;;; lazy-voice-lock.el --- Support mode for voice locking  parts of a buffer
;;; $Id: lazy-voice-lock.el,v 17.0 2002/11/23 01:29:01 raman Exp $
;;; $Author: raman $ 
;;; Description:  lazy Voice lock mode for Emacspeak
;;{{{  LCD Archive entry: 

;;; LCD Archive Entry:
;;; emacspeak| T. V. Raman |raman@cs.cornell.edu 
;;; A speech interface to Emacs |
;;; $Date: 2002/11/23 01:29:01 $ |
;;;  $Revision: 17.0 $ | 
;;; Location undetermined
;;;

;;}}}
;;{{{  Copyright:

;;;Copyright (C) 1995 -- 2002, T. V. Raman 
;;; Copyright (c) 1994, 1995 by Digital Equipment Corporation.
;;; All Rights Reserved. 
;;;
;;; This file is not part of GNU Emacs, but the same permissions apply.
;;;
;;; 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 2, 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.

;;}}}
;;; lazy-voice-lock.el --- Lazy demand-driven voiceification for fastVoice Lock mode.

;; Copyright (C) 1994, 1995, 1996 Free Software Foundation, Inc.

;; Author: Simon Marshall <simon@gnu.ai.mit.edu>

;; Version: 2.06

;;; 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 2, 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, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; Purpose:
;;
;; To make visiting buffers in `voice-lock-mode' faster by making voiceification
;; be demand-driven, deferred and stealthy.
;; Voiceification only occurs when, and where, necessary.
;;
;; See caveats and feedback below.
;; See also the fast-lock package.  (But don't use them at the same time!)

;; Installation:
;; 
;; Put in your ~/.emacs:
;;
;; (setq voice-lock-support-mode 'lazy-voice-lock-mode)
;;
;; Start up a new Emacs and use voice-lock as usual (except that you can use the
;; so-called "gaudier" voiceification regexps on big files without frustration).
;;
;; In a buffer (which has `voice-lock-mode' enabled) which is at least
;; `lazy-voice-lock-minimum-size' characters long, buffer voiceification will not
;; occur and only the visible portion of the buffer will be voiceified.  Motion
;; around the buffer will voiceify those visible portions not previously
;; voiceified.  If stealth voiceification is enabled, buffer voiceification will
;; occur in invisible parts of the buffer after `lazy-voice-lock-stealth-time'
;; seconds of idle time.  If on-the-fly voiceification is deferred, on-the-fly
;; voiceification will occur after `lazy-voice-lock-defer-time' seconds of idle time.

;; User-visible differences with version 1:
;;
;; - Version 2 can defer on-the-fly voiceification.  Therefore you need not, and
;; should not, use defer-lock.el with this version of lazy-voice-lock.el.
;;
;; A number of variables have changed meaning:
;;
;; - A value of nil for the variable `lazy-voice-lock-minimum-size' means never turn
;; on demand-driven voiceification.  In version 1 this meant always turn on
;; demand-driven voiceification.  If you really want demand-driven voiceification
;; regardless of buffer size, set this variable to 0.
;;
;; - The variable `lazy-voice-lock-stealth-lines' cannot have a nil value.  In
;; version 1 this meant use `window-height' as the maximum number of lines to
;; voiceify as a stealth chunk.  This makes no sense; stealth voiceification is
;; of a buffer, not a window.

;; Implementation differences with version 1:
;;
;; - Version 1 of lazy-voice-lock.el is a bit of a hack.  Version 1 demand-driven
;; voiceification, the core feature of lazy-voice-lock.el, is implemented by placing a
;; function on `post-command-hook'.  This function voiceifies where necessary,
;; i.e., where a window scroll has occurred.  However, there are a number of
;; problems with using `post-command-hook':
;;
;; (a) As the name suggests, `post-command-hook' is run after every command,
;;     i.e., frequently and regardless of whether scrolling has occurred.
;; (b) Scrolling can occur during a command, when `post-command-hook' is not
;;     run, i.e., it is not necessarily run after scrolling has occurred.
;; (c) When `post-command-hook' is run, there is nothing to suggest where
;;     scrolling might have occurred, i.e., which windows have scrolled.
;;
;; Thus lazy-voice-lock.el's function is called almost as often as possible, usually
;; when it need not be called, yet it is not always called when it is needed.
;; Also, lazy-voice-lock.el's function must check each window to see if a scroll has
;; occurred there.  Worse still, lazy-voice-lock.el's function must voiceify a region
;; twice as large as necessary to make sure the window is completely voiceified.
;; Basically, `post-command-hook' is completely inappropriate for lazy-voice-lock.el.
;;
;; Ideally, we want to attach lazy-voice-lock.el's function to a hook that is run
;; only when scrolling occurs, e.g., `window-start' has changed, and tells us
;; as much information as we need, i.e., the window and its new buffer region.
;; Richard Stallman implemented a `window-scroll-functions' for Emacs 19.30.
;; Functions on it are run when `window-start' has changed, and are supplied
;; with the window and the window's new `window-start' position.  (It would be
;; better if it also supplied the window's new `window-end' position, but that
;; is calculated as part of the redisplay process, and the functions on
;; `window-scroll-functions' are run before redisplay has finished.)  Thus, the
;; hook deals with the above problems (a), (b) and (c).
;;
;; If only life was that easy.  Version 2 demand-driven voiceification is mostly
;; implemented by placing a function on `window-scroll-functions'.  However,
;; not all scrolling occurs when `window-start' has changed.  A change in
;; window size, e.g., via C-x 1, or a significant deletion, e.g., of a number
;; of lines, causes `window-end' to change without changing `window-start'.
;; Arguably, these events are not scrolling events, but voiceification must
;; occur for lazy-voice-lock.el to work.  Hooks `window-size-change-functions' and
;; `redisplay-end-trigger-functions' were added for these circumstances.
;;
;; Ben Wing thinks these hooks are "horribly horribly kludgy", and implemented
;; a `pre-idle-hook', a `mother-of-all-post-command-hooks', for XEmacs 19.14.
;; He then hacked up a version 1 lazy-voice-lock.el to use `pre-idle-hook' rather
;; than `post-command-hook'.  Whereas functions on `post-command-hook' are
;; called almost as often as possible, functions on `pre-idle-hook' really are
;; called as often as possible, even when the mouse moves and, on some systems,
;; while XEmacs is idle.  Thus, the hook deals with the above problem (b), but
;; unfortunately it makes (a) worse and does not address (c) at all.
;;
;; I freely admit that `redisplay-end-trigger-functions' and, to a much lesser
;; extent, `window-size-change-functions' are not pretty.  However, I feel that
;; a `window-scroll-functions' feature is cleaner than a `pre-idle-hook', and
;; the result is faster and smaller, less intrusive and more targeted, code.
;; Since `pre-idle-hook' is pretty much like `post-command-hook', there is no
;; point in making this version of lazy-voice-lock.el work with it.  Anyway, that's
;; Lit 30 of my humble opinion.
;;
;; - Version 1 stealth voiceification is also implemented by placing a function
;; on `post-command-hook'.  This function waits for a given amount of time,
;; and, if Emacs remains idle, voiceifies where necessary.  Again, there are a
;; number of problems with using `post-command-hook':
;;
;; (a) Functions on `post-command-hook' are run sequentially, so this function
;;     can interfere with other functions on the hook, and vice versa.
;; (b) This function waits for a given amount of time, so it can interfere with
;;     various features that are dealt with by Emacs after a command, e.g.,
;;     region highlighting, asynchronous updating and keystroke echoing.
;; (c) Voiceification may be required during a command, when `post-command-hook'
;;     is not run.  (Version 2 deferred voiceification only.)
;;
;; Again, `post-command-hook' is completely inappropriate for lazy-voice-lock.el.
;; Richard Stallman and Morten Welinder implemented internal Timers and Idle
;; Timers for Emacs 19.31.  Functions can be run independently at given times
;; or after given amounts of idle time.  Thus, the feature deals with the above
;; problems (a), (b) and (c).  Version 2 deferral and stealth are implemented
;; by functions on Idle Timers.  (A function on XEmacs' `pre-idle-hook' is
;; similar to an Emacs Idle Timer function with a fixed zero second timeout.
;; Hey, maybe I could stop using `window-scroll-functions' for demand-driven
;; voiceification and use a zero second Emacs Idle Timer instead?  Only joking!)

;; Caveats:
;;
;; Lazy Lock mode does not work efficiently with Outline mode.  This is because
;; when in Outline mode, although text may be hidden (not visible in the
;; window), the text is visible to Emacs Lisp code (not surprisingly) and Lazy
;; Lock voiceifies it mercilessly.  Maybe it will be fixed one day.
;;
;; Because buffer text is not necessarily voiceified, other packages that expect
;; buffer text to be voiceified inVoice Lock mode either might not work as
;; expected, or might not display buffer text as expected.  An example of the
;; latter is `occur', which copies lines of buffer text into another buffer.
;;
;; In Emacs 19.30, Lazy Lock mode does not ensure that an existing buffer is
;; voiceified if it is made visible via a minibuffer-less command that replaces
;; an existing window's buffer (e.g., via the Buffers menu).  Upgrade!
;;
;; In Emacs 19.30, Lazy Lock mode does not work well with Transient Mark mode
;; or modes based on Comint mode (e.g., Shell mode), and also interferes with
;; the echoing of keystrokes in the minibuffer.  This is because of the way
;; deferral and stealth have to be implemented for Emacs 19.30.  Upgrade!
;;
;; Currently XEmacs does not have the features to support this version of
;; lazy-voice-lock.el.  Maybe it will one day.

;; Feedback:
;;
;; Feedback is welcome.
;; To submit a bug report (or make comments) please use the mechanism provided:
;;
;; M-x lazy-voice-lock-submit-bug-report RET

;; History:
;;
;; 1.15--2.00:
;; - Rewrite for Emacs 19.30 and the features rms added to support lazy-voice-lock.el
;;   so that it could work correctly and efficiently.
;; - Many thanks to those who reported bugs, fixed bugs, made suggestions or
;;   otherwise contributed in the version 1 cycle; Jari Aalto, Kevin Broadey,
;;   Ulrik Dickow, Bill Dubuque, Bob Glickstein, Boris Goldowsky,
;;   Jonas Jarnestrom, David Karr, Michael Kifer, Erik Naggum, Rick Sladkey,
;;   Jim Thompson, Ben Wing, Ilya Zakharevich, and Richard Stallman.
;; 2.00--2.01:
;; - Made `lazy-voice-lock-voiceify-after-command' always `sit-for' and so redisplay
;; - Use `buffer-name' not `buffer-live-p' (Bill Dubuque hint)
;; - Made `lazy-voice-lock-install' do `add-to-list' not `setq' of `current-buffer'
;; - Made `lazy-voice-lock-voiceify-after-install' loop over buffer list
;; - Made `lazy-voice-lock-arrange-before-change' to arrange `window-end' triggering
;; - Made `lazy-voice-lock-let-buffer-state' wrap both `befter-change-functions'
;; - Made `lazy-voice-lock-voiceify-region' do `condition-case' (Hyman Rosen report)
;; 2.01--2.02:
;; - Use `buffer-live-p' as `buffer-name' can barf (Richard Stanton report)
;; - Made `lazy-voice-lock-install' set `voice-lock-voiceified' (Kevin Davidson report)
;; - Made `lazy-voice-lock-install' add hooks only if needed
;; - Made `lazy-voice-lock-unstall' add `voice-lock-after-change-function' if needed
;; 2.02--2.03:
;; - Made `lazy-voice-lock-voiceify-region' do `condition-case' for `quit' too
;; - Made `lazy-voice-lock-mode' respect the value of `voice-lock-inhibit-thing-lock'
;; - Added `lazy-voice-lock-after-unvoiceify-buffer'
;; - Removed `lazy-voice-lock-voiceify-after-install' hack
;; - Made `lazy-voice-lock-voiceify-after-scroll' not `set-buffer' to `window-buffer'
;; - Made `lazy-voice-lock-voiceify-after-trigger' not `set-buffer' to `window-buffer'
;; - Made `lazy-voice-lock-voiceify-after-idle' be interruptible (Scott Burson hint)
;; 2.03--2.04:
;; - Rewrite for Emacs 19.31 idle timers
;; - Renamed `buffer-windows' to `get-buffer-window-list'
;; - Removed `buffer-live-p'
;; - Made `lazy-voice-lock-defer-after-change' always save `current-buffer'
;; - Made `lazy-voice-lock-voiceify-after-defer' just process buffers
;; - Made `lazy-voice-lock-install-hooks' add hooks correctly (Kevin Broadey report)
;; - Made `lazy-voice-lock-install' cope if `lazy-voice-lock-defer-time' is a list
;; 2.04--2.05:
;; - Rewrite for Common Lisp macros
;; - Added `do-while' macro
;; - Renamed `lazy-voice-lock-let-buffer-state' macro to `save-buffer-state'
;; - Returned `lazy-voice-lock-voiceify-after-install' hack (Darren Hall hint)
;; - Added `lazy-voice-lock-defer-driven' functionality (Scott Byer hint)
;; - Made `lazy-voice-lock-mode' wrap `voice-lock-support-mode'
;; 2.05--2.06:
;; - Made `lazy-voice-lock-voiceify-after-defer' swap correctly (Scott Byer report)

(require 'cl)
(declaim  (optimize  (safety 0) (speed 3)))
(eval-when (load compile)
  (provide 'lazy-voice-lock)	 ;prevent byte compiler from recursing
  (require 'voice-lock))

;; Make sure lazy-voice-lock.el is supported.
;;commenting out  
					;(if (if (save-match-data (string-match "Lucid\\|XEmacs" (emacs-version)))
					;	t
					;      (and (= emacs-major-version 19) (< emacs-minor-version 30)))
					;    (error "`lazy-voice-lock' was written for Emacs 19.30 or later"))

;; Flush out those lusers who didn't read all of the Commentary.
					;(if (or (memq 'turn-on-defer-lock voice-lock-mode-hook)
					;	(memq 'defer-lock-mode voice-lock-mode-hook))
					;    (error "`lazy-voice-lock' was written for use without `defer-lock'"))
  
(eval-when-compile
  ;;
  ;; We don't do this at the top-level as idle timers are not necessarily used.
  (require 'timer)
  ;; We don't do this at the top-level as we only use non-autoloaded macros.
  (require 'cl)
  ;;
  ;; Well, shouldn't Lazy Lock mode be as lazy as possible?
  (setq byte-compile-dynamic t byte-compile-dynamic-docstrings t)
  ;; But, we make sure that the code is as zippy as can be.
  (setq byte-optimize t)
  ;;
  ;; We use this to preserve or protect things when modifying text properties.
  (defmacro save-buffer-state (varlist &rest body)
    "Bind variables according to VARLIST and eval BODY restoring buffer state."
    (` (let* ((,@ (append varlist
			  '((modified (buffer-modified-p))
			    (inhibit-read-only t) (buffer-undo-list t)
			    before-change-functions after-change-functions
			    deactivate-mark buffer-file-name buffer-file-truename))))
	 (,@ body)
	 (when (and (not modified) (buffer-modified-p))
	   (set-buffer-modified-p nil)))))
  (put 'save-buffer-state 'lisp-indent-function 1)
  ;;
  ;; We use this for clarity and speed.  Naughty but nice.
  (defmacro do-while (test &rest body)
    "(do-while TEST BODY...): eval BODY... and repeat if TEST yields non-nil.
The order of execution is thus BODY, TEST, BODY, TEST and so on
until TEST returns nil."
    (` (while (progn (,@ body) (, test)))))
  (put 'do-while 'lisp-indent-function (get 'while 'lisp-indent-function)))

;; User Variables:

(defvar lazy-voice-lock-minimum-size (* 25 1024)
  "*Minimum size of a buffer for demand-driven voiceification.
On-demand voiceification occurs if the buffer size is greater than this value.
If nil, means demand-driven voiceification is never performed.
If a list, each element should be a cons pair of the form (MAJOR-MODE . SIZE),
where MAJOR-MODE is a symbol or t (meaning the default).  For example:
 ((c-mode . 25600) (c++-mode . 25600) (rmail-mode . 1048576))
means that the minimum size is 25K for buffers in C or C++ modes, one megabyte
for buffers in Rmail mode, and size is irrelevant otherwise.

The value of this variable is used when Lazy Lock mode is turned on.")

(defvar lazy-voice-lock-defer-driven nil
  "*If non-nil, means voiceification should be defer-driven.
If nil, means demand-driven voiceification is performed.  This means when
scrolling into unvoiceified areas of the buffer, those areas are immediately
voiceified.  Thus scrolling never presents unvoiceified areas.  However, since
voiceification occurs during scrolling, scrolling may be slow.
If t, means defer-driven voiceification is performed.  This means voiceification
of those areas is deferred.  Thus scrolling may present momentarily unvoiceified
areas.  However, since voiceification does not occur during scrolling, scrolling
will be faster than demand-driven voiceification.
If any other value, e.g., `eventually', means demand-driven voiceification is
performed until the buffer is voiceified, then buffer voiceification becomes
defer-driven.  Thus scrolling never presents unvoiceified areas until the buffer
is first voiceified, after which subsequent scrolling may present future buffer
insertions momentarily unvoiceified.  However, since voiceification does not
occur during scrolling after the buffer is first voiceified, scrolling will
become faster.

The value of this variable is used when Lazy Lock mode is turned on.")

(defvar lazy-voice-lock-defer-time
  (if (featurep 'lisp-float-type) (/ (float 1) (float 4)) 1)
  "*Time in seconds to delay before beginning deferred voiceification.
Deferred voiceification occurs if there is no input within this time.
If nil, means voiceification is never deferred.  However, voiceification occurs
on-the-fly or during scrolling, which may be slow.
If a list, it should be of the form (MAJOR-MODES . TIME), where MAJOR-MODES is
a list of `major-mode' symbols for which deferred voiceification should occur.
The sense of the list is negated if it begins with `not'.  For example:
 ((c-mode c++-mode) . 0.25)
means that the deferral time is 0.25s for buffers in C or C++ modes, and
deferral does not occur otherwise.

The value of this variable is used when Lazy Lock mode is turned on.")

(defvar lazy-voice-lock-stealth-time 30
  "*Time in seconds to delay before beginning stealth voiceification.
Stealth voiceification occurs if there is no input within this time.
If nil, means stealth voiceification is never performed.

The value of this variable is used when Lazy Lock mode is turned on.")

(defvar lazy-voice-lock-stealth-lines 150
  "*Maximum size of a chunk of stealth voiceification.
Each iteration of stealth voiceification can voiceify this number of lines.
To speed up input response during stealth voiceification, at the cost of stealth
taking longer to voiceify, you could reduce the value of this variable.")

(defvar lazy-voice-lock-stealth-nice
  (if (featurep 'lisp-float-type) (/ (float 1) (float 8)) 1)
  "*Time in seconds to pause between chunks of stealth voiceification.
Each iteration of stealth voiceification is separated by this amount of time.
To reduce machine load during stealth voiceification, at the cost of stealth
taking longer to voiceify, you could increase the value of this variable.")

(defvar lazy-voice-lock-stealth-verbose nil
  "*If non-nil, means stealth voiceification should show status messages.")

(defvar lazy-voice-lock-mode nil)
(defvar lazy-voice-lock-buffers nil)	; for deferral
(defvar lazy-voice-lock-timers (cons nil nil)) ; for deferral and stealth

;; User Functions:

;;;###autoload
(defun lazy-voice-lock-mode (&optional arg)
  "Toggle Lazy Lock mode.
With arg, turn Lazy Lock mode on if and only if arg is positive.  Enable it
automatically in your `~/.emacs' by:

 (setq voice-lock-support-mode 'lazy-voice-lock-mode)

When Lazy Lock mode is enabled, voiceification can be lazy in a number of ways:

 - Demand-driven buffer voiceification if `lazy-voice-lock-minimum-size' is non-nil.
   This means initial voiceification does not occur if the buffer is greater
   than `lazy-voice-lock-minimum-size' characters in length.  Instead, voiceification
   occurs when necessary, such as when scrolling through the buffer would
   otherwise reveal unvoiceified areas.  This is useful if buffer voiceification
   is too slow for large buffers.

 - Defer-driven buffer voiceification if `lazy-voice-lock-defer-driven' is non-nil.
   This means all voiceification is deferred, such as voiceification that occurs
   when scrolling through the buffer would otherwise reveal unvoiceified areas.
   Instead, these areas are seen momentarily unvoiceified.  This is useful if
   demand-driven voiceification is too slow to keep up with scrolling.

 - Deferred on-the-fly voiceification if `lazy-voice-lock-defer-time' is non-nil.
   This means on-the-fly voiceification does not occur as you type.  Instead,
   voiceification is deferred until after `lazy-voice-lock-defer-time' seconds of
   Emacs idle time, while Emacs remains idle.  This is useful if on-the-fly
   voiceification is too slow to keep up with your typing.

 - Stealthy buffer voiceification if `lazy-voice-lock-stealth-time' is non-nil.
   This means remaining unvoiceified areas of buffers are voiceified if Emacs has
   been idle for `lazy-voice-lock-stealth-time' seconds, while Emacs remains idle.
   This is useful if any buffer has demand- or defer-driven voiceification.

See also variables `lazy-voice-lock-stealth-lines', `lazy-voice-lock-stealth-nice' and
`lazy-voice-lock-stealth-verbose' for stealth voiceification.

Use \\[lazy-voice-lock-submit-bug-report] to send bug reports or feedback."
  (interactive "P")
  (set (make-local-variable 'lazy-voice-lock-mode)
       (and (not (memq 'lazy-voice-lock-mode voice-lock-inhibit-thing-lock))
	    (if arg (> (prefix-numeric-value arg) 0) (not lazy-voice-lock-mode))))
  (cond ((and lazy-voice-lock-mode (not voice-lock-mode))
	 ;; Turned on `lazy-voice-lock-mode' rather than `voice-lock-mode'.
	 (let ((voice-lock-support-mode 'lazy-voice-lock-mode))
	   (voice-lock-mode t)))
	(lazy-voice-lock-mode
	 ;; Turn ourselves on.
	 (lazy-voice-lock-install))
	(t
	 ;; Turn ourselves off.
	 (lazy-voice-lock-unstall))))

(defun lazy-voice-lock-submit-bug-report ()
  "Submit via mail a bug report on lazy-voice-lock.el."
  (interactive)
  (let ((reporter-prompt-for-summary-p t))
    (reporter-submit-bug-report "simon@gnu.ai.mit.edu" "lazy-voice-lock 2.06"
				'(lazy-voice-lock-minimum-size lazy-voice-lock-defer-driven lazy-voice-lock-defer-time
							       lazy-voice-lock-stealth-time lazy-voice-lock-stealth-nice lazy-voice-lock-stealth-lines
							       lazy-voice-lock-stealth-verbose)
				nil nil
				(concat "Hi Si.,

I want to report a bug.  I've read the `Bugs' section of `Info' on Emacs, so I
know how to make a clear and unambiguous report.  To reproduce the bug:

Start a fresh Emacs via `" invocation-name " -no-init-file -no-site-file'.
In the `*scratch*' buffer, evaluate:"))))

;;;###autoload
(defun turn-on-lazy-voice-lock ()
  "Unconditionally turn on Lazy Lock mode."
  (lazy-voice-lock-mode t))

(defun lazy-voice-lock-install ()
  (let ((min-size (voice-lock-value-in-major-mode lazy-voice-lock-minimum-size)))
    ;;
    ;; TellVoice Lock whether Lazy Lock will do voiceification.
    (make-local-variable 'voice-lock-voiceified)
    (setq voice-lock-voiceified (and min-size (>= (buffer-size) min-size)))
    ;;
    ;; Add the text properties and voiceify.
    (if (not voice-lock-voiceified)
	(lazy-voice-lock-after-voiceify-buffer)
      ;; Make sure we voiceify in any existing windows showing the buffer.
      (let ((windows (get-buffer-window-list (current-buffer) 'nomini t)))
	(lazy-voice-lock-after-unvoiceify-buffer)
	(while windows
	  (lazy-voice-lock-voiceify-conservatively (car windows))
	  (setq windows (cdr windows)))))
    ;;
    ;; Add the voiceification hooks.
    (lazy-voice-lock-install-hooks
     (or (numberp lazy-voice-lock-defer-time)
	 (if (eq (car (car lazy-voice-lock-defer-time)) 'not)
	     (not (memq major-mode (cdr (car lazy-voice-lock-defer-time))))
	   (memq major-mode (car lazy-voice-lock-defer-time))))
     voice-lock-voiceified
     (eq lazy-voice-lock-defer-driven t))
    ;;
    ;; Add the voiceification timers.
    (lazy-voice-lock-install-timers
     (or (cdr-safe lazy-voice-lock-defer-time) lazy-voice-lock-defer-time)
     lazy-voice-lock-stealth-time)))

(defun lazy-voice-lock-install-hooks (deferring voiceifying defer-driven)
  ;;
  ;; Add hook if lazy-voice-lock.el is deferring or is voiceifying on scrolling.
  (when (or deferring voiceifying)
    (make-local-hook 'window-scroll-functions)
    (add-hook 'window-scroll-functions (if (and deferring defer-driven)
					   'lazy-voice-lock-defer-after-scroll
					 'lazy-voice-lock-voiceify-after-scroll)
	      nil t))
  ;;
  ;; Add hook if lazy-voice-lock.el is not deferring and is voiceifying.
  (when (and (not deferring) voiceifying)
    (make-local-hook 'before-change-functions)
    (add-hook 'before-change-functions 'lazy-voice-lock-arrange-before-change nil t))
  ;;
  ;; Add hook if lazy-voice-lock.el is deferring.
  (when deferring
    (remove-hook 'after-change-functions 'voice-lock-after-change-function t)
    (add-hook 'after-change-functions 'lazy-voice-lock-defer-after-change nil t))
  ;;
  ;; Add package-specific hooks.
  (make-local-hook 'outline-view-change-hook)
  (add-hook 'outline-view-change-hook 'lazy-voice-lock-voiceify-after-outline nil t))

(defun lazy-voice-lock-install-timers (dtime stime)
  ;; Schedule or re-schedule the deferral and stealth timers.
  ;; The layout of `lazy-voice-lock-timers' is:
  ;;  ((DEFER-TIME . DEFER-TIMER) (STEALTH-TIME . STEALTH-TIMER)
  ;; If an idle timeout has changed, cancel the existing idle timer (if there
  ;; is one) and schedule a new one (if the new idle timeout is non-nil).
  (unless (eq dtime (car (car lazy-voice-lock-timers)))
    (let ((defer (car lazy-voice-lock-timers)))
      (when (cdr defer)
	(cancel-timer (cdr defer)))
      (setcar lazy-voice-lock-timers (cons dtime (and dtime
						      (run-with-idle-timer dtime t 'lazy-voice-lock-voiceify-after-defer))))))
  (unless (eq stime (car (cdr lazy-voice-lock-timers)))
    (let ((stealth (cdr lazy-voice-lock-timers)))
      (when (cdr stealth)
	(cancel-timer (cdr stealth)))
      (setcdr lazy-voice-lock-timers (cons stime (and stime
						      (run-with-idle-timer stime t 'lazy-voice-lock-voiceify-after-idle)))))))

(defun lazy-voice-lock-unstall ()
  ;;
  ;; Remove the text properties.
  (lazy-voice-lock-after-unvoiceify-buffer)
  ;;
  ;; Remove the voiceification hooks.
  (remove-hook 'window-scroll-functions 'lazy-voice-lock-voiceify-after-scroll t)
  (remove-hook 'window-scroll-functions 'lazy-voice-lock-defer-after-scroll t)
  (remove-hook 'before-change-functions 'lazy-voice-lock-arrange-before-change t)
  (remove-hook 'after-change-functions 'lazy-voice-lock-defer-after-change t)
  (remove-hook 'outline-view-change-hook 'lazy-voice-lock-voiceify-after-outline t)
  ;;
  ;; IfVoice Lock mode is still enabled, reinstall its hook.
  (when voice-lock-mode
    (add-hook 'after-change-functions 'voice-lock-after-change-function nil t)))

;; Hook functions.

(defun lazy-voice-lock-voiceify-after-scroll (window window-start)
  ;; Called from `window-scroll-functions'.
  ;; Voiceify WINDOW from WINDOW-START.  We cannot use `window-end' so we work
  ;; out what it would be via `vertical-motion'.
  (save-excursion
    (goto-char window-start)
    (vertical-motion (window-height window) window)
    (lazy-voice-lock-voiceify-region window-start (point)))
  ;; A prior deletion that did not cause scrolling, followed by a scroll, would
  ;; result in an unnecessary trigger after this if we did not cancel it now.
  (set-window-redisplay-end-trigger window nil))

(defun lazy-voice-lock-voiceify-after-trigger (window trigger-point)
  ;; Called from `redisplay-end-trigger-functions'.
  ;; Voiceify WINDOW from TRIGGER-POINT.  We cannot use `window-end' so we work
  ;; out what it would be via `vertical-motion'.
  ;; We could probably just use `lazy-voice-lock-voiceify-after-scroll' without loss:
  ;;  (lazy-voice-lock-voiceify-after-scroll window (window-start window))
  (save-excursion
    (goto-char (window-start window))
    (vertical-motion (window-height window) window)
    (lazy-voice-lock-voiceify-region trigger-point (point))))

(defun lazy-voice-lock-voiceify-after-resize (frame)
  ;; Called from `window-size-change-functions'.
  ;; Voiceify windows in FRAME.  We cannot use `window-start' or `window-end' so
  ;; we voiceify conservatively.
  (save-excursion
    (save-selected-window
      (select-frame frame)
      (walk-windows (function (lambda (window)
				(set-buffer (window-buffer window))
				(when lazy-voice-lock-mode
				  (lazy-voice-lock-voiceify-conservatively window))
				(set-window-redisplay-end-trigger window nil)))
		    'nomini frame))))

(defun lazy-voice-lock-arrange-before-change (beg end)
  ;; Called from `before-change-functions'.
  ;; Arrange that if text becomes visible it will be voiceified (if a deletion
  ;; is pending, text might become visible at the bottom).
  (unless (eq beg end)
    (let ((windows (get-buffer-window-list (current-buffer) 'nomini t)) window)
      (while windows
	(setq window (car windows))
	(unless (markerp (window-redisplay-end-trigger window))
	  (set-window-redisplay-end-trigger window (make-marker)))
	(set-marker (window-redisplay-end-trigger window) (window-end window))
	(setq windows (cdr windows))))))

(defun lazy-voice-lock-defer-after-scroll (window window-start)
  ;; Called from `window-scroll-functions'.
  ;; Defer voiceification following the scroll.  Save the current buffer so that
  ;; we subsequently voiceify in all windows showing the buffer.
  (unless (memq (current-buffer) lazy-voice-lock-buffers)
    (push (current-buffer) lazy-voice-lock-buffers)))

(defun lazy-voice-lock-defer-after-change (beg end old-len)
  ;; Called from `after-change-functions'.
  ;; Defer voiceification of the current line.  Save the current buffer so that
  ;; we subsequently voiceify in all windows showing the buffer.
  (save-buffer-state nil
		     (unless (memq (current-buffer) lazy-voice-lock-buffers)
		       (push (current-buffer) lazy-voice-lock-buffers))
		     (remove-text-properties
		      (max (1- beg) (point-min)) (min (1+ end) (point-max)) '(lazy-voice-lock nil))))

(defun lazy-voice-lock-voiceify-after-defer ()
  ;; Called from `timer-idle-list'.
  ;; Voiceify all windows where deferral has occurred for its buffer.
  (while (and lazy-voice-lock-buffers (not (input-pending-p)))
    (let ((windows (get-buffer-window-list (car lazy-voice-lock-buffers) 'nomini t)))
      (while windows
	(lazy-voice-lock-voiceify-window (car windows))
	(setq windows (cdr windows)))
      (setq lazy-voice-lock-buffers (cdr lazy-voice-lock-buffers))))
  ;; Add hook if voiceification should now be defer-driven in this buffer.
  (when (and lazy-voice-lock-mode lazy-voice-lock-defer-driven
	     (memq 'lazy-voice-lock-voiceify-after-scroll window-scroll-functions)
	     (not (or (input-pending-p) (lazy-voice-lock-unvoiceified-p))))
    (remove-hook 'window-scroll-functions 'lazy-voice-lock-voiceify-after-scroll t)
    (add-hook 'window-scroll-functions 'lazy-voice-lock-defer-after-scroll nil t)))

(defun lazy-voice-lock-voiceify-after-idle ()
  ;; Called from `timer-idle-list'.
  ;; Voiceify all buffers that need it, stealthily while idle.
  (unless (or executing-kbd-macro (window-minibuffer-p (selected-window)))
    ;; Loop over all buffers, voiceify stealthily for each if necessary.
    (let ((emacspeak-speak-messages nil)
          (buffers (buffer-list))
          (continue t) message message-log-max)
      (save-excursion
	(do-while (and buffers continue)
		  (set-buffer (car buffers))
		  (if (not (and lazy-voice-lock-mode (lazy-voice-lock-unvoiceified-p)))
		      (setq continue (not (input-pending-p)))
		    ;; Voiceify regions in this buffer while there is no input.
		    (do-while (and (lazy-voice-lock-unvoiceified-p)
				   (setq continue (sit-for lazy-voice-lock-stealth-nice)))
			      (when lazy-voice-lock-stealth-verbose
				(if message
				    (message "Voiceifying stealthily... %2d%% of %s"
					     (lazy-voice-lock-percent-voiceified) (buffer-name))
				  (message "Voiceifying stealthily...")
				  (setq message t)))
			      (lazy-voice-lock-voiceify-chunk)))
		  (setq buffers (cdr buffers))))
      (when message
	(message "Voiceifying stealthily...%s" (if continue "done" "quit"))))))

(defun lazy-voice-lock-voiceify-after-outline ()
  ;; Called from `outline-view-change-hook'.
  ;; Voiceify windows showing the current buffer, as its visibility has changed.
  ;; This is a conspiracy hack between lazy-voice-lock.el and noutline.el.
  (let ((windows (get-buffer-window-list (current-buffer) 'nomini t)))
    (while windows
      (lazy-voice-lock-voiceify-conservatively (car windows))
      (setq windows (cdr windows)))))

(defun lazy-voice-lock-after-voiceify-buffer ()
  ;; Called from `voice-lock-after-voiceify-buffer'.
  ;; Mark the current buffer as voiceified.
  ;; This is a conspiracy hack between lazy-voice-lock.el and voice-lock.el.
  (save-buffer-state nil
		     (add-text-properties (point-min) (point-max) '(lazy-voice-lock t))))

(defun lazy-voice-lock-after-unvoiceify-buffer ()
  ;; Called from `voice-lock-after-unvoiceify-buffer'.
  ;; Mark the current buffer as unvoiceified.
  ;; This is a conspiracy hack between lazy-voice-lock.el and voice-lock.el.
  (save-buffer-state nil
		     (remove-text-properties (point-min) (point-max) '(lazy-voice-lock nil))))

;; Voiceification functions.

;; If packages want to ensure that some region of the buffer is voiceified, they
;; should use this function.  For an example, see ps-print.el.
(defun lazy-voice-lock-voiceify-region (beg end)
  ;; Voiceify between BEG and END, where necessary, in the current buffer.
  (when (setq beg (text-property-any beg end 'lazy-voice-lock nil))
    (save-excursion
      (save-match-data
	(save-buffer-state
	 ;; Ensure syntactic voiceification is always correct.
	 (voice-lock-beginning-of-syntax-function next)
	 ;; Find successive unvoiceified regions between BEG and END.
	 (condition-case data
	     (do-while beg
		       (setq next (or (text-property-any beg end 'lazy-voice-lock t) end))
		       ;; Make sure the region end points are at beginning of line.
		       (goto-char beg)
		       (unless (bolp)
			 (beginning-of-line)
			 (setq beg (point)))
		       (goto-char next)
		       (unless (bolp)
			 (forward-line)
			 (setq next (point)))
		       ;; Voiceify the region, then flag it as voiceified.
		       (voice-lock-voiceify-region beg next)
		       (add-text-properties beg next '(lazy-voice-lock t))
		       (setq beg (text-property-any next end 'lazy-voice-lock nil)))
	   ((error quit) (message "Voiceifying region...%s" data))))))))

(defun lazy-voice-lock-voiceify-chunk ()
  ;; Voiceify the nearest chunk, for stealth, in the current buffer.
  (save-excursion
    (save-restriction
      (widen)
      ;; Move to end of line in case the character at point is not voiceified.
      (end-of-line)
      ;; Find where the previous, and next, unvoiceified regions end, and begin.
      (let ((prev (previous-single-property-change (point) 'lazy-voice-lock))
	    (next (text-property-any (point) (point-max) 'lazy-voice-lock nil)))
	;; Voiceify from the nearest unvoiceified position.
	(if (or (null prev) (and next (< (- next (point)) (- (point) prev))))
	    ;; The next, or neither, region is the nearest not voiceified.
	    (lazy-voice-lock-voiceify-region
	     (progn (goto-char (or next (point-min)))
		    (beginning-of-line)
		    (point))
	     (progn (goto-char (or next (point-min)))
		    (forward-line lazy-voice-lock-stealth-lines)
		    (point)))
	  ;; The previous region is the nearest not voiceified.
	  (lazy-voice-lock-voiceify-region
	   (progn (goto-char prev)
		  (forward-line (- lazy-voice-lock-stealth-lines))
		  (point))
	   (progn (goto-char prev)
		  (forward-line)
		  (point))))))))

(defun lazy-voice-lock-voiceify-window (window)
  ;; Voiceify in WINDOW between `window-start' and `window-end'.
  ;; We can only do this when we can use `window-start' and `window-end'.
  (save-excursion
    (set-buffer (window-buffer window))
    (lazy-voice-lock-voiceify-region (window-start window) (window-end window))))

(defun lazy-voice-lock-voiceify-conservatively (window)
  ;; Voiceify in WINDOW conservatively around point.
  ;; Where we cannot use `window-start' and `window-end' we do `window-height'
  ;; lines around point.  That way we guarantee to have done enough.
  (save-excursion
    (set-buffer (window-buffer window))
    (lazy-voice-lock-voiceify-region
     (save-excursion
       (vertical-motion (- (window-height window)) window) (point))
     (save-excursion
       (vertical-motion (window-height window) window) (point)))))

(defun lazy-voice-lock-unvoiceified-p ()
  ;; Return non-nil if there is anywhere still to be voiceified.
  (save-restriction
    (widen)
    (text-property-any (point-min) (point-max) 'lazy-voice-lock nil)))

(defun lazy-voice-lock-percent-voiceified ()
  ;; Return the percentage (of characters) of the buffer that are voiceified.
  (save-restriction
    (widen)
    (let ((beg (point-min)) (end (point-max)) (size 0) next)
      ;; Find where the next voiceified region begins.
      (while (setq beg (text-property-any beg end 'lazy-voice-lock t))
	(setq next (or (text-property-any beg end 'lazy-voice-lock nil) end)
	      size (+ size (- next beg))
	      beg next))
      (/ (* size 100) (buffer-size)))))

;; Version dependent workarounds and fixes.

(when (if (save-match-data (string-match "Lucid\\|XEmacs" (emacs-version)))
	  nil
	(and (= emacs-major-version 19) (= emacs-minor-version 30)))
  ;;
  ;; We use `post-command-idle-hook' for deferral and stealth.  Oh Lordy.
  (defun lazy-voice-lock-install-timers (foo bar)
    (add-hook 'post-command-idle-hook 'lazy-voice-lock-voiceify-post-command t)
    (add-hook 'post-command-idle-hook 'lazy-voice-lock-voiceify-post-idle t)
    (add-to-list 'lazy-voice-lock-install (current-buffer))
    (add-hook 'post-command-hook 'lazy-voice-lock-voiceify-after-install))
  (defun lazy-voice-lock-voiceify-post-command ()
    (and lazy-voice-lock-buffers (not executing-kbd-macro)
	 (progn
	   (and deactivate-mark (deactivate-mark))
	   (sit-for
	    (or (cdr-safe lazy-voice-lock-defer-time) lazy-voice-lock-defer-time 0)))
	 (lazy-voice-lock-voiceify-after-defer)))
  (defun lazy-voice-lock-voiceify-post-idle ()
    (and lazy-voice-lock-stealth-time (not executing-kbd-macro)
	 (not (window-minibuffer-p (selected-window)))
	 (progn
	   (and deactivate-mark (deactivate-mark))
	   (sit-for lazy-voice-lock-stealth-time))
	 (lazy-voice-lock-voiceify-after-idle)))
  ;;
  ;; Simulate running of `window-scroll-functions' in `set-window-buffer'.
  (defvar lazy-voice-lock-install nil)
  (defun lazy-voice-lock-voiceify-after-install ()
    (remove-hook 'post-command-hook 'lazy-voice-lock-voiceify-after-install)
    (while lazy-voice-lock-install
      (mapcar 'lazy-voice-lock-voiceify-conservatively
	      (get-buffer-window-list (pop lazy-voice-lock-install) 'nomini t)))))

;; Possibly absent.

(unless (boundp 'voice-lock-inhibit-thing-lock)
  ;;Voice Lock mode uses this to direct Lazy and Fast Lock modes to stay off.
  (defvar voice-lock-inhibit-thing-lock nil
    "List ofVoice Lock mode related modes that should not be turned on."))

(unless (fboundp 'voice-lock-value-in-major-mode)
  (defun voice-lock-value-in-major-mode (alist)
    ;; Return value in ALIST for `major-mode'.
    (if (consp alist)
	(cdr (or (assq major-mode alist) (assq t alist)))
      alist)))

(unless (fboundp 'get-buffer-window-list)
  ;; We use this to get all windows showing a buffer we have to voiceify.
  (defun get-buffer-window-list (buffer &optional minibuf frame)
    "Return windows currently displaying BUFFER, or nil if none."
    (let ((buffer (if (bufferp buffer) buffer (get-buffer buffer))) windows)
      (walk-windows (function (lambda (window)
				(when (eq (window-buffer window) buffer)
				  (push window windows))))
		    minibuf frame)
      windows)))

;; Install ourselves:

(add-hook 'window-size-change-functions 'lazy-voice-lock-voiceify-after-resize)
(add-hook 'redisplay-end-trigger-functions 'lazy-voice-lock-voiceify-after-trigger)

(unless (assq 'lazy-voice-lock-mode minor-mode-alist)
  (setq minor-mode-alist (append minor-mode-alist '((lazy-voice-lock-mode nil)))))

;; Provide ourselves:

(provide 'lazy-voice-lock)
;;{{{ end of file 

;;; local variables:
;;; folded-file: t
;;; byte-compile-dynamic: t
;;; end: 

;;}}}

;;; lazy-voice-lock.el ends here

