Fix issue where manually interpolated keyframes could animate incorre…

…ctly (airbnb#2285)

Example/Example/ExampleApp.swift

@@ -5,11 +5,24 @@ import SwiftUI
 
 @main
 struct ExampleApp: App {
+
+ // MARK: Lifecycle
+
+ init() {
+ // Register fonts from the Samples/Fonts directory
+ for fontAssetURL in Bundle.main.urls(forResourcesWithExtension: "ttf", subdirectory: "Samples/Fonts") ?? [] {
+ CTFontManagerRegisterFontsForURL(fontAssetURL as CFURL, .process, nil)
+ }
+ }
+
+ // MARK: Internal
+
  var body: some Scene {
  WindowGroup {
  NavigationStack {
  AnimationListView(content: .directory("Samples"))
  }
  }
  }
+
 }

Sources/Private/CoreAnimation/Extensions/Keyframes+combined.swift

@@ -256,7 +256,11 @@ enum Keyframes {
 
  let minimumTime = times.min() ?? 0
  let maximumTime = times.max() ?? 0
- let animationLocalTimeRange = Int(minimumTime)...Int(maximumTime)
+
+ // We disable Core Animation interpolation when using manually interpolated keyframes,
+ // so we don't animate between these values. To prevent the animation from being choppy
+ // even at low playback speed, we have to interpolate at a very high fidelity.
+ let animationLocalTimeRange = stride(from: minimumTime, to: maximumTime, by: 0.1)
 
  let interpolatedKeyframes = try animationLocalTimeRange.compactMap { localTime -> Keyframe<CombinedResult>? in
  let interpolatedValues = untypedInterpolators.map { interpolator in
@@ -272,7 +276,10 @@ enum Keyframes {
 
  return Keyframe(
  value: combinedResult,
- time: AnimationFrameTime(localTime))
+ time: AnimationFrameTime(localTime),
+ // Since we already manually interpolated the keyframes, have Core Animation display
+ // each value as a static keyframe rather than trying to interpolate between them.
+ isHold: true)
  }
 
  return KeyframeGroup(keyframes: ContiguousArray(interpolatedKeyframes))

Tests/SnapshotConfiguration.swift

@@ -171,6 +171,12 @@ extension SnapshotConfiguration {
  10, // Should show frame 10
  ]),
 
+ "Issues/issue_2226": SnapshotConfiguration.default
+ .framesToSnapshot([
+ 19.25,
+ 113,
+ ]),
+
  // Test cases for `AnimationFontProvider`
  "Nonanimating/Text_Glyph": .customFontProvider(HardcodedFontProvider(font: UIFont(name: "Chalkduster", size: 36)!)),
 

Tests/SnapshotTests.swift

@@ -92,6 +92,11 @@ class SnapshotTests: XCTestCase {
  }
 
  override func setUp() {
+ // Register fonts from the Samples/Fonts directory
+ for fontAssetURL in Bundle.lottie.urls(forResourcesWithExtension: "ttf", subdirectory: "Samples/Fonts") ?? [] {
+ CTFontManagerRegisterFontsForURL(fontAssetURL as CFURL, .process, nil)
+ }
+
  LottieLogger.shared = .printToConsole
  TestHelpers.snapshotTestsAreRunning = true
  isRecording = false // Change it here to `true` if you want to generate the snapshots

Tests/__Snapshots__/AutomaticEngineTests/testAutomaticEngineDetection.Issues-issue_1939.txt

@@ -0,0 +1 @@
+Supports Core Animation engine

Tests/__Snapshots__/AutomaticEngineTests/testAutomaticEngineDetection.Issues-issue_2226.txt

@@ -0,0 +1 @@
+Supports Core Animation engine