applyGrowthDirectionToScrollDirection function

ScrollDirection applyGrowthDirectionToScrollDirection (
  1. ScrollDirection scrollDirection,
  2. GrowthDirection growthDirection
)

Flips the ScrollDirection if the GrowthDirection is GrowthDirection.reverse.

Specifically, returns scrollDirection if scrollDirection is GrowthDirection.forward, otherwise returns flipScrollDirection applied to scrollDirection.

This function is useful in RenderSliver subclasses that are given both an ScrollDirection and a GrowthDirection and wish to compute the ScrollDirection in which growth will occur.

Implementation

ScrollDirection applyGrowthDirectionToScrollDirection(ScrollDirection scrollDirection, GrowthDirection growthDirection) {
  assert(scrollDirection != null);
  assert(growthDirection != null);
  switch (growthDirection) {
    case GrowthDirection.forward:
      return scrollDirection;
    case GrowthDirection.reverse:
      return flipScrollDirection(scrollDirection);
  }
  return null;
}