Re: Dia XML format, Graphviz, Instaviz etc.

[Hans Breuer <hans breuer org>]

At 23.03.2009 23:15, Glen Low wrote:
> Lars, All
>
> On 24/03/2009, at 1:06 AM, dia-list-request gnome org wrote:
>
> > > Hi All
> > >
> > > I'm the author of the iPhone graph sketching program http://
> > > instaviz.com and sometime contributor to AT&T Graphviz project (CPL-
> > > licensed).
> > >
> > > I'm currently working on a Visio VDX exporter for Graphviz. I was
> > > curious about whether I could generalize it to output DIA as well,
> > > since the DIA support in Graphviz is rather old. Do you have any
> > > documentation about the Dia XML format, I don't see anything that's
> > > easily Googleable?
As already pointed out documentation on Dia's internal format is rather 
weak. There is just the dtd, which does not help much in writing correct 
Dia files with completely defined objects. And it will probably stay that 
way becuase a typical Dia installation has about 1000 different object 
types available, which all can define their own interdepending properties.)

But if you consider to read code as documentation, there is something new:
http://svn.gnome.org/viewvc/dia/trunk/plug-ins/python/diastddia.py?revision=4332&view=markup

About 300 lines of Python code (half of it XML) implementing a Dia export 
filter to a simplified - but complete - Dia file.
The simplifcation comes from only using the 'Standard' set of Dia objects; 
the one guaranteed to be always available with Dia.

Currently missing for the dot->Dia use case are connections, IMO the most 
interesting part of the given use case.

> > Given that I never got anything usable out of graphviz' Dia output, I
> > think that'd be great -- dunno how easily all the bezier splines will
> > convert, but you may have better ideas than me there.
I think the bezire line generation of dot's Dia output is already working 
quite nicely, as I said: just connecting the objects is missing.

> Could you email me a couple of representative .dia files? Preferably 
> with a .pdf or .svg to compare against so I know what I'm looking at.
Checking the validity of Dia files is impossible outside of Dia. And given 
that the dot output probably is a very small subset (box, ellipse, 
bezierline, text) it may be more useful to start from other side.

If you can send me some small, but representive dot files I would convert 
the to Dia's format for you.

> Does Dia not have bezier splines?
Sure, see above.

> I'll have to see if I can get Dia running on my PS3 Fedora Core box. 
> Otherwise I have nothing I can quickly test it on.
Where does you graphiz development take place? (I think Dia is available 
for that platform, too. The Dia version should not matter much, given that 
the file format is rather stable.)

Regards,
        Hans

-------- Hans "at" Breuer "dot" Org -----------
Tell me what you need, and I'll tell you how to
get along without it.                -- Dilbert