Using GradientValueProvider triggers an assertion when Rendering Engine is set to Automatic

[opera-ddrechny]

Lottie 4.0.1

I have an animation that renders as expected in Lottie 4.0.1 with renderingEngine set to .automatic, but triggers an assertion as soon as I call setValueProvider with an instance of GradientValueProvider:

Lottie/ValueProviderStore.swift:22: Assertion failed: The Core Animation rendering engine doesn't support Value Providers that vend a closure, because that would require calling the closure on the main thread once per frame.

I can work around this by setting renderingEngine set to .mainThread, but as I understand .automatic option should be backward-compatible with 3.x. Of course ideally I'd like to use the Core Animation engine.

The animation file:

{"v":"5.7.4","fr":60,"ip":0,"op":68,"w":450,"h":450,"nm":"GX_fab_rings","ddd":0,"assets":[],"layers":[{"ddd":0,"ind":1,"ty":4,"nm":".accent","cl":"accent","sr":1,"ks":{"o":{"a":1,"k":[{"i":{"x":[0.667],"y":[1]},"o":{"x":[0.333],"y":[0]},"t":0,"s":[0]},{"i":{"x":[0.667],"y":[1]},"o":{"x":[0.333],"y":[0]},"t":16,"s":[100]},{"i":{"x":[0.724],"y":[1]},"o":{"x":[0.305],"y":[0]},"t":32,"s":[80]},{"i":{"x":[0.833],"y":[1]},"o":{"x":[0.42],"y":[0]},"t":52,"s":[80]},{"t":66,"s":[0]}],"ix":11},"r":{"a":0,"k":-45,"ix":10},"p":{"a":0,"k":[225,225,0],"ix":2,"l":2},"a":{"a":0,"k":[0,0,0],"ix":1,"l":2},"s":{"a":1,"k":[{"i":{"x":[0.537,0.537,0.667],"y":[1.001,1.001,1]},"o":{"x":[0.333,0.333,0.333],"y":[0,0,0]},"t":0,"s":[13.667,13.667,100]},{"i":{"x":[0.538,0.538,0.667],"y":[0.938,0.938,1]},"o":{"x":[0.586,0.586,0.333],"y":[0.015,0.015,0]},"t":16,"s":[90.667,90.667,100]},{"i":{"x":[0.472,0.472,0.667],"y":[1.057,1.057,1]},"o":{"x":[0.264,0.264,0.333],"y":[-0.013,-0.013,0]},"t":32,"s":[67.712,67.712,100]},{"i":{"x":[0.667,0.667,0.667],"y":[1,1,1]},"o":{"x":[0.333,0.333,0.333],"y":[0,0,0]},"t":50,"s":[74.667,74.667,100]},{"i":{"x":[0.284,0.284,0.667],"y":[1,1,1]},"o":{"x":[0.333,0.333,0.333],"y":[0,0,0]},"t":52,"s":[74.667,74.667,100]},{"t":66,"s":[5.667,5.667,100]}],"ix":6,"l":2}},"ao":0,"shapes":[{"ty":"gr","it":[{"d":1,"ty":"el","s":{"a":0,"k":[450,450],"ix":2},"p":{"a":0,"k":[0,0],"ix":3},"nm":"Ellipse Path 1","mn":"ADBE Vector Shape - Ellipse","hd":false},{"ty":"tr","p":{"a":0,"k":[0,0],"ix":2},"a":{"a":0,"k":[0,0],"ix":1},"s":{"a":0,"k":[100,100],"ix":3},"r":{"a":0,"k":0,"ix":6},"o":{"a":0,"k":100,"ix":7},"sk":{"a":0,"k":0,"ix":4},"sa":{"a":0,"k":0,"ix":5},"nm":"Transform"}],"nm":"Ellipse 1","np":1,"cix":2,"bm":0,"ix":1,"mn":"ADBE Vector Group","hd":false},{"ty":"gf","o":{"a":0,"k":100,"ix":10},"r":1,"bm":0,"g":{"p":3,"k":{"a":0,"k":[0,0.98,0.118,0.306,0.5,0.98,0.118,0.306,1,0.98,0.118,0.306,0,1,0.5,0.75,1,0.5],"ix":9}},"s":{"a":0,"k":[0,-180],"ix":5},"e":{"a":0,"k":[0,212],"ix":6},"t":1,"nm":"Gradient Fill 1","mn":"ADBE Vector Graphic - G-Fill","hd":false}],"ip":0,"op":68,"st":0,"bm":0}],"markers":[]}

The call:

let animation = LottieAnimationView(name: "GX_fab_rings")
animation.setValueProvider(GradientValueProvider([LottieColor(r: 0, g: 0, b: 0, a: 0),
                                                  LottieColor(r: 1, g: 1, b: 1, a: 0.5),
                                                  LottieColor(r: 1, g: 1, b: 1, a: 1)]),
                           keypath: AnimationKeypath(keypath: "**.Colors"))

[calda]

Thanks for the report. This is currently unimplemented for the Core Animation rendering engine, but should be feasible to support. PRs are welcome if anyone in the community is interested in helping out!

In the meantime, continuing to use the main thread rendering engine for this use case is the best workaround.