performBoxLayout method

@override void performBoxLayout(BoxConstraints constraints)

Perform layout with typed box constraints

Subclasses override this instead of performLayout. The default implementation sizes to the maxima, treating an unbounded axis as the corresponding lower bound.

Implementation

@override
void performBoxLayout(BoxConstraints constraints) {
  if (_child != null) {
    // Layout child with same constraints
    _child!.layout(constraints);

    // Position child at origin
    positionChild(_child!, 0, 0);

    // Size to child
    size = Size(
      constraints.constrainWidth(_child!.width),
      constraints.constrainHeight(_child!.height),
    );
  } else {
    // No child, size to smallest possible within constraints
    size = Size(
      constraints.constrainWidth(0),
      constraints.constrainHeight(0),
    );
  }
}