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Re: UA: indicate missing content

From: Helder Magalh„es <helder.magalhaes@gmail.com>
Date: Tue, 29 Jul 2008 09:42:03 +0100
Message-ID: <2a1ddf8a0807290142t187ddbedy46afdcebbe531b6c@mail.gmail.com>
To: www-svg <www-svg@w3.org>

> If this doesn't meet your needs, let us know specifically where it needs
> work, and suggest specific remedies.  The current working plan is that if no
> fallback content is provided for an element with no specified dimensions,
> nothing would be displayed.  Note that for SVG Full, <use> does have 'width'
> and 'height' attributes.

I've read the clarifications but (please correct me if I didn't
understood them as expected) I don't feel they address what's being
discussed within this thread. I'd suggest clarifying what should
happen with the bounding box while external resources bring (can this
happen?) the main document to an error state:
 * While the resources aren't yet available and
"externalResourcesRequired" is set to "false" or not specified;
 * When "externalResourcesRequired" is set to "true" and resource
fetching has reached a dead end (timeout or not found);
 * If an external resource is available but contain an error (parse
error, invalid attribute values, etc.);
 * Probably more I'm missing at a first glance.

Note that I haven't found evidence that external resources will bring
the document which refer them into an error state: I didn't found
information regarding this but I believe that, if this specific
behavior isn't already specified, then IMHO it should be (too). :-)

I agree with Jonathan in respect to the need of somehow marking these
error situations in a coherent way, so that it's clear across
different implementations that the external resources which should be
there are erroneous. Although I wasn't able to find a reference to
related HTML recommendations on the subject, I believe the behavior
for broken images (for example) is more or less familiar across
implementations. Specifying general fall back mechanisms [1] for
external content and placing alternate text as mandatory [2] (though
also commonly misused just to pass validation) were important steps
taken by HTML in the past. SVG already contains equivalent (and IMO
even more powerful) mechanisms, such as the "switch" for fall back
behavior and the "title"/"desc" elements for alternate text (which,
for example, can be used  for cases when a given element can't be
rendered).

(Erik)
>>> In case a checkerboard pattern is desired here note that <use> elements
>>> in general don't specify their dimensions, and that in 1.2T there are no
>>> 'width' and 'height' attributes on <use>.
Oops, this is no good regarding what's being discussed here... Doug
has stated that SVG full does have these properties so, if visual
marking for unresolved external resources is to be made, this may need
to be revised... :-|

Regards,

 Helder Magalh„es

[1] http://www.w3.org/TR/REC-html40/struct/objects.html#h-13.3.1
[2] http://www.w3.org/TR/REC-html40/struct/objects.html#h-13.8
Received on Tuesday, 29 July 2008 08:42:40 GMT

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