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68 changes: 68 additions & 0 deletions
68
Sources/MapboxMaps/Foundation/Camera/GestureDecelerationCameraAnimator.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,68 @@ | ||
| import UIKit | ||
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| internal final class GestureDecelerationCameraAnimator: NSObject, CameraAnimatorInterface { | ||
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| private var location: CGPoint | ||
| private var velocity: CGPoint | ||
| private let decelerationRate: CGFloat | ||
| private let locationChangeHandler: (CGPoint) -> Void | ||
| private var previousDate: Date? | ||
| private let dateProvider: DateProvider | ||
| internal var completion: (() -> Void)? | ||
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| internal init(location: CGPoint, | ||
| velocity: CGPoint, | ||
| decelerationRate: CGFloat, | ||
| locationChangeHandler: @escaping (CGPoint) -> Void, | ||
| dateProvider: DateProvider) { | ||
| self.location = location | ||
| self.velocity = velocity | ||
| self.decelerationRate = decelerationRate | ||
| self.locationChangeHandler = locationChangeHandler | ||
| self.dateProvider = dateProvider | ||
| } | ||
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| internal private(set) var state: UIViewAnimatingState = .inactive | ||
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| internal func cancel() { | ||
| stopAnimation() | ||
| } | ||
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| internal func startAnimation() { | ||
| previousDate = dateProvider.now | ||
| state = .active | ||
| } | ||
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| internal func stopAnimation() { | ||
| state = .inactive | ||
| completion?() | ||
| completion = nil | ||
| } | ||
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| internal func update() { | ||
| guard state == .active, let previousDate = previousDate else { | ||
| return | ||
| } | ||
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| let currentDate = dateProvider.now | ||
| self.previousDate = currentDate | ||
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| let elapsedTime = CGFloat(currentDate.timeIntervalSince(previousDate)) | ||
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| // calculate new location showing how far we have traveled | ||
| location.x += velocity.x * elapsedTime | ||
| location.y += velocity.y * elapsedTime | ||
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| locationChangeHandler(location) | ||
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| // deceleration rate is a factor that should | ||
| // be applied to the velocity once per millisecond | ||
| velocity.x *= pow(decelerationRate, (elapsedTime * 1000)) | ||
| velocity.y *= pow(decelerationRate, (elapsedTime * 1000)) | ||
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| guard abs(velocity.x) >= 1 || abs(velocity.y) >= 1 else { | ||
| stopAnimation() | ||
| return | ||
| } | ||
| } | ||
| } |
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97 changes: 97 additions & 0 deletions
97
Tests/MapboxMapsTests/Foundation/Camera/GestureDecelerationCameraAnimatorTests.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
| import XCTest | ||
| @testable import MapboxMaps | ||
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| final class GestureDecelerationCameraAnimatorTests: XCTestCase { | ||
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| var location: CGPoint! | ||
| var velocity: CGPoint! | ||
| var decelerationRate: CGFloat! | ||
| var locationChangeHandler: Stub<CGPoint, Void>! | ||
| var dateProvider: MockDateProvider! | ||
| var completion: Stub<Void, Void>! | ||
| var animator: GestureDecelerationCameraAnimator! | ||
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| override func setUp() { | ||
| super.setUp() | ||
| location = .zero | ||
| velocity = CGPoint(x: 1000, y: -1000) | ||
| decelerationRate = 0.7 | ||
| locationChangeHandler = Stub() | ||
| dateProvider = MockDateProvider() | ||
| completion = Stub() | ||
| animator = GestureDecelerationCameraAnimator( | ||
| location: location, | ||
| velocity: velocity, | ||
| decelerationRate: decelerationRate, | ||
| locationChangeHandler: locationChangeHandler.call(with:), | ||
| dateProvider: dateProvider) | ||
| animator.completion = completion.call | ||
| } | ||
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| override func tearDown() { | ||
| animator = nil | ||
| completion = nil | ||
| dateProvider = nil | ||
| locationChangeHandler = nil | ||
| decelerationRate = nil | ||
| velocity = nil | ||
| location = nil | ||
| super.tearDown() | ||
| } | ||
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| func testStateIsInitiallyInactive() { | ||
| XCTAssertEqual(animator.state, .inactive) | ||
| } | ||
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| func testStartAnimation() { | ||
| animator.startAnimation() | ||
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| XCTAssertEqual(animator.state, .active) | ||
| } | ||
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| func testStopAnimation() { | ||
| animator.startAnimation() | ||
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| animator.stopAnimation() | ||
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| XCTAssertEqual(animator.state, .inactive) | ||
| XCTAssertEqual(completion.invocations.count, 1) | ||
| } | ||
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| func testUpdate() { | ||
| animator.startAnimation() | ||
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| // Simulate advancing by 10 ms | ||
| dateProvider.nowStub.defaultReturnValue += 0.01 | ||
| animator.update() | ||
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| // Expected value is duration * velocity; | ||
| XCTAssertEqual(locationChangeHandler.parameters, [CGPoint(x: 10, y: -10)]) | ||
| // The previous update() should also have reduced the velocity | ||
| // by multiplying it by the decelerationRate once for each elapsed | ||
| // millisecond. In this simulateion, 10 ms have elapsed. | ||
| let expectedVelocityAdjustmentFactor = pow(decelerationRate, 10) | ||
| locationChangeHandler.reset() | ||
| // Make sure the animation didn't end yet | ||
| XCTAssertEqual(animator.state, .active) | ||
| XCTAssertEqual(completion.invocations.count, 0) | ||
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| // This time, advance by 20 ms to keep it distinct | ||
| // from the first update() call. | ||
| dateProvider.nowStub.defaultReturnValue += 0.02 | ||
| animator.update() | ||
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| // The expected value this time is the previous location + the reduced | ||
| // velocity (velocity * expectedVelocityAdjustmentFactor) times the elapsed duration | ||
| XCTAssertEqual( | ||
| locationChangeHandler.parameters, [ | ||
| CGPoint( | ||
| x: 10 + (velocity.x * expectedVelocityAdjustmentFactor) * 0.02, | ||
| y: -10 + (velocity.y * expectedVelocityAdjustmentFactor) * 0.02)]) | ||
| locationChangeHandler.reset() | ||
| // After the previous update() call, the velocity should have also been reduced | ||
| // to be sufficiently low (< 1 in both x and y) to end the animation. | ||
| XCTAssertEqual(animator.state, .inactive) | ||
| XCTAssertEqual(completion.invocations.count, 1) | ||
| } | ||
| } |
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