in js/popper-utils.js [346:393]
function getBoundingClientRect(element) {
var rect = {};
// IE10 10 FIX: Please, don't ask, the element isn't
// considered in DOM in some circumstances...
// This isn't reproducible in IE10 compatibility mode of IE11
try {
if (isIE(10)) {
rect = element.getBoundingClientRect();
var scrollTop = getScroll(element, 'top');
var scrollLeft = getScroll(element, 'left');
rect.top += scrollTop;
rect.left += scrollLeft;
rect.bottom += scrollTop;
rect.right += scrollLeft;
} else {
rect = element.getBoundingClientRect();
}
} catch (e) {}
var result = {
left: rect.left,
top: rect.top,
width: rect.right - rect.left,
height: rect.bottom - rect.top
};
// subtract scrollbar size from sizes
var sizes = element.nodeName === 'HTML' ? getWindowSizes(element.ownerDocument) : {};
var width = sizes.width || element.clientWidth || result.width;
var height = sizes.height || element.clientHeight || result.height;
var horizScrollbar = element.offsetWidth - width;
var vertScrollbar = element.offsetHeight - height;
// if an hypothetical scrollbar is detected, we must be sure it's not a `border`
// we make this check conditional for performance reasons
if (horizScrollbar || vertScrollbar) {
var styles = getStyleComputedProperty(element);
horizScrollbar -= getBordersSize(styles, 'x');
vertScrollbar -= getBordersSize(styles, 'y');
result.width -= horizScrollbar;
result.height -= vertScrollbar;
}
return getClientRect(result);
}