layout method

@override void layout(LayoutExpansion parentLayoutExpansion)

Lays out the legend area.

Evenly divides the availableWidth to all legend items.

Implementation

@override
void layout(LayoutExpansion parentLayoutExpansion) {
  if (!chartTopContainer.data.chartOptions.legendOptions.isLegendContainerShown) {
    return;
  }
  ChartOptions options = chartTopContainer.data.chartOptions;
  double containerMarginTB = options.legendOptions.legendContainerMarginTB;
  double containerMarginLR = options.legendOptions.legendContainerMarginLR;

  List<String> dataRowsLegends = chartTopContainer.data.dataRowsLegends;

  // Initially all [LabelContainer]s share same text style object from options.
  LabelStyle labelStyle = LabelStyle(
    textStyle: options.labelCommonOptions.labelTextStyle,
    textDirection: options.labelCommonOptions.labelTextDirection,
    textAlign: options.legendOptions.legendTextAlign, // keep left, close to indicator
    textScaleFactor: options.labelCommonOptions.labelTextScaleFactor,
  );

  // First paint all legends, to figure out max height of legends to center all
  // legends label around common center.

  double legendItemWidth = (parentLayoutExpansion.width - 2.0 * containerMarginLR) / dataRowsLegends.length;

  _legendItemContainers = List<LegendItemContainer>.empty(growable: true);

  // Layout legend core: for each row, create and position
  //   - an indicator rectangle and it's paint
  //   - label painter
  for (int index = 0; index < dataRowsLegends.length; index++) {
    ui.Paint indicatorPaint = ui.Paint();
    List<ui.Color> dataRowsColors = chartTopContainer.data.dataRowsColors; //!;
    indicatorPaint.color = dataRowsColors[index % dataRowsColors.length];

    var legendItemLayoutExpansion = parentLayoutExpansion.cloneWith(
      width: legendItemWidth,
    );
    var legendItemContainer = LegendItemContainer(
      label: dataRowsLegends[index],
      labelStyle: labelStyle,
      indicatorPaint: indicatorPaint,
      options: options,
    );

    legendItemContainer.layout(legendItemLayoutExpansion);

    legendItemContainer.applyParentOffset(
      ui.Offset(
        containerMarginLR + index * legendItemWidth,
        containerMarginTB,
      ),
    );

    _legendItemContainers.add(legendItemContainer);
  }

  layoutSize = ui.Size(
    parentLayoutExpansion.width,
    _legendItemContainers.map((legendItemContainer) => legendItemContainer.layoutSize.height).reduce(math.max) +
        (2.0 * containerMarginTB),
  );
}