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 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., 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.
33Defaults should be of the form:
34
35 (KEYWORDS [KEYWORDS-ONLY [CASE-FOLD [SYNTAX-ALIST [SYNTAX-BEGIN ...]]]])
36
37KEYWORDS may be a symbol (a variable or function whose value is the keywords to
38use for fontification) or a list of symbols.  If KEYWORDS-ONLY is non-nil,
39syntactic fontification (strings and comments) is not performed.
40If CASE-FOLD is non-nil, the case of the keywords is ignored when fontifying.
41If 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
43keyword and syntactic fontification (see `modify-syntax-entry').
44
45If SYNTAX-BEGIN is non-nil, it should be a function with no args used to move
46backwards outside any enclosing syntactic block, for syntactic fontification.
47Typical values are `beginning-of-line' (i.e., the start of the line is known to
48be 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
50known to move outside a syntactic block).  If nil, the beginning of the buffer
51is used as a position outside of a syntactic block, in the worst case.
52
53These 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
58Further item elements are alists of the form (VARIABLE . VALUE) and are in no
59particular order.  Each VARIABLE is made buffer-local before set to VALUE.
60
61Currently, appropriate variables include `font-lock-mark-block-function'.
62If this is non-nil, it should be a function with no args used to mark any
63enclosing block of text, for fontification via \\[font-lock-fontify-block].
64Typical values are `mark-defun' for programming modes or `mark-paragraph' for
65textual modes (i.e., the mode-dependent function is known to put point and mark
66around a text block relevant to that mode).
67
68Other variables include that for syntactic keyword fontification,
69`font-lock-syntactic-keywords' and those for buffer-specialized fontification
70functions, `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
78Each item should be a list of the form:
79
80 (MAJOR-MODE . FONT-LOCK-DEFAULTS)
81
82where MAJOR-MODE is a symbol and FONT-LOCK-DEFAULTS is a list of default
83settings.  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.
88It 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.
95With arg, turn Font Lock mode off if and only if arg is a non-positive
96number; if arg is nil, toggle Font Lock mode; anything else turns Font
97Lock on.
98\(Font Lock is also known as \"syntax highlighting\".)
99
100When 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
107To customize the faces (colors, fonts, etc.) used by Font Lock for
108fontifying different parts of buffer text, use \\[customize-face].
109
110You can enable Font Lock mode in any major mode automatically by turning on in
111the major mode's hook.  For example, put in your ~/.emacs:
112
113 (add-hook 'c-mode-hook 'turn-on-font-lock)
114
115Alternatively, you can use Global Font Lock mode to automagically turn on Font
116Lock mode in buffers whose major mode supports it and whose major mode is one
117of `font-lock-global-modes'.  For example, put in your ~/.emacs:
118
119 (global-font-lock-mode t)
120
121Where major modes support different levels of fontification, you can use
122the variable `font-lock-maximum-decoration' to specify which level you
123generally prefer.  When you turn Font Lock mode on/off the buffer is
124fontified/defontified, though fontification occurs only if the buffer is
125less than `font-lock-maximum-size'.
126
127To add your own highlighting for some major mode, and modify the highlighting
128selected automatically via the variable `font-lock-maximum-decoration', you can
129use `font-lock-add-keywords'.
130
131To fontify a buffer, without turning on Font Lock mode and regardless of buffer
132size, you can use \\[font-lock-fontify-buffer].
133
134To fontify a block (the function or paragraph containing point, or a number of
135lines around point), perhaps because modification on the current line caused
136syntactic change on other lines, you can use \\[font-lock-fontify-block].
137
138See the variable `font-lock-defaults-alist' for the Font Lock mode default
139settings.  You can set your own default settings for some mode, by setting a
140buffer local value for `font-lock-defaults', via its mode hook.
141
142The above is the default behavior of `font-lock-mode'; you may specify
143your 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.
165A major mode that uses `font-lock-face' properties might want to put
166this 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-enabled' 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.
268Global Font Lock mode is controlled by the command `global-font-lock-mode'.
269If nil, means no modes have Font Lock mode automatically turned on.
270If t, all modes that support Font Lock mode have it automatically turned on.
271If a list, it should be a list of `major-mode' symbol names for which Font Lock
272mode should be automatically turned on.  The sense of the list is negated if it
273begins with `not'.  For example:
274 (c-mode c++-mode)
275means 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-enabled ()
285  (unless (and (eq (car-safe font-lock-global-modes) 'not)
286	       (memq major-mode (cdr font-lock-global-modes)))
287    (let (inhibit-quit)
288      (turn-on-font-lock))))
289
290(define-globalized-minor-mode global-font-lock-mode
291  font-lock-mode turn-on-font-lock-if-enabled
292  :extra-args (dummy)
293  :initialize 'custom-initialize-safe-default
294  :init-value (not (or noninteractive emacs-basic-display))
295  :group 'font-lock
296  :version "22.1")
297
298;;; End of Global Font Lock mode.
299
300(provide 'font-core)
301
302;; arch-tag: f8c286e1-02f7-41d9-b89b-1b67780aed71
303;;; font-core.el ends here
304