<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="../../../resources/js-test.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>

<script>
description("Tests deletion behavior for texture, renderbuffer, shader, and program");

if (window.internals)
    window.internals.settings.setWebGLErrorsToConsoleEnabled(false);

var wtu = WebGLTestUtils;
var gl = wtu.create3DContext();
var shouldGenerateGLError = wtu.shouldGenerateGLError;

debug("");
debug("shader and program deletion");

var vertexShader = wtu.loadStandardVertexShader(gl);
assertMsg(vertexShader, "vertex shader loaded");
var fragmentShader = wtu.loadStandardFragmentShader(gl);
assertMsg(fragmentShader, "fragment shader loaded");

var program = gl.createProgram();
shouldBeNonNull("program");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.attachShader(program, vertexShader)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.attachShader(program, fragmentShader)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.linkProgram(program)");
shouldBeTrue("gl.getProgramParameter(program, gl.LINK_STATUS)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.useProgram(program)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteShader(vertexShader)");
shouldBeTrue("gl.isShader(vertexShader)");
shouldBeTrue("gl.getShaderParameter(vertexShader, gl.DELETE_STATUS)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.detachShader(program, vertexShader)");
shouldBeFalse("gl.isShader(vertexShader)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteShader(fragmentShader)");
shouldBeTrue("gl.isShader(fragmentShader)");
shouldBeTrue("gl.getShaderParameter(fragmentShader, gl.DELETE_STATUS)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteProgram(program)");
shouldBeTrue("gl.isProgram(program)");
shouldBeTrue("gl.getProgramParameter(program, gl.DELETE_STATUS)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.useProgram(null)");
shouldBeFalse("gl.isProgram(program)");
shouldBeFalse("gl.isShader(fragmentShader)");

debug("");
debug("texture deletion");

var fbo = gl.createFramebuffer(), fbo2 = gl.createFramebuffer(), fbo3 = gl.createFramebuffer();
shouldBeNonNull("fbo");
shouldBeNonNull("fbo2");
shouldBeNonNull("fbo3");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");

var tex = gl.createTexture();
shouldBeNonNull("tex");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_2D, tex)");
shouldBe("gl.getParameter(gl.TEXTURE_BINDING_2D)", "tex");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0)");
shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "tex");
shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE)", "gl.TEXTURE");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteTexture(tex)");
// Deleting a texture bound to the currently-bound fbo is the same as
// detaching the textue from fbo first, then delete the texture.
shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE)", "gl.NONE");
shouldGenerateGLError(gl, gl.INVALID_ENUM, "gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)");
shouldBeFalse("gl.isTexture(tex)");
shouldBeNull("gl.getParameter(gl.TEXTURE_BINDING_2D)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_2D, tex)");
shouldBeNull("gl.getParameter(gl.TEXTURE_BINDING_2D)");

var texCubeMap = gl.createTexture();
shouldBeNonNull("texCubeMap");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_CUBE_MAP, texCubeMap)");
shouldBe("gl.getParameter(gl.TEXTURE_BINDING_CUBE_MAP)", "texCubeMap");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteTexture(texCubeMap)");
shouldBeFalse("gl.isTexture(texCubeMap)");
shouldBeNull("gl.getParameter(gl.TEXTURE_BINDING_CUBE_MAP)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_CUBE_MAP, texCubeMap)");
shouldBeNull("gl.getParameter(gl.TEXTURE_BINDING_CUBE_MAP)");

var t = gl.createTexture();
shouldBeNonNull("t");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_2D, t)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteTexture(t)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_2D, t)");
shouldGenerateGLError(gl, gl.INVALID_OPERATION, "gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE)");

var t2 = gl.createTexture();
shouldBeNonNull("t2");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.activeTexture(gl.TEXTURE0)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_2D, t2)");
shouldBe("gl.getParameter(gl.TEXTURE_BINDING_2D)", "t2");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.activeTexture(gl.TEXTURE1)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_2D, t2)");
shouldBe("gl.getParameter(gl.TEXTURE_BINDING_2D)", "t2");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteTexture(t2)");
shouldBeNull("gl.getParameter(gl.TEXTURE_BINDING_2D)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.activeTexture(gl.TEXTURE0)");
shouldBeNull("gl.getParameter(gl.TEXTURE_BINDING_2D)");

debug("");
debug("renderbuffer deletion");

var rbo = gl.createRenderbuffer(), rbo2 = gl.createRenderbuffer(), rbo3 = gl.createRenderbuffer();
shouldBeNonNull("rbo");
shouldBeNonNull("rbo2");
shouldBeNonNull("rbo3");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindRenderbuffer(gl.RENDERBUFFER, rbo)");
shouldBe("gl.getParameter(gl.RENDERBUFFER_BINDING)", "rbo");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo)");
shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "rbo");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteRenderbuffer(rbo)");
// Deleting a renderbuffer bound to the currently-bound fbo is the same as
// detaching the renderbuffer from fbo first, then delete the renderbuffer.
shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE)", "gl.NONE");
shouldGenerateGLError(gl, gl.INVALID_ENUM, "gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)");
shouldBeFalse("gl.isRenderbuffer(rbo)");
shouldBeNull("gl.getParameter(gl.RENDERBUFFER_BINDING)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindRenderbuffer(gl.RENDERBUFFER, rbo)");
shouldBeNull("gl.getParameter(gl.RENDERBUFFER_BINDING)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindRenderbuffer(gl.RENDERBUFFER, rbo2)");
shouldBe("gl.getParameter(gl.RENDERBUFFER_BINDING)", "rbo2");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteRenderbuffer(rbo3)");
shouldBe("gl.getParameter(gl.RENDERBUFFER_BINDING)", "rbo2");

debug("");
debug("using deleted renderbuffer");
rbo = gl.createRenderbuffer();
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindRenderbuffer(gl.RENDERBUFFER, rbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA4, 16, 16)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo)");
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE) {
  // make backbuffer red
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(1,0,0,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  // make fbo green
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,1,0,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  // Bind backbuffer.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  // delete renderbuffer. It should still be attached to fbo though.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteRenderbuffer(rbo)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [255,0,0,255], "backbuffer should be red")');
  // Use fbo that has deleted rbo.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [0,255,0,255], "fbo should be green")');
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,0,1,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [0,0,255,255], "fbo should be blue")');
  // Bind backbuffer.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [255,0,0,255], "backbuffer should be red")');
}

debug("");
debug("renderbuffer attached twice to same framebuffer");
rbo = gl.createRenderbuffer();
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindRenderbuffer(gl.RENDERBUFFER, rbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA4, 16, 16)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo)");
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE) {
  rbo2 = gl.createRenderbuffer();
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindRenderbuffer(gl.RENDERBUFFER, rbo2)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA4, 16, 16)");
  // attach rbo2 at two attachment points incompatible with it
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, rbo2)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.RENDERBUFFER, rbo2)");
  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "rbo2");
  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "rbo2");
  // fbo can't be complete as rbo2 is attached at incompatible attachment points
  shouldNotBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
  // now we delete rbo2, which detaches it from the two attachment points where it currently is attached
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteRenderbuffer(rbo2)");
  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE)", "gl.NONE");
  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE)", "gl.NONE");
  // we should now be in the same state as before with only rbo attached, so fbo should be complete again
  shouldBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "rbo");
}
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteRenderbuffer(rbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");


debug("");
debug("using deleted texture");
tex = gl.createTexture();
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_2D, tex)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, null)");
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE) {
  // make fbo green
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,1,0,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  // Bind backbuffer.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  // delete texture. It should still be attached to fbo though.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteTexture(tex)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 1, 1, [255,0,0,255], "backbuffer should be red")');
  // Use fbo that has deleted texture.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0,255,0,255], "fbo should be green")');
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,0,1,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0,0,255,255], "fbo should be blue")');
  // Bind backbuffer.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [255,0,0,255], "backbuffer should be red")');
}

debug("");
debug("using deleted renderbuffer");
rbo = gl.createRenderbuffer();
shouldBeNonNull("rbo");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindRenderbuffer(gl.RENDERBUFFER, rbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA4, 16, 16)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo)");
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE) {
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo2)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo)");
  shouldBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
  // make backbuffer red
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(1,0,0,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  // make fbo green
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,1,0,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  // delete renderbuffer. It should still be attached to fbo2 though.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteRenderbuffer(rbo)");
  // fbo has no attachments
  shouldNotBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
  // Use fbo2 that has deleted rbo.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo2)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [0,255,0,255], "fbo should be green")');
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,0,1,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [0,0,255,255], "fbo should be blue")');
  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "rbo");

  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
  shouldGenerateGLError(gl, gl.INVALID_ENUM, "gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)");
  shouldGenerateGLError(gl, gl.NONE, "gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE)");
  shouldNotBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
  // Bind backbuffer.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [255,0,0,255], "backbuffer should be red")');
}

debug("");
debug("using deleted texture");
tex = gl.createTexture();
shouldBeNonNull("tex");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindTexture(gl.TEXTURE_2D, tex)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, null)");
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE) {
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo2)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, tex, 0)");
  // make fbo green
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,1,0,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  // delete texture. It should still be attached to fbo2 though.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteTexture(tex)");
  // fbo has no attachments
  shouldNotBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
  // Use fbo that has deleted texture.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo2)");
  shouldBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0,255,0,255], "fbo should be green")');
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,0,1,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 1, 1, [0,0,255,255], "fbo should be blue")');
  shouldBe("gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)", "tex");

  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
  shouldGenerateGLError(gl, gl.INVALID_ENUM, "gl.getFramebufferAttachmentParameter(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.FRAMEBUFFER_ATTACHMENT_OBJECT_NAME)");
  shouldNotBe("gl.checkFramebufferStatus(gl.FRAMEBUFFER)", "gl.FRAMEBUFFER_COMPLETE");
  // Bind backbuffer.
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [255,0,0,255], "backbuffer should be red")');
}

debug("");
debug("buffer deletion");

var buffer = gl.createBuffer();
shouldBeNonNull("buffer");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ARRAY_BUFFER, buffer)");
shouldBe("gl.getParameter(gl.ARRAY_BUFFER_BINDING)", "buffer");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteBuffer(buffer)");
shouldBeFalse("gl.isBuffer(buffer)");
shouldBeNull("gl.getParameter(gl.ARRAY_BUFFER_BINDING)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ARRAY_BUFFER, buffer)");
shouldBeNull("gl.getParameter(gl.ARRAY_BUFFER_BINDING)");

var buffer2 = gl.createBuffer();
shouldBeNonNull("buffer2");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ARRAY_BUFFER, buffer2)");
shouldBe("gl.getParameter(gl.ARRAY_BUFFER_BINDING)", "buffer2");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ARRAY_BUFFER, null)");
shouldBeNull("gl.getParameter(gl.ARRAY_BUFFER_BINDING)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteBuffer(buffer2)");
shouldBeFalse("gl.isBuffer(buffer2)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ARRAY_BUFFER, buffer2)");
shouldBeNull("gl.getParameter(gl.ARRAY_BUFFER_BINDING)");

var bufferElement = gl.createBuffer();
shouldBeNonNull("bufferElement");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, bufferElement)");
shouldBe("gl.getParameter(gl.ELEMENT_ARRAY_BUFFER_BINDING)", "bufferElement");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteBuffer(bufferElement)");
shouldBeFalse("gl.isBuffer(bufferElement)");
shouldBeNull("gl.getParameter(gl.ELEMENT_ARRAY_BUFFER_BINDING)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, bufferElement)");
shouldBeNull("gl.getParameter(gl.ELEMENT_ARRAY_BUFFER_BINDING)");

var b = gl.createBuffer();
shouldBeNonNull("b");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ARRAY_BUFFER, b)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bufferData(gl.ARRAY_BUFFER, 1, gl.STATIC_DRAW)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteBuffer(b)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ARRAY_BUFFER, b)");
shouldGenerateGLError(gl, gl.INVALID_OPERATION, "gl.bufferData(gl.ARRAY_BUFFER, 1, gl.STATIC_DRAW)");

var b1 = gl.createBuffer();
shouldBeNonNull("b1");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ARRAY_BUFFER, b1);");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.enableVertexAttribArray(1);");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.vertexAttribPointer(1, 4, gl.FLOAT, false, 0, 0);");
var b2 = gl.createBuffer();
shouldBeNonNull("b2");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindBuffer(gl.ARRAY_BUFFER, b2);");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.enableVertexAttribArray(2);");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.vertexAttribPointer(2, 4, gl.FLOAT, false, 0, 0);");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.enableVertexAttribArray(3);");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.vertexAttribPointer(3, 4, gl.FLOAT, false, 0, 0);");
shouldBe("gl.getVertexAttrib(1, gl.VERTEX_ATTRIB_ARRAY_BUFFER_BINDING)", "b1");
shouldBe("gl.getVertexAttrib(2, gl.VERTEX_ATTRIB_ARRAY_BUFFER_BINDING)", "b2");
shouldBe("gl.getVertexAttrib(3, gl.VERTEX_ATTRIB_ARRAY_BUFFER_BINDING)", "b2");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteBuffer(b2);");
shouldBe("gl.getVertexAttrib(1, gl.VERTEX_ATTRIB_ARRAY_BUFFER_BINDING)", "b1");
shouldBeNull("gl.getVertexAttrib(2, gl.VERTEX_ATTRIB_ARRAY_BUFFER_BINDING)");
shouldBeNull("gl.getVertexAttrib(3, gl.VERTEX_ATTRIB_ARRAY_BUFFER_BINDING)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteBuffer(b1);");
shouldBeNull("gl.getVertexAttrib(1, gl.VERTEX_ATTRIB_ARRAY_BUFFER_BINDING)");

debug("");
debug("framebuffer deletion");

shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
shouldBe("gl.getParameter(gl.FRAMEBUFFER_BINDING)", "fbo");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteFramebuffer(fbo)");
shouldBeFalse("gl.isFramebuffer(fbo)");
shouldBeNull("gl.getParameter(gl.FRAMEBUFFER_BINDING)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
shouldBeNull("gl.getParameter(gl.FRAMEBUFFER_BINDING)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo2)");
shouldBe("gl.getParameter(gl.FRAMEBUFFER_BINDING)", "fbo2");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteFramebuffer(fbo3)");
shouldBe("gl.getParameter(gl.FRAMEBUFFER_BINDING)", "fbo2");

fbo = gl.createFramebuffer();
rbo = gl.createRenderbuffer();
shouldBeNonNull("fbo");
shouldBeNonNull("rbo");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindRenderbuffer(gl.RENDERBUFFER, rbo)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.renderbufferStorage(gl.RENDERBUFFER, gl.RGBA4, 16, 16)");
shouldGenerateGLError(gl, gl.NO_ERROR, "gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, rbo)");
if (gl.checkFramebufferStatus(gl.FRAMEBUFFER) == gl.FRAMEBUFFER_COMPLETE) {
  // set backbuffer to red
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(1,0,0,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  // set framebuffer to green
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, fbo)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,1,0,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  // check framebuffer
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 16, 16, [0,255,0,255], "fbo should be green")');
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 16, 16, 1, 1, [0,0,0,0], "outside fbo should be black")');
  // delete framebuffer. because this was the bound fbo the backbuffer should be active now
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.deleteFramebuffer(fbo)");
  // check backbuffer
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 300, 150, [255,0,0,255], "backbuffer should be red")');
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 300, 0, 300, 300, [0,0,0,0], "outside backbuffer should be black")');
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 150, 300, 300, [0,0,0,0], "outside backbuffer should be black")');
  // check drawing to backbuffer
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clearColor(0,1,0,1)");
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.clear(gl.COLOR_BUFFER_BIT)");
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 300, 150, [0,255,0,255], "fbo should be green")');
  shouldGenerateGLError(gl, gl.NO_ERROR, "gl.bindFramebuffer(gl.FRAMEBUFFER, null)");
  // check again because many buggy implementations will have bound to the true backbuffer on deleteFramebuffer.
  shouldGenerateGLError(gl, gl.NO_ERROR, 'wtu.checkCanvasRect(gl, 0, 0, 300, 150, [0,255,0,255], "fbo should be green")');
}
</script>
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