updateGeometry method Null safety

  1. @override
double updateGeometry()
override

Updates geometry, and returns the new value for childMainAxisPosition.

This is used by performLayout.

Implementation

@override
double updateGeometry() {
  final double minExtent = this.minExtent;
  final double minAllowedExtent = constraints.remainingPaintExtent > minExtent ?
    minExtent :
    constraints.remainingPaintExtent;
  final double maxExtent = this.maxExtent;
  final double paintExtent = maxExtent - _effectiveScrollOffset!;
  final double clampedPaintExtent = paintExtent.clamp(
    minAllowedExtent,
    constraints.remainingPaintExtent,
  );
  final double layoutExtent = maxExtent - constraints.scrollOffset;
  final double stretchOffset = stretchConfiguration != null ?
    constraints.overlap.abs() :
    0.0;
  geometry = SliverGeometry(
    scrollExtent: maxExtent,
    paintOrigin: math.min(constraints.overlap, 0.0),
    paintExtent: clampedPaintExtent,
    layoutExtent: layoutExtent.clamp(0.0, clampedPaintExtent),
    maxPaintExtent: maxExtent + stretchOffset,
    maxScrollObstructionExtent: minExtent,
    hasVisualOverflow: true, // Conservatively say we do have overflow to avoid complexity.
  );
  return 0.0;
}