bug#57468: 29.0.50; Text cursor continues to blink when frame loses focus

[Bob Rogers]

   I have a number of independent emacs sessions, each with a single GUI
frame, some remote via SSH and some as root.  In the sessions using
emacs built recently from master with blink-cursor-mode enabled, the
cursor continues to blink even when the (single) frame loses focus, when
it should become a steady hollow box.  This also happens in "emacs -Q"
(somewhat intermittently, along with failure to start blinking, and some
stranger things).  The following test code:

        (let ((count 0))
          (while t
            (message "focus state at %d:  %S"
                     (cl-incf count) (frame-focus-state))
            (sit-for 2)))

shows that the focus state never changes from `t'.  The problem appears
to be that handle-focus-out is never called, but I don't know the emacs
window system interface well enough to follow it any farther.

   FWIW, the problem doesn't happen in 28.1, or in an emacs built from
the master branch on 24-May.  I should also mention that one of my
sessions started behaving properly again while I was trying to debug
this, but I have no idea what, if anything, I did.  Also, this is under
KDE/Plasma on X11 in a recent openSUSE Leap 15.4 upgrade, so there may
be an underlying window system issue.

   TIA,

                                        -- Bob Rogers
                                           http://www.rgrjr.com/

------------------------------------------------------------------------
In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.31, cairo 
version 1.16.0)
 of 2022-08-20 built on orion
Repository revision: 7e9d744033f07286c21f092f8ea3646a51e37a19
Repository branch: rgr-smtpmail-env-from
Windowing system distributor 'The X.Org Foundation', version 11.0.12003000
System Description: openSUSE Leap 15.4

Configured using:
 'configure --with-dbus=no --with-gsettings=no --with-gif=ifavailable
 --with-tiff=no --with-gnutls=yes --with-gconf=no'

Configured features:
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MODULES NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS
TOOLKIT_SCROLL_BARS X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

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