import { FCPMetricWithAttribution, AttributionReportOpts } from '../types.js';
/**
 * Calculates the [FCP](https://web.dev/articles/fcp) value for the current page and
 * calls the `callback` function once the value is ready, along with the
 * relevant `paint` performance entry used to determine the value. The reported
 * value is a `DOMHighResTimeStamp`.
 */
export declare const onFCP: (onReport: (metric: FCPMetricWithAttribution) => void, opts?: AttributionReportOpts) => void;