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lisp/help.el

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+;; Help commands for Emacs
+;; Copyright (C) 1985, 1986 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 1, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to
+;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;;###autoload
+(defvar help-map (make-sparse-keymap)
+  "Keymap for characters following the Help key.")
+
+(define-key global-map "\C-h" 'help-command)
+(fset 'help-command help-map)
+
+(define-key help-map "\C-h" 'help-for-help)
+(define-key help-map "?" 'help-for-help)
+
+(define-key help-map "\C-c" 'describe-copying)
+(define-key help-map "\C-d" 'describe-distribution)
+(define-key help-map "\C-w" 'describe-no-warranty)
+(define-key help-map "a" 'command-apropos)
+
+(define-key help-map "b" 'describe-bindings)
+
+(define-key help-map "c" 'describe-key-briefly)
+(define-key help-map "k" 'describe-key)
+
+(define-key help-map "d" 'describe-function)
+(define-key help-map "f" 'describe-function)
+
+(define-key help-map "i" 'info)
+
+(define-key help-map "l" 'view-lossage)
+
+(define-key help-map "m" 'describe-mode)
+
+(define-key help-map "\C-n" 'view-emacs-news)
+(define-key help-map "n" 'view-emacs-news)
+
+(define-key help-map "s" 'describe-syntax)
+
+(define-key help-map "t" 'help-with-tutorial)
+
+(define-key help-map "w" 'where-is)
+
+(define-key help-map "v" 'describe-variable)
+
+(defun help-with-tutorial ()
+  "Select the Emacs learn-by-doing tutorial."
+  (interactive)
+  (let ((file (expand-file-name "~/TUTORIAL")))
+    (delete-other-windows)
+    (if (get-file-buffer file)
+	(switch-to-buffer (get-file-buffer file))
+      (switch-to-buffer (create-file-buffer file))
+      (setq buffer-file-name file)
+      (setq default-directory (expand-file-name "~/"))
+      (setq auto-save-file-name nil)
+      (insert-file-contents (expand-file-name "TUTORIAL" exec-directory))
+      (goto-char (point-min))
+      (search-forward "\n<<")
+      (beginning-of-line)
+      (delete-region (point) (progn (end-of-line) (point)))
+      (newline (- (window-height (selected-window))
+		  (count-lines (point-min) (point))
+		  6))
+      (goto-char (point-min))
+      (set-buffer-modified-p nil))))
+
+(defun describe-key-briefly (key)
+  "Print the name of the function KEY invokes.  KEY is a string."
+  (interactive "kDescribe key briefly: ")
+  (let ((defn (key-binding key)))
+    (if (or (null defn) (integerp defn))
+        (message "%s is undefined" (key-description key))
+      (message "%s runs the command %s"
+	       (key-description key)
+	       (if (symbolp defn) defn (prin1-to-string defn))))))
+
+(defun print-help-return-message (&optional function)
+  "Display or return message saying how to restore windows after help command.
+Computes a message and applies the optional argument FUNCTION to it.
+If FUNCTION is nil, applies `message' to it, thus printing it."
+  (and (not (get-buffer-window standard-output))
+       (funcall (or function 'message)
+		(concat
+		 (substitute-command-keys
+		  (if (one-window-p t)
+		      (if pop-up-windows
+			  "Type \\[delete-other-windows] to remove help window."
+			"Type \\[switch-to-buffer] RET to remove help window.")
+		    "Type \\[switch-to-buffer-other-window] RET to restore the other window."))
+		 (substitute-command-keys
+		  "  \\[scroll-other-window] to scroll the help.")))))
+
+(defun describe-key (key)
+  "Display documentation of the function invoked by KEY.  KEY is a string."
+  (interactive "kDescribe key: ")
+  (let ((defn (key-binding key)))
+    (if (or (null defn) (integerp defn))
+        (message "%s is undefined" (key-description key))
+      (with-output-to-temp-buffer "*Help*"
+	(prin1 defn)
+	(princ ":\n")
+	(if (documentation defn)
+	    (princ (documentation defn))
+	  (princ "not documented"))
+	(print-help-return-message)))))
+
+(defun describe-mode (&optional minor)
+  "Display documentation of current major mode.
+If optional MINOR is non-nil (or prefix argument is given if interactive),
+display documentation of active minor modes as well.
+For this to work correctly for a minor mode, the mode's indicator variable
+(listed in `minor-mode-alist') must also be a function whose documentation
+describes the minor mode."
+  (interactive)
+  (with-output-to-temp-buffer "*Help*"
+    (princ mode-name)
+    (princ " Mode:\n")
+    (princ (documentation major-mode))
+    (let ((minor-modes minor-mode-alist)
+	  (locals (buffer-local-variables)))
+      (while minor-modes
+	(let* ((minor-mode (car (car minor-modes)))
+	       (indicator (car (cdr (car minor-modes))))
+	       (local-binding (assq minor-mode locals)))
+	  ;; Document a minor mode if it is listed in minor-mode-alist,
+	  ;; bound locally in this buffer, non-nil, and has a function
+	  ;; definition.
+	  (if (and local-binding
+		   (cdr local-binding)
+		   (fboundp minor-mode))
+	      (progn
+		(princ (format "\n\n\n%s minor mode (indicator%s):\n"
+			       minor-mode indicator))
+		(princ (documentation minor-mode)))))
+	(setq minor-modes (cdr minor-modes))))
+    (print-help-return-message)))
+
+;; So keyboard macro definitions are documented correctly
+(fset 'defining-kbd-macro (symbol-function 'start-kbd-macro))
+
+(defun describe-distribution ()
+  "Display info on how to obtain the latest version of GNU Emacs."
+  (interactive)
+  (find-file-read-only
+   (expand-file-name "DISTRIB" exec-directory)))
+
+(defun describe-copying ()
+  "Display info on how you may redistribute copies of GNU Emacs."
+  (interactive)
+  (find-file-read-only
+   (expand-file-name "COPYING" exec-directory))
+  (goto-char (point-min)))
+
+(defun describe-no-warranty ()
+  "Display info on all the kinds of warranty Emacs does NOT have."
+  (interactive)
+  (describe-copying)
+  (let (case-fold-search)
+    (search-forward "NO WARRANTY")
+    (recenter 0)))
+
+(defun view-emacs-news ()
+  "Display info on recent changes to Emacs."
+  (interactive)
+  (find-file-read-only (expand-file-name "NEWS" exec-directory)))
+
+(defun view-lossage ()
+  "Display last 100 input keystrokes."
+  (interactive)
+  (with-output-to-temp-buffer "*Help*"
+    (princ (key-description (recent-keys)))
+    (save-excursion
+      (set-buffer standard-output)
+      (goto-char (point-min))
+      (while (progn (move-to-column 50) (not (eobp)))
+	(search-forward " " nil t)
+	(insert "\n")))
+    (print-help-return-message)))
+
+(defun help-for-help ()
+  "You have typed C-h, the help character.  Type a Help option:
+
+A  command-apropos.   Give a substring, and see a list of commands
+              (functions interactively callable) that contain
+	      that substring.  See also the  apropos  command.
+B  describe-bindings.  Display table of all key bindings.
+C  describe-key-briefly.  Type a command key sequence;
+	      it prints the function name that sequence runs.
+F  describe-function.  Type a function name and get documentation of it.
+I  info. The  info  documentation reader.
+K  describe-key.  Type a command key sequence;
+	      it displays the full documentation.
+L  view-lossage.  Shows last 100 characters you typed.
+M  describe-mode.  Print documentation of current major mode,
+	      which describes the commands peculiar to it.
+N  view-emacs-news.  Shows emacs news file.
+S  describe-syntax.  Display contents of syntax table, plus explanations
+T  help-with-tutorial.  Select the Emacs learn-by-doing tutorial.
+V  describe-variable.  Type name of a variable;
+	      it displays the variable's documentation and value.
+W  where-is.  Type command name; it prints which keystrokes
+	      invoke that command.
+C-c print Emacs copying permission (General Public License).
+C-d print Emacs ordering information.
+C-n print news of recent Emacs changes.
+C-w print information on absence of warranty for GNU Emacs."
+  (interactive)
+  (message
+ "A B C F I K L M N S T V W C-c C-d C-n C-w.  Type C-h again for more help: ")
+  (let ((char (read-char)))
+    (if (or (= char ?\C-h) (= char ??))
+	(save-window-excursion
+	  (switch-to-buffer "*Help*")
+	  (delete-other-windows)
+	  (erase-buffer)
+	  (insert (documentation 'help-for-help))
+	  (goto-char (point-min))
+	  (while (memq char '(?\C-h ?? ?\C-v ?\  ?\177 ?\M-v))
+	    (if (memq char '(?\C-v ?\ ))
+		(scroll-up))
+	    (if (memq char '(?\177 ?\M-v))
+		(scroll-down))
+	    (message "A B C F I K L M N S T V W C-c C-d C-n C-w%s: "
+		     (if (pos-visible-in-window-p (point-max))
+			 "" " or Space to scroll"))
+	    (let ((cursor-in-echo-area t))
+	      (setq char (read-char))))))
+    (let ((defn (cdr (assq (downcase char) (cdr help-map)))))
+      (if defn (call-interactively defn) (ding)))))
+
+
+;; Return a function which is called by the list containing point.
+;; If that gives no function, return a function whose name is around point.
+;; If that doesn't give a function, return nil.
+(defun function-called-at-point ()
+  (or (condition-case ()
+	  (save-excursion
+	    (save-restriction
+	      (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
+	      (backward-up-list 1)
+	      (forward-char 1)
+	      (let (obj)
+		(setq obj (read (current-buffer)))
+		(and (symbolp obj) (fboundp obj) obj))))
+	(error nil))
+      (condition-case ()
+	  (save-excursion
+	    (forward-sexp -1)
+	    (skip-chars-forward "'")
+	    (let ((obj (read (current-buffer))))
+	      (and (symbolp obj) (fboundp obj) obj)))
+	(error nil))))
+
+(defun describe-function (function)
+  "Display the full documentation of FUNCTION (a symbol)."
+  (interactive
+   (let ((fn (function-called-at-point))
+	 (enable-recursive-minibuffers t)	     
+	 val)
+     (setq val (completing-read (if fn
+				    (format "Describe function (default %s): " fn)
+				  "Describe function: ")
+				obarray 'fboundp t))
+     (list (if (equal val "")
+	       fn (intern val)))))
+  (with-output-to-temp-buffer "*Help*"
+    (prin1 function)
+    (princ ": ")
+    (let* ((def (symbol-function function))
+	   (beg (if (commandp def) "an interactive " "a ")))
+      (princ (cond ((stringp def) "a keyboard macro.")
+		   ((subrp def)
+		    (concat beg "built-in function."))
+		   ((compiled-function-p def)
+		    (concat beg "compiled Lisp function."))
+		   ((symbolp def)
+		    (format "alias for `%s'." def))
+		   ((eq (car-safe def) 'lambda)
+		    (concat beg "Lisp function."))
+		   ((eq (car-safe def) 'macro)
+		    "a Lisp macro.")
+		   ((eq (car-safe def) 'mocklisp)
+		    "a mocklisp function.")
+		   ((eq (car-safe def) 'autoload)
+		    (format "%sLisp %s to autoload from `%s'."
+			    beg
+			    (if (nth 4 def) "macro" "function")
+			    (nth 1 def)))
+		   (t "")))
+      (terpri))
+    (if (documentation function)
+        (princ (documentation function))
+      (princ "not documented"))
+    (print-help-return-message)
+    ;; Return the text we displayed.
+    (save-excursion (set-buffer standard-output) (buffer-string))))
+
+(defun variable-at-point ()
+  (condition-case ()
+      (save-excursion
+	(forward-sexp -1)
+	(skip-chars-forward "'")
+	(let ((obj (read (current-buffer))))
+	  (and (symbolp obj) (boundp obj) obj)))
+    (error nil)))
+
+(defun describe-variable (variable)
+  "Display the full documentation of VARIABLE (a symbol).
+Returns the documentation as a string, also."
+  (interactive 
+   (let ((v (variable-at-point))
+	 (enable-recursive-minibuffers t)
+	 val)
+     (setq val (completing-read (if v
+				    (format "Describe variable (default %s): " v)
+				  "Describe variable: ")
+				obarray 'boundp t))
+     (list (if (equal val "")
+	       v (intern val)))))
+  (with-output-to-temp-buffer "*Help*"
+    (prin1 variable)
+    (princ "'s value is ")
+    (if (not (boundp variable))
+        (princ "void.")
+      (prin1 (symbol-value variable)))
+    (terpri) (terpri)
+    (princ "Documentation:")
+    (terpri)
+    (let ((doc (documentation-property variable 'variable-documentation)))
+      (if doc
+	  (princ (substitute-command-keys doc))
+	(princ "not documented as a variable.")))
+    (print-help-return-message)
+    ;; Return the text we displayed.
+    (save-excursion (set-buffer standard-output) (buffer-string))))
+
+(defun command-apropos (string)
+  "Like apropos but lists only symbols that are names of commands
+\(interactively callable functions).  Argument REGEXP is a regular expression
+that is matched against command symbol names.  Returns list of symbols and
+documentation found."
+  (interactive "sCommand apropos (regexp): ")
+  (let ((message
+	 (let ((standard-output (get-buffer-create "*Help*")))
+	   (print-help-return-message 'identity))))
+    (apropos string 'commandp)
+    (and message (message message))))
+
+(defun locate-library (library &optional nosuffix)
+  "Show the full path name of Emacs library LIBRARY.
+This command searches the directories in `load-path' like `M-x load-library'
+to find the file that `M-x load-library RET LIBRARY RET' would load.
+Optional second arg NOSUFFIX non-nil means don't add suffixes `.elc' or `.el'
+to the specified name LIBRARY (a la calling `load' instead of `load-library')."
+  (interactive "sLocate library: ")
+  (catch 'answer
+    (mapcar
+     '(lambda (dir)
+	(mapcar
+	 '(lambda (suf)
+	    (let ((try (expand-file-name (concat library suf) dir)))
+	      (and (file-readable-p try)
+		   (null (file-directory-p try))
+		   (progn
+		     (message "Library is file %s" try)
+		     (throw 'answer try)))))
+	 (if nosuffix '("") '(".elc" ".el" ""))))
+     load-path)
+    (message "No library %s in search path" library)
+    nil))