findBar static method

ChartInteractionResult? findBar(Offset tapPosition, List<ChartDataSet> dataSets, Size chartSize, double minX, double maxX, double minY, double maxY, double barWidth,)

Find bar at tap location (optimized with early exit).

Searches through all data sets to find the bar containing the tap position. Uses efficient bounds checking and coordinate conversion.

Parameters:

• tapPosition - The position where the user tapped
• dataSets - List of chart data sets to search through
• chartSize - Size of the chart area
• minX, maxX, minY, maxY - Data bounds for coordinate conversion
• barWidth - Width of each bar in canvas coordinates

Returns a ChartInteractionResult if a bar is found, null otherwise.

Implementation

static ChartInteractionResult? findBar(
  Offset tapPosition,
  List<ChartDataSet> dataSets,
  Size chartSize,
  double minX,
  double maxX,
  double minY,
  double maxY,
  double barWidth,
) {
  // Early exit if no data
  if (dataSets.isEmpty) return null;

  // Validate inputs using helper methods
  if (!_isValidSize(chartSize) ||
      !_isValidPosition(tapPosition) ||
      !_isValidBounds(minX, maxX, minY, maxY) ||
      !_isValidPositiveValue(barWidth) ||
      !_isValidPositiveValue(maxY)) {
    return null;
  }

  final xRange = maxX - minX;
  if (xRange == 0 || !xRange.isFinite) return null;

  // Pre-calculate half bar width and cache chart height
  final halfBarWidth = barWidth / 2;
  final chartHeight = chartSize.height;

  for (int dsIndex = 0; dsIndex < dataSets.length; dsIndex++) {
    final dataSet = dataSets[dsIndex];
    final point = dataSet.dataPoint;

    // Validate point values
    if (!_isValidPoint(point)) continue;

    // Calculate bar horizontal position
    final canvasX = ((point.x - minX) / xRange) * chartSize.width;
    if (!canvasX.isFinite) continue;

    // Early exit if tap is clearly to the left or right of bar
    if (tapPosition.dx < canvasX - halfBarWidth ||
        tapPosition.dx > canvasX + halfBarWidth) {
      continue;
    }

    // Calculate bar vertical position
    final barHeight = (point.y / maxY) * chartHeight;
    if (!barHeight.isFinite) continue;

    final barY = chartHeight - barHeight;
    if (!barY.isFinite) continue;

    // Check if tap is within bar vertical bounds
    if (tapPosition.dy >= barY && tapPosition.dy <= chartHeight) {
      return ChartInteractionResult(
        point: point,
        datasetIndex: dsIndex,
        elementIndex: 0,
        isHit: true,
      );
    }
  }

  return null;
}