Based on Stefan Kangas comments, this minor mode mode changes the cursor
appearance to indicate overwrite mode or read-only buffers.

This is extracted from `cua-enable-cursor-indications'.

-------------------- Start of forwarded message --------------------
From: Stefan Kangas <stefankangas@gmail.com>
Subject: Re: Should 'cua-overwrite-cursor-color' be standalone?
To: Elijah Gabe Pérez <eg642616@gmail.com>,  emacs-devel@gnu.org
Date: Sat, 22 Mar 2025 02:01:11 -0500 (1 day, 15 hours, 49 minutes ago)

Elijah Gabe Pérez <eg642616@gmail.com> writes:

> I've noticed about this variable today, but
> Should not this option be part of =overwrite= instead =cua=?
> Or be a standalone minor-mode?
>
> IMO, I find this useful outside =cua=.

I think a standalone mode is probably best, because if you want the
cursor color changed for overwrite-mode, you might want it for
buffer-read-only too.

In other words, I'd do both of these:

    cua-overwrite-cursor-color
    cua-read-only-cursor-color

FWIW, I have this in my init file since forever:

    (setq my/set-cursor-color-color "")
    (setq my/set-cursor-color-buffer "")
    (defun my/set-cursor-color-according-to-mode ()
      "Change cursor color according to some minor modes."
      ;; set-cursor-color is somewhat costly, so we only call it when needed:
      (let ((color
             (if buffer-read-only "#8888FF"
               (if overwrite-mode "#000000"
                 "#FF0000"))))
        (unless (and
                 (string= color my/set-cursor-color-color)
                 (string= (buffer-name) my/set-cursor-color-buffer))
          (set-cursor-color (setq my/set-cursor-color-color color))
          (setq my/set-cursor-color-buffer (buffer-name)))))
    (add-hook 'post-command-hook 'my/set-cursor-color-according-to-mode)

I picked it up on EmacsWiki years ago.


-------------------- End of forwarded message --------------------