Include animation duration when computing cost/complexity of Core Animation time remapping (#2381)

Author: calda

Sources/Private/CoreAnimation/CoreAnimationLayer.swift

@@ -537,11 +537,26 @@ extension CoreAnimationLayer: RootAnimationLayer {
   /// every frame of every animation. For very large animations with a huge number of layers,
   /// this can be prohibitively expensive.
   func validateReasonableNumberOfTimeRemappingLayers() throws {
+    let numberOfLayersWithTimeRemapping = numberOfLayersWithTimeRemapping
+    let numberOfFrames = Int(animation.framerate * animation.duration)
+    let totalCost = numberOfLayersWithTimeRemapping * numberOfFrames
+
+    /// Cap the cost / complexity of animations that use Core Animation time remapping.
+    ///  - Short, simple animations perform well, but long and complex animations perform poorly.
+    ///  - We count the total number of frames that will need to be manually interpolated, which is
+    ///    the number of layers with time remapping enabled times the total number of frames.
+    ///  - The cap is arbitrary, and is currently:
+    ///      - 1000 layers for a one second animation at 60fp
+    ///      - 500 layers for a two second animation at 60fps, etc
+    ///  - All of the sample animations in the lottie-ios repo below this cap perform well.
+    ///    If users report animations below this cap that perform poorly, we can lower the cap.
+    let maximumAllowedCost = 1000 * 60
+
     try layerContext.compatibilityAssert(
-      numberOfLayersWithTimeRemapping < 500,
+      totalCost < maximumAllowedCost,
       """
-      This animation has a very large number of layers with time remapping (\(numberOfLayersWithTimeRemapping)),
-      so will perform poorly with the Core Animation rendering engine.
+      This animation has a very large number of layers with time remapping (\(numberOfLayersWithTimeRemapping) \
+      layers over \(numberOfFrames) frames) so will perform poorly with the Core Animation rendering engine.
       """)
   }
 

Tests/Samples/Issues/issue_2330.json

@@ -1 +1,2 @@
-Supports Core Animation engine
+Does not support Core Animation engine. Encountered compatibility issues:
+[root layer] This animation has a very large number of layers with time remapping (289 layers over 360 frames) so will perform poorly with the Core Animation rendering engine.

Tests/__Snapshots__/AutomaticEngineTests/testAutomaticEngineDetection.Issues-issue_1403.txt

@@ -0,0 +1,2 @@
+Does not support Core Animation engine. Encountered compatibility issues:
+[root layer] This animation has a very large number of layers with time remapping (406 layers over 193 frames) so will perform poorly with the Core Animation rendering engine.

Tests/__Snapshots__/AutomaticEngineTests/testAutomaticEngineDetection.Issues-issue_2330.txt

@@ -1,2 +1,2 @@
 Does not support Core Animation engine. Encountered compatibility issues:
-[root layer] This animation has a very large number of layers with time remapping (3670), so will perform poorly with the Core Animation rendering engine.
+[root layer] This animation has a very large number of layers with time remapping (3670 layers over 1001 frames) so will perform poorly with the Core Animation rendering engine.