emacs/lisp/indent.el

;;; indent.el --- indentation commands for Emacs

;; Copyright (C) 1985 Free Software Foundation, Inc.

;; Maintainer: FSF

;; This file is part of GNU Emacs.

;; GNU Emacs 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 2, or (at your option)
;; any later version.

;; 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
;; along with GNU Emacs; see the file COPYING.  If not, write to
;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

;;; Commentary:

;; Commands for making and changing indentation in text.  These are
;; described in the Emacs manual.

;;; Code:

(defvar standard-indent 4 "\
Default number of columns for margin-changing functions to indent.")

(defvar indent-line-function 'indent-to-left-margin "\
Function to indent current line.")

(defun indent-according-to-mode ()
  "Indent line in proper way for current major mode."
  (interactive)
  (funcall indent-line-function))

(defun indent-for-tab-command ()
  "Indent line in proper way for current major mode."
  (interactive)
  (if (eq indent-line-function 'indent-to-left-margin)
      (insert-tab)
    (funcall indent-line-function)))

(defun insert-tab ()
  (if abbrev-mode
      (expand-abbrev))
  (if indent-tabs-mode
      (insert ?\t)
    (indent-to (* tab-width (1+ (/ (current-column) tab-width))))))

(defun indent-rigidly (start end arg)
  "Indent all lines starting in the region sideways by ARG columns.
Called from a program, takes three arguments, START, END and ARG."
  (interactive "r\np")
  (save-excursion
    (goto-char end)
    (setq end (point-marker))
    (goto-char start)
    (or (bolp) (forward-line 1))
    (while (< (point) end)
      (let ((indent (current-indentation))
	    eol-flag)
	(save-excursion
	  (skip-chars-forward " \t")
	  (setq eol-flag (eolp)))
	(or eol-flag
	    (indent-to (max 0 (+ indent arg)) 0))
	(delete-region (point) (progn (skip-chars-forward " \t") (point))))
      (forward-line 1))
    (move-marker end nil)))

(defun indent-line-to (column)
  "Indent current line to COLUMN.
This function removes or adds spaces and tabs at beginning of line
only if necessary.  It leaves point at end of indentation."
  (beginning-of-line)
  (let ((bol (point))
	(cur-col (current-indentation)))
    (cond ((> cur-col column) ; too far right (after tab?)
	   (let ((beg (progn (move-to-column column t) (point))))
	     (back-to-indentation)
	     (delete-region beg (point))))
	  ((< cur-col column)
	   (back-to-indentation)
	   (indent-to column)))))

(defun current-left-margin ()
  "Return the left margin to use for this line.
This is the value of the buffer-local variable `left-margin' plus the value
of the `left-margin' text-property at the start of the line."
  (save-excursion
    (back-to-indentation)
    (max 0
	 (+ left-margin (or (get-text-property (point) 'left-margin) 0)))))

(defun move-to-left-margin (&optional n)
  "Move to the left margin of the current line.
With optional argument, move forward N-1 lines first.
The column moved to is the one given by the `left-margin' function, or the
column where text actually starts if the region is centered or right-justified.
When called interactively, this function corrects the line's indentation
if it appears to be incorrect.
When called noninteractively, however, it just moves to the beginning of
the text in this case."
  (interactive "p")
  (beginning-of-line n)
  (skip-chars-forward " \t")
  (if (not (memq (current-justification) '(right center)))
      (let ((cc (current-column))
	    (lm (current-left-margin)))
	(cond ((> cc lm)
	       (move-to-column lm t))
	      ((and (< cc lm) (interactive-p))
	       (indent-to-left-margin))))))

;; This is the default indent-line-function,
;; used in Fundamental Mode, Text Mode, etc.
(defun indent-to-left-margin ()
  "Indent current line to `left-margin'."
  (indent-line-to (current-left-margin)))

(defun delete-to-left-margin (from to)
  "Remove left-margin indentation from region.
This is careful only to delete whitespace, and not to delete any more than 
the \(current-left-margin) value for each line."
  (save-excursion
    (goto-char to)
    (setq to (point-marker))
    (goto-char from)
    (or (bolp) (forward-line 1))
    (while (< (point) to)
      (delete-region (point) (let ((lm (current-left-margin)))
			       (skip-chars-forward " \t")
			       (if (> (current-column) lm)
				   (move-to-column lm))
			       (point)))
      (forward-line 1))
    (move-marker to nil)))

(defun set-left-margin (from to lm)
  "Set the left margin of the region to WIDTH.
If `auto-fill-mode' is active, re-fill the region to fit the new margin."
  (interactive "r\nNSet left margin to column: ")
  (if (interactive-p) (setq lm (prefix-numeric-value lm)))
  (save-excursion
    ;; If inside indentation, start from BOL.
    (goto-char from)
    (skip-chars-backward " \t")
    (if (bolp) (setq from (point)))
    (goto-char to)
    (setq to (point-marker)))
  ;; Delete indentation first, so that paragraph indentation is preserved.
  (if auto-fill-function (delete-to-left-margin from to))
  (put-text-property from to 'left-margin lm)
  (if auto-fill-function (fill-region from to nil t t))
  (move-marker to nil))

(defun set-right-margin (from to lm)
  "Set the right margin of the region to WIDTH.
If `auto-fill-mode' is active, re-fill the region to fit the new margin."
  (interactive "r\nNSet left margin to column: ")
  (if (interactive-p) (setq lm (prefix-numeric-value lm)))
  (save-excursion
    (goto-char from)
    (skip-chars-backward " \t")
    (if (bolp) (setq from (point))))
  (put-text-property from to 'right-margin lm)
  (if auto-fill-function (fill-region from to nil t t)))

(defun alter-text-property (from to prop func &optional object)
  "Programmatically change value of a text-property.
For each region between FROM and TO that has a single value for PROPERTY,
apply FUNCTION to that value and sets the property to the function's result.
Optional fifth argument OBJECT specifies the string or buffer to operate on."
  (let ((begin from)
	end val)
    (while (setq val (get-text-property begin prop object)
		 end (text-property-not-all begin to prop val object))
      (put-text-property begin end prop (funcall func val) object)
      (setq begin end))
    (if (< begin to)
	(put-text-property begin to prop (funcall func val) object))))

(defun increase-left-margin (from to inc)
  "Increase or decrease the left-margin of the region.
With no prefix argument, this adds `standard-indent' of indentation.
A prefix arg (optional third arg INC noninteractively) specifies the amount
to change the margin by, in characters.
If `auto-fill-mode' is active, re-fill the region to fit the new margin."
  (interactive "*r\nP")
  (setq inc (if inc (prefix-numeric-value inc) standard-indent))
  (save-excursion
    (goto-char from)
    (skip-chars-backward " \t")
    (if (bolp) (setq from (point)))
    (goto-char to)
    (setq to (point-marker)))
  (if auto-fill-function (delete-to-left-margin from to))
  (alter-text-property from to 'left-margin
		       (lambda (v) (max 0 (+ inc (or v 0)))))
  (if auto-fill-function (fill-region from to nil t t))
  (move-marker to nil))

(defun decrease-left-margin (from to inc)
  "Make the left margin of the region smaller.
With no prefix argument, decrease the indentation by `standard-indent'.
A prefix arg (optional third arg INC noninteractively) specifies the amount
to change the margin by, in characters.
If `auto-fill-mode' is active, re-fill the region to fit the new margin."
  (interactive "*r\nP")
  (setq inc (if inc (prefix-numeric-value inc) standard-indent))
  (increase-left-margin from to (- inc)))

(defun increase-right-margin (from to inc)
  "Increase the right-margin of the region.
With no prefix argument, increase the right margin by `standard-indent'.
A prefix arg (optional third arg INC noninteractively) specifies the amount
to change the margin by, in characters.  A negative argument decreases
the right margin width.
If `auto-fill-mode' is active, re-fill the region to fit the new margin."
  (interactive "r\nP")
  (if (interactive-p)
      (setq inc (if inc (prefix-numeric-value current-prefix-arg)
		  standard-indent)))
  (save-excursion
    (alter-text-property from to 'right-margin
       (lambda (v) (max 0 (+ inc (or v 0)))))
    (if auto-fill-function
	(fill-region from to nil t t))))

(defun decrease-right-margin (from to inc)
  "Make the right margin of the region smaller.
With no prefix argument, decrease the right margin by `standard-indent'.
A prefix arg (optional third arg INC noninteractively) specifies the amount
of width to remove, in characters.  A negative argument increases
the right margin width.
If `auto-fill-mode' is active, re-fills region to fit in new margin."
  (interactive "*r\nP")
  (setq inc (if inc (prefix-numeric-value inc) standard-indent))
  (increase-right-margin from to (- inc)))

(defvar indent-region-function nil
  "Function which is short cut to indent region using indent-according-to-mode.
A value of nil means really run indent-according-to-mode on each line.")

(defun indent-region (start end column)
  "Indent each nonblank line in the region.
With no argument, indent each line using `indent-according-to-mode',
or use `indent-region-function' to do the whole region if that's non-nil.
If there is a fill prefix, make each line start with the fill prefix.
With argument COLUMN, indent each line to that column.
Called from a program, takes three args: START, END and COLUMN."
  (interactive "r\nP")
  (if (null column)
      (if fill-prefix
	  (save-excursion
	    (goto-char end)
	    (setq end (point-marker))
	    (goto-char start)
	    (let ((regexp (regexp-quote fill-prefix)))
	      (while (< (point) end)
		(or (looking-at regexp)
		    (and (bolp) (eolp))
		    (insert fill-prefix))
		(forward-line 1))))
	(if indent-region-function
	    (funcall indent-region-function start end)
	  (save-excursion
	    (goto-char end)
	    (setq end (point-marker))
	    (goto-char start)
	    (or (bolp) (forward-line 1))
	    (while (< (point) end)
	      (or (and (bolp) (eolp))
		  (funcall indent-line-function))
	      (forward-line 1))
	    (move-marker end nil))))
    (setq column (prefix-numeric-value column))
    (save-excursion
      (goto-char end)
      (setq end (point-marker))
      (goto-char start)
      (or (bolp) (forward-line 1))
      (while (< (point) end)
	(delete-region (point) (progn (skip-chars-forward " \t") (point)))
	(or (eolp)
	    (indent-to column 0))
	(forward-line 1))
      (move-marker end nil))))

(defun indent-relative-maybe ()
  "Indent a new line like previous nonblank line."
  (interactive)
  (indent-relative t))

(defun indent-relative (&optional unindented-ok)
  "Space out to under next indent point in previous nonblank line.
An indent point is a non-whitespace character following whitespace.
If the previous nonblank line has no indent points beyond the
column point starts at, `tab-to-tab-stop' is done instead."
  (interactive "P")
  (if abbrev-mode (expand-abbrev))
  (let ((start-column (current-column))
	indent)
    (save-excursion
      (beginning-of-line)
      (if (re-search-backward "^[^\n]" nil t)
	  (let ((end (save-excursion (forward-line 1) (point))))
	    (move-to-column start-column)
	    ;; Is start-column inside a tab on this line?
	    (if (> (current-column) start-column)
		(backward-char 1))
	    (or (looking-at "[ \t]")
		unindented-ok
		(skip-chars-forward "^ \t" end))
	    (skip-chars-forward " \t" end)
	    (or (= (point) end) (setq indent (current-column))))))
    (if indent
	(let ((opoint (point-marker)))
	  (delete-region (point) (progn (skip-chars-backward " \t") (point)))
	  (indent-to indent 0)
	  (if (> opoint (point))
	      (goto-char opoint))
	  (move-marker opoint nil))
      (tab-to-tab-stop))))

(defvar tab-stop-list
  '(8 16 24 32 40 48 56 64 72 80 88 96 104 112 120)
  "*List of tab stop positions used by `tab-to-tab-stops'.
This should be a list of integers, ordered from smallest to largest.")

(defvar edit-tab-stops-map nil "Keymap used in `edit-tab-stops'.")
(if edit-tab-stops-map
    nil
  (setq edit-tab-stops-map (make-sparse-keymap))
  (define-key edit-tab-stops-map "\C-x\C-s" 'edit-tab-stops-note-changes)
  (define-key edit-tab-stops-map "\C-c\C-c" 'edit-tab-stops-note-changes))

(defvar edit-tab-stops-buffer nil
  "Buffer whose tab stops are being edited--in case
the variable `tab-stop-list' is local in that buffer.")

(defun edit-tab-stops ()
  "Edit the tab stops used by `tab-to-tab-stop'.
Creates a buffer *Tab Stops* containing text describing the tab stops.
A colon indicates a column where there is a tab stop.
You can add or remove colons and then do \\<edit-tab-stops-map>\\[edit-tab-stops-note-changes] to make changes take effect."
  (interactive)
  (setq edit-tab-stops-buffer (current-buffer))
  (switch-to-buffer (get-buffer-create "*Tab Stops*"))
  (use-local-map edit-tab-stops-map)
  (make-local-variable 'indent-tabs-mode)
  (setq indent-tabs-mode nil)
  (overwrite-mode 1)
  (setq truncate-lines t)
  (erase-buffer)
  (let ((tabs tab-stop-list))
    (while tabs
      (indent-to (car tabs) 0)
      (insert ?:)
      (setq tabs (cdr tabs))))
  (let ((count 0))
    (insert ?\n)
    (while (< count 8)
      (insert (+ count ?0))
    (insert "         ")
      (setq count (1+ count)))
    (insert ?\n)
    (while (> count 0)
      (insert "0123456789")
      (setq count (1- count))))
  (insert "\nTo install changes, type C-c C-c")
  (goto-char (point-min)))

(defun edit-tab-stops-note-changes ()
  "Put edited tab stops into effect."
  (interactive)
    (let (tabs)
      (save-excursion
	(goto-char 1)
	(end-of-line)
	(while (search-backward ":" nil t)
	  (setq tabs (cons (current-column) tabs))))
      (bury-buffer (prog1 (current-buffer)
			  (switch-to-buffer edit-tab-stops-buffer)))
      (setq tab-stop-list tabs))
  (message "Tab stops installed"))

(defun tab-to-tab-stop ()
  "Insert spaces or tabs to next defined tab-stop column.
The variable `tab-stop-list' is a list of columns at which there are tab stops.
Use \\[edit-tab-stops] to edit them interactively."
  (interactive)
  (if abbrev-mode (expand-abbrev))
  (let ((tabs tab-stop-list))
    (while (and tabs (>= (current-column) (car tabs)))
      (setq tabs (cdr tabs)))
    (if tabs
	(let ((opoint (point)))
	  (skip-chars-backward " \t")
	  (delete-region (point) opoint)
	  (indent-to (car tabs)))
      (insert ?\ ))))

(defun move-to-tab-stop ()
  "Move point to next defined tab-stop column.
The variable `tab-stop-list' is a list of columns at which there are tab stops.
Use \\[edit-tab-stops] to edit them interactively."
  (interactive)
  (let ((tabs tab-stop-list))
    (while (and tabs (>= (current-column) (car tabs)))
      (setq tabs (cdr tabs)))
    (if tabs
	(let ((before (point)))
	  (move-to-column (car tabs) t)
	  (save-excursion
	    (goto-char before)
	    ;; If we just added a tab, or moved over one,
	    ;; delete any superfluous spaces before the old point.
	    (if (and (eq (preceding-char) ?\ )
		     (eq (following-char) ?\t))
		(let ((tabend (* (/ (current-column) tab-width) tab-width)))
		  (while (and (> (current-column) tabend)
			      (eq (preceding-char) ?\ ))
		    (forward-char -1))
		  (delete-region (point) before))))))))

(define-key global-map "\t" 'indent-for-tab-command)
(define-key esc-map "\034" 'indent-region)
(define-key ctl-x-map "\t" 'indent-rigidly)
(define-key esc-map "i" 'tab-to-tab-stop)

;;; indent.el ends here