[GSoC] On "ODF Formulas in Writer"

[Matteo Campanelli]

Hi all,
I'm Matteo, a PhD student in Computer Science at City University of New
York.
I am planning to apply to GSoC '14 and a few weeks ago I started hacking
LibreOffice (I've been working on this Easy
Hack<https://bugs.freedesktop.org/show_bug.cgi?id=53472>
).

I'm writing to start a discussion and ask some questions on the idea
project in the subject of this email
([1<https://wiki.documentfoundation.org/Development/GSoC/Ideas#ODF_Formulas_in_Writer>
]).

Could you please give me some feedback on my understanding of the
definition of the problem and current related work in LO (see bullets
below)?
Also - most important question (!!) - would there be anyone interested in
mentoring this project?

My understanding of the issue:
- Currently Writer uses its own, non-standard syntax for formulas. At the
moment this syntax is both what is used/typed by the user and the one used
for internal computations. (At a first glance, the class
SwCalc<http://opengrok.libreoffice.org/search?q=&project=core&defs=SwCalc&refs=&path=&hist=>seems
to be responsible for both parsing and interpreting these formulas,
is that right?)
- The goal of the project would be to enable users to write formulas in the
ODF Format [2]<http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part2.html>
and use this same format for the internal computations.
- As far as I have understood, we may use the ixion library
[3]<https://gitorious.org/ixion> to
interpret ODF-style formulas. This library is already used by Writer for
interpreting formulas in doc/docx files (which, I suppose, are first
converted to the actual ODF format). [is this point of my interpretation
correct? Could anyone provide code pointers for the computation of formula
for .doc files?]
- Part of the project will have to deal with import/export filters and
backward compatibility: first, files with formulas in the old-syntax should
still be parsed correctly; second, users should have the option of saving
in the old syntax or in the default new ODF syntax.

Also, I have two additional questions:
- the project idea page mentions changes in the code for the formula input
bar. What should these changes to the UI consist of specifically? Are they
mostly related to the strings produced by using the "Formula" dropdown menu
in the bar?
- Can anyone who is into the code roughly assess the relative hardness of
the three subparts of this project (i.e. refactoring to use ODF and
delegation to ixion, changes in the UI, adapting import/export filters)? In
other words, which of these parts (if any) is likely to take longer
compared to the others?

References:
[1] ODF Formulas in writer - Original GSoC Project Idea Page
(link<https://wiki.documentfoundation.org/Development/GSoC/Ideas#ODF_Formulas_in_Writer>
)
[2] Open Formula - Official specification
(link<http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part2.html>
)
[3] Ixion Library (link <https://gitorious.org/ixion>)

Comments of any kind are appreciated.
Thanks in advance for your feedback!

Cheers,
Matteo
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