performLayout method

@override void performLayout(Constraints constraints)

Called to perform the actual layout computation for this render object.

Implementation

@override
void performLayout(Constraints constraints) {
  _cachedTitleWidth ??= stringWidth(title);
  final int headerWidth = 2 + _cachedTitleWidth!;
  const int headerH = 1;

  int maxChildWidth = headerWidth;
  int totalChildHeight = 0;

  if (expanded) {
    for (final child in children) {
      child.layout(constraints);
      final ExpansionTileParentData childData =
          child.parentData as ExpansionTileParentData;
      childData.offset = Offset(2, headerH + totalChildHeight);
      maxChildWidth = math.max(maxChildWidth, child.size!.width);
      totalChildHeight += child.size!.height;
    }
  }

  final int childAndBorder = maxChildWidth + 2;
  final int totalWidth = math.max(childAndBorder, headerWidth);
  final int totalHeight = headerH + totalChildHeight;
  size = Size(totalWidth, totalHeight);
}