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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Check that the canvas is NOT recomposited after unsucessful draw call</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>
canvas {
    border: 1px solid black;
}
.correct {
    border: 1px solid black;
    background-color: #ffffff;
}
</style>
</head>
<body>
<pre>
This test must be run manually.

This test tests that a canvas is cleared
even when a draw call has a zero count.

You should see three <span class="correct">white rectangles</span>
with black outlines on success.
</pre>
<canvas id='c1'></canvas>
<canvas id='c2'></canvas>
<canvas id='c3'></canvas>
<div id="console"></div>
<script id="vshader" type="x-shader/x-vertex">
void main() {
  gl_Position = vec4(0,0,0,1);
}
</script>
<script id="fshader" type="x-shader/x-fragment">
precision mediump float;
void main() {
  discard;
}
</script>
<script>
"use strict";
var wtu = WebGLTestUtils;
var c1 = document.getElementById("c1");
var c2 = document.getElementById("c2");
var c3 = document.getElementById("c2");
var gl1 = wtu.create3DContext(c1);
var gl2 = wtu.create3DContext(c2);
var gl3 = wtu.create3DContext(c2);
gl1.clearColor(0,1,0,1);
gl1.clear(gl1.COLOR_BUFFER_BIT);
gl2.clearColor(0,1,0,1);
gl2.clear(gl2.COLOR_BUFFER_BIT);
gl3.clearColor(0,1,0,1);
gl3.clear(gl2.COLOR_BUFFER_BIT);

wtu.waitForComposite(function() {
  // test drawArrays
  gl1.drawArrays(gl1.TRIANGLES, 0, 0);
  wtu.glErrorShouldBe(gl1, gl1.NO_ERROR, "no errors");
});

wtu.waitForComposite(function() {
  // test drawElements
  var buf = gl2.createBuffer();
  gl2.bindBuffer(gl2.ELEMENT_ARRAY_BUFFER, buf);
  gl2.bufferData(gl2.ELEMENT_ARRAY_BUFFER, new Uint8Array(1), gl2.STATIC_DRAW);
  gl2.drawElements(gl2.TRIANGLES, 0, gl2.UNSIGNED_SHORT, 0);
  wtu.glErrorShouldBe(gl2, gl2.NO_ERROR, "no errors");
});

wtu.waitForComposite(function() {
  // test draw with program.
  wtu.setupProgram(gl3, ["vshader", "fshader"]);
  gl1.drawArrays(gl3.TRIANGLES, 0, 0);
  wtu.glErrorShouldBe(gl3, gl2.NO_ERROR, "no errors");
});

</script>
</body>
</html>