Description
I've written an experimental C++ app that uses the Python interpreter and the OCCT 3D viewer together so that it can be a visual REPL for CadQuery. I have implemented a C++ callback for show_object so that the Python code can call show_object(res) to pass the cadquery.Workplane or cadquery.Assembly object to the C++ side. Things work up to a point, but I have struggled getting an OCCT TopoDS_Solid/Shape from OCP to pass to the viewer code. Is there an equivalent of the wrapped attribute on CadQuery objects that will return the underlying C++ instance? Below is a rough implementation of the show_object callback where I am just trying to use pybind11 to get a reference to the underlying OCCT instance to pass to the viewer, which gives me an error that the OCP type cannot be cast to the OCCT type.
static PyObject* show_show_object(PyObject *self, PyObject *args)
{
// Get the argument back from the Python show_object call
PyObject* i;
if(!PyArg_ParseTuple(args, "O", &i))
return NULL;
// Handle a Workplane object differently than an Assembly object
PyTypeObject* type = i->ob_type;
if (strcmp(type->tp_name, "Workplane") == 0) {
printf("cadquery.Workplane object detected.\n");
PyObject* obj = PyObject_CallMethod(i, "val", NULL);
if (obj == NULL) {
printf("Error getting wrapped object from cq.Workplane.\n");
}
else {
PyObject* wrapped = PyObject_GetAttrString(obj, "wrapped");
if (wrapped != NULL) {
if (strcmp(wrapped->ob_type->tp_name, "OCP.TopoDS.TopoDS_Solid") == 0) {
printf("Found OCP TopoDS_Solid object.\n");
py::handle h = wrapped;
TopoDS_Shape* x = *py::cast<TopoDS_Shape>(h);
}
else {
printf("Found some other TopoDS object.\n");
}
}
}
}
else if (strcmp(type->tp_name, "Assembly") == 0) {
printf("cadquery.Assembly object detected.\n");
}
return args;
}The output, including the error, is below.
cadquery.Workplane object detected.
Found OCP TopoDS_Solid object.
terminate called after throwing an instance of 'pybind11::cast_error'
what(): Unable to cast Python instance of type <class 'OCP.TopoDS.TopoDS_Solid'> to C++ type 'TopoDS_Shape'
Aborted