API REFERENCE
renderProgress
re-emitted from the scatter family: a progressively painted chunk landed (done on the last).
Definition
Event name: renderProgress. Names are case-sensitive. Read the payload from detail on CustomEvent<{ drawn: number; total: number; done: boolean }>.
chart.addEventListener('renderProgress', event => {
console.log(event.detail); // { drawn: number; total: number; done: boolean }
});