Function collapsePanel

packages/core/src/widgets/splitPane.ts:266–294

(
  sizes: readonly number[],
  index: number,
  minSizes?: readonly number[],
)

 * @returns Updated sizes with collapsed panel
 */
export function collapsePanel(
  sizes: readonly number[],
  index: number,
  minSizes?: readonly number[],
): readonly number[] {
  if (index < 0 || index >= sizes.length) {
    return sizes;
  }

  const newSizes = [...sizes];
  const currentSize = sizes[index] ?? 0;
  const minSize = minSizes?.[index] ?? 0;
  const delta = currentSize - minSize;

  if (delta <= 0) {
    return sizes;
  }

  newSizes[index] = minSize;

  // Distribute delta to adjacent panels
  if (index > 0) {
    newSizes[index - 1] = (newSizes[index - 1] ?? 0) + delta;
  } else if (index < sizes.length - 1) {
    newSizes[index + 1] = (newSizes[index + 1] ?? 0) + delta;
  }

  return Object.freeze(newSizes);
}

/**
 * Expand a collapsed panel.