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**
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** MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS.
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>WebGL Canvas Conformance Tests</title>
<link rel="stylesheet" href="../../resources/js-test-style.css"/>
<script src="../../resources/js-test-pre.js"></script>
<script src="../resources/webgl-test.js"></script>
<script src="../resources/webgl-test-utils.js"></script>
</head>
<body>
<div id="description"></div>
<div id="console"></div>
<canvas id="canvas" width="50" height="50"> </canvas>

<script id="vshader" type="x-shader/x-vertex">
attribute vec4 vPosition;
void main()
{
  gl_Position = vPosition;
}
</script>

<script id="fshader" type="x-shader/x-fragment">
void main()
{
  gl_FragColor = vec4(1.0,0.0,0.0,1.0);
}
</script>

<script>
"use strict";
function fail(x,y, buf, shouldBe)
{
  var i = (y*50+x) * 4;
  var reason = "pixel at ("+x+","+y+") is ("+buf[i]+","+buf[i+1]+","+buf[i+2]+","+buf[i+3]+"), should be "+shouldBe;
  testFailed(reason);
}

function pass()
{
  testPassed("drawing is correct");
}

function drawTriangleTest(gl)
{
  gl.viewport(0, 0, 50, 50);
  var vertexObject = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, vertexObject);
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([ 0,0.5,0, -0.5,-0.5,0, 0.5,-0.5,0 ]), gl.STATIC_DRAW);
  gl.enableVertexAttribArray(0);
  gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0);

  gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
  gl.drawArrays(gl.TRIANGLES, 0, 3);

  var buf = new Uint8Array(50 * 50 * 4);
  gl.readPixels(0, 0, 50, 50, gl.RGBA, gl.UNSIGNED_BYTE, buf);

  // Test several locations
  // First line should be all black
  for (var i = 0; i < 50; ++i) {
    if (buf[i*4] != 0 || buf[i*4+1] != 0 || buf[i*4+2] != 0 || buf[i*4+3] != 255) {
      fail(i, 0, buf, "(0,0,0,255)");
      return;
    }
  }
  // Line 15 should be red for at least 10 red pixels starting 20 pixels in
  var offset = (15*50+20) * 4;
  for (var i = 0; i < 10; ++i) {
    if (buf[offset+i*4] != 255 || buf[offset+i*4+1] != 0 || buf[offset+i*4+2] != 0 || buf[offset+i*4+3] != 255) {
      fail(20 + i, 15, buf, "(255,0,0,255)");
      return;
    }
  }
  // Last line should be all black
  offset = (49*50) * 4;
  for (var i = 0; i < 50; ++i) {
    if (buf[offset+i*4] != 0 || buf[offset+i*4+1] != 0 || buf[offset+i*4+2] != 0 || buf[offset+i*4+3] != 255) {
      fail(i, 49, buf, "(0,0,0,255)");
      return;
    }
  }
}

description("This test ensures WebGL implementations correctly implement drawingbufferWidth/Height with compositing.");

debug("");

var wtu = WebGLTestUtils;
var err;
var maxSize;
var gl =  wtu.create3DContext("canvas");
if (!gl) {
  testFailed("context does not exist");
} else {
  testPassed("context exists");

  var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["vPosition"]);
  shouldBeNonNull("program");
  gl.enable(gl.DEPTH_TEST);
  gl.clearColor(0, 0, 0, 1);
  shouldBe('gl.getError()', 'gl.NO_ERROR');

  debug("");
  debug("Checking drawingBufferWidth/drawingBufferHeight");

  shouldBe('gl.drawingBufferWidth', 'gl.canvas.width');
  shouldBe('gl.drawingBufferHeight', 'gl.canvas.height');

  // Check that changing the canvas size to something too large falls back to reasonable values.
  maxSize = gl.getParameter(gl.MAX_VIEWPORT_DIMS);
  shouldBeTrue('maxSize[0] > 0');
  shouldBeTrue('maxSize[1] > 0');

  // debug("MAX_VIEWPORT_DIMS = " + maxSize[0] + "x" + maxSize[1]);
  gl.canvas.width = maxSize[0] * 4;
  gl.canvas.height = maxSize[1] * 4;
  shouldBeTrue('gl.drawingBufferWidth > 0');
  shouldBeTrue('gl.drawingBufferHeight > 0');
  shouldBeTrue('gl.drawingBufferWidth <= maxSize[0]');
  shouldBeTrue('gl.drawingBufferHeight <= maxSize[1]');
  shouldBe('gl.getError()', 'gl.NO_ERROR');

  debug("");
  debug("Checking scaling up then back down to 50/50, drawing still works.");
  gl.canvas.width = 50;
  gl.canvas.height = 50;
  shouldBeTrue('gl.drawingBufferWidth == 50');
  shouldBeTrue('gl.drawingBufferHeight == 50');
  shouldBe('gl.getError()', 'gl.NO_ERROR');
  drawTriangleTest(gl);
  shouldBe('gl.getError()', 'gl.NO_ERROR');
}
debug("")
var successfullyParsed = true;
</script>
<script src="../../resources/js-test-post.js"></script>
</body>
</html>