add a test for scale gestures

packages/unit/test/gestures/scale_test.dart

+import 'dart:sky' as sky;
+
+import 'package:sky/gestures.dart';
+import 'package:test/test.dart';
+
+import '../engine/mock_events.dart';
+
+void main() {
+  test('Should recognize scale gestures', () {
+    PointerRouter router = new PointerRouter();
+    ScaleGestureRecognizer scale = new ScaleGestureRecognizer(router: router);
+    TapGestureRecognizer tap = new TapGestureRecognizer(router: router);
+
+    bool didStartScale = false;
+    sky.Point updatedFocalPoint;
+    scale.onStart = (sky.Point focalPoint) {
+      didStartScale = true;
+      updatedFocalPoint = focalPoint;
+    };
+
+    double updatedScale;
+    scale.onUpdate = (double scale, sky.Point focalPoint) {
+      updatedScale = scale;
+      updatedFocalPoint = focalPoint;
+    };
+
+    bool didEndScale = false;
+    scale.onEnd = () {
+      didEndScale = true;
+    };
+
+    bool didTap = false;
+    tap.onTap = () {
+      didTap = true;
+    };
+
+    TestPointer pointer1 = new TestPointer(1);
+
+    sky.PointerEvent down = pointer1.down(new Point(10.0, 10.0));
+    scale.addPointer(down);
+    tap.addPointer(down);
+
+    GestureArena.instance.close(1);
+    expect(didStartScale, isFalse);
+    expect(updatedScale, isNull);
+    expect(updatedFocalPoint, isNull);
+    expect(didEndScale, isFalse);
+    expect(didTap, isFalse);
+
+    // One-finger panning
+    router.route(down);
+    expect(didStartScale, isFalse);
+    expect(updatedScale, isNull);
+    expect(updatedFocalPoint, isNull);
+    expect(didEndScale, isFalse);
+    expect(didTap, isFalse);
+
+    router.route(pointer1.move(new Point(20.0, 30.0)));
+    expect(didStartScale, isTrue);
+    didStartScale = false;
+    expect(updatedFocalPoint, new sky.Point(20.0, 30.0));
+    updatedFocalPoint = null;
+    expect(updatedScale, 1.0);
+    updatedScale = null;
+    expect(didEndScale, isFalse);
+    expect(didTap, isFalse);
+
+    // Two-finger scaling
+    TestPointer pointer2 = new TestPointer(2);
+    sky.PointerEvent down2 = pointer2.down(new Point(10.0, 20.0));
+    scale.addPointer(down2);
+    tap.addPointer(down2);
+    GestureArena.instance.close(2);
+    router.route(down2);
+
+    expect(didEndScale, isTrue);
+    didEndScale = false;
+    expect(updatedScale, isNull);
+    expect(updatedFocalPoint, isNull);
+    expect(didStartScale, isFalse);
+
+    // Zoom in
+    router.route(pointer2.move(new Point(0.0, 10.0)));
+    expect(didStartScale, isTrue);
+    didStartScale = false;
+    expect(updatedFocalPoint, new sky.Point(10.0, 20.0));
+    updatedFocalPoint = null;
+    expect(updatedScale, 2.0);
+    updatedScale = null;
+    expect(didEndScale, isFalse);
+    expect(didTap, isFalse);
+
+    // Zoom out
+    router.route(pointer2.move(new Point(15.0, 25.0)));
+    expect(updatedFocalPoint, new sky.Point(17.5, 27.5));
+    updatedFocalPoint = null;
+    expect(updatedScale, 0.5);
+    updatedScale = null;
+    expect(didTap, isFalse);
+
+    // Three-finger scaling
+    TestPointer pointer3 = new TestPointer(3);
+    sky.PointerEvent down3 = pointer3.down(new Point(25.0, 35.0));
+    scale.addPointer(down3);
+    tap.addPointer(down3);
+    GestureArena.instance.close(3);
+    router.route(down3);
+
+    expect(didEndScale, isTrue);
+    didEndScale = false;
+    expect(updatedScale, isNull);
+    expect(updatedFocalPoint, isNull);
+    expect(didStartScale, isFalse);
+
+    // Zoom in
+    router.route(pointer3.move(new Point(55.0, 65.0)));
+    expect(didStartScale, isTrue);
+    didStartScale = false;
+    expect(updatedFocalPoint, new sky.Point(30.0, 40.0));
+    updatedFocalPoint = null;
+    expect(updatedScale, 5.0);
+    updatedScale = null;
+    expect(didEndScale, isFalse);
+    expect(didTap, isFalse);
+
+    // Return to original positions but with different fingers
+    router.route(pointer1.move(new Point(25.0, 35.0)));
+    router.route(pointer2.move(new Point(20.0, 30.0)));
+    router.route(pointer3.move(new Point(15.0, 25.0)));
+    expect(didStartScale, isFalse);
+    expect(updatedFocalPoint, new sky.Point(20.0, 30.0));
+    updatedFocalPoint = null;
+    expect(updatedScale, 1.0);
+    updatedScale = null;
+    expect(didEndScale, isFalse);
+    expect(didTap, isFalse);
+
+    router.route(pointer1.up());
+    expect(didStartScale, isFalse);
+    expect(updatedFocalPoint, isNull);
+    expect(updatedScale, isNull);
+    expect(didEndScale, isTrue);
+    didEndScale = false;
+    expect(didTap, isFalse);
+
+    // Continue scaling with two fingers
+    router.route(pointer3.move(new Point(10.0, 20.0)));
+    expect(didStartScale, isTrue);
+    didStartScale = false;
+    expect(updatedFocalPoint, new sky.Point(15.0, 25.0));
+    updatedFocalPoint = null;
+    expect(updatedScale, 2.0);
+    updatedScale = null;
+
+    router.route(pointer2.up());
+    expect(didStartScale, isFalse);
+    expect(updatedFocalPoint, isNull);
+    expect(updatedScale, isNull);
+    expect(didEndScale, isTrue);
+    didEndScale = false;
+    expect(didTap, isFalse);
+
+    // Continue panning with one finger
+    router.route(pointer3.move(new Point(0.0, 0.0)));
+    expect(didStartScale, isTrue);
+    didStartScale = false;
+    expect(updatedFocalPoint, new sky.Point(0.0, 0.0));
+    updatedFocalPoint = null;
+    expect(updatedScale, 1.0);
+    updatedScale = null;
+
+    // We are done
+    router.route(pointer3.up());
+    expect(didStartScale, isFalse);
+    expect(updatedFocalPoint, isNull);
+    expect(updatedScale, isNull);
+    expect(didEndScale, isTrue);
+    didEndScale = false;
+    expect(didTap, isFalse);
+
+    scale.dispose();
+    tap.dispose();
+  });
+}