wxWidgets inheritance export?

[Suryavarman]

MyWxClass to python

I use wxWidgets, wxPython and pybind11.

My project code is here: https://framagit.org/Suryavarman/ma/

and here a video

I have create a class from wxControl.

class M_DLL_EXPORT OgreView : public wxControl
{
    public:
            OgreView(wxWindow* parent, wxWindowID id = wxID_ANY, const wxPoint &pos=wxDefaultPosition, const wxSize &size=wxDefaultSize, long style=0,
                     const wxValidator& validator = wxDefaultValidator, const wxString &name=wxPanelNameStr);
[…]
}

Here a part of code to export the OgreView to python.

    py::class_<API::wx::OgreView>(subModule, "wxOgreView")
        .def(py::init<>())
        .def(py::init<>
        (
             [] (py::object inWindow)
             {

                 wxWindow *window = API_Py::wxLoad<wxWindow>(inWindow.release(), "wxWindow");
                 wxASSERT(window);

                 return new API::wx::OgreView(window);
             }
        ), py::arg("inWindow")
        )
        .def("getParentClass", [](const API::wx::OgreView& self){return static_cast<wxControl*>(const_cast<API::wx::OgreView*>(&self));}, py::call_guard<py::gil_scoped_release>(), py::return_value_policy::reference, "Retourne la classe parente de wxOgreView.")
        ;

Here the casters:
wxPy.h
wxPy.tpp
wxPy.cpp

Note: the typed casters are define at the end of wxPy.h file.

M_WX_PY_CASTER(wxWindow, "wx.Window")
M_WX_PY_CASTER_NO_CLASSINFO(wxSize, "wx.Size")
M_WX_PY_CASTER_NO_CLASSINFO(wxPoint, "wx.Point")
M_WX_PY_CASTER(wxValidator, "wx.Validator")
M_WX_PY_CASTER(wxControl, "wx.Control")
M_WX_PY_CASTER(wxAuiNotebook, "wx._aui.AuiNotebook")
M_WX_PY_CASTER(wxFrame, "wx.Frame")

I want to remove the getParentClass to use directly OgreView parent class.
To do that there are two options (see pybind11 documentation)

1. Load and add the PyObject parent

    py::object py_wx_module = py::module::import("wx");
    py::object py_type_wxControl = static_cast<py::object>(py_wx_module.attr("Control"));
    py::class_<API::wx::OgreView>(subModule, "wxOgreView", py_type_wxControl)
        .def(py::init<>
        (

2. Load the wxPython module and let the casters working.

py::object py_wx_module = py::module::import("wx");

py::class_<API::wx::OgreView, wxControl>(subModule, "wxOgreView")
 .def(py::init<>
 (

The both doesn't work.

First option:

1. During the loading module, it's crash here (segmentation fault):

pybind11.h > generic_type::initialize(const type_record &rec)
line: 933

        else if (rec.bases.size() == 1) {
            auto parent_tinfo = get_type_info((PyTypeObject *) rec.bases[0].ptr());
            tinfo->simple_ancestors = parent_tinfo->simple_ancestors;  // <--- crash here line 933
        }

parent_tinfo is null because, get_type_info return a nullptr if the types are not pybind11-registered.
Remark: It will be good to test the parent_tinfo value.

pybnd11/cast.h line 155-167 get_type_info function

// Gets a single pybind11 type info for a python type.  Returns nullptr if neither the type nor any
// ancestors are pybind11-registered.  Throws an exception if there are multiple bases--use
// `all_type_info` instead if you want to support multiple bases.

Second option:

2. During the loading module, pybind11 send this error:

   ImportError: generic_type: type "wxOgreView" referenced unknown base type "wxControl"

Questions:

What does it mean exactly «pybind11-registered»? Define the caster is not enough?

[Suryavarman]

If I execute in a python console (in my case inside Pycharm and my Application's console) :

globals()
import wx
globals()

Here a screenshot

At the first globals() call there no 'wx' reference and at the second there a the reference:

'wx': <module 'wx' from

Now if write the same code with pybind11:

auto py_wx_module = py::module::import("wx");
py::print(py::globals());

There no wxWidgets reference.
Therefore I think that's the reason why I can't define the wxWidgets inheritance.

Even though py::module::import("wx") seem work.

auto py_wx_module = py::module::import("wx");

py::object py_type_wxControl = static_cast<py::object>(py_wx_module.attr("Control"));
py::print(py_type_wxControl);

result:

<class 'wx._core.Control'>

[YannickJadoul]

As far as I know, inheriting C++ from Python classes is not supported. It would be cool if possible, but there's no way we can do that.

Both your original two options fail because of that, I believe.

See #1193 for a further explanation of why this is and what you could do.

Now if write the same code with pybind11:

auto py_wx_module = py::module::import("wx");
py::print(py::globals());

There no wxWidgets reference.
Therefore I think that's the reason why I can't define the wxWidgets inheritance.

No, this is unrelated. This is because the import is not evaluated in the context of globals. This is not an issue.