Re: Slow fontification in C mode buffers

[Alan Mackenzie <acm@muc.de>]

Hello mk.4 Kanru.

On Tue, Dec 13, 2011 at 11:31:36PM +0800, Kan-Ru Chen wrote:
> Alan Mackenzie <acm@muc.de> writes:

> > By a happy coincidence, I've just tracked down another sluggishness (in
> > large array initialisations, reported by Peter Milliken on bug-cc-mode)
> > which looks to have exactly the same cause, namely
> > `c-font-lock-enclosing-decls' which fontifies the innards of a
> > struct/union/enum when jit-lock etc. starts in the middle of it.

> Is this the same problem?

> http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10288

> I cannot find the original report by Peter.


Would you please try the following patch and let me know how it goes.
Thanks!


*** orig/cc-engine.el	2011-12-15 09:06:28.000000000 +0000
--- cc-engine.el	2011-12-15 13:41:25.000000000 +0000
***************
*** 8073,8078 ****
--- 8073,8094 ----
  	    next-open-brace (c-pull-open-brace paren-state)))
      open-brace))
  
+ (defun c-cheap-inside-bracelist-p (paren-state)
+   ;; Return the position of the L-brace if point is inside a brace list
+   ;; initialization of an array, etc.  This is an approximate function,
+   ;; designed for speed over accuracy.  We simply search for "= {" (naturally
+   ;; with syntactic whitespace allowed).  PAREN-STATE is the normal thing that
+   ;; it is everywhere else.
+   (let (b-pos)
+     (save-excursion
+       (while
+ 	  (and (setq b-pos (c-pull-open-brace paren-state))
+ 	       (progn (goto-char b-pos)
+ 		      (c-backward-sws)
+ 		      (c-backward-token-2)
+ 		      (not (looking-at "=")))))
+       b-pos)))
+ 
  (defun c-inside-bracelist-p (containing-sexp paren-state)
    ;; return the buffer position of the beginning of the brace list
    ;; statement if we're inside a brace list, otherwise return nil.
*** orig/cc-fonts.el	2011-12-15 09:06:28.000000000 +0000
--- cc-fonts.el	2011-12-15 13:15:43.000000000 +0000
***************
*** 1394,1399 ****
--- 1394,1405 ----
  	      (c-fontify-recorded-types-and-refs)
  	      nil)
  
+ 	     ;; If point is inside a bracelist, there's no point checking it
+ 	     ;; being at a declarator.
+ 	     ((let ((paren-state (c-parse-state)))
+ 		(c-cheap-inside-bracelist-p paren-state))
+ 	      nil)
+ 
  	     (t
  	      ;; Are we at a declarator?  Try to go back to the declaration
  	      ;; to check this.  If we get there, check whether a "typedef"

> -- 
> Kanru

-- 
Alan Mackenzie (Nuremberg, Germany).