<!--
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>
</head>
<body>
<canvas id="example" width="1" height="1"></canvas>
<div id="description"></div>
<div id="console"></div>

<script id="vs" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vColor;
varying vec4 color;
void main() {
    gl_Position = vPosition;
    color = vColor;
}
</script>
<script id="fs" type="x-shader/x-fragment">
precision mediump float;
varying vec4 color;
void main() {
  gl_FragColor = color;
}
</script>
<script>
"use strict";
description('Test that updating the size of a vertex buffer is properly noticed by the WebGL implementation.')

var wtu = WebGLTestUtils;
var gl = wtu.create3DContext("example");
var program = wtu.setupProgram(gl, ["vs", "fs"], ["vPosition", "vColor"]);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after initialization");

var vertexObject = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexObject);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(
    [-1,1,0, 1,1,0, -1,-1,0,
     -1,-1,0, 1,1,0, 1,-1,0]), gl.STATIC_DRAW);
gl.enableVertexAttribArray(0);
gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after vertex setup");

var texCoordObject = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, texCoordObject);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(
    [0,0, 1,0, 0,1,
     0,1, 1,0, 1,1]), gl.STATIC_DRAW);
gl.enableVertexAttribArray(1);
gl.vertexAttribPointer(1, 2, gl.FLOAT, false, 0, 0);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after texture coord setup");

// Now resize these buffers because we want to change what we're drawing.
gl.bindBuffer(gl.ARRAY_BUFFER, vertexObject);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
    -1,1,0, 1,1,0, -1,-1,0, 1,-1,0,
    -1,1,0, 1,1,0, -1,-1,0, 1,-1,0]), gl.STATIC_DRAW);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after vertex redefinition");
gl.bindBuffer(gl.ARRAY_BUFFER, texCoordObject);
gl.bufferData(gl.ARRAY_BUFFER, new Uint8Array([
    255, 0, 0, 255,
    255, 0, 0, 255,
    255, 0, 0, 255,
    255, 0, 0, 255,
    0, 255, 0, 255,
    0, 255, 0, 255,
    0, 255, 0, 255,
    0, 255, 0, 255]), gl.STATIC_DRAW);
gl.vertexAttribPointer(1, 4, gl.UNSIGNED_BYTE, false, 0, 0);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after texture coordinate / color redefinition");

var numQuads = 2;
var indices = new Uint8Array(numQuads * 6);
for (var ii = 0; ii < numQuads; ++ii) {
    var offset = ii * 6;
    var quad = (ii == (numQuads - 1)) ? 4 : 0;
    indices[offset + 0] = quad + 0;
    indices[offset + 1] = quad + 1;
    indices[offset + 2] = quad + 2;
    indices[offset + 3] = quad + 2;
    indices[offset + 4] = quad + 1;
    indices[offset + 5] = quad + 3;
}
var indexObject = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexObject);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after setting up indices");
gl.drawElements(gl.TRIANGLES, numQuads * 6, gl.UNSIGNED_BYTE, 0);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after drawing");

debug("")
var successfullyParsed = true;
</script>

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