arthur/js/selftest.js

// Assertions over the stages below detection. Runs in the browser so the exact
// module graph the tool uses is what gets tested.
//
// The ring-simplicity check exists because "fixed topology" is load-bearing in
// docs/design.md: because hold parts CUT between poses rather than
// interpolating, a ring whose vertex order is wrong self-intersects and renders
// as blocks meeting at corners. It is invisible at some vertex counts and obvious
// at others, so it needs an assertion rather than an eyeball.

import { LIPS_OUTER, LIPS_INNER, FACE_OVAL, RIGID, subsampleSlots, subsampleRing,
         EYE_R_RING, EYE_L_RING, EYE_R_CORNERS, EYE_L_CORNERS,
         EYE_R_LIDS, EYE_L_LIDS, BROW_A_RING, BROW_B_RING,
         BROW_END_0, BROW_END_1 } from './landmarks.js';
import { fitSimilarity, applySim, procrustesMean, smoothTransforms, offsetRing } from './mathutil.js';
import { stabilize, toRasterRing, smoothContours, selectKeys, activeKey, shiftIndex,
         exposeIndex, eyeSignals, pairIrises, gazeOrigin, quantizeSnap, resolveBlink,
         browSignals, pairBrows } from './pipeline.js';
import { IndexedRaster, hexToRgb } from './raster.js';
import { writeTake } from './take.js';
import { otsuForTest, scaleRing } from './interior.js';
import { synthDense } from './synth.js';

const results = [];
const ok = (name, cond, detail = '') => results.push({ name, pass: !!cond, detail });

/* ---- geometry helpers ---- */

function segmentsCross(a, b, c, d) {
  const o = (p, q, r) => Math.sign((q.x - p.x) * (r.y - p.y) - (q.y - p.y) * (r.x - p.x));
  const o1 = o(a, b, c), o2 = o(a, b, d), o3 = o(c, d, a), o4 = o(c, d, b);
  return o1 !== o2 && o3 !== o4 && o1 !== 0 && o2 !== 0 && o3 !== 0 && o4 !== 0;
}

// A closed ring is simple if no pair of non-adjacent edges crosses.
function ringSelfIntersections(pts) {
  const n = pts.length, hits = [];
  for (let i = 0; i < n; i++) {
    for (let j = i + 1; j < n; j++) {
      if (i === j || (j + 1) % n === i || (i + 1) % n === j) continue;
      if (segmentsCross(pts[i], pts[(i + 1) % n], pts[j], pts[(j + 1) % n])) hits.push([i, j]);
    }
  }
  return hits;
}

const spreadX = (frames, slot) => {
  const xs = frames.map((f) => f[slot].x);
  return Math.max(...xs) - Math.min(...xs);
};

/* ---- the tests ---- */

// Cross-check every el('id') in app.js against the ids in index.html.
//
// This bug class has bitten twice: a knob wired in app.js but absent from the
// markup throws during wiring, which aborts the rest of the module and leaves a
// blank page. The symptom ("nothing happens") points nowhere near the cause, so
// it is worth an automated check rather than vigilance.
export async function runWiring() {
  const out = [];
  try {
    const [app, html] = await Promise.all([
      fetch('./js/app.js').then((r) => r.text()),
      fetch('./index.html').then((r) => r.text()),
    ]);
    const ids = new Set([...app.matchAll(/\bel\(\s*['"]([\w-]+)['"]\s*\)/g)].map((m) => m[1]));
    const list = app.match(/for \(const id of \[([\s\S]*?)\]\)/);
    if (list) {
      for (const m of list[1].matchAll(/'([\w]+)'/g)) { ids.add(m[1]); ids.add(m[1] + 'v'); }
    }
    // Duplicate keys in an object literal are silent in JS - the last one wins.
    // In opts() that meant the teeth vertex slider was quietly driving the lip
    // vertex count while the lip slider did nothing at all.
    const lit = app.match(/const opts = \(\) => \(\{([\s\S]*?)\n\}\);/);
    if (lit) {
      const keys = [...lit[1].matchAll(/^\s*([A-Za-z_$][\w$]*)\s*:/gm)].map((m) => m[1]);
      const dupes = keys.filter((k, i) => keys.indexOf(k) !== i);
      out.push({ name: `opts() has no duplicate keys (${keys.length} checked)`,
                 pass: dupes.length === 0, detail: [...new Set(dupes)].join(', ') });
    } else {
      out.push({ name: 'opts() literal found for duplicate-key check', pass: false, detail: '' });
    }

    const have = new Set([...html.matchAll(/id="([\w-]+)"/g)].map((m) => m[1]));
    const missing = [...ids].filter((i) => !have.has(i));
    out.push({ name: `every el() id exists in index.html (${ids.size} checked)`,
               pass: missing.length === 0, detail: missing.join(', ') });
    const unused = [...have].filter((i) => !ids.has(i));
    out.push({ name: 'no orphaned ids in index.html', pass: unused.length === 0,
               detail: unused.join(', ') });
  } catch (e) {
    out.push({ name: 'wiring check ran', pass: false, detail: e.message });
  }
  return out;
}

export function run() {
  results.length = 0;

  // tables
  ok('LIPS_OUTER has 20 distinct ids', new Set(LIPS_OUTER).size === 20);
  ok('LIPS_INNER has 20 distinct ids', new Set(LIPS_INNER).size === 20);
  ok('FACE_OVAL has 36 distinct ids', new Set(FACE_OVAL).size === 36);
  ok('RIGID excludes every lip vertex',
     !RIGID.some((i) => LIPS_OUTER.includes(i) || LIPS_INNER.includes(i)),
     'a moving feature in the rigid set bleeds performance into stabilisation');

  // subsampling preserves order and count at every budget
  for (let n = 4; n <= 16; n += 2) {
    const s = subsampleSlots(20, n);
    const mono = s.every((v, i) => i === 0 || v > s[i - 1]);
    ok(`subsampleSlots(20,${n}) is strictly increasing, n=${n}`, mono && s.length === n, s.join(','));
  }
  ok('subsampleRing agrees with subsampleSlots',
     subsampleRing(LIPS_OUTER, 8).join(',') === subsampleSlots(20, 8).map((s) => LIPS_OUTER[s]).join(','));

  const dense = synthDense(72);

  // rings must be simple at EVERY vertex budget, on every frame
  for (const [label, table] of [['outer', LIPS_OUTER], ['inner', LIPS_INNER]]) {
    let worst = null;
    for (let n = 4; n <= 16 && !worst; n += 2) {
      const slots = subsampleSlots(table.length, n);
      for (let f = 0; f < dense.length; f++) {
        const pts = slots.map((s) => dense[f][table[s]]);
        const hits = ringSelfIntersections(pts);
        if (hits.length) { worst = `verts=${n} frame=${f} edges ${JSON.stringify(hits[0])}`; break; }
      }
    }
    ok(`${label} ring is simple at every vertex budget`, !worst, worst || '');
  }

  // FACE_OVAL traversal: never checked before, and a wrong ordering here shows up
  // as a lumpy plate rather than an obvious bowtie, so it needs asserting.
  {
    let bad = null;
    for (let f = 0; f < dense.length && !bad; f++) {
      const h = ringSelfIntersections(FACE_OVAL.map((i) => dense[f][i]));
      if (h.length) bad = `frame ${f} edges ${JSON.stringify(h[0])}`;
    }
    ok('FACE_OVAL is a simple ring on every frame', !bad, bad || '');
  }

  // similarity fit recovers a known transform
  const src = [{ x: 0, y: 0 }, { x: 1, y: 0 }, { x: 0, y: 1 }, { x: 2, y: 3 }];
  const truth = { s: 1.7, theta: 0.6, tx: 4, ty: -2 };
  const dst = src.map((p) => applySim(truth, p));
  const got = fitSimilarity(src, dst);
  ok('fitSimilarity recovers a known transform',
     Math.abs(got.s - truth.s) < 1e-9 && Math.abs(got.theta - truth.theta) < 1e-9 &&
     Math.abs(got.tx - truth.tx) < 1e-9 && Math.abs(got.ty - truth.ty) < 1e-9,
     `s=${got.s.toFixed(6)} th=${got.theta.toFixed(6)}`);

  // stabilisation: head motion out, mouth motion kept
  const stab = stabilize(dense, 0);
  const rawSpread = spreadX(dense, 133);
  const stabSpread = (() => {
    const xs = stab.eyes.map((e) => e[0].x);
    return Math.max(...xs) - Math.min(...xs);
  })();
  ok('stabilisation removes >90% of head translation',
     stabSpread < rawSpread * 0.1, `raw ${rawSpread.toFixed(4)} -> ${stabSpread.toFixed(4)}`);
  const apRange = Math.max(...stab.aperture) - Math.min(...stab.aperture);
  ok('stabilisation preserves mouth motion', apRange > 0.05, `aperture range ${apRange.toFixed(4)}`);

  // ASPECT: a shape that is circular in PIXEL space must stay circular in raster
  // space. MediaPipe normalises x by width and y by height, so for a portrait
  // frame equal normalised numbers are unequal pixel distances; feeding those
  // straight through stretches everything horizontally by H/W. This asserts the
  // isotropic conversion, and fails at ~1.78 for a 1080x1920 clip without it.
  for (const [W, H] of [[1080, 1920], [1920, 1080], [640, 640]]) {
    const aspect = W / H;
    const N = 24, cx = 0.5, cy = 0.5, rPx = 200;
    // a true circle of radius rPx, expressed in MediaPipe normalised coords
    const circleFrames = [];
    for (let t = 0; t < 4; t++) {
      const pts = new Array(478).fill(null).map(() => ({ x: 0.5, y: 0.5, z: 0 }));
      RIGID.forEach((id, k) => {
        const a = (k / RIGID.length) * Math.PI * 2;
        pts[id] = { x: cx + (120 * Math.cos(a)) / W, y: cy + (120 * Math.sin(a)) / H, z: 0 };
      });
      LIPS_OUTER.forEach((id, k) => {
        const a = -(k / LIPS_OUTER.length) * Math.PI * 2;
        pts[id] = { x: cx + (rPx * Math.cos(a)) / W, y: cy + (rPx * Math.sin(a)) / H, z: 0 };
      });
      FACE_OVAL.forEach((id, k) => {
        const a = -(k / FACE_OVAL.length) * Math.PI * 2;
        pts[id] = { x: cx + (420 * Math.cos(a)) / W, y: cy + (420 * Math.sin(a)) / H, z: 0 };
      });
      circleFrames.push(pts);
    }
    const st2 = stabilize(circleFrames, 0, aspect);
    const ring = toRasterRing(st2.outer[0], LIPS_OUTER, 16, (p) => p);
    const xs = ring.map((p) => p.x), ys = ring.map((p) => p.y);
    const ratio = (Math.max(...xs) - Math.min(...xs)) / (Math.max(...ys) - Math.min(...ys));
    ok(`circle stays circular at ${W}x${H}`, Math.abs(ratio - 1) < 0.02,
       `w/h ratio ${ratio.toFixed(4)}`);
  }

  // key selection
  const xf = (p) => ({ x: p.x * 320, y: p.y * 200 });
  const shapes = stab.outer.map((r) => toRasterRing(r, LIPS_OUTER, 8, xf));
  const sel = selectKeys(shapes, { minHold: 2, distThresh: 0.6, velSmooth: 3, exposure: 2 });
  ok('keys are strictly increasing in f', sel.keys.every((k, i) => i === 0 || k.f > sel.keys[i - 1].f));
  ok('keys respect the minimum hold',
     sel.keys.every((k, i) => i === 0 || k.src - sel.keys[i - 1].src >= 2));
  ok('keys land on the exposure grid', sel.keys.every((k) => k.f % 2 === 0));
  ok('selection reduces candidates', sel.keys.length < sel.candidates.length,
     `${sel.candidates.length} candidates -> ${sel.keys.length} keys`);
  ok('first key is frame 0', sel.keys[0].f === 0);
  ok('activeKey holds between keys',
     activeKey(sel.keys, sel.keys[1].f - 1).f === sel.keys[0].f);

  // exposure: rip dense, choose the timing here. On 2s every odd frame must
  // reuse the even frame's pose, and the grid must never read from the future -
  // that direction is the lead, which is a different control for a reason.
  ok('exposure 1 is identity', [0, 1, 7, 71].every((f) => exposeIndex(f, 1) === f));
  ok('on 2s holds each pose for two frames',
     [0, 1, 2, 3, 4, 5].map((f) => exposeIndex(f, 2)).join(',') === '0,0,2,2,4,4');
  ok('on 3s holds each pose for three frames',
     [0, 1, 2, 3, 4, 5, 6].map((f) => exposeIndex(f, 3)).join(',') === '0,0,0,3,3,3,6');
  ok('exposure never reads a pose from the future',
     [0, 1, 2, 3, 4, 5, 6, 7].every((f) => exposeIndex(f, 3) <= f));
  {
    // Exposure then lead, in that order: the picture must change on the grid
    // beats and carry a pose shifted by whole frames of the original track.
    const N = 72, at = (f) => shiftIndex(exposeIndex(f, 2), 1, N);
    ok('exposure and lead compose without moving the beats',
       at(0) === 1 && at(1) === 1 && at(2) === 3 && at(3) === 3,
       [0, 1, 2, 3].map(at).join(','));
  }

  // mouth lead: a shift that "feels like it does nothing" is indistinguishable
  // from one that does nothing, so assert the arithmetic directly.
  ok('lead 0 is identity', [0, 5, 71].every((f) => shiftIndex(f, 0, 72) === f));
  ok('positive lead moves the source frame forward', shiftIndex(10, 2, 72) === 12);
  ok('negative lead moves it back', shiftIndex(10, -3, 72) === 7);
  ok('lead clamps at the start', shiftIndex(1, -6, 72) === 0);
  ok('lead clamps at the end', shiftIndex(70, 6, 72) === 71);
  {
    // ...and that it selects different POSES, not merely different indices.
    // Checked across the whole track rather than at one pair: synthetic poses
    // hold for nine-frame beats, so any single pair can legitimately be
    // identical while the shift works perfectly.
    const N = shapes.length;
    let moved = 0, total = 0;
    for (let f = 0; f < N; f++) {
      const a = shapes[shiftIndex(f, 0, N)], b = shapes[shiftIndex(f, 3, N)];
      let d = 0;
      for (let i = 0; i < a.length; i++) d += Math.hypot(a[i].x - b[i].x, a[i].y - b[i].y);
      total++;
      if (d / a.length > 0.5) moved++;
    }
    ok('a lead of 3 changes the pose on a good share of frames', moved / total > 0.2,
       `${moved}/${total} frames differ`);
  }

  // rasteriser: indexed, hard-edged, no blending
  const r = new IndexedRaster(64, 48);
  r.clear(0);
  r.fillPoly([{ x: 8, y: 8 }, { x: 56, y: 8 }, { x: 56, y: 40 }, { x: 8, y: 40 }], 2);
  const present = new Set(r.buf);
  ok('raster contains only written indices', present.size === 2 && present.has(0) && present.has(2),
     `indices ${[...present].join(',')}`);
  let count = 0;
  for (const v of r.buf) if (v === 2) count++;
  ok('axis-aligned rect fills the exact pixel count', count === 48 * 32, `${count} vs ${48 * 32}`);
  const pal = ['#000000', '#ffffff', '#ff8800'];
  const img = r.toImageData(pal, 2);
  const seen = new Set();
  for (let i = 0; i < img.data.length; i += 4) {
    seen.add(`${img.data[i]},${img.data[i + 1]},${img.data[i + 2]}`);
  }
  const allowed = new Set(pal.map((h) => hexToRgb(h).join(',')));
  ok('palette expansion introduces no intermediate colours',
     [...seen].every((c) => allowed.has(c)), `${seen.size} distinct colours`);

  // scaleRing is what pulls the sampled region in from MediaPipe's inner lip
  // landmarks, which sit slightly outside the real opening.
  {
    const ring = [{ x: 0, y: 0 }, { x: 10, y: 0 }, { x: 10, y: 10 }, { x: 0, y: 10 }];
    const small = scaleRing(ring, 0.5);
    const w = Math.max(...small.map((p) => p.x)) - Math.min(...small.map((p) => p.x));
    ok('scaleRing(0.5) halves the extent', Math.abs(w - 5) < 1e-9, `width ${w}`);
    const same = scaleRing(ring, 1);
    ok('scaleRing(1) is identity', same.every((p, i) => Math.abs(p.x - ring[i].x) < 1e-9));
    let cx = 0; for (const p of small) cx += p.x;
    ok('scaleRing keeps the centroid', Math.abs(cx / 4 - 5) < 1e-9);
  }

  // Otsu on a uniform region must report near-zero class separation. It will
  // still return a threshold - that is what Otsu does - so the separation is the
  // only thing that distinguishes "found teeth" from "split noise in a dark
  // mouth", which is what made the band fill the whole cavity.
  {
    const flat = new Uint32Array(256); flat[40] = 500;
    const f = otsuForTest(flat, 500);
    ok('uniform region yields ~no class separation',
       Math.abs(f.mBright - f.mDark) / 255 < 0.02, `sep ${((f.mBright - f.mDark) / 255).toFixed(4)}`);

    const noisy = new Uint32Array(256);
    for (let i = 30; i <= 60; i++) noisy[i] = 20;          // dark cavity, some spread
    const nz = otsuForTest(noisy, 31 * 20);
    ok('dark-but-noisy region stays below a sane gate',
       (nz.mBright - nz.mDark) / 255 < 0.14, `sep ${((nz.mBright - nz.mDark) / 255).toFixed(4)}`);

    const teeth = new Uint32Array(256);
    for (let i = 20; i <= 45; i++) teeth[i] = 40;          // cavity
    for (let i = 180; i <= 220; i++) teeth[i] = 30;        // teeth
    const tt = otsuForTest(teeth, 26 * 40 + 41 * 30);
    ok('real bright/dark split clears the gate',
       (tt.mBright - tt.mDark) / 255 > 0.4, `sep ${((tt.mBright - tt.mDark) / 255).toFixed(4)}`);
  }

  /* ---- eyes ---- */

  ok('eye rings have 16 distinct ids each',
     new Set(EYE_R_RING).size === 16 && new Set(EYE_L_RING).size === 16);
  ok('the two eye rings share no landmark',
     !EYE_R_RING.some((i) => EYE_L_RING.includes(i)));

  // The cardinal contract, asserted rather than trusted: on a 16-slot ring the
  // quarter slots must be the four anatomical cardinals, which is what makes
  // every even vertex budget land on real landmarks instead of between them.
  ok('eye ring slot 0/4/8/12 are outer, upper, inner, lower',
     EYE_R_RING[0] === EYE_R_CORNERS[0] && EYE_R_RING[8] === EYE_R_CORNERS[1] &&
     EYE_R_RING[4] === EYE_R_LIDS[0] && EYE_R_RING[12] === EYE_R_LIDS[1] &&
     EYE_L_RING[0] === EYE_L_CORNERS[0] && EYE_L_RING[8] === EYE_L_CORNERS[1] &&
     EYE_L_RING[4] === EYE_L_LIDS[0] && EYE_L_RING[12] === EYE_L_LIDS[1]);

  // The gaze origin and denominator are built from the eye corners, so if a
  // corner were not rigid a blink could move it and fake a glance.
  ok('every eye corner is a rigid landmark',
     [...EYE_R_CORNERS, ...EYE_L_CORNERS].every((i) => RIGID.includes(i)));

  // Same simplicity requirement as the lips, and for the same reason: a cut
  // part with a self-intersecting ring renders as blocks meeting at corners.
  // Checked on blink frames too, where the ring is nearly degenerate.
  for (const [label, table] of [['right', EYE_R_RING], ['left', EYE_L_RING]]) {
    let worst = null;
    for (let n = 4; n <= 12 && !worst; n += 2) {
      const slots = subsampleSlots(table.length, n);
      for (let f = 0; f < dense.length; f++) {
        const hits = ringSelfIntersections(slots.map((sl) => dense[f][table[sl]]));
        if (hits.length) { worst = `verts=${n} frame=${f} edges ${JSON.stringify(hits[0])}`; break; }
      }
    }
    ok(`${label} eye ring is simple at every vertex budget`, !worst, worst || '');
  }

  // offsetRing must grow by a FIXED amount and survive a degenerate ring - the
  // shut eyelid is exactly the degenerate case, and it is the frame where the
  // lash line is the entire drawing.
  {
    const sq = [{ x: -1, y: 0 }, { x: 0, y: -1 }, { x: 1, y: 0 }, { x: 0, y: 1 }];
    const g = offsetRing(sq, 2);
    ok('offsetRing pushes every vertex out by exactly d',
       g.every((p, i) => Math.abs(Math.hypot(p.x, p.y) - (Math.hypot(sq[i].x, sq[i].y) + 2)) < 1e-9));
    ok('offsetRing(0) is identity', offsetRing(sq, 0) === sq);
    // A shut lid: a flat sliver. The offset must still open it into a band.
    const shutLid = [{ x: -10, y: 0 }, { x: 0, y: -0.02 }, { x: 10, y: 0 }, { x: 0, y: 0.02 }];
    const band = offsetRing(shutLid, 1.5);
    const h = Math.max(...band.map((p) => p.y)) - Math.min(...band.map((p) => p.y));
    ok('offsetRing gives a shut lid a visible lash band', h > 2.9, `height ${h.toFixed(3)}`);
    ok('offsetRing keeps the shut lid simple', ringSelfIntersections(band).length === 0);
  }

  {
    const stE = stabilize(dense, 2);
    const sig = eyeSignals(stE);
    ok('synthetic track carries iris landmarks', sig.hasIris);

    // THE load-bearing eye assertion. The pairing is resolved from geometry
    // rather than declared, so the test feeds a track built the OTHER way round
    // and demands the resolver follow the data. A resolver only ever checked
    // against the convention it was written for is checking nothing.
    const pairA = pairIrises(stE);
    const pairB = pairIrises(stabilize(synthDense(72, { swapIris: true }), 2));
    ok('iris pairing is resolved from the data, not assumed',
       pairA.right === 'irisA' && pairB.right === 'irisB',
       `normal ${pairA.right}, swapped ${pairB.right}`);

    // The eye must TRACK the face, not sit in a fixed socket. An earlier
    // version pinned each eye to its corners' mean over the shot, which does
    // kill the wobble but leaves the drawn eyes hanging still over a registered
    // photo whose eyes are moving. Head-local is the same space the mouth and
    // the underlay live in, so the eye moves with the head exactly as they do.
    {
      const spread = (arr, sel) => {
        const v = arr.map(sel);
        return Math.max(...v) - Math.min(...v);
      };
      const w = Math.hypot(stE.cornersR[0][0].x - stE.cornersR[0][1].x,
                           stE.cornersR[0][0].y - stE.cornersR[0][1].y);
      const moves = Math.max(spread(stE.lidR, (r) => r[0].x), spread(stE.lidR, (r) => r[0].y));
      ok('the eye stays in head-local space and tracks the face', moves / w > 0.02,
         `corner travels ${(moves / w * 100).toFixed(1)}% of an eye width`);

      // Subsampling a 16-slot ring to any even budget must keep the two corners
      // at output indices 0 and n/2. That is what lets the socket be read back
      // off the drawn polygon instead of measured separately, which is what
      // stops the iris drifting relative to the eye it sits in.
      let bad = null;
      for (let n = 4; n <= 12; n += 2) {
        const sl = subsampleSlots(16, n);
        if (sl[0] !== 0 || sl[n / 2] !== 8) bad = `n=${n} -> ${sl.join(',')}`;
      }
      ok('the drawn lid ring carries its own corners at 0 and n/2', !bad, bad || '');

      // The contour average is what removes the jitter, and it is the mouth's
      // knob doing the mouth's job - no second mechanism for the eyes.
      const ring = (rad) => smoothContours(
        stE.lidR.map((r) => toRasterRing(r, EYE_R_RING, 8, (p) => ({ x: p.x * 600, y: p.y * 600 }))), rad);
      const jitter = (rings) => {
        let acc = 0;
        for (let f = 1; f < rings.length; f++) {
          const a = rings[f], b = rings[f - 1];
          acc += Math.hypot((a[0].x + a[4].x) / 2 - (b[0].x + b[4].x) / 2,
                            (a[0].y + a[4].y) / 2 - (b[0].y + b[4].y) / 2);
        }
        return acc / (rings.length - 1);
      };
      ok('contour averaging steadies the eye without pinning it',
         jitter(ring(1)) < jitter(ring(0)) * 0.8,
         `${jitter(ring(0)).toFixed(3)} -> ${jitter(ring(1)).toFixed(3)} px/frame`);
    }

    // Blink: synth shuts the lids for exactly one frame every 19.
    const lo = Math.min(...sig.openR), hi = Math.max(...sig.openR);
    ok('openness collapses on a blink and not otherwise', lo < hi * 0.2,
       `${lo.toFixed(3)} .. ${hi.toFixed(3)}`);

    const shut = resolveBlink(sig.openR, { cut: hi * 0.3, dwell: 0, hold: 3 });
    const runs = [];
    for (let f = 0; f < shut.length; f++) if (shut[f] && !shut[f - 1]) runs.push(f);
    const lens = runs.map((a) => { let n = 0; while (shut[a + n]) n++; return n; });
    ok('blinks are found', runs.length >= 3, `${runs.length} runs at ${runs.join(',')}`);
    // The knob that is not like the teeth: a one-frame blink reads as a dropped
    // frame, so `hold` must stretch it into something legible.
    ok('a one-frame blink is held to the minimum length',
       lens.every((n) => n >= 3), `run lengths ${lens.join(',')}`);
    ok('a shorter hold leaves the blink shorter',
       resolveBlink(sig.openR, { cut: hi * 0.3, dwell: 0, hold: 1 }).filter(Boolean).length <
       shut.filter(Boolean).length);

    // Gaze, against ground truth: synth commands +0.16 eye widths at f12 and
    // -0.16 at f23, holding each for eleven frames.
    const org = gazeOrigin(sig.gazeRaw, 'neutral', 0);
    const gx = (f) => (sig.gazeRaw[f].x - org.x);
    ok('gaze recovers the commanded direction',
       gx(12) > 0.12 && gx(12) < 0.20 && gx(23) < -0.12 && gx(23) > -0.20,
       `f12 ${gx(12).toFixed(3)}, f23 ${gx(23).toFixed(3)}`);

    // Measuring gaze against the lid centroid instead of the corner midpoint
    // would drag the iris down on every blink and fake a glance at the floor,
    // on exactly the frames where the eye is most conspicuous.
    const gy = (f) => (sig.gazeRaw[f].y - org.y);
    ok('a blink does not fake a change of gaze',
       Math.abs(gy(19) - gy(18)) < 0.02, `f18 ${gy(18).toFixed(4)} -> f19 ${gy(19).toFixed(4)}`);

    // Quantisation is what turns drift into saccades: four commanded
    // fixations must come back as a handful of cells, not one per frame.
    // The origin re-points the whole performance, so a wrong one does not bias
    // the gaze slightly - it makes the character look the other way. The median
    // must sit inside the range it summarises; the neutral-frame origin need
    // not, which is exactly the failure mode it has on footage with no
    // deliberate neutral at the top.
    {
      const med = gazeOrigin(sig.gazeRaw, 'median');
      const xs = sig.gazeRaw.map((g) => g.x);
      ok('the median origin lies inside the take\'s own gaze range',
         med.x > Math.min(...xs) && med.x < Math.max(...xs),
         `${med.x.toFixed(3)} in ${Math.min(...xs).toFixed(3)}..${Math.max(...xs).toFixed(3)}`);
      // Synth looks left as much as right, so the rest point is near zero.
      ok('the median origin finds the rest point, not a glance',
         Math.abs(med.x) < 0.08, `median x ${med.x.toFixed(3)}`);
      ok('the two origins actually differ, so the toggle is a real A/B',
         Math.abs(med.x - gazeOrigin(sig.gazeRaw, 'neutral', 12).x) > 0.02);
    }

    const px = sig.gazeRaw.map((g) => ({ x: (g.x - org.x) * 30, y: (g.y - org.y) * 30 }));
    const cells = (a) => new Set(a.map((g) => `${g.x},${g.y}`)).size;
    ok('quantisation collapses drift into a few fixations',
       cells(quantizeSnap(px, 2, 2)) <= 6 && cells(px) > 40,
       `${cells(px)} raw -> ${cells(quantizeSnap(px, 2, 2))} cells`);
    ok('gaze step 0 leaves the track untouched',
       quantizeSnap(px, 0, 2).every((g, i) => g.x === px[i].x && g.y === px[i].y));
    ok('quantised values land on the grid',
       quantizeSnap(px, 2, 0).every((g) => Math.abs(g.x % 2) < 1e-9 && Math.abs(g.y % 2) < 1e-9));
    // A one-frame excursion is noise; the dwell must swallow it.
    {
      const spike = [{ x: 0, y: 0 }, { x: 0, y: 0 }, { x: 4, y: 0 }, { x: 0, y: 0 }, { x: 0, y: 0 }];
      ok('the dwell suppresses a one-frame gaze spike',
         quantizeSnap(spike, 2, 1).every((g) => g.x === 0));
      ok('a sustained move still gets through',
         quantizeSnap([...spike, { x: 4, y: 0 }, { x: 4, y: 0 }, { x: 4, y: 0 }], 2, 1).pop().x === 4);
    }
  }

  /* ---- brows ---- */

  ok('brow rings have 10 distinct ids each',
     new Set(BROW_A_RING).size === 10 && new Set(BROW_B_RING).size === 10);
  ok('the brow rings share no landmark with each other, RIGID, or the lids',
     !BROW_A_RING.some((i) => BROW_B_RING.includes(i)) &&
     ![...BROW_A_RING, ...BROW_B_RING].some((i) =>
       RIGID.includes(i) || EYE_R_RING.includes(i) || EYE_L_RING.includes(i)),
     'a brow in RIGID would bleed expression into the stabilisation');

  {
    let bad = null;
    for (const [label, table] of [['A', BROW_A_RING], ['B', BROW_B_RING]]) {
      for (let n = 4; n <= 10 && !bad; n += 2) {
        const slots = subsampleSlots(table.length, n);
        for (let f = 0; f < dense.length; f++) {
          if (ringSelfIntersections(slots.map((sl) => dense[f][table[sl]])).length) {
            bad = `${label} verts=${n} frame=${f}`; break;
          }
        }
      }
    }
    ok('brow rings are simple at every vertex budget', !bad, bad || '');
  }

  {
    const stB = stabilize(dense, 2);
    const pr = pairBrows(stB);
    ok('brow-to-eye pairing is resolved from geometry',
       pr.right === 'browA' && pr.left === 'browB', JSON.stringify(pr));
    // Getting this backwards mirrors the tilt, so inner-up "worried" renders as
    // outer-up. That is a different expression, not a broken one, which is
    // exactly why it needs an assertion rather than an eyeball.
    ok('the outer end of the brow ring is resolved from geometry', pr.outerAtSlot0 === true);

    // Both ends land on fixed slots whichever edge of the brow is on top, which
    // is what lets the upper/lower ambiguity go unresolved without consequence.
    ok('brow end slots are disjoint and cover both ends',
       !BROW_END_0.some((i) => BROW_END_1.includes(i)) &&
       BROW_END_0.length === 2 && BROW_END_1.length === 2);

    // Ground truth: synth commands rest, surprise, worry and anger as heights
    // above the eye centre in eye widths, holding each for thirteen frames.
    const b = browSignals(stB);
    const at = (f) => [b.R[f].x, b.R[f].y];
    const near = (v, want) => Math.abs(v - want) < 0.02;
    ok('brow raise recovers the commanded rest pose', near(at(0)[0], 0.30) && near(at(0)[1], 0.30),
       at(0).map((v) => v.toFixed(3)).join(', '));
    ok('brow raise recovers surprise - both ends up',
       near(at(14)[0], 0.46) && near(at(14)[1], 0.46), at(14).map((v) => v.toFixed(3)).join(', '));
    ok('brow raise recovers worry - inner end only',
       near(at(27)[0], 0.30) && near(at(27)[1], 0.44), at(27).map((v) => v.toFixed(3)).join(', '));
    ok('brow raise recovers anger - inner end down',
       near(at(40)[0], 0.30) && near(at(40)[1], 0.18), at(40).map((v) => v.toFixed(3)).join(', '));

    // Tilt must be a signed quantity that separates worry from anger. If the
    // outer/inner resolution were mirrored these two would swap.
    ok('tilt separates worry from anger by sign',
       (at(27)[1] - at(27)[0]) > 0.08 && (at(40)[1] - at(40)[0]) < -0.08,
       `worry ${(at(27)[1] - at(27)[0]).toFixed(3)}, anger ${(at(40)[1] - at(40)[0]).toFixed(3)}`);

    // A blink must not read as a brow raise: the raise is measured against the
    // eye's rigid corners, not its lid, which is the same trap the gaze origin
    // has and worth avoiding twice.
    const dR = Math.abs(b.R[19].x - b.R[18].x);
    ok('a blink does not fake a brow raise', dR < 0.01, `f18 -> f19 delta ${dR.toFixed(4)}`);

    // Quantisation: four sustained poses must come back as a handful of levels.
    const rest = gazeOrigin(b.R, 'median');
    const px = b.R.map((g) => ({ x: (g.x - rest.x) * 60, y: (g.y - rest.y) * 60 }));
    const cells = (a) => new Set(a.map((g) => `${g.x},${g.y}`)).size;
    ok('brow quantisation collapses drift into a few poses',
       cells(quantizeSnap(px, 2, 2)) <= 6 && cells(px) > 20,
       `${cells(px)} raw -> ${cells(quantizeSnap(px, 2, 2))} poses`);
    // The dwell is SHARED across both channels, and that is the whole reason
    // brows reuse the gaze quantiser rather than running two independent ones.
    // Here the outer end moves one frame before the inner: with a shared dwell
    // the half-raised pose (2,0) is transient and never commits, so the brow
    // snaps once. Two independent dwells would emit it and the brow would crawl
    // into position over two frames instead of hitting it.
    {
      const staggered = [
        { x: 0, y: 0 }, { x: 0, y: 0 }, { x: 2, y: 0 },
        { x: 2, y: 2 }, { x: 2, y: 2 }, { x: 2, y: 2 },
      ];
      const out = quantizeSnap(staggered, 2, 1);
      ok('a shared dwell never emits a half-raised brow',
         !out.some((g) => g.x === 2 && g.y === 0),
         out.map((g) => `${g.x},${g.y}`).join(' '));
    }
  }

  // The iris is stencilled by the sclera and the pupil by the iris, which is
  // what keeps both inside the lid at any gaze without clamping the gaze itself.
  {
    const rr = new IndexedRaster(40, 40);
    rr.clear(0);
    rr.fillPoly([{ x: 10, y: 10 }, { x: 30, y: 10 }, { x: 30, y: 20 }, { x: 10, y: 20 }], 1);
    rr.fillDisc(28, 15, 9, 2, 1);        // a disc reaching well past the "lid"
    let spill = 0, inside = 0;
    for (let y = 0; y < 40; y++) for (let x = 0; x < 40; x++) {
      const v = rr.buf[y * 40 + x];
      if (v !== 2) continue;
      if (x >= 10 && x < 30 && y >= 10 && y < 20) inside++; else spill++;
    }
    ok('a stencilled disc cannot spill past its clip', spill === 0 && inside > 20,
       `${inside} in, ${spill} out`);
    rr.fillDisc(5, 35, 3, 3);            // no stencil: writes freely
    ok('an unstencilled disc still writes anywhere', rr.buf.includes(3));

    // The stencil chain: pupil over iris over sclera. A pupil placed where the
    // iris has already been cropped must be cropped the same way.
    rr.fillRect(28, 15, 5, 4, 2);
    let pSpill = 0;
    for (let y = 0; y < 40; y++) for (let x = 0; x < 40; x++) {
      if (rr.buf[y * 40 + x] === 4 && !(x >= 10 && x < 30 && y >= 10 && y < 20)) pSpill++;
    }
    ok('the pupil inherits the iris clip transitively', pSpill === 0);
  }

  // A square pupil is only worth having if it is the SAME square every frame:
  // exactly its nominal size at any centre, or it breathes as the gaze moves.
  {
    const sizes = [];
    for (const [cx, cy] of [[20, 20], [20.5, 20.5], [20.49, 19.51], [21, 20]]) {
      const rr = new IndexedRaster(40, 40);
      rr.clear(0);
      rr.fillRect(cx, cy, 3, 1);
      let n = 0, minX = 99, maxX = -1, minY = 99, maxY = -1;
      for (let y = 0; y < 40; y++) for (let x = 0; x < 40; x++) {
        if (rr.buf[y * 40 + x] !== 1) continue;
        n++; minX = Math.min(minX, x); maxX = Math.max(maxX, x);
        minY = Math.min(minY, y); maxY = Math.max(maxY, y);
      }
      sizes.push(`${maxX - minX + 1}x${maxY - minY + 1}:${n}`);
    }
    ok('a 3px pupil is 3x3 at every centre', sizes.every((v) => v === '3x3:9'), sizes.join(' '));
    const rr = new IndexedRaster(40, 40);
    rr.clear(0); rr.fillRect(20, 20, 0, 1);
    ok('pupil size 0 draws nothing', !rr.buf.includes(1));
  }

  // take writer round-trip
  const take = {
    name: 'test', frames: 72, width: 320, height: 200, exposure: 2,
    palette: [{ name: 'bg' }, { name: 'skin' }],
    slot: { x: 160, y: 100 },
    parts: [
      { name: 'head', kind: 'plate', z: 0, interp: 'hold', keys: [{ f: 0, plate: 0 }] },
      { name: 'mouth', kind: 'poly', z: 30, color: 'skin', interp: 'hold',
        keys: sel.keys.map((k) => ({ f: k.f, src: k.src, pts: shapes[k.src] })) },
      { name: 'iris_r', kind: 'disc', z: 22, color: 'iris', interp: 'hold',
        parent: 'eye_r_in', clip: 'eye_r_in',
        keys: [{ f: 0, src: 0, c: { x: 120.4, y: 88.7 }, r: 5.5 }, { f: 2, hidden: true }] },
      { name: 'pupil_r', kind: 'rect', z: 23, color: 'pupil', interp: 'hold',
        parent: 'iris_r', clip: 'iris_r',
        keys: [{ f: 0, src: 0, c: { x: 120, y: 89 }, size: 3 }] },
    ],
  };
  const text = writeTake(take);
  const keyLines = text.split('\n').filter((l) => l.startsWith('key') && l.includes('n='));
  ok('every key line declares n= matching its point count',
     keyLines.every((l) => {
       const n = +l.match(/n=(\d+)/)[1];
       const pts = l.split(/n=\d+\s+/)[1].trim().split(/\s+/);
       return pts.length === n;
     }), `${keyLines.length} key lines`);
  ok('take declares a plate and a part table',
     /^plate\s+0/m.test(text) && /^part\s+mouth/m.test(text));
  ok('a disc part declares its clip', /^part\s+iris_r.*clip=eye_r_in/m.test(text));
  ok('a disc key is three integers', /^key\s+iris_r\s+f=0\s+src=0\s+disc=120,89,6$/m.test(text),
     (text.split('\n').find((l) => l.startsWith('key     iris_r')) || '').trim());
  ok('a hidden disc key emits hidden', /^key\s+iris_r\s+f=2\s+hidden$/m.test(text));
  ok('a pupil key is a square, not a tessellated polygon',
     /^key\s+pupil_r\s+f=0\s+src=0\s+rect=120,89,3$/m.test(text) &&
     /^part\s+pupil_r.*clip=iris_r/m.test(text));
  ok('coordinates are integers', !/-?\d+\.\d/.test(text.split('\n').filter((l) => l.startsWith('key')).join('')));

  return results;
}