alwaysNeedsAddToScene property Null safety
override
This disables retained rendering.
A FollowerLayer copies changes from a LeaderLayer that could be anywhere in the Layer tree, and that leader layer could change without notifying the follower layer. Therefore we have to always call a follower layer's addToScene. In order to call follower layer's addToScene, leader layer's addToScene must be called first so leader layer must also be considered as alwaysNeedsAddToScene.
Implementation
@override
bool get alwaysNeedsAddToScene => true;