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Re: Elliptical Arc as basic shape

From: Dean Jackson <dean@w3.org>
Date: Thu, 26 Aug 2004 16:03:30 +1000
To: Philippe Lhoste <PhiLho@GMX.net>
Cc: "SVG (www) list" <www-svg@w3.org>
Message-ID: <20040826060330.GC19966@grorg.local>

On Mon 23 Aug 2004, Philippe Lhoste wrote:

> I am working on a drawing made only of circular arcs, and a thought came 
> as I rested...
> Why there is no <arc/> basic shape?
> I thought this question was asked many time, and a search in the 
> archives gave some messages on the subject (I found two or three stating 
> that explicitely, maybe there are more). Actually, message 
> <http://www.w3.org/2002/02/mid/199909070016.RAA26280@mail-345.corp.Adobe.COM;list=www-svg> 
> gives a precise answer to the question...
> But it dates back to 1999, so I wondered if I may ask again, in case 
> position could have changed.
> Cons:
> - There is already an arc primitive in the path tag (but also polyline 
> and polygons can be made with path, and are more redundant, IMO);

Unfortunately implementors hate the arc command in path. That's
why it isn't supported in Tiny.

> - They need too many parameters (stated in the message above, seems to 
> be a strange argument...);

That's one reason why implementors and authors hate it :)

> - Because (seems to be the main reason).

Not really. 

> Pros:
> - It would be more consistent (this is still a basic shape, found in 
> many graphic libraries);


> - Such a primitive would be an opportunity to implement arcs specified 
> with center, radii and angles. They are quite missing in the spec. I 
> understand the reason why arcs in path are defined the way they are, but 
> it would be nice to have an alternative way, more natural in some cases 
> (piecharts come to mind, but not only), and defining arc as a basic 
> shape would be that opportunity:
> - Because (people want it!).
> <arc cx="100" cy="100" rx="20" ry="30"
>      x-axis-rotation="0" start-angle="30" end-angle="60"/>
> Fill if needed, stroke only the arc (perhaps need a flag to stroke radii?)
> Doesn't seems overcomplicated...
> So, is the answer still the same, or may it be planned for SVG 1.3? (I 
> understand 1.2 is almost frozen, feature-wise)

Well, 1.2 is pretty much frozen. It was considered for 1.2, but
I think it will have to wait for 1.3. 

> Or should it be definitively put away because stuff like XBL (which I 
> don't know yet) would allow this (with or without scripting?)?

XBL was one reason why we didn't increase the number of basic
shapes in SVG 1.2. Someone has already implemented arc in RCC (before
XBL was around).

I think <arc> is useful. Implementors say that they prefer to
minimise the number of primitives. Messages like this certainly
help :)

Received on Thursday, 26 August 2004 06:03:46 UTC

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