[whatwg] Spellchecking proposal #2

[Ian Hickson]

Based on the fedback recently received about how to do spellchecking in 
HTML, here's a second proposal that uses an attribute to control it. 
Comments? (Don't worry about typos and other such minor mistakes.)


AUTHOR REQUIREMENTS

<textarea> and <input> elements may have a new attribute specified,
"spellcheck".  If specified, it must have either the value "on" or the
value "off" (exactly, case-sensitive). The "on" value indicates that
spellchecking is to be enabled, the "off" value indicates that
spellchecking is to be disabled. If the attribute is omitted, the
default value is to use the user preferences.

In addition, there is a "spellcheck" DOM attribute on all elements. On
HTMLInputElement and HTMLTextareaElement elements, it returns true if
the content attribute is "on", false if the attribute is "off", and
the user's preference if the attribute is not set. On other elements,
it also returns the current state of spellchecking for that element,
but this is not represented in a content attribute. The attribute may
be set to "true" to enable spellchecking, or "false" to disable it. On
elements other than HTMLInputElement and HTMLTextareaElement, this is
only expected to be useful if contenteditable="" is used.

Authors should set the document's language information, to enable user
agents to accurately determine which dictionary to use when checking
the spelling or grammar of user input.


IMPLEMENTATION REQUIREMENTS

All elements can have spellchecking enabled or disabled. UAs may allow
the user to set this flag, and may have defaults that vary based and
various heuristics or user preferences. Spellchecking can be enabled
on an element while its children have it disabled. However, by
default, user agents should enable spellchecking for an element if it
is enabled for its parent element and not explicitly disabled for the
child.

If spellchecking is enabled on an element, the UA should indicate
spelling and/or grammar errors in text nodes that are direct
descendants of the element that the user is able to edit, in
attributes of the element that the user is able to edit, and, for
elements that are form controls that accept arbitrary text input, in
the values of those elements.

If spellchecking is disabled, the UA should not indicate spelling or
grammar errors for that element's text and values.

UAs should use the language of the element to determine what spelling
and grammar rules to use. (Language information can come from the
"lang" and "xml:lang" attributes, Content-Language HTTP headers, or
other sources. q.v.)

The HTMLElement interface has one new DOM attribute:

  attribute boolean spellcheck;

Every element remembers what its "spellcheck" DOM attribute was last
set to, if it has ever been set.

On getting, the "spellcheck" DOM attribute returns a value as
determined by the following algorithm.

 * If the element is an "input" element or a "textarea" element, and
   the element has a "spellcheck" content attribute with the exact
   literal value "on", then the DOM attribute must return true.

 * Otherwise, if the element is an "input" element or a "textarea"
   element, and the element has a "spellcheck" content attribute with
   the exact literal value "off", then the DOM attribute must return
   false.

 * Otherwise, if the element is an "input" element or a "textarea"
   element, then the DOM attribute must return true if spellchecking
   is enabled on the element, and false otherwise.

 * Otherwise, the element is neither an "input" element nor a
   "textarea" element. If the DOM attribute has been set, then it must
   return the value it was last set to.

 * Otherwise, the element is neither an "input" element nor a
   "textarea" element, and the DOM attribute has never been set. The
   DOM attribute must return true if spellchecking is enabled on the
   element, and false otherwise.

Setting the DOM attribute has the effect determined by the following
algorithm:

 * If the element is an "input" element or a "textarea" element, then
   the element's "spellcheck" content attribute must be set to the
   literal value "on" if the attribute is being set to the "true"
   value, and "off" otherwise. (This affects the spellchecking of the
   element, see below.)

 * Otherwise, the element's spellchecking should be enabled if the DOM
   attribute is set to the value true, and should be disabled
   otherwise.

On "input" and "textarea" elements, setting the "spellcheck" attribute
to the value "on" (whether dynamically or in the source markup) should
enable spellchecking, and setting the "spellcheck" attribute to the
value "off" should disable it. User agents must ignore all other
values, such that setting the attribute to a value other than "on" or
"off" does not change the spellchecking state for the element.


-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'