[Security Solution][Resolver] Update the resolver element ref on scroll events if the position of the element has changed within the page

x-pack/plugins/security_solution/public/resolver/view/use_camera.ts

@@ -281,17 +281,61 @@ export function useCamera(): {
  * handle that.
  */
 export function useAutoUpdatingClientRect(): [DOMRect | null, (node: Element | null) => void] {
+ // This hooks returns `rect`.
  const [rect, setRect] = useState<DOMRect | null>(null);
- // Using state as ref.current update does not trigger effect hook when reset
+
+ const { ResizeObserver, requestAnimationFrame } = useContext(SideEffectContext);
+
+ // Keep the current DOM node in state so that we can create a ResizeObserver for it via `useEffect`.
  const [currentNode, setCurrentNode] = useState<Element | null>(null);
 
+ // `ref` will be used with a react element. When the element is available, this function will be called.
  const ref = useCallback((node: Element | null) => {
+ // track the node in state
  setCurrentNode(node);
- if (node !== null) {
- setRect(node.getBoundingClientRect());
- }
  }, []);
- const { ResizeObserver } = useContext(SideEffectContext);
+
+ /**
+ * Any time the DOM node changes (to something other than `null`) recalculate the DOMRect and set it (which will cause it to be returned from the hook.
+ * This effect re-runs when the DOM node has changed.
+ */
+ useEffect(() => {
+ if (currentNode !== null) {
+ // When the DOM node is received, immedaiately calculate its DOM Rect and return that
+ setRect(currentNode.getBoundingClientRect());
+ }
+ }, [currentNode]);
+
+ /**
+ * When scroll events occur, recalculate the DOMRect. DOMRect represents the position of an element relative to the viewport, so that may change during scroll (depending on the layout.)
+ * This effect re-runs when the DOM node has changed.
+ */
+ useEffect(() => {
+ // the last scrollX and scrollY values that we handled
+ let previousX: number = window.scrollX;
+ let previousY: number = window.scrollY;
+
+ const handleScroll = () => {
+ requestAnimationFrame(() => {
+ // synchronously read from the DOM
+ const currentX = window.scrollX;
+ const currentY = window.scrollY;
+
+ if (currentNode !== null && (previousX !== currentX || previousY !== currentY)) {
+ setRect(currentNode.getBoundingClientRect());
+ }
+
+ previousX = currentX;
+ previousY = currentY;
+ });
+ };
+
+ window.addEventListener('scroll', handleScroll, { passive: true });
+ return () => {
+ window.removeEventListener('scroll', handleScroll);
+ };
+ }, [currentNode, requestAnimationFrame]);
+
  useEffect(() => {
  if (currentNode !== null) {
  const resizeObserver = new ResizeObserver((entries) => {