1 ;;; derived.el --- allow inheritance of major modes
2 ;; (formerly mode-clone.el)
4 ;; Copyright (C) 1993-1994, 1999, 2001-2017 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
))))
220 (unless (boundp ',syntax
)
221 (put ',syntax
'definition-name
',child
)
222 (defvar ,syntax
(make-syntax-table)))
223 (unless (get ',syntax
'variable-documentation
)
224 (put ',syntax
'variable-documentation
225 (purecopy ,(format "Syntax table for `%s'." child
))))))
229 (unless (boundp ',abbrev
)
230 (put ',abbrev
'definition-name
',child
)
232 (progn (define-abbrev-table ',abbrev nil
) ,abbrev
)))
233 (unless (get ',abbrev
'variable-documentation
)
234 (put ',abbrev
'variable-documentation
235 (purecopy ,(format "Abbrev table for `%s'." child
))))))
236 (put ',child
'derived-mode-parent
',parent
)
237 ,(if group
`(put ',child
'custom-mode-group
,group
))
245 (,(or parent
'kill-all-local-variables
))
246 ; Identify the child mode.
247 (setq major-mode
(quote ,child
))
248 (setq mode-name
,name
)
249 ; Identify special modes.
252 (if (get (quote ,parent
) 'mode-class
)
253 (put (quote ,child
) 'mode-class
254 (get (quote ,parent
) 'mode-class
)))
255 ; Set up maps and tables.
256 (unless (keymap-parent ,map
)
257 ;; It would probably be better to set the keymap's parent
258 ;; at the toplevel rather than inside the mode function,
259 ;; but this is not easy for at least the following reasons:
260 ;; - the parent (and its keymap) may not yet be loaded.
261 ;; - the parent's keymap name may be called something else
262 ;; than <parent>-mode-map.
263 (set-keymap-parent ,map
(current-local-map)))
264 ,(when declare-syntax
265 `(let ((parent (char-table-parent ,syntax
)))
267 (not (eq parent
(standard-syntax-table))))
268 (set-char-table-parent ,syntax
(syntax-table)))))
269 ,(when declare-abbrev
270 `(unless (or (abbrev-table-get ,abbrev
:parents
)
271 ;; This can happen if the major mode defines
272 ;; the abbrev-table to be its parent's.
273 (eq ,abbrev local-abbrev-table
))
274 (abbrev-table-put ,abbrev
:parents
275 (list local-abbrev-table
))))))
277 ,(when syntax
`(set-syntax-table ,syntax
))
278 ,(when abbrev
`(setq local-abbrev-table
,abbrev
))
279 ; Splice in the body (if any).
282 ;; Run the hooks, if any.
283 (run-mode-hooks ',hook
)
285 `((if delay-mode-hooks
286 (push ',after-hook delayed-after-hook-forms
)
289 ;; PUBLIC: find the ultimate class of a derived mode.
291 (defun derived-mode-class (mode)
292 "Find the class of a major MODE.
293 A mode's class is the first ancestor which is NOT a derived mode.
294 Use the `derived-mode-parent' property of the symbol to trace backwards.
295 Since major-modes might all derive from `fundamental-mode', this function
297 (declare (obsolete derived-mode-p
"22.1"))
298 (while (get mode
'derived-mode-parent
)
299 (setq mode
(get mode
'derived-mode-parent
)))
305 (defun derived-mode-make-docstring (parent child
&optional
306 docstring syntax abbrev
)
307 "Construct a docstring for a new mode if none is provided."
309 (let ((map (derived-mode-map-name child
))
310 (hook (derived-mode-hook-name child
)))
312 (unless (stringp docstring
)
313 ;; Use a default docstring.
317 (format "Major-mode.\nUses keymap `%s'%s%s." map
318 (if abbrev
(format "%s abbrev table `%s'"
319 (if syntax
"," " and") abbrev
) "")
320 (if syntax
(format " and syntax-table `%s'" syntax
) ""))
321 (format "Major mode derived from `%s' by `define-derived-mode'.
322 It inherits all of the parent's attributes, but has its own keymap%s:
326 which more-or-less shadow%s %s's corresponding table%s."
328 (cond ((and abbrev syntax
)
329 ",\nabbrev table and syntax table")
330 (abbrev "\nand abbrev table")
331 (syntax "\nand syntax table")
334 (cond ((and abbrev syntax
)
335 (format ", `%s' and `%s'" abbrev syntax
))
337 (format " and `%s'" (or abbrev syntax
)))
339 (if (or abbrev syntax
) "" "s")
341 (if (or abbrev syntax
) "s" "")))))
343 (unless (string-match (regexp-quote (symbol-name hook
)) docstring
)
344 ;; Make sure the docstring mentions the mode's hook.
350 "\n\nIn addition to any hooks its parent mode "
351 (if (string-match (format "[`‘]%s['’]"
353 (symbol-name parent
)))
356 (format "`%s' " parent
))
357 "might have run,\nthis mode "))
358 (format "runs the hook `%s'" hook
)
359 ", as the final or penultimate step\nduring initialization.")))
361 (unless (string-match "\\\\[{[]" docstring
)
362 ;; And don't forget to put the mode's keymap.
363 (setq docstring
(concat docstring
"\n\n\\{" (symbol-name map
) "}")))
369 ;; The functions below are only provided for backward compatibility with
370 ;; code byte-compiled with versions of derived.el prior to Emacs-21.
372 (defsubst derived-mode-setup-function-name
(mode)
373 "Construct a setup-function name based on a MODE name."
374 (intern (concat (symbol-name mode
) "-setup")))
377 ;; Utility functions for defining a derived mode.
380 (defun derived-mode-init-mode-variables (mode)
381 "Initialize variables for a new MODE.
382 Right now, if they don't already exist, set up a blank keymap, an
383 empty syntax table, and an empty abbrev table -- these will be merged
384 the first time the mode is used."
386 (if (boundp (derived-mode-map-name mode
))
388 (eval `(defvar ,(derived-mode-map-name mode
)
390 ,(format "Keymap for %s." mode
)))
391 (put (derived-mode-map-name mode
) 'derived-mode-unmerged t
))
393 (if (boundp (derived-mode-syntax-table-name mode
))
395 (eval `(defvar ,(derived-mode-syntax-table-name mode
)
396 ;; Make a syntax table which doesn't specify anything
397 ;; for any char. Valid data will be merged in by
398 ;; derived-mode-merge-syntax-tables.
399 (make-char-table 'syntax-table nil
)
400 ,(format "Syntax table for %s." mode
)))
401 (put (derived-mode-syntax-table-name mode
) 'derived-mode-unmerged t
))
403 (if (boundp (derived-mode-abbrev-table-name mode
))
405 (eval `(defvar ,(derived-mode-abbrev-table-name mode
)
407 (define-abbrev-table (derived-mode-abbrev-table-name mode
) nil
)
409 ,(format "Abbrev table for %s." mode
)))))
411 ;; Utility functions for running a derived mode.
413 (defun derived-mode-set-keymap (mode)
414 "Set the keymap of the new MODE, maybe merging with the parent."
415 (let* ((map-name (derived-mode-map-name mode
))
416 (new-map (eval map-name
))
417 (old-map (current-local-map)))
419 (get map-name
'derived-mode-unmerged
)
420 (derived-mode-merge-keymaps old-map new-map
))
421 (put map-name
'derived-mode-unmerged nil
)
422 (use-local-map new-map
)))
424 (defun derived-mode-set-syntax-table (mode)
425 "Set the syntax table of the new MODE, maybe merging with the parent."
426 (let* ((table-name (derived-mode-syntax-table-name mode
))
427 (old-table (syntax-table))
428 (new-table (eval table-name
)))
429 (if (get table-name
'derived-mode-unmerged
)
430 (derived-mode-merge-syntax-tables old-table new-table
))
431 (put table-name
'derived-mode-unmerged nil
)
432 (set-syntax-table new-table
)))
434 (defun derived-mode-set-abbrev-table (mode)
435 "Set the abbrev table for MODE if it exists.
436 Always merge its parent into it, since the merge is non-destructive."
437 (let* ((table-name (derived-mode-abbrev-table-name mode
))
438 (old-table local-abbrev-table
)
439 (new-table (eval table-name
)))
440 (derived-mode-merge-abbrev-tables old-table new-table
)
441 (setq local-abbrev-table new-table
)))
443 (defun derived-mode-run-hooks (mode)
444 "Run the mode hook for MODE."
445 (let ((hooks-name (derived-mode-hook-name mode
)))
446 (if (boundp hooks-name
)
447 (run-hooks hooks-name
))))
449 ;; Functions to merge maps and tables.
451 (defun derived-mode-merge-keymaps (old new
)
452 "Merge an OLD keymap into a NEW one.
453 The old keymap is set to be the last cdr of the new one, so that there will
454 be automatic inheritance."
455 ;; ?? Can this just use `set-keymap-parent'?
457 ;; Scan the NEW map for prefix keys.
459 (and (consp (car tail
))
460 (let* ((key (vector (car (car tail
))))
461 (subnew (lookup-key new key
))
462 (subold (lookup-key old key
)))
463 ;; If KEY is a prefix key in both OLD and NEW, merge them.
464 (and (keymapp subnew
) (keymapp subold
)
465 (derived-mode-merge-keymaps subold subnew
))))
466 (and (vectorp (car tail
))
467 ;; Search a vector of ASCII char bindings for prefix keys.
468 (let ((i (1- (length (car tail
)))))
470 (let* ((key (vector i
))
471 (subnew (lookup-key new key
))
472 (subold (lookup-key old key
)))
473 ;; If KEY is a prefix key in both OLD and NEW, merge them.
474 (and (keymapp subnew
) (keymapp subold
)
475 (derived-mode-merge-keymaps subold subnew
)))
477 (setq tail
(cdr tail
))))
478 (setcdr (nthcdr (1- (length new
)) new
) old
))
480 (defun derived-mode-merge-syntax-tables (old new
)
481 "Merge an OLD syntax table into a NEW one.
482 Where the new table already has an entry, nothing is copied from the old one."
483 (set-char-table-parent new old
))
485 ;; Merge an old abbrev table into a new one.
486 ;; This function requires internal knowledge of how abbrev tables work,
487 ;; presuming that they are obarrays with the abbrev as the symbol, the expansion
488 ;; as the value of the symbol, and the hook as the function definition.
489 (defun derived-mode-merge-abbrev-tables (old new
)
493 (or (intern-soft (symbol-name symbol
) new
)
494 (define-abbrev new
(symbol-name symbol
)
495 (symbol-value symbol
) (symbol-function symbol
))))
500 ;;; derived.el ends here