context-no-alpha-fbo-with-alpha.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.

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<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";

var wtu = WebGLTestUtils;

// This declaration needs to be global for "shouldBe" to see it

var gl;

function init()

    description('Verify that a WebGL context with alpha:false still works correctly after handling textures with an alpha channel.');

    runTest();

function getWebGL(contextAttribs)

    return wtu.create3DContext("c", contextAttribs);

function runTest()

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

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

    // Clear to black. Alpha channel of clearColor() is ignored.

    gl.clearColor(0.0, 0.0, 0.0, 0.7);

    gl.clear(gl.COLOR_BUFFER_BIT);

    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 0, 255],

                        "Alpha channel of clearColor should be ignored");

    wtu.waitForComposite(function() {

        // Make a new framebuffer and attach a texture with an alpha channel.

        var fbo = gl.createFramebuffer();

        gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);

        var texture = gl.createTexture();

        gl.bindTexture(gl.TEXTURE_2D, texture);

        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, null);

        gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);

        // Clear texture. Note that alpha channel is not 1.0.

        gl.clearColor(1.0, 0.0, 0.0, 0.5);

        gl.clear(gl.COLOR_BUFFER_BIT);

        wtu.checkCanvasRect(gl, 0, 0, 1, 1, [255, 0, 0, 128],

                            "Alpha channel of clearColor should be obeyed for FBO with alpha channel",

1);

        // Bind back buffer and check that its alpha channel is still 1.0.

        gl.bindFramebuffer(gl.FRAMEBUFFER, null);

        wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 0, 0, 255],

                            "Alpha channel of back buffer should still be 255");

        finishTest();

});

</script>

</head>

<body onload="init()">

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

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

<canvas width="20" height="20" style="border: 1px solid blue;" id="c"></canvas>

</body>

</html>