lerpTo method Null safety

Linearly interpolates from this to another Decoration (which may be of a different class).

This is called if b's lerpTo did not know how to handle this class.

When implementing this method in subclasses, return null if this class cannot interpolate from b. In that case, lerp will apply a default behavior instead.

Supporting interpolating to null is recommended as the Decoration.lerp method uses this as a fallback when two classes can't interpolate between each other.

The t argument represents position on the timeline, with 0.0 meaning that the interpolation has not started, returning this (or something equivalent to this), 1.0 meaning that the interpolation has finished, returning b (or something equivalent to b), and values in between meaning that the interpolation is at the relevant point on the timeline between this and b. The interpolation can be extrapolated beyond 0.0 and 1.0, so negative values and values greater than 1.0 are valid (and can easily be generated by curves such as Curves.elasticInOut).

Values for t are usually obtained from an Animation<double>, such as an AnimationController.

Instead of calling this directly, use Decoration.lerp.