wings-i18n

Internationalization

The model: author natural text in templates. A build step (gen_i18n) rewrites templates, replacing each translatable string with a stable numeric index and emitting a per-language JSON catalog. At runtime the wi18n package loads the catalog and swaps each index back to the translated string. You never write index numbers by hand.

Enable it

• Blank-import the runtime: _ "github.com/luisfurquim/wings/wi18n" in main.go. It auto-detects the browser language, loads i18n/<lang>.json, and makes wings.Main() wait for the catalog before rendering.
• Generate catalogs at build time. The simplest path is the build orchestrator (go run github.com/luisfurquim/wings/cmd/build@latest dev with i18n options, or the repo's gen_i18n); it produces *.i18n.html + i18n/<deflang>.json.
• Ship i18n/<lang>.json (one per language) in your web root.

What gets translated

• Text nodes: <h2>Dashboard</h2> → extracted.
• Translatable attributes only: title, placeholder, alt, aria-label, data-i18n (wings.TranslatableAttrs). Other attribute text is left alone.
• NOT dynamic text: {{expression}} output passes through untranslated — so translate the template literals, not the data. If you need a data value localized, format it (see formatting below) or translate it in your data.

Opt a subtree out with the standard HTML translate="no" (inherited by children) — useful for code samples, proper nouns, or literal index demos.

For CSS-generated text use data-i18n="..." + content: attr(data-i18n) so it flows through the same pipeline (don't hardcode user-visible text in CSS).

Plurals & gender (flexion)

A single translated string can't express a target language's plural/gender agreement. Use inline flex sigils inside a {{...}} block (see the syntax table in wings-component):

• @var — gender axis (the value selects a gender row).
• %var — count axis (emitted at its position; drives the CLDR plural category).
• ~word — a stem the translator will inflect.
• #N — a rule index auto-assigned by gen_i18n; never write it yourself.

<p>{{@gender %qt ~aluno ~aprovado}}</p>

gen_i18n rewrites this to a #N rule and emits an i18n/<lang>.inflections.json (gender × CLDR-category cells) for translators. For programmable inflection engines see README "Programmable Flex (CustomFlex)".

Locale-aware formatting

A lone {{%var}} (no ~/@) formats a value for the locale — type-directed: ints/floats, time.Time, wi18n.Currency, or any type implementing wi18n.Numerical. Named formats: {{%var:formatName}} keyed by <lang>.fmt.json.

<span>{{%price}}</span>   <!-- formatted "R$ 1.234,50" / "$1,234.50" by locale -->

wi18n.Currency is money as an integer in the currency's minor unit (avoids float rounding), not a float:

type Currency struct {
	Amount int64  // minor units: centavos/cents (123450 == 1234.50)
	Code   string // ISO 4217, e.g. "BRL", "USD", "JPY"
}
// e.g. "price": wi18n.Currency{Amount: 123450, Code: "BRL"}

Physical units (length, temperature, speed, …) have their own measure packages; see README "Physical Measure Packages".

Runtime language switching

Switch language live with wi18n.SetLang:

wi18n.SetLang("es-AR", func(err error) {
	if err != nil { /* handle: revert UI, show dialog */ }
})

• It re-fetches the catalog (cached after first load) and re-binds the DOM.
• Run it off the render goroutine (e.g. go wi18n.SetLang(...)) — calling it synchronously from an event handler that the runtime is also driving can deadlock.
• The error callback is where you branch on failure. With catalog signing on (wi18n.SetCatalogPublicKey, ed25519), a tampered/unsigned catalog yields a typed *wi18n.CatalogSignatureError (errors.As) — the bundle is refused (fail-closed). A language-switcher component should branch on it: revert the <select> to the current locale and surface the error (e.g. open a w-dialog).

Notes

• wi18n.Lang() returns the active tag.
• Empty content in a catalog renders the raw index — a deliberate missing-translation signal.
• Deeper: README "Internationalization", "Flexion (SynPrinter)", "FmtPrinter", "Runtime Locale Switching". Translators use the helpers/wlate GUI.