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;;; move-lines.el --- move current line or lines surrounding region up or down
;; Copyright (C) 2013 Emanuele Tomasi <targzeta@gmail.com>
;;
;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary;
;; There are two entry points: `move-lines-up' moves the text up and
;; `move-lines-down' that moves the text down.
;;
;; Copy this file in a directory which is in the Emacs `load-path'. Then,
;; execute the following code either directly or in your .emacs file:
;;
;; (require 'move-lines)
;; (move-lines-binding)
;;
;; Now, you can move the line(s) up by M-p or M-<up> or down by M-n or M-<down>.
;;; Code:
(defun move-lines--internal (n)
(let* ((start (point)) ;; The position of beginning of line of the first line
(end start) ;; The position of eol+\n of the end line
col-init ;; The current column for the first line
(col-end (current-column)) ;; The current column for the end line
exchange_pm ;; If I had exchanged point and mark
delete-latest-newline) ;; If I had inserted a newline at the end
;; STEP 1: Identifying the line(s) to cut.
;; ---
;; If region is actives, I ensure that point always is at the end of the
;; region and mark at the beginning.
(when (region-active-p)
(when (< (point) (mark))
(setq exchange_pm t)
(exchange-point-and-mark))
(setq start (mark)
end (point)
col-end (current-column)))
(goto-char start) (setq col-init (current-column))
(beginning-of-line) (setq start (point))
(goto-char end) (end-of-line)
;; If point == point-max, this buffers doesn't have the trailing newline.
;; In this case I have to insert a newline otherwise the following
;; `forward-char' (to keep the "\n") will fail.
(when (= (point) (point-max))
(setq delete-latest-newline t)
(insert-char ?\n) (forward-char -1))
(forward-char 1) (setq end (point))
;; STEP 2: Moving the lines.
;; ---
;; The region I'm cutting span from the beginning of line of the current
;; line (or current region) to the end of line + 1 (newline) of the current
;; line (or current region).
(let ((line-text (delete-and-extract-region start end)))
(forward-line n)
;; If the current-column != 0, I have moved the region at the bottom of a
;; buffer doesn't have the trailing newline.
(when (not (= (current-column) 0))
(insert-char ?\n)
(setq delete-latest-newline t))
(setq start (+ (point) col-init)) ;; Now, start is the start of new region
(insert line-text))
;; STEP 3: Restoring
;; ---
;; I'm at the end of new region (or line) and start has setted at the
;; beginning of new region (if a region is active).
;; Restoring the end column.
(forward-line -1)
(forward-char col-end)
(when delete-latest-newline
(save-excursion
(goto-char (point-max))
(delete-char -1)))
(when (region-active-p)
(setq deactivate-mark nil)
(set-mark start)
(if exchange_pm
(exchange-point-and-mark)))))
;;;###autoload
(defun move-lines-up (n)
"Moves the current line or, if region is actives, the lines surrounding
region, up by N lines, or 1 line if N is nil."
(interactive "p")
(if (eq n nil)
(setq n 1))
(move-lines--internal (- n)))
;;;###autoload
(defun move-lines-down (n)
"Moves the current line or, if region is actives, the lines surrounding
region, down by N lines, or 1 line if N is nil."
(interactive "p")
(if (eq n nil)
(setq n 1))
(move-lines--internal n))
;;;###autoload
(defun move-lines-binding ()
"Sets the default key binding for moving lines. M-p or M-<up> for moving up
and M-n or M-<down> for moving down."
(global-set-key (kbd "M-p") 'move-lines-up)
(global-set-key (kbd "M-<up>") 'move-lines-up)
(global-set-key (kbd "M-n") 'move-lines-down)
(global-set-key (kbd "M-<down>") 'move-lines-down))
(provide 'move-lines)
;; move-lines.el ends here
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