Position.fixed constructor
The element is removed from the normal document flow, and no space is created for the element in the page layout.
The element is positioned relative to its initial containing block, which is the viewport in the case of visual
media. Its final position is determined by the values of top, right, bottom, and left.
Implementation
const factory Position.fixed({Unit? top, Unit? left, Unit? bottom, Unit? right}) = _Positioned.fixed;