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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>WebGL ReadPixels conformance test.</title>
<link rel="stylesheet" href="../../resources/js-test-style.css"/>
<script src="../../resources/js-test-pre.js"></script>
<script src="../resources/webgl-test-utils.js"> </script>
</head>
<body>
<canvas id="example" width="200" height="200" style="width: 20px; height: 20px"></canvas>
<div id="description"></div>
<div id="console"></div>
<script>
"use strict";
description("Checks that ReadPixels works as expected.");

var wtu = WebGLTestUtils;
var canvas = document.getElementById("example");
var gl = wtu.create3DContext(canvas);

var actual;
var expected;
var width = 2;
var height = 2;
var continueTestFunc = continueTestPart1;

gl.clearColor(1, 1, 1, 1);
gl.clear(gl.COLOR_BUFFER_BIT);

// Resize the canvas to 2x2. This is an attempt to get stuff in the backbuffer.
// that shouldn't be there.
canvas.addEventListener("webglcontextlost", function(e) { e.preventDefault(); }, false);
canvas.addEventListener("webglcontextrestored", continueTestAfterContextRestored, false);
canvas.width = width;
canvas.height = height;
if (gl.getError() != gl.CONTEXT_LOST_WEBGL) {
  continueTestPart1();
}

function continueTestAfterContextRestored() {
  window.gl = wtu.create3DContext(canvas);
  var func = continueTestFunc;
  window.continueTestFunc = function() { testFailed("should not be here"); };
  func();
}

function continueTestPart1() {
  gl.clearColor(0.5, 0.7, 1.0, 1);
  gl.clear(gl.COLOR_BUFFER_BIT);

  var innerColor = [0.5, 0.7, 1.0, 1];
  var outerColor = [0, 0, 0, 0];

  var tests = [
    { msg: 'in range', checkColor: innerColor, x:  0, y:  0,
      oneColor: innerColor, oneX: 0, oneY: 0},
    { msg: 'off top left', checkColor: outerColor, x: -1, y: -1,
      oneColor: innerColor, oneX: 1, oneY: 1},
    { msg: 'off bottom right', checkColor: outerColor, x:  1, y:  1,
      oneColor: innerColor, oneX: 0, oneY: 0},
    { msg: 'completely off top ', checkColor: outerColor, x:  0, y: -2,
      oneColor: outerColor, oneX: 0, oneY: 0},
    { msg: 'completely off bottom', checkColor: outerColor, x:  0, y:  2,
      oneColor: outerColor, oneX: 0, oneY: 0},
    { msg: 'completely off left', checkColor: outerColor, x: -2, y:  0,
      oneColor: outerColor, oneX: 0, oneY: 0},
    { msg: 'completeley off right', checkColor: outerColor, x:  2, y:  0,
      oneColor: outerColor, oneX: 0, oneY: 0}
  ];

  for (var tt = 0; tt < tests.length; ++tt) {
    var test = tests[tt];
    debug("");
    debug("checking: " + test.msg);
    checkBuffer(test.checkColor, test.x, test.y,
                test.oneColor, test.oneX, test.oneY);
  }

  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "there should be no GL errors");

  function checkBuffer(checkColor, x, y, oneColor, oneX, oneY) {
    var buf = new Uint8Array(width * height * 4);
    gl.readPixels(x, y, width, height, gl.RGBA, gl.UNSIGNED_BYTE, buf);
    for (var yy = 0; yy < height; ++yy) {
      for (var xx = 0; xx < width; ++xx) {
        var offset = (yy * width + xx) * 4;
        var expectedColors = (oneX == xx && oneY == yy) ? oneColor : checkColor;
        for (var cc = 0; cc < 4; ++cc) {
          var expectedColor = expectedColors[cc] * 255;
          var color = buf[offset + cc];
          var diff = Math.abs(expectedColor - color);
          assertMsg(diff < 3,
                    "color pixel at " + xx + ", " + yy + " should be about " + expectedColor);
        }
      }
    }
  }

  var badFormats = [
    {
      format: gl.RGB,
      type: gl.UNSIGNED_BYTE,
      dest: new Uint8Array(3),
      error: gl.INVALID_OPERATION
    },
    {
      format: gl.RGB,
      type: gl.UNSIGNED_SHORT_5_6_5,
      dest: new Uint8Array(3),
      error: gl.INVALID_OPERATION
    },
    {
      format: gl.RGBA,
      type: gl.UNSIGNED_SHORT_5_5_5_1,
      dest: new Uint16Array(1),
      error: gl.INVALID_OPERATION
    },
    {
      format: gl.RGBA,
      type: gl.UNSIGNED_SHORT_4_4_4_4,
      dest: new Uint16Array(1),
      error: gl.INVALID_OPERATION
    },
    {
      format: gl.ALPHA,
      type: gl.UNSIGNED_BYTE,
      dest: new Uint8Array(1),
      error: gl.INVALID_OPERATION
    },
    {
      format: gl.LUMINANCE,
      type: gl.UNSIGNED_BYTE,
      dest: new Uint8Array(1),
      error: gl.INVALID_ENUM
    },
    {
      format: gl.LUMINANCE_ALPHA,
      type: gl.UNSIGNED_BYTE,
      dest: new Uint8Array(2),
      error: gl.INVALID_ENUM
    }
  ];
  debug("");
  debug("check disallowed formats");
  for (var tt = 0; tt < badFormats.length; ++ tt) {
    var info = badFormats[tt]
    var format = info.format;
    var type = info.type;
    var dest = info.dest;
    var error = info.error;
    gl.readPixels(0, 0, 1, 1, format, type, dest);
    // note that the GL error is INVALID_OPERATION if both format and type are invalid, but
    // INVALID_ENUM if only one is.
    wtu.glErrorShouldBe(
        gl, error,
        "Should not be able to read as " + wtu.glEnumToString(gl, format) +
        " / " + wtu.glEnumToString(gl, type));
  }

  debug("");
  debug("check reading with lots of drawing");
  continueTestFunc = continueTestPart2;
  width = 1024;
  height = 1024;
  canvas.width = width;
  canvas.height = height;
  if (gl.getError() != gl.CONTEXT_LOST_WEBGL) {
    continueTestPart2();
  }
}

function continueTestPart2() {
  gl.viewport(0, 0, 1024, 1024);
  var program = wtu.setupTexturedQuad(gl);
  var loc = gl.getUniformLocation(program, "tex");
  gl.disable(gl.BLEND);
  gl.disable(gl.DEPTH_TEST);
  var colors = [[255, 0, 0, 255], [0, 255, 0, 255], [0, 0, 255, 255]];
  var textures = [];
  var results = [];
  for (var ii = 0; ii < colors.length; ++ii) {
    gl.activeTexture(gl.TEXTURE0 + ii);
    var tex = gl.createTexture();
    wtu.fillTexture(gl, tex, 1, 1, colors[ii]);
    textures.push(tex);
  }
  for (var ii = 0; ii < colors.length; ++ii) {
    for (var jj = 0; jj < 300 + ii + 1; ++jj) {
      gl.uniform1i(loc, jj % 3);
      gl.drawArrays(gl.TRIANGLES, 0, 6);
    }
    var buf = new Uint8Array(4);
    gl.readPixels(512, 512, 1, 1, gl.RGBA, gl.UNSIGNED_BYTE, buf);
    results.push(buf);
    for (var kk = 0; kk < 99; ++kk) {
      gl.uniform1i(loc, (jj + kk) % 3);
      gl.drawArrays(gl.TRIANGLES, 0, 6);
    }
  }
  for (var ii = 0; ii < colors.length; ++ii) {
    var buf = results[ii];
    var color = colors[ii];
    actual = [buf[0], buf[1], buf[2], buf[3]];
    expected = [color[0], color[1], color[2], color[3]];
    shouldBe("actual", "expected");
  }
  wtu.glErrorShouldBe(gl, gl.NO_ERROR, "there should be no GL errors");

  debug("");
  finishTest();
}
</script>
</body>
</html>