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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;
}
</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, 7 February 2012</h2>
<dl>
<dt>This version:
<!--<dd><a href="http://www.w3.org/TR/2012/ED-css3-flexbox-20120207/">http://www.w3.org/TR/2012/ED-css3-flexbox-20120207/</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/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>
<p class=issue>Will be a bugzilla URL once I get a component added.</p>
<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/"><acronym
title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a
href="http://www.csail.mit.edu/"><acronym
title="Massachusetts Institute of Technology">MIT</acronym></a>, <a
href="http://www.ercim.eu/"><acronym
title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></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-->
<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>
<ul class=toc>
<li><a href="#display-flexbox"><span class=secno>2.1. </span> New values
for ‘<code class=property>display</code>’ property</a>
<li><a href="#flex-items"><span class=secno>2.2. </span> Flexbox
Items</a>
<ul class=toc>
<li><a href="#abspos-flexbox-items"><span class=secno>2.2.1. </span>
Positioning Absolutely Positioned Flexbox Items</a>
</ul>
</ul>
<li><a href="#ordering-orientation"><span class=secno>3. </span> Ordering
and Orientation</a>
<ul class=toc>
<li><a href="#flex-direction"><span class=secno>3.1. </span> Flexbox
Flow Direction: the ‘<code
class=property>flex-direction</code>’ property</a>
<li><a href="#flex-wrap"><span class=secno>3.2. </span> Flexbox
Wrapping: the ‘<code class=property>flex-wrap</code>’
property</a>
<li><a href="#flex-flow"><span class=secno>3.3. </span> Flex Direction
and Wrap: the ‘<code class=property>flex-flow</code>’
shorthand</a>
<li><a href="#flex-order"><span class=secno>3.4. </span> Display Order:
the ‘<code class=property>flex-order</code>’ property</a>
</ul>
<li><a href="#flexibility"><span class=secno>4. </span> Flexibility: the
‘<code class=css>flex()</code>’ notation</a>
<li><a href="#alignment"><span class=secno>5. </span> Alignment</a>
<ul class=toc>
<li><a href="#flex-pack"><span class=secno>5.1. </span> Main Axis
Alignment: the ‘<code class=property>flex-pack</code>’
property</a>
<li><a href="#flex-align"><span class=secno>5.2. </span> Cross Axis
Alignment: the ‘<code class=property>flex-align</code>’ and
‘<code class=property>flex-item-align</code>’
properties</a>
</ul>
<li><a href="#multi-line"><span class=secno>6. </span> Multi-line
Flexbox</a>
<ul class=toc>
<li><a href="#flex-line-pack"><span class=secno>6.1. </span>
‘<code class=property>flex-line-pack</code>’ property</a>
</ul>
<li><a href="#layout-algorithm"><span class=secno>7. </span> Flexbox
Layout Algorithm</a>
<li><a href="#pagination"><span class=secno>8. </span> Page breaks in
flexbox</a>
<li><a href="#conformance"><span class=secno>9. </span> Conformance</a>
<ul class=toc>
<li><a href="#conventions"><span class=secno>9.1. </span> Document
conventions</a>
<li><a href="#conformance-classes"><span class=secno>9.2. </span>
Conformance classes</a>
<li><a href="#partial
C054
"><span class=secno>9.3. </span> Partial
implementations</a>
<li><a href="#experimental"><span class=secno>9.4. </span> Experimental
implementations</a>
<li><a href="#testing"><span class=secno>9.5. </span> Non-experimental
implementations</a>
<li><a href="#cr-exit-criteria"><span class=secno>9.6. </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-->
<p class=issue>Add "Canonical Order" fields to all the propdef tables, per
<a
href="http://wiki.csswg.org/spec/format-update">http://wiki.csswg.org/spec/format-update</a>.
<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:</p>
<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: flexbox; flex-pack: distribute; }
/* Irrelevant styling for this example removed. */
</style></pre>
<div class=figure> <img height=140 src="images/toolbar-example.svg"
width=400>
<p class=caption>Example rendering of the above code snippet, at two
different flexbox widths.</p>
</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. It also defines a new type
of primitive value, the <a href="#flex-function">flex() notation</a>,
which is accepted by the ‘<code class=property>width</code>’
and ‘<code class=property>height</code>’ properties.
<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 <a
href="#CSS3COLOR" rel=biblioentry>[CSS3COLOR]<!--{{CSS3COLOR}}--></a>,
when combined with this module, expands the definition of the
<color> 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:flexbox</code>’ or
‘<code class=css>display:inline-flexbox</code>’ is a <dfn
id=flexbox>flexbox</dfn>. Children of a flexbox are called <dfn
id=flexbox-item title="flexbox item|flexbox items|flexbox item's">flexbox
items</dfn> 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 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 ‘<a
href="#flex-flow-row"><code class=css>row</code></a>’ and ‘<a
href="#flex-flow-column"><code class=css>column</code></a>’
flexboxes.</p>
</div>
<p>The <dfn id=main-axis>main axis</dfn> of a flexbox is the axis on which
<a href="#flexbox-item"><i>flexbox items</i></a> are laid out along. 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 <a href="#main-axis"><i>main axis</i></a>, 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 <a
href="#main-axis"><i>main axis</i></a>.
<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 <a
href="#cross-axis"><i>cross axis</i></a>, 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 <a
href="#cross-axis"><i>cross axis</i></a>.
<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 ‘<code
class=css>flex()</code>’ function in the ‘<code
class=property>width</code>’ or ‘<code
class=property>height</code>’ property. This "flexing" allows the
items to get bigger or smaller based on the available space in the page.
<
4B6C
/div> 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 "flex" 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.
<h3 id=display-flexbox><span class=secno>2.1. </span> New values for
‘<code class=property>display</code>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td>display
<tr>
<th><a href="http://dev.w3.org/csswg/css-module/#values">New value</a>:
<td>flexbox | inline-flexbox
</table>
<p>You can declare that an element is a flexbox, and thus should use
flexbox layout for its contents, by setting the ‘<code
class=property>display</code>’ property on the element to the value
‘<a href="#flexbox"><code class=property>flexbox</code></a>’
or ‘<code class=property>inline-flexbox</code>’.
<p>The ‘<a href="#flexbox"><code class=css>flexbox</code></a>’
value makes the flexbox a block-level element. The ‘<code
class=css>inline-flexbox</code>’ value makes the flexbox an
inline-level element. When it is necessary to distinguish them, this
specification will refer to the former kind of flexbox as a <dfn
id=block-flexbox title="block flexbox|block flexboxes">block flexbox</dfn>
and the latter type as an <dfn id=inline-flexbox
title="inline flexbox|inline flexboxes">inline flexbox</dfn>.
<p>Flexboxes use a new layout algorithm, and so some properties that were
designed with the assumption of block layout don't make sense 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 flexbox item.
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>’, as
normal, because that occurs before flexbox items are determined (the
algorithm for wrapping children of a flexbox into <a
href="#flexbox-item"><i>flexbox items</i></a> needs the computed value of
‘<code class=property>display</code>’).
<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 ‘<code
class=css>inline-flexbox</code>’ and the element is floated or
absolutely positioned, the computed value of ‘<code
class=property>display</code>’ must be ‘<a
href="#flexbox"><code class=css>flexbox</code></a>’.
<p>A flexbox 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>
establish a new formatting context for its contents.
<h3 id=flex-items><span class=secno>2.2. </span> Flexbox Items</h3>
<p class=issue>Add a ‘<code
class=css>display:flexbox-item</code>’ value, so I can do
flexbox-fixup (wrapping an anonymous flexbox around children that have
declared themselves to be items).
<p>Flexbox layout algorithm operates on <a href="#flexbox-item"><i>flexbox
items</i></a>, which are boxes that satisfy at least one of the following
criteria:
<ol>
<li>Immediate block-level children of flexbox
<li>Atomic inline-level children of flexbox
<li>Contiguous run of non-replaced inline children, wrapped into an
anonymous box
</ol>
<p>Some values of ‘<code class=property>display</code>’ trigger
"fixup" to ensure a sensible tree structure. For example, a lone
‘<code class=css>table-cell</code>’ box is fixed up by
generating ‘<code class=css>table</code>’, ‘<code
class=css>table-row-group</code>’, and ‘<code
class=css>table-row</code>’ boxes 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:</p>
<pre>
<div style="display:flexbox">
<!-- flexbox item: block-level child -->
<div id="item1">block</div>
<!-- not a flexbox item, because it's out-of-flow -->
<div id="not-an-item1.5" style="position: absolute;">block</div>
<!-- flexbox item: block-level child -->
<div id="item2" style="display:table">table</div>
<!-- flexbox item: anonymous table wrapped around table-cell -->
<div id="item3" style="display:table-cell">table-cell</div>
<!-- flexbox item: anonymous block around inline content -->
anonymous item 4
<!-- flexbox item: block-level child -->
<div id="item5">block</div>
<!-- flexbox item: anonymous block around inline content -->
anonymous item 6.1
<span id="item6.1">
text 6.2
<div id="not-an-item6.3">block</div>
text 6.4
</span>
<!-- flexbox item: block-level replaced element -->
<iframe id="item7">
<!-- flexbox item: inline-level replaced element -->
<img id="item7" style="display:inline">
<!-- flexbox item: inline-level replaced element -->
<button id="item8">button</button>
<!-- flexbox item: inline-table -->
<div id="item9" style="display:inline-table">table</div>
<!-- flexbox item: floated inline, which changes to a block -->
<span id="item10" style="float: left;">span</span>
</div></pre>
<p>Notice that block element "not-an-item6.3" is not a separate flexbox
item, because it is contained inside an inline element which is being
wrapped into an anonymous flex item. Similarly, the block element
"not-an-item1.5" is not a flexbox item, because it's absolutely
positioned and thus out of flow.</p>
</div>
<h4 id=abspos-flexbox-items><span class=secno>2.2.1. </span> Positioning
Absolutely Positioned Flexbox Items</h4>
<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 their
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
exception is when the flexbox has ‘<code
class=css>flex-pack:justify</code>’, in which case the anonymous
flexbox item will cause there to be two packing spaces where there would
otherwise be only one, which will appear as a double-size space between
two "real" items.
<h2 id=ordering-orientation><span class=secno>3. </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 using the ‘<code
class=property>float</code>’ property to lay out a horizontal
navigation bar (which then requires further effort with the ‘<code
class=property>clear</code>’ property or others to make the elements
interact nicely with the rest of the page). This functionality is exposed
through the ‘<a href="#flex-flow0"><code
class=property>flex-flow</code></a>’ and ‘<a
href="#flex-order0"><code class=property>flex-order</code></a>’
properties.
<h3 id=flex-direction><span class=secno>3.1. </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="http://dev.w3.org/csswg/css-module/#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
</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 affects the direction that flexbox items are laid out
in, and the meaning of the ‘<a href="#flex-pack0"><code
class=property>flex-pack</code></a>’ property.
<dl>
<dt><dfn id=flex-flow-row>row</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 writing mode (the 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
"start" and "end" directions, respectively, of the current writing mode.
<dt><dfn id=flex-flow-row-reverse>row-reverse</dfn>
<dd>Same as <a href="#flex-flow-row"><i>row</i></a>, 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>column</dfn>
<dd>The flexbox's <a href="#main-axis"><i>main axis</i></a> has the same
orientation as the block axis of the current writing mode (the direction
that blocks are 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
"before" and "after" directions, respectively, of the current writing
mode.
<dt><dfn id=flex-flow-column-reverse>column-reverse</dfn>
<dd>Same as <a href="#flex-flow-column"><i>column</i></a>, except the <a
href="#main-start"><i>main-start</i></a> and <a
href="#main-end"><i>main-end</i></a> directions are swapped.
</dl>
<h3 id=flex-wrap><span class=secno>3.2. </span> Flexbox Wrapping: the
‘<a href="#flex-wrap0"><code
class=property>flex-wrap</code></a>’ property</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=flex-wrap0>flex-wrap</dfn>
<tr>
<th><a href="http://dev.w3.org/csswg/css-module/#values">Value</a>:
<td>none | wrap | wrap-reverse
<tr>
<th>Initial:
<td>none
<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
</table>
<p>The ‘<a href="#flex-wrap0"><code
class=property>flex-wrap</code></a>’ property controls whether the
flexbox is <a href="#single-line"><i>single-line</i></a> or <a
href="#multi-line0"><i>multi-line</i></a>, and the direction of the <a
href="#cross-axis"><i>cross axis</i></a>, which affects the direction new
lines are stacked in and the meaning of the ‘<a
href="#flex-align0"><code class=property>flex-align</code></a>’,
‘<a href="#flex-item-align"><code
class=property>flex-item-align</code></a>’, and ‘<a
href="#flex-line-pack0"><code
class=property>flex-line-pack</code></a>’ properties.
<dl>
<dt><dfn id=flex-flow-none>none</dfn>
<dd>The flexbox is <a href="#single-line"><i>single-line</i></a>. The <a
href="#cross-start"><i>cross-start</i></a> direction is equivalent to
either the "start" or "before" direction of the current writing mode,
whichever is in the <i>cross-axis</i>, and the <a
href="#cross-end"><i>cross-end</i></a> direction is the opposite
direction of <a href="#cross-start"><i>cross-start</i></a>.
<p class=issue>For consistency with ‘<code
class=property>white-space</code>’, we should use ‘<code
class=css>nowrap</code>’. For consistency with ‘<code
class=property>text-wrap</code>’, we should use ‘<a
href="#flex-flow-none"><code class=css>none</code></a>’. ‘<a
href="#flex-flow-none"><code class=css>none</code></a>’ is the
less dumb of these. Can we switch both this and ‘<code
class=property>text-wrap</code>’ to ‘<code
class=css>no-wrap</code>’?</p>
<dt><dfn id=flex-flow-wrap>wrap</dfn>
<dd>The flexbox is <a href="#multi-line0"><i>multi-line</i></a>. The <a
href="#cross-start"><i>cross-start</i></a> direction is equivalent to
either the "start" or "before" direction of the current writing mode,
whichever is in the <i>cross-axis</i>, and the <a
href="#cross-end"><i>cross-end</i></a> direction is the opposite
direction of <a href="#cross-start"><i>cross-start</i></a>.
<dt><dfn id=flex-flow-wrap-reverse>wrap-reverse</dfn>
<dd>Same as <a href="#flex-flow-wrap"><i>wrap</i></a>, except the <a
href="#cross-start"><i>cross-start</i></a> and <a
href="#cross-end"><i>cross-end</i></a> directions are swapped.
</dl>
<h3 id=flex-flow><span class=secno>3.3. </span> Flex Direction and Wrap:
the ‘<a href="#flex-flow0"><code
class=property>flex-flow</code></a>’ shorthand</h3>
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=flex-flow0>flex-flow</dfn>
<tr>
<th><a href="http://dev.w3.org/csswg/css-module/#values">Value</a>:
<td><'flex-direction'> || <'flex-wrap'>
<tr>
<th>Initial:
<td>see individual properties
<tr>
<th>Applies To:
<td>flexboxes
<tr>
<th>Inherited:
<td>see individual properties
<tr>
<th>Computed Value:
<td>see individual properties
<tr>
<th>Media:
<td>visual
<tr>
<th>Animatable:
<td>no
</table>
<p>The ‘<a href="#flex-flow0"><code
class=property>flex-flow</code></a>’ property is a shorthand for
setting the ‘<a href="#flex-direction0"><code
class=property>flex-direction</code></a>’ and ‘<a
href="#flex-wrap0"><code class=property>flex-wrap</code></a>’
properties together.
<div class=example>
<p>Some examples of valid flows:</p>
<table
style="margin: 0 auto; vertical-align: middle; border-spacing: 2em 1em;">
<tbody>
<tr>
<td>
<pre>
div { flex-flow: row; }
/* Initial value. Main axis is
inline, no wrap. */</pre>
<td><img height=80 src="images/flex-flow1.svg" width=240>
<tr>
<td>
<pre>
div { flex-flow: column wrap; }
/* Main axis is block-direction and lines
wrap in the inline direction. For an
English page, the main axis is top-to-bottom
and lines wrap to the right. */</pre>
<td><img height=200 src="images/flex-flow2.svg" width=170>
<tr>
<td>
<pre>
div { writing-mode: vertical-rl;
flex-flow: column wrap-reverse; }
/* Main axis is block direction (right to
left). New lines wrap upwards. */</pre>
<td><img height=170 src="images/flex-flow3.svg" width=200>
</table>
</div>
<h3 id=flex-order><span class=secno>3.4. </span> Display Order: the
‘<a href="#flex-order0"><code
class=property>flex-order</code></a>’ property</h3>
<p><a href="#flexbox-item"><i>Flexbox items</i></a> are, by default,
displayed and laid out in the same order as they appear in the source
document. The ‘<a href="#flex-order0"><code
class=property>flex-order</code></a>’ property may be used to change
this ordering.
<table class=propdef>
<tbody>
<tr>
<th>Name:
<td><dfn id=flex-order0>flex-order</dfn>
<tr>
<th><a href="http://dev.w3.org/csswg/css-module/#values">Value</a>:
<td><number>
<tr>
<th>Initial:
<td>0
<tr>
<th>Applies to:
<td><a href="#flexbox-item"><i>flexbox items</i></a>
<tr>
<th>Inherited:
<td>no
<tr>
<th>Computed value:
<td>specified value
<tr>
<th>Media:
<td>visual
<tr>
<th>Animatable:
<td>yes
</table>
<p>The ‘<a href="#flex-order0"><code
class=property>flex-order</code></a>’ property assigns <a
href="#flexbox-item"><i>flexbox items</i></a> to ordinal groups.
<p>Ordinal groups control the order in which <a
href="#flexbox-item"><i>flexbox items</i></a> appear. A flexbox will lay
out its content starting from the lowest numbered ordinal group and going
up. Items with the same ordinal group are laid out in the order they
appear in the source document. ‘<a href="#flex-order0"><code
class=property>flex-order</code></a>’ has no effect on
stacking/layering; elements must still be drawn over/under each other
based on document order, ‘<code
class=property>z-index</code>’, and other relevant means.
<div class=example>
<p>The following figure shows a simple tabbed interface, where the tab for
the active pane is always in front:</p>
<div class=figure><img src="images/flex-order-example.png"></div>
<p>This could be implemented with the following CSS (showing only the
flexbox-relevant code):</p>
<pre>
.tabs {
display: flexbox;
}
.tabs > .current {