Re: First draft of the blending and compositing spec

Hi!

2012/5/31 Rik Cabanier <cabanier@gmail.com>
>
>
>> I found unclear the way each element, inside the knockout group, is
>> prioritized to determine which element knock-out which other one. It looks
>> like it depend of the z-index of each element but it's not clearly stated.
>> It could also be interpreted as dependent of the source code flow. In the
>> end I presume it depend of the paint order define by each browser. The
>> "knock-out" property definition does not really help much more here.
>>
>
> Correct, it is in paint order.
>

Ok, so in that case it needs some clarification. The paint order to
resolved the knock-out should be specified because if, for whatever reason,
a browser has a different paint order than another one this feature will be
unreliable for authors. In the same spirit, an author should have a way
to specify it's own rendering order for the knock-out. Allowing
this through the z-index property will make sens (we are already used to do
it when dealing with position and in an way, resolving a knock-out is about
performing some positioning).


>
>> 8.1 : This section make some reference about HTML elements. What about
>> SVG ones?
>>
>
> It should be identical. Any SVG element should support the CSS keywords.
>

Ok good new. It was implicite (and say in each property definition) so
maybe it could be a nice enhancement to make it clear ;)


>  Is it planed to have something about compositing and blending fill and
>> stroke independently?
>>
>
> I don't think that that is in the works. Do you believe it is important?
>

Well... what I believe is : Make it short and extensible. I prefer a short
and quickly released spec with a few key properties than a big fat one that
cover everything and take ages to be stabilized and implemented (remember
CSS2 :P).

In terme of functionality, I think it could be a good idea to be able to
specified compositing and blending on stroke and fill independently. For
example, I can imagine having a filled shape that will be blend with the
background and the stroke that will remain unblend. Another example :
having a dotted border (build with dash-array for example) that will
perform a "clear" composition with the fill as the destination (with
clip-to-self enabled) to build some kind of a gear with a
single circle shape. In the end, I think it's not a key feature but it
gives kick-ass tools to authors to imagine cool effects. So IMO it's a
nice-to-have feature, but if it's to difficult to specified it, it's ok to
drop it.

Best,
-- 
Jeremie
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Web : http://jeremie.patonnier.net
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