jacin

Hobby IME toy project bridging Wayland and Neovim.
No Fcitx/IBus needed.
Requires a Wayland compositor that implements.

• zwp_input_method_v2
• zwp_virtual_keyboard_v1
• zwp_input_popup_surface_v2

Requirements

• Neovim >= 0.10
• A Wayland compositor with zwp_input_method_v2, zwp_virtual_keyboard_v1, and zwp_input_popup_surface_v2 support
• A compositor keybind to send SIGUSR1 to jacin for toggling

Hyprland example

bind = ALT, grave, exec, pkill -SIGUSR1 jacin

Configuration

Config file: ~/.config/jacin/config.toml

[keybinds]
commit = "<C-CR>"         # Commit preedit text to application

[completion]
adapter = "native"        # "native" (ext_popupmenu) or "nvim-cmp"

[behavior]
startinsert = true        # true: start in insert mode, false: start in normal mode
recording_blink = true    # Blink the REC indicator while recording a macro
write_to_commit = false   # :w commits preedit text to the application (:wq, :x also work)

[font]
family = "Noto Sans CJK JP"   # Proportional font (preedit/candidates). Default: fontconfig auto
mono_family = "JetBrains Mono" # Monospace font (keypress/mode display). Default: "monospace"
size = 16.0                    # Font size in pixels

All fields are optional and fall back to the defaults shown above.

Completion adapters

• native (default): Uses Neovim's ext_popupmenu UI extension. Works with skkeleton henkan and any plugin that calls complete(), including ddc.vim with ddc-ui-native.
• nvim-cmp: Hooks into nvim-cmp's Lua API directly for candidate extraction (nvim-cmp uses its own floating window, not the native popup menu).

Note: Since jacin sets buftype=nofile on its buffer, ddc.vim requires specialBufferCompletion enabled in your ddc config.

Usage

Kill any running IME (fcitx5, ibus, etc.) before starting jacin. Only one IME can bind zwp_input_method_v2 at a time.

cargo build --release
./target/release/jacin
./target/release/jacin --clean # Start with vanilla Neovim (no user config/plugins)

Toggle the IME by sending SIGUSR1:

pkill -SIGUSR1 jacin

Logging

RUST_LOG=debug ./target/release/jacin

Limitations

Preedit is single-line only. Multiline operations (yy, dd, cc, p, P) are not supported.

Security Warning

jacin grabs your keyboard via the Wayland input method protocol. While the keyboard is grabbed, all keystrokes pass through jacin and the embedded Neovim instance before reaching the focused application. This is inherent to how IMEs work, but be aware that any Neovim plugin loaded in the embedded instance can observe your input. Use --clean to run without user config/plugins if needed.

License

MIT