lisp/indent.el

   1 ;;; indent.el --- indentation commands for Emacs  -*- lexical-binding:t -*-
   2
   3 ;; Copyright (C) 1985, 1995, 2001-2013 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Package: emacs
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software: you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation, either version 3 of the License, or
  13 ;; (at your option) any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  22
  23 ;;; Commentary:
  24
  25 ;; Commands for making and changing indentation in text.  These are
  26 ;; described in the Emacs manual.
  27
  28 ;;; Code:
  29
  30 (defgroup indent nil
  31   "Indentation commands."
  32   :group 'editing)
  33
  34 (defcustom standard-indent 4
  35   "Default number of columns for margin-changing functions to indent."
  36   :group 'indent
  37   :type 'integer)
  38
  39 (defvar indent-line-function 'indent-relative
  40   "Function to indent the current line.
  41 This function will be called with no arguments.
  42 If it is called somewhere where auto-indentation cannot be done
  43 \(e.g. inside a string), the function should simply return `noindent'.
  44 Setting this function is all you need to make TAB indent appropriately.
  45 Don't rebind TAB unless you really need to.")
  46
  47 (defcustom tab-always-indent t
  48   "Controls the operation of the TAB key.
  49 If t, hitting TAB always just indents the current line.
  50 If nil, hitting TAB indents the current line if point is at the left margin
  51 or in the line's indentation, otherwise it inserts a \"real\" TAB character.
  52 If `complete', TAB first tries to indent the current line, and if the line
  53 was already indented, then try to complete the thing at point.
  54
  55 Some programming language modes have their own variable to control this,
  56 e.g., `c-tab-always-indent', and do not respect this variable."
  57   :group 'indent
  58   :type '(choice
  59           (const :tag "Always indent" t)
  60           (const :tag "Indent if inside indentation, else TAB" nil)
  61           (const :tag "Indent, or if already indented complete" complete)))
  62
  63
  64 (defun indent-according-to-mode ()
  65   "Indent line in proper way for current major mode.
  66 Normally, this is done by calling the function specified by the
  67 variable `indent-line-function'.  However, if the value of that
  68 variable is `indent-relative' or `indent-relative-maybe', handle
  69 it specially (since those functions are used for tabbing); in
  70 that case, indent by aligning to the previous non-blank line."
  71   (interactive)
  72   (syntax-propertize (line-end-position))
  73   (if (memq indent-line-function
  74             '(indent-relative indent-relative-maybe))
  75       ;; These functions are used for tabbing, but can't be used for
  76       ;; indenting.  Replace with something ad-hoc.
  77       (let ((column (save-excursion
  78                       (beginning-of-line)
  79                       (skip-chars-backward "\n \t")
  80                       (beginning-of-line)
  81                       (current-indentation))))
  82         (if (<= (current-column) (current-indentation))
  83             (indent-line-to column)
  84           (save-excursion (indent-line-to column))))
  85     ;; The normal case.
  86     (funcall indent-line-function)))
  87
  88 (defun indent-for-tab-command (&optional arg)
  89   "Indent the current line or region, or insert a tab, as appropriate.
  90 This function either inserts a tab, or indents the current line,
  91 or performs symbol completion, depending on `tab-always-indent'.
  92 The function called to actually indent the line or insert a tab
  93 is given by the variable `indent-line-function'.
  94
  95 If a prefix argument is given, after this function indents the
  96 current line or inserts a tab, it also rigidly indents the entire
  97 balanced expression which starts at the beginning of the current
  98 line, to reflect the current line's indentation.
  99
 100 In most major modes, if point was in the current line's
 101 indentation, it is moved to the first non-whitespace character
 102 after indenting; otherwise it stays at the same position relative
 103 to the text.
 104
 105 If `transient-mark-mode' is turned on and the region is active,
 106 this function instead calls `indent-region'.  In this case, any
 107 prefix argument is ignored."
 108   (interactive "P")
 109   (cond
 110    ;; The region is active, indent it.
 111    ((use-region-p)
 112     (indent-region (region-beginning) (region-end)))
 113    ((or ;; indent-to-left-margin is only meant for indenting,
 114         ;; so we force it to always insert a tab here.
 115         (eq indent-line-function 'indent-to-left-margin)
 116         (and (not tab-always-indent)
 117              (or (> (current-column) (current-indentation))
 118                  (eq this-command last-command))))
 119     (insert-tab arg))
 120    (t
 121     (let ((old-tick (buffer-chars-modified-tick))
 122           (old-point (point))
 123           (old-indent (current-indentation)))
 124
 125       ;; Indent the line.
 126       (funcall indent-line-function)
 127
 128       (cond
 129        ;; If the text was already indented right, try completion.
 130        ((and (eq tab-always-indent 'complete)
 131              (eq old-point (point))
 132              (eq old-tick (buffer-chars-modified-tick)))
 133         (completion-at-point))
 134
 135        ;; If a prefix argument was given, rigidly indent the following
 136        ;; sexp to match the change in the current line's indentation.
 137        (arg
 138         (let ((end-marker
 139                (save-excursion
 140                  (forward-line 0) (forward-sexp) (point-marker)))
 141               (indentation-change (- (current-indentation) old-indent)))
 142           (save-excursion
 143             (forward-line 1)
 144             (when (and (not (zerop indentation-change))
 145                        (< (point) end-marker))
 146               (indent-rigidly (point) end-marker indentation-change))))))))))
 147
 148 (defun insert-tab (&optional arg)
 149   (let ((count (prefix-numeric-value arg)))
 150     (if (and abbrev-mode
 151              (eq (char-syntax (preceding-char)) ?w))
 152         (expand-abbrev))
 153     (if indent-tabs-mode
 154         (insert-char ?\t count)
 155       (indent-to (* tab-width (+ count (/ (current-column) tab-width)))))))
 156
 157 (defun indent-rigidly--current-indentation (beg end)
 158   "Return the smallest indentation in range from BEG to END.
 159 Blank lines are ignored."
 160   (save-excursion
 161     (save-match-data
 162       (let ((beg (progn (goto-char beg) (line-beginning-position)))
 163             indent)
 164         (goto-char beg)
 165         (while (re-search-forward "^\\s-*[[:print:]]" end t)
 166           (setq indent (min (or indent (current-indentation))
 167                             (current-indentation))))
 168         indent))))
 169
 170 (defvar indent-rigidly-map
 171   (let ((map (make-sparse-keymap)))
 172     (define-key map [left]
 173       (lambda (beg end) (interactive "r") (indent-rigidly beg end -1)))
 174
 175     (define-key map [right]
 176       (lambda (beg end) (interactive "r") (indent-rigidly beg end 1)))
 177
 178     (define-key map [S-right]
 179       (lambda (beg end) (interactive "r")
 180         (let* ((current (indent-rigidly--current-indentation beg end))
 181                (next (indent--next-tab-stop current)))
 182           (indent-rigidly beg end (- next current)))))
 183
 184     (define-key map [S-left]
 185       (lambda (beg end) (interactive "r")
 186         (let* ((current (indent-rigidly--current-indentation beg end))
 187                (next (indent--next-tab-stop current 'prev)))
 188           (indent-rigidly beg end (- next current)))))
 189     map))
 190
 191 (defun indent-rigidly (start end arg &optional interactive)
 192   "Indent all lines starting in the region sideways by ARG columns.
 193 Called from a program, takes three arguments, START, END and ARG.
 194 You can remove all indentation from a region by giving a large negative ARG.
 195 If used interactively and no prefix argument is given, use a transient
 196 mode that lets you move the text with cursor keys."
 197   (interactive "r\nP\np")
 198   (if (and (not arg) interactive)
 199       (progn
 200         (message "Edit region indentation with <left>, <right>, <S-left> \
 201 and <S-right>.")
 202         (set-temporary-overlay-map indent-rigidly-map t))
 203     (save-excursion
 204       (goto-char end)
 205       (setq end (point-marker))
 206       (goto-char start)
 207       (or (bolp) (forward-line 1))
 208       (while (< (point) end)
 209         (let ((indent (current-indentation))
 210               eol-flag)
 211           (save-excursion
 212             (skip-chars-forward " \t")
 213             (setq eol-flag (eolp)))
 214           (or eol-flag
 215               (indent-to (max 0 (+ indent (prefix-numeric-value arg))) 0))
 216           (delete-region (point) (progn (skip-chars-forward " \t") (point))))
 217         (forward-line 1))
 218       (move-marker end nil))))
 219
 220 (defun indent-line-to (column)
 221   "Indent current line to COLUMN.
 222 This function removes or adds spaces and tabs at beginning of line
 223 only if necessary.  It leaves point at end of indentation."
 224   (back-to-indentation)
 225   (let ((cur-col (current-column)))
 226     (cond ((< cur-col column)
 227            (if (>= (- column (* (/ cur-col tab-width) tab-width)) tab-width)
 228                (delete-region (point)
 229                               (progn (skip-chars-backward " ") (point))))
 230            (indent-to column))
 231           ((> cur-col column) ; too far right (after tab?)
 232            (delete-region (progn (move-to-column column t) (point))
 233                           (progn (back-to-indentation) (point)))))))
 234
 235 (defun current-left-margin ()
 236   "Return the left margin to use for this line.
 237 This is the value of the buffer-local variable `left-margin' plus the value
 238 of the `left-margin' text-property at the start of the line."
 239   (save-excursion
 240     (back-to-indentation)
 241     (max 0
 242          (+ left-margin (or (get-text-property
 243                              (if (and (eobp) (not (bobp)))
 244                                  (1- (point)) (point))
 245                              'left-margin) 0)))))
 246
 247 (defun move-to-left-margin (&optional n force)
 248   "Move to the left margin of the current line.
 249 With optional argument, move forward N-1 lines first.
 250 The column moved to is the one given by the `current-left-margin' function.
 251 If the line's indentation appears to be wrong, and this command is called
 252 interactively or with optional argument FORCE, it will be fixed."
 253   (interactive (list (prefix-numeric-value current-prefix-arg) t))
 254   (beginning-of-line n)
 255   (skip-chars-forward " \t")
 256   (if (minibufferp (current-buffer))
 257       (if (save-excursion (beginning-of-line) (bobp))
 258           (goto-char (minibuffer-prompt-end))
 259         (beginning-of-line))
 260     (let ((lm (current-left-margin))
 261           (cc (current-column)))
 262       (cond ((> cc lm)
 263              (if (> (move-to-column lm force) lm)
 264                  ;; If lm is in a tab and we are not forcing, move before tab
 265                  (backward-char 1)))
 266             ((and force (< cc lm))
 267              (indent-to-left-margin))))))
 268
 269 ;; This used to be the default indent-line-function,
 270 ;; used in Fundamental Mode, Text Mode, etc.
 271 (defun indent-to-left-margin ()
 272   "Indent current line to the column given by `current-left-margin'."
 273   (save-excursion (indent-line-to (current-left-margin)))
 274   ;; If we are within the indentation, move past it.
 275   (when (save-excursion
 276           (skip-chars-backward " \t")
 277           (bolp))
 278     (skip-chars-forward " \t")))
 279
 280 (defun delete-to-left-margin (&optional from to)
 281   "Remove left margin indentation from a region.
 282 This deletes to the column given by `current-left-margin'.
 283 In no case will it delete non-whitespace.
 284 Args FROM and TO are optional; default is the whole buffer."
 285   (save-excursion
 286     (goto-char (or to (point-max)))
 287     (setq to (point-marker))
 288     (goto-char (or from (point-min)))
 289     (or (bolp) (forward-line 1))
 290     (while (< (point) to)
 291       (delete-region (point) (progn (move-to-left-margin nil t) (point)))
 292       (forward-line 1))
 293     (move-marker to nil)))
 294
 295 (defun set-left-margin (from to width)
 296   "Set the left margin of the region to WIDTH.
 297 If `auto-fill-mode' is active, re-fill the region to fit the new margin.
 298
 299 Interactively, WIDTH is the prefix argument, if specified.
 300 Without prefix argument, the command prompts for WIDTH."
 301   (interactive "r\nNSet left margin to column: ")
 302   (save-excursion
 303     ;; If inside indentation, start from BOL.
 304     (goto-char from)
 305     (skip-chars-backward " \t")
 306     (if (bolp) (setq from (point)))
 307     ;; Place end after whitespace
 308     (goto-char to)
 309     (skip-chars-forward " \t")
 310     (setq to (point-marker)))
 311   ;; Delete margin indentation first, but keep paragraph indentation.
 312   (delete-to-left-margin from to)
 313   (put-text-property from to 'left-margin width)
 314   (indent-rigidly from to width)
 315   (if auto-fill-function (save-excursion (fill-region from to nil t t)))
 316   (move-marker to nil))
 317
 318 (defun set-right-margin (from to width)
 319   "Set the right margin of the region to WIDTH.
 320 If `auto-fill-mode' is active, re-fill the region to fit the new margin.
 321
 322 Interactively, WIDTH is the prefix argument, if specified.
 323 Without prefix argument, the command prompts for WIDTH."
 324   (interactive "r\nNSet right margin to width: ")
 325   (save-excursion
 326     (goto-char from)
 327     (skip-chars-backward " \t")
 328     (if (bolp) (setq from (point))))
 329   (put-text-property from to 'right-margin width)
 330   (if auto-fill-function (save-excursion (fill-region from to nil t t))))
 331
 332 (defun alter-text-property (from to prop func &optional object)
 333   "Programmatically change value of a text-property.
 334 For each region between FROM and TO that has a single value for PROPERTY,
 335 apply FUNCTION to that value and sets the property to the function's result.
 336 Optional fifth argument OBJECT specifies the string or buffer to operate on."
 337   (let ((begin from)
 338         end val)
 339     (while (setq val (get-text-property begin prop object)
 340                  end (text-property-not-all begin to prop val object))
 341       (put-text-property begin end prop (funcall func val) object)
 342       (setq begin end))
 343     (if (< begin to)
 344         (put-text-property begin to prop (funcall func val) object))))
 345
 346 (defun increase-left-margin (from to inc)
 347   "Increase or decrease the left-margin of the region.
 348 With no prefix argument, this adds `standard-indent' of indentation.
 349 A prefix arg (optional third arg INC noninteractively) specifies the amount
 350 to change the margin by, in characters.
 351 If `auto-fill-mode' is active, re-fill the region to fit the new margin."
 352   (interactive "*r\nP")
 353   (setq inc (if inc (prefix-numeric-value inc) standard-indent))
 354   (save-excursion
 355     (goto-char from)
 356     (skip-chars-backward " \t")
 357     (if (bolp) (setq from (point)))
 358     (goto-char to)
 359     (setq to (point-marker)))
 360   (alter-text-property from to 'left-margin
 361                        (lambda (v) (max (- left-margin) (+ inc (or v 0)))))
 362   (indent-rigidly from to inc)
 363   (if auto-fill-function (save-excursion (fill-region from to nil t t)))
 364   (move-marker to nil))
 365
 366 (defun decrease-left-margin (from to inc)
 367   "Make the left margin of the region smaller.
 368 With no prefix argument, decrease the indentation by `standard-indent'.
 369 A prefix arg (optional third arg INC noninteractively) specifies the amount
 370 to change the margin by, in characters.
 371 If `auto-fill-mode' is active, re-fill the region to fit the new margin."
 372   (interactive "*r\nP")
 373   (setq inc (if inc (prefix-numeric-value inc) standard-indent))
 374   (increase-left-margin from to (- inc)))
 375
 376 (defun increase-right-margin (from to inc)
 377   "Increase the right-margin of the region.
 378 With no prefix argument, increase the right margin by `standard-indent'.
 379 A prefix arg (optional third arg INC noninteractively) specifies the amount
 380 to change the margin by, in characters.  A negative argument decreases
 381 the right margin width.
 382 If `auto-fill-mode' is active, re-fill the region to fit the new margin."
 383   (interactive "r\nP")
 384   (setq inc (if inc (prefix-numeric-value inc) standard-indent))
 385   (save-excursion
 386     (alter-text-property from to 'right-margin
 387                          (lambda (v) (+ inc (or v 0))))
 388     (if auto-fill-function
 389         (fill-region from to nil t t))))
 390
 391 (defun decrease-right-margin (from to inc)
 392   "Make the right margin of the region smaller.
 393 With no prefix argument, decrease the right margin by `standard-indent'.
 394 A prefix arg (optional third arg INC noninteractively) specifies the amount
 395 of width to remove, in characters.  A negative argument increases
 396 the right margin width.
 397 If `auto-fill-mode' is active, re-fills region to fit in new margin."
 398   (interactive "*r\nP")
 399   (setq inc (if inc (prefix-numeric-value inc) standard-indent))
 400   (increase-right-margin from to (- inc)))
 401
 402 (defun beginning-of-line-text (&optional n)
 403   "Move to the beginning of the text on this line.
 404 With optional argument, move forward N-1 lines first.
 405 From the beginning of the line, moves past the left-margin indentation, the
 406 fill-prefix, and any indentation used for centering or right-justifying the
 407 line, but does not move past any whitespace that was explicitly inserted
 408 \(such as a tab used to indent the first line of a paragraph)."
 409   (interactive "p")
 410   (beginning-of-line n)
 411   (skip-chars-forward " \t")
 412   ;; Skip over fill-prefix.
 413   (if (and fill-prefix
 414            (not (string-equal fill-prefix "")))
 415       (if (equal fill-prefix
 416                  (buffer-substring
 417                   (point) (min (point-max) (+ (length fill-prefix) (point)))))
 418           (forward-char (length fill-prefix)))
 419     (if (and adaptive-fill-mode adaptive-fill-regexp
 420              (looking-at adaptive-fill-regexp))
 421         (goto-char (match-end 0))))
 422   ;; Skip centering or flushright indentation
 423   (if (memq (current-justification) '(center right))
 424       (skip-chars-forward " \t")))
 425
 426 (defvar indent-region-function nil
 427   "Short cut function to indent region using `indent-according-to-mode'.
 428 A value of nil means really run `indent-according-to-mode' on each line.")
 429
 430 (defun indent-region (start end &optional column)
 431   "Indent each nonblank line in the region.
 432 A numeric prefix argument specifies a column: indent each line to that column.
 433
 434 With no prefix argument, the command chooses one of these methods and
 435 indents all the lines with it:
 436
 437   1) If `fill-prefix' is non-nil, insert `fill-prefix' at the
 438      beginning of each line in the region that does not already begin
 439      with it.
 440   2) If `indent-region-function' is non-nil, call that function
 441      to indent the region.
 442   3) Indent each line via `indent-according-to-mode'.
 443
 444 Called from a program, START and END specify the region to indent.
 445 If the third argument COLUMN is an integer, it specifies the
 446 column to indent to; if it is nil, use one of the three methods above."
 447   (interactive "r\nP")
 448   (cond
 449    ;; If a numeric prefix is given, indent to that column.
 450    (column
 451     (setq column (prefix-numeric-value column))
 452     (save-excursion
 453       (goto-char end)
 454       (setq end (point-marker))
 455       (goto-char start)
 456       (or (bolp) (forward-line 1))
 457       (while (< (point) end)
 458         (delete-region (point) (progn (skip-chars-forward " \t") (point)))
 459         (or (eolp)
 460             (indent-to column 0))
 461         (forward-line 1))
 462       (move-marker end nil)))
 463    ;; If a fill-prefix is specified, use it.
 464    (fill-prefix
 465     (save-excursion
 466       (goto-char end)
 467       (setq end (point-marker))
 468       (goto-char start)
 469       (let ((regexp (regexp-quote fill-prefix)))
 470         (while (< (point) end)
 471           (or (looking-at regexp)
 472               (and (bolp) (eolp))
 473               (insert fill-prefix))
 474           (forward-line 1)))))
 475    ;; Use indent-region-function is available.
 476    (indent-region-function
 477     (funcall indent-region-function start end))
 478    ;; Else, use a default implementation that calls indent-line-function on
 479    ;; each line.
 480    (t
 481     (save-excursion
 482       (setq end (copy-marker end))
 483       (goto-char start)
 484       (let ((pr (unless (minibufferp)
 485                   (make-progress-reporter "Indenting region..." (point) end))))
 486         (while (< (point) end)
 487           (or (and (bolp) (eolp))
 488               (indent-according-to-mode))
 489           (forward-line 1)
 490           (and pr (progress-reporter-update pr (point))))
 491         (and pr (progress-reporter-done pr))
 492         (move-marker end nil)))))
 493   ;; In most cases, reindenting modifies the buffer, but it may also
 494   ;; leave it unmodified, in which case we have to deactivate the mark
 495   ;; by hand.
 496   (deactivate-mark))
 497
 498 (defun indent-relative-maybe ()
 499   "Indent a new line like previous nonblank line.
 500 If the previous nonblank line has no indent points beyond the
 501 column point starts at, this command does nothing.
 502
 503 See also `indent-relative'."
 504   (interactive)
 505   (indent-relative t))
 506
 507 (defun indent-relative (&optional unindented-ok)
 508   "Space out to under next indent point in previous nonblank line.
 509 An indent point is a non-whitespace character following whitespace.
 510 The following line shows the indentation points in this line.
 511     ^         ^    ^     ^   ^           ^      ^  ^    ^
 512 If the previous nonblank line has no indent points beyond the
 513 column point starts at, `tab-to-tab-stop' is done instead, unless
 514 this command is invoked with a numeric argument, in which case it
 515 does nothing.
 516
 517 See also `indent-relative-maybe'."
 518   (interactive "P")
 519   (if (and abbrev-mode
 520            (eq (char-syntax (preceding-char)) ?w))
 521       (expand-abbrev))
 522   (let ((start-column (current-column))
 523         indent)
 524     (save-excursion
 525       (beginning-of-line)
 526       (if (re-search-backward "^[^\n]" nil t)
 527           (let ((end (save-excursion (forward-line 1) (point))))
 528             (move-to-column start-column)
 529             ;; Is start-column inside a tab on this line?
 530             (if (> (current-column) start-column)
 531                 (backward-char 1))
 532             (or (looking-at "[ \t]")
 533                 unindented-ok
 534                 (skip-chars-forward "^ \t" end))
 535             (skip-chars-forward " \t" end)
 536             (or (= (point) end) (setq indent (current-column))))))
 537     (if indent
 538         (let ((opoint (point-marker)))
 539           (indent-to indent 0)
 540           (if (> opoint (point))
 541               (goto-char opoint))
 542           (move-marker opoint nil))
 543       (tab-to-tab-stop))))
 544
 545 (defcustom tab-stop-list
 546   nil
 547   "List of tab stop positions used by `tab-to-tab-stop'.
 548 This should be a list of integers, ordered from smallest to largest.
 549 It implicitly extends to infinity by repeating the last step (e.g. '(1 2 5)
 550 is equivalent to '(1 2 5 8 11)).
 551 If the list has less than 2 elements, `tab-width' is used as the \"last step\"."
 552   :group 'indent
 553   :type '(repeat integer))
 554 (put 'tab-stop-list 'safe-local-variable 'listp)
 555
 556 (defvar edit-tab-stops-map
 557   (let ((map (make-sparse-keymap)))
 558     (define-key map "\C-x\C-s" 'edit-tab-stops-note-changes)
 559     (define-key map "\C-c\C-c" 'edit-tab-stops-note-changes)
 560     map)
 561   "Keymap used in `edit-tab-stops'.")
 562
 563 (defvar edit-tab-stops-buffer nil
 564   "Buffer whose tab stops are being edited.
 565 This matters if the variable `tab-stop-list' is local in that buffer.")
 566
 567 (defun edit-tab-stops ()
 568   "Edit the tab stops used by `tab-to-tab-stop'.
 569 Creates a buffer *Tab Stops* containing text describing the tab stops.
 570 A colon indicates a column where there is a tab stop.
 571 You can add or remove colons and then do \\<edit-tab-stops-map>\\[edit-tab-stops-note-changes] to make changes take effect."
 572   (interactive)
 573   (setq edit-tab-stops-buffer (current-buffer))
 574   (switch-to-buffer (get-buffer-create "*Tab Stops*"))
 575   (use-local-map edit-tab-stops-map)
 576   (setq-local indent-tabs-mode nil)
 577   (overwrite-mode 1)
 578   (setq truncate-lines t)
 579   (erase-buffer)
 580   (let ((tabs tab-stop-list))
 581     (while tabs
 582       (indent-to (car tabs) 0)
 583       (insert ?:)
 584       (setq tabs (cdr tabs))))
 585   (let ((count 0))
 586     (insert ?\n)
 587     (while (< count 8)
 588       (insert (+ count ?0))
 589     (insert "         ")
 590       (setq count (1+ count)))
 591     (insert ?\n)
 592     (while (> count 0)
 593       (insert "0123456789")
 594       (setq count (1- count))))
 595   (insert "\nTo install changes, type C-c C-c")
 596   (goto-char (point-min)))
 597
 598 (defun edit-tab-stops-note-changes ()
 599   "Put edited tab stops into effect."
 600   (interactive)
 601     (let (tabs)
 602       (save-excursion
 603         (goto-char 1)
 604         (end-of-line)
 605         (while (search-backward ":" nil t)
 606           (setq tabs (cons (current-column) tabs))))
 607       (bury-buffer (prog1 (current-buffer)
 608                           (switch-to-buffer edit-tab-stops-buffer)))
 609       (setq tab-stop-list tabs))
 610   (message "Tab stops installed"))
 611
 612 (defun indent--next-tab-stop (column &optional prev)
 613   "Return the next tab stop after COLUMN.
 614 If PREV is non-nil, return the previous one instead."
 615   (let ((tabs tab-stop-list))
 616     (while (and tabs (>= column (car tabs)))
 617       (setq tabs (cdr tabs)))
 618     (if tabs
 619         (if (not prev)
 620             (car tabs)
 621           (let ((prevtabs (cdr (memq (car tabs) (reverse tab-stop-list)))))
 622             (if (null prevtabs) 0
 623               (if (= column (car prevtabs))
 624                   (or (nth 1 prevtabs) 0)
 625                 (car prevtabs)))))
 626       ;; We passed the end of tab-stop-list: guess a continuation.
 627       (let* ((last2 (last tab-stop-list 2))
 628              (step (if (cdr last2) (- (cadr last2) (car last2)) tab-width))
 629              (last (or (cadr last2) (car last2) 0)))
 630         ;; Repeat the last tab's length.
 631         (+ last (* step (if prev
 632                             (if (<= column last) -1 (/ (- column last 1) step))
 633                           (1+ (/ (- column last) step)))))))))
 634
 635 (defun tab-to-tab-stop ()
 636   "Insert spaces or tabs to next defined tab-stop column.
 637 The variable `tab-stop-list' is a list of columns at which there are tab stops.
 638 Use \\[edit-tab-stops] to edit them interactively."
 639   (interactive)
 640   (and abbrev-mode (= (char-syntax (preceding-char)) ?w)
 641        (expand-abbrev))
 642   (let ((nexttab (indent--next-tab-stop (current-column))))
 643     (delete-horizontal-space t)
 644     (indent-to nexttab)))
 645
 646 (defun move-to-tab-stop ()
 647   "Move point to next defined tab-stop column.
 648 The variable `tab-stop-list' is a list of columns at which there are tab stops.
 649 Use \\[edit-tab-stops] to edit them interactively."
 650   (interactive)
 651   (let ((nexttab (indent--next-tab-stop (current-column))))
 652     (let ((before (point)))
 653       (move-to-column nexttab t)
 654       (save-excursion
 655         (goto-char before)
 656         ;; If we just added a tab, or moved over one,
 657         ;; delete any superfluous spaces before the old point.
 658         (if (and (eq (preceding-char) ?\s)
 659                  (eq (following-char) ?\t))
 660             (let ((tabend (* (/ (current-column) tab-width) tab-width)))
 661               (while (and (> (current-column) tabend)
 662                           (eq (preceding-char) ?\s))
 663                 (forward-char -1))
 664               (delete-region (point) before)))))))
 665
 666 (define-key global-map "\t" 'indent-for-tab-command)
 667 (define-key esc-map "\C-\\" 'indent-region)
 668 (define-key ctl-x-map "\t" 'indent-rigidly)
 669 (define-key esc-map "i" 'tab-to-tab-stop)
 670
 671 ;;; indent.el ends here