W3C

HTML 5

A vocabulary and associated APIs for HTML and XHTML

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7 User Interaction

This section describes various features that allow authors to enable users to edit documents and parts of documents interactively.

7.1 Introduction

This section is non-normative.

Would be nice to explain how these features work together.

7.2 The hidden attribute

All 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, relevant. 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 — showing all the form controls in one big page with a scrollbar would be equivalent, and no less correct.

Elements in a section hidden by the hidden attribute are still active, e.g. scripts and form controls in such sections still render execute and submit respectively. Only their presentation to the user changes.

The hidden DOM attribute must reflect the content attribute of the same name.

7.3 Activation

element . click()

Acts as if the element was clicked.

Each element has a click in progress flag, initially set to false.

The click() method must run these steps:

  1. If the element's click in progress flag is set to true, then abort these steps.

  2. Set the click in progress flag on the element to true.

  3. If the element has a defined activation behavior, run synthetic click activation steps on the element. Otherwise, fire a click event at the element.

  4. Set the click in progress flag on the element to false.

7.4 Scrolling elements into view

element . scrollIntoView( [ top ] )

Scrolls the element into view. If the top argument is true, then the element will be scrolled to the top of the viewport, otherwise it'll be scrolled to the bottom. The default is the top.

The scrollIntoView([top]) method, when called, must cause the element on which the method was called to have the attention of the user called to it.

In a speech browser, this could happen by having the current playback position move to the start of the given element.

In visual user agents, if the argument is present and has the value false, the user agent should scroll the element into view such that both the bottom and the top of the element are in the viewport, with the bottom of the element aligned with the bottom of the viewport. If it isn't possible to show the entire element in that way, or if the argument is omitted or is true, then the user agent should instead align the top of the element with the top of the viewport. If the entire scrollable part of the content is visible all at once (e.g. if a page is shorter than the viewport), then the user agent should not scroll anything. Visual user agents should further scroll horizontally as necessary to bring the element to the attention of the user.

Non-visual user agents may ignore the argument, or may treat it in some media-specific manner most useful to the user.

7.5 Focus

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.

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 an element is focused, the element matches the CSS :focus pseudo-class.

7.5.1 Sequential focus navigation

The tabindex content attribute specifies whether the element is focusable, whether it can be reached using sequential focus navigation, and 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.

If the attribute is specified, it must be parsed using the rules for parsing integers. The attribute's values have the following meanings:

If the attribute is omitted or parsing the value returns an error

The user agent should follow platform conventions to determine if the element is to be focusable and, if so, whether the element can be reached using sequential focus navigation, and if so, what its relative order should be.

If the value is a negative integer

The user agent must allow the element to be focused, but should not allow the element to be reached using sequential focus navigation.

If the value is a zero

The user agent must allow the element to be focused, should allow the element to be reached using sequential focus navigation, and should follow platform conventions to determine the element's relative order.

If the value is greater than zero

The user agent must allow the element to be focused, 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:

  • before any focusable element whose tabindex attribute has been omitted or whose value, when parsed, returns an error,
  • before any focusable element whose tabindex attribute has a value equal to or less than zero,
  • after any element whose tabindex attribute has a value greater than zero but less than the value of the tabindex attribute on the element,
  • after any element whose 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,
  • before any element whose 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, and
  • before any element whose tabindex attribute has a value greater than the value of the tabindex attribute on the element.

An element is specially focusable if the tabindex attribute's definition above defines the element to be focusable.

An element that is specially focusable 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).

An element is focusable if the user agent's default behavior allows it to be focusable or if the element is specially focusable, but only if the element is being rendered.

User agents should make the following elements focusable, unless platform conventions dictate otherwise:

The tabIndex DOM attribute must reflect the value of the tabindex content attribute. If the attribute is not present, or parsing its value returns an error, then the DOM attribute must return 0 for elements that are focusable and −1 for elements that are not focusable.

7.5.2 Focus management

The focusing steps are as follows:

  1. If focusing the element will remove the focus from another element, then run the unfocusing steps for that element.

  2. 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.

  3. Fire a simple event called focus at the element.

User agents must run the focusing steps for an element whenever the user moves the focus to a focusable element.

The unfocusing steps are as follows:

  1. 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 called change at the element, then broadcast formchange events at the element's form owner.

  2. Unfocus the element.

  3. Fire a simple event called 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 run the focusing steps for the body element, if there is one; if there is not, then the user agent should 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.

7.5.3 Document-level focus APIs

document . activeElement

Returns the currently focused element.

document . hasFocus()

Returns true if the document has focus; otherwise, returns false.

window . focus()

Focuses the window. Use of this method is discouraged. Allow the user to control window focus instead.

window . blur()

Unfocuses the window. Use of this method is discouraged. Allow the user to control window focus instead.

The activeElement attribute on DocumentHTML 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.

The hasFocus() method on DocumentHTML 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.

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.

7.5.4 Element-level focus APIs

element . focus()

Focuses the element.

element . blur()

Unfocuses the element. Use of this method is discouraged. Focus another element instead.

The focus() method, when invoked, must run the following algorithm:

  1. If the element is marked as locked for focus, then abort these steps.

  2. If the element is not focusable, then abort these steps.

  3. Mark the element as locked for focus.

  4. If the element is not already focused, run the focusing steps for the element.

  5. Unmark the element as locked for focus.

The blur() method, when invoked, should run the focusing steps for the body element, if there is one; if there is not, then it 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.

7.6 The accesskey attribute

All 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, each of which must be exactly one Unicode code point in length.

An element's assigned access key is a key combination derived from the element's accesskey content attribute as follows:

  1. If the element has no accesskey attribute, then skip to the fallback step below.

  2. Otherwise, the user agent must must split the attribute's value on spaces, and let keys be the resulting tokens.

  3. For each value in keys in turn, in the order the tokens appeared in the attribute's value, run the following substeps:

    1. If the value is not a string exactly one Unicode code point in length, then skip the remainder of these steps for this value.

    2. If the value does not correspond to a key on the system's keyboard, then skip the remainder of these steps for this value.

    3. If the user agent can find a combination of modifier keys that, with the key that corresponds to the value given in the attribute, can be used as a shortcut key, then the user agent may assign that combination of keys as the element's assigned access key and abort these steps.

  4. Fallback: Optionally, the user agent may assign a key combination of its chosing as the element's assigned access key and then abort these steps.

  5. 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.

When the user presses the key combination corresponding to the assigned access key for an element, if the element defines a command, and the command's Hidden State facet is false (visible), and the command's Disabled State facet is also false (enabled), then the user agent must trigger the Action of the command.

User agents may expose elements that have an accesskey attribute in other ways as well, e.g. in a menu displayed in response to a specific key combination.

The accessKey DOM attribute must reflect the accesskey content attribute.

The accessKeyLabel DOM attribute must return a string that represents the element's assigned access key, if any. If the element does not have one, then the DOM attribute must return the empty string.

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.

7.7 The text selection APIs

Every browsing context has a selection. The selection can be empty, and the selection can have more than one range (a disjointed selection). The user agent should allow the user to change the selection. User agents are not required to let the user select more than one range, and may collapse multiple ranges in the selection to a single range when the user interacts with the selection. (But, of course, the user agent may let the user create selections with multiple ranges.)

This one selection must be shared by all the content of the browsing context (though not by nested browsing contexts), including any editing hosts in the document. (Editing hosts that are not inside a document cannot have a selection.)

If the selection is empty (collapsed, so that it has only one segment and that segment's start and end points are the same) then the selection's position should equal the caret position. 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.

On some platforms (such as those using Wordstar editing conventions), the caret position is totally independent of the start and end of the selection, even when the selection is empty. On such platforms, user agents may ignore the requirement that the cursor position be linked to the position of the selection altogether.

Mostly for historical reasons, in addition to the browsing context's selection, each textarea and input element has an independent selection. These are the text field selections.

User agents may selectively ignore attempts to use the API to adjust the selection made after the user has modified the selection. For example, if the user has just selected part of a word, the user agent could ignore attempts to use the API call to immediately unselect the selection altogether, but could allow attempts to change the selection to select the entire word.

User agents may also allow the user to create selections that are not exposed to the API.

The select element also has a selection, indicating which items have been picked by the user. This is not discussed in this section.

This specification does not specify how selections are presented to the user. The Selectors specification, in conjunction with CSS, can be used to style text selections using the ::selection pseudo-element. [SELECTORS] [CSS]

7.7.1 APIs for the browsing context selection

window . getSelection()
document . getSelection()

Returns the Selection object for the window, which stringifies to the text of the current selection.

The getSelection() method on the Window interface must return the Selection object representing the selection of that Window object's browsing context.

For historical reasons, the getSelection() method on the HTMLDocument interface must return the same Selection object.

interface Selection {
  readonly attribute Node anchorNode;
  readonly attribute long anchorOffset;
  readonly attribute Node focusNode;
  readonly attribute long focusOffset;
  readonly attribute boolean isCollapsed;
  void collapse(in Node parentNode, in long offset);
  void collapseToStart();
  void collapseToEnd();
  void selectAllChildren(in Node parentNode);
  void deleteFromDocument();
  readonly attribute long rangeCount;
  Range getRangeAt(in long index);
  void addRange(in Range range);
  void removeRange(in Range range);
  void removeAllRanges();
  stringifier DOMString ();
};

The Selection interface is represents a list of Range objects. The first item in the list has index 0, and the last item has index count-1, where count is the number of ranges in the list. [DOMRANGE]

All of the members of the Selection interface are defined in terms of operations on the Range objects represented by this 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.

selection . anchorNode

Returns the element that contains the start of the selection.

Returns null if there's no selection.

selection . anchorOffset

Returns the offset of the start of the selection relative to the element that contains the start of the selection.

Returns 0 if there's no selection.

selection . focusNode

Returns the element that contains the end of the selection.

Returns null if there's no selection.

selection . focusOffset

Returns the offset of the end of the selection relative to the element that contains the end of the selection.

Returns 0 if there's no selection.

collapsed = selection . isCollapsed()

Returns true if there's no selection or if the selection is empty. Otherwise, returns false.

selection . collapsed(parentNode, offset)

Replaces the selection with an empty one at the given position.

Throws a WRONG_DOCUMENT_ERR exception if the given node is in a different document.

selection . collapseToStart()

Replaces the selection with an empty one at the position of the start of the current selection.

Throws an INVALID_STATE_ERR exception if there is no selection.

selection . collapseToEnd()

Replaces the selection with an empty one at the position of the end of the current selection.

Throws an INVALID_STATE_ERR exception if there is no selection.

selection . selectAllChildren(parentNode)

Replaces the selection with one that contains all the contents of the given element.

Throws a WRONG_DOCUMENT_ERR exception if the given node is in a different document.

selection . deleteFromDocument()

Deletes the selection.

selection . rangeCount

Returns the number of ranges in the selection.

selection . getRangeAt(index)

Returns the given range.

Throws an INVALID_STATE_ERR exception if the value is out of range.

selection . addRange(range)

Adds the given range to the selection.

selection . removeRange(range)

Removes the given range from the selection, if the range was one of the ones in the selection.

selection . removeAllRanges()

Removes all the ranges in the selection.

The anchorNode attribute must return the value returned by the startContainer attribute of the last Range object in the list, or null if the list is empty.

The anchorOffset attribute must return the value returned by the startOffset attribute of the last Range object in the list, or 0 if the list is empty.

The focusNode attribute must return the value returned by the endContainer attribute of the last Range object in the list, or null if the list is empty.

The focusOffset attribute must return the value returned by the endOffset attribute of the last Range object in the list, or 0 if the list is empty.

The isCollapsed attribute must return true if there are zero ranges, or if there is exactly one range and its collapsed attribute is itself true. Otherwise it must return false.

The collapse(parentNode, offset) method must raise a WRONG_DOCUMENT_ERR DOM exception if parentNode's Document is not the HTMLDocument object with which the Selection object is associated. Otherwise it is, and the method must remove all the ranges in the Selection list, then create a new Range object, add it to the list, and invoke its setStart() and setEnd() methods with the parentNode and offset values as their arguments.

The collapseToStart() method must raise an INVALID_STATE_ERR DOM exception if there are no ranges in the list. Otherwise, it must invoke the collapse() method with the startContainer and startOffset values of the first Range object in the list as the arguments.

The collapseToEnd() method must raise an INVALID_STATE_ERR DOM exception if there are no ranges in the list. Otherwise, it must invoke the collapse() method with the endContainer and endOffset values of the last Range object in the list as the arguments.

The selectAllChildren(parentNode) method must invoke the collapse() method with the parentNode value as the first argument and 0 as the second argument, and must then invoke the selectNodeContents() method on the first (and only) range in the list with the parentNode value as the argument.

The deleteFromDocument() method must invoke the deleteContents() method on each range in the list, if any, from first to last.

The rangeCount attribute must return the number of ranges in the list.

The getRangeAt(index) method must return the indexth range in the list. If index is less than zero or greater or equal to the value returned by the rangeCount attribute, then the method must raise an INDEX_SIZE_ERR DOM exception.

The addRange(range) method must add the given range Range object to the list of selections, at the end (so the newly added range is the new last range). Duplicates are not prevented; a range may be added more than once in which case it appears in the list more than once, which (for example) will cause stringification to return the range's text twice.

The removeRange(range) method must remove the first occurrence of range in the list of ranges, if it appears at all.

The removeAllRanges() method must remove all the ranges from the list of ranges, such that the rangeCount attribute returns 0 after the removeAllRanges() method is invoked (and until a new range is added to the list, either through this interface or via user interaction).

Objects implementing this interface must stringify to a concatenation of the results of invoking the toString() method of the Range object on each of the ranges of the selection, in the order they appear in the list (first to last).

In the following document fragment, the emphasized parts indicate the selection.

<p>The cute girl likes the <cite>Oxford English Dictionary</cite>.</p>

If a script invoked window.getSelection().toString(), the return value would be "the Oxford English".

7.7.2 APIs for the text field selections

The input and textarea elements define the following members in their DOM interfaces for handling their text selection:

  void select();
           attribute unsigned long selectionStart;
           attribute unsigned long selectionEnd;
  void setSelectionRange(in unsigned long start, in unsigned long end);

These methods and attributes expose and control the selection of input and textarea text fields.

element . select()

Selects everything in the text field.

element . selectionStart [ = value ]

Returns the offset to the start of the selection.

Can be set, to change the start of the selection.

element . selectionEnd [ = value ]

Returns the offset to the end of the selection.

Can be set, to change the end of the selection.

element . setSelectionRange(start, end)

Changes the selection to cover the given substring.

When these methods and attributes are used with input elements while they don't apply, they must raise an INVALID_STATE_ERR exception. Otherwise, they must act as described below.

The select() method must cause the contents of the text field to be fully selected.

The selectionStart attribute must, on getting, return the offset (in logical order) to the character that immediately follows the start of the selection. If there is no selection, then it must return the offset (in logical order) to the character that immediately follows the text entry cursor.

On setting, it must act as if the setSelectionRange() method had been called, with the new value as the first argument, and the current value of the selectionEnd attribute as the second argument, unless the current value of the selectionEnd is less than the new value, in which case the second argument must also be the new value.

The selectionEnd attribute must, on getting, return the offset (in logical order) to the character that immediately follows the end of the selection. If there is no selection, then it must return the offset (in logical order) to the character that immediately follows the text entry cursor.

On setting, it must act as if the setSelectionRange() method had been called, with the current value of the selectionStart attribute as the first argument, and new value as the second argument.

The setSelectionRange(start, end) method must set the selection of the text field to the sequence of characters starting with the character at the startth position (in logical order) and ending with the character at the (end-1)th position. Arguments greater than the length of the value in the text field must be treated as pointing at the end of the text field. If end is less than or equal to start then the start of the selection and the end of the selection must both be placed immediately before the character with offset end. In UAs where there is no concept of an empty selection, this must set the cursor to be just before the character with offset end.

To obtain the currently selected text, the following JavaScript suffices:

var selectionText = control.value.substring(control.selectionStart, control.selectionEnd);

...where control is the input or textarea element.

Characters with no visible rendering, such as U+200D ZERO WIDTH JOINER, still count as characters. Thus, for instance, the selection can include just an invisible character, and the text insertion cursor can be placed to one side or another of such a character.

7.8 The contenteditable attribute

The 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.

Specifically, if an HTML element has a contenteditable attribute set to the true state, or it has its contenteditable attribute set to the inherit state and if its nearest ancestor HTML element with the contenteditable attribute set to a state other than the inherit state has its attribute set to the true state, or if it and its ancestors all have their contenteditable attribute set to the inherit state but the Document has designMode enabled, then the UA must treat the element as editable (as described below).

Otherwise, either the HTML element has a contenteditable attribute set to the false state, or its contenteditable attribute is set to the inherit state and its nearest ancestor HTML element with the contenteditable attribute set to a state other than the inherit state has its attribute set to the false state, or all its ancestors have their contenteditable attribute set to the inherit state and the Document itself has designMode disabled; either way, the element is not editable.

element . contentEditable [ = value ]

Returns "true", "false", or "inherit", based on the state of the contenteditable attribute.

Can be set, to change that state.

Throws a SYNTAX_ERR exception if the new value isn't one of those strings.

element . isContentEditable

Returns true if the element is editable; otherwise, returns false.

The contentEditable DOM 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 raise a SYNTAX_ERR exception.

The isContentEditable DOM attribute, on getting, must return true if the element is editable, and false otherwise.

If an element is editable and its parent element is not, or if an element is editable and it has no parent element, then the element is an editing host. Editable elements can be nested. User agents must make editing hosts focusable (which typically means they enter the tab order). An editing host can contain non-editable sections, these are handled as described below. An editing host can contain non-editable sections that contain further editing hosts.

When an editing host has focus, it must have a caret position that specifies where the current editing position is. It may also have a selection.

How the caret and selection are represented depends entirely on the UA.

7.8.1 User editing actions

There are several actions that the user agent should allow the user to perform while the user is interacting with an editing host. How exactly each action is triggered is not defined for every action, but when it is not defined, suggested key bindings are provided to guide implementors.

Move the caret

User agents must allow users to move the caret to any position within an editing host, even into nested editable elements. This could be triggered as the default action of keydown events with various key identifiers and as the default action of mousedown events.

Change the selection

User agents must allow users to change the selection within an editing host, even into nested editable elements. User agents may prevent selections from being made in ways that cross from editable elements into non-editable elements (e.g. by making each non-editable descendant atomically selectable, but not allowing text selection within them). This could be triggered as the default action of keydown events with various key identifiers and as the default action of mousedown events.

Insert text

This action must be triggered as the default action of a textInput event, and may be triggered by other commands as well. It must cause the user agent to insert the specified text (given by the event object's data attribute in the case of the textInput event) at the caret.

If the caret is positioned somewhere where phrasing content is not allowed (e.g. inside an empty ol element), then the user agent must not insert the text directly at the caret position. In such cases the behavior is UA-dependent, but user agents must not, in response to a request to insert text, generate a DOM that is less conformant than the DOM prior to the request.

User agents should allow users to insert new paragraphs into elements that contains only content other than paragraphs.

For example, given the markup:

<section>
 <dl>
  <dt> Ben </dt>
  <dd> Goat </dd>
 </dl>
</section>

...the user agent should allow the user to insert p elements before and after the dl element, as children of the section element.

Break block

UAs should offer a way for the user to request that the current paragraph be broken at the caret, e.g. as the default action of a keydown event whose identifier is the "Enter" key and that has no modifiers set.

The exact behavior is UA-dependent, but user agents must not, in response to a request to break a paragraph, generate a DOM that is less conformant than the DOM prior to the request.

Insert a line separator

UAs should offer a way for the user to request an explicit line break at the caret position without breaking the paragraph, e.g. as the default action of a keydown event whose identifier is the "Enter" key and that has a shift modifier set. Line separators are typically found within a poem verse or an address. To insert a line break, the user agent must insert a br element.

If the caret is positioned somewhere where phrasing content is not allowed (e.g. in an empty ol element), then the user agent must not insert the br element directly at the caret position. In such cases the behavior is UA-dependent, but user agents must not, in response to a request to insert a line separator, generate a DOM that is less conformant than the DOM prior to the request.

Delete

UAs should offer a way for the user to delete text and elements, including non-editable descendants, e.g. as the default action of keydown events whose identifiers are "U+0008" or "U+007F".

Five edge cases in particular need to be considered carefully when implementing this feature: backspacing at the start of an element, backspacing when the caret is immediately after an element, forward-deleting at the end of an element, forward-deleting when the caret is immediately before an element, and deleting a selection whose start and end points do not share a common parent node.

In any case, the exact behavior is UA-dependent, but user agents must not, in response to a request to delete text or an element, generate a DOM that is less conformant than the DOM prior to the request.

Insert, and wrap text in, semantic elements

UAs should offer the user the ability to mark text and paragraphs with semantics that HTML can express.

UAs should similarly offer a way for the user to insert empty semantic elements to subsequently fill by entering text manually.

UAs should also offer a way to remove those semantics from marked up text, and to remove empty semantic element that have been inserted.

In response to a request from a user to mark text up in italics, user agents should use the i element to represent the semantic. The em element should be used only if the user agent is sure that the user means to indicate stress emphasis.

In response to a request from a user to mark text up in bold, user agents should use the b element to represent the semantic. The strong element should be used only if the user agent is sure that the user means to indicate importance.

The exact behavior is UA-dependent, but user agents must not, in response to a request to wrap semantics around some text or to insert or remove a semantic element, generate a DOM that is less conformant than the DOM prior to the request.

Select and move non-editable elements nested inside editing hosts

UAs should offer a way for the user to move images and other non-editable parts around the content within an editing host. This may be done using the drag and drop mechanism. User agents must not, in response to a request to move non-editable elements nested inside editing hosts, generate a DOM that is less conformant than the DOM prior to the request.

Edit form controls nested inside editing hosts

When an editable form control is edited, the changes must be reflected in both its current value and its default value. For input elements this means updating the defaultValue DOM attribute as well as the value DOM attribute; for select elements it means updating the option elements' defaultSelected DOM attribute as well as the selected DOM attribute; for textarea elements this means updating the defaultValue DOM attribute as well as the value DOM attribute. (Updating the default* DOM attributes causes content attributes to be updated as well.)

User agents may perform several commands per user request; for example if the user selects a block of text and hits Enter, the UA might interpret that as a request to delete the content of the selection followed by a request to break the paragraph at that position.

All of the actions defined above, whether triggered by the user or programmatically (e.g. by execCommand() commands), must fire mutation events as appropriate.

7.8.2 Making entire documents editable

Documents have a designMode, which can be either enabled or disabled.

document . 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.

The designMode DOM attribute on the Document object takes two values, "on" and "off". When it is set, 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.

When designMode is enabled, the DOM attribute must return the value "on", and when it is disabled, it 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.

7.9 Spelling and grammar checking

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 (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:

true-by-default
The element will be checked for spelling and grammar if its contents are editable.
false-by-default
The element will never be checked for spelling and grammar.
inherit-by-default
The element's default behavior is the same as its parent element's. Elements that have no parent element cannot have this as their default behavior.

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. The false state indicates that the element is not to be checked.


element . spellcheck [ = value ]

Returns "true", "false", or "default", based on the state of the spellcheck attribute.

Can be set, to change that state.

Throws a SYNTAX_ERR exception if the new value isn't one of those strings.

The spellcheck DOM 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 "default" otherwise. On setting, if the new value is an ASCII case-insensitive match for the string "default" 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 raise a SYNTAX_ERR exception.

The spellcheck DOM 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:

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/or grammar-checking enabled, the UA must use the following algorithm:

  1. If the user has disabled the checking for this text, then the checking is disabled.
  2. Otherwise, if the user has forced the checking for this text to always be enabled, then the checking is enabled.
  3. Otherwise, if the element with which the text is associated has a 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.
  4. Otherwise, if there is an ancestor element with a 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.
  5. Otherwise, if the element's default behavior is true-by-default, then checking is enabled.
  6. Otherwise, if the element's default behavior is false-by-default, then checking is disabled.
  7. Otherwise, if the element's parent element has its checking enabled, then checking is enabled.
  8. Otherwise, checking is disabled.

If the checking is enabled for a word/sentence/text, the user agent should indicate spelling and/or 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>

7.10 Drag and drop

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.

On media without a pointing device, the user would probably have to explicitly indicate his intention to perform a drag-and-drop operation, stating what he wishes to drag and what he wishes to drop, 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).

7.10.1 Introduction

This section is non-normative.

It's also currently non-existent.

7.10.2 The DragEvent and DataTransfer interfaces

The drag-and-drop processing model involves several events. They all use the DragEvent interface.

interface DragEvent : MouseEvent {
  readonly attribute DataTransfer dataTransfer;

  void initDragEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in AbstractView viewArg, in long detailArg, in long screenXArg, in long screenYArg, in long clientXArg, in long clientYArg, in boolean ctrlKeyArg, in boolean altKeyArg, in boolean shiftKeyArg, in boolean metaKeyArg, in unsigned short buttonArg, in EventTarget relatedTargetArg, in DataTransfer dataTransferArg);
  void initDragEventNS(in DOMString namespaceURIArg, in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in AbstractView viewArg, in long detailArg, in long screenXArg, in long screenYArg, in long clientXArg, in long clientYArg, in unsigned short buttonArg, in EventTarget relatedTargetArg, in DOMString modifiersListArg, in DataTransfer dataTransferArg);
};
event . dataTransfer

Returns the DataTransfer object for the event.

The initDragEvent() and initDragEventNS() methods must initialize the event in a manner analogous to the similarly-named methods in the DOM Events interfaces. [DOMEVENTS]

The initDragEvent() and initDragEventNS() methods handle modifier keys differently, much like the equivalent methods on the MouseEvent interface.

The dataTransfer attribute of the DragEvent interface represents the context information for the event.

interface DataTransfer {
           attribute DOMString dropEffect;
           attribute DOMString effectAllowed;

  readonly attribute DOMStringList types;
  void clearData(optional in DOMString format);
  void setData(in DOMString format, in DOMString data);
  DOMString getData(in DOMString format);
  readonly attribute FileList files;

  void setDragImage(in Element image, in long x, in long y);
  void addElement(in Element element);
};

DataTransfer objects can hold pieces of data, each associated with a unique format. Formats are generally given by MIME types, with some values special-cased for legacy reasons. For the purposes of this API, however, the format strings are opaque, case-sensitive, strings, and the empty string is a valid format string.

dataTransfer . 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.

dataTransfer . effectAllowed [ = value ]

Returns the kinds of operations that are to be allowed.

Can be set, to change the allowed operations.

The possible values are none, copy, copyLink, copyMove, link, linkMove, move, all, and uninitialized,

dataTransfer . types

Returns a DOMStringList 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".

dataTransfer . clearData( [ format ] )

Removes the data of the specified formats. Removes all data if the argument is omitted.

dataTransfer . setData(format, data)

Adds the specified data.

data = dataTransfer . getData(format)

Returns the specified data. If there is no such data, returns the empty string.

dataTransfer . files

Returns a FileList of the files being dragged, if any.

dataTransfer . setDragImage(element, x, y)

Uses the given element to update the drag feedback, replacing any previously specified feedback.

dataTransfer . addElement(element)

Adds the given element to the list of elements used to render the drag feedback.

When a DataTransfer object is created, it must be initialized as follows:

The dropEffect attribute controls the drag-and-drop feedback that the user is given during a drag-and-drop operation.

The attribute must ignore any attempts to set it to a value other than none, copy, link, and move. On getting, the attribute must return the last of those four values that it was set to.

The effectAllowed attribute is used in the drag-and-drop processing model to initialize the dropEffect attribute during the dragenter and dragover events.

The attribute must ignore any attempts to set it to a value other than none, copy, copyLink, copyMove, link, linkMove, move, all, and uninitialized. On getting, the attribute must return the last of those values that it was set to.

The types attribute must return a live DOMStringList that contains the list of formats that were added to the DataTransfer object in the corresponding dragstart event. If any files were included in the drag, then the DOMStringList object must in addition include the string "Files".

If the setData() method is invoked with the string "Files", and some files were included in the drag, then the string "Files" will appear twice in the types attribute's list.

The clearData() method, when called with no arguments, must clear the DataTransfer object of all data (for all formats).

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).

When called with an argument, the clearData(format) method must clear the DataTransfer object of any data associated with the given format. If format is the value "Text", then it must be treated as "text/plain". If the format is "URL", then it must be treated as "text/uri-list".

The setData(format, data) method must add data to the data stored in the DataTransfer object, labeled as being of the type format. This must replace any previous data that had been set for that format. If format is the value "Text", then it must be treated as "text/plain". If the format is "URL", then it must be treated as "text/uri-list".

The getData(format) method must return the data that is associated with the type format, if any, and must return the empty string otherwise. If format is the value "Text", then it must be treated as "text/plain". If the format is "URL", then the data associated with the "text/uri-list" format must be parsed as appropriate for text/uri-list data, and the first URL from the list must be returned. If there is no data with that format, or if there is but it has no URLs, then the method must return the empty string. [RFC2483]

The files attribute must return the FileList object that contains the files that are stored in the DataTransfer object. There is one such object per DataTransfer object.

The setDragImage(element, x, y) method sets which element to use to generate the drag feedback. The element argument can be any Element; if it is an img element, then the user agent should use the element's image (at its intrinsic size) to generate the feedback, otherwise the user agent should base the feedback on the given element (but the exact mechanism for doing so is not specified).

The addElement(element) method is an alternative way of specifying how the user agent is to render the drag feedback. It adds an element to the DataTransfer object.

The difference between setDragImage() and addElement() is that the latter automatically generates the image based on the current rendering of the elements added, whereas the former uses the exact specified image.

7.10.3 Events fired during a drag-and-drop action

The following events are involved in the drag-and-drop model.

Whenever the processing model described below causes one of these events to be fired, the event fired must use the DragEvent interface defined above, must have the bubbling and cancelable behaviors given in the table below, and must have the context information set up as described after the table, with the view attribute set to the view with which the user interacted to trigger the drag-and-drop event, the detail attribute set to zero, the mouse and key attributes set according to the state of the input devices as they would be for user interaction events, and the relatedTarget attribute set to null.

If there is no relevant pointing device, the object must have its screenX, screenY, clientX, clientY, and button attributes set to 0.

Event Name Target Bubbles? Cancelable? dataTransfer effectAllowed dropEffect Default Action
dragstart Source node ✓ Bubbles ✓ Cancelable Contains source node unless a selection is being dragged, in which case it is empty; files returns any files included in the drag operation uninitialized none Initiate the drag-and-drop operation
drag Source node ✓ Bubbles ✓ Cancelable Empty Same as last event none Continue the drag-and-drop operation
dragenter Immediate user selection or the body element ✓ Bubbles ✓ Cancelable Empty Same as last event Based on effectAllowed value Reject immediate user selection as potential target element
dragleave Previous target element ✓ Bubbles Empty Same as last event none None
dragover Current target element ✓ Bubbles ✓ Cancelable Empty Same as last event Based on effectAllowed value Reset the current drag operation to "none"
drop Current target element ✓ Bubbles ✓ Cancelable getData() returns data set in dragstart event; files returns any files included in the drag operation Same as last event Current drag operation Varies
dragend Source node ✓ Bubbles Empty Same as last event Current drag operation Varies

The dataTransfer object's contents are empty except for dragstart events and drop events, for which the contents are set as described in the processing model, below.

The effectAllowed attribute must be set to "uninitialized" for dragstart events, and to whatever value the field had after the last drag-and-drop event was fired for all other events (only counting events fired by the user agent for the purposes of the drag-and-drop model described below).

The dropEffect attribute must be set to "none" for dragstart, drag, and dragleave events (except when stated otherwise in the algorithms given in the sections below), to the value corresponding to the current drag operation for drop and dragend events, and to a value based on the effectAllowed attribute's value and to the drag-and-drop source, as given by the following table, for the remaining events (dragenter and dragover):

effectAllowed dropEffect
none none
copy, copyLink, copyMove, all copy
link, linkMove link
move move
uninitialized when what is being dragged is a selection from a text field move
uninitialized when what is being dragged is a selection copy
uninitialized when what is being dragged is an a element with an href attribute link
Any other case copy

7.10.4 Drag-and-drop processing model

When the user attempts to begin a drag operation, the user agent must first determine what is being dragged. If the drag operation was invoked on a selection, then it is the selection that is being dragged. Otherwise, it is the first element, going up the ancestor chain, starting at the node that the user tried to drag, that has the DOM attribute draggable set to true. If there is no such element, then nothing is being dragged, the drag-and-drop operation is never started, and the user agent must not continue with this algorithm.

img elements and a elements with an href attribute have their draggable attribute set to true by default.

If the user agent determines that something can be dragged, a dragstart event must then be fired at the source node.

The source node depends on the kind of drag and how it was initiated. If it is a selection that is being dragged, then the source node is the 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 deepest node that is a common ancestor of all parts of the selection. If it is not a selection that is being dragged, then the source node is the element that is being dragged.

Multiple events are fired on the source node during the course of the drag-and-drop operation.


The list of dragged nodes also depends on the kind of drag. 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 it is a selection that is being dragged, the dataTransfer member of the event must be created with no nodes. Otherwise, it must be created containing just the source node. Script can use the addElement() method to add further elements to the list of what is being dragged. (This list is only used for rendering the drag feedback.)

The dataTransfer member of the event also has data added to it, as follows:


If the event is canceled, then the drag-and-drop operation must not occur; the user agent must not continue with this algorithm.

If it is not canceled, then the drag-and-drop operation must be initiated.

Since events with no event handlers registered are, almost by definition, never canceled, drag-and-drop is always available to the user if the author does not specifically prevent it.

The drag-and-drop feedback must be generated from the first of the following sources that is available:

  1. The element specified in the last call to the setDragImage() method of the dataTransfer object of the dragstart event, if the method was called. In visual media, if this is used, the x and y arguments that were passed to that method should be used as hints for where to put the cursor relative to the resulting image. The values are expressed as distances in CSS pixels from the left side and from the top side of the image respectively. [CSS]
  2. The elements that were added to the dataTransfer object, both before the event was fired, and during the handling of the event using the addElement() method, if any such elements were indeed added.
  3. The selection that the user is dragging.

The user agent must take a note of the data that was placed in the dataTransfer object. This data will be made available again when the drop event is fired.

From this point until the end of the drag-and-drop operation, device input events (e.g. mouse and keyboard events) must be suppressed. In addition, the user agent must track all DOM changes made during the drag-and-drop operation, and add them to its undo history as one atomic operation once the drag-and-drop operation has ended.

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 handlers 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, every 350ms (±200ms), perform the following steps in sequence. (If the user agent is still performing the previous iteration of the sequence when the next iteration becomes due, the user agent must not execute the overdue iteration, effectively "skipping missed frames" of the drag-and-drop operation.)

  1. First, the user agent must fire a drag event at the source node. If this event is canceled, the user agent must set the current drag operation to none (no drag operation).

  2. Next, if the drag event was not canceled and the user has not ended the drag-and-drop operation, the user agent must check the state of the drag-and-drop operation, as follows:

    1. First, 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 the current target element must be updated, as follows:

      1. If the new immediate user selection is null, or is in a non-DOM document or application, then set the current target element to the same value.

      2. Otherwise, the user agent must fire a dragenter event at the immediate user selection.

      3. If the event is canceled, then the current target element must be set to the immediate user selection.

      4. Otherwise, if the current target element is not the body element, the user agent must fire a dragenter event at the body element, and the current target element must be set to the body element, regardless of whether that event was canceled or not. (If the body element is null, then the current target element would be set to null too in this case, it wouldn't be set to the Document object.)

    2. 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, the user agent must fire a dragleave event at the previous target element.

    3. If the current target element is a DOM element, the user agent must fire a dragover event at this current target element.

      If the dragover event is not canceled, the current drag operation must be reset to "none".

      Otherwise, the current drag operation must be set based on the values the effectAllowed and dropEffect attributes of the dataTransfer object had after the event was handled, 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"

      Then, regardless of whether the dragover event was canceled or not, the drag feedback (e.g. the mouse cursor) must be updated 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.
    4. Otherwise, if the current target element is not a DOM element, the user agent must use platform-specific mechanisms to determine what drag operation is being performed (none, copy, link, or move). This sets the current drag operation.

  3. 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. The user agent must execute the following steps, then stop looping.

    1. 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. If the current target element is a DOM element, the user agent must fire a dragleave event at it; otherwise, if it is not null, it must use platform-specific conventions for drag cancellation.

    2. Otherwise, the drag operation was as success. If the current target element is a DOM element, the user agent must fire a drop event at it; otherwise, it must use platform-specific conventions for indicating a drop.

      When the target is a DOM element, the dropEffect attribute of the event's dataTransfer object must be given the value representing the current drag operation (copy, link, or move), and the object must be set up so that the getData() method will return the data that was added during the dragstart event, and the files attribute will return a FileList object with any files that were dragged.

      If the event is canceled, the current drag operation must be set to the value of the dropEffect attribute of the event's dataTransfer object as it stood after the event was handled.

      Otherwise, the event is not canceled, and the user agent must perform the event's default action, which depends on the exact target as follows:

      If the current target element is a text field (e.g. textarea, or an input element whose type attribute is in the Text state)
      The user agent must insert the data associated with the text/plain format, if any, into the text field 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).
      Otherwise
      Reset the current drag operation to "none".
    3. Finally, the user agent must fire a dragend event at the source node, with the dropEffect attribute of the event's dataTransfer object being set to the value corresponding to the current drag operation.

      The current drag operation can change during the processing of the drop event, if one was fired.

      The event is not cancelable. After the event has been handled, the user agent must act as follows:

      If the current target element is a text field (e.g. textarea, or an input element whose type attribute is in the Text state), and a drop event was fired in the previous step, and the current drag operation is "move", and the source of the drag-and-drop operation is a selection in the DOM
      The user agent should delete the range representing the dragged selection from the DOM.
      If the current target element is a text field (e.g. textarea, or an input element whose type attribute is in the Text state), and a drop event was fired in the previous step, and the current drag operation is "move", and the source of the drag-and-drop operation is a selection in a text field
      The user agent should delete the dragged selection from the relevant text field.
      Otherwise
      The event has no default action.
7.10.4.1 When the drag-and-drop operation starts or ends in another document

The model described above is independent of which Document object the nodes involved are from; the events must be fired as described above and the rest of the processing model must be followed as described above, irrespective of how many documents are involved in the operation.

7.10.4.2 When the drag-and-drop operation starts or ends in another application

If the drag is initiated in another application, the source node is not a DOM node, and the user agent must use platform-specific conventions instead when the requirements above involve the source node. User agents in this situation must act as if the dragged data had been added to the DataTransfer object when the drag started, even though no dragstart event was actually fired; user agents must similarly use platform-specific conventions when deciding on what drag feedback to use.

If a drag is started in a document but ends in another application, then the user agent must instead replace the parts of the processing model relating to handling the target according to platform-specific conventions.

In any case, scripts running in the context of the document must not be able to distinguish the case of a drag-and-drop operation being started or ended in another application from the case of a drag-and-drop operation being started or ended in another document from another domain.

7.10.5 The draggable attribute

All 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.

element . 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 DOM 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 DOM attribute is true become draggable as well.

If an element's draggable content attribute has the state true, the draggable DOM attribute must return true.

Otherwise, if the element's draggable content attribute has the state false, the draggable DOM 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 DOM attribute must return true.

Otherwise, the draggable DOM must return false.

If the draggable DOM attribute is set to the value false, the draggable content attribute must be set to the literal value false. If the draggable DOM attribute is set to the value true, the draggable content attribute must be set to the literal value true.

7.10.6 Copy and paste

Copy-and-paste is a form of drag-and-drop: the "copy" part is equivalent to dragging content to another application (the "clipboard"), and the "paste" part is equivalent to dragging content from another application.

Select-and-paste (a model used by mouse operations in the X Window System) is equivalent to a drag-and-drop operation where the source is the selection.

7.10.6.1 Copy to clipboard

When the user invokes a copy operation, the user agent must act as if the user had invoked a drag on the current selection. If the drag-and-drop operation initiates, then the user agent must act as if the user had indicated (as the immediate user selection) a hypothetical application representing the clipboard. Then, the user agent must act as if the user had ended the drag-and-drop operation without canceling it. If the drag-and-drop operation didn't get canceled, the user agent should then follow the relevant platform-specific conventions for copy operations (e.g. updating the clipboard).

7.10.6.2 Cut to clipboard

When the user invokes a cut operation, the user agent must act as if the user had invoked a copy operation (see the previous section), followed, if the copy was completed successfully, by a selection delete operation.

7.10.6.3 Paste from clipboard

When the user invokes a clipboard paste operation, the user agent must act as if the user had invoked a drag on a hypothetical application representing the clipboard, setting the data associated with the drag as the content on the clipboard (in whatever formats are available).

Then, the user agent must act as if the user had indicated (as the immediate user selection) the element with the keyboard focus, and then ended the drag-and-drop operation without canceling it.

7.10.6.4 Paste from selection

When the user invokes a selection paste operation, the user agent must act as if the user had invoked a drag on the current selection, then indicated (as the immediate user selection) the element with the keyboard focus, and then ended the drag-and-drop operation without canceling it.

7.10.7 Security risks in the drag-and-drop model

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.

7.11 Undo history

There has got to be a better way of doing this, surely.

7.11.1 Introduction

...

7.11.2 Definitions

The user agent must associate an undo transaction history with each HTMLDocument object.

The undo transaction history is a list of entries. The entries are of two type: DOM changes and undo objects.

Each DOM changes entry in the undo transaction history consists of batches of one or more of the following:

Undo object entries consist of objects representing state that scripts running in the document are managing. For example, a Web mail application could use an undo object to keep track of the fact that a user has moved an e-mail to a particular folder, so that the user can undo the action and have the e-mail return to its former location.

Broadly speaking, DOM changes entries are handled by the UA in response to user edits of form controls and editing hosts on the page, and undo object entries are handled by script in response to higher-level user actions (such as interactions with server-side state, or in the implementation of a drawing tool).

7.11.3 The UndoManager interface

This API sucks. Seriously. It's a terrible API. Really bad. I hate it. Here are the requirements:

To manage undo object entries in the undo transaction history, the UndoManager interface can be used:

interface UndoManager {
  readonly attribute unsigned long length;
  getter any item(in unsigned long index);
  readonly attribute unsigned long position;
  unsigned long add(in any data, in DOMString title);
  void remove(in unsigned long index);
  void clearUndo();
  void clearRedo();
};
window . undoManager

Returns the UndoManager object.

undoManager . length

Returns the number of entries in the undo history.

data = undoManager . item(index)
undoManager[index]

Returns the entry with index index in the undo history.

Returns null if index is out of range.

undoManager . position

Returns the number of the current entry in the undo history. (Entries at and past this point are redo entries.)

undoManager . add(data, title)

Adds the specified entry to the undo history.

undoManager . remove(index)

Removes the specified entry to the undo history.

Throws an INDEX_SIZE_ERR exception if the given index is out of range.

undoManager . clearUndo()

Removes all entries before the current position in the undo history.

undoManager . clearRedo()

Removes all entries at and after the current position in the undo history.

The undoManager attribute of the Window interface must return the object implementing the UndoManager interface for that Window object's associated HTMLDocument object.

UndoManager objects represent their document's undo transaction history. Only undo object entries are visible with this API, but this does not mean that DOM changes entries are absent from the undo transaction history.

The length attribute must return the number of undo object entries in the undo transaction history. This is the length.

The object's indices of the supported indexed properties are the numbers in the range zero to length-1, unless the length is zero, in which case there are no supported indexed properties.

The item(n) method must return the nth undo object entry in the undo transaction history.

The undo transaction history has a current position. This is the position between two entries in the undo transaction history's list where the previous entry represents what needs to happen if the user invokes the "undo" command (the "undo" side, lower numbers), and the next entry represents what needs to happen if the user invokes the "redo" command (the "redo" side, higher numbers).

The position attribute must return the index of the undo object entry nearest to the undo position, on the "redo" side. If there are no undo object entries on the "redo" side, then the attribute must return the same as the length attribute. If there are no undo object entries on the "undo" side of the undo position, the position attribute returns zero.

Since the undo transaction history contains both undo object entries and DOM changes entries, but the position attribute only returns indices relative to undo object entries, it is possible for several "undo" or "redo" actions to be performed without the value of the position attribute changing.

The add(data, title) method's behavior depends on the current state. Normally, it must insert the data object passed as an argument into the undo transaction history immediately before the undo position, optionally remembering the given title to use in the UI. If the method is called during an undo operation, however, the object must instead be added immediately after the undo position.

If the method is called and there is neither an undo operation in progress nor a redo operation in progress then any entries in the undo transaction history after the undo position must be removed (as if clearRedo() had been called).

We could fire events when someone adds something to the undo history -- one event per undo object entry before the position (or after, during redo addition), allowing the script to decide if that entry should remain or not. Or something. Would make it potentially easier to expire server-held state when the server limitations come into play.

The remove(index) method must remove the undo object entry with the specified index. If the index is less than zero or greater than or equal to length then the method must raise an INDEX_SIZE_ERR exception. DOM changes entries are unaffected by this method.

The clearUndo() method must remove all entries in the undo transaction history before the undo position, be they DOM changes entries or undo object entries.

The clearRedo() method must remove all entries in the undo transaction history after the undo position, be they DOM changes entries or undo object entries.

Another idea is to have a way for scripts to say "startBatchingDOMChangesForUndo()" and after that the changes to the DOM go in as if the user had done them.

7.11.4 Undo: moving back in the undo transaction history

When the user invokes an undo operation, or when the execCommand() method is called with the undo command, the user agent must perform an undo operation.

If the undo position is at the start of the undo transaction history, then the user agent must do nothing.

If the entry immediately before the undo position is a DOM changes entry, then the user agent must remove that DOM changes entry, reverse the DOM changes that were listed in that entry, and, if the changes were reversed with no problems, add a new DOM changes entry (consisting of the opposite of those DOM changes) to the undo transaction history on the other side of the undo position.

If the DOM changes cannot be undone (e.g. because the DOM state is no longer consistent with the changes represented in the entry), then the user agent must simply remove the DOM changes entry, without doing anything else.

If the entry immediately before the undo position is an undo object entry, then the user agent must first remove that undo object entry from the undo transaction history, and then must fire an undo event at the Window object, using the undo object entry's associated undo object as the event's data.

Any calls to add() while the event is being handled will be used to populate the redo history, and will then be used if the user invokes the "redo" command to undo his undo.

7.11.5 Redo: moving forward in the undo transaction history

When the user invokes a redo operation, or when the execCommand() method is called with the redo command, the user agent must perform a redo operation.

This is mostly the opposite of an undo operation, but the full definition is included here for completeness.

If the undo position is at the end of the undo transaction history, then the user agent must do nothing.

If the entry immediately after the undo position is a DOM changes entry, then the user agent must remove that DOM changes entry, reverse the DOM changes that were listed in that entry, and, if the changes were reversed with no problems, add a new DOM changes entry (consisting of the opposite of those DOM changes) to the undo transaction history on the other side of the undo position.

If the DOM changes cannot be redone (e.g. because the DOM state is no longer consistent with the changes represented in the entry), then the user agent must simply remove the DOM changes entry, without doing anything else.

If the entry immediately after the undo position is an undo object entry, then the user agent must first remove that undo object entry from the undo transaction history, and then must fire a redo event at the Window object, using the undo object entry's associated undo object as the event's data.

7.11.6 The UndoManagerEvent interface and the undo and redo events

interface UndoManagerEvent : Event {
  readonly attribute any data;
  void initUndoManagerEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in any dataArg);
  void initUndoManagerEventNS(in DOMString namespaceURIArg, in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in any dataArg);
};
event . data

Returns the data that was passed to the add() method.

The initUndoManagerEvent() and initUndoManagerEventNS() methods must initialize the event in a manner analogous to the similarly-named methods in the DOM Events interfaces. [DOMEVENTS]

The data attribute represents the undo object for the event.

The undo and redo events do not bubble, cannot be canceled, and have no default action. When the user agent fires one of these events it must use the UndoManagerEvent interface, with the data field containing the relevant undo object.

7.11.7 Implementation notes

How user agents present the above conceptual model to the user is not defined. The undo interface could be a filtered view of the undo transaction history, it could manipulate the undo transaction history in ways not described above, and so forth. For example, it is possible to design a UA that appears to have separate undo transaction histories for each form control; similarly, it is possible to design systems where the user has access to more undo information than is present in the official (as described above) undo transaction history (such as providing a tree-based approach to document state). Such UI models should be based upon the single undo transaction history described in this section, however, such that to a script there is no detectable difference.

7.12 Editing APIs

document . execCommand(commandId [, showUI [, value ] ] )

Runs the action specified by the first argument, as described in the list below. The second and third arguments sometimes affect the action. (If they don't they are ignored.)

document . queryCommandEnabled(commandId)

Returns whether the given command is enabled, as described in the list below.

document . queryCommandIndeterm(commandId)

Returns whether the given command is indeterminate, as described in the list below.

document . queryCommandState(commandId)

Returns the state of the command, as described in the list below.

document . queryCommandSupported(commandId)

Returns true if the command is supported; otherwise, returns false.

document . queryCommandValue(commandId)

Returns the value of the command, as described in the list below.

The execCommand(commandId, showUI, value) method on the HTMLDocument interface allows scripts to perform actions on the current selection or at the current caret position. Generally, these commands would be used to implement editor UI, for example having a "delete" button on a toolbar.

There are three variants to this method, with one, two, and three arguments respectively. The showUI and value parameters, even if specified, are ignored unless otherwise stated.

When execCommand() is invoked, the user agent must follow the following steps:

  1. If the given commandId maps to an entry in the list below whose "Enabled When" entry has a condition that is currently false, do nothing; abort these steps.
  2. Otherwise, execute the "Action" listed below for the given commandId.

A document is ready for editing host commands if it has a selection that is entirely within an editing host, or if it has no selection but its caret is inside an editing host.

The queryCommandEnabled(commandId) method, when invoked, must return true if the condition listed below under "Enabled When" for the given commandId is true, and false otherwise.

The queryCommandIndeterm(commandId) method, when invoked, must return true if the condition listed below under "Indeterminate When" for the given commandId is true, and false otherwise.

The queryCommandState(commandId) method, when invoked, must return the value expressed below under "State" for the given commandId.

The queryCommandSupported(commandId) method, when invoked, must return true if the given commandId is in the list below, and false otherwise.

The queryCommandValue(commandId) method, when invoked, must return the value expressed below under "Value" for the given commandId.

The possible values for commandId, and their corresponding meanings, are as follows. These values must be compared to the argument in an ASCII case-insensitive manner.

bold
Summary: Toggles whether the selection is bold.
Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the b element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA).
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: True if the selection, or the caret, if there is no selection, is, or is contained within, a b element. False otherwise.
Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.
createLink
Summary: Toggles whether the selection is a link or not. If the second argument is true, and a link is to be added, the user agent will ask the user for the address. Otherwise, the third argument will be used as the address.
Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the a element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA). If the user agent creates an a element or modifies an existing a element, then if the showUI argument is present and has the value false, then the value of the value argument must be used as the URL of the link. Otherwise, the user agent should prompt the user for the URL of the link.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
delete
Summary: Deletes the selection or the character before the cursor.
Action: The user agent must act as if the user had performed a backspace operation.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
formatBlock
Summary: Wraps the selection in the element given by the second argument. If the second argument doesn't specify an element that is a formatBlock candidate, does nothing.

Action: The user agent must run the following steps:

  1. If the value argument wasn't specified, abort these steps without doing anything.

  2. If the value argument has a leading U+003C LESS-THAN SIGN character ('<') and a trailing U+003E GREATER-THAN SIGN character ('>'), then remove the first and last characters from value.

  3. If value is (now) an ASCII case-insensitive match for the tag name of an element defined by this specification that is defined to be a formatBlock candidate, then, for every position in the selection, take the furthest formatBlock candidate ancestor element of that position that contains only phrasing content, and, if that element is editable and has a parent element whose content model allows that parent to contain any flow content, replace it with an element in the HTML namespace whose name is value, and move all the children that were in it to the new element.

    If there is no selection, then, where in the description above refers to the selection, the user agent must act as if the selection was an empty range (with just one position) at the caret position.

Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
forwardDelete
Summary: Deletes the selection or the character after the cursor.
Action: The user agent must act as if the user had performed a forward delete operation.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertImage
Summary: Toggles whether the selection is an image or not. If the second argument is true, and an image is to be added, the user agent will ask the user for the address. Otherwise, the third argument will be used as the address.
Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the img element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA). If the user agent creates an img element or modifies an existing img element, then if the showUI argument is present and has the value false, then the value of the value argument must be used as the URL of the image. Otherwise, the user agent should prompt the user for the URL of the image.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertHTML
Summary: Replaces the selection with the value of the third argument parsed as HTML.

Action: The user agent must run the following steps:

  1. If the document is an XML document, then throw an INVALID_ACCESS_ERR exception and abort these steps.

  2. If the value argument wasn't specified, abort these steps without doing anything.

  3. If there is a selection, act as if the user had requested that the selection be deleted.

  4. Invoke the HTML fragment parsing algorithm with an arbitrary orphan body element owned by the same Document as the context element and with the value argument as input.

  5. Insert the nodes returned by the previous step into the document at the location of the caret, firing any mutation events as appropriate.

Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertLineBreak
Summary: Inserts a line break.
Action: The user agent must act as if the user had requested a line separator.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertOrderedList
Summary: Toggles whether the selection is an ordered list.
Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the ol element (or unwrapped, or, if there is no selection, have that semantic inserted or removed — the exact behavior is UA-defined).
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertUnorderedList
Summary: Toggles whether the selection is an unordered list.
Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the ul element (or unwrapped, or, if there is no selection, have that semantic inserted or removed — the exact behavior is UA-defined).
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertParagraph
Summary: Inserts a paragraph break.
Action: The user agent must act as if the user had performed a break block editing action.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertText
Summary: Inserts the text given in the third parameter.
Action: The user agent must act as if the user had inserted text corresponding to the value parameter.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
italic
Summary: Toggles whether the selection is italic.
Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the i element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA).
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: True if the selection, or the caret, if there is no selection, is, or is contained within, a i element. False otherwise.
Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.
redo
Summary: Acts as if the user had requested a redo.
Action: The user agent must move forward one step in its undo transaction history, restoring the associated state. If the undo position is at the end of the undo transaction history, the user agent must do nothing. See the undo history.
Enabled When: The undo position is not at the end of the undo transaction history.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
selectAll
Summary: Selects all the editable content.
Action: The user agent must change the selection so that all the content in the currently focused editing host is selected. If no editing host is focused, then the content of the entire document must be selected.
Enabled When: Always.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
subscript
Summary: Toggles whether the selection is subscripted.
Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the sub element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA).
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: True if the selection, or the caret, if there is no selection, is, or is contained within, a sub element. False otherwise.
Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.
superscript
Summary: Toggles whether the selection is superscripted.
Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the sup element (or unwrapped, or, if there is no selection, have that semantic inserted or removed — the exact behavior is UA-defined).
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: True if the selection, or the caret, if there is no selection, is, or is contained within, a sup element. False otherwise.
Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.
undo
Summary: Acts as if the user had requested an undo.
Action: The user agent must move back one step in its undo transaction history, restoring the associated state. If the undo position is at the start of the undo transaction history, the user agent must do nothing. See the undo history.
Enabled When: The undo position is not at the start of the undo transaction history.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
unlink
Summary: Removes all links from the selection.
Action: The user agent must remove all a elements that have href attributes and that are partially or completely included in the current selection.
Enabled When: The document has a selection that is entirely within an editing host and that contains (either partially or completely) at least one a element that has an href attribute.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
unselect
Summary: Unselects everything.
Action: The user agent must change the selection so that nothing is selected.
Enabled When: Always.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
vendorID-customCommandID
Action: User agents may implement vendor-specific extensions to this API. Vendor-specific extensions to the list of commands should use the syntax vendorID-customCommandID so as to prevent clashes between extensions from different vendors and future additions to this specification.
Enabled When: UA-defined.
Indeterminate When: UA-defined.
State: UA-defined.
Value: UA-defined.
Anything else
Action: User agents must do nothing.
Enabled When: Never.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".