public BoxConstraints getBoxConstraints(SliverConstraints constraints)
{
return(constraints.asBoxConstraints(
minExtent: this.mainAxisExtent ?? 0.0f,
maxExtent: this.mainAxisExtent ?? 0.0f,
crossAxisExtent: this.crossAxisExtent ?? 0.0f
));
}
protected override void performLayout()
{
SliverConstraints constraints = this.constraints;
D.assert(constraints.axisDirection == AxisDirection.down);
D.assert(constraints.growthDirection == GrowthDirection.forward);
float layoutExtent =
(_hasLayoutExtent ? 1.0f : 0.0f) * _refreshIndicatorExtent;
if (layoutExtent != layoutExtentOffsetCompensation)
{
geometry = new SliverGeometry(
scrollOffsetCorrection: layoutExtent - layoutExtentOffsetCompensation
);
layoutExtentOffsetCompensation = layoutExtent;
}
bool active = constraints.overlap <0.0 || layoutExtent> 0.0;
float overscrolledExtent =
constraints.overlap < 0.0f ? constraints.overlap.abs() : 0.0f;
child.layout(
constraints.asBoxConstraints(
maxExtent: layoutExtent + overscrolledExtent
),
parentUsesSize: true
);
if (active)
{
geometry = new SliverGeometry(
scrollExtent: layoutExtent,
paintOrigin: -overscrolledExtent - constraints.scrollOffset,
paintExtent: Mathf.Max(
Mathf.Max(child.size.height, layoutExtent) - constraints.scrollOffset, 0.0f),
maxPaintExtent: Mathf.Max(
Mathf.Max(child.size.height, layoutExtent) - constraints.scrollOffset, 0.0f),
layoutExtent: Mathf.Max(layoutExtent - constraints.scrollOffset, 0.0f));
}
else
{
geometry = SliverGeometry.zero;
}
}