bug#32738: 26.1.50; 'read-answer' allows only single characters as short answers

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bug#32738: 26.1.50; 'read-answer' allows only single characters as short answers

Eli Zaretskii
This is a feature request.

The new function read-answer allows only single-character short answers,
and formats them with %c in the prompt displayed to the user.  This has
several disadvantages:

  . Function keys cannot be used as short answers.  For example, it
    would be good to be able to use F1 for "help", but it is currently
    impossible.

  . Character events that aren't valid characters, such as C-M-h,
    cannot be used, because %c barfs when it sees a character event
    with modifiers (it doesn't pass the 'characterp' test).

  . Control characters, like C-h, are shown as raw bytes, with their
    special face, thus standing out unnecessarily.

It would be nice if these restrictions could be lifted.

In GNU Emacs 26.1.50 (build 205, i686-pc-mingw32)
 of 2018-09-15 built on HOME-C4E4A596F7
Repository revision: 20ecc5266e1ffb1cff3e31475631b5c76b99e997
Windowing system distributor 'Microsoft Corp.', version 5.1.2600
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --prefix=/d/usr --with-wide-int --with-modules
 --enable-checking=yes,glyphs --enable-check-lisp-object-type
 'CFLAGS=-O0 -gdwarf-4 -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS MODULES THREADS LCMS2

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1255

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa derived epg
epg-config gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils elec-pair time-date
mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel dos-w32 ls-lisp disp-table term/w32-win w32-win
w32-vars term/common-win tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow isearch timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese composite charscript charprop case-table epa-hook jka-cmpr-hook
help simple abbrev obarray minibuffer cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads w32notify w32 lcms2 multi-tty make-network-process
emacs)

Memory information:
((conses 16 102100 11497)
 (symbols 56 21325 1)
 (miscs 48 42 98)
 (strings 16 31711 1931)
 (string-bytes 1 773712)
 (vectors 16 14876)
 (vector-slots 8 505915 15424)
 (floats 8 55 115)
 (intervals 40 279 103)
 (buffers 880 11))



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bug#32738: 26.1.50; 'read-answer' allows only single characters as short answers

Juri Linkov-2
> This is a feature request.
>
> The new function read-answer allows only single-character short answers,
> and formats them with %c in the prompt displayed to the user.  This has
> several disadvantages:
>
>   . Function keys cannot be used as short answers.  For example, it
>     would be good to be able to use F1 for "help", but it is currently
>     impossible.
>
>   . Character events that aren't valid characters, such as C-M-h,
>     cannot be used, because %c barfs when it sees a character event
>     with modifiers (it doesn't pass the 'characterp' test).
>
>   . Control characters, like C-h, are shown as raw bytes, with their
>     special face, thus standing out unnecessarily.
>
> It would be nice if these restrictions could be lifted.

Do you think it should support only characters with modifiers like C-M-h,
or also key sequences?  I guess the latter since this will lift all
restrictions on the KEY arg of define-key.  Since read-answer should
still support single-character for backward-compatibility, this means
adding key sequences as a new feature, so all of these will work:

(read-answer "Question: "
             `(("help0" ?h "show help")
               ("help1" ,(kbd "<f1>") "show help")
               ("help2" ,(kbd "C-M-h") "show help")
               ("help3" ,(kbd "C-h") "show help")))

diff --git a/lisp/emacs-lisp/map-ynp.el b/lisp/emacs-lisp/map-ynp.el
index a61c0adc8f..262284aaf1 100644
--- a/lisp/emacs-lisp/map-ynp.el
+++ b/lisp/emacs-lisp/map-ynp.el
@@ -308,14 +308,18 @@ read-answer
           (format "%s(%s) " question
                   (mapconcat (lambda (a)
                                (if short
-                                   (format "%c" (nth 1 a))
+                                   (if (characterp (nth 1 a))
+                                       (format "%c" (nth 1 a))
+                                     (key-description (nth 1 a)))
                                  (nth 0 a)))
                              answers-with-help ", ")))
          (message
           (format "Please answer %s."
                   (mapconcat (lambda (a)
                                (format "`%s'" (if short
-                                                  (string (nth 1 a))
+                                                  (if (characterp (nth 1 a))
+                                                      (string (nth 1 a))
+                                                    (key-description (nth 1 a)))
                                                 (nth 0 a))))
                              answers-with-help " or ")))
          (short-answer-map
@@ -325,13 +329,15 @@ read-answer
                          (let ((map (make-sparse-keymap)))
                            (set-keymap-parent map minibuffer-local-map)
                            (dolist (a answers-with-help)
-                             (define-key map (vector (nth 1 a))
+                             (define-key map (if (characterp (nth 1 a))
+                                                 (vector (nth 1 a))
+                                               (nth 1 a))
                                (lambda ()
                                  (interactive)
                                  (delete-minibuffer-contents)
                                  (insert (nth 0 a))
                                  (exit-minibuffer))))
-                           (define-key map [remap self-insert-command]
+                           (define-key map [t]
                              (lambda ()
                                (interactive)
                                (delete-minibuffer-contents)
@@ -370,7 +376,10 @@ read-answer
                       (mapconcat
                        (lambda (a)
                          (format "`%s'%s to %s"
-                                 (if short (string (nth 1 a)) (nth 0 a))
+                                 (if short (if (characterp (nth 1 a))
+                                               (string (nth 1 a))
+                                             (key-description (nth 1 a)))
+                                   (nth 0 a))
                                  (if short (format " (%s)" (nth 0 a)) "")
                                  (nth 2 a)))
                        answers-with-help ",\n")



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bug#32738: 26.1.50; 'read-answer' allows only single characters as short answers

Eli Zaretskii
> From: Juri Linkov <[hidden email]>
> Cc: [hidden email]
> Date: Sun, 16 Sep 2018 01:42:37 +0300
>
> Do you think it should support only characters with modifiers like C-M-h,
> or also key sequences?  I guess the latter since this will lift all
> restrictions on the KEY arg of define-key.

Yes, I agree.

> -                                   (format "%c" (nth 1 a))
> +                                   (if (characterp (nth 1 a))
> +                                       (format "%c" (nth 1 a))
> +                                     (key-description (nth 1 a)))

This will still display C-a s ^A.  I suggest to use
single-key-description instead.

Thanks.



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bug#32738: 26.1.50; 'read-answer' allows only single characters as short answers

Juri Linkov-2
>> -                                   (format "%c" (nth 1 a))
>> +                                   (if (characterp (nth 1 a))
>> +                                       (format "%c" (nth 1 a))
>> +                                     (key-description (nth 1 a)))
>
> This will still display C-a s ^A.  I suggest to use
> single-key-description instead.

I tried single-key-description but it displays ^A,
whereas key-description displays C-a.



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bug#32738: 26.1.50; 'read-answer' allows only single characters as short answers

Juri Linkov-2
In reply to this post by Eli Zaretskii
tags 32738 fixed
close 32738 27.0.50
quit

>> Do you think it should support only characters with modifiers like C-M-h,
>> or also key sequences?  I guess the latter since this will lift all
>> restrictions on the KEY arg of define-key.
>
> Yes, I agree.

So this is pushed to master and closed.