FEM: Handle python vtk user installs that conflict with FreeCAD VTK

src/Mod/Fem/App/AppFemPy.cpp

@@ -40,6 +40,11 @@
 #ifdef FC_USE_VTK
 #include "FemPostPipeline.h"
 #include "FemVTKTools.h"
+#include <LibraryVersions.h>
+#endif
+
+#ifdef FC_USE_VTK_PYTHON
+#include <vtkPythonUtil.h>
 #endif
 
 
@@ -75,6 +80,14 @@ public:
                            &Module::writeResult,
                            "write a CFD or FEM result (auto detect) to a file (file format "
                            "detected from file suffix)");
+        add_varargs_method("getVtkVersion",
+                           &Module::getVtkVersion,
+                           "Returns the VTK version freeCAD is linked against");
+#ifdef FC_USE_VTK_PYTHON
+        add_varargs_method("isVtkCompatible",
+                           &Module::isVtkCompatible,
+                           "Checks if the passed vtkObject is compatible with the c++ VTK version freecad uses");
+#endif
 #endif
         add_varargs_method("show",
                            &Module::show,
@@ -318,6 +331,34 @@ private:
 
         return Py::None();
     }
+
+    Py::Object getVtkVersion(const Py::Tuple& args)
+    {
+        if (!PyArg_ParseTuple(args.ptr(),"")) {
+            throw Py::Exception();
+        }
+
+        return Py::String(fcVtkVersion);
+    }
+
+#ifdef FC_USE_VTK_PYTHON
+    Py::Object isVtkCompatible(const Py::Tuple& args)
+    {
+        PyObject* pcObj = nullptr;
+        if (!PyArg_ParseTuple(args.ptr(),"O", &pcObj)) {
+            throw Py::Exception();
+        }
+
+        // if non is returned the vtk object was created by annother vtk library, and the
+        // python api used to create it cannot be used with FreeCAD
+        vtkObjectBase *obj = vtkPythonUtil::GetPointerFromObject(pcObj, "vtkObject");
+        if (!obj) {
+            PyErr_Clear();
+            return Py::False();
+        }
+        return Py::True();
+    }
+#endif
 #endif
 
     Py::Object show(const Py::Tuple& args)