Re: init_iterator takes window

[Richard Stallman]

    is it possible for there to be two different windows open on the same
    text with different display behaviors?  if so, which window to choose?

Yes, there can be--any buffer can be displayed in multiple windows.
You should simply use the selected window.  That is simple, and
probably right.

    even if not, i'm confused about how to choose a window to to pass to
    init_iterator; might there be a legitimate call to current-column where
    there is no window available?

I believe Emacs always must have a selected window.