lisp/font-core.el

   1 ;;; font-core.el --- Core interface to font-lock
   2
   3 ;; Copyright (C) 1992, 93, 94, 95, 96, 97, 98, 1999, 2000, 2001, 2002
   4 ;;  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 2, 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., 59 Temple Place - Suite 330,
  24 ;; Boston, MA 02111-1307, 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'
  70 and those for buffer-specialised fontification functions,
  71 `font-lock-fontify-buffer-function', `font-lock-unfontify-buffer-function',
  72 `font-lock-fontify-region-function', `font-lock-unfontify-region-function',
  73 `font-lock-inhibit-thing-lock' and `font-lock-maximum-size'.")
  74 (make-variable-buffer-local 'font-lock-defaults)
  75
  76 (defvar font-lock-core-only nil
  77   "If non-nil, then don't load font-lock.el unless necessary.")
  78
  79 ;; This variable is used where font-lock.el itself supplies the
  80 ;; keywords.  Really, this shouldn't need to be in font-core.el, but
  81 ;; we can't avoid it.  In the future, this stuff will hopefully be
  82 ;; moved to cc-mode itself.
  83 (defvar font-lock-defaults-alist
  84   (let (;; We use `beginning-of-defun', rather than nil, for SYNTAX-BEGIN.
  85         ;; Thus the calculation of the cache is usually faster but not
  86         ;; infallible, so we risk mis-fontification.  sm.
  87         (c-mode-defaults
  88          '((c-font-lock-keywords c-font-lock-keywords-1
  89             c-font-lock-keywords-2 c-font-lock-keywords-3)
  90            nil nil ((?_ . "w")) beginning-of-defun
  91            (font-lock-syntactic-face-function
  92             . c-font-lock-syntactic-face-function)
  93            (font-lock-mark-block-function . mark-defun)))
  94         (c++-mode-defaults
  95          '((c++-font-lock-keywords c++-font-lock-keywords-1
  96             c++-font-lock-keywords-2 c++-font-lock-keywords-3)
  97            nil nil ((?_ . "w")) beginning-of-defun
  98            (font-lock-syntactic-face-function
  99             . c-font-lock-syntactic-face-function)
 100            (font-lock-mark-block-function . mark-defun)))
 101         (objc-mode-defaults
 102          '((objc-font-lock-keywords objc-font-lock-keywords-1
 103             objc-font-lock-keywords-2 objc-font-lock-keywords-3)
 104            nil nil ((?_ . "w") (?$ . "w")) nil
 105            (font-lock-syntactic-face-function
 106             . c-font-lock-syntactic-face-function)
 107            (font-lock-mark-block-function . mark-defun)))
 108         (java-mode-defaults
 109          '((java-font-lock-keywords java-font-lock-keywords-1
 110             java-font-lock-keywords-2 java-font-lock-keywords-3)
 111            nil nil ((?_ . "w") (?$ . "w")) nil
 112            (font-lock-syntactic-face-function
 113             . java-font-lock-syntactic-face-function)
 114            (font-lock-mark-block-function . mark-defun))))
 115     (list
 116      (cons 'c-mode                      c-mode-defaults)
 117      (cons 'c++-mode                    c++-mode-defaults)
 118      (cons 'objc-mode                   objc-mode-defaults)
 119      (cons 'java-mode                   java-mode-defaults)))
 120   "Alist of fall-back Font Lock defaults for major modes.
 121
 122 This variable should not be used any more.
 123 Set the buffer-local `font-lock-keywords' in the major mode instead.
 124
 125 Each item should be a list of the form:
 126
 127  (MAJOR-MODE . FONT-LOCK-DEFAULTS)
 128
 129 where MAJOR-MODE is a symbol and FONT-LOCK-DEFAULTS is a list of default
 130 settings.  See the variable `font-lock-defaults', which takes precedence.")
 131 (make-obsolete-variable 'font-lock-defaults-alist 'font-lock-defaults)
 132
 133 (defvar font-lock-multiline nil
 134   "Whether font-lock should cater to multiline keywords.
 135 If nil, don't try to handle multiline patterns.
 136 If t, always handle multiline patterns.
 137 If `undecided', don't try to handle multiline patterns until you see one.
 138 Major/minor modes can set this variable if they know which option applies.")
 139
 140 (defvar font-lock-fontified nil)        ; Whether we have fontified the buffer.
 141
 142 (defvar font-lock-function 'font-lock-default-function
 143   "A function which is called when `font-lock-mode' is toggled.
 144 It will be passed one argument, which is the current value of
 145 `font-lock-mode'.")
 146 (make-variable-buffer-local 'font-lock-default-function)
 147
 148 (define-minor-mode font-lock-mode
 149   "Toggle Font Lock mode.
 150 With arg, turn Font Lock mode off if and only if arg is a non-positive
 151 number; if arg is nil, toggle Font Lock mode; anything else turns Font
 152 Lock on.
 153 \(Font Lock is also known as \"syntax highlighting\".)
 154
 155 When Font Lock mode is enabled, text is fontified as you type it:
 156
 157  - Comments are displayed in `font-lock-comment-face';
 158  - Strings are displayed in `font-lock-string-face';
 159  - Certain other expressions are displayed in other faces according to the
 160    value of the variable `font-lock-keywords'.
 161
 162 To customize the faces (colors, fonts, etc.) used by Font Lock for
 163 fontifying different parts of buffer text, use \\[customize-face].
 164
 165 You can enable Font Lock mode in any major mode automatically by turning on in
 166 the major mode's hook.  For example, put in your ~/.emacs:
 167
 168  (add-hook 'c-mode-hook 'turn-on-font-lock)
 169
 170 Alternatively, you can use Global Font Lock mode to automagically turn on Font
 171 Lock mode in buffers whose major mode supports it and whose major mode is one
 172 of `font-lock-global-modes'.  For example, put in your ~/.emacs:
 173
 174  (global-font-lock-mode t)
 175
 176 There are a number of support modes that may be used to speed up Font Lock mode
 177 in various ways, specified via the variable `font-lock-support-mode'.  Where
 178 major modes support different levels of fontification, you can use the variable
 179 `font-lock-maximum-decoration' to specify which level you generally prefer.
 180 When you turn Font Lock mode on/off the buffer is fontified/defontified, though
 181 fontification occurs only if the buffer is less than `font-lock-maximum-size'.
 182
 183 For example, to specify that Font Lock mode use use Lazy Lock mode as a support
 184 mode and use maximum levels of fontification, put in your ~/.emacs:
 185
 186  (setq font-lock-support-mode 'lazy-lock-mode)
 187  (setq font-lock-maximum-decoration t)
 188
 189 To add your own highlighting for some major mode, and modify the highlighting
 190 selected automatically via the variable `font-lock-maximum-decoration', you can
 191 use `font-lock-add-keywords'.
 192
 193 To fontify a buffer, without turning on Font Lock mode and regardless of buffer
 194 size, you can use \\[font-lock-fontify-buffer].
 195
 196 To fontify a block (the function or paragraph containing point, or a number of
 197 lines around point), perhaps because modification on the current line caused
 198 syntactic change on other lines, you can use \\[font-lock-fontify-block].
 199
 200 See the variable `font-lock-defaults-alist' for the Font Lock mode default
 201 settings.  You can set your own default settings for some mode, by setting a
 202 buffer local value for `font-lock-defaults', via its mode hook.
 203
 204 The above is the default behavior of `font-lock-mode'; you may specify
 205 your own function which is called when `font-lock-mode' is toggled via
 206 `font-lock-function'. "
 207   nil nil nil
 208   ;; Don't turn on Font Lock mode if we don't have a display (we're running a
 209   ;; batch job) or if the buffer is invisible (the name starts with a space).
 210   (when (or noninteractive (eq (aref (buffer-name) 0) ?\ ))
 211     (setq font-lock-mode nil))
 212   (funcall font-lock-function font-lock-mode))
 213
 214 (defun font-lock-default-function (font-lock-mode)
 215   ;; Turn on Font Lock mode.
 216   (when font-lock-mode
 217     (font-lock-set-defaults)
 218     (set (make-local-variable 'char-property-alias-alist)
 219          (copy-tree char-property-alias-alist))
 220     ;; Add `font-lock-face' as an alias for the `face' property.
 221     (let ((elt (assq 'face char-property-alias-alist)))
 222       (if elt
 223           (unless (memq 'font-lock-face (cdr elt))
 224             (setcdr elt (nconc (cdr elt) (list 'font-lock-face))))
 225         (push (list 'face 'font-lock-face) char-property-alias-alist)))
 226     ;; Only do hard work if the mode has specified stuff in
 227     ;; `font-lock-defaults'.
 228     (when font-lock-defaults
 229       (add-hook 'after-change-functions 'font-lock-after-change-function t t)
 230       (font-lock-turn-on-thing-lock)
 231       ;; Fontify the buffer if we have to.
 232       (let ((max-size (font-lock-value-in-major-mode font-lock-maximum-size)))
 233         (cond (font-lock-fontified
 234                nil)
 235               ((or (null max-size) (> max-size (buffer-size)))
 236                (font-lock-fontify-buffer))
 237               (font-lock-verbose
 238                (message "Fontifying %s...buffer size greater than font-lock-maximum-size"
 239                         (buffer-name)))))))
 240   ;; Turn off Font Lock mode.
 241   (unless font-lock-mode
 242     ;; Remove `font-lock-face' as an alias for the `face' property.
 243     (set (make-local-variable 'char-property-alias-alist)
 244          (copy-tree char-property-alias-alist))
 245     (let ((elt (assq 'face char-property-alias-alist)))
 246       (when elt
 247         (setcdr elt (remq 'font-lock-face (cdr elt)))
 248         (when (null (cdr elt))
 249           (setq char-property-alias-alist (delq elt char-property-alias-alist)))))
 250     (when font-lock-defaults
 251       (remove-hook 'after-change-functions 'font-lock-after-change-function t)
 252       (font-lock-unfontify-buffer)
 253       (font-lock-turn-off-thing-lock))))
 254
 255 (defun turn-on-font-lock ()
 256   "Turn on Font Lock mode (only if the terminal can display it)."
 257   (unless font-lock-mode
 258     (font-lock-mode)))
 259
 260 (defvar font-lock-set-defaults nil)     ; Whether we have set up defaults.
 261
 262 (defun font-lock-set-defaults ()
 263   "Set fontification defaults appropriately for this mode.
 264 Sets various variables using `font-lock-defaults' (or, if nil, using
 265 `font-lock-defaults-alist') and `font-lock-maximum-decoration'."
 266   (unless font-lock-set-defaults
 267     (set (make-local-variable 'font-lock-set-defaults) t)
 268     (make-local-variable 'font-lock-fontified)
 269     (make-local-variable 'font-lock-multiline)
 270     (let ((defaults (or font-lock-defaults
 271                         (assq major-mode font-lock-defaults-alist))))
 272       (when (and defaults
 273                  ;; Detect if this is a simple mode, which doesn't use
 274                  ;; any syntactic fontification functions.
 275                  (not (cdr (assq 'font-lock-core-only
 276                                  (nthcdr 5 defaults)))))
 277         (require 'font-lock)
 278         (font-lock-set-defaults-1)))))
 279
 280 ;;; Global Font Lock mode.
 281
 282 ;; A few people have hassled in the past for a way to make it easier to turn on
 283 ;; Font Lock mode, without the user needing to know for which modes s/he has to
 284 ;; turn it on, perhaps the same way hilit19.el/hl319.el does.  I've always
 285 ;; balked at that way, as I see it as just re-moulding the same problem in
 286 ;; another form.  That is; some person would still have to keep track of which
 287 ;; modes (which may not even be distributed with Emacs) support Font Lock mode.
 288 ;; The list would always be out of date.  And that person might have to be me.
 289
 290 ;; Implementation.
 291 ;;
 292 ;; In a previous discussion the following hack came to mind.  It is a gross
 293 ;; hack, but it generally works.  We use the convention that major modes start
 294 ;; by calling the function `kill-all-local-variables', which in turn runs
 295 ;; functions on the hook variable `change-major-mode-hook'.  We attach our
 296 ;; function `font-lock-change-major-mode' to that hook.  Of course, when this
 297 ;; hook is run, the major mode is in the process of being changed and we do not
 298 ;; know what the final major mode will be.  So, `font-lock-change-major-mode'
 299 ;; only (a) notes the name of the current buffer, and (b) adds our function
 300 ;; `turn-on-font-lock-if-enabled' to the hook variables `find-file-hooks' and
 301 ;; `post-command-hook' (for buffers that are not visiting files).  By the time
 302 ;; the functions on the first of these hooks to be run are run, the new major
 303 ;; mode is assumed to be in place.  This way we get a Font Lock function run
 304 ;; when a major mode is turned on, without knowing major modes or their hooks.
 305 ;;
 306 ;; Naturally this requires that (a) major modes run `kill-all-local-variables',
 307 ;; as they are supposed to do, and (b) the major mode is in place after the
 308 ;; file is visited or the command that ran `kill-all-local-variables' has
 309 ;; finished, whichever the sooner.  Arguably, any major mode that does not
 310 ;; follow the convension (a) is broken, and I can't think of any reason why (b)
 311 ;; would not be met (except `gnudoit' on non-files).  However, it is not clean.
 312 ;;
 313 ;; Probably the cleanest solution is to have each major mode function run some
 314 ;; hook, e.g., `major-mode-hook', but maybe implementing that change is
 315 ;; impractical.  I am personally against making `setq' a macro or be advised,
 316 ;; or have a special function such as `set-major-mode', but maybe someone can
 317 ;; come up with another solution?
 318
 319 ;; User interface.
 320 ;;
 321 ;; Although Global Font Lock mode is a pseudo-mode, I think that the user
 322 ;; interface should conform to the usual Emacs convention for modes, i.e., a
 323 ;; command to toggle the feature (`global-font-lock-mode') with a variable for
 324 ;; finer control of the mode's behaviour (`font-lock-global-modes').
 325 ;;
 326 ;; The feature should not be enabled by loading font-lock.el, since other
 327 ;; mechanisms for turning on Font Lock mode, such as M-x font-lock-mode RET or
 328 ;; (add-hook 'c-mode-hook 'turn-on-font-lock), would cause Font Lock mode to be
 329 ;; turned on everywhere.  That would not be intuitive or informative because
 330 ;; loading a file tells you nothing about the feature or how to control it.  It
 331 ;; would also be contrary to the Principle of Least Surprise.  sm.
 332
 333 (defcustom font-lock-global-modes t
 334   "*Modes for which Font Lock mode is automagically turned on.
 335 Global Font Lock mode is controlled by the command `global-font-lock-mode'.
 336 If nil, means no modes have Font Lock mode automatically turned on.
 337 If t, all modes that support Font Lock mode have it automatically turned on.
 338 If a list, it should be a list of `major-mode' symbol names for which Font Lock
 339 mode should be automatically turned on.  The sense of the list is negated if it
 340 begins with `not'.  For example:
 341  (c-mode c++-mode)
 342 means that Font Lock mode is turned on for buffers in C and C++ modes only."
 343   :type '(choice (const :tag "none" nil)
 344                  (const :tag "all" t)
 345                  (set :menu-tag "mode specific" :tag "modes"
 346                       :value (not)
 347                       (const :tag "Except" not)
 348                       (repeat :inline t (symbol :tag "mode"))))
 349   :group 'font-lock)
 350
 351 (defun turn-on-font-lock-if-enabled ()
 352   (when (and (or font-lock-defaults
 353                  (assq major-mode font-lock-defaults-alist))
 354              (or (eq font-lock-global-modes t)
 355                  (if (eq (car-safe font-lock-global-modes) 'not)
 356                      (not (memq major-mode (cdr font-lock-global-modes)))
 357                    (memq major-mode font-lock-global-modes))))
 358     (let (inhibit-quit)
 359       (turn-on-font-lock))))
 360
 361 (easy-mmode-define-global-mode
 362  global-font-lock-mode font-lock-mode turn-on-font-lock-if-enabled
 363  :extra-args (dummy))
 364
 365 ;;; End of Global Font Lock mode.
 366
 367 (provide 'font-core)
 368
 369 ;;; font-core.el ends here
 370