RenderViewport({RenderBox child, Offset paintOffset: Offset.zero, Axis mainAxis: Axis.vertical, ViewportAnchor anchor: ViewportAnchor.start, ViewportDimensionsChangeCallback onPaintOffsetUpdateNeeded })

Creates a render object that's bigger on the inside.

The paintOffset and mainAxis arguments must not be null.

Source 

RenderViewport({
  RenderBox child,
  Offset paintOffset: Offset.zero,
  Axis mainAxis: Axis.vertical,
  ViewportAnchor anchor: ViewportAnchor.start,
  this.onPaintOffsetUpdateNeeded
}) : super(paintOffset, mainAxis, anchor) {
  this.child = child;
}