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06d35594 RS |
1 | ;;; derived.el -- allow inheritance of major modes. |
2 | ;;; (formerly mode-clone.el) | |
76078cf0 | 3 | |
26757b4b | 4 | ;; Copyright (C) 1993, 1994 Free Software Foundation, Inc. |
76078cf0 RS |
5 | |
6 | ;; Author: David Megginson (dmeggins@aix1.uottawa.ca) | |
26757b4b | 7 | ;; Maintainer: FSF |
76078cf0 RS |
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 | |
b578f267 EN |
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. | |
76078cf0 RS |
25 | \f |
26 | ;;; Commentary: | |
27 | ||
28 | ;; GNU Emacs is already, in a sense, object oriented -- each object | |
29 | ;; (buffer) belongs to a class (major mode), and that class defines | |
30 | ;; the relationship between messages (input events) and methods | |
31 | ;; (commands) by means of a keymap. | |
32 | ;; | |
33 | ;; The only thing missing is a good scheme of inheritance. It is | |
34 | ;; possible to simulate a single level of inheritance with generous | |
35 | ;; use of hooks and a bit of work -- sgml-mode, for example, also runs | |
36 | ;; the hooks for text-mode, and keymaps can inherit from other keymaps | |
37 | ;; -- but generally, each major mode ends up reinventing the wheel. | |
38 | ;; Ideally, someone should redesign all of Emacs's major modes to | |
39 | ;; follow a more conventional object-oriented system: when defining a | |
40 | ;; new major mode, the user should need only to name the existing mode | |
41 | ;; it is most similar to, then list the (few) differences. | |
42 | ;; | |
43 | ;; In the mean time, this package offers most of the advantages of | |
b72226e3 | 44 | ;; full inheritance with the existing major modes. The macro |
06d35594 | 45 | ;; `define-derived-mode' allows the user to make a variant of an existing |
76078cf0 RS |
46 | ;; major mode, with its own keymap. The new mode will inherit the key |
47 | ;; bindings of its parent, and will, in fact, run its parent first | |
48 | ;; every time it is called. For example, the commands | |
49 | ;; | |
06d35594 | 50 | ;; (define-derived-mode hypertext-mode text-mode "Hypertext" |
76078cf0 RS |
51 | ;; "Major mode for hypertext.\n\n\\{hypertext-mode-map}" |
52 | ;; (setq case-fold-search nil)) | |
53 | ;; | |
54 | ;; (define-key hypertext-mode-map [down-mouse-3] 'do-hyper-link) | |
55 | ;; | |
56 | ;; will create a function `hypertext-mode' with its own (sparse) | |
57 | ;; keymap `hypertext-mode-map.' The command M-x hypertext-mode will | |
58 | ;; perform the following actions: | |
59 | ;; | |
60 | ;; - run the command (text-mode) to get its default setup | |
61 | ;; - replace the current keymap with 'hypertext-mode-map,' which will | |
62 | ;; inherit from 'text-mode-map'. | |
63 | ;; - replace the current syntax table with | |
64 | ;; 'hypertext-mode-syntax-table', which will borrow its defaults | |
65 | ;; from the current text-mode-syntax-table. | |
26757b4b RS |
66 | ;; - replace the current abbrev table with |
67 | ;; 'hypertext-mode-abbrev-table', which will borrow its defaults | |
68 | ;; from the current text-mode-abbrev table | |
76078cf0 RS |
69 | ;; - change the mode line to read "Hypertext" |
70 | ;; - assign the value 'hypertext-mode' to the 'major-mode' variable | |
71 | ;; - run the body of commands provided in the macro -- in this case, | |
72 | ;; set the local variable `case-fold-search' to nil. | |
73 | ;; - **run the command (hypertext-mode-setup), which is empty by | |
74 | ;; default, but may be redefined by the user to contain special | |
75 | ;; commands (ie. setting local variables like 'outline-regexp') | |
76 | ;; **NOTE: do not use this option -- it will soon be obsolete. | |
77 | ;; - run anything assigned to 'hypertext-mode-hooks' (obsolete, but | |
78 | ;; supported for the sake of compatibility). | |
79 | ;; | |
80 | ;; The advantages of this system are threefold. First, text mode is | |
81 | ;; untouched -- if you had added the new keystroke to `text-mode-map,' | |
82 | ;; possibly using hooks, you would have added it to all text buffers | |
83 | ;; -- here, it appears only in hypertext buffers, where it makes | |
06d35594 RS |
84 | ;; sense. Second, it is possible to build even further, and make |
85 | ;; a derived mode from a derived mode. The commands | |
76078cf0 | 86 | ;; |
06d35594 | 87 | ;; (define-derived-mode html-mode hypertext-mode "HTML") |
76078cf0 RS |
88 | ;; [various key definitions] |
89 | ;; | |
90 | ;; will add a new major mode for HTML with very little fuss. | |
91 | ;; | |
06d35594 RS |
92 | ;; Note also the function `derived-mode-class,' which returns the non-derived |
93 | ;; major mode which a derived mode is based on (ie. NOT necessarily the | |
76078cf0 RS |
94 | ;; immediate parent). |
95 | ;; | |
06d35594 RS |
96 | ;; (derived-mode-class 'text-mode) ==> text-mode |
97 | ;; (derived-mode-class 'hypertext-mode) ==> text-mode | |
98 | ;; (derived-mode-class 'html-mode) ==> text-mode | |
76078cf0 RS |
99 | \f |
100 | ;;; Code: | |
101 | ||
102 | ;; PUBLIC: define a new major mode which inherits from an existing one. | |
103 | ||
104 | ;;;###autoload | |
06d35594 RS |
105 | (defmacro define-derived-mode (child parent name &optional docstring &rest body) |
106 | "Create a new mode as a variant of an existing mode. | |
76078cf0 RS |
107 | |
108 | The arguments to this command are as follow: | |
109 | ||
06d35594 | 110 | CHILD: the name of the command for the derived mode. |
6b410da7 | 111 | PARENT: the name of the command for the parent mode (ie. text-mode). |
b72226e3 RS |
112 | NAME: a string which will appear in the status line (ie. \"Hypertext\") |
113 | DOCSTRING: an optional documentation string--if you do not supply one, | |
114 | the function will attempt to invent something useful. | |
115 | BODY: forms to execute just before running the | |
76078cf0 RS |
116 | hooks for the new mode. |
117 | ||
06d35594 | 118 | Here is how you could define LaTeX-Thesis mode as a variant of LaTeX mode: |
76078cf0 | 119 | |
06d35594 | 120 | (define-derived-mode LaTeX-thesis-mode LaTeX-mode \"LaTeX-Thesis\") |
76078cf0 | 121 | |
b72226e3 RS |
122 | You could then make new key bindings for `LaTeX-thesis-mode-map' |
123 | without changing regular LaTeX mode. In this example, BODY is empty, | |
124 | and DOCSTRING is generated by default. | |
76078cf0 | 125 | |
06d35594 RS |
126 | On a more complicated level, the following command uses sgml-mode as |
127 | the parent, and then sets the variable `case-fold-search' to nil: | |
76078cf0 | 128 | |
06d35594 | 129 | (define-derived-mode article-mode sgml-mode \"Article\" |
76078cf0 RS |
130 | \"Major mode for editing technical articles.\" |
131 | (setq case-fold-search nil)) | |
132 | ||
133 | Note that if the documentation string had been left out, it would have | |
134 | been generated automatically, with a reference to the keymap." | |
135 | ||
136 | ; Some trickiness, since what | |
137 | ; appears to be the docstring | |
138 | ; may really be the first | |
139 | ; element of the body. | |
140 | (if (and docstring (not (stringp docstring))) | |
141 | (progn (setq body (cons docstring body)) | |
142 | (setq docstring nil))) | |
06d35594 | 143 | (setq docstring (or docstring (derived-mode-make-docstring parent child))) |
76078cf0 RS |
144 | |
145 | (` (progn | |
06d35594 | 146 | (derived-mode-init-mode-variables (quote (, child))) |
76078cf0 RS |
147 | (defun (, child) () |
148 | (, docstring) | |
149 | (interactive) | |
150 | ; Run the parent. | |
151 | ((, parent)) | |
152 | ; Identify special modes. | |
153 | (if (get (quote (, parent)) 'special) | |
154 | (put (quote (, child)) 'special t)) | |
155 | ; Identify the child mode. | |
156 | (setq major-mode (quote (, child))) | |
157 | (setq mode-name (, name)) | |
158 | ; Set up maps and tables. | |
06d35594 RS |
159 | (derived-mode-set-keymap (quote (, child))) |
160 | (derived-mode-set-syntax-table (quote (, child))) | |
161 | (derived-mode-set-abbrev-table (quote (, child))) | |
76078cf0 RS |
162 | ; Splice in the body (if any). |
163 | (,@ body) | |
b72226e3 RS |
164 | ;;; ; Run the setup function, if |
165 | ;;; ; any -- this will soon be | |
166 | ;;; ; obsolete. | |
06d35594 | 167 | ;;; (derived-mode-run-setup-function (quote (, child))) |
76078cf0 | 168 | ; Run the hooks, if any. |
06d35594 | 169 | (derived-mode-run-hooks (quote (, child))))))) |
76078cf0 RS |
170 | |
171 | ||
06d35594 | 172 | ;; PUBLIC: find the ultimate class of a derived mode. |
76078cf0 | 173 | |
06d35594 | 174 | (defun derived-mode-class (mode) |
76078cf0 | 175 | "Find the class of a major mode. |
06d35594 RS |
176 | A mode's class is the first ancestor which is NOT a derived mode. |
177 | Use the `derived-mode-parent' property of the symbol to trace backwards." | |
178 | (while (get mode 'derived-mode-parent) | |
179 | (setq mode (get mode 'derived-mode-parent))) | |
76078cf0 RS |
180 | mode) |
181 | ||
182 | \f | |
183 | ;; Inline functions to construct various names from a mode name. | |
184 | ||
06d35594 | 185 | (defsubst derived-mode-setup-function-name (mode) |
76078cf0 RS |
186 | "Construct a setup-function name based on a mode name." |
187 | (intern (concat (symbol-name mode) "-setup"))) | |
188 | ||
06d35594 | 189 | (defsubst derived-mode-hooks-name (mode) |
76078cf0 RS |
190 | "Construct a hooks name based on a mode name." |
191 | (intern (concat (symbol-name mode) "-hooks"))) | |
192 | ||
06d35594 | 193 | (defsubst derived-mode-map-name (mode) |
76078cf0 RS |
194 | "Construct a map name based on a mode name." |
195 | (intern (concat (symbol-name mode) "-map"))) | |
196 | ||
06d35594 | 197 | (defsubst derived-mode-syntax-table-name (mode) |
76078cf0 RS |
198 | "Construct a syntax-table name based on a mode name." |
199 | (intern (concat (symbol-name mode) "-syntax-table"))) | |
200 | ||
06d35594 | 201 | (defsubst derived-mode-abbrev-table-name (mode) |
76078cf0 RS |
202 | "Construct an abbrev-table name based on a mode name." |
203 | (intern (concat (symbol-name mode) "-abbrev-table"))) | |
204 | ||
205 | \f | |
06d35594 | 206 | ;; Utility functions for defining a derived mode. |
76078cf0 | 207 | |
ec830850 | 208 | ;;;###autoload |
06d35594 | 209 | (defun derived-mode-init-mode-variables (mode) |
26757b4b RS |
210 | "Initialise variables for a new mode. |
211 | Right now, if they don't already exist, set up a blank keymap, an | |
212 | empty syntax table, and an empty abbrev table -- these will be merged | |
213 | the first time the mode is used." | |
214 | ||
06d35594 | 215 | (if (boundp (derived-mode-map-name mode)) |
26757b4b | 216 | t |
06d35594 | 217 | (eval (` (defvar (, (derived-mode-map-name mode)) |
26757b4b RS |
218 | (make-sparse-keymap) |
219 | (, (format "Keymap for %s." mode))))) | |
06d35594 | 220 | (put (derived-mode-map-name mode) 'derived-mode-unmerged t)) |
26757b4b | 221 | |
06d35594 | 222 | (if (boundp (derived-mode-syntax-table-name mode)) |
26757b4b | 223 | t |
06d35594 | 224 | (eval (` (defvar (, (derived-mode-syntax-table-name mode)) |
a43944b5 RS |
225 | ;; Make a syntax table which doesn't specify anything |
226 | ;; for any char. Valid data will be merged in by | |
227 | ;; derived-mode-merge-syntax-tables. | |
228 | (make-char-table 'syntax-table nil) | |
26757b4b | 229 | (, (format "Syntax table for %s." mode))))) |
06d35594 | 230 | (put (derived-mode-syntax-table-name mode) 'derived-mode-unmerged t)) |
26757b4b | 231 | |
06d35594 | 232 | (if (boundp (derived-mode-abbrev-table-name mode)) |
26757b4b | 233 | t |
06d35594 RS |
234 | (eval (` (defvar (, (derived-mode-abbrev-table-name mode)) |
235 | (progn (define-abbrev-table (derived-mode-abbrev-table-name mode) nil) | |
26757b4b RS |
236 | (make-abbrev-table)) |
237 | (, (format "Abbrev table for %s." mode))))))) | |
76078cf0 | 238 | |
06d35594 | 239 | (defun derived-mode-make-docstring (parent child) |
76078cf0 RS |
240 | "Construct a docstring for a new mode if none is provided." |
241 | ||
06d35594 | 242 | (format "This major mode is a variant of `%s', created by `define-derived-mode'. |
b72226e3 RS |
243 | It inherits all of the parent's attributes, but has its own keymap, |
244 | abbrev table and syntax table: | |
76078cf0 | 245 | |
b72226e3 | 246 | `%s-map' and `%s-syntax-table' |
76078cf0 RS |
247 | |
248 | which more-or-less shadow | |
249 | ||
b72226e3 | 250 | `%s-map' and `%s-syntax-table' |
76078cf0 RS |
251 | |
252 | \\{%s-map}" parent child child parent parent child)) | |
253 | ||
254 | \f | |
06d35594 | 255 | ;; Utility functions for running a derived mode. |
76078cf0 | 256 | |
06d35594 | 257 | (defun derived-mode-set-keymap (mode) |
76078cf0 | 258 | "Set the keymap of the new mode, maybe merging with the parent." |
06d35594 | 259 | (let* ((map-name (derived-mode-map-name mode)) |
76078cf0 RS |
260 | (new-map (eval map-name)) |
261 | (old-map (current-local-map))) | |
f34e6918 RS |
262 | (and old-map |
263 | (get map-name 'derived-mode-unmerged) | |
264 | (derived-mode-merge-keymaps old-map new-map)) | |
06d35594 | 265 | (put map-name 'derived-mode-unmerged nil) |
26757b4b | 266 | (use-local-map new-map))) |
76078cf0 | 267 | |
06d35594 | 268 | (defun derived-mode-set-syntax-table (mode) |
76078cf0 | 269 | "Set the syntax table of the new mode, maybe merging with the parent." |
06d35594 | 270 | (let* ((table-name (derived-mode-syntax-table-name mode)) |
76078cf0 RS |
271 | (old-table (syntax-table)) |
272 | (new-table (eval table-name))) | |
06d35594 RS |
273 | (if (get table-name 'derived-mode-unmerged) |
274 | (derived-mode-merge-syntax-tables old-table new-table)) | |
275 | (put table-name 'derived-mode-unmerged nil) | |
26757b4b | 276 | (set-syntax-table new-table))) |
76078cf0 | 277 | |
06d35594 | 278 | (defun derived-mode-set-abbrev-table (mode) |
26757b4b RS |
279 | "Set the abbrev table if it exists. |
280 | Always merge its parent into it, since the merge is non-destructive." | |
06d35594 | 281 | (let* ((table-name (derived-mode-abbrev-table-name mode)) |
26757b4b RS |
282 | (old-table local-abbrev-table) |
283 | (new-table (eval table-name))) | |
06d35594 | 284 | (derived-mode-merge-abbrev-tables old-table new-table) |
26757b4b | 285 | (setq local-abbrev-table new-table))) |
76078cf0 | 286 | |
06d35594 | 287 | ;;;(defun derived-mode-run-setup-function (mode) |
b72226e3 | 288 | ;;; "Run the setup function if it exists." |
76078cf0 | 289 | |
06d35594 | 290 | ;;; (let ((fname (derived-mode-setup-function-name mode))) |
b72226e3 RS |
291 | ;;; (if (fboundp fname) |
292 | ;;; (funcall fname)))) | |
76078cf0 | 293 | |
06d35594 | 294 | (defun derived-mode-run-hooks (mode) |
76078cf0 RS |
295 | "Run the hooks if they exist." |
296 | ||
06d35594 | 297 | (let ((hooks-name (derived-mode-hooks-name mode))) |
76078cf0 RS |
298 | (if (boundp hooks-name) |
299 | (run-hooks hooks-name)))) | |
300 | ||
301 | ;; Functions to merge maps and tables. | |
302 | ||
06d35594 | 303 | (defun derived-mode-merge-keymaps (old new) |
26757b4b | 304 | "Merge an old keymap into a new one. |
37a4f4b6 | 305 | The old keymap is set to be the last cdr of the new one, so that there will |
76078cf0 | 306 | be automatic inheritance." |
37a4f4b6 RS |
307 | (let ((tail new)) |
308 | ;; Scan the NEW map for prefix keys. | |
309 | (while (consp tail) | |
310 | (and (consp (car tail)) | |
311 | (let* ((key (vector (car (car tail)))) | |
312 | (subnew (lookup-key new key)) | |
313 | (subold (lookup-key old key))) | |
314 | ;; If KEY is a prefix key in both OLD and NEW, merge them. | |
315 | (and (keymapp subnew) (keymapp subold) | |
316 | (derived-mode-merge-keymaps subold subnew)))) | |
317 | (and (vectorp (car tail)) | |
318 | ;; Search a vector of ASCII char bindings for prefix keys. | |
319 | (let ((i (1- (length (car tail))))) | |
320 | (while (>= i 0) | |
321 | (let* ((key (vector i)) | |
322 | (subnew (lookup-key new key)) | |
323 | (subold (lookup-key old key))) | |
324 | ;; If KEY is a prefix key in both OLD and NEW, merge them. | |
325 | (and (keymapp subnew) (keymapp subold) | |
326 | (derived-mode-merge-keymaps subold subnew))) | |
327 | (setq i (1- i))))) | |
328 | (setq tail (cdr tail)))) | |
26757b4b | 329 | (setcdr (nthcdr (1- (length new)) new) old)) |
76078cf0 | 330 | |
06d35594 | 331 | (defun derived-mode-merge-syntax-tables (old new) |
26757b4b | 332 | "Merge an old syntax table into a new one. |
76078cf0 | 333 | Where the new table already has an entry, nothing is copied from the old one." |
5dee7dae | 334 | (set-char-table-parent new old)) |
26757b4b | 335 | |
56152e17 RS |
336 | ;; Merge an old abbrev table into a new one. |
337 | ;; This function requires internal knowledge of how abbrev tables work, | |
338 | ;; presuming that they are obarrays with the abbrev as the symbol, the expansion | |
339 | ;; as the value of the symbol, and the hook as the function definition. | |
06d35594 | 340 | (defun derived-mode-merge-abbrev-tables (old new) |
56152e17 RS |
341 | (if old |
342 | (mapatoms | |
343 | (function | |
344 | (lambda (symbol) | |
345 | (or (intern-soft (symbol-name symbol) new) | |
346 | (define-abbrev new (symbol-name symbol) | |
347 | (symbol-value symbol) (symbol-function symbol))))) | |
348 | old))) | |
76078cf0 | 349 | |
06d35594 | 350 | (provide 'derived) |
26757b4b | 351 | |
06d35594 | 352 | ;;; derived.el ends here |