lisp/help.el

   1 ;;; help.el --- help commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: help, internal
   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 ;;; Code:
  25
  26 (require 'help-screen)
  27
  28 (defvar help-map (make-sparse-keymap)
  29   "Keymap for characters following the Help key.")
  30
  31 (define-key global-map (char-to-string help-char) 'help-command)
  32 (fset 'help-command help-map)
  33
  34 (define-key help-map (char-to-string help-char) 'help-for-help)
  35 (define-key help-map "?" 'help-for-help)
  36
  37 (define-key help-map "\C-c" 'describe-copying)
  38 (define-key help-map "\C-d" 'describe-distribution)
  39 (define-key help-map "\C-w" 'describe-no-warranty)
  40 (define-key help-map "a" 'command-apropos)
  41
  42 (define-key help-map "b" 'describe-bindings)
  43
  44 (define-key help-map "c" 'describe-key-briefly)
  45 (define-key help-map "k" 'describe-key)
  46
  47 (define-key help-map "d" 'describe-function)
  48 (define-key help-map "f" 'describe-function)
  49
  50 (define-key help-map "i" 'info)
  51 (define-key help-map "\C-f" 'Info-goto-emacs-command-node)
  52 (define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
  53
  54 (define-key help-map "l" 'view-lossage)
  55
  56 (define-key help-map "m" 'describe-mode)
  57
  58 (define-key help-map "\C-n" 'view-emacs-news)
  59 (define-key help-map "n" 'view-emacs-news)
  60
  61 (define-key help-map "p" 'finder-by-keyword)
  62 (autoload 'finder-by-keyword "finder.el")
  63
  64 (define-key help-map "s" 'describe-syntax)
  65
  66 (define-key help-map "t" 'help-with-tutorial)
  67
  68 (define-key help-map "w" 'where-is)
  69
  70 (define-key help-map "v" 'describe-variable)
  71
  72 (defun help-with-tutorial ()
  73   "Select the Emacs learn-by-doing tutorial."
  74   (interactive)
  75   (let ((file (expand-file-name "~/TUTORIAL")))
  76     (delete-other-windows)
  77     (if (get-file-buffer file)
  78         (switch-to-buffer (get-file-buffer file))
  79       (switch-to-buffer (create-file-buffer file))
  80       (setq buffer-file-name file)
  81       (setq default-directory (expand-file-name "~/"))
  82       (setq buffer-auto-save-file-name nil)
  83       (insert-file-contents (expand-file-name "TUTORIAL" data-directory))
  84       (goto-char (point-min))
  85       (search-forward "\n<<")
  86       (beginning-of-line)
  87       (delete-region (point) (progn (end-of-line) (point)))
  88       (newline (- (window-height (selected-window))
  89                   (count-lines (point-min) (point))
  90                   6))
  91       (goto-char (point-min))
  92       (set-buffer-modified-p nil))))
  93
  94 (defun describe-key-briefly (key)
  95   "Print the name of the function KEY invokes.  KEY is a string."
  96   (interactive "kDescribe key briefly: ")
  97   (let ((defn (key-binding key)))
  98     (if (or (null defn) (integerp defn))
  99         (message "%s is undefined" (key-description key))
 100       (message "%s runs the command %s"
 101                (key-description key)
 102                (if (symbolp defn) defn (prin1-to-string defn))))))
 103
 104 (defun print-help-return-message (&optional function)
 105   "Display or return message saying how to restore windows after help command.
 106 Computes a message and applies the optional argument FUNCTION to it.
 107 If FUNCTION is nil, applies `message' to it, thus printing it."
 108   (and (not (get-buffer-window standard-output))
 109        (funcall (or function 'message)
 110                 (concat
 111                  (substitute-command-keys
 112                   (if (one-window-p t)
 113                       (if pop-up-windows
 114                           "Type \\[delete-other-windows] to remove help window."
 115                         "Type \\[switch-to-buffer] RET to remove help window.")
 116                     "Type \\[switch-to-buffer-other-window] RET to restore the other window."))
 117                  (substitute-command-keys
 118                   "  \\[scroll-other-window] to scroll the help.")))))
 119
 120 (defun describe-key (key)
 121   "Display documentation of the function invoked by KEY.  KEY is a string."
 122   (interactive "kDescribe key: ")
 123   (let ((defn (key-binding key)))
 124     (if (or (null defn) (integerp defn))
 125         (message "%s is undefined" (key-description key))
 126       (with-output-to-temp-buffer "*Help*"
 127         (prin1 defn)
 128         (princ ":\n")
 129         (if (documentation defn)
 130             (princ (documentation defn))
 131           (princ "not documented"))
 132         (print-help-return-message)))))
 133
 134 (defun describe-mode (&optional minor)
 135   "Display documentation of current major mode.
 136 If optional MINOR is non-nil (or prefix argument is given if interactive),
 137 display documentation of active minor modes as well.
 138 For this to work correctly for a minor mode, the mode's indicator variable
 139 (listed in `minor-mode-alist') must also be a function whose documentation
 140 describes the minor mode."
 141   (interactive)
 142   (with-output-to-temp-buffer "*Help*"
 143     (princ mode-name)
 144     (princ " Mode:\n")
 145     (princ (documentation major-mode))
 146     (let ((minor-modes minor-mode-alist)
 147           (locals (buffer-local-variables)))
 148       (while minor-modes
 149         (let* ((minor-mode (car (car minor-modes)))
 150                (indicator (car (cdr (car minor-modes))))
 151                (local-binding (assq minor-mode locals)))
 152           ;; Document a minor mode if it is listed in minor-mode-alist,
 153           ;; bound locally in this buffer, non-nil, and has a function
 154           ;; definition.
 155           (if (and local-binding
 156                    (cdr local-binding)
 157                    (fboundp minor-mode))
 158               (progn
 159                 (princ (format "\n\n\n%s minor mode (indicator%s):\n"
 160                                minor-mode indicator))
 161                 (princ (documentation minor-mode)))))
 162         (setq minor-modes (cdr minor-modes))))
 163     (print-help-return-message)))
 164
 165 ;; So keyboard macro definitions are documented correctly
 166 (fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
 167
 168 (defun describe-distribution ()
 169   "Display info on how to obtain the latest version of GNU Emacs."
 170   (interactive)
 171   (find-file-read-only
 172    (expand-file-name "DISTRIB" data-directory)))
 173
 174 (defun describe-copying ()
 175   "Display info on how you may redistribute copies of GNU Emacs."
 176   (interactive)
 177   (find-file-read-only
 178    (expand-file-name "COPYING" data-directory))
 179   (goto-char (point-min)))
 180
 181 (defun describe-no-warranty ()
 182   "Display info on all the kinds of warranty Emacs does NOT have."
 183   (interactive)
 184   (describe-copying)
 185   (let (case-fold-search)
 186     (search-forward "NO WARRANTY")
 187     (recenter 0)))
 188
 189 (defun view-emacs-news ()
 190   "Display info on recent changes to Emacs."
 191   (interactive)
 192   (find-file-read-only (expand-file-name "NEWS" data-directory)))
 193
 194 (defun view-lossage ()
 195   "Display last 100 input keystrokes."
 196   (interactive)
 197   (with-output-to-temp-buffer "*Help*"
 198     (princ (key-description (recent-keys)))
 199     (save-excursion
 200       (set-buffer standard-output)
 201       (goto-char (point-min))
 202       (while (progn (move-to-column 50) (not (eobp)))
 203         (search-forward " " nil t)
 204         (insert "\n")))
 205     (print-help-return-message)))
 206
 207 (make-help-screen help-for-help
 208   "A B C F I K L M N P S T V W C-c C-d C-n C-w.  Type \\[help-for-help] again for more help: "
 209   "You have typed \\[help-for-help], the help character.  Type a Help option:
 210
 211 A  command-apropos.   Give a substring, and see a list of commands
 212               (functions interactively callable) that contain
 213               that substring.  See also the  apropos  command.
 214 B  describe-bindings.  Display table of all key bindings.
 215 C  describe-key-briefly.  Type a command key sequence;
 216               it prints the function name that sequence runs.
 217 F  describe-function.  Type a function name and get documentation of it.
 218 I  info. The  info  documentation reader.
 219 K  describe-key.  Type a command key sequence;
 220               it displays the full documentation.
 221 L  view-lossage.  Shows last 100 characters you typed.
 222 M  describe-mode.  Print documentation of current major mode,
 223               which describes the commands peculiar to it.
 224 N  view-emacs-news.  Shows emacs news file.
 225 P  finder-by-keyword. Find packages matching a given topic keyword.
 226 S  describe-syntax.  Display contents of syntax table, plus explanations
 227 T  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
 228 V  describe-variable.  Type name of a variable;
 229               it displays the variable's documentation and value.
 230 W  where-is.  Type command name; it prints which keystrokes
 231               invoke that command.
 232 C-c print Emacs copying permission (General Public License).
 233 C-d print Emacs ordering information.
 234 C-n print news of recent Emacs changes.
 235 C-w print information on absence of warranty for GNU Emacs."
 236   help-map)
 237
 238 ;; Return a function which is called by the list containing point.
 239 ;; If that gives no function, return a function whose name is around point.
 240 ;; If that doesn't give a function, return nil.
 241 (defun function-called-at-point ()
 242   (or (condition-case ()
 243           (save-excursion
 244             (save-restriction
 245               (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
 246               (backward-up-list 1)
 247               (forward-char 1)
 248               (let (obj)
 249                 (setq obj (read (current-buffer)))
 250                 (and (symbolp obj) (fboundp obj) obj))))
 251         (error nil))
 252       (condition-case ()
 253           (save-excursion
 254             (forward-sexp -1)
 255             (skip-chars-forward "'")
 256             (let ((obj (read (current-buffer))))
 257               (and (symbolp obj) (fboundp obj) obj)))
 258         (error nil))))
 259
 260 (defun describe-function (function)
 261   "Display the full documentation of FUNCTION (a symbol)."
 262   (interactive
 263    (let ((fn (function-called-at-point))
 264          (enable-recursive-minibuffers t)
 265          val)
 266      (setq val (completing-read (if fn
 267                                     (format "Describe function (default %s): " fn)
 268                                   "Describe function: ")
 269                                 obarray 'fboundp t))
 270      (list (if (equal val "")
 271                fn (intern val)))))
 272   (with-output-to-temp-buffer "*Help*"
 273     (prin1 function)
 274     (princ ": ")
 275     (let* ((def (symbol-function function))
 276            (beg (if (commandp def) "an interactive " "a ")))
 277       (princ (cond ((stringp def) "a keyboard macro.")
 278                    ((subrp def)
 279                     (concat beg "built-in function."))
 280                    ((byte-code-function-p def)
 281                     (concat beg "compiled Lisp function."))
 282                    ((symbolp def)
 283                     (format "alias for `%s'." def))
 284                    ((eq (car-safe def) 'lambda)
 285                     (concat beg "Lisp function."))
 286                    ((eq (car-safe def) 'macro)
 287                     "a Lisp macro.")
 288                    ((eq (car-safe def) 'mocklisp)
 289                     "a mocklisp function.")
 290                    ((eq (car-safe def) 'autoload)
 291                     (format "%s autoloaded Lisp %s."
 292                             (if (commandp def) "an interactive" "an")
 293                             (if (nth 4 def) "macro" "function")
 294 ;;; Including the file name made this line too long.
 295 ;;;                         (nth 1 def)
 296                             ))
 297                    (t "")))
 298       (terpri)
 299       (if (documentation function)
 300           (princ (documentation function))
 301         (princ "not documented"))
 302       (cond ((byte-code-function-p def)
 303              (save-excursion
 304                (set-buffer standard-output)
 305                (or (eq (char-after (1- (point-max))) ?\n)
 306                    (terpri)))
 307              (terpri)
 308              (princ (car (append def nil))))
 309             ((eq (car-safe def) 'lambda)
 310              (save-excursion
 311                (set-buffer standard-output)
 312                (or (eq (char-after (1- (point-max))) ?\n)
 313                    (terpri)))
 314              (terpri)
 315              (princ (nth 1 def)))))
 316     (print-help-return-message)
 317     ;; Return the text we displayed.
 318     (save-excursion (set-buffer standard-output) (buffer-string))))
 319
 320 (defun variable-at-point ()
 321   (condition-case ()
 322       (save-excursion
 323         (forward-sexp -1)
 324         (skip-chars-forward "'")
 325         (let ((obj (read (current-buffer))))
 326           (and (symbolp obj) (boundp obj) obj)))
 327     (error nil)))
 328
 329 (defun describe-variable (variable)
 330   "Display the full documentation of VARIABLE (a symbol).
 331 Returns the documentation as a string, also."
 332   (interactive
 333    (let ((v (variable-at-point))
 334          (enable-recursive-minibuffers t)
 335          val)
 336      (setq val (completing-read (if v
 337                                     (format "Describe variable (default %s): " v)
 338                                   "Describe variable: ")
 339                                 obarray 'boundp t))
 340      (list (if (equal val "")
 341                v (intern val)))))
 342   (with-output-to-temp-buffer "*Help*"
 343     (prin1 variable)
 344     (princ "'s value is ")
 345     (if (not (boundp variable))
 346         (princ "void.")
 347       (prin1 (symbol-value variable)))
 348     (terpri) (terpri)
 349     (princ "Documentation:")
 350     (terpri)
 351     (let ((doc (documentation-property variable 'variable-documentation)))
 352       (if doc
 353           (princ (substitute-command-keys doc))
 354         (princ "not documented as a variable.")))
 355     (print-help-return-message)
 356     ;; Return the text we displayed.
 357     (save-excursion (set-buffer standard-output) (buffer-string))))
 358
 359 (defun command-apropos (string)
 360   "Like apropos but lists only symbols that are names of commands
 361 \(interactively callable functions).  Argument REGEXP is a regular expression
 362 that is matched against command symbol names.  Returns list of symbols and
 363 documentation found."
 364   (interactive "sCommand apropos (regexp): ")
 365   (let ((message
 366          (let ((standard-output (get-buffer-create "*Help*")))
 367            (print-help-return-message 'identity))))
 368     (if (apropos string t 'commandp)
 369         (and message (message message)))))
 370
 371 (defun locate-library (library &optional nosuffix)
 372   "Show the full path name of Emacs library LIBRARY.
 373 This command searches the directories in `load-path' like `M-x load-library'
 374 to find the file that `M-x load-library RET LIBRARY RET' would load.
 375 Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
 376 to the specified name LIBRARY (a la calling `load' instead of `load-library')."
 377   (interactive "sLocate library: ")
 378   (catch 'answer
 379     (mapcar
 380      '(lambda (dir)
 381         (mapcar
 382          '(lambda (suf)
 383             (let ((try (expand-file-name (concat library suf) dir)))
 384               (and (file-readable-p try)
 385                    (null (file-directory-p try))
 386                    (progn
 387                      (message "Library is file %s" try)
 388                      (throw 'answer try)))))
 389          (if nosuffix '("") '(".elc" ".el" ""))))
 390      load-path)
 391     (message "No library %s in search path" library)
 392     nil))
 393
 394 ;;; help.el ends here