Localization

The interface ships in the language it is written in (English) plus every language in the table in crates/ui-egui/src/i18n.rs. Today that is English, Simplified Chinese (zh-hans), Traditional Chinese (zh-hant, Taiwan), Japanese (ja), Brazilian Portuguese (pt-br), Spanish (es), German (de), Russian (ru), French (fr), Ukrainian (uk), Czech (cs), Italian (it), Georgian (ka), Swedish (sv), Finnish (fi), Indonesian (id), Vietnamese (vi) and Polish (pl). This file is the reference for adding or maintaining a language; the per-language notes are in localization-zh-hans.md, localization-zh-hant.md, localization-ja.md, localization-pt-br.md, localization-es.md, localization-de.md, localization-ru.md, localization-cs.md, localization-fi.md, localization-ka.md, localization-id.md, localization-vi.md and localization-pl.md.

Adding a language

1. Translate the two catalogs. Copy locales/ja.json and locales/ja-formats.json to locales/<code>.json and locales/<code>-formats.json, then translate the values. Keys are the English source strings and must stay byte-for-byte identical. Both catalogs may grow at their own pace: a message a catalog lacks, or translates as an empty string, shows in English, and nothing fails. The translation gaps report lists what each language lacks (see Testing and looking at it). The formats catalog also holds the date patterns ({year}, {month} {year}, {weekday}, {day} {month} {year}…) that date headings and capture times use in every language but English; weekday names go in the plain catalog.

2. Add the table entry in crates/ui-egui/src/i18n.rs:

   language_table! {
       En, "en";
       ZhHans, "zh-hans", "简体中文", "Hans", include_str!("../locales/zh-hans.json");
       ZhHant, "zh-hant", "繁體中文（台灣）", "Hant", include_str!("../locales/zh-hant.json");
       Ja, "ja", "日本語", "Jpan", include_str!("../locales/ja.json");
       PtBr, "pt-br", "Português (Brasil)", "Latn", include_str!("../locales/pt-br.json");
       De, "de", "Deutsch", "Latn", include_str!("../locales/de.json");
       Ru, "ru", "Русский", "Cyrl", include_str!("../locales/ru.json");
       Uk, "uk", "Українська", "Cyrl", include_str!("../locales/uk.json");
       Cs, "cs", "Čeština", "Latn", include_str!("../locales/cs.json");
       It, "it", "Italiano", "Latn", include_str!("../locales/it.json");
       Ka, "ka", "ქართული", "Geor", include_str!("../locales/ka.json");
       Fi, "fi", "Suomi", "Latn", include_str!("../locales/fi.json");
       Vi, "vi", "Tiếng Việt", "Latn", include_str!("../locales/vi.json");
   }

   The fields are the BCP-47 code (also the settings-file value), the endonym shown in the Language menu, the ISO 15924 script (Latn, Jpan, Hans, Hant, Kore…), and the embedded catalog. build.rs picks up <code>-formats.json by name, so the macro and the format lookup follow automatically. Add the corresponding app.language.<name> entry to LANGUAGE_COMMANDS and language_from_command in src/menus.rs, and to the language_commands_cover_every_language test. Settings read the locale table; menus and the control channel share the language-command mapping.

3. Make sure the glyphs exist. The script drives which craft-fonts faces the UI installs: a language whose script has no face in the build shows boxes (the test says so instead of failing). Fonts live in storytold/craft-fonts, never here; a missing face is added there, not worked around in this repository. Sentence-cased messages go through i18n::upper_first, which leaves Georgian lowercase (upper-casing Mkhedruli would make Mtavruli).

4. Run cargo xtask ci (it includes fmt, clippy, the tests, parity and the wasm check).

How a message is found

tr("Exposure") looks the English label up in the active language's catalog and returns the source text unchanged when there is no entry; tr_format! handles text with runtime values. Both are presentation-only: command ids, file names and user-entered metadata are never translated.

A few messages take a context, for a word whose shared translation reads wrongly in one place. The catalog may then carry "<context>|<English>", which wins there; without it the plain message is used, so only the languages that need it add one. Today the one context is smart album value: the Yes / No of a yes/no rule (Has Edits, Cropped…). Japanese uses it because はい / いいえ answer a question rather than describe a photo ("smart album value|Yes": "あり", "smart album value|No": "なし"); every other language uses its plain Yes / No. A contextual key that names no real value fails the i18n tests.

tr_format! is generated by crates/ui-egui/build.rs: one arm per English message, which formats the active language's translation with format! (English is the fallback arm). Every catalog's format string is therefore checked by Rust against the call site's own arguments:

tr_format!("Added {n} photo{} to “{}”", if n == 1 { "" } else { "s" }, album, n = n)

• A translation is an ordinary Rust format string over the same arguments. Refer to named values by name ({n}) and to positional ones by index when the word order changes ({0}, {1}): "已将 {n} 张照片添加到“{1}”{0:.0}". Keep the source's spec ({:.1}, {d:+}, {:.0}%).
• format! rejects an unused argument, so a value a language does not need — the English plural suffix ("s" / "") — is consumed as {:.0} (a string at precision 0 prints nothing).
• A language whose formats catalog lacks a message shows the English source there, and a tr_format! call whose message is in no catalog formats the English source (the macro's last arm). A new message builds with no catalog entry.

Testing and looking at it

cargo test -p imago-ui-egui i18n::tests                       # catalogs load, placeholders, switching
CRAFT_FONTS_DIR=../craft-fonts cargo test -p imago-ui-egui i18n::tests   # + glyph coverage
cargo test -p imago-ui-egui --lib -- --exact i18n::tests::translation_gaps_report --nocapture

The tests fail on a broken catalog (malformed JSON, a repeated key, placeholders that differ from the source), never on a missing translation. The last command is the translation gaps report: per language, the count and list of plain and format messages it lacks and the number of untranslated What's New lines. It always passes, and cargo xtask ci prints it after its test step. The glyph tests are skipped without CRAFT_FONTS_DIR (there are no CJK faces to check then). To look at a language, render it headless:

IMAGO_LANGUAGE=zh-hans imago-cli snapshot --demo --script tour.jsonl -o out.png --size 1600x1000

or, with the app running (--control 7980), run the language command (engine.execute {"command": "app.language.simplifiedChinese"}) and take a screenshot.

Language codes and settings

The settings file stores the BCP-47 code, never the Rust variant name, so a language can be renamed in code without invalidating anyone's saved preference. IMAGO_LANGUAGE accepts what a system locale looks like (zh_Hans, zh-CN, en_US, ja_JP.UTF-8) and falls back to the base language when a region has no dedicated entry.

Release notes

Help ▸ What's New shows docs/whats-new.md, and each of its lines (a heading, or one wrapped line of a bullet, without the - or ### ) is looked up like any message, so a catalog can translate the notes line by line (German does). A line that is re-wrapped or edited no longer matches its translation and shows in English until the catalog is updated; the translation gaps report counts the untranslated lines.