Add withAnimation API (#416)

* Add withAnimation support

* Add ElasticEaseInEaseOutAnimationExample

Author: Kyle-Ye

Example/HostingExample/ViewController.swift

@@ -66,6 +66,6 @@ class ViewController: NSViewController {
 
 struct ContentView: View {
     var body: some View {
-        ValueActionModifierExample()
+        ElasticEaseInEaseOutView()
     }
 }

Example/SharedExample/Animation/ColorAnimationExample.swift

@@ -7,7 +7,6 @@ import OpenSwiftUI
 #else
 import SwiftUI
 #endif
-import Foundation
 
 struct ColorAnimationExample: View {
     @State private var showRed = false

Example/SharedExample/Animation/ElasticEaseInEaseOutAnimationExample.swift

@@ -0,0 +1,53 @@
+//
+//  ElasticEaseInEaseOutAnimationExample.swift
+//  SharedExample
+
+#if OPENSWIFTUI
+import OpenSwiftUI
+#else
+import SwiftUI
+#endif
+import Foundation
+
+private struct ElasticEaseInEaseOutAnimation: CustomAnimation {
+    let duration: TimeInterval
+
+    func animate<V>(value: V, time: TimeInterval, context: inout AnimationContext<V>) -> V? where V: VectorArithmetic {
+        if time > duration { return nil } // The animation has finished.
+
+        let p = time / duration
+        let s = sin((20 * p - 11.125) * ((2 * Double.pi) / 4.5))
+        if p < 0.5 {
+            return value.scaled(by: -(pow(2, 20 * p - 10) * s) / 2)
+        } else {
+            return value.scaled(by: (pow(2, -20 * p + 10) * s) / 2 + 1)
+        }
+    }
+}
+
+extension Animation {
+    static var elasticEaseInEaseOut: Animation { elasticEaseInEaseOut(duration: 0.35) }
+
+    static func elasticEaseInEaseOut(duration: TimeInterval) -> Animation {
+        Animation(ElasticEaseInEaseOutAnimation(duration: duration))
+    }
+}
+
+struct ElasticEaseInEaseOutView: View {
+    @State private var isActive = false
+
+    var body: some View {
+        VStack(alignment: isActive ? .trailing : .leading) {
+            Color.red
+                .frame(width: 100.0, height: 100.0)
+                .onAppear {
+                    withAnimation(.elasticEaseInEaseOut(duration: 5.0)) {
+                        isActive.toggle()
+                    }
+                }
+            Color.blue
+                .frame(maxWidth: .infinity)
+        }
+        .padding()
+    }
+}

Sources/OpenSwiftUICore/Animation/Transaction/Transaction.swift

@@ -2,7 +2,7 @@
 //  Transaction.swift
 //  OpenSwiftUICore
 //
-//  Audited for iOS 18.0
+//  Audited for 6.0.87
 //  Status: Complete
 //  ID: B2543BCA257433E04979186A1DC2B6BC (SwiftUICore)
 
@@ -51,6 +51,7 @@ import OpenSwiftUI_SPI
 ///                 transaction.animation = .default.repeatCount(3)
 ///             }
 ///         }
+@available(OpenSwiftUI_v5_0, *)
 public protocol TransactionKey {
     /// The associated type representing the type of the transaction key's
     /// value.
@@ -62,12 +63,14 @@ public protocol TransactionKey {
     static func _valuesEqual(_ lhs: Value, _ rhs: Value) -> Swift.Bool
 }
 
+@available(OpenSwiftUI_v5_0, *)
 extension TransactionKey {
     public static func _valuesEqual(_ lhs: Value, _ rhs: Value) -> Bool {
         compareValues(lhs, rhs)
     }
 }
 
+@available(OpenSwiftUI_v5_0, *)
 extension TransactionKey where Value: Equatable {
     public static func _valuesEqual(_ lhs: Value, _ rhs: Value) -> Bool {
         lhs == rhs
@@ -95,6 +98,7 @@ private struct TransactionPropertyKey<Key>: PropertyKey where Key: TransactionKe
 /// The root transaction for a state change comes from the binding that changed,
 /// plus any global values set by calling ``withTransaction(_:_:)`` or
 /// ``withAnimation(_:_:)``
+@available(OpenSwiftUI_v1_0, *)
 @frozen
 public struct Transaction {
     @usableFromInline
@@ -189,6 +193,7 @@ extension Transaction: Sendable {}
 ///
 /// - Returns: The result of executing the closure with the specified
 ///   transaction.
+@available(OpenSwiftUI_v1_0, *)
 public func withTransaction<Result>(
     _ transaction: Transaction,
     _ body: () throws -> Result
@@ -218,6 +223,7 @@ public func withTransaction<Result>(
 ///
 /// - Returns: The result of executing the closure with the specified
 ///   transaction value.
+@available(OpenSwiftUI_v1_0, *)
 @_alwaysEmitIntoClient
 public func withTransaction<R, V>(
     _ keyPath: WritableKeyPath<Transaction, V>,
@@ -240,3 +246,18 @@ private var threadTransactionData: AnyObject? {
         )
     }
 }
+
+/// Returns the result of recomputing the view's body with the provided
+/// animation.
+///
+/// This function sets the given ``Animation`` as the ``Transaction/animation``
+/// property of the thread's current ``Transaction``.
+@available(OpenSwiftUI_v1_0, *)
+public func withAnimation<Result>(
+    _ animation: Animation? = .default,
+    _ body: () throws -> Result
+) rethrows -> Result {
+    var transaction = Transaction()
+    transaction.animation = animation
+    return try withTransaction(transaction, body)
+}