GNU bug report logs - #6883
23.2; `read-key' echos keys in the minibuffer

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Leo <sdl.web <at> gmail.com>
Subject: bug#6883: closed (Re: 23.2; `read-key' echos keys in the minibuffer)
Date: Sat, 21 Aug 2010 13:09:02 +0000

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Your bug report

#6883: 23.2; `read-key' echos keys in the minibuffer

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 6883 <at> debbugs.gnu.org.

-- 
6883: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=6883
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Leo <sdl.web <at> gmail.com>
Cc: thierry.volpiatto <at> gmail.com
Subject: Re: 23.2; `read-key' echos keys in the minibuffer
Date: Sat, 21 Aug 2010 11:00:15 +0200

>> Does the trivial patch below fix the problem?
> Yes and thanks.

Great, I've installed it in the emacs-23 branch,


        Stefan

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From: Leo <sdl.web <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Cc: Stefan Monnier <monnier <at> iro.umontreal.ca>, thierry.volpiatto <at> gmail.com
Subject: 23.2; `read-key' echos keys in the minibuffer
Date: Thu, 19 Aug 2010 16:20:38 +0100

1. Define bookmark-read-search-input as this which inserts a (sit-for 1) to
demonstrate the bug easily:

(defun bookmark-read-search-input ()
  (let ((prompt       (propertize "Pattern: " 'face 'minibuffer-prompt))
        (tmp-list     ()))
    (while
        (let ((char (read-key (concat prompt bookmark-search-pattern))))
          (sit-for 1)
          (case char
            ((?\e ?\r) nil) ; RET or ESC break the search loop.
            (?\C-g (setq bookmark-quit-flag t) nil)
            (?\d (pop tmp-list) t) ; Delete last char of pattern with DEL
            (t
             (if (characterp char)
                 (push char tmp-list)
               (setq unread-command-events
                     (nconc (mapcar 'identity
                                    (this-single-command-raw-keys))
                            unread-command-events))
               nil))))
      (setq bookmark-search-pattern
            (apply 'string (reverse tmp-list))))))

2. and eval

  (let (bookmark-search-pattern) (bookmark-read-search-input))

3. then start typing away.

You should see each key is echoed. So for example if you hit backspace
you may see backspace or DEL in the echo area twice.

With the original definition back (ie without the sit-for) you can
observe a trail for each key you type by for example doing something
like this:

  1. C-x r l to list bookmarks
  2. M-g s and start typing away

That breaks the smooth flow of key strokes.

Thierry Volpiatto, YAMAMOTO Mitsuharu and I can observe this on all
three major platforms. On some platforms, it happens so fast that it is
hardly annoying, on others you can read the echoing literally.
`read-char' does not have this problem and thus Thierry's suggestion to
use it instead.

Leo

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