export declare class ScrollViewportEvent {
    static readonly ON_ITEM_ADDED: string;
    static readonly ON_ITEM_REMOVED: string;
    static readonly ON_ITEM_UPDATED: string;
    static readonly ON_RANGE_UPDATED: string;
    static readonly ON_VIEWPORT_SCROLLED: string;
    static readonly ON_VIEWPORT_READY: string;
    static readonly ON_VIEWPORT_INITIALIZED: string;
}