﻿<!--
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>-1 Index Rendering Test</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>
<canvas id="example" width="50" height="50">
</canvas>
<div id="description"></div>
<div id="console"></div>
<script id="vshader" type="x-shader/x-vertex">
attribute vec4 vPosition;
void main()
{
    gl_Position = vPosition;
}
</script>

<script id="fshader" type="x-shader/x-fragment">
void main()
{
    gl_FragColor = vec4(0.0,1.0,0.0,1.0);
}
</script>

<script>
"use strict";
function init()
{
    description(document.title);

    var wtu = WebGLTestUtils;
    var gl = wtu.create3DContext("example");
    var contextVersion = wtu.getDefault3DContextVersion();
    var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["vPosition"]);

    var vertexObject = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, vertexObject);
    var vertexData = new Float32Array(65536 * 3);
    vertexData[0 * 3 + 0] = 0.0;
    vertexData[0 * 3 + 1] = 0.5;
    vertexData[0 * 3 + 2] = 0.0;
    vertexData[1 * 3 + 0] = -0.5;
    vertexData[1 * 3 + 1] = -0.5;
    vertexData[1 * 3 + 2] = 0.0;
    vertexData[65535 * 3 + 0] = 0.5;
    vertexData[65535 * 3 + 1] = -0.5;
    vertexData[65535 * 3 + 2] = 0.0;
    gl.bufferData(gl.ARRAY_BUFFER, vertexData, gl.STATIC_DRAW);
    gl.enableVertexAttribArray(0);
    gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0);

    var indices = new Uint16Array([0, 1, -1]);
    var indexBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);

    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
    gl.drawElements(gl.TRIANGLES, 3, gl.UNSIGNED_SHORT, 0);

    if (contextVersion <= 1) {
        // This should render a green triangle in the middle of the canvas.
        // Some implementations may incorrectly interpret the -1 index as
        // a primitive restart and not render anything.

        // Test several locations
        // First line should be all black
        wtu.checkCanvasRect(gl, 0, 0, 50, 1, [0, 0, 0, 0]);

        // Line 15 should be green for at least 10 pixels starting from row 20
        wtu.checkCanvasRect(gl, 20, 15, 10, 1, [0, 255, 0, 255]);

        // Last line should be all black
        wtu.checkCanvasRect(gl, 0, 49, 50, 1, [0, 0, 0, 0]);
    } else {
        // For WebGL 2, PRIMITIVE_RESTART_FIXED_INDEX is always enabled.
        // Nothing should be drawn on the canvas.
        wtu.checkCanvasRect(gl, 0, 0, 50, 50, [0, 0, 0, 0]);
    }
}

init();
var successfullyParsed = true;
</script>
<script src="../../js/js-test-post.js"></script>

</body>
</html>
