Re: [Pyobjc-dev] VTK bindings

[Carlos P. <ca...@ci...>]

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^{vt 
>>>> kPropCollection}^{vtkActor2DCollection}^{vtkWindow}[3f][4f][2f][2f][ 
>>>> 2f][2i][2i][3f][3f][4f]}^{vtkCamera}^{vtkLight}^{vtkLightCollection} 
>>>> ^{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

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

Carlos