Function computeVirtualScrollClampBounds

src/hooks/useVirtualScroll.ts:390–430

({
  clampEnabled,
  rangeStart,
  rangeEnd,
  itemCount,
  viewportHeight,
  mountedStartTop,
  mountedEndBottom,
}: VirtualScrollClampBoundsInput)

}

export function computeVirtualScrollClampBounds({
  clampEnabled,
  rangeStart,
  rangeEnd,
  itemCount,
  viewportHeight,
  mountedStartTop,
  mountedEndBottom,
}: VirtualScrollClampBoundsInput): VirtualScrollClampBounds {
  if (!clampEnabled || rangeEnd <= rangeStart || itemCount === 0) {
    return {
      clampMin: undefined,
      clampMax: undefined,
    }
  }

  if (rangeStart > 0 && mountedStartTop === undefined) {
    return {
      clampMin: undefined,
      clampMax: undefined,
    }
  }

  if (rangeEnd < itemCount && mountedEndBottom === undefined) {
    return {
      clampMin: undefined,
      clampMax: undefined,
    }
  }

  const clampMin = rangeStart === 0 ? 0 : mountedStartTop!
  const clampMax =
    rangeEnd === itemCount
      ? Infinity
      : Math.max(clampMin, mountedEndBottom! - viewportHeight)

  return {
    clampMin,
    clampMax,
  }
}

export type VirtualScrollResult = {
  /** [startIndex, endIndex) half-open slice of items to render. */