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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>Draw WebGL to Canvas2D Repeatedly</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>
</head>
<body>
<div id="description"></div>
<div id="console"></div>
<canvas id="canvas-webgl" width="256" height="256"></canvas>
<canvas id="canvas-2d" width="256" height="256"></canvas>
<script>
"use strict";
const wtu = WebGLTestUtils;
const sz = 256;
function drawTo2DCanvas(c2, webGLCanvas) {
// Always clear 2D canvas to solid green first.
c2.clearRect(0, 0, sz, sz);
c2.fillStyle = 'rgb(0,255,0)';
c2.fillRect(0, 0, sz, sz);
// Draw WebGL canvas to this canvas.
c2.drawImage(webGLCanvas, 0, 0);
}
function runTest() {
description();
debug('Repeatedly drawing a WebGL canvas to a 2D canvas should only draw the most recently rendered WebGL content.');
debug('Regression test for <a href="http://crbug.com/894021">http://crbug.com/894021</a>');
let c2 = document.getElementById('canvas-2d').getContext('2d');
let webGLCanvas = document.getElementById('canvas-webgl');
let gl = wtu.create3DContext(webGLCanvas, { alpha: true, antialias: false, premultipliedAlpha: true });
let tolerance = 2;
// Clear left half of WebGL canvas to red and right half to
// transparent black.
gl.disable(gl.SCISSOR_TEST);
gl.clearColor(0.0, 0.0, 0.0, 0.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.scissor(0, 0, sz / 2, sz);
gl.enable(gl.SCISSOR_TEST);
gl.clearColor(1.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
// Draw to 2D canvas.
drawTo2DCanvas(c2, webGLCanvas);
// Clear right half of WebGL canvas to red and left half to
// transparent black.
gl.disable(gl.SCISSOR_TEST);
gl.clearColor(0.0, 0.0, 0.0, 0.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.scissor(sz / 2, 0, sz / 2, sz);
gl.enable(gl.SCISSOR_TEST);
gl.clearColor(1.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
// Draw to 2D canvas.
drawTo2DCanvas(c2, webGLCanvas);
// Clear WebGL canvas to transparent black.
gl.disable(gl.SCISSOR_TEST);
gl.clearColor(0.0, 0.0, 0.0, 0.0);
gl.clear(gl.COLOR_BUFFER_BIT);
// Draw to 2D canvas.
drawTo2DCanvas(c2, webGLCanvas);
// 2D canvas should be green.
// In the error case, the rendering results from earlier draws were
// being accumulated, so the 2D canvas was ultimately red.
wtu.checkCanvasRect(c2, 0, 0, sz, sz,
[ 0, 255, 0, 255 ],
"should be green",
tolerance);
finishTest();
}
requestAnimationFrame(runTest);
</script>
</body>
</html>
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