lisp/help-fns.el

   1 ;;; help-fns.el --- Complex help functions -*- lexical-binding: t -*-
   2
   3 ;; Copyright (C) 1985-1986, 1993-1994, 1998-2017 Free Software
   4 ;; Foundation, Inc.
   5
   6 ;; Maintainer: emacs-devel@gnu.org
   7 ;; Keywords: help, internal
   8 ;; Package: emacs
   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 <https://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26
  27 ;; This file contains those help commands which are complicated, and
  28 ;; which may not be used in every session.  For example
  29 ;; `describe-function' will probably be heavily used when doing elisp
  30 ;; programming, but not if just editing C files.  Simpler help commands
  31 ;; are in help.el
  32
  33 ;;; Code:
  34
  35 (require 'cl-lib)
  36 (require 'help-mode)
  37 (require 'radix-tree)
  38
  39 (defvar help-fns-describe-function-functions nil
  40   "List of functions to run in help buffer in `describe-function'.
  41 Those functions will be run after the header line and argument
  42 list was inserted, and before the documentation will be inserted.
  43 The functions will receive the function name as argument.")
  44
  45 ;; Functions
  46
  47 (defvar help-definition-prefixes nil
  48   ;; FIXME: We keep `definition-prefixes' as a hash-table so as to
  49   ;; avoid pre-loading radix-tree and because it takes slightly less
  50   ;; memory.  But when we use this table it's more efficient to
  51   ;; represent it as a radix tree, since the main operation is to do
  52   ;; `radix-tree-prefixes'.  Maybe we should just bite the bullet and
  53   ;; use a radix tree for `definition-prefixes' (it's not *that*
  54   ;; costly, really).
  55   "Radix-tree representation replacing `definition-prefixes'.")
  56
  57 (defun help-definition-prefixes ()
  58   "Return the up-to-date radix-tree form of `definition-prefixes'."
  59   (when (> (hash-table-count definition-prefixes) 0)
  60     (maphash (lambda (prefix files)
  61                (let ((old (radix-tree-lookup help-definition-prefixes prefix)))
  62                  (setq help-definition-prefixes
  63                        (radix-tree-insert help-definition-prefixes
  64                                           prefix (append old files)))))
  65              definition-prefixes)
  66     (clrhash definition-prefixes))
  67   help-definition-prefixes)
  68
  69 (defun help--loaded-p (file)
  70   "Try and figure out if FILE has already been loaded."
  71   (or (let ((feature (intern-soft file)))
  72         (and feature (featurep feature)))
  73       (let* ((re (load-history-regexp file))
  74              (done nil))
  75         (dolist (x load-history)
  76           (and (car x) (string-match-p re (car x)) (setq done t)))
  77         done)))
  78
  79 (defun help--load-prefixes (prefixes)
  80   (pcase-dolist (`(,prefix . ,files) prefixes)
  81     (setq help-definition-prefixes
  82           (radix-tree-insert help-definition-prefixes prefix nil))
  83     (dolist (file files)
  84       ;; FIXME: Should we scan help-definition-prefixes to remove
  85       ;; other prefixes of the same file?
  86       ;; FIXME: this regexp business is not good enough: for file
  87       ;; `toto', it will say `toto' is loaded when in reality it was
  88       ;; just cedet/semantic/toto that has been loaded.
  89       (unless (help--loaded-p file)
  90         (load file 'noerror 'nomessage)))))
  91
  92 (defun help--symbol-completion-table (string pred action)
  93   (let ((prefixes (radix-tree-prefixes (help-definition-prefixes) string)))
  94     (help--load-prefixes prefixes))
  95   (let ((prefix-completions
  96          (mapcar #'intern (all-completions string definition-prefixes))))
  97     (complete-with-action action obarray string
  98                           (if pred (lambda (sym)
  99                                      (or (funcall pred sym)
 100                                          (memq sym prefix-completions)))))))
 101
 102 (defvar describe-function-orig-buffer nil
 103   "Buffer that was current when `describe-function' was invoked.
 104 Functions on `help-fns-describe-function-functions' can use this
 105 to get buffer-local values.")
 106
 107 ;;;###autoload
 108 (defun describe-function (function)
 109   "Display the full documentation of FUNCTION (a symbol).
 110 When called from lisp, FUNCTION may also be a function object."
 111   (interactive
 112    (let* ((fn (function-called-at-point))
 113           (enable-recursive-minibuffers t)
 114           (val (completing-read
 115                 (if fn
 116                     (format "Describe function (default %s): " fn)
 117                   "Describe function: ")
 118                 #'help--symbol-completion-table
 119                 (lambda (f) (or (fboundp f) (get f 'function-documentation)))
 120                 t nil nil
 121                 (and fn (symbol-name fn)))))
 122      (unless (equal val "")
 123        (setq fn (intern val)))
 124      (unless (and fn (symbolp fn))
 125        (user-error "You didn't specify a function symbol"))
 126      (unless (or (fboundp fn) (get fn 'function-documentation))
 127        (user-error "Symbol's function definition is void: %s" fn))
 128      (list fn)))
 129
 130   ;; We save describe-function-orig-buffer on the help xref stack, so
 131   ;; it is restored by the back/forward buttons.  'help-buffer'
 132   ;; expects (current-buffer) to be a help buffer when processing
 133   ;; those buttons, so we can't change the current buffer before
 134   ;; calling that.
 135   (let ((describe-function-orig-buffer
 136          (or describe-function-orig-buffer
 137              (current-buffer))))
 138
 139     (help-setup-xref
 140      (list (lambda (function buffer)
 141              (let ((describe-function-orig-buffer
 142                     (if (buffer-live-p buffer) buffer)))
 143                (describe-function function)))
 144            function describe-function-orig-buffer)
 145      (called-interactively-p 'interactive))
 146
 147     (save-excursion
 148       (with-help-window (help-buffer)
 149         (if (get function 'reader-construct)
 150             (princ function)
 151           (prin1 function))
 152         ;; Use " is " instead of a colon so that
 153         ;; it is easier to get out the function name using forward-sexp.
 154         (princ " is ")
 155         (describe-function-1 function)
 156         (with-current-buffer standard-output
 157           ;; Return the text we displayed.
 158           (buffer-string))))
 159     ))
 160
 161
 162 ;; Could be this, if we make symbol-file do the work below.
 163 ;; (defun help-C-file-name (subr-or-var kind)
 164 ;;   "Return the name of the C file where SUBR-OR-VAR is defined.
 165 ;; KIND should be `var' for a variable or `subr' for a subroutine."
 166 ;;   (symbol-file (if (symbolp subr-or-var) subr-or-var
 167 ;;               (subr-name subr-or-var))
 168 ;;             (if (eq kind 'var) 'defvar 'defun)))
 169 ;;;###autoload
 170 (defun help-C-file-name (subr-or-var kind)
 171   "Return the name of the C file where SUBR-OR-VAR is defined.
 172 KIND should be `var' for a variable or `subr' for a subroutine."
 173   (let ((docbuf (get-buffer-create " *DOC*"))
 174         (name (if (eq 'var kind)
 175                   (concat "V" (symbol-name subr-or-var))
 176                 (concat "F" (subr-name (advice--cd*r subr-or-var))))))
 177     (with-current-buffer docbuf
 178       (goto-char (point-min))
 179       (if (eobp)
 180           (insert-file-contents-literally
 181            (expand-file-name internal-doc-file-name doc-directory)))
 182       (let ((file (catch 'loop
 183                     (while t
 184                       (let ((pnt (search-forward (concat "\x1f" name "\n"))))
 185                         (re-search-backward "\x1fS\\(.*\\)")
 186                         (let ((file (match-string 1)))
 187                           (if (member file build-files)
 188                               (throw 'loop file)
 189                             (goto-char pnt))))))))
 190         (if (string-match "^ns.*\\(\\.o\\|obj\\)\\'" file)
 191             (setq file (replace-match ".m" t t file 1))
 192           (if (string-match "\\.\\(o\\|obj\\)\\'" file)
 193               (setq file (replace-match ".c" t t file))))
 194         (if (string-match "\\.\\(c\\|m\\)\\'" file)
 195             (concat "src/" file)
 196           file)))))
 197
 198 (defcustom help-downcase-arguments nil
 199   "If non-nil, argument names in *Help* buffers are downcased."
 200   :type 'boolean
 201   :group 'help
 202   :version "23.2")
 203
 204 (defun help-highlight-arg (arg)
 205   "Highlight ARG as an argument name for a *Help* buffer.
 206 Return ARG in face `help-argument-name'; ARG is also downcased
 207 if the variable `help-downcase-arguments' is non-nil."
 208   (propertize (if help-downcase-arguments (downcase arg) arg)
 209               'face 'help-argument-name))
 210
 211 (defun help-do-arg-highlight (doc args)
 212   (with-syntax-table (make-syntax-table emacs-lisp-mode-syntax-table)
 213     (modify-syntax-entry ?\- "w")
 214     (dolist (arg args)
 215       (setq doc (replace-regexp-in-string
 216                  ;; This is heuristic, but covers all common cases
 217                  ;; except ARG1-ARG2
 218                  (concat "\\<"                   ; beginning of word
 219                          "\\(?:[a-z-]*-\\)?"     ; for xxx-ARG
 220                          "\\("
 221                          (regexp-quote arg)
 222                          "\\)"
 223                          "\\(?:es\\|s\\|th\\)?"  ; for ARGth, ARGs
 224                          "\\(?:-[a-z0-9-]+\\)?"  ; for ARG-xxx, ARG-n
 225                          "\\(?:-[{([<`\"‘].*?\\)?"; for ARG-{x}, (x), <x>, [x], `x', ‘x’
 226                          "\\>")                  ; end of word
 227                  (help-highlight-arg arg)
 228                  doc t t 1)))
 229     doc))
 230
 231 (defun help-highlight-arguments (usage doc &rest args)
 232   (when (and usage (string-match "^(" usage))
 233     (with-temp-buffer
 234       (insert usage)
 235       (goto-char (point-min))
 236       (let ((case-fold-search nil)
 237             (next (not (or args (looking-at "\\["))))
 238             (opt nil))
 239         ;; Make a list of all arguments
 240         (skip-chars-forward "^ ")
 241         (while next
 242           (or opt (not (looking-at " &")) (setq opt t))
 243           (if (not (re-search-forward " \\([\\[(]*\\)\\([^] &).]+\\)" nil t))
 244               (setq next nil)
 245             (setq args (cons (match-string 2) args))
 246             (when (and opt (string= (match-string 1) "("))
 247               ;; A pesky CL-style optional argument with default value,
 248               ;; so let's skip over it
 249               (search-backward "(")
 250               (goto-char (scan-sexps (point) 1)))))
 251         ;; Highlight arguments in the USAGE string
 252         (setq usage (help-do-arg-highlight (buffer-string) args))
 253         ;; Highlight arguments in the DOC string
 254         (setq doc (and doc (help-do-arg-highlight doc args))))))
 255   ;; Return value is like the one from help-split-fundoc, but highlighted
 256   (cons usage doc))
 257
 258 ;; The following function was compiled from the former functions
 259 ;; `describe-simplify-lib-file-name' and `find-source-lisp-file' with
 260 ;; some excerpts from `describe-function-1' and `describe-variable'.
 261 ;; The only additional twists provided are (1) locate the defining file
 262 ;; for autoloaded functions, and (2) give preference to files in the
 263 ;; "install directory" (directories found via `load-path') rather than
 264 ;; to files in the "compile directory" (directories found by searching
 265 ;; the loaddefs.el file).  We autoload it because it's also used by
 266 ;; `describe-face' (instead of `describe-simplify-lib-file-name').
 267
 268 ;;;###autoload
 269 (defun find-lisp-object-file-name (object type)
 270   "Guess the file that defined the Lisp object OBJECT, of type TYPE.
 271 OBJECT should be a symbol associated with a function, variable, or face;
 272   alternatively, it can be a function definition.
 273 If TYPE is `defvar', search for a variable definition.
 274 If TYPE is `defface', search for a face definition.
 275 If TYPE is not a symbol, search for a function definition.
 276
 277 The return value is the absolute name of a readable file where OBJECT is
 278 defined.  If several such files exist, preference is given to a file
 279 found via `load-path'.  The return value can also be `C-source', which
 280 means that OBJECT is a function or variable defined in C.  If no
 281 suitable file is found, return nil."
 282   (let* ((autoloaded (autoloadp type))
 283          (file-name (or (and autoloaded (nth 1 type))
 284                         (symbol-file
 285                          ;; FIXME: Why do we have this weird "If TYPE is the
 286                          ;; value returned by `symbol-function' for a function
 287                          ;; symbol" exception?
 288                          object (or (if (symbolp type) type) 'defun)))))
 289     (cond
 290      (autoloaded
 291       ;; An autoloaded function: Locate the file since `symbol-function'
 292       ;; has only returned a bare string here.
 293       (setq file-name
 294             (locate-file file-name load-path '(".el" ".elc") 'readable)))
 295      ((and (stringp file-name)
 296            (string-match "[.]*loaddefs.el\\'" file-name))
 297       ;; An autoloaded variable or face.  Visit loaddefs.el in a buffer
 298       ;; and try to extract the defining file.  The following form is
 299       ;; from `describe-function-1' and `describe-variable'.
 300       (let ((location
 301              (condition-case nil
 302                  (find-function-search-for-symbol object nil file-name)
 303                (error nil))))
 304         (when (cdr location)
 305           (with-current-buffer (car location)
 306             (goto-char (cdr location))
 307             (when (re-search-backward
 308                    "^;;; Generated autoloads from \\(.*\\)" nil t)
 309               (setq file-name
 310                     (locate-file
 311                      (file-name-sans-extension
 312                       (match-string-no-properties 1))
 313                      load-path '(".el" ".elc") 'readable))))))))
 314
 315     (cond
 316      ((and (not file-name) (subrp type))
 317       ;; A built-in function.  The form is from `describe-function-1'.
 318       (if (get-buffer " *DOC*")
 319           (help-C-file-name type 'subr)
 320         'C-source))
 321      ((and (not file-name) (symbolp object)
 322            (integerp (get object 'variable-documentation)))
 323       ;; A variable defined in C.  The form is from `describe-variable'.
 324       (if (get-buffer " *DOC*")
 325           (help-C-file-name object 'var)
 326         'C-source))
 327      ((not (stringp file-name))
 328       ;; If we don't have a file-name string by now, we lost.
 329       nil)
 330      ;; Now, `file-name' should have become an absolute file name.
 331      ;; For files loaded from ~/.foo.elc, try ~/.foo.
 332      ;; This applies to config files like ~/.emacs,
 333      ;; which people sometimes compile.
 334      ((let (fn)
 335         (and (string-match "\\`\\..*\\.elc\\'"
 336                            (file-name-nondirectory file-name))
 337              (string-equal (file-name-directory file-name)
 338                            (file-name-as-directory (expand-file-name "~")))
 339              (file-readable-p (setq fn (file-name-sans-extension file-name)))
 340              fn)))
 341      ;; When the Elisp source file can be found in the install
 342      ;; directory, return the name of that file.
 343      ((let ((lib-name
 344              (if (string-match "[.]elc\\'" file-name)
 345                  (substring-no-properties file-name 0 -1)
 346                file-name)))
 347         (or (and (file-readable-p lib-name) lib-name)
 348             ;; The library might be compressed.
 349             (and (file-readable-p (concat lib-name ".gz")) lib-name))))
 350      ((let* ((lib-name (file-name-nondirectory file-name))
 351              ;; The next form is from `describe-simplify-lib-file-name'.
 352              (file-name
 353               ;; Try converting the absolute file name to a library
 354               ;; name, convert that back to a file name and see if we
 355               ;; get the original one.  If so, they are equivalent.
 356               (if (equal file-name (locate-file lib-name load-path '("")))
 357                   (if (string-match "[.]elc\\'" lib-name)
 358                       (substring-no-properties lib-name 0 -1)
 359                     lib-name)
 360                 file-name))
 361              (src-file (locate-library file-name t nil 'readable)))
 362         (and src-file (file-readable-p src-file) src-file))))))
 363
 364 (defun help-fns--key-bindings (function)
 365   (when (commandp function)
 366     (let ((pt2 (with-current-buffer standard-output (point)))
 367           (remapped (command-remapping function)))
 368       (unless (memq remapped '(ignore undefined))
 369         (let ((keys (where-is-internal
 370                      (or remapped function) overriding-local-map nil nil))
 371               non-modified-keys)
 372           (if (and (eq function 'self-insert-command)
 373                    (vectorp (car-safe keys))
 374                    (consp (aref (car keys) 0)))
 375               (princ "It is bound to many ordinary text characters.\n")
 376             ;; Which non-control non-meta keys run this command?
 377             (dolist (key keys)
 378               (if (member (event-modifiers (aref key 0)) '(nil (shift)))
 379                   (push key non-modified-keys)))
 380             (when remapped
 381               (princ "Its keys are remapped to ")
 382               (princ (if (symbolp remapped)
 383                          (format-message "`%s'" remapped)
 384                        "an anonymous command"))
 385               (princ ".\n"))
 386
 387             (when keys
 388               (princ (if remapped
 389                          "Without this remapping, it would be bound to "
 390                        "It is bound to "))
 391               ;; If lots of ordinary text characters run this command,
 392               ;; don't mention them one by one.
 393               (if (< (length non-modified-keys) 10)
 394                   (princ (mapconcat #'key-description keys ", "))
 395                 (dolist (key non-modified-keys)
 396                   (setq keys (delq key keys)))
 397                 (if keys
 398                     (progn
 399                       (princ (mapconcat #'key-description keys ", "))
 400                       (princ ", and many ordinary text characters"))
 401                   (princ "many ordinary text characters"))))
 402             (when (or remapped keys non-modified-keys)
 403               (princ ".")
 404               (terpri)))))
 405
 406       (with-current-buffer standard-output
 407         (fill-region-as-paragraph pt2 (point))
 408         (unless (looking-back "\n\n" (- (point) 2))
 409           (terpri))))))
 410
 411 (defun help-fns--compiler-macro (function)
 412   (let ((handler (function-get function 'compiler-macro)))
 413     (when handler
 414       (insert "\nThis function has a compiler macro")
 415       (if (symbolp handler)
 416           (progn
 417             (insert (format-message " `%s'" handler))
 418             (save-excursion
 419               (re-search-backward (substitute-command-keys "`\\([^`']+\\)'")
 420                                   nil t)
 421               (help-xref-button 1 'help-function handler)))
 422         ;; FIXME: Obsolete since 24.4.
 423         (let ((lib (get function 'compiler-macro-file)))
 424           (when (stringp lib)
 425             (insert (format-message " in `%s'" lib))
 426             (save-excursion
 427               (re-search-backward (substitute-command-keys "`\\([^`']+\\)'")
 428                                   nil t)
 429               (help-xref-button 1 'help-function-cmacro function lib)))))
 430       (insert ".\n"))))
 431
 432 (defun help-fns--signature (function doc real-def real-function buffer)
 433   "Insert usage at point and return docstring.  With highlighting."
 434   (if (keymapp function)
 435       doc                       ; If definition is a keymap, skip arglist note.
 436     (let* ((advertised (gethash real-def advertised-signature-table t))
 437            (arglist (if (listp advertised)
 438                         advertised (help-function-arglist real-def)))
 439            (usage (help-split-fundoc doc function)))
 440       (if usage (setq doc (cdr usage)))
 441       (let* ((use (cond
 442                    ((and usage (not (listp advertised))) (car usage))
 443                    ((listp arglist)
 444                     (help--make-usage-docstring function arglist))
 445                    ((stringp arglist) arglist)
 446                    ;; Maybe the arglist is in the docstring of a symbol
 447                    ;; this one is aliased to.
 448                    ((let ((fun real-function))
 449                       (while (and (symbolp fun)
 450                                   (setq fun (symbol-function fun))
 451                                   (not (setq usage (help-split-fundoc
 452                                                     (documentation fun)
 453                                                     function)))))
 454                       usage)
 455                     (car usage))
 456                    ((or (stringp real-def)
 457                         (vectorp real-def))
 458                     (format "\nMacro: %s"
 459                             (help--docstring-quote
 460                              (format-kbd-macro real-def))))
 461                    (t "[Missing arglist.  Please make a bug report.]")))
 462              ;; Insert "`X", not "(\` X)", when documenting `X.
 463              (use1 (replace-regexp-in-string
 464                     "\\`(\\\\=\\\\\\\\=` \\([^\n ]*\\))\\'"
 465                     "\\\\=`\\1" use t))
 466              (high (if buffer
 467                        (let (subst-use1 subst-doc)
 468                          (with-current-buffer buffer
 469                            (setq subst-use1 (substitute-command-keys use1))
 470                            (setq subst-doc (substitute-command-keys doc)))
 471                          (help-highlight-arguments subst-use1 subst-doc))
 472                      (cons use1 doc))))
 473         (let ((fill-begin (point))
 474               (high-usage (car high))
 475               (high-doc (cdr high)))
 476           (unless (and (symbolp function)
 477                        (get function 'reader-construct))
 478             (insert high-usage "\n"))
 479           (fill-region fill-begin (point))
 480           high-doc)))))
 481
 482 (defun help-fns--parent-mode (function)
 483   ;; If this is a derived mode, link to the parent.
 484   (let ((parent-mode (and (symbolp function)
 485                           (get function
 486                                'derived-mode-parent))))
 487     (when parent-mode
 488       (insert (substitute-command-keys "\nParent mode: `"))
 489       (let ((beg (point)))
 490         (insert (format "%s" parent-mode))
 491         (make-text-button beg (point)
 492                           'type 'help-function
 493                           'help-args (list parent-mode)))
 494       (insert (substitute-command-keys "'.\n")))))
 495
 496 (defun help-fns--obsolete (function)
 497   ;; Ignore lambda constructs, keyboard macros, etc.
 498   (let* ((obsolete (and (symbolp function)
 499                         (get function 'byte-obsolete-info)))
 500          (use (car obsolete)))
 501     (when obsolete
 502       (insert "\nThis "
 503               (if (eq (car-safe (symbol-function function)) 'macro)
 504                   "macro"
 505                 "function")
 506               " is obsolete")
 507       (when (nth 2 obsolete)
 508         (insert (format " since %s" (nth 2 obsolete))))
 509       (insert (cond ((stringp use) (concat ";\n" use))
 510                     (use (format-message ";\nuse `%s' instead." use))
 511                     (t "."))
 512               "\n"))))
 513
 514 ;; We could use `symbol-file' but this is a wee bit more efficient.
 515 (defun help-fns--autoloaded-p (function file)
 516   "Return non-nil if FUNCTION has previously been autoloaded.
 517 FILE is the file where FUNCTION was probably defined."
 518   (let* ((file (file-name-sans-extension (file-truename file)))
 519          (load-hist load-history)
 520          (target (cons t function))
 521          found)
 522     (while (and load-hist (not found))
 523       (and (caar load-hist)
 524            (equal (file-name-sans-extension (caar load-hist)) file)
 525            (setq found (member target (cdar load-hist))))
 526       (setq load-hist (cdr load-hist)))
 527     found))
 528
 529 (defun help-fns--interactive-only (function)
 530   "Insert some help blurb if FUNCTION should only be used interactively."
 531   ;; Ignore lambda constructs, keyboard macros, etc.
 532   (and (symbolp function)
 533        (not (eq (car-safe (symbol-function function)) 'macro))
 534        (let* ((interactive-only
 535                (or (get function 'interactive-only)
 536                    (if (boundp 'byte-compile-interactive-only-functions)
 537                        (memq function
 538                              byte-compile-interactive-only-functions)))))
 539          (when interactive-only
 540            (insert "\nThis function is for interactive use only"
 541                    ;; Cf byte-compile-form.
 542                    (cond ((stringp interactive-only)
 543                           (format ";\nin Lisp code %s" interactive-only))
 544                          ((and (symbolp 'interactive-only)
 545                                (not (eq interactive-only t)))
 546                           (format-message ";\nin Lisp code use `%s' instead."
 547                                           interactive-only))
 548                          (t "."))
 549                    "\n")))))
 550
 551 (defun help-fns-short-filename (filename)
 552   (let* ((abbrev (abbreviate-file-name filename))
 553          (short abbrev))
 554     (dolist (dir load-path)
 555       (let ((rel (file-relative-name filename dir)))
 556         (if (< (length rel) (length short))
 557             (setq short rel)))
 558       (let ((rel (file-relative-name abbrev dir)))
 559         (if (< (length rel) (length short))
 560             (setq short rel))))
 561     short))
 562
 563 (defun help-fns--analyze-function (function)
 564   ;; FIXME: Document/explain the differences between FUNCTION,
 565   ;; REAL-FUNCTION, DEF, and REAL-DEF.
 566   "Return information about FUNCTION.
 567 Returns a list of the form (REAL-FUNCTION DEF ALIASED REAL-DEF)."
 568   (let* ((advised (and (symbolp function)
 569                        (advice--p (advice--symbol-function function))))
 570          ;; If the function is advised, use the symbol that has the
 571          ;; real definition, if that symbol is already set up.
 572          (real-function
 573           (or (and advised
 574                    (advice--cd*r (advice--symbol-function function)))
 575               function))
 576          ;; Get the real definition, if any.
 577          (def (if (symbolp real-function)
 578                   (cond ((symbol-function real-function))
 579                         ((get real-function 'function-documentation)
 580                          nil)
 581                         (t (signal 'void-function (list real-function))))
 582                 real-function))
 583          (aliased (and def
 584                        (or (symbolp def)
 585                            ;; Advised & aliased function.
 586                            (and advised (symbolp real-function)
 587                                 (not (eq 'autoload (car-safe def))))
 588                            (and (subrp def)
 589                                 (not (string= (subr-name def)
 590                                               (symbol-name function)))))))
 591          (real-def (cond
 592                     ((and aliased (not (subrp def)))
 593                      (let ((f real-function))
 594                        (while (and (fboundp f)
 595                                    (symbolp (symbol-function f)))
 596                          (setq f (symbol-function f)))
 597                        f))
 598                     ((subrp def) (intern (subr-name def)))
 599                     (t def))))
 600     (list real-function def aliased real-def)))
 601
 602 (defun help-fns-function-description-header (function)
 603   "Print a line describing FUNCTION to `standard-output'."
 604   (pcase-let* ((`(,_real-function ,def ,aliased ,real-def)
 605                 (help-fns--analyze-function function))
 606                (file-name (find-lisp-object-file-name function (if aliased 'defun
 607                                                                  def)))
 608                (beg (if (and (or (byte-code-function-p def)
 609                                  (keymapp def)
 610                                  (memq (car-safe def) '(macro lambda closure)))
 611                              (stringp file-name)
 612                              (help-fns--autoloaded-p function file-name))
 613                         (if (commandp def)
 614                             "an interactive autoloaded "
 615                           "an autoloaded ")
 616                       (if (commandp def) "an interactive " "a "))))
 617
 618     ;; Print what kind of function-like object FUNCTION is.
 619     (princ (cond ((or (stringp def) (vectorp def))
 620                   "a keyboard macro")
 621                  ((and (symbolp function)
 622                        (get function 'reader-construct))
 623                   "a reader construct")
 624                  ;; Aliases are Lisp functions, so we need to check
 625                  ;; aliases before functions.
 626                  (aliased
 627                   (format-message "an alias for `%s'" real-def))
 628                  ((subrp def)
 629                   (if (eq 'unevalled (cdr (subr-arity def)))
 630                       (concat beg "special form")
 631                     (concat beg "built-in function")))
 632                  ((autoloadp def)
 633                   (format "%s autoloaded %s"
 634                           (if (commandp def) "an interactive" "an")
 635                           (if (eq (nth 4 def) 'keymap) "keymap"
 636                             (if (nth 4 def) "Lisp macro" "Lisp function"))))
 637                  ((or (eq (car-safe def) 'macro)
 638                       ;; For advised macros, def is a lambda
 639                       ;; expression or a byte-code-function-p, so we
 640                       ;; need to check macros before functions.
 641                       (macrop function))
 642                   (concat beg "Lisp macro"))
 643                  ((byte-code-function-p def)
 644                   (concat beg "compiled Lisp function"))
 645                  ((eq (car-safe def) 'lambda)
 646                   (concat beg "Lisp function"))
 647                  ((eq (car-safe def) 'closure)
 648                   (concat beg "Lisp closure"))
 649                  ((keymapp def)
 650                   (let ((is-full nil)
 651                         (elts (cdr-safe def)))
 652                     (while elts
 653                       (if (char-table-p (car-safe elts))
 654                           (setq is-full t
 655                                 elts nil))
 656                       (setq elts (cdr-safe elts)))
 657                     (concat beg (if is-full "keymap" "sparse keymap"))))
 658                  (t "")))
 659
 660     (if (and aliased (not (fboundp real-def)))
 661         (princ ",\nwhich is not defined.  Please make a bug report.")
 662       (with-current-buffer standard-output
 663         (save-excursion
 664           (save-match-data
 665             (when (re-search-backward (substitute-command-keys
 666                                        "alias for `\\([^`']+\\)'")
 667                                       nil t)
 668               (help-xref-button 1 'help-function real-def)))))
 669
 670       (when file-name
 671         ;; We used to add .el to the file name,
 672         ;; but that's completely wrong when the user used load-file.
 673         (princ (format-message " in `%s'"
 674                                (if (eq file-name 'C-source)
 675                                    "C source code"
 676                                  (help-fns-short-filename file-name))))
 677         ;; Make a hyperlink to the library.
 678         (with-current-buffer standard-output
 679           (save-excursion
 680             (re-search-backward (substitute-command-keys "`\\([^`']+\\)'")
 681                                 nil t)
 682             (help-xref-button 1 'help-function-def function file-name))))
 683       (princ "."))))
 684
 685 ;;;###autoload
 686 (defun describe-function-1 (function)
 687   (let ((pt1 (with-current-buffer (help-buffer) (point))))
 688     (help-fns-function-description-header function)
 689     (with-current-buffer (help-buffer)
 690       (fill-region-as-paragraph (save-excursion (goto-char pt1) (forward-line 0) (point))
 691                                 (point))))
 692   (terpri)(terpri)
 693
 694   (pcase-let* ((`(,real-function ,def ,_aliased ,real-def)
 695                 (help-fns--analyze-function function))
 696                (doc-raw (condition-case nil
 697                             ;; FIXME: Maybe `documentation' should return nil
 698                             ;; for invalid functions i.s.o. signaling an error.
 699                             (documentation function t)
 700                           ;; E.g. an alias for a not yet defined function.
 701                           ((invalid-function void-function) nil)))
 702                (key-bindings-buffer (current-buffer)))
 703
 704     ;; If the function is autoloaded, and its docstring has
 705     ;; key substitution constructs, load the library.
 706     (and (autoloadp real-def) doc-raw
 707          help-enable-auto-load
 708          (string-match "\\([^\\]=\\|[^=]\\|\\`\\)\\\\[[{<]" doc-raw)
 709          (autoload-do-load real-def))
 710
 711     (help-fns--key-bindings function)
 712     (with-current-buffer standard-output
 713       (let ((doc (condition-case nil
 714                      ;; FIXME: Maybe `help-fns--signature' should return `doc'
 715                      ;; for invalid functions i.s.o. signaling an error.
 716                      (help-fns--signature
 717                       function doc-raw
 718                       (if (subrp def) (indirect-function real-def) real-def)
 719                       real-function key-bindings-buffer)
 720                    ;; E.g. an alias for a not yet defined function.
 721                    ((invalid-function void-function) doc-raw))))
 722         (run-hook-with-args 'help-fns-describe-function-functions function)
 723         (insert "\n" (or doc "Not documented.")))
 724       (when (or (function-get function 'pure)
 725                 (function-get function 'side-effect-free))
 726         (insert "\nThis function does not change global state, "
 727                 "including the match data."))
 728       ;; Avoid asking the user annoying questions if she decides
 729       ;; to save the help buffer, when her locale's codeset
 730       ;; isn't UTF-8.
 731       (unless (memq text-quoting-style '(straight grave))
 732         (set-buffer-file-coding-system 'utf-8)))))
 733
 734 ;; Add defaults to `help-fns-describe-function-functions'.
 735 (add-hook 'help-fns-describe-function-functions #'help-fns--obsolete)
 736 (add-hook 'help-fns-describe-function-functions #'help-fns--interactive-only)
 737 (add-hook 'help-fns-describe-function-functions #'help-fns--parent-mode)
 738 (add-hook 'help-fns-describe-function-functions #'help-fns--compiler-macro)
 739
 740 \f
 741 ;; Variables
 742
 743 ;;;###autoload
 744 (defun variable-at-point (&optional any-symbol)
 745   "Return the bound variable symbol found at or before point.
 746 Return 0 if there is no such symbol.
 747 If ANY-SYMBOL is non-nil, don't insist the symbol be bound."
 748   (with-syntax-table emacs-lisp-mode-syntax-table
 749     (or (condition-case ()
 750             (save-excursion
 751               (skip-chars-forward "'")
 752               (or (not (zerop (skip-syntax-backward "_w")))
 753                   (eq (char-syntax (following-char)) ?w)
 754                   (eq (char-syntax (following-char)) ?_)
 755                   (forward-sexp -1))
 756               (skip-chars-forward "'")
 757               (let ((obj (read (current-buffer))))
 758                 (and (symbolp obj) (boundp obj) obj)))
 759           (error nil))
 760         (let* ((str (find-tag-default))
 761                (sym (if str (intern-soft str))))
 762           (if (and sym (or any-symbol (boundp sym)))
 763               sym
 764             (save-match-data
 765               (when (and str (string-match "\\`\\W*\\(.*?\\)\\W*\\'" str))
 766                 (setq sym (intern-soft (match-string 1 str)))
 767                 (and (or any-symbol (boundp sym)) sym)))))
 768         0)))
 769
 770 (defun describe-variable-custom-version-info (variable)
 771   (let ((custom-version (get variable 'custom-version))
 772         (cpv (get variable 'custom-package-version))
 773         (output nil))
 774     (if custom-version
 775         (setq output
 776               (format "This variable was introduced, or its default value was changed, in\nversion %s of Emacs.\n"
 777                       custom-version))
 778       (when cpv
 779         (let* ((package (car-safe cpv))
 780                (version (if (listp (cdr-safe cpv))
 781                             (car (cdr-safe cpv))
 782                           (cdr-safe cpv)))
 783                (pkg-versions (assq package customize-package-emacs-version-alist))
 784                (emacsv (cdr (assoc version pkg-versions))))
 785           (if (and package version)
 786               (setq output
 787                     (format (concat "This variable was introduced, or its default value was changed, in\nversion %s of the %s package"
 788                                     (if emacsv
 789                                         (format " that is part of Emacs %s" emacsv))
 790                                     ".\n")
 791                             version package))))))
 792     output))
 793
 794 ;;;###autoload
 795 (defun describe-variable (variable &optional buffer frame)
 796   "Display the full documentation of VARIABLE (a symbol).
 797 Returns the documentation as a string, also.
 798 If VARIABLE has a buffer-local value in BUFFER or FRAME
 799 \(default to the current buffer and current frame),
 800 it is displayed along with the global value."
 801   (interactive
 802    (let ((v (variable-at-point))
 803          (enable-recursive-minibuffers t)
 804          (orig-buffer (current-buffer))
 805          val)
 806      (setq val (completing-read
 807                 (if (symbolp v)
 808                     (format
 809                      "Describe variable (default %s): " v)
 810                   "Describe variable: ")
 811                 #'help--symbol-completion-table
 812                 (lambda (vv)
 813                   ;; In case the variable only exists in the buffer
 814                   ;; the command we switch back to that buffer before
 815                   ;; we examine the variable.
 816                   (with-current-buffer orig-buffer
 817                     (or (get vv 'variable-documentation)
 818                         (and (boundp vv) (not (keywordp vv))))))
 819                 t nil nil
 820                 (if (symbolp v) (symbol-name v))))
 821      (list (if (equal val "")
 822                v (intern val)))))
 823   (let (file-name)
 824     (unless (buffer-live-p buffer) (setq buffer (current-buffer)))
 825     (unless (frame-live-p frame) (setq frame (selected-frame)))
 826     (if (not (symbolp variable))
 827         (message "You did not specify a variable")
 828       (save-excursion
 829         (let ((valvoid (not (with-current-buffer buffer (boundp variable))))
 830               (permanent-local (get variable 'permanent-local))
 831               val val-start-pos locus)
 832           ;; Extract the value before setting up the output buffer,
 833           ;; in case `buffer' *is* the output buffer.
 834           (unless valvoid
 835             (with-selected-frame frame
 836               (with-current-buffer buffer
 837                 (setq val (symbol-value variable)
 838                       locus (variable-binding-locus variable)))))
 839           (help-setup-xref (list #'describe-variable variable buffer)
 840                            (called-interactively-p 'interactive))
 841           (with-help-window (help-buffer)
 842             (with-current-buffer buffer
 843               (prin1 variable)
 844               (setq file-name (find-lisp-object-file-name variable 'defvar))
 845
 846               (if file-name
 847                   (progn
 848                     (princ (format-message
 849                             " is a variable defined in `%s'.\n"
 850                             (if (eq file-name 'C-source)
 851                                 "C source code"
 852                               (file-name-nondirectory file-name))))
 853                     (with-current-buffer standard-output
 854                       (save-excursion
 855                         (re-search-backward (substitute-command-keys
 856                                              "`\\([^`']+\\)'")
 857                                             nil t)
 858                         (help-xref-button 1 'help-variable-def
 859                                           variable file-name)))
 860                     (if valvoid
 861                         (princ "It is void as a variable.")
 862                       (princ "Its ")))
 863                 (if valvoid
 864                     (princ " is void as a variable.")
 865                   (princ (substitute-command-keys "'s ")))))
 866             (unless valvoid
 867               (with-current-buffer standard-output
 868                 (setq val-start-pos (point))
 869                 (princ "value is")
 870                 (let ((line-beg (line-beginning-position))
 871                       (print-rep
 872                        (let ((rep
 873                               (let ((print-quoted t)
 874                                     (print-circle t))
 875                                 (cl-prin1-to-string val))))
 876                          (if (and (symbolp val) (not (booleanp val)))
 877                              (format-message "`%s'" rep)
 878                            rep))))
 879                   (if (< (+ (length print-rep) (point) (- line-beg)) 68)
 880                       (insert " " print-rep)
 881                     (terpri)
 882                     (let ((buf (current-buffer)))
 883                       (with-temp-buffer
 884                         (insert print-rep)
 885                         (pp-buffer)
 886                         (let ((pp-buffer (current-buffer)))
 887                           (with-current-buffer buf
 888                             (insert-buffer-substring pp-buffer)))))
 889                     ;; Remove trailing newline.
 890                     (and (= (char-before) ?\n) (delete-char -1)))
 891                   (let* ((sv (get variable 'standard-value))
 892                          (origval (and (consp sv)
 893                                        (condition-case nil
 894                                            (eval (car sv))
 895                                          (error :help-eval-error))))
 896                          from)
 897                     (when (and (consp sv)
 898                                (not (equal origval val))
 899                                (not (equal origval :help-eval-error)))
 900                       (princ "\nOriginal value was \n")
 901                       (setq from (point))
 902                       (cl-prin1 origval)
 903                       (save-restriction
 904                         (narrow-to-region from (point))
 905                         (save-excursion (pp-buffer)))
 906                       (if (< (point) (+ from 20))
 907                           (delete-region (1- from) from)))))))
 908             (terpri)
 909             (when locus
 910               (cond
 911                ((bufferp locus)
 912                 (princ (format "Local in buffer %s; "
 913                                (buffer-name buffer))))
 914                ((terminal-live-p locus)
 915                 (princ (format "It is a terminal-local variable; ")))
 916                (t
 917                 (princ (format "It is local to %S" locus))))
 918               (if (not (default-boundp variable))
 919                   (princ "globally void")
 920                 (let ((global-val (default-value variable)))
 921                   (with-current-buffer standard-output
 922                     (princ "global value is ")
 923                     (if (eq val global-val)
 924                         (princ "the same.")
 925                       (terpri)
 926                       ;; Fixme: pp can take an age if you happen to
 927                       ;; ask for a very large expression.  We should
 928                       ;; probably print it raw once and check it's a
 929                       ;; sensible size before prettyprinting.  -- fx
 930                       (let ((from (point)))
 931                         (cl-prin1 global-val)
 932                         (save-restriction
 933                           (narrow-to-region from (point))
 934                           (save-excursion (pp-buffer)))
 935                         ;; See previous comment for this function.
 936                         ;; (help-xref-on-pp from (point))
 937                         (if (< (point) (+ from 20))
 938                             (delete-region (1- from) from)))))))
 939               (terpri))
 940
 941             ;; If the value is large, move it to the end.
 942             (with-current-buffer standard-output
 943               (when (> (count-lines (point-min) (point-max)) 10)
 944                 ;; Note that setting the syntax table like below
 945                 ;; makes forward-sexp move over a `'s' at the end
 946                 ;; of a symbol.
 947                 (set-syntax-table emacs-lisp-mode-syntax-table)
 948                 (goto-char val-start-pos)
 949                 ;; The line below previously read as
 950                 ;; (delete-region (point) (progn (end-of-line) (point)))
 951                 ;; which suppressed display of the buffer local value for
 952                 ;; large values.
 953                 (when (looking-at "value is") (replace-match ""))
 954                 (save-excursion
 955                   (insert "\n\nValue:")
 956                   (set (make-local-variable 'help-button-cache)
 957                        (point-marker)))
 958                 (insert "value is shown ")
 959                 (insert-button "below"
 960                                'action help-button-cache
 961                                'follow-link t
 962                                'help-echo "mouse-2, RET: show value")
 963                 (insert ".\n")))
 964             (terpri)
 965
 966             (let* ((alias (condition-case nil
 967                               (indirect-variable variable)
 968                             (error variable)))
 969                    (obsolete (get variable 'byte-obsolete-variable))
 970                    (watchpoints (get-variable-watchers variable))
 971                    (use (car obsolete))
 972                    (safe-var (get variable 'safe-local-variable))
 973                    (doc (or (documentation-property
 974                              variable 'variable-documentation)
 975                             (documentation-property
 976                              alias 'variable-documentation)))
 977                    (extra-line nil))
 978
 979               ;; Mention if it's a local variable.
 980               (cond
 981                ((and (local-variable-if-set-p variable)
 982                      (or (not (local-variable-p variable))
 983                          (with-temp-buffer
 984                            (local-variable-if-set-p variable))))
 985                 (setq extra-line t)
 986                 (princ "  Automatically becomes ")
 987                 (if permanent-local
 988                     (princ "permanently "))
 989                 (princ "buffer-local when set.\n"))
 990                ((not permanent-local))
 991                ((bufferp locus)
 992                 (setq extra-line t)
 993                 (princ
 994                  (substitute-command-keys
 995                   "  This variable's buffer-local value is permanent.\n")))
 996                (t
 997                 (setq extra-line t)
 998                 (princ (substitute-command-keys
 999                         "  This variable's value is permanent \
1000 if it is given a local binding.\n"))))
1001
1002               ;; Mention if it's an alias.
1003               (unless (eq alias variable)
1004                 (setq extra-line t)
1005                 (princ (format-message
1006                         "  This variable is an alias for `%s'.\n"
1007                         alias)))
1008
1009               (when obsolete
1010                 (setq extra-line t)
1011                 (princ "  This variable is obsolete")
1012                 (if (nth 2 obsolete)
1013                     (princ (format " since %s" (nth 2 obsolete))))
1014                 (princ (cond ((stringp use) (concat ";\n  " use))
1015                              (use (format-message ";\n  use `%s' instead."
1016                                                   (car obsolete)))
1017                              (t ".")))
1018                 (terpri))
1019
1020               (when watchpoints
1021                 (setq extra-line t)
1022                 (princ "  Calls these functions when changed: ")
1023                 (princ watchpoints)
1024                 (terpri))
1025
1026               (when (member (cons variable val)
1027                             (with-current-buffer buffer
1028                               file-local-variables-alist))
1029                 (setq extra-line t)
1030                 (if (member (cons variable val)
1031                              (with-current-buffer buffer
1032                                dir-local-variables-alist))
1033                     (let ((file (and (buffer-file-name buffer)
1034                                       (not (file-remote-p
1035                                             (buffer-file-name buffer)))
1036                                       (dir-locals-find-file
1037                                        (buffer-file-name buffer))))
1038                           (is-directory nil))
1039                       (princ (substitute-command-keys
1040                               "  This variable's value is directory-local"))
1041                       (when (consp file) ; result from cache
1042                         ;; If the cache element has an mtime, we
1043                         ;; assume it came from a file.
1044                         (if (nth 2 file)
1045                             ;; (car file) is a directory.
1046                             (setq file (dir-locals--all-files (car file)))
1047                           ;; Otherwise, assume it was set directly.
1048                           (setq file (car file)
1049                                 is-directory t)))
1050                       (if (null file)
1051                           (princ ".\n")
1052                         (princ ", set ")
1053                         (princ (substitute-command-keys
1054                                 (cond
1055                                  (is-directory "for the directory\n  `")
1056                                  ;; Many files matched.
1057                                  ((and (consp file) (cdr file))
1058                                   (setq file (file-name-directory (car file)))
1059                                   (format "by one of the\n  %s files in the directory\n  `"
1060                                           dir-locals-file))
1061                                  (t (setq file (car file))
1062                                     "by the file\n  `"))))
1063                         (with-current-buffer standard-output
1064                           (insert-text-button
1065                            file 'type 'help-dir-local-var-def
1066                              'help-args (list variable file)))
1067                         (princ (substitute-command-keys "'.\n"))))
1068                   (princ (substitute-command-keys
1069                           "  This variable's value is file-local.\n"))))
1070
1071               (when (memq variable ignored-local-variables)
1072                 (setq extra-line t)
1073                 (princ "  This variable is ignored as a file-local \
1074 variable.\n"))
1075
1076               ;; Can be both risky and safe, eg auto-fill-function.
1077               (when (risky-local-variable-p variable)
1078                 (setq extra-line t)
1079                 (princ "  This variable may be risky if used as a \
1080 file-local variable.\n")
1081                 (when (assq variable safe-local-variable-values)
1082                   (princ (substitute-command-keys
1083                           "  However, you have added it to \
1084 `safe-local-variable-values'.\n"))))
1085
1086               (when safe-var
1087                 (setq extra-line t)
1088                 (princ "  This variable is safe as a file local variable ")
1089                 (princ "if its value\n  satisfies the predicate ")
1090                 (princ (if (byte-code-function-p safe-var)
1091                            "which is a byte-compiled expression.\n"
1092                          (format-message "`%s'.\n" safe-var))))
1093
1094               (if extra-line (terpri))
1095               (princ "Documentation:\n")
1096               (with-current-buffer standard-output
1097                 (insert (or doc "Not documented as a variable."))))
1098
1099             ;; Make a link to customize if this variable can be customized.
1100             (when (custom-variable-p variable)
1101               (let ((customize-label "customize"))
1102                 (terpri)
1103                 (terpri)
1104                 (princ (concat "You can " customize-label " this variable."))
1105                 (with-current-buffer standard-output
1106                   (save-excursion
1107                     (re-search-backward
1108                      (concat "\\(" customize-label "\\)") nil t)
1109                     (help-xref-button 1 'help-customize-variable variable))))
1110               ;; Note variable's version or package version.
1111               (let ((output (describe-variable-custom-version-info variable)))
1112                 (when output
1113                   (terpri)
1114                   (terpri)
1115                   (princ output))))
1116
1117             (with-current-buffer standard-output
1118               ;; Return the text we displayed.
1119               (buffer-string))))))))
1120
1121
1122 (defvar help-xref-stack-item)
1123
1124 ;;;###autoload
1125 (defun describe-symbol (symbol &optional buffer frame)
1126   "Display the full documentation of SYMBOL.
1127 Will show the info of SYMBOL as a function, variable, and/or face.
1128 Optional arguments BUFFER and FRAME specify for which buffer and
1129 frame to show the information about SYMBOL; they default to the
1130 current buffer and the selected frame, respectively."
1131   (interactive
1132    (let* ((v-or-f (symbol-at-point))
1133           (found (if v-or-f (cl-some (lambda (x) (funcall (nth 1 x) v-or-f))
1134                                      describe-symbol-backends)))
1135           (v-or-f (if found v-or-f (function-called-at-point)))
1136           (found (or found v-or-f))
1137           (enable-recursive-minibuffers t)
1138           (val (completing-read (if found
1139                                     (format
1140                                      "Describe symbol (default %s): " v-or-f)
1141                                   "Describe symbol: ")
1142                                 obarray
1143                                 (lambda (vv)
1144                                   (cl-some (lambda (x) (funcall (nth 1 x) vv))
1145                                            describe-symbol-backends))
1146                                 t nil nil
1147                                 (if found (symbol-name v-or-f)))))
1148      (list (if (equal val "")
1149                v-or-f (intern val)))))
1150   (if (not (symbolp symbol))
1151       (user-error "You didn't specify a function or variable"))
1152   (unless (buffer-live-p buffer) (setq buffer (current-buffer)))
1153   (unless (frame-live-p frame) (setq frame (selected-frame)))
1154   (with-current-buffer (help-buffer)
1155     ;; Push the previous item on the stack before clobbering the output buffer.
1156     (help-setup-xref nil nil)
1157     (let* ((docs
1158             (nreverse
1159              (delq nil
1160                    (mapcar (pcase-lambda (`(,name ,testfn ,descfn))
1161                              (when (funcall testfn symbol)
1162                                ;; Don't record the current entry in the stack.
1163                                (setq help-xref-stack-item nil)
1164                                (cons name
1165                                      (funcall descfn symbol buffer frame))))
1166                            describe-symbol-backends))))
1167            (single (null (cdr docs))))
1168       (while (cdr docs)
1169         (goto-char (point-min))
1170         (let ((inhibit-read-only t)
1171               (name (caar docs))        ;Name of doc currently at BOB.
1172               (doc (cdr (cadr docs))))  ;Doc to add at BOB.
1173           (when doc
1174             (insert doc)
1175             (delete-region (point)
1176                            (progn (skip-chars-backward " \t\n") (point)))
1177             (insert "\n\n"
1178                     (eval-when-compile
1179                       (propertize "\n" 'face '(:height 0.1 :inverse-video t)))
1180                     "\n")
1181             (when name
1182               (insert (symbol-name symbol)
1183                       " is also a " name "." "\n\n"))))
1184         (setq docs (cdr docs)))
1185       (unless single
1186         ;; Don't record the `describe-variable' item in the stack.
1187         (setq help-xref-stack-item nil)
1188         (help-setup-xref (list #'describe-symbol symbol) nil))
1189       (goto-char (point-min)))))
1190
1191 ;;;###autoload
1192 (defun describe-syntax (&optional buffer)
1193   "Describe the syntax specifications in the syntax table of BUFFER.
1194 The descriptions are inserted in a help buffer, which is then displayed.
1195 BUFFER defaults to the current buffer."
1196   (interactive)
1197   (setq buffer (or buffer (current-buffer)))
1198   (help-setup-xref (list #'describe-syntax buffer)
1199                    (called-interactively-p 'interactive))
1200   (with-help-window (help-buffer)
1201     (let ((table (with-current-buffer buffer (syntax-table))))
1202       (with-current-buffer standard-output
1203         (describe-vector table 'internal-describe-syntax-value)
1204         (while (setq table (char-table-parent table))
1205           (insert "\nThe parent syntax table is:")
1206           (describe-vector table 'internal-describe-syntax-value))))))
1207
1208 (defun help-describe-category-set (value)
1209   (insert (cond
1210            ((null value) "default")
1211            ((char-table-p value) "deeper char-table ...")
1212            (t (condition-case nil
1213                   (category-set-mnemonics value)
1214                 (error "invalid"))))))
1215
1216 ;;;###autoload
1217 (defun describe-categories (&optional buffer)
1218   "Describe the category specifications in the current category table.
1219 The descriptions are inserted in a buffer, which is then displayed.
1220 If BUFFER is non-nil, then describe BUFFER's category table instead.
1221 BUFFER should be a buffer or a buffer name."
1222   (interactive)
1223   (setq buffer (or buffer (current-buffer)))
1224   (help-setup-xref (list #'describe-categories buffer)
1225                    (called-interactively-p 'interactive))
1226   (with-help-window (help-buffer)
1227     (let* ((table (with-current-buffer buffer (category-table)))
1228            (docs (char-table-extra-slot table 0)))
1229       (if (or (not (vectorp docs)) (/= (length docs) 95))
1230           (error "Invalid first extra slot in this category table\n"))
1231       (with-current-buffer standard-output
1232         (setq-default help-button-cache (make-marker))
1233         (insert "Legend of category mnemonics ")
1234         (insert-button "(longer descriptions at the bottom)"
1235                        'action help-button-cache
1236                        'follow-link t
1237                        'help-echo "mouse-2, RET: show full legend")
1238         (insert "\n")
1239         (let ((pos (point)) (items 0) lines n)
1240           (dotimes (i 95)
1241             (if (aref docs i) (setq items (1+ items))))
1242           (setq lines (1+ (/ (1- items) 4)))
1243           (setq n 0)
1244           (dotimes (i 95)
1245             (let ((elt (aref docs i)))
1246               (when elt
1247                 (string-match ".*" elt)
1248                 (setq elt (match-string 0 elt))
1249                 (if (>= (length elt) 17)
1250                     (setq elt (concat (substring elt 0 14) "...")))
1251                 (if (< (point) (point-max))
1252                     (move-to-column (* 20 (/ n lines)) t))
1253                 (insert (+ i ?\s) ?: elt)
1254                 (if (< (point) (point-max))
1255                     (forward-line 1)
1256                   (insert "\n"))
1257                 (setq n (1+ n))
1258                 (if (= (% n lines) 0)
1259                     (goto-char pos))))))
1260         (goto-char (point-max))
1261         (insert "\n"
1262                 "character(s)\tcategory mnemonics\n"
1263                 "------------\t------------------")
1264         (describe-vector table 'help-describe-category-set)
1265         (set-marker help-button-cache (point))
1266         (insert "Legend of category mnemonics:\n")
1267         (dotimes (i 95)
1268           (let ((elt (aref docs i)))
1269             (when elt
1270               (if (string-match "\n" elt)
1271                   (setq elt (substring elt (match-end 0))))
1272               (insert (+ i ?\s) ": " elt "\n"))))
1273         (while (setq table (char-table-parent table))
1274           (insert "\nThe parent category table is:")
1275           (describe-vector table 'help-describe-category-set))))))
1276
1277 \f
1278 ;;; Replacements for old lib-src/ programs.  Don't seem especially useful.
1279
1280 ;; Replaces lib-src/digest-doc.c.
1281 ;;;###autoload
1282 (defun doc-file-to-man (file)
1283   "Produce an nroff buffer containing the doc-strings from the DOC file."
1284   (interactive (list (read-file-name "Name of DOC file: " doc-directory
1285                                      internal-doc-file-name t)))
1286   (or (file-readable-p file)
1287       (error "Cannot read file `%s'" file))
1288   (pop-to-buffer (generate-new-buffer "*man-doc*"))
1289   (setq buffer-undo-list t)
1290   (insert ".TH \"Command Summary for GNU Emacs\"\n"
1291           ".AU Richard M. Stallman\n")
1292   (insert-file-contents file)
1293   (let (notfirst)
1294     (while (search-forward "\x1f" nil 'move)
1295       (if (= (following-char) ?S)
1296           (delete-region (1- (point)) (line-end-position))
1297         (delete-char -1)
1298         (if notfirst
1299             (insert "\n.DE\n")
1300           (setq notfirst t))
1301         (insert "\n.SH ")
1302         (insert (if (= (following-char) ?F) "Function " "Variable "))
1303         (delete-char 1)
1304         (forward-line 1)
1305         (insert ".DS L\n"))))
1306   (insert "\n.DE\n")
1307   (setq buffer-undo-list nil)
1308   (nroff-mode))
1309
1310 ;; Replaces lib-src/sorted-doc.c.
1311 ;;;###autoload
1312 (defun doc-file-to-info (file)
1313   "Produce a texinfo buffer with sorted doc-strings from the DOC file."
1314   (interactive (list (read-file-name "Name of DOC file: " doc-directory
1315                                      internal-doc-file-name t)))
1316   (or (file-readable-p file)
1317       (error "Cannot read file `%s'" file))
1318   (let ((i 0) type name doc alist)
1319     (with-temp-buffer
1320       (insert-file-contents file)
1321       ;; The characters "@{}" need special treatment.
1322       (while (re-search-forward "[@{}]" nil t)
1323         (backward-char)
1324         (insert "@")
1325         (forward-char 1))
1326       (goto-char (point-min))
1327       (while (search-forward "\x1f" nil t)
1328         (when (/= (following-char) ?S)
1329           (setq type (char-after)
1330                 name (buffer-substring (1+ (point)) (line-end-position))
1331                 doc (buffer-substring (line-beginning-position 2)
1332                                       (if (search-forward  "\x1f" nil 'move)
1333                                           (1- (point))
1334                                         (point)))
1335                 alist (cons (list name type doc) alist))
1336           (backward-char 1))))
1337     (pop-to-buffer (generate-new-buffer "*info-doc*"))
1338     (setq buffer-undo-list t)
1339     ;; Write the output header.
1340     (insert "\\input texinfo  @c -*-texinfo-*-\n"
1341             "@setfilename emacsdoc.info\n"
1342             "@settitle Command Summary for GNU Emacs\n"
1343             "@finalout\n"
1344             "\n@node Top\n"
1345             "@unnumbered Command Summary for GNU Emacs\n\n"
1346             "@table @asis\n\n"
1347             "@iftex\n"
1348             "@global@let@ITEM@item\n"
1349             "@def@item{@filbreak@vskip5pt@ITEM}\n"
1350             "@font@tensy cmsy10 scaled @magstephalf\n"
1351             "@font@teni cmmi10 scaled @magstephalf\n"
1352             "@def\\{{@tensy@char110}}\n" ; this backslash goes with cmr10
1353             "@def|{{@tensy@char106}}\n"
1354             "@def@{{{@tensy@char102}}\n"
1355             "@def@}{{@tensy@char103}}\n"
1356             "@def<{{@teni@char62}}\n"
1357             "@def>{{@teni@char60}}\n"
1358             "@chardef@@64\n"
1359             "@catcode43=12\n"
1360             "@tableindent-0.2in\n"
1361             "@end iftex\n")
1362     ;; Sort the array by name; within each name, by type (functions first).
1363     (setq alist (sort alist (lambda (e1 e2)
1364                               (if (string-equal (car e1) (car e2))
1365                                   (<= (cadr e1) (cadr e2))
1366                                 (string-lessp (car e1) (car e2))))))
1367     ;; Print each function.
1368     (dolist (e alist)
1369       (insert "\n@item "
1370               (if (char-equal (cadr e) ?\F) "Function" "Variable")
1371               " @code{" (car e) "}\n@display\n"
1372               (nth 2 e)
1373               "\n@end display\n")
1374       ;; Try to avoid a save size overflow in the TeX output routine.
1375       (if (zerop (setq i (% (1+ i) 100)))
1376           (insert "\n@end table\n@table @asis\n")))
1377     (insert "@end table\n"
1378             "@bye\n")
1379     (setq buffer-undo-list nil)
1380     (texinfo-mode)))
1381
1382 (provide 'help-fns)
1383
1384 ;;; help-fns.el ends here