lisp/lazy-lock.el

   1 ;;; lazy-lock.el --- lazy demand-driven fontification for fast Font Lock mode
   2
   3 ;; Copyright (C) 1994, 1995, 1996, 1997, 1998, 2001
   4 ;;   Free Software Foundation, Inc.
   5
   6 ;; Author: Simon Marshall <simon@gnu.org>
   7 ;; Maintainer: FSF
   8 ;; Keywords: faces files
   9 ;; Version: 2.11
  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., 59 Temple Place - Suite 330,
  26 ;; Boston, MA 02111-1307, USA.
  27
  28 ;;; Commentary:
  29
  30 ;; Purpose:
  31 ;;
  32 ;; Lazy Lock mode is a Font Lock support mode.
  33 ;; It makes visiting buffers in Font Lock mode faster by making fontification
  34 ;; be demand-driven, deferred and stealthy, so that fontification only occurs
  35 ;; when, and where, necessary.
  36 ;;
  37 ;; See caveats and feedback below.
  38 ;; See also the fast-lock package.  (But don't use them at the same time!)
  39
  40 ;; Installation:
  41 ;;
  42 ;; Put in your ~/.emacs:
  43 ;;
  44 ;; (setq font-lock-support-mode 'lazy-lock-mode)
  45 ;;
  46 ;; Start up a new Emacs and use font-lock as usual (except that you can use the
  47 ;; so-called "gaudier" fontification regexps on big files without frustration).
  48 ;;
  49 ;; In a buffer (which has `font-lock-mode' enabled) which is at least
  50 ;; `lazy-lock-minimum-size' characters long, buffer fontification will not
  51 ;; occur and only the visible portion of the buffer will be fontified.  Motion
  52 ;; around the buffer will fontify those visible portions not previously
  53 ;; fontified.  If stealth fontification is enabled, buffer fontification will
  54 ;; occur in invisible parts of the buffer after `lazy-lock-stealth-time'
  55 ;; seconds of idle time.  If on-the-fly fontification is deferred, on-the-fly
  56 ;; fontification will occur after `lazy-lock-defer-time' seconds of idle time.
  57
  58 ;; User-visible differences with version 1:
  59 ;;
  60 ;; - Version 2 can defer on-the-fly fontification.  Therefore you need not, and
  61 ;; should not, use defer-lock.el with this version of lazy-lock.el.
  62 ;;
  63 ;; A number of variables have changed meaning:
  64 ;;
  65 ;; - A value of nil for the variable `lazy-lock-minimum-size' means never turn
  66 ;; on demand-driven fontification.  In version 1 this meant always turn on
  67 ;; demand-driven fontification.  If you really want demand-driven fontification
  68 ;; regardless of buffer size, set this variable to 0.
  69 ;;
  70 ;; - The variable `lazy-lock-stealth-lines' cannot have a nil value.  In
  71 ;; version 1 this meant use `window-height' as the maximum number of lines to
  72 ;; fontify as a stealth chunk.  This makes no sense; stealth fontification is
  73 ;; of a buffer, not a window.
  74
  75 ;; Implementation differences with version 1:
  76 ;;
  77 ;; - Version 1 of lazy-lock.el is a bit of a hack.  Version 1 demand-driven
  78 ;; fontification, the core feature of lazy-lock.el, is implemented by placing a
  79 ;; function on `post-command-hook'.  This function fontifies where necessary,
  80 ;; i.e., where a window scroll has occurred.  However, there are a number of
  81 ;; problems with using `post-command-hook':
  82 ;;
  83 ;; (a) As the name suggests, `post-command-hook' is run after every command,
  84 ;;     i.e., frequently and regardless of whether scrolling has occurred.
  85 ;; (b) Scrolling can occur during a command, when `post-command-hook' is not
  86 ;;     run, i.e., it is not necessarily run after scrolling has occurred.
  87 ;; (c) When `post-command-hook' is run, there is nothing to suggest where
  88 ;;     scrolling might have occurred, i.e., which windows have scrolled.
  89 ;;
  90 ;; Thus lazy-lock.el's function is called almost as often as possible, usually
  91 ;; when it need not be called, yet it is not always called when it is needed.
  92 ;; Also, lazy-lock.el's function must check each window to see if a scroll has
  93 ;; occurred there.  Worse still, lazy-lock.el's function must fontify a region
  94 ;; twice as large as necessary to make sure the window is completely fontified.
  95 ;; Basically, `post-command-hook' is completely inappropriate for lazy-lock.el.
  96 ;;
  97 ;; Ideally, we want to attach lazy-lock.el's function to a hook that is run
  98 ;; only when scrolling occurs, e.g., `window-start' has changed, and tells us
  99 ;; as much information as we need, i.e., the window and its new buffer region.
 100 ;; Richard Stallman implemented a `window-scroll-functions' for Emacs 19.30.
 101 ;; Functions on it are run when `window-start' has changed, and are supplied
 102 ;; with the window and the window's new `window-start' position.  (It would be
 103 ;; better if it also supplied the window's new `window-end' position, but that
 104 ;; is calculated as part of the redisplay process, and the functions on
 105 ;; `window-scroll-functions' are run before redisplay has finished.)  Thus, the
 106 ;; hook deals with the above problems (a), (b) and (c).
 107 ;;
 108 ;; If only life was that easy.  Version 2 demand-driven fontification is mostly
 109 ;; implemented by placing a function on `window-scroll-functions'.  However,
 110 ;; not all scrolling occurs when `window-start' has changed.  A change in
 111 ;; window size, e.g., via C-x 1, or a significant deletion, e.g., of a number
 112 ;; of lines, causes text previously invisible (i.e., after `window-end') to
 113 ;; become visible without changing `window-start'.  Arguably, these events are
 114 ;; not scrolling events, but fontification must occur for lazy-lock.el to work.
 115 ;; Hooks `window-size-change-functions' and `redisplay-end-trigger-functions'
 116 ;; were added for these circumstances.
 117 ;;
 118 ;; (Ben Wing thinks these hooks are "horribly horribly kludgy", and implemented
 119 ;; a `pre-idle-hook', a `mother-of-all-post-command-hooks', for XEmacs 19.14.
 120 ;; He then hacked up a version 1 lazy-lock.el to use `pre-idle-hook' rather
 121 ;; than `post-command-hook'.  Whereas functions on `post-command-hook' are
 122 ;; called almost as often as possible, functions on `pre-idle-hook' really are
 123 ;; called as often as possible, even when the mouse moves and, on some systems,
 124 ;; while XEmacs is idle.  Thus, the hook deals with the above problem (b), but
 125 ;; unfortunately it makes (a) worse and does not address (c) at all.
 126 ;;
 127 ;; I freely admit that `redisplay-end-trigger-functions' and, to a much lesser
 128 ;; extent, `window-size-change-functions' are not pretty.  However, I feel that
 129 ;; a `window-scroll-functions' feature is cleaner than a `pre-idle-hook', and
 130 ;; the result is faster and smaller, less intrusive and more targeted, code.
 131 ;; Since `pre-idle-hook' is pretty much like `post-command-hook', there is no
 132 ;; point in making this version of lazy-lock.el work with it.  Anyway, that's
 133 ;; Lit 30 of my humble opinion.
 134 ;;
 135 ;; - Version 1 stealth fontification is also implemented by placing a function
 136 ;; on `post-command-hook'.  This function waits for a given amount of time,
 137 ;; and, if Emacs remains idle, fontifies where necessary.  Again, there are a
 138 ;; number of problems with using `post-command-hook':
 139 ;;
 140 ;; (a) Functions on `post-command-hook' are run sequentially, so this function
 141 ;;     can interfere with other functions on the hook, and vice versa.
 142 ;; (b) This function waits for a given amount of time, so it can interfere with
 143 ;;     various features that are dealt with by Emacs after a command, e.g.,
 144 ;;     region highlighting, asynchronous updating and keystroke echoing.
 145 ;; (c) Fontification may be required during a command, when `post-command-hook'
 146 ;;     is not run.  (Version 2 deferred fontification only.)
 147 ;;
 148 ;; Again, `post-command-hook' is completely inappropriate for lazy-lock.el.
 149 ;; Richard Stallman and Morten Welinder implemented internal Timers and Idle
 150 ;; Timers for Emacs 19.31.  Functions can be run independently at given times
 151 ;; or after given amounts of idle time.  Thus, the feature deals with the above
 152 ;; problems (a), (b) and (c).  Version 2 deferral and stealth are implemented
 153 ;; by functions on Idle Timers.  (A function on XEmacs' `pre-idle-hook' is
 154 ;; similar to an Emacs Idle Timer function with a fixed zero second timeout.)
 155
 156 ;; - Version 1 has the following problems (relative to version 2):
 157 ;;
 158 ;; (a) It is slow when it does its job.
 159 ;; (b) It does not always do its job when it should.
 160 ;; (c) It slows all interaction (when it doesn't need to do its job).
 161 ;; (d) It interferes with other package functions on `post-command-hook'.
 162 ;; (e) It interferes with Emacs things within the read-eval loop.
 163 ;;
 164 ;; Ben's hacked-up lazy-lock.el 1.14 almost solved (b) but made (c) worse.
 165 ;;
 166 ;; - Version 2 has the following additional features (relative to version 1):
 167 ;;
 168 ;; (a) It can defer fontification (both on-the-fly and on-scrolling).
 169 ;; (b) It can fontify contextually (syntactically true on-the-fly).
 170
 171 ;; Caveats:
 172 ;;
 173 ;; Lazy Lock mode does not work efficiently with Outline mode.
 174 ;; This is because when in Outline mode, although text may be not visible to
 175 ;; you in the window, the text is visible to Emacs Lisp code (not surprisingly)
 176 ;; and Lazy Lock fontifies it mercilessly.  Maybe it will be fixed one day.
 177 ;;
 178 ;; Because buffer text is not necessarily fontified, other packages that expect
 179 ;; buffer text to be fontified in Font Lock mode either might not work as
 180 ;; expected, or might not display buffer text as expected.  An example of the
 181 ;; latter is `occur', which copies lines of buffer text into another buffer.
 182 ;;
 183 ;; In Emacs 19.30, Lazy Lock mode does not ensure that an existing buffer is
 184 ;; fontified if it is made visible via a minibuffer-less command that replaces
 185 ;; an existing window's buffer (e.g., via the Buffers menu).  Upgrade!
 186 ;;
 187 ;; In Emacs 19.30, Lazy Lock mode does not work well with Transient Mark mode
 188 ;; or modes based on Comint mode (e.g., Shell mode), and also interferes with
 189 ;; the echoing of keystrokes in the minibuffer.  This is because of the way
 190 ;; deferral and stealth have to be implemented for Emacs 19.30.  Upgrade!
 191 ;;
 192 ;; Currently XEmacs does not have the features to support this version of
 193 ;; lazy-lock.el.  Maybe it will one day.
 194 \f
 195 ;; History:
 196 ;;
 197 ;; 1.15--2.00:
 198 ;; - Rewrite for Emacs 19.30 and the features rms added to support lazy-lock.el
 199 ;;   so that it could work correctly and efficiently.
 200 ;; - Many thanks to those who reported bugs, fixed bugs, made suggestions or
 201 ;;   otherwise contributed in the version 1 cycle; Jari Aalto, Kevin Broadey,
 202 ;;   Ulrik Dickow, Bill Dubuque, Bob Glickstein, Boris Goldowsky,
 203 ;;   Jonas Jarnestrom, David Karr, Michael Kifer, Erik Naggum, Rick Sladkey,
 204 ;;   Jim Thompson, Ben Wing, Ilya Zakharevich, and Richard Stallman.
 205 ;; 2.00--2.01:
 206 ;; - Made `lazy-lock-fontify-after-command' always `sit-for' and so redisplay
 207 ;; - Use `buffer-name' not `buffer-live-p' (Bill Dubuque hint)
 208 ;; - Made `lazy-lock-install' do `add-to-list' not `setq' of `current-buffer'
 209 ;; - Made `lazy-lock-fontify-after-install' loop over buffer list
 210 ;; - Made `lazy-lock-arrange-before-change' to arrange `window-end' triggering
 211 ;; - Made `lazy-lock-let-buffer-state' wrap both `befter-change-functions'
 212 ;; - Made `lazy-lock-fontify-region' do `condition-case' (Hyman Rosen report)
 213 ;; 2.01--2.02:
 214 ;; - Use `buffer-live-p' as `buffer-name' can barf (Richard Stanton report)
 215 ;; - Made `lazy-lock-install' set `font-lock-fontified' (Kevin Davidson report)
 216 ;; - Made `lazy-lock-install' add hooks only if needed
 217 ;; - Made `lazy-lock-unstall' add `font-lock-after-change-function' if needed
 218 ;; 2.02--2.03:
 219 ;; - Made `lazy-lock-fontify-region' do `condition-case' for `quit' too
 220 ;; - Made `lazy-lock-mode' respect the value of `font-lock-inhibit-thing-lock'
 221 ;; - Added `lazy-lock-after-unfontify-buffer'
 222 ;; - Removed `lazy-lock-fontify-after-install' hack
 223 ;; - Made `lazy-lock-fontify-after-scroll' not `set-buffer' to `window-buffer'
 224 ;; - Made `lazy-lock-fontify-after-trigger' not `set-buffer' to `window-buffer'
 225 ;; - Made `lazy-lock-fontify-after-idle' be interruptible (Scott Burson hint)
 226 ;; 2.03--2.04:
 227 ;; - Rewrite for Emacs 19.31 idle timers
 228 ;; - Renamed `buffer-windows' to `get-buffer-window-list'
 229 ;; - Removed `buffer-live-p'
 230 ;; - Made `lazy-lock-defer-after-change' always save `current-buffer'
 231 ;; - Made `lazy-lock-fontify-after-defer' just process buffers
 232 ;; - Made `lazy-lock-install-hooks' add hooks correctly (Kevin Broadey report)
 233 ;; - Made `lazy-lock-install' cope if `lazy-lock-defer-time' is a list
 234 ;; 2.04--2.05:
 235 ;; - Rewrite for Common Lisp macros
 236 ;; - Added `do-while' macro
 237 ;; - Renamed `lazy-lock-let-buffer-state' macro to `save-buffer-state'
 238 ;; - Returned `lazy-lock-fontify-after-install' hack (Darren Hall hint)
 239 ;; - Added `lazy-lock-defer-on-scrolling' functionality (Scott Byer hint)
 240 ;; - Made `lazy-lock-mode' wrap `font-lock-support-mode'
 241 ;; 2.05--2.06:
 242 ;; - Made `lazy-lock-fontify-after-defer' swap correctly (Scott Byer report)
 243 ;; 2.06--2.07:
 244 ;; - Added `lazy-lock-stealth-load' functionality (Rob Hooft hint)
 245 ;; - Made `lazy-lock-unstall' call `lazy-lock-fontify-region' if needed
 246 ;; - Made `lazy-lock-mode' call `lazy-lock-unstall' only if needed
 247 ;; - Made `lazy-lock-defer-after-scroll' do `set-window-redisplay-end-trigger'
 248 ;; - Added `lazy-lock-defer-contextually' functionality
 249 ;; - Added `lazy-lock-defer-on-the-fly' from `lazy-lock-defer-time'
 250 ;; - Renamed `lazy-lock-defer-driven' to `lazy-lock-defer-on-scrolling'
 251 ;; - Removed `lazy-lock-submit-bug-report' and bade farewell
 252 ;; 2.07--2.08:
 253 ;; - Made `lazy-lock-fontify-conservatively' fontify around `window-point'
 254 ;; - Made `save-buffer-state' wrap `inhibit-point-motion-hooks'
 255 ;; - Added Custom support
 256 ;; 2.08--2.09:
 257 ;; - Removed `byte-*' variables from `eval-when-compile' (Erik Naggum hint)
 258 ;; - Made various wrapping `inhibit-point-motion-hooks' (Vinicius Latorre hint)
 259 ;; - Made `lazy-lock-fontify-after-idle' wrap `minibuffer-auto-raise'
 260 ;; - Made `lazy-lock-fontify-after-defer' paranoid about deferred buffers
 261 ;; 2.09--2.10:
 262 ;; - Use `window-end' UPDATE arg for Emacs 20.4 and later.
 263 ;; - Made deferral `widen' before unfontifying (Dan Nicolaescu report)
 264 ;; - Use `lazy-lock-fontify-after-visage' for hideshow.el (Dan Nicolaescu hint)
 265 ;; - Use `other' widget where possible (Andreas Schwab fix)
 266 ;; 2.10--2.11:
 267 ;; - Used `with-temp-message' where possible to make messages temporary.
 268 \f
 269 ;;; Code:
 270
 271 (require 'font-lock)
 272
 273 (eval-when-compile
 274   ;; We don't do this at the top-level as we only use non-autoloaded macros.
 275   (require 'cl)
 276   ;;
 277   ;; We use this to preserve or protect things when modifying text properties.
 278   (defmacro save-buffer-state (varlist &rest body)
 279     "Bind variables according to VARLIST and eval BODY restoring buffer state."
 280     (` (let* ((,@ (append varlist
 281                    '((modified (buffer-modified-p)) (buffer-undo-list t)
 282                      (inhibit-read-only t) (inhibit-point-motion-hooks t)
 283                      before-change-functions after-change-functions
 284                      deactivate-mark buffer-file-name buffer-file-truename))))
 285          (,@ body)
 286          (when (and (not modified) (buffer-modified-p))
 287            (set-buffer-modified-p nil)))))
 288   (put 'save-buffer-state 'lisp-indent-function 1)
 289   ;;
 290   ;; We use this for clarity and speed.  Naughty but nice.
 291   (defmacro do-while (test &rest body)
 292     "(do-while TEST BODY...): eval BODY... and repeat if TEST yields non-nil.
 293 The order of execution is thus BODY, TEST, BODY, TEST and so on
 294 until TEST returns nil."
 295     (` (while (progn (,@ body) (, test)))))
 296   (put 'do-while 'lisp-indent-function (get 'while 'lisp-indent-function)))
 297
 298 (defvar lazy-lock-mode nil)                     ; Whether we are turned on.
 299 (defvar lazy-lock-buffers nil)                  ; For deferral.
 300 (defvar lazy-lock-timers (cons nil nil))        ; For deferral and stealth.
 301 \f
 302 ;; User Variables:
 303
 304 (defcustom lazy-lock-minimum-size 25600
 305   "*Minimum size of a buffer for demand-driven fontification.
 306 On-demand fontification occurs if the buffer size is greater than this value.
 307 If nil, means demand-driven fontification is never performed.
 308 If a list, each element should be a cons pair of the form (MAJOR-MODE . SIZE),
 309 where MAJOR-MODE is a symbol or t (meaning the default).  For example:
 310  ((c-mode . 25600) (c++-mode . 25600) (rmail-mode . 1048576))
 311 means that the minimum size is 25K for buffers in C or C++ modes, one megabyte
 312 for buffers in Rmail mode, and size is irrelevant otherwise.
 313
 314 The value of this variable is used when Lazy Lock mode is turned on."
 315   :type '(choice (const :tag "none" nil)
 316                  (integer :tag "size")
 317                  (repeat :menu-tag "mode specific" :tag "mode specific"
 318                          :value ((t . nil))
 319                          (cons :tag "Instance"
 320                                (radio :tag "Mode"
 321                                       (const :tag "all" t)
 322                                       (symbol :tag "name"))
 323                                (radio :tag "Size"
 324                                       (const :tag "none" nil)
 325                                       (integer :tag "size")))))
 326   :group 'lazy-lock)
 327
 328 (defcustom lazy-lock-defer-on-the-fly t
 329   "*If non-nil, means fontification after a change should be deferred.
 330 If nil, means on-the-fly fontification is performed.  This means when changes
 331 occur in the buffer, those areas are immediately fontified.
 332 If a list, it should be a list of `major-mode' symbol names for which deferred
 333 fontification should occur.  The sense of the list is negated if it begins with
 334 `not'.  For example:
 335  (c-mode c++-mode)
 336 means that on-the-fly fontification is deferred for buffers in C and C++ modes
 337 only, and deferral does not occur otherwise.
 338
 339 The value of this variable is used when Lazy Lock mode is turned on."
 340   :type '(choice (const :tag "never" nil)
 341                  (const :tag "always" t)
 342                  (set :menu-tag "mode specific" :tag "modes"
 343                       :value (not)
 344                       (const :tag "Except" not)
 345                       (repeat :inline t (symbol :tag "mode"))))
 346   :group 'lazy-lock)
 347
 348 (defcustom lazy-lock-defer-on-scrolling nil
 349   "*If non-nil, means fontification after a scroll should be deferred.
 350 If nil, means demand-driven fontification is performed.  This means when
 351 scrolling into unfontified areas of the buffer, those areas are immediately
 352 fontified.  Thus scrolling never presents unfontified areas.  However, since
 353 fontification occurs during scrolling, scrolling may be slow.
 354 If t, means defer-driven fontification is performed.  This means fontification
 355 of those areas is deferred.  Thus scrolling may present momentarily unfontified
 356 areas.  However, since fontification does not occur during scrolling, scrolling
 357 will be faster than demand-driven fontification.
 358 If any other value, e.g., `eventually', means demand-driven fontification is
 359 performed until the buffer is fontified, then buffer fontification becomes
 360 defer-driven.  Thus scrolling never presents unfontified areas until the buffer
 361 is first fontified, after which subsequent scrolling may present future buffer
 362 insertions momentarily unfontified.  However, since fontification does not
 363 occur during scrolling after the buffer is first fontified, scrolling will
 364 become faster.  (But, since contextual changes continually occur, such a value
 365 makes little sense if `lazy-lock-defer-contextually' is non-nil.)
 366
 367 The value of this variable is used when Lazy Lock mode is turned on."
 368   :type '(choice (const :tag "never" nil)
 369                  (const :tag "always" t)
 370                  (other :tag "eventually" eventually))
 371   :group 'lazy-lock)
 372
 373 (defcustom lazy-lock-defer-contextually 'syntax-driven
 374   "*If non-nil, means deferred fontification should be syntactically true.
 375 If nil, means deferred fontification occurs only on those lines modified.  This
 376 means where modification on a line causes syntactic change on subsequent lines,
 377 those subsequent lines are not refontified to reflect their new context.
 378 If t, means deferred fontification occurs on those lines modified and all
 379 subsequent lines.  This means those subsequent lines are refontified to reflect
 380 their new syntactic context, either immediately or when scrolling into them.
 381 If any other value, e.g., `syntax-driven', means deferred syntactically true
 382 fontification occurs only if syntactic fontification is performed using the
 383 buffer mode's syntax table, i.e., only if `font-lock-keywords-only' is nil.
 384
 385 The value of this variable is used when Lazy Lock mode is turned on."
 386   :type '(choice (const :tag "never" nil)
 387                  (const :tag "always" t)
 388                  (other :tag "syntax-driven" syntax-driven))
 389   :group 'lazy-lock)
 390
 391 (defcustom lazy-lock-defer-time
 392   (if (featurep 'lisp-float-type) (/ (float 1) (float 4)) 1)
 393   "*Time in seconds to delay before beginning deferred fontification.
 394 Deferred fontification occurs if there is no input within this time.
 395 If nil, means fontification is never deferred, regardless of the values of the
 396 variables `lazy-lock-defer-on-the-fly', `lazy-lock-defer-on-scrolling' and
 397 `lazy-lock-defer-contextually'.
 398
 399 The value of this variable is used when Lazy Lock mode is turned on."
 400   :type '(choice (const :tag "never" nil)
 401                  (number :tag "seconds"))
 402   :group 'lazy-lock)
 403
 404 (defcustom lazy-lock-stealth-time 30
 405   "*Time in seconds to delay before beginning stealth fontification.
 406 Stealth fontification occurs if there is no input within this time.
 407 If nil, means stealth fontification is never performed.
 408
 409 The value of this variable is used when Lazy Lock mode is turned on."
 410   :type '(choice (const :tag "never" nil)
 411                  (number :tag "seconds"))
 412   :group 'lazy-lock)
 413
 414 (defcustom lazy-lock-stealth-lines (if font-lock-maximum-decoration 100 250)
 415   "*Maximum size of a chunk of stealth fontification.
 416 Each iteration of stealth fontification can fontify this number of lines.
 417 To speed up input response during stealth fontification, at the cost of stealth
 418 taking longer to fontify, you could reduce the value of this variable."
 419   :type '(integer :tag "lines")
 420   :group 'lazy-lock)
 421
 422 (defcustom lazy-lock-stealth-load
 423   (if (condition-case nil (load-average) (error)) 200)
 424   "*Load in percentage above which stealth fontification is suspended.
 425 Stealth fontification pauses when the system short-term load average (as
 426 returned by the function `load-average' if supported) goes above this level,
 427 thus reducing the demand that stealth fontification makes on the system.
 428 If nil, means stealth fontification is never suspended.
 429 To reduce machine load during stealth fontification, at the cost of stealth
 430 taking longer to fontify, you could reduce the value of this variable.
 431 See also `lazy-lock-stealth-nice'."
 432   :type (if (condition-case nil (load-average) (error))
 433             '(choice (const :tag "never" nil)
 434                      (integer :tag "load"))
 435           '(const :format "%t: unsupported\n" nil))
 436   :group 'lazy-lock)
 437
 438 (defcustom lazy-lock-stealth-nice
 439   (if (featurep 'lisp-float-type) (/ (float 1) (float 8)) 1)
 440   "*Time in seconds to pause between chunks of stealth fontification.
 441 Each iteration of stealth fontification is separated by this amount of time,
 442 thus reducing the demand that stealth fontification makes on the system.
 443 If nil, means stealth fontification is never paused.
 444 To reduce machine load during stealth fontification, at the cost of stealth
 445 taking longer to fontify, you could increase the value of this variable.
 446 See also `lazy-lock-stealth-load'."
 447   :type '(choice (const :tag "never" nil)
 448                  (number :tag "seconds"))
 449   :group 'lazy-lock)
 450
 451 (defcustom lazy-lock-stealth-verbose
 452   (if (featurep 'lisp-float-type)
 453       (and (not lazy-lock-defer-contextually) (not (null font-lock-verbose))))
 454   "*If non-nil, means stealth fontification should show status messages."
 455   :type 'boolean
 456   :group 'lazy-lock)
 457 \f
 458 ;; User Functions:
 459
 460 ;;;###autoload
 461 (defun lazy-lock-mode (&optional arg)
 462   "Toggle Lazy Lock mode.
 463 With arg, turn Lazy Lock mode on if and only if arg is positive.  Enable it
 464 automatically in your `~/.emacs' by:
 465
 466  (setq font-lock-support-mode 'lazy-lock-mode)
 467
 468 When Lazy Lock mode is enabled, fontification can be lazy in a number of ways:
 469
 470 - Demand-driven buffer fontification if `lazy-lock-minimum-size' is non-nil.
 471   This means initial fontification does not occur if the buffer is greater than
 472   `lazy-lock-minimum-size' characters in length.  Instead, fontification occurs
 473   when necessary, such as when scrolling through the buffer would otherwise
 474   reveal unfontified areas.  This is useful if buffer fontification is too slow
 475   for large buffers.
 476
 477 - Deferred scroll fontification if `lazy-lock-defer-on-scrolling' is non-nil.
 478   This means demand-driven fontification does not occur as you scroll.
 479   Instead, fontification is deferred until after `lazy-lock-defer-time' seconds
 480   of Emacs idle time, while Emacs remains idle.  This is useful if
 481   fontification is too slow to keep up with scrolling.
 482
 483 - Deferred on-the-fly fontification if `lazy-lock-defer-on-the-fly' is non-nil.
 484   This means on-the-fly fontification does not occur as you type.  Instead,
 485   fontification is deferred until after `lazy-lock-defer-time' seconds of Emacs
 486   idle time, while Emacs remains idle.  This is useful if fontification is too
 487   slow to keep up with your typing.
 488
 489 - Deferred context fontification if `lazy-lock-defer-contextually' is non-nil.
 490   This means fontification updates the buffer corresponding to true syntactic
 491   context, after `lazy-lock-defer-time' seconds of Emacs idle time, while Emacs
 492   remains idle.  Otherwise, fontification occurs on modified lines only, and
 493   subsequent lines can remain fontified corresponding to previous syntactic
 494   contexts.  This is useful where strings or comments span lines.
 495
 496 - Stealthy buffer fontification if `lazy-lock-stealth-time' is non-nil.
 497   This means remaining unfontified areas of buffers are fontified if Emacs has
 498   been idle for `lazy-lock-stealth-time' seconds, while Emacs remains idle.
 499   This is useful if any buffer has any deferred fontification.
 500
 501 Basic Font Lock mode on-the-fly fontification behaviour fontifies modified
 502 lines only.  Thus, if `lazy-lock-defer-contextually' is non-nil, Lazy Lock mode
 503 on-the-fly fontification may fontify differently, albeit correctly.  In any
 504 event, to refontify some lines you can use \\[font-lock-fontify-block].
 505
 506 Stealth fontification only occurs while the system remains unloaded.
 507 If the system load rises above `lazy-lock-stealth-load' percent, stealth
 508 fontification is suspended.  Stealth fontification intensity is controlled via
 509 the variable `lazy-lock-stealth-nice' and `lazy-lock-stealth-lines', and
 510 verbosity is controlled via the variable `lazy-lock-stealth-verbose'."
 511   (interactive "P")
 512   (let* ((was-on lazy-lock-mode)
 513          (now-on (unless (memq 'lazy-lock-mode font-lock-inhibit-thing-lock)
 514                    (if arg (> (prefix-numeric-value arg) 0) (not was-on)))))
 515     (cond ((and now-on (not font-lock-mode))
 516            ;; Turned on `lazy-lock-mode' rather than `font-lock-mode'.
 517            (let ((font-lock-support-mode 'lazy-lock-mode))
 518              (font-lock-mode t)))
 519           (now-on
 520            ;; Turn ourselves on.
 521            (set (make-local-variable 'lazy-lock-mode) t)
 522            (lazy-lock-install))
 523           (was-on
 524            ;; Turn ourselves off.
 525            (set (make-local-variable 'lazy-lock-mode) nil)
 526            (lazy-lock-unstall)))))
 527
 528 ;;;###autoload
 529 (defun turn-on-lazy-lock ()
 530   "Unconditionally turn on Lazy Lock mode."
 531   (lazy-lock-mode t))
 532
 533 (defun lazy-lock-install ()
 534   (let ((min-size (font-lock-value-in-major-mode lazy-lock-minimum-size))
 535         (defer-change (and lazy-lock-defer-time lazy-lock-defer-on-the-fly))
 536         (defer-scroll (and lazy-lock-defer-time lazy-lock-defer-on-scrolling))
 537         (defer-context (and lazy-lock-defer-time lazy-lock-defer-contextually
 538                             (or (eq lazy-lock-defer-contextually t)
 539                                 (null font-lock-keywords-only)))))
 540     ;;
 541     ;; Tell Font Lock whether Lazy Lock will do fontification.
 542     (make-local-variable 'font-lock-fontified)
 543     (setq font-lock-fontified (and min-size (>= (buffer-size) min-size)))
 544     ;;
 545     ;; Add the text properties and fontify.
 546     (if (not font-lock-fontified)
 547         (lazy-lock-after-fontify-buffer)
 548       ;; Make sure we fontify in any existing windows showing the buffer.
 549       (let ((windows (get-buffer-window-list (current-buffer) 'nomini t)))
 550         (lazy-lock-after-unfontify-buffer)
 551         (while windows
 552           (lazy-lock-fontify-conservatively (car windows))
 553           (setq windows (cdr windows)))))
 554     ;;
 555     ;; Add the fontification hooks.
 556     (lazy-lock-install-hooks
 557      font-lock-fontified
 558      (cond ((eq (car-safe defer-change) 'not)
 559             (not (memq major-mode (cdr defer-change))))
 560            ((listp defer-change)
 561             (memq major-mode defer-change))
 562            (t
 563             defer-change))
 564      (eq defer-scroll t)
 565      defer-context)
 566     ;;
 567     ;; Add the fontification timers.
 568     (lazy-lock-install-timers
 569      (if (or defer-change defer-scroll defer-context) lazy-lock-defer-time)
 570      lazy-lock-stealth-time)))
 571
 572 (defun lazy-lock-install-hooks (fontifying
 573                                 defer-change defer-scroll defer-context)
 574   ;;
 575   ;; Add hook if lazy-lock.el is fontifying on scrolling or is deferring.
 576   (when (or fontifying defer-change defer-scroll defer-context)
 577     (make-local-hook 'window-scroll-functions)
 578     (add-hook 'window-scroll-functions (if defer-scroll
 579                                            'lazy-lock-defer-after-scroll
 580                                          'lazy-lock-fontify-after-scroll)
 581               nil t))
 582   ;;
 583   ;; Add hook if lazy-lock.el is fontifying and is not deferring changes.
 584   (when (and fontifying (not defer-change) (not defer-context))
 585     (make-local-hook 'before-change-functions)
 586     (add-hook 'before-change-functions 'lazy-lock-arrange-before-change nil t))
 587   ;;
 588   ;; Replace Font Lock mode hook.
 589   (remove-hook 'after-change-functions 'font-lock-after-change-function t)
 590   (add-hook 'after-change-functions
 591             (cond ((and defer-change defer-context)
 592                    'lazy-lock-defer-rest-after-change)
 593                   (defer-change
 594                    'lazy-lock-defer-line-after-change)
 595                   (defer-context
 596                    'lazy-lock-fontify-rest-after-change)
 597                   (t
 598                    'lazy-lock-fontify-line-after-change))
 599             nil t)
 600   ;;
 601   ;; Add package-specific hook.
 602   (make-local-hook 'outline-view-change-hook)
 603   (add-hook 'outline-view-change-hook 'lazy-lock-fontify-after-visage nil t)
 604   (make-local-hook 'hs-hide-hook)
 605   (add-hook 'hs-hide-hook 'lazy-lock-fontify-after-visage nil t))
 606
 607 (defun lazy-lock-install-timers (dtime stime)
 608   ;; Schedule or re-schedule the deferral and stealth timers.
 609   ;; The layout of `lazy-lock-timers' is:
 610   ;;  ((DEFER-TIME . DEFER-TIMER) (STEALTH-TIME . STEALTH-TIMER)
 611   ;; If an idle timeout has changed, cancel the existing idle timer (if there
 612   ;; is one) and schedule a new one (if the new idle timeout is non-nil).
 613   (unless (eq dtime (car (car lazy-lock-timers)))
 614     (let ((defer (car lazy-lock-timers)))
 615       (when (cdr defer)
 616         (cancel-timer (cdr defer)))
 617       (setcar lazy-lock-timers (cons dtime (and dtime
 618               (run-with-idle-timer dtime t 'lazy-lock-fontify-after-defer))))))
 619   (unless (eq stime (car (cdr lazy-lock-timers)))
 620     (let ((stealth (cdr lazy-lock-timers)))
 621       (when (cdr stealth)
 622         (cancel-timer (cdr stealth)))
 623       (setcdr lazy-lock-timers (cons stime (and stime
 624               (run-with-idle-timer stime t 'lazy-lock-fontify-after-idle)))))))
 625
 626 (defun lazy-lock-unstall ()
 627   ;;
 628   ;; If Font Lock mode is still enabled, make sure that the buffer is
 629   ;; fontified, and reinstall its hook.  We must do this first.
 630   (when font-lock-mode
 631     (when (lazy-lock-unfontified-p)
 632       (let ((verbose (if (numberp font-lock-verbose)
 633                          (> (buffer-size) font-lock-verbose)
 634                        font-lock-verbose)))
 635         (with-temp-message
 636             (when verbose
 637               (format "Fontifying %s..." (buffer-name)))
 638           ;; Make sure we fontify etc. in the whole buffer.
 639           (save-restriction
 640             (widen)
 641             (lazy-lock-fontify-region (point-min) (point-max))))))
 642     (add-hook 'after-change-functions 'font-lock-after-change-function nil t))
 643   ;;
 644   ;; Remove the text properties.
 645   (lazy-lock-after-unfontify-buffer)
 646   ;;
 647   ;; Remove the fontification hooks.
 648   (remove-hook 'window-scroll-functions 'lazy-lock-fontify-after-scroll t)
 649   (remove-hook 'window-scroll-functions 'lazy-lock-defer-after-scroll t)
 650   (remove-hook 'before-change-functions 'lazy-lock-arrange-before-change t)
 651   (remove-hook 'after-change-functions 'lazy-lock-fontify-line-after-change t)
 652   (remove-hook 'after-change-functions 'lazy-lock-fontify-rest-after-change t)
 653   (remove-hook 'after-change-functions 'lazy-lock-defer-line-after-change t)
 654   (remove-hook 'after-change-functions 'lazy-lock-defer-rest-after-change t)
 655   (remove-hook 'outline-view-change-hook 'lazy-lock-fontify-after-visage t)
 656   (remove-hook 'hs-hide-hook 'lazy-lock-fontify-after-visage t))
 657 \f
 658 ;; Hook functions.
 659
 660 ;; Lazy Lock mode intervenes when (1) a previously invisible buffer region
 661 ;; becomes visible, i.e., for demand- or defer-driven on-the-scroll
 662 ;; fontification, (2) a buffer modification occurs, i.e., for defer-driven
 663 ;; on-the-fly fontification, (3) Emacs becomes idle, i.e., for fontification of
 664 ;; deferred fontification and stealth fontification, and (4) other special
 665 ;; occasions.
 666
 667 ;; 1.  There are three ways whereby this can happen.
 668 ;;
 669 ;; (a) Scrolling the window, either explicitly (e.g., `scroll-up') or
 670 ;;     implicitly (e.g., `search-forward').  Here, `window-start' changes.
 671 ;;     Fontification occurs by adding `lazy-lock-fontify-after-scroll' (for
 672 ;;     demand-driven fontification) or `lazy-lock-defer-after-scroll' (for
 673 ;;     defer-driven fontification) to the hook `window-scroll-functions'.
 674
 675 (defun lazy-lock-fontify-after-scroll (window window-start)
 676   ;; Called from `window-scroll-functions'.
 677   ;; Fontify WINDOW from WINDOW-START following the scroll.
 678   (let ((inhibit-point-motion-hooks t))
 679     (lazy-lock-fontify-region window-start (window-end window t)))
 680   ;; A prior deletion that did not cause scrolling, followed by a scroll, would
 681   ;; result in an unnecessary trigger after this if we did not cancel it now.
 682   (set-window-redisplay-end-trigger window nil))
 683
 684 (defun lazy-lock-defer-after-scroll (window window-start)
 685   ;; Called from `window-scroll-functions'.
 686   ;; Defer fontification following the scroll.  Save the current buffer so that
 687   ;; we subsequently fontify in all windows showing the buffer.
 688   (unless (memq (current-buffer) lazy-lock-buffers)
 689     (push (current-buffer) lazy-lock-buffers))
 690   ;; A prior deletion that did not cause scrolling, followed by a scroll, would
 691   ;; result in an unnecessary trigger after this if we did not cancel it now.
 692   (set-window-redisplay-end-trigger window nil))
 693
 694 ;; (b) Resizing the window, either explicitly (e.g., `enlarge-window') or
 695 ;;     implicitly (e.g., `delete-other-windows').  Here, `window-end' changes.
 696 ;;     Fontification occurs by adding `lazy-lock-fontify-after-resize' to the
 697 ;;     hook `window-size-change-functions'.
 698
 699 (defun lazy-lock-fontify-after-resize (frame)
 700   ;; Called from `window-size-change-functions'.
 701   ;; Fontify windows in FRAME following the resize.  We cannot use
 702   ;; `window-start' or `window-end' so we fontify conservatively.
 703   (save-excursion
 704     (save-selected-window
 705       (select-frame frame)
 706       (walk-windows (function (lambda (window)
 707                        (set-buffer (window-buffer window))
 708                        (when lazy-lock-mode
 709                          (lazy-lock-fontify-conservatively window))
 710                        (set-window-redisplay-end-trigger window nil)))
 711                     'nomini frame))))
 712
 713 ;; (c) Deletion in the buffer.  Here, a `window-end' marker can become visible.
 714 ;;     Fontification occurs by adding `lazy-lock-arrange-before-change' to
 715 ;;     `before-change-functions' and `lazy-lock-fontify-after-trigger' to the
 716 ;;     hook `redisplay-end-trigger-functions'.  Before every deletion, the
 717 ;;     marker `window-redisplay-end-trigger' position is set to the soon-to-be
 718 ;;     changed `window-end' position.  If the marker becomes visible,
 719 ;;     `lazy-lock-fontify-after-trigger' gets called.  Ouch.  Note that we only
 720 ;;     have to deal with this eventuality if there is no on-the-fly deferral.
 721
 722 (defun lazy-lock-arrange-before-change (beg end)
 723   ;; Called from `before-change-functions'.
 724   ;; Arrange that if text becomes visible it will be fontified (if a deletion
 725   ;; is pending, text might become visible at the bottom).
 726   (unless (eq beg end)
 727     (let ((windows (get-buffer-window-list (current-buffer) 'nomini t)) window)
 728       (while windows
 729         (setq window (car windows))
 730         (unless (markerp (window-redisplay-end-trigger window))
 731           (set-window-redisplay-end-trigger window (make-marker)))
 732         (set-marker (window-redisplay-end-trigger window) (window-end window))
 733         (setq windows (cdr windows))))))
 734
 735 (defun lazy-lock-fontify-after-trigger (window trigger-point)
 736   ;; Called from `redisplay-end-trigger-functions'.
 737   ;; Fontify WINDOW from TRIGGER-POINT following the redisplay.
 738   ;; We could probably just use `lazy-lock-fontify-after-scroll' without loss:
 739   ;;  (inline (lazy-lock-fontify-after-scroll window (window-start window)))
 740   (let ((inhibit-point-motion-hooks t))
 741     (lazy-lock-fontify-region trigger-point (window-end window t))))
 742
 743 ;; 2.  Modified text must be marked as unfontified so it can be identified and
 744 ;;     fontified later when Emacs is idle.  Deferral occurs by adding one of
 745 ;;     `lazy-lock-fontify-*-after-change' (for on-the-fly fontification) or
 746 ;;     `lazy-lock-defer-*-after-change' (for deferred fontification) to the
 747 ;;     hook `after-change-functions'.
 748
 749 (defalias 'lazy-lock-fontify-line-after-change
 750   ;; Called from `after-change-functions'.
 751   ;; Fontify the current change.
 752   'font-lock-after-change-function)
 753
 754 (defun lazy-lock-fontify-rest-after-change (beg end old-len)
 755   ;; Called from `after-change-functions'.
 756   ;; Fontify the current change and defer fontification of the rest of the
 757   ;; buffer.  Save the current buffer so that we subsequently fontify in all
 758   ;; windows showing the buffer.
 759   (lazy-lock-fontify-line-after-change beg end old-len)
 760   (save-buffer-state nil
 761     (unless (memq (current-buffer) lazy-lock-buffers)
 762       (push (current-buffer) lazy-lock-buffers))
 763     (save-restriction
 764       (widen)
 765       (remove-text-properties end (point-max) '(lazy-lock nil)))))
 766
 767 (defun lazy-lock-defer-line-after-change (beg end old-len)
 768   ;; Called from `after-change-functions'.
 769   ;; Defer fontification of the current change.  Save the current buffer so
 770   ;; that we subsequently fontify in all windows showing the buffer.
 771   (save-buffer-state nil
 772     (unless (memq (current-buffer) lazy-lock-buffers)
 773       (push (current-buffer) lazy-lock-buffers))
 774     (remove-text-properties (max (1- beg) (point-min))
 775                             (min (1+ end) (point-max))
 776                             '(lazy-lock nil))))
 777
 778 (defun lazy-lock-defer-rest-after-change (beg end old-len)
 779   ;; Called from `after-change-functions'.
 780   ;; Defer fontification of the rest of the buffer.  Save the current buffer so
 781   ;; that we subsequently fontify in all windows showing the buffer.
 782   (save-buffer-state nil
 783     (unless (memq (current-buffer) lazy-lock-buffers)
 784       (push (current-buffer) lazy-lock-buffers))
 785     (save-restriction
 786       (widen)
 787       (remove-text-properties (max (1- beg) (point-min))
 788                               (point-max)
 789                               '(lazy-lock nil)))))
 790
 791 ;; 3.  Deferred fontification and stealth fontification are done from these two
 792 ;;     functions.  They are set up as Idle Timers.
 793
 794 (defun lazy-lock-fontify-after-defer ()
 795   ;; Called from `timer-idle-list'.
 796   ;; Fontify all windows where deferral has occurred for its buffer.
 797   (save-excursion
 798     (while (and lazy-lock-buffers (not (input-pending-p)))
 799       (let ((buffer (car lazy-lock-buffers)) windows)
 800         ;; Paranoia: check that the buffer is still live and Lazy Lock mode on.
 801         (when (buffer-live-p buffer)
 802           (set-buffer buffer)
 803           (when lazy-lock-mode
 804             (setq windows (get-buffer-window-list buffer 'nomini t))
 805             (while windows
 806               (lazy-lock-fontify-window (car windows))
 807               (setq windows (cdr windows)))))
 808         (setq lazy-lock-buffers (cdr lazy-lock-buffers)))))
 809   ;; Add hook if fontification should now be defer-driven in this buffer.
 810   (when (and lazy-lock-mode lazy-lock-defer-on-scrolling
 811              (memq 'lazy-lock-fontify-after-scroll window-scroll-functions)
 812              (not (or (input-pending-p) (lazy-lock-unfontified-p))))
 813     (remove-hook 'window-scroll-functions 'lazy-lock-fontify-after-scroll t)
 814     (add-hook 'window-scroll-functions 'lazy-lock-defer-after-scroll nil t)))
 815
 816 (defun lazy-lock-fontify-after-idle ()
 817   ;; Called from `timer-idle-list'.
 818   ;; Fontify all buffers that need it, stealthily while idle.
 819   (unless (or executing-kbd-macro (window-minibuffer-p (selected-window)))
 820     ;; Loop over all buffers, fontify stealthily for each if necessary.
 821     (let ((buffers (buffer-list)) (continue t)
 822           message message-log-max minibuffer-auto-raise)
 823       (save-excursion
 824         (do-while (and buffers continue)
 825           (set-buffer (car buffers))
 826           (if (not (and lazy-lock-mode (lazy-lock-unfontified-p)))
 827               (setq continue (not (input-pending-p)))
 828             ;; Fontify regions in this buffer while there is no input.
 829             (with-temp-message
 830                 (when lazy-lock-stealth-verbose
 831                   "Fontifying stealthily...")
 832               (do-while (and (lazy-lock-unfontified-p) continue)
 833                 (if (and lazy-lock-stealth-load
 834                          (> (car (load-average)) lazy-lock-stealth-load))
 835                     ;; Wait a while before continuing with the loop.
 836                     (progn
 837                       (when message
 838                         (message "Fontifying stealthily...suspended")
 839                         (setq message nil))
 840                       (setq continue (sit-for (or lazy-lock-stealth-time 30))))
 841                   ;; Fontify a chunk.
 842                   (when lazy-lock-stealth-verbose
 843                     (if message
 844                         (message "Fontifying stealthily... %2d%% of %s"
 845                                  (lazy-lock-percent-fontified) (buffer-name))
 846                       (message "Fontifying stealthily...")
 847                       (setq message t)))
 848                   ;; Current buffer may have changed during `sit-for'.
 849                   (set-buffer (car buffers))
 850                   (lazy-lock-fontify-chunk)
 851                   (setq continue (sit-for (or lazy-lock-stealth-nice 0)))))))
 852           (setq buffers (cdr buffers)))))))
 853
 854 ;; 4.  Special circumstances.
 855
 856 (defun lazy-lock-fontify-after-visage ()
 857   ;; Called from `outline-view-change-hook' and `hs-hide-hook'.
 858   ;; Fontify windows showing the current buffer, as its visibility has changed.
 859   ;; This is a conspiracy hack between lazy-lock.el, outline.el and
 860   ;; hideshow.el.
 861   (let ((windows (get-buffer-window-list (current-buffer) 'nomini t)))
 862     (while windows
 863       (lazy-lock-fontify-conservatively (car windows))
 864       (setq windows (cdr windows)))))
 865
 866 (defun lazy-lock-after-fontify-buffer ()
 867   ;; Called from `font-lock-after-fontify-buffer'.
 868   ;; Mark the current buffer as fontified.
 869   ;; This is a conspiracy hack between lazy-lock.el and font-lock.el.
 870   (save-buffer-state nil
 871     (add-text-properties (point-min) (point-max) '(lazy-lock t))))
 872
 873 (defun lazy-lock-after-unfontify-buffer ()
 874   ;; Called from `font-lock-after-unfontify-buffer'.
 875   ;; Mark the current buffer as unfontified.
 876   ;; This is a conspiracy hack between lazy-lock.el and font-lock.el.
 877   (save-buffer-state nil
 878     (remove-text-properties (point-min) (point-max) '(lazy-lock nil))))
 879 \f
 880 ;; Fontification functions.
 881
 882 ;; If packages want to ensure that some region of the buffer is fontified, they
 883 ;; should use this function.  For an example, see ps-print.el.
 884 (defun lazy-lock-fontify-region (beg end)
 885   ;; Fontify between BEG and END, where necessary, in the current buffer.
 886   (save-restriction
 887     (widen)
 888     (when (setq beg (text-property-any beg end 'lazy-lock nil))
 889       (save-excursion
 890         (save-match-data
 891           (save-buffer-state
 892            ;; Ensure syntactic fontification is always correct.
 893            (font-lock-beginning-of-syntax-function next)
 894            ;; Find successive unfontified regions between BEG and END.
 895            (condition-case data
 896                (do-while beg
 897                          (setq next (or (text-property-any beg end 'lazy-lock t) end))
 898           ;; Make sure the region end points are at beginning of line.
 899                          (goto-char beg)
 900                          (unless (bolp)
 901                            (beginning-of-line)
 902                            (setq beg (point)))
 903                          (goto-char next)
 904                          (unless (bolp)
 905                            (forward-line)
 906                            (setq next (point)))
 907                      ;; Fontify the region, then flag it as fontified.
 908                          (font-lock-fontify-region beg next)
 909                          (add-text-properties beg next '(lazy-lock t))
 910                          (setq beg (text-property-any next end 'lazy-lock nil)))
 911              ((error quit) (message "Fontifying region...%s" data)))))))))
 912
 913 (defun lazy-lock-fontify-chunk ()
 914   ;; Fontify the nearest chunk, for stealth, in the current buffer.
 915   (let ((inhibit-point-motion-hooks t))
 916     (save-excursion
 917       (save-restriction
 918         (widen)
 919         ;; Move to end of line in case the character at point is not fontified.
 920         (end-of-line)
 921         ;; Find where the previous (next) unfontified regions end (begin).
 922         (let ((prev (previous-single-property-change (point) 'lazy-lock))
 923               (next (text-property-any (point) (point-max) 'lazy-lock nil)))
 924           ;; Fontify from the nearest unfontified position.
 925           (if (or (null prev) (and next (< (- next (point)) (- (point) prev))))
 926               ;; The next, or neither, region is the nearest not fontified.
 927               (lazy-lock-fontify-region
 928                (progn (goto-char (or next (point-min)))
 929                       (beginning-of-line)
 930                       (point))
 931                (progn (goto-char (or next (point-min)))
 932                       (forward-line lazy-lock-stealth-lines)
 933                       (point)))
 934             ;; The previous region is the nearest not fontified.
 935             (lazy-lock-fontify-region
 936              (progn (goto-char prev)
 937                     (forward-line (- lazy-lock-stealth-lines))
 938                     (point))
 939              (progn (goto-char prev)
 940                     (forward-line)
 941                     (point)))))))))
 942
 943 (defun lazy-lock-fontify-window (window)
 944   ;; Fontify in WINDOW between `window-start' and `window-end'.
 945   ;; We can only do this when we can use `window-start' and `window-end'.
 946   (with-current-buffer (window-buffer window)
 947     (lazy-lock-fontify-region (window-start window) (window-end window))))
 948
 949 (defun lazy-lock-fontify-conservatively (window)
 950   ;; Fontify in WINDOW conservatively around point.
 951   ;; Where we cannot use `window-start' and `window-end' we do `window-height'
 952   ;; lines around point.  That way we guarantee to have done enough.
 953   (with-current-buffer (window-buffer window)
 954     (let ((inhibit-point-motion-hooks t))
 955       (lazy-lock-fontify-region
 956        (save-excursion
 957          (goto-char (window-point window))
 958          (vertical-motion (- (window-height window)) window) (point))
 959        (save-excursion
 960          (goto-char (window-point window))
 961          (vertical-motion (window-height window) window) (point))))))
 962
 963 (defun lazy-lock-unfontified-p ()
 964   ;; Return non-nil if there is anywhere still to be fontified.
 965   (save-restriction
 966     (widen)
 967     (text-property-any (point-min) (point-max) 'lazy-lock nil)))
 968
 969 (defun lazy-lock-percent-fontified ()
 970   ;; Return the percentage (of characters) of the buffer that are fontified.
 971   (save-restriction
 972     (widen)
 973     (let ((beg (point-min)) (size 0) next)
 974       ;; Find where the next fontified region begins.
 975       (while (setq beg (text-property-any beg (point-max) 'lazy-lock t))
 976         (setq next (or (text-property-any beg (point-max) 'lazy-lock nil)
 977                        (point-max)))
 978         (incf size (- next beg))
 979         (setq beg next))
 980       ;; Float because using integer multiplication will frequently overflow.
 981       (truncate (* (/ (float size) (point-max)) 100)))))
 982 \f
 983 ;; Version dependent workarounds and fixes.
 984
 985 (when (consp lazy-lock-defer-time)
 986   ;;
 987   ;; In 2.06.04 and below, `lazy-lock-defer-time' could specify modes and time.
 988   (with-output-to-temp-buffer "*Help*"
 989     (princ "The value of the variable `lazy-lock-defer-time' was\n ")
 990     (princ lazy-lock-defer-time)
 991     (princ "\n")
 992     (princ "This variable cannot now be a list of modes and time,\n")
 993     (princ "so instead use ")
 994     (princ (substitute-command-keys "\\[customize-option]"))
 995     (princ " to modify the variables, or put the forms:\n")
 996     (princ " (setq lazy-lock-defer-time ")
 997     (princ (cdr lazy-lock-defer-time))
 998     (princ ")\n")
 999     (princ " (setq lazy-lock-defer-on-the-fly '")
1000     (princ (car lazy-lock-defer-time))
1001     (princ ")\n")
1002     (princ "in your ~/.emacs.  ")
1003     (princ "The above forms have been evaluated for this editor session,\n")
1004     (princ "but you should use ")
1005     (princ (substitute-command-keys "\\[customize-option]"))
1006     (princ " or change your ~/.emacs now."))
1007   (setq lazy-lock-defer-on-the-fly (car lazy-lock-defer-time)
1008         lazy-lock-defer-time (cdr lazy-lock-defer-time)))
1009
1010 (when (boundp 'lazy-lock-defer-driven)
1011   ;;
1012   ;; In 2.06.04 and below, `lazy-lock-defer-driven' was the variable name.
1013   (with-output-to-temp-buffer "*Help*"
1014     (princ "The value of the variable `lazy-lock-defer-driven' is set to ")
1015     (if (memq lazy-lock-defer-driven '(nil t))
1016         (princ lazy-lock-defer-driven)
1017       (princ "`")
1018       (princ lazy-lock-defer-driven)
1019       (princ "'"))
1020     (princ ".\n")
1021     (princ "This variable is now called `lazy-lock-defer-on-scrolling',\n")
1022     (princ "so instead use ")
1023     (princ (substitute-command-keys "\\[customize-option]"))
1024     (princ " to modify the variable, or put the form:\n")
1025     (princ " (setq lazy-lock-defer-on-scrolling ")
1026     (unless (memq lazy-lock-defer-driven '(nil t))
1027       (princ "'"))
1028     (princ lazy-lock-defer-driven)
1029     (princ ")\n")
1030     (princ "in your ~/.emacs.  ")
1031     (princ "The above form has been evaluated for this editor session,\n")
1032     (princ "but you should use ")
1033     (princ (substitute-command-keys "\\[customize-option]"))
1034     (princ " or change your ~/.emacs now."))
1035   (setq lazy-lock-defer-on-scrolling lazy-lock-defer-driven))
1036 \f
1037 ;; Install ourselves:
1038
1039 (add-hook 'window-size-change-functions 'lazy-lock-fontify-after-resize)
1040 (add-hook 'redisplay-end-trigger-functions 'lazy-lock-fontify-after-trigger)
1041
1042 (unless (assq 'lazy-lock-mode minor-mode-alist)
1043   (setq minor-mode-alist (append minor-mode-alist '((lazy-lock-mode nil)))))
1044
1045 ;; Provide ourselves:
1046
1047 (provide 'lazy-lock)
1048
1049 ;;; lazy-lock.el ends here