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<pre class='metadata'>
Title: CSSOM View Module
ED: https://drafts.csswg.org/cssom-view/
TR: https://www.w3.org/TR/cssom-view-1/
Previous Version: https://www.w3.org/TR/2016/WD-cssom-view-1-20160317/
Previous Version: https://www.w3.org/TR/2013/WD-cssom-view-20131217/
Previous Version: https://www.w3.org/TR/2011/WD-cssom-view-20110804/
Previous Version: https://www.w3.org/TR/2009/WD-cssom-view-20090804/
Previous Version: https://www.w3.org/TR/2008/WD-cssom-view-20080222/
Previous Version: https://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/
Group: CSSWG
Status: ED
Work Status: Revising
Shortname: cssom-view
Level: 1
Editor: Simon Pieters, Opera Software ASA http://www.opera.com, simonp@opera.com
Former Editor: Glenn Adams, Cox Communications, Inc. http://www.cox.com, glenn.adams@cos.com, http://www.w3.org/wiki/User:Gadams
Former Editor: Anne van Kesteren, Opera Software ASA http://www.opera.com, annevk@annevk.nl, https://annevankesteren.nl/
!Issues list: <a href="https://www.w3.org/Bugs/Public/buglist.cgi?product=CSS&component=CSSOM%20View&resolution=---">Bugzilla</a> (<a href="https://www.w3.org/Bugs/Public/enter_bug.cgi?product=CSS&component=CSSOM%20View">file a bug</a>)
Abstract: 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.
Ignored Terms: open(), EventTarget, EventListener, Event, EventInit, Element, Range, Node, Text
Ignored Vars: rect, point, quad
</pre>
<pre class='anchors'>
urlPrefix: https://html.spec.whatwg.org/multipage/
urlPrefix: infrastructure.html
type: dfn; text: html elements
urlPrefix: browsers.html
type: interface; text: WindowProxy
type: dfn
text: browsing context
text: auxiliary browsing context
text: familiar with
text: associated Document; url: concept-document-window
text: same origin
text: active document
urlPrefix: webappapis.html
type: dfn
text: responsible browsing context
text: incumbent settings object
text: event handlers
text: event handler event type
text: event handler IDL attributes
urlPrefix: infrastructure.html
type: dfn
text: split a string on commas
text: skip whitespace
text: collect a sequence of characters
text: space character
text: converted to ascii lowercase
text: rules for parsing integers
urlPrefix: https://drafts.csswg.org/cssom/
type: dfn
text: parse a media query list
text: serialize a media query list
urlPrefix: https://dom.spec.whatwg.org/#
type: dfn
text: context object
urlPrefix: https://dom.spec.whatwg.org/#concept-
type: dfn
text: dispatch; url: event-dispatch
text: event
text: event listener
text: quirks mode; url: document-quirks
text: fire an event; url: event-fire
text: node document
urlPrefix: https://dom.spec.whatwg.org/
type: attribute;
for: Event; urlPrefix: #dom-event-
text: type
text: isTrusted
for: Range; urlPrefix: #dom-range-
text: startContainer
text: startOffset
type: dfn; text: dispatch flag
urlPrefix: https://www.w3.org/TR/CSS21/visuren.html
type: dfn; text: anonymous block box; url: #anonymous-block-level
urlPrefix: http://heycam.github.io/webidl/
type: interface; urlPrefix: #idl-
text: double
text: long
type: dfn; text: converted to an IDL value; url: dfn-convert-ecmascript-to-idl-value
url: https://www.w3.org/TR/DOM-Level-3-Events/#interface-MouseEvent; type: interface; text: MouseEvent
</pre>
<pre class='link-defaults'>
spec:css-display-3; type:value; for:display; text:table
spec:css-position-3; type:property; text:position
spec:dom; type:interface; text:Document
</pre>
<script src=https://resources.whatwg.org/file-bug.js async></script>
Background {#background}
========================
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!)
Terminology {#terminology}
==========================
Terminology used in this specification is from
DOM,
CSSOM and
HTML.
[[!DOM]]
[[!CSSOM]]
[[!HTML]]
<dfn>The HTML <code>body</code> element</dfn> is the first
<code>body</code>
<a>HTML element</a> child of the root
<a>HTML element</a> <code>html</code>.
<dfn>Content edge</dfn>, <dfn>padding edge</dfn>, <dfn>border edge</dfn>, <dfn>margin edge</dfn>, and <dfn>viewport</dfn> are defined by CSS.
<!-- These *should* just link to CSS2.1, but it doesn't have actual anchors to link to, because it's THE WORST. -->
Elements and <a>viewports</a> have an associated <dfn>scrolling box</dfn> if has a scrolling mechanism<!--XXX xref--> or it overflows
its content area<!--XXX xref--> and the used value of the 'overflow-x' or 'overflow-y' property is ''overflow/hidden''. [[!CSS3-BOX]]
An element is <dfn>potentially scrollable</dfn> if all of the following conditions are true:
* The element has an associated <a>CSS layout box</a>.
* The element is not <a>the HTML <code>body</code> element</a>, or it is and
the root element's used value of the 'overflow-x' or 'overflow-y' properties is not ''overflow/visible''.
* The element's used value of the 'overflow-x' or 'overflow-y' properties is not ''overflow/visible''.
Note: An element that is <a>potentially scrollable</a> might not have a <a>scrolling box</a>.
For instance, it could have 'overflow' set to ''overflow/auto'' but not have its content overflowing its content area.
A <a>scrolling box</a> of a <a>viewport</a> or element has two <dfn>overflow directions</dfn>, depending on the <a>viewport’s</a> or
element's <a>block flow direction</a> and <a>inline base direction</a>, as follows:
<dl class=switch>
<dt>If the <a>block flow direction</a> is top-to-bottom and the <a>inline base direction</a> is left-to-right
<dt>If the <a>block flow direction</a> is left-to-right and the <a>inline base direction</a> is left-to-right
<dd>Rightward and downward.
<dt>If the <a>block flow direction</a> is top-to-bottom and the <a>inline base direction</a> is right-to-left
<dt>If the <a>block flow direction</a> is right-to-left and the <a>inline base direction</a> is left-to-right
<dd>Leftward and downward.
<dt>If the <a>block flow direction</a> is right-to-left and the <a>inline base direction</a> is right-to-left
<dd>Leftward and upward.
<dt>If the <a>block flow direction</a> is left-to-right and the <a>inline base direction</a> is right-to-left
<dd>Rightward and upward.
</dl>
The term <dfn>scrolling area</dfn> refers to a box of a <a>viewport</a> or an element that has the following edges, depending on the
<a>viewport’s</a> or element's <a>scrolling box’s</a> <a>overflow directions</a>.
<table class="complex data">
<thead>
<tr>
<th>If the <a>overflow directions</a> are…
<th>For a <a>viewport</a>
<th>For an element
<tbody>
<tr>
<td>rightward and downward
<td class=long>
<dl>
<dt>top edge
<dd>The top edge of the <a>initial containing block</a>.
<dt>right edge
<dd>The right-most edge of the right edge of the <a>initial containing block</a> and the right
<a>margin edge</a> of all of the <a>viewport’s</a> descendants' boxes.
<dt>bottom edge
<dd>The bottom-most edge of the bottom edge of the <a>initial containing block</a> and the
bottom <a>margin edge</a> of all of the <a>viewport’s</a> descendants' boxes.
<dt>left edge
<dd>The left edge of the <a>initial containing block</a>.
</dl>
<td class=long>
<dl>
<dt>top edge
<dd>The element's top <a>padding edge</a>.
<dt>right edge
<dd>The right-most edge of the element's right <a>padding edge</a> and the right <a>margin
edge</a> of all of the element's descendants' boxes,
excluding boxes that have an ancestor of the element as their containing block.
<dt>bottom edge
<dd>The bottom-most edge of the element's bottom <a>padding edge</a> and the bottom <a>margin
edge</a> of all of the element's descendants'
boxes, excluding boxes that have an ancestor of the element as their containing block.
<dt>left edge
<dd>The element's left <a>padding edge</a>.
</dl>
<tr>
<td>leftward and downward
<td class=long>
<dl>
<dt>top edge
<dd>The top edge of the <a>initial containing block</a>.
<dt>right edge
<dd>The right edge of the <a>initial containing block</a>.
<dt>bottom edge
<dd>The bottom-most edge of the bottom edge of the <a>initial containing block</a> and the
bottom <a>margin edge</a> of all of the <a>viewport’s</a> descendants' boxes.
<dt>left edge
<dd>The left-most edge of the left edge of the <a>initial containing block</a> and the left
<a>margin edge</a> of all of the <a>viewport’s</a> descendants' boxes.
</dl>
<td class=long>
<dl>
<dt>top edge
<dd>The element's top <a>padding edge</a>.
<dt>right edge
<dd>The element's right <a>padding edge</a>.
<dt>bottom edge
<dd>The bottom-most edge of the element's bottom <a>padding edge</a> and the bottom <a>margin
edge</a> of all of the element's descendants' boxes, excluding boxes that have an ancestor of
the element as their containing block.
<dt>left edge
<dd>The left-most edge of the element's left <a>padding edge</a> and the left <a>margin
edge</a> of all of the element's descendants' boxes, excluding boxes that have an ancestor of
the element as their containing block.
</dl>
<tr>
<td>leftward and upward
<td class=long>
<dl>
<dt>top edge
<dd>The top-most edge of the top edge of the <a>initial containing block</a> and the top
<a>margin edge</a> of all of the <a>viewport’s</a> descendants' boxes.
<dt>right edge
<dd>The right edge of the <a>initial containing block</a>.
<dt>bottom edge
<dd>The bottom edge of the <a>initial containing block</a>.
<dt>left edge
<dd>The left-most edge of the left edge of the <a>initial containing block</a> and the left
<a>margin edge</a> of all of the <a>viewport’s</a> descendants' boxes.
</dl>
<td class=long>
<dl>
<dt>top edge
<dd>The top-most edge of the element's top <a>padding edge</a> and the top <a>margin edge</a>
of all of the element's descendants' boxes, excluding boxes that have an ancestor of the
element as their containing block.
<dt>right edge
<dd>The element's right <a>padding edge</a>.
<dt>bottom edge
<dd>The element's bottom <a>padding edge</a>.
<dt>left edge
<dd>The left-most edge of the element's left <a>padding edge</a> and the left <a>margin
edge</a> of all of the element's descendants' boxes, excluding boxes that have an ancestor of
the element as their containing block.
</dl>
<tr>
<td>rightward and upward
<td class=long>
<dl>
<dt>top edge
<dd>The top-most edge of the top edge of the <a>initial containing block</a> and the top
<a>margin edge</a> of all of the <a>viewport’s</a> descendants' boxes.
<dt>right edge
<dd>The right-most edge of the right edge of the <a>initial containing block</a> and the right
<a>margin edge</a> of all of the <a>viewport’s</a> descendants' boxes.
<dt>bottom edge
<dd>The bottom edge of the <a>initial containing block</a>.
<dt>left edge
<dd>The left edge of the <a>initial containing block</a>.
</dl>
<td class=long>
<dl>
<dt>top edge
<dd>The top-most edge of the element's top <a>padding edge</a> and the top <a>margin edge</a>
of all of the element's descendants' boxes, excluding boxes that have an ancestor of the
element as their containing block.
<dt>right edge
<dd>The right-most edge of the element's right <a>padding edge</a> and the right <a>margin
edge</a> of all of the element's descendants' boxes, excluding boxes that have an ancestor of
the element as their containing block.
<dt>bottom edge
<dd>The element's bottom <a>padding edge</a>.
<dt>left edge
<dd>The element's left <a>padding edge</a>.
</dl>
</table>
The <dfn lt="scrolling area origin">origin</dfn> of a <a>scrolling area</a> is
the origin of the <a>initial containing block</a> if the <a>scrolling area</a> is a <a>viewport</a>,
and otherwise the top left padding edge of the element when the element has its default scroll position.
The x-coordinate increases rightwards, and the y-coordinate increases downwards.
The <dfn>beginning edges</dfn> of a particular set of edges of a box or element are the following edges:
<dl class=switch>
<dt>If the <a>overflow directions</a> are rightward and downward
<dd>The top and left edges.
<dt>If the <a>overflow directions</a> are leftward and downward
<dd>The top and right edges.
<dt>If the <a>overflow directions</a> are leftward and upward
<dd>The bottom and right edges.
<dt>If the <a>overflow directions</a> are rightward and upward
<dd>The bottom and left edges.
</dl>
The <dfn>ending edges</dfn> of a particular set of edges of a box or element are the following edges:
<dl class=switch>
<dt>If the <a>overflow directions</a> are rightward and downward
<dd>The bottom and right edges.
<dt>If the <a>overflow directions</a> are leftward and downward
<dd>The bottom and left edges.
<dt>If the <a>overflow directions</a> are leftward and upward
<dd>The top and left edges.
<dt>If the <a>overflow directions</a> are rightward and upward
<dd>The top and right edges.
</dl>
The term <dfn>CSS layout box</dfn> refers to the same term in CSS. For the purpose
of the requirements in this specification, elements that have a computed value of the
'display' property that is ''table-column'' or
''table-column-group'' must be considered to have an associated <a>CSS layout box</a> (the column or column group, respectively).
The term <dfn>SVG layout box</dfn> refers to the same term in SVG.
<p class=issue>The terms <a>CSS layout box</a> and <a>SVG layout box</a> are not currently defined by CSS or SVG.
The term <dfn>layout box</dfn> refers to either a <a>CSS layout box</a> or an <a>SVG layout box</a>.
The term <dfn>transforms</dfn> refers to SVG transforms and CSS transforms. [[!SVG]] [[!CSS-TRANSFORMS-1]]
When a method or an attribute is said to call another method or attribute, the user agent must invoke its internal API for that attribute or method so that
e.g. the author can't change the behavior by overriding attributes or methods with custom properties or functions in ECMAScript.
Unless otherwise stated, string comparisons are done in a <a>case-sensitive</a> manner.
CSS pixels {#css-pixels}
------------------------
All coordinates and dimensions for the APIs defined in this
specification are in CSS pixels, unless otherwise specified. <!--[[!CSS]]-->
Note: This does not apply to e.g. {{matchMedia()}} as the units are explicitly given there.
Zooming {#zooming}
------------------
There are two kinds of zoom, <dfn>page zoom</dfn> which affects the size of the initial viewport<!-- XXX ref -->, and <dfn>pinch zoom</dfn> which acts like
a magnifying glass and does not affect the initial viewport<!-- XXX ref --> or actual viewport<!-- XXX ref -->. [[!CSS-DEVICE-ADAPT]]
Common Infrastructure {#common-infrastructure}
==============================================
Scrolling {#scrolling}
----------------------
When a user agent is to <dfn>perform a scroll</dfn> of a <a>scrolling box</a> <var>box</var>,
to a given position <var>position</var>,
an associated element <var>element</var> and optionally a scroll behavior <var>behavior</var>
(which is <code>"auto"</code> if omitted),
the following steps must be run:
<ol>
<li><a lt="smooth scroll aborted">Abort</a> any ongoing <a>smooth scroll</a> for <var>box</var>.
<li>If the user agent honors the 'scroll-behavior' property and one of the following are true:
<ul>
<li><var>behavior</var> is <code>"auto"</code> and <var>element</var> is not null and its computed value of the
'scroll-behavior' property is ''smooth''
<li><var>behavior</var> is <code>smooth</code>
</ul>
...then perform a <a>smooth scroll</a> of <var>box</var> to <var>position</var>.
Otherwise, perform an <a>instant scroll</a> of <var>box</var> to <var>position</var>.
</ol>
When a user agent is to perform a <dfn id=concept-smooth-scroll>smooth scroll</dfn> of a <a>scrolling box</a> <var>box</var> to <var>position</var>,
it must update the scroll position of <var>box</var> in a user-agent-defined fashion over a user-agent-defined amount of time. When the scroll is
<dfn lt="smooth scroll completed">completed</dfn>, the scroll position of <var>box</var> must be <var>position</var>. The scroll can also
be <dfn lt="smooth scroll aborted">aborted</dfn>, either by an algorithm or by the user. <!--fingerprint-->
When a user agent is to perform an <dfn id=concept-instant-scroll>instant scroll</dfn> of a <a>scrolling box</a> <var>box</var> to
<var>position</var>, it must update the scroll position of <var>box</var> to <var>position</var>.
To <dfn>scroll to the beginning of the document</dfn> for a document <var>document</var>, follow these steps:
<ol>
<li>Let <var>viewport</var> be the <a>viewport</a> that is associated with <var>document</var>. <!-- This assumes that there is a viewport, since
it is only invoked when navigating -->
<li>Let <var>position</var> be the the scroll position <var>viewport</var> would have by aligning the <a>beginning edges</a> of the
<a>scrolling area</a> with the <a>beginning edges</a> of <var>viewport</var>.
<li>If <var>position</var> is the same as <var>viewport</var>'s current scroll position, and <var>viewport</var> does not have an ongoing
<a>smooth scroll</a>, abort these steps.
<li><a>Perform a scroll</a> of <var>viewport</var> to <var>position</var>,
and <var>document</var>'s root element as the associated element, if there is one, or null otherwise.
</ol>
Note: This algorithm is used when navigating to the <code>#top</code> fragment identifier, as defined in HTML. [[!HTML]]
WebIDL values {#webidl-values}
------------------------------
When asked to <dfn>normalize non-finite values</dfn> for a value <var>x</var>,
if <var>x</var> is one of the three special floating point literal values
(<code>Infinity</code>, <code>-Infinity</code> or <code>NaN</code>),
then <var>x</var> must be changed to the value <code>0</code>. [[!WEBIDL]]
Extensions to the {{Window}} Interface {#extensions-to-the-window-interface}
============================================================================
<pre class=idl>
enum ScrollBehavior { "auto", "instant", "smooth" };
dictionary ScrollOptions {
ScrollBehavior behavior = "auto";
};
dictionary ScrollToOptions : ScrollOptions {
unrestricted double left;
unrestricted double top;
};
partial interface Window {
[NewObject] MediaQueryList matchMedia(DOMString query);
[SameObject, Replaceable] readonly attribute Screen screen;
// browsing context
void moveTo(long x, long y);
void moveBy(long x, long y);
void resizeTo(long x, long y);
void resizeBy(long x, long y);
// viewport
[Replaceable] readonly attribute long innerWidth;
[Replaceable] readonly attribute long innerHeight;
// viewport scrolling
[Replaceable] readonly attribute double scrollX;
[Replaceable] readonly attribute double pageXOffset;
[Replaceable] readonly attribute double scrollY;
[Replaceable] readonly attribute double pageYOffset;
void scroll(optional ScrollToOptions options);
void scroll(unrestricted double x, unrestricted double y);
void scrollTo(optional ScrollToOptions options);
void scrollTo(unrestricted double x, unrestricted double y);
void scrollBy(optional ScrollToOptions options);
void scrollBy(unrestricted double x, unrestricted double y);
// client
[Replaceable] readonly attribute long screenX;
[Replaceable] readonly attribute long screenY;
[Replaceable] readonly attribute long outerWidth;
[Replaceable] readonly attribute long outerHeight;
[Replaceable] readonly attribute double devicePixelRatio;
};
</pre>
When the <dfn method for=Window>matchMedia(<var>query</var>)</dfn> method is invoked these steps must be run:
<ol>
<li>Let <var>parsed media query list</var> be the result of
<a lt='parse a media query list'>parsing</a>
<var>query</var>.
<li>Return a new {{MediaQueryList}} object,
with the <a>context object’s</a>
<a>associated <code>Document</code></a>
as the <a for=MediaQueryList>document</a>,
with <var>parsed media query list</var> as its associated <a>media query list</a>.
</ol>
The <dfn attribute for=Window>screen</dfn> attribute must return the {{Screen}} object
associated with the {{Window}} object.
Note: Accessing {{Window/screen}} through a {{WindowProxy}} object might yield different
results when the {{Document}} is navigated.
The <dfn method for=Window>moveTo(<var>x</var>, <var>y</var>)</dfn> method must follow these steps:
1. Optionally, terminate these steps.
1. Let <var>target</var> be the <a>browsing context</a> of the <a>context object</a>.
1. Let <var>source</var> be the <a>responsible browsing context</a> of the <a>incumbent settings object</a>.
1. If <var>source</var> is not <a>allowed to resize and move</a> <var>target</var>, terminate these steps.
1. Optionally, clamp <var>x</var> and <var>y</var> in a user-agent-defined manner so that the window does not move outside the available space.
1. Move <var>target</var>’s window such that the window’s top left corner is at coordinates (<var>x</var>, <var>y</var>) relative to the top left corner of the output device, measured in CSS pixels of <var>target</var>. The positive axes are rightward and downward.
The <dfn method for=Window>moveBy(<var>x</var>, <var>y</var>)</dfn> method must follow these steps:
1. Optionally, terminate these steps.
1. Let <var>target</var> be the <a>browsing context</a> of the <a>context object</a>.
1. Let <var>source</var> be the <a>responsible browsing context</a> of the <a>incumbent settings object</a>.
1. If <var>source</var> is not <a>allowed to resize and move</a> <var>target</var>, terminate these steps.
1. Optionally, clamp <var>x</var> and <var>y</var> in a user-agent-defined manner so that the window does not move outside the available space.
1. Move <var>target</var>'s window <var>x</var> CSS pixels of <var>target</var> rightward and <var>y</var> CSS pixels of <var>target</var> downward.
The <dfn method for=Window>resizeTo(<var>x</var>, <var>y</var>)</dfn> method must follow these steps:
1. Optionally, terminate these steps.
1. Let <var>target</var> be the <a>browsing context</a> of the <a>context object</a>.
1. Let <var>source</var> be the <a>responsible browsing context</a> of the <a>incumbent settings object</a>.
1. If <var>source</var> is not <a>allowed to resize and move</a> <var>target</var>, terminate these steps.
1. Optionally, clamp <var>x</var> and <var>y</var> in a user-agent-defined manner so that the window does not get too small or bigger than the available space.
1. Resize <var>target</var>'s window by moving its right and bottom edges such that the distance between the left and right edges of the viewport are <var>x</var> CSS pixels of <var>target</var> and the distance between the top and bottom edges of the viewport are <var>y</var> CSS pixels of <var>target</var>.
1. Optionally, move <var>target</var>'s window in a user-agent-defined manner so that it does not grow outside the available space.
The <dfn method for=Window>resizeBy(<var>x</var>, <var>y</var>)</dfn> method must follow these steps:
1. Optionally, terminate these steps.
1. Let <var>target</var> be the <a>browsing context</a> of the <a>context object</a>.
1. Let <var>source</var> be the <a>responsible browsing context</a> of the <a>incumbent settings object</a>.
1. If <var>source</var> is not <a>allowed to resize and move</a> <var>target</var>, terminate these steps.
1. Optionally, clamp <var>x</var> and <var>y</var> in a user-agent-defined manner so that the window does not get too small or bigger than the available space.
1. Resize <var>target</var>'s window by moving its right edge <var>x</var> CSS pixels of <var>target</var> rightward and its bottom edge <var>y</var> CSS pixels of <var>target</var> downward.
1. Optionally, move <var>target</var>'s window in a user-agent-defined manner so that it does not grow outside the available space.
A <a>browsing context</a> <var>A</var> is <dfn>allowed to resize and move</dfn> a <a>browsing context</a> <var>B</var> if all the following conditions are met:
* <var>B</var> is an <a>auxiliary browsing context</a> that was created by a script (as opposed to by an action of the user).
* <var>A</var> is <a>familiar with</a> <var>B</var>.
The <dfn attribute for=Window>innerWidth</dfn> attribute must return the <a>viewport</a> width including the size of a rendered
scroll bar (if any), or zero if there is no <a>viewport</a>. <!--fingerprint-->
<div class='example'>
The following snippet shows how to obtain the width of the viewport:
<pre>var viewportWidth = innerWidth</pre>
</div>
The <dfn attribute for=Window>innerHeight</dfn> attribute must return the <a>viewport</a> height including the size of a rendered
scroll bar (if any), or zero if there is no <a>viewport</a>. <!--fingerprint-->
The <dfn attribute for=Window>scrollX</dfn> attribute attribute must return the x-coordinate,
relative to the <a>initial containing block</a> origin,
of the left of the <a>viewport</a>,
or zero if there is no <a>viewport</a>. <!--fingerprint-->
The <dfn attribute for=Window>pageXOffset</dfn> attribute must return the value returned by the {{scrollX}} attribute.
The <dfn attribute for=Window>scrollY</dfn> attribute attribute must return the y-coordinate,
relative to the <a>initial containing block</a> origin,
of the top of the <a>viewport</a>,
or zero if there is no <a>viewport</a>. <!--fingerprint-->
The <dfn attribute for=Window>pageYOffset</dfn> attribute must return the value returned by the {{scrollY}} attribute.
When the <dfn method for=Window lt="scroll(options)|scroll(x, y)">scroll()</dfn> method is invoked these
steps must be run:
1. If invoked with one argument, follow these substeps:
1. Let <var>options</var> be the argument.
1. Let <var>x</var> be the value of the {{ScrollToOptions/left}} dictionary member of <var>options<
A3CA
/var>, if present,
or the <a>viewport’s</a> current scroll position on the x axis otherwise.
1. Let <var>y</var> be the value of the {{ScrollToOptions/top}} dictionary member of <var>options</var>, if present,
or the <a>viewport’s</a> current scroll position on the y axis otherwise.
1. If invoked with two arguments, follow these substeps:
1. Let <var>options</var> be null <a lt="converted to an IDL value">converted</a> to a {{ScrollToOptions}} dictionary. [[!WEBIDL]]
1. Let <var>x</var> and <var>y</var> be the arguments, respectively.
1. <a>Normalize non-finite values</a> for <var>x</var> and <var>y</var>.
1. If there is no <a>viewport</a>, abort these steps.
1. Let <var>viewport width</var> be the width of the <a>viewport</a> excluding the width of the scroll bar, if any.
1. Let <var>viewport height</var> be the height of the <a>viewport</a> excluding the height of the scroll bar, if any.
1.
<dl class=switch>
<dt>If the <a>viewport</a> has rightward <a>overflow direction</a>
<dd>Let <var>x</var> be max(0, min(<var>x</var>, <a>viewport</a> <a>scrolling area</a> width - <var>viewport width</var>)).
<dt>If the <a>viewport</a> has leftward <a>overflow direction</a>
<dd>Let <var>x</var> be min(0, max(<var>x</var>, <var>viewport width</var> - <a>viewport</a> <a>scrolling area</a> width)).
</dl>
1.
<dl class=switch>
<dt>If the <a>viewport</a> has downward <a>overflow direction</a>
<dd>Let <var>y</var> be max(0, min(<var>y</var>, <a>viewport</a> <a>scrolling area</a> height - <var>viewport height</var>)).
<dt>If the <a>viewport</a> has upward <a>overflow direction</a>
<dd>Let <var>y</var> be min(0, max(<var>y</var>, <var>viewport height</var> - <a>viewport</a> <a>scrolling area</a> height)).
</dl>
1. Let <var>position</var> be the scroll position the <a>viewport</a> would have
by aligning the x-coordinate <var>x</var> of the <a>viewport</a> <a>scrolling area</a>
with the left of the <a>viewport</a>
and aligning the y-coordinate <var>y</var> of the <a>viewport</a> <a>scrolling area</a>
with the top of the <a>viewport</a>.
1. If <var>position</var> is the same as the <a>viewport’s</a> current scroll position,
and the <a>viewport</a> does not have an ongoing <a>smooth scroll</a>, abort these steps.
1. Let <var>document</var> be the <a>viewport’s</a> associated {{Document}}.
1. <a>Perform a scroll</a> of the <a>viewport</a> to <var>position</var>,
<var>document</var>'s root element as the associated element, if there is one, or null otherwise,
and the scroll behavior being the value of the {{ScrollOptions/behavior}} dictionary member of <var>options</var>.
When the <dfn method for=Window lt="scrollTo(options)|scrollTo(x, y)">scrollTo()</dfn> method is invoked, the
user agent must act as if the {{Window/scroll()}} method was invoked with the same arguments.
When the <dfn method for=Window lt="scrollBy(options)|scrollBy(x, y)">scrollBy()</dfn> method is invoked, the
user agent must run these steps:
1. If invoked with two arguments, follow these substeps:
1. Let <var>options</var> be null <a lt="converted to an IDL value">converted</a> to a {{ScrollToOptions}} dictionary. [[!WEBIDL]]
1. Let <var>x</var> and <var>y</var> be the arguments, respectively.
1. Let the {{ScrollToOptions/left}} dictionary member of <var>options</var> have the value <var>x</var>.
1. Let the {{ScrollToOptions/top}} dictionary member of <var>options</var> have the value <var>y</var>.
1. <a>Normalize non-finite values</a> for the {{ScrollToOptions/left}} and {{ScrollToOptions/top}} dictionary members of <var>options</var>.
1. Add the value of {{scrollX}} to the {{ScrollToOptions/left}} dictionary member.
1. Add the value of {{scrollY}} to the {{ScrollToOptions/top}} dictionary member.
1. Act as if the {{Window/scroll()}} method was invoked with <var>options</var> as the only argument.
The <dfn attribute for=Window>screenX</dfn> attribute must return the x-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. <!--fingerprint-->
The <dfn attribute for=Window>screenY</dfn> attribute must return the y-coordinate,
relative to the origin of 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. <!--fingerprint-->
The <dfn attribute for=Window>outerWidth</dfn> attribute must return the width of the
client window. If there is no client window this
attribute must return zero. <!--fingerprint-->
The <dfn attribute for=Window>outerHeight</dfn> attribute must return the height of the
client window. If there is no client window this
attribute must return zero. <!--fingerprint-->
The <dfn attribute for=Window>devicePixelRatio</dfn> attribute must return the result of the following algorithm:
1. If there is no output device, return 1 and abort these steps.
1. Let <var>CSS pixel size</var> be the size of a CSS pixel at the current <a>page zoom</a> scale factor and at a <a>pinch zoom</a> scale factor of 1.0.
1. Let <var>device pixel size</var> be the vertical size of a device pixel of the output device.
1. Return the result of dividing <var>CSS pixel size</var> by <var>device pixel size</var>.
The <var>features</var> argument to the {{Window/open()}} method {#the-features-argument-to-the-open()-method}
--------------------------------------------------------------------------------------------------------------
HTML defines the {{Window/open()}} method but has no defined effect for the third argument, <var>features</var>.
[[!HTML]]
This specification defines the effect of the <var>features</var> argument for user agents that do not opt to ignore it, as follows:
1. If the method does not result in a new <a>auxiliary browsing context</a> being created, terminate these steps.
1. Let <var>target</var> be the new <a>auxiliary browsing context</a>.
1. Let <var>tokens</var> be the result of <a lt="split a string on commas">splitting <var>features</var> on commas</a>.
1. Let <var>parsed features</var> be a new empty dictionary.
1. <i>Token loop</i>: For each token <var>token</var> in <var>tokens</var>, follow these substeps:
1. Let <var>input</var> be <var>token</var>.
1. Let <var>position</var> point at the first character of <var>input</var>.
1. <a>Skip whitespace</a>.
1. <a>Collect a sequence of characters</a> that are not <a>space characters</a> nor "<code>=</code>" (U+003D).
Let <var>name</var> be the collected characters, <a>converted to ASCII lowercase</a>.
1. If <var>name</var> is in <var>parsed features</var> or if <var>name</var> is not a <a>supported <code>open()</code> feature name</a>,
continue <i>token loop</i>.
1. <a>Skip whitespace</a>.
1. If the character at <var>position</var> is not "<code>=</code>" (U+003D), continue <i>token loop</i>.
1. Advance <var>position</var> by one.
1. If <var>position</var> is past the end of <var>input</var>, continue <i>token loop</i>.
1. <a>Collect a sequence of characters</a> that are any characters. Let <var>raw value</var> be the collected characters.
1. Let <var>value</var> be the result of invoking the <a>rules for parsing integers</a> on <var>raw value</var>.
1. If <var>value</var> is an error, continue <i>token loop</i>.
1. Set <var>name</var> in <var>parsed features</var> to <var>value</var>.
1. If <a for="supported open() feature name">left</a> is present in <var>parsed features</var>, follow these substeps:
1. Let <var>x</var> be the value of <a for="supported open() feature name">left</a>.
1. Optionally, clamp <var>x</var> in a user-agent-defined manner so that the window does not move outside the available space.
1. Optionally, move <var>target</var>'s window such that the window's left edge is at the horizontal coordinate <var>x</var> relative to the left edge of
the output device, measured in CSS pixels of <var>target</var>. The positive axis is rightward.
1. If <a for="supported open() feature name">top</a> is present in <var>parsed features</var>, follow these substeps:
1. Let <var>y</var> be the value of <a for="supported open() feature name">top</a>.
1. Optionally, clamp <var>y</var> in a user-agent-defined manner so that the window does not move outside the available space.
1. Optionally, move <var>target</var>'s window such that the window's top edge is at the vertical coordinate <var>y</var> relative to the top edge of
the output device, measured in CSS pixels of <var>target</var>. The positive axis is downward.
1. If <a for="supported open() feature name">width</a> is present in <var>parsed features</var>, follow these substeps:
1. Let <var>x</var> be the value of <a for="supported open() feature name">width</a>.
1. Optionally, clamp <var>x</var> in a user-agent-defined manner so that the window does not get too small or bigger than the available space.
1. Optionally, size <var>target</var>'s window by moving its right edge such that the distance between the left and right edges of the viewport are
<var>x</var> CSS pixels of <var>target</var>.
1. Optionally, move <var>target</var>'s window in a user-agent-defined manner so that it does not grow outside the available space.
1. If <a for="supported open() feature name">height</a> is present in <var>parsed features</var>, follow these substeps:
1. Let <var>y</var> be the value of <a for="supported open() feature name">height</a>.
1. Optionally, clamp <var>y</var> in a user-agent-defined manner so that the window does not get too small or bigger than the available space.
1. Optionally, size <var>target</var>'s window by moving its bottom edge such that the distance between the top and bottom edges of the viewport are
<var>y</var> CSS pixels of <var>target</var>.
1. Optionally, move <var>target</var>'s window in a user-agent-defined manner so that it does not grow outside the available space.
A <dfn export>supported <code>open()</code> feature name</dfn> is one of the following:
<dl dfn-for="supported open() feature name" export>
<dt><dfn>width</dfn>
<dd>The width of the viewport.
<dt><dfn>height</dfn>
<dd>The height of the viewport.
<dt><dfn>left</dfn>
<dd>The left position of the window.
<dt><dfn>top</dfn>
<dd>The top position of the window.
</dl>
The {{MediaQueryList}} Interface {#the-mediaquerylist-interface}
----------------------------------------------------------------
This section integrates with the <a spec=html>event loop</a> defined in HTML. [[!HTML]]
A {{MediaQueryList}} object has an associated <dfn>media query list</dfn>
and an associated <dfn for=MediaQueryList>document</dfn> set on creation.
A {{MediaQueryList}} object has an associated <dfn for=MediaQueryList>media</dfn> which is the
<a lt='serialize a media query list'>serialized</a> form of the associated <a>media query list</a>.
A {{MediaQueryList}} object has an associated <dfn for=MediaQueryList>matches state</dfn> which is
true if the associated <a>media query list</a> matches the state of the <a for=MediaQueryList>document</a>, and false otherwise.
<!--XXX update the matches state when flushing layout (offsetWidth et al), without firing a change event. -->
When asked to <dfn>evaluate media queries and report changes</dfn> for a {{Document}} <var>doc</var>, run these steps:
<ol>
<li>
For each {{MediaQueryList}} object <var>target</var> that has <var>doc</var> as its <a for=MediaQueryList>document</a>,
in the order they were created, oldest first, run these substeps:
<ol>
<li>If <var>target</var>'s <a>matches state</a> has changed since the last time these steps were run,
<a>dispatch</a> a new <a>event</a> to <var>target</var>
using the {{MediaQueryList}} interface,
with its {{Event/type}} attribute initialized to <a event>change</a>,
its {{Event/isTrusted}} attribute initialized to true,
its {{MediaQueryList/media}} attribute initialized to <var>target</var>'s <a>media</a>,
and its {{MediaQueryListEvent/matches}} attribute initialized to <var>target</var>'s <a>matches state</a>. <!--fingerprint-->
</ol>
</ol>
<div class='example'>
A simple piece of code that detects changes in the orientation of the viewport can be written as follows:
<pre class='lang-javascript'>
function handleOrientationChange(event) {
if(event.matches) // landscape
…
else
…
}
var mql = matchMedia("(orientation:landscape)");
mql.onchange = handleOrientationChange;
</pre>
</div>
<pre class=idl>
interface MediaQueryList : EventTarget {
readonly attribute DOMString media;
readonly attribute boolean matches;
void addListener(EventListener? listener);
void removeListener(EventListener? listener);
attribute EventHandler onchange;
};
</pre>
The <dfn attribute for=MediaQueryList>media</dfn> attribute must return
the associated <a>media</a>.
The <dfn attribute for=MediaQueryList>matches</dfn> attribute must return
the associated <a>matches state</a>. <!--fingerprint-->
The <dfn method for=MediaQueryList>addListener(<var>listener</var>)</dfn> method must run these steps:
1. If <var>listener</var> is null, terminate these steps.
1. Append an <a>event listener</a> to the associated list of <a>event listeners</a>
with <b>type</b> set to <code>change</code>,
<b>callback</b> set to <var>listener</var>,
and <b>capture</b> set to false,
unless there already is an <a>event listener</a> in that list
with the same <b>type</b>, <b>callback</b>, and <b>capture</b>.
The <dfn method for=MediaQueryList>removeListener(<var>listener</var>)</dfn> method must run these steps:
1. Remove an <a>event listener</a> from the associated list of <a>event listeners</a>,
whose <b>type</b> is <code>change</code>,
<b>callback</b> is <var>listener</var>,
and <b>capture</b> is false.
Note: This specification initially had a custom callback mechanism with {{addListener()}} and
{{removeListener()}}, and the callback was invoked with the associated media query list as argument.
Now the normal event mechanism is used instead.
For backwards compatibility, the {{addListener()}} and {{removeListener()}} methods
are basically aliases for {{addEventListener()}} and {{removeEventListener()}}, respectively,
and the <code>change</code> event masquerades as a {{MediaQueryList}}.
The following are the <a>event handlers</a>
(and their corresponding <a>event handler event types</a>) that must be supported,
as <a>event handler IDL attributes</a>, by all objects implementing the {{MediaQueryList}} interface:
<table class="complex data">
<thead>
<tr>
<th><a>Event handler</a>
<th><a>Event handler event type</a>
<tbody>
<tr>
<td><dfn attribute for=MediaQueryList>onchange</dfn>
<td><a event>change</a>
</table>
<pre class=idl>
[Constructor(DOMString type, optional MediaQueryListEventInit eventInitDict)]
interface MediaQueryListEvent : Event {
readonly attribute DOMString media;
readonly attribute boolean matches;
};
dictionary MediaQueryListEventInit : EventInit {
DOMString media = "";
boolean matches = false;
};
</pre>
The <dfn attribute for=MediaQueryListEvent>media</dfn> attribute must return the value it was initialized to.
The <dfn attribute for=MediaQueryListEvent>matches</dfn> attribute must return the value it was initialized to.
<h4 id=mediaquerylist-event-summary>Event summary</h4>
<i>This section is non-normative.</i>
<table class="complex data">
<thead>
<tr>
<th>Event
<th>Interface
<th>Interesting targets
<th>Description
<tbody>
<tr>
<td><dfn event for=MediaQueryList>change</dfn>
<td>{{Event}}
<td>{{MediaQueryList}}
<td>Fired at the {{MediaQueryList}} when the <a>matches state</a> changes.
</table>
The {{Screen}} Interface {#the-screen-interface}
------------------------------------------------
As its name suggests, the {{Screen}} interface represents information about the screen of the output device.
<pre class=idl>
interface Screen {
readonly attribute long availWidth;
readonly attribute long availHeight;
readonly attribute long width;
readonly attribute long height;
readonly attribute unsigned long colorDepth;
readonly attribute unsigned long pixelDepth;
};
</pre>
The <dfn attribute for=Screen>availWidth</dfn> attribute must return the available width of the rendering surface of the output device,
in CSS pixels. <!--fingerprint-->
The <dfn attribute for=Screen>availHeight</dfn> attribute must return the available height of the rendering surface of the output
device, in CSS pixels. <!--fingerprint-->
The <dfn attribute for=Screen>width</dfn> attribute must return the width of the output device, in CSS pixels. <!--fingerprint-->
The <dfn attribute for=Screen>height</dfn> attribute must return the height of the output device, in CSS pixels. <!--fingerprint-->
The <dfn attribute for=Screen>colorDepth</dfn> attribute must return 24.
The <dfn attribute for=Screen>pixelDepth</dfn> attribute must return 24.
Note: The {{colorDepth}} and {{pixelDepth}} attributes are useless but are
included for compatibility.
Extensions to the {{Document}} Interface {#extensions-to-the-document-interface}
================================================================================
<pre class=idl>
partial interface Document {
Element? elementFromPoint(double x, double y);
sequence<Element> elementsFromPoint(double x, double y);
CaretPosition? caretPositionFromPoint(double x, double y);
readonly attribute Element? scrollingElement;
};
</pre>
The <dfn method for=Document>elementFromPoint(<var>x</var>, <var>y</var>)</dfn> method must follow these steps:
1. If either argument is negative, <var>x</var> is greater than the <a>viewport</a> width excluding the size of a rendered scroll bar (if any), or
<var>y</var> is greater than the <a>viewport</a> height excluding the size of a rendered scroll bar (if any), or there is no <a>viewport</a>
associated with the document, return null and terminate these steps.
1. If there is a <a>layout box</a> in the <a>viewport</a> that would be a target for hit testing at coordinates <var>x</var>,<var>y</var>,
when applying the <a>transforms</a> that apply to the descendants of the <a>viewport</a>, return the associated element and terminate these steps.
1. If the document has a root element, return the root element and terminate these steps.
1. Return null.
Note: The {{elementFromPoint()}} method does not necessarily return the top-most painted element. For
instance, an element can be excluded from being a target for hit testing by using the 'pointer-events' CSS property.
<p>
The <dfn method for=Document>elementsFromPoint(<var>x</var>, <var>y</var>)</dfn> method must follow these steps:
1. Let <var>sequence</var> be a new empty sequence.
1. If either argument is negative, <var>x</var> is greater than the <a>viewport</a> width excluding the size of a rendered scroll bar (if any), or
<var>y</var> is greater than the <a>viewport</a> height excluding the size of a rendered scroll bar (if any), or there is no <a>viewport</a>
associated with the document, return <var>sequence</var> and terminate these steps.
1. For each <a>layout box</a> in the <a>viewport</a>, in paint order, starting with the topmost box, that would be a target for hit testing at
coordinates <var>x</var>,<var>y</var> even if nothing would be overlapping it, when applying the <a>transforms</a> that apply to the descendants of the
<a>viewport</a>, append the associated element to <var>sequence</var>.
1. If the document has a root element, and the last item in <var>sequence</var> is not the root element, append the root element to <var>sequence</var>.
1. Return <var>sequence</var>.
The <dfn method for=Document>caretPositionFromPoint(<var>x</var>, <var>y</var>)</dfn> method must return the
result of running these steps:
1. If there is no <a>viewport</a> associated with the document, return null.
1. If either argument is negative, <var>x</var> is greater
than the <a>viewport</a> width excluding the size of a rendered
scroll bar (if any), <var>y</var> is greater than the
<a>viewport</a> height excluding the size of a rendered scroll bar
(if any) return null.
1. If at the coordinates <var>x</var>,<var>y</var>
in the <a>viewport</a> no text insertion point indicator would have
been inserted when applying the <a>transforms</a> that apply to the descendants of the <a>viewport</a>, return null.
1. If at the coordinates <var>x</var>,<var>y</var>
in the <a>viewport</a> a text insertion point indicator would have
been inserted in a text entry widget which is also a replaced element, when applying the <a>transforms</a> that apply to the descendants of the
<a>viewport</a>, return a <a>caret position</a> with its properties set as follows:
<dl>
<dt><a>caret node</a>
<dd>The node corresponding to the text entry widget.
<dt><a>caret offset</a>
<dd>The amount of 16-bit units to the left of where the
text insertion point indicator would have inserted.
<dt><a>caret range</a>
<dd>null
</dl>
1. Otherwise, return a <a>caret position</a> where the
<a>caret range</a> is a collapsed
{{Range}} object for the position
where the text insertion point indicator would have been inserted when applying the <a>transforms</a> that apply to the descendants of the
<a>viewport</a>, and the other properties are set as follows:
<dl>
<dt><a>caret node</a>
<dd>The {{Range/startContainer}}
of the <a>caret range</a>.
<dt><a>caret offset</a>
<dd>The {{Range/startOffset}} of
the <a>caret range</a>.
</dl>
Note: The specifics of hit testing are out of scope of this
specification and therefore the exact details of
{{elementFromPoint()}} and {{caretPositionFromPoint()}}
are therefore too. Hit testing will hopefully be defined in a future
revision of CSS or HTML.
<p>The <dfn attribute for=Document>scrollingElement</dfn> attribute, on getting, must run these steps:
1. If the {{Document}} is in <a>quirks mode</a>, follow these substeps:
1. If <a>the HTML <code>body</code> element</a> exists, and it is not <a>potentially scrollable</a>, return <a>the HTML <code>body</code> element</a> and abort these steps.
1. Return null and abort these steps.
1. If there is a root element, return the root element and abort these steps.
1. Return null.
Note: For non-conforming user agents that always use the <a>quirks mode</a> behavior for {{Element/scrollTop}}
and {{Element/scrollLeft}}, the {{Document/scrollingElement}} attribute is expected to also always return
<a>the HTML <code>body</code> element</a> (or null if it does not exist).
This API exists so that Web developers can use it to get the right element to use for scrolling APIs,
without making assumptions about a particular user agent's behavior
or having to invoke a scroll to see which element scrolls the viewport.
Note: <a>The HTML <code>body</code> element</a> is different from HTML's <code>document.body</code>
in that the latter can return a <code>frameset</code> element.
The {{CaretPosition}} Interface {#the-caretposition-interface}
--------------------------------------------------------------
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 {{CaretPosition}} object.
<pre class=idl>
interface CaretPosition {
readonly attribute Node offsetNode;
readonly attribute unsigned long offset;