Re: /srv/bzr/emacs/trunk r101338: * lisp/emacs-lisp/syntax.el (syntax-ppss): More sanity check to catch

[Eli Zaretskii]

> From: Stefan Monnier <address@hidden>
> Cc: address@hidden,  address@hidden
> Date: Fri, 14 Feb 2014 11:53:48 -0500
> 
> > My line of reasoning was that since fontification happens on the
> > display engine level, we need to have a way to call a different
> > fontification function for different portions of text.  And similarly
> > with indentation and other mode-specific behavior.
> 
> And all of those are done in Elisp, so there's no need for C-level changes.

Maybe I'm missing something, but how do you define fontification
functions that are only in effect in a portion of a buffer?

> >> What we need instead is some conventions that major modes need to
> >> follow to play well in things like mmm-mode or mumamo.
> > Like what?
> 
> Like "font-lock-keywords can only look before/after the provided region
> boundaries by calling special functions".

And why would this not play well?

> > Examples, please: which conventions are those?  There's almost no code
> > in Emacs that ignores the buffer restrictions (everything uses BEGV
> > and ZV).
> 
> That's not the issue.  The issue is that code can misbehave if it is
> prevented from seeing some of the "outer" text.  Narrowing is used
> sufficiently rarely that we don't see it too often, but such problems do
> occur already with narrowing.

We are not talking about narrowing to an arbitrary portion of text.
We are talking about narrowing to a portion that presents a
syntactically complete snippet of code.