jacin

Hobby IME toy project bridging Wayland and Neovim.
No Fcitx/IBus needed.

• 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

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

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

[keybinds]
commit = "<C-CR>"         # Commit the buffer (all lines) to the application

[behavior]
startinsert = true        # true: start in insert mode, false: start in normal mode
recording_blink = true    # Blink the REC indicator while recording a macro

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

All fields are optional; omitted ones use the defaults noted in the comments (keybinds and behavior values above are the defaults).

• The popup renders Neovim's window directly from UI events (ext_multigrid), including your colorscheme highlights and floating windows such as the nvim-cmp menu. Neovim's UI is resized to fit the popup, so long lines wrap there. The application receives no preedit; text is only inserted on commit.
• Input can span multiple lines: <CR> inserts a newline, and the commit key (or turning the IME off) commits the whole buffer joined with \n. <CR>/<BS>/commit key are passed to the application only when the buffer is completely empty. Note that in terminals a committed newline acts like Enter.
• Whatever Neovim draws in its window (including floats) appears in the popup; externalized UI (native popup menu, command line, messages) uses jacin's own sections. The native popup menu (ext_popupmenu) works with skkeleton henkan and any plugin that calls complete(), including ddc.vim with ddc-ui-native; nvim-cmp's menu is shown as a floating window.

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

jacin starts Neovim with g:jacin = 1 set before your config is loaded, so you can adjust settings for the IME without affecting your editor. jacin does not change these options itself. Anything drawn inside the window is shown in the popup, so you may want to turn off columns and line decorations:

if vim.g.jacin then
  vim.opt.number = false
  vim.opt.relativenumber = false
  vim.opt.signcolumn = "no"
  vim.opt.foldcolumn = "0"
  vim.opt.cursorline = false
end

The statusline, tabline, intro screen and ~ filler lines are never shown, so they need no configuration.

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

RUST_LOG=debug ./target/release/jacin

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.

MIT