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The Tor Browser
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context-attribute-preserve-drawing-buffer.html (2838B)

      1 <!--
      2 Copyright (c) 2019 The Khronos Group Inc.
      3 Use of this source code is governed by an MIT-style license that can be
      4 found in the LICENSE.txt file.
      5 -->
      6 <!DOCTYPE html>
      7 <html>
      8 <head>
      9 <meta charset="utf-8">
     10 <title>OffscreenCanavs context attribute preserveDrawingBuffer</title>
     11 <link rel="stylesheet" href="../../resources/js-test-style.css"/>
     12 <script src="../../js/js-test-pre.js"></script>
     13 <script src="../../js/webgl-test-utils.js"></script>
     14 <script src="../../js/tests/canvas-tests-utils.js"></script>
     15 </head>
     16 <body>
     17 <div id="description"></div>
     18 <div id="canvases"></div>
     19 <div id="console"></div>
     20 <script>
     21 "use strict";
     22 description("This test checks whether OffscreenCanvas webgl context honors the preserveDrawingBuffer flag.");
     23 const wtu = WebGLTestUtils;
     24 const pixels = new Uint8Array(4);
     25 
     26 function checkPixels(color) {
     27  return (color[0] === pixels[0]) &&
     28    (color[1] === pixels[1]) &&
     29    (color[2] === pixels[2]) &&
     30    (color[3] === pixels[3]);
     31 }
     32 
     33 const nextFrame = () => new Promise(r => requestAnimationFrame(r));
     34 
     35 async function getPixelsFromOffscreenWebgl(preserveFlag, color, msg) {
     36  const canvas = document.createElement("canvas");
     37  document.getElementById("canvases").appendChild(canvas);
     38  const offscreenCanvas = transferredOffscreenCanvasCreation(canvas, 10, 10);
     39  const gl = offscreenCanvas.getContext("webgl", {preserveDrawingBuffer: preserveFlag});
     40 
     41  // Draw some color on gl
     42  gl.clearColor(1, 0, 1, 1);
     43  gl.clear(gl.COLOR_BUFFER_BIT);
     44 
     45  let t;
     46  const t0 = await nextFrame();
     47  const timeDuration = preserveFlag ? 500 : 2000;
     48  for (;;) {
     49    t = await nextFrame();
     50 
     51    gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
     52    if (preserveFlag) {
     53      if (!checkPixels(color)) {
     54        testFailed(msg + '\nexpected: ' + color.toString() + ' was ' + pixels.toString());
     55        return;
     56      }
     57    } else {
     58      if (checkPixels(color)) {
     59        testPassed(msg);
     60        return;
     61      }
     62    }
     63 
     64    // Keep checking until it takes up to a certain time.
     65    // preserveDrawingBuffer:false seems flaky on Chrome's test bots; run that test for longer.
     66    if (t > t0 + timeDuration) {
     67      break;
     68    }
     69  }
     70 
     71  if (preserveFlag) {
     72    testPassed(msg);
     73  } else {
     74    testFailed(msg + '\nafter ' + timeDuration + ' ms, expected: ' + color.toString() + ' was ' + pixels.toString());
     75  }
     76 }
     77 
     78 (async () => {
     79  if (!window.OffscreenCanvas) {
     80      testPassed("No OffscreenCanvas support");
     81  } else {
     82    // Test if OffscreenCanvas.webgl retains contents if preserveDrawingBuffer is true.
     83    await getPixelsFromOffscreenWebgl(true, [255,0,255,255], "should be preserved");
     84 
     85    // Test if OffscreenCanvas.webgl loses contents if preserveDrawingBuffer is false.
     86    await getPixelsFromOffscreenWebgl(false, [0, 0, 0, 0], "should not be preserved");
     87  }
     88  finishTest();
     89 })();
     90 
     91 </script>
     92 </body>
     93 </html>