One question I have about this approach is whether it is possible to
implement the "handle" object (apparently a specially encoded number)
that Matlab uses in the scripting language. How do you take this
number and find the appropriate part of the data structure that
represents the handle graphics state? I think you need to do this so
you can modify the global data structure given just the handle of a
small part of it. It seems to me that this operation would be easy to
do in C++ because the number could be converted to a pointer into the
data structure. But Octave does not have pointers, so it needs to be
done in some other way, perhaps by searching the structure for some ID
tags.