[orx-triangulation] Improve triangulation, add kotlin/js support

orx-triangulation/src/commonMain/kotlin/DelaunayTriangulation.kt

@@ -0,0 +1,71 @@
+package org.openrndr.extra.triangulation
+
+import org.openrndr.math.Vector2
+import org.openrndr.shape.Rectangle
+import org.openrndr.shape.Triangle
+import org.openrndr.shape.contour
+import org.openrndr.shape.contours
+
+/**
+ * Kotlin/OPENRNDR idiomatic interface to `Delaunay`
+ */
+class DelaunayTriangulation(val points: List<Vector2>) {
+    internal val delaunay: Delaunay = Delaunay.from(points)
+
+    fun voronoiDiagram(bounds: Rectangle) = VoronoiDiagram(this, bounds)
+
+    fun neighbors(pointIndex: Int) : Sequence<Int> {
+        return delaunay.neighbors(pointIndex)
+    }
+
+    fun neighborPoints(pointIndex: Int) : List<Vector2> {
+        return neighbors(pointIndex).map { points[it] }.toList()
+    }
+
+    fun triangles(): List<Triangle> {
+        val list = mutableListOf<Triangle>()
+
+        for (i in delaunay.triangles.indices step 3 ) {
+            val t0 = delaunay.triangles[i]
+            val t1 = delaunay.triangles[i + 1]
+            val t2 = delaunay.triangles[i + 2]
+
+            val p1 = points[t0]
+            val p2 = points[t1]
+            val p3 = points[t2]
+
+            // originally they are defined *counterclockwise*
+            list.add(Triangle(p3,  p2, p1))
+        }
+        return list
+    }
+
+    // Inner edges of the delaunay triangulation (without hull)
+    fun halfedges() = contours {
+        for (i in delaunay.halfedges.indices) {
+            val j = delaunay.halfedges[i]
+
+            if (j < i) continue
+            val ti = delaunay.triangles[i]
+            val tj = delaunay.triangles[j]
+
+            moveTo(points[ti])
+            lineTo(points[tj])
+        }
+    }
+
+    fun hull() = contour {
+        for (h in delaunay.hull) {
+            moveOrLineTo(points[2 * h])
+        }
+        close()
+    }
+
+    fun nearest(query: Vector2) : Int = delaunay.find(query.x, query.y)
+
+    fun nearestPoint(query: Vector2) : Vector2 = points[nearest(query)]
+}
+
+fun List<Vector2>.delaunayTriangulation() : DelaunayTriangulation {
+    return DelaunayTriangulation(this)
+}