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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 | |
22 | ;; along with GNU Emacs; see the file COPYING. If not, write to | |
23 | ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. | |
24 | \f | |
25 | ;;; Commentary: | |
26 | ||
27 | ;; GNU Emacs is already, in a sense, object oriented -- each object | |
28 | ;; (buffer) belongs to a class (major mode), and that class defines | |
29 | ;; the relationship between messages (input events) and methods | |
30 | ;; (commands) by means of a keymap. | |
31 | ;; | |
32 | ;; The only thing missing is a good scheme of inheritance. It is | |
33 | ;; possible to simulate a single level of inheritance with generous | |
34 | ;; use of hooks and a bit of work -- sgml-mode, for example, also runs | |
35 | ;; the hooks for text-mode, and keymaps can inherit from other keymaps | |
36 | ;; -- but generally, each major mode ends up reinventing the wheel. | |
37 | ;; Ideally, someone should redesign all of Emacs's major modes to | |
38 | ;; follow a more conventional object-oriented system: when defining a | |
39 | ;; new major mode, the user should need only to name the existing mode | |
40 | ;; it is most similar to, then list the (few) differences. | |
41 | ;; | |
42 | ;; In the mean time, this package offers most of the advantages of | |
b72226e3 | 43 | ;; full inheritance with the existing major modes. The macro |
06d35594 | 44 | ;; `define-derived-mode' allows the user to make a variant of an existing |
76078cf0 RS |
45 | ;; major mode, with its own keymap. The new mode will inherit the key |
46 | ;; bindings of its parent, and will, in fact, run its parent first | |
47 | ;; every time it is called. For example, the commands | |
48 | ;; | |
06d35594 | 49 | ;; (define-derived-mode hypertext-mode text-mode "Hypertext" |
76078cf0 RS |
50 | ;; "Major mode for hypertext.\n\n\\{hypertext-mode-map}" |
51 | ;; (setq case-fold-search nil)) | |
52 | ;; | |
53 | ;; (define-key hypertext-mode-map [down-mouse-3] 'do-hyper-link) | |
54 | ;; | |
55 | ;; will create a function `hypertext-mode' with its own (sparse) | |
56 | ;; keymap `hypertext-mode-map.' The command M-x hypertext-mode will | |
57 | ;; perform the following actions: | |
58 | ;; | |
59 | ;; - run the command (text-mode) to get its default setup | |
60 | ;; - replace the current keymap with 'hypertext-mode-map,' which will | |
61 | ;; inherit from 'text-mode-map'. | |
62 | ;; - replace the current syntax table with | |
63 | ;; 'hypertext-mode-syntax-table', which will borrow its defaults | |
64 | ;; from the current text-mode-syntax-table. | |
26757b4b RS |
65 | ;; - replace the current abbrev table with |
66 | ;; 'hypertext-mode-abbrev-table', which will borrow its defaults | |
67 | ;; from the current text-mode-abbrev table | |
76078cf0 RS |
68 | ;; - change the mode line to read "Hypertext" |
69 | ;; - assign the value 'hypertext-mode' to the 'major-mode' variable | |
70 | ;; - run the body of commands provided in the macro -- in this case, | |
71 | ;; set the local variable `case-fold-search' to nil. | |
72 | ;; - **run the command (hypertext-mode-setup), which is empty by | |
73 | ;; default, but may be redefined by the user to contain special | |
74 | ;; commands (ie. setting local variables like 'outline-regexp') | |
75 | ;; **NOTE: do not use this option -- it will soon be obsolete. | |
76 | ;; - run anything assigned to 'hypertext-mode-hooks' (obsolete, but | |
77 | ;; supported for the sake of compatibility). | |
78 | ;; | |
79 | ;; The advantages of this system are threefold. First, text mode is | |
80 | ;; untouched -- if you had added the new keystroke to `text-mode-map,' | |
81 | ;; possibly using hooks, you would have added it to all text buffers | |
82 | ;; -- here, it appears only in hypertext buffers, where it makes | |
06d35594 RS |
83 | ;; sense. Second, it is possible to build even further, and make |
84 | ;; a derived mode from a derived mode. The commands | |
76078cf0 | 85 | ;; |
06d35594 | 86 | ;; (define-derived-mode html-mode hypertext-mode "HTML") |
76078cf0 RS |
87 | ;; [various key definitions] |
88 | ;; | |
89 | ;; will add a new major mode for HTML with very little fuss. | |
90 | ;; | |
06d35594 RS |
91 | ;; Note also the function `derived-mode-class,' which returns the non-derived |
92 | ;; major mode which a derived mode is based on (ie. NOT necessarily the | |
76078cf0 RS |
93 | ;; immediate parent). |
94 | ;; | |
06d35594 RS |
95 | ;; (derived-mode-class 'text-mode) ==> text-mode |
96 | ;; (derived-mode-class 'hypertext-mode) ==> text-mode | |
97 | ;; (derived-mode-class 'html-mode) ==> text-mode | |
76078cf0 RS |
98 | \f |
99 | ;;; Code: | |
100 | ||
101 | ;; PUBLIC: define a new major mode which inherits from an existing one. | |
102 | ||
103 | ;;;###autoload | |
06d35594 RS |
104 | (defmacro define-derived-mode (child parent name &optional docstring &rest body) |
105 | "Create a new mode as a variant of an existing mode. | |
76078cf0 RS |
106 | |
107 | The arguments to this command are as follow: | |
108 | ||
b72226e3 | 109 | PARENT: the name of the command for the parent mode (ie. text-mode). |
06d35594 | 110 | CHILD: the name of the command for the derived mode. |
b72226e3 RS |
111 | NAME: a string which will appear in the status line (ie. \"Hypertext\") |
112 | DOCSTRING: an optional documentation string--if you do not supply one, | |
113 | the function will attempt to invent something useful. | |
114 | BODY: forms to execute just before running the | |
76078cf0 RS |
115 | hooks for the new mode. |
116 | ||
06d35594 | 117 | Here is how you could define LaTeX-Thesis mode as a variant of LaTeX mode: |
76078cf0 | 118 | |
06d35594 | 119 | (define-derived-mode LaTeX-thesis-mode LaTeX-mode \"LaTeX-Thesis\") |
76078cf0 | 120 | |
b72226e3 RS |
121 | You could then make new key bindings for `LaTeX-thesis-mode-map' |
122 | without changing regular LaTeX mode. In this example, BODY is empty, | |
123 | and DOCSTRING is generated by default. | |
76078cf0 | 124 | |
06d35594 RS |
125 | On a more complicated level, the following command uses sgml-mode as |
126 | the parent, and then sets the variable `case-fold-search' to nil: | |
76078cf0 | 127 | |
06d35594 | 128 | (define-derived-mode article-mode sgml-mode \"Article\" |
76078cf0 RS |
129 | \"Major mode for editing technical articles.\" |
130 | (setq case-fold-search nil)) | |
131 | ||
132 | Note that if the documentation string had been left out, it would have | |
133 | been generated automatically, with a reference to the keymap." | |
134 | ||
135 | ; Some trickiness, since what | |
136 | ; appears to be the docstring | |
137 | ; may really be the first | |
138 | ; element of the body. | |
139 | (if (and docstring (not (stringp docstring))) | |
140 | (progn (setq body (cons docstring body)) | |
141 | (setq docstring nil))) | |
06d35594 | 142 | (setq docstring (or docstring (derived-mode-make-docstring parent child))) |
76078cf0 RS |
143 | |
144 | (` (progn | |
06d35594 | 145 | (derived-mode-init-mode-variables (quote (, child))) |
76078cf0 RS |
146 | (defun (, child) () |
147 | (, docstring) | |
148 | (interactive) | |
149 | ; Run the parent. | |
150 | ((, parent)) | |
151 | ; Identify special modes. | |
152 | (if (get (quote (, parent)) 'special) | |
153 | (put (quote (, child)) 'special t)) | |
154 | ; Identify the child mode. | |
155 | (setq major-mode (quote (, child))) | |
156 | (setq mode-name (, name)) | |
157 | ; Set up maps and tables. | |
06d35594 RS |
158 | (derived-mode-set-keymap (quote (, child))) |
159 | (derived-mode-set-syntax-table (quote (, child))) | |
160 | (derived-mode-set-abbrev-table (quote (, child))) | |
76078cf0 RS |
161 | ; Splice in the body (if any). |
162 | (,@ body) | |
b72226e3 RS |
163 | ;;; ; Run the setup function, if |
164 | ;;; ; any -- this will soon be | |
165 | ;;; ; obsolete. | |
06d35594 | 166 | ;;; (derived-mode-run-setup-function (quote (, child))) |
76078cf0 | 167 | ; Run the hooks, if any. |
06d35594 | 168 | (derived-mode-run-hooks (quote (, child))))))) |
76078cf0 RS |
169 | |
170 | ||
06d35594 | 171 | ;; PUBLIC: find the ultimate class of a derived mode. |
76078cf0 | 172 | |
06d35594 | 173 | (defun derived-mode-class (mode) |
76078cf0 | 174 | "Find the class of a major mode. |
06d35594 RS |
175 | A mode's class is the first ancestor which is NOT a derived mode. |
176 | Use the `derived-mode-parent' property of the symbol to trace backwards." | |
177 | (while (get mode 'derived-mode-parent) | |
178 | (setq mode (get mode 'derived-mode-parent))) | |
76078cf0 RS |
179 | mode) |
180 | ||
181 | \f | |
182 | ;; Inline functions to construct various names from a mode name. | |
183 | ||
06d35594 | 184 | (defsubst derived-mode-setup-function-name (mode) |
76078cf0 RS |
185 | "Construct a setup-function name based on a mode name." |
186 | (intern (concat (symbol-name mode) "-setup"))) | |
187 | ||
06d35594 | 188 | (defsubst derived-mode-hooks-name (mode) |
76078cf0 RS |
189 | "Construct a hooks name based on a mode name." |
190 | (intern (concat (symbol-name mode) "-hooks"))) | |
191 | ||
06d35594 | 192 | (defsubst derived-mode-map-name (mode) |
76078cf0 RS |
193 | "Construct a map name based on a mode name." |
194 | (intern (concat (symbol-name mode) "-map"))) | |
195 | ||
06d35594 | 196 | (defsubst derived-mode-syntax-table-name (mode) |
76078cf0 RS |
197 | "Construct a syntax-table name based on a mode name." |
198 | (intern (concat (symbol-name mode) "-syntax-table"))) | |
199 | ||
06d35594 | 200 | (defsubst derived-mode-abbrev-table-name (mode) |
76078cf0 RS |
201 | "Construct an abbrev-table name based on a mode name." |
202 | (intern (concat (symbol-name mode) "-abbrev-table"))) | |
203 | ||
204 | \f | |
06d35594 | 205 | ;; Utility functions for defining a derived mode. |
76078cf0 | 206 | |
06d35594 | 207 | (defun derived-mode-init-mode-variables (mode) |
26757b4b RS |
208 | "Initialise variables for a new mode. |
209 | Right now, if they don't already exist, set up a blank keymap, an | |
210 | empty syntax table, and an empty abbrev table -- these will be merged | |
211 | the first time the mode is used." | |
212 | ||
06d35594 | 213 | (if (boundp (derived-mode-map-name mode)) |
26757b4b | 214 | t |
06d35594 | 215 | (eval (` (defvar (, (derived-mode-map-name mode)) |
26757b4b RS |
216 | (make-sparse-keymap) |
217 | (, (format "Keymap for %s." mode))))) | |
06d35594 | 218 | (put (derived-mode-map-name mode) 'derived-mode-unmerged t)) |
26757b4b | 219 | |
06d35594 | 220 | (if (boundp (derived-mode-syntax-table-name mode)) |
26757b4b | 221 | t |
06d35594 | 222 | (eval (` (defvar (, (derived-mode-syntax-table-name mode)) |
26757b4b RS |
223 | (make-vector 256 nil) |
224 | (, (format "Syntax table for %s." mode))))) | |
06d35594 | 225 | (put (derived-mode-syntax-table-name mode) 'derived-mode-unmerged t)) |
26757b4b | 226 | |
06d35594 | 227 | (if (boundp (derived-mode-abbrev-table-name mode)) |
26757b4b | 228 | t |
06d35594 RS |
229 | (eval (` (defvar (, (derived-mode-abbrev-table-name mode)) |
230 | (progn (define-abbrev-table (derived-mode-abbrev-table-name mode) nil) | |
26757b4b RS |
231 | (make-abbrev-table)) |
232 | (, (format "Abbrev table for %s." mode))))))) | |
76078cf0 | 233 | |
06d35594 | 234 | (defun derived-mode-make-docstring (parent child) |
76078cf0 RS |
235 | "Construct a docstring for a new mode if none is provided." |
236 | ||
06d35594 | 237 | (format "This major mode is a variant of `%s', created by `define-derived-mode'. |
b72226e3 RS |
238 | It inherits all of the parent's attributes, but has its own keymap, |
239 | abbrev table and syntax table: | |
76078cf0 | 240 | |
b72226e3 | 241 | `%s-map' and `%s-syntax-table' |
76078cf0 RS |
242 | |
243 | which more-or-less shadow | |
244 | ||
b72226e3 | 245 | `%s-map' and `%s-syntax-table' |
76078cf0 RS |
246 | |
247 | \\{%s-map}" parent child child parent parent child)) | |
248 | ||
249 | \f | |
06d35594 | 250 | ;; Utility functions for running a derived mode. |
76078cf0 | 251 | |
06d35594 | 252 | (defun derived-mode-set-keymap (mode) |
76078cf0 | 253 | "Set the keymap of the new mode, maybe merging with the parent." |
06d35594 | 254 | (let* ((map-name (derived-mode-map-name mode)) |
76078cf0 RS |
255 | (new-map (eval map-name)) |
256 | (old-map (current-local-map))) | |
06d35594 RS |
257 | (if (get map-name 'derived-mode-unmerged) |
258 | (derived-mode-merge-keymaps old-map new-map)) | |
259 | (put map-name 'derived-mode-unmerged nil) | |
26757b4b | 260 | (use-local-map new-map))) |
76078cf0 | 261 | |
06d35594 | 262 | (defun derived-mode-set-syntax-table (mode) |
76078cf0 | 263 | "Set the syntax table of the new mode, maybe merging with the parent." |
06d35594 | 264 | (let* ((table-name (derived-mode-syntax-table-name mode)) |
76078cf0 RS |
265 | (old-table (syntax-table)) |
266 | (new-table (eval table-name))) | |
06d35594 RS |
267 | (if (get table-name 'derived-mode-unmerged) |
268 | (derived-mode-merge-syntax-tables old-table new-table)) | |
269 | (put table-name 'derived-mode-unmerged nil) | |
26757b4b | 270 | (set-syntax-table new-table))) |
76078cf0 | 271 | |
06d35594 | 272 | (defun derived-mode-set-abbrev-table (mode) |
26757b4b RS |
273 | "Set the abbrev table if it exists. |
274 | Always merge its parent into it, since the merge is non-destructive." | |
06d35594 | 275 | (let* ((table-name (derived-mode-abbrev-table-name mode)) |
26757b4b RS |
276 | (old-table local-abbrev-table) |
277 | (new-table (eval table-name))) | |
06d35594 | 278 | (derived-mode-merge-abbrev-tables old-table new-table) |
26757b4b | 279 | (setq local-abbrev-table new-table))) |
76078cf0 | 280 | |
06d35594 | 281 | ;;;(defun derived-mode-run-setup-function (mode) |
b72226e3 | 282 | ;;; "Run the setup function if it exists." |
76078cf0 | 283 | |
06d35594 | 284 | ;;; (let ((fname (derived-mode-setup-function-name mode))) |
b72226e3 RS |
285 | ;;; (if (fboundp fname) |
286 | ;;; (funcall fname)))) | |
76078cf0 | 287 | |
06d35594 | 288 | (defun derived-mode-run-hooks (mode) |
76078cf0 RS |
289 | "Run the hooks if they exist." |
290 | ||
06d35594 | 291 | (let ((hooks-name (derived-mode-hooks-name mode))) |
76078cf0 RS |
292 | (if (boundp hooks-name) |
293 | (run-hooks hooks-name)))) | |
294 | ||
295 | ;; Functions to merge maps and tables. | |
296 | ||
06d35594 | 297 | (defun derived-mode-merge-keymaps (old new) |
26757b4b | 298 | "Merge an old keymap into a new one. |
76078cf0 RS |
299 | The old keymap is set to be the cdr of the new one, so that there will |
300 | be automatic inheritance." | |
26757b4b | 301 | (setcdr (nthcdr (1- (length new)) new) old)) |
76078cf0 | 302 | |
06d35594 | 303 | (defun derived-mode-merge-syntax-tables (old new) |
26757b4b | 304 | "Merge an old syntax table into a new one. |
76078cf0 RS |
305 | Where the new table already has an entry, nothing is copied from the old one." |
306 | (let ((idx 0) | |
307 | (end (min (length new) (length old)))) | |
308 | (while (< idx end) | |
309 | (if (not (aref new idx)) | |
310 | (aset new idx (aref old idx))) | |
311 | (setq idx (1+ idx))))) | |
26757b4b | 312 | |
06d35594 | 313 | (defun derived-mode-merge-abbrev-tables (old new) |
26757b4b RS |
314 | "Merge an old abbrev table into a new one. |
315 | This function requires internal knowledge of how abbrev tables work, | |
316 | presuming that they are obarrays with the abbrev as the symbol, the expansion | |
317 | as the value of the symbol, and the hook as the function definition. | |
318 | This could well break with some future version of Gnu Emacs." | |
319 | (mapatoms | |
320 | (function | |
321 | (lambda (symbol) | |
322 | (or (intern-soft (symbol-name symbol) new) | |
323 | (define-abbrev new (symbol-name symbol) | |
324 | (symbol-value symbol) (symbol-function symbol))))) | |
325 | old)) | |
76078cf0 | 326 | |
06d35594 | 327 | (provide 'derived) |
26757b4b | 328 | |
06d35594 | 329 | ;;; derived.el ends here |