completion box will flash when input character

[Eason0210]

Hi,

I use eglot with company, lsp server is clangd/pyright.
And I encouter an issue:

When I input new character, the completion list will update, but the completion box will flash while I input new character.

This will not happens when eglot is disconnected with LSP server.

I not sure this is the issue of company or eglot?

I tested on emacs -Q ,and installcompanyand eglot.

Any one known how to fixed it?

edit: this issue also happen on Arch linux (sudo pacman -S emacs-git)

Platform: macOS
Emacs version:

In GNU Emacs 29.0.50 (build 1, x86_64-apple-darwin19.6.0, NS appkit-1894.60 Version 10.15.7 (Build 19H1615))
 of 2022-01-14 built on Mac-1642119124451.local
Repository revision: d476fd33ece51f506644cec737490eda96daf46c
Repository branch: HEAD
Windowing system distributor 'Apple', version 10.3.2113
System Description:  macOS 12.1

[skangas]

Could you explain in more detail what you mean by "flash" here? Thanks.

[Eason0210]

Thanks, It make sense.

[dgutov]

As long as the problem occurs only together with Eglot and not with any other backend, "asking there" might not help.

We probably need more info here (such as whether a non-default frontend was used for popup, such as company-posframe or company-box, and whether "flashing" depends on the speed with which you enter the next character).

But this sounds vaguely similar to joaotavora/sly#468

[Eason0210]

Hi @dgutov,

Thanks for your information.
The behavior looks similar to the video shows in joaotavora/sly#468, but it is nothing to do with speed I input.
I used the default setting for company and eglot.

Steps to reproduce the issue:

1. start emacs with emacs -Q
2. install company and eglot

• M-x package-install, RET, company
• M-x package-install, RET, eglot

3. create a C++ file( you can use any language you like, I just tested clangd , pyright and gopls)
   M-x find-file test.cpp
4. enable company-mode and eglot

• M-x company-mode
• M-x eglot

5. input codes below, you will see the candidate box will "flashing" when you input character

#include <iostream>

int main ()
{
    std::cout << "Hello" << '\n';
    //   ^
    // when you input the std::co, you will see the flashing
    return 0;
}

6. M-x eglot-shutdown, and try the snippet again, you can see the company box is normal.

[dgutov]

So the problem is still there even if you try to type v e r y s l o w l y?

[Eason0210]

So the problem is still there even if you try to type v e r y s l o w l y?

Yes

[Eason0210]

@dgutov @skangas

You can see the vedio below:

31640.mov

[dgutov]

I'm not 100% sure why it leads to blinking (let me know of your further findings). Probably there is an extra redisplay triggered by the prefix handler. Child frame based frontends are obviously immune to that.

But :exclusive 'no is a mess:

           ;; FIXME: Here we'd need to decide whether there are
          ;; valid completions against the current text.  But this depends
          ;; on the actual completion UI (e.g. with the default completion
          ;; it depends on completion-style) ;-(
          ;; We approximate this result by checking whether prefix
          ;; completion might work, which means that non-prefix completion
          ;; will not work (or not right) for completion functions that
          ;; are non-exclusive.

And yes, it does break non-prefix matching (when there are no proper prefix matches in the current set).

[joaotavora]

Seems to work here with other non-company frontends and for the author of that commit. I haven't tested personally. 🤷

[dgutov]

They just didn't notice the regression.

[joaotavora]

I don't know what you're referring to. If you have noted some regression others haven't, use the appropriate form to communicate it.

[dgutov]

#812

[Eason0210]

@skangas @dgutov

I tried to install only eglot and corfu, the completion box will not flashing.
NOTE: Corfu uses child frames to show the popup.

corfu-eglot-2022-01-16.15.54.14.mov

[dgutov]

I tried to install only eglot and corfu, the completion box will not flashing.
NOTE: Corfu uses child frames to show the popup.

FWIW, if you try company-posframe (an alternative frontend to company), you should have the same result. It also uses child frames.

[Eason0210]

if you try company-posframe (an alternative frontend to company)

Thanks, good to known that.

[jdtsmith]

:exclusive no causes very aggressive try-completion on every key press. Corfu has specific patch code to work around this. See minad/corfu#9 (comment)

[joaotavora]

Interesting, anyway, we're probably going to revert :exclusive no. It causes functional problems problems even without even worrying about performance or "aggressiveness". As described in #812