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Re: A few comments on the custom shaders spec

From: Robert O'Callahan <robert@ocallahan.org>
Date: Mon, 11 Mar 2013 10:40:26 +1300
Message-ID: <CAOp6jLZyWrhaygoFA-ayfah9AdKxz1EhCpV_35HLRHdbdF-viQ@mail.gmail.com>
To: Dirk Schulze <dschulze@adobe.com>
Cc: "public-fx@w3.org" <public-fx@w3.org>
On Fri, Mar 8, 2013 at 5:54 PM, Dirk Schulze <dschulze@adobe.com> wrote:

> The section "Fragment Shaders Differences with GLSL"[1] describes the
> security steps Shaders need to take to fulfill this requirement:
>
> ""
> A normal GLSL shader requires that the fragment shaders computes a
> gl_FragColor value which is the color value for the processed fragment
> (pixel).
> Because of the security restrictions, fragment shaders are not allowed to
> access rendered content pixel values directly.
> ""
>

I'm afraid that isn't nearly precise enough.


> > I thought that to compensate for the lack of access to rendered content,
> we were going to allow fragment shaders to generate a per-pixel color
> matrix which would then be applied to the content. But I don't see any sign
> of that. Is that coming?
>
> In the same section "Fragment Shaders Differences with GLSL"[1] it is
> defined how to influence pixel colors.


OK, I missed that somehow, sorry... Thanks.

> Section 17.2 is totally unclear. In particular, what does "input" mean
> here? I thought the whole point of section 17.1 was to eliminate the need
> to track the origins of rendered content.
>
> In the last WD it was possible to pass a previous filter primitive result
> as texture parameter into the shader (as secondary input) under the
> condition that it is not the direct or indirect result of the pages web
> content. This requires tracking which filter primitive counts as "dirty". I
> removed it in this version. I am looking forward to add it again to allow
> generators like feTurbulence as input.
>

OK but the language in section 17.2 needs to be clarified.

Rob
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Received on Sunday, 10 March 2013 21:40:54 GMT

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