/**
 * Engagement timer
 *
 * Counts time only while the page is:
 * - focused
 * - visible
 * - active (not pagehidden)
 *
 */
import type { WindowLike } from "../types.ts";
export declare function createEngagementTimer({ windowRef, nowMs, }?: {
    windowRef?: WindowLike;
    nowMs?: () => number;
}): {
    start: () => void;
    peek: () => number;
    getAndReset: () => number;
    __internal: {
        sync: () => void;
    };
};