Re: Syntax tables for multiple modes [was: bug#22983: syntax-ppss returns wrong result.]

[Dmitry Gutov <dgutov@yandex.ru>]

On 03/21/2016 04:20 PM, Vitalie Spinu wrote:

> It might be good to not include these (prog-indentation-context including) in
> emacs 25 release.

Of course, none of them. But nor should we put BEFORE-STRING into master 
until we understand that we really need it, and how to use it.

>>> Performance is not a primary concern for indentation. Correctness and conceptual
>>> cleanness is at a much higher stake here. My hope is that generic helper
>>> functions can be optimized to re-use same temp buffer for multiple invocations
>>> of calculate-indent-function.
>
>> So, how about trying my alternative proposal first?
>
> Sorry. What proposal do you mean?

"""
Instead, if you want to know what indentation an inner mode would return 
if STRING-BEFORE was before it, insert that string into the buffer 
(while inhibiting undo history). Call the indentation function, then 
remove the string.
"""

Same with AFTER-STRING. The multi-mode package itself would do that.

>>> Right. Those stale values won't occur in multi-modes because both syntax-ppss
>>> and parse-partial-sexp will always operate on same hard-narrowed regions.
>
>> We could only be sure of that for syntax-ppss calls in facilities that the
>> multi-mode handles specially, like font-lock, syntax-propertize and
>> indentation. Not so with any other functions the user could call.
>
> I assume that multi-mode engine is advising syntax-ppss which I think it should.

Very well, that's an option. Having syntax-ppss-dont-widen (or making 
syntax-ppss respect hard-widen-limits) should be sufficient for it.