<!--
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>
<div id="description"></div>
<div id="console"></div>

<canvas id="canvas" width="1" height="1"></canvas>

<script id="vshader" type="x-shader/x-vertex">
attribute float a_vertex;
void main()
{
    gl_Position = a_vertex == 0.0 ? vec4(9, 9, 9, 1) : vec4(0.5, 0.5, 0.5, 1);
}
</script>

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

<script>
"use strict";
description("Tests that uninitialized WebGLBuffers are zeroed out");

var wtu = WebGLTestUtils;
var gl = wtu.create3DContext(document.getElementById("canvas"));
var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["a_vertex"]);
shouldBeTrue("program != null");

var TEST_LENGTH = 1024;
var TEST_BUFSIZE = TEST_LENGTH * 4;
var data = new Float32Array(TEST_LENGTH / 4); // this array is zeroed

var indices = new Uint16Array(TEST_LENGTH);
for (var i = 0; i < TEST_LENGTH; i++) {
  indices[i] = i;
}

gl.clearColor(0, 1, 0, 1);

function test(initFunction) {
  var uninitializedBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, uninitializedBuffer);
  initFunction();

  var elements = gl.createBuffer();
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, elements);
  gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);

  gl.useProgram(program);
  var vertexLoc = gl.getAttribLocation(program, "a_vertex");
  gl.vertexAttribPointer(vertexLoc, 1, gl.FLOAT, gl.FALSE, 0, 0);
  gl.enableVertexAttribArray(vertexLoc);

  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "no error should result from setup");

  gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
  gl.drawElements(gl.POINTS, TEST_LENGTH, gl.UNSIGNED_SHORT, 0);
  wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0, 255, 0, 255], "buffer should be initialized to zero");

  gl.deleteBuffer(uninitializedBuffer);
}

var REPETITIONS = 50;

var j;
debug("");
debug("testing bufferData(..., size, ...)");
for (j = 0; j < REPETITIONS; j++) {
  test(function() {
    gl.bufferData(gl.ARRAY_BUFFER, TEST_BUFSIZE, gl.STATIC_DRAW);
  });
}

debug("");
debug("testing bufferSubData(..., offset, data) of uninitialized buffer");
for (j = 0; j < REPETITIONS; j++) {
  test(function() {
    gl.bufferData(gl.ARRAY_BUFFER, TEST_BUFSIZE, gl.STATIC_DRAW);
    // bufferSubData the second quarter of the buffer
    gl.bufferSubData(gl.ARRAY_BUFFER, TEST_BUFSIZE / 4, data);
  });
}

var successfullyParsed = true;
</script>

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