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Re: [CSS3, Backgrounds and Borders Module] some questions about border-radius

From: Andrew Fedoniouk <news@terrainformatica.com>
Date: Sat, 22 Aug 2009 21:41:49 -0700
Message-ID: <4A90C88D.5020401@terrainformatica.com>
To: Brad Kemper <brad.kemper@gmail.com>
CC: www-style <www-style@w3.org>
Brad Kemper wrote:
> On Aug 22, 2009, at 8:30 PM, Andrew Fedoniouk wrote:
>> Reading this document
>> http://www.w3.org/TR/2008/WD-css3-background-20080910/#the-border-radius
>> got couple of questions.
>> Phrase after [Example XXI]:
>> "(In such cases its center might not coincide with that of the outer 
>> border curve.)"
>> Not clear what it means. Center of circle having radius zero? It's a 
>> point then. Has no center... Or is this about something else?
> That is how I read it. A point does have a center (it's the same point). 

Mathematically speaking - yes, someone can say that point is a circle of
radius zero but that is pretty unusual way of saying "point".

> That point would no longer align with the center of the center of the 
> circle describing the outside of the border, when the border thickness 
> is thicker than the corner-radius. There may be a better way to say this...

In case of borders of different thickness centers of outer and inner 
circles are different. Is this what you are trying to say?

>> [...]
>> And the main question:
>> "Other effects that clip to the border or padding edge (such as 
>> ‘overflow’) also must clip to the curve."
>> Clipping of content on such border may lead to information lost.
>> Text behind rounded corner will not be seen at all [top-left corner,
>> case #8 above].
> Text that goes outside its boundaries is also "information lost" when 
> overflow is 'hidden'. Thus it is within the author's ability to obscure 
> text with overflow, as always. If I don't want the text to be clipped by 
> the corners, then I can add padding.

It is about overflow:auto rather than hidden.
You cannot see that portion even with overflow:auto. That is the point.

I think we just need to remove "Other effects that clip to the border or 
padding edge (such as ‘overflow’) also must clip to the curve."
statement. It does not create solutions - just problems.

Technically it is even not possible to do such clipping if antialiasing 
is used. Border should be drawn on top of content but not underneath as 
the spec mandates.

Andrew Fedoniouk.

Received on Sunday, 23 August 2009 04:42:26 UTC

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