Re: Reliable after-change-functions (via: Using incremental parsing in Emacs)

[Eli Zaretskii <eliz@gnu.org>]

> Cc: casouri@gmail.com, akrl@sdf.org, emacs-devel@gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 31 Mar 2020 17:31:43 +0300
> 
> On 31.03.2020 16:14, Eli Zaretskii wrote:
> > Why does it need the entire buffer up front? that sounds like a
> > potential performance killer.  Fontifying a small part of a buffer
> > doesn't need its entire text.
> 
> Because the end product of parsing the buffer is an AST, and the author 
> decided to minimize the odds of problems that come with 
> incomplete/broken ASTs.

But it definitely can work with parts of the buffer, and we don't need
it to have a complete AST for this particular job.

> The previous (first) discussion of TreeSitter has an URL to a 
> presentation video. You can give it a watch.

Thanks, I've watched it back in January, when I wrote my message
calling for its integration.

> Regarding performance, their solution is to make first parsing as fast 
> as possible, and updates to an existing AST faster still.

I'm talking about _our_ performance, not theirs.

> As for the difficulty of sending the whole buffer contents... maybe VS 
> Code and Atom somehow make it easier? If so, someone should investigate 
> why it has to be slower in Emacs.

It should be obvious that sending a buffer as a single string is less
efficient than letting tree-sitter access buffer text directly.  We
just need an appropriate API for that (maybe there is one already, I
didn't take a look at their sources since January).