[vtkusers] Building VTK on Mac OS X without using framework

[Theodore Sternberg]

> > The showstopper comes a while later, when building the vtkTkRenderWidget,
> > with a conflict between how X.h and Quickdraw.h define "Cursor".

> I think your Tk installation must be installed in some special way to
> support X-windows on the Mac.  I'm not sure what this means, though.
> Hopefully someone else can answer this.

That may well be.  It's worth noting, however, that on top of this 
possibly misconfigured Tk I'm able to build Python with Tkinter and they 
work fine.  I don't see why VTK needs to be pickier than Python, about my 
Tk.