Curve on livemap.

livemap/src/commonMain/kotlin/org/jetbrains/letsPlot/livemap/api/PathLayerBuilder.kt

@@ -23,6 +23,7 @@ import org.jetbrains.letsPlot.livemap.chart.GrowingPathEffect.GrowingPathEffectC
 import org.jetbrains.letsPlot.livemap.chart.GrowingPathEffect.GrowingPathRenderer
 import org.jetbrains.letsPlot.livemap.chart.IndexComponent
 import org.jetbrains.letsPlot.livemap.chart.LocatorComponent
+import org.jetbrains.letsPlot.livemap.chart.path.CurveRenderer
 import org.jetbrains.letsPlot.livemap.chart.path.PathLocator
 import org.jetbrains.letsPlot.livemap.chart.path.PathRenderer
 import org.jetbrains.letsPlot.livemap.chart.path.PathRenderer.ArrowSpec
@@ -91,6 +92,7 @@ class PathEntityBuilder(
  var animation: Int = 0
  var speed: Double = 0.0
  var flow: Double = 0.0
+ var isCurve: Boolean = false
 
  // Arrow specification
  var arrowAngle: Double? = null
@@ -151,7 +153,7 @@ class PathEntityBuilder(
  +IndexComponent(layerIndex!!, index!!)
  }
  +RenderableComponent().apply {
- renderer = PathRenderer()
+ renderer = if (isCurve) CurveRenderer() else PathRenderer()
  }
  +ChartElementComponent().apply {
  sizeScalingRange = [email protected]

livemap/src/commonMain/kotlin/org/jetbrains/letsPlot/livemap/chart/path/PathRenderer.kt

@@ -19,9 +19,11 @@ import org.jetbrains.letsPlot.livemap.core.ecs.EcsEntity
 import org.jetbrains.letsPlot.livemap.geometry.WorldGeometryComponent
 import org.jetbrains.letsPlot.livemap.mapengine.RenderHelper
 import org.jetbrains.letsPlot.livemap.mapengine.Renderer
+import org.jetbrains.letsPlot.livemap.mapengine.lineTo
+import org.jetbrains.letsPlot.livemap.mapengine.moveTo
 import kotlin.math.*
 
-class PathRenderer : Renderer {
+open class PathRenderer : Renderer {
  override fun render(entity: EcsEntity, ctx: Context2d, renderHelper: RenderHelper) {
  val geometry = entity.get<WorldGeometryComponent>().geometry.multiLineString
  val chartElement = entity.get<ChartElementComponent>()
@@ -37,10 +39,7 @@ class PathRenderer : Renderer {
  val adjustedGeometry = padLineString(lineString, startPadding, endPadding)
 
  ctx.beginPath()
-
- adjustedGeometry[0].let { ctx.moveTo(it.x, it.y) }
- adjustedGeometry.drop(1).forEach { ctx.lineTo(it.x, it.y) }
-
+ drawPath(adjustedGeometry, ctx)
  ctx.restore()
 
  ctx.setStrokeStyle(color)
@@ -58,6 +57,11 @@ class PathRenderer : Renderer {
  }
  }
 
+ open fun drawPath(points: List<WorldPoint>, ctx: Context2d) {
+ points[0].let(ctx::moveTo)
+ points.drop(1).forEach(ctx::lineTo)
+ }
+
  class ArrowSpec private constructor(
  val angle: Double,
  val length: Double,
@@ -222,4 +226,40 @@ class PathRenderer : Renderer {
  return lineString.subList(0, lineString.size - index) + adjustedEndPoint
  }
  }
+}
+
+class CurveRenderer : PathRenderer() {
+ override fun drawPath(points: List<WorldPoint>, ctx: Context2d) {
+ fun lineDot4(a: List<Double>, b: List<Double>): Double {
+ // returns the dot product of the given four-element vectors
+ return a[0] * b[0] + a[1] * b[1] + a[2] * b[2] + a[3] * b[3]
+ }
+ // Matrix to transform basis (b-spline) control points to bezier control points.
+ val lineBasisBezier1 = listOf(0.0, 2.0 / 3.0, 1.0 / 3.0, 0.0)
+ val lineBasisBezier2 = listOf(0.0, 1.0 / 3.0, 2.0 / 3.0, 0.0)
+ val lineBasisBezier3 = listOf(0.0, 1.0 / 6.0, 2.0 / 3.0, 1.0 / 6.0)
+
+ val px = arrayListOf(points[0].x, points[0].x, points[0].x, points[1].x)
+ val py = arrayListOf(points[0].y, points[0].y, points[0].y, points[1].y)
+
+ ctx.moveTo(points[0].x, points[0].y)
+ ctx.lineTo(
+ lineDot4(lineBasisBezier3, px),
+ lineDot4(lineBasisBezier3, py)
+ )
+ for (i in 2..points.size) {
+ val curPoint = if (i < points.size) points[i] else points.last()
+ px.removeFirst(); px.add(curPoint.x)
+ py.removeFirst(); py.add(curPoint.y)
+ ctx.bezierCurveTo(
+ lineDot4(lineBasisBezier1, px),
+ lineDot4(lineBasisBezier1, py),
+ lineDot4(lineBasisBezier2, px),
+ lineDot4(lineBasisBezier2, py),
+ lineDot4(lineBasisBezier3, px),
+ lineDot4(lineBasisBezier3, py)
+ )
+ }
+ ctx.lineTo(points.last().x, points.last().y)
+ }
 }