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) {
    // Use existing infrastructure: deflate constraints by padding amount
    final childConstraints = constraints.deflate(
      width: _padding.left + _padding.right,
      height: _padding.top + _padding.bottom,
    );

    // Layout child with reduced constraints
    _child!.layout(childConstraints);

    // Position child with padding offset (use existing method)
    positionChild(_child!, _padding.left, _padding.top);

    // Size ourselves to child + padding
    size = Size(
      constraints.constrainWidth(
        _child!.width + _padding.left + _padding.right,
      ),
      constraints.constrainHeight(
        _child!.height + _padding.top + _padding.bottom,
      ),
    );
  } else {
    // No child, size to just the padding
    size = Size(
      constraints.constrainWidth(_padding.left + _padding.right),
      constraints.constrainHeight(_padding.top + _padding.bottom),
    );
  }
}