Re: CC Mode with font-lock-maximum-decoration 2

[Alan Mackenzie]

Hello, Eli.

On Tue, Aug 09, 2022 at 14:57:25 +0300, Eli Zaretskii wrote:
> > Date: Tue, 9 Aug 2022 11:24:20 +0000
> > Cc: emacs-devel@gnu.org
> > From: Alan Mackenzie <acm@muc.de>

> > Hello, Eli.

> > On Tue, Aug 09, 2022 at 14:07:33 +0300, Eli Zaretskii wrote:
> > > > Date: Tue, 9 Aug 2022 08:00:16 +0000
> > > > Cc: emacs-devel@gnu.org
> > > > From: Alan Mackenzie <acm@muc.de>

> > > > > > > Then what is the importance of these measurements of yours?

> > > > > > They show that an attempt to speed up CC Mode/2 should be 
> > > > > > concentrating
> > > > > > on the code which isn't fontification code.

> > > > > Please elaborate on this conclusion, because I don't think I
> > > > > understand how you arrived at it, based on your measurements.  With
> > > > > the default value of font-lock-maximum-decoration, the fontifications
> > > > > are also very slow, relatively to other modes.

> > > > I mean CC Mode with font-lock-maximum-decoration = 2, particularly.  The
> > > > fontification in this setup is not slow (72% of Emacs Lisp Mode's
> > > > speed).  The setup as a whole is not fast enough.  Therefore to speed it
> > > > up, fontification is not the aspect to concentrate on.

> > > But if we will never recommend using level 2, those conclusions are
> > > again of no practical value for our users.  Right?

> > I don't agree.  If there is some place in our documentation to do it,
> > then we should recommend level 2 for those, like you, who want rapid
> > response, and level 3 for those, like me, who want accurate
> > fontification.  It's a simple (or complicated) user choice.

> We are not talking about my personal customizations, we are talking
> about what CC Mode does by default.  If we'd changed the default to be
> level 2 for CC Mode, I could understand your line of reasoning.  But
> since you don't think this should be the default, I say what CC Mode
> does at level 2 is not of practical importance for making CC Mode fast
> enough.

Fast enough for what?  CC Mode at level 3 is fast enough for many,
probably most, users.  Over the years there've been fewer complaints
about speed than correctness, and most of these have been in connection
with unusual files.  There's never any objection to more speed, but for
those who really want instantaneous response, there is level 2, or even
level 1, and beyond that, fundamental-mode.

> > You have stated that CC Mode with level 2 is not fast enough.  I intend
> > to make this (what I call CC Mode/2) faster.

> That factoid doesn't do anything for making CC Mode faster for our
> users, even if you assume that I personally will use that level.

This is the old argument that users can't change settings from their
defaults.  I do assume that you use level 2 when you're a user (as
distinct from the maintainer).  Am I right?

-- 
Alan Mackenzie (Nuremberg, Germany).