Creating Custom Transformer

[FullStackDesign]

I would like to be able to create custom transformations like adding a parallax effect. Currently, it is not possible because the class "PageTransformer" is not exposed therefore one cannot extend nor implement the said class. It would be nice to have the option to create your custom transformations like the "ScaleAndFadeTransformer" class or via a builder i.e. PageTransformerBuilder(builder: (Widget child, TransformInfo info) { return ParrallaxContainer(...)