<!--
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.
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>WebGL texel fetch test.</title>
<link rel="stylesheet" href="../../../resources/js-test-style.css"/>
<link rel="stylesheet" href="../../../resources/glsl-feature-tests.css"/>
<script src="../../../js/js-test-pre.js"></script>
<script src="../../../js/webgl-test-utils.js"></script>
</head>
<body>
<canvas id="c" width="256" height="256"></canvas>
<div id="description"></div>
<div id="console"></div>
<script id="vertex-shader" type="x-shader/x-vertex">#version 300 es
  precision highp float;
  in vec4 aPosition;

  void main() {
    gl_Position = aPosition;
  }
</script>
<script id="fragment-shader" type="x-shader/x-fragment">#version 300 es
  precision mediump float;
  uniform sampler2D uSampler;
  uniform ivec2 uTestPos;

  out vec4 my_FragColor;
  void main() {
    my_FragColor = texelFetch(uSampler, uTestPos, 0);
  }
</script>
<script>
"use strict";
description("This test makes sure that texelFetch works to the WebGL 2.0 spec when retrieving a texel outside of the texture's size.");

var wtu = WebGLTestUtils;
var textureSize = 24;

var gl = wtu.create3DContext('c', undefined, 2);

function testFetchAt(x, y, expectedColor) {
  debug("");
  debug("Test fetching a texel of the texture at x = " + x +", y = " + y);
  gl.uniform2i(uTestPos, x, y);
  wtu.clearAndDrawUnitQuad(gl);
  wtu.checkCanvas(gl, expectedColor);
}

var program = wtu.setupProgram(gl, ["vertex-shader", "fragment-shader"]);
var aPosition = gl.getAttribLocation(program, "aPosition");
var uTestPos = gl.getUniformLocation(program, "uTestPos");

debug('Creating a texture with size ' + textureSize + '*' + textureSize);
var tex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
wtu.fillTexture(gl, tex, textureSize, textureSize, [0, 255, 0, 255]);

wtu.setupUnitQuad(gl, aPosition);

testFetchAt(0, 0, [0, 255, 0, 255]);
testFetchAt(textureSize - 1, textureSize - 1, [0, 255, 0, 255]);
testFetchAt(textureSize, 0, [0, 0, 0, 0]);
testFetchAt(0, textureSize, [0, 0, 0, 0]);
testFetchAt(-1, 0, [0, 0, 0, 0]);
testFetchAt(0, -1, [0, 0, 0, 0]);
testFetchAt(-1, 1, [0, 0, 0, 0]);

finishTest();
</script>
</body>
</html>
