fbo-remains-unchanged-after-read-pixels.html

Enable keyboard shortcuts

<!--

Copyright (c) 2019 The Khronos Group Inc.

Use of this source code is governed by an MIT-style license that can be

found in the LICENSE.txt file.

-->

<!DOCTYPE html>

<html>

<head>

<meta charset="utf-8">

<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>

<div id="console"></div>

<canvas id="canvas" width="4" height="4"></canvas>

<script id="vshader" type="x-shader/x-vertex">

attribute vec3 a_pos;

attribute vec4 a_color;

varying vec4 v_color;

void main()

    v_color = a_color;

    gl_Position = vec4(a_pos.xyz, 1.0);

</script>

<script id="fshader" type="x-shader/x-fragment">

precision mediump float;

varying vec4 v_color;

void main()

    gl_FragColor = v_color;

</script>

<script>

"use strict";

description("when antialias is enabled, verify default fbo pixels would not be changed between two readPixels without drawing operations");

var wtu = WebGLTestUtils;

var N = 4;

var vertices = new Float32Array([

         1.0, 1.0, 0.0,

        -1.0, -1.0, 0.0]);

var colors = new Uint8Array([

        255, 0, 0, 255,

        255, 0, 0, 255]);

var canvas = document.getElementById('canvas');

var gl = wtu.create3DContext(canvas, {antialias: true});

if (!gl) {

  testFailed("context does not exist");

} else {

  testPassed("context exists");

  var program = wtu.setupProgram(gl, ["vshader", "fshader"], ["a_pos", "a_color"]);

  gl.clearColor(0, 0, 0, 1);

  gl.clear(gl.COLOR_BUFFER_BIT);

  var colorOffset = vertices.byteLength;

  var vbo = gl.createBuffer();

  gl.bindBuffer(gl.ARRAY_BUFFER, vbo);

  gl.bufferData(gl.ARRAY_BUFFER, colorOffset + colors.byteLength, gl.STATIC_DRAW);

  gl.bufferSubData(gl.ARRAY_BUFFER, 0, vertices);

  gl.bufferSubData(gl.ARRAY_BUFFER, colorOffset, colors);

  gl.vertexAttribPointer(0, 3, gl.FLOAT, false, 0, 0);

  gl.enableVertexAttribArray(0);

  gl.vertexAttribPointer(1, 4, gl.UNSIGNED_BYTE, true, 0, colorOffset);

  gl.enableVertexAttribArray(1);

  gl.drawArrays(gl.LINES, 0, vertices.length / 3);

  var result_1 = new Uint8Array(N * N * 4);

  var result_2 = new Uint8Array(N * N * 4);

  gl.readPixels(0, 0, N, N, gl.RGBA, gl.UNSIGNED_BYTE, result_1);

  gl.readPixels(0, 0, N, N, gl.RGBA, gl.UNSIGNED_BYTE, result_2);

  wtu.glErrorShouldBe(gl, gl.NO_ERROR);

  var tolerance = 0;

  var diff = new Uint8Array(N * N * 4);

  var failed = wtu.comparePixels(result_1, result_2, tolerance, diff);

  if (failed) {

    testFailed("default fbo pixels had be changed between two readPixels without drawing operations");

  } else {

    testPassed("default fbo pixels had not be changed between two readPixels without drawing operations.");

  gl.bindBuffer(gl.ARRAY_BUFFER, null);

  gl.deleteBuffer(vbo);

var successfullyParsed = true;

</script>

<script src="../../js/js-test-post.js"></script>

</body>

</html>