1;;; eldoc.el --- show function arglist or variable docstring in echo area
2
3;; Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 Free Software Foundation, Inc.
5
6;; Author: Noah Friedman <friedman@splode.com>
7;; Maintainer: friedman@splode.com
8;; Keywords: extensions
9;; Created: 1995-10-06
10
11;; This file is part of GNU Emacs.
12
13;; GNU Emacs is free software; you can redistribute it and/or modify
14;; it under the terms of the GNU General Public License as published by
15;; the Free Software Foundation; either version 2, or (at your option)
16;; any later version.
17
18;; GNU Emacs is distributed in the hope that it will be useful,
19;; but WITHOUT ANY WARRANTY; without even the implied warranty of
20;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
21;; GNU General Public License for more details.
22
23;; You should have received a copy of the GNU General Public License
24;; along with GNU Emacs; see the file COPYING.  If not, write to the
25;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
26;; Boston, MA 02110-1301, USA.
27
28;;; Commentary:
29
30;; This program was inspired by the behavior of the "mouse documentation
31;; window" on many Lisp Machine systems; as you type a function's symbol
32;; name as part of a sexp, it will print the argument list for that
33;; function.  Behavior is not identical; for example, you need not actually
34;; type the function name, you need only move point around in a sexp that
35;; calls it.  Also, if point is over a documented variable, it will print
36;; the one-line documentation for that variable instead, to remind you of
37;; that variable's meaning.
38
39;; One useful way to enable this minor mode is to put the following in your
40;; .emacs:
41;;
42;;      (add-hook 'emacs-lisp-mode-hook 'turn-on-eldoc-mode)
43;;      (add-hook 'lisp-interaction-mode-hook 'turn-on-eldoc-mode)
44;;      (add-hook 'ielm-mode-hook 'turn-on-eldoc-mode)
45
46;; Major modes for other languages may use Eldoc by defining an
47;; appropriate function as the buffer-local value of
48;; `eldoc-documentation-function'.
49
50;;; Code:
51
52(require 'help-fns)		       ;For fundoc-usage handling functions.
53
54(defgroup eldoc nil
55  "Show function arglist or variable docstring in echo area."
56  :group 'lisp
57  :group 'extensions)
58
59(defcustom eldoc-idle-delay 0.50
60  "*Number of seconds of idle time to wait before printing.
61If user input arrives before this interval of time has elapsed after the
62last input, no documentation will be printed.
63
64If this variable is set to 0, no idle time is required."
65  :type 'number
66  :group 'eldoc)
67
68;;;###autoload
69(defcustom eldoc-minor-mode-string " ElDoc"
70  "*String to display in mode line when Eldoc Mode is enabled; nil for none."
71  :type '(choice string (const :tag "None" nil))
72  :group 'eldoc)
73
74(defcustom eldoc-argument-case 'upcase
75  "Case to display argument names of functions, as a symbol.
76This has two preferred values: `upcase' or `downcase'.
77Actually, any name of a function which takes a string as an argument and
78returns another string is acceptable."
79  :type '(radio (function-item upcase)
80		(function-item downcase)
81                function)
82  :group 'eldoc)
83
84(defcustom eldoc-echo-area-use-multiline-p 'truncate-sym-name-if-fit
85  "*Allow long eldoc messages to resize echo area display.
86If value is t, never attempt to truncate messages; complete symbol name
87and function arglist or 1-line variable documentation will be displayed
88even if echo area must be resized to fit.
89
90If value is any non-nil value other than t, symbol name may be truncated
91if it will enable the function arglist or documentation string to fit on a
92single line without resizing window.  Otherwise, behavior is just like
93former case.
94
95If value is nil, messages are always truncated to fit in a single line of
96display in the echo area.  Function or variable symbol name may be
97truncated to make more of the arglist or documentation string visible."
98  :type '(radio (const :tag "Always" t)
99                (const :tag "Never" nil)
100                (const :tag "Yes, but truncate symbol names if it will\
101 enable argument list to fit on one line" truncate-sym-name-if-fit))
102  :group 'eldoc)
103
104;;; No user options below here.
105
106(defvar eldoc-message-commands-table-size 31
107  "This is used by eldoc-add-command to initialize eldoc-message-commands
108as an obarray.
109It should probably never be necessary to do so, but if you
110choose to increase the number of buckets, you must do so before loading
111this file since the obarray is initialized at load time.
112Remember to keep it a prime number to improve hash performance.")
113
114(defconst eldoc-message-commands
115  (make-vector eldoc-message-commands-table-size 0)
116  "Commands after which it is appropriate to print in the echo area.
117Eldoc does not try to print function arglists, etc. after just any command,
118because some commands print their own messages in the echo area and these
119functions would instantly overwrite them.  But self-insert-command as well
120as most motion commands are good candidates.
121This variable contains an obarray of symbols; do not manipulate it
122directly.  Instead, use `eldoc-add-command' and `eldoc-remove-command'.")
123
124(defconst eldoc-last-data (make-vector 3 nil)
125  "Bookkeeping; elements are as follows:
126  0 - contains the last symbol read from the buffer.
127  1 - contains the string last displayed in the echo area for that
128      symbol, so it can be printed again if necessary without reconsing.
129  2 - 'function if function args, 'variable if variable documentation.")
130(defvar eldoc-last-message nil)
131
132(defvar eldoc-timer nil "eldoc's timer object.")
133
134(defvar eldoc-current-idle-delay eldoc-idle-delay
135  "idle time delay currently in use by timer.
136This is used to determine if `eldoc-idle-delay' is changed by the user.")
137
138
139;;;###autoload
140(define-minor-mode eldoc-mode
141  "Toggle ElDoc mode on or off.
142In ElDoc mode, the echo area displays information about a
143function or variable in the text where point is.  If point is
144on a documented variable, it displays the first line of that
145variable's doc string.  Otherwise it displays the argument list
146of the function called in the expression point is on.
147
148With prefix ARG, turn ElDoc mode on if and only if ARG is positive."
149  :group 'eldoc :lighter eldoc-minor-mode-string
150  (setq eldoc-last-message nil)
151  (if eldoc-mode
152      (progn
153	(add-hook 'post-command-hook 'eldoc-schedule-timer nil t)
154	(add-hook 'pre-command-hook 'eldoc-pre-command-refresh-echo-area t))
155   (remove-hook 'post-command-hook 'eldoc-schedule-timer)
156   (remove-hook 'pre-command-hook 'eldoc-pre-command-refresh-echo-area)))
157
158;;;###autoload
159(defun turn-on-eldoc-mode ()
160  "Unequivocally turn on ElDoc mode (see command `eldoc-mode')."
161  (interactive)
162  (eldoc-mode 1))
163
164
165(defun eldoc-schedule-timer ()
166  (or (and eldoc-timer
167           (memq eldoc-timer timer-idle-list))
168      (setq eldoc-timer
169            (run-with-idle-timer eldoc-idle-delay t
170                                 'eldoc-print-current-symbol-info)))
171
172  ;; If user has changed the idle delay, update the timer.
173  (cond ((not (= eldoc-idle-delay eldoc-current-idle-delay))
174         (setq eldoc-current-idle-delay eldoc-idle-delay)
175         (timer-set-idle-time eldoc-timer eldoc-idle-delay t))))
176
177(defun eldoc-message (&rest args)
178  (let ((omessage eldoc-last-message))
179    (setq eldoc-last-message
180	  (cond ((eq (car args) eldoc-last-message) eldoc-last-message)
181		((null (car args)) nil)
182		;; If only one arg, no formatting to do, so put it in
183		;; eldoc-last-message so eq test above might succeed on
184		;; subsequent calls.
185		((null (cdr args)) (car args))
186		(t (apply 'format args))))
187    ;; In emacs 19.29 and later, and XEmacs 19.13 and later, all messages
188    ;; are recorded in a log.  Do not put eldoc messages in that log since
189    ;; they are Legion.
190    ;; Emacs way of preventing log messages.
191    (let ((message-log-max nil))
192      (cond (eldoc-last-message (message "%s" eldoc-last-message))
193	    (omessage (message nil)))))
194  eldoc-last-message)
195
196;; This function goes on pre-command-hook for XEmacs or when using idle
197;; timers in Emacs.  Motion commands clear the echo area for some reason,
198;; which make eldoc messages flicker or disappear just before motion
199;; begins.  This function reprints the last eldoc message immediately
200;; before the next command executes, which does away with the flicker.
201;; This doesn't seem to be required for Emacs 19.28 and earlier.
202(defun eldoc-pre-command-refresh-echo-area ()
203  (and eldoc-last-message
204       (if (eldoc-display-message-no-interference-p)
205           (eldoc-message eldoc-last-message)
206         (setq eldoc-last-message nil))))
207
208;; Decide whether now is a good time to display a message.
209(defun eldoc-display-message-p ()
210  (and (eldoc-display-message-no-interference-p)
211       ;; If this-command is non-nil while running via an idle
212       ;; timer, we're still in the middle of executing a command,
213       ;; e.g. a query-replace where it would be annoying to
214       ;; overwrite the echo area.
215       (and (not this-command)
216	    (symbolp last-command)
217	    (intern-soft (symbol-name last-command)
218			 eldoc-message-commands))))
219
220;; Check various conditions about the current environment that might make
221;; it undesirable to print eldoc messages right this instant.
222(defun eldoc-display-message-no-interference-p ()
223  (and eldoc-mode
224       (not executing-kbd-macro)
225       (not (and (boundp 'edebug-active) edebug-active))
226       ;; Having this mode operate in an active minibuffer/echo area causes
227       ;; interference with what's going on there.
228       (not cursor-in-echo-area)
229       (not (eq (selected-window) (minibuffer-window)))))
230
231
232;;;###autoload
233(defvar eldoc-documentation-function nil
234  "If non-nil, function to call to return doc string.
235The function of no args should return a one-line string for displaying
236doc about a function etc. appropriate to the context around point.
237It should return nil if there's no doc appropriate for the context.
238Typically doc is returned if point is on a function-like name or in its
239arg list.
240
241This variable is expected to be made buffer-local by modes (other than
242Emacs Lisp mode) that support Eldoc.")
243
244(defun eldoc-print-current-symbol-info ()
245  (condition-case err
246      (and (eldoc-display-message-p)
247	   (if eldoc-documentation-function
248	       (eldoc-message (funcall eldoc-documentation-function))
249	     (let* ((current-symbol (eldoc-current-symbol))
250		    (current-fnsym  (eldoc-fnsym-in-current-sexp))
251		    (doc (cond
252			  ((eq current-symbol current-fnsym)
253			   (or (eldoc-get-fnsym-args-string current-fnsym)
254			       (eldoc-get-var-docstring current-symbol)))
255			  (t
256			   (or (eldoc-get-var-docstring current-symbol)
257			       (eldoc-get-fnsym-args-string current-fnsym))))))
258	       (eldoc-message doc))))
259    ;; This is run from post-command-hook or some idle timer thing,
260    ;; so we need to be careful that errors aren't ignored.
261    (error (message "eldoc error: %s" err))))
262
263;; Return a string containing the function parameter list, or 1-line
264;; docstring if function is a subr and no arglist is obtainable from the
265;; docstring or elsewhere.
266(defun eldoc-get-fnsym-args-string (sym)
267  (let ((args nil)
268        (doc nil))
269    (cond ((not (and sym (symbolp sym) (fboundp sym))))
270          ((and (eq sym (aref eldoc-last-data 0))
271                (eq 'function (aref eldoc-last-data 2)))
272           (setq doc (aref eldoc-last-data 1)))
273	  ((setq doc (help-split-fundoc (documentation sym t) sym))
274	   (setq args (car doc))
275	   (string-match "\\`[^ )]* ?" args)
276	   (setq args (concat "(" (substring args (match-end 0)))))
277          (t
278           (setq args (eldoc-function-argstring sym))))
279    (cond (args
280           (setq doc (eldoc-docstring-format-sym-doc sym args))
281           (eldoc-last-data-store sym doc 'function)))
282    doc))
283
284;; Return a string containing a brief (one-line) documentation string for
285;; the variable.
286(defun eldoc-get-var-docstring (sym)
287  (when sym
288    (cond ((and (eq sym (aref eldoc-last-data 0))
289		(eq 'variable (aref eldoc-last-data 2)))
290	   (aref eldoc-last-data 1))
291	  (t
292	   (let ((doc (documentation-property sym 'variable-documentation t)))
293	     (cond (doc
294		    (setq doc (eldoc-docstring-format-sym-doc
295			       sym (eldoc-docstring-first-line doc)))
296		    (eldoc-last-data-store sym doc 'variable)))
297	     doc)))))
298
299(defun eldoc-last-data-store (symbol doc type)
300  (aset eldoc-last-data 0 symbol)
301  (aset eldoc-last-data 1 doc)
302  (aset eldoc-last-data 2 type))
303
304;; Note that any leading `*' in the docstring (which indicates the variable
305;; is a user option) is removed.
306(defun eldoc-docstring-first-line (doc)
307  (and (stringp doc)
308       (substitute-command-keys
309        (save-match-data
310          (let ((start (if (string-match "^\\*" doc) (match-end 0) 0)))
311            (cond ((string-match "\n" doc)
312                   (substring doc start (match-beginning 0)))
313                  ((zerop start) doc)
314                  (t (substring doc start))))))))
315
316;; If the entire line cannot fit in the echo area, the symbol name may be
317;; truncated or eliminated entirely from the output to make room for the
318;; description.
319(defun eldoc-docstring-format-sym-doc (sym doc)
320  (save-match-data
321    (let* ((name (symbol-name sym))
322           (ea-multi eldoc-echo-area-use-multiline-p)
323           ;; Subtract 1 from window width since emacs will not write
324           ;; any chars to the last column, or in later versions, will
325           ;; cause a wraparound and resize of the echo area.
326           (ea-width (1- (window-width (minibuffer-window))))
327           (strip (- (+ (length name) (length ": ") (length doc)) ea-width)))
328      (cond ((or (<= strip 0)
329                 (eq ea-multi t)
330                 (and ea-multi (> (length doc) ea-width)))
331             (format "%s: %s" sym doc))
332            ((> (length doc) ea-width)
333             (substring (format "%s" doc) 0 ea-width))
334            ((>= strip (length name))
335             (format "%s" doc))
336            (t
337             ;; Show the end of the partial symbol name, rather
338             ;; than the beginning, since the former is more likely
339             ;; to be unique given package namespace conventions.
340             (setq name (substring name strip))
341             (format "%s: %s" name doc))))))
342
343
344(defun eldoc-fnsym-in-current-sexp ()
345  (let ((p (point)))
346    (eldoc-beginning-of-sexp)
347    (prog1
348        ;; Don't do anything if current word is inside a string.
349        (if (= (or (char-after (1- (point))) 0) ?\")
350            nil
351          (eldoc-current-symbol))
352      (goto-char p))))
353
354(defun eldoc-beginning-of-sexp ()
355  (let ((parse-sexp-ignore-comments t))
356    (condition-case err
357        (while (progn
358                 (forward-sexp -1)
359                 (or (= (char-before) ?\")
360                     (> (point) (point-min)))))
361      (error nil))))
362
363;; returns nil unless current word is an interned symbol.
364(defun eldoc-current-symbol ()
365  (let ((c (char-after (point))))
366    (and c
367         (memq (char-syntax c) '(?w ?_))
368         (intern-soft (current-word)))))
369
370;; Do indirect function resolution if possible.
371(defun eldoc-symbol-function (fsym)
372  (let ((defn (and (fboundp fsym)
373                   (symbol-function fsym))))
374    (and (symbolp defn)
375         (condition-case err
376             (setq defn (indirect-function fsym))
377           (error (setq defn nil))))
378    defn))
379
380(defun eldoc-function-argstring (fn)
381  (eldoc-function-argstring-format (help-function-arglist fn)))
382
383(defun eldoc-function-argstring-format (arglist)
384  (cond ((not (listp arglist))
385         (setq arglist nil))
386        ((symbolp (car arglist))
387         (setq arglist
388               (mapcar (function (lambda (s)
389                                   (if (memq s '(&optional &rest))
390                                       (symbol-name s)
391                                     (funcall eldoc-argument-case
392                                              (symbol-name s)))))
393                       arglist)))
394        ((stringp (car arglist))
395         (setq arglist
396               (mapcar (function (lambda (s)
397                                   (if (member s '("&optional" "&rest"))
398                                       s
399                                     (funcall eldoc-argument-case s))))
400                       arglist))))
401  (concat "(" (mapconcat 'identity arglist " ") ")"))
402
403
404;; When point is in a sexp, the function args are not reprinted in the echo
405;; area after every possible interactive command because some of them print
406;; their own messages in the echo area; the eldoc functions would instantly
407;; overwrite them unless it is more restrained.
408;; These functions do display-command table management.
409
410(defun eldoc-add-command (&rest cmds)
411  (dolist (name cmds)
412    (and (symbolp name)
413         (setq name (symbol-name name)))
414    (set (intern name eldoc-message-commands) t)))
415
416(defun eldoc-add-command-completions (&rest names)
417  (dolist (name names)
418    (apply 'eldoc-add-command (all-completions name obarray 'commandp))))
419
420(defun eldoc-remove-command (&rest cmds)
421  (dolist (name cmds)
422    (and (symbolp name)
423         (setq name (symbol-name name)))
424    (unintern name eldoc-message-commands)))
425
426(defun eldoc-remove-command-completions (&rest names)
427  (dolist (name names)
428    (apply 'eldoc-remove-command
429           (all-completions name eldoc-message-commands))))
430
431
432;; Prime the command list.
433(eldoc-add-command-completions
434 "backward-" "beginning-of-" "move-beginning-of-" "delete-other-windows"
435 "delete-window" "handle-select-window"
436 "end-of-" "move-end-of-" "exchange-point-and-mark" "forward-"
437 "indent-for-tab-command" "goto-" "mark-page" "mark-paragraph"
438 "mouse-set-point" "move-" "pop-global-mark" "next-" "other-window"
439 "previous-" "recenter" "scroll-" "self-insert-command"
440 "split-window-" "up-list" "down-list")
441
442(provide 'eldoc)
443
444;; arch-tag: c9a58f9d-2055-46c1-9b82-7248b71a8375
445;;; eldoc.el ends here
446