[Libreoffice] Incompatible changes for B-spline smoothing in ODF1.2

[Regina Henschel]

Hi all,

Currently smoothing with B-Splines uses the inner data points as control 
points. Therefore the smoothed line does not go through the data points 
and it is no interpolation.

In ODF 1.2 the definition of smoothing with B-Splines does it in a way, 
that you get a real interpolation, that means, the smoothed line goes 
through all data points.

The current behavior is so inscrutable, that I endorse the definition in 
ODF1.2.

The current way exist at least since StarOffice 5.1. But I do not know, 
whether anyone really uses it, because it is not suitable for 
interpolation. On the other hand, there might be users, who know to use 
control points and have calculated them in a way to get a special, 
desired line.

It is possible to add another method in class SplineCalculater. That it 
not the problem. But I see no way, to directly store a distinction 
between the two ways in file format. So a chart in an actual version 
using the new kind of smoothing looks different in an older version and 
existing documents will change their appearance when opened in a new 
version.

So, how to handle the change? I like to hear your opinions and ideas.

I have put libreoffice at lists.freedesktop.org in CC, because I think it 
is important for them too and they might not read this mailing list.

kind regards
Regina