How to navigate to previous cursor positions without using the mark?

Question

I'm often making typing mistakes which will kick me out of the current function block (hitting M-n when I meant C-n). In such cases it would be nice to be able to return immediately to the previous cursor position. My understanding (correct me if I'm wrong) is that the mark ring is not ideally suited to this purpose because it requires setting the mark at positions ahead of time.

I guess I'm asking for a 'trailing mark ring' that stores all cursor positions, say, 2 or 3 moves back...or something like that.

Answer 1

This is doubtless a little simplistic, but I expect it would deal with most cases.

(defvar-local my-track-prev-pos-marker nil
  "Buffer-local marker to remember the previous editing position.")

(add-hook 'pre-command-hook 'my-track-prev-pos-pre-command)

(defun my-track-prev-pos-pre-command ()
  "Track the previous editing position in `my-track-prev-pos-marker'."
  (unless (eq this-command 'my-track-prev-pos-jump)
    (if (markerp my-track-prev-pos-marker)
        (set-marker my-track-prev-pos-marker (point))
      (setq my-track-prev-pos-marker (point-marker)))))

(add-hook 'kill-buffer-hook 'my-track-prev-pos-kill-buffer-hook)

(defun my-track-prev-pos-kill-buffer-hook ()
  "Reclaim the buffer-local marker."
  (setq my-track-prev-pos-marker nil))

(defun my-track-prev-pos-jump ()
  "Jump to the previous editing position."
  (interactive)
  (when (markerp my-track-prev-pos-marker)
    (let ((prev (marker-position my-track-prev-pos-marker)))
      (set-marker my-track-prev-pos-marker (point))
      (goto-char prev))))

(global-set-key (kbd "C-c b") 'my-track-prev-pos-jump)