lerp method

AlignmentGeometry lerp (AlignmentGeometry a, AlignmentGeometry b, double t)

Linearly interpolate between two AlignmentGeometry objects.

If either is null, this function interpolates from Alignment.center, and the result is an object of the same type as the non-null argument.

If lerp is applied to two objects of the same type (Alignment or AlignmentDirectional), an object of that type will be returned (though this is not reflected in the type system). Otherwise, an object representing a combination of both is returned. That object can be turned into a concrete Alignment using resolve.

The t argument represents position on the timeline, with 0.0 meaning that the interpolation has not started, returning a (or something equivalent to a), 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 a 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.

Implementation 

static AlignmentGeometry lerp(AlignmentGeometry a, AlignmentGeometry b, double t) {
  assert(t != null);
  if (a == null && b == null)
    return null;
  if (a == null)
    return b * t;
  if (b == null)
    return a * (1.0 - t);
  if (a is Alignment && b is Alignment)
    return Alignment.lerp(a, b, t);
  if (a is AlignmentDirectional && b is AlignmentDirectional)
    return AlignmentDirectional.lerp(a, b, t);
  return _MixedAlignment(
    ui.lerpDouble(a._x, b._x, t),
    ui.lerpDouble(a._start, b._start, t),
    ui.lerpDouble(a._y, b._y, t),
  );
}