type Measurable = { getBoundingClientRect(): DOMRect; }; /** * 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. */ declare function observeElementRect( /** The element whose rect to observe */ elementToObserve: Measurable, /** The callback which will be called when the rect changes */ callback: CallbackFn): () => void; type CallbackFn = (rect: DOMRect) => void; export { type Measurable, observeElementRect };