Member variable XbpListBox():multiColumn Foundation
Determines whether items in the list box are displayed in multiple columns
By default the instance variable :multiColumn contains the value .F. (false). This means that the listbox displays its items in a single column. If the instance variable is set to .T. (true), items are displayed in multiple columns that can be scrolled horizontally. The vertical scrollbar is automatically hidden and the instance variables :vertScroll and :horizScroll are ignored.
If :addItem() is used to add an item to the list box, the element is appended to the end of the list. However, if the list box object is configured to use multicolumn-mode (:multiColumn is .T.), list elements are added column-by-column. After all elements of a column have been added, the next list item is inserted into the next column to the right. Instead of growing towards the bottom of the display, a multi-column list box object grows towards the right. The number of items per column is defined by the horizontal space available.
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