[x3d-public] x3d.py roundtrip for Metadata nodes in v.3.3 and v.4.0

[Andreas Plesch]

A quick update:

On Tue, Oct 31, 2023 at 3:49 PM Andreas Plesch <andreasplesch at gmail.com> wrote:
>
> Notes:
>
> x3d.py is autogenerated from X3DUOM:
>
> https://www.web3d.org/x3d/stylesheets/python/python.html#autogeneration
> https://sourceforge.net/p/x3d/code/HEAD/tree/www.web3d.org/x3d/stylesheets/X3duomToX3dPythonPackage.xslt
>
> X3DUOM has all necessary containerField default value information.
>
> But the first step may be to modify the stylesheet to generate
> containerField attributes for all nodes, for simplicity. It looks like
> the .XML() function would have to have an additional parameter 'field'
> X3D(indentLevel, syntax, field) for each node.
>
> Postprocessing the generated XML is not possible since information was
> irretrievably lost. But postprocessing the autogenerated x3d.py python
> code may be possible since xslt is not for everyone.

As a proof of concept I hacked a short awk (since I know it) script to
process the latest x3d.py to include containerField support:

https://github.com/andreasplesch/x3d-python-mod/blob/main/src/cfXML.awk

It looks for the Concrete Nodes section, adds a field parameter to the
.XML() output function, adds the containerField attribute to the
output, and adds the field parameter to the .XML() calls for metadata,
SFNode and MFNode field processing.
The awk script is very brittle since it relies on comments in x3d.py
to find the appropriate lines to modify. The hardest part was to get
the quoting and escaping correct.
It generates containerField attributes for all SF/MFNode fields except
'children'. Of course, most are unnecessary but filtering
systematically for defaults would probably require involving X3DUOM
and the generation stylesheet, similar to other XML related 'fields'
such as style or class.

The result is https://raw.githubusercontent.com/andreasplesch/x3d-python-mod/main/x3dcf.py

The modified python script appears to work as expected by adding the
appropriate containerField attributes in XML output for all the
examples I tried.
Realistically, this is as far as I can go with this but I think it may
show how containerField support in XML output could be provided with
x3d.py.

-Andreas