1 ;;; derived.el --- allow inheritance of major modes
2 ;; (formerly mode-clone.el)
4 ;; Copyright (C) 1993-1994, 1999, 2001-2016 Free Software Foundation,
7 ;; Author: David Megginson (dmeggins@aix1.uottawa.ca)
8 ;; Maintainer: emacs-devel@gnu.org
9 ;; Keywords: extensions
12 ;; This file is part of GNU Emacs.
14 ;; GNU Emacs is free software: you can redistribute it and/or modify
15 ;; it under the terms of the GNU General Public License as published by
16 ;; the Free Software Foundation, either version 3 of the License, or
17 ;; (at your option) any later version.
19 ;; GNU Emacs is distributed in the hope that it will be useful,
20 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
21 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 ;; GNU General Public License for more details.
24 ;; You should have received a copy of the GNU General Public License
25 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
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).
94 ;;; PRIVATE: defsubst must be defined before they are first used
96 (defsubst derived-mode-hook-name (mode)
97 "Construct a mode-hook name based on a MODE name."
98 (intern (concat (symbol-name mode) "-hook")))
100 (defsubst derived-mode-map-name (mode)
101 "Construct a map name based on a MODE name."
102 (intern (concat (symbol-name mode) "-map")))
104 (defsubst derived-mode-syntax-table-name (mode)
105 "Construct a syntax-table name based on a MODE name."
106 (intern (concat (symbol-name mode) "-syntax-table")))
108 (defsubst derived-mode-abbrev-table-name (mode)
109 "Construct an abbrev-table name based on a MODE name."
110 (intern (concat (symbol-name mode) "-abbrev-table")))
112 ;; PUBLIC: define a new major mode which inherits from an existing one.
115 (defmacro define-derived-mode (child parent name &optional docstring &rest body)
116 "Create a new mode as a variant of an existing mode.
118 The arguments to this command are as follow:
120 CHILD: the name of the command for the derived mode.
121 PARENT: the name of the command for the parent mode (e.g. `text-mode')
122 or nil if there is no parent.
123 NAME: a string which will appear in the status line (e.g. \"Hypertext\")
124 DOCSTRING: an optional documentation string--if you do not supply one,
125 the function will attempt to invent something useful.
126 BODY: forms to execute just before running the
127 hooks for the new mode. Do not use `interactive' here.
129 BODY can start with a bunch of keyword arguments. The following keyword
130 arguments are currently understood:
132 Declare the customization group that corresponds to this mode.
133 The command `customize-mode' uses this.
135 Use TABLE instead of the default (CHILD-syntax-table).
136 A nil value means to simply use the same syntax-table as the parent.
138 Use TABLE instead of the default (CHILD-abbrev-table).
139 A nil value means to simply use the same abbrev-table as the parent.
141 A single lisp form which is evaluated after the mode hooks have been
142 run. It should not be quoted.
144 Here is how you could define LaTeX-Thesis mode as a variant of LaTeX mode:
146 (define-derived-mode LaTeX-thesis-mode LaTeX-mode \"LaTeX-Thesis\")
148 You could then make new key bindings for `LaTeX-thesis-mode-map'
149 without changing regular LaTeX mode. In this example, BODY is empty,
150 and DOCSTRING is generated by default.
152 On a more complicated level, the following command uses `sgml-mode' as
153 the parent, and then sets the variable `case-fold-search' to nil:
155 (define-derived-mode article-mode sgml-mode \"Article\"
156 \"Major mode for editing technical articles.\"
157 (setq case-fold-search nil))
159 Note that if the documentation string had been left out, it would have
160 been generated automatically, with a reference to the keymap.
162 The new mode runs the hook constructed by the function
163 `derived-mode-hook-name'.
165 See Info node `(elisp)Derived Modes' for more details."
166 (declare (debug (&define name symbolp sexp [&optional stringp]
167 [&rest keywordp sexp] def-body))
171 ;; can do for you, ask what it can do to others. IOW, the
172 ;; missing of indentation setting here is the indentation
173 ;; setting and not an oversight.
176 (when (and docstring (not (stringp docstring)))
177 ;; Some trickiness, since what appears to be the docstring may really be
178 ;; the first element of the body.
179 (push docstring body)
180 (setq docstring nil))
182 (when (eq parent 'fundamental-mode) (setq parent nil))
184 (let ((map (derived-mode-map-name child))
185 (syntax (derived-mode-syntax-table-name child))
186 (abbrev (derived-mode-abbrev-table-name child))
189 (hook (derived-mode-hook-name child))
193 ;; Process the keyword args.
194 (while (keywordp (car body))
196 (`:group (setq group (pop body)))
197 (`:abbrev-table (setq abbrev (pop body)) (setq declare-abbrev nil))
198 (`:syntax-table (setq syntax (pop body)) (setq declare-syntax nil))
199 (`:after-hook (setq after-hook (pop body)))
202 (setq docstring (derived-mode-make-docstring
203 parent child docstring syntax abbrev))
207 ,(format "Hook run after entering %s mode.
208 No problems result if this variable is not bound.
209 `add-hook' automatically binds it. (This is true for all hook variables.)"
211 (unless (boundp ',map)
212 (put ',map 'definition-name ',child))
213 (with-no-warnings (defvar ,map (make-sparse-keymap)))
214 (unless (get ',map 'variable-documentation)
215 (put ',map 'variable-documentation
216 (purecopy ,(format "Keymap for `%s'." child))))
219 (unless (boundp ',syntax)
220 (put ',syntax 'definition-name ',child))
221 (defvar ,syntax (make-syntax-table))
222 (unless (get ',syntax 'variable-documentation)
223 (put ',syntax 'variable-documentation
224 (purecopy ,(format "Syntax table for `%s'." child))))))
227 (put ',abbrev 'definition-name ',child)
229 (progn (define-abbrev-table ',abbrev nil) ,abbrev))
230 (unless (get ',abbrev 'variable-documentation)
231 (put ',abbrev 'variable-documentation
232 (purecopy ,(format "Abbrev table for `%s'." child))))))
233 (put ',child 'derived-mode-parent ',parent)
234 ,(if group `(put ',child 'custom-mode-group ,group))
242 (,(or parent 'kill-all-local-variables))
243 ; Identify the child mode.
244 (setq major-mode (quote ,child))
245 (setq mode-name ,name)
246 ; Identify special modes.
249 (if (get (quote ,parent) 'mode-class)
250 (put (quote ,child) 'mode-class
251 (get (quote ,parent) 'mode-class)))
252 ; Set up maps and tables.
253 (unless (keymap-parent ,map)
254 ;; It would probably be better to set the keymap's parent
255 ;; at the toplevel rather than inside the mode function,
256 ;; but this is not easy for at least the following reasons:
257 ;; - the parent (and its keymap) may not yet be loaded.
258 ;; - the parent's keymap name may be called something else
259 ;; than <parent>-mode-map.
260 (set-keymap-parent ,map (current-local-map)))
261 ,(when declare-syntax
262 `(let ((parent (char-table-parent ,syntax)))
264 (not (eq parent (standard-syntax-table))))
265 (set-char-table-parent ,syntax (syntax-table)))))
266 ,(when declare-abbrev
267 `(unless (or (abbrev-table-get ,abbrev :parents)
268 ;; This can happen if the major mode defines
269 ;; the abbrev-table to be its parent's.
270 (eq ,abbrev local-abbrev-table))
271 (abbrev-table-put ,abbrev :parents
272 (list local-abbrev-table))))))
274 ,(when syntax `(set-syntax-table ,syntax))
275 ,(when abbrev `(setq local-abbrev-table ,abbrev))
276 ; Splice in the body (if any).
279 ;; Run the hooks, if any.
280 (run-mode-hooks ',hook)
282 `((if delay-mode-hooks
283 (push ',after-hook delayed-after-hook-forms)
286 ;; PUBLIC: find the ultimate class of a derived mode.
288 (defun derived-mode-class (mode)
289 "Find the class of a major MODE.
290 A mode's class is the first ancestor which is NOT a derived mode.
291 Use the `derived-mode-parent' property of the symbol to trace backwards.
292 Since major-modes might all derive from `fundamental-mode', this function
294 (declare (obsolete derived-mode-p "22.1"))
295 (while (get mode 'derived-mode-parent)
296 (setq mode (get mode 'derived-mode-parent)))
302 (defun derived-mode-make-docstring (parent child &optional
303 docstring syntax abbrev)
304 "Construct a docstring for a new mode if none is provided."
306 (let ((map (derived-mode-map-name child))
307 (hook (derived-mode-hook-name child)))
309 (unless (stringp docstring)
310 ;; Use a default docstring.
314 (format "Major-mode.\nUses keymap `%s'%s%s." map
315 (if abbrev (format "%s abbrev table `%s'"
316 (if syntax "," " and") abbrev) "")
317 (if syntax (format " and syntax-table `%s'" syntax) ""))
318 (format "Major mode derived from `%s' by `define-derived-mode'.
319 It inherits all of the parent's attributes, but has its own keymap%s:
323 which more-or-less shadow%s %s's corresponding table%s."
325 (cond ((and abbrev syntax)
326 ",\nabbrev table and syntax table")
327 (abbrev "\nand abbrev table")
328 (syntax "\nand syntax table")
331 (cond ((and abbrev syntax)
332 (format ", `%s' and `%s'" abbrev syntax))
334 (format " and `%s'" (or abbrev syntax)))
336 (if (or abbrev syntax) "" "s")
338 (if (or abbrev syntax) "s" "")))))
340 (unless (string-match (regexp-quote (symbol-name hook)) docstring)
341 ;; Make sure the docstring mentions the mode's hook.
347 "\n\nIn addition to any hooks its parent mode "
348 (if (string-match (format "[`‘]%s['’]"
350 (symbol-name parent)))
353 (format "`%s' " parent))
354 "might have run,\nthis mode "))
355 (format "runs the hook `%s'" hook)
356 ", as the final or penultimate step\nduring initialization.")))
358 (unless (string-match "\\\\[{[]" docstring)
359 ;; And don't forget to put the mode's keymap.
360 (setq docstring (concat docstring "\n\n\\{" (symbol-name map) "}")))
366 ;; The functions below are only provided for backward compatibility with
367 ;; code byte-compiled with versions of derived.el prior to Emacs-21.
369 (defsubst derived-mode-setup-function-name (mode)
370 "Construct a setup-function name based on a MODE name."
371 (intern (concat (symbol-name mode) "-setup")))
374 ;; Utility functions for defining a derived mode.
377 (defun derived-mode-init-mode-variables (mode)
378 "Initialize variables for a new MODE.
379 Right now, if they don't already exist, set up a blank keymap, an
380 empty syntax table, and an empty abbrev table -- these will be merged
381 the first time the mode is used."
383 (if (boundp (derived-mode-map-name mode))
385 (eval `(defvar ,(derived-mode-map-name mode)
387 ,(format "Keymap for %s." mode)))
388 (put (derived-mode-map-name mode) 'derived-mode-unmerged t))
390 (if (boundp (derived-mode-syntax-table-name mode))
392 (eval `(defvar ,(derived-mode-syntax-table-name mode)
393 ;; Make a syntax table which doesn't specify anything
394 ;; for any char. Valid data will be merged in by
395 ;; derived-mode-merge-syntax-tables.
396 (make-char-table 'syntax-table nil)
397 ,(format "Syntax table for %s." mode)))
398 (put (derived-mode-syntax-table-name mode) 'derived-mode-unmerged t))
400 (if (boundp (derived-mode-abbrev-table-name mode))
402 (eval `(defvar ,(derived-mode-abbrev-table-name mode)
404 (define-abbrev-table (derived-mode-abbrev-table-name mode) nil)
406 ,(format "Abbrev table for %s." mode)))))
408 ;; Utility functions for running a derived mode.
410 (defun derived-mode-set-keymap (mode)
411 "Set the keymap of the new MODE, maybe merging with the parent."
412 (let* ((map-name (derived-mode-map-name mode))
413 (new-map (eval map-name))
414 (old-map (current-local-map)))
416 (get map-name 'derived-mode-unmerged)
417 (derived-mode-merge-keymaps old-map new-map))
418 (put map-name 'derived-mode-unmerged nil)
419 (use-local-map new-map)))
421 (defun derived-mode-set-syntax-table (mode)
422 "Set the syntax table of the new MODE, maybe merging with the parent."
423 (let* ((table-name (derived-mode-syntax-table-name mode))
424 (old-table (syntax-table))
425 (new-table (eval table-name)))
426 (if (get table-name 'derived-mode-unmerged)
427 (derived-mode-merge-syntax-tables old-table new-table))
428 (put table-name 'derived-mode-unmerged nil)
429 (set-syntax-table new-table)))
431 (defun derived-mode-set-abbrev-table (mode)
432 "Set the abbrev table for MODE if it exists.
433 Always merge its parent into it, since the merge is non-destructive."
434 (let* ((table-name (derived-mode-abbrev-table-name mode))
435 (old-table local-abbrev-table)
436 (new-table (eval table-name)))
437 (derived-mode-merge-abbrev-tables old-table new-table)
438 (setq local-abbrev-table new-table)))
440 (defun derived-mode-run-hooks (mode)
441 "Run the mode hook for MODE."
442 (let ((hooks-name (derived-mode-hook-name mode)))
443 (if (boundp hooks-name)
444 (run-hooks hooks-name))))
446 ;; Functions to merge maps and tables.
448 (defun derived-mode-merge-keymaps (old new)
449 "Merge an OLD keymap into a NEW one.
450 The old keymap is set to be the last cdr of the new one, so that there will
451 be automatic inheritance."
452 ;; ?? Can this just use `set-keymap-parent'?
454 ;; Scan the NEW map for prefix keys.
456 (and (consp (car tail))
457 (let* ((key (vector (car (car tail))))
458 (subnew (lookup-key new key))
459 (subold (lookup-key old key)))
460 ;; If KEY is a prefix key in both OLD and NEW, merge them.
461 (and (keymapp subnew) (keymapp subold)
462 (derived-mode-merge-keymaps subold subnew))))
463 (and (vectorp (car tail))
464 ;; Search a vector of ASCII char bindings for prefix keys.
465 (let ((i (1- (length (car tail)))))
467 (let* ((key (vector i))
468 (subnew (lookup-key new key))
469 (subold (lookup-key old key)))
470 ;; If KEY is a prefix key in both OLD and NEW, merge them.
471 (and (keymapp subnew) (keymapp subold)
472 (derived-mode-merge-keymaps subold subnew)))
474 (setq tail (cdr tail))))
475 (setcdr (nthcdr (1- (length new)) new) old))
477 (defun derived-mode-merge-syntax-tables (old new)
478 "Merge an OLD syntax table into a NEW one.
479 Where the new table already has an entry, nothing is copied from the old one."
480 (set-char-table-parent new old))
482 ;; Merge an old abbrev table into a new one.
483 ;; This function requires internal knowledge of how abbrev tables work,
484 ;; presuming that they are obarrays with the abbrev as the symbol, the expansion
485 ;; as the value of the symbol, and the hook as the function definition.
486 (defun derived-mode-merge-abbrev-tables (old new)
490 (or (intern-soft (symbol-name symbol) new)
491 (define-abbrev new (symbol-name symbol)
492 (symbol-value symbol) (symbol-function symbol))))
497 ;;; derived.el ends here