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503 lines
19 KiB
EmacsLisp
503 lines
19 KiB
EmacsLisp
;;; derived.el --- allow inheritance of major modes
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;; (formerly mode-clone.el)
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;; Copyright (C) 1993-1994, 1999, 2001-2018 Free Software Foundation,
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;; Inc.
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;; Author: David Megginson (dmeggins@aix1.uottawa.ca)
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;; Maintainer: emacs-devel@gnu.org
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;; Keywords: extensions
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;; Package: emacs
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;; GNU Emacs is already, in a sense, object oriented -- each object
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;; (buffer) belongs to a class (major mode), and that class defines
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;; the relationship between messages (input events) and methods
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;; (commands) by means of a keymap.
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;;
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;; The only thing missing is a good scheme of inheritance. It is
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;; possible to simulate a single level of inheritance with generous
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;; use of hooks and a bit of work -- sgml-mode, for example, also runs
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;; the hooks for text-mode, and keymaps can inherit from other keymaps
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;; -- but generally, each major mode ends up reinventing the wheel.
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;; Ideally, someone should redesign all of Emacs's major modes to
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;; follow a more conventional object-oriented system: when defining a
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;; new major mode, the user should need only to name the existing mode
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;; it is most similar to, then list the (few) differences.
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;;
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;; In the mean time, this package offers most of the advantages of
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;; full inheritance with the existing major modes. The macro
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;; `define-derived-mode' allows the user to make a variant of an existing
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;; major mode, with its own keymap. The new mode will inherit the key
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;; bindings of its parent, and will, in fact, run its parent first
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;; every time it is called. For example, the commands
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;;
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;; (define-derived-mode hypertext-mode text-mode "Hypertext"
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;; "Major mode for hypertext.\n\n\\{hypertext-mode-map}"
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;; (setq case-fold-search nil))
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;;
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;; (define-key hypertext-mode-map [down-mouse-3] 'do-hyper-link)
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;;
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;; will create a function `hypertext-mode' with its own (sparse)
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;; keymap `hypertext-mode-map.' The command M-x hypertext-mode will
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;; perform the following actions:
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;;
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;; - run the command (text-mode) to get its default setup
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;; - replace the current keymap with 'hypertext-mode-map,' which will
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;; inherit from 'text-mode-map'.
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;; - replace the current syntax table with
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;; 'hypertext-mode-syntax-table', which will borrow its defaults
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;; from the current text-mode-syntax-table.
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;; - replace the current abbrev table with
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;; 'hypertext-mode-abbrev-table', which will borrow its defaults
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;; from the current text-mode-abbrev table
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;; - change the mode line to read "Hypertext"
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;; - assign the value 'hypertext-mode' to the 'major-mode' variable
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;; - run the body of commands provided in the macro -- in this case,
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;; set the local variable `case-fold-search' to nil.
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;;
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;; The advantages of this system are threefold. First, text mode is
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;; untouched -- if you had added the new keystroke to `text-mode-map,'
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;; possibly using hooks, you would have added it to all text buffers
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;; -- here, it appears only in hypertext buffers, where it makes
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;; sense. Second, it is possible to build even further, and make
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;; a derived mode from a derived mode. The commands
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;;
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;; (define-derived-mode html-mode hypertext-mode "HTML")
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;; [various key definitions]
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;;
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;; will add a new major mode for HTML with very little fuss.
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;;
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;; Note also the function `derived-mode-p' which can tell if the current
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;; mode derives from another. In a hypertext-mode, buffer, for example,
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;; (derived-mode-p 'text-mode) would return non-nil. This should always
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;; be used in place of (eq major-mode 'text-mode).
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;;; Code:
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;;; PRIVATE: defsubst must be defined before they are first used
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(defsubst derived-mode-hook-name (mode)
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"Construct a mode-hook name based on a MODE name."
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(intern (concat (symbol-name mode) "-hook")))
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(defsubst derived-mode-map-name (mode)
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"Construct a map name based on a MODE name."
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(intern (concat (symbol-name mode) "-map")))
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(defsubst derived-mode-syntax-table-name (mode)
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"Construct a syntax-table name based on a MODE name."
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(intern (concat (symbol-name mode) "-syntax-table")))
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(defsubst derived-mode-abbrev-table-name (mode)
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"Construct an abbrev-table name based on a MODE name."
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(intern (concat (symbol-name mode) "-abbrev-table")))
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;; PUBLIC: define a new major mode which inherits from an existing one.
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;;;###autoload
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(defmacro define-derived-mode (child parent name &optional docstring &rest body)
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"Create a new mode as a variant of an existing mode.
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The arguments to this command are as follow:
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CHILD: the name of the command for the derived mode.
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PARENT: the name of the command for the parent mode (e.g. `text-mode')
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or nil if there is no parent.
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NAME: a string which will appear in the status line (e.g. \"Hypertext\")
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DOCSTRING: an optional documentation string--if you do not supply one,
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the function will attempt to invent something useful.
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BODY: forms to execute just before running the
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hooks for the new mode. Do not use `interactive' here.
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BODY can start with a bunch of keyword arguments. The following keyword
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arguments are currently understood:
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:group GROUP
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Declare the customization group that corresponds to this mode.
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The command `customize-mode' uses this.
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:syntax-table TABLE
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Use TABLE instead of the default (CHILD-syntax-table).
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A nil value means to simply use the same syntax-table as the parent.
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:abbrev-table TABLE
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Use TABLE instead of the default (CHILD-abbrev-table).
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A nil value means to simply use the same abbrev-table as the parent.
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:after-hook FORM
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A single lisp form which is evaluated after the mode hooks have been
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run. It should not be quoted.
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Here is how you could define LaTeX-Thesis mode as a variant of LaTeX mode:
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(define-derived-mode LaTeX-thesis-mode LaTeX-mode \"LaTeX-Thesis\")
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You could then make new key bindings for `LaTeX-thesis-mode-map'
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without changing regular LaTeX mode. In this example, BODY is empty,
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and DOCSTRING is generated by default.
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On a more complicated level, the following command uses `sgml-mode' as
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the parent, and then sets the variable `case-fold-search' to nil:
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(define-derived-mode article-mode sgml-mode \"Article\"
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\"Major mode for editing technical articles.\"
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(setq case-fold-search nil))
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Note that if the documentation string had been left out, it would have
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been generated automatically, with a reference to the keymap.
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The new mode runs the hook constructed by the function
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`derived-mode-hook-name'.
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See Info node `(elisp)Derived Modes' for more details."
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(declare (debug (&define name symbolp sexp [&optional stringp]
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[&rest keywordp sexp] def-body))
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(doc-string 4)
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;; Ask not what
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;;(indent 3)
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;; can do for you, ask what it can do to others. IOW, the
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;; missing of indentation setting here is the indentation
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;; setting and not an oversight.
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)
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(when (and docstring (not (stringp docstring)))
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;; Some trickiness, since what appears to be the docstring may really be
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;; the first element of the body.
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(push docstring body)
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(setq docstring nil))
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(when (eq parent 'fundamental-mode) (setq parent nil))
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(let ((map (derived-mode-map-name child))
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(syntax (derived-mode-syntax-table-name child))
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(abbrev (derived-mode-abbrev-table-name child))
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(declare-abbrev t)
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(declare-syntax t)
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(hook (derived-mode-hook-name child))
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(group nil)
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(after-hook nil))
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;; Process the keyword args.
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(while (keywordp (car body))
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(pcase (pop body)
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(`:group (setq group (pop body)))
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(`:abbrev-table (setq abbrev (pop body)) (setq declare-abbrev nil))
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(`:syntax-table (setq syntax (pop body)) (setq declare-syntax nil))
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(`:after-hook (setq after-hook (pop body)))
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(_ (pop body))))
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(setq docstring (derived-mode-make-docstring
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parent child docstring syntax abbrev))
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`(progn
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(defvar ,hook nil)
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(unless (get ',hook 'variable-documentation)
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(put ',hook 'variable-documentation
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,(format "Hook run after entering %s mode.
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No problems result if this variable is not bound.
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`add-hook' automatically binds it. (This is true for all hook variables.)"
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name)))
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(unless (boundp ',map)
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(put ',map 'definition-name ',child))
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(with-no-warnings (defvar ,map (make-sparse-keymap)))
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(unless (get ',map 'variable-documentation)
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(put ',map 'variable-documentation
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(purecopy ,(format "Keymap for `%s'." child))))
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,(if declare-syntax
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`(progn
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(defvar ,syntax)
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(unless (boundp ',syntax)
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(put ',syntax 'definition-name ',child)
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(defvar ,syntax (make-syntax-table)))
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(unless (get ',syntax 'variable-documentation)
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(put ',syntax 'variable-documentation
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(purecopy ,(format "Syntax table for `%s'." child))))))
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,(if declare-abbrev
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`(progn
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(defvar ,abbrev)
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(unless (boundp ',abbrev)
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(put ',abbrev 'definition-name ',child)
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(defvar ,abbrev
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(progn (define-abbrev-table ',abbrev nil) ,abbrev)))
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(unless (get ',abbrev 'variable-documentation)
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(put ',abbrev 'variable-documentation
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(purecopy ,(format "Abbrev table for `%s'." child))))))
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(put ',child 'derived-mode-parent ',parent)
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,(if group `(put ',child 'custom-mode-group ,group))
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(defun ,child ()
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,docstring
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(interactive)
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; Run the parent.
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(delay-mode-hooks
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(,(or parent 'kill-all-local-variables))
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; Identify the child mode.
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(setq major-mode (quote ,child))
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(setq mode-name ,name)
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; Identify special modes.
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,(when parent
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`(progn
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(if (get (quote ,parent) 'mode-class)
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(put (quote ,child) 'mode-class
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(get (quote ,parent) 'mode-class)))
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; Set up maps and tables.
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(unless (keymap-parent ,map)
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;; It would probably be better to set the keymap's parent
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;; at the toplevel rather than inside the mode function,
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;; but this is not easy for at least the following reasons:
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;; - the parent (and its keymap) may not yet be loaded.
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;; - the parent's keymap name may be called something else
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;; than <parent>-mode-map.
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(set-keymap-parent ,map (current-local-map)))
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,(when declare-syntax
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`(let ((parent (char-table-parent ,syntax)))
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(unless (and parent
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(not (eq parent (standard-syntax-table))))
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(set-char-table-parent ,syntax (syntax-table)))))
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,(when declare-abbrev
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`(unless (or (abbrev-table-get ,abbrev :parents)
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;; This can happen if the major mode defines
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;; the abbrev-table to be its parent's.
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(eq ,abbrev local-abbrev-table))
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(abbrev-table-put ,abbrev :parents
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(list local-abbrev-table))))))
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(use-local-map ,map)
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,(when syntax `(set-syntax-table ,syntax))
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,(when abbrev `(setq local-abbrev-table ,abbrev))
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; Splice in the body (if any).
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,@body
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)
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;; Run the hooks, if any.
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(run-mode-hooks ',hook)
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,@(when after-hook
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`((if delay-mode-hooks
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(push (lambda () ,after-hook) delayed-after-hook-functions)
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,after-hook)))))))
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;; PUBLIC: find the ultimate class of a derived mode.
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(defun derived-mode-class (mode)
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"Find the class of a major MODE.
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A mode's class is the first ancestor which is NOT a derived mode.
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Use the `derived-mode-parent' property of the symbol to trace backwards.
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Since major-modes might all derive from `fundamental-mode', this function
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is not very useful."
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(declare (obsolete derived-mode-p "22.1"))
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(while (get mode 'derived-mode-parent)
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(setq mode (get mode 'derived-mode-parent)))
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mode)
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;;; PRIVATE
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(defun derived-mode-make-docstring (parent child &optional
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docstring syntax abbrev)
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"Construct a docstring for a new mode if none is provided."
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(let ((map (derived-mode-map-name child))
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(hook (derived-mode-hook-name child)))
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(unless (stringp docstring)
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;; Use a default docstring.
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(setq docstring
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(if (null parent)
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;; FIXME filling.
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(format "Major-mode.\nUses keymap `%s'%s%s." map
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(if abbrev (format "%s abbrev table `%s'"
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(if syntax "," " and") abbrev) "")
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(if syntax (format " and syntax-table `%s'" syntax) ""))
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(format "Major mode derived from `%s' by `define-derived-mode'.
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It inherits all of the parent's attributes, but has its own keymap%s:
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`%s'%s
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which more-or-less shadow%s %s's corresponding table%s."
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parent
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(cond ((and abbrev syntax)
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",\nabbrev table and syntax table")
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(abbrev "\nand abbrev table")
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(syntax "\nand syntax table")
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(t ""))
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map
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(cond ((and abbrev syntax)
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(format ", `%s' and `%s'" abbrev syntax))
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((or abbrev syntax)
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(format " and `%s'" (or abbrev syntax)))
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(t ""))
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(if (or abbrev syntax) "" "s")
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parent
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(if (or abbrev syntax) "s" "")))))
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(unless (string-match (regexp-quote (symbol-name hook)) docstring)
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;; Make sure the docstring mentions the mode's hook.
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(setq docstring
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(concat docstring
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(if (null parent)
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"\n\nThis mode "
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(concat
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"\n\nIn addition to any hooks its parent mode "
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(if (string-match (format "[`‘]%s['’]"
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(regexp-quote
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(symbol-name parent)))
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docstring)
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nil
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(format "`%s' " parent))
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"might have run,\nthis mode "))
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(format "runs the hook `%s'" hook)
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", as the final or penultimate step\nduring initialization.")))
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(unless (string-match "\\\\[{[]" docstring)
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;; And don't forget to put the mode's keymap.
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(setq docstring (concat docstring "\n\n\\{" (symbol-name map) "}")))
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docstring))
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;;; OBSOLETE
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;; The functions below are only provided for backward compatibility with
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;; code byte-compiled with versions of derived.el prior to Emacs-21.
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(defsubst derived-mode-setup-function-name (mode)
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"Construct a setup-function name based on a MODE name."
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(intern (concat (symbol-name mode) "-setup")))
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;; Utility functions for defining a derived mode.
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;;;###autoload
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(defun derived-mode-init-mode-variables (mode)
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"Initialize variables for a new MODE.
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Right now, if they don't already exist, set up a blank keymap, an
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empty syntax table, and an empty abbrev table -- these will be merged
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the first time the mode is used."
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(if (boundp (derived-mode-map-name mode))
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t
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(eval `(defvar ,(derived-mode-map-name mode)
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(make-sparse-keymap)
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,(format "Keymap for %s." mode)))
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(put (derived-mode-map-name mode) 'derived-mode-unmerged t))
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(if (boundp (derived-mode-syntax-table-name mode))
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t
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(eval `(defvar ,(derived-mode-syntax-table-name mode)
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;; Make a syntax table which doesn't specify anything
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;; for any char. Valid data will be merged in by
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;; derived-mode-merge-syntax-tables.
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(make-char-table 'syntax-table nil)
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,(format "Syntax table for %s." mode)))
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(put (derived-mode-syntax-table-name mode) 'derived-mode-unmerged t))
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(if (boundp (derived-mode-abbrev-table-name mode))
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t
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(eval `(defvar ,(derived-mode-abbrev-table-name mode)
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(progn
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(define-abbrev-table (derived-mode-abbrev-table-name mode) nil)
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(make-abbrev-table))
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,(format "Abbrev table for %s." mode)))))
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;; Utility functions for running a derived mode.
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(defun derived-mode-set-keymap (mode)
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"Set the keymap of the new MODE, maybe merging with the parent."
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(let* ((map-name (derived-mode-map-name mode))
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(new-map (eval map-name))
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(old-map (current-local-map)))
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(and old-map
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(get map-name 'derived-mode-unmerged)
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(derived-mode-merge-keymaps old-map new-map))
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(put map-name 'derived-mode-unmerged nil)
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(use-local-map new-map)))
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(defun derived-mode-set-syntax-table (mode)
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"Set the syntax table of the new MODE, maybe merging with the parent."
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(let* ((table-name (derived-mode-syntax-table-name mode))
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(old-table (syntax-table))
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(new-table (eval table-name)))
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(if (get table-name 'derived-mode-unmerged)
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(derived-mode-merge-syntax-tables old-table new-table))
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(put table-name 'derived-mode-unmerged nil)
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(set-syntax-table new-table)))
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(defun derived-mode-set-abbrev-table (mode)
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"Set the abbrev table for MODE if it exists.
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Always merge its parent into it, since the merge is non-destructive."
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(let* ((table-name (derived-mode-abbrev-table-name mode))
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(old-table local-abbrev-table)
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(new-table (eval table-name)))
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(derived-mode-merge-abbrev-tables old-table new-table)
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(setq local-abbrev-table new-table)))
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(defun derived-mode-run-hooks (mode)
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"Run the mode hook for MODE."
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(let ((hooks-name (derived-mode-hook-name mode)))
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(if (boundp hooks-name)
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(run-hooks hooks-name))))
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;; Functions to merge maps and tables.
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(defun derived-mode-merge-keymaps (old new)
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"Merge an OLD keymap into a NEW one.
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The old keymap is set to be the last cdr of the new one, so that there will
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be automatic inheritance."
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;; ?? Can this just use `set-keymap-parent'?
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(let ((tail new))
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;; 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)
|
||
|
||
;;; derived.el ends here
|