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Re: clipPath inconsistencies

From: Nikolas Zimmermann <zimmermann@physik.rwth-aachen.de>
Date: Wed, 28 Jul 2010 13:22:52 +0200
Cc: www-svg@w3.org
Message-id: <803C4071-401B-483F-8843-AC375C4DD24D@physik.rwth-aachen.de>
To: Erik Dahlstrom <ed@opera.com>

Am 15.07.2010 um 12:40 schrieb Erik Dahlstrom:

> On Thu, 15 Jul 2010 11:39:24 +0200, Nikolas Zimmermann <zimmermann@physik.rwth-aachen.de 
> > wrote:
>> Good morning SVG crowd,
>> I'd like to discuss clipping inconsistencies between Opera/FF and
>> WebKit, when it comes to error handling.
>> In the screenshot you can see WebKit, Firefox and Opera rendering the
>> clip-path-recursive-call-by-child.svg example (attached in this  
>> mail).
> ...
>> I've chosen to ignore the clipPath, which is in error state (as it
>> contains a cycle), but still render the object, which referenced it.
>> Firefox seems to detect the cycle and doesn't render the element at
>> all (probably because of the note in the error processing document).
>> Opera just ignores the cycle and renders both elements.
> No, what Opera does is detect the cycle and break it at the time  
> it's discovered, and we've chosen to follow the spec for what  
> happens if there's an invalid clip-path IRI reference in a child  
> element of a clipPath element:
> [[  If the IRI reference is not valid (e.g it points to an object  
> that doesn't exist or the object is not a ‘clipPath’ element) the  
> ‘clip-path’ property must be treated as if it hadn't been  
> specified. ]]
> Which means that the rect inside the clipPath should be drawn (or in  
> other words: it should contribute to the clipping region), but  
> without the 'clip-path' property applied.
> Note that there's nothing in the spec that says that the 'clip-path'  
> IRI reference means the element in question is "in error", so the  
> error processing rules don't apply in this case.

Ok, I made up my mind, and I think it's a fine solution to handle  
these edge cases. WebKit/SVG will follow the same route, as soon as  
the patch lands :-)

Received on Wednesday, 28 July 2010 11:23:22 UTC

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