<!DOCTYPE HTML>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />

<title>WebGL test: Basic drawing</title>

<script src="/tests/SimpleTest/SimpleTest.js"></script>
<link rel="stylesheet" href="/tests/SimpleTest/test.css">
<script src="driver-info.js"></script>
<script src="webgl-util.js"></script>


<script id="vs" type="x-shader/x-vertex">

attribute vec2 aVertCoord;

void main(void) {
  gl_Position = vec4(aVertCoord, 0.0, 1.0);
}

</script>
<script id="fs" type="x-shader/x-fragment">

precision mediump float;

void main(void) {
  gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);
}

</script>
<body>
<canvas id="c" width="64" height="64"></canvas>
<script>

// Give ourselves a scope to return early from:
(function() {
  var gl = c.getContext('webgl');
  if (!gl) {
    todo(false, 'WebGL is unavailable.');
    return;
  }

  gl.disable(gl.DEPTH_TEST);

  var prog   = WebGLUtil.createProgramByIds(gl, 'vs', 'fs');
  if (!prog) {
    ok(false, 'Program linking should succeed.');
    return;
  }

  prog.aVertCoord = gl.getAttribLocation(prog, "aVertCoord");
  ok(prog.aVertCoord >= 0, '`aVertCoord` should be valid.');

  function checkGLError(func, info, refValue) {
    if (!refValue)
      refValue = 0;

    var error = gl.getError();
    func(error == refValue,
         '[' + info + '] gl.getError should be 0x' + refValue.toString(16) +
                                        ', was 0x' + error.toString(16) + '.');
  }

  var vertCoordArr = new Float32Array([
    -1, -1,
     1, -1,
    -1,  1,
     1,  1,
  ]);
  var vertCoordBuff = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, vertCoordBuff);
  gl.bufferData(gl.ARRAY_BUFFER, vertCoordArr, gl.STATIC_DRAW);

  var indexArr = new Uint16Array([
    0, 1, 2,
    3,
  ]);
  var indexBuff = gl.createBuffer();
  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuff);
  gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indexArr, gl.STATIC_DRAW);


  function testPixel(x, y, refData, func, infoString) {
    var pixel = new Uint8Array(4);
    gl.readPixels(x, y, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, pixel);

    var pixelMatches = pixel[0] == refData[0] &&
                       pixel[1] == refData[1] &&
                       pixel[2] == refData[2] &&
                       pixel[3] == refData[3];
    func(pixelMatches, infoString);
  }

  function preDraw(info) {
    gl.clearColor(1.0, 0.0, 0.0, 1.0);
    gl.clear(gl.COLOR_BUFFER_BIT);

    testPixel(0, 0, [255, 0, 0, 255], ok, '[' + info + '] Should be red before drawing.');
  }

  function postDraw(info) {
    testPixel(0, 0, [0, 255, 0, 255], ok, '[' + info + '] Should be green before drawing.');
  }

  gl.useProgram(prog);
  gl.enableVertexAttribArray(prog.aVertCoord);
  gl.vertexAttribPointer(prog.aVertCoord, 2, gl.FLOAT, false, 0, 0);

  // Start drawing
  checkGLError(ok, 'after setup');

  preDraw('DrawArrays');
  gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
  postDraw('DrawArrays');
  checkGLError(ok, 'after DrawArrays');

  preDraw('DrawElements');
  gl.drawElements(gl.TRIANGLE_STRIP, 4, gl.UNSIGNED_SHORT, 0);
  postDraw('DrawElements');
  checkGLError(ok, 'after DrawElements');

  ok(true, 'Test complete.');
})();

</script>

