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Re: Animating SVG attributes from Web Animations

From: Shane Stephens <shans@google.com>
Date: Mon, 22 Jun 2015 07:12:39 +0000
Message-ID: <CAGTfzwSvxb97xUo7wFXQYSB4EgP7dZP7PkcpuJU7h0+jS6yHbg@mail.gmail.com>
To: Bob Hopgood <frahopgood@gmail.com>, public-fx@w3.org
On Sun, Jun 21, 2015 at 4:24 AM Bob Hopgood <frahopgood@gmail.com> wrote:

> Apologies for responding to the wrong mail list but that is where the
> question arose.

Tab has already pointed out that this is not the appropriate *thread* (not
mailing list). If you want to ask a question that is unrelated to the topic
at hand, please start a new thread and ask it there.

    -Shane Stephens

> You say:
> "(But there's nothing wrong with putting strings like that in CSS; I'm
> unsure why you think there's a meaningful difference between <path
> d="giant string"> and <path style="d: 'giant string'">.)"
> I didn't say there was a meaningful difference. I just asked whether CSS
> implementations were capable of handling 1 Megabyte or even 50 kbyte
> strings. Current SVG implementations have a problem handling very large
> numbers  of animated path descriptions while handling long path
> descriptions pretty well. (In consequence I have to distort the structure
> of an animation by compounding paths together to get reasonable
> performance.)
> The question was whether CSS implementations would be better or worse than
> the SVG implementation ?
> The intrinsic difference is best shown by:
> (1)
> path.abc {d:giantstring}  in a stylesheet xyz.css and
> <path class="abc"/> in the file ashape.svg
> in the SVG document compared with:
> (2)
> <path d="giant string" /> in the file aus.svg
> As it currently exists in SVG 1.1, in (2) the d attribute is tightly bound
> to the svg document before rendering.
> In (1), depending on the stylesheet applied to the document, it defines
> either the outline of Australia or New Zealand dependent on the style
> sheet  which may even be supplied by the user overriding the intention of
> the author.
> You also say:
> "A <path> carries no intrinsic meaning, just like an <img>; it is
> completely opaque to a search engine, screen-reader, or other machines.  It
> is entirely unlike text content."
> The example above in HTML would be:
> (1)
> h2.abc {text:giantstring}  in a stylesheet xyz.css and
> <h2 class="abc" text=""/> in the file sometext.htm
> in the HTML document compared with:
> (2)
> <h2 text="giant text string" /> in the file meaningfultext.htm
> There is a difference in how the XML elements are written in SVG and HTML.
> HTML writes the content of the element as  the content of the h2 whereas
> SVG writes the content of the path element as a d attribute. HTML quite
> rightly does not allow  the text content of the h2 to be changed by styling
> otherwise  the search engines would produce rubbish.  Similarly, SVG 1.1
> does not allow the graphical content of the path element to be restyled by
> a stylesheet. Otherwise a person reading the path description on a high
> quality search engine or screen reader could not understand the meaning at
> a superficial level.
> Even the simplest of search engines should be able to see that:
> <path d="M0,0h30v-30h-60v30h30v30h30v30h-60v-30h30"/> defines a flow
> diagram with two boxes just as a search engine should be able to recognise
> <h2>Schemat przeplywu</h2>
> Students at Oxford Brookes University since 2000 have regularly had exam
> papers with path descriptions much more complicated than the one above that
> they must understand and most get good grades with no real difficulty. Only
> three have  had any idea what the HTML meant.They were European Union
> Erasmus exchange students from Poland.
> Personally I have no problem with theSVG and have no ability to say what
> the HTML means.  I tried Google for the HTML and the first 50 responses
> were in a language that I did not understand. I tried M0,0h30 and at least
> there was one entry in the top 10 that was concerned with SVG.
> Zaineb BEN FREDJ's  thesis "Enquiring and Reasoning Over Diagrams Using
> the Semantic Web" describes a system GraSSML built on SVG that can be used
> by blind users to reason over a range of formal diagrams. There is also
> interest in geometric search engines, see
> http://visionair.ge.imati.cnr.it/gse/.
> The main point is that the text in HTML is content as is the d attribute
> of SVG and neither should be changed by a stylesheet and a decent search
> engine should be able to extract meaning from both, which is the reason
> that a stylesheet should not be allowed to change rthe content in either.
Received on Monday, 22 June 2015 07:13:19 UTC

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