context-size-change.html

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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">

<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>

"use strict";

// These declarations need to be global for "shouldBe" to see them

var gl;

var pixel = [0, 0, 0, 1];

var canvas;

function init()

    description('Verify that changing the size of an antialiased WebGL context does not cause it to stop working.');

    runTest();

function getWebGL(canvasWidth, canvasHeight, contextAttribs)

    canvas = document.createElement("canvas");

    if (!canvas)

        return null;

    canvas.width = canvasWidth;

    canvas.height = canvasHeight;

    gl = WebGLTestUtils.create3DContext(canvas, contextAttribs);

    if (!gl)

        return null;

    return gl;

function runTest()

    shouldBeNonNull("gl = getWebGL(1, 1, { alpha: false, antialias: true })");

    // Clear to black.

    gl.clearColor(0.0, 0.0, 0.0, 1.0);

    gl.clear(gl.COLOR_BUFFER_BIT);

    // Check that the pixel's R channel is 0.

    var buf = new Uint8Array(1 * 1 * 4);

    gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, buf);

    pixel[0] = buf[0];

    shouldBeTrue("pixel[0] == 0");

    // Change the size of the canvas.

    canvas.width = 3;

    canvas.height = 3;

    // Clear to black.

    gl.clearColor(0.0, 0.0, 0.0, 1.0);

    gl.clear(gl.COLOR_BUFFER_BIT);

    // Clear the top-left pixel to white.

    gl.enable(gl.SCISSOR_TEST);

    gl.scissor(0, 0, 1, 1);

    gl.clearColor(1.0, 1.0, 1.0, 1.0);

    gl.clear(gl.COLOR_BUFFER_BIT);

    // Check that the top-left pixel has R channel 255.

    gl.readPixels(0, 0, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, buf);

    pixel[0] = buf[0];

    shouldBeTrue("pixel[0] == 255");

    // Check that the bottom-right pixel has R channel 0.

    gl.readPixels(2, 2, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, buf);

    pixel[0] = buf[0];

    shouldBeTrue("pixel[0] == 0");

    finishTest();

</script>

</head>

<body onload="init()">

<div id="description"></div>

<div id="console"></div>

</body>

</html>