Re: State of the overlay tree branch?

[Eli Zaretskii]

> From: Sebastian Sturm <address@hidden>
> Date: Sun, 18 Mar 2018 21:14:53 +0100
> 
> [1] I'm using cquery for my C++ editing needs, which comes with an 
> overlay-based semantic highlighting mechanism. With my emacs 
> configuration, lsp-mode/lsp-ui emit 6 calls to line-number-at-pos per 
> character insertion, which consume ~20 to 25 ms each when performing 
> edits close to the bottom of a 66KB C++ file (measured using 
> (benchmark-run 1000 (line-number-at-pos (point))) on a release build of 
> emacs-27/git commit #9942734...). Using the noverlay branch, this figure 
> drops to ~160us per call.

If lsp-mode/lsp-ui needs a fast line counter, one can easily be
provided by exposing find_newline to Lisp.  IME, it's lightning-fast,
and should run circles around count-lines (used by line-number-at-pos).

(I'm not sure I even understand how overlays come into play here,
btw.)