import Affix from './Affix';
export declare function getTargetRect(target: HTMLElement | Window | null | undefined): DOMRect;
export declare function getFixedTop(placeholderRect: DOMRect, targetRect: DOMRect, offsetTop: number | undefined): number | undefined;
export declare function getFixedBottom(placeholderReact: DOMRect, targetRect: DOMRect, offsetBottom: number | undefined): number | undefined;
export declare function addObserveTarget(target: HTMLElement | Window | null, affix: Affix): void;
export declare function removeObserveTarget(affix: Affix): void;