using UIWidgets.foundation; namespace UIWidgets.rendering { public enum ScrollDirection { idle, forward, reverse, } public abstract class ViewportOffset : ChangeNotifier { protected ViewportOffset() { } public static ViewportOffset @fixed(double value) { return null; } public static ViewportOffset zero() { return null; } public abstract double pixels { get; } public abstract bool applyViewportDimension(double viewportDimension); public abstract bool applyContentDimensions(double minScrollExtent, double maxScrollExtent); public abstract void correctBy(double correction); public abstract void jumpTo(double pixels); } }