A layout algorithm that supports virtualization of items. In other words,
only the items that are visible need to be created as display objects, and
those outside of the view port bounds are represented with empty space until
they are scrolled into view. Useful in components like
GridView where dozens or hundreds of items are needed, but
only a small subset of them are visible at any given moment.
Used by the layout to store additional data for virtual items (items that are not currently represeted by display objects). For instance, it might store the width and height of an item so that this value may be used to calculate the total layout dimensions when the item is out of bounds.
getVisibleIndices(itemCount:Int, width:Float, height:Float, ?result:VirtualLayoutRange):VirtualLayoutRange
Used internally by a UI component (such as
GridView) to determine which indices are visible with the specified
view port bounds and scroll position. Indices that aren't included in
the result typically do not receive display objects to represent them.