<!--
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 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;

void main()
{
    gl_FragColor = vec4(0, 1, 0, 1);
}
</script>

<script>
"use strict";
var wtu = WebGLTestUtils;

// Check a single 32-bit RGBA pixel.
function checkPixel(buf, index, correct) {
    for (var i = 0; i < 4; ++i) {
        if (buf[index + i] != correct[i]) {
            return false;
        }
    }
    return true;
}

// Check the line loop by reading the pixels and making sure just the edge
// pixels are green and the rest are black.
function checkLineLoop(gl, w) {
    var buf = new Uint8Array(w * w * 4);
    gl.readPixels(0, 0, w, w, gl.RGBA, gl.UNSIGNED_BYTE, buf);
    var green = [0,255,0,255];
    var black = [0,0,0,255];
    var isCorrect = true;
    for (var j = 0; j < w * w * 4; j += 4) {
        var correct = black;
        if (j < w * 4 || j > w * (w - 1) * 4 || j % (w * 4) == 0 || j % (w * 4) == (w - 1) * 4) {
            correct = green;
        }
        // ignore corner pixels
        if ((j == 0) || (j == 4*(w-1)) || (j == 4*w*(w-1)) || (j== 4*(w*w - 1))) {
            continue;
        }
        if (!checkPixel(buf, j, correct)) {
            isCorrect = false;
            break;
        }
    }
    if (isCorrect) {
        testPassed("Line loop was drawn correctly.");
    } else {
        testFailed("Line loop was drawn incorrectly.");
    }
}

// Check the tri fan by reading the pixels and making sure they are all green.
function checkTriFan(gl, w) {
    var buf = new Uint8Array(w * w * 4);
    gl.readPixels(0, 0, w, w, gl.RGBA, gl.UNSIGNED_BYTE, buf);
    var filled = true;
    for (var j = 0; j < w * w * 4; j += 4) {
        if (!checkPixel(buf, j, [0,255,0,255])) {
            filled = false;
            break;
        }
    }
    if (filled) {
        testPassed("Triangle fan was drawn correctly.");
    } else {
        testFailed("Triangle fan was drawn incorrectly.");
    }
}

function runTest() {
    var gl = wtu.create3DContext('testbed', { antialias: false });
    if (!gl) {
        testFailed('could not create context');
        return;
    }
    gl.clearColor(0, 0, 0, 1);
    var program = wtu.setupProgram(gl, ['vshader', 'fshader'], ['pos'])
    var w = document.getElementById('testbed').width;

    gl.enableVertexAttribArray(0);

    //---------- LINE_LOOP----------
    var d = 1/w;
    var vertices = new Float32Array([-1+d, -1+d, 1-d, -1+d, 1-d, 1-d, -1+d, 1-d]);
    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);
    var indBuf = gl.createBuffer();
    var indices = new Uint16Array([0, 1, 2, 3]);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indBuf);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);

    debug('Draw a square using a line loop and verify that it draws all four sides and nothing else.');
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawArrays(gl.LINE_LOOP, 0, vertices.length / 2);
    checkLineLoop(gl, w);

    debug('Draw a square using an indexed line loop and verify that it draws all four sides and nothing else.');
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawElements(gl.LINE_LOOP, indices.length, gl.UNSIGNED_SHORT, 0);
    checkLineLoop(gl, w);

    vertices = new Float32Array([0, 0, 0, 0, 0, 0, -1+d, -1+d, 1-d, -1+d, 1-d, 1-d, -1+d, 1-d]);
    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);
    indBuf = gl.createBuffer();
    indices = new Uint16Array([0, 1, 2, 3, 4, 5, 6]);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indBuf);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);

    debug('Draw a square using a line loop with a vertex buffer offset and verify that it draws all four sides and nothing else.');
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawArrays(gl.LINE_LOOP, 3, vertices.length / 2 - 3);
    checkLineLoop(gl, w);

    debug('Draw a square using an indexed line loop with an index buffer offset and verify that it draws all four sides and nothing else.');
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawElements(gl.LINE_LOOP, indices.length - 3, gl.UNSIGNED_SHORT, 3 * 2);
    checkLineLoop(gl, w);

    //---------- LINE_LOOP UBYTE ----------
    var degenVerts = new Array(252 * 2);
    for (var j = 0; j < 252 * 2; ++j) {
        degenVerts[j] = -1+d;
    }
    degenVerts = degenVerts.concat([-1+d, -1+d, 1-d, -1+d, 1-d, 1-d, -1+d, 1-d]);
    vertices = new Float32Array(degenVerts);
    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);
    indBuf = gl.createBuffer();
    var degenInd = new Array(252);
    for (var j = 0; j < 252; ++j) {
        degenInd[j] = j;
    }
    degenInd = degenInd.concat([252, 253, 254, 255]);
    indices = new Uint16Array(degenInd);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indBuf);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);

    debug('Draw a square using an ubyte indexed line loop with 256 indices and verify that it draws all four sides and nothing else.');
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawElements(gl.LINE_LOOP, indices.length, gl.UNSIGNED_SHORT, 0);
    checkLineLoop(gl, w);

    //---------- TRIANGLE_FAN ----------
    vertices = new Float32Array([0, 0, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1]);
    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);
    indices = new Uint16Array([0,1,2,3,4,5]);
    indBuf = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indBuf);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);

    debug('Draw a filled square using a triangle fan and verify that it fills the entire canvas.');
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawArrays(gl.TRIANGLE_FAN, 0, vertices.length / 2);
    checkTriFan(gl, w);

    debug('Draw a filled square using an indexed triangle fan and verify that it fills the entire canvas.');
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawElements(gl.TRIANGLE_FAN, indices.length, gl.UNSIGNED_SHORT, 0);
    checkTriFan(gl, w);

    vertices = new Float32Array([1, 1, 1, 1, 1, 1, 0, 0, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1]);
    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);
    indices = new Uint16Array([0,1,2,3,4,5,6,7,8]);
    indBuf = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indBuf);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);

    debug('Draw a filled square using a triangle fan with a vertex buffer offset and verify that it fills the entire canvas.');
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawArrays(gl.TRIANGLE_FAN, 3, vertices.length / 2 - 3);
    checkTriFan(gl, w);

    debug('Draw a filled square using an indexed triangle fan with an index buffer offset and verify that it fills the entire canvas.');
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawElements(gl.TRIANGLE_FAN, indices.length - 3, gl.UNSIGNED_SHORT, 3 * 2);
    checkTriFan(gl, w);
}
</script>
</head>
<body>
<canvas id="testbed" width="10" height="10" style="width:50px; height:50px"></canvas>
<div id="description"></div>
<div id="console"></div>
<script>
"use strict";
description('Verify that LINE_LOOP and TRIANGLE_FAN works correctly.');
runTest();
var successfullyParsed = true;
</script>
<script src="../../js/js-test-post.js"></script>

</body>
</html>
