* @param part
* @param point
* @return
*/
private FlowBox getClosestBox() {
FlowBox closestBox = null;
List fragments = getLines(_part);
// if there is one which are at the same line with relative,
// calculate that line first;
for (int i = 0; i < fragments.size(); i++) {
FlowBox box = (FlowBox) fragments.get(i);
Rectangle boxRect = getAbsoluteBounds(box);
if (boxRect.contains(_point.x, _point.y)) {
closestBox = box;
break;
}