W3C home > Mailing lists > Public > www-svg@w3.org > March 2013

Re: Presentation attributes with disabled browser styling

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Tue, 19 Mar 2013 17:54:14 +0100
To: www-svg@w3.org, john@nextraweb.com
Message-Id: <201303191754.14756.Dr.O.Hoffmann@gmx.de>
Hello,

(just my own observations and opinion - the problem is annoying
for me as well for a long time and results together with some other
fundamental bugs in the impression, that Mozilla/Gecko is not ready 
for use for SVG documents).

This behaviour of firefox is pretty annoying for users, because
for typical SVG documents, that use only presentation attributes, 
because they matter for content and are not just for decoration, 
the display with the interpretation of such presentation attributes
becomes almost useless.
A simple workaround seems to be to provide an empty file with
an XML stylesheet processing instruction, for example with the
name 'no CSS' - users do not have to switch off interpretation 
completely to get rid off decorative styling (if the document contains
no style attributes), they only have to chose this empty stylesheet
to see the content including presentation attributes.

I think, the behaviour is the same in firefox for SVG tiny documents,
which do not even allow decoration with stylesheets
(for them there is no simple workaround, because one may not
provide any stylesheets, empty or not).
For such SVG tiny documents the behaviour of firefox is clearly
wrong - because there is no CSS layer, it cannot make a difference,
if CSS interpretation is disabled or not.
And of course for basic or full profiles the behaviour should be the
same. Presentation attributes matter for content, not just for 
decoration.

Concerning 
http://www.w3.org/TR/SVG11/styling.html
if the interpretation of CSS is disabled, we have the scenario 1
of 6.2 with the presentation attributes, they apply independently
from the stylesheets.
Therefore it a user switches the interpretation of CSS stylesheets,
the usages scenario is switched at the same time. 
If switched off, one automatically gets scenario 1, where presentation
attributes matter, because there are no decorative properties.
There is no magic switch to remove the presentation attributes from the
content - either they matter as relevant content or with CSS interpretation
as properties with low specifity.

Concerning 6.4, if the interpretation of stylesheets is disabled, the
viewer automatically becomes a viewer without CSS capabilities,
therefore the presentation attributes are not mapped to properties anymore,
they simply apply without a cascade, therefore no need or no way to
integrate them into a not existing cascade.

It is noted:
"For user agents that support CSS, the presentation attributes must be 
translated to corresponding CSS style rules according to rules described in 
Precedence of non-CSS presentational hints ([CSS2], section 6.4.4), with the 
additional clarification that the presentation attributes are conceptually 
inserted into a new author style sheet which is the first in the author style 
sheet collection. "
If interpretation of CSS is disabled, the user agent does not support CSS 
anymore (in this specific situation) and this does not apply and it is wrong 
to claim, that the behaviour of Mozilla/Gecko has something to do with what
is recommended for SVG.

The bug is comparable to the situation, if scripting is disabled -
several user agents nevertheless claim via feature string to interprete
scripting - effectively they therefore fail to get the correct content with
a feature string switch. I did not check, if this applies as well, if styling
is disabled and there is a switch for example with a feature string for the
style element.

I think, there is no need to clarify something in the recommendations,
there is only a need to fix bugs in Mozilla/Gecko ;o)


Olaf

 
Received on Tuesday, 19 March 2013 16:54:49 UTC

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