test_offlineRendering_promise_release.html

Enable keyboard shortcuts

<!doctype html>

<meta charset="utf-8">

<title>Completed offline rendering does not keep output alive</title>

<script src="/tests/SimpleTest/SimpleTest.js"></script>

<link rel="stylesheet" href="/tests/SimpleTest/test.css">

<script>

SimpleTest.waitForExplicitFinish();

async function collect() {

  await new Promise(resolve => SpecialPowers.exactGC(resolve));

async function render() {

  const context = new OfflineAudioContext(2, 48000, 48000);

  const source = new ConstantSourceNode(context, {offset: 0.25});

  source.connect(context.destination);

  source.start();

  const completed = new Promise(resolve => {

    context.addEventListener("complete", event => resolve(event.renderedBuffer),

                             {once: true});

});

  const promise = context.startRendering();

  const buffer = await promise;

  is(await completed, buffer, "The completion event uses the promise result");

  is(context.state, "closed", "The offline context is closed");

  is(buffer.getChannelData(0)[0], 0.25, "The first sample is preserved");

  is(buffer.getChannelData(1)[buffer.length - 1], 0.25,

     "The last sample is preserved");

  try {

    await context.startRendering();

    ok(false, "A completed render cannot be restarted");

  } catch (error) {

    is(error.name, "InvalidStateError", "Restart rejects with InvalidStateError");

  return {context, promise, weakBuffer: new WeakRef(buffer)};

async function run() {

  const result = await render();

  await collect();

  ok(result.weakBuffer.deref(), "A caller-held promise keeps its output alive");

  // Start a new task so WeakRef.deref() no longer keeps the buffer alive.

  await new Promise(resolve => setTimeout(resolve));

  result.promise = null;

  await collect();

  is(result.weakBuffer.deref(), undefined,

     "A completed context does not keep a dropped output alive");

  is(result.context.state, "closed", "The context remains available");

  is(result.context.length, 48000, "The context retains its length");

run().catch(error => ok(false, String(error))).then(() => SimpleTest.finish());

</script>