Function _getActualBoundingClientRect

src/js/utils/bounds.js:157–183

* Same as native getBoundingClientRect, except it takes into account parent offsets * if the element lies within a nested document ( or -like). * @param node

(node)

 * @param node
 */
function _getActualBoundingClientRect(node) {
  let boundingRect = node.getBoundingClientRect();

  // The original object returned by getBoundingClientRect is immutable, so we clone it
  // We can't use extend because the properties are not considered part of the object by hasOwnProperty in IE9
  let rect = {};
  for (let k in boundingRect) {
    rect[k] = boundingRect[k];
  }

  try {
    if (node.ownerDocument !== document) {
      let { frameElement } = node.ownerDocument.defaultView;
      if (frameElement) {
        let frameRect = _getActualBoundingClientRect(frameElement);
        rect.top += frameRect.top;
        rect.bottom += frameRect.top;
        rect.left += frameRect.left;
        rect.right += frameRect.left;
      }
    }
  } catch (err) {
    // Ignore "Access is denied" in IE11/Edge
  }

  return rect;
}

function _getOrigin(body) {
  // getBoundingClientRect is unfortunately too accurate.  It introduces a pixel or two of