GNU bug report logs - #11545
24.0.96-mac-2.92; Strange speed problem scrolling in C++ code

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Message #32 received at submit <at> debbugs.gnu.org (full text, mbox):

From: John Wiegley <jwiegley <at> gmail.com>
To: YAMAMOTO Mitsuharu <mituharu <at> math.s.chiba-u.ac.jp>
Cc: bug-cc-mode <at> gnu.org, bug-gnu-emacs <at> gnu.org,
	mituharu+bug-gnu-emacs-mac <at> math.s.chiba-u.ac.jp
Subject: Re: 24.0.96-mac-2.92; Strange speed problem scrolling in C++ code
Date: Mon, 28 May 2012 18:05:15 -0500

>>>>> John Wiegley <jwiegley <at> gmail.com> writes:

>>>>>> YAMAMOTO Mitsuharu <mituharu <at> math.s.chiba-u.ac.jp> writes:
>> With the Time Profiler in Instrument.app, I found that fontification
>> of CC Mode in Emacs 24 is much heavier and causes frequent GCs than
>> that in Emacs 23.  Please try the following:
>> 
>>   1. Start Emacs 24 Mac port with -Q (alternatively, pressing the
>>      shift key.)
>>   2. M-x load-file PREFIX/share/emacs/23.4/lisp/progmodes/cc-fonts.elc
>>      RTE.
>>   3. Replay scrolling a large C++ file.
>> 
>> I'm not sure if this slowdown is intended or expected.
> 
> Indeed, this makes the speed situation much better on Emacs 24.0.97.

I can now confirm that loading CC-Mode 5.32.3 into Emacs 23.4 causes the
identical speed issues that I was seeing with Emacs 24.0.97, so this is a
performance issue in the latest CC-Mode, not a bug in Emacs 24 or with
Mac-Port Emacs.

To the CC-Mode maintainers: is there a way to disable the slower, "more
correct" mode in the latest CC-Mode, and go back to the entirely sufficient
(for me) mode of previous versions?

Thanks,
  John

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