lerp method

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

Linearly interpolates between two font weights.

Rather than using fractional weights, the interpolation rounds to the nearest weight.

Any null values for a or b are interpreted as equivalent to normal (also known as w400).

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). The result is clamped to the range w100–w900.

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

Implementation 

static FontWeight lerp(FontWeight a, FontWeight b, double t) {
  assert(t != null);
  return values[lerpDouble(a?.index ?? normal.index, b?.index ?? normal.index, t).round().clamp(0, 8)];
}