I think the overlay can be deleted in ns-delete-working-text, because new overlay is always created in ns-insert-working-text.
在 2019年12月19日 +0800 PM1:57，tsuucat <tsuucat@icloud.com>，写道：
>
> > Since the working text is not the final text to insert to buffer, how about displaying it using after-string property of overlay? Such as:
> >
> > (overlay-put (setq ns-working-overlay (make-overlay start (point)))
> >    ‘after-string (propertize ns-working-text ‘face 'ns-working-text-face))
>
>
> I did it. It is good undo behavior.
>
> After this, working text appears in read-only buffer. (Mac port-like
> behavior)
>
>
>
> --
> tsuucat