Language switcher & RTL

Language switcher UI

Use the ui-languages.json manifest to build a language selector. ai-i18n-tools exports two display helpers — see Runtime helpers → Display helpers for signatures.

Example LanguageSelect component (React)

import { useMemo } from 'react';
import { useTranslation } from 'react-i18next';
import {
  getUILanguageLabel,
  getUILanguageLabelNative,
  type UiLanguageManifestRow,
} from 'ai-i18n-tools/runtime';
import uiLanguages from './locales/ui-languages.json';
import { loadLocale } from './i18n';

function LanguageSelect({
  value,
  onChange,
}: {
  value: string;
  onChange: (code: string) => void;
}) {
  const { t, i18n } = useTranslation();

  const options = useMemo(
    () =>
      (uiLanguages as UiLanguageManifestRow[]).map((lang) => ({
        code: lang.code,
        // Settings/content dropdowns: shows translated name when available
        label: getUILanguageLabel(lang, t),
        // Header globe menu: shows "English / Deutsch"-style label, no t() call
        nativeLabel: getUILanguageLabelNative(lang),
      })),
    [t]
  );

  const handleChange = async (code: string) => {
    await loadLocale(code);
    await i18n.changeLanguage(code);
    onChange(code);
  };

  return (
    <select value={value} onChange={(e) => handleChange(e.target.value)}>
      {options.map((row) => (
        <option key={row.code} value={row.code}>
          {row.label}
        </option>
      ))}
    </select>
  );
}

getUILanguageLabel(lang, t) - shows t(englishName) when translated, or englishName / t(englishName) when both differ. Suitable for settings screens.

getUILanguageLabelNative(lang) - shows englishName / label (no t() call on each row). Suitable for header menus where you want the native name visible.

The ui-languages.json manifest is a JSON array of "{ code, label, englishName, direction }" entries (direction is "ltr" or "rtl"). Example:

[
  { "code": "en-GB", "label": "English (UK)",   "englishName": "English (UK)",    "direction": "ltr" },
  { "code": "pt-BR", "label": "Português (BR)", "englishName": "Portuguese (BR)", "direction": "ltr" },
  { "code": "de",    "label": "Deutsch",        "englishName": "German",          "direction": "ltr" },
  { "code": "fr",    "label": "Français",       "englishName": "French",          "direction": "ltr" },
  { "code": "ar",    "label": "العربية",           "englishName": "Arabic",          "direction": "rtl" }
]

The manifest is generated by generate-ui-languages or extract from sourceLocale + targetLocales and the bundled master catalog. It is written to languagesManifestPath (defaults to {ui.flatOutputDir}/ui-languages.json when omitted). If you change locales in config, run generate-ui-languages or extract again to refresh the file.

RTL languages

ai-i18n-tools exports getTextDirection(lng) and applyDirection(lng) — see Runtime helpers → RTL helpers.

import { getTextDirection, applyDirection } from 'ai-i18n-tools/runtime';

getTextDirection('ar')    // 'rtl'
getTextDirection('en-GB') // 'ltr'

// Applied automatically via i18n.on('languageChanged', applyDirection) — see Wire i18next

applyDirection sets document.documentElement.dir (browser) or is a no-op (Node.js). Pass an optional element argument to target a specific element. Wire it in your i18n bootstrap — Wire i18next.

For strings that may contain → arrows, flip them for RTL layouts:

import { flipUiArrowsForRtl } from 'ai-i18n-tools/runtime';
const { i18n } = useTranslation();
const isRtl = getTextDirection(i18n.language) === 'rtl';
const label = flipUiArrowsForRtl(t('Next → Step'), isRtl);