strans

strans is a small, single-user input method for Korean, Japanese, English, emoji and symbols, with Vietnamese Telex as a compatibility mode. One engine serves four frontends: zwp_input_method_v2 on Wayland — sway and any other compositor that offers it — IBus, which GTK 4 and Qt use, XIM, and a GTK 3 module.

Modes

Key	Mode
Ctrl+S	Korean Hangul (2-beolsik)
Ctrl+N	Japanese Hiragana, converting to Kanji
Ctrl+K	Japanese Katakana
Ctrl+T	English
Ctrl+V	Vietnamese Telex
Ctrl+E	Emoji and symbol search
Ctrl+H	One-shot Hanja and symbol search

Only a plain Ctrl chord is a strans key: with Shift, Alt or Super held it commits what is pending and goes to the application, so Ctrl+Shift+V still pastes. Backspace, Enter, Tab, Esc and the arrow and page keys do the same under Ctrl, so Ctrl+Backspace still deletes a word. The mode switched to — 한, あ, ア, ă, A — shows in the popup until the next key. A Korean keyboard's 한/영 and 한자 keys stand for Ctrl+S/Ctrl+T and Ctrl+H; a Japanese one's 半角/全角, ひらがな/カタカナ, 変換 and 無変換 for the kana modes, Space and English.

Composing

Japanese composes a whole reading and then offers its Kanji with none chosen. Space and Tab step through the candidates and wrap (Shift reverses), the reading in Katakana last, so a word the dictionary lacks converts with one Space; Up/Down and PageUp/PageDown move without wrapping. A chosen candidate takes the reading's place in the preedit, so it stands where it will land, and Enter commits it, or the reading, as 0 and typing on always do. Once a candidate is chosen 1-9 take that row of the page shown; before that the digits type. Backspace deletes the last kana shown, and romaji that made no kana stays as typed until it is mended; Esc cancels the reading, and on a chosen candidate both go back to it. The dictionary keys verbs and adjectives by stem and okurigana, so kaku offers かく's readings and then 書く and its kin — typing the okurigana with Shift, as SKK does, kaKu, asks for that split first. Katakana mode does not convert, so there Space and Tab commit the reading and go on to the application.

Korean composes one syllable at a time. Enter, Tab, Esc and any key that is not a jamo commit the syllable and go on to the application, so Esc still leaves insert mode. Two lone consonants join into the compound final they make (rt → ㄳ), and a vowel typed before its consonant is reordered under it (kr → 가), as in libhangul.

A search takes the keys until Enter, Space or 1-9 picks a result or Esc cancels, then returns to the previous mode. Emoji matches the typed keys, and what they spell in the current mode, against a prefix of every emoji's CLDR name and keywords in English, Korean and Japanese, and against ASCII aliases such as -> and <=. Ctrl+H takes the syllable being composed as its query and composes on from it, converting a word as well as a syllable — 한자 gives 漢字, 대한민국 gives 大韓民國 — and Esc gives the syllable back. A word is committed a syllable at a time, so the reading also reaches back into the text the application already holds, as far as the dictionary knows the whole of it: type 한자 and then Ctrl+H and the query is 한자, not 자, and picking 漢字 takes the 한 back. Backspace gives that reach back before it deletes what was typed, so 상 written with 태 typed answers 狀態, and one Backspace answers 態 for the syllable alone. A reading is also the start of the longer words it begins, whose conversions follow its own, so 대한 answers 大寒 first and 大韓民國 further down. A lone consonant is a reading too, and answers with the symbol table a Korean keyboard's 한자 key has always offered: ㅁ gives ※ ○ △ ㈜, ㄴ the brackets 「」『』, ㄹ the units ℃ ㎏ ℓ, ㅇ the circled numbers ①②③.

Reaching back needs the application to hand over the text around its cursor and to take some of it away again. The Wayland input method, IBus and the GTK 3 module all can; XIM has no such request, so there the reading is what is still being composed and nothing else, and an IBus client that reads a key's effects only after the call returns is not asked for its text either, since a deletion could not be ordered before the commit.

Dead keys and Compose sequences are composed by strans itself for the Wayland, XIM and IBus frontends, from XCOMPOSEFILE or the locale; the GTK 3 module leaves them to GtkIMContextSimple.

Preedit and candidates

Frontend	Preedit	Candidates	Reaches back
Wayland input method	inline in the client	popup	yes
GTK 3 and IBus	inline in the client	popup	yes
XIM PreeditCallbacks	inline through XIM callbacks	popup	no
XIM PreeditPosition, PreeditNothing	popup	popup	no

On Wayland the popup is a surface the compositor places at the text cursor, flipping it above the line when there is no room below. Elsewhere it is an X11 window, placed from the XIM spot or from the GTK caret, and XIM text travels as COMPOUND_TEXT. Either way GDK_SCALE sizes it for HiDPI displays.

Build and test

git submodule update --init
make docker-image
make docker-build

That leaves strans, the daemon, and gtk/im-strans.so, the GTK 3 module. Tests come in three tiers:

make check          # generated-map validation and unit tests
make check-live     # one IBus, GTK, XIM and IPC daemon smoke each
make check-stress   # randomized, capacity, collision, failure and restart

make docker-check runs all three in the container, and make docker-valgrind the unit suite under Valgrind; rerun make docker-image after changing Dockerfile. UNITARGS=hangul filters the unit suite alone, not the other tiers.

A native build wants a C toolchain, Make, pkg-config and Plan 9 port, plus development files for D-Bus, XCB and xcb-imdkit, Wayland and wayland-scanner, xkbcommon, Pango and Cairo, and GTK 3; the tests also want Xvfb, Python 3 and fonts covering Latin, CJK and emoji. Dockerfile names the exact packages.

Run

./run.sh          # restart the daemon in the background
./strans map      # or run it in the foreground

./strans DIR reads hira.map, kata.map, telex.map, kanji.dict, emoji.dict and hanja.dict from DIR at runtime; nothing but the GTK module is installed. A service supervisor wants the session's XDG_RUNTIME_DIR and its WAYLAND_DISPLAY or DISPLAY: the GTK module finds the daemon at $XDG_RUNTIME_DIR/strans.sock, else /tmp/strans.UID, and IBus clients through the address file libibus expects under ~/.config/ibus/bus/, which strans writes as ibus-daemon would.

strans shows one popup per session, so it picks a frontend at startup: a compositor offering zwp_input_method_v2 gets the Wayland frontend, and then neither XIM nor the X11 popup runs; every other session gets XIM. The IBus endpoint and the GTK 3 module are served in both.

On Wayland, then, set none of the variables below. GTK, Qt and Firefox speak text-input-v3 themselves — GTK 4 binds it with GTK_IM_MODULE unset — and setting these is what pushes them off the path that works: such a client still composes inline but shows no candidates, because the popup belongs to the Wayland frontend. Chromium is beyond help either way, since it asks for text-input-v1, which wlroots does not implement.

export XMODIFIERS=@im=strans      # XIM
doas make -C gtk install          # GTK 3 module
export GTK_IM_MODULE=strans
GLFW_IM_MODULE=ibus kitty         # IBus client example

strans provides its own IBus endpoint, so ibus-daemon and fcitx are not needed. Building the GTK module wants GTK development files; installing one built elsewhere does not. The install target takes GTK_MODULE_DIR when set, else asks GTK where its modules live; doas make -C gtk uninstall removes it. With neither WAYLAND_DISPLAY nor DISPLAY the daemon still serves IBus and its socket, but nothing draws a popup.

Dictionary data

After changing an input source, regenerate and verify:

python3 map/mktelex.py >map/telex.map
map/mkemoji >map/emoji.dict
map/mkhanja >map/hanja.dict
make verify-map

map/README says where the emoji, Hanja and Japanese data comes from.

Benchmark

make bench builds bench/bench. With the daemon stopped, ./bench.sh starts one, warms it up and records the workload with Linux perf into bench/perf.data.

Licensing

Third-party notices are in LICENSES. The repository declares no license for the strans source as a whole.