import Modifier from 'ember-modifier';
import type EmberFreestyleService from '../services/ember-freestyle';
export default class FreestyleScrollSpy extends Modifier {
    emberFreestyle: EmberFreestyleService;
    private intersectionObserver;
    private mutationObserver;
    private visibleElements;
    private observedElements;
    private _isDestroyed;
    private _service;
    private _pendingMutationFrame;
    modify(element: HTMLElement): void;
    /**
     * Diff-based re-observation: only observe/unobserve elements that changed,
     * preserving the IntersectionObserver's internal state and visibleElements set.
     */
    private syncObservedElements;
    private updateActive;
    willDestroy(): void;
}