export interface ItemObserverOptions {
    /** Invoked, coalesced to once per frame, when any observed item's box changes. */
    onChange: () => void;
    /**
     * Also attach one-shot `load`/`error` listeners to images inside observed
     * items. Covers layouts where the wrapper's box does not change even though
     * its content settles. Default: true
     */
    watchImages?: boolean;
}
export interface ItemObserver {
    /** Start observing an element. Idempotent; `null` is ignored. */
    observe(el: HTMLElement | null): void;
    /** Stop observing a single element and drop its listeners. */
    unobserve(el: HTMLElement): void;
    /** Stop observing everything; the observer stays usable afterwards. */
    reset(): void;
    /** Tear down permanently. */
    disconnect(): void;
}
/**
 * Watch individual grid items for size changes and report them.
 *
 * This is what makes the grid self-healing. Item heights are measured once
 * during layout, but real content settles *after* that: images decode, fonts
 * swap, embeds resize, text reflows, collapsible sections open. Without this,
 * the only trigger for a fresh layout is a container **width** change — so an
 * image gallery lays out against zero-height images and stays broken until the
 * window happens to be resized.
 *
 * Every notification is funnelled through one animation-frame scheduler, so a
 * gallery of 200 images finishing at once costs a single relayout, not 200.
 */
export declare function createItemObserver(options: ItemObserverOptions): ItemObserver;