// the vertical scrollbar is on the right side.

var target = document.getElementById("target");
var scroller = document.getElementById("scroller");
var scrollbar_width = scroller.offsetWidth - scroller.clientWidth;

var scroller_width = scroller.offsetWidth;
var scroller_height = scroller.offsetHeight;
var box_width = target.offsetWidth;
var box_height = target.offsetHeight;

var expectedX = {
    inlineStart: box_width,
    inlineCenter: (3*box_width - scroller_width)/2 + scrollbar_width/2,
    inlineEnd: