Re: Updated to the blending and compositing spec (was: minutes, December 10 2012, FXTF telcon)

Hi Lea,

thanks for the clarification!

On Tue, Dec 11, 2012 at 2:02 PM, Lea Verou <lea@w3.org> wrote:

> I realized what I’m suggesting below might not be very clear (hence the
> misunderstanding in the telcon), so I’ll make an attempt at making it more
> concise. **Naming is off the top of my head, please don’t focus on that.**
>
> What I’m suggesting is that mix-blend-mode becomes a list that accepts
> multiple comma-separated blending modes. mix-blend could be a shorthand of
> mix-blend-mode and mix-blend-area. The latter would accept values like [
> box-shadow | text-shadow | background | element ]# (regarding the hash
> multiplier: [1])
>
> So, if you wanted to specify a multiply blending mode on both text-shadow
> and box-shadow, as well as a screen blending mode to the entire element, it
> could go like:
>
> mix-blend-mode: screen, multiply;
> mix-blend-area: element, box-shadow, text-shadow;
>
> or, by using the shorthand:
>
> mix-blend: screen element, multiply box-shadow, multiply text-shadow;
>
> I believe that’s more elegant, concise and consistent with the rest of CSS
> than:
>
> mix-blend-mode: screen;
> box-shadow-blend-mode: multiply;
> text-shadow-blend-mode: multiply;
>
> and doesn’t require more than one new property.
>

I don't particularly like that this forces you to always specify what part
of the element you want to blend.
Most likely, 99% of blending will just target the element and now those
users will have to write either 2 css properties or put 'element' in the
shorthand.

How about we drop the '-area' property and assume in the shorthand that no
area means that that blend should apply to the whole element?
So your case becomes:

mix-blend: screen, multiply box-shadow, multiply text-shadow;

The mix shorthand could look like this:

mix: screen source-out, multiply box-shadow, overlay destination-over
text-shadow


What do you think?


> On Dec 11, 2012, at 23:13, Lea Verou wrote:
>
> This change sacrifices the previous flexibility with no obvious benefit
> for authors. The only one that benefits from this change is implementors.
> It doesn’t make the feature any easier to use or more elegant, nor does it
> simplify the additions to the language. With the previous design, the
> syntax would still be exactly the same, if all you wanted was to apply the
> same blending mode to all shadows/backgrounds/etc, due to the way CSS lists
> work.
>
> The whole reason I suggested dropping that kind of flexibility was to
> avoid adding all these properties in the first place. I.e. if each "layer"
> of the element can only have one blending mode as a whole, then which
> blending modes apply to which parts of the element can be controlled by a
> single CSS property that accepts a comma separated list of identifiers
> (properties and some keyword that means the entire element) that correspond
> to a comma separated list of blending modes from mix-blend-mode.
>
> Lea Verou
> W3C developer relations
> http://w3.org/people/all#lea ✿ http://lea.verou.me ✿ @leaverou
>
>
>
>
>
>
> On Dec 11, 2012, at 20:02, Rik Cabanier wrote:
>
>
>
> On Tue, Dec 11, 2012 at 9:38 AM, Lea Verou <lea@w3.org> wrote:
>
>> Hi Rik,
>>
>> I thought we agreed that the use case of applying different blending
>> modes to different shadows/background images/etc was pretty rare and we'd
>> resort to simpler syntax for now that covers the more common use cases? Did
>> I misunderstand?
>>
>
> No, you didn't misunderstand.
> The spec is updated so you blend the composited result of the shadows and
> the background images.
> For instance, see
> https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html#box-shadow-blend-mode
> :
>
> Sets the blend mode of the composited result of all the box shadows.
>
>
> I did not update background-composite since we didn't discuss it and
> currently matches an existing webkit only feature.
>
> Rik
>
>
>
>> On Dec 11, 2012, at 03:52, Rik Cabanier wrote:
>>
>> All,
>>
>> I updated the spec per today's decision:
>> https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html
>> Please let me know if you have any questions or ideas for improvement.
>>
>> Thanks!
>>    Rik
>>
>>
>>
>
>
>