/**
 * Observes an element's rectangle on screen (getBoundingClientRect)
 * This is useful to track elements on the screen and attach other elements
 * that might be in different layers, etc.
 */
export declare function observeElementRect(
/** The element whose rect to observe */
elementToObserve: HTMLElement | SVGElement, 
/** The callback which will be called when the rect changes */
callback: CallbackFn): () => void;
declare type CallbackFn = (rect: ClientRect) => void;
export {};