compatibility.bs

<pre class="metadata">
Title: Compatibility Standard
Group: WHATWG
H1: Compatibility
Shortname: compat
Repository: whatwg/compat
Status: LS
No Editor: true
Abstract: This standard describes a collection of non-standard (and often vendor-prefixed) CSS properties and DOM APIs that web browsers need to support for compatibility with the de facto web.
Logo: https://resources.whatwg.org/logo-compat.svg
!Participate: <a href=https://github.com/whatwg/compat>GitHub whatwg/compat</a> (<a href=https://github.com/whatwg/compat/issues/new>new issue</a>, <a href=https://github.com/whatwg/compat/issues>open issues</a>)
!Participate: <a href=https://wiki.whatwg.org/wiki/IRC>IRC: #whatwg on Freenode</a>
!Commits: <a href="https://github.com/whatwg/compat/commits">GitHub whatwg/compat/commits</a>
!Commits: <a href="https://twitter.com/compatstandard">@compatstandard</a>
Indent: 2
Boilerplate: omit conformance
</pre>

<script src=https://resources.whatwg.org/file-issue.js async></script>

<pre class="anchors">
urlPrefix: https://drafts.fxtf.org/geometry/; spec: geometry-1
  type: interface;
    text: DOMMatrix; url: #dommatrix
    text: DOMMatrixReadOnly; url: #dommatrixreadonly
  type: attribute;
    text: m11 element; url: #m11-element
    text: m12 element; url: #m12-element
    text: m13 element; url: #m13-element
    text: m14 element; url: #m14-element
    text: m21 element; url: #m21-element
    text: m22 element; url: #m22-element
    text: m23 element; url: #m23-element
    text: m24 element; url: #m24-element
    text: m31 element; url: #m31-element
    text: m32 element; url: #m32-element
    text: m33 element; url: #m33-element
    text: m34 element; url: #m34-element
    text: m41 element; url: #m41-element
    text: m42 element; url: #m42-element
    text: m43 element; url: #m43-element
    text: m44 element; url: #m44-element
    text: m11 attribute; url: #dom-dommatrixreadonly-m11
    text: m12 attribute; url: #dom-dommatrixreadonly-m12
    text: m13 attribute; url: #dom-dommatrixreadonly-m13
    text: m14 attribute; url: #dom-dommatrixreadonly-m14
    text: m21 attribute; url: #dom-dommatrixreadonly-m21
    text: m22 attribute; url: #dom-dommatrixreadonly-m22
    text: m23 attribute; url: #dom-dommatrixreadonly-m23
    text: m24 attribute; url: #dom-dommatrixreadonly-m24
    text: m31 attribute; url: #dom-dommatrixreadonly-m31
    text: m32 attribute; url: #dom-dommatrixreadonly-m32
    text: m33 attribute; url: #dom-dommatrixreadonly-m33
    text: m34 attribute; url: #dom-dommatrixreadonly-m34
    text: m41 attribute; url: #dom-dommatrixreadonly-m41
    text: m42 attribute; url: #dom-dommatrixreadonly-m42
    text: m43 attribute; url: #dom-dommatrixreadonly-m43
    text: m44 attribute; url: #dom-dommatrixreadonly-m44
    text: a attribute; url: #dom-dommatrixreadonly-a
    text: b attribute; url: #dom-dommatrixreadonly-b
    text: c attribute; url: #dom-dommatrixreadonly-c
    text: d attribute; url: #dom-dommatrixreadonly-d
    text: e attribute; url: #dom-dommatrixreadonly-e
    text: f attribute; url: #dom-dommatrixreadonly-f
    text:  is2d; url: #dommatrixreadonly-is2d
  type: method;
    text: fromString; url: #dom-dommatrixreadonly-fromstring0
urlPrefix: https://heycam.github.io/webidl/
  type: dfn
    text: NotSupportedError; url: #notsupportederror
    text: DOMException; url: #idl-DOMException
urlPrefix: https://html.spec.whatwg.org/multipage/; spec: HTML
  type: interface
    urlPrefix: browsers.html
      text: Window; url: #window
  type: element
    urlPrefix: semantics.html
      text: body; url: #the-body-element
  type: dfn
    urlPrefix: webappapis.html
      text: event handler; url: #event-handlers
      text: event handler event type; url: #event-handler-event-type
      text: responsible document; url: #responsible-document
    urlPrefix: browsers.html
      text: active document; url: #active-document
urlPrefix: https://dom.spec.whatwg.org/; spec: WHATWG-DOM
  type: interface
    text: Document; url: #document
  type: interface
    text: Event; url: #event
  type: method
    text: createEvent; url: #dom-document-createevent
  type: attribute
    text: type; url: #dom-event-type
  type: dfn; url: #concept-event-fire
    text: fire an event
urlPrefix: https://w3c.github.io/screen-orientation/;
  type: interface
    text: ScreenOrientation; url: #screenorientation-interface
  type: dfn
    text: update the orientation information; url: #dfn-update-the-orientation-information
urlPrefix: http://www.w3.org/TR/CSS/; spec: CSS22
  type: dfn
    text: vendor prefix; url: #vendor-prefix
urlPrefix: http://www.w3.org/TR/mediaqueries-4/; spec: mediaqueries-4
  type: dfn
    text: media query; url: #media-query
    text: media feature; url: #media-feature
    text: resolution; url: #descdef-resolution
    text: min-resolution; url: #descdef-resolution
    text: max-resolution; url: #descdef-resolution
    text: prefixes on range features; url: #mq-min-max
urlPrefix: http://www.w3.org/TR/2011/WD-css3-images-20110217/; spec: css3-images-20110217
  type: dfn
    text: linear-gradient; url: #ltlinear-gradient
    text: radial-gradient; url: #ltradial-gradient
    text: repeating-linear-gradient; url: #ltrepeating-linear-gradient
    text: repeating-radial-gradient; url: #ltrepeating-radial-gradient
</pre>

<pre class=link-defaults>
spec:css-transforms-1; type:property; text:backface-visibility
spec:css-transforms-1; type:property; text:perspective
spec:css-transforms-1; type:property; text:perspective-origin
spec:css-transforms-1; type:property; text:transform-origin
spec:css-transforms-1; type:property; text:transform-style
spec:css-transforms-1; type:property; text:transform
</pre>

<pre class=biblio>
{
    "CSS22": {
        "authors": [
            "Bert Bos"
        ],
        "href": "https://drafts.csswg.org/css2/",
        "title": "Cascading Style Sheets Level 2 Revision 2 (CSS 2.2) Specification",
        "status": "Draft",
        "publisher": "W3C",
        "deliveredBy": [
            "http://www.w3.org/Style/CSS/"
        ]
    },
    "CSS3-BG4": {
        "authors": [
            "Bert Bos", "Elika J. Etemad", "Lea Verou"
        ],
        "href": "https://drafts.csswg.org/css-backgrounds-4/",
        "title": "CSS Backgrounds and Borders Module Level 4",
        "status": "Draft",
        "publisher": "W3C",
        "deliveredBy": [
            "http://www.w3.org/Style/CSS/"
        ]
    }
}
</pre>

<!-- Commented out until we know what the heck to put here:
<h2 id='goals'>Goals</h2> -->

<h2 id='introduction'>Introduction</h2>
<em>This section is non-normative.</em>

There exists an increasingly large corpus of web content that depends on web browsers supporting a number of <code>webkit</code>-prefixed CSS properties and DOM APIs for functionality or layout. This holds especially true for mobile-optimized web content.

This specification aims to describe the minimal set of <code>webkit</code>-prefixed CSS properties and DOM APIs that user agents are required to support for web compatibility.

<div class="XXX">
The <a href="https://wiki.mozilla.org/Compatibility/Mobile/Non_Standard_Compatibility">Non-Standard Compatibility</a> wiki page will serve as a rough guide for what this specification intends to cover.
</div>

<h2 id='conformance'>Conformance</h2>
All diagrams, examples, and notes in this specification are
non-normative, as are all sections explicitly marked non-normative.
Everything else in this specification is normative.

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC 2119.
For readability, these words do not appear in all uppercase letters in this
specification. [[!RFC2119]]

Requirements phrased in the imperative as part of algorithms
(such as "strip any leading space characters" or "return false and
terminate these steps") are to be interpreted with the meaning of the
keyword ("must", "should", "may", etc.) used in introducing the
algorithm.

Conformance requirements phrased as algorithms or specific steps
may be implemented in any manner, so long as the end result is
equivalent. (In particular, the algorithms defined in this
specification are intended to be easy to follow, and not intended to
be performant.)

<h2 id="css-compat-section">CSS Compatibility</h2>

<h3 id="css-at-rules">CSS At-rules</h3>

The following <code>-webkit-</code> <a>vendor prefixed</a> at-rules must be supported as aliases of the corresponding unprefixed at-rules:

<table>
  <thead>
    <tr>
     <th><code>-webkit-</code> prefixed at-rule alias</th>
     <th>unprefixed at-rule</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td><code><dfn type=at-rule>@-webkit-keyframes</dfn></code></td>
      <td><code><a>@keyframes</a></code></td>
    </tr>
  </tbody>
</table>

<h3 id="css-media-queries">CSS Media Queries</h3>

<h4 id="css-media-queries-webkit-device-pixel-ratio">
  <code>'-webkit-device-pixel-ratio'</code>
</h4>

<pre class='descdef mq'>
Name: -webkit-device-pixel-ratio
Value: <<number>>
For: @media
Type: range
</pre>

<code>'-webkit-device-pixel-ratio'</code> must be treated as an alias of the <code><a>resolution</a></code> range type <a>media feature</a>, with its value interpreted as a <a>dppx</a> unit.

The <code>min-</code> or <code>max-</code> <a>prefixes on range features</a> must not apply to <code>'-webkit-device-pixel-ratio'</code>, instead the following aliases must be used:

<table>
  <thead>
    <tr>
     <th>legacy <code>-webkit-</code> prefixed range <a>media feature</a> alias</th>
     <th>standard prefixed range <a>media feature</a></th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td><code><dfn descriptor for="@media">-webkit-min-device-pixel-ratio</dfn></code></td>
      <td><code><a>min-resolution</a></code></td>
    </tr>
    <tr>
      <td><code><dfn descriptor for="@media">-webkit-max-device-pixel-ratio</dfn></code></td>
      <td><code><a>max-resolution</a></code></td>
    </tr>
  </tbody>
</table>

<h4 id="css-media-queries-webkit-transform-3d">
  <code>'-webkit-transform-3d'</code>
</h4>

<pre class='descdef mq'>
Name: -webkit-transform-3d
Value: <<mq-boolean>>
For: @media
Accepts min/max prefixes: no
</pre>

The <code>'-webkit-transform-3d'</code> media feature is used to query whether the user agent supports CSS 3D transforms. [[css-transforms-1]]

If the user agent supports 3D transforms, the value will be 1. Otherwise the value is 0.

<h3 id="css-<image>-type">CSS Gradients</h3>

<!-- Uncomment when I add -webkit-gradient()
Both the [[css3-images-20110217]] draft <code>-webkit-</code> prefixed <<image>> gradient functions and the 2008 <code>-webkit-gradient()</code> (<a href="https://webkit.org/blog/175/introducing-css-gradients/">blog post</a>, <a href="https://developer.apple.com/library/safari/documentation/InternetWeb/Conceptual/SafariVisualEffectsProgGuide/Gradients/Gradient.html#//apple_ref/doc/uid/TP40008032-CH10-SW34">Safari developer documentation</a>) must be supported for compatibility.
-->

<h4 id="css-gradients-webkit-linear-gradient">
  <code>''-webkit-linear-gradient()''</code>
</h4>

<code><dfn>-webkit-linear-gradient()</dfn></code> must be treated as an alias of <a>linear-gradient</a> as defined in [[css3-images-20110217]].
<!-- The stupid parens outside of the ref link are a hack because bikeshed hates me and my attempts to link to http://www.w3.org/TR/2011/WD-css3-images-20110217/#ltlinear-gradient. Pull requests welcome? -->

<h4 id="css-gradients-webkit-radial-gradient">
  <code>''-webkit-radial-gradient()''</code>
</h4>

<code><dfn>-webkit-radial-gradient()</dfn></code> must be treated as an alias of <a>radial-gradient</a> as defined in [[css3-images-20110217]].

<h4 id="css-gradients-repeating-webkit-linear-gradient">
  <code>''-webkit-repeating-linear-gradient()''</code>
</h4>

<code><dfn>-webkit-repeating-linear-gradient()</dfn></code> must be treated as an alias of <a>repeating-linear-gradient</a> as defined in [[css3-images-20110217]].

<h4 id="css-gradients-repeating-webkit-radial-gradient">
  <code>''-webkit-repeating-radial-gradient()''</code>
</h4>

<code><dfn>-webkit-repeating-radial-gradient()</dfn></code> must be treated as an alias of <a>repeating-radial-gradient</a> as defined in [[css3-images-20110217]].

<!--
<h4 id="css-gradients-webkit-gradient">
  <code>-webkit-gradient()</code>
</h4>

<div class="XXX">TODO</div> -->

<h3 id="css-properties">CSS Properties</h3>

<h4 id="css-simple-aliases">Simple property aliases</h4>

The following <code>-webkit-</code> <a>vendor prefixed</a> properties must be supported as aliases of the corresponding unprefixed property:

<table>
  <thead>
    <tr>
     <th><code>-webkit-</code> prefixed property alias</th>
     <th>unprefixed property</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td><code><dfn type=property>-webkit-animation-name</dfn></code></td>
      <td><code>'animation-name'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-animation-duration</dfn></code></td>
      <td><code>'animation-duration'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-animation-timing-function</dfn></code></td>
      <td><code>'animation-timing-function'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-animation-iteration-count</dfn></code></td>
      <td><code>'animation-iteration-count'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-animation-direction</dfn></code></td>
      <td><code>'animation-direction'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-animation-play-state</dfn></code></td>
      <td><code>'animation-play-state'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-animation-delay</dfn></code></td>
      <td><code>'animation-delay'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-animation-fill-mode</dfn></code></td>
      <td><code>'animation-fill-mode'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-animation</dfn></code></td>
      <td><code>'animation'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-backface-visibility</dfn></code></td>
      <td><code>'backface-visibility'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-background-clip</dfn></code></td>
      <td><code>'background-clip'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-background-origin</dfn></code></td>
      <td><code>'background-origin'</code></td>
    </tr>
    <tr>
      <td>
        <code><dfn type=property>-webkit-background-size</dfn></code>
        <p class="XXX">
          Not simple. See <a href="https://github.com/whatwg/compat/issues/28">issue #28</a>.
        </p>
      </td>
      <td><code>'background-size'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-border-bottom-left-radius</dfn></code></td>
      <td><code>'border-bottom-left-radius'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-border-bottom-right-radius</dfn></code></td>
      <td><code>'border-bottom-right-radius'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-border-top-left-radius</dfn></code></td>
      <td><code>'border-top-right-radius'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-border-top-right-radius</dfn></code></td>
      <td><code>'border-top-right-radius'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-border-radius</dfn></code></td>
      <td><code>'border-radius'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-box-shadow</dfn></code></td>
      <td><code>'box-shadow'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-box-sizing</dfn></code></td>
      <td><code>'box-sizing'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-filter</dfn></code></td>
      <td><code>'filter'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-perspective</dfn></code></td>
      <td><code>'perspective'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-perspective-origin</dfn></code></td>
      <td><code>'perspective-origin'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-transform-origin</dfn></code></td>
      <td><code>'transform-origin'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-transform-style</dfn></code></td>
      <td><code>'transform-style'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-transform</dfn></code></td>
      <td><code>'transform'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-transition-delay</dfn></code></td>
      <td><code>'transition-delay'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-transition-duration</dfn></code></td>
      <td><code>'transition-duration'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-transition-property</dfn></code></td>
      <td><code>'transition-property'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-transition-timing-function</dfn></code></td>
      <td><code>'transition-timing-function'</code></td>
    </tr>
    <tr>
      <td><code><dfn type=property>-webkit-transition</dfn></code></td>
      <td><code>'transition'</code></td>
    </tr>
  </tbody>
</table>

<h4 id="css-prefixed-aliases">Prefixed property aliases</h4>

The following <code>-webkit-</code> <a>vendor prefixed</a> properties must be supported as aliases of the corresponding unprefixed properties. If the user agent does not ship the unprefixed equivalent, the <code>-webkit-</code> prefixed property must be treated as an alias of the user agent's own vendor prefixed property.

<table>
  <thead>
    <tr>
     <th><code>-webkit-</code> prefixed property alias</th>
     <th>(vendor prefixed) property</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td><code><dfn type=property>-webkit-text-size-adjust</dfn></code></td>
      <td><code>(-prefix-)'text-size-adjust'</code></td>
    </tr>
  </tbody>
</table>

<br>
<div class="note"> As soon as https://drafts.csswg.org/css-size-adjust/#text-size-adjust is unprefixable it can be defined as a "simple" alias.</div>

<h4 id="css-property-mappings">Property mappings</h4>

The following <code>-webkit-</code> <a>vendor prefixed</a> properties must be supported as mappings to the corresponding unprefixed property:

<table>
  <thead>
    <tr>
     <th><code>-webkit-</code> prefixed property</th>
     <th>unprefixed property</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td><code><dfn type=property>-webkit-box-flex</dfn></code></td>
      <td><code>'flex-grow'</code></td>
    </tr>
      <td><code><dfn type=property>-webkit-box-ordinal-group</dfn></code></td>
      <td><code>'order'</code></td>
    </tr>
      <td><code><dfn type=property>-webkit-box-align</dfn></code></td>
      <td><code>'align-items'</code></td>
    </tr>
      <td><code><dfn type=property>-webkit-box-pack</dfn></code></td>
      <td><code>'justify-content'</code></td>
    </tr>
  </tbody>
</table>

<h4 id="css-keyword-mappings">Keyword mappings</h4>

The following <code>-webkit-</code> <a>vendor prefixed</a> keywords must be supported as mappings to the corresponding unprefixed keyword:

<table>
  <thead>
    <tr>
     <th><code>-webkit-</code> prefixed keyword</th>
     <th>unprefixed property keyword</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td><code><dfn type=property>-webkit-box</dfn></code></td>
      <td><code>''flex''</code></td>
    </tr>
  </tbody>
</table>

<h2 id="dom-compat-section">DOM Compatibility</h2>

<h3 id="webkitcssmatrix-interface">The {{WebKitCSSMatrix}} interface</h3>

<!-- cf. https://github.com/WebKit/webkit/blob/master/Source/WebCore/css/WebKitCSSMatrix.idl -->
<pre class="idl">
[Constructor,
 Constructor(DOMString transformList),
 Exposed=Window]
interface WebKitCSSMatrix : DOMMatrix {
    // Mutable transform methods
    WebKitCSSMatrix setMatrixValue(DOMString transformList);

    // Immutable transform methods
    WebKitCSSMatrix multiply(WebKitCSSMatrix other);
    WebKitCSSMatrix inverse();
    WebKitCSSMatrix translate(optional unrestricted double tx = 0,
                              optional unrestricted double ty = 0,
                              optional unrestricted double tz = 0);
    WebKitCSSMatrix scale(optional unrestricted double scaleX = 1,
                          optional unrestricted double scaleY,
                          optional unrestricted double scaleZ = 1);
    WebKitCSSMatrix rotate(optional unrestricted double rotX = 0,
                           optional unrestricted double rotY,
                           optional unrestricted double rotZ);
    WebKitCSSMatrix rotateAxisAngle(optional unrestricted double x = 0,
                                    optional unrestricted double y = 0,
                                    optional unrestricted double z = 0,
                                    optional unrestricted double angle = 0);
    WebKitCSSMatrix skewX(optional unrestricted double sx = 0);
    WebKitCSSMatrix skewY(optional unrestricted double sy = 0);
};
</pre>

The {{WebKitCSSMatrix}} interface represents a 4×4 homogeneous matrix with methods useful for 2D and 3D transform operations.

The {{WebKitCSSMatrix}} interface may be implemented as a subclass of the {{DOMMatrix}} and {{DOMMatrixReadOnly}} interfaces, defined in Geometry Interfaces Module Level 1 [[!geometry-1]], with key differences noted below.

<h4 id="webkitcssmatrix-constructors">Constructors</h4>

<dl class=domintro>
  <dt>
    <code><var>matrix</var> = new <a constructor
    lt="WebKitCSSMatrix()">WebKitCSSMatrix()</a></code>
  </dt>
  <dd>
    Returns a new {{WebKitCSSMatrix}} object.
  </dd>
</dl>

The <dfn constructor dfn-for="WebKitCSSMatrix" lt="WebKitCSSMatrix()">WebKitCSSMatrix()</dfn>
constructor, when invoked, must run these steps:

<ol>
  <li>
    Let <var>m</var> be a new {{WebKitCSSMatrix}} object.
  </li>
  <li>For m, set the
    <a attribute spec="geometry-1">m11 element</a>,
    <a attribute spec="geometry-1">m22 element</a>,
    <a attribute spec="geometry-1">m33 element</a>,
    <a attribute spec="geometry-1">m44 element</a> to 1. Set the
    <a attribute spec="geometry-1">m12 element</a>,
    <a attribute spec="geometry-1">m13 element</a>,
    <a attribute spec="geometry-1">m14 element</a>,
    <a attribute spec="geometry-1">m21 element</a>,
    <a attribute spec="geometry-1">m23 element</a>,
    <a attribute spec="geometry-1">m24 element</a>,
    <a attribute spec="geometry-1">m31 element</a>,
    <a attribute spec="geometry-1">m32 element</a>,
    <a attribute spec="geometry-1">m34 element</a>,
    <a attribute spec="geometry-1">m41 element</a>,
    <a attribute spec="geometry-1">m42 element</a>,
    <a attribute spec="geometry-1">m43 element</a> to 0.</li>
  <li>
    Return <var>m</var>.
  </li>
</ol>

<dl class=domintro>
  <dt>
    <code><var>matrix</var> = new <a constructor
    lt="WebKitCSSMatrix(transformList)">WebKitCSSMatrix</a>(transformList)</code>
  </dt>
  <dd>
    Returns a new {{WebKitCSSMatrix}} object.
  </dd>
</dl>

The
<dfn constructor dfn-for="WebKitCSSMatrix" lt="WebKitCSSMatrix(transformList)">WebKitCSSMatrix(transformList)</dfn>
constructor, when invoked, must run these steps:

<ol>
  <li>
    Let <var>m</var> be a new {{WebKitCSSMatrix}} object.
  </li>
  <li>Return the result of the algorithm for the static {{DOMMatrixReadOnly}} <a method for=DOMMatrixReadOnly spec="geometry-1">fromString(transformList)</a> method, as <var>m</var>.
  </li>
</ol>

<h4 id="webkitcssmatrix-attributes">{{WebKitCSSMatrix}} attributes</h4>

{{WebKitCSSMatrix}} objects must inherit the following attributes from {{DOMMatrixReadOnly}}:

<a attribute spec="geometry-1">m11 attribute</a>,
<a attribute spec="geometry-1">m22 attribute</a>,
<a attribute spec="geometry-1">m33 attribute</a>,
<a attribute spec="geometry-1">m44 attribute</a>,
<a attribute spec="geometry-1">m12 attribute</a>,
<a attribute spec="geometry-1">m13 attribute</a>,
<a attribute spec="geometry-1">m14 attribute</a>,
<a attribute spec="geometry-1">m21 attribute</a>,
<a attribute spec="geometry-1">m23 attribute</a>,
<a attribute spec="geometry-1">m24 attribute</a>,
<a attribute spec="geometry-1">m31 attribute</a>,
<a attribute spec="geometry-1">m32 attribute</a>,
<a attribute spec="geometry-1">m34 attribute</a>,
<a attribute spec="geometry-1">m41 attribute</a>,
<a attribute spec="geometry-1">m42 attribute</a>,
<a attribute spec="geometry-1">m43 attribute</a>,
<a attribute spec="geometry-1">a attribute</a>,
<a attribute spec="geometry-1">b attribute</a>,
<a attribute spec="geometry-1">c attribute</a>,
<a attribute spec="geometry-1">d attribute</a>,
<a attribute spec="geometry-1">e attribute</a>,
<a attribute spec="geometry-1">f attribute</a>.

<h4 id="webkitcssmatrix-mutable-methods">{{WebKitCSSMatrix}} mutable methods</h4>

The following method modifies the current matrix, returning the matrix it was invoked on.

When the <dfn method for="WebKitCSSMatrix"><code>setMatrixValue(transformList)</code></dfn>
method is invoked, the user agent must run the following steps:

1. Return the result of the algorithm for the {{DOMMatrix}} <a method for="DOMMatrix" spec="geometry-1">setMatrixValue(transformList)</a> method.

<h4 id="webkitcssmatrix-immutable-methods">{{WebKitCSSMatrix}} immutable methods</h4>

The following methods do not modify the current matrix and return a new {{WebKitCSSMatrix}} object.

When the <code>{{multiply(other)}}</code> method is invoked, the user agent must run the following steps:

1. Return the result of the algorithm for the {{DOMMatrixReadOnly}} <a method for="DOMMatrixReadOnly" spec="geometry-1">multiply(other)</a> method as a new {{WebKitCSSMatrix}} object.

When the <code>{{inverse()}}</code> method is invoked, the user agent must run the following steps:

1. Let <var>result</var> be the resulting matrix initialized to the value of the current matrix.

2. Invert the matrix <var>result</var>.

3. If the matrix <var>result</var> is not invertable, throw a <a>NotSupportedError</a> <a>DOMException</a>.

4. Return <var>result</var> as a new {{WebKitCSSMatrix}} object.

When the <code>{{translate(tx, ty, tz)}}</code> method is invoked, the user agent must run the following steps:

1. Return the result of the algorithm for the {{DOMMatrixReadOnly}} <a method for="DOMMatrixReadOnly" spec="geometry-1">translate(x, y, z)</a> method as a new {{WebKitCSSMatrix}} object.

When the <code>{{scale(scaleX, scaleY, scaleZ)}}</code> method is invoked, the user agent must run the following steps:

1. If <var>scaleY</var> is undefined, let <var>scaleY</var> be the value of <var>scaleX</var>.

2. Return the result of the algorithm for the {{DOMMatrixReadOnly}} <a method for="DOMMatrixReadOnly" spec="geometry-1">scaleNonUniform(scaleX, scaleY, scaleZ)</a> method as a new {{WebKitCSSMatrix}} object.

When the <code>{{rotate(rotX, rotY, rotZ)}}</code> method is invoked, the user agent must run the following steps:

1. Let <var>result</var> be the resulting matrix initialized to the values of the current matrix.

2. If <var>rotY</var> and <var>rotZ</var> are undefined, let <var>rotZ</var> be the value of <var>rotX</var> and let <var>rotX</var> and <var>rotY</var> be 0.

3. Else, if any of <var>rotX</var>, <var>rotY</var> or <var>rotZ</var> are undefined, let the undefined argument be 0.

4. If <var>rotX</var> or <var>rotY</var> are non-zero, set the <a attribute spec="geometry-1">is2d</a> flag to false.

5. Post-multiply <var>result</var> by each of its 3 rotation matrices about the major axes, first Z using <var>rotZ</var>, then Y using <var>rotY</var>, then X using <var>rotX</var>.

6. Return the result as a new {{WebKitCSSMatrix}} object.

The current matrix is not modified.

When the <code>{{rotateAxisAngle(x, y, z, angle)}}</code> method is invoked, the user agent must run the following steps:

1. Return the result of the algorithm for the {{DOMMatrixReadOnly}} <a method for="DOMMatrixReadOnly" spec="geometry-1">rotateAxisAngle(x, y, z, angle)</a> method as a new {{WebKitCSSMatrix}} object.

When the <code>{{skewX(sx)}}</code> method is invoked, the user agent must run the following steps:

1. Return the result of the algorithm for the {{DOMMatrixReadOnly}} <a method for="DOMMatrixReadOnly" spec="geometry-1">skewX(sx)</a> method as a new {{WebKitCSSMatrix}} object.

<!--

open question: is https://github.com/WebKit/webkit/blob/d055853e59dd6cc4cfd835b143e79258bb13c552/Source/WebCore/css/WebKitCSSMatrix.h#L138 needed for compat?

-->

When the <code>{{skewY(sy)}}</code> method is invoked, the user agent must run the following steps:

1. Return the result of {{DOMMatrixReadOnly}} <a method for="DOMMatrixReadOnly" spec="geometry-1">skewY(sy)</a> as a new {{WebKitCSSMatrix}} object.

<!--

open question: is https://github.com/WebKit/webkit/blob/d055853e59dd6cc4cfd835b143e79258bb13c552/Source/WebCore/css/WebKitCSSMatrix.h#L144 needed for compat?

-->

<!-- TODO: add note about common usage that requires support for webkitTransform, etc.

      var box = document.getElementById('box');
      var tranString = window.getComputedStyle(box).webkitTransform;
      var m = new WebKitCSSMatrix(tranString);
      box.style.webkitTransform = m.rotateAxisAngle(3,1,2,1);
-->

<h3 id="windoworientation-interface"><a attribute lt="orientation"><code>window.orientation</code></a> API</h3>

<pre class="idl">
partial interface Window {
    readonly attribute short orientation;
    attribute EventHandler onorientationchange;
};

partial interface HTMLBodyElement {
    attribute EventHandler onorientationchange;
};
</pre>

When getting the <dfn attribute for="Window">orientation</dfn> attribute, the user agent must run the following steps:

1. Return the <a>responsible document</a>'s current <a href="#dfn-window-orientation-angle"><code>window.orientation</code> angle</a>.

Whenever the viewport is drawn at a different angle compared to the device's natural orientation, the user agent must run the following steps:

1. <a lt="fire an event">Fire an event</a> named <code><dfn id="event-orientationchange" lt="orientationchange">orientationchange</dfn></code> at the {{Window}} object of the <a>active document</a>.

User agents implementing the <a attribute lt="orientation"><code>window.orientation</code></a> attribute and its associated <a>orientationchange</a> event must not expose them on Desktop platforms.

<div class="note">iOS Safari also fires an <code>orientationchange</code> event on the <code><{body}></code> element, but other implementations do not, suggesting it's not required for compability with the web.</div>

<h4 id="dfn-window-orientation-angle"><a attribute lt="orientation"><code>window.orientation</code></a> angle</h4>

The possible values for the <a attribute lt="orientation"><code>window.orientation</code></a> angle are: <code>-90</code>, <code>0</code>, <code>90</code>, <code>180</code>. User agents must support the <code>-90</code>, <code>0</code> and <code>90</code> values and may optionally support <code>180</code>.

<p class="note"><code>0</code> represents the natural orientation. <code>-90</code> represents a rotation 90 degrees clockwise from the natural orientation. <code>90</code> represents a rotation 90 degrees counterclockwise from the natural orientation. <code>180</code> represents a rotation 180 degrees from the natural orientation.
</p>

In order to determine the current <a attribute lt="orientation"><code>window.orientation</code></a> angle, the user agent must run the following steps:

<ol>
  <li>Return the result of step 3 of the {{ScreenOrientation}}'s <a>update the orientation information</a> algorithm with the following changes:
    <ol>
      <li>If the orientation angle is less than or equal to 180, return the orientation angle
      <li>If the orientation angle is greater than 180, return the orientation angle - 360.
      <li>If the resulting orientation angle is 180 and the user agent does not support that value, return 0.
      <!-- This is what Windows phone, some iPhones running various iOSes, and Chrome Mobile do on some of my test Androids. It's possible something else happens! -->
    </ol>
  </li>
</ol>

<h4 id="event-handlers">Event Handlers on {{Window}} objects and <code><{body}></code> elements</h4>

The following are the event handlers and their corresponding event handler event types that must be supported on all {{Window}} objects and <code><{body}></code> elements as attributes:

<table>
  <thead>
    <tr>
     <th><a>event handler</a></th>
     <th><a>event handler event type</a></th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>
          <code>{{onorientationchange}}</code>
      </td>
      <td>
        <code><a lt="orientationchange">orientationchange</a></code>
      </td>
    </tr>
  </tbody>
</table>

<div class="XXX">
WebKit also has this on <a href="https://github.com/WebKit/webkit/blob/e455672f9e6861ced85d8be01cb7bc03a30a0555/LayoutTests/fast/dom/event-handler-attributes.html#L335">HTMLFrameSetElement</a>. It's unclear if this is needed for compatibility.
</div>

<h2 id="acknowledgements" class="no-num">Acknowledgements</h2>
Thanks to Alan Cutter, Chris Rebert, Daniel Holbert, hexalys, Jacob Rossi, Philip Jägenstedt, Simon Pieters, Stanley Stuart, William Chen and Your Name Here for feedback and contributions to this standard.

Thanks to Simon Pieters, Dirk Schulze and Rik Cabanier for defining the {{DOMMatrix}} and {{DOMMatrixReadOnly}} interfaces. [[!geometry-1]]

Thanks to Mounir Lamouri and Marcos Cáceres for defining the {{ScreenOrientation}} interface. [[!screen-orientation]]

This standard is written by
<a href="https://miketaylr.com/">Mike Taylor</a>
(<a href="https://www.mozilla.org/">Mozilla</a>,
<a href=mailto:miket@mozilla.com>miket@mozilla.com</a>).

Per <a rel="license" href="//creativecommons.org/publicdomain/zero/1.0/">CC0</a>, to
the extent possible under law, the editors have waived all copyright and related or
neighboring rights to this work.

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