RE: Advice on troubleshooting function to "unscroll"

[Drew Adams]

> I'll have to go back and look at what "interactive" actually means.

It means that you invoked it by name or via a key binding (which
includes a menu-item binding).

More precisely, it means that `called-interactively-p' returns
non-nil.  See also `interactive-p'.

> 'scroll-up' is advised (and invoked?) in the code below.

Advised, not invoked.  Invoked means called.  `scroll-up' is not
called in the advice definition you show.

> Not sure if that means that I am also invoking it interactively.

The advice applies whenever and however the function is called,
in particular, whether it is called interactively or not.

> I thought being invoked, "as a command", meant that I was
> invoking it using `M-x scroll-up`.

`M-x' invokes commands interactively, but it is not the only way
to do that - see above.  Note that `M-: (scroll-up)' does *not*
invoke `scroll-up' interactively.

> Marcin, I also wondering what prompted the addition of
> scroll-up-command.  I think Drew addresses this but I probably need to
> look at the docstrings for both to grasp it more clearly.

Look too at the beginning of the code for `scroll-up-command':
  (cond ((null scroll-error-top-bottom)
         (scroll-up arg))
        ...

That tells you that when the option is nil (the default value)
`scroll-up-command' just calls `scroll-up'.