Subject: Re: bug#9639: 24.0.90; Problem with bury-buffer in minibuffer-hide-completions

From: martin rudalics <[email-masked]>
Date: Sat, 01 Oct 2011 11:08:09 +0200

> 1. emacs -Q
 > 2. Type `M-x glo TAB' and at the completion "M-x global-" type TAB again,
 >    making a *Completions* buffer pop up.
 > 3. Type `v TAB', yielding the completion "M-x global-visual-line-mode".
 > => The window that had been displaying the *Completions* buffer now
 > displays the *Messages* buffer.
 >
 > AFAICT this is due to the following cond clause in bury-buffer (which is
 > called by minibuffer-hide-completions):
 >
 >      ((not (window-dedicated-p))
 >       (switch-to-prev-buffer nil 'bury))

... plus the fact that switching buffers should not delete windows ...

 > Only after typing RET in the minibuffer to accept the completion is the
 > window that had been displaying the *Completions* buffer and now
 > displays the *Messages* buffer deleted; in Emacs 23.2 it is deleted as
 > soon as the sole completion is displayed in the minibuffer.  Commenting
 > out the above clause restores the 23.2 behavior.  But this presumably
 > has bad effects elsewhere.

Presumably `minibuffer-hide-completions' should iconify a standalone
completions frame while deleting a split-off completions window.  So
maybe the following DTRT:

(defun minibuffer-hide-completions ()
   "Get rid of an out-of-date *Completions* buffer."
   ;; FIXME: We could/should use minibuffer-scroll-window here, but it
   ;; can also point to the minibuffer-parent-window, so it's a bit tricky.
   (let* ((window (get-buffer-window "*Completions*" 0))
	 (buffer (window-buffer window)))
     (when window
       (let ((deletable (window-deletable-p window)))
	(cond
	 ((eq deletable 'frame)
	  ;; Iconify frame.
	  (iconify-frame (window-frame window))
	  (bury-buffer-internal buffer))
	 (deletable
	  ;; Delete window
	  (delete-window window)
	  (bury-buffer-internal buffer))
	 (t
	  ;; Switch to another buffer.
	  (switch-to-prev-buffer window 'bury)))))))

 > (Interestingly, the C code of bury-buffer prior to the move to Lisp in
 > revision 104559 (and long before that) has the equivalent of the above
 > clause.)

ISTR that completion windows were dedicated then and typing "v TAB"
would trigger the following code in `minibuffer-completion-help'

       ;; If there are no completions, or if the current input is already the
       ;; only possible completion, then hide (previous&stale) completions.
       (let ((window (and (get-buffer "*Completions*")
                          (get-buffer-window "*Completions*" 0))))
         (when (and (window-live-p window) (window-dedicated-p window))
           (condition-case ()
               (delete-window window)
             (error (iconify-frame (window-frame window))))))

which I can't find anymore.  But I might be wrong.

martin