<!--
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>WebGL Slow Shader example.</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="1024" height="1024" style="width: 40px; height: 40px;">
</canvas>
<div id="description"></div>
<div id="console"></div>
<script id="slow" type="text/something-not-javascript">
precision mediump float;
uniform sampler2D tex;
varying vec2 texCoord;
void main() {
  gl_FragColor = texture2D(tex, texture2D(tex, texture2D(tex, texCoord).xy).xy);
}
</script>
<script>
"use strict";
window.onload = main;

debug("Tests drawing a very slow shader.");
var wtu = WebGLTestUtils;
var canvas = document.getElementById("example");
canvas.addEventListener("webglcontextlost", function(e) { e.preventDefault(); }, false);
canvas.addEventListener("webglcontextrestored", function(e) { }, false);
var gl = wtu.create3DContext(canvas);
var maxTexSize = gl.getParameter(gl.MAX_TEXTURE_SIZE);
var texSize = Math.min(maxTexSize, 4096);
debug("Max Texture size: " + maxTexSize);
debug("Texture size: " + texSize);
var shaderSource =
    document.getElementById("slow").text.replace(/\$size/g, texSize + ".0");
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after getting a context");
var program = wtu.setupProgram(
    gl,
    [wtu.simpleTextureVertexShader, shaderSource],
    ['vPosition', 'texCoord0'],
    [0, 1]);
wtu.setupUnitQuad(gl, 0, 1);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after program setup");
var tex = gl.createTexture();
gl.enable(gl.BLEND);
gl.disable(gl.DEPTH_TEST);

wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after creating texture");
debug("preparing...");
var numBytes = texSize * texSize * 4;
var pixelBuf = new ArrayBuffer(numBytes);
var pixels = new Uint8Array(pixelBuf);
for (var ii = 0; ii < numBytes; ++ii) {
  pixels[ii] = Math.random() * 255;
}
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texImage2D(
      gl.TEXTURE_2D, 0, gl.RGBA, texSize, texSize, 0,
      gl.RGBA, gl.UNSIGNED_BYTE, pixels);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after texture setup");

gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after texture param setting");

var loc = gl.getUniformLocation(program, "tex");
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after getting tex location");
gl.uniform1i(loc, 0);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after setting tex uniform");

var numQuads = 1000;
var indexBuf = new ArrayBuffer(numQuads * 6);
var indices = new Uint8Array(indexBuf);
for (var ii = 0; ii < numQuads; ++ii) {
  var offset = ii * 6;
  indices[offset + 0] = 0;
  indices[offset + 1] = 1;
  indices[offset + 2] = 2;
  indices[offset + 3] = 3;
  indices[offset + 4] = 4;
  indices[offset + 5] = 5;
}
var indexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indices, gl.STATIC_DRAW);
wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after setting up indices");

function main () {
  if (confirm(
      "After clicking OK your machine may become unresponsive or crash.")) {
    gl.drawElements(gl.TRIANGLES, numQuads * 6, gl.UNSIGNED_BYTE, 0);
    wtu.glErrorShouldBe(gl, gl.NO_ERROR, "after drawing");
  } else {
    debug("cancelled");
  }
}

var successfullyParsed = true;
</script>
</body>
</html>
