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b035a678 | 1 | ;;; derived.el --- allow inheritance of major modes. |
06d35594 | 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. | |
e2154af9 | 77 | ;; - run anything assigned to 'hypertext-mode-hook' (obsolete, but |
76078cf0 RS |
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 | |
7ada1a07 RS |
146 | (derived-mode-init-mode-variables '(, child)) |
147 | (put '(, child) 'derived-mode-parent '(, parent)) | |
76078cf0 RS |
148 | (defun (, child) () |
149 | (, docstring) | |
150 | (interactive) | |
151 | ; Run the parent. | |
152 | ((, parent)) | |
153 | ; Identify special modes. | |
7ada1a07 RS |
154 | (if (get '(, parent) 'special) |
155 | (put '(, child) 'special t)) | |
76078cf0 | 156 | ; Identify the child mode. |
7ada1a07 | 157 | (setq major-mode '(, child)) |
76078cf0 RS |
158 | (setq mode-name (, name)) |
159 | ; Set up maps and tables. | |
7ada1a07 RS |
160 | (derived-mode-set-keymap '(, child)) |
161 | (derived-mode-set-syntax-table '(, child)) | |
162 | (derived-mode-set-abbrev-table '(, child)) | |
76078cf0 RS |
163 | ; Splice in the body (if any). |
164 | (,@ body) | |
b72226e3 RS |
165 | ;;; ; Run the setup function, if |
166 | ;;; ; any -- this will soon be | |
167 | ;;; ; obsolete. | |
7ada1a07 | 168 | ;;; (derived-mode-run-setup-function '(, child)) |
e2154af9 | 169 | ; Run the hook, if any. |
7ada1a07 | 170 | (derived-mode-run-hooks '(, child)))))) |
76078cf0 RS |
171 | |
172 | ||
06d35594 | 173 | ;; PUBLIC: find the ultimate class of a derived mode. |
76078cf0 | 174 | |
06d35594 | 175 | (defun derived-mode-class (mode) |
76078cf0 | 176 | "Find the class of a major mode. |
06d35594 RS |
177 | A mode's class is the first ancestor which is NOT a derived mode. |
178 | Use the `derived-mode-parent' property of the symbol to trace backwards." | |
179 | (while (get mode 'derived-mode-parent) | |
180 | (setq mode (get mode 'derived-mode-parent))) | |
76078cf0 RS |
181 | mode) |
182 | ||
183 | \f | |
184 | ;; Inline functions to construct various names from a mode name. | |
185 | ||
06d35594 | 186 | (defsubst derived-mode-setup-function-name (mode) |
76078cf0 RS |
187 | "Construct a setup-function name based on a mode name." |
188 | (intern (concat (symbol-name mode) "-setup"))) | |
189 | ||
e2154af9 RS |
190 | (defsubst derived-mode-hook-name (mode) |
191 | "Construct the mode hook name based on mode name MODE." | |
192 | (intern (concat (symbol-name mode) "-hook"))) | |
76078cf0 | 193 | |
06d35594 | 194 | (defsubst derived-mode-map-name (mode) |
76078cf0 RS |
195 | "Construct a map name based on a mode name." |
196 | (intern (concat (symbol-name mode) "-map"))) | |
197 | ||
06d35594 | 198 | (defsubst derived-mode-syntax-table-name (mode) |
76078cf0 RS |
199 | "Construct a syntax-table name based on a mode name." |
200 | (intern (concat (symbol-name mode) "-syntax-table"))) | |
201 | ||
06d35594 | 202 | (defsubst derived-mode-abbrev-table-name (mode) |
76078cf0 RS |
203 | "Construct an abbrev-table name based on a mode name." |
204 | (intern (concat (symbol-name mode) "-abbrev-table"))) | |
205 | ||
206 | \f | |
06d35594 | 207 | ;; Utility functions for defining a derived mode. |
76078cf0 | 208 | |
ec830850 | 209 | ;;;###autoload |
06d35594 | 210 | (defun derived-mode-init-mode-variables (mode) |
26757b4b RS |
211 | "Initialise variables for a new mode. |
212 | Right now, if they don't already exist, set up a blank keymap, an | |
213 | empty syntax table, and an empty abbrev table -- these will be merged | |
214 | the first time the mode is used." | |
215 | ||
06d35594 | 216 | (if (boundp (derived-mode-map-name mode)) |
26757b4b | 217 | t |
06d35594 | 218 | (eval (` (defvar (, (derived-mode-map-name mode)) |
26757b4b RS |
219 | (make-sparse-keymap) |
220 | (, (format "Keymap for %s." mode))))) | |
06d35594 | 221 | (put (derived-mode-map-name mode) 'derived-mode-unmerged t)) |
26757b4b | 222 | |
06d35594 | 223 | (if (boundp (derived-mode-syntax-table-name mode)) |
26757b4b | 224 | t |
06d35594 | 225 | (eval (` (defvar (, (derived-mode-syntax-table-name mode)) |
a43944b5 RS |
226 | ;; Make a syntax table which doesn't specify anything |
227 | ;; for any char. Valid data will be merged in by | |
228 | ;; derived-mode-merge-syntax-tables. | |
229 | (make-char-table 'syntax-table nil) | |
26757b4b | 230 | (, (format "Syntax table for %s." mode))))) |
06d35594 | 231 | (put (derived-mode-syntax-table-name mode) 'derived-mode-unmerged t)) |
26757b4b | 232 | |
06d35594 | 233 | (if (boundp (derived-mode-abbrev-table-name mode)) |
26757b4b | 234 | t |
06d35594 RS |
235 | (eval (` (defvar (, (derived-mode-abbrev-table-name mode)) |
236 | (progn (define-abbrev-table (derived-mode-abbrev-table-name mode) nil) | |
26757b4b RS |
237 | (make-abbrev-table)) |
238 | (, (format "Abbrev table for %s." mode))))))) | |
76078cf0 | 239 | |
06d35594 | 240 | (defun derived-mode-make-docstring (parent child) |
76078cf0 RS |
241 | "Construct a docstring for a new mode if none is provided." |
242 | ||
06d35594 | 243 | (format "This major mode is a variant of `%s', created by `define-derived-mode'. |
b72226e3 RS |
244 | It inherits all of the parent's attributes, but has its own keymap, |
245 | abbrev table and syntax table: | |
76078cf0 | 246 | |
b72226e3 | 247 | `%s-map' and `%s-syntax-table' |
76078cf0 RS |
248 | |
249 | which more-or-less shadow | |
250 | ||
b72226e3 | 251 | `%s-map' and `%s-syntax-table' |
76078cf0 RS |
252 | |
253 | \\{%s-map}" parent child child parent parent child)) | |
254 | ||
255 | \f | |
06d35594 | 256 | ;; Utility functions for running a derived mode. |
76078cf0 | 257 | |
06d35594 | 258 | (defun derived-mode-set-keymap (mode) |
76078cf0 | 259 | "Set the keymap of the new mode, maybe merging with the parent." |
06d35594 | 260 | (let* ((map-name (derived-mode-map-name mode)) |
76078cf0 RS |
261 | (new-map (eval map-name)) |
262 | (old-map (current-local-map))) | |
f34e6918 RS |
263 | (and old-map |
264 | (get map-name 'derived-mode-unmerged) | |
265 | (derived-mode-merge-keymaps old-map new-map)) | |
06d35594 | 266 | (put map-name 'derived-mode-unmerged nil) |
26757b4b | 267 | (use-local-map new-map))) |
76078cf0 | 268 | |
06d35594 | 269 | (defun derived-mode-set-syntax-table (mode) |
76078cf0 | 270 | "Set the syntax table of the new mode, maybe merging with the parent." |
06d35594 | 271 | (let* ((table-name (derived-mode-syntax-table-name mode)) |
76078cf0 RS |
272 | (old-table (syntax-table)) |
273 | (new-table (eval table-name))) | |
06d35594 RS |
274 | (if (get table-name 'derived-mode-unmerged) |
275 | (derived-mode-merge-syntax-tables old-table new-table)) | |
276 | (put table-name 'derived-mode-unmerged nil) | |
26757b4b | 277 | (set-syntax-table new-table))) |
76078cf0 | 278 | |
06d35594 | 279 | (defun derived-mode-set-abbrev-table (mode) |
26757b4b RS |
280 | "Set the abbrev table if it exists. |
281 | Always merge its parent into it, since the merge is non-destructive." | |
06d35594 | 282 | (let* ((table-name (derived-mode-abbrev-table-name mode)) |
26757b4b RS |
283 | (old-table local-abbrev-table) |
284 | (new-table (eval table-name))) | |
06d35594 | 285 | (derived-mode-merge-abbrev-tables old-table new-table) |
26757b4b | 286 | (setq local-abbrev-table new-table))) |
76078cf0 | 287 | |
06d35594 | 288 | ;;;(defun derived-mode-run-setup-function (mode) |
b72226e3 | 289 | ;;; "Run the setup function if it exists." |
76078cf0 | 290 | |
06d35594 | 291 | ;;; (let ((fname (derived-mode-setup-function-name mode))) |
b72226e3 RS |
292 | ;;; (if (fboundp fname) |
293 | ;;; (funcall fname)))) | |
76078cf0 | 294 | |
06d35594 | 295 | (defun derived-mode-run-hooks (mode) |
e2154af9 | 296 | "Run the mode hook for MODE." |
76078cf0 | 297 | |
e2154af9 | 298 | (let ((hooks-name (derived-mode-hook-name mode))) |
76078cf0 RS |
299 | (if (boundp hooks-name) |
300 | (run-hooks hooks-name)))) | |
301 | ||
302 | ;; Functions to merge maps and tables. | |
303 | ||
06d35594 | 304 | (defun derived-mode-merge-keymaps (old new) |
26757b4b | 305 | "Merge an old keymap into a new one. |
37a4f4b6 | 306 | The old keymap is set to be the last cdr of the new one, so that there will |
76078cf0 | 307 | be automatic inheritance." |
37a4f4b6 RS |
308 | (let ((tail new)) |
309 | ;; Scan the NEW map for prefix keys. | |
310 | (while (consp tail) | |
311 | (and (consp (car tail)) | |
312 | (let* ((key (vector (car (car tail)))) | |
313 | (subnew (lookup-key new key)) | |
314 | (subold (lookup-key old key))) | |
315 | ;; If KEY is a prefix key in both OLD and NEW, merge them. | |
316 | (and (keymapp subnew) (keymapp subold) | |
317 | (derived-mode-merge-keymaps subold subnew)))) | |
318 | (and (vectorp (car tail)) | |
319 | ;; Search a vector of ASCII char bindings for prefix keys. | |
320 | (let ((i (1- (length (car tail))))) | |
321 | (while (>= i 0) | |
322 | (let* ((key (vector i)) | |
323 | (subnew (lookup-key new key)) | |
324 | (subold (lookup-key old key))) | |
325 | ;; If KEY is a prefix key in both OLD and NEW, merge them. | |
326 | (and (keymapp subnew) (keymapp subold) | |
327 | (derived-mode-merge-keymaps subold subnew))) | |
328 | (setq i (1- i))))) | |
329 | (setq tail (cdr tail)))) | |
26757b4b | 330 | (setcdr (nthcdr (1- (length new)) new) old)) |
76078cf0 | 331 | |
06d35594 | 332 | (defun derived-mode-merge-syntax-tables (old new) |
26757b4b | 333 | "Merge an old syntax table into a new one. |
76078cf0 | 334 | Where the new table already has an entry, nothing is copied from the old one." |
5dee7dae | 335 | (set-char-table-parent new old)) |
26757b4b | 336 | |
56152e17 RS |
337 | ;; Merge an old abbrev table into a new one. |
338 | ;; This function requires internal knowledge of how abbrev tables work, | |
339 | ;; presuming that they are obarrays with the abbrev as the symbol, the expansion | |
340 | ;; as the value of the symbol, and the hook as the function definition. | |
06d35594 | 341 | (defun derived-mode-merge-abbrev-tables (old new) |
56152e17 RS |
342 | (if old |
343 | (mapatoms | |
344 | (function | |
345 | (lambda (symbol) | |
346 | (or (intern-soft (symbol-name symbol) new) | |
347 | (define-abbrev new (symbol-name symbol) | |
348 | (symbol-value symbol) (symbol-function symbol))))) | |
349 | old))) | |
76078cf0 | 350 | |
06d35594 | 351 | (provide 'derived) |
26757b4b | 352 | |
06d35594 | 353 | ;;; derived.el ends here |