@ionic/core/dist/collection/utils/input-shims/hacks/scroll-data.js

Base components for Ionic

const SCROLL_ASSIST_SPEED = 0.3;
export const getScrollData = (componentEl, contentEl, keyboardHeight) => {
  const itemEl = componentEl.closest('ion-item,[ion-item]') || componentEl;
  return calcScrollData(itemEl.getBoundingClientRect(), contentEl.getBoundingClientRect(), keyboardHeight, componentEl.ownerDocument.defaultView.innerHeight);
};
const calcScrollData = (inputRect, contentRect, keyboardHeight, platformHeight) => {
  // compute input's Y values relative to the body
  const inputTop = inputRect.top;
  const inputBottom = inputRect.bottom;
  // compute visible area
  const visibleAreaTop = contentRect.top;
  const visibleAreaBottom = Math.min(contentRect.bottom, platformHeight - keyboardHeight);
  // compute safe area
  const safeAreaTop = visibleAreaTop + 15;
  const safeAreaBottom = visibleAreaBottom * 0.75;
  // figure out if each edge of the input is within the safe area
  const distanceToBottom = safeAreaBottom - inputBottom;
  const distanceToTop = safeAreaTop - inputTop;
  // desiredScrollAmount is the negated distance to the safe area according to our calculations.
  const desiredScrollAmount = Math.round((distanceToBottom < 0)
    ? -distanceToBottom
    : (distanceToTop > 0)
      ? -distanceToTop
      : 0);
  // our calculations make some assumptions that aren't always true, like the keyboard being closed when an input
  // gets focus, so make sure we don't scroll the input above the visible area
  const scrollAmount = Math.min(desiredScrollAmount, inputTop - visibleAreaTop);
  const distance = Math.abs(scrollAmount);
  const duration = distance / SCROLL_ASSIST_SPEED;
  const scrollDuration = Math.min(400, Math.max(150, duration));
  return {
    scrollAmount,
    scrollDuration,
    scrollPadding: keyboardHeight,
    inputSafeY: -(inputTop - safeAreaTop) + 4
  };
};