lisp/paren.el

   1 ;;; paren.el --- highlight matching paren
   2
   3 ;; Copyright (C) 1993, 1996, 2001-2017 Free Software Foundation, Inc.
   4
   5 ;; Author: rms@gnu.org
   6 ;; Maintainer: emacs-devel@gnu.org
   7 ;; Keywords: languages, faces
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software: you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation, either version 3 of the License, or
  14 ;; (at your option) any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  23
  24 ;;; Commentary:
  25
  26 ;; Put this into your ~/.emacs:
  27
  28 ;;  (show-paren-mode t)
  29
  30 ;; It will display highlighting on whatever paren matches the one
  31 ;; before or after point.
  32
  33 ;;; Code:
  34
  35 (defgroup paren-showing nil
  36   "Showing (un)matching of parens and expressions."
  37   :prefix "show-paren-"
  38   :group 'paren-matching)
  39
  40 (defcustom show-paren-style 'parenthesis
  41   "Style used when showing a matching paren.
  42 Valid styles are `parenthesis' (meaning show the matching paren),
  43 `expression' (meaning show the entire expression enclosed by the paren) and
  44 `mixed' (meaning show the matching paren if it is visible, and the expression
  45 otherwise)."
  46   :type '(choice (const parenthesis) (const expression) (const mixed)))
  47
  48 (defcustom show-paren-delay 0.125
  49   "Time in seconds to delay before showing a matching paren.
  50 If you change this without using customize while `show-paren-mode' is
  51 active, you must toggle the mode off and on again for this to take effect."
  52   :type '(number :tag "seconds")
  53   :initialize 'custom-initialize-default
  54   :set (lambda (sym val)
  55          (if (not show-paren-mode)
  56              (set sym val)
  57            (show-paren-mode -1)
  58            (set sym val)
  59            (show-paren-mode 1))))
  60
  61 (defcustom show-paren-priority 1000
  62   "Priority of paren highlighting overlays."
  63   :type 'integer
  64   :version "21.1")
  65
  66 (defcustom show-paren-ring-bell-on-mismatch nil
  67   "If non-nil, beep if mismatched paren is detected."
  68   :type 'boolean
  69   :version "20.3")
  70
  71 (defcustom show-paren-when-point-inside-paren nil
  72   "If non-nil, show parens when point is just inside one.
  73 This will only be done when point isn't also just outside a paren."
  74   :type 'boolean
  75   :version "25.1")
  76
  77 (defcustom show-paren-when-point-in-periphery nil
  78   "If non-nil, show parens when point is in the line's periphery.
  79 The periphery is at the beginning or end of a line or in any
  80 whitespace there."
  81   :type 'boolean
  82   :version "25.1")
  83
  84 (defcustom show-paren-highlight-openparen t
  85   "Non-nil turns on openparen highlighting when matching forward.
  86 When nil, and point stands just before an open paren, the paren
  87 is not highlighted, the cursor being regarded as adequate to mark
  88 its position."
  89   :type 'boolean)
  90
  91 (defvar show-paren--idle-timer nil)
  92 (defvar show-paren--overlay
  93   (let ((ol (make-overlay (point) (point) nil t))) (delete-overlay ol) ol)
  94   "Overlay used to highlight the matching paren.")
  95 (defvar show-paren--overlay-1
  96   (let ((ol (make-overlay (point) (point) nil t))) (delete-overlay ol) ol)
  97   "Overlay used to highlight the paren at point.")
  98
  99
 100 ;;;###autoload
 101 (define-minor-mode show-paren-mode
 102   "Toggle visualization of matching parens (Show Paren mode).
 103 With a prefix argument ARG, enable Show Paren mode if ARG is
 104 positive, and disable it otherwise.  If called from Lisp, enable
 105 the mode if ARG is omitted or nil.
 106
 107 Show Paren mode is a global minor mode.  When enabled, any
 108 matching parenthesis is highlighted in `show-paren-style' after
 109 `show-paren-delay' seconds of Emacs idle time."
 110   :global t :group 'paren-showing
 111   ;; Enable or disable the mechanism.
 112   ;; First get rid of the old idle timer.
 113   (when show-paren--idle-timer
 114     (cancel-timer show-paren--idle-timer)
 115     (setq show-paren--idle-timer nil))
 116   (setq show-paren--idle-timer (run-with-idle-timer
 117                                 show-paren-delay t
 118                                 #'show-paren-function))
 119   (unless show-paren-mode
 120     (delete-overlay show-paren--overlay)
 121     (delete-overlay show-paren--overlay-1)))
 122
 123 (defun show-paren--unescaped-p (pos)
 124   "Determine whether the paren after POS is unescaped."
 125   (save-excursion
 126     (goto-char pos)
 127     (= (logand (skip-syntax-backward "/\\") 1) 0)))
 128
 129 (defun show-paren--categorize-paren (pos)
 130   "Determine whether the character after POS has paren syntax,
 131 and if so, return a cons (DIR . OUTSIDE), where DIR is 1 for an
 132 open paren, -1 for a close paren, and OUTSIDE is the buffer
 133 position of the outside of the paren.  If the character isn't a
 134 paren, or it is an escaped paren, return nil."
 135   (cond
 136    ((and (eq (syntax-class (syntax-after pos)) 4)
 137          (show-paren--unescaped-p pos))
 138     (cons 1 pos))
 139    ((and (eq (syntax-class (syntax-after pos)) 5)
 140          (show-paren--unescaped-p pos))
 141     (cons -1 (1+ pos)))))
 142
 143 (defun show-paren--locate-near-paren ()
 144   "Locate an unescaped paren \"near\" point to show.
 145 If one is found, return the cons (DIR . OUTSIDE), where DIR is 1
 146 for an open paren, -1 for a close paren, and OUTSIDE is the buffer
 147 position of the outside of the paren.  Otherwise return nil."
 148   (let* ((ind-pos (save-excursion (back-to-indentation) (point)))
 149          (eol-pos
 150           (save-excursion
 151             (end-of-line) (skip-chars-backward " \t" ind-pos) (point)))
 152          (before (show-paren--categorize-paren (1- (point))))
 153          (after (show-paren--categorize-paren (point))))
 154     (cond
 155      ;; Point is immediately outside a paren.
 156      ((eq (car before) -1) before)
 157      ((eq (car after) 1) after)
 158      ;; Point is immediately inside a paren.
 159      ((and show-paren-when-point-inside-paren before))
 160      ((and show-paren-when-point-inside-paren after))
 161      ;; Point is in the whitespace before the code.
 162      ((and show-paren-when-point-in-periphery
 163            (<= (point) ind-pos))
 164       (or (show-paren--categorize-paren ind-pos)
 165           (show-paren--categorize-paren (1- eol-pos))))
 166      ;; Point is in the whitespace after the code.
 167      ((and show-paren-when-point-in-periphery
 168            (>= (point) eol-pos))
 169       (show-paren--categorize-paren (1- eol-pos))))))
 170
 171 (defvar show-paren-data-function #'show-paren--default
 172   "Function to find the opener/closer \"near\" point and its match.
 173 The function is called with no argument and should return either nil
 174 if there's no opener/closer near point, or a list of the form
 175 \(HERE-BEG HERE-END THERE-BEG THERE-END MISMATCH)
 176 Where HERE-BEG..HERE-END is expected to be near point.")
 177
 178 (defun show-paren--default ()
 179   (let* ((temp (show-paren--locate-near-paren))
 180          (dir (car temp))
 181          (outside (cdr temp))
 182          pos mismatch here-beg here-end)
 183     ;;
 184     ;; Find the other end of the sexp.
 185     (when dir
 186       (setq here-beg (if (eq dir 1) outside (1- outside))
 187             here-end (if (eq dir 1) (1+ outside) outside))
 188       (save-restriction
 189         ;; Determine the range within which to look for a match.
 190         (when blink-matching-paren-distance
 191           (narrow-to-region
 192            (max (point-min) (- (point) blink-matching-paren-distance))
 193            (min (point-max) (+ (point) blink-matching-paren-distance))))
 194         ;; Scan across one sexp within that range.
 195         ;; Errors or nil mean there is a mismatch.
 196         (condition-case ()
 197             (setq pos (scan-sexps outside dir))
 198           (error (setq pos t mismatch t)))
 199         ;; Move back the other way and verify we get back to the
 200         ;; starting point.  If not, these two parens don't really match.
 201         ;; Maybe the one at point is escaped and doesn't really count,
 202         ;; or one is inside a comment.
 203         (when (integerp pos)
 204           (unless (condition-case ()
 205                       (eq outside (scan-sexps pos (- dir)))
 206                     (error nil))
 207             (setq pos nil)))
 208         ;; If found a "matching" paren, see if it is the right
 209         ;; kind of paren to match the one we started at.
 210         (if (not (integerp pos))
 211             (if mismatch (list here-beg here-end nil nil t))
 212           (let ((beg (min pos outside)) (end (max pos outside)))
 213             (unless (eq (syntax-class (syntax-after beg)) 8)
 214               (setq mismatch
 215                     (not (or (eq (char-before end)
 216                                  ;; This can give nil.
 217                                  (cdr (syntax-after beg)))
 218                              (eq (char-after beg)
 219                                  ;; This can give nil.
 220                                  (cdr (syntax-after (1- end))))
 221                              ;; The cdr might hold a new paren-class
 222                              ;; info rather than a matching-char info,
 223                              ;; in which case the two CDRs should match.
 224                              (eq (cdr (syntax-after (1- end)))
 225                                  (cdr (syntax-after beg)))))))
 226             (list here-beg here-end
 227                   (if (= dir 1) (1- pos) pos)
 228                   (if (= dir 1) pos (1+ pos))
 229                   mismatch)))))))
 230
 231 ;; Find the place to show, if there is one,
 232 ;; and show it until input arrives.
 233 (defun show-paren-function ()
 234   (let ((data (and show-paren-mode (funcall show-paren-data-function))))
 235     (if (not data)
 236         (progn
 237           ;; If show-paren-mode is nil in this buffer or if not at a paren that
 238           ;; has a match, turn off any previous paren highlighting.
 239           (delete-overlay show-paren--overlay)
 240           (delete-overlay show-paren--overlay-1))
 241
 242       ;; Found something to highlight.
 243       (let* ((here-beg (nth 0 data))
 244              (here-end (nth 1 data))
 245              (there-beg (nth 2 data))
 246              (there-end (nth 3 data))
 247              (mismatch (nth 4 data))
 248              (face
 249               (if mismatch
 250                   (progn
 251                     (if show-paren-ring-bell-on-mismatch
 252                         (beep))
 253                     'show-paren-mismatch)
 254                 'show-paren-match)))
 255         ;;
 256         ;; If matching backwards, highlight the closeparen
 257         ;; before point as well as its matching open.
 258         ;; If matching forward, and the openparen is unbalanced,
 259         ;; highlight the paren at point to indicate misbalance.
 260         ;; Otherwise, turn off any such highlighting.
 261         (if (or (not here-beg)
 262                 (and (not show-paren-highlight-openparen)
 263                      (> here-end (point))
 264                      (<= here-beg (point))
 265                      (integerp there-beg)))
 266             (delete-overlay show-paren--overlay-1)
 267           (move-overlay show-paren--overlay-1
 268                         here-beg here-end (current-buffer))
 269           ;; Always set the overlay face, since it varies.
 270           (overlay-put show-paren--overlay-1 'priority show-paren-priority)
 271           (overlay-put show-paren--overlay-1 'face face))
 272         ;;
 273         ;; Turn on highlighting for the matching paren, if found.
 274         ;; If it's an unmatched paren, turn off any such highlighting.
 275         (if (not there-beg)
 276             (delete-overlay show-paren--overlay)
 277           (if (or (eq show-paren-style 'expression)
 278                   (and (eq show-paren-style 'mixed)
 279                        (let ((closest (if (< there-beg here-beg)
 280                                           (1- there-end) (1+ there-beg))))
 281                          (not (pos-visible-in-window-p closest)))))
 282               (move-overlay show-paren--overlay
 283                             (if (< there-beg here-beg) here-end here-beg)
 284                             (if (< there-beg here-beg) there-beg there-end)
 285                             (current-buffer))
 286             (move-overlay show-paren--overlay
 287                           there-beg there-end (current-buffer)))
 288           ;; Always set the overlay face, since it varies.
 289           (overlay-put show-paren--overlay 'priority show-paren-priority)
 290           (overlay-put show-paren--overlay 'face face))))))
 291
 292 (provide 'paren)
 293
 294 ;;; paren.el ends here