Re: [GSoC] On ODF Formulas in Writer
So, although this will not be a GSOC task, I'd like to answer some of the questions for archival purposes. On Tue, 2014-03-11 at 12:53 +0100, Michael Stahl wrote: that is the part of the idea proposal that i'm not sure about currently: just using this ixion library for Writer formulas would put us in a similar situation like what we currently are with text edition components, where Writer has its own core and everything else uses EditEngine instead; this duplication creates additional maintenance burden. of course there are a lot of formulas (ODF part 2 is hundreds of pages), and to me it appears quite sub-optimal to have multiple implementations of all that. there is already a formula module which Eike claims is not just used by Calc but also by some Report(Builder/Designer/whatever) application, which means it would probably be possible to use this from Writer too. the problem is that apparently formula only contains the code to parse and tokenize formulas; the actual evaluation is still in Calc's core and tied to Calc's internals. so i would welcome some input on what the architecture should look like here: 1) is it possible to somehow abstract the formula evaluation implementations from Calc internals (suppose it's mostly about addressing/accessing the cells?) such that it could be used from Writer too? Possible? Yes, in the sense that anything is possible given enough time. But IMO probably not realistic and perhaps its risk outweighs its potential benefit. Calc's current formula interpreter code is so tied to Calc's own internal model not just from functionality point of view but also performance optimization point of view. Ripping that out and abstracting it for other apps to use would probably be not worth the disruption it would bring. Even the current sc/formula split just to make the parser part of the formula engine available for other parts of the code base has made the handling of formula engine a bit more awkward inside Calc, to say the least. 2) would it be a good long-term plan to migrate Calc to ixion too so we eventually end up with just one formula evaluation engine? This was the initial thinking behind the inception of ixion. But 4 years has passed, and the likelihood of ixion replacing Calc's formula engine has diminished. The possibility is still there, but let's say that won't be happening in the next 5 years. 3) or is it unrealistic to ever share the formula evaluation part? I'd say yes. It's unrealistic. So, if I were to implement this feature, I would still consider using ixion despite the downside of duplication you've already cited. The reality is that we do have to duplicate functionality sometimes for many reasons even though we all know that it's something to be frowned upon. At least with ixion you'll get formula parser, interpreter, A1 style cell address handler and lightweight dependency tracking for free right now. And although I don't think ixion is ready for heavy-lifting formula calculation uses, it should work well enough for light-weight uses such as Writer table's formula handling. Anyway, since we won't be working on this feature anytime soon, we can shelve this discussion for now, I suppose. Kohei ___ LibreOffice mailing list LibreOffice@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/libreoffice
Re: [GSoC] On ODF Formulas in Writer
Okay, thank you guys for all the help. In the meantime I got my patch accepted! :) Given the news (ODF formulas in Writer not being a valid GSoC talks anymore), I'm going to apply for another project but in case my submission to GSoC were not successful I might consider working on a sub-part of this issue anyway this summer 'cause it had intrigued me at the beginning. Best, Matteo On Tue, Mar 11, 2014 at 10:23 PM, Kohei Yoshida kohei.yosh...@collabora.com wrote: On Tue, 2014-03-11 at 12:53 +0100, Michael Stahl wrote: However, for now, I would suggest focusing getting your easy hack ready accepted; that's required even in case at the end you're interested in some other LibreOffice idea. absolutely - here are usually more GSoC applicants than available mentors, and the most important thing to get accepted is to show that you can get useful work done. if we find that this one won't work out, it's always possible to choose a different GSoC project. And it appears that this idea has been moved out of the Ideas page, which means it's no longer a valid GSOC task. To be honest, I don't even know why this task was left on that page in the first place. I believe it was one of those left-over tasks that we forgot to clean up. Kohei ___ LibreOffice mailing list LibreOffice@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/libreoffice
Re: [GSoC] On ODF Formulas in Writer
Hi Matteo, On Sun, Mar 09, 2014 at 01:21:37AM -0500, Matteo Campanelli matteo.campane...@gmail.com wrote: I am planning to apply to GSoC '14 and a few weeks ago I started hacking LibreOffice (I've been working on this Easy Hackhttps://bugs.freedesktop.org/show_bug.cgi?id=53472 ). Great! :-) Please don't forget to push your patch for review once you're happy with it. I'm writing to start a discussion and ask some questions on the idea project in the subject of this email ([1https://wiki.documentfoundation.org/Development/GSoC/Ideas#ODF_Formulas_in_Writer ]). Also - most important question (!!) - would there be anyone interested in mentoring this project? AFAIK the project idea is from Cédric, but he's not mentoring Writer projects this year. This doesn't mean you can't propose to work on this project, but it's not the best Writer project you could pick up. ;-) 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 SwCalchttp://opengrok.libreoffice.org/search?q=project=coredefs=SwCalcrefs=path=hist=seems to be responsible for both parsing and interpreting these formulas, is that right?) Yes, that sounds correct. - 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. Correct, what's currently written is like this: table:table-cell table:style-name=Table1.B1 table:formula=ooow:lt;A1gt;+lt;A2gt; office:value-type=float office:value=3 The ooow part clearly indicates that it's something LO inherited from OOo. - 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?] The ixion library is currently not part of LibreOffice in any way. Regarding, .doc files, this is not handled in the filter (AFACS), just the result of the formula is written to the file as a plain string. - 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. We have a general mechanism for that, in ODF 1.2 extended, probably you could just write the new syntax, and you only need to make sure that the old syntax can be read. 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? Probably the largest part is to make Writer core use the ODF formulas (with the help of ixion), after that the ODF import/export is just filter work, much easier. Regarding UI, it's about to change it, so that it generates the ODF-syntax formulas, that's probably something you can do incrementally once core support is there. Additionally here, is a starter patch: http://cgit.freedesktop.org/libreoffice/build/tree/patches/dev300/fields-table-formula.diff?h=master-backup If you're interested in this project, you probably want to start with porting that to current master. :-) However, for now, I would suggest focusing getting your easy hack ready accepted; that's required even in case at the end you're interested in some other LibreOffice idea. Best, Miklos signature.asc Description: Digital signature ___ LibreOffice mailing list LibreOffice@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/libreoffice
Re: [GSoC] On ODF Formulas in Writer
On 11/03/14 12:29, Miklos Vajna wrote: Hi Matteo, On Sun, Mar 09, 2014 at 01:21:37AM -0500, Matteo Campanelli matteo.campane...@gmail.com wrote: I'm writing to start a discussion and ask some questions on the idea project in the subject of this email ([1https://wiki.documentfoundation.org/Development/GSoC/Ideas#ODF_Formulas_in_Writer ]). Also - most important question (!!) - would there be anyone interested in mentoring this project? AFAIK the project idea is from Cédric, but he's not mentoring Writer projects this year. This doesn't mean you can't propose to work on this project, but it's not the best Writer project you could pick up. ;-) right, and i dont' know much anything about formulas either. - 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. Correct, what's currently written is like this: table:table-cell table:style-name=Table1.B1 table:formula=ooow:lt;A1gt;+lt;A2gt; office:value-type=float office:value=3 The ooow part clearly indicates that it's something LO inherited from OOo. it also indicates it's not standard ODF. - 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?] The ixion library is currently not part of LibreOffice in any way. Regarding, .doc files, this is not handled in the filter (AFACS), just the result of the formula is written to the file as a plain string. that is the part of the idea proposal that i'm not sure about currently: just using this ixion library for Writer formulas would put us in a similar situation like what we currently are with text edition components, where Writer has its own core and everything else uses EditEngine instead; this duplication creates additional maintenance burden. of course there are a lot of formulas (ODF part 2 is hundreds of pages), and to me it appears quite sub-optimal to have multiple implementations of all that. there is already a formula module which Eike claims is not just used by Calc but also by some Report(Builder/Designer/whatever) application, which means it would probably be possible to use this from Writer too. the problem is that apparently formula only contains the code to parse and tokenize formulas; the actual evaluation is still in Calc's core and tied to Calc's internals. so i would welcome some input on what the architecture should look like here: 1) is it possible to somehow abstract the formula evaluation implementations from Calc internals (suppose it's mostly about addressing/accessing the cells?) such that it could be used from Writer too? 2) would it be a good long-term plan to migrate Calc to ixion too so we eventually end up with just one formula evaluation engine? 3) or is it unrealistic to ever share the formula evaluation part? - 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. We have a general mechanism for that, in ODF 1.2 extended, probably you could just write the new syntax, and you only need to make sure that the old syntax can be read. yep, that is just a simple matter of programming. 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? i think we shouldn't even start thinking about any UI changes until the core work is mostly done, since the amount of time required there is very difficult to predict. However, for now, I would suggest focusing getting your easy hack ready accepted; that's required even in case at the end you're interested in some other LibreOffice idea. absolutely - here are usually more GSoC applicants than available mentors, and the most important thing to get accepted is to show that you can get useful work done. if we find that this one won't work out, it's always possible to choose a different GSoC project. regards, michael ___ LibreOffice mailing list LibreOffice@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/libreoffice
Re: [GSoC] On ODF Formulas in Writer
On Tue, 2014-03-11 at 12:53 +0100, Michael Stahl wrote: However, for now, I would suggest focusing getting your easy hack ready accepted; that's required even in case at the end you're interested in some other LibreOffice idea. absolutely - here are usually more GSoC applicants than available mentors, and the most important thing to get accepted is to show that you can get useful work done. if we find that this one won't work out, it's always possible to choose a different GSoC project. And it appears that this idea has been moved out of the Ideas page, which means it's no longer a valid GSOC task. To be honest, I don't even know why this task was left on that page in the first place. I believe it was one of those left-over tasks that we forgot to clean up. Kohei ___ LibreOffice mailing list LibreOffice@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/libreoffice
