Re: Nested sit-for's

[martin rudalics]

> If we simply document that "timers (and process filters) should avoid
> using sit-for", it should be clear to the reader that rare exceptions
> may exist (especially if we add a comment to jit-lock-stealth-fontify
> stating this).  After the release, we can probably rework
> jit-lock-stealth-fontify to avoid using sit-for, but I don't think the
> current situation is bad enough to block the release.

If you accept a pre-command-hook the attached patch would be a first
step in that direction.

*** jit-lock.el.~1.53.~ Tue Aug 15 10:00:50 2006
--- jit-lock.el Thu Aug 17 17:52:02 2006
***************
*** 220,229 ****
         (jit-lock-refontify)

         ;; Install an idle timer for stealth fontification.
!        (when (and jit-lock-stealth-time (null jit-lock-stealth-timer))
!          (setq jit-lock-stealth-timer
!                (run-with-idle-timer jit-lock-stealth-time t
!                                     'jit-lock-stealth-fontify)))

         ;; Init deferred fontification timer.
         (when (and jit-lock-defer-time (null jit-lock-defer-timer))
--- 220,231 ----
         (jit-lock-refontify)

         ;; Install an idle timer for stealth fontification.
!        (when jit-lock-stealth-time
!          (add-hook 'pre-command-hook 'jit-lock-reset-stealth-buffers nil t)
!          (when (null jit-lock-stealth-timer)
!            (setq jit-lock-stealth-timer
!                  (run-with-idle-timer
!                   jit-lock-stealth-time t 'jit-lock-stealth-fontify))))

         ;; Init deferred fontification timer.
         (when (and jit-lock-defer-time (null jit-lock-defer-timer))
***************
*** 265,270 ****
--- 267,273 ----
             (setq jit-lock-defer-timer nil)))

         ;; Remove hooks.
+        (remove-hook 'pre-command-hook 'jit-lock-reset-stealth-buffers t)
         (remove-hook 'after-change-functions 'jit-lock-after-change t)
         (remove-hook 'fontification-functions 'jit-lock-function))))

***************
*** 386,399 ****
             ;; eagerly extend the refontified region with
             ;; jit-lock-after-change-extend-region-functions.
             (when (< start orig-start)
!              (lexical-let ((start start)
                             (orig-start orig-start)
                             (buf (current-buffer)))
                 (run-with-timer
                  0 nil (lambda ()
!                         (with-buffer-prepared-for-jit-lock
!                             (put-text-property start orig-start
!                                                'fontified t buf))))))

           ;; Find the start of the next chunk, if any.
           (setq start (text-property-any next end 'fontified nil))))))))
--- 389,403 ----
             ;; eagerly extend the refontified region with
             ;; jit-lock-after-change-extend-region-functions.
             (when (< start orig-start)
!            (lexical-let ((start start)
                             (orig-start orig-start)
                             (buf (current-buffer)))
                 (run-with-timer
                  0 nil (lambda ()
!                       (with-current-buffer buf
!                         (with-buffer-prepared-for-jit-lock
!                          (put-text-property start orig-start
!                                             'fontified t)))))))

           ;; Find the start of the next chunk, if any.
           (setq start (text-property-any next end 'fontified nil))))))))
***************
*** 402,408 ****
  ;;; Stealth fontification.

  (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
--- 406,412 ----
  ;;; Stealth fontification.

  (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
***************
*** 442,513 ****
                           (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."
!   ;; 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.

--- 446,492 ----
                           (t next))))
        result))))

+ (defvar jit-lock-stealth-buffers nil
+   "List of buffers that should be fontified stealthily.
+ Installed in `pre-command-hook' when `jit-lock-stealth-time' is non-nil
+ and JIT lock is turned on.")
+ 
+ (defun jit-lock-reset-stealth-buffers ()
+   "Reset `jit-lock-stealth-buffers' to nil."
+   (setq jit-lock-stealth-buffers nil))

  (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 (input-pending-p)
!             (eq jit-lock-stealth-buffers t)
!             executing-kbd-macro
              memory-full
              (window-minibuffer-p (selected-window)))
!     (unless jit-lock-stealth-buffers
!       (setq jit-lock-stealth-buffers (or (buffer-list) t)))
!     (let ((buffer (car jit-lock-stealth-buffers))
          minibuffer-auto-raise
!         message-log-max
!         start)
!       (when (and buffer
!                (or (not jit-lock-stealth-load)
!                    (<= (car (load-average)) jit-lock-stealth-load)))
!       (with-local-quit
!         (with-current-buffer buffer
!           (if (and jit-lock-mode
!                    (setq start (jit-lock-stealth-chunk-start (point))))
!               ;; fontify a block.
!               (with-temp-message (if jit-lock-stealth-verbose
!                                      (concat "JIT stealth lock "
!                                              (buffer-name)))
!                 (jit-lock-fontify-now start (+ start jit-lock-chunk-size)))
!             (setq jit-lock-stealth-buffers
!                   (or (cdr jit-lock-stealth-buffers) t)))))))
!     (unless (eq jit-lock-stealth-buffers t)
!       (run-at-time (min jit-lock-stealth-nice 0.1) nil
!                  'jit-lock-stealth-fontify))))
  
  ;;; Deferred fontification.