strans/README.md

# strans

strans is a small, single-user input method for Korean, Japanese, English,
and emoji on X11 and Wayland.  It provides one engine shared by XIM, GTK 3,
IBus, and Wayland input-method-v2 frontends.  The existing Vietnamese Telex
mode remains available for compatibility, but is not an actively developed
language mode.

## Input behavior

English is direct passthrough.  Korean uses 2-beolsik composition.  Japanese
Hiragana keeps the complete kana reading until it is committed, so `kanji`
forms `かんじ` and offers whole-reading candidates such as `漢字` and `幹事`.
An apostrophe resolves an ambiguous `n` without forwarding the apostrophe:
for example, `n'ya` forms `んや`.  Katakana is direct Katakana composition
and does not perform Kanji dictionary conversion.

A Japanese composition is committed by Enter, candidate selection, a real
input boundary, or an explicit mode change.  Backspace first removes pending
romaji, then accumulated kana.  The Japanese modes support doubled consonants
and combinations such as `nya`, `nnya`, and `matcha`.

Modes are selected with Ctrl and one letter:

```text
Ctrl+N  Japanese Hiragana and Kanji conversion
Ctrl+K  Japanese Katakana
Ctrl+S  Korean Hangul
Ctrl+T  English passthrough
Ctrl+V  Vietnamese Telex compatibility mode
Ctrl+E  Emoji and symbol search
Ctrl+P  Toggle popup preedit
```

While candidates are visible, Up and Down move the selection, Enter accepts
the selected candidate, and an unmodified `1`-`9` selects the corresponding
visible row.  Tab cycles emoji search results.  `0` commits an unconverted
language reading.  Escape cancels the current composition.  Ctrl, Alt, or
Super combined with a number does not select a candidate.

Emoji search is temporary and returns to the previous mode.  Queries may use
English aliases or the active language's input rules, including Japanese
`egao` becoming `えがお` or `エガオ`:

```text
Ctrl+E → smile → Enter → 😀
```

## Build and test

The supported build uses Docker so host and container toolchains are not
mixed.  Only Docker and Make are needed on the host:

```sh
git submodule update --init
make docker-image
make docker-build
make docker-check
```

`docker-image` creates the Arch Linux dependency image, `docker-build`
compiles the runtime components, and `docker-check` runs the map verifiers and
test suites.  Docker targets force their own compilation, so newer host
objects cannot be reused.  `docker` is a convenience alias for the image and
build steps.
The resulting runtime artifacts are:

```text
strans              daemon, IBus and Wayland frontends
xim/strans-xim      XIM frontend
gtk/im-strans.so    GTK 3 frontend
```

Use `make docker-check TESTARGS=hangul` to filter the C unit tests.  A native
build is still possible with the dependencies and Plan 9 setup recorded in
`Dockerfile`; use `make all`, `make check`, and `make bench` inside that
environment.

After editing `map/emoji.src`, regenerate and verify its dictionary with:

```sh
map/mkemoji >map/emoji.dict
make verify-map
```

Japanese dictionary regeneration and verification are documented in
[`map/README`](map/README).  The converter output is deterministic UTF-8,
tab-separated data consumable by the runtime dictionary reader.

## Run and install

Start the daemon with the installed map and font directories:

```sh
./strans map font &
```

The IPC socket is placed at `$XDG_RUNTIME_DIR/strans.sock` when
`XDG_RUNTIME_DIR` is an absolute path.  Otherwise strans uses the per-user
fallback `/tmp/strans.<uid>`.  A second daemon will not replace a live
daemon's socket.

For XIM applications:

```sh
./xim/strans-xim &
export XMODIFIERS=@im=strans
xterm
```

For GTK 3 applications, install with normal `DESTDIR` semantics.  A staged
install does not update the host GTK module cache:

```sh
make -C gtk install DESTDIR="$pkgdir"
```

For IBus clients such as kitty:

```sh
GLFW_IM_MODULE=ibus kitty
```

Wayland needs no environment variable.  Start `strans` after a compositor
that supports input-method-v2.  Neither ibus-daemon nor fcitx is required.
Starting without `DISPLAY` is supported: the optional X popup is disabled,
while input processing and non-X frontends continue to run.

## Ownership and rendering constraints

There is one global composition, not one independent engine per frontend
context.  The first meaningful key from a new context resets the previous
composition and transfers ownership.  Reset, focus loss, context destruction,
and disconnect affect the engine only when they come from its active owner;
stale events cannot clear a newer owner's preedit.

The popup is an optional X window, including when the active frontend is
Wayland.  It uses deterministic font fallback and fixed-width rune cells;
U+FE0E and U+FE0F variation selectors use zero cells.  It does not perform
OpenType shaping, color-emoji rendering, or general grapheme clustering, and
there is no native Wayland popup renderer.  Multi-rune emoji are committed
intact but are drawn as their constituent rune cells under this boundary.  A
supplied caret rectangle is used when available, with the pointer as fallback.
The X renderer accepts only a 24-depth, 32-bpp TrueColor root format and
disables itself cleanly on other visuals.

## Data, third-party code, and licensing

Data and third-party provenance is recorded in
[`docs/PROVENANCE.md`](docs/PROVENANCE.md), with font-specific details in
[`font/PROVENANCE`](font/PROVENANCE).  The historical SKK-derived Kanji
dictionary is distributed under GPL version 2 or later; its license text is
in [`LICENSES/GPL-2.0-or-later.txt`](LICENSES/GPL-2.0-or-later.txt).

The repository does not currently declare a license for the strans project
source as a whole.  The licenses of bundled data, fonts, generated protocol
code, and third-party components do not by themselves license the original
strans source.