Refactor constraints static methods to module functions

src/ol/rotationconstraint.js

@@ -0,0 +1,80 @@
+/**
+ * @module ol/rotationconstraint
+ */
+import {toRadians} from './math.js';
+
+/**
+ * @param {number|undefined} rotation Rotation.
+ * @param {number} delta Delta.
+ * @return {number|undefined} Rotation.
+ */
+export function disable(rotation, delta) {
+  if (rotation !== undefined) {
+    return 0;
+  } else {
+    return undefined;
+  }
+}
+
+
+/**
+ * @param {number|undefined} rotation Rotation.
+ * @param {number} delta Delta.
+ * @return {number|undefined} Rotation.
+ */
+export function none(rotation, delta) {
+  if (rotation !== undefined) {
+    return rotation + delta;
+  } else {
+    return undefined;
+  }
+}
+
+
+/**
+ * @param {number} n N.
+ * @return {ol.RotationConstraintType} Rotation constraint.
+ */
+export function createSnapToN(n) {
+  const theta = 2 * Math.PI / n;
+  return (
+    /**
+     * @param {number|undefined} rotation Rotation.
+     * @param {number} delta Delta.
+     * @return {number|undefined} Rotation.
+     */
+    function(rotation, delta) {
+      if (rotation !== undefined) {
+        rotation = Math.floor((rotation + delta) / theta + 0.5) * theta;
+        return rotation;
+      } else {
+        return undefined;
+      }
+    });
+}
+
+
+/**
+ * @param {number=} opt_tolerance Tolerance.
+ * @return {ol.RotationConstraintType} Rotation constraint.
+ */
+export function createSnapToZero(opt_tolerance) {
+  const tolerance = opt_tolerance || toRadians(5);
+  return (
+    /**
+     * @param {number|undefined} rotation Rotation.
+     * @param {number} delta Delta.
+     * @return {number|undefined} Rotation.
+     */
+    function(rotation, delta) {
+      if (rotation !== undefined) {
+        if (Math.abs(rotation + delta) <= tolerance) {
+          return 0;
+        } else {
+          return rotation + delta;
+        }
+      } else {
+        return undefined;
+      }
+    });
+}