EditContext: Chinese IME and Vim issue

[aiday-mar]

I'm using extension VSCodeVim. Sometimes, I forget to disable the Chinese IME when i'm doing navigation in NORMAL mode, like typing jjj. So just switch back to US keyboard without clearing the typing first. With experimentalEditContextEnabled, the jjj is not passed as actions in NORMAL mode, but inserted as sth like j'j' in the editor, which didn't happen before.

Disabling experimentalEditContextEnabled fixes my problem.

BTW, macOS 15.3.1, VSCode 1.101.0.

Originally posted by @laggardkernel in #251608

[aiday-mar]

Hi @laggardkernel thanks for commenting. I am following the following steps:

1. Start with the normal mode using the VIM extension
2. Use the simplified pinyin IME on MacOS
3. Input jjj, this text is inserted as j'j'j' by the IME
4. Change to Swiss keyboard (assumed same as US) using the shortcuts ctrl+option+spacebar
5. The cursor moves several lines down (is this a bug?)
6. Press j, the cursor moves as expected downwards

Please see the screen recording below for what I saw.

You mentioned that after changing to the US keyboard with the EditContext enabled, the letter j was inserted as though the composition was continuing. Could you please include a screen recording of the incorrect behavior and a screen recording of the correct behavior? Could you alsp share your settings in this issue?

Screen.Recording.2025-06-18.at.15.59.34.mov

[llleixx]

Incorrect behavior:

incorrect.MP4

Correct behavior:

correct.MP4

As you can see, the jj were incorrectly inserted in the incorrect case. I enabled editor.experimentalEditContextEnabled in the incorrect case and disabled it in the correct case.

[aiday-mar]

Hi @llleixx thank you for filing this issue. I have tested this on the PR #251826 and I see the following:

Screen.Recording.2025-06-18.at.18.26.33.mov

What this screen recording shows is that if the above PR goes in, when you will be in the normal VIM mode, you will still be able to compose as usual in Chinese. I have verified that the VIM extension does not override the CompositionType command which is why you will still be able to compose in the normal mode. I would argue that this is desirable behavior for IME users because you can use the English keyboard to use the vim commands and use the Chinese keyboard to type without having to change the VIM mode. I will therefore mark this issue as being under discussion.

If the above PR goes in, feel free to open an issue with VIM about the future behavior. Perhaps they will override the CompositionType command on their side.

[llleixx]

Hi @aiday-mar,

Thank you for your work on this.

I don't think this behavior is desirable. In Vim's normal mode, everything you type should be interpreted as a command. Therefore, if you type Chinese characters (after typing some letters and selecting a candidate), the Chinese characters should also be treated as commands, which Vim obviously cannot recognize. As a result, Vim ignores them, just like it would any other unrecognized command.

The core issue is determining the expected behavior when you type some letters while using a Chinese input method (during candidate selection) and then switch to the US keyboard layout.

In my opinion, the expected behavior is that the letters typed before the switch should convert to just English letters, as if they had been typed directly using the US keyboard. This is the behavior in versions of VSCode prior to 1.101.0, or when the experimentalEditContextEnabled setting is disabled in VSCode 1.101.0.

For example, in Vim's normal mode, if you type jj using the Chinese-Pinyin input method and then switch to the US keyboard layout, the cursor should move two lines down.

[laggardkernel]

I'm afraid that's not the expected behavior.

When using an IME, the typing is not used as final input directly, but a special layer is added. Characters from an IME is treated as preedit strings, or composition strings, which basically means the input text is not ready, the typed characters may be changed into some other characters by the IME. (In Chinese IME, latin characters -> Chinese characters)

The final characters are used by an editor, only after a user confirms the conversion in an IME. But when a user cancelled, the editor should revert the preedit strings to the user's original typing. It seems our new edit context doesn't handle the cancel part right.

In my case, Chinese Pinyin IME uses latin letter as phonetic symbols for Chinese character. When jj is typed, the IME tried to find some chinese characters sounds like jfoo jbar. And it changed jj -> j'j to indicate we're matching two chinese characters now, cause jj could only mean two syllables. When I realized I'm in Vim NORMAL mode, i switch to US IME, the preedit string j'j didn't got reset back as jj.

ref

• How IMEs work
• Firefox IME handling guide

[aiday-mar]

Hi, thank you for letting me know. I will investigate this today and see if I can fix this issue.