Function getPageSize

packages/react/src/TreeView/useRovingTabIndex.ts:217–222

* Determine the page size for the given tree based on an item in the tree. We * estimate this size by trying to see how many items will fit in the given * tree. If the tree is within a scroll container, we will use the height of * that container. Otherwise, we'll use the current window height

(root: Element, item: HTMLElement | null)

 * that container. Otherwise, we'll use the current window height
 */
function getPageSize(root: Element, item: HTMLElement | null) {
  const scrollContainer = getScrollContainer(root)
  const {height: itemHeight} = item?.getBoundingClientRect() ?? defaultSize
  const availableHeight = scrollContainer?.clientHeight ?? window.innerHeight
  return Math.floor(availableHeight / itemHeight)
}

function getNextPageElement(element: HTMLElement): HTMLElement | undefined {
  const root = element.closest('[role="tree"]')