fdo#61135 New feature in Calc: Stepped Lines graphs - first part of code submitted

[Markus Mohrhard]

Hey Eric,

>
>>
>> I have added my first real code for submission to LO :-) It's in gerrit:
>> https://gerrit.libreoffice.org/2476.
>
> I'm going to review it in the next days.
>

so here is the inital review for your change. Your patch looks already
quite good but there are some small changes necessary before we can
merge it.

First we need to move the new values in CurveStyle.idl to the end and
remove all the GNM_* values. Moving the values to the end ensures that
the old values stay unchanged which causes as little trouble for
extension developers using the API as possible.

The import for files written by gnumeric should map the values to the
corresponding ODF values and during export we only want to export them
as ODF and never into the gnumeric namespace. This also means to
remove all the references to the GNM_* values in the other source
files. For that to correctly work we need to register the gnumeric
namespace and map the elements in the chart namespace and the elements
in the gnumeric namesapce to the same UNO attributes.
Your current export code is producing invalid xml files because you
were exporting the gnumeric values without registering the namespace.
However this problem should be gone once we no longer export elements
into the gnumeric namespace. Additionally we need to take care of the
ODF version during export and make sure we only export it into ODF1.2
extended. I think Thorsten was fine with exporting the elements into
the chart namespace but only for ODF 1.2 extended.

The code in AreaChart.cxx looks mostly good and I will have a final
look at it when all the other problems are fixed.

Additionally it would be nice if you would provide at least one of
your test documents from gnumeric and one of your test documents for
normal ODF as MPL/LGPL licensed test documents that we can add to our
test file repository. If you are interested it would also be nice if
you could add a test case for it to our new chart2 import test at
chart2/qa/extras/chart2import.cxx.

Please let me know if I should help you with any of the above tasks. I
can take care of them if neccesary.

Thanks a lot for your great work. It is highly appreciated and feel
free to ask for any help you need. For the UI part of the task it
might make sense to first convert the relevant dialog to the new UI
format and then add the new elements into it.

Regards,
Markus