fix(jassub): [PKG-JASSUB-08] transfer offscreen canvas before queued rendering

test/jassub-offscreen.test.js

@@ -0,0 +1,69 @@
+import assert from 'node:assert/strict'
+// eslint-disable-next-line test/no-import-node-test -- Offscreen protocol ordering needs deterministic queue coverage.
+import test from 'node:test'
+import { jassubCandidate, jassubEnvironment } from './helpers/jassub.js'
+
+const candidate = await jassubCandidate()
+function environment(offscreen = true) {
+  const code = `${candidate.code}\nObject.defineProperty(module.exports.default || module.exports, '__canvasClass', { value: HTMLCanvasElement });`
+  const env = jassubEnvironment({ ...candidate, code })
+  const transferred = []
+  if (offscreen) {
+    env.factory.__canvasClass.prototype.transferControlToOffscreen = function () {
+      const canvas = { width: this.width, height: this.height }
+      transferred.push(canvas)
+      return canvas
+    }
+  }
+  return { ...env, transferred }
+}
+
+test('JASSUB initializes offscreen ownership before queued resize, track and ready-listener messages', async () => {
+  const env = environment()
+  const { instance } = env.factory()(env.art)
+  instance.resize(640, 360)
+  instance.setTrack('[Script Info]')
+  instance.addEventListener('ready', () => instance.resize(320, 180))
+  await env.ready()
+  const messages = env.workers[0].messages
+  assert.deepEqual(messages.slice(0, 2).map(message => message.target), ['init', 'offscreenCanvas'])
+  assert.equal(messages[1].transferable[0], env.transferred[0])
+  assert(messages.slice(2).some(message => message.target === 'canvas'))
+  assert(messages.slice(2).some(message => message.target === 'setTrack'))
+  assert.equal(instance._ctx, false)
+  instance.destroy()
+})
+
+test('JASSUB duplicate readiness does not transfer the initial offscreen canvas twice', async () => {
+  const env = environment()
+  const { instance } = env.factory()(env.art)
+  await env.ready()
+  await env.ready()
+  assert.equal(env.workers[0].messages.filter(message => message.target === 'offscreenCanvas').length, 1)
+  instance.destroy()
+})
+
+test('JASSUB destroy before readiness never transfers its offscreen canvas', async () => {
+  const env = environment()
+  const { instance } = env.factory()(env.art)
+  instance.destroy()
+  await env.flush()
+  instance._ready()
+  await env.flush()
+  assert.equal(env.workers[0].messages.length, 0)
+  assert.equal(env.workers[0].terminated, 1)
+})
+
+for (const option of [{ offscreenRender: false }, 'unsupported', 'custom']) {
+  test(`JASSUB main-thread canvas has no initial transfer for ${JSON.stringify(option)}`, async () => {
+    const env = environment(option !== 'unsupported')
+    const options = option === 'custom' ? { canvas: env.createCanvas() } : typeof option === 'object' ? option : {}
+    const { instance } = env.factory(options)(env.art)
+    await env.ready()
+    instance.resize(640, 360)
+    await env.flush()
+    assert.equal(env.workers[0].messages.some(message => message.target === 'offscreenCanvas'), false)
+    assert.equal(instance._ctx, instance._canvas.context)
+    instance.destroy()
+  })
+}