[vtk-developers] Tcl wrapping and output array arguments

David Lonie david.lonie at kitware.com
Tue Mar 24 09:26:55 EDT 2015

On Mon, Mar 23, 2015 at 5:51 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi David,
> It's apparent to me that part of the difficulty surrounding this change is
> due to the name of the method.  Why not use a new name?
> bool ComputeBoundsForViewport(vtkViewport *, double bounds[6]);
> I confess that I have an ulterior motive.  I like all Get() or Set()
> methods
> to get/set a property that depends only on the the object itself.  Here,
> the Bounds depend on both the object and on a second object.  So I
> don't consider this method to be a "getter" in the strict sense, hence
> "ComputeBounds" rather than "GetBounds".
> Basically, I like it when Get methods are associated with properties/traits
> of the object.  Eventually, VTK's wrappers might associate Set/Get
> methods with Python properties.  In fact, this idea can already be seen
> in action in tvtk, Enthought's Traited VTK.

Hmm, and this also wouldn't require the 'using' wrapper support right
away...I like it! The distinction between Get/Compute makes sense.

The name is a bit long, and "ForViewport" is implied by the arguments. I'd
like ComputeBounds, but that's already a virtual on many of these classes.

Now I'm leaning towards

vtkBoundingBox ComputeBoundingBox(vtkViewport *)

That would also:
- eliminate the output-array-arg issues with the Tcl wrappers (Yay!)
- encourage use of the vtkBoundingBox class, which is a really nice API for
working with a bounding box that leads to much, much more consistent and
readable usage (there are a few approaches used for, e.g. invalid bounds,
that aren't always consistent).

It needs a couple hints to be wrapped properly, but that's not nearly as
much trouble :)

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