Datepicker placement in IE11

[smtoneill]

In IE11, the Datepicker widget is overlapping the input control as shown:

It looks like the element height is being incorrectly reported to setChildPosition from the height function for mainEl. height uses window.getComputedStyle to calculate the height but it does not look like that respects border-box within IE (see this StackOverflow question). getBoundingClientRect does seem to report the correct values for the element and I was able to hack a simple fix by replacing mainElHeight with mainElRect.height:

if ((mainElRect.top + mainElHeight + childElHeight) > window.innerHeight && mainElRect.top > childElHeight) {
    childEl.style.top = Math.round(mainElRect.top + scrollY - childElHeight - 3) + 'px';
} else {
    childEl.style.top = Math.round(mainElRect.top + scrollY + mainElRect.height + 3) + 'px';
}