native-ts/yoga-layout/index.ts

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/**
 * Pure-TypeScript port of yoga-layout (Meta's flexbox engine).
 *
 * This matches the `yoga-layout/load` API surface used by src/ink/layout/yoga.ts.
 * The upstream C++ source is ~2500 lines in CalculateLayout.cpp alone; this port
 * is a simplified single-pass flexbox implementation that covers the subset of
 * features Ink actually uses:
 *   - flex-direction (row/column + reverse)
 *   - flex-grow / flex-shrink / flex-basis
 *   - align-items / align-self (stretch, flex-start, center, flex-end)
 *   - justify-content (all six values)
 *   - margin / padding / border / gap
 *   - width / height / min / max (point, percent, auto)
 *   - position: relative / absolute
 *   - display: flex / none
 *   - measure functions (for text nodes)
 *
 * Also implemented for spec parity (not used by Ink):
 *   - margin: auto (main + cross axis, overrides justify/align)
 *   - multi-pass flex clamping when children hit min/max constraints
 *   - flex-grow/shrink against container min/max when size is indefinite
 *
 * Also implemented for spec parity (not used by Ink):
 *   - flex-wrap: wrap / wrap-reverse (multi-line flex)
 *   - align-content (positions wrapped lines on cross axis)
 *
 * Also implemented for spec parity (not used by Ink):
 *   - display: contents (children lifted to grandparent, box removed)
 *
 * Also implemented for spec parity (not used by Ink):
 *   - baseline alignment (align-items/align-self: baseline)
 *
 * Not implemented (not used by Ink):
 *   - aspect-ratio
 *   - box-sizing: content-box
 *   - RTL direction (Ink always passes Direction.LTR)
 *
 * Upstream: https://github.com/facebook/yoga
 */

import {
  Align,
  BoxSizing,
  Dimension,
  Direction,
  Display,
  Edge,
  Errata,
  ExperimentalFeature,
  FlexDirection,
  Gutter,
  Justify,
  MeasureMode,
  Overflow,
  PositionType,
  Unit,
  Wrap,
} from './enums.js'

export {
  Align,
  BoxSizing,
  Dimension,
  Direction,
  Display,
  Edge,
  Errata,
  ExperimentalFeature,
  FlexDirection,
  Gutter,
  Justify,
  MeasureMode,
  Overflow,
  PositionType,
  Unit,
  Wrap,
}

// --
// Value types

export type Value = {
  unit: Unit
  value: number
}

const UNDEFINED_VALUE: Value = { unit: Unit.Undefined, value: NaN }
const AUTO_VALUE: Value = { unit: Unit.Auto, value: NaN }

function pointValue(v: number): Value {
  return { unit: Unit.Point, value: v }
}
function percentValue(v: number): Value {
  return { unit: Unit.Percent, value: v }
}

function resolveValue(v: Value, ownerSize: number): number {
  switch (v.unit) {
    case Unit.Point:
      return v.value
    case Unit.Percent:
      return isNaN(ownerSize) ? NaN : (v.value * ownerSize) / 100
    default:
      return NaN
  }
}

function isDefined(n: number): boolean {
  return !isNaN(n)
}

// NaN-safe equality for layout-cache input comparison
function sameFloat(a: number, b: number): boolean {
  return a === b || (a !== a && b !== b)
}

// --
// Layout result (computed values)

type Layout = {
  left: number
  top: number
  width: number
  height: number
  // Computed per-edge values (resolved to physical edges)
  border: [number, number, number, number] // left, top, right, bottom
  padding: [number, number, number, number]
  margin: [number, number, number, number]
}

// --
// Style (input values)

type Style = {
  direction: Direction
  flexDirection: FlexDirection
  justifyContent: Justify
  alignItems: Align
  alignSelf: Align
  alignContent: Align
  flexWrap: Wrap
  overflow: Overflow
  display: Display
  positionType: PositionType

  flexGrow: number
  flexShrink: number
  flexBasis: Value

  // 9-edge arrays indexed by Edge enum
  margin: Value[]
  padding: Value[]
  border: Value[]
  position: Value[]

  // 3-gutter array indexed by Gutter enum
  gap: Value[]

  width: Value
  height: Value
  minWidth: Value
  minHeight: Value
  maxWidth: Value
  maxHeight: Value
}

function defaultStyle(): Style {
  return {
    direction: Direction.Inherit,
    flexDirection: FlexDirection.Column,
    justifyContent: Justify.FlexStart,
    alignItems: Align.Stretch,
    alignSelf: Align.Auto,
    alignContent: Align.FlexStart,
    flexWrap: Wrap.NoWrap,
    overflow: Overflow.Visible,
    display: Display.Flex,
    positionType: PositionType.Relative,
    flexGrow: 0,
    flexShrink: 0,
    flexBasis: AUTO_VALUE,
    margin: new Array(9).fill(UNDEFINED_VALUE),
    padding: new Array(9).fill(UNDEFINED_VALUE),
    border: new Array(9).fill(UNDEFINED_VALUE),
    position: new Array(9).fill(UNDEFINED_VALUE),
    gap: new Array(3).fill(UNDEFINED_VALUE),
    width: AUTO_VALUE,
    height: AUTO_VALUE,
    minWidth: UNDEFINED_VALUE,
    minHeight: UNDEFINED_VALUE,
    maxWidth: UNDEFINED_VALUE,
    maxHeight: UNDEFINED_VALUE,
  }
}

// --
// Edge resolution — yoga's 9-edge model collapsed to 4 physical edges

const EDGE_LEFT = 0
const EDGE_TOP = 1
const EDGE_RIGHT = 2
const EDGE_BOTTOM = 3

function resolveEdge(
  edges: Value[],
  physicalEdge: number,
  ownerSize: number,
  // For margin/position we allow auto; for padding/border auto resolves to 0
  allowAuto = false,
): number {
  // Precedence: specific edge > horizontal/vertical > all
  let v = edges[physicalEdge]!
  if (v.unit === Unit.Undefined) {
    if (physicalEdge === EDGE_LEFT || physicalEdge === EDGE_RIGHT) {
      v = edges[Edge.Horizontal]!
    } else {
      v = edges[Edge.Vertical]!
    }
  }
  if (v.unit === Unit.Undefined) {
    v = edges[Edge.All]!
  }
  // Start/End map to Left/Right for LTR (Ink is always LTR)
  if (v.unit === Unit.Undefined) {
    if (physicalEdge === EDGE_LEFT) v = edges[Edge.Start]!
    if (physicalEdge === EDGE_RIGHT) v = edges[Edge.End]!
  }
  if (v.unit === Unit.Undefined) return 0
  if (v.unit === Unit.Auto) return allowAuto ? NaN : 0
  return resolveValue(v, ownerSize)
}

function resolveEdgeRaw(edges: Value[], physicalEdge: number): Value {
  let v = edges[physicalEdge]!
  if (v.unit === Unit.Undefined) {
    if (physicalEdge === EDGE_LEFT || physicalEdge === EDGE_RIGHT) {
      v = edges[Edge.Horizontal]!
    } else {
      v = edges[Edge.Vertical]!
    }
  }
  if (v.unit === Unit.Undefined) v = edges[Edge.All]!
  if (v.unit === Unit.Undefined) {
    if (physicalEdge === EDGE_LEFT) v = edges[Edge.Start]!
    if (physicalEdge === EDGE_RIGHT) v = edges[Edge.End]!
  }
  return v
}

function isMarginAuto(edges: Value[], physicalEdge: number): boolean {
  return resolveEdgeRaw(edges, physicalEdge).unit === Unit.Auto
}

// Setter helpers for the _hasAutoMargin / _hasPosition fast-path flags.
// Unit.Undefined = 0, Unit.Auto = 3.
function hasAnyAutoEdge(edges: Value[]): boolean {
  for (let i = 0; i < 9; i++) if (edges[i]!.unit === 3) return true
  return false
}
function hasAnyDefinedEdge(edges: Value[]): boolean {
  for (let i = 0; i < 9; i++) if (edges[i]!.unit !== 0) return true
  return false
}

// Hot path: resolve all 4 physical edges in one pass, writing into `out`.
// Equivalent to calling resolveEdge() 4× with allowAuto=false, but hoists the
// shared fallback lookups (Horizontal/Vertical/All/Start/End) and avoids
// allocating a fresh 4-array on every layoutNode() call.
function resolveEdges4Into(
  edges: Value[],
  ownerSize: number,
  out: [number, number, number, number],
): void {
  // Hoist fallbacks once — the 4 per-edge chains share these reads.
  const eH = edges[6]! // Edge.Horizontal
  const eV = edges[7]! // Edge.Vertical
  const eA = edges[8]! // Edge.All
  const eS = edges[4]! // Edge.Start
  const eE = edges[5]! // Edge.End
  const pctDenom = isNaN(ownerSize) ? NaN : ownerSize / 100

  // Left: edges[0] → Horizontal → All → Start
  let v = edges[0]!
  if (v.unit === 0) v = eH
  if (v.unit === 0) v = eA
  if (v.unit === 0) v = eS
  out[0] = v.unit === 1 ? v.value : v.unit === 2 ? v.value * pctDenom : 0

  // Top: edges[1] → Vertical → All
  v = edges[1]!
  if (v.unit === 0) v = eV
  if (v.unit === 0) v = eA
  out[1] = v.unit === 1 ? v.value : v.unit === 2 ? v.value * pctDenom : 0

  // Right: edges[2] → Horizontal → All → End
  v = edges[2]!
  if (v.unit === 0) v = eH
  if (v.unit === 0) v = eA
  if (v.unit === 0) v = eE
  out[2] = v.unit === 1 ? v.value : v.unit === 2 ? v.value * pctDenom : 0

  // Bottom: edges[3] → Vertical → All
  v = edges[3]!
  if (v.unit === 0) v = eV
  if (v.unit === 0) v = eA
  out[3] = v.unit === 1 ? v.value : v.unit === 2 ? v.value * pctDenom : 0
}

// --
// Axis helpers

function isRow(dir: FlexDirection): boolean {
  return dir === FlexDirection.Row || dir === FlexDirection.RowReverse
}
function isReverse(dir: FlexDirection): boolean {
  return dir === FlexDirection.RowReverse || dir === FlexDirection.ColumnReverse
}
function crossAxis(dir: FlexDirection): FlexDirection {
  return isRow(dir) ? FlexDirection.Column : FlexDirection.Row
}
function leadingEdge(dir: FlexDirection): number {
  switch (dir) {
    case FlexDirection.Row:
      return EDGE_LEFT
    case FlexDirection.RowReverse:
      return EDGE_RIGHT
    case FlexDirection.Column:
      return EDGE_TOP
    case FlexDirection.ColumnReverse:
      return EDGE_BOTTOM
  }
}
function trailingEdge(dir: FlexDirection): number {
  switch (dir) {
    case FlexDirection.Row:
      return EDGE_RIGHT
    case FlexDirection.RowReverse:
      return EDGE_LEFT
    case FlexDirection.Column:
      return EDGE_BOTTOM
    case FlexDirection.ColumnReverse:
      return EDGE_TOP
  }
}

// --
// Public types

export type MeasureFunction = (
  width: number,
  widthMode: MeasureMode,
  height: number,
  heightMode: MeasureMode,
) => { width: number; height: number }

export type Size = { width: number; height: number }

// --
// Config

export type Config = {
  pointScaleFactor: number
  errata: Errata
  useWebDefaults: boolean
  free(): void
  isExperimentalFeatureEnabled(_: ExperimentalFeature): boolean
  setExperimentalFeatureEnabled(_: ExperimentalFeature, __: boolean): void
  setPointScaleFactor(factor: number): void
  getErrata(): Errata
  setErrata(errata: Errata): void
  setUseWebDefaults(v: boolean): void
}

function createConfig(): Config {
  const config: Config = {
    pointScaleFactor: 1,
    errata: Errata.None,
    useWebDefaults: false,
    free() {},
    isExperimentalFeatureEnabled() {
      return false
    },
    setExperimentalFeatureEnabled() {},
    setPointScaleFactor(f) {
      config.pointScaleFactor = f
    },
    getErrata() {
      return config.errata
    },
    setErrata(e) {
      config.errata = e
    },
    setUseWebDefaults(v) {
      config.useWebDefaults = v
    },
  }
  return config
}

// --
// Node implementation

export class Node {
  style: Style
  layout: Layout
  parent: Node | null
  children: Node[]
  measureFunc: MeasureFunction | null
  config: Config
  isDirty_: boolean
  isReferenceBaseline_: boolean

  // Per-layout scratch (not public API)
  _flexBasis = 0
  _mainSize = 0
  _crossSize = 0
  _lineIndex = 0
  // Fast-path flags maintained by style setters. Per CPU profile, the
  // positioning loop calls isMarginAuto 6× and resolveEdgeRaw(position) 4×
  // per child per layout pass — ~11k calls for the 1000-node bench, nearly
  // all of which return false/undefined since most nodes have no auto
  // margins and no position insets. These flags let us skip straight to
  // the common case with a single branch.
  _hasAutoMargin = false
  _hasPosition = false
  // Same pattern for the 3× resolveEdges4Into calls at the top of every
  // layoutNode(). In the 1000-node bench ~67% of those calls operate on
  // all-undefined edge arrays (most nodes have no border; only cols have
  // padding; only leaf cells have margin) — a single-branch skip beats
  // ~20 property reads + ~15 compares + 4 writes of zeros.
  _hasPadding = false
  _hasBorder = false
  _hasMargin = false
  // -- Dirty-flag layout cache. Mirrors upstream CalculateLayout.cpp's
  // layoutNodeInternal: skip a subtree entirely when it's clean and we're
  // asking the same question we cached the answer to. Two slots since
  // each node typically sees a measure call (performLayout=false, from
  // computeFlexBasis) followed by a layout call (performLayout=true) with
  // different inputs per parent pass — a single slot thrashes. Re-layout
  // bench (dirty one leaf, recompute root) went 2.7x→1.1x with this:
  // clean siblings skip straight through, only the dirty chain recomputes.
  _lW = NaN
  _lH = NaN
  _lWM: MeasureMode = 0
  _lHM: MeasureMode = 0
  _lOW = NaN
  _lOH = NaN
  _lFW = false
  _lFH = false
  // _hasL stores INPUTS early (before compute) but layout.width/height are
  // mutated by the multi-entry cache and by subsequent compute calls with
  // different inputs. Without storing OUTPUTS, a _hasL hit returns whatever
  // layout.width/height happened to be left by the last call — the scrollbox
  // vpH=33→2624 bug. Store + restore outputs like the multi-entry cache does.
  _lOutW = NaN
  _lOutH = NaN
  _hasL = false
  _mW = NaN
  _mH = NaN
  _mWM: MeasureMode = 0
  _mHM: MeasureMode = 0
  _mOW = NaN
  _mOH = NaN
  _mOutW = NaN
  _mOutH = NaN
  _hasM = false
  // Cached computeFlexBasis result. For clean children, basis only depends
  // on the container's inner dimensions — if those haven't changed, skip the
  // layoutNode(performLayout=false) recursion entirely. This is the hot path
  // for scroll: 500-message content container is dirty, its 499 clean
  // children each get measured ~20× as the dirty chain's measure/layout
  // passes cascade. Basis cache short-circuits at the child boundary.
  _fbBasis = NaN
  _fbOwnerW = NaN
  _fbOwnerH = NaN
  _fbAvailMain = NaN
  _fbAvailCross = NaN
  _fbCrossMode: MeasureMode = 0
  // Generation at which _fbBasis was written. Dirty nodes from a PREVIOUS
  // generation have stale cache (subtree changed), but within the SAME
  // generation the cache is fresh — the dirty chain's measure→layout
  // cascade invokes computeFlexBasis ≥2^depth times per calculateLayout on
  // fresh-mounted items, and the subtree doesn't change between calls.
  // Gating on generation instead of isDirty_ lets fresh mounts (virtual
  // scroll) cache-hit after first compute: 105k visits → ~10k.
  _fbGen = -1
  // Multi-entry layout cache — stores (inputs → computed w,h) so hits with
  // different inputs than _hasL can restore the right dimensions. Upstream
  // yoga uses 16; 4 covers Ink's dirty-chain depth. Packed as flat arrays
  // to avoid per-entry object allocs. Slot i uses indices [i*8, i*8+8) in
  // _cIn (aW,aH,wM,hM,oW,oH,fW,fH) and [i*2, i*2+2) in _cOut (w,h).
  _cIn: Float64Array | null = null
  _cOut: Float64Array | null = null
  _cGen = -1
  _cN = 0
  _cWr = 0

  constructor(config?: Config) {
    this.style = defaultStyle()
    this.layout = {
      left: 0,
      top: 0,
      width: 0,
      height: 0,
      border: [0, 0, 0, 0],
      padding: [0, 0, 0, 0],
      margin: [0, 0, 0, 0],
    }
    this.parent = null
    this.children = []
    this.measureFunc = null
    this.config = config ?? DEFAULT_CONFIG
    this.isDirty_ = true
    this.isReferenceBaseline_ = false
    _yogaLiveNodes++
  }

  // -- Tree

  insertChild(child: Node, index: number): void {
    child.parent = this
    this.children.splice(index, 0, child)
    this.markDirty()
  }
  removeChild(child: Node): void {
    const idx = this.children.indexOf(child)
    if (idx >= 0) {
      this.children.splice(idx, 1)
      child.parent = null
      this.markDirty()
    }
  }
  getChild(index: number): Node {
    return this.children[index]!
  }
  getChildCount(): number {
    return this.children.length
  }
  getParent(): Node | null {
    return this.parent
  }

  // -- Lifecycle

  free(): void {
    this.parent = null
    this.children = []
    this.measureFunc = null
    this._cIn = null
    this._cOut = null
    _yogaLiveNodes--
  }
  freeRecursive(): void {
    for (const c of this.children) c.freeRecursive()
    this.free()
  }
  reset(): void {
    this.style = defaultStyle()
    this.children = []
    this.parent = null
    this.measureFunc = null
    this.isDirty_ = true
    this._hasAutoMargin = false
    this._hasPosition = false
    this._hasPadding = false
    this._hasBorder = false
    this._hasMargin = false
    this._hasL = false
    this._hasM = false
    this._cN = 0
    this._cWr = 0
    this._fbBasis = NaN
  }

  // -- Dirty tracking

  markDirty(): void {
    this.isDirty_ = true
    if (this.parent && !this.parent.isDirty_) this.parent.markDirty()
  }
  isDirty(): boolean {
    return this.isDirty_
  }
  hasNewLayout(): boolean {
    return true
  }
  markLayoutSeen(): void {}

  // -- Measure function

  setMeasureFunc(fn: MeasureFunction | null): void {
    this.measureFunc = fn
    this.markDirty()
  }
  unsetMeasureFunc(): void {
    this.measureFunc = null
    this.markDirty()
  }

  // -- Computed layout getters

  getComputedLeft(): number {
    return this.layout.left
  }
  getComputedTop(): number {
    return this.layout.top
  }
  getComputedWidth(): number {
    return this.layout.width
  }
  getComputedHeight(): number {
    return this.layout.height
  }
  getComputedRight(): number {
    const p = this.parent
    return p ? p.layout.width - this.layout.left - this.layout.width : 0
  }
  getComputedBottom(): number {
    const p = this.parent
    return p ? p.layout.height - this.layout.top - this.layout.height : 0
  }
  getComputedLayout(): {
    left: number
    top: number
    right: number
    bottom: number
    width: number
    height: number
  } {
    return {
      left: this.layout.left,
      top: this.layout.top,
      right: this.getComputedRight(),
      bottom: this.getComputedBottom(),
      width: this.layout.width,
      height: this.layout.height,
    }
  }
  getComputedBorder(edge: Edge): number {
    return this.layout.border[physicalEdge(edge)]!
  }
  getComputedPadding(edge: Edge): number {
    return this.layout.padding[physicalEdge(edge)]!
  }
  getComputedMargin(edge: Edge): number {
    return this.layout.margin[physicalEdge(edge)]!
  }

  // -- Style setters: dimensions

  setWidth(v: number | 'auto' | string | undefined): void {
    this.style.width = parseDimension(v)
    this.markDirty()
  }
  setWidthPercent(v: number): void {
    this.style.width = percentValue(v)
    this.markDirty()
  }
  setWidthAuto(): void {
    this.style.width = AUTO_VALUE
    this.markDirty()
  }
  setHeight(v: number | 'auto' | string | undefined): void {
    this.style.height = parseDimension(v)
    this.markDirty()
  }
  setHeightPercent(v: number): void {
    this.style.height = percentValue(v)
    this.markDirty()
  }
  setHeightAuto(): void {
    this.style.height = AUTO_VALUE
    this.markDirty()
  }
  setMinWidth(v: number | string | undefined): void {
    this.style.minWidth = parseDimension(v)
    this.markDirty()
  }
  setMinWidthPercent(v: number): void {
    this.style.minWidth = percentValue(v)
    this.markDirty()
  }
  setMinHeight(v: number | string | undefined): void {
    this.style.minHeight = parseDimension(v)
    this.markDirty()
  }
  setMinHeightPercent(v: number): void {
    this.style.minHeight = percentValue(v)
    this.markDirty()
  }
  setMaxWidth(v: number | string | undefined): void {
    this.style.maxWidth = parseDimension(v)
    this.markDirty()
  }
  setMaxWidthPercent(v: number): void {
    this.style.maxWidth = percentValue(v)
    this.markDirty()
  }
  setMaxHeight(v: number | string | undefined): void {
    this.style.maxHeight = parseDimension(v)
    this.markDirty()
  }
  setMaxHeightPercent(v: number): void {
    this.style.maxHeight = percentValue(v)
    this.markDirty()
  }

  // -- Style setters: flex

  setFlexDirection(dir: FlexDirection): void {
    this.style.flexDirection = dir
    this.markDirty()
  }
  setFlexGrow(v: number | undefined): void {
    this.style.flexGrow = v ?? 0
    this.markDirty()
  }
  setFlexShrink(v: number | undefined): void {
    this.style.flexShrink = v ?? 0
    this.markDirty()
  }
  setFlex(v: number | undefined): void {
    if (v === undefined || isNaN(v)) {
      this.style.flexGrow = 0
      this.style.flexShrink = 0
    } else if (v > 0) {
      this.style.flexGrow = v
      this.style.flexShrink = 1
      this.style.flexBasis = pointValue(0)
    } else if (v < 0) {
      this.style.flexGrow = 0
      this.style.flexShrink = -v
    } else {
      this.style.flexGrow = 0
      this.style.flexShrink = 0
    }
    this.markDirty()
  }
  setFlexBasis(v: number | 'auto' | string | undefined): void {
    this.style.flexBasis = parseDimension(v)
    this.markDirty()
  }
  setFlexBasisPercent(v: number): void {
    this.style.flexBasis = percentValue(v)
    this.markDirty()
  }
  setFlexBasisAuto(): void {
    this.style.flexBasis = AUTO_VALUE
    this.markDirty()
  }
  setFlexWrap(wrap: Wrap): void {
    this.style.flexWrap = wrap
    this.markDirty()
  }

  // -- Style setters: alignment

  setAlignItems(a: Align): void {
    this.style.alignItems = a
    this.markDirty()
  }
  setAlignSelf(a: Align): void {
    this.style.alignSelf = a
    this.markDirty()
  }
  setAlignContent(a: Align): void {
    this.style.alignContent = a
    this.markDirty()
  }
  setJustifyContent(j: Justify): void {
    this.style.justifyContent = j
    this.markDirty()
  }

  // -- Style setters: display / position / overflow

  setDisplay(d: Display): void {
    this.style.display = d
    this.markDirty()
  }
  getDisplay(): Display {
    return this.style.display
  }
  setPositionType(t: PositionType): void {
    this.style.positionType = t
    this.markDirty()
  }
  setPosition(edge: Edge, v: number | string | undefined): void {
    this.style.position[edge] = parseDimension(v)
    this._hasPosition = hasAnyDefinedEdge(this.style.position)
    this.markDirty()
  }
  setPositionPercent(edge: Edge, v: number): void {
    this.style.position[edge] = percentValue(v)
    this._hasPosition = true
    this.markDirty()
  }
  setPositionAuto(edge: Edge): void {
    this.style.position[edge] = AUTO_VALUE
    this._hasPosition = true
    this.markDirty()
  }
  setOverflow(o: Overflow): void {
    this.style.overflow = o
    this.markDirty()
  }
  setDirection(d: Direction): void {
    this.style.direction = d
    this.markDirty()
  }
  setBoxSizing(_: BoxSizing): void {
    // Not implemented — Ink doesn't use content-box
  }

  // -- Style setters: spacing

  setMargin(edge: Edge, v: number | 'auto' | string | undefined): void {
    const val = parseDimension(v)
    this.style.margin[edge] = val
    if (val.unit === Unit.Auto) this._hasAutoMargin = true
    else this._hasAutoMargin = hasAnyAutoEdge(this.style.margin)
    this._hasMargin =
      this._hasAutoMargin || hasAnyDefinedEdge(this.style.margin)
    this.markDirty()
  }
  setMarginPercent(edge: Edge, v: number): void {
    this.style.margin[edge] = percentValue(v)
    this._hasAutoMargin = hasAnyAutoEdge(this.style.margin)
    this._hasMargin = true
    this.markDirty()
  }
  setMarginAuto(edge: Edge): void {
    this.style.margin[edge] = AUTO_VALUE
    this._hasAutoMargin = true
    this._hasMargin = true
    this.markDirty()
  }
  setPadding(edge: Edge, v: number | string | undefined): void {
    this.style.padding[edge] = parseDimension(v)
    this._hasPadding = hasAnyDefinedEdge(this.style.padding)
    this.markDirty()
  }
  setPaddingPercent(edge: Edge, v: number): void {
    this.style.padding[edge] = percentValue(v)
    this._hasPadding = true
    this.markDirty()
  }
  setBorder(edge: Edge, v: number | undefined): void {
    this.style.border[edge] = v === undefined ? UNDEFINED_VALUE : pointValue(v)
    this._hasBorder = hasAnyDefinedEdge(this.style.border)
    this.markDirty()
  }
  setGap(gutter: Gutter, v: number | string | undefined): void {
    this.style.gap[gutter] = parseDimension(v)
    this.markDirty()
  }
  setGapPercent(gutter: Gutter, v: number): void {
    this.style.gap[gutter] = percentValue(v)
    this.markDirty()
  }

  // -- Style getters (partial — only what tests need)

  getFlexDirection(): FlexDirection {
    return this.style.flexDirection
  }
  getJustifyContent(): Justify {
    return this.style.justifyContent
  }
  getAlignItems(): Align {
    return this.style.alignItems
  }
  getAlignSelf(): Align {
    return this.style.alignSelf
  }
  getAlignContent(): Align {
    return this.style.alignContent
  }
  getFlexGrow(): number {
    return this.style.flexGrow
  }
  getFlexShrink(): number {
    return this.style.flexShrink
  }
  getFlexBasis(): Value {
    return this.style.flexBasis
  }
  getFlexWrap(): Wrap {
    return this.style.flexWrap
  }
  getWidth(): Value {
    return this.style.width
  }
  getHeight(): Value {
    return this.style.height
  }
  getOverflow(): Overflow {
    return this.style.overflow
  }
  getPositionType(): PositionType {
    return this.style.positionType
  }
  getDirection(): Direction {
    return this.style.direction
  }

  // -- Unused API stubs (present for API parity)

  copyStyle(_: Node): void {}
  setDirtiedFunc(_: unknown): void {}
  unsetDirtiedFunc(): void {}
  setIsReferenceBaseline(v: boolean): void {
    this.isReferenceBaseline_ = v
    this.markDirty()
  }
  isReferenceBaseline(): boolean {
    return this.isReferenceBaseline_
  }
  setAspectRatio(_: number | undefined): void {}
  getAspectRatio(): number {
    return NaN
  }
  setAlwaysFormsContainingBlock(_: boolean): void {}

  // -- Layout entry point

  calculateLayout(
    ownerWidth: number | undefined,
    ownerHeight: number | undefined,
    _direction?: Direction,
  ): void {
    _yogaNodesVisited = 0
    _yogaMeasureCalls = 0
    _yogaCacheHits = 0
    _generation++
    const w = ownerWidth === undefined ? NaN : ownerWidth
    const h = ownerHeight === undefined ? NaN : ownerHeight
    layoutNode(
      this,
      w,
      h,
      isDefined(w) ? MeasureMode.Exactly : MeasureMode.Undefined,
      isDefined(h) ? MeasureMode.Exactly : MeasureMode.Undefined,
      w,
      h,
      true,
    )
    // Root's own position = margin + position insets (yoga applies position
    // to the root even without a parent container; this matters for rounding
    // since the root's abs top/left seeds the pixel-grid walk).
    const mar = this.layout.margin
    const posL = resolveValue(
      resolveEdgeRaw(this.style.position, EDGE_LEFT),
      isDefined(w) ? w : 0,
    )
    const posT = resolveValue(
      resolveEdgeRaw(this.style.position, EDGE_TOP),
      isDefined(w) ? w : 0,
    )
    this.layout.left = mar[EDGE_LEFT] + (isDefined(posL) ? posL : 0)
    this.layout.top = mar[EDGE_TOP] + (isDefined(posT) ? posT : 0)
    roundLayout(this, this.config.pointScaleFactor, 0, 0)
  }
}

const DEFAULT_CONFIG = createConfig()

const CACHE_SLOTS = 4
function cacheWrite(
  node: Node,
  aW: number,
  aH: number,
  wM: MeasureMode,
  hM: MeasureMode,
  oW: number,
  oH: number,
  fW: boolean,
  fH: boolean,
  wasDirty: boolean,
): void {
  if (!node._cIn) {
    node._cIn = new Float64Array(CACHE_SLOTS * 8)
    node._cOut = new Float64Array(CACHE_SLOTS * 2)
  }
  // First write after a dirty clears stale entries from before the dirty.
  // _cGen < _generation means entries are from a previous calculateLayout;
  // if wasDirty, the subtree changed since then → old dimensions invalid.
  // Clean nodes' old entries stay — same subtree → same result for same
  // inputs, so cross-generation caching works (the scroll hot path where
  // 499 clean messages cache-hit while one dirty leaf recomputes).
  if (wasDirty && node._cGen !== _generation) {
    node._cN = 0
    node._cWr = 0
  }
  // LRU write index wraps; _cN stays at CACHE_SLOTS so the read scan always
  // checks all populated slots (not just those since last wrap).
  const i = node._cWr++ % CACHE_SLOTS
  if (node._cN < CACHE_SLOTS) node._cN = node._cWr
  const o = i * 8
  const cIn = node._cIn
  cIn[o] = aW
  cIn[o + 1] = aH
  cIn[o + 2] = wM
  cIn[o + 3] = hM
  cIn[o + 4] = oW
  cIn[o + 5] = oH
  cIn[o + 6] = fW ? 1 : 0
  cIn[o + 7] = fH ? 1 : 0
  node._cOut![i * 2] = node.layout.width
  node._cOut![i * 2 + 1] = node.layout.height
  node._cGen = _generation
}

// Store computed layout.width/height into the single-slot cache output fields.
// _hasL/_hasM inputs are committed at the TOP of layoutNode (before compute);
// outputs must be committed HERE (after compute) so a cache hit can restore
// the correct dimensions. Without this, a _hasL hit returns whatever
// layout.width/height was left by the last call — which may be the intrinsic
// content height from a heightMode=Undefined measure pass rather than the
// constrained viewport height from the layout pass. That's the scrollbox
// vpH=33→2624 bug: scrollTop clamps to 0, viewport goes blank.
function commitCacheOutputs(node: Node, performLayout: boolean): void {
  if (performLayout) {
    node._lOutW = node.layout.width
    node._lOutH = node.layout.height
  } else {
    node._mOutW = node.layout.width
    node._mOutH = node.layout.height
  }
}

// --
// Core flexbox algorithm

// Profiling counters — reset per calculateLayout, read via getYogaCounters.
// Incremented on each calculateLayout(). Nodes stamp _fbGen/_cGen when
// their cache is written; a cache entry with gen === _generation was
// computed THIS pass and is fresh regardless of isDirty_ state.
let _generation = 0
let _yogaNodesVisited = 0
let _yogaMeasureCalls = 0
let _yogaCacheHits = 0
let _yogaLiveNodes = 0
export function getYogaCounters(): {
  visited: number
  measured: number
  cacheHits: number
  live: number
} {
  return {
    visited: _yogaNodesVisited,
    measured: _yogaMeasureCalls,
    cacheHits: _yogaCacheHits,
    live: _yogaLiveNodes,
  }
}

function layoutNode(
  node: Node,
  availableWidth: number,
  availableHeight: number,
  widthMode: MeasureMode,
  heightMode: MeasureMode,
  ownerWidth: number,
  ownerHeight: number,
  performLayout: boolean,
  // When true, ignore style dimension on this axis — the flex container
  // has already determined the main size (flex-basis + grow/shrink result).
  forceWidth = false,
  forceHeight = false,
): void {
  _yogaNodesVisited++
  const style = node.style
  const layout = node.layout

  // Dirty-flag skip: clean subtree + matching inputs → layout object already
  // holds the answer. A cached layout result also satisfies a measure request
  // (positions are a superset of dimensions); the reverse does not hold.
  // Same-generation entries are fresh regardless of isDirty_ — they were
  // computed THIS calculateLayout, the subtree hasn't changed since.
  // Previous-generation entries need !isDirty_ (a dirty node's cache from
  // before the dirty is stale).
  // sameGen bypass only for MEASURE calls — a layout-pass cache hit would
  // skip the child-positioning recursion (STEP 5), leaving children at
  // stale positions. Measure calls only need w/h which the cache stores.
  const sameGen = node._cGen === _generation && !performLayout
  if (!node.isDirty_ || sameGen) {
    if (
      !node.isDirty_ &&
      node._hasL &&
      node._lWM === widthMode &&
      node._lHM === heightMode &&
      node._lFW === forceWidth &&
      node._lFH === forceHeight &&
      sameFloat(node._lW, availableWidth) &&
      sameFloat(node._lH, availableHeight) &&
      sameFloat(node._lOW, ownerWidth) &&
      sameFloat(node._lOH, ownerHeight)
    ) {
      _yogaCacheHits++
      layout.width = node._lOutW
      layout.height = node._lOutH
      return
    }
    // Multi-entry cache: scan for matching inputs, restore cached w/h on hit.
    // Covers the scroll case where a dirty ancestor's measure→layout cascade
    // produces N>1 distinct input combos per clean child — the single _hasL
    // slot thrashed, forcing full subtree recursion. With 500-message
    // scrollbox and one dirty leaf, this took dirty-leaf relayout from
    // 76k layoutNode calls (21.7×nodes) to 4k (1.2×nodes), 6.86ms → 550µs.
    // Same-generation check covers fresh-mounted (dirty) nodes during
    // virtual scroll — the dirty chain invokes them ≥2^depth times, first
    // call writes cache, rest hit: 105k visits → ~10k for 1593-node tree.
    if (node._cN > 0 && (sameGen || !node.isDirty_)) {
      const cIn = node._cIn!
      for (let i = 0; i < node._cN; i++) {
        const o = i * 8
        if (
          cIn[o + 2] === widthMode &&
          cIn[o + 3] === heightMode &&
          cIn[o + 6] === (forceWidth ? 1 : 0) &&
          cIn[o + 7] === (forceHeight ? 1 : 0) &&
          sameFloat(cIn[o]!, availableWidth) &&
          sameFloat(cIn[o + 1]!, availableHeight) &&
          sameFloat(cIn[o + 4]!, ownerWidth) &&
          sameFloat(cIn[o + 5]!, ownerHeight)
        ) {
          layout.width = node._cOut![i * 2]!
          layout.height = node._cOut![i * 2 + 1]!
          _yogaCacheHits++
          return
        }
      }
    }
    if (
      !node.isDirty_ &&
      !performLayout &&
      node._hasM &&
      node._mWM === widthMode &&
      node._mHM === heightMode &&
      sameFloat(node._mW, availableWidth) &&
      sameFloat(node._mH, availableHeight) &&
      sameFloat(node._mOW, ownerWidth) &&
      sameFloat(node._mOH, ownerHeight)
    ) {
      layout.width = node._mOutW
      layout.height = node._mOutH
      _yogaCacheHits++
      return
    }
  }
  // Commit cache inputs up front so every return path leaves a valid entry.
  // Only clear isDirty_ on the LAYOUT pass — the measure pass (computeFlexBasis
  // → layoutNode(performLayout=false)) runs before the layout pass in the same
  // calculateLayout call. Clearing dirty during measure lets the subsequent
  // layout pass hit the STALE _hasL cache from the previous calculateLayout
  // (before children were inserted), so ScrollBox content height never grows
  // and sticky-scroll never follows new content. A dirty node's _hasL entry is
  // stale by definition — invalidate it so the layout pass recomputes.
  const wasDirty = node.isDirty_
  if (performLayout) {
    node._lW = availableWidth
    node._lH = availableHeight
    node._lWM = widthMode
    node._lHM = heightMode
    node._lOW = ownerWidth
    node._lOH = ownerHeight
    node._lFW = forceWidth
    node._lFH = forceHeight
    node._hasL = true
    node.isDirty_ = false
    // Previous approach cleared _cN here to prevent stale pre-dirty entries
    // from hitting (long-continuous blank-screen bug). Now replaced by
    // generation stamping: the cache check requires sameGen || !isDirty_, so
    // previous-generation entries from a dirty node can't hit. Clearing here
    // would wipe fresh same-generation entries from an earlier measure call,
    // forcing recompute on the layout call.
    if (wasDirty) node._hasM = false
  } else {
    node._mW = availableWidth
    node._mH = availableHeight
    node._mWM = widthMode
    node._mHM = heightMode
    node._mOW = ownerWidth
    node._mOH = ownerHeight
    node._hasM = true
    // Don't clear isDirty_. For DIRTY nodes, invalidate _hasL so the upcoming
    // performLayout=true call recomputes with the new child set (otherwise
    // sticky-scroll never follows new content — the bug from 4557bc9f9c).
    // Clean nodes keep _hasL: their layout from the previous generation is
    // still valid, they're only here because an ancestor is dirty and called
    // with different inputs than cached.
    if (wasDirty) node._hasL = false
  }

  // Resolve padding/border/margin against ownerWidth (yoga uses ownerWidth for %)
  // Write directly into the pre-allocated layout arrays — avoids 3 allocs per
  // layoutNode call and 12 resolveEdge calls (was the #1 hotspot per CPU profile).
  // Skip entirely when no edges are set — the 4-write zero is cheaper than
  // the ~20 reads + ~15 compares resolveEdges4Into does to produce zeros.
  const pad = layout.padding
  const bor = layout.border
  const mar = layout.margin
  if (node._hasPadding) resolveEdges4Into(style.padding, ownerWidth, pad)
  else pad[0] = pad[1] = pad[2] = pad[3] = 0
  if (node._hasBorder) resolveEdges4Into(style.border, ownerWidth, bor)
  else bor[0] = bor[1] = bor[2] = bor[3] = 0
  if (node._hasMargin) resolveEdges4Into(style.margin, ownerWidth, mar)
  else mar[0] = mar[1] = mar[2] = mar[3] = 0

  const paddingBorderWidth = pad[0] + pad[2] + bor[0] + bor[2]
  const paddingBorderHeight = pad[1] + pad[3] + bor[1] + bor[3]

  // Resolve style dimensions
  const styleWidth = forceWidth ? NaN : resolveValue(style.width, ownerWidth)
  const styleHeight = forceHeight
    ? NaN
    : resolveValue(style.height, ownerHeight)

  // If style dimension is defined, it overrides the available size
  let width = availableWidth
  let height = availableHeight
  let wMode = widthMode
  let hMode = heightMode
  if (isDefined(styleWidth)) {
    width = styleWidth
    wMode = MeasureMode.Exactly
  }
  if (isDefined(styleHeight)) {
    height = styleHeight
    hMode = MeasureMode.Exactly
  }

  // Apply min/max constraints to the node's own dimensions
  width = boundAxis(style, true, width, ownerWidth, ownerHeight)
  height = boundAxis(style, false, height, ownerWidth, ownerHeight)

  // Measure-func leaf node
  if (node.measureFunc && node.children.length === 0) {
    const innerW =
      wMode === MeasureMode.Undefined
        ? NaN
        : Math.max(0, width - paddingBorderWidth)
    const innerH =
      hMode === MeasureMode.Undefined
        ? NaN
        : Math.max(0, height - paddingBorderHeight)
    _yogaMeasureCalls++
    const measured = node.measureFunc(innerW, wMode, innerH, hMode)
    node.layout.width =
      wMode === MeasureMode.Exactly
        ? width
        : boundAxis(
            style,
            true,
            (measured.width ?? 0) + paddingBorderWidth,
            ownerWidth,
            ownerHeight,
          )
    node.layout.height =
      hMode === MeasureMode.Exactly
        ? height
        : boundAxis(
            style,
            false,
            (measured.height ?? 0) + paddingBorderHeight,
            ownerWidth,
            ownerHeight,
          )
    commitCacheOutputs(node, performLayout)
    // Write cache even for dirty nodes — fresh-mounted items during virtual
    // scroll are dirty on first layout, but the dirty chain's measure→layout
    // cascade invokes them ≥2^depth times per calculateLayout. Writing here
    // lets the 2nd+ calls hit cache (isDirty_ was cleared in the layout pass
    // above). Measured: 105k visits → 10k for a 1593-node fresh-mount tree.
    cacheWrite(
      node,
      availableWidth,
      availableHeight,
      widthMode,
      heightMode,
      ownerWidth,
      ownerHeight,
      forceWidth,
      forceHeight,
      wasDirty,
    )
    return
  }

  // Leaf node with no children and no measure func
  if (node.children.length === 0) {
    node.layout.width =
      wMode === MeasureMode.Exactly
        ? width
        : boundAxis(style, true, paddingBorderWidth, ownerWidth, ownerHeight)
    node.layout.height =
      hMode === MeasureMode.Exactly
        ? height
        : boundAxis(style, false, paddingBorderHeight, ownerWidth, ownerHeight)
    commitCacheOutputs(node, performLayout)
    // Write cache even for dirty nodes — fresh-mounted items during virtual
    // scroll are dirty on first layout, but the dirty chain's measure→layout
    // cascade invokes them ≥2^depth times per calculateLayout. Writing here
    // lets the 2nd+ calls hit cache (isDirty_ was cleared in the layout pass
    // above). Measured: 105k visits → 10k for a 1593-node fresh-mount tree.
    cacheWrite(
      node,
      availableWidth,
      availableHeight,
      widthMode,
      heightMode,
      ownerWidth,
      ownerHeight,
      forceWidth,
      forceHeight,
      wasDirty,
    )
    return
  }

  // Container with children — run flexbox algorithm
  const mainAxis = style.flexDirection
  const crossAx = crossAxis(mainAxis)
  const isMainRow = isRow(mainAxis)

  const mainSize = isMainRow ? width : height
  const crossSize = isMainRow ? height : width
  const mainMode = isMainRow ? wMode : hMode
  const crossMode = isMainRow ? hMode : wMode
  const mainPadBorder = isMainRow ? paddingBorderWidth : paddingBorderHeight
  const crossPadBorder = isMainRow ? paddingBorderHeight : paddingBorderWidth

  const innerMainSize = isDefined(mainSize)
    ? Math.max(0, mainSize - mainPadBorder)
    : NaN
  const innerCrossSize = isDefined(crossSize)
    ? Math.max(0, crossSize - crossPadBorder)
    : NaN

  // Resolve gap
  const gapMain = resolveGap(
    style,
    isMainRow ? Gutter.Column : Gutter.Row,
    innerMainSize,
  )

  // Partition children into flow vs absolute. display:contents nodes are
  // transparent — their children are lifted into the grandparent's child list
  // (recursively), and the contents node itself gets zero layout.
  const flowChildren: Node[] = []
  const absChildren: Node[] = []
  collectLayoutChildren(node, flowChildren, absChildren)

  // ownerW/H are the reference sizes for resolving children's percentage
  // values. Per CSS, a % width resolves against the parent's content-box
  // width. If this node's width is indefinite, children's % widths are also
  // indefinite — do NOT fall through to the grandparent's size.
  const ownerW = isDefined(width) ? width : NaN
  const ownerH = isDefined(height) ? height : NaN
  const isWrap = style.flexWrap !== Wrap.NoWrap
  const gapCross = resolveGap(
    style,
    isMainRow ? Gutter.Row : Gutter.Column,
    innerCrossSize,
  )

  // STEP 1: Compute flex-basis for each flow child and break into lines.
  // Single-line (NoWrap) containers always get one line; multi-line containers
  // break when accumulated basis+margin+gap exceeds innerMainSize.
  for (const c of flowChildren) {
    c._flexBasis = computeFlexBasis(
      c,
      mainAxis,
      innerMainSize,
      innerCrossSize,
      crossMode,
      ownerW,
      ownerH,
    )
  }
  const lines: Node[][] = []
  if (!isWrap || !isDefined(innerMainSize) || flowChildren.length === 0) {
    for (const c of flowChildren) c._lineIndex = 0
    lines.push(flowChildren)
  } else {
    // Line-break decisions use the min/max-clamped basis (flexbox spec §9.3.5:
    // "hypothetical main size"), not the raw flex-basis.
    let lineStart = 0
    let lineLen = 0
    for (let i = 0; i < flowChildren.length; i++) {
      const c = flowChildren[i]!
      const hypo = boundAxis(c.style, isMainRow, c._flexBasis, ownerW, ownerH)
      const outer = Math.max(0, hypo) + childMarginForAxis(c, mainAxis, ownerW)
      const withGap = i > lineStart ? gapMain : 0
      if (i > lineStart && lineLen + withGap + outer > innerMainSize) {
        lines.push(flowChildren.slice(lineStart, i))
        lineStart = i
        lineLen = outer
      } else {
        lineLen += withGap + outer
      }
      c._lineIndex = lines.length
    }
    lines.push(flowChildren.slice(lineStart))
  }
  const lineCount = lines.length
  const isBaseline = isBaselineLayout(node, flowChildren)

  // STEP 2+3: For each line, resolve flexible lengths and lay out children to
  // measure cross sizes. Track per-line consumed main and max cross.
  const lineConsumedMain: number[] = new Array(lineCount)
  const lineCrossSizes: number[] = new Array(lineCount)
  // Baseline layout tracks max ascent (baseline + leading margin) per line so
  // baseline-aligned items can be positioned at maxAscent - childBaseline.
  const lineMaxAscent: number[] = isBaseline ? new Array(lineCount).fill(0) : []
  let maxLineMain = 0
  let totalLinesCross = 0
  for (let li = 0; li < lineCount; li++) {
    const line = lines[li]!
    const lineGap = line.length > 1 ? gapMain * (line.length - 1) : 0
    let lineBasis = lineGap
    for (const c of line) {
      lineBasis += c._flexBasis + childMarginForAxis(c, mainAxis, ownerW)
    }
    // Resolve flexible lengths against available inner main. For indefinite
    // containers with min/max, flex against the clamped size.
    let availMain = innerMainSize
    if (!isDefined(availMain)) {
      const mainOwner = isMainRow ? ownerWidth : ownerHeight
      const minM = resolveValue(
        isMainRow ? style.minWidth : style.minHeight,
        mainOwner,
      )
      const maxM = resolveValue(
        isMainRow ? style.maxWidth : style.maxHeight,
        mainOwner,
      )
      if (isDefined(maxM) && lineBasis > maxM - mainPadBorder) {
        availMain = Math.max(0, maxM - mainPadBorder)
      } else if (isDefined(minM) && lineBasis < minM - mainPadBorder) {
        availMain = Math.max(0, minM - mainPadBorder)
      }
    }
    resolveFlexibleLengths(
      line,
      availMain,
      lineBasis,
      isMainRow,
      ownerW,
      ownerH,
    )

    // Lay out each child in this line to measure cross
    let lineCross = 0
    for (const c of line) {
      const cStyle = c.style
      const childAlign =
        cStyle.alignSelf === Align.Auto ? style.alignItems : cStyle.alignSelf
      const cMarginCross = childMarginForAxis(c, crossAx, ownerW)
      let childCrossSize = NaN
      let childCrossMode: MeasureMode = MeasureMode.Undefined
      const resolvedCrossStyle = resolveValue(
        isMainRow ? cStyle.height : cStyle.width,
        isMainRow ? ownerH : ownerW,
      )
      const crossLeadE = isMainRow ? EDGE_TOP : EDGE_LEFT
      const crossTrailE = isMainRow ? EDGE_BOTTOM : EDGE_RIGHT
      const hasCrossAutoMargin =
        c._hasAutoMargin &&
        (isMarginAuto(cStyle.margin, crossLeadE) ||
          isMarginAuto(cStyle.margin, crossTrailE))
      // Single-line stretch goes directly to the container cross size.
      // Multi-line wrap measures intrinsic cross (Undefined mode) so
      // flex-grow grandchildren don't expand to the container — the line
      // cross size is determined first, then items are re-stretched.
      if (isDefined(resolvedCrossStyle)) {
        childCrossSize = resolvedCrossStyle
        childCrossMode = MeasureMode.Exactly
      } else if (
        childAlign === Align.Stretch &&
        !hasCrossAutoMargin &&
        !isWrap &&
        isDefined(innerCrossSize) &&
        crossMode === MeasureMode.Exactly
      ) {
        childCrossSize = Math.max(0, innerCrossSize - cMarginCross)
        childCrossMode = MeasureMode.Exactly
      } else if (!isWrap && isDefined(innerCrossSize)) {
        childCrossSize = Math.max(0, innerCrossSize - cMarginCross)
        childCrossMode = MeasureMode.AtMost
      }
      const cw = isMainRow ? c._mainSize : childCrossSize
      const ch = isMainRow ? childCrossSize : c._mainSize
      layoutNode(
        c,
        cw,
        ch,
        isMainRow ? MeasureMode.Exactly : childCrossMode,
        isMainRow ? childCrossMode : MeasureMode.Exactly,
        ownerW,
        ownerH,
        performLayout,
        isMainRow,
        !isMainRow,
      )
      c._crossSize = isMainRow ? c.layout.height : c.layout.width
      lineCross = Math.max(lineCross, c._crossSize + cMarginCross)
    }
    // Baseline layout: line cross size must fit maxAscent + maxDescent of
    // baseline-aligned children (yoga STEP 8). Only applies to row direction.
    if (isBaseline) {
      let maxAscent = 0
      let maxDescent = 0
      for (const c of line) {
        if (resolveChildAlign(node, c) !== Align.Baseline) continue
        const mTop = resolveEdge(c.style.margin, EDGE_TOP, ownerW)
        const mBot = resolveEdge(c.style.margin, EDGE_BOTTOM, ownerW)
        const ascent = calculateBaseline(c) + mTop
        const descent = c.layout.height + mTop + mBot - ascent
        if (ascent > maxAscent) maxAscent = ascent
        if (descent > maxDescent) maxDescent = descent
      }
      lineMaxAscent[li] = maxAscent
      if (maxAscent + maxDescent > lineCross) {
        lineCross = maxAscent + maxDescent
      }
    }
    // layoutNode(c) at line ~1117 above already resolved c.layout.margin[] via
    // resolveEdges4Into with the same ownerW — read directly instead of
    // re-resolving through childMarginForAxis → 2× resolveEdge.
    const mainLead = leadingEdge(mainAxis)
    const mainTrail = trailingEdge(mainAxis)
    let consumed = lineGap
    for (const c of line) {
      const cm = c.layout.margin
      consumed += c._mainSize + cm[mainLead]! + cm[mainTrail]!
    }
    lineConsumedMain[li] = consumed
    lineCrossSizes[li] = lineCross
    maxLineMain = Math.max(maxLineMain, consumed)
    totalLinesCross += lineCross
  }
  const totalCrossGap = lineCount > 1 ? gapCross * (lineCount - 1) : 0
  totalLinesCross += totalCrossGap

  // STEP 4: Determine container dimensions. Per yoga's STEP 9, for both
  // AtMost (FitContent) and Undefined (MaxContent) the node sizes to its
  // content — AtMost is NOT a hard clamp, items may overflow the available
  // space (CSS "fit-content" behavior). Only Scroll overflow clamps to the
  // available size. Wrap containers that broke into multiple lines under
  // AtMost fill the available main size since they wrapped at that boundary.
  const isScroll = style.overflow === Overflow.Scroll
  const contentMain = maxLineMain + mainPadBorder
  const finalMainSize =
    mainMode === MeasureMode.Exactly
      ? mainSize
      : mainMode === MeasureMode.AtMost && isScroll
        ? Math.max(Math.min(mainSize, contentMain), mainPadBorder)
        : isWrap && lineCount > 1 && mainMode === MeasureMode.AtMost
          ? mainSize
          : contentMain
  const contentCross = totalLinesCross + crossPadBorder
  const finalCrossSize =
    crossMode === MeasureMode.Exactly
      ? crossSize
      : crossMode === MeasureMode.AtMost && isScroll
        ? Math.max(Math.min(crossSize, contentCross), crossPadBorder)
        : contentCross
  node.layout.width = boundAxis(
    style,
    true,
    isMainRow ? finalMainSize : finalCrossSize,
    ownerWidth,
    ownerHeight,
  )
  node.layout.height = boundAxis(
    style,
    false,
    isMainRow ? finalCrossSize : finalMainSize,
    ownerWidth,
    ownerHeight,
  )
  commitCacheOutputs(node, performLayout)
  // Write cache even for dirty nodes — fresh-mounted items during virtual scroll
  cacheWrite(
    node,
    availableWidth,
    availableHeight,
    widthMode,
    heightMode,
    ownerWidth,
    ownerHeight,
    forceWidth,
    forceHeight,
    wasDirty,
  )

  if (!performLayout) return

  // STEP 5: Position lines (align-content) and children (justify-content +
  // align-items + auto margins).
  const actualInnerMain =
    (isMainRow ? node.layout.width : node.layout.height) - mainPadBorder
  const actualInnerCross =
    (isMainRow ? node.layout.height : node.layout.width) - crossPadBorder
  const mainLeadEdgePhys = leadingEdge(mainAxis)
  const mainTrailEdgePhys = trailingEdge(mainAxis)
  const crossLeadEdgePhys = isMainRow ? EDGE_TOP : EDGE_LEFT
  const crossTrailEdgePhys = isMainRow ? EDGE_BOTTOM : EDGE_RIGHT
  const reversed = isReverse(mainAxis)
  const mainContainerSize = isMainRow ? node.layout.width : node.layout.height
  const crossLead = pad[crossLeadEdgePhys]! + bor[crossLeadEdgePhys]!

  // Align-content: distribute free cross space among lines. Single-line
  // containers use the full cross size for the one line (align-items handles
  // positioning within it).
  let lineCrossOffset = crossLead
  let betweenLines = gapCross
  const freeCross = actualInnerCross - totalLinesCross
  if (lineCount === 1 && !isWrap && !isBaseline) {
    lineCrossSizes[0] = actualInnerCross
  } else {
    const remCross = Math.max(0, freeCross)
    switch (style.alignContent) {
      case Align.FlexStart:
        break
      case Align.Center:
        lineCrossOffset += freeCross / 2
        break
      case Align.FlexEnd:
        lineCrossOffset += freeCross
        break
      case Align.Stretch:
        if (lineCount > 0 && remCross > 0) {
          const add = remCross / lineCount
          for (let i = 0; i < lineCount; i++) lineCrossSizes[i]! += add
        }
        break
      case Align.SpaceBetween:
        if (lineCount > 1) betweenLines += remCross / (lineCount - 1)
        break
      case Align.SpaceAround:
        if (lineCount > 0) {
          betweenLines += remCross / lineCount
          lineCrossOffset += remCross / lineCount / 2
        }
        break
      case Align.SpaceEvenly:
        if (lineCount > 0) {
          betweenLines += remCross / (lineCount + 1)
          lineCrossOffset += remCross / (lineCount + 1)
        }
        break
      default:
        break
    }
  }

  // For wrap-reverse, lines stack from the trailing cross edge. Walk lines in
  // order but flip the cross position within the container.
  const wrapReverse = style.flexWrap === Wrap.WrapReverse
  const crossContainerSize = isMainRow ? node.layout.height : node.layout.width
  let lineCrossPos = lineCrossOffset
  for (let li = 0; li < lineCount; li++) {
    const line = lines[li]!
    const lineCross = lineCrossSizes[li]!
    const consumedMain = lineConsumedMain[li]!
    const n = line.length

    // Re-stretch children whose cross is auto and align is stretch, now that
    // the line cross size is known. Needed for multi-line wrap (line cross
    // wasn't known during initial measure) AND single-line when the container
    // cross was not Exactly (initial stretch at ~line 1250 was skipped because
    // innerCrossSize wasn't defined — the container sized to max child cross).
    if (isWrap || crossMode !== MeasureMode.Exactly) {
      for (const c of line) {
        const cStyle = c.style
        const childAlign =
          cStyle.alignSelf === Align.Auto ? style.alignItems : cStyle.alignSelf
        const crossStyleDef = isDefined(
          resolveValue(
            isMainRow ? cStyle.height : cStyle.width,
            isMainRow ? ownerH : ownerW,
          ),
        )
        const hasCrossAutoMargin =
          c._hasAutoMargin &&
          (isMarginAuto(cStyle.margin, crossLeadEdgePhys) ||
            isMarginAuto(cStyle.margin, crossTrailEdgePhys))
        if (
          childAlign === Align.Stretch &&
          !crossStyleDef &&
          !hasCrossAutoMargin
        ) {
          const cMarginCross = childMarginForAxis(c, crossAx, ownerW)
          const target = Math.max(0, lineCross - cMarginCross)
          if (c._crossSize !== target) {
            const cw = isMainRow ? c._mainSize : target
            const ch = isMainRow ? target : c._mainSize
            layoutNode(
              c,
              cw,
              ch,
              MeasureMode.Exactly,
              MeasureMode.Exactly,
              ownerW,
              ownerH,
              performLayout,
              isMainRow,
              !isMainRow,
            )
            c._crossSize = target
          }
        }
      }
    }

    // Justify-content + auto margins for this line
    let mainOffset = pad[mainLeadEdgePhys]! + bor[mainLeadEdgePhys]!
    let betweenMain = gapMain
    let numAutoMarginsMain = 0
    for (const c of line) {
      if (!c._hasAutoMargin) continue
      if (isMarginAuto(c.style.margin, mainLeadEdgePhys)) numAutoMarginsMain++
      if (isMarginAuto(c.style.margin, mainTrailEdgePhys)) numAutoMarginsMain++
    }
    const freeMain = actualInnerMain - consumedMain
    const remainingMain = Math.max(0, freeMain)
    const autoMarginMainSize =
      numAutoMarginsMain > 0 && remainingMain > 0
        ? remainingMain / numAutoMarginsMain
        : 0
    if (numAutoMarginsMain === 0) {
      switch (style.justifyContent) {
        case Justify.FlexStart:
          break
        case Justify.Center:
          mainOffset += freeMain / 2
          break
        case Justify.FlexEnd:
          mainOffset += freeMain
          break
        case Justify.SpaceBetween:
          if (n > 1) betweenMain += remainingMain / (n - 1)
          break
        case Justify.SpaceAround:
          if (n > 0) {
            betweenMain += remainingMain / n
            mainOffset += remainingMain / n / 2
          }
          break
        case Justify.SpaceEvenly:
          if (n > 0) {
            betweenMain += remainingMain / (n + 1)
            mainOffset += remainingMain / (n + 1)
          }
          break
      }
    }

    const effectiveLineCrossPos = wrapReverse
      ? crossContainerSize - lineCrossPos - lineCross
      : lineCrossPos

    let pos = mainOffset
    for (const c of line) {
      const cMargin = c.style.margin
      // c.layout.margin[] was populated by resolveEdges4Into inside the
      // layoutNode(c) call above (same ownerW). Read resolved values directly
      // instead of re-running the edge fallback chain 4× via resolveEdge.
      // Auto margins resolve to 0 in layout.margin, so autoMarginMainSize
      // substitution still uses the isMarginAuto check against style.
      const cLayoutMargin = c.layout.margin
      let autoMainLead = false
      let autoMainTrail = false
      let autoCrossLead = false
      let autoCrossTrail = false
      let mMainLead: number
      let mMainTrail: number
      let mCrossLead: number
      let mCrossTrail: number
      if (c._hasAutoMargin) {
        autoMainLead = isMarginAuto(cMargin, mainLeadEdgePhys)
        autoMainTrail = isMarginAuto(cMargin, mainTrailEdgePhys)
        autoCrossLead = isMarginAuto(cMargin, crossLeadEdgePhys)
        autoCrossTrail = isMarginAuto(cMargin, crossTrailEdgePhys)
        mMainLead = autoMainLead
          ? autoMarginMainSize
          : cLayoutMargin[mainLeadEdgePhys]!
        mMainTrail = autoMainTrail
          ? autoMarginMainSize
          : cLayoutMargin[mainTrailEdgePhys]!
        mCrossLead = autoCrossLead ? 0 : cLayoutMargin[crossLeadEdgePhys]!
        mCrossTrail = autoCrossTrail ? 0 : cLayoutMargin[crossTrailEdgePhys]!
      } else {
        // Fast path: no auto margins — read resolved values directly.
        mMainLead = cLayoutMargin[mainLeadEdgePhys]!
        mMainTrail = cLayoutMargin[mainTrailEdgePhys]!
        mCrossLead = cLayoutMargin[crossLeadEdgePhys]!
        mCrossTrail = cLayoutMargin[crossTrailEdgePhys]!
      }

      const mainPos = reversed
        ? mainContainerSize - (pos + mMainLead) - c._mainSize
        : pos + mMainLead

      const childAlign =
        c.style.alignSelf === Align.Auto ? style.alignItems : c.style.alignSelf
      let crossPos = effectiveLineCrossPos + mCrossLead
      const crossFree = lineCross - c._crossSize - mCrossLead - mCrossTrail
      if (autoCrossLead && autoCrossTrail) {
        crossPos += Math.max(0, crossFree) / 2
      } else if (autoCrossLead) {
        crossPos += Math.max(0, crossFree)
      } else if (autoCrossTrail) {
        // stays at leading
      } else {
        switch (childAlign) {
          case Align.FlexStart:
          case Align.Stretch:
            if (wrapReverse) crossPos += crossFree
            break
          case Align.Center:
            crossPos += crossFree / 2
            break
          case Align.FlexEnd:
            if (!wrapReverse) crossPos += crossFree
            break
          case Align.Baseline:
            // Row direction only (isBaselineLayout checked this). Position so
            // the child's baseline aligns with the line's max ascent. Per
            // yoga: top = currentLead + maxAscent - childBaseline + leadingPosition.
            if (isBaseline) {
              crossPos =
                effectiveLineCrossPos +
                lineMaxAscent[li]! -
                calculateBaseline(c)
            }
            break
          default:
            break
        }
      }

      // Relative position offsets. Fast path: no position insets set →
      // skip 4× resolveEdgeRaw + 4× resolveValue + 4× isDefined.
      let relX = 0
      let relY = 0
      if (c._hasPosition) {
        const relLeft = resolveValue(
          resolveEdgeRaw(c.style.position, EDGE_LEFT),
          ownerW,
        )
        const relRight = resolveValue(
          resolveEdgeRaw(c.style.position, EDGE_RIGHT),
          ownerW,
        )
        const relTop = resolveValue(
          resolveEdgeRaw(c.style.position, EDGE_TOP),
          ownerW,
        )
        const relBottom = resolveValue(
          resolveEdgeRaw(c.style.position, EDGE_BOTTOM),
          ownerW,
        )
        relX = isDefined(relLeft)
          ? relLeft
          : isDefined(relRight)
            ? -relRight
            : 0
        relY = isDefined(relTop)
          ? relTop
          : isDefined(relBottom)
            ? -relBottom
            : 0
      }

      if (isMainRow) {
        c.layout.left = mainPos + relX
        c.layout.top = crossPos + relY
      } else {
        c.layout.left = crossPos + relX
        c.layout.top = mainPos + relY
      }
      pos += c._mainSize + mMainLead + mMainTrail + betweenMain
    }
    lineCrossPos += lineCross + betweenLines
  }

  // STEP 6: Absolute-positioned children
  for (const c of absChildren) {
    layoutAbsoluteChild(
      node,
      c,
      node.layout.width,
      node.layout.height,
      pad,
      bor,
    )
  }
}

function layoutAbsoluteChild(
  parent: Node,
  child: Node,
  parentWidth: number,
  parentHeight: number,
  pad: [number, number, number, number],
  bor: [number, number, number, number],
): void {
  const cs = child.style
  const posLeft = resolveEdgeRaw(cs.position, EDGE_LEFT)
  const posRight = resolveEdgeRaw(cs.position, EDGE_RIGHT)
  const posTop = resolveEdgeRaw(cs.position, EDGE_TOP)
  const posBottom = resolveEdgeRaw(cs.position, EDGE_BOTTOM)

  const rLeft = resolveValue(posLeft, parentWidth)
  const rRight = resolveValue(posRight, parentWidth)
  const rTop = resolveValue(posTop, parentHeight)
  const rBottom = resolveValue(posBottom, parentHeight)

  // Absolute children's percentage dimensions resolve against the containing
  // block's padding-box (parent size minus border), per CSS §10.1.
  const paddingBoxW = parentWidth - bor[0] - bor[2]
  const paddingBoxH = parentHeight - bor[1] - bor[3]
  let cw = resolveValue(cs.width, paddingBoxW)
  let ch = resolveValue(cs.height, paddingBoxH)

  // If both left+right defined and width not, derive width
  if (!isDefined(cw) && isDefined(rLeft) && isDefined(rRight)) {
    cw = paddingBoxW - rLeft - rRight
  }
  if (!isDefined(ch) && isDefined(rTop) && isDefined(rBottom)) {
    ch = paddingBoxH - rTop - rBottom
  }

  layoutNode(
    child,
    cw,
    ch,
    isDefined(cw) ? MeasureMode.Exactly : MeasureMode.Undefined,
    isDefined(ch) ? MeasureMode.Exactly : MeasureMode.Undefined,
    paddingBoxW,
    paddingBoxH,
    true,
  )

  // Margin of absolute child (applied in addition to insets)
  const mL = resolveEdge(cs.margin, EDGE_LEFT, parentWidth)
  const mT = resolveEdge(cs.margin, EDGE_TOP, parentWidth)
  const mR = resolveEdge(cs.margin, EDGE_RIGHT, parentWidth)
  const mB = resolveEdge(cs.margin, EDGE_BOTTOM, parentWidth)

  const mainAxis = parent.style.flexDirection
  const reversed = isReverse(mainAxis)
  const mainRow = isRow(mainAxis)
  const wrapReverse = parent.style.flexWrap === Wrap.WrapReverse
  // alignSelf overrides alignItems for absolute children (same as flow items)
  const alignment =
    cs.alignSelf === Align.Auto ? parent.style.alignItems : cs.alignSelf

  // Position
  let left: number
  if (isDefined(rLeft)) {
    left = bor[0] + rLeft + mL
  } else if (isDefined(rRight)) {
    left = parentWidth - bor[2] - rRight - child.layout.width - mR
  } else if (mainRow) {
    // Main axis — justify-content, flipped for reversed
    const lead = pad[0] + bor[0]
    const trail = parentWidth - pad[2] - bor[2]
    left = reversed
      ? trail - child.layout.width - mR
      : justifyAbsolute(
          parent.style.justifyContent,
          lead,
          trail,
          child.layout.width,
        ) + mL
  } else {
    left =
      alignAbsolute(
        alignment,
        pad[0] + bor[0],
        parentWidth - pad[2] - bor[2],
        child.layout.width,
        wrapReverse,
      ) + mL
  }

  let top: number
  if (isDefined(rTop)) {
    top = bor[1] + rTop + mT
  } else if (isDefined(rBottom)) {
    top = parentHeight - bor[3] - rBottom - child.layout.height - mB
  } else if (mainRow) {
    top =
      alignAbsolute(
        alignment,
        pad[1] + bor[1],
        parentHeight - pad[3] - bor[3],
        child.layout.height,
        wrapReverse,
      ) + mT
  } else {
    const lead = pad[1] + bor[1]
    const trail = parentHeight - pad[3] - bor[3]
    top = reversed
      ? trail - child.layout.height - mB
      : justifyAbsolute(
          parent.style.justifyContent,
          lead,
          trail,
          child.layout.height,
        ) + mT
  }

  child.layout.left = left
  child.layout.top = top
}

function justifyAbsolute(
  justify: Justify,
  leadEdge: number,
  trailEdge: number,
  childSize: number,
): number {
  switch (justify) {
    case Justify.Center:
      return leadEdge + (trailEdge - leadEdge - childSize) / 2
    case Justify.FlexEnd:
      return trailEdge - childSize
    default:
      return leadEdge
  }
}

function alignAbsolute(
  align: Align,
  leadEdge: number,
  trailEdge: number,
  childSize: number,
  wrapReverse: boolean,
): number {
  // Wrap-reverse flips the cross axis: flex-start/stretch go to trailing,
  // flex-end goes to leading (yoga's absoluteLayoutChild flips the align value
  // when the containing block has wrap-reverse).
  switch (align) {
    case Align.Center:
      return leadEdge + (trailEdge - leadEdge - childSize) / 2
    case Align.FlexEnd:
      return wrapReverse ? leadEdge : trailEdge - childSize
    default:
      return wrapReverse ? trailEdge - childSize : leadEdge
  }
}

function computeFlexBasis(
  child: Node,
  mainAxis: FlexDirection,
  availableMain: number,
  availableCross: number,
  crossMode: MeasureMode,
  ownerWidth: number,
  ownerHeight: number,
): number {
  // Same-generation cache hit: basis was computed THIS calculateLayout, so
  // it's fresh regardless of isDirty_. Covers both clean children (scrolling
  // past unchanged messages) AND fresh-mounted dirty children (virtual
  // scroll mounts new items — the dirty chain's measure→layout cascade
  // invokes this ≥2^depth times, but the child's subtree doesn't change
  // between calls within one calculateLayout). For clean children with
  // cache from a PREVIOUS generation, also hit if inputs match — isDirty_
  // gates since a dirty child's previous-gen cache is stale.
  const sameGen = child._fbGen === _generation
  if (
    (sameGen || !child.isDirty_) &&
    child._fbCrossMode === crossMode &&
    sameFloat(child._fbOwnerW, ownerWidth) &&
    sameFloat(child._fbOwnerH, ownerHeight) &&
    sameFloat(child._fbAvailMain, availableMain) &&
    sameFloat(child._fbAvailCross, availableCross)
  ) {
    return child._fbBasis
  }
  const cs = child.style
  const isMainRow = isRow(mainAxis)

  // Explicit flex-basis
  const basis = resolveValue(cs.flexBasis, availableMain)
  if (isDefined(basis)) {
    const b = Math.max(0, basis)
    child._fbBasis = b
    child._fbOwnerW = ownerWidth
    child._fbOwnerH = ownerHeight
    child._fbAvailMain = availableMain
    child._fbAvailCross = availableCross
    child._fbCrossMode = crossMode
    child._fbGen = _generation
    return b
  }

  // Style dimension on main axis
  const mainStyleDim = isMainRow ? cs.width : cs.height
  const mainOwner = isMainRow ? ownerWidth : ownerHeight
  const resolved = resolveValue(mainStyleDim, mainOwner)
  if (isDefined(resolved)) {
    const b = Math.max(0, resolved)
    child._fbBasis = b
    child._fbOwnerW = ownerWidth
    child._fbOwnerH = ownerHeight
    child._fbAvailMain = availableMain
    child._fbAvailCross = availableCross
    child._fbCrossMode = crossMode
    child._fbGen = _generation
    return b
  }

  // Need to measure the child to get its natural size
  const crossStyleDim = isMainRow ? cs.height : cs.width
  const crossOwner = isMainRow ? ownerHeight : ownerWidth
  let crossConstraint = resolveValue(crossStyleDim, crossOwner)
  let crossConstraintMode: MeasureMode = isDefined(crossConstraint)
    ? MeasureMode.Exactly
    : MeasureMode.Undefined
  if (!isDefined(crossConstraint) && isDefined(availableCross)) {
    crossConstraint = availableCross
    crossConstraintMode =
      crossMode === MeasureMode.Exactly && isStretchAlign(child)
        ? MeasureMode.Exactly
        : MeasureMode.AtMost
  }

  // Upstream yoga (YGNodeComputeFlexBasisForChild) passes the available inner
  // width with mode AtMost when the subtree will call a measure-func — so text
  // nodes don't report unconstrained intrinsic width as flex-basis, which
  // would force siblings to shrink and the text to wrap at the wrong width.
  // Passing Undefined here made Ink's <Text> inside <Box flexGrow={1}> get
  // width = intrinsic instead of available, dropping chars at wrap boundaries.
  //
  // Two constraints on when this applies:
  //   - Width only. Height is never constrained during basis measurement —
  //     column containers must measure children at natural height so
  //     scrollable content can overflow (constraining height clips ScrollBox).
  //   - Subtree has a measure-func. Pure layout subtrees (no measure-func)
  //     with flex-grow children would grow into the AtMost constraint,
  //     inflating the basis (breaks YGMinMaxDimensionTest flex_grow_in_at_most
  //     where a flexGrow:1 child should stay at basis 0, not grow to 100).
  let mainConstraint = NaN
  let mainConstraintMode: MeasureMode = MeasureMode.Undefined
  if (isMainRow && isDefined(availableMain) && hasMeasureFuncInSubtree(child)) {
    mainConstraint = availableMain
    mainConstraintMode = MeasureMode.AtMost
  }

  const mw = isMainRow ? mainConstraint : crossConstraint
  const mh = isMainRow ? crossConstraint : mainConstraint
  const mwMode = isMainRow ? mainConstraintMode : crossConstraintMode
  const mhMode = isMainRow ? crossConstraintMode : mainConstraintMode

  layoutNode(child, mw, mh, mwMode, mhMode, ownerWidth, ownerHeight, false)
  const b = isMainRow ? child.layout.width : child.layout.height
  child._fbBasis = b
  child._fbOwnerW = ownerWidth
  child._fbOwnerH = ownerHeight
  child._fbAvailMain = availableMain
  child._fbAvailCross = availableCross
  child._fbCrossMode = crossMode
  child._fbGen = _generation
  return b
}

function hasMeasureFuncInSubtree(node: Node): boolean {
  if (node.measureFunc) return true
  for (const c of node.children) {
    if (hasMeasureFuncInSubtree(c)) return true
  }
  return false
}

function resolveFlexibleLengths(
  children: Node[],
  availableInnerMain: number,
  totalFlexBasis: number,
  isMainRow: boolean,
  ownerW: number,
  ownerH: number,
): void {
  // Multi-pass flex distribution per CSS flexbox spec §9.7 "Resolving Flexible
  // Lengths": distribute free space, detect min/max violations, freeze all
  // violators, redistribute among unfrozen children. Repeat until stable.
  const n = children.length
  const frozen: boolean[] = new Array(n).fill(false)
  const initialFree = isDefined(availableInnerMain)
    ? availableInnerMain - totalFlexBasis
    : 0
  // Freeze inflexible items at their clamped basis
  for (let i = 0; i < n; i++) {
    const c = children[i]!
    const clamped = boundAxis(c.style, isMainRow, c._flexBasis, ownerW, ownerH)
    const inflexible =
      !isDefined(availableInnerMain) ||
      (initialFree >= 0 ? c.style.flexGrow === 0 : c.style.flexShrink === 0)
    if (inflexible) {
      c._mainSize = Math.max(0, clamped)
      frozen[i] = true
    } else {
      c._mainSize = c._flexBasis
    }
  }
  // Iteratively distribute until no violations. Free space is recomputed each
  // pass: initial free space minus the delta frozen children consumed beyond
  // (or below) their basis.
  const unclamped: number[] = new Array(n)
  for (let iter = 0; iter <= n; iter++) {
    let frozenDelta = 0
    let totalGrow = 0
    let totalShrinkScaled = 0
    let unfrozenCount = 0
    for (let i = 0; i < n; i++) {
      const c = children[i]!
      if (frozen[i]) {
        frozenDelta += c._mainSize - c._flexBasis
      } else {
        totalGrow += c.style.flexGrow
        totalShrinkScaled += c.style.flexShrink * c._flexBasis
        unfrozenCount++
      }
    }
    if (unfrozenCount === 0) break
    let remaining = initialFree - frozenDelta
    // Spec §9.7 step 4c: if sum of flex factors < 1, only distribute
    // initialFree × sum, not the full remaining space (partial flex).
    if (remaining > 0 && totalGrow > 0 && totalGrow < 1) {
      const scaled = initialFree * totalGrow
      if (scaled < remaining) remaining = scaled
    } else if (remaining < 0 && totalShrinkScaled > 0) {
      let totalShrink = 0
      for (let i = 0; i < n; i++) {
        if (!frozen[i]) totalShrink += children[i]!.style.flexShrink
      }
      if (totalShrink < 1) {
        const scaled = initialFree * totalShrink
        if (scaled > remaining) remaining = scaled
      }
    }
    // Compute targets + violations for all unfrozen children
    let totalViolation = 0
    for (let i = 0; i < n; i++) {
      if (frozen[i]) continue
      const c = children[i]!
      let t = c._flexBasis
      if (remaining > 0 && totalGrow > 0) {
        t += (remaining * c.style.flexGrow) / totalGrow
      } else if (remaining < 0 && totalShrinkScaled > 0) {
        t +=
          (remaining * (c.style.flexShrink * c._flexBasis)) / totalShrinkScaled
      }
      unclamped[i] = t
      const clamped = Math.max(
        0,
        boundAxis(c.style, isMainRow, t, ownerW, ownerH),
      )
      c._mainSize = clamped
      totalViolation += clamped - t
    }
    // Freeze per spec §9.7 step 5: if totalViolation is zero freeze all; if
    // positive freeze min-violators; if negative freeze max-violators.
    if (totalViolation === 0) break
    let anyFrozen = false
    for (let i = 0; i < n; i++) {
      if (frozen[i]) continue
      const v = children[i]!._mainSize - unclamped[i]!
      if ((totalViolation > 0 && v > 0) || (totalViolation < 0 && v < 0)) {
        frozen[i] = true
        anyFrozen = true
      }
    }
    if (!anyFrozen) break
  }
}

function isStretchAlign(child: Node): boolean {
  const p = child.parent
  if (!p) return false
  const align =
    child.style.alignSelf === Align.Auto
      ? p.style.alignItems
      : child.style.alignSelf
  return align === Align.Stretch
}

function resolveChildAlign(parent: Node, child: Node): Align {
  return child.style.alignSelf === Align.Auto
    ? parent.style.alignItems
    : child.style.alignSelf
}

// Baseline of a node per CSS Flexbox §8.5 / yoga's YGBaseline. Leaf nodes
// (no children) use their own height. Containers recurse into the first
// baseline-aligned child on the first line (or the first flow child if none
// are baseline-aligned), returning that child's baseline + its top offset.
function calculateBaseline(node: Node): number {
  let baselineChild: Node | null = null
  for (const c of node.children) {
    if (c._lineIndex > 0) break
    if (c.style.positionType === PositionType.Absolute) continue
    if (c.style.display === Display.None) continue
    if (
      resolveChildAlign(node, c) === Align.Baseline ||
      c.isReferenceBaseline_
    ) {
      baselineChild = c
      break
    }
    if (baselineChild === null) baselineChild = c
  }
  if (baselineChild === null) return node.layout.height
  return calculateBaseline(baselineChild) + baselineChild.layout.top
}

// A container uses baseline layout only for row direction, when either
// align-items is baseline or any flow child has align-self: baseline.
function isBaselineLayout(node: Node, flowChildren: Node[]): boolean {
  if (!isRow(node.style.flexDirection)) return false
  if (node.style.alignItems === Align.Baseline) return true
  for (const c of flowChildren) {
    if (c.style.alignSelf === Align.Baseline) return true
  }
  return false
}

function childMarginForAxis(
  child: Node,
  axis: FlexDirection,
  ownerWidth: number,
): number {
  if (!child._hasMargin) return 0
  const lead = resolveEdge(child.style.margin, leadingEdge(axis), ownerWidth)
  const trail = resolveEdge(child.style.margin, trailingEdge(axis), ownerWidth)
  return lead + trail
}

function resolveGap(style: Style, gutter: Gutter, ownerSize: number): number {
  let v = style.gap[gutter]!
  if (v.unit === Unit.Undefined) v = style.gap[Gutter.All]!
  const r = resolveValue(v, ownerSize)
  return isDefined(r) ? Math.max(0, r) : 0
}

function boundAxis(
  style: Style,
  isWidth: boolean,
  value: number,
  ownerWidth: number,
  ownerHeight: number,
): number {
  const minV = isWidth ? style.minWidth : style.minHeight
  const maxV = isWidth ? style.maxWidth : style.maxHeight
  const minU = minV.unit
  const maxU = maxV.unit
  // Fast path: no min/max constraints set. Per CPU profile this is the
  // overwhelmingly common case (~32k calls/layout on the 1000-node bench,
  // nearly all with undefined min/max) — skipping 2× resolveValue + 2× isNaN
  // that always no-op. Unit.Undefined = 0.
  if (minU === 0 && maxU === 0) return value
  const owner = isWidth ? ownerWidth : ownerHeight
  let v = value
  // Inlined resolveValue: Unit.Point=1, Unit.Percent=2. `m === m` is !isNaN.
  if (maxU === 1) {
    if (v > maxV.value) v = maxV.value
  } else if (maxU === 2) {
    const m = (maxV.value * owner) / 100
    if (m === m && v > m) v = m
  }
  if (minU === 1) {
    if (v < minV.value) v = minV.value
  } else if (minU === 2) {
    const m = (minV.value * owner) / 100
    if (m === m && v < m) v = m
  }
  return v
}

function zeroLayoutRecursive(node: Node): void {
  for (const c of node.children) {
    c.layout.left = 0
    c.layout.top = 0
    c.layout.width = 0
    c.layout.height = 0
    // Invalidate layout cache — without this, unhide → calculateLayout finds
    // the child clean (!isDirty_) with _hasL intact, hits the cache at line
    // ~1086, restores stale _lOutW/_lOutH, and returns early — skipping the
    // child-positioning recursion. Grandchildren stay at (0,0,0,0) from the
    // zeroing above and render invisible. isDirty_=true also gates _cN and
    // _fbBasis via their (sameGen || !isDirty_) checks — _cGen/_fbGen freeze
    // during hide so sameGen is false on unhide.
    c.isDirty_ = true
    c._hasL = false
    c._hasM = false
    zeroLayoutRecursive(c)
  }
}

function collectLayoutChildren(node: Node, flow: Node[], abs: Node[]): void {
  // Partition a node's children into flow and absolute lists, flattening
  // display:contents subtrees so their children are laid out as direct
  // children of this node (per CSS display:contents spec — the box is removed
  // from the layout tree but its children remain, lifted to the grandparent).
  for (const c of node.children) {
    const disp = c.style.display
    if (disp === Display.None) {
      c.layout.left = 0
      c.layout.top = 0
      c.layout.width = 0
      c.layout.height = 0
      zeroLayoutRecursive(c)
    } else if (disp === Display.Contents) {
      c.layout.left = 0
      c.layout.top = 0
      c.layout.width = 0
      c.layout.height = 0
      // Recurse — nested display:contents lifts all the way up. The contents
      // node's own margin/padding/position/dimensions are ignored.
      collectLayoutChildren(c, flow, abs)
    } else if (c.style.positionType === PositionType.Absolute) {
      abs.push(c)
    } else {
      flow.push(c)
    }
  }
}

function roundLayout(
  node: Node,
  scale: number,
  absLeft: number,
  absTop: number,
): void {
  if (scale === 0) return
  const l = node.layout
  const nodeLeft = l.left
  const nodeTop = l.top
  const nodeWidth = l.width
  const nodeHeight = l.height

  const absNodeLeft = absLeft + nodeLeft
  const absNodeTop = absTop + nodeTop

  // Upstream YGRoundValueToPixelGrid: text nodes (has measureFunc) floor their
  // positions so wrapped text never starts past its allocated column. Width
  // uses ceil-if-fractional to avoid clipping the last glyph. Non-text nodes
  // use standard round. Matches yoga's PixelGrid.cpp — without this, justify
  // center/space-evenly positions are off-by-one vs WASM and flex-shrink
  // overflow places siblings at the wrong column.
  const isText = node.measureFunc !== null
  l.left = roundValue(nodeLeft, scale, false, isText)
  l.top = roundValue(nodeTop, scale, false, isText)

  // Width/height rounded via absolute edges to avoid cumulative drift
  const absRight = absNodeLeft + nodeWidth
  const absBottom = absNodeTop + nodeHeight
  const hasFracW = !isWholeNumber(nodeWidth * scale)
  const hasFracH = !isWholeNumber(nodeHeight * scale)
  l.width =
    roundValue(absRight, scale, isText && hasFracW, isText && !hasFracW) -
    roundValue(absNodeLeft, scale, false, isText)
  l.height =
    roundValue(absBottom, scale, isText && hasFracH, isText && !hasFracH) -
    roundValue(absNodeTop, scale, false, isText)

  for (const c of node.children) {
    roundLayout(c, scale, absNodeLeft, absNodeTop)
  }
}

function isWholeNumber(v: number): boolean {
  const frac = v - Math.floor(v)
  return frac < 0.0001 || frac > 0.9999
}

function roundValue(
  v: number,
  scale: number,
  forceCeil: boolean,
  forceFloor: boolean,
): number {
  let scaled = v * scale
  let frac = scaled - Math.floor(scaled)
  if (frac < 0) frac += 1
  // Float-epsilon tolerance matches upstream YGDoubleEqual (1e-4)
  if (frac < 0.0001) {
    scaled = Math.floor(scaled)
  } else if (frac > 0.9999) {
    scaled = Math.ceil(scaled)
  } else if (forceCeil) {
    scaled = Math.ceil(scaled)
  } else if (forceFloor) {
    scaled = Math.floor(scaled)
  } else {
    // Round half-up (>= 0.5 goes up), per upstream
    scaled = Math.floor(scaled) + (frac >= 0.4999 ? 1 : 0)
  }
  return scaled / scale
}

// --
// Helpers

function parseDimension(v: number | string | undefined): Value {
  if (v === undefined) return UNDEFINED_VALUE
  if (v === 'auto') return AUTO_VALUE
  if (typeof v === 'number') {
    // WASM yoga's YGFloatIsUndefined treats NaN and ±Infinity as undefined.
    // Ink passes height={Infinity} (e.g. LogSelector maxHeight default) and
    // expects it to mean "unconstrained" — storing it as a literal point value
    // makes the node height Infinity and breaks all downstream layout.
    return Number.isFinite(v) ? pointValue(v) : UNDEFINED_VALUE
  }
  if (typeof v === 'string' && v.endsWith('%')) {
    return percentValue(parseFloat(v))
  }
  const n = parseFloat(v)
  return isNaN(n) ? UNDEFINED_VALUE : pointValue(n)
}

function physicalEdge(edge: Edge): number {
  switch (edge) {
    case Edge.Left:
    case Edge.Start:
      return EDGE_LEFT
    case Edge.Top:
      return EDGE_TOP
    case Edge.Right:
    case Edge.End:
      return EDGE_RIGHT
    case Edge.Bottom:
      return EDGE_BOTTOM
    default:
      return EDGE_LEFT
  }
}

// --
// Module API matching yoga-layout/load

export type Yoga = {
  Config: {
    create(): Config
    destroy(config: Config): void
  }
  Node: {
    create(config?: Config): Node
    createDefault(): Node
    createWithConfig(config: Config): Node
    destroy(node: Node): void
  }
}

const YOGA_INSTANCE: Yoga = {
  Config: {
    create: createConfig,
    destroy() {},
  },
  Node: {
    create: (config?: Config) => new Node(config),
    createDefault: () => new Node(),
    createWithConfig: (config: Config) => new Node(config),
    destroy() {},
  },
}

export function loadYoga(): Promise<Yoga> {
  return Promise.resolve(YOGA_INSTANCE)
}

export default YOGA_INSTANCE