bug#8911: bs-cycle-next deletes window in some cases.

[martin rudalics <rudalics@gmx.at>]

 > Presumably you mean all is needed is that, plus an entry in
 > `display-buffer-alist'.

If the user wants to change the default behavior, yes.

 > But I don't see a way to say "OK, abort, this
 > window is strongly dedicated so the buffer shouldn't be shown
 > anywhere, just throw an error to the user". Care to show how to say
 > that?

I'm not sure whether we want to do that.  If so, there are two ways.
Either, in `bs-cycle-next' write something like:

   (if (and (window-dedicated-p) (not (eq (window-buffer) next)))
       (error "Selected window is dedicated to its buffer")
     (display-buffer-same-window next))

which gives the user no choice wrt what to do when the selected window
is dedicated or write

(defun reuse-same-window-unless-dedicated (buffer &rest args)
   "..."
   (if (and (window-dedicated-p) (not (eq (window-buffer) next)))
       (error "Selected window is dedicated to its buffer")
     (display-buffer-same-window buffer)))

(display-buffer
   next '((fun-with-args reuse-same-window-unless-dedicated)) 'bs-cycle-next)

and allow the user to specify her own deviant behavior when the selected
window is dedicated.

martin