1;;; ehelp.el --- bindings for electric-help mode
2
3;; Copyright (C) 1986, 1995, 2000, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 Free Software Foundation, Inc.
5
6;; Maintainer: FSF
7;; Keywords: help, extensions
8
9;; This file is part of GNU Emacs.
10
11;; GNU Emacs is free software; you can redistribute it and/or modify
12;; it under the terms of the GNU General Public License as published by
13;; the Free Software Foundation; either version 2, or (at your option)
14;; any later version.
15
16;; GNU Emacs is distributed in the hope that it will be useful,
17;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19;; GNU General Public License for more details.
20
21;; You should have received a copy of the GNU General Public License
22;; along with GNU Emacs; see the file COPYING.  If not, write to the
23;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
24;; Boston, MA 02110-1301, USA.
25
26;;; Commentary:
27
28;; This package provides a pre-packaged `Electric Help Mode' for
29;; browsing on-line help screens.  There is one entry point,
30;; `with-electric-help'; all you have to give it is a no-argument
31;; function that generates the actual text of the help into the current
32;; buffer.
33
34;; To make this the default, you must do
35;; (require 'ehelp)
36;; (define-key global-map "\C-h" 'ehelp-command)
37;; (define-key global-map [help] 'ehelp-command)
38;; (define-key global-map [f1] 'ehelp-command)
39
40;;; Code:
41
42(require 'electric)
43(defvar electric-help-map ()
44  "Keymap defining commands available in `electric-help-mode'.")
45
46(defvar electric-help-form-to-execute nil)
47
48(defgroup electric-help ()
49  "Electric help facility."
50  :version "21.1"
51  :group 'help)
52
53(defcustom electric-help-shrink-window t
54  "If set, adjust help window sizes to buffer sizes when displaying help."
55  :type 'boolean
56  :group 'electric-help)
57
58(defcustom electric-help-mode-hook nil
59  "Hook run by `with-electric-help' after initializing the buffer."
60  :type 'hook
61  :group 'electric-help)
62
63(put 'electric-help-undefined 'suppress-keymap t)
64(if electric-help-map
65    ()
66  (let ((map (make-keymap)))
67    ;; allow all non-self-inserting keys - search, scroll, etc, but
68    ;; let M-x and C-x exit ehelp mode and retain buffer:
69    (suppress-keymap map)
70    (define-key map "\C-u" 'electric-help-undefined)
71    (define-key map [?\C-0] 'electric-help-undefined)
72    (define-key map [?\C-1] 'electric-help-undefined)
73    (define-key map [?\C-2] 'electric-help-undefined)
74    (define-key map [?\C-3] 'electric-help-undefined)
75    (define-key map [?\C-4] 'electric-help-undefined)
76    (define-key map [?\C-5] 'electric-help-undefined)
77    (define-key map [?\C-6] 'electric-help-undefined)
78    (define-key map [?\C-7] 'electric-help-undefined)
79    (define-key map [?\C-8] 'electric-help-undefined)
80    (define-key map [?\C-9] 'electric-help-undefined)
81    (define-key map (char-to-string help-char) 'electric-help-help)
82    (define-key map "?" 'electric-help-help)
83    (define-key map " " 'scroll-up)
84    (define-key map "\^?" 'scroll-down)
85    (define-key map "." 'beginning-of-buffer)
86    (define-key map "<" 'beginning-of-buffer)
87    (define-key map ">" 'end-of-buffer)
88    ;(define-key map "\C-g" 'electric-help-exit)
89    (define-key map "Q" 'electric-help-exit)
90    (define-key map "q" 'electric-help-exit)
91    ;;a better key than this?
92    (define-key map "R" 'electric-help-retain)
93    (define-key map "r" 'electric-help-retain)
94    (define-key map "\ex" 'electric-help-execute-extended)
95    (define-key map "\C-x" 'electric-help-ctrl-x-prefix)
96
97    (setq electric-help-map map)))
98
99(defun electric-help-mode ()
100  "`with-electric-help' temporarily places its buffer in this mode.
101\(On exit from `with-electric-help', the buffer is put in `default-major-mode'.)"
102  (setq buffer-read-only t)
103  (setq mode-name "Help")
104  (setq major-mode 'help)
105  (setq mode-line-buffer-identification '(" Help:  %b"))
106  (use-local-map electric-help-map)
107  (add-hook 'mouse-leave-buffer-hook 'electric-help-retain)
108  (view-mode -1)
109  ;; this is done below in with-electric-help
110  ;(run-hooks 'electric-help-mode-hook)
111  )
112
113;;;###autoload
114(defun with-electric-help (thunk &optional buffer noerase minheight)
115  "Pop up an \"electric\" help buffer.
116THUNK is a function of no arguments which is called to initialize the
117contents of BUFFER.  BUFFER defaults to `*Help*'.  BUFFER will be
118erased before THUNK is called unless NOERASE is non-nil.  THUNK will
119be called while BUFFER is current and with `standard-output' bound to
120the buffer specified by BUFFER.
121
122If THUNK returns nil, we display BUFFER starting at the top, and
123shrink the window to fit.  If THUNK returns non-nil, we don't do those things.
124
125After THUNK has been called, this function \"electrically\" pops up a window
126in which BUFFER is displayed and allows the user to scroll through that buffer
127in `electric-help-mode'. The window's height will be at least MINHEIGHT if
128this value is non-nil.
129
130If THUNK returns nil, we display BUFFER starting at the top, and
131shrink the window to fit if `electric-help-shrink-window' is non-nil.
132If THUNK returns non-nil, we don't do those things.
133
134When the user exits (with `electric-help-exit', or otherwise), the help
135buffer's window disappears (i.e., we use `save-window-excursion'), and
136BUFFER is put into `default-major-mode' (or `fundamental-mode')."
137  (setq buffer (get-buffer-create (or buffer "*Help*")))
138  (let ((one (one-window-p t))
139	(config (current-window-configuration))
140        (bury nil)
141        (electric-help-form-to-execute nil))
142    (unwind-protect
143         (save-excursion
144           (when one
145	     (goto-char (window-start (selected-window))))
146           (let ((pop-up-windows t))
147             (pop-to-buffer buffer))
148           (save-excursion
149             (set-buffer buffer)
150             (when (and minheight (< (window-height) minheight))
151	       (enlarge-window (- minheight (window-height))))
152             (electric-help-mode)
153	     (setq buffer-read-only nil)
154	     (unless noerase
155	       (erase-buffer)))
156           (let ((standard-output buffer))
157             (unless (funcall thunk)
158	       (set-buffer buffer)
159	       (set-buffer-modified-p nil)
160	       (goto-char (point-min))
161	       (when (and one electric-help-shrink-window)
162		 (shrink-window-if-larger-than-buffer))))
163           (set-buffer buffer)
164           (run-hooks 'electric-help-mode-hook)
165	   (setq buffer-read-only t)
166           (if (eq (car-safe (electric-help-command-loop)) 'retain)
167               (setq config (current-window-configuration))
168	     (setq bury t))
169	   ;; Remove the hook.
170	   (when (memq 'electric-help-retain mouse-leave-buffer-hook)
171	     (remove-hook 'mouse-leave-buffer-hook 'electric-help-retain)))
172      (message "")
173      (set-buffer buffer)
174      (setq buffer-read-only nil)
175
176      ;; We should really get a usable *Help* buffer when retaining
177      ;; the electric one with `r'.  The problem is that a simple
178      ;; call to help-mode won't cut it; at least RET is bound wrong
179      ;; afterwards.  It's also not clear that `help-mode' is always
180      ;; the right thing, maybe we should add an optional parameter.
181      (condition-case ()
182          (funcall (or default-major-mode 'fundamental-mode))
183        (error nil))
184
185      (set-window-configuration config)
186      (when bury
187	;;>> Perhaps this shouldn't be done,
188	;; so that when we say "Press space to bury" we mean it
189	(replace-buffer-in-windows buffer)
190	;; must do this outside of save-window-excursion
191	(bury-buffer buffer))
192      (eval electric-help-form-to-execute))))
193
194(defun electric-help-command-loop ()
195  (catch 'exit
196    (if (pos-visible-in-window-p (point-max))
197	(progn (message "%s" (substitute-command-keys "<<< Press Space to bury the help buffer, Press \\[electric-help-retain] to retain it >>>"))
198	       (if (equal (setq unread-command-events (list (read-event)))
199			  '(?\s))
200		   (progn (setq unread-command-events nil)
201			  (throw 'exit t)))))
202    (let (up down both neither
203	  (standard (and (eq (key-binding " " nil t)
204			     'scroll-up)
205			 (eq (key-binding "\^?" nil t)
206			     'scroll-down)
207			 (eq (key-binding "q" nil t)
208			     'electric-help-exit)
209			 (eq (key-binding "r" nil t)
210			     'electric-help-retain))))
211      (Electric-command-loop
212        'exit
213	(function (lambda ()
214	  (sit-for 0) ;necessary if last command was end-of-buffer or
215	              ;beginning-of-buffer - otherwise pos-visible-in-window-p
216	              ;will yield a wrong result.
217	  (let ((min (pos-visible-in-window-p (point-min)))
218		(max (pos-visible-in-window-p (1- (point-max)))))
219	    (cond (isearch-mode 'noprompt)
220		  ((and min max)
221		   (cond (standard "Press q to exit, r to retain ")
222			 (neither)
223			 (t (setq neither (substitute-command-keys "Press \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))
224		  (min
225		   (cond (standard "Press SPC to scroll, q to exit, r to retain ")
226			 (up)
227			 (t (setq up (substitute-command-keys "Press \\[scroll-up] to scroll, \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))
228		  (max
229		   (cond (standard "Press DEL to scroll back, q to exit, r to retain ")
230			 (down)
231			 (t (setq down (substitute-command-keys "Press \\[scroll-down] to scroll back, \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))
232		  (t
233		   (cond (standard "Press SPC to scroll, DEL to scroll back, q to exit, r to retain ")
234			 (both)
235			 (t (setq both (substitute-command-keys "Press \\[scroll-up] to scroll, \\[scroll-down] to scroll back, \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))))))
236		    t))))
237
238
239
240;(defun electric-help-scroll-up (arg)
241;  ">>>Doc"
242;  (interactive "P")
243;  (if (and (null arg) (pos-visible-in-window-p (point-max)))
244;      (electric-help-exit)
245;    (scroll-up arg)))
246
247(defun electric-help-exit ()
248  "Exit `with-electric-help', restoring the previous window/buffer configuration.
249\(The *Help* buffer will be buried.)"
250  (interactive)
251  ;; Make sure that we don't throw twice, even if two events cause
252  ;; calling this function:
253  (if (memq 'electric-help-retain mouse-leave-buffer-hook)
254      (progn
255	(remove-hook 'mouse-leave-buffer-hook 'electric-help-retain)
256	(throw 'exit t))))
257
258(defun electric-help-retain ()
259  "Exit `with-electric-help', retaining the current window/buffer configuration.
260\(The *Help* buffer will not be selected, but \\[switch-to-buffer-other-window] RET
261will select it.)"
262  (interactive)
263  ;; Make sure that we don't throw twice, even if two events cause
264  ;; calling this function:
265  (if (memq 'electric-help-retain mouse-leave-buffer-hook)
266      (progn
267	(remove-hook 'mouse-leave-buffer-hook 'electric-help-retain)
268	(throw 'exit '(retain)))))
269
270
271(defun electric-help-undefined ()
272  (interactive)
273  (error "%s is undefined -- Press %s to exit"
274	 (mapconcat 'single-key-description (this-command-keys) " ")
275	 (if (eq (key-binding "q" nil t) 'electric-help-exit)
276	     "q"
277	   (substitute-command-keys "\\[electric-help-exit]"))))
278
279
280;>>> this needs to be hairified (recursive help, anybody?)
281(defun electric-help-help ()
282  (interactive)
283  (if (and (eq (key-binding "q" nil t) 'electric-help-exit)
284	   (eq (key-binding " " nil t) 'scroll-up)
285	   (eq (key-binding "\^?" nil t) 'scroll-down)
286	   (eq (key-binding "r" nil t) 'electric-help-retain))
287      (message "SPC scrolls up, DEL scrolls down, q exits burying help buffer, r exits")
288    (message "%s" (substitute-command-keys "\\[scroll-up] scrolls up, \\[scroll-down] scrolls down, \\[electric-help-exit] exits burying help buffer, \\[electric-help-retain] exits")))
289  (sit-for 2))
290
291
292;;;###autoload
293(defun electric-helpify (fun &optional name)
294  (let ((name (or name "*Help*")))
295    (if (save-window-excursion
296	  ;; kludge-o-rama
297	  (let* ((p (symbol-function 'print-help-return-message))
298		 (b (get-buffer name))
299		 (m (buffer-modified-p b)))
300	    (and b (not (get-buffer-window b))
301		 (setq b nil))
302	    (unwind-protect
303		(progn
304		  (message "%s..." (capitalize (symbol-name fun)))
305		  ;; with-output-to-temp-buffer marks the buffer as unmodified.
306		  ;; kludging excessively and relying on that as some sort
307		  ;;  of indication leads to the following abomination...
308		  ;;>> This would be doable without such icky kludges if either
309		  ;;>> (a) there were a function to read the interactive
310		  ;;>>     args for a command and return a list of those args.
311		  ;;>>     (To which one would then just apply the command)
312		  ;;>>     (The only problem with this is that interactive-p
313		  ;;>>      would break, but that is such a misfeature in
314		  ;;>>      any case that I don't care)
315		  ;;>>     It is easy to do this for emacs-lisp functions;
316		  ;;>>     the only problem is getting the interactive spec
317		  ;;>>     for subrs
318		  ;;>> (b) there were a function which returned a
319		  ;;>>     modification-tick for a buffer.  One could tell
320		  ;;>>     whether a buffer had changed by whether the
321		  ;;>>     modification-tick were different.
322		  ;;>>     (Presumably there would have to be a way to either
323		  ;;>>      restore the tick to some previous value, or to
324		  ;;>>      suspend updating of the tick in order to allow
325		  ;;>>      things like momentary-string-display)
326		  (and b
327		       (save-excursion
328			 (set-buffer b)
329			 (set-buffer-modified-p t)))
330		  (fset 'print-help-return-message 'ignore)
331		  (call-interactively fun)
332		  (and (get-buffer name)
333		       (get-buffer-window (get-buffer name))
334		       (or (not b)
335			   (not (eq b (get-buffer name)))
336			   (not (buffer-modified-p b)))))
337	      (fset 'print-help-return-message p)
338	      (and b (buffer-name b)
339		   (save-excursion
340		     (set-buffer b)
341		     (set-buffer-modified-p m))))))
342	(with-electric-help 'ignore name t))))
343
344
345
346;; This is to be bound to M-x in ehelp mode. Retains ehelp buffer and then
347;; continues with execute-extended-command.
348(defun electric-help-execute-extended (prefixarg)
349  (interactive "p")
350  (setq electric-help-form-to-execute '(execute-extended-command nil))
351  (electric-help-retain))
352
353;; This is to be buond to C-x in ehelp mode. Retains ehelp buffer and then
354;; continues with ctrl-x prefix.
355(defun electric-help-ctrl-x-prefix (prefixarg)
356  (interactive "p")
357  (setq electric-help-form-to-execute '(progn (message nil) (setq unread-command-char ?\C-x)))
358  (electric-help-retain))
359
360
361(defun electric-describe-key ()
362  (interactive)
363  (electric-helpify 'describe-key))
364
365(defun electric-describe-mode ()
366  (interactive)
367  (electric-helpify 'describe-mode))
368
369(defun electric-view-lossage ()
370  (interactive)
371  (electric-helpify 'view-lossage))
372
373;(defun electric-help-for-help ()
374;  "See help-for-help"
375;  (interactive)
376;  )
377
378(defun electric-describe-function ()
379  (interactive)
380  (electric-helpify 'describe-function))
381
382(defun electric-describe-variable ()
383  (interactive)
384  (electric-helpify 'describe-variable))
385
386(defun electric-describe-bindings ()
387  (interactive)
388  (electric-helpify 'describe-bindings))
389
390(defun electric-describe-syntax ()
391  (interactive)
392  (electric-helpify 'describe-syntax))
393
394(defun electric-command-apropos ()
395  (interactive)
396  (electric-helpify 'command-apropos "*Apropos*"))
397
398;(define-key help-map "a" 'electric-command-apropos)
399
400(defun electric-apropos ()
401  (interactive)
402  (electric-helpify 'apropos))
403
404
405;;;; ehelp-map
406
407(defvar ehelp-map ())
408(if ehelp-map
409    nil
410  (let ((map (copy-keymap help-map)))
411    (substitute-key-definition 'apropos 'electric-apropos map)
412    (substitute-key-definition 'command-apropos 'electric-command-apropos map)
413    (substitute-key-definition 'describe-key 'electric-describe-key map)
414    (substitute-key-definition 'describe-mode 'electric-describe-mode map)
415    (substitute-key-definition 'view-lossage 'electric-view-lossage map)
416    (substitute-key-definition 'describe-function 'electric-describe-function map)
417    (substitute-key-definition 'describe-variable 'electric-describe-variable map)
418    (substitute-key-definition 'describe-bindings 'electric-describe-bindings map)
419    (substitute-key-definition 'describe-syntax 'electric-describe-syntax map)
420
421    (setq ehelp-map map)))
422
423;;;###(autoload 'ehelp-command "ehelp" "Prefix command for ehelp." t 'keymap)
424(defalias 'ehelp-command ehelp-map)
425(put 'ehelp-command 'documentation "Prefix command for ehelp.")
426
427(provide 'ehelp)
428
429;;; arch-tag: e0e3037f-42c0-433e-ba18-322c5d951f46
430;;; ehelp.el ends here
431