lerp<T> method Null safety

ColorSwatch<T>? lerp<T>(
  1. ColorSwatch<T>? a,
  2. ColorSwatch<T>? b,
  3. double t
)
override

Linearly interpolate between two ColorSwatches.

It delegates to Color.lerp to interpolate the different colors of the swatch.

If either color is null, this function linearly interpolates from a transparent instance of the other color.

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). Each channel will be clamped to the range 0 to 255.

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

Implementation

static ColorSwatch<T>? lerp<T>(ColorSwatch<T>? a, ColorSwatch<T>? b, double t) {
  final Map<T, Color> swatch;
  if (b == null) {
    if (a == null) {
      return null;
    } else {
      swatch = a._swatch.map((T key, Color color) => MapEntry<T, Color>(key, Color.lerp(color, null, t)!));
    }
  } else {
    if (a == null) {
      swatch = b._swatch.map((T key, Color color) => MapEntry<T, Color>(key, Color.lerp(null, color, t)!));
    } else {
      swatch = a._swatch.map((T key, Color color) => MapEntry<T, Color>(key, Color.lerp(color, b[key], t)!));
    }
  }
  return ColorSwatch<T>(Color.lerp(a, b, t)!.value, swatch);
}