bug#81533: c-ts-mode: Improved block comment indentation

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Hello Stefan!

Den sön 2 aug. 2026 kl 20:02 skrev Stefan Monnier 
<[email protected]>:
 > My comment was just meant to state the direction in which I think we
 > should move to better integrate with the rest of the infrastructure.

I agree, but leave that job for you guys. :) I just want to scratch my
own itch: block comment indentation in c-ts-mode.

 > >> The rule (1) sounds right, but rules (2) and (3) should simply refrain
 > >> from modifying the line and return `noindent`.
 > > Why indent lines prefixed with "*" be indented but not other lines?
 >
 > Yeah, it's not great, it's a heuristic that will sometimes fail,

If indenting is right 99.5% of the time I think we can let the 0.5%
suffer. The needs of the many outweigh the needs of the few.

 > > You could make the function public so that other modes could add it to
 > > their default rules:
 > >
 > > ((parent-is "comment") parent c-ts-mode-common-block-comment-offset)
 >
 > Indeed.  But then its name shouldn't start with "c-ts-", it shouldn't
 > hard code "*", and it should live in another file.
 > That's a way to "handle [it] once for all tree-sitter modes".

The previous c-ts-mode block comment indentation code called three
functions: c-ts-common-looking-at-star,
c-ts-common-comment-start-after-first-star, and
c-ts-common-comment-2nd-line-matcher. Hard coding "star" in function
names is clearly worse than hard coding the "*" character so I belive
my patch is -- if not a step in the right direction -- at least not a
step in the wrong direction. :)

Conceivably, other ts progmodes, such as php-ts-mode, that call those
three functions could call c-ts-mode-common-block-comment-offset
instead. But I didn't change them because I didn't want to create an
uber long patch and because I'm not 100% familiar with those languages
conventions for block comments.

 > Side note about your patch: `line-number-at-pos` takes time proportional
 > to the size of the buffer (well, proportional to (point), actually, but
 > you get the ... point 🙂), so calling it twice just to check if two
 > buffer positions are on consecutive lines is very inefficient.
 > Better use things like

Thanks! Attached is a new patch with those issues fixed.


--
mvh/best regards Björn Lindqvist
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