Add Shift.kt with utilities for contour shifting

Author: edwinRNDR

orx-shapes/src/commonMain/kotlin/utilities/Shift.kt

@@ -0,0 +1,37 @@
+package org.openrndr.extra.shapes.utilities
+
+import org.openrndr.extra.shapes.rectify.RectifiedContour
+import org.openrndr.shape.ShapeContour
+
+/**
+ * Shifts the starting point of the current `ShapeContour` by a specified normalized distance `dt`.
+ *
+ * @param dt the normalized distance by which to shift the starting point. The value is interpreted
+ * as a fraction of the total contour length (from 0.0 to 1.0). Positive values shift forward along
+ * the contour, while negative values shift backward.
+ * @return a new `ShapeContour` with the starting point shifted by the specified distance.
+ * If the contour is not closed, the original contour is returned unaltered.
+ */
+fun ShapeContour.shift(dt: Double): ShapeContour {
+    if (!closed) return this
+
+    val t = dt.mod(1.0)
+    val parts = splitAt(listOf(t))
+    return ShapeContour.fromContours(parts.reversed(), closed)
+}
+
+/**
+ * Shifts the contour by a specified amount along its parameterized path.
+ * If the contour is not closed, it returns the original contour unaltered.
+ *
+ * @param dt the shift amount, where 1.0 represents the entire length of the contour
+ *           and positive values move forward while negative values move backward.
+ * @return a new shifted `ShapeContour` if the contour is closed, or the original contour otherwise.
+ */
+fun RectifiedContour.shift(dt: Double): ShapeContour {
+    if (!contour.closed) return contour
+
+    val t = dt.mod(1.0)
+    val parts = splitAt(listOf(t))
+    return ShapeContour.fromContours(parts.reversed(), contour.closed)
+}