--text follows this line--

Attempting to bind unicode characters (e.g. \u111E) to keys in a minor mode
with syntax like
  (define-key my-test-mode-map (kbd "c") "\u221E")
usually works. In this case, C-h k c shows

c runs the command #<string CB7> (found in my-test-mode-map), which is
a keyboard macro.
It is bound to c.
Macro: M-\20636
Keyboard macro.

However the same syntax fails for some characters (so far I've noticed this
for \u00B0 to \u00B6 but there will be more) e.g
after (define-key my-test-mode-map (kbd "a") "\u00B2") C-h k shows

a runs the command #<string B6B> (found in my-test-mode-map), which is
a keyboard macro.
It is bound to a.
Macro: M-2
Keyboard macro.

and the effect of pressing "a" is to invoke command-digit-argument rather
than insert the required character

A workaround is to use a lambda expression to bypass whatever emacs is
doing when processing the unicode character, e.g.
  (define-key my-test-mode-map (kbd "b") (lambda () (interactive) (insert
"\u00B2")))

and then this does insert the character (superscript 2) when "b" is pressed.

To replicate:

1. run emacs -Q

2. paste the following into the scratch buffer:

;; This buffer is for text that is not saved, and for Lisp evaluation.
;; To create a file, visit it with ‘C-x C-f’ and enter text in its buffer.

(progn
  ;; 1. Explicitly create the keymap variable and initialize it.
  (defvar my-test-mode-map (make-sparse-keymap)
    "Keymap for `my-test-mode'.")

  ;; 2. Define the minor mode, telling it to use our explicitly created map.
  (define-minor-mode my-test-mode
    "A test minor mode."
    :global t
    :lighter " my-test"
    :keymap my-test-mode-map
    )

  ;; 3. Define keys on the explicitly created and linked map.

;; normal bind fails at least for characters in range \u00B0 to \u00B6, but
probably more, e.g. \u00B2
  (define-key my-test-mode-map (kbd "a") "\u00B2")

  ;; workaround is to use a lambda
  (define-key my-test-mode-map (kbd "b") (lambda () (interactive) (insert
"\u00B2")))

; normal bind does succeeds with other characters I've tried so far, e.g.
\u221E
  (define-key my-test-mode-map (kbd "c") "\u221E")

  ;; 4. Enable the minor mode.
  (my-test-mode 1)
  )

===

This creates a new mode "my-test-mode" with the key maps and puts it into
effect. Then try pressing a, b and c.

(acknowledgements to assistance from gemini 2.5 on all this!)


In GNU Emacs 30.1 (build 2, x86_64-w64-mingw32) of 2025-02-23 built on
 AVALON
Windowing system distributor 'Microsoft Corp.', version 10.0.26100
System Description: Microsoft Windows 10 Pro (v10.0.2009.26100.4061)

Configured using:
 'configure --with-modules --without-dbus --with-native-compilation=aot
 --without-compress-install --with-tree-sitter CFLAGS=-O2
 prefix=/g/rel/install/emacs-30.1'

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
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(NATIVE_COMP present but libgccjit not available)

Important settings:
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  locale-coding-system: cp1252

Major mode: Lisp Interaction

Minor modes in effect:
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Load-path shadows:
None found.

Features:
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term/common-win tool-bar dnd fontset image regexp-opt fringe
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charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
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code-pages mule custom widget keymap hashtable-print-readable backquote
threads w32notify w32 lcms2 multi-tty move-toolbar make-network-process
native-compile emacs)

Memory information:
((conses 16 51324 17148) (symbols 48 5411 0) (strings 32 15047 1817)
 (string-bytes 1 418055) (vectors 16 8994)
 (vector-slots 8 128954 11248) (floats 8 24 21) (intervals 56 313 5)
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