bug#56682: Fix the long lines font locking related slowdowns

[Dmitry Gutov]

On 01.08.2022 12:34, Gregory Heytings wrote:
> Given your and Dmitry's feedback, I just tried to add an explicit call 
> to (syntax-ppss (point-max)), without narrowing, when the buffer is 
> opened (see below).
>
> The problem is that this is, as I said, slow.  On my laptop, opening a 1 
> GB file takes about 6 seconds.  The call to syntax-ppss adds 70 seconds, 
> so opening a large file becomes an order of magnitude slower (13 times 
> slower).  Which I think is too much for the added benefit.

But that only has to happen when the buffer is scrolled to the bottom, 
right?

And syntax-ppss's speed depends on the rules applied by the particular 
major mode. Those could be sped up. Some optimization of this function's 
speed is not out of the question either.