RE: How to know the buffer I will return to from the minibuffer?

[Drew Adams <drew.adams@oracle.com>]

> I am writing an interactive command to be used while in the minibuffer.
> I need to know the buffer I was in when I issued the command that put
> me in the minibuffer (like M-: or M-!).  I tried (other-buffer
> (current-buffer)) and (last-buffer (current-buffer)), but to no avail.
> Then I re-read the docs for `other-buffer' and used this: (other-buffer
> (current-buffer) t), and it seemed to work.  The question is, how
> reliable it is.  Am I doing this correctly?

If you use Icicles then that buffer is the value of variable
`icicle-pre-minibuffer-buffer':

  Buffer that was current before the minibuffer became active.

and its window is the last-used window showing it:

(icicle-mru-window-for-buffer
  icicle-pre-minibuffer-buffer 'noMNI 0)

When minibuffer setup occurs, the variable is set using
function `icicle-last-non-minibuffer-buffer', which does this:

(let ((live-bufs  (icicle-remove-if
                    (lambda (buf) (not (buffer-live-p buf)))
                    (buffer-list))))
  (or (car bufs)  (car live-bufs)))

If you don't use Icicles you can do the same kind of thing.
Use `minibuffer-setup-hook' to set a variable to the last
live non-minibuffer buffer.

This is `icicle-mru-window-for-buffer':

(defun icicle-mru-window-for-buffer (buffer &optional
                                     minibuf all-frames)
  "Return the most recently used window for BUFFER.
Optional args MINIBUF and ALL-FRAMES are as for
`get-buffer-window-list'."
    (let* ((wins      (get-buffer-window-list
                        buffer minibuf all-frames))
           (mru-win   (car wins))
           (mru-time  (window-use-time mru-win))
           wtime)
      (unless (listp mru-time)
        (setq mru-time  (seconds-to-time mru-time)))
      (dolist (win  (cdr wins))
        (setq wtime  (window-use-time win))
        (unless (listp wtime)
          (setq wtime  (seconds-to-time wtime)))
        (unless (time-less-p wtime mru-time)
          (setq mru-time  wtime
                mru-win   win)))
      mru-win))