Re: [Pyobjc-dev] VTK bindings

[Ronald O. <ous...@ci...>]

On 6 dec 2003, at 18:04, Carlos Phillips wrote:

>
> On Dec 2, 2003, at 1:13 PM, Bob Ippolito wrote:
>
>>
>> On Dec 2, 2003, at 12:38 PM, Ronald Oussoren wrote:
>>
>>>
>>> On 2 dec 2003, at 16:23, b.bum wrote:
>>>
>>>> On Dec 2, 2003, at 1:12 AM, Carlos Phillips wrote:
>>>>> 2003-12-02 03:30:46.165 Simple1[1541] PyObjCPointer created: at  
>>>>> 0x6d16080 of type  
>>>>> {vtkRenderer={?={?={?=^^?i}C{vtkTimeStamp=^^? 
>>>>> L}^{vtkSubjectHelper}}^{vtkAssemblyPath}^{vtkPropCollection}iIff^{v 
>>>>> tkPropCollection}^{vtkActor2DCollection}^{vtkWindow}[3f][4f][2f][2f 
>>>>> ][2f][2i][2i][3f][3f][4f]}^{vtkCamera}^{vtkLight}^{vtkLightCollecti 
>>>>> on}^{vtkCullerCollection}^{vtkActorCollection}^{vtkVolumeCollection 
>>>>> }[3f]^{vtkRenderWindow}ffiii*{vtkTimeStamp=^^? 
>>>>> L}fii^^{vtkProp}i^^{vtkAssemblyPath}iii[6f]f}8@0:4
>>>>
>>>> Like Bob said, once a PyObjCPointer is created, you are generally  
>>>> out of luck.  PyObjC transparently bridged Objective-C.  In this  
>>>> case, you are asking it to transparently bridge a relatively  
>>>> complex C data type.
>>>
>>> The problem is that PyObjCPointer is a not really a wrapped pointer,  
>>> when the PyObjCPointer object is created the value pointed-to is  
>>> copied into an internal buffer. Most of the time that doesn't work,  
>>> vtkRenderer is probably a C++ class and the copied value is invalid.
>>>
>>> I'll put creation of a real pointer wrapper on my todo-list, a  
>>> generic version of the types used to wrapped some other pointer  
>>> types (see pointer-support.m).
>>>
>>> Is VTK itself wrapped? If so, you could use the functions in  
>>> pointer-support.m to convert vtkRenderer* to the Python wrapper from  
>>> the VTK wrapper.
>>
>> VTK itself does have python wrappers.. they probably work on OS X by  
>> now, but there were problems last time I tried (a long while ago, due  
>> to linking issues).
>>
>> -bob
>>
>
> I am trying to create a wrapper for the following methods in VTKView.
> -(vtkRenderer *)renderer;
> -(vtkRenderWindow *)renderWindow;
> -(vtkRenderWindowInteractor *)renderWindowInteractor;
>
> Each return value is  a C++ class which has a VTK python wrapper. In  
> VTK, there is a function available to convert pointers along with type  
> descriptions into python objects. Thus all I need to do is create a  
> wrapper for these methods which returns the appropriate python object  
> instead of the C++ object.
>
> To do this, I have created a module similar to the AppKit module which  
> installs a wrapper method with the following call.
>
> if (PyObjC_RegisterMethodMapping( classVTKView,
> 				    @selector(renderer),
> 				    call_VTKView_renderer,
> 				    PyObjCUnsupportedMethod_IMP) < 0)
>
> call_VTKView_renderer does the following:
> 1) Unwrap the VTKView python proxy. Call the unwrapped objc object  
> self_objc.
> 2) rend = [self_objc renderer]
> 3) Wrap rend using VTK function.
> 4) Return wrapped rend
>
> I use PyObjCUnsupportedMethod_IMP as the fourth argument to  
> PyObjC_RegisterMethodMapping but I'm not sure what this argument is  
> for.
>
> When I compile the new module and load it into python. I gain access  
> to the VTKView class and can instantiate it. When I call renderer() on  
> an instance, I get the following python error:
>
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: argument list must be a tuple

Do you parse the method arguments using PyArg_ParseTuple? See one of  
the method mappings in the Foundation and AppKit wrappers for an  
example of argument parsing.


>
> Is this because I don't have a callPython argument in my  
> PyObjCUnsupportedMethod_IMP call? If so what needs to be put there?

You can leave the PyObjCUnsupportedMethod_IMP as it is, you only have  
to change that when you want to be able to override the method in  
Python.

Ronald