Re: arc in shapes

[Lars Clausen <lrclause cs uiuc edu>]

On Fri, 15 Jun 2001, Elena Zotova wrote:

> Lars Clausen wrote:
>
> > On Thu, 14 Jun 2001, Elena Zotova wrote:
> >
> > >     Hello.
> > > I am russian and speak English very bad. Excuse me, please.
> > >
> > > I made a patch for dia-0.88.1. This patch allow use arc of circle and
> > > arc of ellipse in shapes.
> > > Are you interested it?
> >
> > Possibly.  The current shapes format allows ellipses and arcs (like the
> > standard objects) in them, what's the difference between that and yours?
> >
> > Here is an example ellipse and arc:
> >     <svg:ellipse style="stroke-width: 0.1; stroke: #000000" cx="8.45"
> >       cy="8.45" rx="3.2" ry="1.8"/>
> >     <svg:path style="stroke-width: 0.1; stroke: #000000" d="M
> >       8.35315,8.98804 A 1.84244,1.84244 0 0 1 8.37768,10.0654"/>
>
> In first, in shapes for dia-0.88.1 simbol A in path ansupported. Excuse,
> if it allow in more new version.  (Quotation from castom-shapes for
> dia-0.88.1:"The line, polyline, polygon, rect, circle, ellipse, path and
> g elements are supported.  Note that the path element only supports the
> M,m,L,l,H,h,V,v,C,c,S,s,Z and z commands.", and my attempt copy this
> exaple call warning:"** WARNING **: unsupported path codde 'A' " and
> don't show enithing in this shape).

I see, I didn't actually test that (that's output from exporting to shape).
I believe you are right, it is unsupported. 

> Two, in this example IMHO too many parameters (IMHO 6 enough, against 7
> in example) and it use is slightly complication.

Nope, 7 is what is specified.  See
<URL:http://www.w3.org/TR/2000/CR-SVG-20001102/paths.html#PathData>.
Now actually *implementing* the proper use of these is tricky.  We could
just have a subset thatcan handle 'our' kinds of arcs, for now.

> And will be good, if path allow build arc across three point, but it is
> only dream.
>
> I made arc as individual svg-node like circle or ellipse. And for more
> easy in 
> use separately for circle arc and ellipse arc.
> <svg:carc cx="..." cy="..." r="..." a1="..." a2="..."/>
>  This is a arc of circle with centre (cx,cy) and radius r from angle a1
> to angle 
> a2. The angles are measured in degrees counter-clockwise.
> <svg:earc cx="..." cy="..." r="..." a1="..." a2="..."/>
>  This is a arc of ellipse with centre (cx,cy) and radius rx in the x
> direction 
> and ry in the y direction from angle a1 to angle a2. The angles are
> measured in 
> degrees counter-clockwise.

Problem with this is that SVG doesn't include carc and earc.  We don't want
to make our own extensions to SVG:)  However, implementing the subset of
A/a that does what your arcs do ought to be simple, given your code.  

-Lars

-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause) | Hårdgrim of Numenor
"I do not agree with a word that you say, but I    | Retainer of Sir Kegg
will defend to the death your right to say it."    |   of Westfield
    --Evelyn Beatrice Hall paraphrasing Voltaire   | Chaos Berserker of Khorne