src/common/js/winjs/js/ui.js
function _LayoutCommon_groupFromOffset(offset) {
                    return offset < this._groups[0].offset ?
                        0 :
                        this._groupFrom(function (group) {
                            return offset < group.offset;
                        });
                }
function _LayoutCommon_groupFromOffset(offset) {
                    return offset < this._groups[0].offset ?
                        0 :
                        this._groupFrom(function (group) {
                            return offset < group.offset;
                        });
                }
function _LayoutCommon_groupFromOffset ( offset ) { return offset < this . _groups [ 0 ] . offset ? 0 : this . _groupFrom ( function ( group ) { return offset < group . offset ; } ) ; }
offset should be relative to the grid layout's content box
offset should be relative to the grid layout s content box