skey-engine

Stateless Vietnamese input method engine written in Rust — used by skey, a fcitx5 Vietnamese input method addon.

Why

skey only needs a stateless input → output transform for Vietnamese text processing. Most existing engines carry unnecessary state-machine complexity. skey-engine provides the same functionality in ~700 lines of straightforward Rust, with a simple Letter-based accumulator model.

Design

• Stateless — input string → output string, no internal mutable state
• Unikey-compatible transforms — dd→đ, aa→â, aw→ă, ow→ơ, uw→ư, vaya→vây, toiws→tới, tone replacement, and more
• String-based is_valid() — CVC validation works on the composed string directly, not tied to engine state
• 4 input methods — Telex, VNI, VIQR, and combined Telex+VNI
• Embedded dictionary — optional dictionary mode for auto-restore: validates the composed output against a ~7.9k-word Vietnamese list compiled into the binary (no runtime file loading), extensible with user words
• Thin FFI — 10 C functions covering lifecycle, config, transform, and validation

API

// Lifecycle
SkeyEngine *skey_engine_new(int32_t method);        // 0=Telex, 1=VNI, 2=VIQR, 3=TeipVni
void        skey_engine_free(SkeyEngine *e);

// Configuration
void skey_engine_set_method(SkeyEngine *e, int32_t method);
void skey_engine_set_tone_style(SkeyEngine *e, int32_t modern);    // 0=traditional, 1=modern
void skey_engine_set_short_w(SkeyEngine *e, int32_t enabled);      // standalone w→ư
void skey_engine_set_free_marking(SkeyEngine *e, int32_t free);    // reserved
void skey_engine_set_bracket_uo(SkeyEngine *e, int32_t enabled);   // reserved
void skey_engine_set_dict(SkeyEngine *e, int32_t enabled);         // auto-restore checks real words
void skey_engine_add_word(SkeyEngine *e, const char *word);        // user word override

// Core
char   *skey_engine_transform(SkeyEngine *e, const char *input);
int32_t skey_engine_is_valid(const char *s);
void    skey_free_string(char *s);

Build

cargo build --release
# → target/release/libskey_engine.a

Release

Bump version and create a tag:

# 1. Edit version in Cargo.toml
sed -i 's/^version = ".*"/version = "0.2.0"/' Cargo.toml

# 2. Commit & tag
git add Cargo.toml
git commit -m "chore: bump version to 0.2.0"
git tag v0.2.0
git push origin main --tags

Pushing a v* tag triggers the release workflow which builds libskey_engine.a, runs tests, and publishes the artifact to GitHub Releases.

License

GPL-3.0