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<!DOCTYPE html>
<html>
<head>
<meta charset='utf-8'>
<title>
Selection API
</title>
<script src='https://www.w3.org/Tools/respec/respec-w3c' async class=
'remove'></script>
<script class='remove'>
var respecConfig = {
specStatus: "ED",
shortName: "selection-api",
editors: [
{
name: "Ryosuke Niwa",
mailto: "[email protected]",
company: "Apple Inc.",
companyURL: "https://www.apple.com/",
w3cid: "49910",
},
],
group: "webediting",
testSuiteURI: "https://github.com/web-platform-tests/wpt/tree/master/selection",
github: "w3c/selection-api",
xref: "web-platform",
testSuiteURI: "https://wpt.fyi/results/selection/",
};
</script>
</head>
<body>
<section id='abstract'>
<p>
This document is a preliminary draft of a specification for the
Selection API and selection related functionality. It replaces a couple
of old sections of the <a href="https://www.w3.org/TR/html5/">HTML
specification</a>, the selection part of the old <a href=
"https://www.w3.org/TR/2000/REC-DOM-Level-2-Traversal-Range-20001113/ranges.html">
DOM Range specification</a>.
</p>
<p>
This document defines APIs for selection, which allows users and
authors to select a portion of a document or specify a point of
interest for copy, paste, and other editing operations.
</p>
</section>
<section id='sotd'>
<p>
This is work in progress.
</p>
</section>
<section class="informative">
<h2>
Background
</h2>
<p>
IE9 and Firefox 6.0a2 allow arbitrary ranges in the selection, which
follows what this spec originally said. However, this leads to
unpleasant corner cases that authors, implementers, and spec writers
all have to deal with, and they don't make any real sense. Chrome 14
dev and Opera 11.11 aggressively normalize selections, like not letting
them lie inside empty elements and things like that, but this is also
viewed as a bad idea, because it takes flexibility away from authors.
</p>
<p>
So I changed the spec to a made-up compromise that allows some
simplification but doesn't constrain authors much. See <a href=
"https://lists.w3.org/Archives/Public/public-whatwg-archive/2011Jun/0193.html">
discussion</a>. Basically it would throw exceptions in some places to
try to stop the selection from containing a range that had a
<a>boundary point</a> other than an Element or Text node, or a boundary
point that didn't descend from a Document.
</p>
<p>
But this meant getRangeAt() had to start returning a copy, not a
reference. Also, it would be prone to things failing weirdly in corner
cases. Perhaps most significantly, all sorts of problems might arise
when DOM mutations transpire, like if a boundary point's node is
removed from its parent and the mutation rules would place the new
boundary point inside a non-Text/Element node. And finally, the
previously-specified behavior had the advantage of matching two major
implementations, while the new behavior matched no one. So I changed it
back.
</p>
<div class="note">
<p>
See <a href=
"https://www.w3.org/Bugs/Public/show_bug.cgi?id=15470">bug 15470</a>.
IE9, Firefox 12.0a1, Chrome 17 dev, and Opera Next 12.00 alpha all
make the range initially null.
</p>
</div>
</section>
<section>
<h2>
Definition
</h2>
<p>
Every <a>document</a> with a [=Document/browsing context=] has a unique
<dfn>selection</dfn> associated with it.
</p>
<p class="note">
This is a requirement of the HTML spec. IE9 and Opera Next 12.00 alpha
seem to follow it, while Firefox 12.0a1 and Chrome 17 dev seem not to.
See <a href=
"https://bugzilla.mozilla.org/show_bug.cgi?id=717339">Mozilla bug</a>,
<a href="https://bugs.webkit.org/show_bug.cgi?id=76114">WebKit bug</a>.
</p>
<p>
This one <a>selection</a> must be shared by all the content of the
<a>document</a> (though not by nested <a>documents</a>), including any
[=editing hosts=] in the <a>document</a>.
</p>
<p>
Each <a>selection</a> can be associated with a single <a>range</a>.
When there is no <a>range</a> associated with the <a>selection</a>, the
selection is <dfn>empty</dfn>. The selection must be initially
<a>empty</a>.
</p>
<p class="note">
A <a>document</a>'s <a>selection</a> is a singleton object associated
with that <a>document</a>, so it gets replaced with a new object when
<code>Document.open()</code> is called. See <a href=
"https://www.w3.org/Bugs/Public/show_bug.cgi?id=15470">bug 15470</a>.
IE9 and Opera Next 12.00 alpha allow the user to reset the range to
null after the fact by clicking somewhere; Firefox 12.0a1 and Chrome 17
dev do not. We follow Gecko/WebKit, because it lessens the chance of
getRangeAt(0) throwing.
</p>
<p>
Once a <a>selection</a> is associated with a given <a>range</a>, it
must continue to be associated with that same <a>range</a> until this
specification requires otherwise.
</p>
<p class="note" data-link-for="Selection">
For instance, if the DOM changes in a way that changes the range's
boundary points, or a script modifies the boundary points of the range,
the same range object must continue to be associated with the
selection. However, if the user changes the selection or a script calls
{{addRange()}}, the selection must be associated with a new range
object, as required elsewhere in this specification.
</p>
<p>
If the <a>selection</a>'s <a>range</a> is not null and is
[=range/collapsed=], then the caret position must be at that
<a>range</a>'s <a>boundary point</a>. When the <a>selection</a> is not
[=range/collapsed=], this specification does not define the caret
position; user agents should follow platform conventions in deciding
whether the caret is at the start of the <a>selection</a>, the end of
the <a>selection</a>, or somewhere else.
</p>
<p>
Each <a>selection</a> has a <dfn>direction</dfn>: <dfn>forwards</dfn>,
<dfn>backwards</dfn>, or <dfn>directionless</dfn>. If the user creates
a <a>selection</a> by indicating first one <a>boundary point</a> of the
<a>range</a> and then the other (such as by clicking on one point and
dragging to another), and the first indicated <a>boundary point</a> is
[=boundary point/after=] the second, then the corresponding
<a>selection</a> must initially be <a>backwards</a>. If the first
indicated <a>boundary point</a> is [=boundary point/before=] the
second, then the corresponding <a>selection</a> must initially be
<a>forwards</a>. Otherwise, it must be <a>directionless</a>.
</p>
<p>
When the <a>selection</a>'s <a>range</a> is mutated by scripts, e.g.
via {{Range/selectNode(node)}}, <a>direction</a> of the
<a>selection</a> must be preserved.
</p>
<p>
Each <a>selection</a>s also have an <dfn>anchor</dfn> and a
<dfn>focus</dfn>. If the <a>selection</a>'s <a>range</a> is null, its
<a>anchor</a> and <a>focus</a> are both null. If the <a>selection</a>'s
<a>range</a> is not null and its <a>direction</a> is <a>forwards</a>,
its <a>anchor</a> is the <a>range</a>'s [=range/start=], and its
<a>focus</a> is the [=range/end=]. Otherwise, its <a>focus</a> is the
[=range/start=] and its <a>anchor</a> is the [=range/end=].
</p>
<p class="note">
<a>anchor</a> and <a>focus</a> of <a>selection</a> need not to be in
the [=document tree=]. It could be in a [=shadow tree=] of the same
[=document=].
</p>
<p>
Each <a>document</a>, <a>input</a> element, and <a>textarea</a> element
has a boolean <dfn>has scheduled selectionchange event</dfn>, which is
initially false.
</p>
</section>
<section data-dfn-for="Selection">
<h2>
Selection interface
</h2>
<p>
<a>Selection</a> interface provides a way to interact with the
<a>selection</a> associated with each document.
</p>
<pre class="idl">
[Exposed=Window]
interface Selection {
readonly attribute Node? anchorNode;
readonly attribute unsigned long anchorOffset;
readonly attribute Node? focusNode;
readonly attribute unsigned long focusOffset;
readonly attribute boolean isCollapsed;
readonly attribute unsigned long rangeCount;
readonly attribute DOMString type;
readonly attribute DOMString direction;
Range getRangeAt(unsigned long index);
undefined addRange(Range range);
undefined removeRange(Range range);
undefined removeAllRanges();
undefined empty();
sequence<StaticRange> getComposedRanges(optional GetComposedRangesOptions options = {});
undefined collapse(Node? node, optional unsigned long offset = 0);
undefined setPosition(Node? node, optional unsigned long offset = 0);
undefined collapseToStart();
undefined collapseToEnd();
undefined extend(Node node, optional unsigned long offset = 0);
undefined setBaseAndExtent(Node anchorNode, unsigned long anchorOffset, Node focusNode, unsigned long focusOffset);
undefined selectAllChildren(Node node);
undefined modify(optional DOMString alter, optional DOMString direction, optional DOMString granularity);
[CEReactions] undefined deleteFromDocument();
boolean containsNode(Node node, optional boolean allowPartialContainment = false);
stringifier;
};
dictionary GetComposedRangesOptions {
sequence<ShadowRoot> shadowRoots = [];
};
</pre>
<dl>
<dt>
<dfn>anchorNode</dfn>
</dt>
<dd>
<p>
The attribute must return the <a>anchor</a> [=boundary point/node=]
of [=this=], or `null` if the <a>anchor</a> is null or
<a>anchor</a> is not in the [=document tree=].
</p>
</dd>
<dt>
<dfn>anchorOffset</dfn>
</dt>
<dd>
<p>
The attribute must return the <a>anchor</a> [=boundary
point/offset=] of [=this=], or <code>0</code> if the <a>anchor</a>
is null or <a>anchor</a> is not in the [=document tree=].
</p>
</dd>
<dt>
<dfn>focusNode</dfn>
</dt>
<dd>
<p>
The attribute must return the <a>focus</a> [=boundary point/node=]
of [=this=], or `null` if the <a>focus</a> is null or <a>focus</a>
is not in the [=document tree=].
</p>
</dd>
<dt>
<dfn>focusOffset</dfn>
</dt>
<dd>
<p>
The attribute must return the <a>focus</a> [=boundary
point/offset=] of [=this=], or <code>0</code> if the <a>focus</a>
is null or <a>focus</a> is not in the [=document tree=].
</p>
</dd>
<dt>
<dfn>isCollapsed</dfn>
</dt>
<dd>
<p>
The attribute must return true if and only if the
<span>anchor</span> and <span>focus</span> are the same (including
if both are null). Otherwise it must return false.
</p>
</dd>
<dt>
<dfn>rangeCount</dfn>
</dt>
<dd>
<p>
The attribute must return <code>0</code> if [=this=] is
<a>empty</a> or either <a>focus</a> or <a>anchor</a> is not in the
[=document tree=], and must return <code>1</code> otherwise.
</p>
</dd>
<dt>
<dfn>type</dfn>
</dt>
<dd>
<p>
The attribute must return `"None"` if [=this=] is <a>empty</a> or
either <a>focus</a> or <a>anchor</a> is not in the [=document
tree=], `"Caret"` if [=this=]'s <a>range</a> is
[=range/collapsed=], and `"Range"` otherwise.
</p>
</dd>
<dt>
<dfn>direction</dfn>
</dt>
<dd>
<p>
The attribute must return `"none"` if [=this=] is <a>empty</a> or
this selection is <a>directionless</a>. `"forward"` if this
selection's direction is <a>forwards</a> and `"backward"` if this
selection's direction is <a>backwards</a>.
</p>
</dd>
<dt>
<dfn>getRangeAt()</dfn> method
</dt>
<dd>
<p data-tests="getRangeAt.html">
The method must throw an {{IndexSizeError}} exception if
<var>index</var> is not <code>0</code>, or if [=this=] is
<a>empty</a> or either <a>focus</a> or <a>anchor</a> is not in the
[=document tree=]. Otherwise, it must return a reference to (not a
copy of) [=this=]'s <a>range</a>.
</p>
<p class="note">
Thus subsequent calls of this method returns the same <a>range</a>
object if nothing has removed [=this=]'s range in the meantime. In
particular, <code>getSelection().getRangeAt(0) ===
getSelection().getRangeAt(0)</code> evaluates to <code>true</code>
if the <a>selection</a> is not <a>empty</a>.
</p>
</dd>
<dt>
<dfn>addRange()</dfn> method
</dt>
<dd>
<p>
The method must follow these steps:
</p>
<ol>
<li>If the [=tree/root=] of the <var>range</var>'s boundary points
are not the <a>document</a> associated with [=this=], abort these
steps.
</li>
<li>If <code>rangeCount</code> is not <code>0</code>, abort these
steps.
</li>
<li>Set [=this=]'s range to <var>range</var> by a strong reference
(not by making a copy).
</li>
</ol>
<p class="note">
Since <a>range</a> is added by reference, subsequent calls to
<code>getRangeAt(0)</code> returns the same object, and any changes
that a script makes to <a>range</a> after it is added must be
reflected in the <a>selection</a>, until something else removes or
replaces [=this=]'s <a>range</a>. In particular, the
<a>selection</a> will contain <var>b</var> as opposed to
<var>a</var> after running the following code: <code>var r =
document.createRange(); r.selectNode(a);
getSelection().addRange(r); r.selectNode(b);</code>
</p>
<div class="note">
<p>
At Step 2, Chrome 58 and Edge 25 do nothing. Firefox 51 gives you
a multi-range selection. At least they keep the exisiting
<a>range</a>.
</p>
<p>
At Step 3, Chrome 58 and Firefox 51 store a reference, as
described here. Edge 25 stores a copy. Firefox 51 changes its
selection if the <a>range</a> is modified.
</p>
</div>
</dd>
<dt>
<dfn>removeRange()</dfn> method
</dt>
<dd>
<p>
The method must make [=this=] <a>empty</a> by disassociating its
<a>range</a> if [=this=]'s <a>range</a> is <var>range</var>.
Otherwise, it must throw a {{NotFoundError}}.
</p>
</dd>
<dt>
<dfn>removeAllRanges()</dfn> method
</dt>
<dd>
<p>
The method must make [=this=] <a>empty</a> by disassociating its
<a>range</a> if [=this=] has an associated <a>range</a>.
</p>
</dd>
<dt>
<dfn>empty()</dfn> method
</dt>
<dd>
<p>
The method must be an alias, and behave identically, to
<code>removeAllRanges()</code>.
</p>
</dd>
<dt>
<dfn>getComposedRanges()</dfn> method
</dt>
<dd>
<ol>
<li>If [=this=] is <a>empty</a>, return an empty array.
</li>
<li>Otherwise, let <var>startNode</var> be [=range/start node=] of
the [=range=] associated with [=this=], and let
<var>startOffset</var> be [=range/start offset=] of the [=range=].
</li>
<li>While <var>startNode</var> is a [=node=],
<var>startNode</var>'s [=tree/root=] is a [=shadow root=], and
<var>startNode</var>'s [=tree/root=] is not a [=shadow-including
inclusive ancestor=] of any of
<var>options</var>["{{GetComposedRangesOptions/shadowRoots}}"],
repeat these steps:
<ol>
<li>Set <var>startOffset</var> to [=tree/index=] of
<var>startNode</var>'s [=tree/root=]'s [=host=].
</li>
<li>Set <var>startNode</var> to <var>startNode</var>'s
[=tree/root=]'s [=host=]'s [=tree/parent=].
</li>
</ol>
</li>
<li>Let <var>endNode</var> be [=range/end node=] of the [=range=]
associated with [=this=], and let <var>endOffset</var> be
[=range/end offset=] of the [=range=].
</li>
<li>While <var>endNode</var> is a [=node=], <var>endNode</var>'s
[=tree/root=] is a [=shadow root=], and <var>endNode</var>'s
[=tree/root=] is not a [=shadow-including inclusive ancestor=] of
any of
<var>options</var>["{{GetComposedRangesOptions/shadowRoots}}"],
repeat these steps:
<ol>
<li>Set <var>endOffset</var> to [=tree/index=] of
<var>endNode</var>'s [=tree/root=]'s [=host=] plus 1.
</li>
<li>Set <var>endNode</var> to <var>endNode</var>'s
[=tree/root=]'s [=host=]'s [=tree/parent=].
</li>
</ol>
</li>
<li>Return an array consisting of new {{StaticRange}} whose
[=range/start node=] is <var>startNode</var>, [=range/start
offset=] is <var>startOffset</var>, [=range/end node=] is
<var>endNode</var>, and [=range/end offset=] is
<var>endOffset</var>.
</li>
</ol>
</dd>
<dt>
<dfn>collapse()</dfn> method
</dt>
<dd>
<p>
The method must follow these steps:
</p>
<ol>
<li>If <var>node</var> is null, this method must behave identically
as <code>removeAllRanges()</code> and abort these steps.
</li>
<li>The method must throw an {{IndexSizeError}} exception if <var>
offset</var> is longer than <var>node</var>'s [=Node/length=] and
abort these steps.
</li>
<li>If <a>document</a> associated with [=this=] is not a
[=shadow-including inclusive ancestor=] of <var>node</var>, abort
these steps.
</li>
<li>Otherwise, let <var>newRange</var> be a new <a>range</a>.
</li>
<li>[=Range/Set the start=] the [=range/start=] and the
[=range/end=] of <var>newRange</var> to (<var>node</var>,
<var>offset</var>).
</li>
<li>Set [=this=]'s <a>range</a> to <var>newRange</var>.
</li>
</ol>
</dd>
<dt>
<dfn>setPosition()</dfn> method
</dt>
<dd>
<p>
The method must be an alias, and behave identically, to
<code>collapse()</code>.
</p>
</dd>
<dt>
<dfn>collapseToStart()</dfn> method
</dt>
<dd>
<p>
The method must throw {{InvalidStateError}} exception if the
[=this=] is <a>empty</a>. Otherwise, it must create a new
<a>range</a>, [=Range/set the start=] both its [=range/start=] and
[=range/end=] to the [=range/start=] of [=this=]'s <a>range</a>,
and then set [=this=]'s <a>range</a> to the newly-created
<a>range</a>.
</p>
<p class="note">
For collapseToStart/End, IE9 mutates the existing range, while
Firefox 9.0a2 and Chrome 15 dev replace it with a new one. The spec
follows the majority and replaces it with a new one, leaving the
old Range object unchanged.
</p>
</dd>
<dt>
<dfn>collapseToEnd()</dfn> method
</dt>
<dd>
<p>
The method must throw {{InvalidStateError}} exception if the
[=this=] is <a>empty</a>. Otherwise, it must create a new
<a>range</a>, [=Range/set the start=] both its [=range/start=] and
[=range/end=] to the [=range/end=] of [=this=]'s <a>range</a>, and
then set [=this=]'s <a>range</a> to the newly-created <a>range</a>.
</p>
</dd>
<dt>
<dfn>extend()</dfn> method
</dt>
<dd>
<p>
The method must follow these steps:
</p>
<ol>
<li>If the <a>document</a> associated with [=this=] is not a
[=shadow-including inclusive ancestor=] of <var>node</var>, abort
these steps.
</li>
<li>If [=this=] is <a>empty</a>, throw an {{InvalidStateError}}
exception and abort these steps.
</li>
<li>Let <var>oldAnchor</var> and <var>oldFocus</var> be the
[=this=]'s <a>anchor</a> and <a>focus</a>, and let
<var>newFocus</var> be the <a>boundary point</a> (<var>node</var>,
<var>offset</var>).
</li>
<li>Let <var>newRange</var> be a new <a>range</a>.
</li>
<li>If <var>node</var>'s [=tree/root=] is not the same as the
[=this=]'s <a>range</a>'s [=tree/root=], [=Range/set the start=]
<var>newRange</var>'s [=range/start=] and [=range/end=] to
<var>newFocus</var>.
</li>
<li>Otherwise, if <var>oldAnchor</var> is [=boundary point/before=]
or equal to <var>newFocus</var>, [=Range/set the start=]
<var>newRange</var>'s [=range/start=] to <var>oldAnchor</var>, then
set its [=range/end=] to <var>newFocus</var>.
</li>
<li>Otherwise, [=Range/set the start=] <var>newRange</var>'s
[=range/start=] to <var>newFocus</var>, then set its [=range/end=]
to <var>oldAnchor</var>.
</li>
<li>Set [=this=]'s <a>range</a> to <var>newRange</var>.
</li>
<li>If <var>newFocus</var> is [=boundary point/before=]
<var>oldAnchor</var>, set [=this=]'s <a>direction</a> to
<a>backwards</a>. Otherwise, set it to <a>forwards</a>.
</li>
</ol>
<p class="note">
Reverse-engineered circa January 2011. IE doesn't support it, so
I'm relying on Firefox (implemented extend() sometime before 2000)
and WebKit (implemented extend() in 2007). I'm mostly ignoring
Opera, because gsnedders tells me its implementation isn't
compatible. Firefox 12.0a1 seems to mutate the existing range. IE9
doesn't support extend(), and it's impossible to tell whether
Chrome 17 dev or Opera Next 12.00 alpha mutate or replace, because
getRangeAt() returns a copy anyway. Nevertheless, I go against
Gecko here, to be consistent with collapse().
</p>
</dd>
<dt>
<dfn>setBaseAndExtent()</dfn> method
</dt>
<dd>
<p>
The method must follow these steps:
</p>
<ol>
<li>If <var>anchorOffset</var> is longer than
<var>anchorNode</var>'s [=Node/length=] or if
<var>focusOffset</var> is longer than <var>focusNode</var>'s
[=Node/length=], throw an {{IndexSizeError}} exception and abort
these steps.
</li>
<li>If <a>document</a> associated with [=this=] is not a
[=shadow-including inclusive ancestor=] of <var>anchorNode</var> or
<var>focusNode</var>, abort these steps.
</li>
<li>Let <var>anchor</var> be the <a>boundary point</a>
(<var>anchorNode</var>, <var>anchorOffset</var>) and let
<var>focus</var> be the <a>boundary point</a>
(<var>focusNode</var>, <var>focusOffset</var>).
</li>
<li>Let <var>newRange</var> be a new <a>range</a>.
</li>
<li>If <var>anchor</var> is [=boundary point/before=]
<var>focus</var>, [=Range/set the start=] the <var>newRange</var>'s
[=range/start=] to <var>anchor</var> and its [=range/end=] to <var>
focus</var>. Otherwise, [=Range/set the start=] them to
<var>focus</var> and <var>anchor</var> respectively.
</li>
<li>Set [=this=]'s <a>range</a> to <var>newRange</var>.
</li>
<li>If <var>focus</var> is [=boundary point/before=]
<var>anchor</var>, set [=this=]'s <a>direction</a> to
<a>backwards</a>. Otherwise, set it to <a>forwards</a>
</li>
</ol>
</dd>
<dt>
<dfn>selectAllChildren()</dfn> method
</dt>
<dd>
<p>
The method must follow these steps:
</p>
<ol>
<li>If <var>node</var>'s [=tree/root=] is not the <a>document</a>
associated with [=this=], abort these steps.
</li>
<li>Let <var>newRange</var> be a new <a>range</a> and
<var>childCount</var> be the number of [=tree/children=] of
<var>node</var>.
</li>
<li>Set <var>newRange</var>'s [=range/start=] to (<var>node</var>,
<code>0</code>).
</li>
<li>Set <var>newRange</var>'s [=range/end=] to (<var>node</var>,
<var>childCount</var>).
</li>
<li>Set [=this=]'s <a>range</a> to <var>newRange</var>.
</li>
<li>Set [=this=]'s <a>direction</a> to <var>forwards</var>.
</li>
</ol>
<div class="note">
<p>
Based mostly on Firefox 9.0a2. It has a bug that I didn't
reproduce, namely that if you pass a Document as the argument,
the end offset becomes 1 instead of the number of children it
has. It also throws a RangeException instead of DOMException,
because its implementation predated their merging.
</p>
<p>
IE9 behaves similarly but with glitches. It throws "Unspecified
error." if the node is detached or display:none, and apparently
in some random other cases too. It throws "Invalid argument." for
detached comments (only!). Finally, if you pass it a comment, it
seems to select the whole comment, unlike with text nodes.
</p>
<p>
Chrome 16 dev behaves as you'd expect given its Selection
implementation. It refuses to select anything that's not visible,
so it's almost always wrong. Opera 11.50 just does nothing in all
my tests, as usual.
</p>
<p>
The new range replaces any existing one, doesn't mutate it. This
matches IE9 and Firefox 12.0a1. (Chrome 17 dev and Opera Next
12.00 alpha can't be tested, because getRangeAt() returns a copy
anyway.)
</p>
</div>
</dd>
<dt>
<dfn>modify()</dfn> method
</dt>
<dd data-cite="css-writing-modes-4">
<p>
The method must follow these steps:
</p>
<ol>
<li>If <var>alter</var> is not <a>ASCII case-insensitive</a> match
with "extend" or "move", abort these steps.
</li>
<li>If <var>direction</var> is not <a>ASCII case-insensitive</a>
match with "forward", "backward", "left", or "right", abort these
steps.
</li>
<li>If <var>granularity</var> is not <a>ASCII case-insensitive</a>
match with "character", "word", "sentence", "line", "paragraph",
"lineboundary", "sentenceboundary", "paragraphboundary",
"documentboundary", abort these steps.
</li>
<li>If <a>this</a> <a>selection</a> is empty, abort these steps.
</li>
<li>Let <var>effectiveDirection</var> be <a>backwards</a>.
</li>
<li>If <var>direction</var> is <a>ASCII case-insensitive</a> match
with "forward", set <var>effectiveDirection</var> to
<a>forwards</a>.
</li>
<li>If <var>direction</var> is <a>ASCII case-insensitive</a> match
with "right" and [=inline base direction=] of <a>this</a>
<a>selection</a>'s <a>focus</a> is <a data-xref-type="css-value"
data-xref-for="direction">ltr</a>, set
<var>effectiveDirection</var> to <a>forwards</a>.
</li>
<li>If <var>direction</var> is <a>ASCII case-insensitive</a> match
with "left" and [=inline base direction=] of <a>this</a>
<a>selection</a>'s <a>focus</a> is <a data-xref-type="css-value"
data-xref-for="direction">rtl</a>, set
<var>effectiveDirection</var> to <a>forwards</a>.
</li>
<li>Set <a>this</a> <a>selection</a>'s <a>direction</a> to
<var>effectiveDirection</var>.
</li>
<li>If <var>alter</var> is <a>ASCII case-insensitive</a> match with
"extend", set <a>this</a> <a>selection</a>'s <a>focus</a> to the
location as if the user had requested to extend selection by <var>
granularity</var>.
</li>
<li>Otherwise, set <a>this</a> <a>selection</a>'s <a>focus</a> and
<a>anchor</a> to the location as if the user had requested to move
selection by <var>granularity</var>.
</li>
</ol>
<p class="note">
We need to more precisely define what it means to extend or move
selection by each granularity.
</p>
</dd>
<dt>
<dfn>deleteFromDocument()</dfn> method
</dt>
<dd>
<p>
The method must invoke {{Range/deleteContents()}} on [=this=]'s
<a>range</a> if [=this=] is not <a>empty</a> and both <a>focus</a>
and <a>anchor</a> are in the [=document tree=]. Otherwise the
method must do nothing.
</p>
<p class="note">
This is the one method that actually mutates the range instead of
replacing it. This matches IE9 and Firefox 12.0a1. (Chrome 17 dev
and Opera Next 12.00 alpha can't be tested, because getRangeAt()
returns a copy anyway.)
</p>
</dd>
<dt>
<dfn>containsNode()</dfn> method
</dt>
<dd>
<p>
The method must return <code>false</code> if [=this=] is
<a>empty</a> or if <var>node</var>'s [=tree/root=] is not the
document associated with [=this=].
</p>
<p>
Otherwise, if <var>allowPartialContainment</var> is
<code>false</code>, the method must return <code>true</code> if and
only if [=range/start=] of its <a>range</a> is [=boundary
point/before=] or visually equivalent to the first <a>boundary
point</a> in the <var>node</var> <strong>and</strong> [=range/end=]
of its <a>range</a> is [=boundary point/after=] or visually
equivalent to the last <a>boundary point</a> in the
<var>node</var>.
</p>
<p>
If <var>allowPartialContainment</var> is <code>true</code>, the
method must return <code>true</code> if and only if [=range/start=]
of its <a>range</a> is [=boundary point/before=] or visually
equivalent to the last <a>boundary point</a> in the <var>node</var>
<strong>and</strong> [=range/end=] of its <a>range</a> is
[=boundary point/after=] or visually equivalent to the first
<a>boundary point</a> in the <var>node</var>.
</p>
</dd>
<dt>
<dfn>stringifier</dfn>
</dt>
<dd>
<p>
The stringification must return the string, which is the
concatenation of the rendered text if there is a [=range=]
associated with [=this=].
</p>
<p>
If the selection is within a <a>textarea</a> or <a>input</a>
element, it must return the selected substring in its value.
</p>
</dd>
</dl>
<p class="note">
See also <a href=
"https://mxr.mozilla.org/mozilla/source/content/base/public/nsISelection.idl">
nsISelection.idl</a> from Gecko. This spec doesn't have everything from
there yet, in particular selectionLanguageChange() and containsNode()
are missing. They are missing because I couldn't work out how to define
them in terms of Ranges.
</p>
<div class="note">
<p>
Originally, the Selection interface was a Netscape feature. The
original implementation was carried on into Gecko (Firefox), and the
feature was later implemented independently by other browser engines.
The Netscape implementation always allowed multiple ranges in a
single selection, for instance so the user could select a column of a
table However, multi-range selections proved to be an unpleasant
corner case that web developers didn't know about and even Gecko
developers rarely handled correctly. Other browser engines never
implemented the feature, and clamped selections to a single range in
various incompatible fashions.
</p>
<p>
This specification follows non-Gecko engines in restricting
selections to at most one range, but the API was still originally
designed for selections with arbitrary numbers of ranges. This
explains oddities like the coexistence of <code>removeRange()</code>
and <code>removeAllRanges()</code>, and a <code>getRangeAt()</code>
method that takes an integer argument that must always be zero.
</p>
</div>
<p>
All of the members of the {{Selection}} interface are defined in terms
of operations on the <code><a>range</a></code> object (if any)
represented by the object. These operations can raise exceptions, as
defined for the {{Range}} interface; this can therefore result in the
members of the <a>Selection</a> interface raising exceptions as well,
in addition to any explicitly called out above.
</p>
</section>
<section>
<h2>
Extensions to Other Interfaces
</h2>
<p>
This specification extends several interfaces to provide entry points
to the interfaces defined in this specification.
</p>
<section data-dfn-for="Document">
<h3>
Extensions to <code>Document</code> interface
</h3>
<p>
The <code><dfn data-cite="dom#document">Document</dfn></code>
interface is defined in [[HTML]].
</p>
<pre class="idl" data-cite="HTML">
partial interface Document {
Selection? getSelection();
};
</pre>
<dl>
<dt>
<dfn>getSelection()</dfn> method
</dt>
<dd>
<p>
The method must return the <a>selection</a> associated with
[=this=] if [=this=] has an associated [=Document/browsing
context=], and it must return `null` otherwise.
</p>
</dd>
</dl>
</section>
<section data-dfn-for="Window" data-link-for="Window">
<h3>
Extensions to `Window` interface
</h3>
<p>
The <code><dfn data-cite=
"html/window-object.html#window">Window</dfn></code> interface is
defined in [[HTML]].
</p>
<pre class="idl">
partial interface Window {
Selection? getSelection();
};
</pre>
<dl>
<dt>
<dfn>getSelection()</dfn> method
</dt>
<dd>
<p>
The method must invoke and return the result of
{{Document/getSelection()}} on [=this=]'s {{Window.document}} attribute.
</p>
</dd>
</dl>
</section>
<section data-dfn-for="GlobalEventHandlers">
<h3>
Extensions to `GlobalEventHandlers` interface
</h3>
<p>
The <code><dfn data-cite=
"html/webappapis.html#globaleventhandlers">GlobalEventHandlers</dfn></code>
interface is defined in [[HTML]].
</p>
<pre class="idl">
partial interface mixin GlobalEventHandlers {
attribute EventHandler onselectstart;
attribute EventHandler onselectionchange;
};
</pre>
<dl>
<dt>
<dfn>onselectstart</dfn>
</dt>
<dd>
<p>
The attribute must be an <a>event handler IDL attribute</a> for
the <a>selectstart</a> event supported by all <a>HTML
elements</a>, {{Document}} objects, and {{Window}} objects.
</p>
</dd>
<dt>
<dfn>onselectionchange</dfn>
</dt>
<dd>
<p>
The attribute must be an <a>event handler IDL attribute</a> for
the <a>selectionchange</a> event supported by all <a>HTML
elements</a>, {{Document}} objects, and {{Window}} objects.
</p>
</dd>
</dl>
</section>
</section>
<section>
<h2>
Responding to DOM Mutations
</h2>
<p>
When the user agent is to [=replace data=] or [=CharacterData/substring
data=] on {{CharacterData}}, the user agent must update the
<a>range</a> associated with <a>selection</a> of the [=Node/node
document=] of the {{CharacterData}} as if it's a <a>live range</a>.
</p>
<p>
When the user agent is to split a {{Text}} [=node=], the user agent
must update the <a>range</a> associated with <a>selection</a> of the
[=Node/node document=] of the {{Text}} as if it's a <a>live range</a>.
</p>
<p>
When the user agent is to run steps for <code>normalize()</code>
method, the user agent must update the <a>range</a> associated with
<a>selection</a> of the [=Node/node document=] of [=this=] as if it's a
<a>live range</a>.
</p>
<p>
When the user agent is to [=remove=] or [=insert=] a [=node=], the user
agent must update the <a>range</a> associated with <a>selection</a> of
the [=Node/node document=] of the [=node=] as if it's a <a>live
range</a>.
</p>
</section>
<section>
<h2>
User Interactions
</h2>
<p>
The user agent should allow the user to change the <a>selection</a>
associated with the [=navigable/active document=]. If the user makes
any modification to a <a>selection</a>, the user agent must create a
new <a>range</a> with suitable [=range/start=] and [=range/end=] of the
<a>range</a> and associate the <a>selection</a> with this new
<a>range</a> (not modify the existing <a>range</a>), and set update
<a>selection</a>'s <a>direction</a> to <a>forwards</a> if the
[=range/start=] is [=boundary point/before=] or equal to the
[=range/end=], <a>backwards</a> if if the [=range/end=] is [=boundary
point/before=] the [=range/start=], or <a>directionless</a> if the
[=range/start=] and the [=range/end=] cannot be ordered due to the
platform convention.
</p>
<p>
The user agent must not make a <a>selection</a> <a>empty</a> if it was
not already <a>empty</a> in response to any user actions (e.g. clicking
on a non-editable region).
</p>
<p class="note">
See <a href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=15470">bug
15470</a>. IE9 and Opera Next 12.00 alpha allow the user to reset the
range to null after the fact by clicking somewhere; Firefox 12.0a1 and
Chrome 17 dev do not. I follow Gecko/WebKit, because it lessens the
chance of getRangeAt(0) throwing.
</p>
<section>
<h3>
<code><dfn data-dfn-type="event">selectstart</dfn></code> event
</h3>
<p>
When the user agent is about to associate a new range
<var>newRange</var> to the <a>selection</a> in response to a user
initiated action, the user agent must <a>fire an event</a> named
<code>selectstart</code>, which bubbles and is cancelable, at the
[=boundary point/node=] associated with the <a>boundary point</a> of
<var>newRange</var>'s [=range/start=] prior to changing the selection