Steps to Reproduce

Run fiddle:
http://zkfiddle.org/sample/2im5kjg/2-Columns-and-Cells-not-in-sync-after-appending-column#source-1
Click on Append column
Click on show all

Current Result

When appending a column, the scrollbar faker is removed if the grid doesn't currently need to display a scrollbar (content height < grid height)
However, when more items are added to the grid and a scrollbar is shown, the column faker is still not available, which cause the grid content to scroll further than the headers.

Expected Result

Adding a column should not remove the scrollbar faker div

Debug Info

https://github.com/zkoss/zk/blob/7b60924474ecaf28deb0855a6a5714b2e03df825/zul/src/archive/web/js/zul/mesh/HeadWidget.js#L196-L210

Root Cause

Workaround

rerender the grid on adding a column:

<script><![CDATA[
		zk.afterLoad('zul.mesh', function() {
			var xColumnMenuWidget = {};
			zk.override(zul.mesh.ColumnMenuWidget.prototype, xColumnMenuWidget ,{
				onChildAdded_ : function() {
					var result = xColumnMenuWidget.onChildAdded_.apply(this, arguments);
					this.rerender();
					return result;
				}
			});//zk.override
		});//zk.afterLoad
		]]></script>