Fix curve with zero angle and curve direction on a livemap

commons/src/commonMain/kotlin/org/jetbrains/letsPlot/commons/geometry/Curve.kt

@@ -17,6 +17,17 @@ fun curve(
  curvature: Double,
  angle: Double,
  ncp: Int
+): List<DoubleVector> {
+ val controlPoints = calcControlPoints(start, end, curvature, angle, ncp)
+ return listOf(start) + controlPoints + listOf(end)
+}
+
+private fun calcControlPoints(
+ start: DoubleVector,
+ end: DoubleVector,
+ curvature: Double,
+ angle: Double,
+ ncp: Int
 ): List<DoubleVector> {
  // straight line
  if (curvature == 0.0 || abs(angle) !in 1.0..179.0) {
@@ -89,12 +100,11 @@ fun curve(
  )
  }
 
- val controlPoints = indices.map { index ->
+ return indices.map { index ->
  start.add(
  cp[index].subtract(start).rotate(-beta)
  )
  }
- return listOf(start) + controlPoints + listOf(end)
 }
 
 private fun calcOrigin(

plot-livemap/src/commonMain/kotlin/org/jetbrains/letsPlot/core/plot/livemap/DataPointsConverter.kt

@@ -227,7 +227,7 @@ internal class DataPointsConverter(
 
  val start = it.toLocation(Aes.X, Aes.Y) ?: return@process emptyList()
  val end = it.toLocation(Aes.XEND, Aes.YEND) ?: return@process emptyList()
- val (_, geometry) = elementHelper.createCurve(start, end, geom.curvature, -geom.angle, geom.ncp, it) ?: return@process emptyList()
+ val (_, geometry) = elementHelper.createCurve(start, end, geom.curvature, geom.angle, geom.ncp, it) ?: return@process emptyList()
  geometry
  }
  }