Internationalization

FluxGantt ships English only, and will keep doing so — the library bundles no translations and no catalog format. What it gives you instead is a place to put your own.

There is very little to translate. The chart's visible text is almost entirely your data (task names, your own column headers) plus dates, and dates already go through Intl: set locale and they format themselves in any language the browser knows.

createGantt({ tasks, locale: 'vi' }); // dates become "5 thg 1, 2026"

That leaves exactly two strings the library itself composes, and both are accessible names — text a screen reader announces rather than text you see on screen.

The chart's name

createGantt({ tasks, locale: 'vi', ariaLabel: 'Kế hoạch dự án' });

ariaLabel names the chart as a whole. It defaults to 'Gantt chart', and it is also what exportSvg() / exportPng() write into the exported file's <title> — so setting it localizes your exports too.

The per-task sentence

Each task bar announces something like:

Design mockups, Jan 5, 2026–Jan 8, 2026 (50% complete), critical path, selected

To say that in another language, supply messages.taskLabel. It receives every piece of state and returns the finished sentence:

createGantt({
  tasks,
  locale: 'vi',
  messages: {
    taskLabel: ({ name, startLabel, endLabel, progressPct, isCritical, isSelected }) => {
      let s = `${name}, ${startLabel}–${endLabel} (hoàn thành ${progressPct}%)`;
      if (isCritical) s += ', đường găng';
      if (isSelected) s += ', đang chọn';
      return s;
    },
  },
});

Why a whole sentence, not a table of fragments

The obvious design — a { criticalPath: 'đường găng', selected: 'đang chọn' } lookup table — does not actually work, and FluxGantt deliberately does not offer one.

The English sentence used to be built by appending: take the base clause, add ', critical path', then add ', selected'. Swapping the fragments for translated ones keeps that order and that punctuation. Plenty of languages cannot accept it — a verb-final language needs the clauses rearranged, an inflecting one needs the task name's ending to change depending on the clause that follows it. No fragment table can express either.

So the library hands you all of the state and none of the grammar. You control the order, the inflection and the punctuation, which is what makes the string genuinely translatable. It also means FluxGantt bundles no message-format parser at all.

What you get

If your function throws or returns a non-string, FluxGantt falls back to the English sentence rather than breaking the chart. It does so silently: this runs once per task per repaint, so a warning would print thousands of identical lines in a single paint of a large chart.

Construction-time only

locale, ariaLabel and messages are all read once, when the chart mounts. There is no setLocale() or setMessages(). To switch language at runtime, recreate the instance — in React, change the key prop:

<FluxGantt key={locale} tasks={tasks} locale={locale} messages={messages[locale]} />

Not yet supported

• Translated built-in strings. Core ships English only; the two library-composed strings are yours to supply through messages (above). RTL geometry is supported — see Right-to-left charts.
• A different date skeleton. Dates arrive pre-formatted; you cannot currently ask for a different Intl.DateTimeFormatOptions per message.
• Other message keys — grid column headers, tooltips, empty state. These either localize through Intl already or have no library-composed text today. GanttMessages is an interface of optional keys, so adding them later is not a breaking change.