@base-ui/react/esm/internals/shadowDom.js

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 { isShadowRoot } from '@floating-ui/utils/dom';
export function activeElement(doc) {
  let element = doc.activeElement;
  while (element?.shadowRoot?.activeElement != null) {
    element = element.shadowRoot.activeElement;
  }
  return element;
}
export function contains(parent, child) {
  if (!parent || !child) {
    return false;
  }
  const rootNode = child.getRootNode?.();

  // First, attempt with the faster native method.
  if (parent.contains(child)) {
    return true;
  }

  // Then fall back to traversing out of shadow roots when needed.
  if (rootNode && isShadowRoot(rootNode)) {
    let next = child;
    while (next) {
      if (parent === next) {
        return true;
      }
      next = next.parentNode || next.host;
    }
  }
  return false;
}
export function getTarget(event) {
  if ('composedPath' in event) {
    return event.composedPath()[0];
  }

  // TS assumes `composedPath()` always exists, but older browsers without
  // shadow DOM support still fall back to `target`.
  return event.target;
}