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Copyright (c) 2019 The Khronos Group Inc.
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<head>
<meta charset="utf-8">
<title>Bug - the precision qualifier of a constant variable should affect the precision of a consuming operation</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>
<script src="../../../js/glsl-conformance-test.js"></script>
</head>
<body>
<div id="description"></div>
<div id="console"></div>
<script id="fshader" type="x-shader/x-fragment">
// It is assumed that uTest is set to 0. It's here to make the expression not constant.
uniform mediump float uTest;

void main() {
    // exact representation of 4096.5 requires 13 bits of relative precision.
    const highp float c = 4096.5;
    mediump float a = 0.0;
    // Below, addition should be evaluated at highp, since one of the operands has the highp qualifier.
    // Thus fract should also be evaluated at highp.
    // See OpenGL ES Shading Language spec section 4.5.2.
    // This should make the result 0.5, since highp provides at least 16 bits of relative precision.
    // (exceptions for operation precision are allowed for a small number of computationally
    // intensive built-in functions, but it is reasonable to think that fract is not one of those).
    // However, if fract() is incorrectly evaluated at minimum precision fulfilling mediump criteria,
    // or at IEEE half float precision, the result is 0.0.
    a = fract(c + uTest);

    // Multiply by 2.0 to make the color green.
    gl_FragColor = vec4(0.0, 2.0 * a, 0.0, 1.0);
}
</script>
<script id="fshaderNoConstants" type="x-shader/x-fragment">
// This shader has the same functionality as the one above, but it doesn't contain
// operations that can be constant folded at compile-time.
// It's here to provide a point of comparison.
uniform mediump float uTest;
uniform highp float uTestHigh;

void main() {
    highp float c = 4096.5 + uTestHigh;
    mediump float a = 0.0;
    a = fract(c + uTest);
    gl_FragColor = vec4(0.0, 2.0 * a, 0.0, 1.0);
}
</script>
<script id="fshaderAllHighp" type="x-shader/x-fragment">
// This shader has the same functionality as the one above, but it only uses highp.
// It's here to provide a point of comparison.
uniform highp float uTest;

void main() {
    highp float c = 4096.5 + uTest;
    highp float a = 0.0;
    a = fract(c + uTest);
    gl_FragColor = vec4(0.0, 2.0 * a, 0.0, 1.0);
}
</script>
<script type="application/javascript">
"use strict";
description();

function test() {
  var wtu = WebGLTestUtils;
  var gl = wtu.create3DContext();
  if (!gl) {
    testFailed("context does not exist");
    finishTest();
    return;
  }
  if (gl.getShaderPrecisionFormat(gl.FRAGMENT_SHADER, gl.HIGH_FLOAT).precision == 0) {
    testPassed("highp precision not supported");
    finishTest();
  } else {
    GLSLConformanceTester.runRenderTests([
    {
      fShaderId: 'fshader',
      fShaderSuccess: true,
      linkSuccess: true,
      passMsg: 'The precision qualifier of a constant affects built-in function results',
      uniforms: [{name: "uTest", functionName: "uniform1f", value: 0}]
    },
    {
      fShaderId: 'fshaderNoConstants',
      fShaderSuccess: true,
      linkSuccess: true,
      passMsg: 'The precision qualifier of a variable affects built-in function results',
      uniforms: [{name: "uTest", functionName: "uniform1f", value: 0},
                 {name: "uTestHigh", functionName: "uniform1f", value: 0}]
    },
    {
      fShaderId: 'fshaderAllHighp',
      fShaderSuccess: true,
      linkSuccess: true,
      passMsg: 'All variables are qualified as highp',
      uniforms: [{name: "uTest", functionName: "uniform1f", value: 0}]
    },
    ]);
  }
};

test();
var successfullyParsed = true;
</script>
</body>
</html>
