BugNos UA: indicate missing content

Batik: https://issues.apache.org/bugzilla/show_bug.cgi?id=45486
Opera: bug-350923@bugs.opera.com


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
>