Re: Word completion in text modes

[Eshel Yaron <me@eshelyaron.com>]

[-- Attachment #1: Type: text/plain, Size: 1137 bytes --]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Eshel Yaron <me@eshelyaron.com>
>> Cc: emacs-devel@gnu.org
>> Date: Sat, 18 Nov 2023 20:03:45 +0100
>>
>> Eli Zaretskii <eliz@gnu.org> writes:
>>
>> > ...We could make the old UI an opt-in behavior, but tossing it
>> > altogether is not something I'd welcome.
>>
>> I think we mostly agree then, because I didn't suggest tossing the old
>> UI anywhere.  To opt-in to the old behavior, you'd say:
>>
>>   (keymap-set text-mode-map "C-M-i" #'ispell-complete-word)
>>
>> That seems to me like a simple enough tip for users that we could appear
>> in a NEWS entry.  Does that sound reasonable?
>
> I'd prefer a solution that didn't require key bindings.  Something
> like a user option.

That'd indeed be more convenient for some users, I suppose.
I'm attaching below a patch that facilitates using `completion-at-point`
in Text mode instead of `ispell-complete-word` by default.  Other than
the somewhat awkward name of the user option that restores the binding,
I'm pretty happy with this patch as it brings about the three benefits I
outlined in my original message in this thread.  WDYT?



[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-Unbind-C-M-i-in-Text-mode.patch --]
[-- Type: text/x-patch, Size: 9589 bytes --]

From 8d03bec5f8825704f4e85cd0e5b57877a29bf40f Mon Sep 17 00:00:00 2001
From: Eshel Yaron <me@eshelyaron.com>
Date: Tue, 21 Nov 2023 12:39:23 +0100
Subject: [PATCH] Unbind 'C-M-i' in Text mode

Remove the binding of 'C-M-i' to 'ispell-complete-word' in Text mode.
Define a new 'ispell-completion-at-point' function and add that to
'completion-at-point-functions' in Text mode, such that
'completion-at-point' provides the same word completions as
'ispell-complete-word' does OOTB.

* lisp/textmodes/ispell.el (ispell-completion-at-point): New function.
* lisp/textmodes/text-mode.el (text-mode): Add it to 'c-a-p-functions'.
(text-mode-map): Remove 'C-M-i' binding.
(text-mode-meta-tab-ispell-complete-word): New user option.
* etc/NEWS: Announce it.
* doc/emacs/fixit.texi (Spelling)
* doc/emacs/text.texi (Text Mode)
* doc/lispref/modes.texi (Basic Major Modes)
(Example Major Modes): Update.
* lisp/mail/sendmail.el (mail-abbrevs-loaded)
* lisp/nxml/nxml-mode.el (nxml-mode-map): Remove superfluous binding.
---
 doc/emacs/fixit.texi        | 16 ++++------------
 doc/emacs/text.texi         | 12 ++++++------
 doc/lispref/modes.texi      | 13 +------------
 etc/NEWS                    |  9 +++++++++
 lisp/mail/sendmail.el       |  1 -
 lisp/nxml/nxml-mode.el      |  1 -
 lisp/textmodes/ispell.el    | 22 ++++++++++++++++++++++
 lisp/textmodes/text-mode.el | 18 +++++++++++++++---
 8 files changed, 57 insertions(+), 35 deletions(-)

diff --git a/doc/emacs/fixit.texi b/doc/emacs/fixit.texi
index 78503d31a38..51814ab30e0 100644
--- a/doc/emacs/fixit.texi
+++ b/doc/emacs/fixit.texi
@@ -292,11 +292,6 @@ Spelling
 Restart the spell-checker process, using @var{dict} as the dictionary.
 @item M-x ispell-kill-ispell
 Kill the spell-checker subprocess.
-@item M-@key{TAB}
-@itemx @key{ESC} @key{TAB}
-@itemx C-M-i
-Complete the word before point based on the spelling dictionary
-(@code{ispell-complete-word}).
 @item M-x flyspell-mode
 Enable Flyspell mode, which highlights all misspelled words.
 @item M-x flyspell-prog-mode
@@ -398,14 +393,11 @@ Spelling
 Show the list of options.
 @end table
 
-@findex ispell-complete-word
-  In Text mode and related modes, @kbd{M-@key{TAB}}
-(@code{ispell-complete-word}) performs in-buffer completion based on
-spelling correction.  Insert the beginning of a word, and then type
-@kbd{M-@key{TAB}}; this shows a list of completions.  (If your
+  Use the command @kbd{M-@key{TAB}} (@code{completion-at-point}) to
+complete the word at point.  Insert the beginning of a word, and then
+type @kbd{M-@key{TAB}} to select from a list of completions.  (If your
 window manager intercepts @kbd{M-@key{TAB}}, type @w{@kbd{@key{ESC}
-@key{TAB}}} or @kbd{C-M-i}.)  Each completion is listed with a digit or
-character; type that digit or character to choose it.
+@key{TAB}}} or @kbd{C-M-i}.)
 
 @cindex @code{ispell} program
 @findex ispell-kill-ispell
diff --git a/doc/emacs/text.texi b/doc/emacs/text.texi
index 6f57bae8fef..b6a9dd6de53 100644
--- a/doc/emacs/text.texi
+++ b/doc/emacs/text.texi
@@ -943,12 +943,12 @@ Text Mode
 composition, for instance.
 
 @kindex M-TAB @r{(Text mode)}
-  Text mode binds @kbd{M-@key{TAB}} to @code{ispell-complete-word}.
-This command performs completion of the partial word in the buffer
-before point, using the spelling dictionary as the space of possible
-words.  @xref{Spelling}.  If your window manager defines
-@kbd{M-@key{TAB}} to switch windows, you can type @kbd{@key{ESC}
-@key{TAB}} or @kbd{C-M-i} instead.
+  The command @kbd{M-@key{TAB}} (@code{completion-at-point}) performs
+completion of the partial word in the buffer before point, using the
+spelling dictionary as the space of possible words by default.
+@xref{Spelling}.  If your window manager defines @kbd{M-@key{TAB}} to
+switch windows, you can type @kbd{@key{ESC} @key{TAB}} or @kbd{C-M-i}
+instead.
 
 @vindex text-mode-hook
   Entering Text mode runs the mode hook @code{text-mode-hook}
diff --git a/doc/lispref/modes.texi b/doc/lispref/modes.texi
index 8670807cbdf..ffd7ad7f51d 100644
--- a/doc/lispref/modes.texi
+++ b/doc/lispref/modes.texi
@@ -981,9 +981,7 @@ Basic Major Modes
 @deffn Command text-mode
 Text mode is a major mode for editing human languages.  It defines the
 @samp{"} and @samp{\} characters as having punctuation syntax
-(@pxref{Syntax Class Table}), and binds @kbd{M-@key{TAB}} to
-@code{ispell-complete-word} (@pxref{Spelling,,, emacs, The GNU Emacs
-Manual}).
+(@pxref{Syntax Class Table}).
 
 An example of a major mode derived from Text mode is HTML mode.
 @xref{HTML Mode,,SGML and HTML Modes, emacs, The GNU Emacs Manual}.
@@ -1377,15 +1375,6 @@ Example Major Modes
     st)
   "Syntax table used while in `text-mode'.")
 @end group
-
-;; @r{Create the keymap for this mode.}
-@group
-(defvar-keymap text-mode-map
-  :doc "Keymap for `text-mode'.
-Many other modes, such as `mail-mode' and `outline-mode', inherit all
-the commands defined in this map."
-  "C-M-i" #'ispell-complete-word)
-@end group
 @end smallexample
 
   Here is how the actual mode command is defined now:
diff --git a/etc/NEWS b/etc/NEWS
index e14d15a7487..b0653a3ff20 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1116,6 +1116,15 @@ showcases all their customization options.
 \f
 * Incompatible Lisp Changes in Emacs 30.1
 
++++
+** 'M-TAB' now invokes 'completion-at-point' also in Text mode.
+Text mode no longer binds 'M-TAB' to 'ispell-complete-word', and
+instead this mode arranges for 'completion-at-point', globally bound
+to 'M-TAB', to perform word completion as well.  If you want 'M-TAB'
+to invoke 'ispell-complete-word', as it did in previous Emacs
+versions, customize the new option
+'text-mode-meta-tab-ispell-complete-word' to non-nil.
+
 ** 'pp' and 'pp-to-string' now always include a terminating newline.
 In the past they included a terminating newline in most cases but not all.
 
diff --git a/lisp/mail/sendmail.el b/lisp/mail/sendmail.el
index 8306bd3b30c..b5dd5322ec1 100644
--- a/lisp/mail/sendmail.el
+++ b/lisp/mail/sendmail.el
@@ -269,7 +269,6 @@ mail-citation-prefix-regexp
 (defvar mail-abbrevs-loaded nil)
 (defvar mail-mode-map
   (let ((map (make-sparse-keymap)))
-    (define-key map "\M-\t" 'completion-at-point)
     (define-key map "\C-c?" 'describe-mode)
     (define-key map "\C-c\C-f\C-t" 'mail-to)
     (define-key map "\C-c\C-f\C-b" 'mail-bcc)
diff --git a/lisp/nxml/nxml-mode.el b/lisp/nxml/nxml-mode.el
index 67d136b5a66..bc32598003e 100644
--- a/lisp/nxml/nxml-mode.el
+++ b/lisp/nxml/nxml-mode.el
@@ -390,7 +390,6 @@ nxml-mode-map
   "C-c C-u" #'nxml-insert-named-char
   "C-c C-o" nxml-outline-prefix-map
   "/"       #'nxml-electric-slash
-  "M-TAB"   #'completion-at-point
   "S-<mouse-2>" #'nxml-mouse-hide-direct-text-content)
 
 (defvar nxml-font-lock-keywords
diff --git a/lisp/textmodes/ispell.el b/lisp/textmodes/ispell.el
index b71e85b0e37..8fdf9a764aa 100644
--- a/lisp/textmodes/ispell.el
+++ b/lisp/textmodes/ispell.el
@@ -3680,6 +3680,28 @@ ispell-horiz-scroll
 	  (if (>= column (- (window-width) 2))
 	      (scroll-left (max (- column (window-width) -3) 10)))))))
 
+;;;###autoload
+(defun ispell-completion-at-point ()
+  "Word completion function for use in `completion-at-point-functions'."
+  (pcase (bounds-of-thing-at-point 'word)
+    (`(,beg . ,end)
+     (when (and (< beg (point)) (<= (point) end))
+       (let* ((word (buffer-substring-no-properties beg end))
+              (len (length word))
+              (inhibit-message t)
+              (all (cons word (ispell-lookup-words word)))
+              (cur all))
+         (while cur
+           (unless (string-prefix-p word (car cur))
+             (setcar cur (concat word (substring (car cur) len))))
+           (while (when-let ((next (cadr cur)))
+                    (not (string-prefix-p word next t)))
+             (setcdr cur (cddr cur)))
+           (setq cur (cdr cur)))
+         (list beg end (cdr all)
+               :annotation-function (lambda (_) " Dictionary word")
+               :exclusive 'no))))))
+
 
 ;;; Interactive word completion.
 ;; Forces "previous-word" processing.  Do we want to make this selectable?
diff --git a/lisp/textmodes/text-mode.el b/lisp/textmodes/text-mode.el
index ccba1b063ab..607702da48f 100644
--- a/lisp/textmodes/text-mode.el
+++ b/lisp/textmodes/text-mode.el
@@ -73,8 +73,19 @@ text-mode-syntax-table
 (defvar-keymap text-mode-map
   :doc "Keymap for `text-mode'.
 Many other modes, such as `mail-mode' and `outline-mode', inherit
-all the commands defined in this map."
-  "C-M-i" #'ispell-complete-word)
+all the commands defined in this map.")
+
+(defcustom text-mode-meta-tab-ispell-complete-word nil
+  "Whether M-TAB invokes `ispell-complete-word' in Text mode.
+
+This user option only takes effect when you customize it in
+Custom or with `setopt', not with `setq'."
+  :group 'text
+  :type 'boolean
+  :set (lambda (sym val)
+         (if (set sym val)
+	     (keymap-set text-mode-map "C-M-i" #'ispell-complete-word)
+           (keymap-unset text-mode-map "C-M-i" t))))
 
 (easy-menu-define text-mode-menu text-mode-map
   "Menu for `text-mode'."
@@ -131,7 +142,8 @@ text-mode
 
   ;; Enable text conversion in this buffer.
   (setq-local text-conversion-style t)
-  (add-hook 'context-menu-functions 'text-mode-context-menu 10 t))
+  (add-hook 'context-menu-functions 'text-mode-context-menu 10 t)
+  (add-hook 'completion-at-point-functions #'ispell-completion-at-point 10 t))
 
 (define-derived-mode paragraph-indent-text-mode text-mode "Parindent"
   "Major mode for editing text, with leading spaces starting a paragraph.
-- 
2.42.0