Re: How to add pseudo vector types

["Clément Pit-Claudel" <cpitclaudel@gmail.com>]

On 7/16/21 10:05 PM, Yuan Fu wrote:
> My conclusion is that after-change-hook is pretty insignificant, and the initial parse is a bit slow (on large files).

I have no idea if it makes sense, but: does the initial parse need to be synchronous, or could you instead run the parsing in one thread, and the rest of Emacs in another? (I'm talking about concurrent execution, not cooperative threading).

In most cases there should be very limited contention, if at at all: in large buffers most of Emacs' activity will be focused on the (relatively few) characters around the gap, and most of the parser's activity will be reading from the buffer at other positions.  You do need to be careful to not read the garbage data from the gap, but otherwise seeing stale or even inconsistent data from the parser thread shouldn't be an issue, since tree-sitter is supposed to be robust to bad parses.

In fact, depending on how robust tree-sitter is, you might even be able to do the concurrency-control optimistically (parse everything up to close to the gap, check that the gap hasn't moved into the region that you read, and then resume reading or rollback).

Alternatively, maybe you could even do a full parse with minimal concurrency control: you'd make sure that the Emacs thread records not just changes to the buffer text but also movements of the gap, and then you could use that list of changes for the next parse?

Anyway, thanks for working on this!