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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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<!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 id="vshader" type="x-shader/x-vertex">

attribute vec2 pos;

void main()

    gl_Position = vec4(pos, 0, 1);

</script>

<script id="fshader" type="x-shader/x-fragment">

precision mediump float;

uniform vec4 col;

void main()

    gl_FragColor = col;

</script>

<script>

"use strict";

var wtu = WebGLTestUtils;

function draw(gl, arr, colLoc, col) {

    var vertices = new Float32Array(arr);

    var vertBuf = gl.createBuffer();

    gl.bindBuffer(gl.ARRAY_BUFFER, vertBuf);

    gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

    gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);

    gl.uniform4fv(colLoc, col);

    gl.drawArrays(gl.TRIANGLE_STRIP, 0, vertices.length / 2);

function clear(gl, col) {

    gl.clearColor(col[0], col[1], col[2], col[3]);

    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

function check(gl, winding, shoulddraw) {

    var msg = winding + ' face was ' + (shoulddraw ? '' : 'not ') + 'drawn.';

    wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 255, 0, 255], msg);

function runTest() {

    var cwVertices = [-1, -1, -1, 1, 1, -1, 1, 1];

    var ccwVertices = [-1, 1, -1, -1, 1, 1, 1, -1];

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

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

    var ok;

    var gl = wtu.create3DContext('testbed', { antialias: false });

    if (!gl) {

        testFailed('could not create context');

        return;

    var program = wtu.setupProgram(gl, ['vshader', 'fshader'], ['pos']);

    var colLoc = gl.getUniformLocation(program, 'col');

    gl.enableVertexAttribArray(0);

    debug('CULL_FACE should be off by default');

    clear(gl, red);

    draw(gl, ccwVertices, colLoc, green);

    check(gl, 'CCW', true);

    clear(gl, red);

    draw(gl, cwVertices, colLoc, green);

    check(gl, 'CW', true);

    debug('Enabling CULL_FACE');

    gl.enable(gl.CULL_FACE);

    debug('BACK and CCW should be set by default');

    clear(gl, red);

    draw(gl, ccwVertices, colLoc, green);

    check(gl, 'CCW', true);

    clear(gl, green);

    draw(gl, cwVertices, colLoc, red);

    check(gl, 'CW', false);

    var tests = [{ cullFace : 'BACK', frontFace : 'CCW', drawCCW : true, drawCW : false},

                 { cullFace : 'BACK', frontFace : 'CW', drawCCW : false, drawCW : true},

                 { cullFace : 'FRONT', frontFace : 'CCW', drawCCW : false, drawCW : true },

                 { cullFace : 'FRONT', frontFace : 'CW', drawCCW : true, drawCW : false},

                 { cullFace : 'FRONT_AND_BACK', frontFace : 'CCW', drawCCW : false, drawCW : false},

                 { cullFace : 'FRONT_AND_BACK', frontFace : 'CW', drawCCW : false, drawCW : false}];

    for (var i = 0; i < tests.length; ++i) {

        var t = tests[i];

        debug('Setting ' + t.cullFace + ' and ' + t.frontFace);

        gl.cullFace(gl[t.cullFace]);

        gl.frontFace(gl[t.frontFace]);

        clear(gl, t.drawCCW ? red : green);

        draw(gl, ccwVertices, colLoc, t.drawCCW ? green : red);

        check(gl, 'CCW', t.drawCCW);

        clear(gl, t.drawCW ? red : green);

        draw(gl, cwVertices, colLoc, t.drawCW ? green : red);

        check(gl, 'CW', t.drawCW);

</script>

</head>

<body>

<canvas id="testbed" width="16" height="16" style="width:50px; height:50px"></canvas>

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

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

<script>

"use strict";

description('Verify that culling works');

runTest();

var successfullyParsed = true;

</script>

<script src="../../js/js-test-post.js"></script>

</body>

</html>