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Copyright (c) 2019 The Khronos Group Inc.
Use of this source code is governed by an MIT-style license that can be
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>CopyTexSubImage2D partial destination texture 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>
</head>
<body>
<div id="description"></div>
<canvas id="canvas"></canvas>
<div id="console"></div>

<script>
"use strict";
description("Verifies that copyTexSubImage2D redefining part of the destination texture works as expected.");

function runTest() {
    var wtu = WebGLTestUtils;
    var canvas = document.getElementById("canvas");
    canvas.width = 256;
    canvas.height = 256;
    var gl = wtu.create3DContext(canvas);
    // Try this test multiple times.
    for (var ii = 0; ii < 10; ++ii) {
        gl.clearColor(0.0, 1.0, 0.0, 1.0);
        gl.clear(gl.COLOR_BUFFER_BIT);
        var tex = gl.createTexture();
        gl.bindTexture(gl.TEXTURE_2D, tex);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
        // Allocate a texture twice as tall as the canvas.
        // Conceptually, it is filled with zeros.
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, canvas.width, 2 * canvas.height,
                      0, gl.RGBA, gl.UNSIGNED_BYTE, null);
        // Copy the entire framebuffer into the top part of this texture.
        gl.copyTexSubImage2D(gl.TEXTURE_2D, 0, 0, 0, 0, 0, canvas.width, canvas.height);
        // Draw the texture back into the canvas.
        var program = wtu.setupTexturedQuad(gl);
        wtu.drawUnitQuad(gl);
        gl.deleteProgram(program);
        gl.deleteTexture(tex);
        wtu.checkCanvasRect(gl, 0, 0, canvas.width, canvas.height / 2, [0, 255, 0, 255],
                            "should be green");
        wtu.checkCanvasRect(gl, 0, canvas.height / 2, canvas.width, canvas.height / 2, [0, 0, 0, 0],
                            "should be transparent black");
    }
}

runTest();

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

</body>
</html>
