Function renderColorDiff

src/components/StructuredDiff.tsx:51–104

(
  patch: StructuredPatchHunk,
  firstLine: string | null,
  filePath: string,
  fileContent: string | null,
  theme: string,
  width: number,
  dim: boolean,
  splitGutter: boolean,
)

}

function renderColorDiff(
  patch: StructuredPatchHunk,
  firstLine: string | null,
  filePath: string,
  fileContent: string | null,
  theme: string,
  width: number,
  dim: boolean,
  splitGutter: boolean,
): CachedRender | null {
  const ColorDiff = expectColorDiff();
  if (!ColorDiff) return null;

  // Defensive: if the gutter would eat the whole render width (narrow
  // terminal), skip the split. Rust already wraps to `width` so the
  // single-column output stays correct; we just lose noSelect. Without
  // this, sliceAnsi(line, gutterWidth) would return empty content and
  // RawAnsi(width<=0) is untested.
  const rawGutterWidth = splitGutter ? computeGutterWidth(patch) : 0;
  const gutterWidth = rawGutterWidth > 0 && rawGutterWidth < width ? rawGutterWidth : 0;

  const key = `${theme}|${width}|${dim ? 1 : 0}|${gutterWidth}|${firstLine ?? ''}|${filePath}`;

  let perHunk = RENDER_CACHE.get(patch);
  const hit = perHunk?.get(key);
  if (hit) return hit;

  const lines = new ColorDiff(patch, firstLine, filePath, fileContent).render(theme, width, dim);
  if (lines === null) return null;

  // Pre-split the gutter column once (cold-cache). sliceAnsi preserves
  // styles across the cut; the Rust module already pads the gutter to
  // gutterWidth so the narrow RawAnsi column's width matches its cells.
  let gutters: string[] | null = null;
  let contents: string[] | null = null;
  if (gutterWidth > 0) {
    gutters = lines.map(l => sliceAnsi(l, 0, gutterWidth));
    contents = lines.map(l => sliceAnsi(l, gutterWidth));
  }

  const entry: CachedRender = { lines, gutterWidth, gutters, contents };

  if (!perHunk) {
    perHunk = new Map();
    RENDER_CACHE.set(patch, perHunk);
  }
  // Cap the inner map: width is part of the key, so terminal resize while a
  // diff is visible accumulates a full render copy per distinct width. Four
  // variants (two widths × dim on/off) covers the steady state; beyond that
  // the user is actively resizing and old widths are stale.
  if (perHunk.size >= 4) perHunk.clear();
  perHunk.set(key, entry);
  return entry;
}

export const StructuredDiff = memo(function StructuredDiff({
  patch,