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Re: [compositing-1] please move non-separable effects to Level 2

From: Dirk Schulze <dschulze@adobe.com>
Date: Sat, 19 Apr 2014 06:09:33 +0000
To: "robert@ocallahan.org" <robert@ocallahan.org>
CC: Dean Jackson <dino@apple.com>, Rik Cabanier <cabanier@gmail.com>, FX <public-fx@w3.org>
Message-ID: <6D5B173C-C2F1-4D67-BAD4-E8EF70DFC385@adobe.com>

On Apr 19, 2014, at 7:45 AM, Robert O'Callahan <robert@ocallahan.org> wrote:

> On Sat, Apr 19, 2014 at 5:38 PM, Dean Jackson <dino@apple.com> wrote:
> We support them in software mode too, just not in compositing mode. Since we don’t want to have blending disappear if an element becomes composited (99.9% of developers would not be able to explain all the cases in which this could happen), we’d only ship an implementation that supports them everywhere.
> In Gecko, blending doesn't disappear, instead we prevent the content from being offloaded to the compositor. So we support them everywhere, but they cause performance degradation in some cases.

“Disappear”  might not be the right word. Isolated is more correct. Don’t elements get isolated in Firefox when you have opacity, 3D transforms and all the other cases where many implementations currently have to create a compositing layer?

> I'll note that Safari 6 release notes claim support for SVG filters. I'm pretty sure you can implement all the blend modes in terms of SVG filters. So either Webkit's SVG filter support is partial (in which case partial support for mix-blend-mode should be OK too right?) or whatever implementation tradeoffs you made for SVG filters you're declining to make for mix-blend-mode (which I think is not accurately described as "can't implement”).

SVG Filters do not support the non-separatable blend modes. SVG Filters are also not accelerated in WebKit yet.

If there is implementation feedback that a feature can not be implemented, why shouldn’t we reflect that in the spec? After all, interoperability in feature support is an important factor for W3C specs. For FX specs we need two implementations supporting each feature.

I think this is a very good justification to object to a feature being in the spec, not for keeping it in the spec.


> Rob
> -- 
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Received on Saturday, 19 April 2014 06:10:05 UTC

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