@base-ui/react/utils/scrollable.mjs

Base UI is a library of headless ('unstyled') React components and low-level hooks. You gain complete control over your app's CSS and accessibility features.

import { getComputedStyle, getParentNode, isHTMLElement, isLastTraversableNode } from '@floating-ui/utils/dom';
export function isScrollable(element, axis,
// When true, a container that overflows only once extra space is added (e.g. drawer
// keyboard scroll slack) still counts, as long as it has layout size on the axis.
allowOverflowIntent = false) {
  const style = getComputedStyle(element);
  if (axis === 'vertical') {
    const overflowY = style.overflowY;
    if (overflowY !== 'auto' && overflowY !== 'scroll') {
      return false;
    }
    return allowOverflowIntent ? element.clientHeight > 0 : element.scrollHeight > element.clientHeight;
  }
  const overflowX = style.overflowX;
  if (overflowX !== 'auto' && overflowX !== 'scroll') {
    return false;
  }
  return allowOverflowIntent ? element.clientWidth > 0 : element.scrollWidth > element.clientWidth;
}
export function hasScrollableAncestor(target, root, axes) {
  // `getParentNode` crosses shadow boundaries (and slots), so a target inside a shadow root
  // still walks up to scrollable ancestors in the light DOM.
  let node = target;
  while (isHTMLElement(node) && node !== root && !isLastTraversableNode(node)) {
    for (const axis of axes) {
      if (isScrollable(node, axis)) {
        return true;
      }
    }
    node = getParentNode(node);
  }
  return false;
}
export function findScrollableTouchTarget(target, root, axis = 'vertical', allowOverflowIntent = false) {
  // `getParentNode` crosses shadow boundaries (and slots), so a target inside a shadow root
  // still reaches a scrollable ancestor in the light DOM.
  let node = isHTMLElement(target) ? target : null;
  while (isHTMLElement(node) && node !== root && !isLastTraversableNode(node)) {
    if (isScrollable(node, axis, allowOverflowIntent)) {
      return node;
    }
    node = getParentNode(node);
  }
  return isScrollable(root, axis, allowOverflowIntent) ? root : null;
}