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<!--
Copyright (c) 2019 The Khronos Group Inc.
Use of this source code is governed by an MIT-style license that can be
found in the LICENSE.txt file.
-->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>OffscreenCanavs context attribute preserveDrawingBuffer</title>
<link rel="stylesheet" href="../../resources/js-test-style.css"/>
<script src="../../js/js-test-pre.js"></script>
<script src="../../js/webgl-test-utils.js"></script>
<script src="../../js/tests/canvas-tests-utils.js"></script>
</head>
<body>
<div id="description"></div>
<div id="canvases"></div>
<div id="console"></div>
<script>
"use strict";
description("This test checks whether OffscreenCanvas webgl context honors the preserveDrawingBuffer flag.");
const wtu = WebGLTestUtils;
const pixels = new Uint8Array(4);
function checkPixels(color) {
return (color[0] === pixels[0]) &&
(color[1] === pixels[1]) &&
(color[2] === pixels[2]) &&
(color[3] === pixels[3]);
}
const nextFrame = () => new Promise(r => requestAnimationFrame(r));
async function getPixelsFromOffscreenWebgl(preserveFlag, color, msg) {
const canvas = document.createElement("canvas");
document.getElementById("canvases").appendChild(canvas);
const offscreenCanvas = transferredOffscreenCanvasCreation(canvas, 10, 10);
const gl = offscreenCanvas.getContext("webgl", {preserveDrawingBuffer: preserveFlag});
// Draw some color on gl
gl.clearColor(1, 0, 1, 1);
gl.clear(gl.COLOR_BUFFER_BIT);
let t;
const t0 = await nextFrame();
const timeDuration = preserveFlag ? 500 : 2000;
for (;;) {
t = await nextFrame();
gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, pixels);
if (preserveFlag) {
if (!checkPixels(color)) {
testFailed(msg + '\nexpected: ' + color.toString() + ' was ' + pixels.toString());
return;
}
} else {
if (checkPixels(color)) {
testPassed(msg);
return;
}
}
// Keep checking until it takes up to a certain time.
// preserveDrawingBuffer:false seems flaky on Chrome's test bots; run that test for longer.
if (t > t0 + timeDuration) {
break;
}
}
if (preserveFlag) {
testPassed(msg);
} else {
testFailed(msg + '\nafter ' + timeDuration + ' ms, expected: ' + color.toString() + ' was ' + pixels.toString());
}
}
(async () => {
if (!window.OffscreenCanvas) {
testPassed("No OffscreenCanvas support");
} else {
// Test if OffscreenCanvas.webgl retains contents if preserveDrawingBuffer is true.
await getPixelsFromOffscreenWebgl(true, [255,0,255,255], "should be preserved");
// Test if OffscreenCanvas.webgl loses contents if preserveDrawingBuffer is false.
await getPixelsFromOffscreenWebgl(false, [0, 0, 0, 0], "should not be preserved");
}
finishTest();
})();
</script>
</body>
</html>