Function writeLineToScreen

src/ink/output.ts:755–956

* Write a single line's characters into the screen buffer. * Extracted from Output.get() so JSC can optimize this tight, * monomorphic loop independently — better register allocation, * setCellAt inlining, and type feedback than when buried inside * a 300-line dispatch function. * * Returns th

(
  screen: Screen,
  line: string,
  x: number,
  y: number,
  screenWidth: number,
  stylePool: StylePool,
  charCache: Map<string, ClusteredChar[]>,
)

 * line via stringWidth(). Caller computes the debug cell-count as end-x.
 */
function writeLineToScreen(
  screen: Screen,
  line: string,
  x: number,
  y: number,
  screenWidth: number,
  stylePool: StylePool,
  charCache: Map<string, ClusteredChar[]>,
): number {
  const writeLineStart = performance.now()
  if (line.length >= 16 && isPlainAsciiLine(line)) {
    const writeLoopStart = performance.now()
    const endX = writePlainAsciiLineAt(screen, x, y, line, stylePool.none)
    recordWriteLineToScreenStats({
      lineLength: line.length,
      clusteredChars: Math.max(0, endX - x),
      cacheHit: false,
      usedPlainAsciiFastPath: true,
      materializeDurationMs: 0,
      writeLineDurationMs: performance.now() - writeLineStart,
      writeLoopDurationMs: performance.now() - writeLoopStart,
    })
    return endX
  }

  let characters = charCache.get(line)
  let materializeDurationMs = 0
  let usedPlainAsciiFastPath = false
  if (!characters) {
    const materializeStart = performance.now()
    const plainAsciiCharacters = tryBuildPlainAsciiClusters(line, stylePool.none)
    if (plainAsciiCharacters) {
      characters = plainAsciiCharacters
      usedPlainAsciiFastPath = true
    } else {
      characters = reorderBidi(
        styledCharsWithGraphemeClustering(
          styledCharsFromTokens(tokenize(line)),
          stylePool,
        ),
      )
    }
    materializeDurationMs = performance.now() - materializeStart
    charCache.set(line, characters)
  }

  let offsetX = x
  const writeLoopStart = performance.now()

  for (let charIdx = 0; charIdx < characters.length; charIdx++) {
    const character = characters[charIdx]!
    const codePoint = character.value.codePointAt(0)

    // Handle C0 control characters (0x00-0x1F) that cause cursor movement
    // mismatches. stringWidth treats these as width 0, but terminals may
    // move the cursor differently.
    if (codePoint !== undefined && codePoint <= 0x1f) {
      // Tab (0x09): expand to spaces to reach next tab stop