Function scrollToFocus

packs/standalone/src/animation.ts:142–174

(
  stepPair: Tuple<Step>,
  dimensions?: Dimensions
)

}

export function scrollToFocus(
  stepPair: Tuple<Step>,
  dimensions?: Dimensions
): Animation<number> {
  if (!dimensions) {
    return () => 0;
  }

  const [prevStep, nextStep] = stepPair.spread();

  const prevCenter = prevStep
    ? prevStep.focusCenter * dimensions.lineHeight
    : 0;
  const nextCenter = nextStep
    ? nextStep.focusCenter * dimensions.lineHeight
    : 0;

  const animation = chain(
    [
      [EXIT, undefined],
      [
        SCROLL,
        t => ({
          scroll: tween(prevCenter, nextCenter, t, easing.easeInOutCubic)
        })
      ],
      [ENTER, undefined]
    ],
    { scroll: prevCenter }
  );

  return t => animation(t).scroll;
}

export function scaleToFocus(
  stepPair: Tuple<Step>,