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1 : ;;; font-core.el --- Core interface to font-lock
2 :
3 : ;; Copyright (C) 1992-2017 Free Software Foundation, Inc.
4 :
5 : ;; Maintainer: emacs-devel@gnu.org
6 : ;; Keywords: languages, faces
7 : ;; Package: emacs
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 : ;;; Code:
25 :
26 : ;; This variable is used by mode packages that support Font Lock mode by
27 : ;; defining their own keywords to use for `font-lock-keywords'. (The mode
28 : ;; command should make it buffer-local and set it to provide the set up.)
29 : (defvar font-lock-defaults nil
30 : "Defaults for Font Lock mode specified by the major mode.
31 : Defaults should be of the form:
32 :
33 : (KEYWORDS [KEYWORDS-ONLY [CASE-FOLD [SYNTAX-ALIST ...]]])
34 :
35 : KEYWORDS may be a symbol (a variable or function whose value is the keywords
36 : to use for fontification) or a list of symbols (specifying different levels
37 : of fontification).
38 :
39 : If KEYWORDS-ONLY is non-nil, syntactic fontification (strings and
40 : comments) is not performed.
41 :
42 : If CASE-FOLD is non-nil, the case of the keywords is ignored when fontifying.
43 :
44 : If SYNTAX-ALIST is non-nil, it should be a list of cons pairs of the form
45 : \(CHAR-OR-STRING . STRING) used to set the local Font Lock syntax table, for
46 : keyword and syntactic fontification (see `modify-syntax-entry').
47 :
48 : These item elements are used by Font Lock mode to set the variables
49 : `font-lock-keywords', `font-lock-keywords-only',
50 : `font-lock-keywords-case-fold-search', `font-lock-syntax-table'.
51 :
52 : Further item elements are alists of the form (VARIABLE . VALUE) and are in no
53 : particular order. Each VARIABLE is made buffer-local before set to VALUE.
54 :
55 : Currently, appropriate variables include `font-lock-mark-block-function'.
56 : If this is non-nil, it should be a function with no args used to mark any
57 : enclosing block of text, for fontification via \\[font-lock-fontify-block].
58 : Typical values are `mark-defun' for programming modes or `mark-paragraph' for
59 : textual modes (i.e., the mode-dependent function is known to put point and mark
60 : around a text block relevant to that mode).
61 :
62 : Other variables include that for syntactic keyword fontification,
63 : `font-lock-syntactic-keywords' and those for buffer-specialized fontification
64 : functions, `font-lock-fontify-buffer-function',
65 : `font-lock-unfontify-buffer-function', `font-lock-fontify-region-function',
66 : `font-lock-unfontify-region-function', and `font-lock-inhibit-thing-lock'.")
67 : ;;;###autoload
68 : (put 'font-lock-defaults 'risky-local-variable t)
69 : (make-variable-buffer-local 'font-lock-defaults)
70 :
71 : (defvar font-lock-function 'font-lock-default-function
72 : "A function which is called when `font-lock-mode' is toggled.
73 : It will be passed one argument, which is the current value of
74 : `font-lock-mode'.")
75 :
76 : ;; The mode for which font-lock was initialized, or nil if none.
77 : (defvar font-lock-major-mode)
78 :
79 : (define-minor-mode font-lock-mode
80 : "Toggle syntax highlighting in this buffer (Font Lock mode).
81 : With a prefix argument ARG, enable Font Lock mode if ARG is
82 : positive, and disable it otherwise. If called from Lisp, enable
83 : the mode if ARG is omitted or nil.
84 :
85 : When Font Lock mode is enabled, text is fontified as you type it:
86 :
87 : - Comments are displayed in `font-lock-comment-face';
88 : - Strings are displayed in `font-lock-string-face';
89 : - Certain other expressions are displayed in other faces
90 : according to the value of the variable `font-lock-keywords'.
91 :
92 : To customize the faces (colors, fonts, etc.) used by Font Lock for
93 : fontifying different parts of buffer text, use \\[customize-face].
94 :
95 : You can enable Font Lock mode in any major mode automatically by
96 : turning on in the major mode's hook. For example, put in your
97 : ~/.emacs:
98 :
99 : (add-hook \\='c-mode-hook \\='turn-on-font-lock)
100 :
101 : Alternatively, you can use Global Font Lock mode to automagically
102 : turn on Font Lock mode in buffers whose major mode supports it
103 : and whose major mode is one of `font-lock-global-modes'. For
104 : example, put in your ~/.emacs:
105 :
106 : (global-font-lock-mode t)
107 :
108 : Where major modes support different levels of fontification, you
109 : can use the variable `font-lock-maximum-decoration' to specify
110 : which level you generally prefer. When you turn Font Lock mode
111 : on/off the buffer is fontified/defontified, though fontification
112 : occurs only if the buffer is less than `font-lock-maximum-size'.
113 :
114 : To add your own highlighting for some major mode, and modify the
115 : highlighting selected automatically via the variable
116 : `font-lock-maximum-decoration', you can use
117 : `font-lock-add-keywords'.
118 :
119 : To fontify a buffer, without turning on Font Lock mode and
120 : regardless of buffer size, you can use \\[font-lock-fontify-buffer].
121 :
122 : To fontify a block (the function or paragraph containing point,
123 : or a number of lines around point), perhaps because modification
124 : on the current line caused syntactic change on other lines, you
125 : can use \\[font-lock-fontify-block].
126 :
127 : You can set your own default settings for some mode, by setting a
128 : buffer local value for `font-lock-defaults', via its mode hook.
129 :
130 : The above is the default behavior of `font-lock-mode'; you may
131 : specify your own function which is called when `font-lock-mode'
132 : is toggled via `font-lock-function'. "
133 : nil nil nil
134 : :after-hook (font-lock-initial-fontify)
135 : ;; Don't turn on Font Lock mode if we don't have a display (we're running a
136 : ;; batch job) or if the buffer is invisible (the name starts with a space).
137 0 : (when (or noninteractive (eq (aref (buffer-name) 0) ?\s))
138 0 : (setq font-lock-mode nil))
139 0 : (funcall font-lock-function font-lock-mode)
140 : ;; Arrange to unfontify this buffer if we change major mode later.
141 0 : (if font-lock-mode
142 0 : (add-hook 'change-major-mode-hook 'font-lock-change-mode nil t)
143 0 : (remove-hook 'change-major-mode-hook 'font-lock-change-mode t)))
144 :
145 : ;; Get rid of fontification for the old major mode.
146 : ;; We do this when changing major modes.
147 : (defun font-lock-change-mode ()
148 0 : (font-lock-mode -1))
149 :
150 : (defun font-lock-defontify ()
151 : "Clear out all `font-lock-face' properties in current buffer.
152 : A major mode that uses `font-lock-face' properties might want to put
153 : this function onto `change-major-mode-hook'."
154 1 : (let ((modp (buffer-modified-p))
155 : (inhibit-read-only t))
156 1 : (save-restriction
157 1 : (widen)
158 1 : (remove-list-of-text-properties (point-min) (point-max)
159 1 : '(font-lock-face)))
160 1 : (restore-buffer-modified-p modp)))
161 :
162 : (defvar font-lock-set-defaults)
163 : (defun font-lock-default-function (mode)
164 : ;; Turn on Font Lock mode.
165 0 : (when mode
166 0 : (set (make-local-variable 'char-property-alias-alist)
167 0 : (copy-tree char-property-alias-alist))
168 : ;; Add `font-lock-face' as an alias for the `face' property.
169 0 : (let ((elt (assq 'face char-property-alias-alist)))
170 0 : (if elt
171 0 : (unless (memq 'font-lock-face (cdr elt))
172 0 : (setcdr elt (nconc (cdr elt) (list 'font-lock-face))))
173 0 : (push (list 'face 'font-lock-face) char-property-alias-alist))))
174 : ;; Turn off Font Lock mode.
175 0 : (unless mode
176 : ;; Remove `font-lock-face' as an alias for the `face' property.
177 0 : (set (make-local-variable 'char-property-alias-alist)
178 0 : (copy-tree char-property-alias-alist))
179 0 : (let ((elt (assq 'face char-property-alias-alist)))
180 0 : (when elt
181 0 : (setcdr elt (remq 'font-lock-face (cdr elt)))
182 0 : (when (null (cdr elt))
183 0 : (setq char-property-alias-alist
184 0 : (delq elt char-property-alias-alist))))))
185 :
186 : ;; Only do hard work if the mode has specified stuff in
187 : ;; `font-lock-defaults'.
188 0 : (when (font-lock-specified-p mode)
189 0 : (font-lock-mode-internal mode)))
190 :
191 : (defun turn-on-font-lock ()
192 : "Turn on Font Lock mode (only if the terminal can display it)."
193 0 : (unless font-lock-mode
194 0 : (font-lock-mode)))
195 :
196 : ;;; Global Font Lock mode.
197 :
198 : ;; A few people have hassled in the past for a way to make it easier to turn on
199 : ;; Font Lock mode, without the user needing to know for which modes s/he has to
200 : ;; turn it on, perhaps the same way hilit19.el/hl319.el does. I've always
201 : ;; balked at that way, as I see it as just re-molding the same problem in
202 : ;; another form. That is; some person would still have to keep track of which
203 : ;; modes (which may not even be distributed with Emacs) support Font Lock mode.
204 : ;; The list would always be out of date. And that person might have to be me.
205 :
206 : ;; Implementation.
207 : ;;
208 : ;; In a previous discussion the following hack came to mind. It is a gross
209 : ;; hack, but it generally works. We use the convention that major modes start
210 : ;; by calling the function `kill-all-local-variables', which in turn runs
211 : ;; functions on the hook variable `change-major-mode-hook'. We attach our
212 : ;; function `font-lock-change-major-mode' to that hook. Of course, when this
213 : ;; hook is run, the major mode is in the process of being changed and we do not
214 : ;; know what the final major mode will be. So, `font-lock-change-major-mode'
215 : ;; only (a) notes the name of the current buffer, and (b) adds our function
216 : ;; `turn-on-font-lock-if-desired' to the hook variables
217 : ;; `after-change-major-mode-hook' and `post-command-hook' (for modes
218 : ;; that do not yet run `after-change-major-mode-hook'). By the time
219 : ;; the functions on the first of these hooks to be run are run, the new major
220 : ;; mode is assumed to be in place. This way we get a Font Lock function run
221 : ;; when a major mode is turned on, without knowing major modes or their hooks.
222 : ;;
223 : ;; Naturally this requires that major modes run `kill-all-local-variables'
224 : ;; and `after-change-major-mode-hook', as they are supposed to. For modes
225 : ;; that do not run `after-change-major-mode-hook' yet, `post-command-hook'
226 : ;; takes care of things if the mode is set directly or indirectly by
227 : ;; an interactive command; however, problems can occur if the mode is
228 : ;; set by a timer or process: in that case, proper handling of Font Lock mode
229 : ;; may be delayed until the next interactive command.
230 :
231 : ;; User interface.
232 : ;;
233 : ;; Although Global Font Lock mode is a pseudo-mode, I think that the user
234 : ;; interface should conform to the usual Emacs convention for modes, i.e., a
235 : ;; command to toggle the feature (`global-font-lock-mode') with a variable for
236 : ;; finer control of the mode's behavior (`font-lock-global-modes').
237 : ;;
238 : ;; The feature should not be enabled by loading font-lock.el, since other
239 : ;; mechanisms for turning on Font Lock mode, such as M-x font-lock-mode RET or
240 : ;; (add-hook 'c-mode-hook 'turn-on-font-lock), would cause Font Lock mode to be
241 : ;; turned on everywhere. That would not be intuitive or informative because
242 : ;; loading a file tells you nothing about the feature or how to control it. It
243 : ;; would also be contrary to the Principle of Least Surprise. sm.
244 :
245 : (defcustom font-lock-global-modes t
246 : "Modes for which Font Lock mode is automagically turned on.
247 : Global Font Lock mode is controlled by the command `global-font-lock-mode'.
248 : If nil, means no modes have Font Lock mode automatically turned on.
249 : If t, all modes that support Font Lock mode have it automatically turned on.
250 : If a list, it should be a list of `major-mode' symbol names for which Font Lock
251 : mode should be automatically turned on. The sense of the list is negated if it
252 : begins with `not'. For example:
253 : (c-mode c++-mode)
254 : means that Font Lock mode is turned on for buffers in C and C++ modes only."
255 : :type '(choice (const :tag "none" nil)
256 : (const :tag "all" t)
257 : (set :menu-tag "mode specific" :tag "modes"
258 : :value (not)
259 : (const :tag "Except" not)
260 : (repeat :inline t (symbol :tag "mode"))))
261 : :group 'font-lock)
262 :
263 : (defun turn-on-font-lock-if-desired ()
264 0 : (when (cond ((eq font-lock-global-modes t)
265 : t)
266 0 : ((eq (car-safe font-lock-global-modes) 'not)
267 0 : (not (memq major-mode (cdr font-lock-global-modes))))
268 0 : (t (memq major-mode font-lock-global-modes)))
269 0 : (let (inhibit-quit)
270 0 : (turn-on-font-lock))))
271 :
272 : (define-globalized-minor-mode global-font-lock-mode
273 : font-lock-mode turn-on-font-lock-if-desired
274 : ;; What was this :extra-args thingy for? --Stef
275 : ;; :extra-args (dummy)
276 : :initialize 'custom-initialize-delay
277 : :init-value (not (or noninteractive emacs-basic-display))
278 : :group 'font-lock
279 : :version "22.1")
280 :
281 : ;;; End of Global Font Lock mode.
282 :
283 : (provide 'font-core)
284 :
285 : ;;; font-core.el ends here
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