lisp/help-fns.el

   1 ;;; help-fns.el --- Complex help functions
   2
   3 ;; Copyright (C) 1985, 1986, 1993, 1994, 1998, 1999, 2000, 2001, 2002
   4 ;;   Free Software Foundation, Inc.
   5
   6 ;; Maintainer: FSF
   7 ;; Keywords: help, internal
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  24 ;; Boston, MA 02111-1307, USA.
  25
  26 ;;; Commentary:
  27
  28 ;; This file contains those help commands which are complicated, and
  29 ;; which may not be used in every session.  For example
  30 ;; `describe-function' will probably be heavily used when doing elisp
  31 ;; programming, but not if just editing C files.  Simpler help commands
  32 ;; are in help.el
  33
  34 ;;; Code:
  35
  36 (require 'help-mode)
  37
  38
  39 ;;;###autoload
  40 (defun help-with-tutorial (&optional arg)
  41   "Select the Emacs learn-by-doing tutorial.
  42 If there is a tutorial version written in the language
  43 of the selected language environment, that version is used.
  44 If there's no tutorial in that language, `TUTORIAL' is selected.
  45 With arg, you are asked to choose which language."
  46   (interactive "P")
  47   (let ((lang (if arg
  48                   (read-language-name 'tutorial "Language: " "English")
  49                 (if (get-language-info current-language-environment 'tutorial)
  50                     current-language-environment
  51                   "English")))
  52         file filename)
  53     (setq filename (get-language-info lang 'tutorial))
  54     (setq file (expand-file-name (concat "~/" filename)))
  55     (delete-other-windows)
  56     (if (get-file-buffer file)
  57         (switch-to-buffer (get-file-buffer file))
  58       (switch-to-buffer (create-file-buffer file))
  59       (setq buffer-file-name file)
  60       (setq default-directory (expand-file-name "~/"))
  61       (setq buffer-auto-save-file-name nil)
  62       (insert-file-contents (expand-file-name filename data-directory))
  63       (goto-char (point-min))
  64       (search-forward "\n<<")
  65       (beginning-of-line)
  66       ;; Convert the <<...>> line to the proper [...] line,
  67       ;; or just delete the <<...>> line if a [...] line follows.
  68       (cond ((save-excursion
  69                (forward-line 1)
  70                (looking-at "\\["))
  71              (delete-region (point) (progn (forward-line 1) (point))))
  72             ((looking-at "<<Blank lines inserted.*>>")
  73              (replace-match "[Middle of page left blank for didactic purposes.   Text continues below]"))
  74             (t
  75              (looking-at "<<")
  76              (replace-match "[")
  77              (search-forward ">>")
  78              (replace-match "]")))
  79       (beginning-of-line)
  80       (let ((n (- (window-height (selected-window))
  81                   (count-lines (point-min) (point))
  82                   6)))
  83         (if (< n 8)
  84             (progn
  85               ;; For a short gap, we don't need the [...] line,
  86               ;; so delete it.
  87               (delete-region (point) (progn (end-of-line) (point)))
  88               (newline n))
  89           ;; Some people get confused by the large gap.
  90           (newline (/ n 2))
  91
  92           ;; Skip the [...] line (don't delete it).
  93           (forward-line 1)
  94           (newline (- n (/ n 2)))))
  95       (goto-char (point-min))
  96       (set-buffer-modified-p nil))))
  97
  98 ;;;###autoload
  99 (defun locate-library (library &optional nosuffix path interactive-call)
 100   "Show the precise file name of Emacs library LIBRARY.
 101 This command searches the directories in `load-path' like `M-x load-library'
 102 to find the file that `M-x load-library RET LIBRARY RET' would load.
 103 Optional second arg NOSUFFIX non-nil means don't add suffixes `load-suffixes'
 104 to the specified name LIBRARY.
 105
 106 If the optional third arg PATH is specified, that list of directories
 107 is used instead of `load-path'.
 108
 109 When called from a program, the file name is normaly returned as a
 110 string.  When run interactively, the argument INTERACTIVE-CALL is t,
 111 and the file name is displayed in the echo area."
 112   (interactive (list (read-string "Locate library: ")
 113                      nil nil
 114                      t))
 115   (catch 'answer
 116     (dolist (dir (or path load-path))
 117       (dolist (suf (append (unless nosuffix load-suffixes) '("")))
 118           (let ((try (expand-file-name (concat library suf) dir)))
 119           (and (file-readable-p try)
 120                (null (file-directory-p try))
 121                (progn
 122                  (if interactive-call
 123                      (message "Library is file %s" (abbreviate-file-name try)))
 124                  (throw 'answer try))))))
 125     (if interactive-call
 126         (message "No library %s in search path" library))
 127     nil))
 128
 129 \f
 130 ;; Functions
 131
 132 ;;;###autoload
 133 (defun describe-function (function)
 134   "Display the full documentation of FUNCTION (a symbol)."
 135   (interactive
 136    (let ((fn (function-called-at-point))
 137          (enable-recursive-minibuffers t)
 138          val)
 139      (setq val (completing-read (if fn
 140                                     (format "Describe function (default %s): " fn)
 141                                   "Describe function: ")
 142                                 obarray 'fboundp t nil nil (symbol-name fn)))
 143      (list (if (equal val "")
 144                fn (intern val)))))
 145   (if (null function)
 146       (message "You didn't specify a function")
 147     (help-setup-xref (list #'describe-function function) (interactive-p))
 148     (save-excursion
 149       (with-output-to-temp-buffer (help-buffer)
 150         (prin1 function)
 151         ;; Use " is " instead of a colon so that
 152         ;; it is easier to get out the function name using forward-sexp.
 153         (princ " is ")
 154         (describe-function-1 function)
 155         (print-help-return-message)
 156         (with-current-buffer standard-output
 157           ;; Return the text we displayed.
 158           (buffer-string))))))
 159
 160 ;;;###autoload
 161 (defun describe-function-1 (function)
 162   (let* ((def (if (symbolp function)
 163                   (symbol-function function)
 164                 function))
 165          file-name string
 166          (beg (if (commandp def) "an interactive " "a ")))
 167     (setq string
 168           (cond ((or (stringp def)
 169                      (vectorp def))
 170                  "a keyboard macro")
 171                 ((subrp def)
 172                  (if (eq 'unevalled (cdr (subr-arity def)))
 173                      (concat beg "special form")
 174                    (concat beg "built-in function")))
 175                 ((byte-code-function-p def)
 176                  (concat beg "compiled Lisp function"))
 177                 ((symbolp def)
 178                  (while (symbolp (symbol-function def))
 179                    (setq def (symbol-function def)))
 180                  (format "an alias for `%s'" def))
 181                 ((eq (car-safe def) 'lambda)
 182                  (concat beg "Lisp function"))
 183                 ((eq (car-safe def) 'macro)
 184                  "a Lisp macro")
 185                 ((eq (car-safe def) 'autoload)
 186                  (setq file-name (nth 1 def))
 187                  (format "%s autoloaded %s"
 188                          (if (commandp def) "an interactive" "an")
 189                          (if (eq (nth 4 def) 'keymap) "keymap"
 190                            (if (nth 4 def) "Lisp macro" "Lisp function"))
 191                          ))
 192                 ;; perhaps use keymapp here instead
 193                 ((eq (car-safe def) 'keymap)
 194                  (let ((is-full nil)
 195                        (elts (cdr-safe def)))
 196                    (while elts
 197                      (if (char-table-p (car-safe elts))
 198                          (setq is-full t
 199                                elts nil))
 200                      (setq elts (cdr-safe elts)))
 201                    (if is-full
 202                        "a full keymap"
 203                      "a sparse keymap")))
 204                 (t "")))
 205     (princ string)
 206     (with-current-buffer standard-output
 207       (save-excursion
 208         (save-match-data
 209           (if (re-search-backward "alias for `\\([^`']+\\)'" nil t)
 210               (help-xref-button 1 'help-function def)))))
 211     (or file-name
 212         (setq file-name (symbol-file function)))
 213     (when (equal file-name "loaddefs.el")
 214       ;; Find the real def site of the preloaded function.
 215       ;; This is necessary only for defaliases.
 216       (let ((location
 217              (condition-case nil
 218                  (find-function-search-for-symbol function nil "loaddefs.el")
 219                (error nil))))
 220         (when location
 221           (with-current-buffer (car location)
 222             (goto-char (cdr location))
 223             (when (re-search-backward
 224                    "^;;; Generated autoloads from \\(.*\\)" nil t)
 225               (setq file-name (match-string 1)))))))
 226     (cond
 227      (file-name
 228       (princ " in `")
 229       ;; We used to add .el to the file name,
 230       ;; but that's completely wrong when the user used load-file.
 231       (princ file-name)
 232       (princ "'")
 233       ;; Make a hyperlink to the library.
 234       (with-current-buffer standard-output
 235         (save-excursion
 236           (re-search-backward "`\\([^`']+\\)'" nil t)
 237           (help-xref-button 1 'help-function-def function file-name)))))
 238     (princ ".")
 239     (terpri)
 240     (when (commandp function)
 241       (let* ((remapped (remap-command function))
 242              (keys (where-is-internal
 243                    (or remapped function) overriding-local-map nil nil)))
 244         (when remapped
 245           (princ "It is remapped to `")
 246           (princ (symbol-name remapped))
 247           (princ "'"))
 248         (when keys
 249           (princ (if remapped " which is bound to " "It is bound to "))
 250           ;; FIXME: This list can be very long (f.ex. for self-insert-command).
 251           (princ (mapconcat 'key-description keys ", ")))
 252         (when (or remapped keys)
 253           (princ ".")
 254           (terpri))))
 255     ;; Handle symbols aliased to other symbols.
 256     (setq def (indirect-function def))
 257     ;; If definition is a macro, find the function inside it.
 258     (if (eq (car-safe def) 'macro)
 259         (setq def (cdr def)))
 260     (let ((arglist (cond ((byte-code-function-p def)
 261                           (car (append def nil)))
 262                          ((eq (car-safe def) 'lambda)
 263                           (nth 1 def))
 264                          ((and (eq (car-safe def) 'autoload)
 265                                (not (eq (nth 4 def) 'keymap)))
 266                           (concat "[Arg list not available until "
 267                                   "function definition is loaded.]"))
 268                          (t t))))
 269       (cond ((listp arglist)
 270              (princ (cons (if (symbolp function) function "anonymous")
 271                           (mapcar (lambda (arg)
 272                                     (if (memq arg '(&optional &rest))
 273                                         arg
 274                                       (intern (upcase (symbol-name arg)))))
 275                                   arglist)))
 276              (terpri))
 277             ((stringp arglist)
 278              (princ arglist)
 279              (terpri))))
 280     (let ((obsolete (get function 'byte-obsolete-info)))
 281       (when obsolete
 282         (terpri)
 283         (princ "This function is obsolete")
 284         (if (nth 2 obsolete) (princ (format " since %s" (nth 2 obsolete))))
 285         (princ ";") (terpri)
 286         (princ (if (stringp (car obsolete)) (car obsolete)
 287                  (format "use `%s' instead." (car obsolete))))
 288         (terpri)))
 289     (let ((doc (documentation function)))
 290       (if doc
 291           (progn (terpri)
 292                  (princ doc)
 293                  (if (subrp def)
 294                      (with-current-buffer standard-output
 295                        (beginning-of-line)
 296                        ;; Builtins get the calling sequence at the end of
 297                        ;; the doc string.  Move it to the same place as
 298                        ;; for other functions.
 299
 300                        ;; In cases where `function' has been fset to a
 301                        ;; subr we can't search for function's name in
 302                        ;; the doc string.  Kluge round that using the
 303                        ;; printed representation.  The arg list then
 304                        ;; shows the wrong function name, but that
 305                        ;; might be a useful hint.
 306                        (let* ((rep (prin1-to-string def))
 307                               (name (progn
 308                                       (string-match " \\([^ ]+\\)>$" rep)
 309                                       (match-string 1 rep))))
 310                          (if (looking-at (format "(%s[ )]" (regexp-quote name)))
 311                              (let ((start (point-marker)))
 312                                (goto-char (point-min))
 313                                (forward-paragraph)
 314                                (insert-buffer-substring (current-buffer) start)
 315                                (insert ?\n)
 316                                (delete-region (1- start) (point-max)))
 317                            (goto-char (point-min))
 318                            (forward-paragraph)
 319                            (insert
 320                             "[Missing arglist.  Please make a bug report.]\n")))
 321                        (goto-char (point-max)))))
 322         (princ "Not documented.")))))
 323
 324 \f
 325 ;; Variables
 326
 327 ;;;###autoload
 328 (defun variable-at-point ()
 329   "Return the bound variable symbol found around point.
 330 Return 0 if there is no such symbol."
 331   (condition-case ()
 332       (with-syntax-table emacs-lisp-mode-syntax-table
 333         (save-excursion
 334           (or (not (zerop (skip-syntax-backward "_w")))
 335               (eq (char-syntax (following-char)) ?w)
 336               (eq (char-syntax (following-char)) ?_)
 337               (forward-sexp -1))
 338           (skip-chars-forward "'")
 339           (let ((obj (read (current-buffer))))
 340             (or (and (symbolp obj) (boundp obj) obj)
 341                 0))))
 342     (error 0)))
 343
 344 ;;;###autoload
 345 (defun describe-variable (variable &optional buffer)
 346   "Display the full documentation of VARIABLE (a symbol).
 347 Returns the documentation as a string, also.
 348 If VARIABLE has a buffer-local value in BUFFER (default to the current buffer),
 349 it is displayed along with the global value."
 350   (interactive
 351    (let ((v (variable-at-point))
 352          (enable-recursive-minibuffers t)
 353          val)
 354      (setq val (completing-read (if (symbolp v)
 355                                     (format
 356                                      "Describe variable (default %s): " v)
 357                                   "Describe variable: ")
 358                                 obarray 'boundp t nil nil
 359                                 (if (symbolp v) (symbol-name v))))
 360      (list (if (equal val "")
 361                v (intern val)))))
 362   (unless (buffer-live-p buffer) (setq buffer (current-buffer)))
 363   (if (not (symbolp variable))
 364       (message "You did not specify a variable")
 365     (save-excursion
 366       (let (valvoid)
 367         (help-setup-xref (list #'describe-variable variable buffer)
 368                          (interactive-p))
 369         (with-output-to-temp-buffer (help-buffer)
 370           (with-current-buffer buffer
 371             (prin1 variable)
 372             (if (not (boundp variable))
 373                 (progn
 374                   (princ " is void")
 375                   (setq valvoid t))
 376               (let ((val (symbol-value variable)))
 377                 (with-current-buffer standard-output
 378                   (princ "'s value is ")
 379                   (terpri)
 380                   (let ((from (point)))
 381                     (pp val)
 382                     (help-xref-on-pp from (point))
 383                     (if (< (point) (+ from 20))
 384                         (save-excursion
 385                           (goto-char from)
 386                           (delete-char -1)))))))
 387             (terpri)
 388             (when (local-variable-p variable)
 389               (princ (format "Local in buffer %s; " (buffer-name)))
 390               (if (not (default-boundp variable))
 391                   (princ "globally void")
 392                 (let ((val (default-value variable)))
 393                   (with-current-buffer standard-output
 394                     (princ "global value is ")
 395                     (terpri)
 396                     ;; Fixme: pp can take an age if you happen to
 397                     ;; ask for a very large expression.  We should
 398                     ;; probably print it raw once and check it's a
 399                     ;; sensible size before prettyprinting.  -- fx
 400                     (let ((from (point)))
 401                       (pp val)
 402                       (help-xref-on-pp from (point))
 403                       (if (< (point) (+ from 20))
 404                         (delete-region (1- from) from))))))
 405               (terpri))
 406             (terpri)
 407             (with-current-buffer standard-output
 408               (when (> (count-lines (point-min) (point-max)) 10)
 409                 ;; Note that setting the syntax table like below
 410                 ;; makes forward-sexp move over a `'s' at the end
 411                 ;; of a symbol.
 412                 (set-syntax-table emacs-lisp-mode-syntax-table)
 413                 (goto-char (point-min))
 414                 (if valvoid
 415                     (forward-line 1)
 416                   (forward-sexp 1)
 417                   (delete-region (point) (progn (end-of-line) (point)))
 418                   (insert " value is shown below.\n\n")
 419                   (save-excursion
 420                     (insert "\n\nValue:"))))
 421               ;; Add a note for variables that have been make-var-buffer-local.
 422               (when (and (local-variable-if-set-p variable)
 423                          (or (not (local-variable-p variable))
 424                              (with-temp-buffer
 425                                (local-variable-if-set-p variable))))
 426                 (save-excursion
 427                   (forward-line -1)
 428                   (insert "Automatically becomes buffer-local when set in any fashion.\n"))))
 429             (princ "Documentation:")
 430             (terpri)
 431             (let ((obsolete (get variable 'byte-obsolete-variable)))
 432               (when obsolete
 433                 (princ "This variable is obsolete")
 434                 (if (cdr obsolete) (princ (format " since %s" (cdr obsolete))))
 435                 (princ "; ") (terpri)
 436                 (princ (if (stringp (car obsolete)) (car obsolete)
 437                          (format "use `%s' instead." (car obsolete))))
 438                 (terpri)))
 439             (let ((doc (documentation-property variable 'variable-documentation)))
 440               (princ (or doc "Not documented as a variable.")))
 441
 442             ;; Make a link to customize if this variable can be customized.
 443             ;; Note, it is not reliable to test only for a custom-type property
 444             ;; because those are only present after the var's definition
 445             ;; has been loaded.
 446             (if (or (get variable 'custom-type) ; after defcustom
 447                     (get variable 'custom-loads) ; from loaddefs.el
 448                     (get variable 'standard-value)) ; from cus-start.el
 449                 (let ((customize-label "customize"))
 450                   (terpri)
 451                   (terpri)
 452                   (princ (concat "You can " customize-label " this variable."))
 453                   (with-current-buffer standard-output
 454                     (save-excursion
 455                       (re-search-backward
 456                        (concat "\\(" customize-label "\\)") nil t)
 457                       (help-xref-button 1 'help-customize-variable variable)))))
 458             ;; Make a hyperlink to the library if appropriate.  (Don't
 459             ;; change the format of the buffer's initial line in case
 460             ;; anything expects the current format.)
 461             (let ((file-name (symbol-file variable)))
 462               (when (equal file-name "loaddefs.el")
 463                 ;; Find the real def site of the preloaded variable.
 464                 (let ((location
 465                        (condition-case nil
 466                            (find-variable-noselect variable file-name)
 467                          (error nil))))
 468                   (when location
 469                     (with-current-buffer (car location)
 470                       (goto-char (cdr location))
 471                       (when (re-search-backward
 472                              "^;;; Generated autoloads from \\(.*\\)" nil t)
 473                         (setq file-name (match-string 1)))))))
 474               (when file-name
 475                 (princ "\n\nDefined in `")
 476                 (princ file-name)
 477                 (princ "'.")
 478                 (with-current-buffer standard-output
 479                   (save-excursion
 480                     (re-search-backward "`\\([^`']+\\)'" nil t)
 481                     (help-xref-button 1 'help-variable-def
 482                                       variable file-name)))))
 483
 484             (print-help-return-message)
 485             (save-excursion
 486               (set-buffer standard-output)
 487               ;; Return the text we displayed.
 488               (buffer-string))))))))
 489
 490
 491 ;;;###autoload
 492 (defun describe-syntax (&optional buffer)
 493   "Describe the syntax specifications in the syntax table of BUFFER.
 494 The descriptions are inserted in a help buffer, which is then displayed.
 495 BUFFER defaults to the current buffer."
 496   (interactive)
 497   (setq buffer (or buffer (current-buffer)))
 498   (help-setup-xref (list #'describe-syntax buffer) (interactive-p))
 499   (with-output-to-temp-buffer (help-buffer)
 500     (let ((table (with-current-buffer buffer (syntax-table))))
 501       (with-current-buffer standard-output
 502         (describe-vector table 'internal-describe-syntax-value)
 503         (while (setq table (char-table-parent table))
 504           (insert "\nThe parent syntax table is:")
 505           (describe-vector table 'internal-describe-syntax-value))))))
 506
 507 (defun help-describe-category-set (value)
 508   (insert (cond
 509            ((null value) "default")
 510            ((char-table-p value) "deeper char-table ...")
 511            (t (condition-case err
 512                   (category-set-mnemonics value)
 513                 (error "invalid"))))))
 514
 515 ;;;###autoload
 516 (defun describe-categories (&optional buffer)
 517   "Describe the category specifications in the current category table.
 518 The descriptions are inserted in a buffer, which is then displayed."
 519   (interactive)
 520   (setq buffer (or buffer (current-buffer)))
 521   (help-setup-xref (list #'describe-categories buffer) (interactive-p))
 522   (with-output-to-temp-buffer (help-buffer)
 523     (let ((table (with-current-buffer buffer (category-table))))
 524       (with-current-buffer standard-output
 525         (describe-vector table 'help-describe-category-set)
 526         (let ((docs (char-table-extra-slot table 0)))
 527           (if (or (not (vectorp docs)) (/= (length docs) 95))
 528               (insert "Invalid first extra slot in this char table\n")
 529             (insert "Meanings of mnemonic characters are:\n")
 530             (dotimes (i 95)
 531               (let ((elt (aref docs i)))
 532                 (when elt
 533                   (insert (+ i ?\ ) ": " elt "\n"))))
 534             (while (setq table (char-table-parent table))
 535               (insert "\nThe parent category table is:")
 536               (describe-vector table 'help-describe-category-set))))))))
 537
 538 (provide 'help-fns)
 539
 540 ;;; help-fns.el ends here