Re: jit-lock timer etc.

[martin rudalics]

> Each time Emacs becomes idle, `jit-lock-stealth-fontify' is called;
> with this patch, it requeues itself as a non-idle timer until it
> finishes fontifying.  What happens if Emacs becomes idle again before
> fontification finishes?  (This may happen if jit-lock-stealth-time is
> very short, or if a timer or process filter makes Emacs idle.)  It
> seems to me that this will set off another series of non-idle timers,
> which is not what we want.
> I think that if jit-lock-stealth-fontify is called with no argument,
> and fontification is proceeding, it should do nothing.

Not really.  `buffer-list' may have changed in between and I have to
recalculate `jit-lock-stealth-buffers'.  I also should care about the
liveness of my buffers here.  Anyway your reasoning is valid, I could
pile up a sequence of timers all working on the same possibly stale
version of `jit-lock-stealth-buffers'.  Sooner or later they should stop
but that's no justification for what I wrote.

> One way to do
> this is to introduce a new `jit-lock-stealth-fontifying' variable.
> (This may not work well if stealth fontification is so slow that the
> buffer list changes significantly before fontification finishes, but I
> think there's not much we can do about this.)

I'll simply use another timer.

> Now the nitpicks.  First, jit-lock-stealth-buffers should be
> defvar'ed.

It _was_ in my first patch.  Please convince yourself that I'm not
completely imbecile.

> Second, this part is rather hard to read:
>
>     (let (....
>           load-delay)
>       (when (or (not jit-lock-stealth-load)
>                 (or (<= (car (load-average)) jit-lock-stealth-load)
>                     (not (setq load-delay t))))
>          ...))
> I suggest changing it to
>
>     (let (...
>      (load-delay (and jit-lock-stealth-load
>                       (>= (car (load-average)) jit-lock-stealth-load))))
>       (when (not load-delay)
>          ...))
>

I want to call myself with a zero delay when there's nothing to fontify
in the car of `jit-lock-stealth-buffers' and there are buffers left.
But you're right, obviously.

> Finally, is it really necessary to test jit-lock-stealth-time here?
> If it's invalid, jit-lock-stealth-fontify wouldn't get called in the
> first place.
>
>   (when (and jit-lock-stealth-buffers jit-lock-stealth-time)
>     (run-at-time
>       (if load-delay jit-lock-stealth-time (or jit-lock-stealth-nice 0))
>       nil 'jit-lock-stealth-fontify t))
>

Paranoia.  The user could have set this to nil in between two calls.
Emacs timers are vindictive.

> Other than that, I think this proposal is good.

Not much left, I suppose.  Please look again at the new patch.

*** jit-lock.el.~1.54.~ Mon Aug 21 14:35:24 2006
--- jit-lock.el Tue Aug 22 00:14:42 2006
***************
*** 444,513 ****
        result))))


! (defun jit-lock-stealth-fontify ()
    "Fontify buffers stealthily.
! This functions is called after Emacs has been idle for
! `jit-lock-stealth-time' seconds."
!   ;; I used to check `inhibit-read-only' here, but I can't remember why.  
-stef
!   (unless (or executing-kbd-macro
              memory-full
!             (window-minibuffer-p (selected-window)))
!     (let ((buffers (buffer-list))
!         (outer-buffer (current-buffer))
          minibuffer-auto-raise
!         message-log-max)
!       (with-local-quit
!       (while (and buffers (not (input-pending-p)))
!         (with-current-buffer (pop buffers)
!           (when jit-lock-mode
!             ;; This is funny.  Calling sit-for with 3rd arg non-nil
!             ;; so that it doesn't redisplay, internally calls
!             ;; wait_reading_process_input also with a parameter
!             ;; saying "don't redisplay."  Since this function here
!             ;; is called periodically, this effectively leads to
!             ;; process output not being redisplayed at all because
!             ;; redisplay_internal is never called.  (That didn't
!             ;; work in the old redisplay either.)  So, we learn that
!             ;; we mustn't call sit-for that way here.  But then, we
!             ;; have to be cautious not to call sit-for in a widened
!             ;; buffer, since this could display hidden parts of that
!             ;; buffer.  This explains the seemingly weird use of
!             ;; save-restriction/widen here.
! 
!             (with-temp-message (if jit-lock-stealth-verbose
!                                    (concat "JIT stealth lock "
!                                            (buffer-name)))
! 
!               ;; In the following code, the `sit-for' calls cause a
!               ;; redisplay, so it's required that the
!               ;; buffer-modified flag of a buffer that is displayed
!               ;; has the right value---otherwise the mode line of
!               ;; an unmodified buffer would show a `*'.
!               (let (start
!                     (nice (or jit-lock-stealth-nice 0))
!                     (point (point-min)))
!                 (while (and (setq start
!                                   (jit-lock-stealth-chunk-start point))
!                             ;; In case sit-for runs any timers,
!                             ;; give them the expected current buffer.
!                             (with-current-buffer outer-buffer
!                               (sit-for nice)))
! 
!                   ;; fontify a block.
                    (jit-lock-fontify-now start (+ start jit-lock-chunk-size))
!                   ;; If stealth jit-locking is done backwards, this leads to
!                   ;; excessive O(n^2) refontification.   -stef
!                   ;; (when (>= jit-lock-context-unfontify-pos start)
!                   ;;   (setq jit-lock-context-unfontify-pos end))
! 
!                   ;; Wait a little if load is too high.
!                   (when (and jit-lock-stealth-load
!                              (> (car (load-average)) jit-lock-stealth-load))
!                     ;; In case sit-for runs any timers,
!                     ;; give them the expected current buffer.
!                     (with-current-buffer outer-buffer
!                       (sit-for (or jit-lock-stealth-time 30))))))))))))))
! 

  
  ;;; Deferred fontification.
--- 444,507 ----
        result))))


! (defvar jit-lock-stealth-buffers nil
!   "List of buffers that should be fontified stealthily.")
! 
! (defvar jit-lock-stealth-repeat-timer nil
!   "Timer for repeated stealth fontification.")
! 
! (defun jit-lock-stealth-fontify (&optional repeat)
    "Fontify buffers stealthily.
! This function is called repeatedly after Emacs has become idle for
! `jit-lock-stealth-time' seconds.  Optional argument REPEAT is expected
! non-nil in a repeated invocation of this function."
!   (unless (or (input-pending-p)
!             executing-kbd-macro
              memory-full
!             (window-minibuffer-p (selected-window))
!             (null (if repeat
!                       ;; In repeated invocations `jit-lock-stealth-buffers'
!                       ;; has been already set up.
!                       jit-lock-stealth-buffers
!                     ;; In first invocation set up `jit-lock-stealth-buffers'
!                     ;; from `buffer-list'.
!                     (setq jit-lock-stealth-buffers (buffer-list)))))
!     (when (timerp jit-lock-stealth-repeat-timer)
!       ;; Cancel timer for repated invocations.
!       (cancel-timer jit-lock-stealth-repeat-timer))
!     (let ((buffer (car jit-lock-stealth-buffers))
          minibuffer-auto-raise
!         message-log-max
!         start delay)
!       (if (and jit-lock-stealth-load
!              (> (car (load-average)) jit-lock-stealth-load))
!         ;; If load is too high, run again after `jit-lock-stealth-time'
!         ;; seconds.
!         (setq delay jit-lock-stealth-time)
!       (if (buffer-live-p buffer)
!           (with-current-buffer buffer
!             (if (and jit-lock-mode
!                      (setq start (jit-lock-stealth-chunk-start (point))))
!                 ;; Fontify one block of at most `jit-lock-chunk-size'
!                 ;; characters.
!                 (with-temp-message (if jit-lock-stealth-verbose
!                                        (concat "JIT stealth lock "
!                                                (buffer-name)))
                    (jit-lock-fontify-now start (+ start jit-lock-chunk-size))
!                   ;; Run again after `jit-lock-stealth-nice' seconds.
!                   (setq delay (or jit-lock-stealth-nice 0)))
!               ;; Nothing to fontify here.  Remove this buffer from
!               ;; `jit-lock-stealth-buffers' and run again immediately.
!               (setq delay 0)
!               (setq jit-lock-stealth-buffers (cdr jit-lock-stealth-buffers))))
!         ;; Buffer is no more live, remove it from `jit-lock-stealth-buffers'
!         ;; and run again instantaneously.
!         (setq delay 0)
!         (setq jit-lock-stealth-buffers (cdr jit-lock-stealth-buffers))))
!       (when (and jit-lock-stealth-buffers jit-lock-stealth-time)
!       ;; Call us again.
!       (setq jit-lock-stealth-repeat-timer
!             (run-at-time delay nil 'jit-lock-stealth-fontify t))))))

  
  ;;; Deferred fontification.