Re: Problems with syntax-ppss

[Lennart Borgman (gmail)]

Stefan Monnier wrote:
> > Would it not be a good idea to (i) redefine syntax-ppss as calculating
> > the syntax from BOB (as opposed to (point-min));
>
> That's already what it does, when it can.  Maybe it could be improved as
> follows: signal an error if it needs to recompute from (point-min) and
> (point-min) is not the beginning of the buffer, unless the caller sets
> a `syntax-ppss-narrowed-is-ok' variable (for use in modes like Info and
> Rmail).  Maybe that variable should be shared with font-lock-dont-widen.

Until I had to start reading the code I thought that 
font-lock-dont-widen already took care of this. I think there have to be 
a way to tell syntax-ppss not to widen otherwise I can't see what 
purpose font-lock-dont-widen could have (but I guess I am missing 
something there?).

Adding a new variable syntax-ppss-narrowed-is-ok might be good, but 
should not font-lock-dont-widen be honored regardless of this? Or should 
perhaps font-lock set the new variable as needed?


> > (ii) have several caches, each associated with a particular syntax
> > table (how many modes are going to use more than 2 or, perhaps, 3?);
>
> This may incur a significant cost.  I much prefer to let the caller
> decide when a change of syntax-table requires flushing the cache.

Looks better to me since flushing is done based on the position in the 
buffer.

> Another approach might be to introduce a `syntax-ppss-syntax-table'.