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Re: [css3-background] border-radius color transitions using gradients recommended but undefined

From: Andrew Fedoniouk <news@terrainformatica.com>
Date: Tue, 26 Jan 2010 09:35:37 -0800
Message-ID: <4B5F27E9.5080604@terrainformatica.com>
To: Sylvain Galineau <sylvaing@microsoft.com>
CC: fantasai <fantasai.lists@inkedblade.net>, "www-style@w3.org" <www-style@w3.org>, Brian Manthos <brianman@microsoft.com>
Sylvain Galineau wrote:
>> From: fantasai [mailto:fantasai.lists@inkedblade.net]
>> I'm not comfortable with normatively requiring a particular gradient
>> form or a particular type of corner join in css3-background. I don't
>> think we have clear answers as to what would look best--other than it
>> should be a type of conic gradient--so I want to leave implementations
>> free to experiment. It's fine IMO to leave this detail of border
>> rendering undefined in CSS3: it gives it a chance to evolve as
>> implementers learn from each other and from author feedback.
> I understand the intent. But I am not comfortable with recommending that a CR property 
> have an undefined behavior that is important to designers just as it is seeing broad 
> adoption. It's one thing for browsers to experiment with background gradients behind 
> -moz, -webkit, -ms or -o. The author can and must choose to depend on such features.
> But if it's a side-effect of border-radius in the next Firefox or IE, the author has 
> no choice in the matter. One browser may use a gradient, and the other may not. Or they
> may do it differently.  So while both finally agree on the shape of the border based
> on the same syntax, a new interop issue has been introduced when 2+ border colors are
> specified. 
> If we don't know what this should look like and would like to experiment further, we can
> keep css3-background at the WD stage. Or we can remove this recommendation; this will allow
> border-radius to interoperate in a testable manner and browsers can still experiment with 
> gradient transitions behind the prefixed version of this property until CSS4, if they so desire.
> If authors *do* want us to recommend incompatibility in this area so that browser vendors can
> gather their feedback, it's a different matter. I am not getting that message, however. 
> So again, I would love to hear from other implementors.

There are actually not too many alternatives.

The most viable solution is to a) use conic gradient in the area (B) on 
this image: 
Center of conic gradient is right/bottom corner of the area (B).

Here are examples of gradients on border radius (renderings in htmalyout 
and Sciter engines):

Using method (B):

And for the record the same but using method (A) on the figure above:

Note case #10. (B) variant I think is least controversial.

Andrew Fedoniouk.

Received on Tuesday, 26 January 2010 17:36:05 UTC

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