lisp/ehelp.el

   1 ;;; ehelp.el --- bindings for electric-help mode
   2
   3 ;; Copyright (C) 1986 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: help, extensions
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to
  22 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  23
  24 ;;; Commentary:
  25
  26 ;; This package provides a pre-packaged `Electric Help Mode' for
  27 ;; browsing on-line help screens.  There is one entry point,
  28 ;; `with-electric-help'; All you have to give it is a no-argument
  29 ;; function that generates the actual text of the help into the current
  30 ;; buffer.
  31
  32 ;;; Code:
  33
  34 (require 'electric)
  35 (defvar electric-help-map ()
  36   "Keymap defining commands available in `electric-help-mode'.")
  37
  38 (put 'electric-help-undefined 'suppress-keymap t)
  39 (if electric-help-map
  40     ()
  41   (let ((map (make-keymap)))
  42     (fillarray (car (cdr map)) 'electric-help-undefined)
  43     (define-key map (char-to-string meta-prefix-char) (copy-keymap map))
  44     (define-key map (char-to-string help-char) 'electric-help-help)
  45     (define-key map "?" 'electric-help-help)
  46     (define-key map " " 'scroll-up)
  47     (define-key map "\^?" 'scroll-down)
  48     (define-key map "." 'beginning-of-buffer)
  49     (define-key map "<" 'beginning-of-buffer)
  50     (define-key map ">" 'end-of-buffer)
  51     ;(define-key map "\C-g" 'electric-help-exit)
  52     (define-key map "q" 'electric-help-exit)
  53     (define-key map "Q" 'electric-help-exit)
  54     ;;a better key than this?
  55     (define-key map "r" 'electric-help-retain)
  56
  57     (setq electric-help-map map)))
  58
  59 (defun electric-help-mode ()
  60   "`with-electric-help' temporarily places its buffer in this mode.
  61 \(On exit from `with-electric-help', the buffer is put in `default-major-mode'.)"
  62   (setq buffer-read-only t)
  63   (setq mode-name "Help")
  64   (setq major-mode 'help)
  65   (setq mode-line-buffer-identification '(" Help:  %b"))
  66   (use-local-map electric-help-map)
  67   ;; this is done below in with-electric-help
  68   ;(run-hooks 'electric-help-mode-hook)
  69   )
  70
  71 (defun with-electric-help (thunk &optional buffer noerase)
  72   "Arguments are THUNK &optional BUFFER NOERASE.  BUFFER defaults to \"*Help*\"
  73 THUNK is a function of no arguments which is called to initialize
  74 the contents of BUFFER.  BUFFER will be erased before THUNK is called unless
  75 NOERASE is non-nil.  THUNK will be called with `standard-output' bound to
  76 the buffer specified by BUFFER
  77
  78 After THUNK has been called, this function \"electrically\" pops up a window
  79 in which BUFFER is displayed and allows the user to scroll through that buffer
  80 in electric-help-mode.
  81 When the user exits (with `electric-help-exit', or otherwise) the help
  82 buffer's window disappears (i.e., we use `save-window-excursion')
  83 BUFFER is put into `default-major-mode' (or `fundamental-mode') when we exit"
  84   (setq buffer (get-buffer-create (or buffer "*Help*")))
  85   (let ((one (one-window-p t))
  86         (config (current-window-configuration))
  87         (bury nil))
  88     (unwind-protect
  89          (save-excursion
  90            (if one (goto-char (window-start (selected-window))))
  91            (let ((pop-up-windows t))
  92              (pop-to-buffer buffer))
  93            (save-excursion
  94              (set-buffer buffer)
  95              (electric-help-mode)
  96              (setq buffer-read-only nil)
  97              (or noerase (erase-buffer)))
  98            (let ((standard-output buffer))
  99              (if (not (funcall thunk))
 100                  (progn
 101                    (set-buffer buffer)
 102                    (set-buffer-modified-p nil)
 103                    (goto-char (point-min))
 104                    (if one (shrink-window-if-larger-than-buffer (selected-window))))))
 105            (set-buffer buffer)
 106            (run-hooks 'electric-help-mode-hook)
 107            (if (eq (car-safe (electric-help-command-loop))
 108                    'retain)
 109                (setq config (current-window-configuration))
 110                (setq bury t)))
 111       (message "")
 112       (set-buffer buffer)
 113       (setq buffer-read-only nil)
 114       (condition-case ()
 115           (funcall (or default-major-mode 'fundamental-mode))
 116         (error nil))
 117       (set-window-configuration config)
 118       (if bury
 119           (progn
 120             ;;>> Perhaps this shouldn't be done.
 121             ;; so that when we say "Press space to bury" we mean it
 122             (replace-buffer-in-windows buffer)
 123             ;; must do this outside of save-window-excursion
 124             (bury-buffer buffer))))))
 125
 126 (defun electric-help-command-loop ()
 127   (catch 'exit
 128     (if (pos-visible-in-window-p (point-max))
 129         (progn (message "<<< Press Space to bury the help buffer >>>")
 130                (if (equal (setq unread-command-events (list (read-event)))
 131                           '(?\ ))
 132                    (progn (setq unread-command-events nil)
 133                           (throw 'exit t)))))
 134     (let (up down both neither
 135           (standard (and (eq (key-binding " ")
 136                              'scroll-up)
 137                          (eq (key-binding "\^?")
 138                              'scroll-down)
 139                          (eq (key-binding "Q")
 140                              'electric-help-exit)
 141                          (eq (key-binding "q")
 142                              'electric-help-exit))))
 143       (Electric-command-loop
 144         'exit
 145         (function (lambda ()
 146           (let ((min (pos-visible-in-window-p (point-min)))
 147                 (max (pos-visible-in-window-p (point-max))))
 148             (cond ((and min max)
 149                    (cond (standard "Press Q to exit ")
 150                          (neither)
 151                          (t (setq neither (substitute-command-keys "Press \\[scroll-up] to exit ")))))
 152                   (min
 153                    (cond (standard "Press SPC to scroll, Q to exit ")
 154                          (up)
 155                          (t (setq up (substitute-command-keys "Press \\[scroll-up] to scroll; \\[electric-help-exit] to exit ")))))
 156                   (max
 157                    (cond (standard "Press DEL to scroll back, Q to exit ")
 158                          (down)
 159                          (t (setq down (substitute-command-keys "Press \\[scroll-down] to scroll back, \\[scroll-up] to exit ")))))
 160                   (t
 161                    (cond (standard "Press SPC to scroll, DEL to scroll back, Q to exit ")
 162                          (both)
 163                          (t (setq both (substitute-command-keys "Press \\[scroll-up] to scroll, \\[scroll-down] to scroll back, \\[electric-help-exit] to exit ")))))))))
 164                     t))))
 165
 166
 167 \f
 168 ;(defun electric-help-scroll-up (arg)
 169 ;  ">>>Doc"
 170 ;  (interactive "P")
 171 ;  (if (and (null arg) (pos-visible-in-window-p (point-max)))
 172 ;      (electric-help-exit)
 173 ;    (scroll-up arg)))
 174
 175 (defun electric-help-exit ()
 176   ">>>Doc"
 177   (interactive)
 178   (throw 'exit t))
 179
 180 (defun electric-help-retain ()
 181   "Exit `electric-help', retaining the current window/buffer configuration.
 182 \(The *Help* buffer will not be selected, but \\[switch-to-buffer-other-window] RET
 183 will select it.)"
 184   (interactive)
 185   (throw 'exit '(retain)))
 186
 187
 188 (defun electric-help-undefined ()
 189   (interactive)
 190   (error "%s is undefined -- Press %s to exit"
 191          (mapconcat 'single-key-description (this-command-keys) " ")
 192          (if (eq (key-binding "Q") 'electric-help-exit)
 193              "Q"
 194            (substitute-command-keys "\\[electric-help-exit]"))))
 195
 196
 197 ;>>> this needs to be hairified (recursive help, anybody?)
 198 (defun electric-help-help ()
 199   (interactive)
 200   (if (and (eq (key-binding "Q") 'electric-help-exit)
 201            (eq (key-binding " ") 'scroll-up)
 202            (eq (key-binding "\^?") 'scroll-down))
 203       (message "SPC scrolls forward, DEL scrolls back, Q exits and burys help buffer")
 204     ;; to give something for user to look at while slow substitute-cmd-keys
 205     ;;  grinds away
 206     (message "Help...")
 207     (message "%s" (substitute-command-keys "\\[scroll-up] scrolls forward, \\[scroll-down] scrolls back, \\[electric-help-exit] exits.")))
 208   (sit-for 2))
 209
 210 \f
 211 (defun electric-helpify (fun)
 212   (let ((name "*Help*"))
 213     (if (save-window-excursion
 214           ;; kludge-o-rama
 215           (let* ((p (symbol-function 'print-help-return-message))
 216                  (b (get-buffer name))
 217                  (m (buffer-modified-p b)))
 218             (and b (not (get-buffer-window b))
 219                  (setq b nil))
 220             (unwind-protect
 221                 (progn
 222                   (message "%s..." (capitalize (symbol-name fun)))
 223                   ;; with-output-to-temp-buffer marks the buffer as unmodified.
 224                   ;; kludging excessively and relying on that as some sort
 225                   ;;  of indication leads to the following abomination...
 226                   ;;>> This would be doable without such icky kludges if either
 227                   ;;>> (a) there were a function to read the interactive
 228                   ;;>>     args for a command and return a list of those args.
 229                   ;;>>     (To which one would then just apply the command)
 230                   ;;>>     (The only problem with this is that interactive-p
 231                   ;;>>      would break, but that is such a misfeature in
 232                   ;;>>      any case that I don't care)
 233                   ;;>>     It is easy to do this for emacs-lisp functions;
 234                   ;;>>     the only problem is getting the interactive spec
 235                   ;;>>     for subrs
 236                   ;;>> (b) there were a function which returned a
 237                   ;;>>     modification-tick for a buffer.  One could tell
 238                   ;;>>     whether a buffer had changed by whether the
 239                   ;;>>     modification-tick were different.
 240                   ;;>>     (Presumably there would have to be a way to either
 241                   ;;>>      restore the tick to some previous value, or to
 242                   ;;>>      suspend updating of the tick in order to allow
 243                   ;;>>      things like momentary-string-display)
 244                   (and b
 245                        (save-excursion
 246                          (set-buffer b)
 247                          (set-buffer-modified-p t)))
 248                   (fset 'print-help-return-message 'ignore)
 249                   (call-interactively fun)
 250                   (and (get-buffer name)
 251                        (get-buffer-window (get-buffer name))
 252                        (or (not b)
 253                            (not (eq b (get-buffer name)))
 254                            (not (buffer-modified-p b)))))
 255               (fset 'print-help-return-message p)
 256               (and b (buffer-name b)
 257                    (save-excursion
 258                      (set-buffer b)
 259                      (set-buffer-modified-p m))))))
 260         (with-electric-help 'ignore name t))))
 261
 262 \f
 263 (defun electric-describe-key ()
 264   (interactive)
 265   (electric-helpify 'describe-key))
 266
 267 (defun electric-describe-mode ()
 268   (interactive)
 269   (electric-helpify 'describe-mode))
 270
 271 (defun electric-view-lossage ()
 272   (interactive)
 273   (electric-helpify 'view-lossage))
 274
 275 ;(defun electric-help-for-help ()
 276 ;  "See help-for-help"
 277 ;  (interactive)
 278 ;  )
 279
 280 (defun electric-describe-function ()
 281   (interactive)
 282   (electric-helpify 'describe-function))
 283
 284 (defun electric-describe-variable ()
 285   (interactive)
 286   (electric-helpify 'describe-variable))
 287
 288 (defun electric-describe-bindings ()
 289   (interactive)
 290   (electric-helpify 'describe-bindings))
 291
 292 (defun electric-describe-syntax ()
 293   (interactive)
 294   (electric-helpify 'describe-syntax))
 295
 296 (defun electric-command-apropos ()
 297   (interactive)
 298   (electric-helpify 'command-apropos))
 299
 300 ;(define-key help-map "a" 'electric-command-apropos)
 301
 302
 303 \f
 304 ;;;; ehelp-map
 305
 306 (defvar ehelp-map ())
 307 (if ehelp-map
 308     nil
 309   (let ((map (copy-keymap help-map)))
 310     (substitute-key-definition 'describe-key 'electric-describe-key map)
 311     (substitute-key-definition 'describe-mode 'electric-describe-mode map)
 312     (substitute-key-definition 'view-lossage 'electric-view-lossage map)
 313     (substitute-key-definition 'describe-function 'electric-describe-function map)
 314     (substitute-key-definition 'describe-variable 'electric-describe-variable map)
 315     (substitute-key-definition 'describe-bindings 'electric-describe-bindings map)
 316     (substitute-key-definition 'describe-syntax 'electric-describe-syntax map)
 317
 318     (setq ehelp-map map)
 319     (fset 'ehelp-command map)))
 320
 321 ;; Do (define-key global-map "\C-h" 'ehelp-command) if you want to win
 322
 323 (provide 'ehelp)
 324
 325 ;;; ehelp.el ends here