Source

emacs / lisp / lazy-lock.el

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
;;; lazy-lock.el --- Lazy demand-driven fontification for fast Font Lock mode.

;; Copyright (C) 1994, 1995, 1996, 1997 Free Software Foundation, Inc.

;; Author: Simon Marshall <simon@gnu.ai.mit.edu>
;; Keywords: faces files
;; Version: 2.08.04

;;; 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:
;;
;; Lazy Lock mode is a Font Lock support mode.
;; It makes visiting buffers in Font Lock mode faster by making fontification
;; be demand-driven, deferred and stealthy, so that fontification 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 font-lock-support-mode 'lazy-lock-mode)
;;
;; Start up a new Emacs and use font-lock as usual (except that you can use the
;; so-called "gaudier" fontification regexps on big files without frustration).
;;
;; In a buffer (which has `font-lock-mode' enabled) which is at least
;; `lazy-lock-minimum-size' characters long, buffer fontification will not
;; occur and only the visible portion of the buffer will be fontified.  Motion
;; around the buffer will fontify those visible portions not previously
;; fontified.  If stealth fontification is enabled, buffer fontification will
;; occur in invisible parts of the buffer after `lazy-lock-stealth-time'
;; seconds of idle time.  If on-the-fly fontification is deferred, on-the-fly
;; fontification will occur after `lazy-lock-defer-time' seconds of idle time.

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

;; Implementation differences with version 1:
;;
;; - Version 1 of lazy-lock.el is a bit of a hack.  Version 1 demand-driven
;; fontification, the core feature of lazy-lock.el, is implemented by placing a
;; function on `post-command-hook'.  This function fontifies 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-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-lock.el's function must check each window to see if a scroll has
;; occurred there.  Worse still, lazy-lock.el's function must fontify a region
;; twice as large as necessary to make sure the window is completely fontified.
;; Basically, `post-command-hook' is completely inappropriate for lazy-lock.el.
;;
;; Ideally, we want to attach lazy-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 fontification 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 text previously invisible (i.e., after `window-end') to
;; become visible without changing `window-start'.  Arguably, these events are
;; not scrolling events, but fontification must occur for lazy-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-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-lock.el work with it.  Anyway, that's
;; Lit 30 of my humble opinion.
;;
;; Steve Baur reverted to a non-hacked version 1 lazy-lock.el for XEmacs 19.15
;; and 20.0.  Obviously, the above `post-command-hook' problems still apply.)
;;
;; - Version 1 stealth fontification 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, fontifies 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) Fontification may be required during a command, when `post-command-hook'
;;     is not run.  (Version 2 deferred fontification only.)
;;
;; Again, `post-command-hook' is completely inappropriate for lazy-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.)

;; - Version 1 has the following problems (relative to version 2):
;;
;; (a) It is slow when it does its job.
;; (b) It does not always do its job when it should.
;; (c) It slows all interaction (when it doesn't need to do its job).
;; (d) It interferes with other package functions on `post-command-hook'.
;; (e) It interferes with Emacs things within the read-eval loop.
;;
;; Ben's hacked-up lazy-lock.el 1.14 almost solved (b) but made (c) worse.
;;
;; - Version 2 has the following additional features (relative to version 1):
;;
;; (a) It can defer fontification (both on-the-fly and on-scrolling).
;; (b) It can fontify contextually (syntactically true on-the-fly).

;; Caveats:
;;
;; Lazy Lock mode does not work efficiently with Outline mode.
;; This is because when in Outline mode, although text may be not visible to
;; you in the window, the text is visible to Emacs Lisp code (not surprisingly)
;; and Lazy Lock fontifies it mercilessly.  Maybe it will be fixed one day.
;;
;; Because buffer text is not necessarily fontified, other packages that expect
;; buffer text to be fontified in Font 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
;; fontified 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-lock.el.  Maybe it will one day.

;; History:
;;
;; 1.15--2.00:
;; - Rewrite for Emacs 19.30 and the features rms added to support lazy-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-lock-fontify-after-command' always `sit-for' and so redisplay
;; - Use `buffer-name' not `buffer-live-p' (Bill Dubuque hint)
;; - Made `lazy-lock-install' do `add-to-list' not `setq' of `current-buffer'
;; - Made `lazy-lock-fontify-after-install' loop over buffer list
;; - Made `lazy-lock-arrange-before-change' to arrange `window-end' triggering
;; - Made `lazy-lock-let-buffer-state' wrap both `befter-change-functions'
;; - Made `lazy-lock-fontify-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-lock-install' set `font-lock-fontified' (Kevin Davidson report)
;; - Made `lazy-lock-install' add hooks only if needed
;; - Made `lazy-lock-unstall' add `font-lock-after-change-function' if needed
;; 2.02--2.03:
;; - Made `lazy-lock-fontify-region' do `condition-case' for `quit' too
;; - Made `lazy-lock-mode' respect the value of `font-lock-inhibit-thing-lock'
;; - Added `lazy-lock-after-unfontify-buffer'
;; - Removed `lazy-lock-fontify-after-install' hack
;; - Made `lazy-lock-fontify-after-scroll' not `set-buffer' to `window-buffer'
;; - Made `lazy-lock-fontify-after-trigger' not `set-buffer' to `window-buffer'
;; - Made `lazy-lock-fontify-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-lock-defer-after-change' always save `current-buffer'
;; - Made `lazy-lock-fontify-after-defer' just process buffers
;; - Made `lazy-lock-install-hooks' add hooks correctly (Kevin Broadey report)
;; - Made `lazy-lock-install' cope if `lazy-lock-defer-time' is a list
;; 2.04--2.05:
;; - Rewrite for Common Lisp macros
;; - Added `do-while' macro
;; - Renamed `lazy-lock-let-buffer-state' macro to `save-buffer-state'
;; - Returned `lazy-lock-fontify-after-install' hack (Darren Hall hint)
;; - Added `lazy-lock-defer-on-scrolling' functionality (Scott Byer hint)
;; - Made `lazy-lock-mode' wrap `font-lock-support-mode'
;; 2.05--2.06:
;; - Made `lazy-lock-fontify-after-defer' swap correctly (Scott Byer report)
;; 2.06--2.07:
;; - Added `lazy-lock-stealth-load' functionality (Rob Hooft hint)
;; - Made `lazy-lock-unstall' call `lazy-lock-fontify-region' if needed
;; - Made `lazy-lock-mode' call `lazy-lock-unstall' only if needed
;; - Made `lazy-lock-defer-after-scroll' do `set-window-redisplay-end-trigger'
;; - Added `lazy-lock-defer-contextually' functionality
;; - Added `lazy-lock-defer-on-the-fly' from `lazy-lock-defer-time'
;; - Renamed `lazy-lock-defer-driven' to `lazy-lock-defer-on-scrolling'
;; - Removed `lazy-lock-submit-bug-report' and bade farewell
;; 2.07--2.08:
;; - Made `lazy-lock-fontify-conservatively' fontify around `window-point'
;; - Made `save-buffer-state' wrap `inhibit-point-motion-hooks'
;; - Added Custom support
;; 2.08--2.09:
;; - Removed `byte-*' variables from `eval-when-compile' (Erik Naggum hint)
;; - Made various wrapping `inhibit-point-motion-hooks' (Vinicius Latorre hint)
;; - Made `lazy-lock-fontify-after-idle' wrap `minibuffer-auto-raise'

;;; Code:

(require 'font-lock)

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

(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)
  ;;
  ;; 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)) (buffer-undo-list t)
		     (inhibit-read-only t) (inhibit-point-motion-hooks 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))
  ;;
  ;; We use this for clarity and speed.  Borrowed from a future Emacs.
  (or (fboundp 'with-current-buffer)
      (defmacro with-current-buffer (buffer &rest body)
	"Execute the forms in BODY with BUFFER as the current buffer.
The value returned is the value of the last form in BODY."
	(` (save-excursion (set-buffer (, buffer)) (,@ body)))))
  (put 'with-current-buffer 'lisp-indent-function 1)
  ;;
  ;; We use this for compatibility with a future Emacs.
  (or (fboundp 'defcustom)
      (defmacro defcustom (symbol value doc &rest args) 
	(` (defvar (, symbol) (, value) (, doc))))))

;(defun lazy-lock-submit-bug-report ()
;  "Submit via mail a bug report on lazy-lock.el."
;  (interactive)
;  (let ((reporter-prompt-for-summary-p t))
;    (reporter-submit-bug-report "simon@gnu.ai.mit.edu" "lazy-lock 2.08.04"
;     '(lazy-lock-minimum-size lazy-lock-defer-on-the-fly
;       lazy-lock-defer-on-scrolling lazy-lock-defer-contextually
;       lazy-lock-defer-time lazy-lock-stealth-time
;       lazy-lock-stealth-load lazy-lock-stealth-nice lazy-lock-stealth-lines
;       lazy-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 editor via `" invocation-name " -no-init-file -no-site-file'.
;In the `*scratch*' buffer, evaluate:"))))

(defvar lazy-lock-mode nil)			; Whether we are turned on.
(defvar lazy-lock-buffers nil)			; For deferral.
(defvar lazy-lock-timers (cons nil nil))	; For deferral and stealth.

;; User Variables:

(defcustom lazy-lock-minimum-size (* 25 1024)
  "*Minimum size of a buffer for demand-driven fontification.
On-demand fontification occurs if the buffer size is greater than this value.
If nil, means demand-driven fontification 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."
  :type '(choice (const :tag "none" nil)
		 (integer :tag "size")
		 (repeat :menu-tag "mode specific" :tag "mode specific"
			 :value ((t . nil))
			 (cons :tag "Instance"
			       (radio :tag "Mode"
				      (const :tag "all" t)
				      (symbol :tag "name"))
			       (radio :tag "Size"
				      (const :tag "none" nil)
				      (integer :tag "size")))))
  :group 'lazy-lock)

(defcustom lazy-lock-defer-on-the-fly t
  "*If non-nil, means fontification after a change should be deferred.
If nil, means on-the-fly fontification is performed.  This means when changes
occur in the buffer, those areas are immediately fontified.
If a list, it should be a list of `major-mode' symbol names for which deferred
fontification should occur.  The sense of the list is negated if it begins with
`not'.  For example:
 (c-mode c++-mode)
means that on-the-fly fontification is deferred for buffers in C and C++ modes
only, and deferral does not occur otherwise.

The value of this variable is used when Lazy Lock mode is turned on."
  :type '(choice (const :tag "never" nil)
		 (const :tag "always" t)
		 (set :menu-tag "mode specific" :tag "modes"
		      :value (not)
		      (const :tag "Except" not)
		      (repeat :inline t (symbol :tag "mode"))))
  :group 'lazy-lock)

(defcustom lazy-lock-defer-on-scrolling nil
  "*If non-nil, means fontification after a scroll should be deferred.
If nil, means demand-driven fontification is performed.  This means when
scrolling into unfontified areas of the buffer, those areas are immediately
fontified.  Thus scrolling never presents unfontified areas.  However, since
fontification occurs during scrolling, scrolling may be slow.
If t, means defer-driven fontification is performed.  This means fontification
of those areas is deferred.  Thus scrolling may present momentarily unfontified
areas.  However, since fontification does not occur during scrolling, scrolling
will be faster than demand-driven fontification.
If any other value, e.g., `eventually', means demand-driven fontification is
performed until the buffer is fontified, then buffer fontification becomes
defer-driven.  Thus scrolling never presents unfontified areas until the buffer
is first fontified, after which subsequent scrolling may present future buffer
insertions momentarily unfontified.  However, since fontification does not
occur during scrolling after the buffer is first fontified, scrolling will
become faster.  (But, since contextual changes continually occur, such a value
makes little sense if `lazy-lock-defer-contextually' is non-nil.)

The value of this variable is used when Lazy Lock mode is turned on."
  :type '(choice (const :tag "never" nil)
		 (const :tag "always" t)
		 (sexp :tag "eventually" :format "%t\n" eventually))
  :group 'lazy-lock)

(defcustom lazy-lock-defer-contextually 'syntax-driven
  "*If non-nil, means deferred fontification should be syntactically true.
If nil, means deferred fontification occurs only on those lines modified.  This
means where modification on a line causes syntactic change on subsequent lines,
those subsequent lines are not refontified to reflect their new context.
If t, means deferred fontification occurs on those lines modified and all
subsequent lines.  This means those subsequent lines are refontified to reflect
their new syntactic context, either immediately or when scrolling into them.
If any other value, e.g., `syntax-driven', means deferred syntactically true
fontification occurs only if syntactic fontification is performed using the
buffer mode's syntax table, i.e., only if `font-lock-keywords-only' is nil.

The value of this variable is used when Lazy Lock mode is turned on."
  :type '(choice (const :tag "never" nil)
		 (const :tag "always" t)
		 (sexp :tag "syntax-driven" :format "%t\n" syntax-driven))
  :group 'lazy-lock)

(defcustom lazy-lock-defer-time
  (if (featurep 'lisp-float-type) (/ (float 1) (float 4)) 1)
  "*Time in seconds to delay before beginning deferred fontification.
Deferred fontification occurs if there is no input within this time.
If nil, means fontification is never deferred, regardless of the values of the
variables `lazy-lock-defer-on-the-fly', `lazy-lock-defer-on-scrolling' and
`lazy-lock-defer-contextually'.

The value of this variable is used when Lazy Lock mode is turned on."
  :type '(choice (const :tag "never" nil)
		 (number :tag "seconds"))
  :group 'lazy-lock)

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

The value of this variable is used when Lazy Lock mode is turned on."
  :type '(choice (const :tag "never" nil)
		 (number :tag "seconds"))
  :group 'lazy-lock)

(defcustom lazy-lock-stealth-lines (if font-lock-maximum-decoration 100 250)
  "*Maximum size of a chunk of stealth fontification.
Each iteration of stealth fontification can fontify this number of lines.
To speed up input response during stealth fontification, at the cost of stealth
taking longer to fontify, you could reduce the value of this variable."
  :type '(integer :tag "lines")
  :group 'lazy-lock)

(defcustom lazy-lock-stealth-load
  (if (condition-case nil (load-average) (error)) 200)
  "*Load in percentage above which stealth fontification is suspended.
Stealth fontification pauses when the system short-term load average (as
returned by the function `load-average' if supported) goes above this level,
thus reducing the demand that stealth fontification makes on the system.
If nil, means stealth fontification is never suspended.
To reduce machine load during stealth fontification, at the cost of stealth
taking longer to fontify, you could reduce the value of this variable.
See also `lazy-lock-stealth-nice'."
  :type (if (condition-case nil (load-average) (error))
	    '(choice (const :tag "never" nil)
		     (integer :tag "load"))
	  '(const :format "%t: unsupported\n" nil))
  :group 'lazy-lock)

(defcustom lazy-lock-stealth-nice
  (if (featurep 'lisp-float-type) (/ (float 1) (float 8)) 1)
  "*Time in seconds to pause between chunks of stealth fontification.
Each iteration of stealth fontification is separated by this amount of time,
thus reducing the demand that stealth fontification makes on the system.
If nil, means stealth fontification is never paused.
To reduce machine load during stealth fontification, at the cost of stealth
taking longer to fontify, you could increase the value of this variable.
See also `lazy-lock-stealth-load'."
  :type '(choice (const :tag "never" nil)
		 (number :tag "seconds"))	  
  :group 'lazy-lock)

(defcustom lazy-lock-stealth-verbose
  (if (featurep 'lisp-float-type)
      (and (not lazy-lock-defer-contextually) (not (null font-lock-verbose))))
  "*If non-nil, means stealth fontification should show status messages."
  :type 'boolean
  :group 'lazy-lock)

;; User Functions:

;;;###autoload
(defun lazy-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 font-lock-support-mode 'lazy-lock-mode)

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

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

- Deferred scroll fontification if `lazy-lock-defer-on-scrolling' is non-nil.
  This means demand-driven fontification does not occur as you scroll.
  Instead, fontification is deferred until after `lazy-lock-defer-time' seconds
  of Emacs idle time, while Emacs remains idle.  This is useful if
  fontification is too slow to keep up with scrolling.

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

- Deferred context fontification if `lazy-lock-defer-contextually' is non-nil.
  This means fontification updates the buffer corresponding to true syntactic
  context, after `lazy-lock-defer-time' seconds of Emacs idle time, while Emacs
  remains idle.  Otherwise, fontification occurs on modified lines only, and
  subsequent lines can remain fontified corresponding to previous syntactic
  contexts.  This is useful where strings or comments span lines.

- Stealthy buffer fontification if `lazy-lock-stealth-time' is non-nil.
  This means remaining unfontified areas of buffers are fontified if Emacs has
  been idle for `lazy-lock-stealth-time' seconds, while Emacs remains idle.
  This is useful if any buffer has any deferred fontification.

Basic Font Lock mode on-the-fly fontification behaviour fontifies modified
lines only.  Thus, if `lazy-lock-defer-contextually' is non-nil, Lazy Lock mode
on-the-fly fontification may fontify differently, albeit correctly.  In any
event, to refontify some lines you can use \\[font-lock-fontify-block].

Stealth fontification only occurs while the system remains unloaded.
If the system load rises above `lazy-lock-stealth-load' percent, stealth
fontification is suspended.  Stealth fontification intensity is controlled via
the variable `lazy-lock-stealth-nice' and `lazy-lock-stealth-lines', and
verbosity is controlled via the variable `lazy-lock-stealth-verbose'."
  (interactive "P")
  (let* ((was-on lazy-lock-mode)
	 (now-on (unless (memq 'lazy-lock-mode font-lock-inhibit-thing-lock)
		   (if arg (> (prefix-numeric-value arg) 0) (not was-on)))))
    (cond ((and now-on (not font-lock-mode))
	   ;; Turned on `lazy-lock-mode' rather than `font-lock-mode'.
	   (let ((font-lock-support-mode 'lazy-lock-mode))
	     (font-lock-mode t)))
	  (now-on
	   ;; Turn ourselves on.
	   (set (make-local-variable 'lazy-lock-mode) t)
	   (lazy-lock-install))
	  (was-on
	   ;; Turn ourselves off.
	   (set (make-local-variable 'lazy-lock-mode) nil)
	   (lazy-lock-unstall)))))

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

(defun lazy-lock-install ()
  (let ((min-size (font-lock-value-in-major-mode lazy-lock-minimum-size))
	(defer-change (and lazy-lock-defer-time lazy-lock-defer-on-the-fly))
	(defer-scroll (and lazy-lock-defer-time lazy-lock-defer-on-scrolling))
	(defer-context (and lazy-lock-defer-time lazy-lock-defer-contextually
			    (or (eq lazy-lock-defer-contextually t)
				(null font-lock-keywords-only)))))
    ;;
    ;; Tell Font Lock whether Lazy Lock will do fontification.
    (make-local-variable 'font-lock-fontified)
    (setq font-lock-fontified (and min-size (>= (buffer-size) min-size)))
    ;;
    ;; Add the text properties and fontify.
    (if (not font-lock-fontified)
	(lazy-lock-after-fontify-buffer)
      ;; Make sure we fontify in any existing windows showing the buffer.
      (let ((windows (get-buffer-window-list (current-buffer) 'nomini t)))
	(lazy-lock-after-unfontify-buffer)
	(while windows
	  (lazy-lock-fontify-conservatively (car windows))
	  (setq windows (cdr windows)))))
    ;;
    ;; Add the fontification hooks.
    (lazy-lock-install-hooks
     font-lock-fontified
     (cond ((eq (car-safe defer-change) 'not)
	    (not (memq major-mode (cdr defer-change))))
	   ((listp defer-change)
	    (memq major-mode defer-change))
	   (t
	    defer-change))
     (eq defer-scroll t)
     defer-context)
    ;;
    ;; Add the fontification timers.
    (lazy-lock-install-timers
     (if (or defer-change defer-scroll defer-context) lazy-lock-defer-time)
     lazy-lock-stealth-time)))

(defun lazy-lock-install-hooks (fontifying
				defer-change defer-scroll defer-context)
  ;;
  ;; Add hook if lazy-lock.el is fontifying on scrolling or is deferring.
  (when (or fontifying defer-change defer-scroll defer-context)
    (make-local-hook 'window-scroll-functions)
    (add-hook 'window-scroll-functions (if defer-scroll
					   'lazy-lock-defer-after-scroll
					 'lazy-lock-fontify-after-scroll)
	      nil t))
  ;;
  ;; Add hook if lazy-lock.el is fontifying and is not deferring changes.
  (when (and fontifying (not defer-change) (not defer-context))
    (make-local-hook 'before-change-functions)
    (add-hook 'before-change-functions 'lazy-lock-arrange-before-change nil t))
  ;;
  ;; Replace Font Lock mode hook.
  (remove-hook 'after-change-functions 'font-lock-after-change-function t)
  (add-hook 'after-change-functions
	    (cond ((and defer-change defer-context)
		   'lazy-lock-defer-rest-after-change)
		  (defer-change
		   'lazy-lock-defer-line-after-change)
		  (defer-context
		   'lazy-lock-fontify-rest-after-change)
		  (t
		   'lazy-lock-fontify-line-after-change))
	    nil t)
  ;;
  ;; Add package-specific hook.
  (make-local-hook 'outline-view-change-hook)
  (add-hook 'outline-view-change-hook 'lazy-lock-fontify-after-outline nil t))

(defun lazy-lock-install-timers (dtime stime)
  ;; Schedule or re-schedule the deferral and stealth timers.
  ;; The layout of `lazy-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-lock-timers)))
    (let ((defer (car lazy-lock-timers)))
      (when (cdr defer)
	(cancel-timer (cdr defer)))
      (setcar lazy-lock-timers (cons dtime (and dtime
	      (run-with-idle-timer dtime t 'lazy-lock-fontify-after-defer))))))
  (unless (eq stime (car (cdr lazy-lock-timers)))
    (let ((stealth (cdr lazy-lock-timers)))
      (when (cdr stealth)
	(cancel-timer (cdr stealth)))
      (setcdr lazy-lock-timers (cons stime (and stime
	      (run-with-idle-timer stime t 'lazy-lock-fontify-after-idle)))))))

(defun lazy-lock-unstall ()
  ;;
  ;; If Font Lock mode is still enabled, make sure that the buffer is
  ;; fontified, and reinstall its hook.  We must do this first.
  (when font-lock-mode
    (when (lazy-lock-unfontified-p)
      (let ((verbose (if (numberp font-lock-verbose)
			 (> (buffer-size) font-lock-verbose)
		       font-lock-verbose)))
	(if verbose (message "Fontifying %s..." (buffer-name)))
	;; Make sure we fontify etc. in the whole buffer.
	(save-restriction
	  (widen)
	  (lazy-lock-fontify-region (point-min) (point-max)))
	(if verbose (message "Fontifying %s...%s" (buffer-name)
			     (if (lazy-lock-unfontified-p) "quit" "done")))))
    (add-hook 'after-change-functions 'font-lock-after-change-function nil t))
  ;;
  ;; Remove the text properties.
  (lazy-lock-after-unfontify-buffer)
  ;;
  ;; Remove the fontification hooks.
  (remove-hook 'window-scroll-functions 'lazy-lock-fontify-after-scroll t)
  (remove-hook 'window-scroll-functions 'lazy-lock-defer-after-scroll t)
  (remove-hook 'before-change-functions 'lazy-lock-arrange-before-change t)
  (remove-hook 'after-change-functions 'lazy-lock-fontify-line-after-change t)
  (remove-hook 'after-change-functions 'lazy-lock-fontify-rest-after-change t)
  (remove-hook 'after-change-functions 'lazy-lock-defer-line-after-change t)
  (remove-hook 'after-change-functions 'lazy-lock-defer-rest-after-change t)
  (remove-hook 'outline-view-change-hook 'lazy-lock-fontify-after-outline t))

;; Hook functions.

;; Lazy Lock mode intervenes when (1) a previously invisible buffer region
;; becomes visible, i.e., for demand- or defer-driven on-the-scroll
;; fontification, (2) a buffer modification occurs, i.e., for defer-driven
;; on-the-fly fontification, (3) Emacs becomes idle, i.e., for fontification of
;; deferred fontification and stealth fontification, and (4) other special
;; occasions.

;; 1.  There are three ways whereby this can happen.
;;
;; (a) Scrolling the window, either explicitly (e.g., `scroll-up') or
;;     implicitly (e.g., `search-forward').  Here, `window-start' changes.
;;     Fontification occurs by adding `lazy-lock-fontify-after-scroll' (for
;;     demand-driven fontification) or `lazy-lock-defer-after-scroll' (for
;;     defer-driven fontification) to the hook `window-scroll-functions'.

(defun lazy-lock-fontify-after-scroll (window window-start)
  ;; Called from `window-scroll-functions'.
  ;; Fontify WINDOW from WINDOW-START following the scroll.  We cannot use
  ;; `window-end' so we work out what it would be via `vertical-motion'.
  (let ((inhibit-point-motion-hooks t))
    (save-excursion
      (goto-char window-start)
      (vertical-motion (window-height window) window)
      (lazy-lock-fontify-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-lock-defer-after-scroll (window window-start)
  ;; Called from `window-scroll-functions'.
  ;; Defer fontification following the scroll.  Save the current buffer so that
  ;; we subsequently fontify in all windows showing the buffer.
  (unless (memq (current-buffer) lazy-lock-buffers)
    (push (current-buffer) lazy-lock-buffers))
  ;; 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))

;; (b) Resizing the window, either explicitly (e.g., `enlarge-window') or
;;     implicitly (e.g., `delete-other-windows').  Here, `window-end' changes.
;;     Fontification occurs by adding `lazy-lock-fontify-after-resize' to the
;;     hook `window-size-change-functions'.

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

;; (c) Deletion in the buffer.  Here, a `window-end' marker can become visible.
;;     Fontification occurs by adding `lazy-lock-arrange-before-change' to
;;     `before-change-functions' and `lazy-lock-fontify-after-trigger' to the
;;     hook `redisplay-end-trigger-functions'.  Before every deletion, the
;;     marker `window-redisplay-end-trigger' position is set to the soon-to-be
;;     changed `window-end' position.  If the marker becomes visible,
;;     `lazy-lock-fontify-after-trigger' gets called.  Ouch.  Note that we only
;;     have to deal with this eventuality if there is no on-the-fly deferral.

(defun lazy-lock-arrange-before-change (beg end)
  ;; Called from `before-change-functions'.
  ;; Arrange that if text becomes visible it will be fontified (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-lock-fontify-after-trigger (window trigger-point)
  ;; Called from `redisplay-end-trigger-functions'.
  ;; Fontify 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-lock-fontify-after-scroll' without loss:
  ;;  (lazy-lock-fontify-after-scroll window (window-start window))
  (let ((inhibit-point-motion-hooks t))
    (save-excursion
      (goto-char (window-start window))
      (vertical-motion (window-height window) window)
      (lazy-lock-fontify-region trigger-point (point)))))

;; 2.  Modified text must be marked as unfontified so it can be identified and
;;     fontified later when Emacs is idle.  Deferral occurs by adding one of
;;     `lazy-lock-fontify-*-after-change' (for on-the-fly fontification) or
;;     `lazy-lock-defer-*-after-change' (for deferred fontification) to the
;;     hook `after-change-functions'.

(defalias 'lazy-lock-fontify-line-after-change
  ;; Called from `after-change-functions'.
  ;; Fontify the current change.
  'font-lock-after-change-function)

(defun lazy-lock-fontify-rest-after-change (beg end old-len)
  ;; Called from `after-change-functions'.
  ;; Fontify the current change and defer fontification of the rest of the
  ;; buffer.  Save the current buffer so that we subsequently fontify in all
  ;; windows showing the buffer.
  (lazy-lock-fontify-line-after-change beg end old-len)
  (save-buffer-state nil
    (unless (memq (current-buffer) lazy-lock-buffers)
      (push (current-buffer) lazy-lock-buffers))
    (remove-text-properties end (point-max) '(lazy-lock nil))))

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

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

;; 3.  Deferred fontification and stealth fontification are done from these two
;;     functions.  They are set up as Idle Timers.

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

(defun lazy-lock-fontify-after-idle ()
  ;; Called from `timer-idle-list'.
  ;; Fontify all buffers that need it, stealthily while idle.
  (unless (or executing-kbd-macro (window-minibuffer-p (selected-window)))
    ;; Loop over all buffers, fontify stealthily for each if necessary.
    (let ((buffers (buffer-list)) (continue t)
	  message message-log-max minibuffer-auto-raise)
      (save-excursion
	(do-while (and buffers continue)
	  (set-buffer (car buffers))
	  (if (not (and lazy-lock-mode (lazy-lock-unfontified-p)))
	      (setq continue (not (input-pending-p)))
	    ;; Fontify regions in this buffer while there is no input.
	    (do-while (and (lazy-lock-unfontified-p) continue)
	      (if (and lazy-lock-stealth-load
		       (> (car (load-average)) lazy-lock-stealth-load))
		  ;; Wait a while before continuing with the loop.
		  (progn
		    (when message
		      (message "Fontifying stealthily...suspended")
		      (setq message nil))
		    (setq continue (sit-for (or lazy-lock-stealth-time 30))))
		;; Fontify a chunk.
		(when lazy-lock-stealth-verbose
		  (if message
		      (message "Fontifying stealthily... %2d%% of %s"
			       (lazy-lock-percent-fontified) (buffer-name))
		    (message "Fontifying stealthily...")
		    (setq message t)))
		(lazy-lock-fontify-chunk)
		(setq continue (sit-for (or lazy-lock-stealth-nice 0))))))
	  (setq buffers (cdr buffers))))
      (when message
	(message "Fontifying stealthily...%s" (if continue "done" "quit"))))))

;; 4.  Special circumstances.

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

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

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

;; If packages want to ensure that some region of the buffer is fontified, they
;; should use this function.  For an example, see ps-print.el.
(defun lazy-lock-fontify-region (beg end)
  ;; Fontify between BEG and END, where necessary, in the current buffer.
  (when (setq beg (text-property-any beg end 'lazy-lock nil))
    (save-excursion
      (save-match-data
	(save-buffer-state
	    ;; Ensure syntactic fontification is always correct.
	    (font-lock-beginning-of-syntax-function next)
	  ;; Find successive unfontified regions between BEG and END.
	  (condition-case data
	      (do-while beg
		(setq next (or (text-property-any beg end 'lazy-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)))
		;; Fontify the region, then flag it as fontified.
		(font-lock-fontify-region beg next)
		(add-text-properties beg next '(lazy-lock t))
		(setq beg (text-property-any next end 'lazy-lock nil)))
	    ((error quit) (message "Fontifying region...%s" data))))))))

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

(defun lazy-lock-fontify-window (window)
  ;; Fontify in WINDOW between `window-start' and `window-end'.
  ;; We can only do this when we can use `window-start' and `window-end'.
  (with-current-buffer (window-buffer window)
    (lazy-lock-fontify-region (window-start window) (window-end window))))

(defun lazy-lock-fontify-conservatively (window)
  ;; Fontify 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.
  (with-current-buffer (window-buffer window)
    (let ((inhibit-point-motion-hooks t))
      (lazy-lock-fontify-region
       (save-excursion
	 (goto-char (window-point window))
	 (vertical-motion (- (window-height window)) window) (point))
       (save-excursion
	 (goto-char (window-point window))
	 (vertical-motion (window-height window) window) (point))))))

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

(defun lazy-lock-percent-fontified ()
  ;; Return the percentage (of characters) of the buffer that are fontified.
  (save-restriction
    (widen)
    (let ((beg (point-min)) (size 0) next)
      ;; Find where the next fontified region begins.
      (while (setq beg (text-property-any beg (point-max) 'lazy-lock t))
	(setq next (or (text-property-any beg (point-max) 'lazy-lock nil)
		       (point-max)))
	(incf size (- next beg))
	(setq beg next))
      ;; Float because using integer multiplication will frequently overflow.
      (truncate (* (/ (float size) (point-max)) 100)))))

;; 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-lock-install-timers (foo bar)
    (add-hook 'post-command-idle-hook 'lazy-lock-fontify-post-command t)
    (add-hook 'post-command-idle-hook 'lazy-lock-fontify-post-idle t)
    (add-to-list 'lazy-lock-install (current-buffer))
    (add-hook 'post-command-hook 'lazy-lock-fontify-after-install))
  (defun lazy-lock-fontify-post-command ()
    (and lazy-lock-buffers (not executing-kbd-macro)
	 (progn
	   (and deactivate-mark (deactivate-mark))
	   (sit-for
	    (or (cdr-safe lazy-lock-defer-time) lazy-lock-defer-time 0)))
	 (lazy-lock-fontify-after-defer)))
  (defun lazy-lock-fontify-post-idle ()
    (and lazy-lock-stealth-time (not executing-kbd-macro)
	 (not (window-minibuffer-p (selected-window)))
	 (progn
	   (and deactivate-mark (deactivate-mark))
	   (sit-for lazy-lock-stealth-time))
	 (lazy-lock-fontify-after-idle)))
  ;;
  ;; Simulate running of `window-scroll-functions' in `set-window-buffer'.
  (defvar lazy-lock-install nil)
  (defun lazy-lock-fontify-after-install ()
    (remove-hook 'post-command-hook 'lazy-lock-fontify-after-install)
    (while lazy-lock-install
      (mapcar 'lazy-lock-fontify-conservatively
	      (get-buffer-window-list (pop lazy-lock-install) 'nomini t)))))

(when (consp lazy-lock-defer-time)
  ;;
  ;; In 2.06.04 and below, `lazy-lock-defer-time' could specify modes and time.
  (with-output-to-temp-buffer "*Help*"
    (princ "The value of the variable `lazy-lock-defer-time' was\n ")
    (princ lazy-lock-defer-time)
    (princ "\n")
    (princ "This variable cannot now be a list of modes and time, ")
    (princ "so instead use the forms:\n")
    (princ " (setq lazy-lock-defer-time ")
    (princ (cdr lazy-lock-defer-time))
    (princ ")\n")
    (princ " (setq lazy-lock-defer-on-the-fly '")
    (princ (car lazy-lock-defer-time))
    (princ ")\n")
    (princ "in your ~/.emacs.  ")
    (princ "The above forms have been evaluated for this editor session,\n")
    (princ "but you should change your ~/.emacs now."))
  (setq lazy-lock-defer-on-the-fly (car lazy-lock-defer-time)
	lazy-lock-defer-time (cdr lazy-lock-defer-time)))

(when (boundp 'lazy-lock-defer-driven)
  ;;
  ;; In 2.06.04 and below, `lazy-lock-defer-driven' was the variable name.
  (with-output-to-temp-buffer "*Help*"
    (princ "The value of the variable `lazy-lock-defer-driven' is set to ")
    (if (memq lazy-lock-defer-driven '(nil t))
	(princ lazy-lock-defer-driven)
      (princ "`")
      (princ lazy-lock-defer-driven)
      (princ "'"))
    (princ ".\n")
    (princ "This variable is now called `lazy-lock-defer-on-scrolling',\n")
    (princ "so instead use the form:\n")
    (princ " (setq lazy-lock-defer-on-scrolling ")
    (unless (memq lazy-lock-defer-driven '(nil t))
      (princ "'"))
    (princ lazy-lock-defer-driven)
    (princ ")\n")
    (princ "in your ~/.emacs.  ")
    (princ "The above form has been evaluated for this editor session,\n")
    (princ "but you should change your ~/.emacs now."))
  (setq lazy-lock-defer-on-scrolling lazy-lock-defer-driven))

;; Possibly absent.

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

(unless (fboundp 'font-lock-value-in-major-mode)
  (defun font-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 fontify.
  (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-lock-fontify-after-resize)
(add-hook 'redisplay-end-trigger-functions 'lazy-lock-fontify-after-trigger)

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

;; Provide ourselves:

(provide 'lazy-lock)

;;; lazy-lock.el ends here
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.