lisp/font-core.el

   1 ;;; font-core.el --- Core interface to font-lock
   2
   3 ;; Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
   4 ;;   2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
   5
   6 ;; Maintainer: FSF
   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, or (at your option)
  14 ;; 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; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  24 ;; Boston, MA 02110-1301, USA.
  25
  26 ;;; Code:
  27
  28 ;; This variable is used by mode packages that support Font Lock mode by
  29 ;; defining their own keywords to use for `font-lock-keywords'.  (The mode
  30 ;; command should make it buffer-local and set it to provide the set up.)
  31 (defvar font-lock-defaults nil
  32   "Defaults for Font Lock mode specified by the major mode.
  33 Defaults should be of the form:
  34
  35  (KEYWORDS [KEYWORDS-ONLY [CASE-FOLD [SYNTAX-ALIST [SYNTAX-BEGIN ...]]]])
  36
  37 KEYWORDS may be a symbol (a variable or function whose value is the keywords to
  38 use for fontification) or a list of symbols.  If KEYWORDS-ONLY is non-nil,
  39 syntactic fontification (strings and comments) is not performed.
  40 If CASE-FOLD is non-nil, the case of the keywords is ignored when fontifying.
  41 If SYNTAX-ALIST is non-nil, it should be a list of cons pairs of the form
  42 \(CHAR-OR-STRING . STRING) used to set the local Font Lock syntax table, for
  43 keyword and syntactic fontification (see `modify-syntax-entry').
  44
  45 If SYNTAX-BEGIN is non-nil, it should be a function with no args used to move
  46 backwards outside any enclosing syntactic block, for syntactic fontification.
  47 Typical values are `beginning-of-line' (i.e., the start of the line is known to
  48 be outside a syntactic block), or `beginning-of-defun' for programming modes or
  49 `backward-paragraph' for textual modes (i.e., the mode-dependent function is
  50 known to move outside a syntactic block).  If nil, the beginning of the buffer
  51 is used as a position outside of a syntactic block, in the worst case.
  52
  53 These item elements are used by Font Lock mode to set the variables
  54 `font-lock-keywords', `font-lock-keywords-only',
  55 `font-lock-keywords-case-fold-search', `font-lock-syntax-table' and
  56 `font-lock-beginning-of-syntax-function', respectively.
  57
  58 Further item elements are alists of the form (VARIABLE . VALUE) and are in no
  59 particular order.  Each VARIABLE is made buffer-local before set to VALUE.
  60
  61 Currently, appropriate variables include `font-lock-mark-block-function'.
  62 If this is non-nil, it should be a function with no args used to mark any
  63 enclosing block of text, for fontification via \\[font-lock-fontify-block].
  64 Typical values are `mark-defun' for programming modes or `mark-paragraph' for
  65 textual modes (i.e., the mode-dependent function is known to put point and mark
  66 around a text block relevant to that mode).
  67
  68 Other variables include that for syntactic keyword fontification,
  69 `font-lock-syntactic-keywords' and those for buffer-specialized fontification
  70 functions, `font-lock-fontify-buffer-function',
  71 `font-lock-unfontify-buffer-function', `font-lock-fontify-region-function',
  72 `font-lock-unfontify-region-function', and `font-lock-inhibit-thing-lock'.")
  73 (make-variable-buffer-local 'font-lock-defaults)
  74
  75 (defvar font-lock-defaults-alist nil
  76   "Alist of fall-back Font Lock defaults for major modes.
  77
  78 Each item should be a list of the form:
  79
  80  (MAJOR-MODE . FONT-LOCK-DEFAULTS)
  81
  82 where MAJOR-MODE is a symbol and FONT-LOCK-DEFAULTS is a list of default
  83 settings.  See the variable `font-lock-defaults', which takes precedence.")
  84 (make-obsolete-variable 'font-lock-defaults-alist 'font-lock-defaults)
  85
  86 (defvar font-lock-function 'font-lock-default-function
  87   "A function which is called when `font-lock-mode' is toggled.
  88 It will be passed one argument, which is the current value of
  89 `font-lock-mode'.")
  90
  91 ;; The mode for which font-lock was initialized, or nil if none.
  92 (defvar font-lock-mode-major-mode)
  93 (define-minor-mode font-lock-mode
  94   "Toggle Font Lock mode.
  95 With arg, turn Font Lock mode off if and only if arg is a non-positive
  96 number; if arg is nil, toggle Font Lock mode; anything else turns Font
  97 Lock on.
  98 \(Font Lock is also known as \"syntax highlighting\".)
  99
 100 When Font Lock mode is enabled, text is fontified as you type it:
 101
 102  - Comments are displayed in `font-lock-comment-face';
 103  - Strings are displayed in `font-lock-string-face';
 104  - Certain other expressions are displayed in other faces according to the
 105    value of the variable `font-lock-keywords'.
 106
 107 To customize the faces (colors, fonts, etc.) used by Font Lock for
 108 fontifying different parts of buffer text, use \\[customize-face].
 109
 110 You can enable Font Lock mode in any major mode automatically by turning on in
 111 the major mode's hook.  For example, put in your ~/.emacs:
 112
 113  (add-hook 'c-mode-hook 'turn-on-font-lock)
 114
 115 Alternatively, you can use Global Font Lock mode to automagically turn on Font
 116 Lock mode in buffers whose major mode supports it and whose major mode is one
 117 of `font-lock-global-modes'.  For example, put in your ~/.emacs:
 118
 119  (global-font-lock-mode t)
 120
 121 Where major modes support different levels of fontification, you can use
 122 the variable `font-lock-maximum-decoration' to specify which level you
 123 generally prefer.  When you turn Font Lock mode on/off the buffer is
 124 fontified/defontified, though fontification occurs only if the buffer is
 125 less than `font-lock-maximum-size'.
 126
 127 To add your own highlighting for some major mode, and modify the highlighting
 128 selected automatically via the variable `font-lock-maximum-decoration', you can
 129 use `font-lock-add-keywords'.
 130
 131 To fontify a buffer, without turning on Font Lock mode and regardless of buffer
 132 size, you can use \\[font-lock-fontify-buffer].
 133
 134 To fontify a block (the function or paragraph containing point, or a number of
 135 lines around point), perhaps because modification on the current line caused
 136 syntactic change on other lines, you can use \\[font-lock-fontify-block].
 137
 138 See the variable `font-lock-defaults-alist' for the Font Lock mode default
 139 settings.  You can set your own default settings for some mode, by setting a
 140 buffer local value for `font-lock-defaults', via its mode hook.
 141
 142 The above is the default behavior of `font-lock-mode'; you may specify
 143 your own function which is called when `font-lock-mode' is toggled via
 144 `font-lock-function'. "
 145   nil nil nil
 146   ;; Don't turn on Font Lock mode if we don't have a display (we're running a
 147   ;; batch job) or if the buffer is invisible (the name starts with a space).
 148   (when (or noninteractive (eq (aref (buffer-name) 0) ?\s))
 149     (setq font-lock-mode nil))
 150   (funcall font-lock-function font-lock-mode)
 151   ;; Arrange to unfontify this buffer if we change major mode later.
 152   (if font-lock-mode
 153       (add-hook 'change-major-mode-hook 'font-lock-change-mode nil t)
 154     (remove-hook 'change-major-mode-hook 'font-lock-change-mode t))
 155   (when font-lock-mode
 156     (setq font-lock-mode-major-mode major-mode)))
 157
 158 ;; Get rid of fontification for the old major mode.
 159 ;; We do this when changing major modes.
 160 (defun font-lock-change-mode ()
 161   (font-lock-mode -1))
 162
 163 (defun font-lock-defontify ()
 164   "Clear out all `font-lock-face' properties in current buffer.
 165 A major mode that uses `font-lock-face' properties might want to put
 166 this function onto `change-major-mode-hook'."
 167   (let ((modp (buffer-modified-p))
 168         (inhibit-read-only t))
 169     (save-restriction
 170       (widen)
 171       (remove-list-of-text-properties (point-min) (point-max)
 172                                       '(font-lock-face)))
 173     (restore-buffer-modified-p modp)))
 174
 175 (defvar font-lock-set-defaults)
 176 (defun font-lock-default-function (mode)
 177   ;; Turn on Font Lock mode.
 178   (when mode
 179     (set (make-local-variable 'char-property-alias-alist)
 180          (copy-tree char-property-alias-alist))
 181     ;; Add `font-lock-face' as an alias for the `face' property.
 182     (let ((elt (assq 'face char-property-alias-alist)))
 183       (if elt
 184           (unless (memq 'font-lock-face (cdr elt))
 185             (setcdr elt (nconc (cdr elt) (list 'font-lock-face))))
 186         (push (list 'face 'font-lock-face) char-property-alias-alist))))
 187   ;; Turn off Font Lock mode.
 188   (unless mode
 189     ;; Remove `font-lock-face' as an alias for the `face' property.
 190     (set (make-local-variable 'char-property-alias-alist)
 191          (copy-tree char-property-alias-alist))
 192     (let ((elt (assq 'face char-property-alias-alist)))
 193       (when elt
 194         (setcdr elt (remq 'font-lock-face (cdr elt)))
 195         (when (null (cdr elt))
 196           (setq char-property-alias-alist
 197                 (delq elt char-property-alias-alist))))))
 198
 199   ;; Only do hard work if the mode has specified stuff in
 200   ;; `font-lock-defaults'.
 201   (when (or font-lock-defaults
 202             (if (boundp 'font-lock-keywords) font-lock-keywords)
 203             (with-no-warnings
 204               (cdr (assq major-mode font-lock-defaults-alist)))
 205             (and mode
 206                  (boundp 'font-lock-set-defaults)
 207                  font-lock-set-defaults
 208                  font-lock-mode-major-mode
 209                  (not (eq font-lock-mode-major-mode major-mode))))
 210     (font-lock-mode-internal mode)))
 211
 212 (defun turn-on-font-lock ()
 213   "Turn on Font Lock mode (only if the terminal can display it)."
 214   (unless font-lock-mode
 215     (font-lock-mode)))
 216
 217 ;;; Global Font Lock mode.
 218
 219 ;; A few people have hassled in the past for a way to make it easier to turn on
 220 ;; Font Lock mode, without the user needing to know for which modes s/he has to
 221 ;; turn it on, perhaps the same way hilit19.el/hl319.el does.  I've always
 222 ;; balked at that way, as I see it as just re-moulding the same problem in
 223 ;; another form.  That is; some person would still have to keep track of which
 224 ;; modes (which may not even be distributed with Emacs) support Font Lock mode.
 225 ;; The list would always be out of date.  And that person might have to be me.
 226
 227 ;; Implementation.
 228 ;;
 229 ;; In a previous discussion the following hack came to mind.  It is a gross
 230 ;; hack, but it generally works.  We use the convention that major modes start
 231 ;; by calling the function `kill-all-local-variables', which in turn runs
 232 ;; functions on the hook variable `change-major-mode-hook'.  We attach our
 233 ;; function `font-lock-change-major-mode' to that hook.  Of course, when this
 234 ;; hook is run, the major mode is in the process of being changed and we do not
 235 ;; know what the final major mode will be.  So, `font-lock-change-major-mode'
 236 ;; only (a) notes the name of the current buffer, and (b) adds our function
 237 ;; `turn-on-font-lock-if-desired' to the hook variables
 238 ;; `after-change-major-mode-hook' and `post-command-hook' (for modes
 239 ;; that do not yet run `after-change-major-mode-hook').  By the time
 240 ;; the functions on the first of these hooks to be run are run, the new major
 241 ;; mode is assumed to be in place.  This way we get a Font Lock function run
 242 ;; when a major mode is turned on, without knowing major modes or their hooks.
 243 ;;
 244 ;; Naturally this requires that major modes run `kill-all-local-variables'
 245 ;; and `after-change-major-mode-hook', as they are supposed to.  For modes
 246 ;; that do not run `after-change-major-mode-hook' yet, `post-command-hook'
 247 ;; takes care of things if the mode is set directly or indirectly by
 248 ;; an interactive command; however, problems can occur if the mode is
 249 ;; set by a timer or process: in that case, proper handling of Font Lock mode
 250 ;; may be delayed until the next interactive command.
 251
 252 ;; User interface.
 253 ;;
 254 ;; Although Global Font Lock mode is a pseudo-mode, I think that the user
 255 ;; interface should conform to the usual Emacs convention for modes, i.e., a
 256 ;; command to toggle the feature (`global-font-lock-mode') with a variable for
 257 ;; finer control of the mode's behaviour (`font-lock-global-modes').
 258 ;;
 259 ;; The feature should not be enabled by loading font-lock.el, since other
 260 ;; mechanisms for turning on Font Lock mode, such as M-x font-lock-mode RET or
 261 ;; (add-hook 'c-mode-hook 'turn-on-font-lock), would cause Font Lock mode to be
 262 ;; turned on everywhere.  That would not be intuitive or informative because
 263 ;; loading a file tells you nothing about the feature or how to control it.  It
 264 ;; would also be contrary to the Principle of Least Surprise.  sm.
 265
 266 (defcustom font-lock-global-modes t
 267   "*Modes for which Font Lock mode is automagically turned on.
 268 Global Font Lock mode is controlled by the command `global-font-lock-mode'.
 269 If nil, means no modes have Font Lock mode automatically turned on.
 270 If t, all modes that support Font Lock mode have it automatically turned on.
 271 If a list, it should be a list of `major-mode' symbol names for which Font Lock
 272 mode should be automatically turned on.  The sense of the list is negated if it
 273 begins with `not'.  For example:
 274  (c-mode c++-mode)
 275 means that Font Lock mode is turned on for buffers in C and C++ modes only."
 276   :type '(choice (const :tag "none" nil)
 277                  (const :tag "all" t)
 278                  (set :menu-tag "mode specific" :tag "modes"
 279                       :value (not)
 280                       (const :tag "Except" not)
 281                       (repeat :inline t (symbol :tag "mode"))))
 282   :group 'font-lock)
 283
 284 (defun turn-on-font-lock-if-desired ()
 285   (when (cond ((eq font-lock-global-modes t)
 286                t)
 287               ((eq (car-safe font-lock-global-modes) 'not)
 288                (not (memq major-mode (cdr font-lock-global-modes))))
 289               (t (memq major-mode (cdr font-lock-global-modes))))
 290     (let (inhibit-quit)
 291       (turn-on-font-lock))))
 292
 293 (define-globalized-minor-mode global-font-lock-mode
 294   font-lock-mode turn-on-font-lock-if-desired
 295   :extra-args (dummy)
 296   :initialize 'custom-initialize-safe-default
 297   :init-value (not (or noninteractive emacs-basic-display))
 298   :group 'font-lock
 299   :version "22.1")
 300
 301 ;;; End of Global Font Lock mode.
 302
 303 (provide 'font-core)
 304
 305 ;; arch-tag: f8c286e1-02f7-41d9-b89b-1b67780aed71
 306 ;;; font-core.el ends here