Re: Eglot "inlay hints" landed

[João Távora]

On Thu, Feb 23, 2023 at 5:17 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: João Távora <joaotavora@gmail.com>
> > Date: Thu, 23 Feb 2023 16:09:24 +0000
> > Cc: dalal.chinmay.0101@gmail.com, emacs-devel@gnu.org, 
> > dimitri@belopopsky.com,
> >       luangruo@yahoo.com
> >
> > > If there's a change in A that affects B, jit-lock will call
> > > fontification-functions in both A and B, each one when it's about to
> > > display the corresponding window.
> >
> > Sure, but you're in charge of coding up the "affection" by asking
> > the LSP server.  In other words, only the LSP server knows that the
> > change in A affects B. You must assume that it does and ask it "Hey LSP
> > server, given that I've just changed document A, in your document B from
> > 42 to 420 is are there any new or different inlay hints you'd like to
> > give me?" jit-lock cannot foresee that upfront, it will only act on B's
> > display if B's buffer is changed.
>
> That's no for jit-lock to do.  And I don't see how it could be
> relevant to the issue we are discussing.  How do you do this now?

I don't.  I was just pointing out that jit-lock by itself doesn't
solve this A -> B dependency, which you seemed to suggest it does when
you wrote:

> > If there's a change in A that affects B, jit-lock will call
> > fontification-functions in both A and B, each one when it's about to
> > display the corresponding window.

So I agree with you shouldn't be continuing the discussion of this
topic: it is for later.

> That might be so, but one problem it does NOT have is missing the
> cases when you MUST ask the LSP server, because something is going to
> change on display.

That's true.  But then so does the other more naive implementation
which you get when you set eglot-lazy-inlay-hints to nil, and I'm
not sure which one is more performance.

> window-scroll-functions cannot promise that, since
> they are only called "when the window is scrolled", and there's more
> to that condition than meets the eye, believe me.

I believe you.  But as far as I can tell so far, it's the least
imperfect of the methods, and I haven't seen demonstrations of
problems so far, only your speculation of hypothetical problems.
Which again, I believe in, but I would like to measure the actual
problems quantitatively and qualitatively to make a good decision.

I'd love to switch over to the jit-lock implementation as it has
potential to be much neater.  But I can't seem to get it to not
over-request stuff. I attach the patch I've been trying, and it's
clearly got some thinkos when you test it.  It doesn't help that
`window-start` and `window-end` aren't -- apparently -- reliable
when called from a jit-lock function.

João

better-inlay-hints-maybe.patch
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