NSKK — Next-generation SKK for Emacs

Overview

NSKK is a modern, zero-dependency Japanese input method for Emacs built on SKK (Simple Kana to Kanji) principles. It delivers:

• Clean architecture — 7-layer modular design with full lexical-binding
• DDSKK compatibility — Familiar keybindings and behavior
• Extensible — Embedded Prolog engine for customizable conversion logic

NSKK = Next-generation SKK = 次世代 SKK

Features

Zero Dependencies

Only Emacs 29.1+ built-in packages:

• cl-lib (Emacs 24.3+)
• subr-x (Emacs 24.4+)

No external ELPA packages required.

Modern Architecture

Component	Description
Lexical binding	All 25 modules use lexical-binding: t
Prolog engine	Conversion rules as facts/queries
Layer separation	7 strict layers, zero circular deps
Test coverage	5,000+ unit/integration/E2E tests

DDSKK Compatibility

• Same keybindings (C-j, SPC, x, q, l, etc.)
• Same mode indicators (かな, カナ, SKK, 全英, aA)
• Same dictionary format (SKK-JISYO)
• Same conversion markers (▽ for preedit, ▼ for conversion)

Installation

use-package

(use-package nskk
  :vc (:url "https://github.com/takeokunn/nskk.el" :rev :newest
       :lisp-dir "src")
  :custom
  (nskk-dict-system-dictionary-files
   '("/usr/share/skk/SKK-JISYO.L"))
  :config
  (nskk-global-mode 1))

Quick Start

Minimal Configuration

(require 'nskk)
(nskk-global-mode 1)

;; NSKK uses Emacs's built-in ja-dic by default when available.
;; You can still override it with `nskk-dict-system-dictionary-files'.

;; After nskk-global-mode is enabled:
;; C-j       → switch to hiragana input (from ascii mode)
;; C-x C-j   → toggle nskk-mode on/off in current buffer

With System Dictionary

;; Debian/Ubuntu: apt install skktools
;; macOS: brew install skk-jisyo
;; NixOS: environment.systemPackages = [ skk-jisyo ];

(setopt nskk-dict-system-dictionary-files
        '("/usr/share/skk/SKK-JISYO.L"
          "/usr/share/skk/SKK-JISYO.jinmei"
          "/usr/share/skk/SKK-JISYO.geo"))
(nskk-global-mode 1)

Recommended Configuration

(use-package nskk
  :vc (:url "https://github.com/takeokunn/nskk.el" :rev :newest
       :lisp-dir "src")
  :custom
  ;; Start in hiragana mode (optional, default is ascii)
  (nskk-state-default-mode 'hiragana)

  ;; System dictionaries
  (nskk-dict-system-dictionary-files
   '("/usr/share/skk/SKK-JISYO.L"))

  ;; User dictionary location
  (nskk-dict-user-dictionary-file "~/.nskk/jisyo")

  ;; Show candidate list after 2nd SPC (default: 5)
  (nskk-henkan-show-candidates-nth 2)

  ;; Enable dictionary caching
  (nskk-dict-cache-enabled t)

  ;; AZIK romaji style (optional)
  ;; (nskk-converter-romaji-style 'azik)

  :config
  (nskk-global-mode 1))

Usage

Mode Switching

From	Key	To	Indicator
Any	C-x C-j	Toggle on/off	—
ascii	C-j	hiragana	かな
hiragana	q	katakana	カナ
hiragana	l	ascii	SKK
hiragana	L	full-width	全英
hiragana	/	abbrev	aA

Conversion Flow

stateDiagram-v2
    [*] --> ASCII: nskk-global-mode (default)

    ASCII --> Hiragana: C-j
    Hiragana --> ASCII: l
    Hiragana --> Katakana: q
    Hiragana --> FullWidth: L
    Hiragana --> Abbrev: slash
    Abbrev --> Conversion: SPC
    Abbrev --> Hiragana: C-j / C-g

    Katakana --> Hiragana: q
    Katakana --> Hiragana: C-j
    Katakana --> ASCII: l

    FullWidth --> Hiragana: C-j

    Hiragana --> Preedit: Uppercase
    Katakana --> Preedit: Uppercase
    Preedit --> Conversion: SPC
    Preedit --> Hiragana: C-g (returns to kana mode)

    Conversion --> Hiragana: C-j (commit, returns to kana mode)
    Conversion --> Conversion: SPC (next)
    Conversion --> Conversion: x (prev)
    Conversion --> Preedit: C-g (rollback)

Loading

Key Bindings

Mode Control

Key	Command	Description
C-x C-j	nskk-toggle-mode	Toggle NSKK in current buffer
C-j	nskk-kakutei	Commit (hiragana) / enter hiragana (ascii) / newline
q	nskk-handle-q	Toggle hiragana ↔ katakana
l	nskk-handle-l	Switch to ASCII mode
L	nskk-handle-upper-l	Switch to full-width latin (JIS X 0208)
/	nskk-handle-slash	Enter abbrev mode

Conversion (Henkan)

Key	Command	Description
SPC	nskk-handle-space	Start conversion / next candidate
x	nskk-handle-x	Previous candidate
X	nskk-handle-upper-x	Purge candidate from user dictionary
RET	nskk-handle-return	Commit candidate + newline
C-g	nskk-handle-cancel	Cancel conversion or preedit
a=–=l	direct select	Select candidate in list mode
C-n	nskk-handle-ctrl-n	Next candidate OR next line
C-p	nskk-handle-ctrl-p	Prev candidate OR previous line
C-/	nskk-undo-kakutei	Undo last kakutei (revert commit)

Cursor Movement (in Conversion Mode)

Key	Behavior
↑ / C-p	Commit candidate + move to previous line
↓ / C-n	Commit candidate + move to next line
← / C-b	Commit candidate + move backward
→ / C-f	Commit candidate + move forward

Line Navigation

Key	Behavior
C-a / <home>	Commit candidate (if converting) / go to beginning of line
C-e / <end>	Commit candidate (if converting) / go to end of line

Other Keys

Key	Command	Description
DEL	nskk-handle-backspace	Delete last preedit char / cancel conversion
TAB	nskk-handle-tab	Dynamic completion (preedit) / indent-for-tab-command

Input Modes

Mode	Indicator	Description
ascii	SKK	Direct ASCII input (pass-through)
hiragana	かな	Hiragana input
katakana	カナ	Katakana input
jisx0208-latin	全英	Full-width latin (JIS X 0208)
abbrev	aA	Abbreviation expansion

Configuration

Common Options

;; Set initial input mode
(setopt nskk-state-default-mode 'hiragana)

;; System dictionary files
(setopt nskk-dict-system-dictionary-files
        '("/usr/share/skk/SKK-JISYO.L"))

;; User dictionary location
(setopt nskk-dict-user-dictionary-file "~/.nskk/jisyo")

;; Candidate display
(setopt nskk-henkan-show-candidates-nth 2)
(setopt nskk-henkan-number-to-display-candidates 7)

SKK Server (skkserv)

;; Connect to a running skkserv for extended dictionary lookup
(setopt nskk-server-enable t)
(setopt nskk-server-host "localhost")
(setopt nskk-server-portnum 1178)

Hooks

;; Run when NSKK is disabled
(add-hook 'nskk-mode-off-hook
          (lambda () (message "NSKK deactivated")))

AZIK Extended Romaji

;; Enable AZIK for more efficient romaji input
(setopt nskk-converter-romaji-style 'azik)

;; Keyboard layout (us101 or jp106, default: us101)
(setopt nskk-azik-keyboard-type 'jp106)

AZIK replaces standard romaji with efficiency shortcuts:

• f → ん hatsuon (e.g. kf → かん)
• j → ん hatsuon (e.g. sj → さん)
• Double consonant suffixes → double vowels (e.g. kk → きん, sh → すう)

Optional Features

All optional features are auto-loaded when NSKK starts if their modules are present.

Feature	Module	Enable with
Annotation display	nskk-annotation	(setopt nskk-show-annotation t)
Inline mode display	nskk-show-mode	(setopt nskk-show-mode-show t)
Dynamic dcomp multi	nskk-inline	(setopt nskk-dcomp-multiple-activate t)
Context auto-mode	nskk-context	(nskk-context-global-mode 1)
Isearch integration	nskk-isearch	(setopt nskk-isearch-enable t)
Region operations	nskk-region	Available as M-x nskk-region-* commands

Customization Group

M-x customize-group RET nskk RET

Development

Setup

git clone https://github.com/takeokunn/nskk.el.git
cd nskk.el

# Using Nix (recommended)
nix develop

# Or without Nix (requires Emacs 29.1+)
make compile
make test

The project includes flake.nix for reproducible development environments. nix develop provides Emacs 29.1+ with all necessary dependencies preconfigured.

Commands

Command	Description
make compile	Byte-compile all modules
make test	Run all tests
make test-unit	Run unit tests only
make test-integration	Run integration tests only
make test-e2e	Run end-to-end tests only
make lint	Run checkdoc
make clean	Remove *.elc files

Changelog

See CHANGELOG.md.

Contributing

1. Fork and create a feature branch
2. Add tests and ensure they pass (make test)
3. Commit and create a pull request

Code Style

• nskk- prefix for public symbols
• nskk-- prefix for internal symbols
• All files must have lexical-binding: t

License

GPL-3.0-or-later

Copyright (C) 2026 NSKK Contributors

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Acknowledgments

• DDSKK — A long-standing and widely used SKK implementation for Emacs
• All SKK dictionary contributors