Re: [css4-images] element() behavior

On Thu, Aug 2, 2012 at 12:48 PM, Tab Atkins Jr. <jackalmage@gmail.com>wrote:

> On Thu, Aug 2, 2012 at 12:42 PM, Simon Fraser <smfr@me.com> wrote:
> > We know that authors don't understand stacking contexts, so that seems
> > like it would be a source of author confusion.
>
> Another possibility is to require an explicit property on the element
> target (unless it provides a paint source), which has the side-effect
> of making it a stacking context.  We might be able to attach other
> useful abilities to this property, I dunno.
>
> > It might be simpler to just say that element() doesn't render things
> outside
> > of the stacking context of the element() target.
>

I think the new css 'isolation' keyword [1] would fit the bill.
In addition to creating a stacking context, it also forces everything in
that group to be composited/blended/filtered only with things in that group.
So, apart from regular alpha blending, an isolated group would look exactly
the same when it is in the regular tree and used in the element() syntax.




>
> I don't understand what you mean.  Are you implying that we walk up
> the ancestor chain until we find a stacking context, and then render
> that?
>
>
1:
https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html#enable-background