[css-compositing] update enable-background (was: some proposals)

>
>
> >f. update enable-background
> >- remove the ability to set up x, y, width & height. I believe there's
> already consensus on this.
> >- clarify the description and refer to the filters spec which already
> defines this parameter
> >- maybe replace the keyword with 'isolate' which is Adobe's equivalent.
> 'isolate: true' = 'enable-background: new'. I think this is a little easier
> to grasp and it is also familiar to designers.
>
> We really wanted 'isolate' earlier in the SVG spec development. I think
> the horse has
> bolted but if there's any way to align the enable-background model with
> isolate groups
> I'd be eager to hear it.
>
>
Since their behaviors match, it should be no problem to rename it.
If a boolean is not acceptable, how about: 'isolation: isolate/accumulate'.
We can put a note in the spec that says that enable-background is
deprecated but that you can still use it.

Rik