Possible to access the second-last clipboard contents (clipboard history)

Question

Is there a way to access the second last value of the clipboard in Emacs?

I assume it's possible to make this work within Emacs.

• Intercept the copy function.
• Read the clipboard and add it to a list.
• Set the clipboard as expected.

---

Note, the reason I'm asking this is I'd like to make a shortcut to paste the second last item in the clipboard, so I can copy things while keeping access to what was already in the clipboard.

Answer 1

You're in luck; this is already built in. C-y yanks the last thing that you've killed or copied, and M-y replaces it with the next item from the kill-ring, which contains everything you've killed or copied in your current Emacs session.

Answer 2

This can be done by advising the function that sets the clipboard.

;; Clipboard history.
(defvar my-clipboard-history-limit 10)
(defvar my-clipboard-history--list nil)

(defun my-clipboard-history-paste (&optional index)
  (insert (nth (or index 0) my-clipboard-history--list)))

(defun my-clipboard-history-paste-penultimate ()
  (interactive)
  (my-clipboard-history-paste))

(defun my-clipboard-history--gui-set-selection (orig-fn type data)
  (when (eq type 'CLIPBOARD)
    (let ((old-data (gui-get-selection type)))
      (when old-data
        (let ((trim-number (- (length my-clipboard-history--list)
                              my-clipboard-history-limit)))
          (when (> 0 trim-number)
            (nbutlast my-clipboard-history--list trim-number)))
        (push old-data my-clipboard-history--list))))
  (funcall orig-fn type data))

;;;###autoload
(define-minor-mode my-clipboard-history-mode
  "Highlight block under the cursor."
  :global t
  :lighter
  ""
  (cond
   (my-clipboard-history-mode
    (advice-add
     'gui-set-selection :around
     #'my-clipboard-history--gui-set-selection))
   (t
    (advice-remove
     'gui-set-selection
     #'my-clipboard-history--gui-set-selection))))

(provide 'my-clipboard-history-mode)

You can bind this to Alt-P in evil mode, for example:

(define-key evil-normal-state-map (kbd "M-p")
  'my-clipboard-history-paste-penultimate)
(define-key evil-insert-state-map (kbd "M-p")
  'my-clipboard-history-paste-penultimate)