Re: emacs rendering comparisson between emacs23 and emacs26.3

[Eli Zaretskii]

> From: Richard Stallman <address@hidden>
> Cc: address@hidden, address@hidden, address@hidden
> Date: Fri, 27 Mar 2020 22:48:38 -0400
> 
>   > It's not possible.  Bidirectional editing support in Emacs is
>   > unconditional, it isn't an optional feature.
> 
> It isn't optional _now_ but maybe there is an opportunity to optimize
> redisplay if the userssays "no BIDI".
> 
> Maybe some of the pre-bidi code could be brought back and used
> when the user says there is no BIDI in the buffer.

If you find volunteers to work on such changes, sure, why not.  I
don't volunteer, mind you: the display code is complicated enough even
without that.

> It would be interesting to compare 24 and 23, to see what slowdown
> there is.

I expect an average twofold slowdown due to bidirectional support.
The OP indicates less than that (comparing Emacs 23 with Emacs 26), so
it's reasonable, IMO, and probably means the CC Mode contribution is
relatively minor.

The tricky part is testing the bidirectional part and the CC Mode part
separately, by loading the old Emacs-23 CC Mode files into later
versions of Emacs.  Maybe Alan could help by providing a Lisp file
which, when loaded, would load CC Mode from a given directory -- this
should be run before visiting any C/C++ file.