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<!DOCTYPE html>
<html lang=en>
<head><meta content="text/html; charset=utf-8" http-equiv=Content-Type>
<title>CSS Flexible Box Layout 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" rel=stylesheet
type="text/css">
<style>
code.one-line { white-space: pre; }
.code-and-figure {
display: table;
margin: 0 auto;
border-spacing: 1em;
}
.code-and-figure > div {
display: table-cell;
vertical-align: middle;
}
:not(code) var { font-style: normal; color: #005A9C; }
</style>
<body>
<div class=head> <!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt=W3C height=48
src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
<h1 id=head-box-flexible>CSS Flexible Box Layout Module</h1>
<h2 class="no-num no-toc" id=w3c-working>Editor's Draft, 8 May 2012</h2>
<dl>
<dt>This version:
<!--<dd><a href="http://www.w3.org/TR/2012/ED-css3-flexbox-20120508/">http://www.w3.org/TR/2012/WD-css3-flexbox-20120508/</a>-->
<dd><a
href="http://dev.w3.org/csswg/css3-flexbox/">http://dev.w3.org/csswg/css3-flexbox/</a>
<dt>Latest version:
<!--<dd><a href="http://www.w3.org/TR/css3-flexbox/">http://www.w3.org/TR/css3-flexbox/</a>-->
<dd><a
href="http://www.w3.org/TR/css3-flexbox/">http://www.w3.org/TR/css3-flexbox/</a>
<dt>Editor's Draft:
<dd><a
href="http://dev.w3.org/csswg/css3-flexbox/">http://dev.w3.org/csswg/css3-flexbox/</a>
<dt>Previous versions:
<dd><a
href="http://www.w3.org/TR/2012/WD-css3-flexbox-20120322/">http://www.w3.org/TR/2012/WD-css3-flexbox-20120322/</a>
<dd><a
href="http://www.w3.org/TR/2011/WD-css3-flexbox-20111129/">http://www.w3.org/TR/2011/WD-css3-flexbox-20111129/</a>
<dd><a
href="http://www.w3.org/TR/2011/WD-css3-flexbox-20110322/">http://www.w3.org/TR/2011/WD-css3-flexbox-20110322/</a>
<dd><a
href="http://www.w3.org/TR/2009/WD-css3-flexbox-20090723/">http://www.w3.org/TR/2009/WD-css3-flexbox-20090723/</a>
<dt>Issues List:
<dd><a
href="https://www.w3.org/Bugs/Public/buglist.cgi?product=CSS&component=Flexbox&resolution=---">Bugzilla
Bugs for Flexbox</a>
<dt>Discussion:
<dd><a
href="http://lists.w3.org/Archives/Public/www-style/">www-style@w3.org</a>
with subject line "<code>[css3-flexbox] …message topic…</code>"
<dt>Editors:
<dd><a href="http://www.xanthir.com/contact">Tab Atkins Jr.</a>, Google
Inc.
<dd>Alex Mogilevsky, Microsoft Corporation, <a
href="mailto:alexmog@microsoft.com">alexmog@microsoft.com</a>
<dd>L. David Baron, Mozilla Corporation, <a
href="mailto:dbaron@dbaron.org">dbaron@dbaron.org</a>
<dt>Authors and former editors:
<dd>Neil Deakin, Mozilla Corporation, <a
href="mailto:enndeakin@gmail.com">enndeakin@gmail.com</a>
<dd>Ian Hickson, formerly of Opera Software, <a
href="mailto:ian@hixie.ch">ian@hixie.ch</a>
<dd>David Hyatt, formerly of Netscape Corporation, <a
href="mailto:hyatt@apple.com">hyatt@apple.com</a>
</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 specification describes a CSS box model optimized for user interface
design. In the flexbox layout model, the children of a flexbox can be laid
out in any direction, and can "flex" their sizes, either growing to fill
unused space or shrinking to avoid overflowing the parent. Both horizontal
and vertical alignment of the children can be easily manipulated. Nesting
of these boxes (horizontal inside vertical, or vertical inside horizontal)
can be used to build layouts in two dimensions.
<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-flexbox%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-flexbox” in the subject, preferably like this:
“[<!---->css3-flexbox<!---->] <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> The following features are at-risk:
<ul>
<li>Flexbox pagination rules
</ul>
<h2 class="no-num no-toc" id=table>Table of contents</h2>
<!--begin-toc-->
<ul class=toc>
<li><a href="#intro"><span class=secno>1. </span> Introduction</a>
<ul class=toc>
<li><a href="#placement"><span class=secno>1.1. </span> Module
interactions</a>
<li><a href="#values"><span class=secno>1.2. </span> Values</a>
</ul>
<li><a href="#box-model"><span class=secno>2. </span> The Flexbox Box
Model</a>
<li><a href="#display-flexbox"><span class=secno>3. </span> Flexboxes: the
‘<code class=css>flex</code>’ and ‘<code
class=css>inline-flex</code>’ ‘<code
class=property>display</code>’ values</a>
<li><a href="#flex-items"><span class=secno>4. </span> Flexbox Items</a>
<ul class=toc>
<li><a href="#abspos-flexbox-items"><span class=secno>4.1. </span>
Absolutely Positioned Flexbox Children</a>
</ul>
<li><a href="#multi-line"><span class=secno>5. </span> Multi-line
Flexbox</a>
<li><a href="#ordering-and-orientation"><span class=secno>6. </span>
Ordering and Orientation</a>
<ul class=toc>
<li><a href="#flex-direction"><span class=secno>6.1. </span> Flexbox
Flow Direction: the ‘<code
class=property>flex-direction</code>’ property</a>
<li><a href="#flex-wrap"><span class=secno>6.2. </span> Flexbox
Wrapping: the ‘<code class=property>flex-wrap</code>’
property</a>
<li><a href="#flex-flow"><span class=secno>6.3. </span> Flex Direction
and Wrap: the ‘<code class=property>flex-flow</code>’
shorthand</a>
<li><a href="#flex-order"><span class=secno>6.4. </span> Display Order:
the ‘<code class=property>flex-order</code>’ property</a>
</ul>
<li><a href="#flexibility"><span class=secno>7. </span> Flexibility: the
‘<code class=property>flex</code>’ property</a>
<ul class=toc>
<li><a href="#flexibility-components"><span class=secno>7.1. </span>
‘<code class=property>Flex-grow</code>’, ‘<code
class=property>flex-shrink</code>’ and ‘<code
class=property>flex-basis</code>’: components of flexibility</a>
</ul>
<li><a href="#alignment"><span class=secno>8. </span> Alignment</a>
<ul class=toc>
<li><a href="#auto-margins"><span class=secno>8.1. </span> Aligning with
‘<code class=css>auto</code>’ margins</a>
<li><a href="#flex-pack"><span class=secno>8.2. </span> Axis Alignment:
the ‘<code class=property>flex-pack</code>’ property</a>
<li><a href="#flex-align"><span class=secno>8.3. </span> Cross-axis
Alignment: the ‘<code class=property>flex-align</code>’ and
‘<code class=property>flex-item-align</code>’
properties</a>
<li><a href="#flex-line-pack"><span class=secno>8.4. </span>
‘<code class=property>flex-line-pack</code>’ property</a>
</ul>
<li><a href="#layout-algorithm"><span class=secno>9. </span> Flexbox
Layout Algorithm</a>
<ul class=toc>
<li><a href="#box-manip"><span class=secno>9.1. </span> Initial
Setup</a>
<li><a href="#line-sizing"><span class=secno>9.2. </span> Line Length
Determination</a>
<li><a href="#main-sizing"><span class=secno>9.3. </span> Main Size
Determination</a>
<li><a href="#cross-sizing"><span class=secno>9.4. </span> Cross size
determination</a>
<li><a href="#main-alignment"><span class=secno>9.5. </span> Main-Axis
Alignment</a>
<li><a href="#cross-alignment"><span class=secno>9.6. </span> Cross-Axis
Alignment</a>
<li><a href="#resolve-flexible-lengths"><span class=secno>9.7. </span>
Resolving Flexible Lengths</a>
</ul>
<li><a href="#pagination"><span class=secno>10. </span> Page breaks in
flexbox</a>
<li><a href="#conformance"><span class=secno>11. </span> Conformance</a>
<ul class=toc>
<li><a href="#conventions"><span class=secno>11.1. </span> Document
conventions</a>
<li><a href="#conformance-classes"><span class=secno>11.2. </span>
Conformance classes</a>
<li><a href="#partial"><span class=secno>11.3. </span> Partial
implementations</a>
<li><a href="#experimental"><span class=secno>11.4. </span> Experimental
implementations</a>
<li><a href="#testing"><span class=secno>11.5. </span> Non-experimental
implementations</a>
<li><a href="#cr-exit-criteria"><span class=secno>11.6. </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">Normative references</a>
<li class=no-num><a href="#informative">Other references</a>
</ul>
<li class=no-num><a href="#property">Property index</a>
<li class=no-num><a href="#index">Index</a>
</ul>
<!--end-toc-->
<h2 id=intro><span class=secno>1. </span> Introduction</h2>
<p><em>This section is not normative.</em>
<p>CSS 2.1 defined four layout modes — algorithms which determine the
size and position of boxes based on their relationships with their sibling
and ancestor boxes: block layout, designed for laying out documents;
inline layout, designed for laying out text; table layout, designed for
laying out information in a tabular format; and positioned layout,
designed for very explicit positioning without much regard for other
elements in the document. This module introduces a new layout mode,
flexbox layout, which is designed for laying out more complex applications
and webpages.
<p>Flexbox layout is superficially similar to block layout. It lacks many
of the more complex text or document-formatting properties that can be
used in block layout, such as ‘<code
class=property>float</code>’ and ‘<code
class=property>columns</code>’, but in return it gains more simple
and powerful tools for aligning its contents in ways that webapps and
complex web pages often need.
<p>The contents of a flexbox can be laid out in any direction (left, right,
down, or even up!), can have their order swapped around dynamically (i.e.,
display order is independent of source order), and can "flex" their sizes
and positions to respond to the available space. If a flexbox is <a
href="#multi-line0"><i>multi-line</i></a>, the flexbox items flow in two
dimensions, wrapping into separate lines in a fashion similar to how text
is wrapped into multiple lines.
<div class=example>
<p>For example, the following HTML snippet uses flexbox to create a
toolbar with icons. The flexbox is horizontal, and the children's widths
don't fill the flexbox's width, so the additional space is distributed
around and between the children. As the flexbox grows (perhaps because
the user is viewing the page on a wider screen), the children spread out
evenly and automatically:
<pre>
<ul>
<li><button><img src='new.svg' alt="New"></button></li>
<li><button><img src='upload.svg' alt="Upload"></button></li>
<li><button><img src='save.svg' alt="Save"></button></li>
<li><button><img src='trash.svg' alt="trash"></button></li>
</ul>
<style>
ul { display: flex; flex-pack: distribute; }
/* Irrelevant styling for this example removed. */
</style></pre>
<div class=figure> <img alt height=140 src="images/toolbar-example.svg"
width=400>
<p class=caption>Example rendering of the above code snippet, at two
different flexbox widths.
</div>
</div>
<h3 id=placement><span class=secno>1.1. </span> Module interactions</h3>
<p>This module extends the definition of the ‘<code
class=property>display</code>’ property.
<h3 id=values><span class=secno>1.2. </span> Values</h3>
<p>This specification follows the <a
href="http://www.w3.org/TR/CSS21/about.html#property-defs">CSS property
definition conventions</a> from <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. Value types not defined in
this specification are defined in CSS Level 2 Revision 1 <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>. Other CSS
modules may expand the definitions of these value types: for example
[[CSS3VALUES]], when combined with this module, expands the definition of
the <length> value type as used in this specification.
<p>In addition to the property-specific values listed in their definitions,
all properties defined in this specification also accept the <a
href="http://www.w3.org/TR/CSS21/cascade.html#value-def-inherit">‘<code
class=css>inherit</code>’</a> keyword as their property value. For
readability it has not been repeated explicitly.
<h2 id=box-model><span class=secno>2. </span> The Flexbox Box Model</h2>
<p>An element with ‘<code class=css>display:flex</code>’ or
‘<code class=css>display:inline-flex</code>’ is a <dfn
id=flexbox>flexbox</dfn>. Children of a flexbox are called <a
href="#flexbox-item"><i>flexbox items</i></a> and are laid out using the
flexbox box model.
<p>Unlike block layout, which is normally biased towards laying things out
vertically, and inline layout, which is normally biased toward laying
things out horizontally, the flexbox layout algorithm is agnostic as to
the direction the flexbox happens to be laid out in. To make it easier to
talk about flexbox layout in a general way, we will define several
direction-agnostic terms here to make the rest of the spec easier to read
and understand.
<div class=figure> <img alt height=300
src="images/flex-direction-terms.svg" width=510>
<p class=caption>An illustration of the various directions and sizing
terms used in this specification, respectively for ‘<code
class=css>row</code>’ and ‘<code
class=css>column</code>’ flexboxes.
</div>
<p> The <dfn id=main-axis>main axis</dfn> of a flexbox is the axis along
which <a href="#flexbox-item"><i>flexbox items</i></a> are laid out. The
<a href="#flexbox-item"><i>flexbox items</i></a> are ordered such that
they start on the <dfn id=main-start>main-start</dfn> side of the flexbox,
and go toward the <dfn id=main-end>main-end</dfn> side. A <a
href="#flexbox-item"><i>flexbox item's</i></a> width or height, whichever
is in the <i>main dimension</i>, is the item's <dfn id=main-size>main
size</dfn>. The <a href="#flexbox-item"><i>flexbox item's</i></a> <dfn
id=main-size-property>main size property</dfn> is either the ‘<code
class=property>width</code>’ or ‘<code
class=property>height</code>’ property, whichever is in the <i>main
dimension</i>.
<p> The axis perpendicular to the <a href="#main-axis"><i>main axis</i></a>
is called the <dfn id=cross-axis>cross axis</dfn>, and similarly has <dfn
id=cross-start>cross-start</dfn> and <dfn id=cross-end>cross-end</dfn>
directions and sides defined. The width or height of a <a
href="#flexbox-item"><i>flexbox item</i></a>, whichever is in the <i>cross
dimension</i>, is the item's <dfn id=cross-size>cross size</dfn>, and
similarly the <dfn id=cross-size-property>cross size property</dfn> is
whichever of ‘<code class=property>width</code>’ or
‘<code class=property>height</code>’ that is in the <i>cross
dimension</i>.
<p> The contents of a flexbox can be easily and powerfully manipulated with
a handful of properties. Most significantly, <a
href="#flexbox-item"><i>flexbox items</i></a> can "flex" their <a
href="#main-size"><i>main size</i></a> by using the ‘<a
href="#flex"><code class=property>flex</code></a>’ property. This
"flexing" allows the items to get bigger or smaller based on the available
space in the page. If there is leftover space in the flexbox after all of
the <a href="#flexbox-item"><i>flexbox items</i></a> have finished
flexing, the items can be aligned, centered, or distributed with the
‘<a href="#flex-pack0"><code
class=property>flex-pack</code></a>’ property. <a
href="#flexbox-item"><i>Flexbox items</i></a> can also be completely
rearranged within the flexbox with the ‘<a href="#flex-order0"><code
class=property>flex-order</code></a>’ property.
<p> In the <a href="#cross-axis"><i>cross axis</i></a>, <a
href="#flexbox-item"><i>flexbox items</i></a> can either "stretch" to fill
the available space or be aligned within the space with the ‘<a
href="#flex-align0"><code class=property>flex-align</code></a>’
property. If a flexbox is <a href="#multi-line0"><i>multi-line</i></a>,
new lines are added in the <a href="#cross-end"><i>cross-end</i></a>
direction, and can similarly be aligned, centered, or distributed within
the flexbox with the ‘<a href="#flex-line-pack0"><code
class=property>flex-line-pack</code></a>’ property.
<h2 id=display-flexbox><span class=secno>3. </span> Flexboxes: the
‘<a href="#flex"><code class=css>flex</code></a>’ and
‘<a href="#display-inline-flex"><code
class=css>inline-flex</code></a>’ ‘<code
class=property>display</code>’ values</h2>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td>display
<tr>
<th><a href="#values">New value</a>:
<td><dfn id=display-flex>flex</dfn> | <dfn
id=display-inline-flex>inline-flex</dfn>
</table>
<p> An element whose computed ‘<code
class=property>display</code>’ is either ‘<a
href="#flex"><code class=css>flex</code></a>’ or ‘<a
href="#display-inline-flex"><code class=css>inline-flex</code></a>’
is a flexbox, and establishes a new <dfn
id=flexbox-formatting-context>flexbox formatting context</dfn> for its
contents. This is similar to a block formatting context root: floats do
not intrude into the flexbox, and the flexbox's margins do not collapse
with the margins of its contents. Additionally, each of the <a
href="#flexbox-item"><i>flexbox items</i></a> establishes a new formatting
context for its contents.
<p> The ‘<a href="#flex"><code class=css>flex</code></a>’ value
makes the flexbox a block-level element. The ‘<a
href="#display-inline-flex"><code class=css>inline-flex</code></a>’
value makes the flexbox an atomic inline-level element.
<p> Flexboxes are not block containers, and so some properties that were
designed with the assumption of block layout don't apply in a flexbox
context. In particular:
<ul>
<li> all of the ‘<code class=css>column-*</code>’ properties
in the Multicol module have no effect on a flexbox.
<li> ‘<code class=property>float</code>’ and ‘<code
class=property>clear</code>’ have no effect on a <a
href="#flexbox-item"><i>flexbox item</i></a>. Using ‘<code
class=property>float</code>’ on an element still causes that
element's ‘<code class=property>display</code>’ property to
compute to ‘<code class=css>block</code>’, and thus
‘<code class=property>float</code>’ may affect whether an
element becomes a flexbox item or is wrapped in one. (See <a
href="http://www.w3.org/TR/CSS2/visuren.html#dis-pos-flo">CSS 2.1 Chapter
9.7</a>.)
<li> ‘<code class=property>vertical-align</code>’ has no
effect on the alignment of a flexbox item in the flexbox
</ul>
<p> If an element's specified value for ‘<code
class=property>display</code>’ is ‘<a
href="#display-inline-flex"><code class=css>inline-flex</code></a>’
and the element is floated or absolutely positioned, the computed value of
‘<code class=property>display</code>’ is ‘<a
href="#flex"><code class=css>flex</code></a>’. The table in <a
href="http://www.w3.org/TR/CSS2/visuren.html#dis-pos-flo">CSS 2.1 Chapter
9.7</a> is thus amended to contain an additional row, with ‘<a
href="#display-inline-flex"><code class=css>inline-flex</code></a>’
in the "Specified Value" column and ‘<a href="#flex"><code
class=css>flex</code></a>’ in the "Computed Value" column.
<p> The baseline of a flexbox is:
<ul>
<li> If any of the <a href="#flexbox-item"><i>flexbox items</i></a> on the
flexbox's first line (after reordering with ‘<a
href="#flex-order0"><code class=property>flex-order</code></a>’)
have a computed value of ‘<code class=css>baseline</code>’
for ‘<a href="#flex-item-align"><code
class=property>flex-item-align</code></a>’, the flexbox's baseline
is the baseline of those <a href="#flexbox-item"><i>flexbox
items</i></a>.
<li> Otherwise, if the flexbox has at least one <a
href="#flexbox-item"><i>flexbox item</i></a>, and the baseline of its
first <a href="#flexbox-item"><i>flexbox item</i></a> (after reordering
with ‘<a href="#flex-order0"><code
class=property>flex-order</code></a>’) is parallel to the flexbox's
<i>main-axis</i>, the flexbox's baseline is the baseline of its first <a
href="#flexbox-item"><i>flexbox item</i></a>.
<li> Otherwise, the flexbox's baseline is the "after" edge of its content
box.
</ul>
<h2 id=flex-items><span class=secno>4. </span> Flexbox Items</h2>
<p> The flexbox layout algorithm operates on boxes generated by <dfn
id=flexbox-item title="flexbox item|flexbox items|flexbox item's">flexbox
items</dfn>. A <a href="#flexbox-item"><i>flexbox item</i></a> is:
<ol>
<li> A block-level child of a flexbox element
<li> An atomic inline-level child of a flexbox element
<li> An anonymous block element wrapped around a contiguous run of
non-replaced inline child elements. However, if the contents of the
anonymous block would be solely an anonymous inline containing only
whitespace, the box is not generated, as if it had ‘<code
class=css>display:none</code>’.
</ol>
<p> Some values of ‘<code class=property>display</code>’
trigger the generation of anonymous boxes. For example, a ‘<code
class=css>table-cell</code>’ child of a block container is fixed up
by generating ‘<code class=css>table</code>’ and ‘<code
class=css>table-row</code>’ elements around it. This fixup must
occur <em>before</em> a flexbox's contents are checked to see if it's
necessary to generate anonymous flexbox items.
<p class=note> In the future, other kinds of fixup such as ‘<code
class=css>display:run-in</code>’ or ‘<code
class=css>display:ruby</code>’ should also run before flexbox fixup.
<div class=example>
<p>Examples of flexbox items:
<pre>
<div style="display:flex">
<!-- flexbox item: block-level child -->
<div id="item1">block</div>
<!-- not a flexbox item, because it's out-of-flow -->
<!-- however, an anonymous flexbox item is wrapped around
the placeholder it leaves behind-->
<div id="not-an-item2" style="position: absolute;">block</div>
<!-- flexbox item: block-level child -->
<div id="item3" style="display:table">table</div>
<!-- flexbox item: anonymous table wrapped around table-cell -->
<div id="item4" style="display:table-cell">table-cell</div>
<!-- flexbox item: anonymous block box around inline content -->
anonymous item 5
<!-- flexbox item: block-level child -->
<div id="item6">block</div>
<!-- flexbox item: anonymous block around inline content -->
anonymous item 7.1
<span id="item7.1">
text 7.2
<div id="not-an-item7.3">block</div>
text 7.4
</span>
<!-- flexbox item: block-level replaced element -->
<iframe id="item8" style="display:block;"></iframe>
<!-- flexbox item: inline-level replaced element -->
<img id="item9">
<!-- flexbox item: atomic inline-level element -->
<button id="item10">button</button>
<!-- flexbox item: inline-table -->
<div id="item11" style="display:inline-table">table</div>
<!-- flexbox item: floated inline, which changes to a block -->
<span id="item12" style="float: left;">span</span>
</div></pre>
<p> Notice that block element "not-an-item7.3" is not a separate flexbox
item, because it is contained inside an inline element which is being
wrapped into an anonymous flexbox item. Similarly, the block element
"not-an-item2" is not a flexbox item, because it's absolutely positioned
and thus out of flow.
</div>
<p> The computed value for ‘<code
class=property>display</code>’ for elements that are <a
href="#flexbox-item"><i>flexbox items</i></a> must be determined by
applying the table in <a
href="http://www.w3.org/TR/CSS2/visuren.html#dis-pos-flo">CSS 2.1 Chapter
9.7</a>.
<h3 id=abspos-flexbox-items><span class=secno>4.1. </span> Absolutely
Positioned Flexbox Children</h3>
<p> Absolutely positioned children of a flexbox are not <a
href="#flexbox-item"><i>flexbox items</i></a>, but they leave behind
"placeholders" in their normal position in the box tree. These
placeholders are anonymous inline boxes with a width and height of
‘<code class=css>0px</code>’, and they interact normally with
the flexbox layout algorithm. In particular, they'll trigger the creation
an anonymous flexbox item wrapper boxes, or join neighboring inline
elements in <em>their</em> anonymous flexbox item wrapper boxes.
<p> The "static position" of an absolutely positioned child of a flexbox
(the position when the ‘<code
class=property>top</code>’/‘<code
class=property>right</code>’/‘<code
class=property>bottom</code>’/‘<code
class=property>left</code>’ properties are ‘<code
class=css>auto</code>’), then, is the final position of its
corresponding placeholder, after flexbox layout has been performed.
<p class=note> Note: In most cases, this means that absolutely positioned
items will have no effect on flexbox layout, even if they force the
generation of an anonymous flexbox item wrapper, because those wrapper
items will also collapse to zero size and have no effect. The only
exceptions are when the flexbox has ‘<code
class=css>flex-pack:justify</code>’ or ‘<code
class=css>flex-pack:distribute</code>’, in which case the anonymous
flexbox item will cause there to be two packing spaces where there would
otherwise be only one, resulting in a double-size space between two "real"
items.
<h2 id=multi-line><span class=secno>5. </span> Multi-line Flexbox</h2>
<p> A flexbox can be either <a href="#single-line"><i>single-line</i></a>
or <a href="#multi-line0"><i>multi-line</i></a>, depending on the
‘<a href="#flex-wrap0"><code
class=property>flex-wrap</code></a>’ property. A <dfn
id=single-line>single-line</dfn> flexbox lays out all of its children in a
single line, even if that would cause the flexbox to overflow its bounds.
A <dfn id=multi-line0>multi-line</dfn> flexbox breaks its <a
href="#flexbox-item"><i>flexbox items</i></a> across multiple lines to
avoid overflowing, similar to how text is broken onto a new line when it
gets too wide to fit on the existing line. Every line contains at least
one <a href="#flexbox-item"><i>flexbox item</i></a>, unless the flexbox
itself is completely empty.
<p> When additional lines are created, they are stacked in the flexbox
along the <a href="#cross-axis"><i>cross axis</i></a>. Once content is
broken into lines, each line is laid out independently; flexible lengths
and the ‘<a href="#flex-pack0"><code
class=property>flex-pack</code></a>’ and ‘<a
href="#flex-item-align"><code
class=property>flex-item-align</code></a>’ properties only consider
the items on a single line at a time.
<p> The <a href="#main-size"><i>main size</i></a> of a line is the same as
the <a href="#main-size"><i>main size</i></a> of the flexbox's content
box. the <a href="#cross-size"><i>cross size</i></a> of a line is the
minimum size necessary to contain the <a href="#flexbox-item"><i>flexbox
items</i></a> on the line, after aligment due to ‘<a
href="#flex-item-align"><code
class=property>flex-item-align</code></a>’. The lines themselves are
then aligned within the flexbox with the ‘<a
href="#flex-line-pack0"><code
class=property>flex-line-pack</code></a>’ property.
<div class=example>
<p> This example shows four buttons that do not fit horizontally.
<pre><style>
#div1 {
display: flex;
flex-flow: row wrap;
width: 300px;
}
button {
flex:80px 1;
}
<style>
<div id="div1">
<button id="button1">Elephant</button>
<button id="button2">Tiger</button>
<button id="button3">Antelope</button>
<button id="button4">Wildebeest</button>
</div></pre>
<p> The buttons are first set to their preferred widths, in this case 80
pixels. This will allow the first three buttons to fit in 240 pixels with
60 pixels left over of remaining space. Because the ‘<a
href="#flex-flow0"><code class=property>flex-flow</code></a>’
property specifies a multi-line flexbox (due to the ‘<code
class=css>wrap</code>’ keyword appearing in its value), the flexbox
will create an additional line to contain the last button.
<p> Flexibility is applied to each element, separately for each line. The
first line has 60 pixels of remaining space and all of the buttons have
the same flexibility, so each of the three buttons on that line will
receive 20 pixels of extra width, ending up 100px wide. The remaining
button is on a line of its own and will stretch to the entire width of
the line, or 300 pixels.
<div style="width:300px; border:medium solid green; overflow: hidden;">
<button style="width:100px; float: left;">Elephant</button> <button
style="width:100px; float: left;">Tiger</button> <button
style="width:100px; float: left;">Antelope</button> <button
style="width:300px; float: left;">Wildebeest</button></div>
<p> If the box was resized, the buttons may rearrange onto different lines
as necessary.
<p> If the style rules in the example above were changed to the following:
<pre>
#div1 {
display: flex;
flex-flow: row wrap;
flex-pack: center;
width: 300px;
}
button {
flex:80px 1;
max-width: 90px;
}</pre>
<p> Similar to the previous example, the first three buttons will fit on
the first line, and the last button will wrap onto a new line. However,
when the buttons attempt to flex they can only grow to 90px each, due to
their ‘<code class=property>max-width</code>’ property. This
leaves 30px of free space on the first line and 210px of free space on
the second line. Because ‘<a href="#flex-pack0"><code
class=property>flex-pack</code></a>’ is set to ‘<code
class=css>center</code>’, the buttons will be centered on each
line, with the free space split equally on either side.
<div style="width:300px; border:medium solid green; text-align:center;">
<button
style="width:90px; float: left; margin-left: 15px;">Elephant</button>
<button style="width:90px; float: left;">Tiger</button> <button
style="width:90px; float: left;">Antelope</button> <button
style="width:90px">Wildebeest</button></div>
</div>
<h2 id=ordering-and-orientation><span class=secno>6. </span> Ordering and
Orientation</h2>
<p> The first level of flexbox functionality is the ability to lay out a
flexbox's contents in any direction and in any order. This allows an
author to trivially achieve effects that would previously have required
complex or fragile methods, such as hacks using the ‘<code
class=property>float</code>’ and ‘<code
class=property>clear</code>’ properties. This functionality is
exposed through the ‘<a href="#flex-direction0"><code
class=property>flex-direction</code></a>’, ‘<a
href="#flex-wrap0"><code class=property>flex-wrap</code></a>’, and
‘<a href="#flex-order0"><code
class=property>flex-order</code></a>’ properties.
<h3 id=flex-direction><span class=secno>6.1. </span> Flexbox Flow
Direction: the ‘<a href="#flex-direction0"><code
class=property>flex-direction</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=flex-direction0>flex-direction</dfn>
<tr>
<th><a href="#values">Value</a>:
<td>row | row-reverse | column | column-reverse
<tr>
<th>Initial:
<td>row
<tr>
<th>Applies To:
<td>flexboxes
<tr>
<th>Inherited:
<td>no
<tr>
<th>Computed Value:
<td>specified value
<tr>
<th>Media:
<td>visual
<tr>
<th>Animatable:
<td>no
<tr>
<th>Canonical Order:
<td>as specified
</table>
<p> The ‘<a href="#flex-direction0"><code
class=property>flex-direction</code></a>’ property specifies how <a
href="#flexbox-item"><i>flexbox items</i></a> are placed in the flexbox,
by setting the direction of the flexbox's <a href="#main-axis"><i>main
axis</i></a>. This determines the direction that flexbox items are laid
out in.
<dl>
<dt><dfn id=flex-flow-row>‘<code class=css>row</code>’</dfn>
<dd> The flexbox's <a href="#main-axis"><i>main axis</i></a> has the same
orientation as the inline axis of the current <a
href="http://www.w3.org/TR/css3-writing-modes/#writing-mode">writing
mode</a> (the primary direction that text is laid out in). The <a
href="#main-start"><i>main-start</i></a> and <a
href="#main-end"><i>main-end</i></a> directions are equivalent to the <a
href="http://www.w3.org/TR/css3-writing-modes/#start">start</a> and <a
href="http://www.w3.org/TR/css3-writing-modes/#end">end</a> directions,
respectively, of the current <a
href="http://www.w3.org/TR/css3-writing-modes/#writing-mode">writing
mode</a>.
<dt><dfn id=flex-flow-row-reverse>‘<code
class=css>row-reverse</code>’</dfn>
<dd> Same as ‘<code class=css>row</code>’, except the <a
href="#main-start"><i>main-start</i></a> and <a
href="#main-end"><i>main-end</i></a> directions are swapped.
<dt><dfn id=flex-flow-column>‘<code
class=css>column</code>’</dfn>