Re: Plot idl

[Havoc Pennington <rhpennin midway uchicago edu>]

Dean was kind enough to forward this; I've subscribed to gnumeric-list now
too. Still I think we should keep guppi-list in the CC line since it
relates to Guppi. 

Miguel wrote:
> > Agreed on keeping the IDL simple for now. We'll see how I can do this
> > inside Guppi and then worry about exporting it.
>
> Ok, this seems to me the most sensible thing.
> Please tell me that you will consider having 3d plots in the future.

Guppi uses gmodule to load code for particular kinds of plot, so it will
have any kind of plot people want to write. 3D should be no problem, other
than the inherent problem of writing the code. :-) Could also have
variants on the same sort of plot, i.e. you could probably write a
ScatterPlot with GnomeCanvas that had spiffy Canvas features, 
or one with GtkDPS that was true WYSIWYG, in addition to the current
version.

> > Other big gaps are PostScript and load/save; I don't even want to
> > think about it. :-)
>
> Yes, decent printing is such a pain in Unix.
> 
> Regarind Load/Save I suggest you use the Gnome-Xml library to save the
> information in XML format.

XML is the plan, but I don't know anything about XML. So if someone could
contribute code and a DTD that would be wonderful. Otherwise I will learn
about XML someday, but probably not soon.

Guppi's internal representation is structured like this:

      GuppiDoc
  /              \
list of         list of plots
data sets         |
                  stuff that depends on the plot type.

Obviously "stuff that depends on the plot type" is the challenging part; I
don't know how it will work but presumably each plot plugin will know how
to load and save itself in XML. It has to be possible to add new
parameters to the format as Guppi develops; also it has to be possible to
skip over a plot if the plugin for that type isn't available to interpret
it. So there's some complexity. 

I guess some existing DTD could be adapted, if one exists.

Havoc