Regarding ODF import and Export support for HistogramChart

[Devansh Varshney]

Thanks, Regina, for such detailed information. This helped me to approach
the
import/export for the Histogram Chart.

I have added changes to the ODF Export for the Histogram Chart.
Have to add support for the Import and addition in the RNG file.

https://gerrit.libreoffice.org/c/core/+/177364

Would anyone from the community be able to help me by reviewing the PR?


On Sun, 1 Dec 2024 at 02:03, Regina Henschel <rb.henschel at t-online.de>
wrote:

> Hi Devansh,
>
> I have put the dev list in CC, because such questions should go to the
> dev list. There are other people too that can answer your questions. I'm
> not an expert for charts and I have not always time to answers in a
> reasonable time frame.
>
> Devansh Varshney schrieb am 29.11.2024 um 14:38:
> > Hi Regina,
> >
> > I have been working on adding the Histogram Chart to the LO
> > codebase(part of GSoC-24), and it is working well.
>
> I think, it is still a lot to do:
>
> Missing "bin"-properties
>
> Filesave, bug 164108.
>
> The use and meaning of "Y-Values" in the wizard is unclear, bug 164109.
> Problem with empty "Categories" in the wizard, no bug report yet. The
> role "values-y-original" is undocumented.
>
> >
> > Now I am tasked to add the import and export support for the same but
> > what I am unable to get is where to begin exactly I have added the
> > entries in the token files -
> https://gerrit.libreoffice.org/c/core/+/177364
> >
> > These two are the import files for the import and export -
> >
> > xmloff/source/chart/SchXMLExport.cxx
> >
> > xmloff/source/chart/SchXMLImport.cxx
> > I have looked for ODF-related PRs and even on OOo but could not find
> > anything related to adding new chart support for ODF.
>
> The type of a chart is determined by the chart:class attribute of the
> <chart:chart> element. The value of the chart:class attribute is a
> namespaced token. The twelve predefined chart types use the namespace
> 'chart'. Since a histogram chart does not belong to the predefined chart
> types, it needs a namespace other than 'chart'. So you should write it
> out as chart:class="loext:histogram".
>
> Because your new chart type needs some properties, which will be in
> loext namespace as well, you can write the new chart type only in an
> extended ODF version.
>
> The chart:class attribute is specified in section 19.15.1 in ODF 1.3, [1].
>
> Properties of the new chart type do not become attributes of the
> <chart:chart> element, but become attributes of the
> <style:chart-properties> child element of the <style:style> element
> which is referenced by the chart:style-name attribute of an affected
> element. That is a <chart:plot-area>, <chart:series> or <chart:axis>
> element, for example.
>
> That is currently wrong for ofPie charts, see bug 163921. So you cannot
> use ofPie charts as template.
>
> Such properties belong to the property map aXMLChartPropMap[].
>
> In your case the labels of the x-axis are generated strings which are
> not contained in the sheet. So you cannot use the
> chart:cell-range-address attribute of the <chart:categories> element
> with a reference into the sheet.
> In your case the values in y-direction are generated values which are
> not contained in the sheet. So you cannot use the
> chart:value-cell-range-address of the <chart:series> element with a
> reference into the sheet.
>
> I have no ready to use solution to solve the problems. The same problems
> are visible in the chart wizard as mentioned above.
> There can currently only be one local table. So using an additional
> local table would require changes in that area.
> Changing the <chart:categories> and <chart:series> elements so that they
> can carry fixed values might be a solution too.
> OOXML does not save the values themselves but only writes the layout
> properties. So that idea might be a way to go as well. In that case we
> would need to decide whether new attributes of <chart:categories> and
> <chart:series> are used or new entries in <style:chart-properties>
> I think these problems need some discussion.
>
> [1]
>
> https://docs.oasis-open.org/office/OpenDocument/v1.3/os/part3-schema/OpenDocument-v1.3-os-part3-schema.html
> The change to version 1.4 is ongoing. In your case you can still use the
> v1.3 specification. The access to the ODF 1.3 specification is easier.
>
> Kind regards,
> Regina
>
>
>
>
>
>
>

-- 
*Regards,*
*Devansh*
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