(eval-when-compile
(defmacro with-buffer-unmodified (&rest body)
"Eval BODY, preserving the current buffer's modified state."
(let ((modified (make-symbol "modified")))
`(let ((,modified (buffer-modified-p)))
(unwind-protect
(progn ,@body)
(unless ,modified
(restore-buffer-modified-p nil))))))
(defmacro with-buffer-prepared-for-jit-lock (&rest body)
"Execute BODY in current buffer, overriding several variables.
Preserves the `buffer-modified-p' state of the current buffer."
`(with-buffer-unmodified
(let ((buffer-undo-list t)
(inhibit-read-only t)
(inhibit-point-motion-hooks t)
(inhibit-modification-hooks t)
deactivate-mark
buffer-file-name
buffer-file-truename)
,@body))))
(defcustom jit-lock-chunk-size 500
"*Jit-lock chunks of this many characters, or smaller."
:type 'integer
:group 'jit-lock)
(defcustom jit-lock-stealth-time 3
"*Time in seconds to wait before beginning stealth fontification.
Stealth fontification occurs if there is no input within this time.
If nil, stealth fontification is never performed.
The value of this variable is used when JIT Lock mode is turned on."
:type '(choice (const :tag "never" nil)
(number :tag "seconds"))
:group 'jit-lock)
(defcustom jit-lock-stealth-nice 0.125
"*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 `jit-lock-stealth-load'."
:type '(choice (const :tag "never" nil)
(number :tag "seconds"))
:group 'jit-lock)
(defcustom jit-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 `jit-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 'jit-lock)
(defcustom jit-lock-stealth-verbose nil
"*If non-nil, means stealth fontification should show status messages."
:type 'boolean
:group 'jit-lock)
(defcustom jit-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 JIT Lock mode is turned on."
:type '(choice (const :tag "never" nil)
(const :tag "always" t)
(other :tag "syntax-driven" syntax-driven))
:group 'jit-lock)
(defvar jit-lock-mode nil
"Non-nil means Just-in-time Lock mode is active.")
(make-variable-buffer-local 'jit-lock-mode)
(defvar jit-lock-functions nil
"Functions to do the actual fontification.
They are called with two arguments: the START and END of the region to fontify.")
(make-variable-buffer-local 'jit-lock-functions)
(defvar jit-lock-first-unfontify-pos nil
"Consider text after this position as contextually unfontified.
If nil, contextual fontification is disabled.")
(make-variable-buffer-local 'jit-lock-first-unfontify-pos)
(defvar jit-lock-stealth-timer nil
"Timer for stealth fontification in Just-in-time Lock mode.")
(defun jit-lock-mode (arg)
"Toggle Just-in-time Lock mode.
Turn Just-in-time Lock mode on if and only if ARG is non-nil.
Enable it automatically by customizing group `font-lock'.
When Just-in-time Lock mode is enabled, fontification is different in the
following ways:
- Demand-driven buffer fontification triggered by Emacs C code.
This means initial fontification of the whole buffer does not occur.
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.
- Stealthy buffer fontification if `jit-lock-stealth-time' is non-nil.
This means remaining unfontified areas of buffers are fontified if Emacs has
been idle for `jit-lock-stealth-time' seconds, while Emacs remains idle.
This is useful if any buffer has any deferred fontification.
- Deferred context fontification if `jit-lock-defer-contextually' is
non-nil. This means fontification updates the buffer corresponding to
true syntactic context, after `jit-lock-stealth-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.
Stealth fontification only occurs while the system remains unloaded.
If the system load rises above `jit-lock-stealth-load' percent, stealth
fontification is suspended. Stealth fontification intensity is controlled via
the variable `jit-lock-stealth-nice'."
(setq jit-lock-mode arg)
(cond ( jit-lock-mode
(jit-lock-refontify)
(when (and jit-lock-stealth-time (null jit-lock-stealth-timer))
(setq jit-lock-stealth-timer
(run-with-idle-timer jit-lock-stealth-time
jit-lock-stealth-time
'jit-lock-stealth-fontify)))
(when (eq jit-lock-defer-contextually t)
(setq jit-lock-first-unfontify-pos
(or jit-lock-first-unfontify-pos (point-max))))
(add-hook 'after-change-functions 'jit-lock-after-change nil t)
(add-hook 'fontification-functions 'jit-lock-function))
(t
(when jit-lock-stealth-timer
(cancel-timer jit-lock-stealth-timer)
(setq jit-lock-stealth-timer nil))
(remove-hook 'after-change-functions 'jit-lock-after-change t)
(remove-hook 'fontification-functions 'jit-lock-function))))
(defun jit-lock-register (fun &optional contextual)
"Register FUN as a fontification function to be called in this buffer.
FUN will be called with two arguments START and END indicating the region
that needs to be (re)fontified.
If non-nil, CONTEXTUAL means that a contextual fontification would be useful."
(add-hook 'jit-lock-functions fun nil t)
(when (and contextual jit-lock-defer-contextually)
(set (make-local-variable 'jit-lock-defer-contextually) t))
(jit-lock-mode t))
(defun jit-lock-unregister (fun)
"Unregister FUN as a fontification function.
Only applies to the current buffer."
(remove-hook 'jit-lock-functions fun t)
(unless jit-lock-functions (jit-lock-mode nil)))
(defun jit-lock-refontify (&optional beg end)
"Force refontification of the region BEG..END (default whole buffer)."
(with-buffer-prepared-for-jit-lock
(save-restriction
(widen)
(add-text-properties (or beg (point-min)) (or end (point-max))
'(fontified nil)))))
(defun jit-lock-function (start)
"Fontify current buffer starting at position START.
This function is added to `fontification-functions' when `jit-lock-mode'
is active."
(when jit-lock-mode
(jit-lock-fontify-now start (+ start jit-lock-chunk-size))))
(defun jit-lock-fontify-now (&optional start end)
"Fontify current buffer from START to END.
Defaults to the whole buffer. END can be out of bounds."
(with-buffer-prepared-for-jit-lock
(save-excursion
(save-restriction
(widen)
(unless start (setq start (point-min)))
(setq end (if end (min end (point-max)) (point-max)))
(let (next)
(save-match-data
(while start
(setq next (or (text-property-any start end 'fontified t)
end))
(goto-char next) (setq next (line-beginning-position 2))
(goto-char start) (setq start (line-beginning-position))
(add-text-properties start next '(fontified t))
(run-hook-with-args 'jit-lock-functions start next)
(setq start (text-property-any next end 'fontified nil)))))))))
(defsubst jit-lock-stealth-chunk-start (around)
"Return the start of the next chunk to fontify around position AROUND..
Value is nil if there is nothing more to fontify."
(if (zerop (buffer-size))
nil
(save-restriction
(widen)
(let* ((next (text-property-any around (point-max) 'fontified nil))
(prev (previous-single-property-change around 'fontified))
(prop (get-text-property (max (point-min) (1- around))
'fontified))
(start (cond
((null prev)
(if prop
nil
(max (point-min)
(- around (/ jit-lock-chunk-size 2)))))
(prop
(max (or (previous-single-property-change prev 'fontified)
(point-min))
(- prev jit-lock-chunk-size)))
(t
(max prev (- around jit-lock-chunk-size)))))
(result (cond ((null start) next)
((null next) start)
((< (- around start) (- next around)) start)
(t next))))
result))))
(defun jit-lock-stealth-fontify ()
"Fontify buffers stealthily.
This functions is called after Emacs has been idle for
`jit-lock-stealth-time' seconds."
(unless (or executing-kbd-macro
(window-minibuffer-p (selected-window)))
(let ((buffers (buffer-list))
minibuffer-auto-raise
message-log-max)
(while (and buffers (not (input-pending-p)))
(let ((buffer (car buffers)))
(setq buffers (cdr buffers))
(with-current-buffer buffer
(when jit-lock-mode
(with-temp-message (if jit-lock-stealth-verbose
(concat "JIT stealth lock "
(buffer-name)))
(when jit-lock-first-unfontify-pos
(save-restriction
(widen)
(when (and (>= jit-lock-first-unfontify-pos (point-min))
(< jit-lock-first-unfontify-pos (point-max)))
(with-buffer-prepared-for-jit-lock
(put-text-property jit-lock-first-unfontify-pos
(point-max) 'fontified nil))
(setq jit-lock-first-unfontify-pos (point-max)))))
(let (start
(nice (or jit-lock-stealth-nice 0))
(point (point)))
(while (and (setq start
(jit-lock-stealth-chunk-start point))
(sit-for nice))
(when (and jit-lock-stealth-load
(> (car (load-average)) jit-lock-stealth-load))
(sit-for (or jit-lock-stealth-time 30)))
(unless (input-pending-p)
(jit-lock-fontify-now
start (+ start jit-lock-chunk-size)))))))))))))
(defun jit-lock-after-change (start end old-len)
"Mark the rest of the buffer as not fontified after a change.
Installed on `after-change-functions'.
START and END are the start and end of the changed text. OLD-LEN
is the pre-change length.
This function ensures that lines following the change will be refontified
in case the syntax of those lines has changed. Refontification
will take place when text is fontified stealthily."
(when jit-lock-mode
(save-excursion
(with-buffer-prepared-for-jit-lock
(goto-char start)
(setq start (line-beginning-position))
(when (get-text-property start 'font-lock-multiline)
(setq start (or (previous-single-property-change
start 'font-lock-multiline)
(point-min))))
(setq end (min (max end (1+ start)) (point-max)))
(put-text-property start end 'fontified nil))
(when jit-lock-first-unfontify-pos
(setq jit-lock-first-unfontify-pos
(min jit-lock-first-unfontify-pos start))))))
(provide 'jit-lock)