lisp/ehelp.el

   1 ;;; ehelp.el --- bindings for electric-help mode -*- lexical-binding: t -*-
   2
   3 ;; Copyright (C) 1986, 1995, 2000-2011  Free Software Foundation, Inc.
   4
   5 ;; Author: Richard Mlynarik
   6 ;; (according to ack.texi and authors.el)
   7 ;; Maintainer: FSF
   8 ;; Keywords: help, extensions
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software: you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation, either version 3 of the License, or
  15 ;; (at your option) any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26
  27 ;; This package provides a pre-packaged `Electric Help Mode' for
  28 ;; browsing on-line help screens.  There is one entry point,
  29 ;; `with-electric-help'; all you have to give it is a no-argument
  30 ;; function that generates the actual text of the help into the current
  31 ;; buffer.
  32
  33 ;; To make this the default, you must do
  34 ;; (require 'ehelp)
  35 ;; (define-key global-map "\C-h" 'ehelp-command)
  36 ;; (define-key global-map [help] 'ehelp-command)
  37 ;; (define-key global-map [f1] 'ehelp-command)
  38
  39 ;;; Code:
  40
  41 (require 'electric)
  42
  43 (defvar electric-help-form-to-execute nil)
  44
  45 (defgroup electric-help ()
  46   "Electric help facility."
  47   :version "21.1"
  48   :group 'help)
  49
  50 (defcustom electric-help-shrink-window t
  51   "If set, adjust help window sizes to buffer sizes when displaying help."
  52   :type 'boolean
  53   :group 'electric-help)
  54
  55 (defcustom electric-help-mode-hook nil
  56   "Hook run by `with-electric-help' after initializing the buffer."
  57   :type 'hook
  58   :group 'electric-help)
  59
  60 (put 'electric-help-undefined 'suppress-keymap t)
  61
  62 (defvar electric-help-map
  63   (let ((map (make-keymap)))
  64     ;; allow all non-self-inserting keys - search, scroll, etc, but
  65     ;; let M-x and C-x exit ehelp mode and retain buffer:
  66     (suppress-keymap map)
  67     (define-key map "\C-u" 'electric-help-undefined)
  68     (define-key map [?\C-0] 'electric-help-undefined)
  69     (define-key map [?\C-1] 'electric-help-undefined)
  70     (define-key map [?\C-2] 'electric-help-undefined)
  71     (define-key map [?\C-3] 'electric-help-undefined)
  72     (define-key map [?\C-4] 'electric-help-undefined)
  73     (define-key map [?\C-5] 'electric-help-undefined)
  74     (define-key map [?\C-6] 'electric-help-undefined)
  75     (define-key map [?\C-7] 'electric-help-undefined)
  76     (define-key map [?\C-8] 'electric-help-undefined)
  77     (define-key map [?\C-9] 'electric-help-undefined)
  78     (define-key map (char-to-string help-char) 'electric-help-help)
  79     (define-key map "?" 'electric-help-help)
  80     (define-key map " " 'scroll-up)
  81     (define-key map "\^?" 'scroll-down)
  82     (define-key map "." 'beginning-of-buffer)
  83     (define-key map "<" 'beginning-of-buffer)
  84     (define-key map ">" 'end-of-buffer)
  85     ;(define-key map "\C-g" 'electric-help-exit)
  86     (define-key map "Q" 'electric-help-exit)
  87     (define-key map "q" 'electric-help-exit)
  88     ;;a better key than this?
  89     (define-key map "R" 'electric-help-retain)
  90     (define-key map "r" 'electric-help-retain)
  91     (define-key map "\ex" 'electric-help-execute-extended)
  92     (define-key map "\C-x" 'electric-help-ctrl-x-prefix)
  93     map)
  94   "Keymap defining commands available in `electric-help-mode'.")
  95
  96 (defvar electric-help-orig-major-mode nil)
  97 (make-variable-buffer-local 'electric-help-orig-major-mode)
  98
  99 (defun electric-help-mode ()
 100   "`with-electric-help' temporarily places its buffer in this mode.
 101 \(On exit from `with-electric-help', the original `major-mode' is restored.)"
 102   (setq buffer-read-only t)
 103   (setq electric-help-orig-major-mode major-mode)
 104   (setq mode-name "Help")
 105   (setq major-mode 'help)
 106   (setq mode-line-buffer-identification '(" Help:  %b"))
 107   (use-local-map electric-help-map)
 108   (add-hook 'mouse-leave-buffer-hook 'electric-help-retain)
 109   (view-mode -1)
 110   ;; this is done below in with-electric-help
 111   ;(run-hooks 'electric-help-mode-hook)
 112   )
 113
 114 ;;;###autoload
 115 (defun with-electric-help (thunk &optional buffer noerase minheight)
 116   "Pop up an \"electric\" help buffer.
 117 THUNK is a function of no arguments which is called to initialize the
 118 contents of BUFFER.  BUFFER defaults to `*Help*'.  BUFFER will be
 119 erased before THUNK is called unless NOERASE is non-nil.  THUNK will
 120 be called while BUFFER is current and with `standard-output' bound to
 121 the buffer specified by BUFFER.
 122
 123 If THUNK returns nil, we display BUFFER starting at the top, and shrink
 124 the window to fit.  If THUNK returns non-nil, we don't do those things.
 125
 126 After THUNK has been called, this function \"electrically\" pops up a
 127 window in which BUFFER is displayed and allows the user to scroll
 128 through that buffer in `electric-help-mode'.  The window's height will
 129 be at least MINHEIGHT if this value is non-nil.
 130
 131 If THUNK returns nil, we display BUFFER starting at the top, and
 132 shrink the window to fit if `electric-help-shrink-window' is non-nil.
 133 If THUNK returns non-nil, we don't do those things.
 134
 135 When the user exits (with `electric-help-exit', or otherwise), the help
 136 buffer's window disappears (i.e., we use `save-window-excursion'), and
 137 BUFFER is put back into its original major mode."
 138   (setq buffer (get-buffer-create (or buffer "*Help*")))
 139   (let ((one (one-window-p t))
 140         (config (current-window-configuration))
 141         (bury nil)
 142         (electric-help-form-to-execute nil))
 143     (unwind-protect
 144          (save-excursion
 145            (when one
 146              (goto-char (window-start (selected-window))))
 147            (let ((pop-up-windows t))
 148              (pop-to-buffer buffer))
 149            (with-current-buffer buffer
 150              (when (and minheight (< (window-height) minheight))
 151                (enlarge-window (- minheight (window-height))))
 152              (electric-help-mode)
 153              (setq buffer-read-only nil)
 154              (unless noerase
 155                (erase-buffer)))
 156            (let ((standard-output buffer))
 157              (unless (funcall thunk)
 158                (set-buffer buffer)
 159                (set-buffer-modified-p nil)
 160                (goto-char (point-min))
 161                (when (and one electric-help-shrink-window)
 162                  (shrink-window-if-larger-than-buffer))))
 163            (set-buffer buffer)
 164            (run-hooks 'electric-help-mode-hook)
 165            (setq buffer-read-only t)
 166            (if (eq (car-safe (electric-help-command-loop)) 'retain)
 167                (setq config (current-window-configuration))
 168              (setq bury t))
 169            ;; Remove the hook.
 170            (when (memq 'electric-help-retain mouse-leave-buffer-hook)
 171              (remove-hook 'mouse-leave-buffer-hook 'electric-help-retain)))
 172       (message "")
 173       (set-buffer buffer)
 174       (setq buffer-read-only nil)
 175
 176       ;; Restore the original major mode saved by `electric-help-mode'.
 177       ;; We should really get a usable *Help* buffer when retaining
 178       ;; the electric one with `r'.  The problem is that a simple
 179       ;; call to `help-mode' won't cut it; e.g. RET is bound wrong
 180       ;; afterwards (`View-scroll-line-forward' instead of `help-follow').
 181       ;; That's because Help mode should be set with `with-help-window'
 182       ;; instead of the direct call to `help-mode'. But at least
 183       ;; RET works correctly on links after using `help-mode'.
 184       ;; This is satisfactory enough.
 185       (condition-case ()
 186           (funcall (or electric-help-orig-major-mode 'fundamental-mode))
 187         (error nil))
 188
 189       (set-window-configuration config)
 190       (when bury
 191         ;;>> Perhaps this shouldn't be done,
 192         ;; so that when we say "Press space to bury" we mean it
 193         (replace-buffer-in-windows buffer)
 194         ;; must do this outside of save-window-excursion
 195         (bury-buffer buffer))
 196       (eval electric-help-form-to-execute))))
 197
 198 (defun electric-help-command-loop ()
 199   (catch 'exit
 200     (if (pos-visible-in-window-p (point-max))
 201         (progn (message "%s" (substitute-command-keys "<<< Press Space to bury the help buffer, Press \\[electric-help-retain] to retain it >>>"))
 202                (if (equal (setq unread-command-events (list (read-event)))
 203                           '(?\s))
 204                    (progn (setq unread-command-events nil)
 205                           (throw 'exit t)))))
 206     (let (up down both neither
 207           (standard (and (eq (key-binding " " nil t)
 208                              'scroll-up)
 209                          (eq (key-binding "\^?" nil t)
 210                              'scroll-down)
 211                          (eq (key-binding "q" nil t)
 212                              'electric-help-exit)
 213                          (eq (key-binding "r" nil t)
 214                              'electric-help-retain))))
 215       (Electric-command-loop
 216         'exit
 217         (function (lambda ()
 218           (sit-for 0) ;necessary if last command was end-of-buffer or
 219                       ;beginning-of-buffer - otherwise pos-visible-in-window-p
 220                       ;will yield a wrong result.
 221           (let ((min (pos-visible-in-window-p (point-min)))
 222                 (max (pos-visible-in-window-p (1- (point-max)))))
 223             (cond (isearch-mode 'noprompt)
 224                   ((and min max)
 225                    (cond (standard "Press q to exit, r to retain ")
 226                          (neither)
 227                          (t (setq neither (substitute-command-keys "Press \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))
 228                   (min
 229                    (cond (standard "Press SPC to scroll, q to exit, r to retain ")
 230                          (up)
 231                          (t (setq up (substitute-command-keys "Press \\[scroll-up] to scroll, \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))
 232                   (max
 233                    (cond (standard "Press DEL to scroll back, q to exit, r to retain ")
 234                          (down)
 235                          (t (setq down (substitute-command-keys "Press \\[scroll-down] to scroll back, \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))
 236                   (t
 237                    (cond (standard "Press SPC to scroll, DEL to scroll back, q to exit, r to retain ")
 238                          (both)
 239                          (t (setq both (substitute-command-keys "Press \\[scroll-up] to scroll, \\[scroll-down] to scroll back, \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))))))
 240                     t))))
 241
 242
 243 \f
 244 ;(defun electric-help-scroll-up (arg)
 245 ;  ">>>Doc"
 246 ;  (interactive "P")
 247 ;  (if (and (null arg) (pos-visible-in-window-p (point-max)))
 248 ;      (electric-help-exit)
 249 ;    (scroll-up arg)))
 250
 251 (defun electric-help-exit ()
 252   "Exit `with-electric-help', restoring the previous window/buffer configuration.
 253 \(The *Help* buffer will be buried.)"
 254   (interactive)
 255   ;; Make sure that we don't throw twice, even if two events cause
 256   ;; calling this function:
 257   (if (memq 'electric-help-retain mouse-leave-buffer-hook)
 258       (progn
 259         (remove-hook 'mouse-leave-buffer-hook 'electric-help-retain)
 260         (throw 'exit t))))
 261
 262 (defun electric-help-retain ()
 263   "Exit `with-electric-help', retaining the current window/buffer configuration.
 264 \(The *Help* buffer will not be selected, but \\[switch-to-buffer-other-window] RET
 265 will select it.)"
 266   (interactive)
 267   ;; Make sure that we don't throw twice, even if two events cause
 268   ;; calling this function:
 269   (if (memq 'electric-help-retain mouse-leave-buffer-hook)
 270       (progn
 271         (remove-hook 'mouse-leave-buffer-hook 'electric-help-retain)
 272         (throw 'exit '(retain)))))
 273
 274
 275 (defun electric-help-undefined ()
 276   (interactive)
 277   (error "%s is undefined -- Press %s to exit"
 278          (mapconcat 'single-key-description (this-command-keys) " ")
 279          (if (eq (key-binding "q" nil t) 'electric-help-exit)
 280              "q"
 281            (substitute-command-keys "\\[electric-help-exit]"))))
 282
 283
 284 ;>>> this needs to be hairified (recursive help, anybody?)
 285 (defun electric-help-help ()
 286   (interactive)
 287   (if (and (eq (key-binding "q" nil t) 'electric-help-exit)
 288            (eq (key-binding " " nil t) 'scroll-up)
 289            (eq (key-binding "\^?" nil t) 'scroll-down)
 290            (eq (key-binding "r" nil t) 'electric-help-retain))
 291       (message "SPC scrolls up, DEL scrolls down, q exits burying help buffer, r exits")
 292     (message "%s" (substitute-command-keys "\\[scroll-up] scrolls up, \\[scroll-down] scrolls down, \\[electric-help-exit] exits burying help buffer, \\[electric-help-retain] exits")))
 293   (sit-for 2))
 294
 295 \f
 296 ;;;###autoload
 297 (defun electric-helpify (fun &optional name)
 298   (let ((name (or name "*Help*")))
 299     (if (save-window-excursion
 300           ;; kludge-o-rama
 301           (let* ((p (symbol-function 'help-print-return-message))
 302                  (b (get-buffer name))
 303                  (m (buffer-modified-p b)))
 304             (and b (not (get-buffer-window b))
 305                  (setq b nil))
 306             (unwind-protect
 307                 (progn
 308                   (message "%s..." (capitalize (symbol-name fun)))
 309                   ;; with-output-to-temp-buffer marks the buffer as unmodified.
 310                   ;; kludging excessively and relying on that as some sort
 311                   ;;  of indication leads to the following abomination...
 312                   ;;>> This would be doable without such icky kludges if either
 313                   ;;>> (a) there were a function to read the interactive
 314                   ;;>>     args for a command and return a list of those args.
 315                   ;;>>     (To which one would then just apply the command)
 316                   ;;>>     (The only problem with this is that interactive-p
 317                   ;;>>      would break, but that is such a misfeature in
 318                   ;;>>      any case that I don't care)
 319                   ;;>>     It is easy to do this for emacs-lisp functions;
 320                   ;;>>     the only problem is getting the interactive spec
 321                   ;;>>     for subrs
 322                   ;;>> (b) there were a function which returned a
 323                   ;;>>     modification-tick for a buffer.  One could tell
 324                   ;;>>     whether a buffer had changed by whether the
 325                   ;;>>     modification-tick were different.
 326                   ;;>>     (Presumably there would have to be a way to either
 327                   ;;>>      restore the tick to some previous value, or to
 328                   ;;>>      suspend updating of the tick in order to allow
 329                   ;;>>      things like momentary-string-display)
 330                   (and b
 331                        (with-current-buffer b
 332                          (set-buffer-modified-p t)))
 333                   (fset 'help-print-return-message 'ignore)
 334                   (call-interactively fun)
 335                   (and (get-buffer name)
 336                        (get-buffer-window (get-buffer name))
 337                        (or (not b)
 338                            (not (eq b (get-buffer name)))
 339                            (not (buffer-modified-p b)))))
 340               (fset 'help-print-return-message p)
 341               (and b (buffer-name b)
 342                    (with-current-buffer b
 343                      (set-buffer-modified-p m))))))
 344         (with-electric-help 'ignore name t))))
 345
 346 \f
 347
 348 ;; This is to be bound to M-x in ehelp mode. Retains ehelp buffer and then
 349 ;; continues with execute-extended-command.
 350 (defun electric-help-execute-extended (_prefixarg)
 351   (interactive "p")
 352   (setq electric-help-form-to-execute '(execute-extended-command nil))
 353   (electric-help-retain))
 354
 355 ;; This is to be buond to C-x in ehelp mode. Retains ehelp buffer and then
 356 ;; continues with ctrl-x prefix.
 357 (defun electric-help-ctrl-x-prefix (_prefixarg)
 358   (interactive "p")
 359   (setq electric-help-form-to-execute '(progn (message nil) (setq unread-command-char ?\C-x)))
 360   (electric-help-retain))
 361
 362 \f
 363 (defun electric-describe-key ()
 364   (interactive)
 365   (electric-helpify 'describe-key))
 366
 367 (defun electric-describe-mode ()
 368   (interactive)
 369   (electric-helpify 'describe-mode))
 370
 371 (defun electric-view-lossage ()
 372   (interactive)
 373   (electric-helpify 'view-lossage))
 374
 375 ;(defun electric-help-for-help ()
 376 ;  "See help-for-help"
 377 ;  (interactive)
 378 ;  )
 379
 380 (defun electric-describe-function ()
 381   (interactive)
 382   (electric-helpify 'describe-function))
 383
 384 (defun electric-describe-variable ()
 385   (interactive)
 386   (electric-helpify 'describe-variable))
 387
 388 (defun electric-describe-bindings ()
 389   (interactive)
 390   (electric-helpify 'describe-bindings))
 391
 392 (defun electric-describe-syntax ()
 393   (interactive)
 394   (electric-helpify 'describe-syntax))
 395
 396 (defun electric-command-apropos ()
 397   (interactive)
 398   (electric-helpify 'command-apropos "*Apropos*"))
 399
 400 ;(define-key help-map "a" 'electric-command-apropos)
 401
 402 (defun electric-apropos ()
 403   (interactive)
 404   (electric-helpify 'apropos))
 405
 406 \f
 407 ;;;; ehelp-map
 408
 409 (defvar ehelp-map
 410   (let ((map (copy-keymap help-map)))
 411     (substitute-key-definition 'apropos 'electric-apropos map)
 412     (substitute-key-definition 'command-apropos 'electric-command-apropos map)
 413     (substitute-key-definition 'describe-key 'electric-describe-key map)
 414     (substitute-key-definition 'describe-mode 'electric-describe-mode map)
 415     (substitute-key-definition 'view-lossage 'electric-view-lossage map)
 416     (substitute-key-definition 'describe-function 'electric-describe-function map)
 417     (substitute-key-definition 'describe-variable 'electric-describe-variable map)
 418     (substitute-key-definition 'describe-bindings 'electric-describe-bindings map)
 419     (substitute-key-definition 'describe-syntax 'electric-describe-syntax map)
 420     map))
 421
 422 ;;;###(autoload 'ehelp-command "ehelp" "Prefix command for ehelp." t 'keymap)
 423 (defalias 'ehelp-command ehelp-map)
 424 (put 'ehelp-command 'documentation "Prefix command for ehelp.")
 425
 426 (provide 'ehelp)
 427
 428 ;;; ehelp.el ends here