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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>WebGL required buffer clear behaviour test</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>
<style type="text/css">
body {
    height: 3000px;
}
</style>
</head>
<body>
<!-- Important to put the canvas at the top so that it's always visible even in the test suite runner.
     Otherwise it just doesn't get composited in Firefox. -->
<canvas width="20" height="20" style="border: 1px solid blue;" id="c"></canvas>
<div id="description"></div>
<div id="console"></div>
<script type="application/javascript">
"use strict";

description("This test ensures WebGL implementations correctly clear the drawing buffer " +
            "on composite if preserveDrawingBuffer is false.");
debug("");

var wtu = WebGLTestUtils;

var gl = wtu.create3DContext("c");
shouldBeTrue("gl != null");
shouldBeTrue('gl.getContextAttributes().preserveDrawingBuffer == false');

gl.clearColor(1, 0, 0, 1);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT | gl.STENCIL_BUFFER_BIT);

// enable scissor here, before compositing, to make sure it's correctly
// ignored and restored
gl.scissor(0, 10, 10, 10);
gl.enable(gl.SCISSOR_TEST);

function clear() {
    // scissor was set earlier
    gl.clearColor(0, 0, 1, 1);
    gl.clear(gl.COLOR_BUFFER_BIT);

    wtu.checkCanvasRect(gl, 0, 10, 10, 10, [0, 0, 255, 255],
        "cleared corner should be blue, stencil should be preserved");
    wtu.checkCanvasRect(gl, 0, 0, 10, 10, [0, 0, 0, 0],
        "remainder of buffer should be cleared");

    finishTest();
    return;
}

wtu.waitForComposite(clear);

var successfullyParsed = true;
</script>
</body>
</html>
