Re: [filter-effects] @support condition for custom filters

On Feb 12, 2013, at 7:59 AM, Sylvain Galineau <sylvaing@microsoft.com> wrote:

> [Dirk Schulze:]
>> 
>> 
>> On Feb 11, 2013, at 5:55 PM, James Robinson <jamesr@google.com> wrote:
>> 
>>> 
>>> 
>>> On Mon, Feb 11, 2013 at 3:05 PM, Dirk Schulze <dschulze@adobe.com>
>> wrote:
>>> Hi all,
>>> 
>>> The Filter Effects[1] specification defines the custom() filter function
>> to extend the predefined filters by new, customized filters including CSS
>> Shaders, but not limited to CSS Shaders. This was discussed and accepted
>> by the SVG WG [2].
>>> 
>>> Feature detection is important to support future extensions of the spec
>> and test for the availability. I have an action from the SVG WG to ask for
>> a new condition 'filter' on the @support rule. This filter descriptor can
>> take different feature keywords. For CSS Shaders I would suggest 'webgl'
>> because of the relation to WebGL. More feature keywords can be added by
>> future versions of Filter Effects allowing other or future shading
>> languages and parameterized SVG filters. The filter condition would look
>> like in the following demonstration:
>>> 
>>> Supporting webgl and supporting CSS shaders are very different things
>> and I would not expect support for one to imply or match support of the
>> other.  I think you should pick a different keyword.
>> 
>> I am happy with a different keyword as well. This name was proposed during
>> the F2F, since CSS Shaders use the by WebGL defined shader language (GLSL
>> ES with restrictions). In theory you can use a different shading language
>> to archive the same results. I am open for other name proposals.
>> 
> 
> Aren't you really trying to check for support for a function e.g. something
> like @supports (filter:custom()) ?
> 

We have to differentiate two different things:

1) Is a function supported. This would be done with @support (filter: custom()) or @support (filter: url())

2) Does Filter Effects support a specific extension. In this case CSS Shaders.

The suggestion for the second case is a conditional function like

	@support filter(webgl)

Greetings,
Dirk