;;; help.el --- help commands for Emacs
-;; Copyright (C) 1985, 1986, 1993, 1994 Free Software Foundation, Inc.
+;; Copyright (C) 1985, 1986, 1993, 1994, 1998 Free Software Foundation, Inc.
;; Maintainer: FSF
;; Keywords: help, internal
(define-key help-map "F" 'view-emacs-FAQ)
(define-key help-map "i" 'info)
+(define-key help-map "4i" 'info-other-window)
(define-key help-map "\C-f" 'Info-goto-emacs-command-node)
(define-key help-map "\C-k" 'Info-goto-emacs-key-command-node)
(define-key help-map "\C-i" 'info-lookup-symbol)
(define-key help-map "q" 'help-quit)
-(defvar help-font-lock-keywords
- (eval-when-compile
- (let ((name-char "[-+a-zA-Z0-9_*]") (sym-char "[-+a-zA-Z0-9_:*]"))
- (list
- ;;
- ;; The symbol itself.
- (list (concat "\\`\\(" name-char "+\\)\\(\\(:\\)\\|\\('\\)\\)")
- '(1 (if (match-beginning 3)
- font-lock-function-name-face
- font-lock-variable-name-face)))
- ;;
- ;; Words inside `' which tend to be symbol names.
- (list (concat "`\\(" sym-char sym-char "+\\)'")
- 1 'font-lock-reference-face t)
- ;;
- ;; CLisp `:' keywords as references.
- (list (concat "\\<:" sym-char "+\\>") 0 'font-lock-reference-face t))))
- "Default expressions to highlight in Help mode.")
+(define-key help-mode-map [mouse-2] 'help-follow-mouse)
+(define-key help-mode-map "\C-c\C-b" 'help-go-back)
+(define-key help-mode-map "\C-c\C-c" 'help-follow)
+(define-key help-mode-map "\t" 'help-next-ref)
+(define-key help-mode-map [backtab] 'help-previous-ref)
+(define-key help-mode-map [(shift tab)] 'help-previous-ref)
+;; Documentation only, since we use minor-mode-overriding-map-alist.
+(define-key help-mode-map "\r" 'help-follow)
+
+;; Font-locking is incompatible with the new xref stuff.
+;(defvar help-font-lock-keywords
+; (eval-when-compile
+; (let ((name-char "[-+a-zA-Z0-9_*]") (sym-char "[-+a-zA-Z0-9_:*]"))
+; (list
+; ;;
+; ;; The symbol itself.
+; (list (concat "\\`\\(" name-char "+\\)\\(\\(:\\)\\|\\('\\)\\)")
+; '(1 (if (match-beginning 3)
+; font-lock-function-name-face
+; font-lock-variable-name-face)))
+; ;;
+; ;; Words inside `' which tend to be symbol names.
+; (list (concat "`\\(" sym-char sym-char "+\\)'")
+; 1 'font-lock-constant-face t)
+; ;;
+; ;; CLisp `:' keywords as references.
+; (list (concat "\\<:" sym-char "+\\>") 0 'font-lock-builtin-face t))))
+; "Default expressions to highlight in Help mode.")
+
+(defvar help-xref-stack nil
+ "A stack of ways by which to return to help buffers after following xrefs.
+Used by `help-follow' and `help-xref-go-back'.
+An element looks like (POSITION FUNCTION ARGS...).
+To use the element, do (apply FUNCTION ARGS) then (goto-char POSITION).")
+(put 'help-xref-stack 'permanent-local t)
+
+(defvar help-xref-stack-item nil
+ "An item for `help-follow' in this buffer to push onto `help-xref-stack'.
+The format is (FUNCTION ARGS...).")
+(put 'help-xref-stack-item 'permanent-local t)
+
+(setq-default help-xref-stack nil help-xref-stack-item nil)
(defun help-mode ()
- "Major mode for viewing help text.
+ "Major mode for viewing help text and navigating references in it.
Entry to this mode runs the normal hook `help-mode-hook'.
Commands:
\\{help-mode-map}"
(setq mode-name "Help")
(setq major-mode 'help-mode)
(make-local-variable 'font-lock-defaults)
- (setq font-lock-defaults '(help-font-lock-keywords))
+ (setq font-lock-defaults nil) ; font-lock would defeat xref
(view-mode)
+ (make-local-variable 'view-no-disable-on-exit)
+ (setq view-no-disable-on-exit t)
+ ;; `help-make-xrefs' would be run here if not invoked from
+ ;; `help-mode-maybe'.
(run-hooks 'help-mode-hook))
+(defun help-mode-maybe ()
+ (if (eq major-mode 'fundamental-mode)
+ (help-mode))
+ (when (eq major-mode 'help-mode)
+ ;; View mode's read-only status of existing *Help* buffer is lost
+ ;; by with-output-to-temp-buffer.
+ (toggle-read-only 1)
+ (help-make-xrefs (current-buffer)))
+ (setq view-return-to-alist
+ (list (cons (selected-window) help-return-method))))
+
+(add-hook 'temp-buffer-show-hook 'help-mode-maybe)
+
(defun help-quit ()
(interactive)
nil)
(defun help-with-tutorial (&optional arg)
"Select the Emacs learn-by-doing tutorial.
-A tutorial written in the current primary language is selected.
-If there's no tutorial in the language, \"TUTORIAL\" is selected.
-With arg, users are asked to select language."
+If there is a tutorial version written in the language
+of the selected language environment, that version is used.
+If there's no tutorial in that language, `TUTORIAL' is selected.
+With arg, you are asked to choose which language."
(interactive "P")
- (let (lang filename file)
- (if arg
- (or (setq lang (read-language-name 'tutorial "Language: "))
- (error "No tutorial file of the specified language"))
- (setq lang primary-language))
- (setq filename (or (get-language-info lang 'tutorial)
- "TUTORIAL"))
+ (let ((lang (if arg
+ (read-language-name 'tutorial "Language: " "English")
+ (if (get-language-info current-language-environment 'tutorial)
+ current-language-environment
+ "English")))
+ file filename)
+ (setq filename (get-language-info lang 'tutorial))
(setq file (expand-file-name (concat "~/" filename)))
(delete-other-windows)
(if (get-file-buffer file)
"Print the name of the function KEY invokes. KEY is a string.
If INSERT (the prefix arg) is non-nil, insert the message in the buffer."
(interactive "kDescribe key briefly: \nP")
- ;; If this key seq ends with a down event, discard the
- ;; following click or drag event. Otherwise that would
- ;; erase the message.
- (let ((type (aref key (1- (length key)))))
- (if (listp type) (setq type (car type)))
- (and (symbolp type)
- (memq 'down (event-modifiers type))
- (read-event)))
(save-excursion
(let ((modifiers (event-modifiers (aref key 0)))
(standard-output (if insert (current-buffer) t))
(if (or (null defn) (integerp defn))
(princ (format "%s is undefined" key-desc))
(princ (format (if insert
- "%s (%s)"
+ "`%s' (`%s')"
(if (windowp window)
"%s at that spot runs the command %s"
"%s runs the command %s"))
key-desc
(if (symbolp defn) defn (prin1-to-string defn)))))))))
+(defvar help-return-method nil
+ "What to do to \"exit\" the help buffer.
+This is a list
+ (WINDOW . t) delete the selected window, go to WINDOW.
+ (WINDOW . quit-window) do quit-window, then select WINDOW.
+ (WINDOW BUF START POINT) display BUF at START, POINT, then select WINDOW.")
+
(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.
(and (not (get-buffer-window standard-output))
(let ((first-message
(cond ((special-display-p (buffer-name standard-output))
+ (setq help-return-method (cons (selected-window) t))
;; If the help output buffer is a special display buffer,
;; don't say anything about how to get rid of it.
;; First of all, the user will do that with the window
;; so we don't know whether its frame will be selected.
nil)
((not (one-window-p t))
+ (setq help-return-method
+ (cons (selected-window) 'quit-window))
"Type \\[switch-to-buffer-other-window] RET to restore the other window.")
(pop-up-windows
+ (setq help-return-method (cons (selected-window) t))
"Type \\[delete-other-windows] to remove help window.")
(t
+ (setq help-return-method
+ (list (selected-window) (window-buffer)
+ (window-start) (window-point)))
"Type \\[switch-to-buffer] RET to remove help window."))))
(funcall (or function 'message)
(concat
(defun describe-key (key)
"Display documentation of the function invoked by KEY. KEY is a string."
(interactive "kDescribe key: ")
- ;; If this key seq ends with a down event, discard the
- ;; following click or drag event. Otherwise that would
- ;; erase the message.
- (let ((type (aref key (1- (length key)))))
- (if (listp type) (setq type (car type)))
- (and (symbolp type)
- (memq 'down (event-modifiers type))
- (read-event)))
(save-excursion
(let ((modifiers (event-modifiers (aref key 0)))
window position)
(princ " at that spot"))
(princ " runs the command ")
(prin1 defn)
- (princ ":\n")
- (let ((doc (documentation defn)))
- (if doc
- (progn (terpri)
- (princ doc))
- (princ "not documented")))
- (save-excursion
- (set-buffer standard-output)
- (help-mode))
+ (princ "\n which is ")
+ (describe-function-1 defn nil)
(print-help-return-message)))))))
(defun describe-mode ()
(princ mode-name)
(princ " mode:\n")
(princ (documentation major-mode))
- (save-excursion
- (set-buffer standard-output)
- (help-mode))
+ (help-setup-xref (list #'help-xref-mode (current-buffer)) (interactive-p))
(print-help-return-message)))
;; So keyboard macro definitions are documented correctly
;; run describe-prefix-bindings.
(setq prefix-help-command 'describe-prefix-bindings)
-(defun view-emacs-news ()
- "Display info on recent changes to Emacs."
- (interactive)
- (find-file-read-only (expand-file-name "NEWS" data-directory)))
+(defun view-emacs-news (&optional arg)
+ "Display info on recent changes to Emacs.
+With numeric argument display information on correspondingly older changes."
+ (interactive "P")
+ (let* ((arg (if arg (prefix-numeric-value arg) 0)))
+ (find-file-read-only
+ (expand-file-name (concat (make-string arg ?O) "NEWS")
+ data-directory))))
(defun view-emacs-FAQ ()
"Display the Emacs Frequently Asked Questions (FAQ) file."
(while (progn (move-to-column 50) (not (eobp)))
(search-forward " " nil t)
(insert "\n"))
- (help-mode))
+ (setq help-xref-stack nil
+ help-xref-stack-item nil))
(print-help-return-message)))
(defalias 'help 'help-for-help)
(make-help-screen help-for-help
- "a b c f C-f i k C-k l m n p s t v w C-c C-d C-n C-w, or ? for more help:"
+ "a b c C f F C-f i I k C-k l L m n p s t v w C-c C-d C-n C-p C-w; ? for help:"
"You have typed \\[help-command], the help character. Type a Help option:
\(Use SPC or DEL to scroll through this text. Type \\<help-map>\\[help-quit] to exit the Help 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.
+C describe-coding-system. This describes either a specific coding system
+ (if you type its name) or the coding systems currently in use
+ (if you type just RET).
f describe-function. Type a function name and get documentation of it.
C-f Info-goto-emacs-command-node. Type a function name;
it takes you to the Info node for that command.
-F view-emacs-FAQ. Shows emacs frequently asked questions file.
i info. The info documentation reader.
+I describe-input-method. Describe a specific input method (if you type
+ its name) or the current input method (if you type just RET).
k describe-key. Type a command key sequence;
it displays the full documentation.
C-k Info-goto-emacs-key-command-node. Type a command key sequence;
it takes you to the Info node for the command bound to that key.
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.
+L describe-language-environment. This describes either the a
+ specific language environment (if you type its name)
+ or the current language environment (if you type just RET).
+m describe-mode. Print documentation of current minor modes,
+ and the current major mode, including their special commands.
n view-emacs-news. Shows emacs news file.
p finder-by-keyword. Find packages matching a given topic keyword.
s describe-syntax. Display contents of syntax table, plus explanations
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-p print information about the GNU project.
-C-w print information on absence of warranty for GNU Emacs."
+
+F Display the frequently asked questions file.
+h Display the HELLO file which illustrates various scripts.
+C-c Display Emacs copying permission (General Public License).
+C-d Display Emacs ordering information.
+C-n Display news of recent Emacs changes.
+C-p Display information about the GNU project.
+C-w Display information on absence of warranty for GNU Emacs."
help-map)
;; 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 ()
- (let ((stab (syntax-table)))
- (unwind-protect
+ (let ((stab (syntax-table)))
+ (set-syntax-table emacs-lisp-mode-syntax-table)
+ (unwind-protect
+ (or (condition-case ()
+ (save-excursion
+ (save-restriction
+ (narrow-to-region (max (point-min) (- (point) 1000)) (point-max))
+ ;; Move up to surrounding paren, then after the open.
+ (backward-up-list 1)
+ (forward-char 1)
+ ;; If there is space here, this is probably something
+ ;; other than a real Lisp function call, so ignore it.
+ (if (looking-at "[ \t]")
+ (error "Probably not a Lisp function call"))
+ (let (obj)
+ (setq obj (read (current-buffer)))
+ (and (symbolp obj) (fboundp obj) obj))))
+ (error nil))
+ (condition-case ()
(save-excursion
- (set-syntax-table emacs-lisp-mode-syntax-table)
(or (not (zerop (skip-syntax-backward "_w")))
(eq (char-syntax (following-char)) ?w)
(eq (char-syntax (following-char)) ?_)
(skip-chars-forward "'")
(let ((obj (read (current-buffer))))
(and (symbolp obj) (fboundp obj) obj)))
- (set-syntax-table stab)))
- (error nil))))
+ (error nil)))
+ (set-syntax-table stab))))
(defun describe-function-find-file (function)
(let ((files load-history)
(setq val (completing-read (if fn
(format "Describe function (default %s): " fn)
"Describe function: ")
- obarray 'fboundp t))
+ obarray 'fboundp t nil nil (symbol-name fn)))
(list (if (equal val "")
fn (intern val)))))
(if function
(with-output-to-temp-buffer "*Help*"
(prin1 function)
- (princ ": ")
- (let* ((def (symbol-function function))
- file-name
- (beg (if (commandp def) "an interactive " "a ")))
- (princ (cond ((or (stringp def)
- (vectorp def))
- "a keyboard macro")
- ((subrp def)
- (concat beg "built-in function"))
- ((byte-code-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)
- (setq file-name (nth 1 def))
- (format "%s autoloaded Lisp %s"
- (if (commandp def) "an interactive" "an")
- (if (nth 4 def) "macro" "function")
- ))
- (t "")))
- (or file-name
- (setq file-name (describe-function-find-file function)))
- (if file-name
- (progn
- (princ " in `")
- ;; We used to add .el to the file name,
- ;; but that's completely wrong when the user used load-file.
- (princ file-name)
- (princ "'")))
- (princ ".")
- (terpri)
- (let ((arglist (cond ((byte-code-function-p def)
- (car (append def nil)))
- ((eq (car-safe def) 'lambda)
- (nth 1 def))
- (t t))))
- (if (listp arglist)
- (progn
- (princ (cons function
- (mapcar (lambda (arg)
- (if (memq arg '(&optional &rest))
- arg
- (intern (upcase (symbol-name arg)))))
- arglist)))
- (terpri))))
- (let ((doc (documentation function)))
- (if doc
- (progn (terpri)
- (princ doc))
- (princ "not documented"))))
+ ;; Use " is " instead of a colon so that
+ ;; it is easier to get out the function name using forward-sexp.
+ (princ " is ")
+ (describe-function-1 function nil)
(print-help-return-message)
(save-excursion
(set-buffer standard-output)
- (help-mode)
;; Return the text we displayed.
(buffer-string)))
(message "You didn't specify a function")))
+(defun describe-function-1 (function parens)
+ (let* ((def (symbol-function function))
+ file-name string need-close
+ (beg (if (commandp def) "an interactive " "a ")))
+ (setq string
+ (cond ((or (stringp def)
+ (vectorp def))
+ "a keyboard macro")
+ ((subrp def)
+ (concat beg "built-in function"))
+ ((byte-code-function-p def)
+ (concat beg "compiled Lisp function"))
+ ((symbolp def)
+ (while (symbolp (symbol-function def))
+ (setq def (symbol-function 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)
+ (setq file-name (nth 1 def))
+ (format "%s autoloaded Lisp %s"
+ (if (commandp def) "an interactive" "an")
+ (if (nth 4 def) "macro" "function")
+ ))
+ (t "")))
+ (when (and parens (not (equal string "")))
+ (setq need-close t)
+ (princ "("))
+ (princ string)
+ (or file-name
+ (setq file-name (describe-function-find-file function)))
+ (if file-name
+ (progn
+ (princ " in `")
+ ;; We used to add .el to the file name,
+ ;; but that's completely wrong when the user used load-file.
+ (princ file-name)
+ (princ "'")
+ ;; Make a hyperlink to the library.
+ (with-current-buffer "*Help*"
+ (save-excursion
+ (re-search-backward "`\\([^`']+\\)'" nil t)
+ (help-xref-button 1 #'(lambda (arg)
+ (let ((location
+ (find-function-noselect arg)))
+ (pop-to-buffer (car location))
+ (goto-char (cdr location))))
+ function)))))
+ (if need-close (princ ")"))
+ (princ ".")
+ (terpri)
+ ;; Handle symbols aliased to other symbols.
+ (setq def (indirect-function def))
+ ;; If definition is a macro, find the function inside it.
+ (if (eq (car-safe def) 'macro)
+ (setq def (cdr def)))
+ (let ((arglist (cond ((byte-code-function-p def)
+ (car (append def nil)))
+ ((eq (car-safe def) 'lambda)
+ (nth 1 def))
+ (t t))))
+ (if (listp arglist)
+ (progn
+ (princ (cons function
+ (mapcar (lambda (arg)
+ (if (memq arg '(&optional &rest))
+ arg
+ (intern (upcase (symbol-name arg)))))
+ arglist)))
+ (terpri))))
+ (let ((doc (documentation function)))
+ (if doc
+ (progn (terpri)
+ (princ doc)
+ (help-setup-xref (list #'describe-function function) (interactive-p)))
+ (princ "not documented")))))
+
;; We return 0 if we can't find a variable to return.
(defun variable-at-point ()
(condition-case ()
(setq val (completing-read (if (symbolp v)
(format "Describe variable (default %s): " v)
"Describe variable: ")
- obarray 'boundp t))
+ obarray 'boundp t nil nil
+ (if (symbolp v) (symbol-name v))))
(list (if (equal val "")
v (intern val)))))
(if (symbolp variable)
(terpri)
(let ((doc (documentation-property variable 'variable-documentation)))
(princ (or doc "not documented as a variable.")))
+ (help-setup-xref (list #'describe-variable variable) (interactive-p))
+
+ ;; Make a link to customize if this variable can be customized.
+ ;; Note, it is not reliable to test for a custom-type property
+ ;; because those are only present after the var's definition
+ ;; has been loaded.
+ (if (user-variable-p variable)
+ (let ((customize-label "customize"))
+ (terpri)
+ (terpri)
+ (princ (concat "You can " customize-label " this variable."))
+ (with-current-buffer "*Help*"
+ (save-excursion
+ (re-search-backward
+ (concat "\\(" customize-label "\\)") nil t)
+ (help-xref-button 1 #'(lambda (v)
+ (customize-variable v)) variable)
+ ))))
+
(print-help-return-message)
(save-excursion
(set-buffer standard-output)
- (help-mode)
;; Return the text we displayed.
(buffer-string))))
(message "You did not specify a variable")))
+(defun describe-bindings (&optional prefix buffer)
+ "Show a list of all defined keys, and their definitions.
+We put that list in a buffer, and display the buffer.
+
+The optional argument PREFIX, if non-nil, should be a key sequence;
+then we display only bindings that start with that prefix.
+The optional argument BUFFER specifies which buffer's bindings
+to display (default, the current buffer)."
+ (interactive "P")
+ (or buffer (setq buffer (current-buffer)))
+ (with-current-buffer buffer
+ (describe-bindings-internal nil prefix))
+ (with-current-buffer "*Help*"
+ (help-setup-xref (list #'describe-bindings prefix buffer)
+ (interactive-p))))
+
(defun where-is (definition &optional insert)
"Print message listing key sequences that invoke specified command.
Argument is a command definition, usually a symbol with a function definition.
(throw 'answer try)))))
(if nosuffix
'("")
- (let ((basic '(".elc" ".el" ""))
- (compressed '(".Z" ".gz" "")))
- ;; If autocompression mode is on,
- ;; consider all combinations of library suffixes
- ;; and compression suffixes.
- (if (rassq 'jka-compr-handler file-name-handler-alist)
- (apply 'nconc
- (mapcar (lambda (compelt)
- (mapcar (lambda (baselt)
- (concat baselt compelt))
- basic))
- compressed))
- basic)))))
+ '(".elc" ".el" "")
+;;; load doesn't handle this yet.
+;;; (let ((basic '(".elc" ".el" ""))
+;;; (compressed '(".Z" ".gz" "")))
+;;; ;; If autocompression mode is on,
+;;; ;; consider all combinations of library suffixes
+;;; ;; and compression suffixes.
+;;; (if (rassq 'jka-compr-handler file-name-handler-alist)
+;;; (apply 'nconc
+;;; (mapcar (lambda (compelt)
+;;; (mapcar (lambda (baselt)
+;;; (concat baselt compelt))
+;;; basic))
+;;; compressed))
+;;; basic))
+ )))
(or path load-path)))
(and interactive-call
(if result
(message "No library %s in search path" library)))
result))
+\f
+;;; Grokking cross-reference information in doc strings and
+;;; hyperlinking it.
+
+;; This may have some scope for extension and the same or something
+;; similar should be done for widget doc strings, which currently use
+;; another mechanism.
+
+(defcustom help-highlight-p t
+ "*If non-nil, `help-make-xrefs' highlight cross-references.
+Under a window system it highlights them with face defined by
+`help-highlight-face'. On a character terminal highlighted
+references look like cross-references in info mode."
+ :group 'help
+ :version "20.3"
+ :type 'boolean)
+
+(defcustom help-highlight-face 'underline
+ "Face used by `help-make-xrefs' to highlight cross-references.
+Must be previously-defined."
+ :group 'help
+ :version "20.3"
+ :type 'face)
+
+(defvar help-back-label "[back]"
+ "Label to use by `help-make-xrefs' for the go-back reference.")
+
+(defvar help-xref-symbol-regexp
+ (concat "\\(\\<\\(\\(variable\\|option\\)\\|"
+ "\\(function\\|command\\)\\|"
+ "\\(symbol\\)\\)\\s-+\\)?"
+ ;; Note starting with word-syntax character:
+ "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'")
+ "Regexp matching doc string references to symbols.
+
+The words preceding the quoted symbol can be used in doc strings to
+distinguish references to variables, functions and symbols.")
+
+(defvar help-xref-info-regexp
+ "\\<info\\s-+node\\s-`\\([^']+\\)'"
+ "Regexp matching doc string references to an Info node.")
+
+(defun help-setup-xref (item interactive-p)
+ "Invoked from commands using the \"*Help*\" buffer to install some xref info.
+
+ITEM is a (FUNCTION . ARGS) pair appropriate for recreating the help
+buffer after following a reference. INTERACTIVE-P is non-nil if the
+calling command was invoked interactively. In this case the stack of
+items for help buffer \"back\" buttons is cleared."
+ (if interactive-p
+ (setq help-xref-stack nil))
+ (setq help-xref-stack-item item))
+
+(defun help-make-xrefs (&optional buffer)
+ "Parse and hyperlink documentation cross-references in the given BUFFER.
+
+Find cross-reference information in a buffer and, if
+`help-highlight-p' is non-nil, highlight it with face defined by
+`help-highlight-face'; activate such cross references for selection
+with `help-follow'. Cross-references have the canonical form `...'
+and the type of reference may be disambiguated by the preceding
+word(s) used in `help-xref-symbol-regexp'.
+
+A special reference `back' is made to return back through a stack of
+help buffers. Variable `help-back-label' specifies the text for
+that."
+ (interactive "b")
+ (save-excursion
+ (set-buffer (or buffer (current-buffer)))
+ (goto-char (point-min))
+ ;; Skip the header-type info, though it might be useful to parse
+ ;; it at some stage (e.g. "function in `library'").
+ (forward-paragraph)
+ (let ((old-modified (buffer-modified-p)))
+ (let ((stab (syntax-table))
+ (case-fold-search t)
+ (inhibit-read-only t))
+ (set-syntax-table emacs-lisp-mode-syntax-table)
+ ;; The following should probably be abstracted out.
+ (unwind-protect
+ (progn
+ ;; Quoted symbols
+ (save-excursion
+ (while (re-search-forward help-xref-symbol-regexp nil t)
+ (let* ((data (match-string 6))
+ (sym (intern-soft data)))
+ (if sym
+ (cond
+ ((match-string 3) ; `variable' &c
+ (and (boundp sym) ; `variable' doesn't ensure
+ ; it's actually bound
+ (help-xref-button 6 #'describe-variable sym)))
+ ((match-string 4) ; `function' &c
+ (and (fboundp sym) ; similarly
+ (help-xref-button 6 #'describe-function sym)))
+ ((match-string 5)) ; nothing for symbol
+ ((and (boundp sym) (fboundp sym))
+ ;; We can't intuit whether to use the
+ ;; variable or function doc -- supply both.
+ (help-xref-button 6 #'help-xref-interned sym))
+ ((boundp sym)
+ (help-xref-button 6 #'describe-variable sym))
+ ((fboundp sym)
+ (help-xref-button 6 #'describe-function sym)))))))
+ ;; Info references
+ (save-excursion
+ (while (re-search-forward help-xref-info-regexp nil t)
+ (help-xref-button 1 #'Info-goto-node (list (match-data 1)))))
+ ;; An obvious case of a key substitution:
+ (save-excursion
+ (while (re-search-forward
+ "\\<M-x\\s-+\\(\\sw\\(\\sw\\|\\s_\\)+\\)" nil t)
+ (let ((sym (intern-soft (match-string 1))))
+ (if (fboundp sym)
+ (help-xref-button 1 #'describe-function sym)))))
+ ;; Look for commands in whole keymap substitutions:
+ (save-excursion
+ ;; Make sure to find the first keymap.
+ (goto-char (point-min))
+ ;; Find a header and the column at which the command
+ ;; name will be found.
+ (while (re-search-forward "^key +binding\n\\(-+ +\\)-+\n\n"
+ nil t)
+ (let ((col (- (match-end 1) (match-beginning 1))))
+ (while
+ ;; Ignore single blank lines in table, but not
+ ;; double ones, which should terminate it.
+ (and (looking-at "^\n?[^\n]")
+ (progn
+ (if (and (> (move-to-column col) 0)
+ (looking-at "\\(\\sw\\|\\s_\\)+$"))
+ ;;
+ (let ((sym (intern-soft (match-string 0))))
+ (if (fboundp sym)
+ (help-xref-button
+ 0 #'describe-function sym))))
+ t)
+ (zerop (forward-line))
+ (move-to-column 0)))))))
+ (set-syntax-table stab))
+ ;; Make a back-reference in this buffer if appropriate.
+ (when help-xref-stack
+ (goto-char (point-max))
+ (save-excursion
+ (insert "\n\n" help-back-label))
+ ;; Just to provide the match data:
+ (looking-at (concat "\n\n\\(" (regexp-quote help-back-label) "\\)"))
+ (help-xref-button 1 #'help-xref-go-back (current-buffer))))
+ ;; View mode steals RET from us.
+ (set (make-local-variable 'minor-mode-overriding-map-alist)
+ (list (cons 'view-mode
+ (let ((map (make-sparse-keymap)))
+ (set-keymap-parent map view-mode-map)
+ (define-key map "\r" 'help-follow)
+ map))))
+ (set-buffer-modified-p old-modified))))
+
+(defun help-xref-button (match-number function data)
+ "Make a hyperlink for cross-reference text previously matched.
+
+MATCH-NUMBER is the subexpression of interest in the last matched
+regexp. FUNCTION is a function to invoke when the button is
+activated, applied to DATA. DATA may be a single value or a list.
+See `help-make-xrefs'."
+ (add-text-properties (match-beginning match-number)
+ (match-end match-number)
+ (list 'mouse-face 'highlight
+ 'help-xref (cons function
+ (if (listp data)
+ data
+ (list data)))))
+ (if help-highlight-p
+ (put-text-property (match-beginning match-number)
+ (match-end match-number)
+ 'face help-highlight-face)))
+
+\f
+;; Additional functions for (re-)creating types of help buffers.
+(defun help-xref-interned (symbol)
+ "Follow a hyperlink which appeared to be an arbitrary interned SYMBOL.
+
+Both variable and function documentation are extracted into a single
+help buffer."
+ (let ((fdoc (describe-function symbol)))
+ (describe-variable symbol)
+ ;; We now have a help buffer on the variable. Insert the function
+ ;; text after it.
+ (goto-char (point-max))
+ (insert "\n\n" fdoc))
+ (goto-char (point-min))
+ (help-setup-xref (list #'help-xref-interned symbol) nil))
+
+(defun help-xref-mode (buffer)
+ "Do a `describe-mode' for the specified BUFFER."
+ (save-excursion
+ (set-buffer buffer)
+ (describe-mode)))
+\f
+;;; Navigation/hyperlinking with xrefs
+
+(defun help-follow-mouse (click)
+ "Follow the cross-reference that you click on."
+ (interactive "e")
+ (let* ((start (event-start click))
+ (window (car start))
+ (pos (car (cdr start))))
+ (with-current-buffer (window-buffer window)
+ (help-follow pos))))
+
+(defun help-xref-go-back (buffer)
+ "Go back to the previous help buffer text using info on `help-xref-stack'."
+ (interactive)
+ (let (item position method args)
+ (with-current-buffer buffer
+ (when help-xref-stack
+ (setq help-xref-stack (cdr help-xref-stack)) ; due to help-follow
+ (setq item (car help-xref-stack)
+ position (car item)
+ method (cadr item)
+ args (cddr item))
+ (setq help-xref-stack (cdr help-xref-stack))))
+ (apply method args)
+ (goto-char position)))
+
+(defun help-go-back ()
+ (interactive)
+ (help-follow (1- (point-max))))
+
+(defun help-follow (&optional pos)
+ "Follow cross-reference at POS, defaulting to point.
+
+For the cross-reference format, see `help-make-xrefs'."
+ (interactive "d")
+ (let* ((help-data (or (and (not (= pos (point-max)))
+ (get-text-property pos 'help-xref))
+ (and (not (= pos (point-min)))
+ (get-text-property (1- pos) 'help-xref))))
+ (method (car help-data))
+ (args (cdr help-data)))
+ (setq help-xref-stack (cons (cons (point) help-xref-stack-item)
+ help-xref-stack))
+ (setq help-xref-stack-item nil)
+ (when help-data
+ ;; There is a reference at point. Follow it.
+ (apply method args))))
+
+;; For tabbing through buffer.
+(defun help-next-ref ()
+ "Find the next help cross-reference in the buffer."
+ (interactive)
+ (let (pos)
+ (while (not pos)
+ (if (get-text-property (point) 'help-xref) ; move off reference
+ (goto-char (or (next-single-property-change (point) 'help-xref)
+ (point))))
+ (cond ((setq pos (next-single-property-change (point) 'help-xref))
+ (if pos (goto-char pos)))
+ ((bobp)
+ (message "No cross references in the buffer.")
+ (setq pos t))
+ (t ; be circular
+ (goto-char (point-min)))))))
+
+(defun help-previous-ref ()
+ "Find the previous help cross-reference in the buffer."
+ (interactive)
+ (let (pos)
+ (while (not pos)
+ (if (get-text-property (point) 'help-xref) ; move off reference
+ (goto-char (or (previous-single-property-change (point) 'help-xref)
+ (point))))
+ (cond ((setq pos (previous-single-property-change (point) 'help-xref))
+ (if pos (goto-char pos)))
+ ((bobp)
+ (message "No cross references in the buffer.")
+ (setq pos t))
+ (t ; be circular
+ (goto-char (point-max)))))))
+
;;; help.el ends here