feat: implement content transition APIs and backend descriptors

Example/Shared/Animation/Transition/NumericTextTransitionExample.swift

@@ -0,0 +1,36 @@
+//
+//  NumericTextTransitionExample.swift
+//  Shared
+
+#if OPENSWIFTUI
+import OpenSwiftUI
+#else
+import SwiftUI
+#endif
+
+// Tap to compare the numeric transition with the default text transition.
+// FIXME: OpenSwiftUI currently replaces both values directly. Text does not
+// yet attach its interpolator group, and content interpolation is incomplete.
+struct NumericTextTransitionExample: View {
+    @State private var counter = 0
+
+    var body: some View {
+        VStack {
+            Text("\(counter)")
+                .contentTransition(.numericText())
+                .font(.title)
+            Text("\(counter)")
+                .font(.title)
+        }
+        .padding()
+        .onTapGesture {
+            withAnimation(.interactiveSpring) {
+                counter += 1
+            }
+        }
+    }
+}
+
+#Preview {
+    NumericTextTransitionExample()
+}

Sources/OpenSwiftUI/Render/SymbolEffect/SymbolEffect.swift

@@ -792,7 +792,7 @@ extension SymbolEffect {
             case .effects:
                 let effect = ContentTransition.Effect(
                     type: ContentTransition.EffectType(
-                        type: .symbolAppearDisappear,
+                        type: .appearDisappear,
                         arg0: .int(config.base.transitionFlags.rawValue),
                         arg1: .float(1)
                     )

Sources/OpenSwiftUI/Render/SymbolEffect/SymbolEffectAPI.swift

@@ -340,7 +340,7 @@ public struct SymbolEffectTransition: Transition {
             }
             let effect = ContentTransition.Effect(
                 type: ContentTransition.EffectType(
-                    type: .symbolAppearDisappear,
+                    type: .appearDisappear,
                     arg0: .int(hidden.transitionFlags.rawValue),
                     arg1: .float(_SymbolEffect.Options(options).speed)
                 )

Sources/OpenSwiftUICore/Animation/Animation/TransactionAnimation.swift

@@ -66,9 +66,9 @@ extension Transaction {
     }
 
     package var disablesContentTransitions: Bool {
-        get { self[DisablesContentTransactionKey.self] }
-        set { self[DisablesContentTransactionKey.self] = newValue }
-      }
+        get { self[DisablesContentTransitionsKey.self] }
+        set { self[DisablesContentTransitionsKey.self] = newValue }
+    }
 
     package mutating func disableAnimations() {
         animation = nil
@@ -107,6 +107,6 @@ private struct AnimationReasonKey: TransactionKey {
     static var defaultValue: UInt32? { nil }
 }
 
-private struct DisablesContentTransactionKey: TransactionKey {
+private struct DisablesContentTransitionsKey: TransactionKey {
     static var defaultValue: Bool { false }
 }