Internationalisation

GearUI Kit carries its own strings for the copy inside components ("Confirm", "Cancel", the empty-state text, picker titles), resolves them from a BCP 47 language tag, and lets downstream libraries hang their own strongly-typed packs off the same environment. Apps set the language once.

Setting the language

App(
    languageTag = "zh-Hans",          // BCP 47; "en-US", "zh-Hant", "vi-VN", …
    fallbackLanguageTag = "en-US",    // used when no pack matches languageTag
) { … }

Change languageTag and every string in the tree updates. There is nothing to reload.

Overriding built-in copy

Field-level, per language, no need to fork a pack:

App(
    languageTag = "en-US",
    stringsOverrides = mapOf(
        "en-US" to StringsPatch(common = CommonStringsPatch(confirm = "Got it")),
    ),
) { … }

Strings are grouped into domains (common, theme, field, dateTime, feedback, media, guide), each an @Immutable data class with a matching …Patch whose fields are all nullable. This is not just tidiness: a single flat class with every string in it hits Android's 255-constructor-parameter limit and DEX method ceilings. The split is a hard requirement.

Reading strings in your own code

val strings = I18n.strings          // inside composition
Text(strings.buttonConfirm)

Downstream libraries

If you are writing a library on top of GearUI Kit (a product UI layer, a brand theme pack), do not ask the app for a language tag. Read the one App already provides:

@Composable
fun MyLibI18nProvider(overrides: Map<String, MyLibStringsPatch> = emptyMap(), content: @Composable () -> Unit) {
    val tag = LocalLanguageTag.current
    val fallback = LocalFallbackLanguageTag.current
    val strings = remember(tag, fallback, overrides) {
        resolveLanguagePack(tag, MyLibStringPacks.builtIn, fallback).merge(overrides)
    }
    CompositionLocalProvider(LocalMyLibStrings provides strings, content = content)
}

Mount it inside App, outside your pages. Language switching then reaches your library for free, and the app never has to pass the tag twice. The full walkthrough is docs/I18N_INTEGRATION.md in the repository.

Built-in languages

Tag
en-US	English (the fallback)
zh-Hans	简体中文
zh-Hant	繁體中文

Tags are normalised on the way in, so zh_CN, zh-CN and zh-Hans all resolve to the Simplified Chinese pack. Any other language is a matter of supplying a Strings pack through stringsOverrides for the tag you need; downstream libraries add their own languages the same way and are not limited to this list.