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Spring animations now take velocity into account when determining duration. #56

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Nov 22, 2017
Merged

Spring animations now take velocity into account when determining duration. #56

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a49a909
Spring animations now take velocity into account when determining dur…
Nov 21, 2017
7f7a49a
Add tests.
Nov 21, 2017
a658438
Merge branch 'develop' into settling
jverkoey Nov 22, 2017
9f04e5b
Merge branch 'develop' into settling
jverkoey Nov 22, 2017
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20 changes: 14 additions & 6 deletions src/private/CABasicAnimation+MotionAnimator.m
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Original file line number Diff line number Diff line change
Expand Up @@ -47,13 +47,8 @@
spring.mass = timing.curve.data[MDMSpringMotionCurveDataIndexMass];
spring.stiffness = timing.curve.data[MDMSpringMotionCurveDataIndexTension];
spring.damping = timing.curve.data[MDMSpringMotionCurveDataIndexFriction];
spring.duration = timing.duration;

// This API is only available on iOS 9+
if ([spring respondsToSelector:@selector(settlingDuration)]) {
spring.duration = spring.settlingDuration;
} else {
spring.duration = timing.duration;
}
animation = spring;
break;
}
Expand Down Expand Up @@ -225,4 +220,17 @@ void MDMConfigureAnimation(CABasicAnimation *animation,
springAnimation.initialVelocity = absoluteInitialVelocity / displacement;
}
}

// Update the animation's duration to match the proposed settling duration.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wpartial-availability"
if ([animation isKindOfClass:[CASpringAnimation class]]) {
CASpringAnimation *springAnimation = (CASpringAnimation *)animation;
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Is referencing the class before it was introduced OK? I believe CASpringAnimation was introduced in iOS 9?
https://developer.apple.com/documentation/quartzcore/caspringanimation

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Not strictly an encouraged behavior, no. But this allows us to expand our min SDK support to iOS 8. Is a trade-off, but a relatively safe one.

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Ok. As long as it doesn't crash with undefined symbols (or generate compiler errors). Sounds good to me.

#pragma clang diagnostic pop

// This API is only available on iOS 9+
if ([springAnimation respondsToSelector:@selector(settlingDuration)]) {
animation.duration = springAnimation.settlingDuration;
}
}
}
13 changes: 13 additions & 0 deletions tests/unit/InitialVelocityTests.swift
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Expand Up @@ -121,6 +121,19 @@ class InitialVelocityTests: XCTestCase {
}
}

func testVelocityInfluencesDuration() {
let velocity: CGFloat = 50
animate(from: 0, to: 100, withVelocity: velocity)

XCTAssertEqual(addedAnimations.count, 3)
addedAnimations.flatMap { $0 as? CASpringAnimation }.forEach { animation in
XCTAssertEqual(animation.duration, animation.settlingDuration,
"from: \(animation.fromValue!), "
+ "to: \(animation.toValue!), "
+ "withVelocity: \(velocity)")
}
}

private func animate(from: CGFloat, to: CGFloat, withVelocity velocity: CGFloat) {
let timing = MotionTiming(delay: 0,
duration: 0.7,
Expand Down