bug#81626: 32.0.50; string-pixel-width can return an incorrect value after commit 165152e

Hello,

After commit  165152e
   Fix an infloop during cursor movement
   * src/xdisp.c (move_it_vertically_backward): Prevent infloop due
   to overlays with embedded newlines at BOB.  (Bug#81567)

`string-pixel-width' no more return a correct value if the
passed string is wider than the window body.  Here is a simple recipe to
test in the *scratch* buffer, running emacs -Q:

(window-body-width)
80
(window-body-width nil t)
960
(string-pixel-width (make-string 80 ?x))
960 <=== CORRECT
(string-pixel-width (make-string 81 ?x))
12  <=== INCORRECT

Before this commit the result is correct:

(window-body-width)
80
(window-body-width nil t)
960
(string-pixel-width (make-string 80 ?x))
960 <=== CORRECT
(string-pixel-width (make-string 81 ?x))
972 <=== CORRECT

Thanks


In GNU Emacs 32.0.50 (build 9, x86_64-pc-linux-gnu, GTK+ Version
  3.24.52, cairo version 1.18.4) of 2026-08-15
Repository revision: ef448d2ca996410f1f87b19740c1d4c2c6f37f7f
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101024
System Description: Fedora Linux 44 (KDE Plasma Desktop Edition)

Configured using:
  'configure --with-native-compilation=no --with-tree-sitter=no --with-x
  --with-x-toolkit=gtk3 --with-cairo
  PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:/usr/lib/pkgconfig'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG
LCMS2 LIBSYSTEMD LIBXML2 MODULES NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP
SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS WEBP X11 XDBE XIM
XINERAMA XINPUT2 XPM XRANDR GTK3 ZLIB

Important settings:
   value of $LC_TIME: fr_FR.utf8
   value of $LANG: fr_FR.UTF-8
   locale-coding-system: utf-8-unix