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Re: [css3-values] RE: CSSStyleDeclaration#length and shorthands.

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Wed, 01 Feb 2012 15:15:01 -0500
Message-ID: <4F299D45.7080200@mit.edu>
To: www-style@w3.org
On 2/1/12 3:06 PM, Glenn Adams wrote:
> While (a) and possibly (c) appear to be the case for current
> implementations, I'm not sure if this is intended or sanctioned by
> existing spec text, either in DOM2 Style or current CSSOM ED.

The DOM2 Style text is basically nuts.  I wouldn't worry too much about it.

We should make the CSSOM ED say whatever the right behavior is.  First 
we need to decide on that behavior.

>   * the existing specs are ambiguous;
>   * this has resulted in significant differences in implementations, and
>     possibly differences from the intentions of the published spec text;

Yes.

Note that the "intentions" of the DOM2 Style authors may simply not be 
achievable, because it was written by people who didn't understand CSS 
very well as far as I can tell.  It makes some clear normative 
requirements that are impossible to satisfy for a CSS OM.

>  1. On query operations (e.g., getting cssText, length, invoking item,
>     getPropertyValue, etc.), does ElementCSSInlineStyle.style represent
>     *only* the declarative content of @style? *OR*
>  2. On query operations, does ElementCSSInlineStyle.style represent the
>     UA's so-called "specified values" [1] state of all properties that
>     do or could apply to the element? i.e., the results of applying the
>     cascading and inheritance steps of the property resolution process?

Depending on what you mean by "declarative content", the aswer is either 
#1 or "neither".

>  3. On mutation operations (e.g., setting cssText, invoking setProperty,
>     etc), does ElementCSSInlineStyle.style represent *only* the
>     declarative content of @style? *OR*
>  4. *On mutation operations, does ElementCSSInlineStyle.style represent
>     the *the UA's "specified values" [1] state of all properties that do
>     or could apply to the element?

Again, no idea what #3 means.  #4 makes no sense for mutations.

>  5. Does mutation implicitly trigger reapplication of the entire
>     property resolution process *and* reformatting?

Yes.  The conceptual model has generally been that any mutation throw 
away all computed data (style and layout) and recomputes everything. 
Modulo the transition-starting mess, that's still the conceptual model; 
everything else is optimizations.

> [Is there an implied
>     delay before acting on this trigger, e.g., in order to coalesce
>     multiple mutations? Or does each mutation require serialized and
>     distinct re-resolution and reformatting?]

Is this observable?

>  6. Do the length and item() members of the CSSStyleDeclaration instance
>     referenced by *ElementCSSInlineStyle.style represent only* the
>     declarations present in cssText or not? If not, then what exactly do
>     they represent? Longhand equivalents only? Longhand equivalents plus
>     shorthand?

This is what we need to decide, yes.

-Boris
Received on Wednesday, 1 February 2012 20:15:29 GMT

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