performLayout method
Implementation
@override
void performLayout(fw.BoxConstraints constraints) {
child?.layout(fw.BoxConstraints(
minWidth: direction == AxisDirection.horizontal ? 0 : constraints.minWidth,
maxWidth: direction == AxisDirection.horizontal ? 0x3FFFFFFF : constraints.maxWidth,
minHeight: direction == AxisDirection.vertical ? 0 : constraints.minHeight,
maxHeight: direction == AxisDirection.vertical ? 0x3FFFFFFF : constraints.maxHeight,
));
setSize(constraints.maxWidth, constraints.maxHeight);
final childH = child?.height ?? 0;
final maxScroll = (childH - constraints.maxHeight).clamp(0, childH);
_scrollOffset = _scrollOffset > maxScroll ? maxScroll : _scrollOffset;
child?.setOffset(0, -_scrollOffset);
}