bug#52456: 28.0.90; Incomplete application of 'help-key-binding' face

[Eli Zaretskii]

When some text is popped up that includes key bindings, the
'help-key-binding' face is not applied to all the characters of a key
sequence.  Simple keys, like 'C-g', and sequences like 'C-x o', are
shown in that face in their entirety, but key sequences with a prefix
argument, like 'C-u C-x =', don't have the face applied to the space
between "C-u" and "C-x =".  This looks ugly.

I've seen this in the *Warning* buffer popped up by
select-safe-coding-system-interactively.


In GNU Emacs 28.0.90 (build 2, i686-pc-mingw32)
 of 2021-12-02 built on HOME-C4E4A596F7
Windowing system distributor 'Microsoft Corp.', version 5.1.2600
System Description: Microsoft Windows XP Service Pack 3 (v5.1.0.2600)

Configured using:
 'configure -C --prefix=/d/usr --with-wide-int --with-native-compilation
 'CFLAGS=-Og -gdwarf-4 -g3''

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF TOOLKIT_SCROLL_BARS
XPM ZLIB

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
  show-paren-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
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug comp comp-cstr warnings rx cl-extra
help-mode message rmc puny dired dired-loaddefs rfc822 mml mml-sec epa
derived epg rfc6068 epg-config gnus-util rmail rmail-loaddefs
auth-source cl-seq eieio eieio-core cl-macs eieio-loaddefs
password-cache json map text-property-search time-date subr-x seq
byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs cl-lib
sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
iso-transl tooltip eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode 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 lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer 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 emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice
button loaddefs faces cus-face macroexp files window 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 native-compile emacs)

Memory information:
((conses 16 93759 7935)
 (symbols 48 9023 1)
 (strings 16 25604 2557)
 (string-bytes 1 765697)
 (vectors 16 17012)
 (vector-slots 8 318892 12460)
 (floats 8 29 157)
 (intervals 40 263 112)
 (buffers 888 11))