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

[Bob Rogers]

   From: Bob Rogers <rogers@rgrjr.com>
   Date: Wed, 31 Aug 2022 12:02:04 -0700

   . . .

   I've also tried a slightly newer version of master ... on the
   previous openSUSE release, and the cursor behaves normally WRT
   focus-in/out . . .

Minutes after I sent this email, I saw the bug rear its head in openSUSE
Leap 15.3.  To test, I had three instances, two with my initializations,
and one "emacs -Q".  Pretty much the only thing I did after sending the
email was to quit the "emacs -Q" and fire up another instance as root
(su and then "emacs &"), but curiously only one of the two instances
(the second one launched) was affected.  So I ran the following
augmented code in both the new root and the affected instance to see
what was going on:

        (defvar rgr-event-count 0)
        (defun rgr-focus-in ()
          (interactive)
          (message "focus in %d" (cl-incf rgr-event-count)))
        (define-key special-event-map [ focus-in ] 'rgr-focus-in)
        (defun rgr-focus-out ()
          (interactive)
          (message "focus out %d" (cl-incf rgr-event-count)))
        (define-key special-event-map [ focus-out ] 'rgr-focus-out)

As expected, the affected instance saw no in/out events, but the root
instance saw a single focus-out event when the other window caught the
focus, then a quick in/out/in sequence when the focus came back.  (I had
also seen this odd triplet when debugging under openSUSE Leap 15.4, but
at a higher level in the cursor blinking code, so I didn't mention it in
the initial bug report, thinking it might be a separate bug.)

                                        -- Bob