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[SVGF1.12 LC] marker direction if average direction is zero?

From: Anthony Grasso <Anthony.Grasso@cisra.canon.com.au>
Date: Wed, 6 Oct 2010 05:34:01 +0000
To: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>, "www-svg@w3.org" <www-svg@w3.org>
Message-ID: <923A4276C1903646BE5299CA8462B0A005533A@EXM02-WVP.cisra.canon.com.au>
Hi Dr. Hoffmann,

Nice find! This is a very interesting case you raise. We noted this comment (ISSUE-2337 [1]) in our list of SVG Full 1.1 Last Comments to address.

After discussion in our telephone conference [2], I was assigned ACTION- 2814 [3] to add wording to the specification. We decided that for this particular case in SVG Full 1.1 2nd that the behaviour is undefined. The wording has now been added and can be found in the current unpublished version of the SVG Full 1.1 2nd Edition specification [4]. We will however, look to define a behaviour for this case in SVG 2 [5].

Please let the SVG Working Group know at your earliest convenience if the change satisfactory.

Kind Regards,

Anthony Grasso.

[1] http://www.w3.org/Graphics/SVG/WG/track/issues/2337
[2] http://www.w3.org/2010/07/06-svg-minutes.html
[3] http://www.w3.org/Graphics/SVG/WG/track/actions/2814
[4] http://dev.w3.org/SVG/profiles/1.1F2/master/painting.html#OrientAttribute
[5] http://www.w3.org/Graphics/SVG/WG/track/issues/2381


> -----Original Message-----
> From: www-svg-request@w3.org [mailto:www-svg-request@w3.org] On
> Behalf Of Dr. Olaf Hoffmann
> Sent: Sunday, 23 May 2010 10:27 PM
> To: www-svg@w3.org
> Subject: marker direction if average direction is zero?
>
> Hello www-svg,
>
> if a path itself has a directionality at the corners/vertices, but the average is
> zero, what is the correct behaviour?
> See attachment for examples.
>
> I found a definition, if the path has no directionality, but not about the
> problem, that the average direction can be a zero vector (the tangent
> vectors have an opposite direction).
>
> Even worse, current viewers display it typically different from each other.
> I'm not sure, what a useful behaviour could be, therefore maybe the usual
> local x-axis should apply.
> For the next SVG version it might be useful as well to have an additional
> property to suppress markers for vertices with no directionality or with an
> average resulting in a zero vector.
>
> Results with the usual suspects Opera, Batik/Squiggle, adobe-plugin, Gecko,
> WebKit, Konqueror+KSVG look like random choice, result in Inkscape (0.46)
> is completely nonsense.
>
> Well, even for cases with a defined direction, the results are often quite
> different for non-trivial samples.
> I think, currently the adobe plugin provides results almost as specified in
> the recommendation. the Geckos quite often provide a correct result.
> Others are more often wrong, therefore results from these viewers are
> anyway no reliable source for a direction of a path as specified ;o)
>
>
> Olaf
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Received on Wednesday, 6 October 2010 05:34:41 GMT

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