24 Dec 2011
Elisp, jump to last edit location across whole session
Scenario
Coding, editing —> an interesting function —> anther interesting function —> …
“My god, where have I been, how can I jump right back to the last edit position”
How other handle it
Eclipse has a handing feature: Last Edit Location, binding to Ctrl+Q, It works globally: all visited files, even those being edited, but currently closed.
Exiting solution
-
EmacsSession has a function called
session-jump-to-last-change, but per buffer - GotoLastChange, but per buffer
Elisp to the rescue
I’ve being using emacs for several month, it serves me well, it lacks this very handing feature. Thanks to elisp, I can implement it myself.
Code
;;; record two different file's last change. cycle them
(defvar feng-last-change-pos1 nil)
(defvar feng-last-change-pos2 nil)
(defun feng-swap-last-changes ()
(when feng-last-change-pos2
(let ((tmp feng-last-change-pos2))
(setf feng-last-change-pos2 feng-last-change-pos1
feng-last-change-pos1 tmp))))
(defun feng-goto-last-change ()
(interactive)
(when feng-last-change-pos1
(let* ((buffer (find-file-noselect (car feng-last-change-pos1)))
(win (get-buffer-window buffer)))
(if win
(select-window win)
(switch-to-buffer-other-window buffer))
(goto-char (cdr feng-last-change-pos1))
(feng-swap-last-changes))))
(defun feng-buffer-change-hook (beg end len)
(let ((bfn (buffer-file-name))
(file (car feng-last-change-pos1)))
(when bfn
(if (or (not file) (equal bfn file)) ;; change the same file
(setq feng-last-change-pos1 (cons bfn end))
(progn (setq feng-last-change-pos2 (cons bfn end))
(feng-swap-last-changes))))))
(add-hook 'after-change-functions 'feng-buffer-change-hook)
;;; just quick to reach
(global-set-key (kbd "M-`") 'feng-goto-last-change)