[orx-turtle] Add orx-turtle module

orx-turtle/src/commonMain/kotlin/Turtle.kt

@@ -0,0 +1,96 @@
+package org.openrndr.extra.turtle
+
+import org.openrndr.math.*
+import org.openrndr.math.transforms.rotateZ
+import org.openrndr.shape.*
+
+class Turtle(initialPosition: Vector2) {
+    val cb = ContourBuilder(multipleContours = true).apply {
+        moveTo(initialPosition)
+    }
+
+    var orientation = Matrix44.fromColumnVectors(Vector4.UNIT_X, -Vector4.UNIT_Y, Vector4.UNIT_Z, Vector4.UNIT_W)
+    private val orientationStack = ArrayDeque<Matrix44>()
+    fun pushOrientation() {
+        orientationStack.addLast(orientation)
+    }
+
+    fun popOrientation() {
+        orientation = orientationStack.removeLastOrNull() ?: error("orientation stack underflow")
+    }
+
+    var position: Vector2
+        get() {
+            return cb.cursor
+        }
+        set(value) {
+            cb.moveTo(value)
+        }
+
+    private val positionStack = ArrayDeque<Vector2>()
+    fun pushPosition() {
+        positionStack.addLast(position)
+    }
+
+    fun popPosition() {
+        position = positionStack.removeLastOrNull() ?: error("position stack underflow")
+    }
+
+    fun close() {
+        cb.close()
+    }
+
+    fun resetOrientation() {
+        orientation = Matrix44.fromColumnVectors(Vector4.UNIT_X, -Vector4.UNIT_Y, Vector4.UNIT_Z, Vector4.UNIT_W)
+    }
+
+    var direction: Vector2
+        get() = (orientation * Vector4.UNIT_X).xy
+        set(value) {
+            val directionNormalized = value.normalized
+            orientation = Matrix44.fromColumnVectors(
+                directionNormalized.xy00,
+                directionNormalized.perpendicular().xy00,
+                Vector4.UNIT_Z,
+                Vector4.UNIT_W
+            )
+        }
+
+    var isPenDown = true
+
+    fun penUp() {
+        isPenDown = false
+    }
+
+    fun penDown() {
+        isPenDown = true
+    }
+
+    fun push() {
+        pushOrientation()
+        pushPosition()
+    }
+
+    fun pop() {
+        popPosition()
+        popOrientation()
+    }
+
+    fun rotate(degrees: Double) {
+        orientation *= Matrix44.rotateZ(degrees)
+    }
+
+    fun forward(distance: Double) {
+        if (distance >= 1E-6) {
+            if (isPenDown) {
+                cb.lineTo(position + direction * distance)
+            } else {
+                cb.moveTo(position + direction * distance)
+            }
+        }
+    }
+}
+
+fun turtle(initalPosition: Vector2, program: Turtle.() -> Unit): List<ShapeContour> {
+    return Turtle(initalPosition).apply(program).cb.result
+}