angleBetween, tests

Author: kurkle

src/elements/element.line.js

@@ -2,8 +2,8 @@
 
 import defaults from '../core/core.defaults';
 import Element from '../core/core.element';
-import {_steppedLineTo, _bezierCurveTo} from '../helpers/helpers.canvas';
-import {_angleDiff, _angleDiffPD, _normalizeAngle, _pointInLine, _steppedInterpolation, _bezierInterpolation} from '../helpers/helpers.math';
+import {_bezierCurveTo, _steppedLineTo} from '../helpers/helpers.canvas';
+import {_angleBetween, _angleDiff, _bezierInterpolation, _normalizeAngle, _pointInLine, _steppedInterpolation} from '../helpers/helpers.math';
 
 const defaultColor = defaults.global.defaultColor;
 
@@ -167,15 +167,10 @@ function useFastPath(vm, options) {
 	return !vm.tension && !vm.steppedLine && !vm.fill && (!vm.borderDash || !vm.borderDash.length) && !options.bounds;
 }
 
-function angleBetween(a, s, e) {
-	return a === s || a === e ||
-		(_angleDiffPD(a, s) > _angleDiffPD(a, e) && _angleDiffPD(s, a) < _angleDiffPD(e, a));
-}
-
 function propertyFn(property) {
 	if (property === 'angle') {
 		return {
-			between: angleBetween,
+			between: _angleBetween,
 			compare: _angleDiff,
 			normalize: _normalizeAngle,
 		};

src/helpers/helpers.math.js

@@ -181,7 +181,7 @@ export function _bezierInterpolation(p1, p2, t) {
 }
 
 /**
- * Shortest distance between agnles, in either direction.
+ * Shortest distance between angles, in either direction.
  * @private
  */
 export function _angleDiff(a, b) {
@@ -197,9 +197,15 @@ export function _normalizeAngle(a) {
 }
 
 /**
- * Angle difference in positive direction.
  * @private
  */
-export function _angleDiffPD(a, b) {
-	return _normalizeAngle(_normalizeAngle(b) - _normalizeAngle(a));
+export function _angleBetween(angle, start, end) {
+	const a = _normalizeAngle(angle);
+	const s = _normalizeAngle(start);
+	const e = _normalizeAngle(end);
+	const angleToStart = _normalizeAngle(s - a);
+	const angleToEnd = _normalizeAngle(e - a);
+	const startToAngle = _normalizeAngle(a - s);
+	const endToAngle = _normalizeAngle(a - e);
+	return a === s || a === e || (angleToStart > angleToEnd && startToAngle < endToAngle);
 }

test/specs/helpers.math.tests.js

@@ -106,4 +106,36 @@ describe('Chart.helpers.math', function() {
 		expect(math.isNumber(undefined)).toBe(false);
 		expect(math.isNumber('cbc')).toBe(false);
 	});
+
+	it('should compute shortest distance between angles', function() {
+		expect(math._angleDiff(1, 2)).toEqual(-1);
+		expect(math._angleDiff(2, 1)).toEqual(1);
+		expect(math._angleDiff(0, 3.15)).toBeCloseTo(3.13, 2);
+		expect(math._angleDiff(0, 3.13)).toEqual(-3.13);
+		expect(math._angleDiff(6.2, 0)).toBeCloseTo(-0.08, 2);
+		expect(math._angleDiff(6.3, 0)).toBeCloseTo(0.02, 2);
+		expect(math._angleDiff(4 * Math.PI, -4 * Math.PI)).toBeCloseTo(0, 4);
+		expect(math._angleDiff(4 * Math.PI, -3 * Math.PI)).toBeCloseTo(-3.14, 2);
+		expect(math._angleDiff(6.28, 3.1)).toBeCloseTo(-3.1, 2);
+		expect(math._angleDiff(6.28, 3.2)).toBeCloseTo(3.08, 2);
+	});
+
+	it('should normalize angles correctly', function() {
+		expect(math._normalizeAngle(-Math.PI)).toEqual(Math.PI);
+		expect(math._normalizeAngle(Math.PI)).toEqual(Math.PI);
+		expect(math._normalizeAngle(2)).toEqual(2);
+		expect(math._normalizeAngle(5 * Math.PI)).toEqual(Math.PI);
+		expect(math._normalizeAngle(-50 * Math.PI)).toBeCloseTo(6.28, 2);
+	});
+
+	it('should determine if angle is between boundaries', function() {
+		expect(math._angleBetween(2, 1, 3)).toBeTrue();
+		expect(math._angleBetween(2, 3, 1)).toBeFalse();
+		expect(math._angleBetween(-3.14, 2, 4)).toBeTrue();
+		expect(math._angleBetween(-3.14, 4, 2)).toBeFalse();
+		expect(math._angleBetween(0, -1, 1)).toBeTrue();
+		expect(math._angleBetween(-1, 0, 1)).toBeFalse();
+		expect(math._angleBetween(-15 * Math.PI, 3.1, 3.2)).toBeTrue();
+		expect(math._angleBetween(15 * Math.PI, -3.2, -3.1)).toBeTrue();
+	});
 });