W3C home > Mailing lists > Public > www-style@w3.org > June 2010

Re: [css3-background] vastly different takes on "blur"

From: Brad Kemper <brad.kemper@gmail.com>
Date: Wed, 23 Jun 2010 08:52:12 -0700
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, robert@ocallahan.org, Simon Fraser <smfr@me.com>, fantasai <fantasai.lists@inkedblade.net>, Brian Manthos <brianman@microsoft.com>, "www-style@w3.org" <www-style@w3.org>
Message-Id: <8CBAADB2-6827-4C45-B7B6-97E505C80C74@gmail.com>
To: Brendan Kenny <bckenny@gmail.com>

On Jun 23, 2010, at 8:33 AM, Brendan Kenny wrote:

>> Oh, jeez.  I was looking at webkit's rendering twice, rather than
>> looking at webkit and then firefox.  I feel silly.  You're correct -
>> for a 100px blur, the shadow extends outward 79px.
>> That still doesn't explain Simon's statement that the blur extends
>> outward by the full blur length.  I continue to measure a nearly
>> perfect half-blur-length of shadow extending from the main shadow body
>> in Chrome, whether the blur is 8px or 100px.
>> ~TJ
> http://lists.w3.org/Archives/Public/www-style/2010Jun/0563.html
> =)
> looks like Safari and Chrome handle the argument differently.

So are we saying that even for 'text-shadow' we have wild inconsistencies, and no one really noticed before? That the outer part of a 100px blur might be 100px, 79px, or 50px?

If this is the case, then the current behavior of 'text-shadow' need not restrict us too much, because there is no consistent current behavior. We can fix that and box-shadow to be whatever is most sensible instead of whatever was implemented.

On Jun 22, 2010, at 3:39 PM, Simon Fraser wrote:

> I think we agree that the following should all match:
> * text-shadow
> * box-shadow
> * SVG gaussian blur

Nice-to-have, but I'm much less concerned about SVG than I am about text-shadow. I don't like the idea of us always having to follow what SVG does, just because they finished their spec first, possibly with less deliberation. But most CSS authors are not SVG authors, and SVG authors could probably live through having to use a shadow attribute that was half the number they used for CSS.

> * hypothetical future blur filter in CSS

That one should be easy, since it so far only exists in out imaginations.

> * PhotoShop, probably

I wouldn't want to be too slavish there. PhotoShop occasionally does some things in a less intuitive way, and we don't need to repeat their mistakes in those instances. If PhotoShop drop shadows used amounts that were half of what CSS used, it would not be a burden for people converting between the two.
Received on Wednesday, 23 June 2010 15:52:49 UTC

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