lisp/ehelp.el

   1 ;; Copyright (C) 1986 Free Software Foundation, Inc.
   2
   3 ;; This file is part of GNU Emacs.
   4
   5 ;; GNU Emacs is free software; you can redistribute it and/or modify
   6 ;; it under the terms of the GNU General Public License as published by
   7 ;; the Free Software Foundation; either version 1, or (at your option)
   8 ;; any later version.
   9
  10 ;; GNU Emacs is distributed in the hope that it will be useful,
  11 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 ;; GNU General Public License for more details.
  14
  15 ;; You should have received a copy of the GNU General Public License
  16 ;; along with GNU Emacs; see the file COPYING.  If not, write to
  17 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  18
  19 (require 'electric)
  20 (provide 'ehelp)
  21
  22 (defvar electric-help-map ()
  23   "Keymap defining commands available in `electric-help-mode'.")
  24
  25 (put 'electric-help-undefined 'suppress-keymap t)
  26 (if electric-help-map
  27     ()
  28   (let ((map (make-keymap)))
  29     (fillarray map 'electric-help-undefined)
  30     (define-key map (char-to-string meta-prefix-char) (copy-keymap map))
  31     (define-key map (char-to-string help-char) 'electric-help-help)
  32     (define-key map "?" 'electric-help-help)
  33     (define-key map " " 'scroll-up)
  34     (define-key map "\^?" 'scroll-down)
  35     (define-key map "." 'beginning-of-buffer)
  36     (define-key map "<" 'beginning-of-buffer)
  37     (define-key map ">" 'end-of-buffer)
  38     ;(define-key map "\C-g" 'electric-help-exit)
  39     (define-key map "q" 'electric-help-exit)
  40     (define-key map "Q" 'electric-help-exit)
  41     ;;a better key than this?
  42     (define-key map "r" 'electric-help-retain)
  43
  44     (setq electric-help-map map)))
  45
  46 (defun electric-help-mode ()
  47   "`with-electric-help' temporarily places its buffer in this mode.
  48 \(On exit from `with-electric-help', the buffer is put in `default-major-mode'.)"
  49   (setq buffer-read-only t)
  50   (setq mode-name "Help")
  51   (setq major-mode 'help)
  52   (setq mode-line-buffer-identification '(" Help:  %b"))
  53   (use-local-map electric-help-map)
  54   ;; this is done below in with-electric-help
  55   ;(run-hooks 'electric-help-mode-hook)
  56   )
  57
  58 (defun with-electric-help (thunk &optional buffer noerase)
  59   "Arguments are THUNK &optional BUFFER NOERASE.  BUFFER defaults to \"*Help*\"
  60 THUNK is a function of no arguments which is called to initialize
  61 the contents of BUFFER.  BUFFER will be erased before THUNK is called unless
  62 NOERASE is non-nil.  THUNK will be called with `standard-output' bound to
  63 the buffer specified by BUFFER
  64
  65 After THUNK has been called, this function \"electrically\" pops up a window
  66 in which BUFFER is displayed and allows the user to scroll through that buffer
  67 in electric-help-mode.
  68 When the user exits (with `electric-help-exit', or otherwise) the help
  69 buffer's window disappears (i.e., we use `save-window-excursion')
  70 BUFFER is put into `default-major-mode' (or `fundamental-mode') when we exit"
  71   (setq buffer (get-buffer-create (or buffer "*Help*")))
  72   (let ((one (one-window-p t))
  73         (config (current-window-configuration))
  74         (bury nil))
  75     (unwind-protect
  76          (save-excursion
  77            (if one (goto-char (window-start (selected-window))))
  78            (let ((pop-up-windows t))
  79              (pop-to-buffer buffer))
  80            (save-excursion
  81              (set-buffer buffer)
  82              (electric-help-mode)
  83              (setq buffer-read-only nil)
  84              (or noerase (erase-buffer)))
  85            (let ((standard-output buffer))
  86              (if (not (funcall thunk))
  87                  (progn
  88                    (set-buffer buffer)
  89                    (set-buffer-modified-p nil)
  90                    (goto-char (point-min))
  91                    (if one (shrink-window-if-larger-than-buffer (selected-window))))))
  92            (set-buffer buffer)
  93            (run-hooks 'electric-help-mode-hook)
  94            (if (eq (car-safe (electric-help-command-loop))
  95                    'retain)
  96                (setq config (current-window-configuration))
  97                (setq bury t)))
  98       (message "")
  99       (set-buffer buffer)
 100       (setq buffer-read-only nil)
 101       (condition-case ()
 102           (funcall (or default-major-mode 'fundamental-mode))
 103         (error nil))
 104       (set-window-configuration config)
 105       (if bury
 106           (progn
 107             ;;>> Perhaps this shouldn't be done.
 108             ;; so that when we say "Press space to bury" we mean it
 109             (replace-buffer-in-windows buffer)
 110             ;; must do this outside of save-window-excursion
 111             (bury-buffer buffer))))))
 112
 113 (defun electric-help-command-loop ()
 114   (catch 'exit
 115     (if (pos-visible-in-window-p (point-max))
 116         (progn (message "<<< Press Space to bury the help buffer >>>")
 117                (if (= (setq unread-command-char (read-char)) ?\  )
 118                    (progn (setq unread-command-char -1)
 119                           (throw 'exit t)))))
 120     (let (up down both neither
 121           (standard (and (eq (key-binding " ")
 122                              'scroll-up)
 123                          (eq (key-binding "\^?")
 124                              'scroll-down)
 125                          (eq (key-binding "Q")
 126                              'electric-help-exit)
 127                          (eq (key-binding "q")
 128                              'electric-help-exit))))
 129       (Electric-command-loop
 130         'exit
 131         (function (lambda ()
 132           (let ((min (pos-visible-in-window-p (point-min)))
 133                 (max (pos-visible-in-window-p (point-max))))
 134             (cond ((and min max)
 135                    (cond (standard "Press Q to exit ")
 136                          (neither)
 137                          (t (setq neither (substitute-command-keys "Press \\[scroll-up] to exit ")))))
 138                   (min
 139                    (cond (standard "Press SPC to scroll, Q to exit ")
 140                          (up)
 141                          (t (setq up (substitute-command-keys "Press \\[scroll-up] to scroll; \\[electric-help-exit] to exit ")))))
 142                   (max
 143                    (cond (standard "Press DEL to scroll back, Q to exit ")
 144                          (down)
 145                          (t (setq down (substitute-command-keys "Press \\[scroll-down] to scroll back, \\[scroll-up] to exit ")))))
 146                   (t
 147                    (cond (standard "Press SPC to scroll, DEL to scroll back, Q to exit ")
 148                          (both)
 149                          (t (setq both (substitute-command-keys "Press \\[scroll-up] to scroll, \\[scroll-down] to scroll back, \\[electric-help-exit] to exit ")))))))))
 150                     t))))
 151
 152
 153 \f
 154 ;(defun electric-help-scroll-up (arg)
 155 ;  ">>>Doc"
 156 ;  (interactive "P")
 157 ;  (if (and (null arg) (pos-visible-in-window-p (point-max)))
 158 ;      (electric-help-exit)
 159 ;    (scroll-up arg)))
 160
 161 (defun electric-help-exit ()
 162   ">>>Doc"
 163   (interactive)
 164   (throw 'exit t))
 165
 166 (defun electric-help-retain ()
 167   "Exit `electric-help', retaining the current window/buffer configuration.
 168 \(The *Help* buffer will not be selected, but \\[switch-to-buffer-other-window] RET
 169 will select it.)"
 170   (interactive)
 171   (throw 'exit '(retain)))
 172
 173
 174 (defun electric-help-undefined ()
 175   (interactive)
 176   (error "%s is undefined -- Press %s to exit"
 177          (mapconcat 'single-key-description (this-command-keys) " ")
 178          (if (eq (key-binding "Q") 'electric-help-exit)
 179              "Q"
 180            (substitute-command-keys "\\[electric-help-exit]"))))
 181
 182
 183 ;>>> this needs to be hairified (recursive help, anybody?)
 184 (defun electric-help-help ()
 185   (interactive)
 186   (if (and (eq (key-binding "Q") 'electric-help-exit)
 187            (eq (key-binding " ") 'scroll-up)
 188            (eq (key-binding "\^?") 'scroll-down))
 189       (message "SPC scrolls forward, DEL scrolls back, Q exits and burys help buffer")
 190     ;; to give something for user to look at while slow substitute-cmd-keys
 191     ;;  grinds away
 192     (message "Help...")
 193     (message "%s" (substitute-command-keys "\\[scroll-up] scrolls forward, \\[scroll-down] scrolls back, \\[electric-help-exit] exits.")))
 194   (sit-for 2))
 195
 196 \f
 197 (defun electric-helpify (fun)
 198   (let ((name "*Help*"))
 199     (if (save-window-excursion
 200           ;; kludge-o-rama
 201           (let* ((p (symbol-function 'print-help-return-message))
 202                  (b (get-buffer name))
 203                  (m (buffer-modified-p b)))
 204             (and b (not (get-buffer-window b))
 205                  (setq b nil))
 206             (unwind-protect
 207                 (progn
 208                   (message "%s..." (capitalize (symbol-name fun)))
 209                   ;; with-output-to-temp-buffer marks the buffer as unmodified.
 210                   ;; kludging excessively and relying on that as some sort
 211                   ;;  of indication leads to the following abomination...
 212                   ;;>> This would be doable without such icky kludges if either
 213                   ;;>> (a) there were a function to read the interactive
 214                   ;;>>     args for a command and return a list of those args.
 215                   ;;>>     (To which one would then just apply the command)
 216                   ;;>>     (The only problem with this is that interactive-p
 217                   ;;>>      would break, but that is such a misfeature in
 218                   ;;>>      any case that I don't care)
 219                   ;;>>     It is easy to do this for emacs-lisp functions;
 220                   ;;>>     the only problem is getting the interactive spec
 221                   ;;>>     for subrs
 222                   ;;>> (b) there were a function which returned a
 223                   ;;>>     modification-tick for a buffer.  One could tell
 224                   ;;>>     whether a buffer had changed by whether the
 225                   ;;>>     modification-tick were different.
 226                   ;;>>     (Presumably there would have to be a way to either
 227                   ;;>>      restore the tick to some previous value, or to
 228                   ;;>>      suspend updating of the tick in order to allow
 229                   ;;>>      things like momentary-string-display)
 230                   (and b
 231                        (save-excursion
 232                          (set-buffer b)
 233                          (set-buffer-modified-p t)))
 234                   (fset 'print-help-return-message 'ignore)
 235                   (call-interactively fun)
 236                   (and (get-buffer name)
 237                        (get-buffer-window (get-buffer name))
 238                        (or (not b)
 239                            (not (eq b (get-buffer name)))
 240                            (not (buffer-modified-p b)))))
 241               (fset 'print-help-return-message p)
 242               (and b (buffer-name b)
 243                    (save-excursion
 244                      (set-buffer b)
 245                      (set-buffer-modified-p m))))))
 246         (with-electric-help 'ignore name t))))
 247
 248 \f
 249 (defun electric-describe-key ()
 250   (interactive)
 251   (electric-helpify 'describe-key))
 252
 253 (defun electric-describe-mode ()
 254   (interactive)
 255   (electric-helpify 'describe-mode))
 256
 257 (defun electric-view-lossage ()
 258   (interactive)
 259   (electric-helpify 'view-lossage))
 260
 261 ;(defun electric-help-for-help ()
 262 ;  "See help-for-help"
 263 ;  (interactive)
 264 ;  )
 265
 266 (defun electric-describe-function ()
 267   (interactive)
 268   (electric-helpify 'describe-function))
 269
 270 (defun electric-describe-variable ()
 271   (interactive)
 272   (electric-helpify 'describe-variable))
 273
 274 (defun electric-describe-bindings ()
 275   (interactive)
 276   (electric-helpify 'describe-bindings))
 277
 278 (defun electric-describe-syntax ()
 279   (interactive)
 280   (electric-helpify 'describe-syntax))
 281
 282 (defun electric-command-apropos ()
 283   (interactive)
 284   (electric-helpify 'command-apropos))
 285
 286 ;(define-key help-map "a" 'electric-command-apropos)
 287
 288
 289 \f
 290 ;;;; ehelp-map
 291
 292 (defvar ehelp-map ())
 293 (if ehelp-map
 294     nil
 295   (let ((map (copy-keymap help-map)))
 296     (substitute-key-definition 'describe-key 'electric-describe-key map)
 297     (substitute-key-definition 'describe-mode 'electric-describe-mode map)
 298     (substitute-key-definition 'view-lossage 'electric-view-lossage map)
 299     (substitute-key-definition 'describe-function 'electric-describe-function map)
 300     (substitute-key-definition 'describe-variable 'electric-describe-variable map)
 301     (substitute-key-definition 'describe-bindings 'electric-describe-bindings map)
 302     (substitute-key-definition 'describe-syntax 'electric-describe-syntax map)
 303
 304     (setq ehelp-map map)
 305     (fset 'ehelp-command map)))
 306
 307 ;; Do (define-key global-map "\C-h" 'ehelp-command) if you want to win