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On Tue, Jul 9, 2019 at 4:40 PM Stefan Monnier <address@hidden> wrote:

IOW make it so that font-lock:
- delays refontification after the current line if the end of line is
now within a string/comment (and wasn't before).
- "un-delays" this fontification if the end of line is now outside of any
string/comment (but was within it before).
- of course, with some kind of timeout, but one longer than 0.5s.

Or something like that.

Here's my take on that. Clément/Dmitry if you find the time test this. ..

It should, in principle, reduce "blinking" in all modes (for people who

aren't using electric-pair-mode or something like that). If it doesn't,

I've made some kind of false assumption.

Btw to restart jit-lock-mode in a running emacs, you need to

do sth like this:

(progn

(jit-lock-mode -1)

(cancel-timer jit-lock-context-timer)

(setq jit-lock-context-timer nil)

(jit-lock-mode 1))

João

diff --git a/lisp/jit-lock.el b/lisp/jit-lock.el
index 48998a81fe..0d7c434f3f 100644
--- a/lisp/jit-lock.el
+++ b/lisp/jit-lock.el
@@ -123,6 +123,15 @@ jit-lock-context-time
:type '(number :tag "seconds")
:group 'jit-lock)

+(defcustom jit-lock-multiline-string-grace 2
+ "Like `jit-lock-context-time' but for unterminated multiline strings.
+If the user has just opened an unterminated string at EOL, give
+him/her some grace time before deciding it is a multi-line string
+and fontifying accordingly, do so only if the user stares idle at
+that string for more than this many seconds."
+ :type '(number :tag "seconds")
+ :group 'jit-lock)
+
(defcustom jit-lock-defer-time nil ;; 0.25
"Idle time after which deferred fontification should take place.
If nil, fontification is not deferred.
@@ -232,7 +241,7 @@ jit-lock-mode
(unless jit-lock-context-timer
(setq jit-lock-context-timer
(run-with-idle-timer jit-lock-context-time t
- 'jit-lock-context-fontify)))
+ (jit--lock-context-timer-function))))
(setq jit-lock-context-unfontify-pos
(or jit-lock-context-unfontify-pos (point-max))))

@@ -306,6 +315,44 @@ jit-lock--debug-fontify
pos 'fontified)))))))))
(setq jit-lock-defer-buffers nil))))

+(defun jit--lock-context-timer-function ()
+ (let (last ; point marker the last time context timer was run
+ in-s-or-c-p ; t if in string or comment that time around
+ grace-timer ; idle timer for fontifying unterminated s-or-c, or nil
+ )
+ (lambda ()
+ (let ((point (point-marker))
+ (new-in-s-or-c-p
+ (nth 8 (save-excursion (syntax-ppss (line-end-position))))))
+ (if (and jit-lock-multiline-string-grace
+ last
+ (eq (marker-buffer last) (current-buffer))
+ (eq (line-number-at-pos last) (line-number-at-pos)))
+ (cond ((and (null in-s-or-c-p) new-in-s-or-c-p (null grace-timer))
+ (setq grace-timer
+ (run-with-idle-timer jit-lock-multiline-string-grace nil
+ (lambda ()
+ (jit-lock-context-fontify)
+ (setq grace-timer nil)))))
+ ((and in-s-or-c-p
+ (null new-in-s-or-c-p)
+ grace-timer)
+ (cancel-timer grace-timer)
+ (setq grace-timer nil))
+ (t
+ ;; no state change, leave everything as it was
+ ))
+ ;; left the line somehow or customized feature away: cancel
+ ;; everything, resume normal operation.
+ (when grace-timer
+ (cancel-timer grace-timer)
+ (setq grace-timer nil)))
+ ;; proceed as usual, unless grace-timer is counting
+ (unless grace-timer
+ (jit-lock-context-fontify))
+ (setq last point in-s-or-c-p new-in-s-or-c-p)))))
+
+
(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