[Feature] QPDFFormFieldObjectHelper setFormFieldName

[amargerandhw]

I would like to add the method setFormFieldName of QPDFAcroFormDocumentHelper :
https://github.com/qpdf/qpdf/blob/main/libqpdf/QPDFAcroFormDocumentHelper.cc#L154
https://github.com/qpdf/qpdf/blob/58c31fdd5e9e633281cb6830d63427da050fbe41/include/qpdf/QPDFAcroFormDocumentHelper.hh#L107

But I dont really know well pybind11, where should I start to make my PR. Is there an example of a method from this QPDF class already implemented ?

[jbarlow83]

Please see general contributing guidelines.
https://pikepdf.readthedocs.io/en/latest/references/contributing.html

I don't have time or need to implement this feature myself (PDF is too big for one person), but I can support your work on a PR.

embeddedfiles.cpp is probably close as to a template since it creates the pikepdf Attachments class which binds QPDFEmbeddedFileDocumentHelper, and several object QPDF*ObjectHelper classes. At a glance, it's possible a property acroform.cpp would similarly succinct and straightforward - a lot of the time the C++ code is giving Pythonic names to C++ methods.

Object helpers must specify shared_ptr as their holder type or you will get lots of segfaults. Document helper must omit this, because it uses the default unique_ptr. The entire class hierachy has to use the same holder type or everything goes boom.

py::class_<QPDFEFStreamObjectHelper,
        std::shared_ptr<QPDFEFStreamObjectHelper>,  // <--- holder type spec
        QPDFObjectHelper>(m, "AttachedFile")

You'll also to ensure #include <pybind11/stl.h> in the cpp file.

QPDF has several functions that return std::vector<QPDFAnnotationObjectHelper>. That's going to be interesting, because I don't have any other code that specifically returns a vector of object helpers. When #include <pybind11/stl.h> is present pybind11 should (!) pull that std::vector apart and construct a Python list of object helpers. I think the pybind11 defaults should be fine here. But it's possible the wheels could fall off the wagon at this point.

[amargerandhw]

@jbarlow83 Ok thank you I'll look into it and submit a PR asap

[amargerandhw]

@jbarlow83

I started to try implementing the method here : https://github.com/pikepdf/pikepdf/pull/580/files

But I dont understand what I'm doing wrong, I have this error message :

      In file included from src/core/acroform.cpp:13:
      /private/var/folders/6q/0czph51n4zs82xv5w7l5c66m0000gn/T/pip-build-env-1zxqsgo5/overlay/lib/python3.12/site-packages/pybind11/include/pybind11/pybind11.h:1572:5: error: static assertion failed due to requirement 'detail::integral_constant<bool, false>::value': Unknown/invalid class_ template parameters provided
          static_assert(detail::all_of<is_valid_class_option<options>...>::value,
          ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      src/core/acroform.cpp:20:5: note: in instantiation of template class 'pybind11::class_<QPDFAcroFormDocumentHelper, std::shared_ptr<QPDFAcroFormDocumentHelper>, QPDFObjectHelper>' requested here
          py::class_<QPDFAcroFormDocumentHelper,
          ^
      src/core/acroform.cpp:23:10: error: no member named 'def' in 'pybind11::class_<QPDFAcroFormDocumentHelper, std::shared_ptr<QPDFAcroFormDocumentHelper>, QPDFObjectHelper>'
              .def(
               ^
      2 errors generated.

Could you help me understand it ? 🙏

[jbarlow83]

I suspect the error is due to QPDFAcroFormDocumentHelper not being a subclass of QPDFObjectHelper.