This changes the GoObject.Width of each item to the new ItemWidth value, if the new width is positive. Furthermore, if the item is an instance of GoText, the GoText.WrappingWidth is set to the same new item width. A non-positive value does not change either GoObject.Width or GoText.WrappingWidth. You may wish to override this method in order to customize how the properties of the items are set when the item width is changed.