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1 ;;; jit-lock.el --- just-in-time fontification -*- lexical-binding: t -*-
3 ;; Copyright (C) 1998, 2000-2015 Free Software Foundation, Inc.
5 ;; Author: Gerd Moellmann <gerd@gnu.org>
6 ;; Keywords: faces files
7 ;; Package: emacs
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is free software: you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation, either version 3 of the License, or
14 ;; (at your option) any later version.
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
24 ;;; Commentary:
26 ;; Just-in-time fontification, triggered by C redisplay code.
28 ;;; Code:
33 "Execute BODY in current buffer, overriding several variables.
34 Preserves the `buffer-modified-p' state of the current buffer."
39 \f
40 ;;; Customization.
43 "Font Lock support mode to fontify just-in-time."
48 "Jit-lock fontifies chunks of at most this many characters at a time.
50 This variable controls both display-time and stealth fontification."
56 "Time in seconds to wait before beginning stealth fontification.
57 Stealth fontification occurs if there is no input within this time.
58 If nil, stealth fontification is never performed.
60 The value of this variable is used when JIT Lock mode is turned on."
67 "Time in seconds to pause between chunks of stealth fontification.
68 Each iteration of stealth fontification is separated by this amount of time,
69 thus reducing the demand that stealth fontification makes on the system.
70 If nil, means stealth fontification is never paused.
71 To reduce machine load during stealth fontification, at the cost of stealth
72 taking longer to fontify, you could increase the value of this variable.
73 See also `jit-lock-stealth-load'."
81 "Load in percentage above which stealth fontification is suspended.
82 Stealth fontification pauses when the system short-term load average (as
83 returned by the function `load-average' if supported) goes above this level,
84 thus reducing the demand that stealth fontification makes on the system.
85 If nil, means stealth fontification is never suspended.
86 To reduce machine load during stealth fontification, at the cost of stealth
87 taking longer to fontify, you could reduce the value of this variable.
88 See also `jit-lock-stealth-nice'."
97 "If non-nil, means stealth fontification should show status messages."
104 "If non-nil, means fontification should be syntactically true.
105 If nil, means fontification occurs only on those lines modified. This
106 means where modification on a line causes syntactic change on subsequent lines,
107 those subsequent lines are not refontified to reflect their new context.
108 If t, means fontification occurs on those lines modified and all
109 subsequent lines. This means those subsequent lines are refontified to reflect
110 their new syntactic context, after `jit-lock-context-time' seconds.
111 If any other value, e.g., `syntax-driven', means syntactically true
112 fontification occurs only if syntactic fontification is performed using the
113 buffer mode's syntax table, i.e., only if `font-lock-keywords-only' is nil.
115 The value of this variable is used when JIT Lock mode is turned on."
122 "Idle time after which text is contextually refontified, if applicable."
127 "Idle time after which deferred fontification should take place.
128 If nil, fontification is not deferred.
129 If 0, then fontification is only deferred while there is input pending."
133 \f
134 ;;; Variables that are not customizable.
140 "Functions to do the actual fontification.
144 "Consider text after this position as contextually unfontified.
160 \f
161 ;;; JIT lock mode
164 "Toggle Just-in-time Lock mode.
165 Turn Just-in-time Lock mode on if and only if ARG is non-nil.
166 Enable it automatically by customizing group `font-lock'.
168 When Just-in-time Lock mode is enabled, fontification is different in the
169 following ways:
171 - Demand-driven buffer fontification triggered by Emacs C code.
172 This means initial fontification of the whole buffer does not occur.
173 Instead, fontification occurs when necessary, such as when scrolling
174 through the buffer would otherwise reveal unfontified areas. This is
175 useful if buffer fontification is too slow for large buffers.
177 - Stealthy buffer fontification if `jit-lock-stealth-time' is non-nil.
178 This means remaining unfontified areas of buffers are fontified if Emacs has
179 been idle for `jit-lock-stealth-time' seconds, while Emacs remains idle.
180 This is useful if any buffer has any deferred fontification.
182 - Deferred context fontification if `jit-lock-contextually' is
183 non-nil. This means fontification updates the buffer corresponding to
184 true syntactic context, after `jit-lock-context-time' seconds of Emacs
185 idle time, while Emacs remains idle. Otherwise, fontification occurs
186 on modified lines only, and subsequent lines can remain fontified
187 corresponding to previous syntactic contexts. This is useful where
188 strings or comments span lines.
190 Stealth fontification only occurs while the system remains unloaded.
191 If the system load rises above `jit-lock-stealth-load' percent, stealth
192 fontification is suspended. Stealth fontification intensity is controlled via
193 the variable `jit-lock-stealth-nice'.
195 If you need to debug code run from jit-lock, see `jit-lock-debug-mode'."
199 ;; We're in an indirect buffer. This doesn't work because jit-lock relies
200 ;; on the `fontified' text-property which is shared with the base buffer.
206 ;; Mark the buffer for refontification.
209 ;; Install an idle timer for stealth fontification.
215 ;; Create, but do not activate, the idle timer for repeated
216 ;; stealth fontification.
222 ;; Init deferred fontification timer.
228 ;; Initialize contextual fontification if requested.
237 ;; Setup our hooks.
241 ;; Turn Just-in-time Lock mode off.
243 ;; Cancel our idle timers.
245 jit-lock-context-timer)
246 ;; Only if there's no other buffer using them.
261 ;; Remove hooks.
266 "Minor mode to help debug code run from jit-lock.
267 When this minor mode is enabled, jit-lock runs as little code as possible
268 during redisplay and moves the rest to a timer, where things
269 like `debug-on-error' and Edebug can be used."
281 "Fontify what was deferred for debugging."
286 ;; Mark the deferred regions back to `fontified = nil'
290 ;; (message "Jit-Debug %s" (buffer-name))
298 pos 'fontified
307 "Register FUN as a fontification function to be called in this buffer.
308 FUN will be called with two arguments START and END indicating the region
309 that needs to be (re)fontified.
310 If non-nil, CONTEXTUAL means that a contextual fontification would be useful."
317 "Unregister FUN as a fontification function.
318 Only applies to the current buffer."
323 "Force refontification of the region BEG..END (default whole buffer)."
329 \f
330 ;;; On demand fontification.
333 "Fontify current buffer starting at position START.
334 This function is added to `fontification-functions' when `jit-lock-mode'
335 is active."
340 ;; No deferral.
342 ;; Record the buffer for later fontification.
345 ;; Mark the area as defer-fontified so that the redisplay engine
346 ;; is happy and so that the idle timer can find the places to fontify.
350 start 'fontified nil
358 'jit-lock-functions
365 ;; If all functions don't fontify the same region, we currently
366 ;; just try to "still be correct". But we could go further and for
367 ;; the chunks of text that was fontified by some functions but not
368 ;; all, we could add text-properties indicating which functions were
369 ;; already run to avoid running them redundantly when we get to
370 ;; those chunks.
375 nil)))
379 "Fontify current buffer from START to END.
380 Defaults to the whole buffer. END can be out of bounds."
385 ;; This did bind `font-lock-beginning-of-syntax-function' to
386 ;; nil at some point, for an unknown reason. Don't do this; it
387 ;; can make highlighting slow due to expensive calls to
388 ;; `parse-partial-sexp' in function
389 ;; `font-lock-fontify-syntactically-region'. Example: paging
390 ;; from the end of a buffer to its start, can do repeated
391 ;; `parse-partial-sexp' starting from `point-min', which can
392 ;; take a long time in a large buffer.
395 ;; Fontify chunks beginning at START. The end of a
396 ;; chunk is either `end', or the start of a region
397 ;; before `end' that has already been fontified.
399 ;; Determine the end of this chunk.
401 end))
403 ;; Fontify the chunk, and mark it as fontified.
404 ;; We mark it first, to make sure that we don't indefinitely
405 ;; re-execute this fontification if an error occurs.
408 ;; `tight' is the part we've fully refontified, and `loose'
409 ;; is the part we've partly refontified (some of the
410 ;; functions have refontified it but maybe not all).
414 ;; If the user quits (which shouldn't happen in normal
415 ;; on-the-fly jit-locking), make sure the fontification
416 ;; will be performed before displaying the block again.
420 ;; In case we fontified more than requested, take advantage of the
421 ;; good news.
425 ;; Make sure the contextual refontification doesn't re-refontify
426 ;; what's already been refontified.
430 ;; Don't move boundary forward if we have to
431 ;; refontify previous text. Otherwise, we risk moving
432 ;; it past the end of the multiline property and thus
433 ;; forget about this multiline region altogether.
438 ;; The redisplay engine has already rendered the buffer up-to
439 ;; `orig-start' and won't notice if the above jit-lock-functions
440 ;; changed the appearance of any part of the buffer prior
441 ;; to that. So if `loose-beg' is before `orig-start', we need to
442 ;; cause a new redisplay cycle after this one so that the changes
443 ;; are properly reflected on screen.
444 ;; To make such repeated redisplay happen less often, we can
445 ;; eagerly extend the refontified region with
446 ;; jit-lock-after-change-extend-region-functions.
452 ;; Find the start of the next chunk, if any.
457 "Force the display engine to re-render START's buffer from START to END.
458 This applies to the buffer associated with marker START."
466 ;; Don't cause refontification (it's already been done), but just do
467 ;; some random buffer change, so as to force redisplay.
469 \f
470 ;;; Stealth fontification.
473 "Return the start of the next chunk to fontify around position AROUND.
474 Value is nil if there is nothing more to fontify."
476 nil
483 ;; There is no property change between AROUND
484 ;; and the start of the buffer. If PROP is
485 ;; non-nil, everything in front of AROUND is
486 ;; fontified, otherwise nothing is fontified.
488 nil
492 ;; PREV is the start of a region of fontified
493 ;; text containing AROUND. Start fontifying a
494 ;; chunk size before the end of the unfontified
495 ;; region in front of that.
500 ;; PREV is the start of a region of unfontified
501 ;; text containing AROUND. Start at PREV or
502 ;; chunk size in front of AROUND, whichever is
503 ;; nearer.
509 result)))
512 "Fontify buffers stealthily.
513 This function is called repeatedly after Emacs has become idle for
514 `jit-lock-stealth-time' seconds. Optional argument REPEAT is expected
515 non-nil in a repeated invocation of this function."
516 ;; Cancel timer for repeated invocations.
520 memory-full
522 ;; For first invocation set up `jit-lock-stealth-buffers'.
523 ;; In repeated invocations it's already been set up.
525 jit-lock-stealth-buffers
529 minibuffer-auto-raise
530 message-log-max
531 start)
533 ;; load-average can return nil. The w32 emulation does
534 ;; that during the first few dozens of seconds after
535 ;; startup.
537 ;; Wait a little if load is too high.
543 ;; Fontify one block of at most `jit-lock-chunk-size'
544 ;; characters.
550 ;; Run again after `jit-lock-stealth-nice' seconds.
552 ;; Nothing to fontify here. Remove this buffer from
553 ;; `jit-lock-stealth-buffers' and run again immediately.
555 ;; Buffer is no longer live. Remove it from
556 ;; `jit-lock-stealth-buffers' and run again immediately.
558 ;; Call us again.
564 \f
565 ;;; Deferred fontification.
568 "Fontify what was deferred."
570 ;; Mark the deferred regions back to `fontified = nil'
574 ;; (message "Jit-Defer %s" (buffer-name))
587 ;; Force fontification of the visible parts.
589 ;; (message "Jit-Defer Now")
591 ;; (message "Jit-Defer Done")
592 )))
596 "Refresh fontification to take new context into account."
601 ;; (message "Jit-Context %s" (buffer-name))
603 ;; Don't be blindsided by narrowing that starts in the middle
604 ;; of a jit-lock-defer-multiline.
608 ;; If we're in text that matches a complex multi-line
609 ;; font-lock pattern, make sure the whole text will be
610 ;; redisplayed eventually.
611 ;; Despite its name, we treat jit-lock-defer-multiline here
612 ;; rather than in jit-lock-defer since it has to do with multiple
613 ;; lines, i.e. with context.
618 jit-lock-context-unfontify-pos
622 ;; Force contextual refontification.
630 "Hook that can extend the text to refontify after a change.
631 This is run after every buffer change. The functions are called with
632 the three arguments of `after-change-functions': START END OLD-LEN.
633 The extended region to refontify is returned indirectly by modifying
634 the variables `jit-lock-start' and `jit-lock-end'.
636 Note that extending the region this way is not strictly necessary, except
637 that the nature of the redisplay code tends to otherwise leave some of
638 the rehighlighted text displayed with the old highlight until the next
642 "Mark the rest of the buffer as not fontified after a change.
643 Installed on `after-change-functions'.
644 START and END are the start and end of the changed text. OLD-LEN
645 is the pre-change length.
646 This function ensures that lines following the change will be refontified
647 in case the syntax of those lines has changed. Refontification
648 will take place when text is fontified stealthily."
654 start end old-len)
655 ;; Make sure we change at least one char (in case of deletions).
657 ;; Request refontification.
661 ;; Mark the change for deferred contextual refontification.
664 ;; Here we use `start' because nothing guarantees that the
665 ;; text between start and end will be otherwise refontified:
666 ;; usually it will be refontified by virtue of being
667 ;; displayed, but if it's outside of any displayed area in the
668 ;; buffer, only jit-lock-context-* will re-fontify it.
673 ;;; jit-lock.el ends here