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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>WebGL Rapid Resizing Test</title>
<link rel="stylesheet" href="../../resources/js-test-style.css"/>
<script src="../../resources/js-test-pre.js"></script>
<script src="../resources/webgl-test-utils.js"></script>
</head>
<body>
<div id="description"></div>
<canvas id="canvas" style="width: 256px; height: 256px;"> </canvas>
<div id="console"></div>
<script id="vshader" type="x-shader/x-vertex">
attribute vec2 position;
void main()
{
  gl_Position = vec4(position, 0.0, 1.0);
}
</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";

description("Verifies that rapidly resizing the canvas works correctly.");

debug("");
debug("Regression test for Chromium <a href='http://crbug.com/299371'>Issue 299371</a>");
debug("");

var err;
var wtu = WebGLTestUtils;
var canvas = document.getElementById("canvas");
var largeSize = 256;
var smallSize = 128;
var currentSize = largeSize;
canvas.width = largeSize;
canvas.height = largeSize;
var gl = wtu.create3DContext(canvas);
var numFrames = 0;

if (!gl) {
  testFailed("context does not exist");
} else {
  testPassed("context exists");

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

  var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["position"]);
  shouldBeNonNull("program");

  // Prepare to draw quads
  var quadSize = 0.1;

  var vertexBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
    // Lower left
    -1, -1 + quadSize,
    -1, -1,
    -1 + quadSize, -1,
    -1 + quadSize, -1 + quadSize,

    // Lower right
    1 - quadSize, -1 + quadSize,
    1 - quadSize, -1,
    1, -1,
    1, -1 + quadSize,

    // Upper right
    1 - quadSize, 1,
    1 - quadSize, 1 - quadSize,
    1, 1 - quadSize,
    1, 1,

    // Upper left
    -1, 1,
    -1, 1 - quadSize,
    -1 + quadSize, 1 - quadSize,
    -1 + quadSize, 1
  ]), gl.STATIC_DRAW);
  gl.enableVertexAttribArray(0);
  gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);

  var indexBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
  gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array([
    0, 1, 2,
    0, 2, 3,

    4, 5, 6,
    4, 6, 7,

    8, 9, 10,
    8, 10, 11,

    12, 13, 14,
    12, 14, 15
  ]), gl.STATIC_DRAW);

  wtu.requestAnimFrame(render);
}

function render() {
  if (++numFrames < 30) {
    if (currentSize == largeSize) {
      canvas.height = smallSize;
      currentSize = smallSize;
    } else {
      canvas.height = largeSize;
      currentSize = largeSize;
    }
  }

  gl.viewport(0, 0, largeSize, currentSize);
  gl.clear(gl.COLOR_BUFFER_BIT);
  gl.drawElements(gl.TRIANGLES, 24, gl.UNSIGNED_SHORT, 0);

  // Check the four corners
  var green = [ 0, 255, 0, 255 ];
  var inset = 3;
  wtu.checkCanvasRect(gl, inset, inset, 1, 1, green, "lower left should be green", 1);
  wtu.checkCanvasRect(gl, largeSize - inset, inset, 1, 1, green, "lower right should be green", 1);
  wtu.checkCanvasRect(gl, inset, currentSize - inset, 1, 1, green, "upper left should be green", 1);
  wtu.checkCanvasRect(gl, largeSize - inset, currentSize - inset, 1, 1, green, "upper right should be green", 1);

  if (numFrames < 60) {
    wtu.requestAnimFrame(render);
  } else {
    finishTest();
  }
}

</script>

</body>
</html>