Re: Syntax Highlighting Latency in Emacs

[Kai Grossjohann]

jab3 <manual@helpdesk.org> writes:

> I don't want to start a war or anything (because it probably has something
> to do with my system), but I am curious about something I've noticed with
> Emacs as compared with vim.  If I'm looking at a source code file in vim,
> (and it doesn't even have to be that large - maybe a few thousand K) the
> syntax highlighting is automatic.  And if I edit something, which changes
> the highlighting of the rest of the file, it is instantaneous.  But in
> Emacs, there is a 2 or 3 second delay in the updating of the highlighting. 

I think Emacs now uses jit-lock as the font-lock-support-mode.  This
exhibits the symptoms you're mentioning.  You can also turn off
font-lock-support-mode completely, then font-locking should be
instantaneous.  However, then you also have to wait long after opening
a large file, because font-lock then goes through and fontifies the
whole file.

(lazy-lock is another alternative for font-lock-support-mode which
works similarly to jit-lock but is implemented in Lisp.)

Of course, there are various tunables, as others have mentioned.

Kai