Allow nil animation (#42)

Additionally:

- Tidy up the demo's settings UI by removing outdated setting screen
footers.
- Improve the demo's settings UX by dynamically displaying pickers
relevant only to the currently selected animation.

Author: davdroman

Demo/Demo.xcodeproj/project.pbxproj

@@ -167,6 +167,8 @@
 				Base,
 			);
 			mainGroup = D5535812290E9691009E5D72;
+			packageReferences = (
+			);
 			productRefGroup = D553581C290E9691009E5D72 /* Products */;
 			projectDirPath = "";
 			projectRoot = "";

Demo/Demo/AppState.swift

@@ -70,63 +70,128 @@ final class AppState: ObservableObject {
         }
     }
 
-    struct Animation {
-        enum Curve: CaseIterable, CustomStringConvertible, Hashable {
-            case linear
-            case easeInOut
-            case spring
-
-            var description: String {
-                switch self {
-                case .linear:
-                    return "Linear"
-                case .easeInOut:
-                    return "Ease In Out"
-                case .spring:
-                    return "Spring"
-                }
-            }
-        }
-
-        enum Duration: CaseIterable, CustomStringConvertible, Hashable {
-            case slow
-            case medium
-            case fast
-
-            var description: String {
-                switch self {
-                case .slow:
-                    return "Slow"
-                case .medium:
-                    return "Medium"
-                case .fast:
-                    return "Fast"
-                }
-            }
+    enum Animation: CaseIterable, CustomStringConvertible, Hashable {
+        case none
+        case linear
+        case easeInOut
+        case spring
 
-            func callAsFunction() -> Double {
-                switch self {
-                case .slow:
-                    return 1
-                case .medium:
-                    return 0.6
-                case .fast:
-                    return 0.35
-                }
+        var description: String {
+            switch self {
+            case .none:
+                return "None"
+            case .linear:
+                return "Linear"
+            case .easeInOut:
+                return "Ease In Out"
+            case .spring:
+                return "Spring"
             }
         }
 
-        var curve: Curve
-        var duration: Duration
-
-        func callAsFunction() -> AnyNavigationTransition.Animation {
-            switch curve {
+        func callAsFunction(
+            duration: Duration,
+            stiffness: Stiffness,
+            damping: Damping
+        ) -> AnyNavigationTransition.Animation? {
+            switch self {
+            case .none:
+                return .none
             case .linear:
                 return .linear(duration: duration())
             case .easeInOut:
                 return .easeInOut(duration: duration())
             case .spring:
-                return .interpolatingSpring(stiffness: 120, damping: 50)
+                return .interpolatingSpring(stiffness: stiffness(), damping: damping())
+            }
+        }
+    }
+
+    enum Duration: CaseIterable, CustomStringConvertible, Hashable {
+        case slow
+        case medium
+        case fast
+
+        var description: String {
+            switch self {
+            case .slow:
+                return "Slow"
+            case .medium:
+                return "Medium"
+            case .fast:
+                return "Fast"
+            }
+        }
+
+        func callAsFunction() -> Double {
+            switch self {
+            case .slow:
+                return 1
+            case .medium:
+                return 0.6
+            case .fast:
+                return 0.35
+            }
+        }
+    }
+
+    enum Stiffness: CaseIterable, CustomStringConvertible, Hashable {
+        case low
+        case medium
+        case high
+
+        var description: String {
+            switch self {
+            case .low:
+                return "Low"
+            case .medium:
+                return "Medium"
+            case .high:
+                return "High"
+            }
+        }
+
+        func callAsFunction() -> Double {
+            switch self {
+            case .low:
+                return 300
+            case .medium:
+                return 120
+            case .high:
+                return 50
+            }
+        }
+    }
+
+    enum Damping: CaseIterable, CustomStringConvertible, Hashable {
+        case low
+        case medium
+        case high
+        case veryHigh
+
+        var description: String {
+            switch self {
+            case .low:
+                return "Low"
+            case .medium:
+                return "Medium"
+            case .high:
+                return "High"
+            case .veryHigh:
+                return "Very High"
+            }
+        }
+
+        func callAsFunction() -> Double {
+            switch self {
+            case .low:
+                return 20
+            case .medium:
+                return 25
+            case .high:
+                return 30
+            case .veryHigh:
+                return 50
             }
         }
     }
@@ -160,7 +225,12 @@ final class AppState: ObservableObject {
     }
 
     @Published var transition: Transition = .slide
-    @Published var animation: Animation = .init(curve: .easeInOut, duration: .fast)
+
+    @Published var animation: Animation = .spring
+    @Published var duration: Duration = .fast
+    @Published var stiffness: Stiffness = .low
+    @Published var damping: Damping = .high
+
     @Published var interactivity: Interactivity = .edgePan
 
     @Published var isPresentingSettings: Bool = false

Demo/Demo/RootView.swift

@@ -17,12 +17,25 @@ struct RootView: View {
                 .navigationViewStyle(.stack)
             }
         }
-        .navigationTransition(
-            appState.transition().animation(appState.animation()),
-            interactivity: appState.interactivity()
-        )
+        .navigationTransition(transition.animation(animation), interactivity: interactivity)
         .sheet(isPresented: $appState.isPresentingSettings) {
             SettingsView().environmentObject(appState)
         }
     }
+
+    var transition: AnyNavigationTransition {
+        appState.transition()
+    }
+
+    var animation: AnyNavigationTransition.Animation? {
+        appState.animation(
+            duration: appState.duration,
+            stiffness: appState.stiffness,
+            damping: appState.damping
+        )
+    }
+
+    var interactivity: AnyNavigationTransition.Interactivity {
+        appState.interactivity()
+    }
 }

Demo/Demo/SettingsView.swift

@@ -7,13 +7,21 @@ struct SettingsView: View {
     var body: some View {
         NavigationView {
             Form {
-                Section(header: Text("Transition"), footer: transitionFooter) {
+                Section(header: Text("Transition")) {
                     picker("Transition", $appState.transition)
                 }
 
-                Section(header: Text("Animation"), footer: animationFooter) {
-                    picker("Curve", $appState.animation.curve)
-                    picker("Duration", $appState.animation.duration)
+                Section(header: Text("Animation")) {
+                    picker("Animation", $appState.animation)
+                    switch appState.animation {
+                    case .none:
+                        EmptyView()
+                    case .linear, .easeInOut:
+                        picker("Duration", $appState.duration)
+                    case .spring:
+                        picker("Stiffness", $appState.stiffness)
+                        picker("Damping", $appState.damping)
+                    }
                 }
 
                 Section(header: Text("Interactivity"), footer: interactivityFooter) {
@@ -31,22 +39,6 @@ struct SettingsView: View {
         .navigationViewStyle(.stack)
     }
 
-    var transitionFooter: some View {
-        Text(
-            """
-            "Swing" is a custom transition exclusive to this demo (only 12 lines of code!).
-            """
-        )
-    }
-
-    var animationFooter: some View {
-        Text(
-            """
-            Note: Duration is ignored when the Spring curve is selected.
-            """
-        )
-    }
-
     var interactivityFooter: some View {
         Text(
             """
@@ -76,8 +68,12 @@ struct SettingsView: View {
 
     func shuffle() {
         appState.transition = .allCases.randomElement()!
-        appState.animation.curve = .allCases.randomElement()!
-        appState.animation.duration = .allCases.randomElement()!
+
+        appState.animation = .allCases.randomElement()!
+        appState.duration = .allCases.randomElement()!
+        appState.stiffness = .allCases.randomElement()!
+        appState.damping = .allCases.randomElement()!
+
         appState.interactivity = .allCases.randomElement()!
     }
 

Sources/NavigationTransition/AnyNavigationTransition.swift

@@ -22,7 +22,7 @@ public struct AnyNavigationTransition {
 
     @_spi(package)public let isDefault: Bool
     @_spi(package)public let handler: Handler
-    @_spi(package)public var animation: Animation = .default
+    @_spi(package)public var animation: Animation? = .default
 
     public init<T: NavigationTransition>(_ transition: T) {
         self.isDefault = false
@@ -42,7 +42,7 @@ extension AnyNavigationTransition {
     public typealias Animation = _Animation
 
     /// Attaches an animation to this transition.
-    public func animation(_ animation: Animation) -> Self {
+    public func animation(_ animation: Animation?) -> Self {
         var copy = self
         copy.animation = animation
         return copy

Sources/NavigationTransitions/NavigationTransitionDelegate.swift

@@ -5,29 +5,40 @@ import UIKit
 
 final class NavigationTransitionDelegate: NSObject, UINavigationControllerDelegate {
     let transition: AnyNavigationTransition
-    weak var baseDelegate: UINavigationControllerDelegate?
+    private weak var baseDelegate: UINavigationControllerDelegate?
     var interactionController: UIPercentDrivenInteractiveTransition?
+    private var initialAreAnimationsEnabled = UIView.areAnimationsEnabled
 
     init(transition: AnyNavigationTransition, baseDelegate: UINavigationControllerDelegate?) {
         self.transition = transition
         self.baseDelegate = baseDelegate
     }
 
     func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
+        initialAreAnimationsEnabled = UIView.areAnimationsEnabled
+        UIView.setAnimationsEnabled(transition.animation != nil)
         baseDelegate?.navigationController?(navigationController, willShow: viewController, animated: animated)
     }
 
     func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
         baseDelegate?.navigationController?(navigationController, didShow: viewController, animated: animated)
+        UIView.setAnimationsEnabled(initialAreAnimationsEnabled)
     }
 
     func navigationController(_ navigationController: UINavigationController, interactionControllerFor animationController: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
         return interactionController
     }
 
     func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationController.Operation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
-        if let operation = NavigationTransitionOperation(operation) {
-            return NavigationTransitionAnimatorProvider(transition: transition, operation: operation)
+        if
+            let animation = transition.animation,
+            let operation = NavigationTransitionOperation(operation)
+        {
+            return NavigationTransitionAnimatorProvider(
+                transition: transition,
+                animation: animation,
+                operation: operation
+            )
         } else {
             return nil
         }
@@ -36,15 +47,17 @@ final class NavigationTransitionDelegate: NSObject, UINavigationControllerDelega
 
 final class NavigationTransitionAnimatorProvider: NSObject, UIViewControllerAnimatedTransitioning {
     let transition: AnyNavigationTransition
+    let animation: Animation
     let operation: NavigationTransitionOperation
 
-    init(transition: AnyNavigationTransition, operation: NavigationTransitionOperation) {
+    init(transition: AnyNavigationTransition, animation: Animation, operation: NavigationTransitionOperation) {
         self.transition = transition
+        self.animation = animation
         self.operation = operation
     }
 
     func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
-        transition.animation.duration
+        animation.duration
     }
 
     func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
@@ -67,7 +80,7 @@ final class NavigationTransitionAnimatorProvider: NSObject, UIViewControllerAnim
         }
         let animator = UIViewPropertyAnimator(
             duration: transitionDuration(using: transitionContext),
-            timingParameters: transition.animation.timingParameters
+            timingParameters: animation.timingParameters
         )
         cachedAnimators[ObjectIdentifier(transitionContext)] = animator