LuaExpressionTransform

The LuaExpressionTransform class represents a function that is called repeatedly on a list of items to create complex animations, such as the MusicWheel.

Arguments
The transform function receives four arguments:
 * 1) The item it is being applied to.
 * 2) The offset of this item.  When the animation stops, the current selection is at offset 0, the previous item is -1, the next item is 1, and so on.  If the animation is between items, this can be a fractional number.
 * 3) The item's index in the list.  This does not change based on the selection or animation.
 * 4) The total number of items in the list.

The function can be as complex or as simple as needed, and it can include any command defined in the object's Lua interface.

Examples
The following function could be used for a vertically-scrolling music wheel in which the current song "slides" smoothly out to the left: