bug#22763: 25.1.50; Feature Request -- A faster method to obtain line number at position.

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> My suggestion is instead to expose display_count_lines to Lisp via a
> simple wrapper (that would need to take care of narrowing and such
> likes, something that your proposed API doesn't do, btw). 

I've now added this to Emacs 28 -- line-number-at-position.  In my
tests, it makes `count-lines' about 2x faster than the previous
implementation.

Now, there's a function called `line-number-at-pos' in simple.el (that
I've amended to use `line-number-at-position', so it's even faster), and
it has almost exactly the signature that the new function has.  But it
has the POS parameter optional, and it has an ABSOLUTE parameter.

I didn't actually discover it before I had finished writing the new
function, so I think I'll just extend the new function to have the same
signature, and then remove the simple.el function.

Unless somebody else has a different opinion in the next ten minutes...

-- 
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   bloggy blog: http://lars.ingebrigtsen.no