A lot of widgets like ColumnSuper, RowSuper, FitHorizontally, Box, WrapSuper, TextOneLine, Delayed, Pad, ButtonBarSuper, NormalizedOverflowBox, showDialogSuper, and much more.
When your desired layout or animation is too complex for Columns and Rows, this widget is a life saver. It lets you declaratively position/size its child in complex ways.