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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang="en-US">
<head>
<title>CSSOM View Module</title>
<style type="text/css">
pre.idl { border:solid thin; background:#eee; color:#000; padding:0.5em }
pre.idl :link, pre.idl :visited { color:inherit; background:transparent }
dfn { font-weight:bold; font-style:normal }
div.example { margin-left:1em; padding-left:1em; border-left:double; color:#222; background:#fcfcfc }
div.example code { color:inherit }
p.note { margin-left:2em; color:green; font-style:italic; font-weight:bold }
p.note::before { content:"Note: " }
.XXX { padding:.5em; border:solid red }
.XXX::before { content:"Issue: " }
em.ct { font-weight:bold; font-style:normal }
code { color:orangered }
code :link, code :visited { color:inherit }
</style>
<link rel="stylesheet" href="http://www.w3.org/StyleSheets/TR/W3C-[STATUS]">
</head>
<body class="draft">
<div class="head">
<!--logo-->
<h1 id="cssom-view-module">CSSOM View Module</h1>
<h2 class="no-num no-toc" id="w3c-doctype">[LONGSTATUS] [DATE: 3 August 2002]</h2>
<dl>
<dt>This Version:</dt>
<dd><a href="[VERSION]/">http://www.w3.org/TR/[YEAR]/ED-cssom-view-[CDATE]/</a></dd>
<dt>Latest Version:</dt>
<dd><a href="http://www.w3.org/TR/cssom-view/">http://www.w3.org/TR/cssom-view/</a></dd>
<dt>Latest Editor Version:</dt>
<dd><a href="http://dev.w3.org/csswg/cssom-view/">http://dev.w3.org/csswg/cssom-view/</a></dd>
<dt>Previous Versions:</dt>
<dd><a href="http://www.w3.org/TR/2009/WD-cssom-view-20090804/">http://www.w3.org/TR/2009/WD-cssom-view-20090804/</a></dd>
<dd><a href="http://www.w3.org/TR/2008/WD-cssom-view-20080222/">http://www.w3.org/TR/2008/WD-cssom-view-20080222/</a></dd>
<dt>Editor:</dt>
<dd><a href="http://annevankesteren.nl/">Anne van Kesteren</a>
(<a href="http://www.opera.com/">Opera Software ASA</a>)
<<a href="mailto:annevk@opera.com">annevk@opera.com</a>></dd>
</dl>
<!-- copyright -->
</div>
<hr>
<h2 id="abstract" class="no-num no-toc">Abstract</h2>
<p>The APIs introduced by this specification provide authors with a way to
inspect and manipulate the visual view of a document. This includes
getting the position of element layout boxes, obtaining the width
of the viewport through script, and also scrolling an element.</p>
<h2 id="sotd" class="no-num no-toc">Status of this Document</h2>
<!-- status -->
<h2 id="toc" class="no-num no-toc">Table of Contents</h2>
<h2 id="background">Background</h2>
<p>Many of the features defined in this specification have been supported
by browsers for a long period of time. The goal of this specification is
to define these features in such a way that they can be implemented by all
browsers in an interoperable manner. The specification also defines a
couple of new features that will hopefully be useful to authors. (If they
are not you can bug us!)</p>
<h2 id="conformance">Conformance Criteria</h2>
<p>Everything in this specification is normative except for diagrams,
examples, notes and sections marked non-normative.</p>
<!--<p>The key word <em class="ct">must</em>, <em class="ct">must not</em>,
<em class="ct">should</em> and <em class="ct">may</em> in this document
are to be interpreted as described in RFC 2119.-->
<p>The key word <em class="ct">must</em> in this document is to be
interpreted as described in RFC 2119.
[<cite><span>RFC2119</span></cite>]</p>
<p>A conforming user agent implements all the requirements made by this
specification.</p>
<h3 id="webidl">Web IDL</h3>
<p>The IDL fragments in this specification <em class="ct">must</em> be
interpreted as required for conforming IDL fragments, as described in the
Web IDL specification. [<cite><span>WebIDL</span></cite>]</p>
<h3 id="terminology">Terminology</h3>
<p><dfn><code>Document</code></dfn> and <dfn><code>Element</code></dfn>
are defined by DOM Level 3 Core. [<cite><span>DOM3Core</span></cite>]</p>
<p><dfn><code>Range</code></dfn> is defined in
DOM Level 2 Traversal and Range. [<cite><span>DOM2TR</span></cite>]</p>
<p><dfn><code>MouseEvent</code></dfn> is defined in DOM Level 2 Events.
[<cite><span>DOM2Events</span></cite>]</p>
<p>
<dfn>Compare lists of media queries</dfn> and
<dfn>parse a list of media queries</dfn>
are defined by the CSSOM. [<cite><span>CSSOM</span></cite>]</p>
<p>
<dfn id="fire-a-simple-event" title="Fire a simple event">Firing a simple event named <var title="">e</var></dfn>,
<dfn>HTML element</dfn>,
<dfn><code>HTMLElement</code></dfn>,
<dfn>queue a task</dfn>,
<dfn>quirks mode</dfn>,
<dfn>task</dfn>, and
<dfn><code>Window</code></dfn>
are defined by HTML5. [<cite><span>HTML5</span></cite>]</p>
<p><dfn>The HTML <code>body</code> element</dfn> is the first
<code>body</code> <span>HTML element</span> child of the root
<span>HTML element</span> <code>html</code>.</p>
<p><dfn id="content-edge">Content edge</dfn>,
<dfn id="padding-edge">padding edge</dfn>,
<dfn id="border-edge">border edge</dfn>, and
<dfn id="canvas">canvas</dfn> are defined by CSS 2.1.
[<cite><span>CSS21</span></cite>]</p>
<p><dfn id="viewport">Viewport</dfn> and
<dfn id="initial-containing-block">initial containing block</dfn> are
defined by CSS 2.1 unless there is an ancestor <code>foreignObject</code>
element in the <code>http://www.w3.org/2000/svg</code> namespace in which
case that element acts as viewport and initial containing block.
[<cite><span>CSS21</span></cite>]
[<cite><span>SVG</span></cite>]</p>
<p>The term <dfn>content</dfn> refers to the dimensions of the element's
content area, including overflown content.
[<cite><span>CSS21</span></cite>]</p>
<p>The term <dfn>document content</dfn> refers to the area on the
<span>canvas</span> that is rendered upon, excluding content on negative
axis.</p>
<h3>CSS pixels</h3>
<p>All coordinates and dimensions for the APIs defined in this
specification are in CSS pixels. [<cite><span>CSS21</span></cite>]</p>
<p class="note">This does not apply to e.g.
<code title="dom-Window-matchMedia">matchMedia()</code> as the units
are explicitly given there.</p>
<h2 id="extensions-to-the-window-interface">Extensions to the <code title="">Window</code> Interface</h2>
<pre class="idl">[Supplemental] interface <span>Window</span> {
<span>MediaQueryList</span> <span>matchMedia</span>(DOMString <var title="">media_query_list</var>);
readonly attribute <span>Screen</span> <span title="dom-Window-screen">screen</span>;
// viewport
readonly attribute long <span>innerWidth</span>;
readonly attribute long <span>innerHeight</span>;
readonly attribute long <span>pageXOffset</span>;
readonly attribute long <span>pageYOffset</span>;
void <span title="dom-Window-scroll">scroll</span>(long <var title="">x</var>, long <var title="">y</var>);
void <span title="dom-Window-scrollto">scrollTo</span>(long <var title="">x</var>, long <var title="">y</var>);
void <span title="dom-Window-scrollby">scrollBy</span>(long <var title="">x</var>, long <var title="">y</var>);
// client
readonly attribute long <span>screenX</span>;
readonly attribute long <span>screenY</span>;
readonly attribute long <span>outerWidth</span>;
readonly attribute long <span>outerHeight</span>;
};</pre>
<p>When the
<dfn id="dom-window-matchmedia" title="dom-Window-matchMedia"><code>matchMedia(<var title="">media_query_list</var>)</code></dfn>
method is invoked these steps must be run:</p>
<ol>
<li><p>Let <var title="">parsed_media_query_list</var> be the result of
<span title="parse a list of media queries">parsing</span>
<var title="">media_query_list</var>.</p></li>
<li><p>Return a <em>new</em> <code>MediaQueryList</code> object,
associated with the <code>Window</code> object, with
<var title="">parsed_media_query_list</var> as its associated
media query list.</p></li>
</ol>
<p>The
<dfn id="dom-window-screen" title="dom-Window-screen"><code>screen</code></dfn>
attribute <em class="ct">must</em> return the <code>Screen</code> object
associated with the <code>Window</code> object. It always returns the same
object.</p>
<p class="note">Accessing <code title="dom-Window-screen">screen</code> through a <code>WindowProxy</code> object might yield different results
when the <code>Document</code> is navigated.</p>
<p>The <dfn id="dom-window-innerwidth"><code>innerWidth</code></dfn>
attribute <em class="ct">must</em> return the
<span>viewport</span> width including the size of a rendered scroll bar
(if any).</p>
<div class="example">
<p>The following snippet shows how to obtain the width of the
viewport:</p>
<pre><code>var viewportWidth = innerWidth</code></pre>
</div>
<p>The <dfn id="dom-window-innerheight"><code>innerHeight</code></dfn>
attribute <em class="ct">must</em> return the
<span>viewport</span> height including the size of a rendered scroll bar
(if any).</p>
<p>The <dfn id="dom-window-pagexoffset"><code>pageXOffset</code></dfn>
attribute <em class="ct">must</em> return the x-coordinate,
relative to the <span>initial containing block</span> origin, of the left
of the <span>viewport</span>.</p>
<p>The <dfn id="dom-window-pageyoffset"><code>pageYOffset</code></dfn>
attribute <em class="ct">must</em> return the y-coordinate,
relative to the <span>initial containing block</span> origin, of the top
of the <span>viewport</span>.</p>
<p>When the
<dfn id="dom-window-scroll" title="dom-Window-scroll"><code>scroll(<var title="">x</var>,<var title="">y</var>)</code></dfn>
method is invoked these steps <em class="ct">must</em> be run:</p>
<ol>
<li><p>If either <var title="">x</var> or <var title="">y</var> is
infinite or NaN stop this algorithm.</p></li>
<li>
<dl>
<dt>If <span>document content</span> can have overflow to the right
<dd>
<ol>
<li><p>Let <var title="">x</var> be min(<var title="">x</var>,
<span>content</span> width - <span>content edge</span>
width).</p></li>
<li><p>If <var title="">x</var> is negative let it be zero.</p></li>
</ol>
<dt>If <span>document content</span> can have overflow to the left
(under right-to-left conditions)
<dd>
<ol>
<li><p>Let <var title="">x</var> be max(<var title="">x</var>,
<span>content edge</span> width - <span>content</span>
width).</p></li>
<li><p>If <var title="">x</var> is non-negative let it be
zero.</p></li>
</ol>
</dl>
<li><p>Let <var title="">y</var> be min(<var title="">y</var>,
<span>document content</span> height - <span>viewport</span>
height excluding the size of a rendered scroll bar (if any)).</p></li>
<li><p>If <var title="">y</var> is negative let it be zero.</p></li>
<li><p>Align the x-coordinate <var title="">x</var> of the
<span>document content</span> with the left of the <span>viewport</span>
and align the y-coordinate <var title="">y</var> of the <span>document
content</span> with the top of the <span>viewport</span>.</p></li>
<li><p>If the aligning caused content to move <span>queue a task</span>
to <span>fire a simple event</span> named
<code title="event-scroll">scroll</code> that bubbles at the
<code>Document</code> object, unless a
<span>task</span> to fire that event at the <code>Document</code> object
was already <span title="queue a task">queued</span>.</p></li>
</ol>
<p>When the
<dfn id="dom-window-scrollto" title="dom-Window-scrollto"><code>scrollTo(<var title="">x</var>,<var title="">y</var>)</code></dfn>
method is invoked, the user agent <em class="ct">must</em> act as if the
<code title="dom-Window-scroll">scroll()</code> method was invoked with
the same arguments.</p>
<p>When the
<dfn id="dom-window-scrollby" title="dom-Window-scrollby"><code>scrollBy(<var title="">x</var>,<var title="">y</var>)</code></dfn>
method is invoked, the user agent <em class="ct">must</em> act as if the
<code title="dom-Window-scroll">scroll()</code> method was invoked with
<var title="">x</var> plus <code>pageXOffset</code> as first argument and
<var title="">y</var> plus <code>pageYOffset</code> as second
argument.</p>
<p>The <dfn id="dom-window-screenx"><code>screenX</code></dfn>
attribute <em class="ct">must</em> return the x-coordinate,
relative to the origin of
8026
the screen of the output device, of the top of
the client window as number of pixels, or zero if there is no such
thing.</p>
<p>The <dfn id="dom-window-screeny"><code>screenY</code></dfn>
attribute <em class="ct">must</em> return the y-coordinate,
relative to the origin of the screen of the output device, of the left of
the client window as number of pixels, or zero if there is no such
thing.</p>
<p>The <dfn id="dom-window-outerwidth"><code>outerWidth</code></dfn>
attribute <em class="ct">must</em> return the width of the
client window. If there is no client window this
attribute <em class="ct">must</em> return zero.</p>
<p>The <dfn id="dom-window-outerheight"><code>outerHeight</code></dfn>
attribute <em class="ct">must</em> return the height of the
client window. If there is no client window
this attribute <em class="ct">must</em> return zero.</p>
<h3 id="the-mediaquerylist-interface">The <code title="">MediaQueryList</code> Interface</h3>
<p>A <code>MediaQueryList</code> object has an associated media query list
set on creation and an associated
<dfn>list of media query list listeners</dfn>, which is initially
empty.</p>
<p>If the associated media query list changes in evaluation then, for each
listener in the <span>list of media query list listeners</span> — in
appending order, <span>queue a task</span> that invokes the listener,
passing as argument the <code>MediaQueryList</code> object.</p>
<div class="example">
<p>A simple piece of code that detects changes in the orientation of the
viewport can be written as follows:</p>
<pre><code>function handleOrientationChange(mql) {
if(mql.matches) // landscape
…
else
…
}
var mql = matchMedia("(orientation:landscape)")
mql.addListener(handleOrientationChange)</code></pre>
</div>
<pre class="idl">interface <dfn id="mediaquerylist">MediaQueryList</dfn> {
readonly attribute DOMString <span title="dom-MediaQueryList-media">media</span>;
readonly attribute DOMString <span title="dom-MediaQueryList-matches">matches</span>;
void <span title="dom-MediaQueryList-addListener">addListener</span>(<span>MediaQueryListListener</span> <var title="">listener</var>);
void <span title="dom-MediaQueryList-removeListener">removeListener</span>(<span>MediaQueryListListener</span> <var title="">listener</var>);
};
[Callback=FunctionOnly, NoInterfaceObject]
interface <dfn id="mediaquerylistlistener">MediaQueryListListener</dfn> {
void <span>handleChange</span>(<span>MediaQueryList</span> <var title="">mql</var>);
};</pre>
<p>The
<dfn id="dom-MediaQueryList-media" title="dom-MediaQueryList-media"><code>media</code></dfn>
<em class="ct">must</em> return the
<span title="serialize a media query list">serialized</span> form of the associated media query list.</p>
<p>The
<dfn id="dom-MediaQueryList-matches" title="dom-MediaQueryList-matches"><code>matches</code></dfn>
<em class="ct">must</em> return true if the associated media query list
matches the state of the rendered <code>Document</code> and false if it
does not.</p>
<p>When the
<dfn id="dom-mediaquerylist-addlistener" title="dom-MediaQueryList-addListener"><code>addListener(<var title="">listener</var>)</code></dfn>
is invoked <var title="">listener</var> <em class="ct">must</em> be
appended to the <span>list of media query list listeners</span>.</p>
<p>When the
<dfn id="dom-mediaquerylist-removelistener" title="dom-MediaQueryList-removeListener"><code>removeListener(<var title="">listener</var>)</code></dfn>
is invoked the last listener in the
<span>list of media query list listeners</span> that matches
<var title="">listener</var> <e class="ct">must</em> be removed from the
<span>list of media query list listeners</span>.</p>
<h3 id="the-screen-interface">The <code title="">Screen</code> Interface</h3>
<p>As its name suggests, the <code>Screen</code> interface represents
information about the screen of the output device.</p>
<pre class="idl">interface <dfn id="screen">Screen</dfn> {
readonly attribute unsigned long <span>availWidth</span>;
readonly attribute unsigned long <span>availHeight</span>;
readonly attribute unsigned long <span>width</span>;
readonly attribute unsigned long <span>height</span>;
readonly attribute unsigned long <span>colorDepth</span>;
readonly attribute unsigned long <span>pixelDepth</span>;
};</pre>
<p>The <dfn id="dom-screen-availwidth"><code>availWidth</code></dfn>
attribute <em class="ct">must</em> return the available width of the
rendering surface of the output device.</p>
<p>The <dfn id="dom-screen-availheight"><code>availHeight</code></dfn>
attribute <em class="ct">must</em> return the available height of the
rendering surface of the output device.</p>
<p>The <dfn id="dom-screen-width"><code>width</code></dfn> attribute
<em class="ct">must</em> return the width of the output device.</p>
<p>The <dfn id="dom-screen-height"><code>height</code></dfn> attribute
<em class="ct">must</em> return the height of the output device.</p>
<p>The <dfn id="dom-screen-colordepth"><code>colorDepth</code></dfn> and
<dfn id="dom-screen-pixeldepth"><code>pixelDepth</code></dfn> attributes
<em class="ct">must</em> both return the number of bits allocated to
colors (i.e. excluding the alpha channel) in the output device. If the
output device does not support colors these attributes
<em class="ct">must</em> return zero.</p>
<!-- pixelDepth is not supported by Internet Explorer 7 -->
<h2 id="extensions-to-the-document-interface">Extensions to the <code title="">Document</code> Interface</h2>
<pre class="idl">[Supplemental] interface <span>Document</span> {
Element <span>elementFromPoint</span>(float <var title="">x</var>, float <var title="">y</var>);
<span>CaretPosition</span> <span>caretPositionFromPoint</span>(float <var title="">x</var>, float <var title="">y</var>);
};</pre>
<p>The
<dfn id="dom-document-elementfrompoint" title="elementfrompoint"><code>elementFromPoint(<var title="">x</var>,
<var title="">y</var>)</code></dfn> method, when invoked,
<em class="ct">must</em> return the element at coordinates
<var>x</var>,<var>y</var> in the <span>viewport</span>. The element to be
returned is determined through hit testing. If either argument is
negative, <var title="">x</var> is greater than the <span>viewport</span>
width excluding the size of a rendered scroll bar (if any), or
<var title="">y</var> is greather than the <span>viewport</span> height
excluding the size of a rendered scroll bar (if any), the method
<em class="ct">must</em> return <code>null</code>. If there is no element
at the given position the method <em class="ct">must</em> return the root
element, if any, or <code>null</code> otherwise.</p>
<p>The
<dfn id="dom-document-caretpositionfrompoint" title="caretpositionfrompoint"><code>caretPositionFromPoint(&
EB5C
lt;var title="">x</var>,
<var title="">y</var>)</code></dfn> method, when invoked,
<em class="ct">must</em> return the result of running these steps:</p>
<ol>
<li><p>If either argument is negative, <var title="">x</var> is greater
than the <span>viewport</span> width excluding the size of a rendered
scroll bar (if any), <var title="">y</var> is greather than the
<span>viewport</span> height excluding the size of a rendered scroll bar
(if any) return null.</p></li>
<li><p>If at the coordinates <var title="">x</var>,<var title="">y</var>
in the <span>viewport</span> no text insertion point indicator would have
been inserted return null.</p></li>
<li>
<p>If at the coordinates <var title="">x</var>,<var title="">y</var>
in the <span>viewport</span> a text insertion point indicator would have
been inserted in a text entry widget which is also a replaced element
return a <span>caret position</span> with its properties set as
follows:</p>
<dl>
<dt><span>caret node</span></dt>
<dd><p>The node corresponding to the text entry widget.</p></dd>
<dt><span>caret offset</span></dt>
<dd><p>The amount of 16-bit units to the left of where the
text insertion point indicator would have inserted.</p></dd>
<dt><span>caret range</span></dt>
<dd><p>null</p></dd>
</dl>
</li>
<li>
<p>Otherwise, return a <span>caret position</span> where the
<span>caret range</span> is a collapsed <code>Range</code> object for
the position where the text insertion point indicator would have been
inserted and the other properties are set as follows:</p>
<dl>
<dt><span>caret node</span></dt>
<dd><p>The <code title="dom-Range-startContainer">startContainer</code>
of the <span>caret range</span>.</p></dd>
<dt><span>caret offset</span></dt>
<dd><p>The <code title="dom-Range-startOffset">startOffset</code> of
the <span>caret range</span>.</p>
</dl>
</li>
</ol>
<p class="note">The specifics of hit testing are out of scope of this
specification and therefore the exact details of
<code>elementFromPoint()</code> and <code>caretPositionFromPoint()</code>
are therefore too. Hit testing will hopefully be defined in a future
revision of CSS or HTML.</p>
<h3 id="the-caretposition-interface">The <code title="">CaretPosition</code> Interface</h3>
<p>A <dfn>caret position</dfn> gives the position of a
text insertion point indicator. It always has an associated
<dfn>caret node</dfn>, <dfn>caret offset</dfn>, and
<dfn>caret range</dfn>. It is represented by a <code>CaretPosition</code>
object.</p>
<pre class="idl">interface <dfn id="caretposition">CaretPosition</dfn> {
readonly attribute <span>Node</span> <span title="dom-CaretPosition-offsetNode">offsetNode</span>;
readonly attribute unsigned long <span title="dom-CaretPosition-offset">offset</span>;
readonly attribute <span>Range</span> <span title="dom-CaretPosition-range">range</span>;
};</pre>
<p>The
<dfn id="dom-caretposition-offsetnode" title="dom-CaretPosition-offsetNode"><code>offsetNode</code></dfn>
attribute <em class="ct">must</em> return the <span>caret node</span>.</p>
<p>The
<dfn id="dom-caretposition-offset" title="dom-CaretPosition-offset"><code>offset</code></dfn>
attribute <em class="ct">must</em> return the <span>caret offset</span>.</p>
<p>The
<dfn id="dom-caretposition-range" title="dom-CaretPosition-range"><code>range</code></dfn>
attribute <em class="ct">must</em> return the <span>caret range</span>.</p>
<!-- https://bugs.webkit.org/show_bug.cgi?id=27046 -->
<h2 id="extensions-to-the-element-interface">Extensions to the <code title="">Element</code> Interface</h2>
<pre class="idl">[Supplemental] interface <span>Element</span> {
<span>ClientRectList</span> <span>getClientRects</span>();
<span>ClientRect</span> <span>getBoundingClientRect</span>();
attribute long <span>scrollTop</span>; // scroll on setting
attribute long <span>scrollLeft</span>; // scroll on setting
readonly attribute long <span>scrollWidth</span>;
readonly attribute long <span>scrollHeight</span>;
readonly attribute long <span>clientTop</span>;
readonly attribute long <span>clientLeft</span>;
readonly attribute long <span>clientWidth</span>;
readonly attribute long <span>clientHeight</span>;
};</pre>
<h3>The <code title="">getClientRects()</code> and
<code title="">getBoundingClientRect()</code> methods</h3>
<p>The <code>getClientRects()</code> and <code>getBoundingClientRect()</code>
methods provide information about the position of the border box edges of
an element relative to the viewport. The objects these methods return
<em class="ct">must</em> be static. That is, changes to the underlying
document are not reflected in the objects.</p>
<p>The
<dfn id="dom-element-getclientrects"><code>getClientRects()</code></dfn>
method, when invoked, <em class="ct">must</em> return the result of the
following algorithm:</p>
<ol>
<li><p>If the element on which it was invoked does not have an associated
CSS layout box and is not in the <code>http://www.w3.org/2000/svg</code>
namespace return an empty <code>ClientRectList</code> object and stop
this algorithm.</p></li>
<li><p>If the element does not have an associated CSS layout box and is
in the <code>http://www.w3.org/2000/svg</code> namespace return a
<code>ClientRectList</code> object containing a single
<code>ClientRect</code> object that describes the bounding box of the
element as defined by the SVG specification.
[<cite><span>SVG</span></cite>]</p></li>
<li>
<p>Return a <code>ClientRectList</code> object containing a list of
<code>ClientRect</code> objects in content order describing the border
boxes (including those with a height or width of zero) with the
following constraints:</p>
<ul>
<li><p>If the element on which the method was invoked has a computed
value for <code>display</code> property of <code>table</code> or
<code>inline-table</code> include both the table box and the caption
box, if any, but not the anonymous container box.
[<cite><span>CSS21</span></cite>]</p></li>
<li><p>Replace each
<a href="http://www.w3.org/TR/CSS21/visuren.html#anonymous-block-level">anonymous
block box</a> with its child box(es) and repeat this until no anonymous
block boxes are left in the final list.
[<cite><span>CSS21</span></cite>]</p></li>
</ul>
</li>
</ol>
<p>The
<dfn id="dom-element-getboundingclientrect"><code>getBoundingClientRect()</code></dfn>
method, when invoked, <em class="ct">must</em> return the result of the
following algorithm:</p>
<ol>
<li><p>Let <var>list</var> be the result of invoking
<code>getClientRects()</code> on the same element this method was invoked
on.</p></li>
<li><p>If the <var>list</var> is empty return a <code>ClientRect</code>
object whose <code title="dom-clientrect-top">top</code>,
<code title="dom-clientrect-right">right</code>,
<code title="dom-clientrect-bottom">bottom</code> and
<code title="dom-clientrect-left">left</code> members are zero.</p></li>
<li><p>Otherwise, return a <code>ClientRect</code> object describing the
smallest rectangle that includes the first rectangle in <var>list</var>
and all of the remaining rectangles of which the height or width is not
zero.</p></li>
</ol>
<div class="example">
<p>The following snippet gets the dimensions of the first
<code>div</code> element in a document:</p>
<pre><code>var example = document.getElementsByTagName("div")[0].getBoundingClientRect();
var exampleWidth = example.width;
var exampleHeight = example.height;</code></pre>
</div>
<h3 id="scroll-attributes">The <code title="">scrollTop</code>,
<code title="">scrollLeft</code>, <code title="">scrollWidth</code>, and
<code title="">scrollHeight</code> attributes</h3>
<p>The <dfn id="dom-element-scrolltop"><code>scrollTop</code></dfn>
attribute <em class="ct">must</em> return the result of running these
steps:</p>
<ol>
<li><p>If the element does not have any associated CSS layout box or the
element is the root element and the <code>Document</code> is in
<span>quirks mode</span> return zero and terminate these steps.</p></li>
<li><p>If the element is the root element return the value of
<code>pageYOffset</code>.</p></li>
<li><p>If the element is <span>the HTML <code>body</code> element</span>,
the <code>Document</code> is in <span>quirks mode</span>, and the element
does not have any overflow, return the value of
<code>pageYOffset</code>.</p></li>
<li><p>Return the y-coordinate of the <span>content</span> at the
alignment point with the top of the <span>content edge</span> of the
element.</p></li>
</ol>
<p>When setting the <code>scrollTop</code> attribute these steps
<em class="ct">must</em> be run:</p>
<ol>
<li><p>Let <var title="">y</var> be the given value.</p></li>
<li><p>If the element does not have any associated CSS layout box, the
element is the root element and the <code>Document</code> is in
<span>quirks mode</span>, or the element has no overflow, terminate these
steps.</p></li>
<li><p>If the element is the root element invoke
<code title="dom-Window-scroll">scroll()</code> with zero as first
argument and <var title="">y</var> as second.</p></li>
<li><p>If the element is <span>the HTML <code>body</code> element</span>,
the <code>Document</code> is in <span>quirks mode</span>, and the element
does not have any vertical overflow, invoke
<code title="dom-Window-scroll">scroll()</code> with zero as first
argument and <var title="">y</var> as second.</p></li>
<li><p>If <var title="">y</var> is infinite or NaN stop this
algorithm.</p>
<li><p>Let <var title="">y</var> be max(0, min(<var title="">y</var>,
<span>content</span> height - <span>content edge</span> height)).</p></li>
<li><p>Align <span>content</span> y-coordinate <var title="">y</var> with
the top of the <span>content edge</span> of the element.</p></li>
<li><p>If the aligning caused content to move <span>queue a task</span>
to <span>fire a simple event</span> named
<code title="event-scroll">scroll</code> at the element, unless a
<span>task</span> to fire that event at the element was already
<span title="queue a task">queued</span>.</p></li>
</ol>
<p>The <dfn id="dom-element-scrollleft"><code>scrollLeft</code></dfn>
attribute <em class="ct">must</em> return the result of running these
steps:</p>
<ol>
<li><p>If the element does not have any associated CSS layout box or the
element is the root element and the <code>Document</code> is in
<span>quirks mode</span> return zero and terminate these steps.</p></li>
<li><p>If the element is the root element return the value of
<code>pageXOffset</code>.</p></li>
<li><p>If the element is <span>the HTML <code>body</code> element</span>,
the <code>Document</code> is in <span>quirks mode</span>, and the element
does not have any overflow, return the value of
<code>pageXOffset</code>.</p></li>
<li><p>Return the x-coordinate of the <span>content</span> at the
alignment point with the left of the <span>content edge</span> of the
element.</p></li>
</ol>
<p>When setting the <code>scrollLeft</code> attribute these steps
<em class="ct">must</em> be run:</p>
<ol>
<li><p>Let <var title="">x</var> be the given value.</p></li>
<li><p>If the element does not have any associated CSS layout box, the
element is the root element and the <code>Document</code> is in
<span>quirks mode</span>, or the element has no overflow, terminate these
steps.</p></li>
<li><p>If the element is the root element invoke
<code title="dom-Window-scroll">scroll()</code> with
<var title="">x</var> as first argument and zero as second.</p></li>
<li><p>If the element is <span>the HTML <code>body</code> element</span>,
the <code>Document</code> is in <span>quirks mode</span>, and the element
does not have any vertical overflow, invoke
<code title="dom-Window-scroll">scroll()</code> with
<var title="">x</var> as first argument and zero as second.</p></li>
<li><p>If <var title="">x</var> is infinite or NaN stop this
algorithm.</p>
<li>
<dl>
<dt>If the element can have overflow to the right</dt>
<dd><p>Let <var title="">x</var> be max(0, min(<var title="">x</var>,
<span>content</span> width -
<span>content edge</span> width)).</p></dd>
<dt>If the element can have overflow to the left (under right-to-left
conditions)</dt>
<dd><p>Let <var title="">x</var> be min(0, max(<var title="">x</var>,
<span>content edge</span> width -
<span>content</span> width)).</p></dd>
</dl>
</li>
<li><p>Align <span>content</span> x-coordinate <var title="">x</var> with
the left of the <span>content edge</span> of <var>A</var>.</p></li>
<li><p>If the aligning caused content to move <span>queue a task</span>
to <span>fire a simple event</span> named
<code title="event-scroll">scroll</code> at the element, unless a
<span>task</span> to fire that event at the element was already
<span title="queue a task">queued</span>.</p></li>
</ol>
<p>The <dfn id="dom-element-scrollwidth"><code>scrollWidth</code></dfn>
attribute <em class="ct">must</em> return the result of running these
steps:</p>
<ol>
<li><p>If the element does not have any associated CSS layout box return
zero and terminate these steps.</p></li>
<li><p>If the element is the root element and the <code>Document</code>
is not in <span>quirks mode</span> return the value of
<code>innerWidth</code>.</p></li>
<li><p>If the element is <span>the HTML <code>body</code> element</span>
and the <code>Document</code> is in <span>quirks mode</span> return the
value of <code>innerWidth</code>.</p></li>
<li><p>Return the computed value of the '<code>padding-left</code>'
property, plus the computed value of the '<code>padding-right</code>',
plus the <span>content</span> width of the element.</p></li>
</ol>
<p>The <dfn id="dom-element-scrollheight"><code>scrollHeight</code></dfn>
attribute <em class="ct">must</em> return the result of running these
steps:</p>
<ol>
<li><p>If the element does not have any associated CSS layout box return
zero and terminate these steps.</p></li>
<li><p>If the element is the root element and the <code>Document</code>
is not in <span>quirks mode</span> return the value of
<code>innerHeight</code>.</p></li>
<li><p>If the element is <span>the HTML <code>body</code> element</span>
and the <code>Document</code> is in <span>quirks mode</span> return the
value of <code>innerHeight</code>.</p></li>
<li><p>Return the computed value of the '<code>padding-top</code>'
property, plus the computed value of the '<code>padding-bottom</code>',
plus the <span>content</span> height of the element.</p></li>
</ol>
<!-- for inline boxes offsetWidth and offsetHeight are identical to offset* -->
<h3 id="client-attributes">The <code title="">clientTop</code>,
<code title="">clientLeft</code>, <code title="">clientWidth</code>, and
<code title="">clientHeight</code> attributes</h3>
<p>The <dfn id="dom-element-clienttop"><code>clientTop</code></dfn>,
<dfn id="dom-element-clientleft"><code>clientLeft</code></dfn>,
<dfn id="dom-element-clientwidth"><code>clientWidth</code></dfn>, and
<dfn id="dom-element-clientheight"><code>clientHeight</code></dfn>
attributes <em class="ct">must</em> return zero if the element does not
have any associated CSS layout box or if the CSS layout box is inline.
Otherwise, these attributes <em class="ct">must</em> behave as defined in
the remainder of this section.</p>
<p>The <code>clientTop</code> attribute returns the computed value of the
'<code>border-top-width</code>' property plus the width of any scrollbar
rendered between the top <span>padding edge</span> and the top
<span>border edge</span>.</p>
<p>The <code>clientLeft</code> attribute returns the computed
value of the '<code>border-left-width</code>' property plus the width of
any scrollbar rendered between the left <span>padding edge</span> and the
left <span>border edge</span>.
<p>The <code>clientWidth</code> attribute returns the
<span>viewport</span> width excluding the size of a rendered scroll bar
(if any) if the element is the root element and the
width of the <span>padding edge</span> (excluding the width of any
rendered scrollbar between the <span>padding edge</span> and the
<span>border edge</span>) otherwise.</p>
<p>The <code>clientHeight</code> attribute returns the
<span>viewport</span> height excluding the size of a rendered scroll bar
(if any) if the element is the root element and the
height of the <span>padding edge</span> (excluding the width of any
rendered scrollbar between the <span>padding edge</span> and the
<span>border edge</span>) otherwise.</p>
<h2 id="extensions-to-the-htmlelement-interface">Extensions to the <code title="">HTMLElement</code> Interface</h2>
<pre class="idl">[Supplemental] interface <span>HTMLElement</span> {
readonly attribute Element <span>offsetParent</span>;
readonly attribute long <span>offsetTop</span>;
readonly attribute long <span>offsetLeft</span>;
readonly attribute long <span>offsetWidth</span>;
readonly attribute long <span>offsetHeight</span>;
};</pre>
<h3 id="offset-attributes">The <code title="">offsetParent</code>,
<code title="">offsetTop</code>, <code title="">offsetLeft</code>,
<code title="">offsetWidth</code>, and <code title="">offsetHeight</code>
attributes</h3>
<p>The
<dfn id="dom-htmlelement-offsetparent"><code>offsetParent</code></dfn>
attribute <em class="ct">must</em> return the result of running these
steps:</p>
<ol>
<li>
<p>If any of the following holds true return null and terminate this
algorithm:</p>
<ul>
<li>The element does not have an associated CSS layout box.</li>
<li>The element is the root element.</li>
<li>The element is
<span>the HTML <code>body</code> element</span>.</li>
<li>The element's computed value of the '<code>position</code>'
property is <code>fixed</code>.</li>
</ul>
</li>
<li>
<p>Return the nearest ancestor element of the element for which at least
one of the following is true and stop this algorithm if such an ancestor
is found:</p>
<ul>
<li>The computed value of the '<code>position</code>' property is not
<code>static</code>.</li>
<li>It is <span>the HTML <code>body</code> element</span>.</li>
<li>The computed value of the '<code>position</code>' property of
the element is <code>static</code> and the ancestor is one of the
following <span title="HTML element">HTML elements</span>:
<code>td</code>, <code>th</code>, or <code>table</code>.</li>
</ul>
</li>
<li><p>Return null.</p></li>
</ol>
<p>The <dfn id="dom-htmlelement-offsettop"><code>offsetTop</code></dfn>
attribute <em class="ct">must</em> return the result of running these
steps:</p>
<ol>
<li><p>If the element is <span>the HTML <code>body</code> element</span>
or does not have any associated CSS layout box return zero and terminate
this algorithm.</p></li>
<li><p>If the <code>offsetParent</code> of the element is null return the
y-coordinate of the top <span>border edge</span> of the first
CSS layout box associated with the element, relative to the
<span>initial containing block</span> origin, and terminate this
algorithm.</p></li>
<li>
<p>Return the result of subtracting the y-coordinate of the top
<span>padding edge</span> of the first CSS layout box associated with
the <code>offsetParent</code> of the element from the y-coordinate of
the top <span>border edge</span> of the first CSS layout box associated
with the element, relative to the <span>initial containing block</span>
origin.</p>
<p class="note">An inline element that consists of multiple line boxes
will only have its first CSS layout box considered.</p>
</li>
</ol>
<p>The <dfn id="dom-htmlelement-offsetleft"><code>offsetLeft</code></dfn>
attribute <em class="ct">must</em> return the result of running these
steps:</p>
<ol>
<li><p>If the element is <span>the HTML <code>body</code>
element</span> or does not have any associated CSS layout box return zero
and terminate this algorithm.</p></li>
<li><p>If the <code>offsetParent</code> of the element is null return the
x-coordinate of the left <span>border edge</span> of the first
CSS layout box associated with the element, relative to the
<span>initial containing block</span> origin, and terminate this
algorithm.</p></li>
<li>
<p>Return the result of subtracting the x-coordinate of the left
<span>padding edge</span> of the first CSS layout box associated with
the <code>offsetParent</code> of the element from the x-coordinate of
the left <span>border edge</span> of the first CSS layout box associated
with the element, relative to the <span>initial containing block</span>
origin.</p>
</li>
</ol>
<p>The
<dfn id="dom-htmlelement-offsetwidth"><code>offsetWidth</code></dfn>
attribute <em class="ct">must</em> return the result of running these
steps:</p>
<ol>
<li><p>If the element does not have any associated CSS layout box return
zero and terminate this algorithm.</p></li>
<li><p>Return the <span>border edge</span> width of the first
CSS layout box associated with the element.</p></li>
</ol>
<p>The
<dfn id="dom-htmlelement-offsetheight"><code>offsetHeight</code></dfn>
attribute <em class="ct">must</em> return the result of running these