js/theme.js
function getBoundaries(popper, reference, padding, boundariesElement) {
    var fixedPosition = arguments.length > 4 && arguments[4] !== undefined ? arguments[4] : false; // NOTE: 1 DOM access here

    var boundaries = {
      top: 0,
      left: 0
    };
    var offsetParent = fixedPosition ? getFixedPositionOffsetParent(popper) : findCommonOffsetParent(popper, reference); // Handle viewport case

    if (boundariesElement === 'viewport') {
      boundaries = getViewportOffsetRectRelativeToArtbitraryNode(offsetParent, fixedPosition);
    } else {
      // Handle other cases based on DOM element used as boundaries
      var boundariesNode = void 0;

      if (boundariesElement === 'scrollParent') {
        boundariesNode = getScrollParent(getParentNode(reference));

        if (boundariesNode.nodeName === 'BODY') {
          boundariesNode = popper.ownerDocument.documentElement;
        }
      } else if (boundariesElement === 'window') {
        boundariesNode = popper.ownerDocument.documentElement;
      } else {
        boundariesNode = boundariesElement;
      }

      var offsets = getOffsetRectRelativeToArbitraryNode(boundariesNode, offsetParent, fixedPosition); // In case of HTML, we need a different computation

      if (boundariesNode.nodeName === 'HTML' && !isFixed(offsetParent)) {
        var _getWindowSizes = getWindowSizes(popper.ownerDocument),
            height = _getWindowSizes.height,
            width = _getWindowSizes.width;

        boundaries.top += offsets.top - offsets.marginTop;
        boundaries.bottom = height + offsets.top;
        boundaries.left += offsets.left - offsets.marginLeft;
        boundaries.right = width + offsets.left;
      } else {
        // for all the other DOM elements, this one is good
        boundaries = offsets;
      }
    } // Add paddings


    padding = padding || 0;
    var isPaddingNumber = typeof padding === 'number';
    boundaries.left += isPaddingNumber ? padding : padding.left || 0;
    boundaries.top += isPaddingNumber ? padding : padding.top || 0;
    boundaries.right -= isPaddingNumber ? padding : padding.right || 0;
    boundaries.bottom -= isPaddingNumber ? padding : padding.bottom || 0;
    return boundaries;
  }
function getBoundaries(popper, reference, padding, boundariesElement) {
    var fixedPosition = arguments.length > 4 && arguments[4] !== undefined ? arguments[4] : false; // NOTE: 1 DOM access here

    var boundaries = {
      top: 0,
      left: 0
    };
    var offsetParent = fixedPosition ? getFixedPositionOffsetParent(popper) : findCommonOffsetParent(popper, reference); // Handle viewport case

    if (boundariesElement === 'viewport') {
      boundaries = getViewportOffsetRectRelativeToArtbitraryNode(offsetParent, fixedPosition);
    } else {
      // Handle other cases based on DOM element used as boundaries
      var boundariesNode = void 0;

      if (boundariesElement === 'scrollParent') {
        boundariesNode = getScrollParent(getParentNode(reference));

        if (boundariesNode.nodeName === 'BODY') {
          boundariesNode = popper.ownerDocument.documentElement;
        }
      } else if (boundariesElement === 'window') {
        boundariesNode = popper.ownerDocument.documentElement;
      } else {
        boundariesNode = boundariesElement;
      }

      var offsets = getOffsetRectRelativeToArbitraryNode(boundariesNode, offsetParent, fixedPosition); // In case of HTML, we need a different computation

      if (boundariesNode.nodeName === 'HTML' && !isFixed(offsetParent)) {
        var _getWindowSizes = getWindowSizes(popper.ownerDocument),
            height = _getWindowSizes.height,
            width = _getWindowSizes.width;

        boundaries.top += offsets.top - offsets.marginTop;
        boundaries.bottom = height + offsets.top;
        boundaries.left += offsets.left - offsets.marginLeft;
        boundaries.right = width + offsets.left;
      } else {
        // for all the other DOM elements, this one is good
        boundaries = offsets;
      }
    } // Add paddings


    padding = padding || 0;
    var isPaddingNumber = typeof padding === 'number';
    boundaries.left += isPaddingNumber ? padding : padding.left || 0;
    boundaries.top += isPaddingNumber ? padding : padding.top || 0;
    boundaries.right -= isPaddingNumber ? padding : padding.right || 0;
    boundaries.bottom -= isPaddingNumber ? padding : padding.bottom || 0;
    return boundaries;
  }
Computed the boundaries limits and return them
@method
@memberof Popper.Utils
@param {HTMLElement} popper
@param {HTMLElement} reference
@param {number} padding
@param {HTMLElement} boundariesElement - Element used to define the boundaries
@param {Boolean} fixedPosition - Is in fixed position mode
@returns {Object} Coordinates of the boundaries