test_offscreencanvas_dynamic_fallback.html

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<!DOCTYPE HTML>

<html>

<head>

<title>WebGL in OffscreenCanvas</title>

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

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

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

</head>

<body>

<script>

SimpleTest.waitForExplicitFinish();

function createCanvas(initWithMask) {

  var canvas = document.createElement("canvas");

  canvas.width = 64;

  canvas.height = 64;

  document.body.appendChild(canvas);

  if (initWithMask) {

    canvas.style.mask = "url('offscreencanvas_mask.svg#fade_mask_both')";

  return canvas;

async function getRefSnapshot(initWithMask) {

  var refCanvas = createCanvas(!initWithMask);

  var ctx = refCanvas.getContext("2d");

  ctx.rect(0, 0, 64, 64);

  ctx.fillStyle = "#00FF00";

  ctx.fill();

  var result = await snapshotWindow(window);

  document.body.removeChild(refCanvas);

  return result;

function runTest(initWithMask) {

  var htmlCanvas = createCanvas(initWithMask);

  var worker = new Worker("offscreencanvas.js");

  worker.onmessage = async function(evt) {

    var msg = evt.data || {};

    if (msg.type == "draw") {

      if (msg.count === 10) {

        // Change the fallback state dynamically when drawing count reaches 10.

        if (initWithMask) {

          htmlCanvas.style.mask = "";

        } else {

          htmlCanvas.style.mask = "url('offscreencanvas_mask.svg#fade_mask_both')";

      } else if (msg.count === 20) {

        worker.terminate();

        var snapshotFallback = await snapshotWindow(window);

        document.body.removeChild(htmlCanvas);

        var results = compareSnapshots(snapshotFallback, await getRefSnapshot(initWithMask), true);

        ok(results[0], "after dynamic fallback, screenshots should be the same");

        if (initWithMask) {

          SimpleTest.finish();

        } else {

          runTest(true);

  var offscreenCanvas = htmlCanvas.transferControlToOffscreen();

  worker.postMessage({test: 'webgl_fallback', canvas: offscreenCanvas}, [offscreenCanvas]);

SpecialPowers.pushPrefEnv({'set': [

  ['webgl.force-enabled', true],

]}, runTest.bind(false));

</script>

</body>

</html>