Subject: 29.1.90; Registers' preview can delete existing window when finishing

From: Dmitry Gutov <[email-masked]>
Date: Mon, 18 Dec 2023 20:18:55 +0200

Set up:

(defun split-window-prefer-side-by-side (&optional window)
   (let ((split-height-threshold (and (< (window-width window)
                                         split-width-threshold)
                                      split-height-threshold)))
     (split-window-sensibly window)))

(setq split-window-preferred-function 'split-window-prefer-side-by-side)

Split the frame, e.g. 'C-x 3'.

Then create some register (e.g. using 'C-x r C-@') and then invoke
another command reading it. E.g. 'C-x r j'.

Wait the necessary 1 second for the preview to appear - it will use one
of the existing windows to show the list of registers.

Then, whether you choose the register, or C-g out of the choice, the
window used to display the list will be deleted.

Previously mentioned in bug#66394.

Not a regression on master, just reproduced it in 29.