Re: Change in goffice graph file format

[Emmanuel Pacaud <emmanuel pacaud univ-poitiers fr>]

Le samedi 14 juillet 2007 �9:18 +0200, Jean Br�rt a �it :
> Le samedi 14 juillet 2007 �0:16 +0200, Emmanuel Pacaud a �it :
> > Le mardi 03 juillet 2007 �2:18 +0200, Emmanuel Pacaud a �it :
> > > During my recent work on graph fill support for xy and polar plots, it
> > > came clearly (at least for me:) ) that the interpolation property in
> > > GogStyle is out of place, and should be put in GogSeries. I'd like to do
> > > the move, but if I do that, that would mean a file format change, since
> > > GogStyle properties are handled differently than the other GogObjet
> > > properties. I guess it's not an issue for gnumeric, since we have not
> > > yet released a stable version that uses this property. But that would
> > > break other applications that already use the goffice 0.4 version (and
> > > use also the interpolation property, of course).
> > 
> > Here's the path that does the move. 
> > 
> > Any comments ?
> > 
> > 	Emmanuel.
> 
> I'm not sure it's a good idea. With the current implementation, we might
> apply interpolation to objects which are not series such as trend lines
> (when playing with non linear regressions, I encountered cases were the
> current spline interpolation does not give an acceptable result).

In my opinion, the line interpolation property is not a style property:

  - theming doesn't make a lot of sense
  - it's only related to series objects
  - more importantly, its interpretation depends on the current plot
(step interpolation in a polar plots is not the same as in xy plots),
which mean this property can't be handled at the renderer level.

Regarding the need for this property in trend line objects, I'm not sure
it would be a good idea to add a line interpolation selector for them.
We really should try to have a good output without user interaction.

Finally, moving the the property to GogSeries means simpler code
(GogStyle is already too complex, and the additional GogEditor API is
something I need for area fill support).

	Emmanuel.