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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: 
http://www.terrainformatica.com/w3/border-radius-transition-areas-fig.png
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):
http://www.terrainformatica.com/w3/round-corners-sciter-b.png

And for the record the same but using method (A) on the figure above:
http://www.terrainformatica.com/w3/round-corners-sciter.png

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


-- 
Andrew Fedoniouk.

http://terrainformatica.com
Received on Tuesday, 26 January 2010 17:36:05 GMT

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