bug#29504: 26.0.90; Can't enter Japanes text in a read-only buffer even if inhibit-read-only is t

[Katsumi Yamaoka <yamaoka@jpl.org>]

Hi,

Not only Japanese, every input method should work in a read-only
buffer (such as that of eww) where the `inhibit-read-only' text
or overlay property is set in some areas.  Here is a recipe to
reproduce the problem:

Launch Emacs with -Q, eval this form in the *scratch* buffer,
and type `C-x o', `C-\', and `a'.  "あ" should appear.

(set-input-method 'japanese)

(let ((buffer (get-buffer-create "*texting*")))
  (with-current-buffer buffer
    (setq buffer-read-only nil)
    (erase-buffer)
    (insert (propertize " " 'inhibit-read-only t 'front-sticky t))
    (setq buffer-read-only t)
    (goto-char (point-min)))
  (display-buffer buffer))

Thanks.