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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 HTML specification, the selection part of the old DOM Range specification.
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.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.
This is work in progress.
This document was published by the Web Applications Working Group as a Working Draft. This document is intended to become a W3C Recommendation.
GitHub Issues are preferred for discussion of this specification.
Publication as a Working Draft does not imply endorsement by the W3C Membership.
This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
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This document is governed by the 15 September 2020 W3C Process Document.
This section is non-normative.
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.
So I changed the spec to a made-up compromise that allows some simplification but doesn't constrain authors much. See discussion. Basically it would throw exceptions in some places to try to stop the selection from containing a range that had a boundary point other than an Element or Text node, or a boundary point that didn't descend from a Document.
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.
See bug 15470. IE9, Firefox 12.0a1, Chrome 17 dev, and Opera Next 12.00 alpha all make the range initially null.
Every document with a browsing context has a unique selection associated with it.
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 Mozilla bug, WebKit bug.
This one selection must be shared by all the content of the document (though not by nested documents), including any editing hosts in the document. Editing hosts that are not inside a document cannot have a selection
Each selection can be associated with a single range. When there is no range associated with the selection, the selection is empty. The selection must be initially empty.
A document's selection is a singleton object associated
with that document, so it gets replaced with a new object when
Document.open()
is called. See bug 15470.
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.
Once a selection is associated with a given range, it must continue to be associated with that same range until this specification requires otherwise.
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.
If the selection's range is not null and is collapsed, then the caret position must be at that range's boundary point. When the selection is not empty, 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 selection, the end of the selection, or somewhere else.
This short-changes Mac users. See bug 13909.
Each selection has a direction, forwards, backwards, or directionless. If the user creates a selection by indicating first one boundary point of the range and then the other (such as by clicking on one point and dragging to another), and the first indicated boundary point is after the second, then the corresponding selection must initially be backwards. If the first indicated boundary point is before the second, then the corresponding selection must initially be forwards. Otherwise, it must be directionless.
Each selections also have an anchor and a focus. If the selection's range is null, its anchor and focus are both null. If the selection's range is not null and its direction is forwards, its anchor is the range's start, and its focus is the end. Otherwise, its focus is the start and its anchor is the end.
Selection interface provides a way to interact with the selection associated with each document.
WebIDL[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
;
Range getRangeAt
(unsigned long index);
undefined addRange
(Range range);
undefined removeRange
(Range range);
undefined removeAllRanges
();
undefined empty
();
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);
[CEReactions]
undefined deleteFromDocument
();
boolean containsNode
(Node node, optional boolean allowPartialContainment = false);
stringifier
;
};
anchorNode
The attribute must return the anchor node
of this, or null
if the anchor is null.
anchorOffset
The attribute must return the anchor offset of this, or 0
if the anchor
is null.
focusNode
The attribute must return the focus node
of this, or null
if the focus is null.
focusOffset
The attribute must return the focus offset of this, or 0
if the focus
is null.
isCollapsed
The attribute must return true if and only if the anchor and focus are the same (including if both are null). Otherwise it must return false.
rangeCount
The attribute must return 0
if this is
empty, and must return 1
otherwise.
type
The attribute must return "None"
if this is empty,
"Caret"
if this's range is collapsed, and
"Range"
otherwise.
getRangeAt()
method
The method must throw an IndexSizeError
exception if
index is not 0
, or if this is
empty. Otherwise, it must return a reference to (not a copy
of) this's range.
addRange()
method
The method must follow these steps:
rangeCount
is not 0
, abort these
steps.
Since range is added by reference, subsequent calls to
getRangeAt(0)
returns the same object, and any changes
that a script makes to range after it is added must be
reflected in the selection, until something else removes or
replaces this's range. In particular, the
selection will contain b as opposed to
a after running the following code: var r =
document.createRange(); r.selectNode(a);
getSelection().addRange(r); r.selectNode(b);
removeRange()
method
The method must make this empty by disassociating its
range if this's range is range.
Otherwise, it must throw a NotFoundError
.
removeAllRanges()
method
The method must make this empty by disassociating its range if this has an associated range.
empty
The method must be an alias, and behave identically, to
removeAllRanges()
.
collapse()
method
The method must follow these steps:
removeAllRanges()
and abort these steps.
IndexSizeError
exception if
offset is longer than node's length and
abort these steps.
setPosition()
method
The method must be an alias, and behave identically, to
collapse()
.
collapseToStart()
method
The method must throw InvalidStateError
exception if the
this is empty. Otherwise, it must create a new
range, set the start both its start and
end to the start of this's range,
and then set this's range to the newly-created
range.
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.
collapseToEnd()
method
The method must throw InvalidStateError
exception if the
this is empty. Otherwise, it must create a new
range, set the start both its start and
end to the end of this's range, and
then set this's range to the newly-created range.
extend()
method
The method must follow these steps:
InvalidStateError
exception and abort these steps.
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().
setBaseAndExtent()
method
The method must follow these steps:
IndexSizeError
exception and abort
these steps.
selectAllChildren()
method
The method must follow these steps:
0
).
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.
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.
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.
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.)
deleteFromDocument()
method
The method must invoke deleteContents
()
on this's
range if this is not empty. Otherwise the method
must do nothing.
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.)
containsNode()
method
The method must return false
if this is
empty or if node's root is not the
document associated with this.
Otherwise, if allowPartialContainment is
false
, the method must return true
if and
only if start of its range is before or visually equivalent to the first boundary
point in the node and end
of its range is after or visually
equivalent to the last boundary point in the
node.
If allowPartialContainment is true
, the
method must return true
if and only if start
of its range is before or visually
equivalent to the first boundary point in the
node or end of its
range is after or visually equivalent to
the last boundary point in the node.
See also nsISelection.idl 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.
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.
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 removeRange()
and removeAllRanges()
, and a getRangeAt()
method that takes an integer argument that must always be zero.
All of the members of the Selection
interface are defined in terms
of operations on the range
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 Selection interface raising exceptions as well,
in addition to any explicitly called out below.
This specification extends several interfaces to provide entry points to the interfaces defined in this specification.
Document
interface
The Document
interface is defined in [HTML].
WebIDLpartial interface Document
{
Selection? getSelection
();
};
getSelection()
method
The method must return the selection associated with
this if this has an associated browsing context, and it must return null
otherwise.
If we create a Document object with no browsing context (say via
document.implementation.createHTMLDocument("")
and call
getSelection
()
on it), IE9 seems to return a different Selection
object. Firefox 12.0a1 and Opera Next 12.00 alpha return the same
object as for the current window. Chrome 17 dev returns null. See
discussion. There's no meaningful selection associated with such
a document, so we follow WebKit and require returning null
.
Window
interface
The Window
interface is
defined in [HTML].
WebIDLpartial interface Window
{
Selection? getSelection
();
};
getSelection()
method
The method must invoke and return the result of
getSelection
()
on this's Window
.document
attribute.
GlobalEventHandlers
interface
The GlobalEventHandlers
interface is defined in [HTML].
WebIDLpartial interface mixin GlobalEventHandlers
{
attribute EventHandler onselectstart
;
attribute EventHandler onselectionchange
;
};
onselectstart
The attribute must be an event handler IDL attribute for
the selectstart
event supported by all HTML
elements, Document
objects, and Window
objects.
onselectionchange
The attribute must be an event handler IDL attribute for
the selectionchange
event supported by all HTML
elements, Document
objects, and Window
objects.
The user agent should allow the user to change the selection associated with the active document. If the user makes any modification to a selection, the user agent must create a new range with suitable start and end of the range and associate the selection with this new range (not modify the existing range), and set update selection's direction to forwards if the start is before or equal to the end, backwards if if the end is before the start, or directionless if the start and the end cannot be ordered due to the platform convention.
The user agent must not make a selection empty if it was not already empty in response to any user actions (e.g. clicking on a non-editable region).
See bug 15470. 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.
selectstart
event
When the user agent is about to associate a new range
newRange to the selection in response to a user
initiated action, the user agent must fire an event with the
name selectstart
, which bubbles and is cancelable, at
the node associated with the boundary point
of newRange's start prior to changing the
selection if the selection was previously empty or the
previously associated range was collapsed.
If the event is canceled, the user agent must not change the selection.
The user agent must not fire an event when the user agent sets the selection empty.
selectionchange
event
When the selection is dissociated with its range,
associated with a new range or the associated range's
boundary point is mutated either by the user or the content
script, the user agent must queue a task to fire an
event with the name selectionchange
, which does not
bubble and is not cancelable, at the document associated with
the selection.
When an input
or textarea
element provide a text selection
and its selection changes (in either extent or direction), the
user agent must queue a task to fire an event with the name
selectionchange
, which does bubble but is not
cancelable, at the element.
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
This specification defines conformance criteria that apply to a single product: the user agent that implements the interfaces that it contains.
Many thanks to
Referenced in:
Referenced in:
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