Re: How can I predict which regions xdisp will present me for font-locking?

[Alan Mackenzie]

Hello again, John.

On Mon, Mar 12, 2012 at 01:47:00PM -0400, John Yates wrote:
> On Sun, Mar 11, 2012 at 5:45 PM, Eli Zaretskii <address@hidden> wrote:
> >> Date: Sun, 11 Mar 2012 20:59:03 +0000

[ .... ]

> I am seeing a horrendous slowdown when editing atypical macros (though
> no more than 50 lines long).  Worse still I see the same slowdown when
> editing a comment if even a fragment of my atypical macro is visible.

What does horrendous mean?  It could mean 10s per key (i.e. totally
broken) or ¼s per key (very sluggish).  Is the horrenditity any worse 
typing the comma?

> The pattern of the macro is

> #define LIST_NAME \
>   _ROW_( <literal columns> ) \
> , _ROW_( <literal columns> ) \
> ... \
> , _ROW_( <literal columns> ) \

Here's an update to the latest current state of my optimisations.  Try it
out, please, and see if it make things any better.


=== modified file 'lisp/progmodes/cc-engine.el'
*** lisp/progmodes/cc-engine.el 2012-03-02 22:16:21 +0000
--- lisp/progmodes/cc-engine.el 2012-03-12 18:32:00 +0000
***************
*** 1246,1252 ****
                       (c-at-vsemi-p))))
              (throw 'done vsemi-pos))
             ;; In a string/comment?
!            ((setq lit-range (c-literal-limits))
              (goto-char (cdr lit-range)))
             ((eq (char-after) ?:)
              (forward-char)
--- 1246,1252 ----
                       (c-at-vsemi-p))))
              (throw 'done vsemi-pos))
             ;; In a string/comment?
!            ((setq lit-range (c-literal-limits from))
              (goto-char (cdr lit-range)))
             ((eq (char-after) ?:)
              (forward-char)
***************
*** 3250,3257 ****
              (if scan-forward-p
                  (progn (narrow-to-region (point-min) here)
                         (c-append-to-state-cache good-pos))
! 
!               (c-get-cache-scan-pos good-pos))))
  
         (t ; (eq strategy 'IN-LIT)
        (setq c-state-cache nil
--- 3250,3256 ----
              (if scan-forward-p
                  (progn (narrow-to-region (point-min) here)
                         (c-append-to-state-cache good-pos))
!               good-pos)))
  
         (t ; (eq strategy 'IN-LIT)
        (setq c-state-cache nil
***************
*** 4563,4568 ****
--- 4562,4599 ----
        (point-min))
         (t
        (c-determine-limit (- how-far-back count) base try-size))))))
+ 
+ (defun c-determine-+ve-limit (how-far &optional start-pos)
+   ;; Return a buffer position about HOW-FAR non-literal characters forward
+   ;; from START-POS (default point), which must not be inside a literal.
+   (save-excursion
+     (let ((pos (or start-pos (point)))
+         (count how-far)
+         (s (parse-partial-sexp (point) (point)))) ; null state
+       (while (and (not (eobp))
+                 (> count 0))
+       ;; Scan over counted characters.
+       (setq s (parse-partial-sexp
+                pos
+                (min (+ pos count) (point-max))
+                nil                    ; target-depth
+                nil                    ; stop-before
+                s                      ; state
+                'syntax-table))        ; stop-comment
+       (setq count (- count (- (point) pos) 1)
+             pos (point))
+       ;; Scan over literal characters.
+       (if (nth 8 s)
+           (setq s (parse-partial-sexp
+                    pos
+                    (point-max)
+                    nil                ; target-depth
+                    nil                ; stop-before
+                    s                  ; state
+                    'syntax-table)     ; stop-comment
+                 pos (point))))
+       (point))))
+ 
  
  ;; `c-find-decl-spots' and accompanying stuff.
  
***************
*** 8635,8641 ****
        (setq pos (point)))
        (and
         c-macro-with-semi-re
-        (not (c-in-literal))
         (eq (skip-chars-backward " \t") 0)
  
         ;; Check we've got nothing after this except comments and empty lines
--- 8666,8671 ----
***************
*** 8666,8672 ****
             (c-backward-syntactic-ws)
             t))
         (c-simple-skip-symbol-backward)
!        (looking-at c-macro-with-semi-re)))))
  
  (defun c-macro-vsemi-status-unknown-p () t) ; See cc-defs.el.
  
--- 8696,8704 ----
             (c-backward-syntactic-ws)
             t))
         (c-simple-skip-symbol-backward)
!        (looking-at c-macro-with-semi-re)
!        (goto-char pos)
!        (not (c-in-literal))))))               ; The most expensive check 
last. 
  
  (defun c-macro-vsemi-status-unknown-p () t) ; See cc-defs.el.
  
***************
*** 9571,9577 ****
         ;; CASE 5B: After a function header but before the body (or
         ;; the ending semicolon if there's no body).
         ((save-excursion
!           (when (setq placeholder (c-just-after-func-arglist-p lim))
              (setq tmp-pos (point))))
          (cond
  
--- 9603,9610 ----
         ;; CASE 5B: After a function header but before the body (or
         ;; the ending semicolon if there's no body).
         ((save-excursion
!           (when (setq placeholder (c-just-after-func-arglist-p
!                                    (max lim (c-determine-limit 500))))
              (setq tmp-pos (point))))
          (cond
  

=== modified file 'lisp/progmodes/cc-mode.el'
*** lisp/progmodes/cc-mode.el   2012-02-22 19:34:32 +0000
--- lisp/progmodes/cc-mode.el   2012-03-12 18:31:49 +0000
***************
*** 925,932 ****
      ;; inside a string, comment, or macro.
      (setq new-bounds (c-extend-font-lock-region-for-macros
                      c-new-BEG c-new-END old-len))
!     (setq c-new-BEG (car new-bounds)
!         c-new-END (cdr new-bounds))
      ;; Clear all old relevant properties.
      (c-clear-char-property-with-value c-new-BEG c-new-END 'syntax-table '(1))
      (c-clear-char-property-with-value c-new-BEG c-new-END 'category 
'c-cpp-delimiter)
--- 925,932 ----
      ;; inside a string, comment, or macro.
      (setq new-bounds (c-extend-font-lock-region-for-macros
                      c-new-BEG c-new-END old-len))
!     (setq c-new-BEG (max (car new-bounds) (c-determine-limit 500 begg))
!         c-new-END (min (cdr new-bounds) (c-determine-+ve-limit 500 endd)))
      ;; Clear all old relevant properties.
      (c-clear-char-property-with-value c-new-BEG c-new-END 'syntax-table '(1))
      (c-clear-char-property-with-value c-new-BEG c-new-END 'category 
'c-cpp-delimiter)


> /john

-- 
Alan Mackenzie (Nuremberg, Germany).