I'm aware of the multiple and checkbox widgets. I'm looking for a widget whose name I don't know. It consists of two side-by-side boxes, each box can contain a list of items, and usually starts off with all the items in the left-hand box. Between the two boxes are two arrows, usually one on top of the other, one pointing to the right, one to the left. The left-hand box contains those items not 'chosen'; the right-hand box contains those chosen. To 'choose' items (that is, to move an item from the left-hand box to the right-hand box) one selects the item(s) (ctrl-click, shift-click, etc.) in the left-hand box, then presses the right-pointing arrow. The selected items move from the left-hand box to the right-hand box. To 'un-choose' items one selects items in the right-hand box, then presses the left-pointing arrow.
1. What is this widget usually called? 2. Does web2py have such a widget?