the
regions flow breaking rules.</p>
<!--
<p>In the <a href="http://www.w3.org/TR/CSS21/visuren.html">CSS formatting
model</a>, elements and pseudo-elements can be in the <em>normal flow</em> or out of the
<em>(normal) flow</em>. Boxes generated by elements in the normal flow are
subject to their container box's normal layout scheme. Boxes generated by
elements out of the normal flow are subject to a different layout scheme.
For example, absolutely positioned elements are subject to absolute
positioning into their <a href=
"http://www.w3.org/TR/CSS21/visudet.html#containing-block-details">containing
block</a>. This can be described by saying that the absolutely positioned
elements are part of a special flow (called <span title=
"positioned-flow">positioned flow</span>) which is subject to a special
layout by its container box (i.e., its container box positions it into the
containing block's box).</p>
<p> </p>
<p>In both cases, there is a notion of flow containing a sequence of
elements and there is a notion of <a href=
"http://www.w3.org/Style/Group/css2-src/visuren.html#block-boxes">(block)
container box</a> into which the elements flow.</p>
<p> </p>
<p>The CSS regions module generalizes the concept of flow by adding the
concept of a <em>named flow</em>. This module lets authors explicitly place
elements into a <em>named flow</em>.</p>
<p> </p>
<p>With this model, all elements are moved to a flow as part of the visual
formatting. That flow may be the normal flow, a named flow or a positioned
flow, for example. A flow gets formatted visually when associated with one
or several elements' container box(es). When an flow is associated with
container boxes, the boxes generated by the flow's elements are laid out
according to the container box's layout scheme and the flow is subject to
the <a href='#flow-breaking-rules'>'flow breaking rules'</a> described
below.</p>
<p>A container's layout scheme is the strategy used by a container to
position the boxes generated by its children and itself. Examples are the
normal layout (block and inline formatting) ([[CSS21]]), table layout
([[CSS21]]), the multi-column layout ([[CSS3COL]]) or the grid layout
([[CSS3-GRID-LAYOUT]]).</p>
-->
<h3 id="regions-flow-breaking-rules">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 [[CSS3PAGE]]) or a multi-column element's content
across column boxes (see [[CSS3COL]]). One difference is that
page boxes are generated based on the available content whereas regions are
a predefined set of recipient boxes for the named flow content.</p>
<p><span title=
"region">Regions</span> are organized in to a <span title=
"region-chain">region chain</span> (see the 'region-order' property).</p>
<p>Each region in turn consumes content from its associated <span title=
"named-flow">named flow</span>. The named flow content is
positioned in the <dfn title="current-region">current region</dfn> until a
natural or forced region break occurs, at which point the <span title=
"current-region">current region</span> becomes the next one in the
<span title="region-chain">region chain</span>. If there is no more
<span>region</span> in the region chain and there is still content in the
flow, the positioning of the remaining content is controlled by the
'region-overflow' property on the last <span>region</span> in the
chain.</p>
<!--
<h3 id="the-visual-formatting-model-and-flows">The Visual Formatting Model
and Flows</h3>
<p>This section describes the flows to which elements formatted according
to the CSS <a href="http://www.w3.org/TR/CSS21/visuren.html">Visual
Formatting Model</a> and other layout modules (such as Multi-Column Layout
[[CSS3COL]]) belong to.</p>
<p>In particular, this section describes the 'generated flow' where
generated content of pseudo-elements is placed and several <dfn id=
"auto-flow" title="auto flows">'auto flows'</dfn> where children of content
elements are automatically placed.</p>
<h4 id="normal-flow">Normal flow</h4>
<p>In the CSS formatting model, elements are by default placed in the
<dfn id="normal-flow-def">normal flow</dfn> of their container. Also by
default, a container element gets its content from its <em>normal
flow</em>. This means that by default, a container element will visually
format its children elements and will be the only container associated with
its normal flow.</p>
<p>Note that floats and relatively positioned elements, in this model, are
part of the same flow of content and flow into the same container but are
positioned in different ways.</p>
<p>The <em>normal flow</em> is one of the <em>auto flows</em>.</p>
<h4 id="positioned-flow">Positioned flow</h4>
<p>An absolutely positioned element is placed into the <dfn title=
"positioned-flow">positioned flow</dfn> of its container. The container
positions this element into its <em>containing block</em>.</p>
<p>If a container has children in the <em>normal flow</em> and in the
<em>positioned flow</em>, it applies different positioning schemes to each
flow.</p>
<p>The <em>positioned flow</em> is one of the <em>auto flows</em>.</p>
<h4 id="column-flow">Column flow</h4>
<p>Children of the multi-column element are placed in the element's
<dfn id="column-flow-def">column flow</dfn>. The column boxes are then
implicitly associated with the element's 'column flow'. In this model,
multiple regions (column boxes) get their content from a single flow (the
element's 'column flow', which is the content of the element).</p>
<p>The <em>column flow</em> is one of the <em>auto flows</em>.</p>
<div class="issue">
Need to add a <dfn id="grid-cell-flow">grid cell flow</dfn> section.
</div>
<div class="issue">
Need to add examples for the different flow types.
</div>
<h4 id="generated-flow">Generated flow</h4>
<p>In the CSS formatting model, when the ''::before'' or ''::after''
pseudo-elements have their content property set to one of
''<string>'', ''<uri>'', ''<counter>'',
''attr(<identifier>)'', ''open-quote'', ''close-quote'',
''no-open-quote'' or ''no-close-quote'', they create a <dfn id=
"generated-flow-def">generated flow</dfn> which they format visually.</p>
-->
<h3 id="relation-to-document-events">Relation to document events</h3>
<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-Level-3-Events/#dom-event-architecture">event's
bubble and capture phases</a> happen following the document tree order.</p>
<h2 id="properties-and-rules">Properties and rules</h2>
<!-- Commented out following section because it was redundant with the introduction -->
<!--
<p>The main CSS regions module properties are the ‘flow-into’ and 'content'
properties. The ‘flow-into’ property may place an element into a specific named
flow. The ‘content’ property binds a region with a particular named flow. When multiple
regions are bound to the same flow, the 'region-order' property determines
the order in which content flows into the sequence of regions. This
sequences of regions is called a <dfn>region chain</dfn>.</p>
<p>The “break-*” properties control how content is broken into segments which are
then fitted in regions.</p>
<p>Styling that is unique to the region can be specified by ‘@region’ rules.</p>
-->
<h3 id="the-flow-into-property">The 'flow-into' property</h3>
<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.</p>
<table class="propdef" summary="flow property definition">
<tr>
<th>Name:</th>
<td><dfn id="flow-into">flow-into</dfn></td>
</tr>
<tr>
<th>Value:</th>
<td><ident> | auto</td>
</tr>
<tr>
<th>Initial:</th>
<td>auto</td>
</tr>
<tr>
<th>Applies to:</th>
<td>any element</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 value:</th>
<td>as specified</td>
</tr>
</table>
<dl>
<dt>auto</dt>
<dd>The element is not moved to a named flow and normal CSS processing takes place.</dd>
<dt><a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier"><ident></a></dt>
<dd>The element is placed into the flow with the name '<ident>'. The
element is said to have a <dfn id="specified-flow">specified
flow</dfn>. The values 'none', 'inherit', 'default' and 'initial' are invalid flow
names.</dd>
</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>
<p>The children of an element with a specified flow may themselves have a
specified flow.</p>
<p>If an element has a the same specified flow value as one of its
ancestors, it becomes a
sibling of it's ancestor for the purpose of layout in the regions laying out content
content from that flow.</p>
<p>The 'flow-into' property does not affect the CSS cascade and inheritance for
the elements on which it is specified. The 'flow-into' property affects the visual
formatting of elements placed into a named flow and of regions laying out
content from a named flow.</p>
<p>The edges of the first region in a region chain associated with a named flow establish
the rectangle that is the initial containing block of the named flow.</p>
<p>Elements in a named flow are sequenced in document order.</p>
<div class="note">
<p><em>This note is informative.</em></p>
<p>The 'flow-into' 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 'table-content' named flow. However, the</p>
<pre>table * {flow-into: table-content}</pre>
<p>selector will move all
the descendants of table elements in the 'table-content' named flow. This will make all
the descendants of table elements siblings in the named flow. Having the descendants become siblings
in the named flow results
in a different processing (see the <a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/tables.html#anonymous-boxes">CSS 2.1's anonymous table objects</a>). This note illustrates how authors must exercise caution when choosing a particular
selector for setting the 'flow-into' property to avoid unintended results.</p>
</div>
<p>
If the ‘flow-into’ property is specified on an
<code class=
"html"><iframe></code>, an <code class=
"html"><object></code> or a <code class=
"html"><embed></code> element, the
‘display’ property is computed to ‘none’ and the referenced document within the element is used as the named flow.
In the case of the <code class="html"><object></code> element if fallback occurs and the fallback element has a referenced document then that
document is used as the named flow, otherwise the fallback element itself is added to the named flow.
</p>
<p>
Any properties set on the <code class=
"html"><iframe></code>/<code class=
"html"><object></code>/<code class=
"html"><embed></code> elements (including margin, border, padding, background) have no effect.
This redirection of content does not change representation of the elements in the document tree, just as for any other
source of named flow; in this case the <code class="html"><iframe></code> still provides security checks for script in content (and sandbox if required).
Events and CSS cascading work the same way as in a documents hosted in regular <code class="html"><iframe></code>s.
</p>
<p>
Region styling applies to content coming from <code class=
"html"><iframe></code>/<code class=
"html"><object></code>/<code class=
"html"><embed></code> sources the same way it applies to other flow content.
</p>
<br />
<p>The 'flow-into' does not apply to the <code class="css">::first-line</code> and <code class="css">::first-character</code>.</p>
<p>The effect of 'flow-into' on generated content such as <code class="css">::marker</code>,
<code class="css">::before</code> and <code class="css">::after</code>
is undefined. This may change depending on implementation feedback.</p>
<h3 id="the-content-property">The 'content' property</h3>
<p>This specification extends the definition of the 'content' property.</p>
<table class="propdef" summary="content property definition">
<tr>
<th>Name:</th>
<td><dfn id="content-from">content</dfn></td>
</tr>
<tr>
<th>Value:</th>
<td>normal | none | flow-from(<ident>)| [ <string> |
<uri> | <counter> | attr(<identifier>) |
open-quote | close-quote | no-open-quote | no-close-quote ]+ |
inherit</td>
</tr>
<tr>
<th>Initial:</th>
<td>normal</td>
</tr>
<tr>
<th>Applies to:</th>
<td>non-replaced block elements and the ::before and ::after
pseudo-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 value:</th>
<td>as specified</td>
</tr>
</table>
<dl>
<dt><a name="x9" id="x9"><span class="index-inst" title=
"none"><strong>none</strong></span></a></dt>
<dd>For ''::before'' and ''::after'' pseudo-elements, the
pseudo-element is not generated. For other elements, the element will
not get any content for its visual formatting</dd>
<dt><strong>normal</strong></dt>
<dd>Computes to 'none' for the ''::before'' and ''::after''
pseudo-elements. For other elements, the element formats its
children as defined by the CSS Visual Formatting Model [[CSS21]].</a></dd>
<dt><strong><string></strong></dt>
<dd>Text content (see the section on <a href=
"syndata.html#strings">strings</a>).</dd>
<dt><strong><uri></strong></dt>
<dd>The value is a URI that designates an external resource (such as an
image). If the user agent cannot display the resource it must either
leave it out as if it were not specified or display some indication
that the resource cannot be displayed.</dd>
<dt><strong><counter></strong></dt>
<dd><a href="syndata.html#counter">Counters</a> may be specified with
two different functions: 'counter()' or 'counters()'. The former has
two forms: 'counter(<var>name</var>)' or 'counter(<var>name</var>,
<var>style</var>)'. The generated text is the value of the innermost
counter of the given name in scope at this pseudo-element; it is
formatted in the indicated <a href="#counter-styles">style</a>
('decimal' by default). The latter function also has two forms:
'counters(<var>name</var>, <var>string</var>)' or
'counters(<var>name</var>, <var>string</var>, <var>style</var>)'. The
generated text is the value of all counters with the given name in
scope at this pseudo-element, from outermost to innermost separated by
the specified string. The counters are rendered in the indicated
<a href="#counter-styles">style</a> ('decimal' by default). See the
section on <a href="#counters">automatic counters and numbering</a> for
more information. The name must not be 'none', 'inherit' or 'initial'.
Such a name causes the declaration to be ignored.</dd>
<dt><strong>open-quote</strong> and <strong>close-quote</strong></dt>
<dd>These values are replaced by the appropriate string from the
<a href="http://www.w3.org/TR/CSS21/generate.html#propdef-quotes"
class="noxref"><span class=
"propinst-quotes"><strong>'quotes'</strong></span></a> property.</dd>
<dt><strong>no-open-quote</strong> and
<strong>no-close-quote</strong></dt>
<dd>Introduces no content, but increments (decrements) the level of
nesting for quotes.</dd>
<dt><strong>attr(X)</strong></dt>
<dd>This function returns as a string the value of attribute X for the
subject of the selector. The string is not parsed by the CSS processor.
If the subject of the selector does not have an attribute X, an empty
string is returned. The case-sensitivity of attribute names depends on
the document language.</dd>
<dt><dfn id="flow-from-name">flow-from(<ident>)</dfn></dt>
<dd>If the element is not a <a href="http://www.w3.org/TR/CSS21/visuren.html#block-boxes">block container box</a>, the value evaluates to 'normal'. <br />
Otherwise, the element becomes a <span>region</span> and is ordered in a
<span>region chain</span> according to its document order and
'region-order' property. The content from the flow with the <a href="http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-identifier"><ident></a>
name will be <a href="#region-flow-break">broken into segments</a> and visually formatted in the
<a href="http://www.w3.org/TR/CSS21/visuren.html#principal-box">principal boxes</a> of the regions in the region chain. If there is no flow with name
<ident>, then the element does not format any content visually. <br/>Likewise, if
the element is part of the flow with name <ident>, then
the element does not format any content visually.
<br />
This might be expanded in future versions of the specification
to allow other types of containers to receive flow content.
</dd>
</dl>
<p>When the 'content' property is set to a value other than 'normal', the element's document children are not visually formatted unless they are directed to a named flow
referenced by one or more regions.</p>
<div class="note">
<p><em>This note is informative.</em></p>
<p>The 'content' property applies to block-level elements and the
'::before' and '::after' pseudo elements. User agents may apply the
content property to inline elements. The behavior is undefined in that
case, but is generally expected to be similar to that of inline
'::before' and '::after' pseudo-elements.</p>
<p>In particular, note that the behavior of a '::before' or '::after'
pseudo-element with a 'display' value that makes it an inline element
combined with a 'content' value set to 'flow-from(<ident>)' is
undefined.</p>
</div>
<div class="issue resolved">
<p><a href="http://lists.w3.org/Archives/Public/www-style/2011Aug/0069.html">Third resolution on
Regions at the Seattle Face to Face meeting, July 2011</a>
<p><strong>content: flow-from(<flow-name>) v.s. flow-from: <flow-name></strong></p>
<p><a href="http://lists.w3.org/Archives/Public/www-style/2011Jun/0413.html">WG Conference Call, CSSWG Minutes and Resolutions 2011-06-15</a>.</p>
<p>See <a href="http://wiki.csswg.org/spec/css3-regions#contentflow-flow-from-name-vs-flow-fromflow-name">issue</a></p>
</div>
<div class="issue stale">
<p>NOTE: stale issue because the spec. now contains a way to address these
requirements.</p>
<p>Should we consider adding the ability to do the following:</p>
<ul>
<li>Support repeatable content. For example, have a repeatable
heading at the start of each region where content flows.</li>
<li>Support flow breaking marks. It might be very useful to support
a <em>mark</em> (such as "<code class="html">...</code>") at the
region breaking points to indicate that content has been broken out
and is continuing on a different region.</li><!--
<li>Support "atomic pull-outs". For example, we could have a named
flow made of a set of atomic quotes that should be placed, one by
one, in discrete regions. In that use case, we would need a
property to specify that content should be taken atomically from
the flow. May be something like the following.
<pre class="code">
<div id="quote_1" class="quote">...</div>
...
<div id="quote_n" class="quote">...</div>
<div id="pull-out-1" class="pull-out"></div>
...
<div id="pull-out-n" class="pull-out"></div>
<style>
.quote {
flow-into: "quotes";
}
.pull-out {
content: flow-from(quotes);
content-consume: atomic;
}
</style>
</pre>
</li>
-->
</ul>
</div>
<div class="issue resolved">
<p><a href="http://lists.w3.org/Archives/Public/www-style/2011Aug/0069.html">First resolution on
Regions at the Seattle Face to Face meeting, July 2011</a>
<p><a href=
"http://lists.w3.org/Archives/Public/www-style/2011May/0521.html">Mailing
list comment</a></p>
<p>''content: flow-from(<ident>)'' moves an element to a named
flow. Should we allow the content to be copied to a flow instead of
moved to a flow. For example:</p>
<div class="code">
#quote_A { flow-into: "quotes"; content: contents; }
</div>
<p>would keep ''#quote_A'' in the normal flow but also copy its content
to the ''quotes'' flow. This essentially clones the node and raises
questions regarding DOM access, CSSOM view and the computed style.</p>
</div>
<p><span title="region">Regions</span> create a new stacking context.</p>
<p><span title="region">Regions</span> establish a new <a href="http://www.w3.org/TR/CSS2/visuren.html#block-formatting">block formatting Context</a>.</p>
<div class="note">
<p><em>This note is informative.</em></p>
<p>With regions, an element may be split across multiple regions and these
regions may overlap (for example if they are absolutely positioned).
So fragments of the same element can overlap each other.
Since each element has a single z-index, it would be required to
find another mechanism to decide in which order the
fragments are rendered. Since each region creates a new stacking
context, it is clear that each region is rendered separately and their
rendering order follows the regular CSS rendering model.
</p>
</div>
<p>
Floats or other exclusions (see [[CSS3EXCLUSIONS]]) potentially impact the
content laid out in regions, just as for non-regions.</p>
<div class="example">
<p>In the following example, the inline content coming from the
<code class="html">body_text</code> <span title="named-flow">named
flow</span> wraps around the <code class="html">#float</code> box.</p>
<pre>
<style>
#float {
float: left;
width: 100px;
height: 300px;
}
#region1, #region2 {
width: 200px;
height: 200px;
content: flow-from(body_text);
}
#content {
flow-into: body_text;
}
</style>
<div id="float"></div>
<div id="region1"></div>
<div id="region2"></div>
<div id="content"></div>
</pre>
</div>
<h3 id="the-region-order-property">The 'region-order' property</h3>
<p>Defines the ordering of the chain of regions into which content flows.
If region A and region B are in the same chain of regions and the
‘region-order’ of region A is lower than that of region B, then region A
will precede region B in that chain: content will flow into region A before
it flows into region B.</p>
<table class="propdef" summary="region-order property definition">
<tr>
<th>Name:</th>
<td><dfn id="region-order">region-order</dfn></td>
</tr>
<tr>
<th>Value:</th>
<td><integer></td>
</tr>
<tr>
<th>Initial:</th>
<td>0</td>
</tr>
<tr>
<th>Applies to:</th>
<td>any block container</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 value:</th>
<td>as specified</td>
</tr>
</table>
<dl>
<dt><integer></dt>
<dd>Specifies the region's priority in the chain it belongs to, i.e..,
the chain of regions associated with the same content flow. Negative
values are allowed.</dd>
</dl>
<p>If two or more regions with the same 'flow-from( <ident>)' value
for their 'content' property, they are first sorted according to their
'region-order' value. If multiple regions in have the same 'region-order'