1
0
mirror of https://git.savannah.gnu.org/git/emacs.git synced 2024-12-24 10:38:38 +00:00
emacs/lisp/emacs-lisp/derived.el
2009-01-05 03:18:22 +00:00

452 lines
17 KiB
EmacsLisp
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

;;; derived.el --- allow inheritance of major modes
;; (formerly mode-clone.el)
;; Copyright (C) 1993, 1994, 1999, 2001, 2002, 2003, 2004,
;; 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
;; Author: David Megginson (dmeggins@aix1.uottawa.ca)
;; Maintainer: FSF
;; Keywords: extensions
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; GNU Emacs is already, in a sense, object oriented -- each object
;; (buffer) belongs to a class (major mode), and that class defines
;; the relationship between messages (input events) and methods
;; (commands) by means of a keymap.
;;
;; The only thing missing is a good scheme of inheritance. It is
;; possible to simulate a single level of inheritance with generous
;; use of hooks and a bit of work -- sgml-mode, for example, also runs
;; the hooks for text-mode, and keymaps can inherit from other keymaps
;; -- but generally, each major mode ends up reinventing the wheel.
;; Ideally, someone should redesign all of Emacs's major modes to
;; follow a more conventional object-oriented system: when defining a
;; new major mode, the user should need only to name the existing mode
;; it is most similar to, then list the (few) differences.
;;
;; In the mean time, this package offers most of the advantages of
;; full inheritance with the existing major modes. The macro
;; `define-derived-mode' allows the user to make a variant of an existing
;; major mode, with its own keymap. The new mode will inherit the key
;; bindings of its parent, and will, in fact, run its parent first
;; every time it is called. For example, the commands
;;
;; (define-derived-mode hypertext-mode text-mode "Hypertext"
;; "Major mode for hypertext.\n\n\\{hypertext-mode-map}"
;; (setq case-fold-search nil))
;;
;; (define-key hypertext-mode-map [down-mouse-3] 'do-hyper-link)
;;
;; will create a function `hypertext-mode' with its own (sparse)
;; keymap `hypertext-mode-map.' The command M-x hypertext-mode will
;; perform the following actions:
;;
;; - run the command (text-mode) to get its default setup
;; - replace the current keymap with 'hypertext-mode-map,' which will
;; inherit from 'text-mode-map'.
;; - replace the current syntax table with
;; 'hypertext-mode-syntax-table', which will borrow its defaults
;; from the current text-mode-syntax-table.
;; - replace the current abbrev table with
;; 'hypertext-mode-abbrev-table', which will borrow its defaults
;; from the current text-mode-abbrev table
;; - change the mode line to read "Hypertext"
;; - assign the value 'hypertext-mode' to the 'major-mode' variable
;; - run the body of commands provided in the macro -- in this case,
;; set the local variable `case-fold-search' to nil.
;;
;; The advantages of this system are threefold. First, text mode is
;; untouched -- if you had added the new keystroke to `text-mode-map,'
;; possibly using hooks, you would have added it to all text buffers
;; -- here, it appears only in hypertext buffers, where it makes
;; sense. Second, it is possible to build even further, and make
;; a derived mode from a derived mode. The commands
;;
;; (define-derived-mode html-mode hypertext-mode "HTML")
;; [various key definitions]
;;
;; will add a new major mode for HTML with very little fuss.
;;
;; Note also the function `derived-mode-p' which can tell if the current
;; mode derives from another. In a hypertext-mode, buffer, for example,
;; (derived-mode-p 'text-mode) would return non-nil. This should always
;; be used in place of (eq major-mode 'text-mode).
;;; Code:
(eval-when-compile (require 'cl))
;;; PRIVATE: defsubst must be defined before they are first used
(defsubst derived-mode-hook-name (mode)
"Construct a mode-hook name based on a MODE name."
(intern (concat (symbol-name mode) "-hook")))
(defsubst derived-mode-map-name (mode)
"Construct a map name based on a MODE name."
(intern (concat (symbol-name mode) "-map")))
(defsubst derived-mode-syntax-table-name (mode)
"Construct a syntax-table name based on a MODE name."
(intern (concat (symbol-name mode) "-syntax-table")))
(defsubst derived-mode-abbrev-table-name (mode)
"Construct an abbrev-table name based on a MODE name."
(intern (concat (symbol-name mode) "-abbrev-table")))
;; PUBLIC: define a new major mode which inherits from an existing one.
;;;###autoload
(defmacro define-derived-mode (child parent name &optional docstring &rest body)
"Create a new mode as a variant of an existing mode.
The arguments to this command are as follow:
CHILD: the name of the command for the derived mode.
PARENT: the name of the command for the parent mode (e.g. `text-mode')
or nil if there is no parent.
NAME: a string which will appear in the status line (e.g. \"Hypertext\")
DOCSTRING: an optional documentation string--if you do not supply one,
the function will attempt to invent something useful.
BODY: forms to execute just before running the
hooks for the new mode. Do not use `interactive' here.
BODY can start with a bunch of keyword arguments. The following keyword
arguments are currently understood:
:group GROUP
Declare the customization group that corresponds to this mode.
The command `customize-mode' uses this.
:syntax-table TABLE
Use TABLE instead of the default.
A nil value means to simply use the same syntax-table as the parent.
:abbrev-table TABLE
Use TABLE instead of the default.
A nil value means to simply use the same abbrev-table as the parent.
Here is how you could define LaTeX-Thesis mode as a variant of LaTeX mode:
(define-derived-mode LaTeX-thesis-mode LaTeX-mode \"LaTeX-Thesis\")
You could then make new key bindings for `LaTeX-thesis-mode-map'
without changing regular LaTeX mode. In this example, BODY is empty,
and DOCSTRING is generated by default.
On a more complicated level, the following command uses `sgml-mode' as
the parent, and then sets the variable `case-fold-search' to nil:
(define-derived-mode article-mode sgml-mode \"Article\"
\"Major mode for editing technical articles.\"
(setq case-fold-search nil))
Note that if the documentation string had been left out, it would have
been generated automatically, with a reference to the keymap.
The new mode runs the hook constructed by the function
`derived-mode-hook-name'.
See Info node `(elisp)Derived Modes' for more details."
(declare (debug (&define name symbolp sexp [&optional stringp]
[&rest keywordp sexp] def-body))
(doc-string 4))
(when (and docstring (not (stringp docstring)))
;; Some trickiness, since what appears to be the docstring may really be
;; the first element of the body.
(push docstring body)
(setq docstring nil))
(when (eq parent 'fundamental-mode) (setq parent nil))
(let ((map (derived-mode-map-name child))
(syntax (derived-mode-syntax-table-name child))
(abbrev (derived-mode-abbrev-table-name child))
(declare-abbrev t)
(declare-syntax t)
(hook (derived-mode-hook-name child))
(group nil))
;; Process the keyword args.
(while (keywordp (car body))
(case (pop body)
(:group (setq group (pop body)))
(:abbrev-table (setq abbrev (pop body)) (setq declare-abbrev nil))
(:syntax-table (setq syntax (pop body)) (setq declare-syntax nil))
(t (pop body))))
(setq docstring (derived-mode-make-docstring
parent child docstring syntax abbrev))
`(progn
(unless (get ',hook 'variable-documentation)
(put ',hook 'variable-documentation
,(format "Hook run when entering %s mode.
No problems result if this variable is not bound.
`add-hook' automatically binds it. (This is true for all hook variables.)"
name)))
(unless (boundp ',map)
(put ',map 'definition-name ',child))
(defvar ,map (make-sparse-keymap))
,(if declare-syntax
`(progn
(unless (boundp ',syntax)
(put ',syntax 'definition-name ',child))
(defvar ,syntax (make-syntax-table))))
,(if declare-abbrev
`(progn
(put ',abbrev 'definition-name ',child)
(defvar ,abbrev
(progn (define-abbrev-table ',abbrev nil) ,abbrev))))
(put ',child 'derived-mode-parent ',parent)
,(if group `(put ',child 'custom-mode-group ,group))
(defun ,child ()
,docstring
(interactive)
; Run the parent.
(delay-mode-hooks
(,(or parent 'kill-all-local-variables))
; Identify the child mode.
(setq major-mode (quote ,child))
(setq mode-name ,name)
; Identify special modes.
,(when parent
`(progn
(if (get (quote ,parent) 'mode-class)
(put (quote ,child) 'mode-class
(get (quote ,parent) 'mode-class)))
; Set up maps and tables.
(unless (keymap-parent ,map)
;; It would probably be better to set the keymap's parent
;; at the toplevel rather than inside the mode function,
;; but this is not easy for at least the following reasons:
;; - the parent (and its keymap) may not yet be loaded.
;; - the parent's keymap name may be called something else
;; than <parent>-mode-map.
(set-keymap-parent ,map (current-local-map)))
,(when declare-syntax
`(let ((parent (char-table-parent ,syntax)))
(unless (and parent
(not (eq parent (standard-syntax-table))))
(set-char-table-parent ,syntax (syntax-table)))))))
(use-local-map ,map)
,(when syntax `(set-syntax-table ,syntax))
,(when abbrev `(setq local-abbrev-table ,abbrev))
; Splice in the body (if any).
,@body
)
;; Run the hooks, if any.
(run-mode-hooks ',hook)))))
;; PUBLIC: find the ultimate class of a derived mode.
(defun derived-mode-class (mode)
"Find the class of a major MODE.
A mode's class is the first ancestor which is NOT a derived mode.
Use the `derived-mode-parent' property of the symbol to trace backwards.
Since major-modes might all derive from `fundamental-mode', this function
is not very useful."
(while (get mode 'derived-mode-parent)
(setq mode (get mode 'derived-mode-parent)))
mode)
(make-obsolete 'derived-mode-class 'derived-mode-p "22.1")
;;; PRIVATE
(defun derived-mode-make-docstring (parent child &optional
docstring syntax abbrev)
"Construct a docstring for a new mode if none is provided."
(let ((map (derived-mode-map-name child))
(hook (derived-mode-hook-name child)))
(unless (stringp docstring)
;; Use a default docstring.
(setq docstring
(if (null parent)
(format "Major-mode.
Uses keymap `%s', abbrev table `%s' and syntax-table `%s'." map abbrev syntax)
(format "Major mode derived from `%s' by `define-derived-mode'.
It inherits all of the parent's attributes, but has its own keymap,
abbrev table and syntax table:
`%s', `%s' and `%s'
which more-or-less shadow %s's corresponding tables."
parent map abbrev syntax parent))))
(unless (string-match (regexp-quote (symbol-name hook)) docstring)
;; Make sure the docstring mentions the mode's hook.
(setq docstring
(concat docstring
(if (null parent)
"\n\nThis mode "
(concat
"\n\nIn addition to any hooks its parent mode "
(if (string-match (regexp-quote (format "`%s'" parent))
docstring) nil
(format "`%s' " parent))
"might have run,\nthis mode "))
(format "runs the hook `%s'" hook)
", as the final step\nduring initialization.")))
(unless (string-match "\\\\[{[]" docstring)
;; And don't forget to put the mode's keymap.
(setq docstring (concat docstring "\n\n\\{" (symbol-name map) "}")))
docstring))
;;; OBSOLETE
;; The functions below are only provided for backward compatibility with
;; code byte-compiled with versions of derived.el prior to Emacs-21.
(defsubst derived-mode-setup-function-name (mode)
"Construct a setup-function name based on a MODE name."
(intern (concat (symbol-name mode) "-setup")))
;; Utility functions for defining a derived mode.
;;;###autoload
(defun derived-mode-init-mode-variables (mode)
"Initialize variables for a new MODE.
Right now, if they don't already exist, set up a blank keymap, an
empty syntax table, and an empty abbrev table -- these will be merged
the first time the mode is used."
(if (boundp (derived-mode-map-name mode))
t
(eval `(defvar ,(derived-mode-map-name mode)
(make-sparse-keymap)
,(format "Keymap for %s." mode)))
(put (derived-mode-map-name mode) 'derived-mode-unmerged t))
(if (boundp (derived-mode-syntax-table-name mode))
t
(eval `(defvar ,(derived-mode-syntax-table-name mode)
;; Make a syntax table which doesn't specify anything
;; for any char. Valid data will be merged in by
;; derived-mode-merge-syntax-tables.
(make-char-table 'syntax-table nil)
,(format "Syntax table for %s." mode)))
(put (derived-mode-syntax-table-name mode) 'derived-mode-unmerged t))
(if (boundp (derived-mode-abbrev-table-name mode))
t
(eval `(defvar ,(derived-mode-abbrev-table-name mode)
(progn
(define-abbrev-table (derived-mode-abbrev-table-name mode) nil)
(make-abbrev-table))
,(format "Abbrev table for %s." mode)))))
;; Utility functions for running a derived mode.
(defun derived-mode-set-keymap (mode)
"Set the keymap of the new MODE, maybe merging with the parent."
(let* ((map-name (derived-mode-map-name mode))
(new-map (eval map-name))
(old-map (current-local-map)))
(and old-map
(get map-name 'derived-mode-unmerged)
(derived-mode-merge-keymaps old-map new-map))
(put map-name 'derived-mode-unmerged nil)
(use-local-map new-map)))
(defun derived-mode-set-syntax-table (mode)
"Set the syntax table of the new MODE, maybe merging with the parent."
(let* ((table-name (derived-mode-syntax-table-name mode))
(old-table (syntax-table))
(new-table (eval table-name)))
(if (get table-name 'derived-mode-unmerged)
(derived-mode-merge-syntax-tables old-table new-table))
(put table-name 'derived-mode-unmerged nil)
(set-syntax-table new-table)))
(defun derived-mode-set-abbrev-table (mode)
"Set the abbrev table for MODE if it exists.
Always merge its parent into it, since the merge is non-destructive."
(let* ((table-name (derived-mode-abbrev-table-name mode))
(old-table local-abbrev-table)
(new-table (eval table-name)))
(derived-mode-merge-abbrev-tables old-table new-table)
(setq local-abbrev-table new-table)))
(defun derived-mode-run-hooks (mode)
"Run the mode hook for MODE."
(let ((hooks-name (derived-mode-hook-name mode)))
(if (boundp hooks-name)
(run-hooks hooks-name))))
;; Functions to merge maps and tables.
(defun derived-mode-merge-keymaps (old new)
"Merge an OLD keymap into a NEW one.
The old keymap is set to be the last cdr of the new one, so that there will
be automatic inheritance."
;; ?? Can this just use `set-keymap-parent'?
(let ((tail new))
;; Scan the NEW map for prefix keys.
(while (consp tail)
(and (consp (car tail))
(let* ((key (vector (car (car tail))))
(subnew (lookup-key new key))
(subold (lookup-key old key)))
;; If KEY is a prefix key in both OLD and NEW, merge them.
(and (keymapp subnew) (keymapp subold)
(derived-mode-merge-keymaps subold subnew))))
(and (vectorp (car tail))
;; Search a vector of ASCII char bindings for prefix keys.
(let ((i (1- (length (car tail)))))
(while (>= i 0)
(let* ((key (vector i))
(subnew (lookup-key new key))
(subold (lookup-key old key)))
;; If KEY is a prefix key in both OLD and NEW, merge them.
(and (keymapp subnew) (keymapp subold)
(derived-mode-merge-keymaps subold subnew)))
(setq i (1- i)))))
(setq tail (cdr tail))))
(setcdr (nthcdr (1- (length new)) new) old))
(defun derived-mode-merge-syntax-tables (old new)
"Merge an OLD syntax table into a NEW one.
Where the new table already has an entry, nothing is copied from the old one."
(set-char-table-parent new old))
;; Merge an old abbrev table into a new one.
;; This function requires internal knowledge of how abbrev tables work,
;; presuming that they are obarrays with the abbrev as the symbol, the expansion
;; as the value of the symbol, and the hook as the function definition.
(defun derived-mode-merge-abbrev-tables (old new)
(if old
(mapatoms
(lambda (symbol)
(or (intern-soft (symbol-name symbol) new)
(define-abbrev new (symbol-name symbol)
(symbol-value symbol) (symbol-function symbol))))
old)))
(provide 'derived)
;; arch-tag: 630be248-47d1-4f02-afa0-8207de0ebea0
;;; derived.el ends here