calculateMarkerRadius function

double calculateMarkerRadius({ double? pointMarkerSize, required double minMarkerSize, required double maxMarkerSize, required double extraMaxPixels, required bool isContinuousXY, bool isActive = false, double defaultRadius = 3.5, double activeRadius = 5.5, double minRadius = 4, })

The radius of one marker, in logical pixels.

Ports calculateMarkerRadius (utilities.ts:2317-2360).

The cross-plan contract homes getScatterXDomainExtent and getDomainPaddingForMarkers in axis/domain_range.dart but leaves this function and getRangeForScatterMarkerSize unowned; ScatterChart, LineChart and PolarChart all call both, so they live here rather than being written three times.

pointMarkerSize is deliberately nullable AND checked for zero, because upstream's if (!pointMarkerSize) (utilities.ts:2342) treats 0 as absent.

Implementation

double calculateMarkerRadius({
  double? pointMarkerSize,
  required double minMarkerSize,
  required double maxMarkerSize,
  required double extraMaxPixels,
  required bool isContinuousXY,
  bool isActive = false,
  // 3.5 and 5.5 are the destructured defaults at `utilities.ts:2324-2325`.
  double defaultRadius = 3.5,
  double activeRadius = 5.5,
  // The visibility floor at `utilities.ts:2326`.
  double minRadius = 4,
}) {
  // parity: utilities.ts:2342 — JS falsiness means 0 and undefined behave alike.
  if (pointMarkerSize == null || pointMarkerSize == 0) {
    return isActive ? activeRadius : defaultRadius;
  }
  final double radius;
  if (isContinuousXY && maxMarkerSize != 0) {
    // utilities.ts:2349 — a marker table that already fits the pixel budget is
    // used as written; otherwise the whole table is scaled down to fit.
    radius = maxMarkerSize < extraMaxPixels
        ? pointMarkerSize
        : (pointMarkerSize / maxMarkerSize) * extraMaxPixels;
  } else if (!isContinuousXY && maxMarkerSize != minMarkerSize) {
    // utilities.ts:2352 — a band scale has no spare domain to measure, so the
    // sizes are normalised into a fixed pixel range instead.
    radius =
        kMarkerMinPixel +
        ((pointMarkerSize - minMarkerSize) / (maxMarkerSize - minMarkerSize)) *
            (kMarkerMaxPixel - kMarkerMinPixel);
  } else {
    // utilities.ts:2353-2356.
    return isActive ? activeRadius : defaultRadius;
  }
  // utilities.ts:2359. `math.max` rather than a comparison so that a NaN radius
  // propagates exactly as `Math.max` lets it.
  return math.max(radius, minRadius);
}