bug#54862: 28.1; window-text-pixel-size sometimes fails to report accurate pixel-width

[Markus Triska <triska@metalevel.at>]

To reproduce this regression, please invoke Emacs with:

    $ emacs -Q

and then evaluate the following form:

    (let ((width 20))
      (= width (let* ((height (line-pixel-height))
                      (data (with-temp-buffer
                              (insert (format "P1\n%s %s\n" width height))
                              (dotimes (_ height)
                                (insert (make-string width ?1) "\n"))
                              (buffer-string))))
                 (insert " ")
                 (let ((from (point)))
                   (insert-image `(image :type pbm :data ,data :ascent center) "t")
                   (car (window-text-pixel-size nil from (point)))))))

The expected result, obtained for example in Emacs 26.1 and 27.1, is: t.

Whereas with Emacs 28.1, evaluating the form unexpectedly yields: nil.

If possible, could you please restore the previous behaviour?

Thank you and all the best,
Markus

In GNU Emacs 28.1 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 1.16.0, Xaw scroll bars)
 of 2022-04-11 built on debian
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian

Configured using:
 'configure --with-gif=ifavailable --with-tiff=ifavailable
 --with-gnutls=ifavailable'

Configured features:
CAIRO FREETYPE GLIB GMP GSETTINGS JPEG LIBSELINUX LIBXML2 MODULES NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS TOOLKIT_SCROLL_BARS X11
XDBE XIM XPM LUCID ZLIB