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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
  <title>gl-fragcoord 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>
<canvas id="example" width="32" height="32">
</canvas>
<div id="description"></div>
<div id="console"></div>
  <script id="vshader" type="x-shader/x-vertex">
    attribute vec4 vPosition;
    void main()
    {
      gl_Position = vPosition;
    }
  </script>

  <script id="fshader" type="x-shader/x-fragment">
    precision mediump float;
    void main()
    {
      gl_FragColor = vec4(
        floor(gl_FragCoord.x * 4.0 / 32.0) / 4.0,
        floor(gl_FragCoord.y * 4.0 / 32.0) / 4.0,
        floor(gl_FragCoord.z * 4.0) / 4.0,
        1);
    }
  </script>

  <script>
    "use strict";
    function init()
    {
      description("tests gl_FragCoord");

      var wtu = WebGLTestUtils;
      var gl = wtu.create3DContext("example");
      var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["vPosition"]);

      var vertexObject = gl.createBuffer();
      gl.bindBuffer(gl.ARRAY_BUFFER, vertexObject);
      gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(
        [-1, -1, -1,  1, -1,  0, -1,  1,  0,
         -1,  1,  0,  1, -1,  0,  1,  1,  1]),
                    gl.STATIC_DRAW);
      gl.enableVertexAttribArray(0);
      gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0);

      gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
      gl.drawArrays(gl.TRIANGLES, 0, 6);
      wtu.glErrorShouldBe(gl, gl.NO_ERROR, "no errors from draw");

      for (var xx = 0; xx < 32; xx += 4) {
        for (var yy = 0; yy < 32; yy += 4) {
          var zz = (xx / 64) + (yy / 64);
          var color = [
             Math.floor(Math.floor(xx * 4.0 / 32.0) / 4 * 256),
             Math.floor(Math.floor(yy * 4.0 / 32.0) / 4 * 256),
             Math.floor(Math.floor(zz * 4.0) / 4 * 256)
          ];
          var msg = "should be " + color;
          wtu.checkCanvasRect(
              gl, xx, yy, 1, 1, color, msg, 4);
        }
      }
    }

    init();
    var successfullyParsed = true;
  </script>
<script src="../../../resources/js-test-post.js"></script>

</body>
</html>
