W3C home > Mailing lists > Public > www-svg@w3.org > July 2008

Re: UA: indicate missing content

From: Jonathan Chetwynd <j.chetwynd@btinternet.com>
Date: Sat, 26 Jul 2008 13:16:51 +0100
Message-Id: <B9AF7427-714B-4E28-957C-712DF6BE31CF@btinternet.com>
To: Helder Magalhães <helder.magalhaes@gmail.com>, www-svg <www-svg@w3.org>
Helder,

thanks once again, I'm content to file bugs with the UAs, however this  
wasn't my intent.

Rather that the description given is not sufficient.
Graphics are a complex area, and describing what is missing and where,  
will be hard if it is to be consistent across UA.
which users expect, perhaps demand...

as you indicate there appears to be no guidance on the author  
providing 'alt' content, nor a method or technique.

a test case is here: http://www.openicon.org/feeds/exResReq.svg


What is the rationale for the default being false?
this must inherently be confusing for the user, as they will not be  
aware of the issue.
and the author too who has not considered this matter, does not refer  
to the specs or uses a tool that does not require or automate this  
matter.

regards



Jonathan Chetwynd

j.chetwynd@btinternet.com
http://www.openicon.org/

+44 (0) 20 7978 1764


On 26 Jul 2008, at 11:43, Helder Magalhães wrote:

>
>> current UA do not indicate missing content either with graphic or  
>> text.
>> iirc batik wont display at all, others ignore.
>> Is there a recommendation on this issue?
> [...]
>> html UA generally provide an empty box with a cross or similar and  
>> alt
>> content
>
> The external resources property [1] seems to imply a recommendation on
> this: error processing notes [2] states that:
> «A highly perceivable indication of error shall occur. For visual
> rendering situations, an example of an indication of error would be to
> render a translucent colored pattern such as a checkerboard on top of
> the area where the SVG content is rendered.»
>
> I'd interpret the whole as: if a document portion is marked with
> "externalResourcesRequired" set to "true" and the external resource(s)
> is(are) not available, then mark that portion with a checkerboard (or
> similar). Please correct me if this sounds naive!
>
> So, if your findings are correct (didn't check implementations
> myself), user agents seem to be the ones which need to catch up. ;-)
>
> As an implementation suggestion, one might use conditional processing
> [3] to achieve a desired fall back. Using a "switch" containing
> external resources required feature string [4] for UA which support
> external resource loading (with proper error processing) and
> alternative content for cases (where the UA doesn't contain the
> feature string) might do the trick! :-)
>
>
>
>> I recognise the SVGWG may not be chartered to consider UA issues,  
>> however
>> and there does not seem to be another suitable public space to  
>> raise this.
>
> I believe the SVGWG is the proper place for discussing user agent
> matter (which relates to SVG, of course). For instance, there are
> guidelines for user agent behavior spread over the specification (for
> example, in implementation notes section [5]).
>
>
>
> Hope this helps,
>
> Helder Magalhães
>
> [1] http://www.w3.org/TR/SVG/struct.html#ExternalResourcesRequired
> [2] http://www.w3.org/TR/SVG/implnote.html#ErrorProcessing
> [3] http://www.w3.org/TR/SVG/struct.html#ConditionalProcessing
> [4] http://www.w3.org/TR/SVG/feature.html#ExternalResourcesRequired
> [5] http://www.w3.org/TR/SVG/implnote.html
>
Received on Saturday, 26 July 2008 12:17:34 GMT

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