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1 | ;;; help-at-pt.el --- local help through the keyboard |
2 | ||
3 | ;; Copyright (C) 2003 Free Software Foundation, Inc. | |
4 | ||
5 | ;; Author: Luc Teirlinck <teirllm@auburn.edu> | |
6 | ;; Keywords: help | |
7 | ||
8 | ;; This file is part of GNU Emacs. | |
9 | ||
10 | ;; GNU Emacs is free software; you can redistribute it and/or modify | |
11 | ;; it under the terms of the GNU General Public License as published by | |
12 | ;; the Free Software Foundation; either version 2, or (at your option) | |
13 | ;; any later version. | |
14 | ||
15 | ;; GNU Emacs is distributed in the hope that it will be useful, | |
16 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
18 | ;; GNU General Public License for more details. | |
19 | ||
20 | ;; You should have received a copy of the GNU General Public License | |
21 | ;; along with GNU Emacs; see the file COPYING. If not, write to the | |
22 | ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
23 | ;; Boston, MA 02111-1307, USA. | |
24 | ||
25 | ;;; Commentary: | |
26 | ||
27 | ;; This file contains functionality to make the help provided by the | |
28 | ;; help-echo text or overlay property available to the keyboard user. | |
29 | ;; It also supports a more keyboard oriented alternative to | |
30 | ;; `help-echo', namely a new text or overlay property `kbd-help'. | |
31 | ;; | |
32 | ;; It provides facilities to access the local help available at point | |
33 | ;; either on demand, using the command `display-local-help', or | |
34 | ;; automatically after a suitable idle time, through the customizable | |
35 | ;; variable `help-at-pt-display-when-idle'. | |
36 | ;; | |
37 | ;; You can get a more global overview of the local help available in | |
38 | ;; the buffer, using the commands `scan-buf-next-region' and | |
39 | ;; `scan-buf-previous-region', which move to the start of the next or | |
40 | ;; previous region with available local help and print the help found | |
41 | ;; there. | |
42 | ;; | |
43 | ;; You do not have to do anything special to use the functionality | |
44 | ;; provided by this file, because all important functions autoload. | |
45 | ||
46 | ;;; Code: | |
47 | ||
48 | (defgroup help-at-pt nil | |
49 | "Features for displaying local help." | |
50 | :group 'help | |
51 | :version "21.4") | |
52 | ||
53 | ;;;###autoload | |
54 | (defun help-at-pt-string (&optional kbd) | |
55 | "Return the help-echo string at point. | |
56 | Normally, the string produced by the `help-echo' text or overlay | |
57 | property, or nil, is returned. | |
58 | If KBD is non-nil, `kbd-help' is used instead, and any | |
59 | `help-echo' property is ignored. In this case, the return value | |
60 | can also be t, if that is the value of the `kbd-help' property." | |
61 | (let* ((prop (if kbd 'kbd-help 'help-echo)) | |
62 | (pair (get-char-property-and-overlay (point) prop)) | |
63 | (val (car pair)) | |
64 | (ov (cdr pair))) | |
65 | (if (functionp val) | |
66 | (funcall val (selected-window) (if ov ov (current-buffer)) (point)) | |
67 | (eval val)))) | |
68 | ||
69 | ;;;###autoload | |
70 | (defun help-at-pt-kbd-string () | |
71 | "Return the keyboard help string at point. | |
72 | If the `kbd-help' text or overlay property at point produces a | |
73 | string, return it. Otherwise, use the `help-echo' property. If | |
74 | this produces no string either, return nil." | |
75 | (let ((kbd (help-at-pt-string t)) | |
76 | (echo (help-at-pt-string))) | |
77 | (if (and kbd (not (eq kbd t))) kbd echo))) | |
78 | ||
79 | ;;;###autoload | |
80 | (defun display-local-help (&optional arg) | |
81 | "Display local help in the echo area. | |
82 | This displays a short help message, namely the string produced by | |
83 | the `kbd-help' property at point. If `kbd-help' does not produce | |
84 | a string, but the `help-echo' property does, then that string is | |
85 | printed instead. | |
86 | ||
87 | A numeric argument ARG prevents display of a message in case | |
88 | there is no help. While ARG can be used interactively, it is | |
89 | mainly meant for use from Lisp." | |
90 | (interactive "P") | |
91 | (let ((help (help-at-pt-kbd-string))) | |
92 | (if help | |
93 | (message "%s" help) | |
94 | (if (not arg) (message "No local help at point"))))) | |
95 | ||
96 | (defcustom help-at-pt-timer-delay 1 | |
97 | "*Delay before displaying local help. | |
98 | This is used if `help-at-pt-display-when-idle' is enabled. | |
99 | The value may be an integer or floating point number. | |
100 | ||
101 | If a timer is already active, there are two ways to make the new | |
102 | value take effect immediately. After setting the value, you can | |
103 | first call `help-at-pt-cancel-timer' and then set a new timer | |
e4ff63a2 | 104 | with `help-at-pt-set-timer'. Alternatively, you can set this |
cc531412 LT |
105 | variable through Custom. This will not set a timer if none is |
106 | active, but if one is already active, Custom will make it use the | |
107 | new value." | |
108 | :group 'help-at-pt | |
109 | :type 'number | |
110 | :set (lambda (variable value) | |
111 | (set-default variable value) | |
112 | (when (and (boundp 'help-at-pt-timer) help-at-pt-timer) | |
113 | (timer-set-idle-time help-at-pt-timer value t)))) | |
114 | ||
115 | (defvar help-at-pt-timer nil | |
116 | "Non-nil means that a timer is set that checks for local help. | |
117 | If non-nil, this is the value returned by the call of | |
118 | `run-with-idle-timer' that set that timer. This variable is used | |
119 | internally to enable `help-at-pt-display-when-idle'. Do not set it | |
120 | yourself.") | |
121 | ||
122 | ;;;###autoload | |
123 | (defun help-at-pt-cancel-timer () | |
124 | "Cancel any timer set by `help-at-pt-set-timer'. | |
125 | This disables `help-at-pt-display-when-idle'." | |
126 | (interactive) | |
127 | (let ((inhibit-quit t)) | |
128 | (when help-at-pt-timer | |
129 | (cancel-timer help-at-pt-timer) | |
130 | (setq help-at-pt-timer nil)))) | |
131 | ||
132 | ;;;###autoload | |
133 | (defun help-at-pt-set-timer () | |
134 | "Enable `help-at-pt-display-when-idle'. | |
135 | This is done by setting a timer, if none is currently active." | |
136 | (interactive) | |
137 | (unless help-at-pt-timer | |
138 | (setq help-at-pt-timer | |
139 | (run-with-idle-timer | |
140 | help-at-pt-timer-delay t #'help-at-pt-maybe-display)))) | |
141 | ||
142 | ;;;###autoload | |
143 | (defcustom help-at-pt-display-when-idle 'never | |
144 | "*Automatically show local help on point-over. | |
145 | If the value is t, the string obtained from any `kbd-help' or | |
146 | `help-echo' property at point is automatically printed in the | |
147 | echo area, if nothing else is already displayed there, or after a | |
148 | quit. If both `kbd-help' and `help-echo' produce help strings, | |
149 | `kbd-help' is used. If the value is a list, the help only gets | |
150 | printed if there is a text or overlay property at point that is | |
151 | included in this list. Suggested properties are `keymap', | |
152 | `local-map', `button' and `kbd-help'. Any value other than t or | |
153 | a non-empty list disables the feature. | |
154 | ||
155 | This variable only takes effect after a call to | |
156 | `help-at-pt-set-timer'. The help gets printed after Emacs has | |
157 | been idle for `help-at-pt-timer-delay' seconds. You can call | |
158 | `help-at-pt-cancel-timer' to cancel the timer set by, and the | |
159 | effect of, `help-at-pt-set-timer'. | |
160 | ||
161 | When this variable is set through Custom, `help-at-pt-set-timer' | |
162 | is called automatically, unless the value is `never', in which | |
163 | case `help-at-pt-cancel-timer' is called. Specifying an empty | |
164 | list of properties through Custom will set the timer, thus | |
165 | enabling buffer local values. It sets the actual value to nil. | |
166 | Thus, Custom distinguishes between a nil value and other values | |
167 | that disable the feature, which Custom identifies with `never'. | |
168 | The default is `never'." | |
169 | :group 'help-at-pt | |
170 | :type '(choice (const :tag "Always" | |
171 | :format "%t\n%h" | |
172 | :doc | |
173 | "This choice can get noisy. | |
174 | The text printed from the `help-echo' property is often only | |
175 | relevant when using the mouse. If you mind about too many | |
176 | messages getting printed in the echo area, use \"In certain | |
177 | situations\". See the documentation there for more information." | |
178 | t) | |
179 | (repeat :tag "In certain situations" | |
180 | ;; unless we specify 0 offset the doc string | |
181 | ;; for this choice gets indented very | |
182 | ;; differently than for the other two | |
183 | ;; choices, when "More" is selected. | |
184 | :offset 0 | |
185 | :format "%{%t%}:\n%v%i\n%h" | |
186 | :doc | |
187 | "This choice lets you specify a list of \ | |
188 | text properties. | |
189 | Presence of any of these properties will trigger display of | |
190 | available local help on point-over. | |
191 | If you use this alternative through Custom without listing any | |
192 | properties, a timer will be set anyway. This will enable buffer | |
193 | local values. Use \"Never\" if you do not want a timer to be set. | |
194 | ||
195 | Suggested properties: | |
196 | The `keymap' and `local-map' properties change keybindings in | |
197 | parts of the buffer. Some of these keymaps are mode independent | |
198 | and are not mentioned in the mode documentation. Hence, the help | |
199 | text is likely to be useful. | |
200 | Specifying `button' is relevant in Custom and similar buffers. | |
201 | In these buffers, most, but not all, of the text shown this way is | |
202 | available by default when using tab, but not on regular point-over. | |
203 | The presence of a `kbd-help' property guarantees that non mouse | |
204 | specific help is available." | |
205 | :value (keymap local-map button kbd-help) | |
206 | symbol) | |
207 | (other :tag "Never" | |
208 | :format "%t\n%h" | |
209 | :doc | |
210 | "This choice normally disables buffer local values. | |
211 | If you choose this value through Custom and a timer checking for | |
212 | local help is currently active, it will be canceled. No new | |
213 | timer will be set. Call `help-at-pt-set-timer' after choosing | |
214 | this option, or use \"In certain situations\" and specify no text | |
215 | properties, to enable buffer local values." | |
216 | never)) | |
217 | :initialize 'custom-initialize-default | |
218 | :set #'(lambda (variable value) | |
219 | (set-default variable value) | |
220 | (if (eq value 'never) | |
221 | (help-at-pt-cancel-timer) | |
222 | (help-at-pt-set-timer))) | |
223 | :set-after '(help-at-pt-timer-delay) | |
224 | :require 'help-at-pt) | |
225 | ||
226 | ;; Function for use in `help-at-pt-set-timer'. | |
227 | (defun help-at-pt-maybe-display () | |
228 | (and (or (eq help-at-pt-display-when-idle t) | |
229 | (and (consp help-at-pt-display-when-idle) | |
230 | (catch 'found | |
231 | (dolist (prop help-at-pt-display-when-idle) | |
232 | (if (get-char-property (point) prop) | |
233 | (throw 'found t)))))) | |
234 | (or (not (current-message)) | |
235 | (string= (current-message) "Quit")) | |
236 | (display-local-help t))) | |
237 | ||
238 | ;;;###autoload | |
239 | (defun scan-buf-move-to-region (prop &optional arg hook) | |
240 | "Go to the start of the next region with non-nil PROP property. | |
241 | Then run HOOK, which should be a quoted symbol that is a normal | |
242 | hook.variable, or an expression evaluating to such a symbol. | |
243 | Adjacent areas with different non-nil PROP properties are | |
244 | considered different regions. | |
245 | ||
246 | With numeric argument ARG, move to the start of the ARGth next | |
247 | such region, then run HOOK. If ARG is negative, move backward. | |
248 | If point is already in a region, then that region does not count | |
249 | toward ARG. If ARG is 0 and point is inside a region, move to | |
250 | the start of that region. If ARG is 0 and point is not in a | |
251 | region, print a message to that effect, but do not move point and | |
252 | do not run HOOK. If there are not enough regions to move over, | |
253 | an error results and the number of available regions is mentioned | |
254 | in the error message. Point is not moved and HOOK is not run." | |
255 | (cond ((> arg 0) | |
256 | (if (= (point) (point-max)) | |
257 | (error "No further `%s' regions" prop)) | |
258 | (let ((pos (point))) | |
259 | (dotimes (x arg) | |
260 | (setq pos (next-single-char-property-change pos prop)) | |
261 | (unless (get-char-property pos prop) | |
262 | (setq pos (next-single-char-property-change pos prop)) | |
263 | (unless (get-char-property pos prop) | |
264 | (cond ((= x 0) | |
265 | (error "No further `%s' regions" prop)) | |
266 | ((= x 1) | |
267 | (error "There is only one further `%s' region" prop)) | |
268 | (t | |
269 | (error | |
270 | "There are only %d further `%s' regions" | |
271 | x prop)))))) | |
272 | (goto-char pos) | |
273 | (run-hooks hook))) | |
274 | ((= arg 0) | |
275 | (let ((val (get-char-property (point) prop))) | |
276 | (cond ((not val) | |
277 | (message "Point is not in a `%s' region" prop)) | |
278 | ((eq val (get-char-property (1- (point)) prop)) | |
279 | (goto-char | |
280 | (previous-single-char-property-change (point) prop)) | |
281 | (run-hooks hook)) | |
282 | (t (run-hooks hook))))) | |
283 | ((< arg 0) | |
284 | (let ((pos (point)) (val (get-char-property (point) prop))) | |
285 | (and val | |
286 | (eq val (get-char-property (1- pos) prop)) | |
287 | (setq pos | |
288 | (previous-single-char-property-change pos prop))) | |
289 | (if (= pos (point-min)) | |
290 | (error "No prior `%s' regions" prop)) | |
291 | (dotimes (x (- arg)) | |
292 | (setq pos (previous-single-char-property-change pos prop)) | |
293 | (unless (get-char-property pos prop) | |
294 | (setq pos (previous-single-char-property-change pos prop)) | |
295 | (unless (get-char-property pos prop) | |
296 | (cond ((= x 0) | |
297 | (error "No prior `%s' regions" prop)) | |
298 | ((= x 1) | |
299 | (error "There is only one prior `%s' region" prop)) | |
300 | (t | |
301 | (error "There are only %d prior `%s' regions" | |
302 | x prop)))))) | |
303 | (goto-char pos) | |
304 | (run-hooks hook))))) | |
305 | ||
306 | ;; To be moved to a different file and replaced by a defcustom in a | |
307 | ;; future version. | |
308 | (defvar scan-buf-move-hook '(display-local-help) | |
309 | "Normal hook run by `scan-buf-next-region'. | |
310 | Also used by `scan-buf-previous-region'. The hook is run after | |
311 | positioning point.") | |
312 | ||
313 | ;;;###autoload | |
314 | (defun scan-buf-next-region (&optional arg) | |
315 | "Go to the start of the next region with non-nil help-echo. | |
316 | Print the help found there using `display-local-help'. Adjacent | |
317 | areas with different non-nil help-echo properties are considered | |
318 | different regions. | |
319 | ||
320 | With numeric argument ARG, move to the start of the ARGth next | |
321 | help-echo region. If ARG is negative, move backward. If point | |
322 | is already in a help-echo region, then that region does not count | |
323 | toward ARG. If ARG is 0 and point is inside a help-echo region, | |
324 | move to the start of that region. If ARG is 0 and point is not | |
325 | in such a region, just print a message to that effect. If there | |
326 | are not enough regions to move over, an error results and the | |
327 | number of available regions is mentioned in the error message. | |
328 | ||
329 | A potentially confusing subtlety is that point can be in a | |
330 | help-echo region without any local help being available. This is | |
331 | because `help-echo' can be a function evaluating to nil. This | |
332 | rarely happens in practice." | |
333 | (interactive "p") | |
334 | (scan-buf-move-to-region 'help-echo arg 'scan-buf-move-hook)) | |
335 | ||
336 | ;;;###autoload | |
337 | (defun scan-buf-previous-region (&optional arg) | |
338 | "Go to the start of the previous region with non-nil help-echo. | |
339 | Print the help found there using `display-local-help'. Adjacent | |
340 | areas with different non-nil help-echo properties are considered | |
341 | different regions. With numeric argument ARG, behaves like | |
342 | `scan-buf-next-region' with argument -ARG.." | |
343 | (interactive "p") | |
344 | (scan-buf-move-to-region 'help-echo (- arg) 'scan-buf-move-hook)) | |
345 | ||
346 | (defvar help-at-pt-unload-hook '(help-at-pt-cancel-timer) | |
347 | "Normal hook run when `help-at-pt' is unloaded.") | |
348 | ||
349 | ;; Suggested key bindings: | |
350 | ;; | |
351 | ;; (global-set-key [C-tab] 'scan-buf-next-region) | |
352 | ;; (global-set-key [C-M-tab] 'scan-buf-previous-region) | |
353 | ||
354 | (provide 'help-at-pt) | |
355 | ||
5074ca95 | 356 | ;;; arch-tag: d0b8b86d-d23f-45d0-a82d-208d6205a583 |
cc531412 | 357 | ;;; help-at-pt.el ends here |