Add option make main thread rendering engine force display update on …

…every frame (airbnb#2168)

Sources/Private/CoreAnimation/CoreAnimationLayer.swift

@@ -94,8 +94,8 @@ final class CoreAnimationLayer: BaseAnimationLayer {
     }
   }
 
-  /// The parent `LottieAnimationView` that manages this layer
-  weak var animationView: LottieAnimationView?
+  /// The parent `LottieAnimationLayer` that manages this layer
+  weak var lottieAnimationLayer: LottieAnimationLayer?
 
   /// A closure that is called after this layer sets up its animation.
   /// If the animation setup was unsuccessful and encountered compatibility issues,
@@ -316,7 +316,7 @@ final class CoreAnimationLayer: BaseAnimationLayer {
     else { return }
 
     if isAnimationPlaying == true {
-      animationView?.updateInFlightAnimation()
+      lottieAnimationLayer?.updateInFlightAnimation()
     } else {
       let currentFrame = currentFrame
       removeAnimations()

Sources/Private/MainThread/LayerContainers/MainThreadAnimationLayer.swift

@@ -140,7 +140,7 @@ final class MainThreadAnimationLayer: CALayer, RootAnimationLayer {
       newFrame = floor(newFrame)
     }
     for animationLayer in animationLayers {
-      animationLayer.displayWithFrame(frame: newFrame, forceUpdates: false)
+      animationLayer.displayWithFrame(frame: newFrame, forceUpdates: forceDisplayUpdateOnEachFrame)
     }
   }
 
@@ -149,8 +149,16 @@ final class MainThreadAnimationLayer: CALayer, RootAnimationLayer {
   /// The animatable Current Frame Property
   @NSManaged var currentFrame: CGFloat
 
-  /// The parent `LottieAnimationView` that manages this layer
-  weak var animationView: LottieAnimationView?
+  /// The parent `LottieAnimationLayer` that manages this layer
+  weak var lottieAnimationLayer: LottieAnimationLayer?
+
+  /// Whether or not to use `forceDisplayUpdate()` when rendering each individual frame.
+  ///  - The main thread rendering engine implements optimizations to decrease the amount
+  ///    of properties that have to be re-rendered on each frame. There are some cases
+  ///    where this can result in bugs / incorrect behavior, so we allow it to be disabled.
+  ///  - Forcing a full render on every frame will decrease performance, and is not recommended
+  ///    except as a workaround to a bug in the main thread rendering engine.
+  var forceDisplayUpdateOnEachFrame = false
 
   var animationLayers: ContiguousArray<CompositionLayer>
 

Sources/Private/RootAnimationLayer.swift

@@ -7,7 +7,7 @@ import QuartzCore
 
 /// A root `CALayer` responsible for playing a Lottie animation
 protocol RootAnimationLayer: CALayer {
-  var animationView: LottieAnimationView? { get set }
+  var lottieAnimationLayer: LottieAnimationLayer? { get set }
 
   var currentFrame: AnimationFrameTime { get set }
   var renderScale: CGFloat { get set }

Sources/Public/Animation/LottieAnimationLayer.swift

@@ -703,9 +703,19 @@ public class LottieAnimationLayer: CALayer {
     }
   }
 
-  public var animationView: LottieAnimationView? {
-    set { rootAnimationLayer?.animationView = newValue }
-    get { rootAnimationLayer?.animationView }
+  /// Whether or not the Main Thread rendering engine should use `forceDisplayUpdate()`
+  /// when rendering each individual frame.
+  ///  - The main thread rendering engine implements optimizations to decrease the amount
+  ///    of properties that have to be re-rendered on each frame. There are some cases
+  ///    where this can result in bugs / incorrect behavior, so we allow it to be disabled.
+  ///  - Forcing a full render on every frame will decrease performance, and is not recommended
+  ///    except as a workaround to a bug in the main thread rendering engine.
+  ///  - Has no effect when using the Core Animation rendering engine.
+  public var mainThreadRenderingEngineShouldForceDisplayUpdateOnEachFrame = false {
+    didSet {
+      (rootAnimationLayer as? MainThreadAnimationLayer)?.forceDisplayUpdateOnEachFrame
+        = mainThreadRenderingEngineShouldForceDisplayUpdateOnEachFrame
+    }
   }
 
   /// Sets the lottie file backing the animation layer. Setting this will clear the
@@ -1085,6 +1095,8 @@ public class LottieAnimationLayer: CALayer {
       return
     }
 
+    animationLayer.lottieAnimationLayer = self
+
     animationLayerDidLoad?(self, renderingEngine)
 
     animationLayer.renderScale = screenScale
@@ -1098,13 +1110,16 @@ public class LottieAnimationLayer: CALayer {
   }
 
   fileprivate func makeMainThreadAnimationLayer(for animation: LottieAnimation) -> MainThreadAnimationLayer {
-    MainThreadAnimationLayer(
+    let mainThreadAnimationLayer = MainThreadAnimationLayer(
       animation: animation,
       imageProvider: imageProvider.cachedImageProvider,
       textProvider: textProvider,
       fontProvider: fontProvider,
       maskAnimationToBounds: maskAnimationToBounds,
       logger: logger)
+
+    mainThreadAnimationLayer.forceDisplayUpdateOnEachFrame = mainThreadRenderingEngineShouldForceDisplayUpdateOnEachFrame
+    return mainThreadAnimationLayer
   }
 
   fileprivate func makeCoreAnimationLayer(for animation: LottieAnimation) -> CoreAnimationLayer? {

Sources/Public/Animation/LottieAnimationView.swift

@@ -573,6 +573,19 @@ open class LottieAnimationView: LottieAnimationViewBase {
     lottieAnimationLayer.currentPlaybackMode
   }
 
+  /// Whether or not the Main Thread rendering engine should use `forceDisplayUpdate()`
+  /// when rendering each individual frame.
+  ///  - The main thread rendering engine implements optimizations to decrease the amount
+  ///    of properties that have to be re-rendered on each frame. There are some cases
+  ///    where this can result in bugs / incorrect behavior, so we allow it to be disabled.
+  ///  - Forcing a full render on every frame will decrease performance, and is not recommended
+  ///    except as a workaround to a bug in the main thread rendering engine.
+  ///  - Has no effect when using the Core Animation rendering engine.
+  public var mainThreadRenderingEngineShouldForceDisplayUpdateOnEachFrame: Bool {
+    get { lottieAnimationLayer.mainThreadRenderingEngineShouldForceDisplayUpdateOnEachFrame }
+    set { lottieAnimationLayer.mainThreadRenderingEngineShouldForceDisplayUpdateOnEachFrame = newValue }
+  }
+
   /// Sets the lottie file backing the animation view. Setting this will clear the
   /// view's contents, completion blocks and current state. The new animation will
   /// be loaded up and set to the beginning of its timeline.
@@ -805,11 +818,10 @@ open class LottieAnimationView: LottieAnimationViewBase {
       self.setNeedsLayout()
     }
 
-    lottieAnimationLayer.animationLayerDidLoad = { [weak self] lottieAnimationLayer, _ in
+    lottieAnimationLayer.animationLayerDidLoad = { [weak self] _, _ in
       guard let self = self else { return }
       self.invalidateIntrinsicContentSize()
       self.setNeedsLayout()
-      lottieAnimationLayer.animationView = self
     }
   }