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Re: [1.2T-LC] foreignObject content and referenced resource (ISSUE-2062)

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Sat, 18 Oct 2008 12:49:56 +0200
To: www-svg@w3.org
Message-Id: <200810181249.57226.Dr.O.Hoffmann@gmx.de>


Anthony Grasso:


> An additional paragraph was inserted before the last paragraph in The
> 'foreignObject' element section [1].
> The 'xlink:href' attribute of 'foreignObject' had a sentence added to the
> end of the paragraph [2].

Yes, this clarifies the usage an appearance of foreignObject, that is fine ;o)


> The 'foreignObject' element was added to the list of elements that
> establish new viewports [3].

Ok, with this it is somehow defined, how the foreign content is embedded, 
After this almost satisfactory improvement, this change results in some
minor further notes/questions/adjustments:

Note, that in the attribute table Appendix L an attribute
like preserveAspectRatio should be noted to be applicable for foreignObject
as well, because the section about preserveAspectRatio notes, that this
is applicable for elements establishing a new viewport.
Looking at this, I (un)fortunately noted another inconsistency for the
viewBox attribute.
In viewBox section itself is noted:  
"All elements that establish a new viewport (see elements that establish 
viewports) can have the 'viewBox' attribute specified on them."

In Appendix L it is noted, that only the element svg can have a viewBox.
This should be adjusted/harmonised too.
(Obviously due to the rules for example for image, the viewBox value
has no effect, but this is still a difference to the assumption of the table,
that one cannot note the viewBox for image).

Does or should viewBox have an effect on foreignObject?
Maybe this is similar to image and some advanced approach can be
left to SVG1.2 full.

Another note about testing/testability: Because now viewport-fill 
(and viewport-fill-opacity) is applicable for foreignObject, the
appearance of this element and the interpretation of attributes
is testable now without further assumptions, whether some foreign
format inside is interpreted or not. Having a visible viewport-fill 
there should be at least a visible rectangle for the foreignObject 
as an indication. This could be used to have a visual feedback 
about the interpretation of foreignObject.


P.S. Suggestion for another improvement about the foreignObject
It is noted, that 
"The rendered content of a foreignObject must be treated as atomic from the 
point of view of SVG compositing and transformation, as if it was a single 
replaced element."

For a 'normal' reader without specific disposition, it is not obvious, what
'atomic' in this content means. My dispositions for this are typically related
to old greek philosophy and physics (today it turns out, that the meaning,
what an atom is, changed completely ;o) I know as well, that there is an
XML language related to this wording and I think in WAI-ARIA I read 
something about some treatment of areas, if they are updated, related
to this wording.
Nothing of this seems to be unambiguously applicable here - would be
fine, to define or to explain or to reference, what 'atomic' in this 
context really means (contrary to another situation, where something
is not 'atomic') - I think, this is not used or defined elsewhere in the
draft, but maybe I'm wrong ...
Received on Saturday, 18 October 2008 11:06:50 UTC

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