Re: [Emacs-diffs] scratch/widen-less a4ba846: Replace prog-widen with consolidating widen calls

[Dmitry Gutov <dgutov@yandex.ru>]

On 11/30/17 8:59 AM, Dmitry Gutov wrote:
> On 11/30/17 1:53 AM, Stefan Monnier wrote:
>>>      Replace prog-widen with consolidating widen calls
>>
>> So, IIUC the idea is that the multi-major-mode framework will *have* to
>> use narrowing to indicate to the sub-modes the boundaries of the current
>> chunk, right?
> 
> Yes. Just like it would *have* to bind prog-indentation-context to a 
> complex-ish value in the previous proposal.

And while the difference isn't night and day, allow me to elaborate why 
I think this is a move in a good direction:

- Major mode authors have been forgetting to widen in all the cases they 
actually have to. Or they would do that in indent-line-function, but 
forget in beginning-of-defun-function, etc. Now, they are *mandated* to 
obey the current narrowing (deleting code is easy, and some won't have 
delete anything at all). The indentation code might fail to work inside 
narrowing (like all of CC Mode, probably), but that's an orthogonal issue.

- Multi-mode packages have been using narrowing for this purpose for 
years, so they won't have to change much.

And, it's kind of funny, mhtml-indent-line which we've reviewed and 
added recently, uses narrow-to-region too. :-) While disregarding the 
second element of prog-indentation-context (which it set to the value 
"widen all you want"). Which works well enough because SMIE doesn't 
widen, and I've removed the `widen' call from js-mode indentation code 
3.5 years ago.

I'm adding Tom and Vitalie to Cc. Maybe they have something to add.