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Re: [filter-effects] url() as pass-through on invalid reference?

From: Dirk Schulze <dschulze@adobe.com>
Date: Sun, 14 Jul 2013 07:20:43 -0700
To: Boris Zbarsky <bzbarsky@MIT.EDU>
CC: "www-style@w3.org" <www-style@w3.org>, "public-fx@w3.org" <public-fx@w3.org>
Message-ID: <7F0EEB71-B7D8-4AA3-A7D1-4DF840DD7856@adobe.com>

On Jul 12, 2013, at 2:31 PM, Boris Zbarsky <bzbarsky@MIT.EDU> wrote:

> On 7/12/13 5:25 PM, Robert O'Callahan wrote:
>> I feel pretty strongly that the SVG behavior is not appropriate. I think
>> any sort of invalid 'filter' value, including a <filter> element with a
>> child element of unknown type, should cause the filtered element to be
>> rendered normally (i.e. 'filter' treated as 'none'). Otherwise I think
>> introducing new <fe> SVG element types does not get useful fallback.
> OK, should that be raised as an issue on SVG, then?  I feel like we 
> should have consistency between the case when there is only one url() in 
> 'filter' and the case when there are multiple things including a url()

I forgot to paste the link to the Filter Effects specification that allows multiple declarations on url() [1]. Sorry for that.

1) SVG 1.1 was not clear about what happens if the specified URL is not referencing an existing <filter> element. Implementations treat this case as if 'none' was specified.
2) For SVG 1.1: if one of the primitives is in an error state (which used to happen quite often in earlier versions of the spec.) then nothing gets rendered at all.

I agree with you Boris that we should not treat both cases differently. However, I am more in favor of just not applying the filter then stop rendering of the filtered element entirely (suggestion from roc).

With Filter Effects we have a new situation since we allow multiple filter functions or url()s. The reason why it changes the way to look at the topic is the following:

A) Treat errors as "filter: none" and refuse the whole filter chain

might be described similarly with

B) Treat failing filter function as pass-through and still apply the other filter functions.

Both, A) and B) just make a difference on applying multiple filter functions if we agree on the behavior of 1).


[1] http://dev.w3.org/fxtf/filters/#FilterProperty

CCed public-fx again.

> -Boris
Received on Sunday, 14 July 2013 14:21:09 UTC

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