LayoutTests/fast/canvas/webgl/object-deletion-behaviour.html - WebKit - Git at Google

 <!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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