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Re: UA: indicate missing content

From: Doug Schepers <schepers@w3.org>
Date: Tue, 29 Jul 2008 05:13:26 -0400
Message-ID: <488EDF36.6040809@w3.org>
To: www-svg <www-svg@w3.org>

Hi, Jonathan-

Jonathan Chetwynd wrote (on 7/29/08 3:59 AM):
> 
> I read the proposed wording and it doesn't address the issue raised.
> if width and height are not part of the svg1.2 spec then how would
>>> the user agent should provide a placeholder rectangle or image with the 
> position and dimensions specified by the element's attributes,
> ever be satisfied?

This is not only for <use> elements, but for any "replaced content" 
elements (<use>, <image>, <animation>, <video>, and <audio>).  While 
neither <use> nor <audio> have 'width' or 'height' attributes in SVG 1.2 
Tiny, all the rest of those do, so we need to specify the behavior for 
all of those elements, not just <use>.  For elements which do not have 
'width' or 'height' attributes (or which are missing those values), the 
proposal suggests that the browser create a rectangle of custom size to 
contain the fallback text or file name (if that's the only fallback 
available).


If you had read all the sections I explicitly pointed to, you would have 
seen this.  This is the fourth (and final) time I have asked you to read 
the proposed text.


> your supposed solution is at best a hack.

Frankly, I don't think you are considering the various parameters of the 
problem.  Please stop using insulting language.


> This is a really complex area, and the current solution has by at least 
> on correspondent been described as naive.

You have misunderstood what Helder said.  He was asking if his 
interpretation of the spec was naive, not accusing the spec or someone 
else of naivité.


> users will learn little if anything from a broken link.

This is why my proposed text provides a rich fallback solution, as well 
as text alternatives.  If there is no fallback provided, then users 
learn that they are not seeing the SVG image as it was intended to be 
rendered by the author, which may be enough.  The alternative is 
rendering nothing at all (also an option for authors), which is what 
happens now, and which is less useful than a broken-link indication.


> alt content at least needs to be discussed by a wide audience.

No, it needs to be described by people who understand the problem and 
can articulate a solution that will be interoperably implemented, and 
provides an easy way for authors to do this.


> the case against re-introduction of height and width needs to be stated 
> clearly, hence my request to erik

Your meaning here is unclear.


Regards-
-Doug Schepers
W3C Team Contact, WebApps, SVG, and CDF
Received on Tuesday, 29 July 2008 09:14:01 GMT

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