bug#69071: Emacs master branch: c-ts-mode is slow with large C functions.

[Eli Zaretskii]

> Date: Mon, 12 Feb 2024 11:30:00 +0000
> From: Alan Mackenzie <acm@muc.de>
> 
> Using Emacs master:
> 
> c-ts-mode is slow on large C functions when editing towards the end of
> such a function.
> 
> As an extreme example, there is a function proto_register_rrc in the
> file packet-rrc.c which is part of Wireshark.  This file is "available"
> from Github, but sadly no longer freely available - you need to allow
> Microsoft's scripts to run on your machine.  I'm willing to send this
> file by email to anybody who needs it.  It is almost 10 MB in size.
> 
> proto_register_rrc is around 50,000 lines long, total size about 2¼ MB.
> 
> Near the end of the function, after typing a character, there is a delay
> of between 9 and 10 seconds (on my 7 year old machine) before redisplay
> happens.  This is too long.  Some optimisation seems needed.
> 
> On disabling font-lock-mode, the response becomes instantaneous.

Yuan, could you please look into this?