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Re: [css3-background] Where we are with Blur value discussion

From: Bjoern Hoehrmann <derhoermi@gmx.net>
Date: Wed, 14 Jul 2010 02:06:58 +0200
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: www-style@w3.org
Message-ID: <3dvp36hctlpaf3ae5bohbmd3i5q4upqd4i@hive.bjoern.hoehrmann.de>
* Tab Atkins Jr. wrote:
>On Tue, Jul 13, 2010 at 4:37 PM, L. David Baron <dbaron@dbaron.org> wrote:
>> If you want that, the appropriate way to get that is to find out how
>> existing graphics systems do blurring and describe it using the same
>> terms already in use, not to invent a new set of terms and a new
>> mechanism that's different from what existing systems do.
>
>Explaining it in terms of existing graphics libraries may help
>implementors, but it does nothing for authors, who have no idea how
>the graphics libraries work or what the relationship is between a
>radius parameter and "how big my shadow will be".
>
>Including an example conversion into graphics-library terms may be
>useful, but it's something that should be supplemental at best, not
>something that we elevate as the primary definition of the feature.

David is just arguing to prefer re-use over re-invention. If there is
some well-known mechanism, and that mechanism is described using well-
known terms, then it is preferable to use that mechanism and describe
it in those terms, over coming up with new, unproven mechanisms and
terms, unless that is shown to be necessary. He is not arguing to de-
fine something by saying "Do this like Photoshop does that", or "Do
this as if you were using Cairo and called function X and then Y.".

At least as I understand him, there is no reason to expect readers of
the specification will have difficulty predicting the dimensions of
the shadow knowing the radius parameter and the specification but not
some particular graphics library, due to following the advice above.
-- 
Björn Höhrmann · mailto:bjoern@hoehrmann.de · http://bjoern.hoehrmann.de
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Received on Wednesday, 14 July 2010 00:07:33 GMT

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