A vocabulary and associated APIs for HTML and XHTML
hidden
attributeAll HTML elements may have the hidden
content attribute set. The hidden
attribute is a boolean
attribute. When specified on an element, it indicates that
the element is not yet, or is no longer, directly relevant to the
page's current state, or that it is being used to declare content to
be reused by other parts of the page as opposed to being directly
accessed by the user. User agents should not
render elements that have the hidden
attribute specified.
In the following skeletal example, the attribute is used to hide the Web game's main screen until the user logs in:
<h1>The Example Game</h1> <section id="login"> <h2>Login</h2> <form> ... <!-- calls login() once the user's credentials have been checked --> </form> <script> function login() { // switch screens document.getElementById('login').hidden = true; document.getElementById('game').hidden = false; } </script> </section> <section id="game" hidden> ... </section>
The hidden
attribute must not be
used to hide content that could legitimately be shown in another
presentation. For example, it is incorrect to use hidden
to hide panels in a tabbed dialog,
because the tabbed interface is merely a kind of overflow
presentation — one could equally well just show all the form
controls in one big page with a scrollbar. It is similarly incorrect
to use this attribute to hide content just from one presentation
— if something is marked hidden
, it is hidden from all
presentations, including, for instance, printers.
Elements that are not themselves hidden
must not hyperlink to
elements that are hidden
. The for
attributes of label
and
output
elements that are not themselves hidden
must similarly not refer to
elements that are hidden
. In both
cases, such references would cause user confusion.
Elements and scripts may, however, refer to elements that are
hidden
in other contexts.
For example, it would be incorrect to use the href
attribute to link to a
section marked with the hidden
attribute. If the content is not applicable or relevant, then there
is no reason to link to it.
It would be fine, however, to use the ARIA aria-describedby
attribute to
refer to descriptions that are themselves hidden
. While hiding the descriptions
implies that they are not useful alone, they could be written in
such a way that they are useful in the specific context of being
referenced from the images that they describe.
Similarly, a canvas
element with the hidden
attribute could be used by a
scripted graphics engine as an off-screen buffer, and a form
control could refer to a hidden form
element using its
form
attribute.
Accessibility APIs are encouraged to provide a way to expose structured content while marking it as hidden in the default view. Such content should not be perceivable to users in the normal document flow in any modality, whether using Assistive Technology (AT) or mainstream User Agents.
When such features are available, User Agents may use them to
expose the full semantics of hidden
elements to AT when appropriate, if such content is referenced
indirectly by an ID reference or
valid hash-name reference. This allows ATs to access the
structure of these hidden
elements
upon user request, while keeping the content hidden in all
presentations of the normal document flow. Authors who wish to prevent
user-initiated viewing of a hidden
element should not reference the element with such a mechanism.
Because some User Agents have flattened hidden content when
exposing such content to AT, authors should not reference hidden
content which would lose essential
meaning when flattened.
For example, it would be appropriate for the structure of hidden
table headers referenced from a
headers
attribute to be exposed
to users of AT with such an API.
Cases where it would be inappropriate for the structure of hidden
elements to be exposed to users of
AT with such an API include:
hidden
element referenced by
an href
attribute within the
same documenthidden
form element referenced
by a label
element's for
attribute (because the sorts of
elements referenced from a label
element's for
attribute lose meaning when
flattened)Specifications which define elements and attributes which may be included in conforming HTML5 documents (such as SVG, MathML, and WAI-ARIA) may define how or whether this applies to their elements and attributes. [ARIA] [MATHML] [SVG]
Elements in a section hidden by the hidden
attribute are still active,
e.g. scripts and form controls in such sections still execute
and submit respectively. Only their presentation to the user
changes.
The hidden
IDL
attribute must reflect the content attribute of the
same name.
A subtree of a Document
can be marked as
inert. When a node or one of its ancestors is
inert, then the user agent must act as if the element
was absent for the purposes of targeting user interaction events,
may ignore the node for the purposes of text search user interfaces
(commonly known as "find in page"), and may prevent the user from
selecting text in that node. User agents should allow the user to
override the restrictions on search and text selection, however.
For example, consider a page that consists of
just a single inert paragraph positioned in the middle
of a body
. If a user moves their pointing device from
the body
over to the inert paragraph and
clicks on the paragraph, no mouseover
event would be fired, and
the mousemove
and click
events would be fired on the
body
element rather than the paragraph.
When a node or one of its ancestors is inert, it also can't be focusable.
An entire Document
can be marked as blocked by
a modal dialog subject. While a
Document
is so marked, every node that is in the Document
, with the
exception of the subject element, its ancestors,
and its descendants, must be marked inert. (The
elements excepted by this paragraph can additionally be marked
inert through other means; being part of a modal dialog
does not "protect" a node from being marked inert.)
Only one element at a time can mark a Document
as
being blocked by a modal dialog. When a new
dialog
is made to block a Document
, the previous element,
if any, stops blocking the Document
.
The dialog
element's showModal()
method makes use of
this mechanism.
click
()Acts as if the element was clicked.
The click()
method must
run synthetic click activation steps on the
element.
When an element is focused, key events received by the
document must be targeted at that element. There may be no element
focused; when no element is focused, key events received by the
document must be targeted at the body element, if there
is one, or else at the Document
's root element, if
there is one. If there is no root element, key events must not be
fired.
User agents may track focus for each browsing
context or Document
individually, or may support
only one focused element per top-level browsing context
— user agents should follow platform conventions in this
regard.
Which elements within a top-level browsing context currently have focus must be independent of whether or not the top-level browsing context itself has the system focus.
When a child browsing context is focused, its browsing context container must also have focus.
When an element is focused, the element matches the
CSS :focus
pseudo-class.
tabindex
attributeThe tabindex
content attribute allows authors to control whether an element is
supposed to be focusable, whether it is supposed to be reachable
using sequential focus navigation, and what is to be the relative
order of the element for the purposes of sequential focus
navigation. The name "tab index" comes from the common use of the
"tab" key to navigate through the focusable elements. The term
"tabbing" refers to moving forward through the focusable elements
that can be reached using sequential focus navigation.
The tabindex
attribute, if
specified, must have a value that is a valid
integer.
Each element can have a tabindex focus flag set, as defined below. This flag is a factor that contributes towards determining whether an element is focusable, as described in the next section.
If the attribute is specified, it must be parsed using the rules for parsing integers. The attribute's values have the following meanings:
The user agent should follow platform conventions to determine if the element's tabindex focus flag is set and, if so, whether the element can be reached using sequential focus navigation, and if so, what its relative order should be.
Modulo platform conventions, it is suggested that for the following elements, the tabindex focus flag be set:
a
elements that have an href
attributelink
elements that have an href
attributebutton
elementsinput
elements whose type
attribute are not in the
Hidden stateselect
elementstextarea
elementsdraggable
attribute set, if that would enable the user agent to allow the
user to begin a drag operations for those elements without the use
of a pointing deviceth
elementsOne valid reason to ignore the platform conventions and always allow an element to be focused (by setting its tabindex focus flag) would be if the user's only mechanism for activating an element is through a keyboard action that triggers the focused element.
The user agent must set the element's tabindex focus flag, but should not allow the element to be reached using sequential focus navigation.
One valid reason to ignore the requirement that
sequential focus navigation not allow the author to lead to the
element would be if the user's only mechanism for moving the focus
is sequential focus navigation. For instance, a keyboard-only user
would be unable to click on a text field with a negative tabindex
, so that user's user agent
would be well justified in allowing the user to tab to the control
regardless.
The user agent must set the element's tabindex focus flag, should allow the element to be reached using sequential focus navigation, and should follow platform conventions to determine the element's relative order.
The user agent must set the element's tabindex focus flag, should allow the element to be reached using sequential focus navigation, and should place the element in the sequential focus navigation order so that it is:
tabindex
attribute has been omitted
or whose value, when parsed, returns an error,tabindex
attribute has a value equal
to or less than zero,tabindex
attribute has a value
greater than zero but less than the value of the tabindex
attribute on the
element,tabindex
attribute has a value equal
to the value of the tabindex
attribute on the element but that is earlier in the document in
tree order than the element,tabindex
attribute has a value equal
to the value of the tabindex
attribute on the element but that is later in the document in
tree order than the element, andtabindex
attribute has a value
greater than the value of the tabindex
attribute on the
element.An element that has its tabindex focus flag set but does not otherwise have an activation behavior defined has an activation behavior that does nothing.
This means that an element that is only focusable
because of its tabindex
attribute
will fire a click
event in response
to a non-mouse activation (e.g. hitting the "enter" key while the
element is focused).
The tabIndex
IDL
attribute must reflect the value of the tabindex
content attribute. Its default
value is 0 for elements that are focusable and −1 for
elements that are not focusable.
An element is focusable if all of the following conditions are met:
canvas
element that represents embedded
content.In addition, each shape that is generated for an area
element, any
user-agent-provided interface components of media elements
(e.g. a play button), and distinct user interface components of form controls (e.g. "up" and
"down" buttons on an <input type=number>
spin
control), should be focusable, unless platform conventions dictate otherwise or
unless their corresponding element is disabled. (A
single area
element can correspond to multiple shapes, since image maps can be reused
with multiple images on a page.)
The user agent may also make part of a details
element's rendering
focusable, to enable the element to be opened or closed using keyboard input.
However, this is distinct from the details
or summary
element being
focusable.
Notwithstanding the above, user agents may make any element or part of an element focusable, especially to aid with accessibility or to better match platform conventions.
The focusing steps for an element are as follows:
If the element is not in a
Document
, or if the element's
Document
has no browsing context, or if
the element's Document
's browsing context
has no top-level browsing context, or if the element
is not focusable, or if the element is already
focused, then abort these steps.
If focusing the element will remove the focus from another element, then run the unfocusing steps for that element.
Make the element the currently focused element in its top-level browsing context.
Some elements, most notably area
, can correspond
to more than one distinct focusable area. If a particular area was
indicated when the element was focused, then that is the area that
must get focus; otherwise, e.g. when using the focus()
method, the first such region in
tree order is the one that must be focused.
The user agent may apply relevant platform-specific conventions for focusing widgets.
For example, some platforms select the contents of a text field when that field is focused.
Fire a simple event named focus
at the element.
User agents must synchronously run the focusing steps for an element whenever the user moves the focus to a focusable element.
The unfocusing steps for an element are as follows:
If the element is an input
element, and the
change
event applies to the
element, and the element does not have a defined activation
behavior, and the user has changed the element's value or its list of selected files
while the control was focused without committing that change, then
fire a simple event that bubbles named change
at the element.
Unfocus the element.
Fire a simple event named blur
at the element.
When an element that is focused stops being a focusable element, or stops being focused without another element being explicitly focused in its stead, the user agent should synchronously run the unfocusing steps for the affected element only.
For example, this might happen because the
element is removed from its Document
, or has a hidden
attribute added. It would also
happen to an input
element when the element gets disabled.
activeElement
Returns the currently focused element.
hasFocus
()Returns true if the document has focus; otherwise, returns false.
focus
()Focuses the window. Use of this method is discouraged. Allow the user to control window focus instead.
blur
()Unfocuses the window. Use of this method is discouraged. Allow the user to control window focus instead.
The activeElement
attribute on Document
objects must return the
element in the document that is focused. If no element in the
Document
is focused, this must return the body
element.
When a child browsing context is
focused, its browsing context container is also
focused, by definition. For
example, if the user moves the focus to a text field in an
iframe
, the iframe
is the element with
focus in the parent browsing context.
The hasFocus()
method
on Document
objects must return true if the
Document
's browsing context is focused,
and all its ancestor
browsing contexts are also focused, and the top-level
browsing context has the system focus. If the
Document
has no browsing context or if its
browsing context has no top-level browsing
context, then the method will always return false.
The focus()
method on the Window
object, when invoked, provides a
hint to the user agent that the script believes the user might be
interested in the contents of the browsing context of
the Window
object on which the method was invoked.
User agents are encouraged to have this focus()
method trigger some kind of
notification.
The blur()
method
on the Window
object, when invoked, provides a hint to
the user agent that the script believes the user probably is not
currently interested in the contents of the browsing
context of the Window
object on which the method
was invoked, but that the contents might become interesting again in
the future.
User agents are encouraged to ignore calls to this blur()
method entirely.
Historically the focus()
and blur()
methods actually affected the
system focus, but hostile sites widely abuse this behavior to the
user's detriment.
focus
()Focuses the element.
blur
()Unfocuses the element. Use of this method is discouraged. Focus another element instead.
Do not use this method to hide the focus ring. Do not use any other method that hides the focus ring from keyboard users, in particular do not use a CSS rule to override the 'outline' property. Removal of the focus ring leads to serious accessibility issues for users who navigate and interact with interactive content using the keyboard.
The focus()
method,
when invoked, must run the following algorithm:
If the element is marked as locked for focus, then abort these steps.
Mark the element as locked for focus.
Run the focusing steps for the element.
Unmark the element as locked for focus.
The blur()
method, when
invoked, should run the unfocusing steps for the
element on which the method was called instead. User agents may
selectively or uniformly ignore calls to this method for usability
reasons.
For example, if the blur()
method is unwisely being used to
remove the focus ring for aesthetics reasons, the page would become
unusable by keyboard users. Ignoring calls to this method would thus
allow keyboard users to interact with the page.
This section is non-normative.
Each element that can be activated or focused can be assigned a
single key combination to activate it, using the accesskey
attribute.
The exact shortcut is determined by the user agent, based on
information about the user's keyboard, what keyboard shortcuts
already exist on the platform, and what other shortcuts have been
specified on the page, using the information provided in the accesskey
attribute as a guide.
In order to ensure that a relevant keyboard shortcut is available
on a wide variety of input devices, the author can provide a number
of alternatives in the accesskey
attribute.
Each alternative consists of a single character, such as a letter or digit.
User agents can provide users with a list of the keyboard
shortcuts, but authors are encouraged to do so also. The accessKeyLabel
IDL attribute
returns a string representing the actual key combination assigned by
the user agent.
In this example, an author has provided a button that can be invoked using a shortcut key. To support full keyboards, the author has provided "C" as a possible key. To support devices equipped only with numeric keypads, the author has provided "1" as another possibly key.
<input type=button value=Collect onclick="collect()" accesskey="C 1" id=c>
To tell the user what the shortcut key is, the author has this script here opted to explicitly add the key combination to the button's label:
function addShortcutKeyLabel(button) { if (button.accessKeyLabel != '') button.value += ' (' + button.accessKeyLabel + ')'; } addShortcutKeyLabel(document.getElementById('c'));
Browsers on different platforms will show different labels, even for the same key combination, based on the convention prevalent on that platform. For example, if the key combination is the Control key, the Shift key, and the letter C, a Windows browser might display "Ctrl+Shift+C", whereas a Mac browser might display "^⇧C", while an Emacs browser might just display "C-C". Similarly, if the key combination is the Alt key and the Escape key, Windows might use "Alt+Esc", Mac might use "⌥⎋", and an Emacs browser might use "M-ESC" or "ESC ESC".
In general, therefore, it is unwise to attempt to parse the
value returned from the accessKeyLabel
IDL attribute.
accesskey
attributeAll HTML elements may have the accesskey
content attribute set. The
accesskey
attribute's value is
used by the user agent as a guide for creating a keyboard shortcut
that activates or focuses the element.
If specified, the value must be an ordered set of unique space-separated tokens that are case-sensitive, each of which must be exactly one Unicode code point in length.
In the following example, a variety of links are given with access keys so that keyboard users familiar with the site can more quickly navigate to the relevant pages:
<nav> <p> <a title="Consortium Activities" accesskey="A" href="/Consortium/activities">Activities</a> | <a title="Technical Reports and Recommendations" accesskey="T" href="/TR/">Technical Reports</a> | <a title="Alphabetical Site Index" accesskey="S" href="/Consortium/siteindex">Site Index</a> | <a title="About This Site" accesskey="B" href="/Consortium/">About Consortium</a> | <a title="Contact Consortium" accesskey="C" href="/Consortium/contact">Contact</a> </p> </nav>
In the following example, the search field is given two possible access keys, "s" and "0" (in that order). A user agent on a device with a full keyboard might pick Ctrl+Alt+S as the shortcut key, while a user agent on a small device with just a numeric keypad might pick just the plain unadorned key 0:
<form action="/search"> <label>Search: <input type="search" name="q" accesskey="s 0"></label> <input type="submit"> </form>
In the following example, a button has possible access keys described. A script then tries to update the button's label to advertise the key combination the user agent selected.
<input type=submit accesskey="N @ 1" value="Compose"> ... <script> function labelButton(button) { if (button.accessKeyLabel) button.value += ' (' + button.accessKeyLabel + ')'; } var inputs = document.getElementsByTagName('input'); for (var i = 0; i < inputs.length; i += 1) { if (inputs[i].type == "submit") labelButton(inputs[i]); } </script>
On one user agent, the button's label might become "Compose (⌘N)". On another, it might become "Compose (Alt+⇧+1)". If the user agent doesn't assign a key, it will be just "Compose". The exact string depends on what the assigned access key is, and on how the user agent represents that key combination.
An element's assigned access key is a key combination
derived from the element's accesskey
content attribute.
Initially, an element must not have an assigned access
key.
Whenever an element's accesskey
attribute is set, changed,
or removed, the user agent must update the element's assigned
access key by running the following steps:
If the element has no accesskey
attribute, then skip to the
fallback step below.
Otherwise, split the attribute's value on spaces, and let keys be the resulting tokens.
For each value in keys in turn, in the order the tokens appeared in the attribute's value, run the following substeps:
If the value is not a string exactly one Unicode code point in length, then skip the remainder of these steps for this value.
If the value does not correspond to a key on the system's keyboard, then skip the remainder of these steps for this value.
If the user agent can find a mix of zero or more modifier keys that, combined with the key that corresponds to the value given in the attribute, can be used as the access key, then the user agent may assign that combination of keys as the element's assigned access key and abort these steps.
Fallback: Optionally, the user agent may assign a key combination of its choosing as the element's assigned access key and then abort these steps.
If this step is reached, the element has no assigned access key.
Once a user agent has selected and assigned an access key for an
element, the user agent should not change the element's
assigned access key unless the accesskey
content attribute is changed
or the element is moved to another Document
.
The accessKey
IDL
attribute must reflect the accesskey
content attribute.
The accessKeyLabel
IDL
attribute must return a string that represents the element's
assigned access key, if any. If the element does not
have one, then the IDL attribute must return the empty string.
contenteditable
content attributeThe contenteditable
attribute is an
enumerated attribute whose keywords are the empty string, true
,
and false
. The empty string and the true
keyword map
to the true state. The false
keyword maps to the false state.
In addition, there is a third state, the inherit state, which is the missing value
default (and the invalid value default).
The true state indicates that the element is editable. The inherit state indicates that the element is editable if its parent is. The false state indicates that the element is not editable.
contentEditable
[ = value ]Returns "true
", "false
", or "inherit
", based on the state of the contenteditable
attribute.
Can be set, to change that state.
Throws a SyntaxError
exception if the new value isn't one of those strings.
isContentEditable
Returns true if the element is editable; otherwise, returns false.
The contentEditable
IDL attribute, on
getting, must return the string "true
" if the content attribute is set to
the true state, "false
" if the content attribute is set to the false state,
and "inherit
" otherwise. On setting, if the new value is an ASCII
case-insensitive match for the string "inherit
" then the content
attribute must be removed, if the new value is an ASCII case-insensitive match for
the string "true
" then the content attribute must be set to the string
"true
", if the new value is an ASCII case-insensitive match for
the string "false
" then the content attribute must be set to the string
"false
", and otherwise the attribute setter must throw a
SyntaxError
exception.
The isContentEditable
IDL attribute, on
getting, must return true if the element is either an editing host or
editable, and false otherwise.
designMode
IDL attributeDocuments have a designMode
, which can be either enabled or
disabled.
designMode
[ = value ]Returns "on
" if the document is editable,
and "off
" if it isn't.
Can be set, to change the document's current state. This focuses the document and resets the selection in that document.
The designMode
IDL attribute on the
Document
object takes two values, "on
" and "off
". On setting, the new value must be compared in an ASCII
case-insensitive manner to these two values; if it matches the "on
"
value, then designMode
must be enabled, and if it
matches the "off
" value, then designMode
must be disabled. Other values must be
ignored.
On getting, if designMode
is enabled, the IDL
attribute must return the value "on
"; otherwise it is disabled, and the
attribute must return the value "off
".
The last state set must persist until the document is destroyed or the state is changed.
Initially, documents must have their designMode
disabled.
When the designMode
changes from being disabled to
being enabled, the user agent must synchronously reset the document's active range's
start and end boundary points to be at the start of the Document
and then run the
focusing steps for the root element of the Document
, if any.
Authors are encouraged to set the 'white-space' property on editing hosts and on markup that was originally created through these editing mechanisms to the value 'pre-wrap'. Default HTML whitespace handling is not well suited to WYSIWYG editing, and line wrapping will not work correctly in some corner cases if 'white-space' is left at its default value.
As an example of problems that occur if the default 'normal' value is used instead, consider the case of the user typing "yellow␣␣ball", with two spaces (here represented by "␣") between the words. With the editing rules in place for the default value of 'white-space' ('normal'), the resulting markup will either consist of "yellow ball" or "yellow ball"; i.e., there will be a non-breaking space between the two words in addition to the regular space. This is necessary because the 'normal' value for 'white-space' requires adjacent regular spaces to be collapsed together.
In the former case, "yellow⍽" might wrap to the next line ("⍽" being used here to represent a non-breaking space) even though "yellow" alone might fit at the end of the line; in the latter case, "⍽ball", if wrapped to the start of the line, would have visible indentation from the non-breaking space.
When 'white-space' is set to 'pre-wrap', however, the editing rules will instead simply put two regular spaces between the words, and should the two words be split at the end of a line, the spaces would be neatly removed from the rendering.
The definition of the terms active range, editing
host, and editable, the user interface requirements
of elements that are editing hosts
or editable, the
execCommand()
,
queryCommandEnabled()
,
queryCommandIndeterm()
,
queryCommandState()
,
queryCommandSupported()
, and
queryCommandValue()
methods, text selections, and the delete the selection
algorithm are defined in the HTML Editing APIs specification. The
interaction of editing and the undo/redo features in user agents is
defined by the UndoManager and DOM Transaction specification. [EDITING] [UNDO]
User agents can support the checking of spelling and grammar of
editable text, either in form controls (such as the value of
textarea
elements), or in elements in an editing
host (e.g. using contenteditable
).
For each element, user agents must establish a default behavior, either through defaults or through preferences expressed by the user. There are three possible default behaviors for each element:
The spellcheck
attribute is an enumerated attribute whose keywords are
the empty string, true
and false
. The empty string and the true
keyword map to the true state. The false
keyword maps to the false state. In
addition, there is a third state, the default state, which is
the missing value default (and the invalid value
default).
The true state indicates that the element is
to have its spelling and grammar checked. The default state
indicates that the element is to act according to a default
behavior, possibly based on the parent element's own spellcheck
state, as defined below.
The false state indicates that the element is not to be
checked.
spellcheck
[ = value ]Returns true if the element is to have its spelling and grammar checked; otherwise, returns false.
Can be set, to override the default and set the spellcheck
content attribute.
The spellcheck
IDL
attribute, on getting, must return true if the element's spellcheck
content attribute is in
the true state, or if the element's spellcheck
content attribute is in
the default state and the element's default behavior is true-by-default, or
if the element's spellcheck
content attribute is in the default state and the element's
default behavior is
inherit-by-default
and the element's parent element's spellcheck
IDL attribute would return
true; otherwise, if none of those conditions applies, then the
attribute must instead return false.
The spellcheck
IDL attribute is not affected by user preferences that override the
spellcheck
content attribute,
and therefore might not reflect the actual spellchecking state.
On setting, if the new value is true, then the element's spellcheck
content attribute must be
set to the literal string "true
", otherwise it
must be set to the literal string "false
".
User agents must only consider the following pieces of text as checkable for the purposes of this feature:
input
elements to which the readonly
attribute applies,
whose type
attributes are not
in the Password
state, and that are mutable (i.e.
that do not have the readonly
attribute specified and
that are not disabled).textarea
elements that do not have a
readonly
attribute and
that are not disabled.Text
nodes that are
children of editing hosts or
editable elements.For text that is part of a Text
node, the element
with which the text is associated is the element that is the
immediate parent of the first character of the word, sentence, or
other piece of text. For text in attributes, it is the attribute's
element. For the values of input
and
textarea
elements, it is the element itself.
To determine if a word, sentence, or other piece of text in an applicable element (as defined above) is to have spelling- and grammar-checking enabled, the UA must use the following algorithm:
spellcheck
content
attribute, then: if that attribute is in the true state,
then checking is enabled; otherwise, if that attribute is in the
false state, then checking is disabled.spellcheck
content attribute that is
not in the default state, then: if the nearest such
ancestor's spellcheck
content
attribute is in the true state, then checking is enabled;
otherwise, checking is disabled.If the checking is enabled for a word/sentence/text, the user agent should indicate spelling
and grammar errors in that text. User agents should take into account the other semantics given in
the document when suggesting spelling and grammar corrections. User agents may use the language of
the element to determine what spelling and grammar rules to use, or may use the user's preferred
language settings. UAs should use input
element attributes such as pattern
to ensure that the resulting value is valid, where
possible.
If checking is disabled, the user agent should not indicate spelling or grammar errors for that text.
The element with ID "a" in the following example would be the one used to determine if the word "Hello" is checked for spelling errors. In this example, it would not be.
<div contenteditable="true"> <span spellcheck="false" id="a">Hell</span><em>o!</em> </div>
The element with ID "b" in the following example would have
checking enabled (the leading space character in the attribute's
value on the input
element causes the attribute to be
ignored, so the ancestor's value is used instead, regardless of the
default).
<p spellcheck="true"> <label>Name: <input spellcheck=" false" id="b"></label> </p>
This specification does not define the user interface for spelling and grammar checkers. A user agent could offer on-demand checking, could perform continuous checking while the checking is enabled, or could use other interfaces.
This section defines an event-based drag-and-drop mechanism.
This specification does not define exactly what a drag-and-drop operation actually is.
On a visual medium with a pointing device, a drag operation could
be the default action of a mousedown
event that is followed by a
series of mousemove
events, and
the drop could be triggered by the mouse being released.
When using an input modality other than a pointing device, users would probably have to explicitly indicate their intention to perform a drag-and-drop operation, stating what they wish to drag and where they wish to drop it, respectively.
However it is implemented, drag-and-drop operations must have a starting point (e.g. where the mouse was clicked, or the start of the selection or element that was selected for the drag), may have any number of intermediate steps (elements that the mouse moves over during a drag, or elements that the user picks as possible drop points as he cycles through possibilities), and must either have an end point (the element above which the mouse button was released, or the element that was finally selected), or be canceled. The end point must be the last element selected as a possible drop point before the drop occurs (so if the operation is not canceled, there must be at least one element in the middle step).
This section is non-normative.
To make an element draggable is simple: give the element a draggable
attribute, and set an event
listener for dragstart
that
stores the data being dragged.
The event handler typically needs to check that it's not a text
selection that is being dragged, and then needs to store data into
the DataTransfer
object and set the allowed effects
(copy, move, link, or some combination).
For example:
<p>What fruits do you like?</p> <ol ondragstart="dragStartHandler(event)"> <li draggable="true" data-value="fruit-apple">Apples</li> <li draggable="true" data-value="fruit-orange">Oranges</li> <li draggable="true" data-value="fruit-pear">Pears</li> </ol> <script> var internalDNDType = 'text/x-example'; // set this to something specific to your site function dragStartHandler(event) { if (event.target instanceof HTMLLIElement) { // use the element's data-value="" attribute as the value to be moving: event.dataTransfer.setData(internalDNDType, event.target.dataset.value); event.dataTransfer.effectAllowed = 'move'; // only allow moves } else { event.preventDefault(); // don't allow selection to be dragged } } </script>
To accept a drop, the drop target has to have a dropzone
attribute and listen to the
drop
event.
The value of the dropzone
attribute specifies what kind of data to accept (e.g. "string:text/plain
" to accept any text strings, or
"file:image/png
" to accept a PNG image file) and what
kind of feedback to give (e.g. "move
" to indicate that
the data will be moved).
Instead of using the dropzone
attribute, a drop target can
handle the dragenter
event (to
report whether or not the drop target is to accept the drop) and the
dragover
event (to specify what
feedback is to be shown to the user).
The drop
event allows the actual
drop to be performed. This event needs to be canceled, so that the
dropEffect
attribute's value can be used by the source (otherwise it's
reset).
For example:
<p>Drop your favorite fruits below:</p> <ol dropzone="move string:text/x-example" ondrop="dropHandler(event)"> <!-- don't forget to change the "text/x-example" type to something specific to your site --> </ol> <script> var internalDNDType = 'text/x-example'; // set this to something specific to your site function dropHandler(event) { var li = document.createElement('li'); var data = event.dataTransfer.getData(internalDNDType); if (data == 'fruit-apple') { li.textContent = 'Apples'; } else if (data == 'fruit-orange') { li.textContent = 'Oranges'; } else if (data == 'fruit-pear') { li.textContent = 'Pears'; } else { li.textContent = 'Unknown Fruit'; } event.target.appendChild(li); } </script>
To remove the original element (the one that was dragged) from
the display, the dragend
event
can be used.
For our example here, that means updating the original markup to handle that event:
<p>What fruits do you like?</p> <ol ondragstart="dragStartHandler(event)" ondragend="dragEndHandler(event)"> ...as before... </ol> <script> function dragStartHandler(event) { // ...as before... } function dragEndHandler(event) { // remove the dragged element event.target.parentNode.removeChild(event.target); } </script>
The data that underlies a drag-and-drop operation, known as the drag data store, consists of the following information:
A drag data store item list, which is a list of items representing the dragged data, each consisting of the following information:
The kind of data:
Text.
Binary data with a file name.
A Unicode string giving the type or format of the data, generally given by a MIME type. Some values that are not MIME types are special-cased for legacy reasons. The API does not enforce the use of MIME types; other values can be used as well. In all cases, however, the values are all converted to ASCII lowercase by the API.
Strings that contain space characters cannot be used with the dropzone
attribute, so authors are
encouraged to use only MIME types
or custom strings (without spaces).
There is a limit of one Plain Unicode string item per item type string.
A Unicode or binary string, in some cases with a file name (itself a Unicode string), as per the drag data item kind.
The drag data store item list is ordered in the order that the items were added to the list; most recently added last.
The following information, used to generate the UI feedback during the drag:
A drag data store mode, which is one of the following:
For the dragstart
event.
New data can be added to the drag data store.
For the drop
event. The list of
items representing dragged data can be read, including the data.
No new data can be added.
For all other events. The formats and kinds in the drag data store list of items representing dragged data can be enumerated, but the data itself is unavailable and no new data can be added.
A drag data store allowed effects state, which is a string.
When a drag data store is created, it must be initialized such that its
drag data store item list is empty, it has no
drag data store default feedback, it has no drag
data store bitmap and drag data store hot spot
coordinate, its drag data store mode is protected mode, and its drag data
store allowed effects state is the string "uninitialized
".
DataTransfer
interfaceDataTransfer
objects are used to expose the
drag data store that underlies a drag-and-drop
operation.
interface DataTransfer { attribute DOMString dropEffect; attribute DOMString effectAllowed; readonly attribute DataTransferItemList items; void setDragImage(Element image, long x, long y); /* old interface */ readonly attribute DOMString[] types; DOMString getData(DOMString format); void setData(DOMString format, DOMString data); void clearData(optional DOMString format); readonly attribute FileList files; };
dropEffect
[ = value ]Returns the kind of operation that is currently selected. If
the kind of operation isn't one of those that is allowed by the
effectAllowed
attribute, then the operation will fail.
Can be set, to change the selected operation.
The possible values are "none
", "copy
", "link
", and "move
".
effectAllowed
[ = value ]Returns the kinds of operations that are to be allowed.
Can be set (during the dragstart
event), to change the
allowed operations.
The possible values are "none
", "copy
", "copyLink
", "copyMove
", "link
", "linkMove
", "move
", "all
", and "uninitialized
",
items
Returns a DataTransferItemList
object, with the drag data.
setDragImage
(element, x, y)Uses the given element to update the drag feedback, replacing any previously specified feedback.
types
Returns an array listing the formats that were set in the dragstart
event. In addition, if
any files are being dragged, then one of the types will be the
string "Files
".
getData
(format)Returns the specified data. If there is no such data, returns the empty string.
setData
(format, data)Adds the specified data.
clearData
( [ format ] )Removes the data of the specified formats. Removes all data if the argument is omitted.
files
Returns a FileList
of the files being dragged, if any.
DataTransfer
objects are used during the drag-and-drop events, and are only valid while
those events are being fired.
A DataTransfer
object is associated with a
drag data store while it is valid.
The dropEffect
attribute controls the drag-and-drop feedback that the user is given
during a drag-and-drop operation. When the DataTransfer
object is created, the dropEffect
attribute is
set to a string value. On getting, it must return its current value.
On setting, if the new value is one of "none
",
"copy
", "link
", or
"move
", then the attribute's current value
must be set to the new value. Other values must be ignored.
The effectAllowed
attribute is used in the drag-and-drop processing model to
initialize the dropEffect
attribute
during the dragenter
and dragover
events. When the
DataTransfer
object is created, the effectAllowed
attribute is set to a string value. On getting, it must return its
current value. On setting, if drag data store's mode is the read/write mode and the new value is
one of "none
", "copy
",
"copyLink
", "copyMove
",
"link
", "linkMove
",
"move
", "all
", or "uninitialized
", then the attribute's current value
must be set to the new value. Otherwise it must be left
unchanged.
The items
attribute must return a DataTransferItemList
object
associated with the DataTransfer
object. The same
object must be returned each time.
The setDragImage(element, x, y)
method must run the following
steps:
If the DataTransfer
object is no longer
associated with a drag data store, abort these steps.
Nothing happens.
If the drag data store's mode is not the read/write mode, abort these steps. Nothing happens.
If the element argument is an
img
element, then set the drag data store
bitmap to the element's image (at its intrinsic size);
otherwise, set the drag data store bitmap to an image
generated from the given element (the exact mechanism for doing so
is not currently specified).
Set the drag data store hot spot coordinate to the given x, y coordinate.
The types
attribute must return a live read only array giving the
strings that the following steps would produce. The same object must
be returned each time.
Start with an empty list L.
If the DataTransfer
object is no longer
associated with a drag data store, the array is empty.
Abort these steps; return the empty list L.
For each item in the drag data store item list whose kind is Plain Unicode string, add an entry to the list L consisting of the item's type string.
If there are any items in the drag data store item
list whose kind
is File, then add an entry to the list L
consisting of the string "Files
". (This value
can be distinguished from the other values because it is not
lowercase.)
The strings produced by these steps are those in the list L.
The getData(format)
method
must run the following steps:
If the DataTransfer
object is no longer
associated with a drag data store, return the empty
string and abort these steps.
If the drag data store's mode is the protected mode, return the empty string and abort these steps.
Let format be the first argument, converted to ASCII lowercase.
Let convert-to-URL be false.
If format equals "text
", change it to "text/plain
".
If format equals "url
", change it to "text/uri-list
" and set convert-to-URL to true.
If there is no item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to format, return the empty string and abort these steps.
Let result be the data of the item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to format.
If convert-to-URL is true, then parse
result as appropriate for text/uri-list
data, and then set result to the first URL from the list, if any, or
the empty string otherwise. [RFC2483]
Return result.
The setData(format, data)
method
must run the following steps:
If the DataTransfer
object is no longer
associated with a drag data store, abort these steps.
Nothing happens.
If the drag data store's mode is not the read/write mode, abort these steps. Nothing happens.
Let format be the first argument, converted to ASCII lowercase.
If format equals "text
", change it to "text/plain
".
If format equals "url
", change it to "text/uri-list
".
Remove the item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to format, if there is one.
Add an item to the drag data store item list whose kind is Plain Unicode string, whose type string is equal to format, and whose data is the string given by the method's second argument.
The clearData()
method must run the following steps:
If the DataTransfer
object is no longer
associated with a drag data store, abort these steps.
Nothing happens.
If the drag data store's mode is not the read/write mode, abort these steps. Nothing happens.
If the method was called with no arguments, remove each item in the drag data store item list whose kind is Plain Unicode string, and abort these steps.
Let format be the first argument, converted to ASCII lowercase.
If format equals "text
", change it to "text/plain
".
If format equals "url
", change it to "text/uri-list
".
Remove the item in the drag data store item list whose kind is Plain Unicode string and whose type string is equal to format, if there is one.
The clearData()
method does
not affect whether any files were included in the drag, so the types
attribute's list might
still not be empty after calling clearData()
(it would
still contain the "Files
" string if any files
were included in the drag).
The files
attribute must return a live FileList
sequence consisting of File
objects representing the
files found by the following steps. The same object must be returned
each time. Furthermore, for a given FileList
object and
a given underlying file, the same File
object must be
used each time.
Start with an empty list L.
If the DataTransfer
object is no longer
associated with a drag data store, the
FileList
is empty. Abort these steps; return the
empty list L.
If the drag data store's mode is the protected mode, abort these steps; return the empty list L.
For each item in the drag data store item list whose kind is File , add the item's data (the file, in particular its name and contents, as well as its type) to the list L.
The files found by these steps are those in the list L.
This version of the API does not expose the types of the files during the drag.
DataTransferItemList
interfaceEach DataTransfer
object is associated with a
DataTransferItemList
object.
interface DataTransferItemList { readonly attribute unsigned long length; getter DataTransferItem (unsigned long index); void remove(unsigned long index); void clear(); DataTransferItem? add(DOMString data, DOMString type); DataTransferItem? add(File data); };
length
Returns the number of items in the drag data store.
Returns the DataTransferItem
object representing the indexth entry in the drag data store.
delete
items[index]Removes the indexth entry in the drag data store.
clear
()Removes all the entries in the drag data store.
add
(data)add
(data, type)Adds a new entry for the given data to the drag data store. If the data is plain text then a type string has to be provided also.
While the DataTransferItemList
object's
DataTransfer
object is associated with a drag
data store, the DataTransferItemList
object's
mode is the same as the drag data store mode.
When the DataTransferItemList
object's
DataTransfer
object is not associated with a
drag data store, the DataTransferItemList
object's mode is the disabled mode. The drag
data store referenced in this section (which is used only
when the DataTransferItemList
object is not in the
disabled mode) is the drag data store with which
the DataTransferItemList
object's
DataTransfer
object is associated.
The length
attribute must return zero if the object is in the disabled
mode; otherwise it must return the number of items in the
drag data store item list.
When a DataTransferItemList
object is not in the
disabled mode, its supported property indices
are the numbers in the range
0 .. n-1,
where n is the number of items in the drag
data store item list.
To determine the value of
an indexed property i of a
DataTransferItemList
object, the user agent must return a
DataTransferItem
object representing the ith item in the drag data store. The
same object must be returned each time a particular item is obtained
from this DataTransferItemList
object. The
DataTransferItem
object must be associated with the
same DataTransfer
object as the
DataTransferItemList
object when it is first created.
The remove()
method, when
invoked with the argument i, must run these steps:
If the DataTransferItemList
object is not in the
read/write mode, throw an
InvalidStateError
exception and abort these
steps.
Remove the ith item from the drag data store.
The clear
method,
if the DataTransferItemList
object is in the read/write mode, must remove all the
items from the drag data store. Otherwise, it must do
nothing.
The add()
method
must run the following steps:
If the DataTransferItemList
object is not in the
read/write mode, return null and
abort these steps.
Jump to the appropriate set of steps from the following list:
If there is already an item in the drag data store item
list whose kind is Plain Unicode string and whose type string is
equal to the value of the method's second argument,
converted to ASCII lowercase, then throw a
NotSupportedError
exception and abort these
steps.
Otherwise, add an item to the drag data store item list whose kind is Plain Unicode string, whose type string is equal to the value of the method's second argument, converted to ASCII lowercase, and whose data is the string given by the method's first argument.
File
Add an item to the drag data store item list
whose kind is
File, whose type string is the type
of the File
,
converted to ASCII lowercase, and whose data is the
same as the File
's data.
Determine the value
of the indexed property corresponding to the newly added
item, and return that value (a newly created
DataTransferItem
object).
DataTransferItem
interfaceEach DataTransferItem
object is associated with a
DataTransfer
object.
interface DataTransferItem { readonly attribute DOMString kind; readonly attribute DOMString type; void getAsString(FunctionStringCallback? _callback); File? getAsFile(); }; callback FunctionStringCallback void (DOMString data);
kind
Returns the drag data item kind, one of: "string", "file".
type
Returns the drag data item type string.
getAsString
(callback)Invokes the callback with the string data as the argument, if the drag data item kind is Plain Unicode string.
getAsFile
()Returns a File
object, if the drag data item kind is File.
While the DataTransferItem
object's
DataTransfer
object is associated with a drag
data store and that drag data store's drag
data store item list still contains the item that the
DataTransferItem
object represents, the
DataTransferItem
object's mode is the same as
the drag data store mode. When the
DataTransferItem
object's DataTransfer
object is not associated with a drag data
store, or if the item that the DataTransferItem
object represents has been removed from the relevant drag data
store item list, the DataTransferItem
object's
mode is the disabled mode. The drag data
store referenced in this section (which is used only when the
DataTransferItem
object is not in the disabled
mode) is the drag data store with which the
DataTransferItem
object's DataTransfer
object is associated.
The kind
attribute
must return the empty string if the DataTransferItem
object is in the disabled mode; otherwise it must return the
string given in the cell from the second column of the following
table from the row whose cell in the first column contains the
drag data item kind of the item represented by the
DataTransferItem
object:
Kind | String |
---|---|
Plain Unicode string | "string "
|
File | "file "
|
The type
attribute
must return the empty string if the DataTransferItem
object is in the disabled mode; otherwise it must return
the drag data item type string of the item represented
by the DataTransferItem
object.
The getAsString(callback)
method must run the following
steps:
If the callback is null, abort these steps.
If the DataTransferItem
object is not in the read/write mode or the read-only mode, abort these steps. The
callback is never invoked.
If the drag data item kind is not Plain Unicode string, abort these steps. The callback is never invoked.
Otherwise, queue a task to invoke callback, passing the actual data of the item
represented by the DataTransferItem
object as the
argument.
The getAsFile()
method must run the following steps:
If the DataTransferItem
object is not in the read/write mode or the read-only mode, return null and abort
these steps.
If the drag data item kind is not File, then return null and abort these steps.
Return a new File
object representing the
actual data of the item represented by the
DataTransferItem
object.
DragEvent
interfaceThe drag-and-drop processing model involves several events. They
all use the DragEvent
interface.
[Constructor(DOMString type, optional DragEventInit eventInitDict)] interface DragEvent : MouseEvent { readonly attribute DataTransfer? dataTransfer; }; dictionary DragEventInit : MouseEventInit { DataTransfer? dataTransfer; };
dataTransfer
Returns the DataTransfer
object for the event.
Although, for consistency with other event interfaces, the DragEvent
interface has a constructor, it is not particularly useful. In particular, there's no way to
create a useful DataTransfer
object from script, as DataTransfer
objects
have a processing and security model that is coordinated by the browser during drag-and-drops.
The dataTransfer
attribute of the
DragEvent
interface must return the value it was initialized to. When the object is
created, this attribute must be initialized to null. It represents the context information for the
event.
When a user agent is required to fire a DND event named e at an element, using a particular drag data store, the user agent must run the following steps:
If e is dragstart
, set the
drag data store mode to the read/write
mode.
If e is drop
, set the drag data
store mode to the read-only mode.
Let dataTransfer be a newly created DataTransfer
object
associated with the given drag data store.
Set the effectAllowed
attribute to the drag data
store's drag data store allowed effects state.
Set the dropEffect
attribute to "none
"
if e is dragstart
, drag
, dragexit
, or dragleave
; to the value corresponding to the current drag
operation if e is drop
or dragend
; and to a value based on the effectAllowed
attribute's value and the
drag-and-drop source, as given by the following table, otherwise (i.e. if e
is dragenter
or dragover
):
effectAllowed |
dropEffect |
---|---|
"none " |
"none " |
"copy " |
"copy " |
"copyLink " |
"copy ", or, if appropriate, "link " |
"copyMove " |
"copy ", or, if appropriate, "move " |
"all " |
"copy ", or, if appropriate, either "link " or "move " |
"link " |
"link " |
"linkMove " |
"link ", or, if appropriate, "move " |
"move " |
"move " |
"uninitialized " when what is being dragged is a selection from a text field |
"move ", or, if appropriate, either "copy " or "link " |
"uninitialized " when what is being dragged is a selection |
"copy ", or, if appropriate, either "link " or "move " |
"uninitialized " when what is being dragged is an a element with an href attribute |
"link ", or, if appropriate, either "copy " or "move " |
Any other case | "copy ", or, if appropriate, either "link " or "move " |
Where the table above provides possibly appropriate alternatives, user agents may instead use the listed alternative values if platform conventions dictate that the user has requested those alternate effects.
For example, Windows platform conventions are such that dragging while
holding the "alt" key indicates a preference for linking the data, rather than moving or copying
it. Therefore, on a Windows system, if "link
" is an option according to
the table above while the "alt" key is depressed, the user agent could select that instead of
"copy
" or "move
".
Create a trusted DragEvent
object
and initialize it to have the given name e, to bubble, to be cancelable
unless e is dragexit
, dragleave
, or dragend
, and to
have the detail
attribute initialized to zero, the mouse
and key attributes initialized according to the state of the input devices as they would be for
user interaction events, the relatedTarget
attribute initialized to null,
and the dataTransfer
attribute initialized to
dataTransfer, the DataTransfer
object created above.
If there is no relevant pointing device, the object must have its screenX
, screenY
, clientX
, clientY
, and button
attributes set to 0.
Dispatch the newly created
DragEvent
object at the specified target element.
Set the drag data store allowed effects state to the current value of dataTransfer's effectAllowed
attribute. (It can only have changed value if e is dragstart
.)
Set the drag data store mode back to the protected mode if it was changed in the first step.
Break the association between dataTransfer and the drag data store.
When the user attempts to begin a drag operation, the user agent must run the following steps. User agents must act as if these steps were run even if the drag actually started in another document or application and the user agent was not aware that the drag was occurring until it intersected with a document under the user agent's purview.
Determine what is being dragged, as follows:
If the drag operation was invoked on a selection, then it is the selection that is being dragged.
Otherwise, if the drag operation was invoked on a Document
, it is the first
element, going up the ancestor chain, starting at the node that the user tried to drag, that has
the IDL attribute draggable
set to true. If there is no such
element, then nothing is being dragged; abort these steps, the drag-and-drop operation is never
started.
Otherwise, the drag operation was invoked outside the user agent's purview. What is being dragged is defined by the document or application where the drag was started.
img
elements and a
elements with an href
attribute have their draggable
attribute set to true by default.
Create a drag data store. All the DND events fired subsequently by the steps in this section must use this drag data store.
Establish which DOM node is the source node, as follows:
If it is a selection that is being dragged, then the source node is the
Text
node that the user started the drag on (typically the Text
node
that the user originally clicked). If the user did not specify a particular node, for example if
the user just told the user agent to begin a drag of "the selection", then the source
node is the first Text
node containing a part of the selection.
Otherwise, if it is an element that is being dragged, then the source node is the element that is being dragged.
Otherwise, the source node is part of another document or application. When this specification requires that an event be dispatched at the source node in this case, the user agent must instead follow the platform-specific conventions relevant to that situation.
Multiple events are fired on the source node during the course of the drag-and-drop operation.
Determine the list of dragged nodes, as follows:
If it is a selection that is being dragged, then the list of dragged nodes contains, in tree order, every node that is partially or completely included in the selection (including all their ancestors).
Otherwise, the list of dragged nodes contains only the source node, if any.
If it is a selection that is being dragged, then add an item to the drag data store item list, with its properties set as follows:
text/plain
"Otherwise, if any files are being dragged, then add one item per file to the drag data store item list, with their properties set as follows:
application/octet-stream
" otherwise.Dragging files can currently only happen from outside a browsing context, for example from a file system manager application.
If the drag initiated outside of the application, the user agent must add items to the drag data store item list as appropriate for the data being dragged, honoring platform conventions where appropriate; however, if the platform conventions do not use MIME types to label dragged data, the user agent must make a best-effort attempt to map the types to MIME types, and, in any case, all the drag data item type strings must be converted to ASCII lowercase.
User agents may also add one or more items representing the selection or dragged element(s) in other forms, e.g. as HTML.
If the list of dragged nodes is not empty, then extract the microdata from those nodes into a JSON form, and add one item to the drag data store item list, with its properties set as follows:
application/microdata+json
Run the following substeps:
Let urls be an empty list of absolute URLs.
For each node in the list of dragged nodes:
If urls is still empty, abort these substeps.
Let url string be the result of concatenating the strings in urls, in the order they were added, separated by a U+000D CARRIAGE RETURN U+000A LINE FEED character pair (CRLF).
Add one item to the drag data store item list, with its properties set as follows:
text/uri-list
Update the drag data store default feedback as appropriate for the user agent (if the user is dragging the selection, then the selection would likely be the basis for this feedback; if the user is dragging an element, then that element's rendering would be used; if the drag began outside the user agent, then the platform conventions for determining the drag feedback should be used).
Fire a DND event named dragstart
at the
source node.
If the event is canceled, then the drag-and-drop operation should not occur; abort these steps.
Since events with no event listeners registered are, almost by definition, never canceled, drag-and-drop is always available to the user if the author does not specifically prevent it.
Initiate the drag-and-drop operation in a manner consistent with platform conventions, and as described below.
The drag-and-drop feedback must be generated from the first of the following sources that is available:
From the moment that the user agent is to initiate the drag-and-drop operation, until the end of the drag-and-drop operation, device input events (e.g. mouse and keyboard events) must be suppressed.
During the drag operation, the element directly indicated by the user as the drop target is called the immediate user selection. (Only elements can be selected by the user; other nodes must not be made available as drop targets.) However, the immediate user selection is not necessarily the current target element, which is the element currently selected for the drop part of the drag-and-drop operation.
The immediate user selection changes as the user selects different elements (either by pointing at them with a pointing device, or by selecting them in some other way). The current target element changes when the immediate user selection changes, based on the results of event listeners in the document, as described below.
Both the current target element and the immediate user selection can be null, which means no target element is selected. They can also both be elements in other (DOM-based) documents, or other (non-Web) programs altogether. (For example, a user could drag text to a word-processor.) The current target element is initially null.
In addition, there is also a current drag operation, which can take on the values
"none
", "copy
", "link
", and
"move
". Initially, it has the value "none
". It is
updated by the user agent as described in the steps below.
User agents must, as soon as the drag operation is initiated and every 350ms (±200ms) thereafter for as long as the drag operation is ongoing, queue a task to perform the following steps in sequence:
If the user agent is still performing the previous iteration of the sequence (if any) when the next iteration becomes due, abort these steps for this iteration (effectively "skipping missed frames" of the drag-and-drop operation).
Fire a DND event named drag
at the
source node. If this event is canceled, the user agent must set the current
drag operation to "none
" (no drag operation).
If the drag
event was not canceled and the user has not ended
the drag-and-drop operation, check the state of the drag-and-drop operation, as follows:
If the user is indicating a different immediate user selection than during the
last iteration (or if this is the first iteration), and if this immediate user
selection is not the same as the current target element, then fire a
DND event named dragexit
at the current
target element, and then update the current target element as follows:
Set the current target element to null also.
Set the current target element to the immediate user selection.
Fire a DND event named dragenter
at the
immediate user selection.
If the event is canceled, then set the current target element to the immediate user selection.
Otherwise, run the appropriate step from the following list:
textarea
, or an input
element whose type
attribute is in the Text state) or an editing host or
editable element, and the drag data store item list has an item
with the drag data item type string "text/plain
" and the
drag data item kind Plain Unicode stringSet the current target element to the immediate user selection anyway.
dropzone
attribute that matches the drag data storeSet the current target element to the immediate user selection anyway.
dropzone
attribute that matches the drag data storeLet new target be the nearest (deepest) such ancestor element.
If the immediate user selection is new target, then leave the current target element unchanged.
Otherwise, fire a DND event named dragenter
at new target. Then, set the
current target element to new target, regardless of
whether that event was canceled or not.
Leave the current target element unchanged.
Fire a DND event named dragenter
at
the body element, if there is one, or at the Document
object, if
not. Then, set the current target element to the body element,
regardless of whether that event was canceled or not.
If the previous step caused the current target element to change, and if the
previous target element was not null or a part of a non-DOM document, then fire a DND
event named dragleave
at the previous target
element.
If the current target element is a DOM element, then fire a DND
event named dragover
at this current target
element.
If the dragover
event is not canceled, run the
appropriate step from the following list:
textarea
,
or an input
element whose type
attribute is
in the Text state) or an editing host
or editable element, and the drag data store item list has an item
with the drag data item type string "text/plain
" and the drag
data item kind Plain Unicode stringSet the current drag operation to either "copy
" or
"move
", as appropriate given the platform conventions.
dropzone
attribute that matches the drag data store and specifies an operationSet the current drag operation to the operation specified by the dropzone
attribute of the current target
element.
dropzone
attribute that matches the drag data store and does not
specify an operationSet the current drag operation to "copy
".
Reset the current drag operation to "none
".
Otherwise (if the dragover
event is canceled),
set the current drag operation based on the values of the effectAllowed
and dropEffect
attributes of the DragEvent
object's dataTransfer
object as they stood
after the event dispatch finished, as per the
following table:
effectAllowed |
dropEffect |
Drag operation |
---|---|---|
"uninitialized ", "copy ", "copyLink ", "copyMove ", or "all " |
"copy " |
"copy " |
"uninitialized ", "link ", "copyLink ", "linkMove ", or "all " |
"link " |
"link " |
"uninitialized ", "move ", "copyMove ", "linkMove ", or "all " |
"move " |
"move " |
Any other case | "none " |
Otherwise, if the current target element is not a DOM element, use platform-specific mechanisms to determine what drag operation is being performed (none, copy, link, or move), and set the current drag operation accordingly.
Update the drag feedback (e.g. the mouse cursor) to match the current drag operation, as follows:
Drag operation | Feedback |
---|---|
"copy " |
Data will be copied if dropped here. |
"link " |
Data will be linked if dropped here. |
"move " |
Data will be moved if dropped here. |
"none " |
No operation allowed, dropping here will cancel the drag-and-drop operation. |
Otherwise, if the user ended the drag-and-drop operation (e.g. by releasing the mouse button
in a mouse-driven drag-and-drop interface), or if the drag
event
was canceled, then this will be the last iteration. Run the following steps, then stop the
drag-and-drop operation:
If the current drag operation is "none
" (no drag
operation), or, if the user ended the drag-and-drop operation by canceling it (e.g. by hitting
the Escape key), or if the current target element is null, then the
drag operation failed. Run these substeps:
Let dropped be false.
If the current target element is a DOM element, fire a DND
event named dragleave
at it; otherwise, if it is
not null, use platform-specific conventions for drag cancellation.
Otherwise, the drag operation might be a success; run these substeps:
Let dropped be true.
If the current target element is a DOM element, fire a DND
event named drop
at it; otherwise, use
platform-specific conventions for indicating a drop.
If the event is canceled, set the current drag operation to the value of the
dropEffect
attribute of the
DragEvent
object's dataTransfer
object as it stood after the event dispatch
finished.
Otherwise, the event is not canceled; perform the event's default action, which depends on the exact target as follows:
textarea
,
or an input
element whose type
attribute
is in the Text state) or an editing
host or editable element, and the drag data store item
list has an item with the drag data item type string
"text/plain
" and the drag data item kind Plain Unicode
stringInsert the actual data of the first item in the drag data store item
list to have a drag data item type
string of "text/plain
" and a drag
data item kind that is Plain Unicode string into the text field or
editing host or editable element in a manner consistent with
platform-specific conventions (e.g. inserting it at the current mouse cursor position, or
inserting it at the end of the field).
Reset the current drag operation to "none
".
Fire a DND event named dragend
at the
source node.
Run the appropriate steps from the following list as the default action of the dragend
event:
move
", and the source of the drag-and-drop operation is a selection in the
DOM that is entirely contained within an editing hostmove
", and the source of the drag-and-drop operation is a selection in a text
fieldThe user agent should delete the dragged selection from the relevant text field.
none
"The drag was canceled. If the platform conventions dictate that this be represented to the user (e.g. by animating the dragged selection going back to the source of the drag-and-drop operation), then do so.
The event has no default action.
For the purposes of this step, a text field is a textarea
element or an
input
element whose type
attribute is in one
of the
Text,
Search,
Tel,
URL,
E-mail,
Password, or
Number
states.
User agents are encouraged to consider how to react to drags near the edge of scrollable regions. For example, if a user drags a link to the bottom of the viewport on a long page, it might make sense to scroll the page so that the user can drop the link lower on the page.
This model is independent of which Document
object the nodes involved
are from; the events are fired as described above and the rest of the processing model runs as
described above, irrespective of how many documents are involved in the operation.
This section is non-normative.
The following events are involved in the drag-and-drop model.
Event Name | Target | Cancelable? | Drag data store mode | dropEffect |
Default Action |
---|---|---|---|---|---|
dragstart |
Source node | ✓ Cancelable | Read/write mode | "none " |
Initiate the drag-and-drop operation |
drag |
Source node | ✓ Cancelable | Protected mode | "none " |
Continue the drag-and-drop operation |
dragenter |
Immediate user selection or the body element | ✓ Cancelable | Protected mode | Based on effectAllowed value |
Reject immediate user selection as potential target element |
dragexit |
Previous target element | — | Protected mode | "none " |
None |
dragleave |
Previous target element | — | Protected mode | "none " |
None |
dragover |
Current target element | ✓ Cancelable | Protected mode | Based on effectAllowed value |
Reset the current drag operation to "none" |
drop |
Current target element | ✓ Cancelable | Read-only mode | Current drag operation | Varies |
dragend |
Source node | — | Protected mode | Current drag operation | Varies |
Not shown in the above table: all these events bubble, and the
effectAllowed
attribute always has the value it had after the dragstart
event, defaulting to "uninitialized
" in the dragstart
event.
draggable
attributeAll HTML elements may have the draggable
content attribute set. The
draggable
attribute is an
enumerated attribute. It has three states. The first
state is true and it has the keyword true
. The second state is false and it has
the keyword false
. The third state is
auto; it has no keywords but it is the missing value
default.
The true state means the element is draggable; the false state means that it is not. The auto state uses the default behavior of the user agent.
An element with a draggable
attribute should also have a title
attribute that names the element for the purpose of non-visual
interactions.
draggable
[ = value ]Returns true if the element is draggable; otherwise, returns false.
Can be set, to override the default and set the draggable
content attribute.
The draggable
IDL
attribute, whose value depends on the content attribute's in the way
described below, controls whether or not the element is
draggable. Generally, only text selections are draggable, but
elements whose draggable
IDL
attribute is true become draggable as well.
If an element's draggable
content attribute has the state true, the draggable
IDL attribute must return
true.
Otherwise, if the element's draggable
content attribute has the
state false, the draggable
IDL attribute must return
false.
Otherwise, the element's draggable
content attribute has the
state auto. If the element is an img
element,
or, if the element is an a
element with an href
content attribute, the draggable
IDL attribute must return
true.
Otherwise, the draggable
IDL attribute
must return false.
If the draggable
IDL attribute
is set to the value false, the draggable
content attribute must be
set to the literal value false
. If the draggable
IDL attribute is set to the
value true, the draggable
content attribute must be set to the literal value true
.
dropzone
attributeAll HTML elements may have the dropzone
content attribute set. When
specified, its value must be an unordered set of unique
space-separated tokens that are ASCII
case-insensitive. The allowed values are the following:
copy
Indicates that dropping an accepted item on the element will result in a copy of the dragged data.
move
Indicates that dropping an accepted item on the element will result in the dragged data being moved to the new location.
link
Indicates that dropping an accepted item on the element will result in a link to the original data.
string:
"Indicates that items with the drag data item kind Plain Unicode string and the drag data item type string set to a value that matches the remainder of the keyword are accepted.
file:
"Indicates that items with the drag data item kind File and the drag data item type string set to a value that matches the remainder of the keyword are accepted.
The dropzone
content
attribute's values must not have more than one of the three feedback
values (copy
, move
, and link
) specified. If none are
specified, the copy
value is
implied.
An element with a dropzone
attribute should also have a title
attribute that names the element for the purpose of non-visual
interactions.
A dropzone
attribute matches a drag data store if
the dropzone
processing
steps result in a match.
A dropzone
attribute specifies an operation if
the dropzone
processing
steps result in a specified operation. The specified
operation is as given by those steps.
The dropzone
processing
steps are as follows. They either result in a match or not,
and separate from this result either in a specified operation or
not, as defined below.
Let value be the value of the dropzone
attribute.
Let keywords be the result of splitting value on spaces.
Let matched be false.
Let operation be unspecified.
For each value in keywords, if any, in the order that they were found in value, run the following steps.
Let keyword be the keyword.
If keyword is one of "copy
", "move
", or "link
", then: run the following
substeps:
If operation is still unspecified, then let operation be the string given by keyword.
Skip to the step labeled end of keyword below.
If keyword does not contain a ":" (U+003A) character, or if the first such character in keyword is either the first character or the last character in the string, then skip to the step labeled end of keyword below.
Let kind code be the substring of keyword from the first character in the string to the last character in the string that is before the first ":" (U+003A) character in the string, converted to ASCII lowercase.
Jump to the appropriate step from the list below, based on the value of kind code:
string
"Let kind be Plain Unicode string.
file
"Let kind be File.
Skip to the step labeled end of keyword below.
Let type be the substring of keyword from the first character after the first ":" (U+003A) character in the string, to the last character in the string, converted to ASCII lowercase.
If there exist any items in the drag data store item list whose drag data item kind is the kind given in kind and whose drag data item type is type, then let matched be true.
End of keyword: Go on to the next keyword, if any, or the next step in the overall algorithm, if there are no more.
The algorithm results in a match if matched is true, and does not otherwise.
The algorithm results in a specified operation if operation is not unspecified. The specified operation, if one is specified, is the one given by operation.
The dropzone
IDL
attribute must reflect the content attribute of the
same name.
In this example, a div
element is made into a drop
target for image files using the dropzone
attribute. Images dropped
into the target are then displayed.
<div dropzone="copy file:image/png file:image/gif file:image/jpeg" ondrop="receive(event, this)"> <p>Drop an image here to have it displayed.</p> </div> <script> function receive(event, element) { var data = event.dataTransfer.items; for (var i = 0; i < data.length; i += 1) { if ((data[i].kind == 'file') && (data[i].type.match('^image/'))) { var img = new Image(); img.src = window.createObjectURL(data[i].getAsFile()); element.appendChild(img); } } } </script>
User agents must not make the data added to the DataTransfer
object during the
dragstart
event available to scripts until the drop
event, because otherwise, if a user were to drag sensitive
information from one document to a second document, crossing a hostile third document in the
process, the hostile document could intercept the data.
For the same reason, user agents must consider a drop to be successful only if the user
specifically ended the drag operation — if any scripts end the drag operation, it must be
considered unsuccessful (canceled) and the drop
event must not be
fired.
User agents should take care to not start drag-and-drop operations in response to script actions. For example, in a mouse-and-window environment, if a script moves a window while the user has his mouse button depressed, the UA would not consider that to start a drag. This is important because otherwise UAs could cause data to be dragged from sensitive sources and dropped into hostile documents without the user's consent.
User agents should filter potentially active (scripted) content (e.g. HTML) when it is dragged and when it is dropped, using a whitelist of known-safe features. Similarly, relative URLs should be turned into absolute URLs to avoid references changing in unexpected ways. This specification does not specify how this is performed.
Consider a hostile page providing some content and getting the user to select and drag and
drop (or indeed, copy and paste) that content to a victim page's contenteditable
region. If the browser does not ensure that
only safe content is dragged, potentially unsafe content such as scripts and event handlers in
the selection, once dropped (or pasted) into the victim site, get the privileges of the victim
site. This would thus enable a cross-site scripting attack.