layout method
Layout this component.
Implementation
@override
void layout(Rectangle<int> componentBounds, Rectangle<int> drawAreaBounds) {
  _componentBounds = componentBounds;
  _drawAreaBounds = drawAreaBounds;
  updateLegend();
}Layout this component.
@override
void layout(Rectangle<int> componentBounds, Rectangle<int> drawAreaBounds) {
  _componentBounds = componentBounds;
  _drawAreaBounds = drawAreaBounds;
  updateLegend();
}