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;;; register.el --- register commands for Emacs      -*- lexical-binding: t; -*-
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;; Copyright (C) 1985, 1993-1994, 2001-2019 Free Software Foundation,
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;; Inc.
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;; Maintainer: emacs-devel@gnu.org
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;; Keywords: internal
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;; Package: emacs
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;; This file is part of GNU Emacs.

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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
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;; GNU Emacs 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
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;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:

;; This package of functions emulates and somewhat extends the venerable
;; TECO's `register' feature, which permits you to save various useful
;; pieces of buffer state to named variables.  The entry points are
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;; documented in the Emacs user's manual: (info "(emacs) Registers").
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(eval-when-compile (require 'cl-lib))
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;;; Code:
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;; FIXME: Clean up namespace usage!

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(cl-defstruct
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  (registerv (:constructor nil)
	     (:constructor registerv--make (&optional data print-func
						      jump-func insert-func))
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	     (:copier nil))
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  (data        nil :read-only t)
  (print-func  nil :read-only t)
  (jump-func   nil :read-only t)
  (insert-func nil :read-only t))

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(cl-defun registerv-make (data &key print-func jump-func insert-func)
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  "Create a register value object.

DATA can be any value.
PRINT-FUNC if provided controls how `list-registers' and
`view-register' print the register.  It should be a function
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receiving one argument DATA and print text that completes
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this sentence:
  Register X contains [TEXT PRINTED BY PRINT-FUNC]
JUMP-FUNC if provided, controls how `jump-to-register' jumps to the register.
INSERT-FUNC if provided, controls how `insert-register' insert the register.
They both receive DATA as argument."
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  (declare (obsolete "Use your own type with methods on register-val-(insert|describe|jump-to)" "27.1"))
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  (registerv--make data print-func jump-func insert-func))

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(defvar register-alist nil
  "Alist of elements (NAME . CONTENTS), one for each Emacs register.
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NAME is a character (a number).  CONTENTS is a string, number, marker, list
or a struct returned by `registerv-make'.
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A list of strings represents a rectangle.
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A list of the form (file . FILE-NAME) represents the file named FILE-NAME.
A list of the form (file-query FILE-NAME POSITION) represents
 position POSITION in the file named FILE-NAME, but query before
 visiting it.
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A list of the form (WINDOW-CONFIGURATION POSITION)
 represents a saved window configuration plus a saved value of point.
A list of the form (FRAME-CONFIGURATION POSITION)
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 represents a saved frame configuration plus a saved value of point.")
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(defgroup register nil
  "Register commands."
  :group 'convenience
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  :version "24.3")
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(defcustom register-separator nil
  "Register containing the text to put between collected texts, or nil if none.
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When collecting text with \\[append-to-register] (or \\[prepend-to-register]),
contents of this register is added to the beginning (or end, respectively)
of the marked text."
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  :group 'register
  :type '(choice (const :tag "None" nil)
		 (character :tag "Use register" :value ?+)))

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(defcustom register-preview-delay 1
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  "If non-nil, time to wait in seconds before popping up a preview window.
If nil, do not show register previews, unless `help-char' (or a member of
`help-event-list') is pressed."
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  :version "24.4"
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  :type '(choice number (const :tag "No preview unless requested" nil))
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  :group 'register)

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(defun get-register (register)
  "Return contents of Emacs register named REGISTER, or nil if none."
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  (alist-get register register-alist))
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(defun set-register (register value)
  "Set contents of Emacs register named REGISTER to VALUE.  Returns VALUE.
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See the documentation of the variable `register-alist' for possible VALUEs."
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  (setf (alist-get register register-alist) value))
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(defun register-describe-oneline (c)
  "One-line description of register C."
  (let ((d (replace-regexp-in-string
            "\n[ \t]*" " "
            (with-output-to-string (describe-register-1 c)))))
    (if (string-match "Register.+? contains \\(?:an? \\|the \\)?" d)
        (substring d (match-end 0))
      d)))

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(defun register-preview-default (r)
  "Default function for the variable `register-preview-function'."
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  (format "%s: %s\n"
	  (single-key-description (car r))
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	  (register-describe-oneline (car r))))

(defvar register-preview-function #'register-preview-default
  "Function to format a register for previewing.
Takes one argument, a cons (NAME . CONTENTS) as found in `register-alist'.
Returns a string.")
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(defun register-preview (buffer &optional show-empty)
  "Pop up a window to show register preview in BUFFER.
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If SHOW-EMPTY is non-nil show the window even if no registers.
Format of each entry is controlled by the variable `register-preview-function'."
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  (when (or show-empty (consp register-alist))
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    (with-current-buffer-window
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     buffer
     (cons 'display-buffer-below-selected
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	   '((window-height . fit-window-to-buffer)
	     (preserve-size . (nil . t))))
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     nil
     (with-current-buffer standard-output
       (setq cursor-in-non-selected-windows nil)
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       (insert (mapconcat register-preview-function register-alist ""))))))
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(defun register-read-with-preview (prompt)
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  "Read and return a register name, possibly showing existing registers.
Prompt with the string PROMPT.  If `register-alist' and
`register-preview-delay' are both non-nil, display a window
listing existing registers after `register-preview-delay' seconds.
If `help-char' (or a member of `help-event-list') is pressed,
display such a window regardless."
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  (let* ((buffer "*Register Preview*")
	 (timer (when (numberp register-preview-delay)
		  (run-with-timer register-preview-delay nil
				  (lambda ()
				    (unless (get-buffer-window buffer)
				      (register-preview buffer))))))
	 (help-chars (cl-loop for c in (cons help-char help-event-list)
			      when (not (get-register c))
			      collect c)))
    (unwind-protect
	(progn
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	  (while (memq (read-key (propertize prompt 'face 'minibuffer-prompt))
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		       help-chars)
	    (unless (get-buffer-window buffer)
	      (register-preview buffer 'show-empty)))
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          (when (or (eq ?\C-g last-input-event)
                    (eq 'escape last-input-event)
                    (eq ?\C-\[ last-input-event))
            (keyboard-quit))
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	  (if (characterp last-input-event) last-input-event
	    (error "Non-character input-event")))
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      (and (timerp timer) (cancel-timer timer))
      (let ((w (get-buffer-window buffer)))
        (and (window-live-p w) (delete-window w)))
      (and (get-buffer buffer) (kill-buffer buffer)))))

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(defun point-to-register (register &optional arg)
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  "Store current location of point in register REGISTER.
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With prefix argument, store current frame configuration.
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Use \\[jump-to-register] to go to that location or restore that configuration.
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Argument is a character, naming the register.

Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list (register-read-with-preview
                      (if current-prefix-arg
                          "Frame configuration to register: "
                        "Point to register: "))
                     current-prefix-arg))
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  ;; Turn the marker into a file-ref if the buffer is killed.
  (add-hook 'kill-buffer-hook 'register-swap-out nil t)
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  (set-register register
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		(if arg (list (current-frame-configuration) (point-marker))
		  (point-marker))))
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(defun window-configuration-to-register (register &optional _arg)
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  "Store the window configuration of the selected frame in register REGISTER.
Use \\[jump-to-register] to restore the configuration.
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Argument is a character, naming the register.

Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list (register-read-with-preview
		      "Window configuration to register: ")
		     current-prefix-arg))
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  ;; current-window-configuration does not include the value
  ;; of point in the current buffer, so record that separately.
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  (set-register register (list (current-window-configuration) (point-marker))))
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;; It has had the optional arg for ages, but never used it.
(set-advertised-calling-convention 'window-configuration-to-register
				   '(register) "24.4")

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(defun frame-configuration-to-register (register &optional _arg)
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  "Store the window configuration of all frames in register REGISTER.
Use \\[jump-to-register] to restore the configuration.
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Argument is a character, naming the register.

Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list (register-read-with-preview
		      "Frame configuration to register: ")
		     current-prefix-arg))
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  ;; current-frame-configuration does not include the value
  ;; of point in the current buffer, so record that separately.
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  (set-register register (list (current-frame-configuration) (point-marker))))
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;; It has had the optional arg for ages, but never used it.
(set-advertised-calling-convention 'frame-configuration-to-register
				   '(register) "24.4")

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(make-obsolete 'frame-configuration-to-register 'frameset-to-register "24.4")
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(defalias 'register-to-point 'jump-to-register)
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(defun jump-to-register (register &optional delete)
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  "Move point to location stored in a register.
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Push the mark if jumping moves point, unless called in succession.
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If the register contains a file name, find that file.
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\(To put a file name in a register, you must use `set-register'.)
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If the register contains a window configuration (one frame) or a frameset
\(all frames), restore that frame or all frames accordingly.
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First argument is a character, naming the register.
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Optional second arg non-nil (interactively, prefix argument) says to
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delete any existing frames that the frameset doesn't mention.
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\(Otherwise, these frames are iconified.)

Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list (register-read-with-preview "Jump to register: ")
		     current-prefix-arg))
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  (let ((val (get-register register)))
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    (register-val-jump-to val delete)))

(cl-defgeneric register-val-jump-to (_val _arg)
  "Execute the \"jump\" operation of VAL.
ARG is the value of the prefix argument or nil."
  (user-error "Register doesn't contain a buffer position or configuration"))

(cl-defmethod register-val-jump-to ((val registerv) _arg)
  (cl-assert (registerv-jump-func val) nil
             "Don't know how to jump to register value %S" val)
  (funcall (registerv-jump-func val) (registerv-data val)))

(cl-defmethod register-val-jump-to ((val marker) _arg)
  (or (marker-buffer val)
      (user-error "That register's buffer no longer exists"))
  (switch-to-buffer (marker-buffer val))
  (unless (or (= (point) (marker-position val))
              (eq last-command 'jump-to-register))
    (push-mark))
  (goto-char val))

(cl-defmethod register-val-jump-to ((val cons) delete)
  (cond
   ((frame-configuration-p (car val))
    (set-frame-configuration (car val) (not delete))
    (goto-char (cadr val)))
   ((window-configuration-p (car val))
    (set-window-configuration (car val))
    (goto-char (cadr val)))
   ((eq (car val) 'file)
    (find-file (cdr val)))
   ((eq (car val) 'file-query)
    (or (find-buffer-visiting (nth 1 val))
	(y-or-n-p (format "Visit file %s again? " (nth 1 val)))
	(user-error "Register access aborted"))
    (find-file (nth 1 val))
    (goto-char (nth 2 val)))
   (t (cl-call-next-method val delete))))
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(defun register-swap-out ()
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  "Turn markers into file-query references when a buffer is killed."
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  (and buffer-file-name
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       (dolist (elem register-alist)
	 (and (markerp (cdr elem))
	      (eq (marker-buffer (cdr elem)) (current-buffer))
	      (setcdr elem
		      (list 'file-query
			    buffer-file-name
			    (marker-position (cdr elem))))))))
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(defun number-to-register (number register)
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  "Store a number in a register.
Two args, NUMBER and REGISTER (a character, naming the register).
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If NUMBER is nil, a decimal number is read from the buffer starting
at point, and point moves to the end of that number.
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Interactively, NUMBER is the prefix arg (none means nil).

Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list current-prefix-arg
		     (register-read-with-preview "Number to register: ")))
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  (set-register register
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		(if number
		    (prefix-numeric-value number)
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		  (if (looking-at "\\s-*-?[0-9]+")
		      (progn
			(goto-char (match-end 0))
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			(string-to-number (match-string 0)))
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		    0))))

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(defun increment-register (prefix register)
  "Augment contents of REGISTER.
Interactively, PREFIX is in raw form.

If REGISTER contains a number, add `prefix-numeric-value' of
PREFIX to it.

If REGISTER is empty or if it contains text, call
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`append-to-register' with `delete-flag' set to PREFIX.

Interactively, reads the register using `register-read-with-preview'."
  (interactive (list current-prefix-arg
		     (register-read-with-preview "Increment register: ")))
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  (let ((register-val (get-register register)))
    (cond
     ((numberp register-val)
      (let ((number (prefix-numeric-value prefix)))
	(set-register register (+ number register-val))))
     ((or (not register-val) (stringp register-val))
      (append-to-register register (region-beginning) (region-end) prefix))
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     (t (user-error "Register does not contain a number or text")))))
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(defun view-register (register)
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  "Display what is contained in register named REGISTER.
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The Lisp value REGISTER is a character.

Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list (register-read-with-preview "View register: ")))
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  (let ((val (get-register register)))
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    (if (null val)
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	(message "Register %s is empty" (single-key-description register))
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      (with-output-to-temp-buffer "*Output*"
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	(describe-register-1 register t)))))

(defun list-registers ()
  "Display a list of nonempty registers saying briefly what they contain."
  (interactive)
  (let ((list (copy-sequence register-alist)))
    (setq list (sort list (lambda (a b) (< (car a) (car b)))))
    (with-output-to-temp-buffer "*Output*"
      (dolist (elt list)
	(when (get-register (car elt))
	  (describe-register-1 (car elt))
	  (terpri))))))

(defun describe-register-1 (register &optional verbose)
  (princ "Register ")
  (princ (single-key-description register))
  (princ " contains ")
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  (let ((val (get-register register)))
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    (register-val-describe val verbose)))

(cl-defgeneric register-val-describe (val verbose)
  "Print description of register value VAL to `standard-output'."
  (princ "Garbage:\n")
  (if verbose (prin1 val)))

(cl-defmethod register-val-describe ((val registerv) _verbose)
  (if (registerv-print-func val)
      (funcall (registerv-print-func val) (registerv-data val))
    (princ "[UNPRINTABLE CONTENTS].")))

(cl-defmethod register-val-describe ((val number) _verbose)
  (princ val))

(cl-defmethod register-val-describe ((val marker) _verbose)
  (let ((buf (marker-buffer val)))
    (if (null buf)
	(princ "a marker in no buffer")
      (princ "a buffer position:\n    buffer ")
      (princ (buffer-name buf))
      (princ ", position ")
      (princ (marker-position val)))))

(cl-defmethod register-val-describe ((val cons) verbose)
  (cond
   ((window-configuration-p (car val))
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    (let* ((stored-window-config (car val))
           (window-config-frame (window-configuration-frame stored-window-config))
           (current-frame (selected-frame)))
      (princ (format "a window configuration: %s."
                     (if (frame-live-p window-config-frame)
                         (with-selected-frame window-config-frame
                           (save-window-excursion
                             (set-window-configuration stored-window-config)
                             (concat
                              (mapconcat (lambda (w) (buffer-name (window-buffer w)))
                                         (window-list (selected-frame)) ", ")
                              (unless (eq current-frame window-config-frame)
                                " in another frame"))))
                       "dead frame")))))
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   ((frame-configuration-p (car val))
    (princ "a frame configuration."))

   ((eq (car val) 'file)
    (princ "the file ")
    (prin1 (cdr val))
    (princ "."))

   ((eq (car val) 'file-query)
    (princ "a file-query reference:\n    file ")
    (prin1 (car (cdr val)))
    (princ ",\n    position ")
    (princ (car (cdr (cdr val))))
    (princ "."))

   (t
    (if verbose
	(progn
	  (princ "the rectangle:\n")
	  (while val
	    (princ "    ")
	    (princ (car val))
	    (terpri)
	    (setq val (cdr val))))
      (princ "a rectangle starting with ")
      (princ (car val))))))

(cl-defmethod register-val-describe ((val string) verbose)
  (setq val (copy-sequence val))
  (if (eq yank-excluded-properties t)
      (set-text-properties 0 (length val) nil val)
    (remove-list-of-text-properties 0 (length val)
				    yank-excluded-properties val))
  (if verbose
      (progn
	(princ "the text:\n")
	(princ val))
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    (cond
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     ;; Extract first N characters starting with first non-whitespace.
     ((string-match (format "[^ \t\n].\\{,%d\\}"
			    ;; Deduct 6 for the spaces inserted below.
			    (min 20 (max 0 (- (window-width) 6))))
		    val)
      (princ "text starting with\n    ")
      (princ (match-string 0 val)))
     ((string-match "^[ \t\n]+$" val)
      (princ "whitespace"))
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     (t
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      (princ "the empty string")))))
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(defun insert-register (register &optional arg)
  "Insert contents of register REGISTER.  (REGISTER is a character.)
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Normally puts point before and mark after the inserted text.
If optional second arg is non-nil, puts mark before and point after.
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Interactively, second arg is nil if prefix arg is supplied and t
otherwise.
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Interactively, reads the register using `register-read-with-preview'."
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  (interactive (progn
		 (barf-if-buffer-read-only)
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		 (list (register-read-with-preview "Insert register: ")
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		       (not current-prefix-arg))))
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  (push-mark)
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  (let ((val (get-register register)))
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    (register-val-insert val))
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  (if (not arg) (exchange-point-and-mark)))

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(cl-defgeneric register-val-insert (_val)
  "Insert register value VAL."
  (user-error "Register does not contain text"))

(cl-defmethod register-val-insert ((val registerv))
  (cl-assert (registerv-insert-func val) nil
             "Don't know how to insert register value %S" val)
  (funcall (registerv-insert-func val) (registerv-data val)))

(cl-defmethod register-val-insert ((val cons))
  (insert-rectangle val))

(cl-defmethod register-val-insert ((val string))
  (insert-for-yank val))

(cl-defmethod register-val-insert ((val number))
  (princ val (current-buffer)))

(cl-defmethod register-val-insert ((val marker))
  (if (marker-position val)
      (princ (marker-position val) (current-buffer))
    (cl-call-next-method val)))

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(defun copy-to-register (register start end &optional delete-flag region)
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  "Copy region into register REGISTER.
With prefix arg, delete as well.
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Called from program, takes five args: REGISTER, START, END, DELETE-FLAG,
and REGION.  START and END are buffer positions indicating what to copy.
The optional argument REGION if non-nil, indicates that we're not just
copying some text between START and END, but we're copying the region.
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Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list (register-read-with-preview "Copy to register: ")
		     (region-beginning)
		     (region-end)
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		     current-prefix-arg
		     t))
  (set-register register (if region
			     (funcall region-extract-function delete-flag)
			   (prog1 (filter-buffer-substring start end)
			     (if delete-flag (delete-region start end)))))
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  (setq deactivate-mark t)
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  (cond (delete-flag)
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	((called-interactively-p 'interactive)
	 (indicate-copied-region))))
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(defun append-to-register (register start end &optional delete-flag)
  "Append region to text in register REGISTER.
With prefix arg, delete as well.
Called from program, takes four args: REGISTER, START, END and DELETE-FLAG.
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START and END are buffer positions indicating what to append.

Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list (register-read-with-preview "Append to register: ")
		     (region-beginning)
		     (region-end)
		     current-prefix-arg))
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  (let ((reg (get-register register))
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        (text (filter-buffer-substring start end))
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	(separator (and register-separator (get-register register-separator))))
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    (set-register
     register (cond ((not reg) text)
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                    ((stringp reg) (concat reg separator text))
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                    (t (user-error "Register does not contain text")))))
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  (setq deactivate-mark t)
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  (cond (delete-flag
	 (delete-region start end))
	((called-interactively-p 'interactive)
	 (indicate-copied-region))))
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(defun prepend-to-register (register start end &optional delete-flag)
  "Prepend region to text in register REGISTER.
With prefix arg, delete as well.
Called from program, takes four args: REGISTER, START, END and DELETE-FLAG.
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START and END are buffer positions indicating what to prepend.

Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list (register-read-with-preview "Prepend to register: ")
		     (region-beginning)
		     (region-end)
		     current-prefix-arg))
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  (let ((reg (get-register register))
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        (text (filter-buffer-substring start end))
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	(separator (and register-separator (get-register register-separator))))
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    (set-register
     register (cond ((not reg) text)
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                    ((stringp reg) (concat text separator reg))
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                    (t (user-error "Register does not contain text")))))
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  (setq deactivate-mark t)
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  (cond (delete-flag
	 (delete-region start end))
	((called-interactively-p 'interactive)
	 (indicate-copied-region))))
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(defun copy-rectangle-to-register (register start end &optional delete-flag)
  "Copy rectangular region into register REGISTER.
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With prefix arg, delete as well.
To insert this register in the buffer, use \\[insert-register].
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Called from a program, takes four args: REGISTER, START, END and DELETE-FLAG.
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START and END are buffer positions giving two corners of rectangle.

Interactively, reads the register using `register-read-with-preview'."
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  (interactive (list (register-read-with-preview
		      "Copy rectangle to register: ")
		     (region-beginning)
		     (region-end)
		     current-prefix-arg))
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  (let ((rectangle (if delete-flag
		       (delete-extract-rectangle start end)
		     (extract-rectangle start end))))
    (set-register register rectangle)
    (when (and (null delete-flag)
	       (called-interactively-p 'interactive))
      (setq deactivate-mark t)
      (indicate-copied-region (length (car rectangle))))))

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(provide 'register)
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;;; register.el ends here