[cssom] serialization order of components of shorthand properties

On Tue, Jul 17, 2012 at 11:47 AM, L. David Baron <dbaron@dbaron.org> wrote:

> It would be great to get an updating reflecting the last paragraph
> of http://lists.w3.org/Archives/Public/www-style/2012May/1208.html
> sooner rather than later, before it does harm by causing
> implementations to change interoperable behavior.
>
> In particular, this affects the second bullet of
> http://dev.w3.org/csswg/cssom/#serializing-css-values , which
> currently says:
>   # Where multiple CSS component values can appear in any order
>   # without changing the meaning of the value (typically represented
>   # by a double bar || in the value syntax), use the order as given
>   # in the syntax.


So, David, what is your position on the following?

(1) should a canonical order be defined for serializing components of
shorthand properties when returning values for those properties from
CSSStyleDeclaration.getPropertyValue(propertyName)? as you point out DOM-2
Style APIs did not define such an order, however the current CSSOM [1] ED
does define an order (in terms of the syntactic order of the specific
property's definition).

[1]
http://dvcs.w3.org/hg/csswg/raw-file/tip/cssom/Overview.html#serializing-css-values

(2) if the answer to (1) is yes, then which syntactic definition should
apply in the face of (historical) discrepancies? e.g., the order of
components of 'background' shorthand vary between CSS2.1 [2] and CSS3
Backgrounds and Borders [3].

[2] http://www.w3.org/TR/CSS21/colors.html#propdef-background
[3] http://www.w3.org/TR/css3-background/#ltfinal-bg-layergt