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;;; show-kill-ring --- Displays Previous Kill Ring Entries -*- lexical-binding: t; coding: utf-8; -*-
;; Show Kill Ring
;; Stolen from Steve Yegge when he wasn't looking
;; enhancements and bugs added by Craig Jennings <c@cjennings.net>
;;
;;; Commentary:
;; Browse items you've previously killed.
;; Yank text  using C-u, the index, then C-y.
;;
;; I've lovingly kept the nice 1970s aesthetic, complete with wood paneling.
;; Maybe I'll give it a makeover at some point.
;;
;;; Code:

(require 'cl-lib)

(defvar show-kill-max-item-size 1000
  "This represents the size of a \='kill ring\=' entry.

A positive number means to limit the display of \='kill-ring\=' items to
that number of characters.")

(defun show-kill-ring-exit ()
  "Exit the show-kill-ring buffer."
  (interactive)
  (quit-window t))

(defun show-kill-ring ()
  "Show the current contents of the kill ring in a separate buffer.

This makes it easy to figure out which prefix to pass to yank."
  (interactive)
  ;; kill existing one, since erasing it doesn't work
  (let ((buf (get-buffer "*Kill Ring*")))
	(and buf (kill-buffer buf)))

  (let* ((buf (get-buffer-create "*Kill Ring*"))
		 (temp kill-ring)
		 (count 1)
		 (bar (make-string 32 ?=))
		 (bar2 (concat " " bar))
		 (item "  Item ")
		 (yptr nil) (ynum 1))
	(set-buffer buf)
	(erase-buffer)

	(show-kill-insert-header)

	;; show each of the items in the kill ring, in order
	(while temp
	  ;; insert our little divider
	  (insert (concat "\n" bar item (prin1-to-string count) "  "
					  (if (< count 10) bar2 bar) "\n"))

	  ;; if this is the yank pointer target, grab it
	  (when (equal temp kill-ring-yank-pointer)
		(setq yptr (car temp) ynum count))

	  ;; insert the item and loop
	  (show-kill-insert-item (car temp))
	  (cl-incf count)
	  (setq temp (cdr temp)))

	;; show info about yank item
	(show-kill-insert-footer yptr ynum)

	;; use define-key instead of local-set-key
	(use-local-map (make-sparse-keymap))
	(define-key (current-local-map) "q" 'show-kill-ring-exit)

	;; show it
	(goto-char (point-min))
	(setq buffer-read-only t)
	(set-buffer-modified-p nil)
	;; display-buffer rather than pop-to-buffer
	;; easier for user to C-u (item#) C-y
	;; while the point is where they want to yank
	(display-buffer buf)))

(defun show-kill-insert-item (item)
  "Insert an ITEM from the kill ring into the current buffer.

If it's too long, truncate it first."
  (let ((max show-kill-max-item-size))
	(cond
	 ((or (not (numberp max))
		  (< max 0)
		  (< (length item) max))
	  (insert item))
	 (t
	  ;; put ellipsis on its own line if item is longer than 1 line
	  (let ((preview (substring item 0 max)))
		(if (< (length item) (- (frame-width) 5))
			(insert (concat preview "..." ))
		  (insert (concat preview "\n..."))))))))

(defun show-kill-insert-header ()
  "Insert the show-kill-ring header or a notice if the kill ring is empty."
  (if kill-ring
	  (insert "Contents of the kill ring:\n")
	(insert "The kill ring is empty")))

(defun show-kill-insert-footer (yptr ynum)
  "Insert final divider and the yank-pointer (YPTR YNUM) info."
  (when kill-ring
	(save-excursion
	  (re-search-backward "^\\(=+  Item [0-9]+\\ +=+\\)$"))
	(insert "\n")
	(insert (make-string (length (match-string 1)) ?=))
	;; Use number-to-string instead of int-to-string
	(insert (concat "\n\nItem " (number-to-string ynum)
					" is the next to be yanked:\n\n"))
	(show-kill-insert-item yptr)
	(insert "\n\nThe prefix arg will yank relative to this item.")))

(defun empty-kill-ring ()
  "Force garbage collection of huge kill ring entries that I don't care about."
  (interactive)
  (setq kill-ring nil)
  (garbage-collect))

(global-set-key (kbd "M-K") 'show-kill-ring)

(provide 'show-kill-ring)
;;; show-kill-ring.el ends here