Re: emacs rendering comparisson between emacs23 and emacs26.3

[Dmitry Gutov]

On 07.04.2020 17:30, Eli Zaretskii wrote:
> > Cc: address@hidden, address@hidden, address@hidden, address@hidden,
> >   address@hidden
> > From: Dmitry Gutov <address@hidden>
> > Date: Mon, 6 Apr 2020 21:59:29 +0300
> >
> > Would I be correct to assume that you see only see this in CC Mode based
> > major mode, and only when editing big enough files? Such as xdisp.c
> > mentioned many times recently.
>
> The former is probably correct.  But not the latter: there are some
> constructs in C that make CC Mode notoriously slow, even in much
> smaller buffers.  And just to make "notoriously slow" quantifiable: I
> mean cases where typing RET takes half a second or a second.

In that case, there are several issues at play.

Scenarios that are made slower if the file is large are probably caused 
by the same architectural decisions that make (find-file "src/xdisp.c") 
slow-ish. All those could likely be improved if CC Mode migrated to 
using syntax-propertize-function, with its on-demand approach to parsing.

Scenarios which are slow no matter what probably deserve a separate bug 
report each, and are likely fixable without significant redesign.