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Re: [css-compositing] Request to move Compositing and Blending spec to CR

From: Rik Cabanier <cabanier@gmail.com>
Date: Wed, 11 Dec 2013 21:45:32 -0800
Message-ID: <CAGN7qDAOQOj7t___roRCDsgjrKrg8nax1MwTGjNJfOPmPke7_g@mail.gmail.com>
To: James Robinson <jamesr@google.com>
Cc: www-svg <www-svg@w3.org>, www-style list <www-style@w3.org>, "public-fx@w3.org" <public-fx@w3.org>
Also note the title:

Compositing and Blending Level 1

and not:

*CSS* Compositing and Blending Level 1


>From the spec:

The (archived <http://lists.w3.org/Archives/Public/public-fx/>) public
mailing list public-fx@w3.org (see
instructions<http://www.w3.org/Mail/Request>)
is preferred for discussion of this specification. When sending e-mail,
please put the text “compositing-1” in the subject, preferably like this: “[
compositing-1] *…summary of comment…*”



On Wed, Dec 11, 2013 at 9:41 PM, Rik Cabanier <cabanier@gmail.com> wrote:

>
>
>
> On Wed, Dec 11, 2013 at 9:28 PM, James Robinson <jamesr@google.com> wrote:
>
>> Why are you trying to define how canvas works in a CSS spec? Canvas is
>> defined as part of HTML, including how the compositing operations are
>> applied. The text here is completely unhelpful.
>>
> This is not a 'CSS' spec; this is done through the fx working group which
> works on graphical operators.
> Some are CSS, others apply to canvas. The Web animation spec is purely
> JavaScript but will eventually define CSS properties as well.
>
> HTML refers to this spec to define compositing; the same is done in the
> filters spec. I don't understand what you think that that is not helpful
> (unless you think compositing should be redefined in every spec)
>
>
>> On Dec 11, 2013 7:16 PM, "Rik Cabanier" <cabanier@gmail.com> wrote:
>>
>>>
>>>
>>>
>>> On Wed, Dec 11, 2013 at 6:57 PM, James Robinson <jamesr@google.com>wrote:
>>>
>>>>
>>>> On Wed, Dec 11, 2013 at 6:44 PM, Rik Cabanier <cabanier@gmail.com>wrote:
>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> Canvas is defined in HTML.  Having text here to define a behavior
>>>>>> that canvas does not use is just confusing with no upside.
>>>>>>
>>>>>
>>>>> No, canvas refers to the compositing spec for the 'globalComposite'
>>>>> operator [1]:
>>>>>
>>>>> The globalCompositeOperation attribute sets the current composition
>>>>> operator, which controls how shapes and images are drawn onto the scratch
>>>>> bitmap<http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#scratch-bitmap>,
>>>>> once they have had globalAlpha<http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-globalalpha> and
>>>>> the current transformation matrix applied. The possible values are those
>>>>> defined in the Compositing and Blending specification. [COMPOSITE]<http://www.whatwg.org/specs/web-apps/current-work/multipage/references.html#refsCOMPOSITE>
>>>>>
>>>>>
>>>>> Do you think the canvas spec should be more clear that compositing is
>>>>> defined in the "Compositing and Blending specification"?
>>>>>
>>>>
>>>> The paragraph in question -  "9.2.3. Clip to self behavior" - describes
>>>> a behavior that is not used by canvas, or (from what you've said) by
>>>> anything in the Compositing and Blending spec.  What value does it have
>>>> other than creating confusion, in that case?
>>>>
>>>
>>> Section 5-10 define a generic model for blending and compositing.
>>> The normative section defines a subsection of that model. Hopefully we
>>> can implement the whole model over the coming years.
>>> By defining it this way, it should be more clear to an implementor how
>>> things are supposed to be work.
>>> For example, the problems that you mentioned earlier:
>>>
>>> Firefox applied the compositing operation to the entire canvas,
>>> respecting the current clip, and WebKit applied the compositing operation
>>> only to the "bounds" of the draw.
>>>
>>>  would not have happened if there had been a definition like you find in
>>> the current spec:
>>> http://dev.w3.org/fxtf/compositing-1/#groupcompositingcliptoself
>>>
>>> I don't really see a way to define how compositing works in canvas
>>> without describing the clip-to-self behavior somehow...
>>>
>>
>
Received on Thursday, 12 December 2013 05:46:00 UTC

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