Function measureDiffSectionGeometry

src/ui/diff/diffSectionGeometry.ts:210–345

(
  file: DiffFile,
  layout: Exclude<LayoutMode, "auto">,
  showHunkHeaders: boolean,
  theme: AppTheme,
  visibleAgentNotes: VisibleAgentNote[] = [],
  width = 0,
  showLineNumbers = true,
  wrapLines = false,
  expandedKeys: ReadonlySet<string> = EMPTY_EXPANDED_GAP_KEYS,
  sourceStatus: FileSourceStatus | undefined = undefined,
  reserveAddNoteColumn = false,
)

/** Measure one file section from the same render plan used by PierreDiffView. */
export function measureDiffSectionGeometry(
  file: DiffFile,
  layout: Exclude<LayoutMode, "auto">,
  showHunkHeaders: boolean,
  theme: AppTheme,
  visibleAgentNotes: VisibleAgentNote[] = [],
  width = 0,
  showLineNumbers = true,
  wrapLines = false,
  expandedKeys: ReadonlySet<string> = EMPTY_EXPANDED_GAP_KEYS,
  sourceStatus: FileSourceStatus | undefined = undefined,
  reserveAddNoteColumn = false,
): DiffSectionGeometry {
  if (file.metadata.hunks.length === 0) {
    return {
      bodyHeight: 1,
      hunkAnchorRows: new Map(),
      hunkBounds: new Map(),
      lineNumberDigits: String(findMaxLineNumber(file)).length,
      plannedRows: [],
      rowBounds: [],
      rowBoundsByKey: new Map(),
      rowBoundsByStableKey: new Map(),
    };
  }

  // Width, wrapping, and line-number visibility all affect rendered row heights, so they must
  // participate in the cache key alongside the structural file/layout inputs. Expansion state
  // changes the row stream, so it has to participate too.
  const themeCacheKey = [
    theme.id,
    theme.syntaxTheme ?? "",
    theme.background,
    theme.panelAlt,
    theme.contextBg,
    theme.addedBg,
    theme.removedBg,
    theme.lineNumberBg,
    theme.lineNumberFg,
  ].join(":");
  const cacheKey = `${file.id}:${layout}:${showHunkHeaders ? 1 : 0}:${themeCacheKey}:${width}:${showLineNumbers ? 1 : 0}:${wrapLines ? 1 : 0}:${reserveAddNoteColumn ? 1 : 0}${expansionCacheKey(expandedKeys, sourceStatus)}${notesCacheKey(visibleAgentNotes)}`;
  const cacheSlot = sectionGeometryCacheSlot(visibleAgentNotes);
  const cached = getCachedSectionGeometry(file, cacheSlot, cacheKey);
  if (cached) {
    return cached;
  }

  const sectionRowPlan = buildDiffSectionRowPlan({
    expandedKeys,
    file,
    layout,
    showHunkHeaders,
    sourceStatus,
    theme,
    visibleAgentNotes,
  });
  const { plannedRows } = sectionRowPlan;
  const hunkAnchorRows = new Map<number, number>();