@base-ui/react/esm/scroll-area/utils/scrollEdges.js

Base UI is a library of headless ('unstyled') React components and low-level hooks. You gain complete control over your app's CSS and accessibility features.

import { clamp } from "../../utils/clamp.js";
export const SCROLL_EDGE_TOLERANCE_PX = 1;
export function normalizeScrollOffset(value, max) {
  if (max <= 0) {
    return 0;
  }
  const clamped = clamp(value, 0, max);
  const startDistance = clamped;
  const endDistance = max - clamped;
  const withinStartTolerance = startDistance <= SCROLL_EDGE_TOLERANCE_PX;
  const withinEndTolerance = endDistance <= SCROLL_EDGE_TOLERANCE_PX;
  if (withinStartTolerance && withinEndTolerance) {
    return startDistance <= endDistance ? 0 : max;
  }
  if (withinStartTolerance) {
    return 0;
  }
  if (withinEndTolerance) {
    return max;
  }
  return clamped;
}