Re: New optimisations for long raw strings in C++ Mode.

[Stefan Monnier <monnier@iro.umontreal.ca>]

> Really?  Then please tell me how is it that we the humans can detect
> incorrect fontifications even when shown partial strings and comments?

That's usually because we can tell the difference between valid C code
and human text and then based on that we can heuristically guess whats
comment/strings/code.
Our guesses can be wrong, tho.  And making such a guess without some
AI-style thingy is somewhat difficult.

`syntax-begin-function` could use such a thing, but we made it obsolete
because making it work well tends to be costly.  But that was used for
"really nearby" (i.e. find a safe spot near enough that we can avoid
scanning 10kB of code, meaning that the heuristic shouldn't take more
time than scanning 10kB of code).  Maybe to speed up `syntax-ppss` in
large buffers, we could re-introduce something like
`syntax-begin-function` but where the idea is to try and find a safe
spot heuristically within the preceding 1MB or so to avoid scanning the
preceding GBs of code: this would give us a higher time-budget for the
heuristic, making it possible to work well enough (and it would be used
only in buffers >1MB).


        Stefan