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Re: [css-backgrounds] Clarification proposal for border colors

From: Simon Sapin <simon.sapin@exyr.org>
Date: Thu, 17 Sep 2015 20:25:03 +0200
To: www-style@w3.org
Message-ID: <55FB057F.9000004@exyr.org>
On 14/09/15 19:15, Simon Fraser wrote:
>> On Sep 14, 2015, at 8:24 AM, Adenilson Cavalcanti
>> <a.cavalcanti@samsung.com <mailto:a.cavalcanti@samsung.com>> wrote:
>> The border style spec
>> (http://dev.w3.org/csswg/css-backgrounds/#the-border-style
>> <http://dev.w3..org/csswg/css-backgrounds/#the-border-style>) is
>> implemented in probably all browsers and has being around for quite a
>> long time.
>> I observed that the description of the behavior for 'groove’ value
>> (and the complementary 'ridge') is a bit vague about what the UA is
>> supposed to do.
>> Quoting: "Looks as if it were carved in the canvas. (This is typically
>> achieved by creating a “shadow” from two colors that are slightly
>> lighter and darker than the ‘border-color’.)"
>> I think the 'two colors' part could be more descriptive.
>> What if we changed it to be clearer and write something like:
>> “The light color should be a percentage of the darker color, between
>> 20% to 50% of its absolute value. And the darker color a percentage in
>> a range of 70% to 90% of border color."
>> Another issue is that the behavior for black border could be explicit.
>> I think we could follow up with: "In case the border color is black, a
>> shade of gray must be used as the lighter color.”

I’m in favor of suggesting a non-normative but well-defined algorithm in 
the spec.

> I think a good way to spec this would be to spec lighten() and darken()
> color functions, which you could then refer to in the groove/inset
> border spec.

Would color(… lightness(…)) from 
https://drafts.csswg.org/css-color/#modifying-colors work?

Simon Sapin
Received on Thursday, 17 September 2015 18:25:37 UTC

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