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1 ;;; derived.el --- allow inheritance of major modes.
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2 ;;; (formerly mode-clone.el)
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3
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4 ;; Copyright (C) 1993, 1994 Free Software Foundation, Inc.
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5
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6 ;; Author: David Megginson (dmeggins@aix1.uottawa.ca)
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7 ;; Maintainer: FSF
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8
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9 ;; This file is part of XEmacs.
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10
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11 ;; XEmacs is free software; you can redistribute it and/or modify it
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12 ;; under the terms of the GNU General Public License as published by
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13 ;; the Free Software Foundation; either version 2, or (at your option)
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14 ;; any later version.
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15
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16 ;; XEmacs is distributed in the hope that it will be useful, but
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17 ;; WITHOUT ANY WARRANTY; without even the implied warranty of
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18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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19 ;; General Public License for more details.
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20
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21 ;; You should have received a copy of the GNU General Public License
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22 ;; along with XEmacs; see the file COPYING. If not, write to the Free
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23 ;; Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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24 ;; 02111-1307, USA.
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25
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26 ;;; Synched up with: FSF 19.34.
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27
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28 ;;; Commentary:
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29
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30 ;; GNU Emacs is already, in a sense, object oriented -- each object
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31 ;; (buffer) belongs to a class (major mode), and that class defines
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32 ;; the relationship between messages (input events) and methods
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33 ;; (commands) by means of a keymap.
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34 ;;
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35 ;; The only thing missing is a good scheme of inheritance. It is
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36 ;; possible to simulate a single level of inheritance with generous
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37 ;; use of hooks and a bit of work -- sgml-mode, for example, also runs
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38 ;; the hooks for text-mode, and keymaps can inherit from other keymaps
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39 ;; -- but generally, each major mode ends up reinventing the wheel.
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40 ;; Ideally, someone should redesign all of Emacs's major modes to
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41 ;; follow a more conventional object-oriented system: when defining a
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42 ;; new major mode, the user should need only to name the existing mode
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43 ;; it is most similar to, then list the (few) differences.
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44 ;;
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45 ;; In the mean time, this package offers most of the advantages of
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46 ;; full inheritance with the existing major modes. The macro
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47 ;; `define-derived-mode' allows the user to make a variant of an existing
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48 ;; major mode, with its own keymap. The new mode will inherit the key
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49 ;; bindings of its parent, and will, in fact, run its parent first
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50 ;; every time it is called. For example, the commands
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51 ;;
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52 ;; (define-derived-mode hypertext-mode text-mode "Hypertext"
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53 ;; "Major mode for hypertext.\n\n\\{hypertext-mode-map}"
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54 ;; (setq case-fold-search nil))
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55 ;;
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56 ;; (define-key hypertext-mode-map [down-mouse-3] 'do-hyper-link)
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57 ;;
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58 ;; will create a function `hypertext-mode' with its own (sparse)
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59 ;; keymap `hypertext-mode-map.' The command M-x hypertext-mode will
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60 ;; perform the following actions:
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61 ;;
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62 ;; - run the command (text-mode) to get its default setup
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63 ;; - replace the current keymap with 'hypertext-mode-map,' which will
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64 ;; inherit from 'text-mode-map'.
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65 ;; - replace the current syntax table with
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66 ;; 'hypertext-mode-syntax-table', which will borrow its defaults
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67 ;; from the current text-mode-syntax-table.
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68 ;; - replace the current abbrev table with
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69 ;; 'hypertext-mode-abbrev-table', which will borrow its defaults
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70 ;; from the current text-mode-abbrev table
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71 ;; - change the mode line to read "Hypertext"
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72 ;; - assign the value 'hypertext-mode' to the 'major-mode' variable
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73 ;; - run the body of commands provided in the macro -- in this case,
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74 ;; set the local variable `case-fold-search' to nil.
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75 ;; - **run the command (hypertext-mode-setup), which is empty by
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76 ;; default, but may be redefined by the user to contain special
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77 ;; commands (ie. setting local variables like 'outline-regexp')
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78 ;; **NOTE: do not use this option -- it will soon be obsolete.
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79 ;; - run anything assigned to 'hypertext-mode-hooks' (obsolete, but
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80 ;; supported for the sake of compatibility).
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81 ;;
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82 ;; The advantages of this system are threefold. First, text mode is
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83 ;; untouched -- if you had added the new keystroke to `text-mode-map,'
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84 ;; possibly using hooks, you would have added it to all text buffers
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85 ;; -- here, it appears only in hypertext buffers, where it makes
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86 ;; sense. Second, it is possible to build even further, and make
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87 ;; a derived mode from a derived mode. The commands
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88 ;;
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89 ;; (define-derived-mode html-mode hypertext-mode "HTML")
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90 ;; [various key definitions]
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91 ;;
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92 ;; will add a new major mode for HTML with very little fuss.
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93 ;;
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94 ;; Note also the function `derived-mode-class,' which returns the non-derived
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95 ;; major mode which a derived mode is based on (ie. NOT necessarily the
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96 ;; immediate parent).
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97 ;;
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98 ;; (derived-mode-class 'text-mode) ==> text-mode
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99 ;; (derived-mode-class 'hypertext-mode) ==> text-mode
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100 ;; (derived-mode-class 'html-mode) ==> text-mode
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101
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102 ;;; Code:
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103
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104 ;; PUBLIC: define a new major mode which inherits from an existing one.
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105
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106 ;; XEmacs -- no autoload
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107 (defmacro define-derived-mode (child parent name &optional docstring &rest body)
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108 "Create a new mode as a variant of an existing mode.
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109
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110 The arguments to this command are as follow:
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111
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112 CHILD: the name of the command for the derived mode.
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113 PARENT: the name of the command for the parent mode (ie. text-mode).
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114 NAME: a string which will appear in the status line (ie. \"Hypertext\")
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115 DOCSTRING: an optional documentation string--if you do not supply one,
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116 the function will attempt to invent something useful.
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117 BODY: forms to execute just before running the
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118 hooks for the new mode.
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119
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120 Here is how you could define LaTeX-Thesis mode as a variant of LaTeX mode:
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121
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122 (define-derived-mode LaTeX-thesis-mode LaTeX-mode \"LaTeX-Thesis\")
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123
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124 You could then make new key bindings for `LaTeX-thesis-mode-map'
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125 without changing regular LaTeX mode. In this example, BODY is empty,
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126 and DOCSTRING is generated by default.
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127
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128 On a more complicated level, the following command uses sgml-mode as
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129 the parent, and then sets the variable `case-fold-search' to nil:
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130
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131 (define-derived-mode article-mode sgml-mode \"Article\"
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132 \"Major mode for editing technical articles.\"
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133 (setq case-fold-search nil))
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134
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135 Note that if the documentation string had been left out, it would have
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136 been generated automatically, with a reference to the keymap."
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137
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138 ; Some trickiness, since what
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139 ; appears to be the docstring
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140 ; may really be the first
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141 ; element of the body.
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142 (if (and docstring (not (stringp docstring)))
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143 (progn (setq body (cons docstring body))
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144 (setq docstring nil)))
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145 (setq docstring (or docstring (derived-mode-make-docstring parent child)))
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146
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147 (` (progn
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148 (derived-mode-init-mode-variables (quote (, child)))
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149 (defun (, child) ()
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150 (, docstring)
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151 (interactive)
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152 ; Run the parent.
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153 ((, parent))
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154 ; Identify special modes.
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155 (if (get (quote (, parent)) 'special)
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156 (put (quote (, child)) 'special t))
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157 ;; XEmacs addition
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158 (let ((mode-class (get (quote (, parent)) 'mode-class)))
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159 (if mode-class
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160 (put (quote (, child)) 'mode-class mode-class)))
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161 ; Identify the child mode.
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162 (setq major-mode (quote (, child)))
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163 (setq mode-name (, name))
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164 ; Set up maps and tables.
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165 (derived-mode-set-keymap (quote (, child)))
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166 (derived-mode-set-syntax-table (quote (, child)))
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167 (derived-mode-set-abbrev-table (quote (, child)))
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168 ; Splice in the body (if any).
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169 (,@ body)
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170 ;;; ; Run the setup function, if
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171 ;;; ; any -- this will soon be
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172 ;;; ; obsolete.
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173 ;;; (derived-mode-run-setup-function (quote (, child)))
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174 ; Run the hooks, if any.
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175 (derived-mode-run-hooks (quote (, child)))))))
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176
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177
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178 ;; PUBLIC: find the ultimate class of a derived mode.
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179
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180 (defun derived-mode-class (mode)
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181 "Find the class of a major mode.
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182 A mode's class is the first ancestor which is NOT a derived mode.
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183 Use the `derived-mode-parent' property of the symbol to trace backwards."
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184 (while (get mode 'derived-mode-parent)
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185 (setq mode (get mode 'derived-mode-parent)))
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186 mode)
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187
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188
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189 ;; Inline functions to construct various names from a mode name.
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190
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191 (defsubst derived-mode-setup-function-name (mode)
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192 "Construct a setup-function name based on a mode name."
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193 (intern (concat (symbol-name mode) "-setup")))
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194
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195 (defsubst derived-mode-hooks-name (mode)
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196 "Construct a hooks name based on a mode name."
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197 ;; XEmacs change from -hooks
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198 (intern (concat (symbol-name mode) "-hook")))
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199
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200 (defsubst derived-mode-map-name (mode)
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201 "Construct a map name based on a mode name."
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202 (intern (concat (symbol-name mode) "-map")))
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203
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204 (defsubst derived-mode-syntax-table-name (mode)
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205 "Construct a syntax-table name based on a mode name."
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206 (intern (concat (symbol-name mode) "-syntax-table")))
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207
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208 (defsubst derived-mode-abbrev-table-name (mode)
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209 "Construct an abbrev-table name based on a mode name."
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210 (intern (concat (symbol-name mode) "-abbrev-table")))
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211
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212
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213 ;; Utility functions for defining a derived mode.
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214
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215 ;; XEmacs -- don't autoload
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216 (defun derived-mode-init-mode-variables (mode)
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217 "Initialise variables for a new mode.
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218 Right now, if they don't already exist, set up a blank keymap, an
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219 empty syntax table, and an empty abbrev table -- these will be merged
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220 the first time the mode is used."
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221
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222 (if (boundp (derived-mode-map-name mode))
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223 t
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224 (eval (` (defvar (, (derived-mode-map-name mode))
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225 ;; XEmacs change
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226 (make-sparse-keymap (derived-mode-map-name mode))
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227 (, (format "Keymap for %s." mode)))))
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228 (put (derived-mode-map-name mode) 'derived-mode-unmerged t))
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229
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230 (if (boundp (derived-mode-syntax-table-name mode))
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231 t
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232 (eval (` (defvar (, (derived-mode-syntax-table-name mode))
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233 ;; XEmacs change
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234 ;; Make a syntax table which doesn't specify anything
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235 ;; for any char. Valid data will be merged in by
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236 ;; derived-mode-merge-syntax-tables.
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237 ;; (make-char-table 'syntax-table nil)
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238 (make-syntax-table)
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239 (, (format "Syntax table for %s." mode)))))
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240 (put (derived-mode-syntax-table-name mode) 'derived-mode-unmerged t))
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241
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242 (if (boundp (derived-mode-abbrev-table-name mode))
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243 t
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244 (eval (` (defvar (, (derived-mode-abbrev-table-name mode))
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245 (progn (define-abbrev-table (derived-mode-abbrev-table-name mode) nil)
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246 (make-abbrev-table))
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247 (, (format "Abbrev table for %s." mode)))))))
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248
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249 (defun derived-mode-make-docstring (parent child)
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250 "Construct a docstring for a new mode if none is provided."
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251
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252 (format "This major mode is a variant of `%s', created by `define-derived-mode'.
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253 It inherits all of the parent's attributes, but has its own keymap,
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254 abbrev table and syntax table:
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255
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256 `%s-map' and `%s-syntax-table'
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257
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258 which more-or-less shadow
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259
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260 `%s-map' and `%s-syntax-table'
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261
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262 \\{%s-map}" parent child child parent parent child))
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263
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264
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265 ;; Utility functions for running a derived mode.
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266
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267 (defun derived-mode-set-keymap (mode)
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268 "Set the keymap of the new mode, maybe merging with the parent."
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269 (let* ((map-name (derived-mode-map-name mode))
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270 (new-map (eval map-name))
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271 (old-map (current-local-map)))
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272 (and old-map
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273 (get map-name 'derived-mode-unmerged)
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274 (derived-mode-merge-keymaps old-map new-map))
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275 (put map-name 'derived-mode-unmerged nil)
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276 (use-local-map new-map)))
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277
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278 (defun derived-mode-set-syntax-table (mode)
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279 "Set the syntax table of the new mode, maybe merging with the parent."
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280 (let* ((table-name (derived-mode-syntax-table-name mode))
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281 (old-table (syntax-table))
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282 (new-table (eval table-name)))
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283 (if (get table-name 'derived-mode-unmerged)
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284 (derived-mode-merge-syntax-tables old-table new-table))
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285 (put table-name 'derived-mode-unmerged nil)
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286 (set-syntax-table new-table)))
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287
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288 (defun derived-mode-set-abbrev-table (mode)
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289 "Set the abbrev table if it exists.
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290 Always merge its parent into it, since the merge is non-destructive."
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291 (let* ((table-name (derived-mode-abbrev-table-name mode))
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292 (old-table local-abbrev-table)
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293 (new-table (eval table-name)))
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294 (derived-mode-merge-abbrev-tables old-table new-table)
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295 (setq local-abbrev-table new-table)))
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296
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297 ;;;(defun derived-mode-run-setup-function (mode)
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298 ;;; "Run the setup function if it exists."
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299
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300 ;;; (let ((fname (derived-mode-setup-function-name mode)))
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301 ;;; (if (fboundp fname)
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302 ;;; (funcall fname))))
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303
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304 (defun derived-mode-run-hooks (mode)
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305 "Run the hooks if they exist."
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306
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307 (let ((hooks-name (derived-mode-hooks-name mode)))
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308 (if (boundp hooks-name)
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309 (run-hooks hooks-name))))
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310
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311 ;; Functions to merge maps and tables.
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312
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313 (defun derived-mode-merge-keymaps (old new)
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314 "Merge an old keymap into a new one.
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315 The old keymap is set to be the parent of the new one, so that there will
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316 be automatic inheritance."
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317 ;; XEmacs change. FSF 19.30 & 19.34 has a whole bunch of weird crap here
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318 ;; for merging prefix keys and such. Hopefully none of this is
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319 ;; necessary in XEmacs.
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320 (set-keymap-parents new (list old)))
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321
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322 (defun derived-mode-merge-syntax-tables (old new)
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323 "Merge an old syntax table into a new one.
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324 Where the new table already has an entry, nothing is copied from the old one."
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325 ;; XEmacs change (no set-char-table-parent)
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326 (let ((idx 0)
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327 (end (min (length new) (length old))))
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328 (while (< idx end)
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329 (if (not (aref new idx))
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330 (aset new idx (aref old idx)))
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331 (setq idx (1+ idx)))))
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332
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333 ;; Merge an old abbrev table into a new one.
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334 ;; This function requires internal knowledge of how abbrev tables work,
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335 ;; presuming that they are obarrays with the abbrev as the symbol, the expansion
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336 ;; as the value of the symbol, and the hook as the function definition.
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337 (defun derived-mode-merge-abbrev-tables (old new)
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338 (if old
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339 (mapatoms
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340 (function
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341 (lambda (symbol)
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342 (or (intern-soft (symbol-name symbol) new)
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343 (define-abbrev new (symbol-name symbol)
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344 (symbol-value symbol) (symbol-function symbol)))))
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345 old)))
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346
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347 (provide 'derived)
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348
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349 ;;; derived.el ends here
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