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[emacs.git] / lisp / derived.el
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1 ;;; derived.el --- allow inheritance of major modes
2 ;;; (formerly mode-clone.el)
4 ;; Copyright (C) 1993, 1994, 1999 Free Software Foundation, Inc.
6 ;; Author: David Megginson (dmeggins@aix1.uottawa.ca)
7 ;; Maintainer: FSF
8 ;; Keywords: extensions
10 ;; This file is part of GNU Emacs.
12 ;; GNU Emacs is free software; you can redistribute it and/or modify
13 ;; it under the terms of the GNU General Public License as published by
14 ;; the Free Software Foundation; either version 2, or (at your option)
15 ;; any later version.
17 ;; GNU Emacs is distributed in the hope that it will be useful,
18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ;; GNU General Public License for more details.
22 ;; You should have received a copy of the GNU General Public License
23 ;; along with GNU Emacs; see the file COPYING. If not, write to the
24 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
25 ;; Boston, MA 02111-1307, USA.
27 ;;; Commentary:
29 ;; GNU Emacs is already, in a sense, object oriented -- each object
30 ;; (buffer) belongs to a class (major mode), and that class defines
31 ;; the relationship between messages (input events) and methods
32 ;; (commands) by means of a keymap.
34 ;; The only thing missing is a good scheme of inheritance. It is
35 ;; possible to simulate a single level of inheritance with generous
36 ;; use of hooks and a bit of work -- sgml-mode, for example, also runs
37 ;; the hooks for text-mode, and keymaps can inherit from other keymaps
38 ;; -- but generally, each major mode ends up reinventing the wheel.
39 ;; Ideally, someone should redesign all of Emacs's major modes to
40 ;; follow a more conventional object-oriented system: when defining a
41 ;; new major mode, the user should need only to name the existing mode
42 ;; it is most similar to, then list the (few) differences.
44 ;; In the mean time, this package offers most of the advantages of
45 ;; full inheritance with the existing major modes. The macro
46 ;; `define-derived-mode' allows the user to make a variant of an existing
47 ;; major mode, with its own keymap. The new mode will inherit the key
48 ;; bindings of its parent, and will, in fact, run its parent first
49 ;; every time it is called. For example, the commands
51 ;; (define-derived-mode hypertext-mode text-mode "Hypertext"
52 ;; "Major mode for hypertext.\n\n\\{hypertext-mode-map}"
53 ;; (setq case-fold-search nil))
55 ;; (define-key hypertext-mode-map [down-mouse-3] 'do-hyper-link)
57 ;; will create a function `hypertext-mode' with its own (sparse)
58 ;; keymap `hypertext-mode-map.' The command M-x hypertext-mode will
59 ;; perform the following actions:
61 ;; - run the command (text-mode) to get its default setup
62 ;; - replace the current keymap with 'hypertext-mode-map,' which will
63 ;; inherit from 'text-mode-map'.
64 ;; - replace the current syntax table with
65 ;; 'hypertext-mode-syntax-table', which will borrow its defaults
66 ;; from the current text-mode-syntax-table.
67 ;; - replace the current abbrev table with
68 ;; 'hypertext-mode-abbrev-table', which will borrow its defaults
69 ;; from the current text-mode-abbrev table
70 ;; - change the mode line to read "Hypertext"
71 ;; - assign the value 'hypertext-mode' to the 'major-mode' variable
72 ;; - run the body of commands provided in the macro -- in this case,
73 ;; set the local variable `case-fold-search' to nil.
75 ;; The advantages of this system are threefold. First, text mode is
76 ;; untouched -- if you had added the new keystroke to `text-mode-map,'
77 ;; possibly using hooks, you would have added it to all text buffers
78 ;; -- here, it appears only in hypertext buffers, where it makes
79 ;; sense. Second, it is possible to build even further, and make
80 ;; a derived mode from a derived mode. The commands
82 ;; (define-derived-mode html-mode hypertext-mode "HTML")
83 ;; [various key definitions]
85 ;; will add a new major mode for HTML with very little fuss.
87 ;; Note also the function `derived-mode-p' which can tell if the current
88 ;; mode derives from another. In a hypertext-mode, buffer, for example,
89 ;; (derived-mode-p 'text-mode) would return non-nil. This should always
90 ;; be used in place of (eq major-mode 'text-mode).
92 ;;; Code:
94 (eval-when-compile (require 'cl))
96 ;;; PRIVATE: defsubst must be defined before they are first used
98 (defsubst derived-mode-hook-name (mode)
99 "Construct the mode hook name based on mode name MODE."
100 (intern (concat (symbol-name mode) "-hook")))
102 (defsubst derived-mode-map-name (mode)
103 "Construct a map name based on a MODE name."
104 (intern (concat (symbol-name mode) "-map")))
106 (defsubst derived-mode-syntax-table-name (mode)
107 "Construct a syntax-table name based on a MODE name."
108 (intern (concat (symbol-name mode) "-syntax-table")))
110 (defsubst derived-mode-abbrev-table-name (mode)
111 "Construct an abbrev-table name based on a MODE name."
112 (intern (concat (symbol-name mode) "-abbrev-table")))
114 ;; PUBLIC: define a new major mode which inherits from an existing one.
116 ;;;###autoload
117 (defmacro define-derived-mode (child parent name &optional docstring &rest body)
118 "Create a new mode as a variant of an existing mode.
120 The arguments to this command are as follow:
122 CHILD: the name of the command for the derived mode.
123 PARENT: the name of the command for the parent mode (e.g. `text-mode')
124 or nil if there is no parent.
125 NAME: a string which will appear in the status line (e.g. \"Hypertext\")
126 DOCSTRING: an optional documentation string--if you do not supply one,
127 the function will attempt to invent something useful.
128 BODY: forms to execute just before running the
129 hooks for the new mode. Do not use `interactive' here.
131 BODY can start with a bunch of keyword arguments. The following keyword
132 arguments are currently understood:
133 :group GROUP
134 Declare the customization group that corresponds to this mode.
135 :syntax-table TABLE
136 Use TABLE instead of the default.
137 A nil value means to simply use the same syntax-table as the parent.
138 :abbrev-table TABLE
139 Use TABLE instead of the default.
140 A nil value means to simply use the same abbrev-table as the parent.
142 Here is how you could define LaTeX-Thesis mode as a variant of LaTeX mode:
144 (define-derived-mode LaTeX-thesis-mode LaTeX-mode \"LaTeX-Thesis\")
146 You could then make new key bindings for `LaTeX-thesis-mode-map'
147 without changing regular LaTeX mode. In this example, BODY is empty,
148 and DOCSTRING is generated by default.
150 On a more complicated level, the following command uses `sgml-mode' as
151 the parent, and then sets the variable `case-fold-search' to nil:
153 (define-derived-mode article-mode sgml-mode \"Article\"
154 \"Major mode for editing technical articles.\"
155 (setq case-fold-search nil))
157 Note that if the documentation string had been left out, it would have
158 been generated automatically, with a reference to the keymap."
160 (when (and docstring (not (stringp docstring)))
161 ;; Some trickiness, since what appears to be the docstring may really be
162 ;; the first element of the body.
163 (push docstring body)
164 (setq docstring nil))
166 (when (eq parent 'fundamental-mode) (setq parent nil))
168 (let ((map (derived-mode-map-name child))
169 (syntax (derived-mode-syntax-table-name child))
170 (abbrev (derived-mode-abbrev-table-name child))
171 (declare-abbrev t)
172 (declare-syntax t)
173 (hook (derived-mode-hook-name child))
174 (group nil))
176 ;; Process the keyword args.
177 (while (keywordp (car body))
178 (case (pop body)
179 (:group (setq group (pop body)))
180 (:abbrev-table (setq abbrev (pop body)) (setq declare-abbrev nil))
181 (:syntax-table (setq syntax (pop body)) (setq declare-syntax nil))
182 (t (pop body))))
184 (setq docstring (derived-mode-make-docstring
185 parent child docstring syntax abbrev))
187 `(progn
188 (defvar ,map (make-sparse-keymap))
189 ,(if declare-syntax
190 `(defvar ,syntax (make-syntax-table)))
191 ,(if declare-abbrev
192 `(defvar ,abbrev
193 (progn (define-abbrev-table ',abbrev nil) ,abbrev)))
194 (put ',child 'derived-mode-parent ',parent)
195 ,(if group `(put ',child 'custom-mode-group ,group))
197 (defun ,child ()
198 ,docstring
199 (interactive)
200 ; Run the parent.
201 (delay-mode-hooks
203 (,(or parent 'kill-all-local-variables))
204 ; Identify the child mode.
205 (setq major-mode (quote ,child))
206 (setq mode-name ,name)
207 ; Identify special modes.
208 ,(when parent
209 `(progn
210 (if (get (quote ,parent) 'mode-class)
211 (put (quote ,child) 'mode-class
212 (get (quote ,parent) 'mode-class)))
213 ; Set up maps and tables.
214 (unless (keymap-parent ,map)
215 (set-keymap-parent ,map (current-local-map)))
216 ,(when declare-syntax
217 `(let ((parent (char-table-parent ,syntax)))
218 (unless (and parent
219 (not (eq parent (standard-syntax-table))))
220 (set-char-table-parent ,syntax (syntax-table)))))))
222 (use-local-map ,map)
223 ,(when syntax `(set-syntax-table ,syntax))
224 ,(when abbrev `(setq local-abbrev-table ,abbrev))
225 ; Splice in the body (if any).
226 ,@body
228 ; Run the hooks, if any.
229 (run-mode-hooks ',hook)))))
231 ;; PUBLIC: find the ultimate class of a derived mode.
233 (defun derived-mode-class (mode)
234 "Find the class of a major MODE.
235 A mode's class is the first ancestor which is NOT a derived mode.
236 Use the `derived-mode-parent' property of the symbol to trace backwards.
237 Since major-modes might all derive from `fundamental-mode', this function
238 is not very useful."
239 (while (get mode 'derived-mode-parent)
240 (setq mode (get mode 'derived-mode-parent)))
241 mode)
242 (make-obsolete 'derived-mode-class 'derived-mode-p "21.4")
245 ;;; PRIVATE
247 (defun derived-mode-make-docstring (parent child &optional
248 docstring syntax abbrev)
249 "Construct a docstring for a new mode if none is provided."
251 (let ((map (derived-mode-map-name child))
252 (hook (derived-mode-hook-name child)))
254 (unless (stringp docstring)
255 ;; Use a default docstring.
256 (setq docstring
257 (if (null parent)
258 (format "Major-mode.
259 Uses keymap `%s', abbrev table `%s' and syntax-table `%s'." map abbrev syntax)
260 (format "Major mode derived from `%s' by `define-derived-mode'.
261 It inherits all of the parent's attributes, but has its own keymap,
262 abbrev table and syntax table:
264 `%s', `%s' and `%s'
266 which more-or-less shadow %s's corresponding tables."
267 parent map abbrev syntax parent))))
269 (unless (string-match (regexp-quote (symbol-name hook)) docstring)
270 ;; Make sure the docstring mentions the mode's hook.
271 (setq docstring
272 (concat docstring
273 (if (null parent)
274 "\n\nThis mode "
275 (concat
276 "\n\nIn addition to any hooks its parent mode "
277 (if (string-match (regexp-quote (format "`%s'" parent))
278 docstring) nil
279 (format "`%s' " parent))
280 "might have run,\nthis mode "))
281 (format "runs the hook `%s'" hook)
282 ", as the final step\nduring initialization.")))
284 (unless (string-match "\\\\[{[]" docstring)
285 ;; And don't forget to put the mode's keymap.
286 (setq docstring (concat docstring "\n\n\\{" (symbol-name map) "}")))
288 docstring))
291 ;;; OBSOLETE
292 ;; The functions below are only provided for backward compatibility with
293 ;; code byte-compiled with versions of derived.el prior to Emacs-21.
295 (defsubst derived-mode-setup-function-name (mode)
296 "Construct a setup-function name based on a MODE name."
297 (intern (concat (symbol-name mode) "-setup")))
300 ;; Utility functions for defining a derived mode.
302 ;;;###autoload
303 (defun derived-mode-init-mode-variables (mode)
304 "Initialise variables for a new MODE.
305 Right now, if they don't already exist, set up a blank keymap, an
306 empty syntax table, and an empty abbrev table -- these will be merged
307 the first time the mode is used."
309 (if (boundp (derived-mode-map-name mode))
311 (eval `(defvar ,(derived-mode-map-name mode)
312 (make-sparse-keymap)
313 ,(format "Keymap for %s." mode)))
314 (put (derived-mode-map-name mode) 'derived-mode-unmerged t))
316 (if (boundp (derived-mode-syntax-table-name mode))
318 (eval `(defvar ,(derived-mode-syntax-table-name mode)
319 ;; Make a syntax table which doesn't specify anything
320 ;; for any char. Valid data will be merged in by
321 ;; derived-mode-merge-syntax-tables.
322 (make-char-table 'syntax-table nil)
323 ,(format "Syntax table for %s." mode)))
324 (put (derived-mode-syntax-table-name mode) 'derived-mode-unmerged t))
326 (if (boundp (derived-mode-abbrev-table-name mode))
328 (eval `(defvar ,(derived-mode-abbrev-table-name mode)
329 (progn
330 (define-abbrev-table (derived-mode-abbrev-table-name mode) nil)
331 (make-abbrev-table))
332 ,(format "Abbrev table for %s." mode)))))
334 ;; Utility functions for running a derived mode.
336 (defun derived-mode-set-keymap (mode)
337 "Set the keymap of the new MODE, maybe merging with the parent."
338 (let* ((map-name (derived-mode-map-name mode))
339 (new-map (eval map-name))
340 (old-map (current-local-map)))
341 (and old-map
342 (get map-name 'derived-mode-unmerged)
343 (derived-mode-merge-keymaps old-map new-map))
344 (put map-name 'derived-mode-unmerged nil)
345 (use-local-map new-map)))
347 (defun derived-mode-set-syntax-table (mode)
348 "Set the syntax table of the new MODE, maybe merging with the parent."
349 (let* ((table-name (derived-mode-syntax-table-name mode))
350 (old-table (syntax-table))
351 (new-table (eval table-name)))
352 (if (get table-name 'derived-mode-unmerged)
353 (derived-mode-merge-syntax-tables old-table new-table))
354 (put table-name 'derived-mode-unmerged nil)
355 (set-syntax-table new-table)))
357 (defun derived-mode-set-abbrev-table (mode)
358 "Set the abbrev table for MODE if it exists.
359 Always merge its parent into it, since the merge is non-destructive."
360 (let* ((table-name (derived-mode-abbrev-table-name mode))
361 (old-table local-abbrev-table)
362 (new-table (eval table-name)))
363 (derived-mode-merge-abbrev-tables old-table new-table)
364 (setq local-abbrev-table new-table)))
366 ;;;(defun derived-mode-run-setup-function (mode)
367 ;;; "Run the setup function if it exists."
369 ;;; (let ((fname (derived-mode-setup-function-name mode)))
370 ;;; (if (fboundp fname)
371 ;;; (funcall fname))))
373 (defun derived-mode-run-hooks (mode)
374 "Run the mode hook for MODE."
375 (let ((hooks-name (derived-mode-hook-name mode)))
376 (if (boundp hooks-name)
377 (run-hooks hooks-name))))
379 ;; Functions to merge maps and tables.
381 (defun derived-mode-merge-keymaps (old new)
382 "Merge an OLD keymap into a NEW one.
383 The old keymap is set to be the last cdr of the new one, so that there will
384 be automatic inheritance."
385 ;; ?? Can this just use `set-keymap-parent'?
386 (let ((tail new))
387 ;; Scan the NEW map for prefix keys.
388 (while (consp tail)
389 (and (consp (car tail))
390 (let* ((key (vector (car (car tail))))
391 (subnew (lookup-key new key))
392 (subold (lookup-key old key)))
393 ;; If KEY is a prefix key in both OLD and NEW, merge them.
394 (and (keymapp subnew) (keymapp subold)
395 (derived-mode-merge-keymaps subold subnew))))
396 (and (vectorp (car tail))
397 ;; Search a vector of ASCII char bindings for prefix keys.
398 (let ((i (1- (length (car tail)))))
399 (while (>= i 0)
400 (let* ((key (vector i))
401 (subnew (lookup-key new key))
402 (subold (lookup-key old key)))
403 ;; If KEY is a prefix key in both OLD and NEW, merge them.
404 (and (keymapp subnew) (keymapp subold)
405 (derived-mode-merge-keymaps subold subnew)))
406 (setq i (1- i)))))
407 (setq tail (cdr tail))))
408 (setcdr (nthcdr (1- (length new)) new) old))
410 (defun derived-mode-merge-syntax-tables (old new)
411 "Merge an OLD syntax table into a NEW one.
412 Where the new table already has an entry, nothing is copied from the old one."
413 (set-char-table-parent new old))
415 ;; Merge an old abbrev table into a new one.
416 ;; This function requires internal knowledge of how abbrev tables work,
417 ;; presuming that they are obarrays with the abbrev as the symbol, the expansion
418 ;; as the value of the symbol, and the hook as the function definition.
419 (defun derived-mode-merge-abbrev-tables (old new)
420 (if old
421 (mapatoms
422 (lambda (symbol)
423 (or (intern-soft (symbol-name symbol) new)
424 (define-abbrev new (symbol-name symbol)
425 (symbol-value symbol) (symbol-function symbol))))
426 old)))
428 (provide 'derived)
430 ;;; derived.el ends here