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Elliptical arc in path (was Re: Tinier SVG)

From: Chris Lilley <chris@w3.org>
Date: Thu, 14 Nov 2002 18:11:20 +0100
Message-ID: <2357554625.20021114181120@w3.org>
To: www-svg@w3.org, "J. David Eisenberg" <catcode@catcode.com>

On Thursday, November 14, 2002, 5:38:23 PM, J. wrote:

JDE> I'm still _really_ concerned that SVG Tiny doesn't have
JDE> elliptical arc. Someone (not sure whether on this mailing list or
JDE> at the SVG group at Yahoo) pointed out that pie charts are
JDE> hellishly difficult to produce without elliptical arc, and those
JDE> would be a the sort of thing a businessperson might want to see
JDE> on his pocket phone/computer/whatever.

They can be simulated with beziers, though.

JDE> Perhaps efforts would be better spent cajoling/coaxing/bribing
JDE> the folks at W3C to include elliptical arc in the Tiny and Basic
JDE> subsets.

Due to the large number of implementations that said "we do SVG path"
followed by a footnote saying "except for elliptical arc", the WG took
the decision long ago to remove that from the path command set.

Its not really that hard to do, and the spec includes all the math to
convert the more comon ellipse formulation (semi-major and
semi-minor radii, centre, rotation, start and end sweep angle) into
the form used in the SVG path command (as with other path commands,
starts withthe current point on the path, has what data it needs, and
ends with an explicit next point on the path). But still, it seemed
that was the best way to get interoperability.

Its arguable, as all decisions are, but it was decided long ago and
that is what the implementations now do, so adding elliptical arc back
again would require all those implementations to be revised.

I would say it is now too late to revisit that decision.




-- 
 Chris                            mailto:chris@w3.org
Received on Thursday, 14 November 2002 12:11:18 GMT

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