Function diffSameWidth

src/ink/screen.ts:1673–1740

* Diff two screens with identical width. * Dispatches each row to a small, JIT-friendly function.

(
  prev: Screen,
  next: Screen,
  startX: number,
  endX: number,
  startY: number,
  endY: number,
  cb: DiffCallback,
)

 * Dispatches each row to a small, JIT-friendly function.
 */
function diffSameWidth(
  prev: Screen,
  next: Screen,
  startX: number,
  endX: number,
  startY: number,
  endY: number,
  cb: DiffCallback,
): boolean {
  const prevCells = prev.cells
  const nextCells = next.cells
  const width = prev.width
  const prevHeight = prev.height
  const nextHeight = next.height
  const stride = width << 1

  const prevCell: Cell = {
    char: ' ',
    styleId: 0,
    width: CellWidth.Narrow,
    hyperlink: undefined,
  }
  const nextCell: Cell = {
    char: ' ',
    styleId: 0,
    width: CellWidth.Narrow,
    hyperlink: undefined,
  }

  const rowEndX = Math.min(endX, width)
  let rowCI = (startY * width + startX) << 1

  for (let y = startY; y < endY; y++) {
    const prevIn = y < prevHeight
    const nextIn = y < nextHeight

    if (prevIn && nextIn) {
      if (
        diffRowBoth(
          prevCells,
          nextCells,
          prev,
          next,
          rowCI,
          y,
          startX,
          rowEndX,
          prevCell,
          nextCell,
          cb,
        )
      )
        return true
    } else if (prevIn) {
      if (diffRowRemoved(prev, rowCI, y, startX, rowEndX, prevCell, cb))
        return true
    } else if (nextIn) {
      if (