[vtk-developers] const arrays in Set methods

[David Gobbi]

I've committed the change outlined below, so now all methods
with array parameters will be properly wrapped in python
and values can be returned in the arrays.

The problem with multi-dimensional arrays still exists so I had
to add //BTX //ETX to a few header files.

 - David

--
  David Gobbi, MSc                       dgobbi at irus.rri.ca
  Advanced Imaging Research Group
  Robarts Research Institute, University of Western Ontario

On Wed, 28 Nov 2001, David Gobbi wrote:

> I've just thought of a reasonable way to handle non-const array
> parameters in the python wrappers.
>
> The main problem with wrapping non-const arrays is that sometimes
> (e.g. in GetXX(float x[3]) they are used to return values.  Usually
> in cases like this there is a "float *GetXX()" method with a
> corresponding hint but not always.
>
> What the python wrappers can do is turn the tuple (or list) into an
> array, pass the array to the C++ method, and (after the C++ method
> has returned) check the array values against the original tuple or
> list to see if any values have changed.  For every value that has
> changed, a python SetItem() call will be used to change the list/tuple
> value.  Trying to change the contents of a tuple will raise an exception,
> which is exactly the desired behaviour.
>
> This won't take much work to implement and will result in many more
> methods being wrapped.  So I'll try to scare up some time to get it
> done before 4.0 is released.
>
>  - David
>
>
> On Wed, 28 Nov 2001, David Gobbi wrote:
>
> > On Wed, 28 Nov 2001, Brad King wrote:
> >
> > > > Some of the python code I have doesn't work with the recent VTK 4.0
> > > > because the SetPosition(float _arg[3]) etc.  methods don't have
> > > > const arguments and therefore aren't being wrapped.
> > > Is there a specific class for which the SetPosition method is not showing
> > > up?  I don't think the VTK wrappers wrap any methods that take array
> > > arguments unless a hint is specified or the method is defined by a macro
> > > like vtkSetVector3Macro.
> >
> > No, as long as the array is declared as const it is wrapped.  I made
> > that change to vtkParse.y around two years ago or so.
> >
> > My plan (at least for the python wrappers) was to eventually wrap
> > non-const arrays as well but to associate them with python lists
> > instead of with python tuples.  That way the returned array elements
> > could be copied into the lists.  I never got around to it, but it
> > would be straightforward to do.
> >
> > Anyway, I've changed my own VTK source to wrap all arrays and will
> > probably commit the change later today if there are no objections.
> > I had to add //BTX //ETX around all VTK methods with parameters
> > of the form <type>[n][m] because vtkParse.l/vtkParse.y don't
> > correctly parse multi-dimensional arrays.
> >
> >  - David
> >
> >
> >
> >
>
>