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7ada1a07ac
property to the defived mode command name.
354 lines
13 KiB
EmacsLisp
354 lines
13 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 Free Software Foundation, Inc.
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;; Author: David Megginson (dmeggins@aix1.uottawa.ca)
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;; Maintainer: FSF
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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 2, or (at your option)
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;; 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; see the file COPYING. If not, write to the
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;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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;; Boston, MA 02111-1307, USA.
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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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;; - **run the command (hypertext-mode-setup), which is empty by
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;; default, but may be redefined by the user to contain special
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;; commands (ie. setting local variables like 'outline-regexp')
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;; **NOTE: do not use this option -- it will soon be obsolete.
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;; - run anything assigned to 'hypertext-mode-hooks' (obsolete, but
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;; supported for the sake of compatibility).
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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-class,' which returns the non-derived
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;; major mode which a derived mode is based on (ie. NOT necessarily the
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;; immediate parent).
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;;
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;; (derived-mode-class 'text-mode) ==> text-mode
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;; (derived-mode-class 'hypertext-mode) ==> text-mode
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;; (derived-mode-class 'html-mode) ==> text-mode
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;;; Code:
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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 (ie. text-mode).
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NAME: a string which will appear in the status line (ie. \"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.
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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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; Some trickiness, since what
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; appears to be the docstring
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; may really be the first
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; element of the body.
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(if (and docstring (not (stringp docstring)))
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(progn (setq body (cons docstring body))
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(setq docstring nil)))
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(setq docstring (or docstring (derived-mode-make-docstring parent child)))
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(` (progn
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(derived-mode-init-mode-variables '(, child))
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(put '(, child) 'derived-mode-parent '(, parent))
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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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((, parent))
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; Identify special modes.
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(if (get '(, parent) 'special)
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(put '(, child) 'special t))
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; Identify the child mode.
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(setq major-mode '(, child))
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(setq mode-name (, name))
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; Set up maps and tables.
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(derived-mode-set-keymap '(, child))
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(derived-mode-set-syntax-table '(, child))
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(derived-mode-set-abbrev-table '(, child))
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; Splice in the body (if any).
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(,@ body)
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;;; ; Run the setup function, if
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;;; ; any -- this will soon be
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;;; ; obsolete.
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;;; (derived-mode-run-setup-function '(, child))
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; Run the hooks, if any.
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(derived-mode-run-hooks '(, child))))))
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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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(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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;; Inline functions to construct various names from a mode name.
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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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(defsubst derived-mode-hooks-name (mode)
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"Construct a hooks name based on a mode name."
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(intern (concat (symbol-name mode) "-hooks")))
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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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;; 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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"Initialise 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 (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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(defun derived-mode-make-docstring (parent child)
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"Construct a docstring for a new mode if none is provided."
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(format "This major mode is a variant of `%s', created by `define-derived-mode'.
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It inherits all of the parent's attributes, but has its own keymap,
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abbrev table and syntax table:
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`%s-map' and `%s-syntax-table'
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which more-or-less shadow
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`%s-map' and `%s-syntax-table'
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\\{%s-map}" parent child child parent parent child))
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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 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-setup-function (mode)
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;;; "Run the setup function if it exists."
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;;; (let ((fname (derived-mode-setup-function-name mode)))
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;;; (if (fboundp fname)
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;;; (funcall fname))))
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(defun derived-mode-run-hooks (mode)
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"Run the hooks if they exist."
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(let ((hooks-name (derived-mode-hooks-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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(let ((tail new))
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;; Scan the NEW map for prefix keys.
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(while (consp tail)
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(and (consp (car tail))
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(let* ((key (vector (car (car tail))))
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(subnew (lookup-key new key))
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(subold (lookup-key old key)))
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;; If KEY is a prefix key in both OLD and NEW, merge them.
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(and (keymapp subnew) (keymapp subold)
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(derived-mode-merge-keymaps subold subnew))))
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(and (vectorp (car tail))
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;; Search a vector of ASCII char bindings for prefix keys.
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(let ((i (1- (length (car tail)))))
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(while (>= i 0)
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(let* ((key (vector i))
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(subnew (lookup-key new key))
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(subold (lookup-key old key)))
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;; If KEY is a prefix key in both OLD and NEW, merge them.
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(and (keymapp subnew) (keymapp subold)
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(derived-mode-merge-keymaps subold subnew)))
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(setq i (1- i)))))
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(setq tail (cdr tail))))
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(setcdr (nthcdr (1- (length new)) new) old))
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(defun derived-mode-merge-syntax-tables (old new)
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"Merge an old syntax table into a new one.
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Where the new table already has an entry, nothing is copied from the old one."
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(set-char-table-parent new old))
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;; Merge an old abbrev table into a new one.
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;; This function requires internal knowledge of how abbrev tables work,
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;; presuming that they are obarrays with the abbrev as the symbol, the expansion
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;; as the value of the symbol, and the hook as the function definition.
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(defun derived-mode-merge-abbrev-tables (old new)
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(if old
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(mapatoms
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(function
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(lambda (symbol)
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(or (intern-soft (symbol-name symbol) new)
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(define-abbrev new (symbol-name symbol)
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(symbol-value symbol) (symbol-function symbol)))))
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old)))
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(provide 'derived)
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;;; derived.el ends here
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