gecko/content/canvas/src/WebGLContextGL.cpp

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 *   Mozilla Corporation.
 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Vladimir Vukicevic <vladimir@pobox.com> (original author)
 *   Mark Steele <mwsteele@gmail.com>
 *   Cedric Vivier <cedricv@neonux.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "WebGLContext.h"

#include "nsString.h"
#include "nsDebug.h"

#include "gfxImageSurface.h"
#include "gfxContext.h"
#include "gfxPlatform.h"
//#include "nsIDOMHTMLCanvasElement.h"

#include "nsContentUtils.h"
#include "nsDOMError.h"
#include "nsLayoutUtils.h"

#include "CanvasUtils.h"

#include "jstypedarray.h"

#if defined(USE_ANGLE)
// shader translator
#include "angle/ShaderLang.h"
#endif

#include "WebGLTexelConversions.h"
#include "WebGLValidateStrings.h"

// needed to check if current OS is lower than 10.7
#if defined(MOZ_WIDGET_COCOA)
#include "nsCocoaFeatures.h"
#endif

using namespace mozilla;

static bool BaseTypeAndSizeFromUniformType(WebGLenum uType, WebGLenum *baseType, WebGLint *unitSize);
static WebGLenum InternalFormatForFormatAndType(WebGLenum format, WebGLenum type, bool isGLES2);

/* Helper macros for when we're just wrapping a gl method, so that
 * we can avoid having to type this 500 times.  Note that these MUST
 * NOT BE USED if we need to check any of the parameters.
 */

#define GL_SAME_METHOD_0(glname, name)                          \
NS_IMETHODIMP WebGLContext::name() {                            \
    if (!IsContextStable()) { return NS_OK; }                         \
    MakeContextCurrent(); gl->f##glname(); return NS_OK;        \
}

#define GL_SAME_METHOD_1(glname, name, t1)          \
NS_IMETHODIMP WebGLContext::name(t1 a1) {           \
    if (!IsContextStable()) { return NS_OK; }             \
    MakeContextCurrent(); gl->f##glname(a1); return NS_OK;  \
}

#define GL_SAME_METHOD_2(glname, name, t1, t2)        \
NS_IMETHODIMP WebGLContext::name(t1 a1, t2 a2) {      \
    if (!IsContextStable()) { return NS_OK; }               \
    MakeContextCurrent(); gl->f##glname(a1,a2); return NS_OK;           \
}

#define GL_SAME_METHOD_3(glname, name, t1, t2, t3)      \
NS_IMETHODIMP WebGLContext::name(t1 a1, t2 a2, t3 a3) { \
    if (!IsContextStable()) { return NS_OK; }                 \
    MakeContextCurrent(); gl->f##glname(a1,a2,a3); return NS_OK;        \
}

#define GL_SAME_METHOD_4(glname, name, t1, t2, t3, t4)         \
NS_IMETHODIMP WebGLContext::name(t1 a1, t2 a2, t3 a3, t4 a4) { \
    if (!IsContextStable()) { return NS_OK; }                        \
    MakeContextCurrent(); gl->f##glname(a1,a2,a3,a4); return NS_OK;     \
}

#define GL_SAME_METHOD_5(glname, name, t1, t2, t3, t4, t5)            \
NS_IMETHODIMP WebGLContext::name(t1 a1, t2 a2, t3 a3, t4 a4, t5 a5) { \
    if (!IsContextStable()) { return NS_OK; }                               \
    MakeContextCurrent(); gl->f##glname(a1,a2,a3,a4,a5); return NS_OK;  \
}

#define GL_SAME_METHOD_6(glname, name, t1, t2, t3, t4, t5, t6)          \
NS_IMETHODIMP WebGLContext::name(t1 a1, t2 a2, t3 a3, t4 a4, t5 a5, t6 a6) { \
    if (!IsContextStable()) { return NS_OK; }                                 \
    MakeContextCurrent(); gl->f##glname(a1,a2,a3,a4,a5,a6); return NS_OK; \
}


//
//  WebGL API
//


/* void GlActiveTexture (in GLenum texture); */
NS_IMETHODIMP
WebGLContext::ActiveTexture(WebGLenum texture)
{
    if (!IsContextStable())
        return NS_OK;

    if (texture < LOCAL_GL_TEXTURE0 || texture >= LOCAL_GL_TEXTURE0 + mBound2DTextures.Length())
        return ErrorInvalidEnum("ActiveTexture: texture unit %d out of range (0..%d)",
                                texture, mBound2DTextures.Length()-1);

    MakeContextCurrent();
    mActiveTexture = texture - LOCAL_GL_TEXTURE0;
    gl->fActiveTexture(texture);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::AttachShader(nsIWebGLProgram *pobj, nsIWebGLShader *shobj)
{
    if (!IsContextStable())
        return NS_OK;

    // if pobj or shobj are null/not specified, it's an error
    if (pobj == nsnull || shobj == nsnull)
        return ErrorInvalidValue("attachShader");

    WebGLuint progname, shadername;
    WebGLProgram *program;
    WebGLShader *shader;
    if (!GetConcreteObjectAndGLName("attachShader: program", pobj, &program, &progname) ||
        !GetConcreteObjectAndGLName("attachShader: shader", shobj, &shader, &shadername))
        return NS_OK;

    // Per GLSL ES 2.0, we can only have one of each type of shader
    // attached.  This renders the next test somewhat moot, but we'll
    // leave it for when we support more than one shader of each type.
    if (program->HasAttachedShaderOfType(shader->ShaderType()))
        return ErrorInvalidOperation("AttachShader: only one of each type of shader may be attached to a program");

    if (!program->AttachShader(shader))
        return ErrorInvalidOperation("AttachShader: shader is already attached");

    return NS_OK;
}


NS_IMETHODIMP
WebGLContext::BindAttribLocation(nsIWebGLProgram *pobj, WebGLuint location, const nsAString& name)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLuint progname;
    if (!GetGLName<WebGLProgram>("bindAttribLocation: program", pobj, &progname))
        return NS_OK;

    if (!ValidateGLSLVariableName(name, "bindAttribLocation"))
        return NS_OK;

    if (!ValidateAttribIndex(location, "bindAttribLocation"))
        return NS_OK;

    MakeContextCurrent();

    gl->fBindAttribLocation(progname, location, NS_LossyConvertUTF16toASCII(name).get());

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::BindBuffer(WebGLenum target, nsIWebGLBuffer *bobj)
{
    WebGLuint bufname;
    WebGLBuffer* buf;
    bool isNull; // allow null objects
    bool isDeleted; // allow deleted objects
    if (!GetConcreteObjectAndGLName("bindBuffer", bobj, &buf, &bufname, &isNull, &isDeleted))
        return NS_OK;

    // silently ignore a deleted buffer
    if (isDeleted)
        return NS_OK;

    if (target != LOCAL_GL_ARRAY_BUFFER &&
        target != LOCAL_GL_ELEMENT_ARRAY_BUFFER)
    {
        return ErrorInvalidEnumInfo("bindBuffer: target", target);
    }

    if (!isNull) {
        if ((buf->Target() != LOCAL_GL_NONE) && (target != buf->Target()))
            return ErrorInvalidOperation("BindBuffer: buffer already bound to a different target");
        buf->SetTarget(target);
        buf->SetHasEverBeenBound(true);
    }

    // we really want to do this AFTER all the validation is done, otherwise our bookkeeping could get confused.
    // see bug 656752
    if (target == LOCAL_GL_ARRAY_BUFFER) {
        mBoundArrayBuffer = buf;
    } else if (target == LOCAL_GL_ELEMENT_ARRAY_BUFFER) {
        mBoundElementArrayBuffer = buf;
    }

    MakeContextCurrent();

    gl->fBindBuffer(target, bufname);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::BindFramebuffer(WebGLenum target, nsIWebGLFramebuffer *fbobj)
{
    WebGLuint framebuffername;
    bool isNull; // allow null objects
    bool isDeleted; // allow deleted objects
    WebGLFramebuffer *wfb;

    if (target != LOCAL_GL_FRAMEBUFFER)
        return ErrorInvalidEnum("BindFramebuffer: target must be GL_FRAMEBUFFER");

    if (!GetConcreteObjectAndGLName("bindFramebuffer", fbobj, &wfb, &framebuffername, &isNull, &isDeleted))
        return NS_OK;

    // silently ignore a deleted frame buffer
    if (isDeleted)
        return NS_OK;

    MakeContextCurrent();

    if (isNull) {
        gl->fBindFramebuffer(target, gl->GetOffscreenFBO());
    } else {
        gl->fBindFramebuffer(target, framebuffername);
        wfb->SetHasEverBeenBound(true);
    }

    mBoundFramebuffer = wfb;

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::BindRenderbuffer(WebGLenum target, nsIWebGLRenderbuffer *rbobj)
{
    WebGLuint renderbuffername;
    bool isNull; // allow null objects
    bool isDeleted; // allow deleted objects
    WebGLRenderbuffer *wrb;

    if (target != LOCAL_GL_RENDERBUFFER)
        return ErrorInvalidEnumInfo("bindRenderbuffer: target", target);

    if (!GetConcreteObjectAndGLName("bindRenderBuffer", rbobj, &wrb, &renderbuffername, &isNull, &isDeleted))
        return NS_OK;

    // silently ignore a deleted buffer
    if (isDeleted)
        return NS_OK;

    if (!isNull)
        wrb->SetHasEverBeenBound(true);

    MakeContextCurrent();

    gl->fBindRenderbuffer(target, renderbuffername);

    mBoundRenderbuffer = wrb;

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::BindTexture(WebGLenum target, nsIWebGLTexture *tobj)
{
    WebGLuint texturename;
    WebGLTexture *tex;
    bool isNull; // allow null objects
    bool isDeleted; // allow deleted objects
    if (!GetConcreteObjectAndGLName("bindTexture", tobj, &tex, &texturename, &isNull, &isDeleted))
        return NS_OK;

    // silently ignore a deleted texture
    if (isDeleted)
        return NS_OK;

    if (target == LOCAL_GL_TEXTURE_2D) {
        mBound2DTextures[mActiveTexture] = tex;
    } else if (target == LOCAL_GL_TEXTURE_CUBE_MAP) {
        mBoundCubeMapTextures[mActiveTexture] = tex;
    } else {
        return ErrorInvalidEnumInfo("bindTexture: target", target);
    }

    MakeContextCurrent();

    if (tex)
        tex->Bind(target);
    else
        gl->fBindTexture(target, 0 /* == texturename */);

    return NS_OK;
}

GL_SAME_METHOD_4(BlendColor, BlendColor, WebGLfloat, WebGLfloat, WebGLfloat, WebGLfloat)

NS_IMETHODIMP WebGLContext::BlendEquation(WebGLenum mode)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateBlendEquationEnum(mode, "blendEquation: mode"))
        return NS_OK;

    MakeContextCurrent();
    gl->fBlendEquation(mode);
    return NS_OK;
}

NS_IMETHODIMP WebGLContext::BlendEquationSeparate(WebGLenum modeRGB, WebGLenum modeAlpha)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateBlendEquationEnum(modeRGB, "blendEquationSeparate: modeRGB") ||
        !ValidateBlendEquationEnum(modeAlpha, "blendEquationSeparate: modeAlpha"))
        return NS_OK;

    MakeContextCurrent();
    gl->fBlendEquationSeparate(modeRGB, modeAlpha);
    return NS_OK;
}

NS_IMETHODIMP WebGLContext::BlendFunc(WebGLenum sfactor, WebGLenum dfactor)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateBlendFuncSrcEnum(sfactor, "blendFunc: sfactor") ||
        !ValidateBlendFuncDstEnum(dfactor, "blendFunc: dfactor"))
        return NS_OK;

    if (!ValidateBlendFuncEnumsCompatibility(sfactor, dfactor, "blendFuncSeparate: srcRGB and dstRGB"))
        return NS_OK;

    MakeContextCurrent();
    gl->fBlendFunc(sfactor, dfactor);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::BlendFuncSeparate(WebGLenum srcRGB, WebGLenum dstRGB,
                                WebGLenum srcAlpha, WebGLenum dstAlpha)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateBlendFuncSrcEnum(srcRGB, "blendFuncSeparate: srcRGB") ||
        !ValidateBlendFuncSrcEnum(srcAlpha, "blendFuncSeparate: srcAlpha") ||
        !ValidateBlendFuncDstEnum(dstRGB, "blendFuncSeparate: dstRGB") ||
        !ValidateBlendFuncDstEnum(dstAlpha, "blendFuncSeparate: dstAlpha"))
        return NS_OK;

    // note that we only check compatibity for the RGB enums, no need to for the Alpha enums, see
    // "Section 6.8 forgetting to mention alpha factors?" thread on the public_webgl mailing list
    if (!ValidateBlendFuncEnumsCompatibility(srcRGB, dstRGB, "blendFuncSeparate: srcRGB and dstRGB"))
        return NS_OK;

    MakeContextCurrent();
    gl->fBlendFuncSeparate(srcRGB, dstRGB, srcAlpha, dstAlpha);
    return NS_OK;
}

GLenum WebGLContext::CheckedBufferData(GLenum target,
                                       GLsizeiptr size,
                                       const GLvoid *data,
                                       GLenum usage)
{
    WebGLBuffer *boundBuffer = NULL;
    if (target == LOCAL_GL_ARRAY_BUFFER) {
        boundBuffer = mBoundArrayBuffer;
    } else if (target == LOCAL_GL_ELEMENT_ARRAY_BUFFER) {
        boundBuffer = mBoundElementArrayBuffer;
    }
    NS_ABORT_IF_FALSE(boundBuffer != nsnull, "no buffer bound for this target");
    
    bool sizeChanges = PRUint32(size) != boundBuffer->ByteLength();
    if (sizeChanges) {
        UpdateWebGLErrorAndClearGLError();
        gl->fBufferData(target, size, data, usage);
        GLenum error = LOCAL_GL_NO_ERROR;
        UpdateWebGLErrorAndClearGLError(&error);
        return error;
    } else {
        gl->fBufferData(target, size, data, usage);
        return LOCAL_GL_NO_ERROR;
    }
}

NS_IMETHODIMP
WebGLContext::BufferData(PRInt32 dummy)
{
    if (!IsContextStable())
        return NS_OK;

    // this should never be called
    LogMessageIfVerbose("BufferData");
    return NS_ERROR_FAILURE;
}

NS_IMETHODIMP
WebGLContext::BufferData_null()
{
    if (!IsContextStable())
        return NS_OK;

    // see http://www.khronos.org/bugzilla/show_bug.cgi?id=386
    return ErrorInvalidValue("bufferData: null object passed");
}


NS_IMETHODIMP
WebGLContext::BufferData_size(WebGLenum target, WebGLsizei size, WebGLenum usage)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLBuffer *boundBuffer = NULL;

    if (target == LOCAL_GL_ARRAY_BUFFER) {
        boundBuffer = mBoundArrayBuffer;
    } else if (target == LOCAL_GL_ELEMENT_ARRAY_BUFFER) {
        boundBuffer = mBoundElementArrayBuffer;
    } else {
        return ErrorInvalidEnumInfo("bufferData: target", target);
    }

    if (size < 0)
        return ErrorInvalidValue("bufferData: negative size");

    if (!ValidateBufferUsageEnum(usage, "bufferData: usage"))
        return NS_OK;

    if (!boundBuffer)
        return ErrorInvalidOperation("BufferData: no buffer bound!");

    MakeContextCurrent();
    
    GLenum error = CheckedBufferData(target, size, 0, usage);
    if (error) {
        LogMessageIfVerbose("bufferData generated error %s", ErrorName(error));
        return NS_OK;
    }

    boundBuffer->SetByteLength(size);
    boundBuffer->InvalidateCachedMaxElements();
    if (!boundBuffer->ZeroDataIfElementArray())
        return ErrorOutOfMemory("bufferData: out of memory");

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::BufferData_buf(WebGLenum target, JSObject *wb, WebGLenum usage)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLBuffer *boundBuffer = NULL;

    if (target == LOCAL_GL_ARRAY_BUFFER) {
        boundBuffer = mBoundArrayBuffer;
    } else if (target == LOCAL_GL_ELEMENT_ARRAY_BUFFER) {
        boundBuffer = mBoundElementArrayBuffer;
    } else {
        return ErrorInvalidEnumInfo("bufferData: target", target);
    }

    if (!ValidateBufferUsageEnum(usage, "bufferData: usage"))
        return NS_OK;

    if (!boundBuffer)
        return ErrorInvalidOperation("BufferData: no buffer bound!");

    MakeContextCurrent();

    GLenum error = CheckedBufferData(target,
                                     JS_GetArrayBufferByteLength(wb),
                                     JS_GetArrayBufferData(wb),
                                     usage);
    if (error) {
        LogMessageIfVerbose("bufferData generated error %s", ErrorName(error));
        return NS_OK;
    }

    boundBuffer->SetByteLength(JS_GetArrayBufferByteLength(wb));
    boundBuffer->InvalidateCachedMaxElements();
    if (!boundBuffer->CopyDataIfElementArray(JS_GetArrayBufferData(wb)))
        return ErrorOutOfMemory("bufferData: out of memory");

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::BufferData_array(WebGLenum target, JSObject *wa, WebGLenum usage)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLBuffer *boundBuffer = NULL;

    if (target == LOCAL_GL_ARRAY_BUFFER) {
        boundBuffer = mBoundArrayBuffer;
    } else if (target == LOCAL_GL_ELEMENT_ARRAY_BUFFER) {
        boundBuffer = mBoundElementArrayBuffer;
    } else {
        return ErrorInvalidEnumInfo("bufferData: target", target);
    }

    if (!ValidateBufferUsageEnum(usage, "bufferData: usage"))
        return NS_OK;

    if (!boundBuffer)
        return ErrorInvalidOperation("BufferData: no buffer bound!");

    MakeContextCurrent();

    GLenum error = CheckedBufferData(target,
                                     JS_GetTypedArrayByteLength(wa),
                                     JS_GetTypedArrayData(wa),
                                     usage);
    if (error) {
        LogMessageIfVerbose("bufferData generated error %s", ErrorName(error));
        return NS_OK;
    }

    boundBuffer->SetByteLength(JS_GetTypedArrayByteLength(wa));
    boundBuffer->InvalidateCachedMaxElements();
    if (!boundBuffer->CopyDataIfElementArray(JS_GetTypedArrayData(wa)))
        return ErrorOutOfMemory("bufferData: out of memory");

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::BufferSubData(PRInt32)
{
    if (!IsContextStable())
        return NS_OK;

    return NS_ERROR_FAILURE;
}

NS_IMETHODIMP
WebGLContext::BufferSubData_null()
{
    if (!IsContextStable())
        return NS_OK;

    return NS_OK; // see http://www.khronos.org/bugzilla/show_bug.cgi?id=386
}

NS_IMETHODIMP
WebGLContext::BufferSubData_buf(GLenum target, WebGLsizei byteOffset, JSObject *wb)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLBuffer *boundBuffer = NULL;

    if (target == LOCAL_GL_ARRAY_BUFFER) {
        boundBuffer = mBoundArrayBuffer;
    } else if (target == LOCAL_GL_ELEMENT_ARRAY_BUFFER) {
        boundBuffer = mBoundElementArrayBuffer;
    } else {
        return ErrorInvalidEnumInfo("bufferSubData: target", target);
    }

    if (byteOffset < 0)
        return ErrorInvalidValue("bufferSubData: negative offset");

    if (!boundBuffer)
        return ErrorInvalidOperation("BufferData: no buffer bound!");

    CheckedUint32 checked_neededByteLength = CheckedUint32(byteOffset) + JS_GetArrayBufferByteLength(wb);
    if (!checked_neededByteLength.valid())
        return ErrorInvalidOperation("bufferSubData: integer overflow computing the needed byte length");

    if (checked_neededByteLength.value() > boundBuffer->ByteLength())
        return ErrorInvalidOperation("BufferSubData: not enough data - operation requires %d bytes, but buffer only has %d bytes",
                                     byteOffset, JS_GetArrayBufferByteLength(wb), boundBuffer->ByteLength());

    MakeContextCurrent();

    boundBuffer->CopySubDataIfElementArray(byteOffset, JS_GetArrayBufferByteLength(wb), JS_GetArrayBufferData(wb));
    boundBuffer->InvalidateCachedMaxElements();

    gl->fBufferSubData(target, byteOffset, JS_GetArrayBufferByteLength(wb), JS_GetArrayBufferData(wb));

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::BufferSubData_array(WebGLenum target, WebGLsizei byteOffset, JSObject *wa)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLBuffer *boundBuffer = NULL;

    if (target == LOCAL_GL_ARRAY_BUFFER) {
        boundBuffer = mBoundArrayBuffer;
    } else if (target == LOCAL_GL_ELEMENT_ARRAY_BUFFER) {
        boundBuffer = mBoundElementArrayBuffer;
    } else {
        return ErrorInvalidEnumInfo("bufferSubData: target", target);
    }

    if (byteOffset < 0)
        return ErrorInvalidValue("bufferSubData: negative offset");

    if (!boundBuffer)
        return ErrorInvalidOperation("BufferData: no buffer bound!");

    CheckedUint32 checked_neededByteLength = CheckedUint32(byteOffset) + JS_GetTypedArrayByteLength(wa);
    if (!checked_neededByteLength.valid())
        return ErrorInvalidOperation("bufferSubData: integer overflow computing the needed byte length");

    if (checked_neededByteLength.value() > boundBuffer->ByteLength())
        return ErrorInvalidOperation("BufferSubData: not enough data -- operation requires %d bytes, but buffer only has %d bytes",
                                     byteOffset, JS_GetTypedArrayByteLength(wa), boundBuffer->ByteLength());

    MakeContextCurrent();

    boundBuffer->CopySubDataIfElementArray(byteOffset, JS_GetTypedArrayByteLength(wa), JS_GetTypedArrayData(wa));
    boundBuffer->InvalidateCachedMaxElements();

    gl->fBufferSubData(target, byteOffset, JS_GetTypedArrayByteLength(wa), JS_GetTypedArrayData(wa));

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CheckFramebufferStatus(WebGLenum target, WebGLenum *retval)
{
    if (!IsContextStable())
    {
        *retval = LOCAL_GL_FRAMEBUFFER_UNSUPPORTED;
        return NS_OK;
    }

    *retval = 0;

    MakeContextCurrent();
    if (target != LOCAL_GL_FRAMEBUFFER)
        return ErrorInvalidEnum("checkFramebufferStatus: target must be FRAMEBUFFER");

    if (mBoundFramebuffer && mBoundFramebuffer->HasBadAttachments())
        *retval = LOCAL_GL_FRAMEBUFFER_UNSUPPORTED;
    else
        *retval = gl->fCheckFramebufferStatus(target);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::Clear(PRUint32 mask)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();

    PRUint32 m = mask & (LOCAL_GL_COLOR_BUFFER_BIT | LOCAL_GL_DEPTH_BUFFER_BIT | LOCAL_GL_STENCIL_BUFFER_BIT);
    if (mask != m)
        return ErrorInvalidValue("clear: invalid mask bits");

    bool needClearCallHere = true;

    if (mBoundFramebuffer) {
        if (!mBoundFramebuffer->CheckAndInitializeRenderbuffers())
            return NS_OK;
    } else {
        // no FBO is bound, so we are clearing the backbuffer here
        EnsureBackbufferClearedAsNeeded();
        bool valuesAreDefault = mColorClearValue[0] == 0.0f &&
                                  mColorClearValue[1] == 0.0f &&
                                  mColorClearValue[2] == 0.0f &&
                                  mColorClearValue[3] == 0.0f &&
                                  mDepthClearValue    == 1.0f &&
                                  mStencilClearValue  == 0;
        if (valuesAreDefault &&
            mBackbufferClearingStatus == BackbufferClearingStatus::ClearedToDefaultValues)
        {
            needClearCallHere = false;
        }
    }

    if (needClearCallHere) {
        gl->fClear(mask);
        mBackbufferClearingStatus = BackbufferClearingStatus::HasBeenDrawnTo;
        Invalidate();
    }

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::ClearColor(WebGLfloat r, WebGLfloat g, WebGLfloat b, WebGLfloat a)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();
    mColorClearValue[0] = r;
    mColorClearValue[1] = g;
    mColorClearValue[2] = b;
    mColorClearValue[3] = a;
    gl->fClearColor(r, g, b, a);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::ClearDepth(WebGLfloat v)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();
    mDepthClearValue = v;
    gl->fClearDepth(v);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::ClearStencil(WebGLint v)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();
    mStencilClearValue = v;
    gl->fClearStencil(v);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::ColorMask(WebGLboolean r, WebGLboolean g, WebGLboolean b, WebGLboolean a)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();
    mColorWriteMask[0] = r;
    mColorWriteMask[1] = g;
    mColorWriteMask[2] = b;
    mColorWriteMask[3] = a;
    gl->fColorMask(r, g, b, a);
    return NS_OK;
}

nsresult
WebGLContext::CopyTexSubImage2D_base(WebGLenum target,
                                     WebGLint level,
                                     WebGLenum internalformat,
                                     WebGLint xoffset,
                                     WebGLint yoffset,
                                     WebGLint x,
                                     WebGLint y,
                                     WebGLsizei width,
                                     WebGLsizei height,
                                     bool sub)
{

    WebGLsizei framebufferWidth =  mBoundFramebuffer ? mBoundFramebuffer->width() : mWidth;
    WebGLsizei framebufferHeight = mBoundFramebuffer ? mBoundFramebuffer->height() : mHeight;

    const char *info = sub ? "copyTexSubImage2D" : "copyTexImage2D";

    MakeContextCurrent();

    if (CanvasUtils::CheckSaneSubrectSize(x, y, width, height, framebufferWidth, framebufferHeight)) {
        if (sub)
            gl->fCopyTexSubImage2D(target, level, xoffset, yoffset, x, y, width, height);
        else
            gl->fCopyTexImage2D(target, level, internalformat, x, y, width, height, 0);
    } else {

        // the rect doesn't fit in the framebuffer

        /*** first, we initialize the texture as black ***/

        // first, compute the size of the buffer we should allocate to initialize the texture as black

        PRUint32 texelSize = 0;
        if (!ValidateTexFormatAndType(internalformat, LOCAL_GL_UNSIGNED_BYTE, -1, &texelSize, info))
            return NS_OK;

        CheckedUint32 checked_neededByteLength = 
            GetImageSize(height, width, texelSize, mPixelStoreUnpackAlignment);

        if (!checked_neededByteLength.valid())
            return ErrorInvalidOperation("%s: integer overflow computing the needed buffer size", info);

        PRUint32 bytesNeeded = checked_neededByteLength.value();

        // now that the size is known, create the buffer

        // We need some zero pages, because GL doesn't guarantee the
        // contents of a texture allocated with NULL data.
        // Hopefully calloc will just mmap zero pages here.
        void *tempZeroData = calloc(1, bytesNeeded);
        if (!tempZeroData)
            return ErrorOutOfMemory("%s: could not allocate %d bytes (for zero fill)", info, bytesNeeded);

        // now initialize the texture as black

        if (sub)
            gl->fTexSubImage2D(target, level, 0, 0, width, height,
                               internalformat, LOCAL_GL_UNSIGNED_BYTE, tempZeroData);
        else
            gl->fTexImage2D(target, level, internalformat, width, height,
                            0, internalformat, LOCAL_GL_UNSIGNED_BYTE, tempZeroData);
        free(tempZeroData);

        // if we are completely outside of the framebuffer, we can exit now with our black texture
        if (   x >= framebufferWidth
            || x+width <= 0
            || y >= framebufferHeight
            || y+height <= 0)
        {
            // we are completely outside of range, can exit now with buffer filled with zeros
            return NS_OK;
        }

        GLint   actual_x             = clamped(x, 0, framebufferWidth);
        GLint   actual_x_plus_width  = clamped(x + width, 0, framebufferWidth);
        GLsizei actual_width   = actual_x_plus_width  - actual_x;
        GLint   actual_xoffset = xoffset + actual_x - x;

        GLint   actual_y             = clamped(y, 0, framebufferHeight);
        GLint   actual_y_plus_height = clamped(y + height, 0, framebufferHeight);
        GLsizei actual_height  = actual_y_plus_height - actual_y;
        GLint   actual_yoffset = yoffset + actual_y - y;

        gl->fCopyTexSubImage2D(target, level, actual_xoffset, actual_yoffset, actual_x, actual_y, actual_width, actual_height);
    }

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CopyTexImage2D(WebGLenum target,
                             WebGLint level,
                             WebGLenum internalformat,
                             WebGLint x,
                             WebGLint y,
                             WebGLsizei width,
                             WebGLsizei height,
                             WebGLint border)
{
    if (!IsContextStable())
        return NS_OK;

    switch (target) {
        case LOCAL_GL_TEXTURE_2D:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_X:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
            break;
        default:
            return ErrorInvalidEnumInfo("copyTexImage2D: target", target);
    }


    switch (internalformat) {
        case LOCAL_GL_RGB:
        case LOCAL_GL_LUMINANCE:
        case LOCAL_GL_RGBA:
        case LOCAL_GL_ALPHA:
        case LOCAL_GL_LUMINANCE_ALPHA:
            break;
        default:
            return ErrorInvalidEnumInfo("CopyTexImage2D: internal format", internalformat);
    }

    if (border != 0)
        return ErrorInvalidValue("copyTexImage2D: border must be 0");

    if (width < 0 || height < 0)
        return ErrorInvalidValue("copyTexImage2D: width and height may not be negative");

    if (level < 0)
        return ErrorInvalidValue("copyTexImage2D: level may not be negative");

    WebGLsizei maxTextureSize = MaxTextureSizeForTarget(target);
    if (!(maxTextureSize >> level))
        return ErrorInvalidValue("copyTexImage2D: 2^level exceeds maximum texture size");

    if (level >= 1) {
        if (!(is_pot_assuming_nonnegative(width) &&
              is_pot_assuming_nonnegative(height)))
            return ErrorInvalidValue("copyTexImage2D: with level > 0, width and height must be powers of two");
    }

    bool texFormatRequiresAlpha = internalformat == LOCAL_GL_RGBA ||
                                    internalformat == LOCAL_GL_ALPHA ||
                                    internalformat == LOCAL_GL_LUMINANCE_ALPHA;
    bool fboFormatHasAlpha = mBoundFramebuffer ? mBoundFramebuffer->ColorAttachment().HasAlpha()
                                                 : bool(gl->ActualFormat().alpha > 0);
    if (texFormatRequiresAlpha && !fboFormatHasAlpha)
        return ErrorInvalidOperation("copyTexImage2D: texture format requires an alpha channel "
                                     "but the framebuffer doesn't have one");

    if (mBoundFramebuffer && !mBoundFramebuffer->CheckAndInitializeRenderbuffers())
        return NS_OK;

    WebGLTexture *tex = activeBoundTextureForTarget(target);
    if (!tex)
        return ErrorInvalidOperation("copyTexImage2D: no texture bound to this target");

    // copyTexImage2D only generates textures with type = UNSIGNED_BYTE
    GLenum type = LOCAL_GL_UNSIGNED_BYTE;

    // check if the memory size of this texture may change with this call
    bool sizeMayChange = true;
    size_t face = WebGLTexture::FaceForTarget(target);
    if (tex->HasImageInfoAt(level, face)) {
        const WebGLTexture::ImageInfo& imageInfo = tex->ImageInfoAt(level, face);

        sizeMayChange = width != imageInfo.mWidth ||
                        height != imageInfo.mHeight ||
                        internalformat != imageInfo.mFormat ||
                        type != imageInfo.mType;
    }

    if (sizeMayChange) {
        UpdateWebGLErrorAndClearGLError();
        CopyTexSubImage2D_base(target, level, internalformat, 0, 0, x, y, width, height, false);
        GLenum error = LOCAL_GL_NO_ERROR;
        UpdateWebGLErrorAndClearGLError(&error);
        if (error) {
            LogMessageIfVerbose("copyTexImage2D generated error %s", ErrorName(error));
            return NS_OK;
        }          
    } else {
        CopyTexSubImage2D_base(target, level, internalformat, 0, 0, x, y, width, height, false);
    }
    
    tex->SetImageInfo(target, level, width, height, internalformat, type);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CopyTexSubImage2D(WebGLenum target,
                                WebGLint level,
                                WebGLint xoffset,
                                WebGLint yoffset,
                                WebGLint x,
                                WebGLint y,
                                WebGLsizei width,
                                WebGLsizei height)
{
    if (!IsContextStable())
        return NS_OK;

    switch (target) {
        case LOCAL_GL_TEXTURE_2D:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_X:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
            break;
        default:
            return ErrorInvalidEnumInfo("CopyTexSubImage2D: target", target);
    }

    if (level < 0)
        return ErrorInvalidValue("copyTexSubImage2D: level may not be negative");

    WebGLsizei maxTextureSize = MaxTextureSizeForTarget(target);
    if (!(maxTextureSize >> level))
        return ErrorInvalidValue("copyTexSubImage2D: 2^level exceeds maximum texture size");

    if (width < 0 || height < 0)
        return ErrorInvalidValue("copyTexSubImage2D: width and height may not be negative");

    if (xoffset < 0 || yoffset < 0)
        return ErrorInvalidValue("copyTexSubImage2D: xoffset and yoffset may not be negative");

    WebGLTexture *tex = activeBoundTextureForTarget(target);
    if (!tex)
        return ErrorInvalidOperation("copyTexSubImage2D: no texture bound to this target");

    WebGLint face = WebGLTexture::FaceForTarget(target);
    if (!tex->HasImageInfoAt(level, face))
        return ErrorInvalidOperation("copyTexSubImage2D: no texture image previously defined for this level and face");

    WebGLsizei texWidth = tex->ImageInfoAt(level, face).mWidth;
    WebGLsizei texHeight = tex->ImageInfoAt(level, face).mHeight;

    if (xoffset + width > texWidth || xoffset + width < 0)
      return ErrorInvalidValue("copyTexSubImage2D: xoffset+width is too large");

    if (yoffset + height > texHeight || yoffset + height < 0)
      return ErrorInvalidValue("copyTexSubImage2D: yoffset+height is too large");

    WebGLenum format = tex->ImageInfoAt(level, face).mFormat;
    bool texFormatRequiresAlpha = format == LOCAL_GL_RGBA ||
                                    format == LOCAL_GL_ALPHA ||
                                    format == LOCAL_GL_LUMINANCE_ALPHA;
    bool fboFormatHasAlpha = mBoundFramebuffer ? mBoundFramebuffer->ColorAttachment().HasAlpha()
                                                 : bool(gl->ActualFormat().alpha > 0);

    if (texFormatRequiresAlpha && !fboFormatHasAlpha)
        return ErrorInvalidOperation("copyTexSubImage2D: texture format requires an alpha channel "
                                     "but the framebuffer doesn't have one");

    if (mBoundFramebuffer && !mBoundFramebuffer->CheckAndInitializeRenderbuffers())
        return NS_OK;

    return CopyTexSubImage2D_base(target, level, format, xoffset, yoffset, x, y, width, height, true);
}


NS_IMETHODIMP
WebGLContext::CreateProgram(nsIWebGLProgram **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    WebGLProgram *prog = new WebGLProgram(this);
    NS_ADDREF(*retval = prog);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CreateShader(WebGLenum type, nsIWebGLShader **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    if (type != LOCAL_GL_VERTEX_SHADER &&
        type != LOCAL_GL_FRAGMENT_SHADER)
    {
        return ErrorInvalidEnumInfo("createShader: type", type);
    }

    WebGLShader *shader = new WebGLShader(this, type);
    NS_ADDREF(*retval = shader);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CullFace(WebGLenum face)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateFaceEnum(face, "cullFace"))
        return NS_OK;

    MakeContextCurrent();
    gl->fCullFace(face);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DeleteBuffer(nsIWebGLBuffer *bobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLuint bufname;
    WebGLBuffer *buf;
    bool isNull, isDeleted;
    if (!GetConcreteObjectAndGLName("deleteBuffer", bobj, &buf, &bufname, &isNull, &isDeleted))
        return NS_OK;

    if (isNull || isDeleted)
        return NS_OK;

    if (mBoundArrayBuffer == buf)
        BindBuffer(LOCAL_GL_ARRAY_BUFFER, nsnull);
    if (mBoundElementArrayBuffer == buf)
        BindBuffer(LOCAL_GL_ELEMENT_ARRAY_BUFFER, nsnull);

    for (int i = 0; i < mGLMaxVertexAttribs; i++) {
        if (mAttribBuffers[i].buf == buf)
            mAttribBuffers[i].buf = nsnull;
    }

    buf->RequestDelete();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DeleteFramebuffer(nsIWebGLFramebuffer *fbobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLFramebuffer *fbuf;
    WebGLuint fbufname;
    bool isNull, isDeleted;
    if (!GetConcreteObjectAndGLName("deleteFramebuffer", fbobj, &fbuf, &fbufname, &isNull, &isDeleted))
        return NS_OK;

    if (isNull || isDeleted)
        return NS_OK;

    fbuf->RequestDelete();

    if (mBoundFramebuffer == fbuf)
        BindFramebuffer(LOCAL_GL_FRAMEBUFFER, nsnull);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DeleteRenderbuffer(nsIWebGLRenderbuffer *rbobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLRenderbuffer *rbuf;
    WebGLuint rbufname;
    bool isNull, isDeleted;
    if (!GetConcreteObjectAndGLName("deleteRenderbuffer", rbobj, &rbuf, &rbufname, &isNull, &isDeleted))
        return NS_OK;

    if (isNull || isDeleted)
        return NS_OK;

    if (mBoundFramebuffer)
        mBoundFramebuffer->DetachRenderbuffer(rbuf);

    if (mBoundRenderbuffer == rbuf)
        BindRenderbuffer(LOCAL_GL_RENDERBUFFER, nsnull);

    rbuf->RequestDelete();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DeleteTexture(nsIWebGLTexture *tobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLTexture *tex;
    WebGLuint texname;
    bool isNull, isDeleted;
    if (!GetConcreteObjectAndGLName("deleteTexture", tobj, &tex, &texname, &isNull, &isDeleted))
        return NS_OK;

    if (isNull || isDeleted)
        return NS_OK;

    if (mBoundFramebuffer)
        mBoundFramebuffer->DetachTexture(tex);

    for (int i = 0; i < mGLMaxTextureUnits; i++) {
        if ((tex->Target() == LOCAL_GL_TEXTURE_2D && mBound2DTextures[i] == tex) ||
            (tex->Target() == LOCAL_GL_TEXTURE_CUBE_MAP && mBoundCubeMapTextures[i] == tex))
        {
            ActiveTexture(LOCAL_GL_TEXTURE0 + i);
            BindTexture(tex->Target(), nsnull);
        }
    }
    ActiveTexture(LOCAL_GL_TEXTURE0 + mActiveTexture);

    tex->RequestDelete();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DeleteProgram(nsIWebGLProgram *pobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLuint progname;
    WebGLProgram *prog;
    bool isNull, isDeleted;
    if (!GetConcreteObjectAndGLName("deleteProgram", pobj, &prog, &progname, &isNull, &isDeleted))
        return NS_OK;

    if (isNull || isDeleted)
        return NS_OK;

    prog->RequestDelete();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DeleteShader(nsIWebGLShader *sobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLuint shadername;
    WebGLShader *shader;
    bool isNull, isDeleted;
    if (!GetConcreteObjectAndGLName("deleteShader", sobj, &shader, &shadername, &isNull, &isDeleted))
        return NS_OK;

    if (isNull || isDeleted)
        return NS_OK;

    shader->RequestDelete();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DetachShader(nsIWebGLProgram *pobj, nsIWebGLShader *shobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLuint progname, shadername;
    WebGLProgram *program;
    WebGLShader *shader;
    bool shaderDeleted;
    if (!GetConcreteObjectAndGLName("detachShader: program", pobj, &program, &progname) ||
        !GetConcreteObjectAndGLName("detachShader: shader", shobj, &shader, &shadername, nsnull, &shaderDeleted))
        return NS_OK;

    // shaderDeleted is ignored -- it's valid to attempt to detach a
    // deleted shader, since it's still a shader
    if (!program->DetachShader(shader))
        return ErrorInvalidOperation("DetachShader: shader is not attached");

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DepthFunc(WebGLenum func)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateComparisonEnum(func, "depthFunc"))
        return NS_OK;

    MakeContextCurrent();
    gl->fDepthFunc(func);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DepthMask(WebGLboolean b)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();
    mDepthWriteMask = b;
    gl->fDepthMask(b);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DepthRange(WebGLfloat zNear, WebGLfloat zFar)
{
    if (!IsContextStable())
        return NS_OK;

    if (zNear > zFar)
        return ErrorInvalidOperation("depthRange: the near value is greater than the far value!");

    MakeContextCurrent();
    gl->fDepthRange(zNear, zFar);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DisableVertexAttribArray(WebGLuint index)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateAttribIndex(index, "disableVertexAttribArray"))
        return NS_OK;

    MakeContextCurrent();

    if (index || gl->IsGLES2())
        gl->fDisableVertexAttribArray(index);

    mAttribBuffers[index].enabled = false;

    return NS_OK;
}

int
WebGLContext::WhatDoesVertexAttrib0Need()
{
  // here we may assume that mCurrentProgram != null

    // work around Mac OSX crash, see bug 631420
#ifdef XP_MACOSX
    if (mAttribBuffers[0].enabled &&
        !mCurrentProgram->IsAttribInUse(0))
        return VertexAttrib0Status::EmulatedUninitializedArray;
#endif

    return (gl->IsGLES2() || mAttribBuffers[0].enabled) ? VertexAttrib0Status::Default
         : mCurrentProgram->IsAttribInUse(0)            ? VertexAttrib0Status::EmulatedInitializedArray
                                                        : VertexAttrib0Status::EmulatedUninitializedArray;
}

bool
WebGLContext::DoFakeVertexAttrib0(WebGLuint vertexCount)
{
    int whatDoesAttrib0Need = WhatDoesVertexAttrib0Need();

    if (whatDoesAttrib0Need == VertexAttrib0Status::Default)
        return true;

    CheckedUint32 checked_dataSize = CheckedUint32(vertexCount) * 4 * sizeof(WebGLfloat);
    
    if (!checked_dataSize.valid()) {
        ErrorOutOfMemory("Integer overflow trying to construct a fake vertex attrib 0 array for a draw-operation "
                         "with %d vertices. Try reducing the number of vertices.", vertexCount);
        return false;
    }
    
    WebGLuint dataSize = checked_dataSize.value();

    if (!mFakeVertexAttrib0BufferObject) {
        gl->fGenBuffers(1, &mFakeVertexAttrib0BufferObject);
    }

    // if the VBO status is already exactly what we need, or if the only difference is that it's initialized and
    // we don't need it to be, then consider it OK
    bool vertexAttrib0BufferStatusOK =
        mFakeVertexAttrib0BufferStatus == whatDoesAttrib0Need ||
        (mFakeVertexAttrib0BufferStatus == VertexAttrib0Status::EmulatedInitializedArray &&
         whatDoesAttrib0Need == VertexAttrib0Status::EmulatedUninitializedArray);

    if (!vertexAttrib0BufferStatusOK ||
        mFakeVertexAttrib0BufferObjectSize < dataSize ||
        mFakeVertexAttrib0BufferObjectVector[0] != mVertexAttrib0Vector[0] ||
        mFakeVertexAttrib0BufferObjectVector[1] != mVertexAttrib0Vector[1] ||
        mFakeVertexAttrib0BufferObjectVector[2] != mVertexAttrib0Vector[2] ||
        mFakeVertexAttrib0BufferObjectVector[3] != mVertexAttrib0Vector[3])
    {
        mFakeVertexAttrib0BufferStatus = whatDoesAttrib0Need;
        mFakeVertexAttrib0BufferObjectSize = dataSize;
        mFakeVertexAttrib0BufferObjectVector[0] = mVertexAttrib0Vector[0];
        mFakeVertexAttrib0BufferObjectVector[1] = mVertexAttrib0Vector[1];
        mFakeVertexAttrib0BufferObjectVector[2] = mVertexAttrib0Vector[2];
        mFakeVertexAttrib0BufferObjectVector[3] = mVertexAttrib0Vector[3];

        gl->fBindBuffer(LOCAL_GL_ARRAY_BUFFER, mFakeVertexAttrib0BufferObject);

        GLenum error = LOCAL_GL_NO_ERROR;
        UpdateWebGLErrorAndClearGLError();

        if (mFakeVertexAttrib0BufferStatus == VertexAttrib0Status::EmulatedInitializedArray) {
            nsAutoArrayPtr<WebGLfloat> array(new WebGLfloat[4 * vertexCount]);
            for(size_t i = 0; i < vertexCount; ++i) {
                array[4 * i + 0] = mVertexAttrib0Vector[0];
                array[4 * i + 1] = mVertexAttrib0Vector[1];
                array[4 * i + 2] = mVertexAttrib0Vector[2];
                array[4 * i + 3] = mVertexAttrib0Vector[3];
            }
            gl->fBufferData(LOCAL_GL_ARRAY_BUFFER, dataSize, array, LOCAL_GL_DYNAMIC_DRAW);
        } else {
            gl->fBufferData(LOCAL_GL_ARRAY_BUFFER, dataSize, nsnull, LOCAL_GL_DYNAMIC_DRAW);
        }
        UpdateWebGLErrorAndClearGLError(&error);
        
        gl->fBindBuffer(LOCAL_GL_ARRAY_BUFFER, mBoundArrayBuffer ? mBoundArrayBuffer->GLName() : 0);

        // note that we do this error checking and early return AFTER having restored the buffer binding above
        if (error) {
            ErrorOutOfMemory("Ran out of memory trying to construct a fake vertex attrib 0 array for a draw-operation "
                             "with %d vertices. Try reducing the number of vertices.", vertexCount);
            return false;
        }
    }

    gl->fBindBuffer(LOCAL_GL_ARRAY_BUFFER, mFakeVertexAttrib0BufferObject);
    gl->fVertexAttribPointer(0, 4, LOCAL_GL_FLOAT, LOCAL_GL_FALSE, 0, 0);
    
    return true;
}

void
WebGLContext::UndoFakeVertexAttrib0()
{
    int whatDoesAttrib0Need = WhatDoesVertexAttrib0Need();

    if (whatDoesAttrib0Need == VertexAttrib0Status::Default)
        return;

    gl->fBindBuffer(LOCAL_GL_ARRAY_BUFFER, mAttribBuffers[0].buf ? mAttribBuffers[0].buf->GLName() : 0);
    gl->fVertexAttribPointer(0,
                             mAttribBuffers[0].size,
                             mAttribBuffers[0].type,
                             mAttribBuffers[0].normalized,
                             mAttribBuffers[0].stride,
                             (const GLvoid *) mAttribBuffers[0].byteOffset);

    gl->fBindBuffer(LOCAL_GL_ARRAY_BUFFER, mBoundArrayBuffer ? mBoundArrayBuffer->GLName() : 0);
}

bool
WebGLContext::NeedFakeBlack()
{
    // handle this case first, it's the generic case
    if (mFakeBlackStatus == DoNotNeedFakeBlack)
        return false;

    if (mFakeBlackStatus == DontKnowIfNeedFakeBlack) {
        for (PRInt32 i = 0; i < mGLMaxTextureUnits; ++i) {
            if ((mBound2DTextures[i] && mBound2DTextures[i]->NeedFakeBlack()) ||
                (mBoundCubeMapTextures[i] && mBoundCubeMapTextures[i]->NeedFakeBlack()))
            {
                mFakeBlackStatus = DoNeedFakeBlack;
                break;
            }
        }

        // we have exhausted all cases where we do need fakeblack, so if the status is still unknown,
        // that means that we do NOT need it.
        if (mFakeBlackStatus == DontKnowIfNeedFakeBlack)
            mFakeBlackStatus = DoNotNeedFakeBlack;
    }

    return mFakeBlackStatus == DoNeedFakeBlack;
}

void
WebGLContext::BindFakeBlackTextures()
{
    // this is the generic case: try to return early
    if (!NeedFakeBlack())
        return;

    if (!mBlackTexturesAreInitialized) {
        GLuint bound2DTex = 0;
        GLuint boundCubeTex = 0;
        gl->fGetIntegerv(LOCAL_GL_TEXTURE_BINDING_2D, (GLint*) &bound2DTex);
        gl->fGetIntegerv(LOCAL_GL_TEXTURE_BINDING_CUBE_MAP, (GLint*) &boundCubeTex);

        const PRUint8 black[] = {0, 0, 0, 255};

        gl->fGenTextures(1, &mBlackTexture2D);
        gl->fBindTexture(LOCAL_GL_TEXTURE_2D, mBlackTexture2D);
        gl->fTexImage2D(LOCAL_GL_TEXTURE_2D, 0, LOCAL_GL_RGBA, 1, 1,
                        0, LOCAL_GL_RGBA, LOCAL_GL_UNSIGNED_BYTE, &black);

        gl->fGenTextures(1, &mBlackTextureCubeMap);
        gl->fBindTexture(LOCAL_GL_TEXTURE_CUBE_MAP, mBlackTextureCubeMap);
        for (WebGLuint i = 0; i < 6; ++i) {
            gl->fTexImage2D(LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, LOCAL_GL_RGBA, 1, 1,
                            0, LOCAL_GL_RGBA, LOCAL_GL_UNSIGNED_BYTE, &black);
        }

        // Reset bound textures
        gl->fBindTexture(LOCAL_GL_TEXTURE_2D, bound2DTex);
        gl->fBindTexture(LOCAL_GL_TEXTURE_CUBE_MAP, boundCubeTex);

        mBlackTexturesAreInitialized = true;
    }

    for (PRInt32 i = 0; i < mGLMaxTextureUnits; ++i) {
        if (mBound2DTextures[i] && mBound2DTextures[i]->NeedFakeBlack()) {
            gl->fActiveTexture(LOCAL_GL_TEXTURE0 + i);
            gl->fBindTexture(LOCAL_GL_TEXTURE_2D, mBlackTexture2D);
        }
        if (mBoundCubeMapTextures[i] && mBoundCubeMapTextures[i]->NeedFakeBlack()) {
            gl->fActiveTexture(LOCAL_GL_TEXTURE0 + i);
            gl->fBindTexture(LOCAL_GL_TEXTURE_CUBE_MAP, mBlackTextureCubeMap);
        }
    }
}

void
WebGLContext::UnbindFakeBlackTextures()
{
    // this is the generic case: try to return early
    if (!NeedFakeBlack())
        return;

    for (PRInt32 i = 0; i < mGLMaxTextureUnits; ++i) {
        if (mBound2DTextures[i] && mBound2DTextures[i]->NeedFakeBlack()) {
            gl->fActiveTexture(LOCAL_GL_TEXTURE0 + i);
            gl->fBindTexture(LOCAL_GL_TEXTURE_2D, mBound2DTextures[i]->GLName());
        }
        if (mBoundCubeMapTextures[i] && mBoundCubeMapTextures[i]->NeedFakeBlack()) {
            gl->fActiveTexture(LOCAL_GL_TEXTURE0 + i);
            gl->fBindTexture(LOCAL_GL_TEXTURE_CUBE_MAP, mBoundCubeMapTextures[i]->GLName());
        }
    }

    gl->fActiveTexture(LOCAL_GL_TEXTURE0 + mActiveTexture);
}

NS_IMETHODIMP
WebGLContext::DrawArrays(GLenum mode, WebGLint first, WebGLsizei count)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateDrawModeEnum(mode, "drawArrays: mode"))
        return NS_OK;

    if (first < 0 || count < 0)
        return ErrorInvalidValue("DrawArrays: negative first or count");

    if (!ValidateStencilParamsForDrawCall())
        return NS_OK;

    // If count is 0, there's nothing to do.
    if (count == 0)
        return NS_OK;

    // If there is no current program, this is silently ignored.
    // Any checks below this depend on a program being available.
    if (!mCurrentProgram)
        return NS_OK;

    PRInt32 maxAllowedCount = 0;
    if (!ValidateBuffers(&maxAllowedCount, "drawArrays"))
        return NS_OK;

    CheckedInt32 checked_firstPlusCount = CheckedInt32(first) + count;

    if (!checked_firstPlusCount.valid())
        return ErrorInvalidOperation("drawArrays: overflow in first+count");

    if (checked_firstPlusCount.value() > maxAllowedCount)
        return ErrorInvalidOperation("drawArrays: bound vertex attribute buffers do not have sufficient size for given first and count");

    MakeContextCurrent();

    if (mBoundFramebuffer) {
        if (!mBoundFramebuffer->CheckAndInitializeRenderbuffers())
            return NS_OK;
    } else {
        EnsureBackbufferClearedAsNeeded();
    }

    BindFakeBlackTextures();
    if (!DoFakeVertexAttrib0(checked_firstPlusCount.value()))
        return NS_OK;

    SetupRobustnessTimer();
    gl->fDrawArrays(mode, first, count);

    UndoFakeVertexAttrib0();
    UnbindFakeBlackTextures();

    mBackbufferClearingStatus = BackbufferClearingStatus::HasBeenDrawnTo;
    Invalidate();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::DrawElements(WebGLenum mode, WebGLsizei count, WebGLenum type, WebGLint byteOffset)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateDrawModeEnum(mode, "drawElements: mode"))
        return NS_OK;

    if (count < 0 || byteOffset < 0)
        return ErrorInvalidValue("DrawElements: negative count or offset");

    if (!ValidateStencilParamsForDrawCall())
        return NS_OK;

    // If count is 0, there's nothing to do.
    if (count == 0)
        return NS_OK;

    CheckedUint32 checked_byteCount;

    if (type == LOCAL_GL_UNSIGNED_SHORT) {
        checked_byteCount = 2 * CheckedUint32(count);
        if (byteOffset % 2 != 0)
            return ErrorInvalidOperation("DrawElements: invalid byteOffset for UNSIGNED_SHORT (must be a multiple of 2)");
    } else if (type == LOCAL_GL_UNSIGNED_BYTE) {
        checked_byteCount = count;
    } else {
        return ErrorInvalidEnum("DrawElements: type must be UNSIGNED_SHORT or UNSIGNED_BYTE");
    }

    if (!checked_byteCount.valid())
        return ErrorInvalidValue("DrawElements: overflow in byteCount");

    // If there is no current program, this is silently ignored.
    // Any checks below this depend on a program being available.
    if (!mCurrentProgram)
        return NS_OK;

    if (!mBoundElementArrayBuffer)
        return ErrorInvalidOperation("DrawElements: must have element array buffer binding");

    if (!mBoundElementArrayBuffer->Data())
        return ErrorInvalidOperation("drawElements: bound element array buffer doesn't have any data");

    CheckedUint32 checked_neededByteCount = checked_byteCount + byteOffset;

    if (!checked_neededByteCount.valid())
        return ErrorInvalidOperation("DrawElements: overflow in byteOffset+byteCount");

    if (checked_neededByteCount.value() > mBoundElementArrayBuffer->ByteLength())
        return ErrorInvalidOperation("DrawElements: bound element array buffer is too small for given count and offset");

    PRInt32 maxAllowedCount = 0;
    if (!ValidateBuffers(&maxAllowedCount, "drawElements"))
      return NS_OK;

    PRInt32 maxIndex
      = type == LOCAL_GL_UNSIGNED_SHORT
        ? mBoundElementArrayBuffer->FindMaxUshortElement()
        : mBoundElementArrayBuffer->FindMaxUbyteElement();

    CheckedInt32 checked_maxIndexPlusOne = CheckedInt32(maxIndex) + 1;

    if (!checked_maxIndexPlusOne.valid() ||
        checked_maxIndexPlusOne.value() > maxAllowedCount)
    {
        // the index array contains invalid indices for the current drawing state, but they
        // might not be used by the present drawElements call, depending on first and count.

        PRInt32 maxIndexInSubArray
          = type == LOCAL_GL_UNSIGNED_SHORT
            ? mBoundElementArrayBuffer->FindMaxElementInSubArray<GLushort>(count, byteOffset)
            : mBoundElementArrayBuffer->FindMaxElementInSubArray<GLubyte>(count, byteOffset);

        CheckedInt32 checked_maxIndexInSubArrayPlusOne = CheckedInt32(maxIndexInSubArray) + 1;

        if (!checked_maxIndexInSubArrayPlusOne.valid() ||
            checked_maxIndexInSubArrayPlusOne.value() > maxAllowedCount)
        {
            return ErrorInvalidOperation(
                "DrawElements: bound vertex attribute buffers do not have sufficient "
                "size for given indices from the bound element array");
        }
    }

    MakeContextCurrent();

    if (mBoundFramebuffer) {
        if (!mBoundFramebuffer->CheckAndInitializeRenderbuffers())
            return NS_OK;
    } else {
        EnsureBackbufferClearedAsNeeded();
    }

    BindFakeBlackTextures();
    if (!DoFakeVertexAttrib0(checked_maxIndexPlusOne.value()))
        return NS_OK;

    SetupRobustnessTimer();
    gl->fDrawElements(mode, count, type, (GLvoid*) (byteOffset));

    UndoFakeVertexAttrib0();
    UnbindFakeBlackTextures();

    mBackbufferClearingStatus = BackbufferClearingStatus::HasBeenDrawnTo;
    Invalidate();

    return NS_OK;
}

NS_IMETHODIMP WebGLContext::Enable(WebGLenum cap)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateCapabilityEnum(cap, "enable"))
        return NS_OK;

    switch(cap) {
        case LOCAL_GL_SCISSOR_TEST:
            mScissorTestEnabled = 1;
            break;
        case LOCAL_GL_DITHER:
            mDitherEnabled = 1;
            break;
    }

    MakeContextCurrent();
    gl->fEnable(cap);
    return NS_OK;
}

NS_IMETHODIMP WebGLContext::Disable(WebGLenum cap)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateCapabilityEnum(cap, "disable"))
        return NS_OK;

    switch(cap) {
        case LOCAL_GL_SCISSOR_TEST:
            mScissorTestEnabled = 0;
            break;
        case LOCAL_GL_DITHER:
            mDitherEnabled = 0;
            break;
    }

    MakeContextCurrent();
    gl->fDisable(cap);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::EnableVertexAttribArray(WebGLuint index)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateAttribIndex(index, "enableVertexAttribArray"))
        return NS_OK;

    MakeContextCurrent();

    gl->fEnableVertexAttribArray(index);
    mAttribBuffers[index].enabled = true;

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::FramebufferRenderbuffer(WebGLenum target, WebGLenum attachment, WebGLenum rbtarget, nsIWebGLRenderbuffer *rbobj)
{
    if (!IsContextStable())
        return NS_OK;

    if (!mBoundFramebuffer)
        return ErrorInvalidOperation("framebufferRenderbuffer: cannot modify framebuffer 0");

    return mBoundFramebuffer->FramebufferRenderbuffer(target, attachment, rbtarget, rbobj);
}

NS_IMETHODIMP
WebGLContext::FramebufferTexture2D(WebGLenum target,
                                   WebGLenum attachment,
                                   WebGLenum textarget,
                                   nsIWebGLTexture *tobj,
                                   WebGLint level)
{
    if (!IsContextStable())
        return NS_OK;

    if (mBoundFramebuffer)
        return mBoundFramebuffer->FramebufferTexture2D(target, attachment, textarget, tobj, level);
    else
        return ErrorInvalidOperation("framebufferTexture2D: cannot modify framebuffer 0");
}

GL_SAME_METHOD_0(Flush, Flush)

GL_SAME_METHOD_0(Finish, Finish)

NS_IMETHODIMP
WebGLContext::FrontFace(WebGLenum mode)
{
    if (!IsContextStable())
        return NS_OK;

    switch (mode) {
        case LOCAL_GL_CW:
        case LOCAL_GL_CCW:
            break;
        default:
            return ErrorInvalidEnumInfo("frontFace: mode", mode);
    }

    MakeContextCurrent();
    gl->fFrontFace(mode);
    return NS_OK;
}

// returns an object: { size: ..., type: ..., name: ... }
NS_IMETHODIMP
WebGLContext::GetActiveAttrib(nsIWebGLProgram *pobj, PRUint32 index, nsIWebGLActiveInfo **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    WebGLuint progname;
    if (!GetGLName<WebGLProgram>("getActiveAttrib: program", pobj, &progname))
        return NS_OK;

    MakeContextCurrent();

    GLint len = 0;
    gl->fGetProgramiv(progname, LOCAL_GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, &len);
    if (len == 0)
        return NS_OK;

    nsAutoArrayPtr<char> name(new char[len]);
    GLint attrsize = 0;
    GLuint attrtype = 0;

    gl->fGetActiveAttrib(progname, index, len, &len, &attrsize, &attrtype, name);
    if (attrsize == 0 || attrtype == 0) {
        *retval = nsnull;
        return NS_OK;
    }

    WebGLActiveInfo *retActiveInfo = new WebGLActiveInfo(attrsize, attrtype, name.get(), len);
    NS_ADDREF(*retval = retActiveInfo);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GenerateMipmap(WebGLenum target)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateTextureTargetEnum(target, "generateMipmap"))
        return NS_OK;

    WebGLTexture *tex = activeBoundTextureForTarget(target);

    if (!tex)
        return ErrorInvalidOperation("generateMipmap: no texture is bound to this target");

    if (!tex->IsFirstImagePowerOfTwo()) {
        return ErrorInvalidOperation("generateMipmap: the width or height of this texture is not a power of two");
    }

    if (!tex->AreAllLevel0ImageInfosEqual()) {
        return ErrorInvalidOperation("generateMipmap: the six faces of this cube map have different dimensions, format, or type.");
    }

    tex->SetGeneratedMipmap();

    MakeContextCurrent();
    gl->fGenerateMipmap(target);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetActiveUniform(nsIWebGLProgram *pobj, PRUint32 index, nsIWebGLActiveInfo **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    WebGLuint progname;
    if (!GetGLName<WebGLProgram>("getActiveUniform: program", pobj, &progname))
        return NS_OK;

    MakeContextCurrent();

    GLint len = 0;
    gl->fGetProgramiv(progname, LOCAL_GL_ACTIVE_UNIFORM_MAX_LENGTH, &len);
    if (len == 0)
        *retval = nsnull;

    nsAutoArrayPtr<char> name(new char[len + 3]); // +3 because we might have to append "[0]", see below

    GLint attrsize = 0;
    GLuint attrtype = 0;

    gl->fGetActiveUniform(progname, index, len, &len, &attrsize, &attrtype, name);
    if (len == 0 || attrsize == 0 || attrtype == 0) {
        *retval = nsnull;
        return NS_OK;
    }

    // OpenGL ES 2.0 specifies that if foo is a uniform array, GetActiveUniform returns its name as "foo[0]".
    // See section 2.10 page 35 in the OpenGL ES 2.0.24 specification:
    //
    // > If the active uniform is an array, the uniform name returned in name will always
    // > be the name of the uniform array appended with "[0]".
    //
    // There is no such requirement in the OpenGL (non-ES) spec and indeed we have OpenGL implementations returning
    // "foo" instead of "foo[0]". So, when implementing WebGL on top of desktop OpenGL, we must check if the
    // returned name ends in [0], and if it doesn't, append that.
    //
    // In principle we don't need to do that on OpenGL ES, but this is such a tricky difference between the ES and non-ES
    // specs that it seems probable that some ES implementers will overlook it. Since the work-around is quite cheap,
    // we do it unconditionally.
    if (attrsize > 1 && name[len-1] != ']') {
        name[len++] = '[';
        name[len++] = '0';
        name[len++] = ']';
    }

    WebGLActiveInfo *retActiveInfo = new WebGLActiveInfo(attrsize, attrtype, name.get(), len);

    NS_ADDREF(*retval = retActiveInfo);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetAttachedShaders(nsIWebGLProgram *pobj, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    WebGLProgram *prog;
    bool isNull;
    if (!GetConcreteObject("getAttachedShaders", pobj, &prog, &isNull)) 
        return NS_OK;

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    MakeContextCurrent();

    if (isNull) {
        wrval->SetAsEmpty();
        // note no return, we still want to return the variant
        ErrorInvalidValue("getAttachedShaders: invalid program");
    } else if (prog->AttachedShaders().Length() == 0) {
        wrval->SetAsEmptyArray();
    } else {
        wrval->SetAsArray(nsIDataType::VTYPE_INTERFACE,
                        &NS_GET_IID(nsIWebGLShader),
                        prog->AttachedShaders().Length(),
                        const_cast<void*>( // @#$% SetAsArray doesn't accept a const void*
                            static_cast<const void*>(
                                prog->AttachedShaders().Elements()
                            )
                        )
                        );
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetAttribLocation(nsIWebGLProgram *pobj,
                                const nsAString& name,
                                PRInt32 *retval)
{
    if (!IsContextStable())
    {
        *retval = -1;
        return NS_OK;
    }

    *retval = 0;

    WebGLuint progname;
    if (!GetGLName<WebGLProgram>("getAttribLocation: program", pobj, &progname))
        return NS_OK;

    if (!ValidateGLSLVariableName(name, "getAttribLocation"))
        return NS_OK; 

    MakeContextCurrent();
    *retval = gl->fGetAttribLocation(progname, NS_LossyConvertUTF16toASCII(name).get());
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetParameter(PRUint32 pname, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    MakeContextCurrent();
    
    if (MinCapabilityMode()) {
        bool override = true;
        switch(pname) {
            //
            // Single-value params
            //
                
// int
            case LOCAL_GL_MAX_VERTEX_ATTRIBS:
                wrval->SetAsInt32(MINVALUE_GL_MAX_VERTEX_ATTRIBS);
                break;
            
            case LOCAL_GL_MAX_FRAGMENT_UNIFORM_VECTORS:
                wrval->SetAsInt32(MINVALUE_GL_MAX_FRAGMENT_UNIFORM_VECTORS);
                break;
            
            case LOCAL_GL_MAX_VERTEX_UNIFORM_VECTORS:
                wrval->SetAsInt32(MINVALUE_GL_MAX_VERTEX_UNIFORM_VECTORS);
                break;
            
            case LOCAL_GL_MAX_VARYING_VECTORS:
                wrval->SetAsInt32(MINVALUE_GL_MAX_VARYING_VECTORS);
                break;
            
            case LOCAL_GL_MAX_TEXTURE_SIZE:
                wrval->SetAsInt32(MINVALUE_GL_MAX_TEXTURE_SIZE);
                break;
            
            case LOCAL_GL_MAX_CUBE_MAP_TEXTURE_SIZE:
                wrval->SetAsInt32(MINVALUE_GL_MAX_CUBE_MAP_TEXTURE_SIZE);
                break;
            
            case LOCAL_GL_MAX_TEXTURE_IMAGE_UNITS:
                wrval->SetAsInt32(MINVALUE_GL_MAX_TEXTURE_IMAGE_UNITS);
                break;
            
            case LOCAL_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS:
                wrval->SetAsInt32(MINVALUE_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS);
                break;
                
            case LOCAL_GL_MAX_RENDERBUFFER_SIZE:
                wrval->SetAsInt32(MINVALUE_GL_MAX_RENDERBUFFER_SIZE);
                break;
            
            default:
                override = false;
        }
        
        if (override) {
            *retval = wrval.forget().get();
            return NS_OK;
        }
    }
    
    switch (pname) {
        //
        // String params
        //

        case LOCAL_GL_VENDOR:
            wrval->SetAsDOMString(NS_LITERAL_STRING("Mozilla"));
            break;
        case LOCAL_GL_RENDERER:
            wrval->SetAsDOMString(NS_LITERAL_STRING("Mozilla"));
            break;
        case LOCAL_GL_VERSION:
            wrval->SetAsDOMString(NS_LITERAL_STRING("WebGL 1.0"));
            break;
        case LOCAL_GL_SHADING_LANGUAGE_VERSION:
            wrval->SetAsDOMString(NS_LITERAL_STRING("WebGL GLSL ES 1.0"));
            break;

        //
        // Single-value params
        //

// int
        case LOCAL_GL_CULL_FACE_MODE:
        case LOCAL_GL_FRONT_FACE:
        case LOCAL_GL_ACTIVE_TEXTURE:
        case LOCAL_GL_STENCIL_CLEAR_VALUE:
        case LOCAL_GL_STENCIL_FUNC:
        case LOCAL_GL_STENCIL_REF:
        case LOCAL_GL_STENCIL_FAIL:
        case LOCAL_GL_STENCIL_PASS_DEPTH_FAIL:
        case LOCAL_GL_STENCIL_PASS_DEPTH_PASS:
        case LOCAL_GL_STENCIL_BACK_FUNC:
        case LOCAL_GL_STENCIL_BACK_REF:
        case LOCAL_GL_STENCIL_BACK_FAIL:
        case LOCAL_GL_STENCIL_BACK_PASS_DEPTH_FAIL:
        case LOCAL_GL_STENCIL_BACK_PASS_DEPTH_PASS:
        case LOCAL_GL_DEPTH_FUNC:
        case LOCAL_GL_BLEND_SRC_RGB:
        case LOCAL_GL_BLEND_SRC_ALPHA:
        case LOCAL_GL_BLEND_DST_RGB:
        case LOCAL_GL_BLEND_DST_ALPHA:
        case LOCAL_GL_BLEND_EQUATION_RGB:
        case LOCAL_GL_BLEND_EQUATION_ALPHA:
        case LOCAL_GL_UNPACK_ALIGNMENT:
        case LOCAL_GL_PACK_ALIGNMENT:
        case LOCAL_GL_GENERATE_MIPMAP_HINT:
        case LOCAL_GL_SUBPIXEL_BITS:
        case LOCAL_GL_MAX_TEXTURE_SIZE:
        case LOCAL_GL_MAX_CUBE_MAP_TEXTURE_SIZE:
        case LOCAL_GL_SAMPLE_BUFFERS:
        case LOCAL_GL_SAMPLES:
        case LOCAL_GL_MAX_VERTEX_ATTRIBS:
        case LOCAL_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS:
        case LOCAL_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS:
        case LOCAL_GL_MAX_TEXTURE_IMAGE_UNITS:
        case LOCAL_GL_MAX_RENDERBUFFER_SIZE:
        case LOCAL_GL_RED_BITS:
        case LOCAL_GL_GREEN_BITS:
        case LOCAL_GL_BLUE_BITS:
        case LOCAL_GL_ALPHA_BITS:
        case LOCAL_GL_DEPTH_BITS:
        case LOCAL_GL_STENCIL_BITS:
        {
            GLint i = 0;
            gl->fGetIntegerv(pname, &i);
            wrval->SetAsInt32(i);
        }
            break;
        case LOCAL_GL_FRAGMENT_SHADER_DERIVATIVE_HINT:
            if (mEnabledExtensions[WebGL_OES_standard_derivatives]) {
                GLint i = 0;
                gl->fGetIntegerv(pname, &i);
                wrval->SetAsInt32(i);
            }
            else
                return ErrorInvalidEnum("getParameter: parameter", pname);
            break;

        case LOCAL_GL_MAX_VERTEX_UNIFORM_VECTORS:
            wrval->SetAsInt32(mGLMaxVertexUniformVectors);
            break;

        case LOCAL_GL_MAX_FRAGMENT_UNIFORM_VECTORS:
            wrval->SetAsInt32(mGLMaxFragmentUniformVectors);
            break;

        case LOCAL_GL_MAX_VARYING_VECTORS:
            wrval->SetAsInt32(mGLMaxVaryingVectors);
            break;

        case LOCAL_GL_NUM_COMPRESSED_TEXTURE_FORMATS:
            wrval->SetAsInt32(0);
            break;
        case LOCAL_GL_COMPRESSED_TEXTURE_FORMATS:
            wrval->SetAsEmpty(); // the spec says we must return null
            break;

// unsigned int. here we may have to return very large values like 2^32-1 that can't be represented as
// javascript integer values. We just return them as doubles and javascript doesn't care.
        case LOCAL_GL_STENCIL_BACK_VALUE_MASK:
        case LOCAL_GL_STENCIL_BACK_WRITEMASK:
        case LOCAL_GL_STENCIL_VALUE_MASK:
        case LOCAL_GL_STENCIL_WRITEMASK:
        {
            GLint i = 0; // the GL api (glGetIntegerv) only does signed ints
            gl->fGetIntegerv(pname, &i);
            GLuint i_unsigned(i); // this is where -1 becomes 2^32-1
            double i_double(i_unsigned); // pass as FP value to allow large values such as 2^32-1.
            wrval->SetAsDouble(i_double);
        }
            break;

// float
        case LOCAL_GL_DEPTH_CLEAR_VALUE:
        case LOCAL_GL_LINE_WIDTH:
        case LOCAL_GL_POLYGON_OFFSET_FACTOR:
        case LOCAL_GL_POLYGON_OFFSET_UNITS:
        case LOCAL_GL_SAMPLE_COVERAGE_VALUE:
        {
            GLfloat f = 0.f;
            gl->fGetFloatv(pname, &f);
            wrval->SetAsFloat(f);
        }
            break;

// bool
        case LOCAL_GL_BLEND:
        case LOCAL_GL_DEPTH_TEST:
        case LOCAL_GL_STENCIL_TEST:
        case LOCAL_GL_CULL_FACE:
        case LOCAL_GL_DITHER:
        case LOCAL_GL_POLYGON_OFFSET_FILL:
        case LOCAL_GL_SCISSOR_TEST:
        case LOCAL_GL_SAMPLE_COVERAGE_INVERT:
        case LOCAL_GL_DEPTH_WRITEMASK:
        {
            realGLboolean b = 0;
            gl->fGetBooleanv(pname, &b);
            wrval->SetAsBool(bool(b));
        }
            break;

// bool, WebGL-specific
        case UNPACK_FLIP_Y_WEBGL:
            wrval->SetAsBool(mPixelStoreFlipY);
            break;
        case UNPACK_PREMULTIPLY_ALPHA_WEBGL:
            wrval->SetAsBool(mPixelStorePremultiplyAlpha);
            break;

// uint, WebGL-specific
        case UNPACK_COLORSPACE_CONVERSION_WEBGL:
            wrval->SetAsUint32(mPixelStoreColorspaceConversion);
            break;

        //
        // Complex values
        //
        case LOCAL_GL_DEPTH_RANGE: // 2 floats
        case LOCAL_GL_ALIASED_POINT_SIZE_RANGE: // 2 floats
        case LOCAL_GL_ALIASED_LINE_WIDTH_RANGE: // 2 floats
        {
            GLfloat fv[2] = { 0 };
            gl->fGetFloatv(pname, fv);
            wrval->SetAsArray(nsIDataType::VTYPE_FLOAT, nsnull,
                              2, static_cast<void*>(fv));
        }
            break;
        
        case LOCAL_GL_COLOR_CLEAR_VALUE: // 4 floats
        case LOCAL_GL_BLEND_COLOR: // 4 floats
        {
            GLfloat fv[4] = { 0 };
            gl->fGetFloatv(pname, fv);
            wrval->SetAsArray(nsIDataType::VTYPE_FLOAT, nsnull,
                              4, static_cast<void*>(fv));
        }
            break;

        case LOCAL_GL_MAX_VIEWPORT_DIMS: // 2 ints
        {
            GLint iv[2] = { 0 };
            gl->fGetIntegerv(pname, iv);
            wrval->SetAsArray(nsIDataType::VTYPE_INT32, nsnull,
                              2, static_cast<void*>(iv));
        }
            break;

        case LOCAL_GL_SCISSOR_BOX: // 4 ints
        case LOCAL_GL_VIEWPORT: // 4 ints
        {
            GLint iv[4] = { 0 };
            gl->fGetIntegerv(pname, iv);
            wrval->SetAsArray(nsIDataType::VTYPE_INT32, nsnull,
                              4, static_cast<void*>(iv));
        }
            break;

        case LOCAL_GL_COLOR_WRITEMASK: // 4 bools
        {
            realGLboolean gl_bv[4] = { 0 };
            gl->fGetBooleanv(pname, gl_bv);
            bool pr_bv[4] = { (bool)gl_bv[0], (bool)gl_bv[1], (bool)gl_bv[2], (bool)gl_bv[3] };
            wrval->SetAsArray(nsIDataType::VTYPE_BOOL, nsnull,
                              4, static_cast<void*>(pr_bv));
        }
            break;

        case LOCAL_GL_ARRAY_BUFFER_BINDING:
            wrval->SetAsISupports(mBoundArrayBuffer);
            break;

        case LOCAL_GL_ELEMENT_ARRAY_BUFFER_BINDING:
            wrval->SetAsISupports(mBoundElementArrayBuffer);
            break;

        case LOCAL_GL_RENDERBUFFER_BINDING:
            wrval->SetAsISupports(mBoundRenderbuffer);
            break;

        case LOCAL_GL_FRAMEBUFFER_BINDING:
            wrval->SetAsISupports(mBoundFramebuffer);
            break;

        case LOCAL_GL_CURRENT_PROGRAM:
            wrval->SetAsISupports(mCurrentProgram);
            break;

        case LOCAL_GL_TEXTURE_BINDING_2D:
            wrval->SetAsISupports(mBound2DTextures[mActiveTexture]);
            break;

        case LOCAL_GL_TEXTURE_BINDING_CUBE_MAP:
            wrval->SetAsISupports(mBoundCubeMapTextures[mActiveTexture]);
            break;

        default:
            return ErrorInvalidEnumInfo("getParameter: parameter", pname);
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetBufferParameter(WebGLenum target, WebGLenum pname, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    if (target != LOCAL_GL_ARRAY_BUFFER && target != LOCAL_GL_ELEMENT_ARRAY_BUFFER)
        return ErrorInvalidEnumInfo("getBufferParameter: target", target);

    MakeContextCurrent();

    switch (pname) {
        case LOCAL_GL_BUFFER_SIZE:
        case LOCAL_GL_BUFFER_USAGE:
        case LOCAL_GL_BUFFER_ACCESS:
        case LOCAL_GL_BUFFER_MAPPED:
        {
            GLint i = 0;
            gl->fGetBufferParameteriv(target, pname, &i);
            wrval->SetAsInt32(i);
        }
            break;

        default:
            return ErrorInvalidEnumInfo("getBufferParameter: parameter", pname);
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetFramebufferAttachmentParameter(WebGLenum target, WebGLenum attachment, WebGLenum pname, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    if (target != LOCAL_GL_FRAMEBUFFER)
        return ErrorInvalidEnumInfo("getFramebufferAttachmentParameter: target", target);

    switch (attachment) {
        case LOCAL_GL_COLOR_ATTACHMENT0:
        case LOCAL_GL_DEPTH_ATTACHMENT:
        case LOCAL_GL_STENCIL_ATTACHMENT:
        case LOCAL_GL_DEPTH_STENCIL_ATTACHMENT:
            break;
        default:
            return ErrorInvalidEnumInfo("GetFramebufferAttachmentParameter: attachment", attachment);
    }

    if (!mBoundFramebuffer)
        return ErrorInvalidOperation("GetFramebufferAttachmentParameter: cannot query framebuffer 0");

    MakeContextCurrent();

    const WebGLFramebufferAttachment& fba = mBoundFramebuffer->GetAttachment(attachment);

    if (fba.Renderbuffer()) {
        switch (pname) {
            case LOCAL_GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE:
                wrval->SetAsInt32(LOCAL_GL_RENDERBUFFER);
                break;

            case LOCAL_GL_FRAMEBUFFER_ATTACHMENT_OBJECT_NAME:
                wrval->SetAsISupports(fba.Renderbuffer());
                break;

            default:
                return ErrorInvalidEnumInfo("GetFramebufferAttachmentParameter: pname", pname);
        }
    } else if (fba.Texture()) {
        switch (pname) {
            case LOCAL_GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE:
                wrval->SetAsInt32(LOCAL_GL_TEXTURE);
                break;

            case LOCAL_GL_FRAMEBUFFER_ATTACHMENT_OBJECT_NAME:
                wrval->SetAsISupports(fba.Texture());
                break;

            case LOCAL_GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_LEVEL:
                wrval->SetAsInt32(fba.TextureLevel());
                break;

            case LOCAL_GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_CUBE_MAP_FACE:
                wrval->SetAsInt32(fba.TextureCubeMapFace());
                break;

            default:
                return ErrorInvalidEnumInfo("GetFramebufferAttachmentParameter: pname", pname);
        }
    } else {
        switch (pname) {
            case LOCAL_GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE:
                wrval->SetAsInt32(LOCAL_GL_NONE);
                break;

            default:
                return ErrorInvalidEnumInfo("GetFramebufferAttachmentParameter: pname", pname);
        }
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetRenderbufferParameter(WebGLenum target, WebGLenum pname, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    if (target != LOCAL_GL_RENDERBUFFER)
        return ErrorInvalidEnumInfo("GetRenderbufferParameter: target", target);

    MakeContextCurrent();

    switch (pname) {
        case LOCAL_GL_RENDERBUFFER_WIDTH:
        case LOCAL_GL_RENDERBUFFER_HEIGHT:
        case LOCAL_GL_RENDERBUFFER_RED_SIZE:
        case LOCAL_GL_RENDERBUFFER_GREEN_SIZE:
        case LOCAL_GL_RENDERBUFFER_BLUE_SIZE:
        case LOCAL_GL_RENDERBUFFER_ALPHA_SIZE:
        case LOCAL_GL_RENDERBUFFER_DEPTH_SIZE:
        case LOCAL_GL_RENDERBUFFER_STENCIL_SIZE:
        {
            GLint i = 0;
            gl->fGetRenderbufferParameteriv(target, pname, &i);
            wrval->SetAsInt32(i);
        }
            break;
        case LOCAL_GL_RENDERBUFFER_INTERNAL_FORMAT:
        {
            GLint i = 0;
            gl->fGetRenderbufferParameteriv(target, pname, &i);
            if (i == LOCAL_GL_DEPTH24_STENCIL8)
            {
                i = LOCAL_GL_DEPTH_STENCIL;
            }
            wrval->SetAsInt32(i);
        }
            break;
        default:
            return ErrorInvalidEnumInfo("GetRenderbufferParameter: parameter", pname);
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CreateBuffer(nsIWebGLBuffer **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    WebGLBuffer *globj = new WebGLBuffer(this);
    NS_ADDREF(*retval = globj);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CreateTexture(nsIWebGLTexture **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    MakeContextCurrent();

    WebGLTexture *globj = new WebGLTexture(this);
    NS_ADDREF(*retval = globj);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetError(WebGLenum *_retval)
{
    if (mContextStatus == ContextStable) {
        MakeContextCurrent();
        UpdateWebGLErrorAndClearGLError();
    } else if (!mContextLostErrorSet) {
        mWebGLError = LOCAL_GL_CONTEXT_LOST;
        mContextLostErrorSet = true;
    }

    *_retval = mWebGLError;
    mWebGLError = LOCAL_GL_NO_ERROR;

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetProgramParameter(nsIWebGLProgram *pobj, PRUint32 pname, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    WebGLuint progname;
    bool isDeleted;
    WebGLProgram *prog;
    if (!GetConcreteObjectAndGLName("getProgramParameter: program", pobj, &prog, &progname, nsnull, &isDeleted))
        return NS_OK;

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    MakeContextCurrent();

    switch (pname) {
        case LOCAL_GL_CURRENT_PROGRAM:
        case LOCAL_GL_ATTACHED_SHADERS:
        case LOCAL_GL_INFO_LOG_LENGTH:
        case LOCAL_GL_ACTIVE_UNIFORMS:
        case LOCAL_GL_ACTIVE_UNIFORM_MAX_LENGTH:
        case LOCAL_GL_ACTIVE_ATTRIBUTES:
        case LOCAL_GL_ACTIVE_ATTRIBUTE_MAX_LENGTH:
        {
            GLint i = 0;
            gl->fGetProgramiv(progname, pname, &i);
            wrval->SetAsInt32(i);
        }
            break;
        case LOCAL_GL_DELETE_STATUS:
            wrval->SetAsBool(prog->IsDeleteRequested());
            break;
        case LOCAL_GL_LINK_STATUS:
        {
            GLint i = 0;
            gl->fGetProgramiv(progname, pname, &i);
            wrval->SetAsBool(bool(i));
        }
            break;
        case LOCAL_GL_VALIDATE_STATUS:
        {
            GLint i = 0;
#ifdef XP_MACOSX
            // See comment in ValidateProgram below.
            i = 1;
#else
            gl->fGetProgramiv(progname, pname, &i);
#endif
            wrval->SetAsBool(bool(i));
        }
            break;

        default:
            return ErrorInvalidEnumInfo("GetProgramParameter: parameter", pname);
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetProgramInfoLog(nsIWebGLProgram *pobj, nsAString& retval)
{
    if (!IsContextStable())
    {
        retval.SetIsVoid(true);
        return NS_OK;
    }

    WebGLuint progname;
    if (!GetGLName<WebGLProgram>("getProgramInfoLog: program", pobj, &progname))
        return NS_OK;

    MakeContextCurrent();

    GLint k = -1;
    gl->fGetProgramiv(progname, LOCAL_GL_INFO_LOG_LENGTH, &k);
    if (k == -1)
        return NS_ERROR_FAILURE; // XXX GL error? shouldn't happen!

    if (k == 0) {
        retval.Truncate();
        return NS_OK;
    }

    nsCAutoString log;
    log.SetCapacity(k);

    gl->fGetProgramInfoLog(progname, k, &k, (char*) log.BeginWriting());

    log.SetLength(k);

    CopyASCIItoUTF16(log, retval);

    return NS_OK;
}

// here we have to support all pnames with both int and float params.
// See this discussion:
//  https://www.khronos.org/webgl/public-mailing-list/archives/1008/msg00014.html
nsresult WebGLContext::TexParameter_base(WebGLenum target, WebGLenum pname,
                                         WebGLint *intParamPtr, WebGLfloat *floatParamPtr)
{
    NS_ENSURE_TRUE(intParamPtr || floatParamPtr, NS_ERROR_FAILURE);

    WebGLint intParam = intParamPtr ? *intParamPtr : WebGLint(*floatParamPtr);
    WebGLfloat floatParam = floatParamPtr ? *floatParamPtr : WebGLfloat(*intParamPtr);

    if (!ValidateTextureTargetEnum(target, "texParameter: target"))
        return NS_OK;

    WebGLTexture *tex = activeBoundTextureForTarget(target);
    if (!tex)
        return ErrorInvalidOperation("texParameter: no texture is bound to this target");

    bool pnameAndParamAreIncompatible = false;

    switch (pname) {
        case LOCAL_GL_TEXTURE_MIN_FILTER:
            switch (intParam) {
                case LOCAL_GL_NEAREST:
                case LOCAL_GL_LINEAR:
                case LOCAL_GL_NEAREST_MIPMAP_NEAREST:
                case LOCAL_GL_LINEAR_MIPMAP_NEAREST:
                case LOCAL_GL_NEAREST_MIPMAP_LINEAR:
                case LOCAL_GL_LINEAR_MIPMAP_LINEAR:
                    tex->SetMinFilter(intParam);
                    break;
                default:
                    pnameAndParamAreIncompatible = true;
            }
            break;
        case LOCAL_GL_TEXTURE_MAG_FILTER:
            switch (intParam) {
                case LOCAL_GL_NEAREST:
                case LOCAL_GL_LINEAR:
                    tex->SetMagFilter(intParam);
                    break;
                default:
                    pnameAndParamAreIncompatible = true;
            }
            break;
        case LOCAL_GL_TEXTURE_WRAP_S:
            switch (intParam) {
                case LOCAL_GL_CLAMP_TO_EDGE:
                case LOCAL_GL_MIRRORED_REPEAT:
                case LOCAL_GL_REPEAT:
                    tex->SetWrapS(intParam);
                    break;
                default:
                    pnameAndParamAreIncompatible = true;
            }
            break;
        case LOCAL_GL_TEXTURE_WRAP_T:
            switch (intParam) {
                case LOCAL_GL_CLAMP_TO_EDGE:
                case LOCAL_GL_MIRRORED_REPEAT:
                case LOCAL_GL_REPEAT:
                    tex->SetWrapT(intParam);
                    break;
                default:
                    pnameAndParamAreIncompatible = true;
            }
            break;
        default:
            return ErrorInvalidEnumInfo("texParameter: pname", pname);
    }

    if (pnameAndParamAreIncompatible) {
        // note that currently all params are enums, and the tex-input-validation test wants INVALID_ENUM errors
        // even for texParameterf. why not.
        if (intParamPtr)
            return ErrorInvalidEnum("texParameteri: pname %x and param %x (decimal %d) are mutually incompatible",
                                    pname, intParam, intParam);
        else
            return ErrorInvalidEnum("texParameterf: pname %x and floating-point param %e are mutually incompatible",
                                    pname, floatParam);
    }

    MakeContextCurrent();
    if (intParamPtr)
        gl->fTexParameteri(target, pname, intParam);
    else
        gl->fTexParameterf(target, pname, floatParam);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::TexParameterf(WebGLenum target, WebGLenum pname, WebGLfloat param)
{
    if (!IsContextStable())
        return NS_OK;

    return TexParameter_base(target, pname, nsnull, &param);
}

NS_IMETHODIMP
WebGLContext::TexParameteri(WebGLenum target, WebGLenum pname, WebGLint param)
{
    if (!IsContextStable())
        return NS_OK;

    return TexParameter_base(target, pname, &param, nsnull);
}

NS_IMETHODIMP
WebGLContext::GetTexParameter(WebGLenum target, WebGLenum pname, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    MakeContextCurrent();

    if (!ValidateTextureTargetEnum(target, "getTexParameter: target"))
        return NS_OK;

    if (!activeBoundTextureForTarget(target))
        return ErrorInvalidOperation("getTexParameter: no texture bound");

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    switch (pname) {
        case LOCAL_GL_TEXTURE_MIN_FILTER:
        case LOCAL_GL_TEXTURE_MAG_FILTER:
        case LOCAL_GL_TEXTURE_WRAP_S:
        case LOCAL_GL_TEXTURE_WRAP_T:
        {
            GLint i = 0;
            gl->fGetTexParameteriv(target, pname, &i);
            wrval->SetAsInt32(i);
        }
            break;

        default:
            return ErrorInvalidEnumInfo("getTexParameter: parameter", pname);
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

/* any getUniform(in WebGLProgram program, in WebGLUniformLocation location) raises(DOMException); */
NS_IMETHODIMP
WebGLContext::GetUniform(nsIWebGLProgram *pobj, nsIWebGLUniformLocation *ploc, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    WebGLuint progname;
    WebGLProgram *prog;
    if (!GetConcreteObjectAndGLName("getUniform: program", pobj, &prog, &progname))
        return NS_OK;

    WebGLUniformLocation *location;
    if (!GetConcreteObject("getUniform: location", ploc, &location))
        return NS_OK;

    if (location->Program() != prog)
        return ErrorInvalidValue("GetUniform: this uniform location corresponds to another program");

    if (location->ProgramGeneration() != prog->Generation())
        return ErrorInvalidOperation("GetUniform: this uniform location is obsolete since the program has been relinked");

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    MakeContextCurrent();

    GLint uniforms = 0;
    GLint uniformNameMaxLength = 0;
    gl->fGetProgramiv(progname, LOCAL_GL_ACTIVE_UNIFORMS, &uniforms);
    gl->fGetProgramiv(progname, LOCAL_GL_ACTIVE_UNIFORM_MAX_LENGTH, &uniformNameMaxLength);

    // we now need the type info to switch between fGetUniformfv and fGetUniformiv
    // the only way to get that is to iterate through all active uniforms by index until
    // one matches the given uniform location.
    GLenum uniformType = 0;
    nsAutoArrayPtr<GLchar> uniformName(new GLchar[uniformNameMaxLength]);
    // this buffer has 16 more bytes to be able to store [index] at the end.
    nsAutoArrayPtr<GLchar> uniformNameBracketIndex(new GLchar[uniformNameMaxLength + 16]);

    GLint index;
    for (index = 0; index < uniforms; ++index) {
        GLsizei length;
        GLint size;
        gl->fGetActiveUniform(progname, index, uniformNameMaxLength, &length,
                              &size, &uniformType, uniformName);
        if (gl->fGetUniformLocation(progname, uniformName) == location->Location())
            break;

        // now we handle the case of array uniforms. In that case, fGetActiveUniform returned as 'size'
        // the biggest index used plus one, so we need to loop over that. The 0 index has already been handled above,
        // so we can start at one. For each index, we construct the string uniformName + "[" + index + "]".
        if (size > 1) {
            bool found_it = false;
            if (uniformName[length - 1] == ']') { // if uniformName ends in [0]
                // remove the [0] at the end
                length -= 3;
                uniformName[length] = 0;
            }
            for (GLint arrayIndex = 1; arrayIndex < size; arrayIndex++) {
                sprintf(uniformNameBracketIndex.get(), "%s[%d]", uniformName.get(), arrayIndex);
                if (gl->fGetUniformLocation(progname, uniformNameBracketIndex) == location->Location()) {
                    found_it = true;
                    break;
                }
            }
            if (found_it) break;
        }
    }

    if (index == uniforms)
        return NS_ERROR_FAILURE; // XXX GL error? shouldn't happen.

    GLenum baseType;
    GLint unitSize;
    if (!BaseTypeAndSizeFromUniformType(uniformType, &baseType, &unitSize))
        return NS_ERROR_FAILURE;

    // this should never happen
    if (unitSize > 16)
        return NS_ERROR_FAILURE;

    if (baseType == LOCAL_GL_FLOAT) {
        GLfloat fv[16] = { GLfloat(0) };
        gl->fGetUniformfv(progname, location->Location(), fv);
        if (unitSize == 1) {
            wrval->SetAsFloat(fv[0]);
        } else {
            wrval->SetAsArray(nsIDataType::VTYPE_FLOAT, nsnull,
                              unitSize, static_cast<void*>(fv));
        }
    } else if (baseType == LOCAL_GL_INT) {
        GLint iv[16] = { 0 };
        gl->fGetUniformiv(progname, location->Location(), iv);
        if (unitSize == 1) {
            wrval->SetAsInt32(iv[0]);
        } else {
            wrval->SetAsArray(nsIDataType::VTYPE_INT32, nsnull,
                              unitSize, static_cast<void*>(iv));
        }
    } else if (baseType == LOCAL_GL_BOOL) {
        GLint iv[16] = { 0 };
        gl->fGetUniformiv(progname, location->Location(), iv);
        if (unitSize == 1) {
            wrval->SetAsBool(iv[0] ? true : false);
        } else {
            bool uv[16] = { 0 };
            for (int k = 0; k < unitSize; k++)
                uv[k] = iv[k] ? true : false;
            wrval->SetAsArray(nsIDataType::VTYPE_BOOL, nsnull,
                              unitSize, static_cast<void*>(uv));
        }
    } else {
        wrval->SetAsVoid();
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetUniformLocation(nsIWebGLProgram *pobj, const nsAString& name, nsIWebGLUniformLocation **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    WebGLuint progname;
    WebGLProgram *prog;
    if (!GetConcreteObjectAndGLName("getUniformLocation: program", pobj, &prog, &progname))
        return NS_OK;

    if (!ValidateGLSLVariableName(name, "getUniformLocation"))
        return NS_OK; 

    MakeContextCurrent();

    GLint intlocation = gl->fGetUniformLocation(progname, NS_LossyConvertUTF16toASCII(name).get());

    WebGLUniformLocation *loc = nsnull;
    if (intlocation >= 0)
        NS_ADDREF(loc = new WebGLUniformLocation(this, prog, intlocation));
    *retval = loc;
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetVertexAttrib(WebGLuint index, WebGLenum pname, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    if (!ValidateAttribIndex(index, "getVertexAttrib"))
        return NS_OK;

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    MakeContextCurrent();

    switch (pname) {
        case LOCAL_GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING:
            wrval->SetAsISupports(mAttribBuffers[index].buf);
            break;

        case LOCAL_GL_VERTEX_ATTRIB_ARRAY_STRIDE:
            wrval->SetAsInt32(mAttribBuffers[index].stride);
            break;

        case LOCAL_GL_VERTEX_ATTRIB_ARRAY_SIZE:
        case LOCAL_GL_VERTEX_ATTRIB_ARRAY_TYPE:
        {
            GLint i = 0;
            gl->fGetVertexAttribiv(index, pname, &i);
            wrval->SetAsInt32(i);
        }
            break;

        case LOCAL_GL_CURRENT_VERTEX_ATTRIB:
        {
            WebGLfloat vec[4] = {0, 0, 0, 1};
            if (index) {
                gl->fGetVertexAttribfv(index, LOCAL_GL_CURRENT_VERTEX_ATTRIB, &vec[0]);
            } else {
                vec[0] = mVertexAttrib0Vector[0];
                vec[1] = mVertexAttrib0Vector[1];
                vec[2] = mVertexAttrib0Vector[2];
                vec[3] = mVertexAttrib0Vector[3];
            }
            wrval->SetAsArray(nsIDataType::VTYPE_FLOAT, nsnull,
                              4, vec);
        }
            break;

        case LOCAL_GL_VERTEX_ATTRIB_ARRAY_ENABLED:
        case LOCAL_GL_VERTEX_ATTRIB_ARRAY_NORMALIZED:
        {
            GLint i = 0;
            gl->fGetVertexAttribiv(index, pname, &i);
            wrval->SetAsBool(bool(i));
        }
            break;

        case LOCAL_GL_VERTEX_ATTRIB_ARRAY_POINTER:
            wrval->SetAsUint32(mAttribBuffers[index].byteOffset);
            break;

        default:
            return ErrorInvalidEnumInfo("getVertexAttrib: parameter", pname);
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

/* GLuint getVertexAttribOffset (in GLuint index, in GLenum pname); */
NS_IMETHODIMP
WebGLContext::GetVertexAttribOffset(WebGLuint index, WebGLenum pname, WebGLuint *retval)
{
    *retval = 0;
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateAttribIndex(index, "getVertexAttribOffset"))
        return NS_OK;

    if (pname != LOCAL_GL_VERTEX_ATTRIB_ARRAY_POINTER)
        return ErrorInvalidEnum("getVertexAttribOffset: bad parameter");

    *retval = mAttribBuffers[index].byteOffset;
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::Hint(WebGLenum target, WebGLenum mode)
{
    if (!IsContextStable())
        return NS_OK;

    bool isValid = false;

    switch (target) {
        case LOCAL_GL_FRAGMENT_SHADER_DERIVATIVE_HINT:
            if (mEnabledExtensions[WebGL_OES_standard_derivatives]) 
                isValid = true;
            break;
    }

    if (isValid) {
        gl->fHint(target, mode);
        return NS_OK;
    }

    return ErrorInvalidEnum("hint: invalid hint");
}

NS_IMETHODIMP
WebGLContext::IsBuffer(nsIWebGLBuffer *bobj, WebGLboolean *retval)
{
    if (!IsContextStable())
    {
        *retval = false;
        return NS_OK;
    }

    bool isDeleted;
    WebGLuint buffername;
    WebGLBuffer *buffer;
    *retval = GetConcreteObjectAndGLName("isBuffer", bobj, &buffer, &buffername, nsnull, &isDeleted) && 
              !isDeleted &&
              buffer->HasEverBeenBound();
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::IsFramebuffer(nsIWebGLFramebuffer *fbobj, WebGLboolean *retval)
{
    if (!IsContextStable())
    {
        *retval = false;
        return NS_OK;
    }

    bool isDeleted;
    WebGLuint fbname;
    WebGLFramebuffer *fb;
    *retval = GetConcreteObjectAndGLName("isFramebuffer", fbobj, &fb, &fbname, nsnull, &isDeleted) &&
              !isDeleted &&
              fb->HasEverBeenBound();
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::IsProgram(nsIWebGLProgram *pobj, WebGLboolean *retval)
{
    if (!IsContextStable())
    {
        *retval = false;
        return NS_OK;
    }

    bool isDeleted;
    WebGLProgram *prog = nsnull;
    *retval = GetConcreteObject("isProgram", pobj, &prog, nsnull, &isDeleted, false) &&
              !isDeleted;
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::IsRenderbuffer(nsIWebGLRenderbuffer *rbobj, WebGLboolean *retval)
{
    if (!IsContextStable())
    {
        *retval = false;
        return NS_OK;
    }

    bool isDeleted;
    WebGLuint rbname;
    WebGLRenderbuffer *rb;
    *retval = GetConcreteObjectAndGLName("isRenderBuffer", rbobj, &rb, &rbname, nsnull, &isDeleted) &&
              !isDeleted &&
              rb->HasEverBeenBound();
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::IsShader(nsIWebGLShader *sobj, WebGLboolean *retval)
{
    if (!IsContextStable())
    {
        *retval = false;
        return NS_OK;
    }

    bool isDeleted;
    WebGLShader *shader = nsnull;
    *retval = GetConcreteObject("isShader", sobj, &shader, nsnull, &isDeleted, false) &&
              !isDeleted;
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::IsTexture(nsIWebGLTexture *tobj, WebGLboolean *retval)
{
    if (!IsContextStable())
    {
        *retval = false;
        return NS_OK;
    }

    bool isDeleted;
    WebGLuint texname;
    WebGLTexture *tex;
    *retval = GetConcreteObjectAndGLName("isTexture", tobj, &tex, &texname, nsnull, &isDeleted) &&
              !isDeleted &&
              tex->HasEverBeenBound();
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::IsEnabled(WebGLenum cap, WebGLboolean *retval)
{
    if (!IsContextStable())
    {
        *retval = false;
        return NS_OK;
    }

    *retval = 0;

    if (!ValidateCapabilityEnum(cap, "isEnabled"))
        return NS_OK;

    MakeContextCurrent();
    *retval = gl->fIsEnabled(cap);
    return NS_OK;
}

GL_SAME_METHOD_1(LineWidth, LineWidth, WebGLfloat)

NS_IMETHODIMP
WebGLContext::LinkProgram(nsIWebGLProgram *pobj)
{
    if (!IsContextStable())
        return NS_OK;

    GLuint progname;
    WebGLProgram *program;
    if (!GetConcreteObjectAndGLName("linkProgram", pobj, &program, &progname))
        return NS_OK;

    if (!program->NextGeneration())
        return NS_ERROR_FAILURE;

    if (!program->HasBothShaderTypesAttached()) {
        program->SetLinkStatus(false);
        return NS_OK;
    }

    MakeContextCurrent();

    gl->fLinkProgram(progname);

    GLint ok;
    gl->fGetProgramiv(progname, LOCAL_GL_LINK_STATUS, &ok);
    if (ok) {
        program->SetLinkStatus(true);
        program->UpdateInfo(gl);
    } else {
        program->SetLinkStatus(false);
    }

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::PixelStorei(WebGLenum pname, WebGLint param)
{
    if (!IsContextStable())
        return NS_OK;

    switch (pname) {
        case UNPACK_FLIP_Y_WEBGL:
            mPixelStoreFlipY = (param != 0);
            break;
        case UNPACK_PREMULTIPLY_ALPHA_WEBGL:
            mPixelStorePremultiplyAlpha = (param != 0);
            break;
        case UNPACK_COLORSPACE_CONVERSION_WEBGL:
            if (param == LOCAL_GL_NONE || param == BROWSER_DEFAULT_WEBGL)
                mPixelStoreColorspaceConversion = param;
            else
                return ErrorInvalidEnumInfo("pixelStorei: colorspace conversion parameter", param);
            break;
        case LOCAL_GL_PACK_ALIGNMENT:
        case LOCAL_GL_UNPACK_ALIGNMENT:
            if (param != 1 &&
                param != 2 &&
                param != 4 &&
                param != 8)
                return ErrorInvalidValue("PixelStorei: invalid pack/unpack alignment value");
            if (pname == LOCAL_GL_PACK_ALIGNMENT)
                mPixelStorePackAlignment = param;
            else if (pname == LOCAL_GL_UNPACK_ALIGNMENT)
                mPixelStoreUnpackAlignment = param;
            MakeContextCurrent();
            gl->fPixelStorei(pname, param);
            break;
        default:
            return ErrorInvalidEnumInfo("PixelStorei: parameter", pname);
    }

    return NS_OK;
}


GL_SAME_METHOD_2(PolygonOffset, PolygonOffset, WebGLfloat, WebGLfloat)

NS_IMETHODIMP
WebGLContext::ReadPixels(PRInt32)
{
    if (!IsContextStable())
        return NS_OK;

    return NS_ERROR_FAILURE;
}

nsresult
WebGLContext::ReadPixels_base(WebGLint x, WebGLint y, WebGLsizei width, WebGLsizei height,
                              WebGLenum format, WebGLenum type, JSObject* pixels)
{
    if (HTMLCanvasElement()->IsWriteOnly() && !nsContentUtils::IsCallerTrustedForRead()) {
        LogMessageIfVerbose("ReadPixels: Not allowed");
        return NS_ERROR_DOM_SECURITY_ERR;
    }

    if (width < 0 || height < 0)
        return ErrorInvalidValue("ReadPixels: negative size passed");

    if (!pixels)
        return ErrorInvalidValue("ReadPixels: null array passed");

    WebGLsizei boundWidth = mBoundFramebuffer ? mBoundFramebuffer->width() : mWidth;
    WebGLsizei boundHeight = mBoundFramebuffer ? mBoundFramebuffer->height() : mHeight;

    void* data = JS_GetTypedArrayData(pixels);
    PRUint32 dataByteLen = JS_GetTypedArrayByteLength(pixels);
    int dataType = JS_GetTypedArrayType(pixels);

    PRUint32 channels = 0;

    // Check the format param
    switch (format) {
        case LOCAL_GL_ALPHA:
            channels = 1;
            break;
        case LOCAL_GL_RGB:
            channels = 3;
            break;
        case LOCAL_GL_RGBA:
            channels = 4;
            break;
        default:
            return ErrorInvalidEnum("readPixels: Bad format");
    }

    PRUint32 bytesPerPixel = 0;
    int requiredDataType = 0;

    // Check the type param
    switch (type) {
        case LOCAL_GL_UNSIGNED_BYTE:
            bytesPerPixel = 1 * channels;
            requiredDataType = js::TypedArray::TYPE_UINT8;
            break;
        case LOCAL_GL_UNSIGNED_SHORT_4_4_4_4:
        case LOCAL_GL_UNSIGNED_SHORT_5_5_5_1:
        case LOCAL_GL_UNSIGNED_SHORT_5_6_5:
            bytesPerPixel = 2;
            requiredDataType = js::TypedArray::TYPE_UINT16;
            break;
        default:
            return ErrorInvalidEnum("readPixels: Bad type");
    }

    // Check the pixels param type
    if (dataType != requiredDataType)
        return ErrorInvalidOperation("readPixels: Mismatched type/pixels types");

    // Check the pixels param size
    CheckedUint32 checked_neededByteLength =
        GetImageSize(height, width, bytesPerPixel, mPixelStorePackAlignment);

    CheckedUint32 checked_plainRowSize = CheckedUint32(width) * bytesPerPixel;

    CheckedUint32 checked_alignedRowSize =
        RoundedToNextMultipleOf(checked_plainRowSize, mPixelStorePackAlignment);

    if (!checked_neededByteLength.valid())
        return ErrorInvalidOperation("ReadPixels: integer overflow computing the needed buffer size");

    if (checked_neededByteLength.value() > dataByteLen)
        return ErrorInvalidOperation("ReadPixels: buffer too small");

    // Check the format and type params to assure they are an acceptable pair (as per spec)
    switch (format) {
        case LOCAL_GL_RGBA: {
            switch (type) {
                case LOCAL_GL_UNSIGNED_BYTE:
                    break;
                default:
                    return ErrorInvalidOperation("readPixels: Invalid format/type pair");
            }
            break;
        }
        default:
            return ErrorInvalidOperation("readPixels: Invalid format/type pair");
    }

    MakeContextCurrent();

    if (mBoundFramebuffer) {
        // prevent readback of arbitrary video memory through uninitialized renderbuffers!
        if (!mBoundFramebuffer->CheckAndInitializeRenderbuffers())
            return NS_OK;
    } else {
        EnsureBackbufferClearedAsNeeded();
    }
    // Now that the errors are out of the way, on to actually reading

    // If we won't be reading any pixels anyways, just skip the actual reading
    if (width == 0 || height == 0)
        return NS_OK;

    if (CanvasUtils::CheckSaneSubrectSize(x, y, width, height, boundWidth, boundHeight)) {
        // the easy case: we're not reading out-of-range pixels
        gl->fReadPixels(x, y, width, height, format, type, data);
    } else {
        // the rectangle doesn't fit entirely in the bound buffer. We then have to set to zero the part
        // of the buffer that correspond to out-of-range pixels. We don't want to rely on system OpenGL
        // to do that for us, because passing out of range parameters to a buggy OpenGL implementation
        // could conceivably allow to read memory we shouldn't be allowed to read. So we manually initialize
        // the buffer to zero and compute the parameters to pass to OpenGL. We have to use an intermediate buffer
        // to accomodate the potentially different strides (widths).

        // zero the whole destination buffer. Too bad for the part that's going to be overwritten, we're not
        // 100% efficient here, but in practice this is a quite rare case anyway.
        memset(data, 0, dataByteLen);

        if (   x >= boundWidth
            || x+width <= 0
            || y >= boundHeight
            || y+height <= 0)
        {
            // we are completely outside of range, can exit now with buffer filled with zeros
            return NS_OK;
        }

        // compute the parameters of the subrect we're actually going to call glReadPixels on
        GLint   subrect_x      = NS_MAX(x, 0);
        GLint   subrect_end_x  = NS_MIN(x+width, boundWidth);
        GLsizei subrect_width  = subrect_end_x - subrect_x;

        GLint   subrect_y      = NS_MAX(y, 0);
        GLint   subrect_end_y  = NS_MIN(y+height, boundHeight);
        GLsizei subrect_height = subrect_end_y - subrect_y;

        if (subrect_width < 0 || subrect_height < 0 ||
            subrect_width > width || subrect_height > height)
            return ErrorInvalidOperation("ReadPixels: integer overflow computing clipped rect size");

        // now we know that subrect_width is in the [0..width] interval, and same for heights.

        // now, same computation as above to find the size of the intermediate buffer to allocate for the subrect
        // no need to check again for integer overflow here, since we already know the sizes aren't greater than before
        PRUint32 subrect_plainRowSize = subrect_width * bytesPerPixel;
	// There are checks above to ensure that this doesn't overflow.
        PRUint32 subrect_alignedRowSize = 
            RoundedToNextMultipleOf(subrect_plainRowSize, mPixelStorePackAlignment).value();
        PRUint32 subrect_byteLength = (subrect_height-1)*subrect_alignedRowSize + subrect_plainRowSize;

        // create subrect buffer, call glReadPixels, copy pixels into destination buffer, delete subrect buffer
        GLubyte *subrect_data = new GLubyte[subrect_byteLength];
        gl->fReadPixels(subrect_x, subrect_y, subrect_width, subrect_height, format, type, subrect_data);

        // notice that this for loop terminates because we already checked that subrect_height is at most height
        for (GLint y_inside_subrect = 0; y_inside_subrect < subrect_height; ++y_inside_subrect) {
            GLint subrect_x_in_dest_buffer = subrect_x - x;
            GLint subrect_y_in_dest_buffer = subrect_y - y;
            memcpy(static_cast<GLubyte*>(data)
                     + checked_alignedRowSize.value() * (subrect_y_in_dest_buffer + y_inside_subrect)
                     + bytesPerPixel * subrect_x_in_dest_buffer, // destination
                   subrect_data + subrect_alignedRowSize * y_inside_subrect, // source
                   subrect_plainRowSize); // size
        }
        delete [] subrect_data;
    }

    // if we're reading alpha, we may need to do fixup.  Note that we don't allow
    // GL_ALPHA to readpixels currently, but we had the code written for it already.
    if (format == LOCAL_GL_ALPHA ||
        format == LOCAL_GL_RGBA)
    {
        bool needAlphaFixup;
        if (mBoundFramebuffer) {
            needAlphaFixup = !mBoundFramebuffer->ColorAttachment().HasAlpha();
        } else {
            needAlphaFixup = gl->ActualFormat().alpha == 0;
        }

        if (needAlphaFixup) {
            if (format == LOCAL_GL_ALPHA && type == LOCAL_GL_UNSIGNED_BYTE) {
                // this is easy; it's an 0xff memset per row
                PRUint8 *row = (PRUint8*)data;
                for (GLint j = 0; j < height; ++j) {
                    memset(row, 0xff, checked_plainRowSize.value());
                    row += checked_alignedRowSize.value();
                }
            } else if (format == LOCAL_GL_RGBA && type == LOCAL_GL_UNSIGNED_BYTE) {
                // this is harder, we need to just set the alpha byte here
                PRUint8 *row = (PRUint8*)data;
                for (GLint j = 0; j < height; ++j) {
                    PRUint8 *rowp = row;
#ifdef IS_LITTLE_ENDIAN
                    // offset to get the alpha byte; we're always going to
                    // move by 4 bytes
                    rowp += 3;
#endif
                    PRUint8 *endrowp = rowp + 4 * width;
                    while (rowp != endrowp) {
                        *rowp = 0xff;
                        rowp += 4;
                    }

                    row += checked_alignedRowSize.value();
                }
            } else {
                NS_WARNING("Unhandled case, how'd we get here?");
                return NS_ERROR_FAILURE;
            }
        }            
    }

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::ReadPixels_array(WebGLint x, WebGLint y, WebGLsizei width, WebGLsizei height,
                               WebGLenum format, WebGLenum type, JSObject *pixels)
{
    if (!IsContextStable())
        return NS_OK;

    return ReadPixels_base(x, y, width, height, format, type, pixels);
}

NS_IMETHODIMP
WebGLContext::RenderbufferStorage(WebGLenum target, WebGLenum internalformat, WebGLsizei width, WebGLsizei height)
{
    if (!IsContextStable())
        return NS_OK;

    if (!mBoundRenderbuffer || !mBoundRenderbuffer->GLName())
        return ErrorInvalidOperation("renderbufferStorage called on renderbuffer 0");

    if (target != LOCAL_GL_RENDERBUFFER)
        return ErrorInvalidEnumInfo("renderbufferStorage: target", target);

    if (width < 0 || height < 0)
        return ErrorInvalidValue("renderbufferStorage: width and height must be >= 0");

    if (!mBoundRenderbuffer || !mBoundRenderbuffer->GLName())
        return ErrorInvalidOperation("renderbufferStorage called on renderbuffer 0");

    // certain OpenGL ES renderbuffer formats may not exist on desktop OpenGL
    WebGLenum internalformatForGL = internalformat;

    switch (internalformat) {
    case LOCAL_GL_RGBA4:
    case LOCAL_GL_RGB5_A1:
        // 16-bit RGBA formats are not supported on desktop GL
        if (!gl->IsGLES2()) internalformatForGL = LOCAL_GL_RGBA8;
        break;
    case LOCAL_GL_RGB565:
        // the RGB565 format is not supported on desktop GL
        if (!gl->IsGLES2()) internalformatForGL = LOCAL_GL_RGB8;
        break;
    case LOCAL_GL_DEPTH_COMPONENT16:
        if (!gl->IsGLES2() || gl->IsExtensionSupported(gl::GLContext::OES_depth24))
            internalformatForGL = LOCAL_GL_DEPTH_COMPONENT24;
        else if (gl->IsExtensionSupported(gl::GLContext::OES_packed_depth_stencil))
            internalformatForGL = LOCAL_GL_DEPTH24_STENCIL8;
        break;
    case LOCAL_GL_STENCIL_INDEX8:
        break;
    case LOCAL_GL_DEPTH_STENCIL:
        // this one is available in newer OpenGL (at least since 3.1); will probably become available
        // in OpenGL ES 3 (at least it will have some DEPTH_STENCIL) and is the same value that
        // is otherwise provided by EXT_packed_depth_stencil and OES_packed_depth_stencil extensions
        // which means it's supported on most GL and GL ES systems already.
        //
        // So we just use it hoping that it's available (perhaps as an extension) and if it's not available,
        // we just let the GL generate an error and don't do anything about it ourselves.
        internalformatForGL = LOCAL_GL_DEPTH24_STENCIL8;
        break;
    default:
        return ErrorInvalidEnumInfo("renderbufferStorage: internalformat", internalformat);
    }

    MakeContextCurrent();

    bool sizeChanges = width != mBoundRenderbuffer->width() ||
                       height != mBoundRenderbuffer->height() ||
                       internalformat != mBoundRenderbuffer->InternalFormat();
    if (sizeChanges) {
        UpdateWebGLErrorAndClearGLError();
        gl->fRenderbufferStorage(target, internalformatForGL, width, height);
        GLenum error = LOCAL_GL_NO_ERROR;
        UpdateWebGLErrorAndClearGLError(&error);
        if (error) {
            LogMessageIfVerbose("bufferData generated error %s", ErrorName(error));
            return NS_OK;
        }
    } else {
        gl->fRenderbufferStorage(target, internalformatForGL, width, height);
    }

    mBoundRenderbuffer->SetInternalFormat(internalformat);
    mBoundRenderbuffer->SetInternalFormatForGL(internalformatForGL);
    mBoundRenderbuffer->setDimensions(width, height);
    mBoundRenderbuffer->SetInitialized(false);

    return NS_OK;
}

GL_SAME_METHOD_2(SampleCoverage, SampleCoverage, WebGLfloat, WebGLboolean)

NS_IMETHODIMP
WebGLContext::Scissor(WebGLint x, WebGLint y, WebGLsizei width, WebGLsizei height)
{
    if (!IsContextStable())
        return NS_OK;

    if (width < 0 || height < 0)
        return ErrorInvalidValue("Scissor: negative size");

    MakeContextCurrent();
    gl->fScissor(x, y, width, height);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::StencilFunc(WebGLenum func, WebGLint ref, WebGLuint mask)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateComparisonEnum(func, "stencilFunc: func"))
        return NS_OK;

    mStencilRefFront = ref;
    mStencilRefBack = ref;
    mStencilValueMaskFront = mask;
    mStencilValueMaskBack = mask;

    MakeContextCurrent();
    gl->fStencilFunc(func, ref, mask);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::StencilFuncSeparate(WebGLenum face, WebGLenum func, WebGLint ref, WebGLuint mask)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateFaceEnum(face, "stencilFuncSeparate: face") ||
        !ValidateComparisonEnum(func, "stencilFuncSeparate: func"))
        return NS_OK;

    switch (face) {
        case LOCAL_GL_FRONT_AND_BACK:
            mStencilRefFront = ref;
            mStencilRefBack = ref;
            mStencilValueMaskFront = mask;
            mStencilValueMaskBack = mask;
            break;
        case LOCAL_GL_FRONT:
            mStencilRefFront = ref;
            mStencilValueMaskFront = mask;
            break;
        case LOCAL_GL_BACK:
            mStencilRefBack = ref;
            mStencilValueMaskBack = mask;
            break;
    }

    MakeContextCurrent();
    gl->fStencilFuncSeparate(face, func, ref, mask);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::StencilMask(WebGLuint mask)
{
    if (!IsContextStable())
        return NS_OK;

    mStencilWriteMaskFront = mask;
    mStencilWriteMaskBack = mask;

    MakeContextCurrent();
    gl->fStencilMask(mask);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::StencilMaskSeparate(WebGLenum face, WebGLuint mask)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateFaceEnum(face, "stencilMaskSeparate: face"))
        return NS_OK;

    switch (face) {
        case LOCAL_GL_FRONT_AND_BACK:
            mStencilWriteMaskFront = mask;
            mStencilWriteMaskBack = mask;
            break;
        case LOCAL_GL_FRONT:
            mStencilWriteMaskFront = mask;
            break;
        case LOCAL_GL_BACK:
            mStencilWriteMaskBack = mask;
            break;
    }

    MakeContextCurrent();
    gl->fStencilMaskSeparate(face, mask);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::StencilOp(WebGLenum sfail, WebGLenum dpfail, WebGLenum dppass)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateStencilOpEnum(sfail, "stencilOp: sfail") ||
        !ValidateStencilOpEnum(dpfail, "stencilOp: dpfail") ||
        !ValidateStencilOpEnum(dppass, "stencilOp: dppass"))
        return NS_OK;

    MakeContextCurrent();
    gl->fStencilOp(sfail, dpfail, dppass);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::StencilOpSeparate(WebGLenum face, WebGLenum sfail, WebGLenum dpfail, WebGLenum dppass)
{
    if (!IsContextStable())
        return NS_OK;

    if (!ValidateFaceEnum(face, "stencilOpSeparate: face") ||
        !ValidateStencilOpEnum(sfail, "stencilOpSeparate: sfail") ||
        !ValidateStencilOpEnum(dpfail, "stencilOpSeparate: dpfail") ||
        !ValidateStencilOpEnum(dppass, "stencilOpSeparate: dppass"))
        return NS_OK;

    MakeContextCurrent();
    gl->fStencilOpSeparate(face, sfail, dpfail, dppass);
    return NS_OK;
}

struct WebGLImageConverter
{
    bool flip;
    size_t width, height, srcStride, dstStride, srcTexelSize, dstTexelSize;
    const PRUint8 *src;
    PRUint8 *dst;

    WebGLImageConverter()
    {
        memset(this, 0, sizeof(WebGLImageConverter));
    }

    template<typename SrcType, typename DstType, typename UnpackType,
         void unpackingFunc(const SrcType*, UnpackType*),
         void packingFunc(const UnpackType*, DstType*)>
    void run()
    {
        // Note -- even though the functions take UnpackType, the
        // pointers below are all in terms of PRUint8; otherwise
        // pointer math starts getting tricky.
        for (size_t src_row = 0; src_row < height; ++src_row) {
            size_t dst_row = flip ? (height - 1 - src_row) : src_row;
            PRUint8 *dst_row_ptr = dst + dst_row * dstStride;
            const PRUint8 *src_row_ptr = src + src_row * srcStride;
            const PRUint8 *src_row_end = src_row_ptr + width * srcTexelSize; // != src_row_ptr + byteStride
            while (src_row_ptr != src_row_end) {
                UnpackType tmp[4];
                unpackingFunc(reinterpret_cast<const SrcType*>(src_row_ptr), tmp);
                packingFunc(tmp, reinterpret_cast<DstType*>(dst_row_ptr));
                src_row_ptr += srcTexelSize;
                dst_row_ptr += dstTexelSize;
            }
        }
    }
};

void
WebGLContext::ConvertImage(size_t width, size_t height, size_t srcStride, size_t dstStride,
                           const PRUint8*src, PRUint8 *dst,
                           int srcFormat, bool srcPremultiplied,
                           int dstFormat, bool dstPremultiplied,
                           size_t dstTexelSize)
{
    if (width <= 0 || height <= 0)
        return;

    if (srcFormat == dstFormat &&
        srcPremultiplied == dstPremultiplied)
    {
        // fast exit path: we just have to memcpy all the rows.
        //
        // The case where absolutely nothing needs to be done is supposed to have
        // been handled earlier (in TexImage2D_base, etc).
        //
        // So the case we're handling here is when even though no format conversion is needed,
        // we still might have to flip vertically and/or to adjust to a different stride.

        NS_ASSERTION(mPixelStoreFlipY || srcStride != dstStride, "Performance trap -- should handle this case earlier, to avoid memcpy");

        size_t row_size = width * dstTexelSize; // doesn't matter, src and dst formats agree
        const PRUint8* src_row = src;
        const PRUint8* src_end = src + height * srcStride;

        PRUint8* dst_row = mPixelStoreFlipY ? dst + (height-1) * dstStride : dst;
        ptrdiff_t dstStrideSigned(dstStride);
        ptrdiff_t dst_delta = mPixelStoreFlipY ? -dstStrideSigned : dstStrideSigned;

        while(src_row != src_end) {
            memcpy(dst_row, src_row, row_size);
            src_row += srcStride;
            dst_row += dst_delta;
        }
        return;
    }

    WebGLImageConverter converter;
    converter.flip = mPixelStoreFlipY;
    converter.width = width;
    converter.height = height;
    converter.srcStride = srcStride;
    converter.dstStride = dstStride;
    converter.dstTexelSize = dstTexelSize;
    converter.src = src;
    converter.dst = dst;

    int premultiplicationOp = (!srcPremultiplied && dstPremultiplied) ? WebGLTexelPremultiplicationOp::Premultiply
                            : (srcPremultiplied && !dstPremultiplied) ? WebGLTexelPremultiplicationOp::Unmultiply
                            : WebGLTexelPremultiplicationOp::None;

#define HANDLE_DSTFORMAT(format, SrcType, DstType, unpackFunc, packFunc) \
        case WebGLTexelFormat::format: \
            switch (premultiplicationOp) { \
                case WebGLTexelPremultiplicationOp::Premultiply: \
                    converter.run<SrcType, DstType, PRUint8,          \
                                  WebGLTexelConversions::unpackFunc, \
                                  WebGLTexelConversions::packFunc##Premultiply>(); \
                break; \
                case WebGLTexelPremultiplicationOp::Unmultiply: \
                    converter.run<SrcType, DstType, PRUint8, \
                                  WebGLTexelConversions::unpackFunc, \
                                  WebGLTexelConversions::packFunc##Unmultiply>(); \
                break; \
                default: \
                    converter.run<SrcType, DstType, PRUint8, \
                                  WebGLTexelConversions::unpackFunc, \
                                  WebGLTexelConversions::packFunc>(); \
                break; \
            } \
            break;

#define HANDLE_SRCFORMAT(format, size, SrcType, unpackFunc) \
        case WebGLTexelFormat::format: \
            converter.srcTexelSize = size; \
            switch (dstFormat) { \
                HANDLE_DSTFORMAT(RGBA8,    SrcType, PRUint8,  unpackFunc, packRGBA8ToRGBA8) \
                HANDLE_DSTFORMAT(RGB8,     SrcType, PRUint8,  unpackFunc, packRGBA8ToRGB8) \
                HANDLE_DSTFORMAT(R8,       SrcType, PRUint8,  unpackFunc, packRGBA8ToR8) \
                HANDLE_DSTFORMAT(RA8,      SrcType, PRUint8,  unpackFunc, packRGBA8ToRA8) \
                HANDLE_DSTFORMAT(RGBA5551, SrcType, PRUint16, unpackFunc, packRGBA8ToUnsignedShort5551) \
                HANDLE_DSTFORMAT(RGBA4444, SrcType, PRUint16, unpackFunc, packRGBA8ToUnsignedShort4444) \
                HANDLE_DSTFORMAT(RGB565,   SrcType, PRUint16, unpackFunc, packRGBA8ToUnsignedShort565) \
                /* A8 needs to be special-cased as it doesn't have color channels to premultiply */ \
                case WebGLTexelFormat::A8: \
                    converter.run<SrcType, PRUint8, PRUint8,          \
                                  WebGLTexelConversions::unpackFunc, \
                                  WebGLTexelConversions::packRGBA8ToA8>(); \
                    break; \
                default: \
                    NS_ASSERTION(false, "Coding error?! Should never reach this point."); \
                    return; \
            } \
            break;

#define HANDLE_FLOAT_DSTFORMAT(format, unpackFunc, packFunc) \
        case WebGLTexelFormat::format: \
            switch (premultiplicationOp) { \
                case WebGLTexelPremultiplicationOp::Premultiply: \
                    converter.run<float, float, float,                \
                                  WebGLTexelConversions::unpackFunc, \
                                  WebGLTexelConversions::packFunc##Premultiply>(); \
                break; \
                case WebGLTexelPremultiplicationOp::Unmultiply: \
                    NS_ASSERTION(false, "Floating point can't be un-premultiplied -- we have no premultiplied source data!"); \
                break; \
                default: \
                    converter.run<float, float, float,                \
                                  WebGLTexelConversions::unpackFunc, \
                                  WebGLTexelConversions::packFunc>(); \
                break; \
            } \
            break;

#define HANDLE_FLOAT_SRCFORMAT(format, size, unpackFunc)                \
        case WebGLTexelFormat::format:                                  \
            converter.srcTexelSize = size;                              \
            switch (dstFormat) {                                        \
                HANDLE_FLOAT_DSTFORMAT(RGB32F, unpackFunc, packRGBA32FToRGB32F) \
                HANDLE_FLOAT_DSTFORMAT(A32F,   unpackFunc, packRGBA32FToA32F) \
                HANDLE_FLOAT_DSTFORMAT(R32F,   unpackFunc, packRGBA32FToR32F) \
                HANDLE_FLOAT_DSTFORMAT(RA32F,  unpackFunc, packRGBA32FToRA32F) \
                default: \
                    NS_ASSERTION(false, "Coding error?! Should never reach this point."); \
                    return; \
            } \
            break;
        
    switch (srcFormat) {
        HANDLE_SRCFORMAT(RGBA8,    4, PRUint8,  unpackRGBA8ToRGBA8)
        HANDLE_SRCFORMAT(RGBX8,    4, PRUint8,  unpackRGB8ToRGBA8)
        HANDLE_SRCFORMAT(RGB8,     3, PRUint8,  unpackRGB8ToRGBA8)
        HANDLE_SRCFORMAT(BGRA8,    4, PRUint8,  unpackBGRA8ToRGBA8)
        HANDLE_SRCFORMAT(BGRX8,    4, PRUint8,  unpackBGR8ToRGBA8)
        HANDLE_SRCFORMAT(BGR8,     3, PRUint8,  unpackBGR8ToRGBA8)
        HANDLE_SRCFORMAT(R8,       1, PRUint8,  unpackR8ToRGBA8)
        HANDLE_SRCFORMAT(A8,       1, PRUint8,  unpackA8ToRGBA8)
        HANDLE_SRCFORMAT(RA8,      2, PRUint8,  unpackRA8ToRGBA8)
        HANDLE_SRCFORMAT(RGBA5551, 2, PRUint16, unpackRGBA5551ToRGBA8)
        HANDLE_SRCFORMAT(RGBA4444, 2, PRUint16, unpackRGBA4444ToRGBA8)
        HANDLE_SRCFORMAT(RGB565,   2, PRUint16, unpackRGB565ToRGBA8)
        HANDLE_FLOAT_SRCFORMAT(RGB32F,  12, unpackRGB32FToRGBA32F)
        HANDLE_FLOAT_SRCFORMAT(RA32F,    8, unpackRA32FToRGBA32F)
        HANDLE_FLOAT_SRCFORMAT(R32F,     4, unpackR32FToRGBA32F)
        HANDLE_FLOAT_SRCFORMAT(A32F,     4, unpackA32FToRGBA32F)
        default:
            NS_ASSERTION(false, "Coding error?! Should never reach this point.");
            return;
    }
}

nsresult
WebGLContext::DOMElementToImageSurface(nsIDOMElement *imageOrCanvas,
                                       gfxImageSurface **imageOut, int *format)
{
    nsCOMPtr<nsIContent> content = do_QueryInterface(imageOrCanvas);
    if (!content) {
        return NS_ERROR_FAILURE;
    }        

    PRUint32 flags =
        nsLayoutUtils::SFE_WANT_NEW_SURFACE |
        nsLayoutUtils::SFE_WANT_IMAGE_SURFACE;

    if (mPixelStoreColorspaceConversion == LOCAL_GL_NONE)
        flags |= nsLayoutUtils::SFE_NO_COLORSPACE_CONVERSION;
    if (!mPixelStorePremultiplyAlpha)
        flags |= nsLayoutUtils::SFE_NO_PREMULTIPLY_ALPHA;

    nsLayoutUtils::SurfaceFromElementResult res =
        nsLayoutUtils::SurfaceFromElement(content->AsElement(), flags);
    if (!res.mSurface)
        return NS_ERROR_FAILURE;
    if (res.mSurface->GetType() != gfxASurface::SurfaceTypeImage) {
        // SurfaceFromElement lied!
        return NS_ERROR_FAILURE;
    }

    // We disallow loading cross-domain images that have not been validated
    // with CORS as WebGL textures. The reason for doing that is that timing
    // attacks on WebGL shaders are able to retrieve approximations of the
    // pixel values in WebGL textures; see bug 655987.
    //
    // To prevent a loophole where a Canvas2D would be used as a proxy to load
    // cross-domain textures, we also disallow loading textures from write-only
    // Canvas2D's.

    // part 1: check that the DOM element is same-origin, or has otherwise been
    // validated for cross-domain use.
    if (!res.mCORSUsed) {
        bool subsumes;
        nsresult rv = HTMLCanvasElement()->NodePrincipal()->Subsumes(res.mPrincipal, &subsumes);
        if (NS_FAILED(rv) || !subsumes) {
            LogMessageIfVerbose("It is forbidden to load a WebGL texture from a cross-domain element that has not been validated with CORS. "
                                "See https://developer.mozilla.org/en/WebGL/Cross-Domain_Textures");
            return NS_ERROR_DOM_SECURITY_ERR;
        }
    }

    // part 2: if the DOM element is a canvas, check that it's not write-only.
    // That would indicate a tainted canvas, i.e. a canvas that could contain
    // cross-domain image data.
    if (nsHTMLCanvasElement* canvas = nsHTMLCanvasElement::FromContent(content)) {
        if (canvas->IsWriteOnly()) {
            LogMessageIfVerbose("The canvas used as source for texImage2D here is tainted (write-only). It is forbidden "
                                "to load a WebGL texture from a tainted canvas. A Canvas becomes tainted for example "
                                "when a cross-domain image is drawn on it. "
                                "See https://developer.mozilla.org/en/WebGL/Cross-Domain_Textures");
            return NS_ERROR_DOM_SECURITY_ERR;
        }
    }

    // End of security checks, now we should be safe regarding cross-domain images
    // Notice that there is never a need to mark the WebGL canvas as write-only, since we reject write-only/cross-domain
    // texture sources in the first place.

    gfxImageSurface* surf = static_cast<gfxImageSurface*>(res.mSurface.get());

    res.mSurface.forget();
    *imageOut = surf;

    switch (surf->Format()) {
        case gfxASurface::ImageFormatARGB32:
            *format = WebGLTexelFormat::BGRA8; // careful, our ARGB means BGRA
            break;
        case gfxASurface::ImageFormatRGB24:
            *format = WebGLTexelFormat::BGRX8; // careful, our RGB24 is not tightly packed. Whence BGRX8.
            break;
        case gfxASurface::ImageFormatA8:
            *format = WebGLTexelFormat::A8;
            break;
        case gfxASurface::ImageFormatRGB16_565:
            *format = WebGLTexelFormat::RGB565;
            break;
        default:
            NS_ASSERTION(false, "Unsupported image format. Unimplemented.");
            return NS_ERROR_NOT_IMPLEMENTED;
    }

    return NS_OK;
}

#define OBTAIN_UNIFORM_LOCATION(info)                                   \
    WebGLUniformLocation *location_object;                              \
    bool isNull;                                                      \
    if (!GetConcreteObject(info, ploc, &location_object, &isNull))      \
        return NS_OK;                                                   \
    if (isNull)                                                         \
        return NS_OK;                                                   \
    /* the need to check specifically for !mCurrentProgram here is explained in bug 657556 */ \
    if (!mCurrentProgram) \
        return ErrorInvalidOperation("%s: no program is currently bound", info); \
    if (mCurrentProgram != location_object->Program()) \
        return ErrorInvalidOperation("%s: this uniform location doesn't correspond to the current program", info); \
    if (mCurrentProgram->Generation() != location_object->ProgramGeneration())            \
        return ErrorInvalidOperation("%s: This uniform location is obsolete since the program has been relinked", info); \
    GLint location = location_object->Location();

#define SIMPLE_ARRAY_METHOD_UNIFORM(name, cnt, arrayType, ptrType)      \
NS_IMETHODIMP                                                           \
WebGLContext::name(PRInt32) {                                     \
     return NS_ERROR_NOT_IMPLEMENTED;                                   \
}                                                                       \
NS_IMETHODIMP                                                           \
WebGLContext::name##_array(nsIWebGLUniformLocation *ploc, JSObject *wa) \
{                                                                       \
    if (!IsContextStable())                                                   \
        return NS_OK;                                                   \
    OBTAIN_UNIFORM_LOCATION(#name ": location")                         \
    if (!wa || JS_GetTypedArrayType(wa) != js::TypedArray::arrayType)   \
        return ErrorInvalidOperation(#name ": array must be " #arrayType);      \
    if (JS_GetTypedArrayLength(wa) == 0 || JS_GetTypedArrayLength(wa) % cnt != 0)\
        return ErrorInvalidValue(#name ": array must be > 0 elements and have a length multiple of %d", cnt); \
    MakeContextCurrent();                                               \
    gl->f##name(location, JS_GetTypedArrayLength(wa) / cnt, (ptrType *)JS_GetTypedArrayData(wa));            \
    return NS_OK;                                                       \
}

#define SIMPLE_MATRIX_METHOD_UNIFORM(name, dim, arrayType, ptrType)     \
NS_IMETHODIMP                                                           \
WebGLContext::name(PRInt32) {                                     \
     return NS_ERROR_NOT_IMPLEMENTED;                                   \
}                                                                       \
NS_IMETHODIMP                                                           \
WebGLContext::name##_array(nsIWebGLUniformLocation *ploc, WebGLboolean transpose, JSObject *wa)  \
{                                                                       \
    if (!IsContextStable())                                                   \
        return NS_OK;                                                   \
    OBTAIN_UNIFORM_LOCATION(#name ": location")                         \
    if (!wa || JS_GetTypedArrayType(wa) != js::TypedArray::arrayType)                   \
        return ErrorInvalidValue(#name ": array must be " #arrayType);      \
    if (JS_GetTypedArrayLength(wa) == 0 || JS_GetTypedArrayLength(wa) % (dim*dim) != 0)                 \
        return ErrorInvalidValue(#name ": array length must be >0 and multiple of %d", dim*dim); \
    if (transpose)                                                      \
        return ErrorInvalidValue(#name ": transpose must be FALSE as per the OpenGL ES 2.0 spec"); \
    MakeContextCurrent();                                               \
    gl->f##name(location, JS_GetTypedArrayLength(wa) / (dim*dim), transpose, (ptrType *)JS_GetTypedArrayData(wa)); \
    return NS_OK;                                                       \
}

#define SIMPLE_METHOD_UNIFORM_1(glname, name, t1)        \
NS_IMETHODIMP WebGLContext::name(nsIWebGLUniformLocation *ploc, t1 a1) {      \
    if (!IsContextStable())                                    \
        return NS_OK;                                    \
    OBTAIN_UNIFORM_LOCATION(#name ": location") \
    MakeContextCurrent(); gl->f##glname(location, a1); return NS_OK; \
}

#define SIMPLE_METHOD_UNIFORM_2(glname, name, t1, t2)        \
NS_IMETHODIMP WebGLContext::name(nsIWebGLUniformLocation *ploc, t1 a1, t2 a2) {      \
    if (!IsContextStable())                                        \
        return NS_OK;                                        \
    OBTAIN_UNIFORM_LOCATION(#name ": location") \
    MakeContextCurrent(); gl->f##glname(location, a1, a2); return NS_OK; \
}

#define SIMPLE_METHOD_UNIFORM_3(glname, name, t1, t2, t3)        \
NS_IMETHODIMP WebGLContext::name(nsIWebGLUniformLocation *ploc, t1 a1, t2 a2, t3 a3) {      \
    if (!IsContextStable())                                            \
        return NS_OK;                                            \
    OBTAIN_UNIFORM_LOCATION(#name ": location") \
    MakeContextCurrent(); gl->f##glname(location, a1, a2, a3); return NS_OK; \
}

#define SIMPLE_METHOD_UNIFORM_4(glname, name, t1, t2, t3, t4)        \
NS_IMETHODIMP WebGLContext::name(nsIWebGLUniformLocation *ploc, t1 a1, t2 a2, t3 a3, t4 a4) {      \
    if (!IsContextStable())                                                \
        return NS_OK;                                                \
    OBTAIN_UNIFORM_LOCATION(#name ": location") \
    MakeContextCurrent(); gl->f##glname(location, a1, a2, a3, a4); return NS_OK; \
}

SIMPLE_METHOD_UNIFORM_1(Uniform1i, Uniform1i, WebGLint)
SIMPLE_METHOD_UNIFORM_2(Uniform2i, Uniform2i, WebGLint, WebGLint)
SIMPLE_METHOD_UNIFORM_3(Uniform3i, Uniform3i, WebGLint, WebGLint, WebGLint)
SIMPLE_METHOD_UNIFORM_4(Uniform4i, Uniform4i, WebGLint, WebGLint, WebGLint, WebGLint)

SIMPLE_METHOD_UNIFORM_1(Uniform1f, Uniform1f, WebGLfloat)
SIMPLE_METHOD_UNIFORM_2(Uniform2f, Uniform2f, WebGLfloat, WebGLfloat)
SIMPLE_METHOD_UNIFORM_3(Uniform3f, Uniform3f, WebGLfloat, WebGLfloat, WebGLfloat)
SIMPLE_METHOD_UNIFORM_4(Uniform4f, Uniform4f, WebGLfloat, WebGLfloat, WebGLfloat, WebGLfloat)

SIMPLE_ARRAY_METHOD_UNIFORM(Uniform1iv, 1, TYPE_INT32, WebGLint)
SIMPLE_ARRAY_METHOD_UNIFORM(Uniform2iv, 2, TYPE_INT32, WebGLint)
SIMPLE_ARRAY_METHOD_UNIFORM(Uniform3iv, 3, TYPE_INT32, WebGLint)
SIMPLE_ARRAY_METHOD_UNIFORM(Uniform4iv, 4, TYPE_INT32, WebGLint)

SIMPLE_ARRAY_METHOD_UNIFORM(Uniform1fv, 1, TYPE_FLOAT32, WebGLfloat)
SIMPLE_ARRAY_METHOD_UNIFORM(Uniform2fv, 2, TYPE_FLOAT32, WebGLfloat)
SIMPLE_ARRAY_METHOD_UNIFORM(Uniform3fv, 3, TYPE_FLOAT32, WebGLfloat)
SIMPLE_ARRAY_METHOD_UNIFORM(Uniform4fv, 4, TYPE_FLOAT32, WebGLfloat)

SIMPLE_MATRIX_METHOD_UNIFORM(UniformMatrix2fv, 2, TYPE_FLOAT32, WebGLfloat)
SIMPLE_MATRIX_METHOD_UNIFORM(UniformMatrix3fv, 3, TYPE_FLOAT32, WebGLfloat)
SIMPLE_MATRIX_METHOD_UNIFORM(UniformMatrix4fv, 4, TYPE_FLOAT32, WebGLfloat)

NS_IMETHODIMP
WebGLContext::VertexAttrib1f(PRUint32 index, WebGLfloat x0)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();

    if (index) {
        gl->fVertexAttrib1f(index, x0);
    } else {
        mVertexAttrib0Vector[0] = x0;
        mVertexAttrib0Vector[1] = 0;
        mVertexAttrib0Vector[2] = 0;
        mVertexAttrib0Vector[3] = 1;
        if (gl->IsGLES2())
            gl->fVertexAttrib1f(index, x0);
    }

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::VertexAttrib2f(PRUint32 index, WebGLfloat x0, WebGLfloat x1)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();

    if (index) {
        gl->fVertexAttrib2f(index, x0, x1);
    } else {
        mVertexAttrib0Vector[0] = x0;
        mVertexAttrib0Vector[1] = x1;
        mVertexAttrib0Vector[2] = 0;
        mVertexAttrib0Vector[3] = 1;
        if (gl->IsGLES2())
            gl->fVertexAttrib2f(index, x0, x1);
    }

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::VertexAttrib3f(PRUint32 index, WebGLfloat x0, WebGLfloat x1, WebGLfloat x2)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();

    if (index) {
        gl->fVertexAttrib3f(index, x0, x1, x2);
    } else {
        mVertexAttrib0Vector[0] = x0;
        mVertexAttrib0Vector[1] = x1;
        mVertexAttrib0Vector[2] = x2;
        mVertexAttrib0Vector[3] = 1;
        if (gl->IsGLES2())
            gl->fVertexAttrib3f(index, x0, x1, x2);
    }

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::VertexAttrib4f(PRUint32 index, WebGLfloat x0, WebGLfloat x1,
                                             WebGLfloat x2, WebGLfloat x3)
{
    if (!IsContextStable())
        return NS_OK;

    MakeContextCurrent();

    if (index) {
        gl->fVertexAttrib4f(index, x0, x1, x2, x3);
    } else {
        mVertexAttrib0Vector[0] = x0;
        mVertexAttrib0Vector[1] = x1;
        mVertexAttrib0Vector[2] = x2;
        mVertexAttrib0Vector[3] = x3;
        if (gl->IsGLES2())
            gl->fVertexAttrib4f(index, x0, x1, x2, x3);
    }

    return NS_OK;
}

#define SIMPLE_ARRAY_METHOD_NO_COUNT(name, cnt, arrayType, ptrType)  \
NS_IMETHODIMP                                                           \
WebGLContext::name(PRInt32) {                                     \
     return NS_ERROR_NOT_IMPLEMENTED;                                   \
}                                                                       \
NS_IMETHODIMP                                                           \
WebGLContext::name##_array(WebGLuint idx, JSObject *wa)           \
{                                                                       \
    if (!IsContextStable())                                                   \
        return NS_OK;                                                   \
    if (!wa || JS_GetTypedArrayType(wa) != js::TypedArray::arrayType)                   \
        return ErrorInvalidOperation(#name ": array must be " #arrayType); \
    if (JS_GetTypedArrayLength(wa) < cnt)                                               \
        return ErrorInvalidOperation(#name ": array must be >= %d elements", cnt); \
    MakeContextCurrent();                                               \
    ptrType *ptr = (ptrType *)JS_GetTypedArrayData(wa);                                  \
    if (idx) {                                                        \
        gl->f##name(idx, ptr);                                          \
    } else {                                                            \
        mVertexAttrib0Vector[0] = ptr[0];                               \
        mVertexAttrib0Vector[1] = cnt > 1 ? ptr[1] : ptrType(0);        \
        mVertexAttrib0Vector[2] = cnt > 2 ? ptr[2] : ptrType(0);        \
        mVertexAttrib0Vector[3] = cnt > 3 ? ptr[3] : ptrType(1);        \
        if (gl->IsGLES2())                                              \
            gl->f##name(idx, ptr);                                      \
    }                                                                   \
    return NS_OK;                                                       \
}

SIMPLE_ARRAY_METHOD_NO_COUNT(VertexAttrib1fv, 1, TYPE_FLOAT32, WebGLfloat)
SIMPLE_ARRAY_METHOD_NO_COUNT(VertexAttrib2fv, 2, TYPE_FLOAT32, WebGLfloat)
SIMPLE_ARRAY_METHOD_NO_COUNT(VertexAttrib3fv, 3, TYPE_FLOAT32, WebGLfloat)
SIMPLE_ARRAY_METHOD_NO_COUNT(VertexAttrib4fv, 4, TYPE_FLOAT32, WebGLfloat)

NS_IMETHODIMP
WebGLContext::UseProgram(nsIWebGLProgram *pobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLProgram *prog;
    WebGLuint progname;
    bool isNull;
    if (!GetConcreteObjectAndGLName("useProgram", pobj, &prog, &progname, &isNull))
        return NS_OK;

    MakeContextCurrent();

    if (prog && !prog->LinkStatus())
        return ErrorInvalidOperation("UseProgram: program was not linked successfully");

    gl->fUseProgram(progname);

    mCurrentProgram = prog;

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::ValidateProgram(nsIWebGLProgram *pobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLuint progname;
    if (!GetGLName<WebGLProgram>("validateProgram", pobj, &progname))
        return NS_OK;

    MakeContextCurrent();

#ifdef XP_MACOSX
    // see bug 593867 for NVIDIA and bug 657201 for ATI. The latter is confirmed with Mac OS 10.6.7
    LogMessageIfVerbose("validateProgram: implemented as a no-operation on Mac to work around crashes");
    return NS_OK;
#endif

    gl->fValidateProgram(progname);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CreateFramebuffer(nsIWebGLFramebuffer **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = 0;

    WebGLFramebuffer *globj = new WebGLFramebuffer(this);
    NS_ADDREF(*retval = globj);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CreateRenderbuffer(nsIWebGLRenderbuffer **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = 0;

    WebGLRenderbuffer *globj = new WebGLRenderbuffer(this);
    NS_ADDREF(*retval = globj);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::Viewport(WebGLint x, WebGLint y, WebGLsizei width, WebGLsizei height)
{
    if (!IsContextStable())
        return NS_OK;

    if (width < 0 || height < 0)
        return ErrorInvalidValue("Viewport: negative size");

    MakeContextCurrent();
    gl->fViewport(x, y, width, height);
    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::CompileShader(nsIWebGLShader *sobj)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLShader *shader;
    WebGLuint shadername;
    if (!GetConcreteObjectAndGLName("compileShader", sobj, &shader, &shadername))
        return NS_OK;

    MakeContextCurrent();

#if defined(USE_ANGLE)
    if (shader->NeedsTranslation() && mShaderValidation) {
        ShHandle compiler = 0;
        ShBuiltInResources resources;
        memset(&resources, 0, sizeof(ShBuiltInResources));

        resources.MaxVertexAttribs = mGLMaxVertexAttribs;
        resources.MaxVertexUniformVectors = mGLMaxVertexUniformVectors;
        resources.MaxVaryingVectors = mGLMaxVaryingVectors;
        resources.MaxVertexTextureImageUnits = mGLMaxVertexTextureImageUnits;
        resources.MaxCombinedTextureImageUnits = mGLMaxTextureUnits;
        resources.MaxTextureImageUnits = mGLMaxTextureImageUnits;
        resources.MaxFragmentUniformVectors = mGLMaxFragmentUniformVectors;
        resources.MaxDrawBuffers = 1;
        if (mEnabledExtensions[WebGL_OES_standard_derivatives])
            resources.OES_standard_derivatives = 1;

        // notice that on Android, we always use SH_GLSL_OUTPUT, we never use the ESSL backend.
        // see bug 709947, the reason is that 1) we dont really need a ESSL backend since the
        // source is already ESSL, and 2) we ran into massive Android crashes when we used the ESSL backend.
        // But if we wanted to use shader transformations on ES platforms, we would have to use the
        // ESSL backend
        compiler = ShConstructCompiler((ShShaderType) shader->ShaderType(),
                                       SH_WEBGL_SPEC,
#ifdef MOZ_WIDGET_ANDROID
                                       SH_GLSL_OUTPUT,
#else
                                       gl->IsGLES2() ? SH_ESSL_OUTPUT : SH_GLSL_OUTPUT,
#endif
                                       &resources);

        // We're storing an actual instance of StripComments because, if we don't, the 
        // cleanSource nsAString instance will be destroyed before the reference is
        // actually used.
        StripComments stripComments(shader->Source());
        const nsAString& cleanSource = nsString(stripComments.result().Elements(), stripComments.length());
        if (!ValidateGLSLString(cleanSource, "compileShader"))
            return NS_OK;

        const nsPromiseFlatString& flatSource = PromiseFlatString(cleanSource);

        // shaderSource() already checks that the source stripped of comments is in the
        // 7-bit ASCII range, so we can skip the NS_IsAscii() check.
        const nsCString& sourceCString = NS_LossyConvertUTF16toASCII(flatSource);
    
        const PRUint32 maxSourceLength = (PRUint32(1)<<18) - 1;
        if (sourceCString.Length() > maxSourceLength)
            return ErrorInvalidValue("compileShader: source has more than %d characters", maxSourceLength);

        const char *s = sourceCString.get();
        
        int compileOptions = SH_OBJECT_CODE;
        
#ifdef XP_MACOSX
        // work around bug 665578
        if (!nsCocoaFeatures::OnLionOrLater() && gl->Vendor() == gl::GLContext::VendorATI)
            compileOptions |= SH_EMULATE_BUILT_IN_FUNCTIONS;
#endif

        if (!ShCompile(compiler, &s, 1, compileOptions)) {
            int len = 0;
            ShGetInfo(compiler, SH_INFO_LOG_LENGTH, &len);

            if (len) {
                nsCAutoString info;
                info.SetLength(len);
                ShGetInfoLog(compiler, info.BeginWriting());
                shader->SetTranslationFailure(info);
            } else {
                shader->SetTranslationFailure(NS_LITERAL_CSTRING("Internal error: failed to get shader info log"));
            }
            ShDestruct(compiler);
            return NS_OK;
        }

        /* If the GL context is really GLES2, we want to use the original provided code,
         * since it's actually GLES2.  We still need to validate it however, which is
         * why we ran it through the above, but we don't want the desktop GLSL.
         */
        if (!gl->IsGLES2()) {
            int len = 0;
            ShGetInfo(compiler, SH_OBJECT_CODE_LENGTH, &len);

            nsCAutoString translatedSrc;
            translatedSrc.SetLength(len);
            ShGetObjectCode(compiler, translatedSrc.BeginWriting());

            nsPromiseFlatCString translatedSrc2(translatedSrc);
            const char *ts = translatedSrc2.get();

            gl->fShaderSource(shadername, 1, &ts, NULL);
        } else {
            gl->fShaderSource(shadername, 1, &s, NULL);
        }

        shader->SetTranslationSuccess();

        ShDestruct(compiler);

        gl->fCompileShader(shadername);
    }
#endif

    return NS_OK;
}


NS_IMETHODIMP
WebGLContext::GetShaderParameter(nsIWebGLShader *sobj, WebGLenum pname, nsIVariant **retval)
{
    if (!IsContextStable())
        return NS_OK;

    *retval = nsnull;

    WebGLShader *shader;
    WebGLuint shadername;
    if (!GetConcreteObjectAndGLName("getShaderParameter: shader", sobj, &shader, &shadername))
        return NS_OK;

    nsCOMPtr<nsIWritableVariant> wrval = do_CreateInstance("@mozilla.org/variant;1");
    NS_ENSURE_TRUE(wrval, NS_ERROR_FAILURE);

    MakeContextCurrent();

    switch (pname) {
        case LOCAL_GL_SHADER_TYPE:
        case LOCAL_GL_INFO_LOG_LENGTH:
        {
            GLint i = 0;
            gl->fGetShaderiv(shadername, pname, &i);
            wrval->SetAsInt32(i);
        }
            break;
        case LOCAL_GL_SHADER_SOURCE_LENGTH:
        {
            wrval->SetAsInt32(PRInt32(shader->Source().Length()) + 1);
        }
            break;
        case LOCAL_GL_DELETE_STATUS:
            wrval->SetAsBool(shader->IsDeleteRequested());
            break;
        case LOCAL_GL_COMPILE_STATUS:
        {
            GLint i = 0;
            gl->fGetShaderiv(shadername, pname, &i);
            wrval->SetAsBool(bool(i));
        }
            break;
        default:
            return NS_ERROR_NOT_IMPLEMENTED;
    }

    *retval = wrval.forget().get();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetShaderInfoLog(nsIWebGLShader *sobj, nsAString& retval)
{
    if (!IsContextStable())
    {
        retval.SetIsVoid(true);
        return NS_OK;
    }

    WebGLShader *shader;
    WebGLuint shadername;
    if (!GetConcreteObjectAndGLName("getShaderInfoLog: shader", sobj, &shader, &shadername))
        return NS_OK;

    const nsCString& tlog = shader->TranslationLog();
    if (!tlog.IsVoid()) {
        CopyASCIItoUTF16(tlog, retval);
        return NS_OK;
    }

    MakeContextCurrent();

    GLint k = -1;
    gl->fGetShaderiv(shadername, LOCAL_GL_INFO_LOG_LENGTH, &k);
    if (k == -1)
        return NS_ERROR_FAILURE; // XXX GL Error? should never happen.

    if (k == 0) {
        retval.Truncate();
        return NS_OK;
    }

    nsCAutoString log;
    log.SetCapacity(k);

    gl->fGetShaderInfoLog(shadername, k, &k, (char*) log.BeginWriting());

    log.SetLength(k);

    CopyASCIItoUTF16(log, retval);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetShaderPrecisionFormat(WebGLenum shadertype, WebGLenum precisiontype, nsIWebGLShaderPrecisionFormat **retval)
{
    *retval = nsnull;
    if (!IsContextStable())
        return NS_OK;

    switch (shadertype) {
        case LOCAL_GL_FRAGMENT_SHADER:
        case LOCAL_GL_VERTEX_SHADER:
            break;
        default:
            return ErrorInvalidEnumInfo("getShaderPrecisionFormat: shadertype", shadertype);
    }

    switch (precisiontype) {
        case LOCAL_GL_LOW_FLOAT:
        case LOCAL_GL_MEDIUM_FLOAT:
        case LOCAL_GL_HIGH_FLOAT:
        case LOCAL_GL_LOW_INT:
        case LOCAL_GL_MEDIUM_INT:
        case LOCAL_GL_HIGH_INT:
            break;
        default:
            return ErrorInvalidEnumInfo("getShaderPrecisionFormat: precisiontype", precisiontype);
    }

    MakeContextCurrent();

    GLint range[2], precision;
    gl->fGetShaderPrecisionFormat(shadertype, precisiontype, range, &precision);

    WebGLShaderPrecisionFormat *retShaderPrecisionFormat
        = new WebGLShaderPrecisionFormat(range[0], range[1], precision);
    NS_ADDREF(*retval = retShaderPrecisionFormat);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::GetShaderSource(nsIWebGLShader *sobj, nsAString& retval)
{
    if (!IsContextStable())
    {
        retval.SetIsVoid(true);
        return NS_OK;
    }

    WebGLShader *shader;
    WebGLuint shadername;
    if (!GetConcreteObjectAndGLName("getShaderSource: shader", sobj, &shader, &shadername))
        return NS_OK;

    retval.Assign(shader->Source());

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::ShaderSource(nsIWebGLShader *sobj, const nsAString& source)
{
    if (!IsContextStable())
        return NS_OK;

    WebGLShader *shader;
    WebGLuint shadername;
    if (!GetConcreteObjectAndGLName("shaderSource: shader", sobj, &shader, &shadername))
        return NS_OK;

    // We're storing an actual instance of StripComments because, if we don't, the 
    // cleanSource nsAString instance will be destroyed before the reference is
    // actually used.
    StripComments stripComments(source);
    const nsAString& cleanSource = nsString(stripComments.result().Elements(), stripComments.length());
    if (!ValidateGLSLString(cleanSource, "compileShader"))
        return NS_OK;

    shader->SetSource(source);

    shader->SetNeedsTranslation();

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::VertexAttribPointer(WebGLuint index, WebGLint size, WebGLenum type,
                                  WebGLboolean normalized, WebGLsizei stride,
                                  WebGLsizeiptr byteOffset)
{
    if (!IsContextStable())
        return NS_OK;

    if (mBoundArrayBuffer == nsnull)
        return ErrorInvalidOperation("VertexAttribPointer: must have valid GL_ARRAY_BUFFER binding");

    WebGLsizei requiredAlignment = 1;
    switch (type) {
      case LOCAL_GL_BYTE:
      case LOCAL_GL_UNSIGNED_BYTE:
          requiredAlignment = 1;
          break;
      case LOCAL_GL_SHORT:
      case LOCAL_GL_UNSIGNED_SHORT:
          requiredAlignment = 2;
          break;
      // XXX case LOCAL_GL_FIXED:
      case LOCAL_GL_FLOAT:
          requiredAlignment = 4;
          break;
      default:
          return ErrorInvalidEnumInfo("VertexAttribPointer: type", type);
    }

    // requiredAlignment should always be a power of two.
    WebGLsizei requiredAlignmentMask = requiredAlignment - 1;

    if (!ValidateAttribIndex(index, "vertexAttribPointer"))
        return NS_OK;

    if (size < 1 || size > 4)
        return ErrorInvalidValue("VertexAttribPointer: invalid element size");

    if (stride < 0 || stride > 255) // see WebGL spec section 6.6 "Vertex Attribute Data Stride"
        return ErrorInvalidValue("VertexAttribPointer: negative or too large stride");

    if (byteOffset < 0)
        return ErrorInvalidValue("VertexAttribPointer: negative offset");

    if (stride & requiredAlignmentMask) {
        return ErrorInvalidOperation("VertexAttribPointer: stride doesn't satisfy the alignment "
                                     "requirement of given type");
    }

    if (byteOffset & requiredAlignmentMask) {
        return ErrorInvalidOperation("VertexAttribPointer: byteOffset doesn't satisfy the alignment "
                                     "requirement of given type");

    }
    
    /* XXX make work with bufferSubData & heterogeneous types 
    if (type != mBoundArrayBuffer->GLType())
        return ErrorInvalidOperation("VertexAttribPointer: type must match bound VBO type: %d != %d", type, mBoundArrayBuffer->GLType());
    */

    WebGLVertexAttribData &vd = mAttribBuffers[index];

    vd.buf = mBoundArrayBuffer;
    vd.stride = stride;
    vd.size = size;
    vd.byteOffset = byteOffset;
    vd.type = type;
    vd.normalized = normalized;

    MakeContextCurrent();

    gl->fVertexAttribPointer(index, size, type, normalized,
                             stride,
                             (void*) (byteOffset));

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::TexImage2D(PRInt32)
{
    if (!IsContextStable())
        return NS_OK;

    return NS_ERROR_FAILURE;
}

GLenum WebGLContext::CheckedTexImage2D(GLenum target,
                                       GLint level,
                                       GLenum internalFormat,
                                       GLsizei width,
                                       GLsizei height,
                                       GLint border,
                                       GLenum format,
                                       GLenum type,
                                       const GLvoid *data)
{
    WebGLTexture *tex = activeBoundTextureForTarget(target);
    NS_ABORT_IF_FALSE(tex != nsnull, "no texture bound");

    bool sizeMayChange = true;
    size_t face = WebGLTexture::FaceForTarget(target);
    
    if (tex->HasImageInfoAt(level, face)) {
        const WebGLTexture::ImageInfo& imageInfo = tex->ImageInfoAt(level, face);
        sizeMayChange = width != imageInfo.mWidth ||
                        height != imageInfo.mHeight ||
                        format != imageInfo.mFormat ||
                        type != imageInfo.mType;
    }
    
    if (sizeMayChange) {
        UpdateWebGLErrorAndClearGLError();
        gl->fTexImage2D(target, level, internalFormat, width, height, border, format, type, data);
        GLenum error = LOCAL_GL_NO_ERROR;
        UpdateWebGLErrorAndClearGLError(&error);
        return error;
    } else {
        gl->fTexImage2D(target, level, internalFormat, width, height, border, format, type, data);
        return LOCAL_GL_NO_ERROR;
    }
}

nsresult
WebGLContext::TexImage2D_base(WebGLenum target, WebGLint level, WebGLenum internalformat,
                              WebGLsizei width, WebGLsizei height, WebGLsizei srcStrideOrZero,
                              WebGLint border,
                              WebGLenum format, WebGLenum type,
                              void *data, PRUint32 byteLength,
                              int jsArrayType, // a TypedArray format enum, or -1 if not relevant
                              int srcFormat, bool srcPremultiplied)
{
    switch (target) {
        case LOCAL_GL_TEXTURE_2D:
            break;
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_X:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
            if (width != height)
                return ErrorInvalidValue("texImage2D: with cube map targets, width and height must be equal");
            break;
        default:
            return ErrorInvalidEnumInfo("texImage2D: target", target);
    }

    switch (format) {
        case LOCAL_GL_RGB:
        case LOCAL_GL_RGBA:
        case LOCAL_GL_ALPHA:
        case LOCAL_GL_LUMINANCE:
        case LOCAL_GL_LUMINANCE_ALPHA:
            break;
        default:
            return ErrorInvalidEnumInfo("texImage2D: internal format", internalformat);
    }

    if (format != internalformat)
        return ErrorInvalidOperation("texImage2D: format does not match internalformat");

    WebGLsizei maxTextureSize = MaxTextureSizeForTarget(target);

    if (level < 0)
        return ErrorInvalidValue("texImage2D: level must be >= 0");

    if (!(maxTextureSize >> level))
        return ErrorInvalidValue("texImage2D: 2^level exceeds maximum texture size");

    if (width < 0 || height < 0)
        return ErrorInvalidValue("texImage2D: width and height must be >= 0");

    if (width > maxTextureSize || height > maxTextureSize)
        return ErrorInvalidValue("texImage2D: width or height exceeds maximum texture size");

    if (level >= 1) {
        if (!(is_pot_assuming_nonnegative(width) &&
              is_pot_assuming_nonnegative(height)))
            return ErrorInvalidValue("texImage2D: with level > 0, width and height must be powers of two");
    }

    if (border != 0)
        return ErrorInvalidValue("TexImage2D: border must be 0");

    PRUint32 texelSize = 0;
    if (!ValidateTexFormatAndType(format, type, jsArrayType, &texelSize, "texImage2D"))
        return NS_OK;

    CheckedUint32 checked_neededByteLength = 
        GetImageSize(height, width, texelSize, mPixelStoreUnpackAlignment); 

    CheckedUint32 checked_plainRowSize = CheckedUint32(width) * texelSize;

    CheckedUint32 checked_alignedRowSize =
        RoundedToNextMultipleOf(checked_plainRowSize.value(), mPixelStoreUnpackAlignment);

    if (!checked_neededByteLength.valid())
        return ErrorInvalidOperation("texImage2D: integer overflow computing the needed buffer size");

    PRUint32 bytesNeeded = checked_neededByteLength.value();

    if (byteLength && byteLength < bytesNeeded)
        return ErrorInvalidOperation("TexImage2D: not enough data for operation (need %d, have %d)",
                                 bytesNeeded, byteLength);

    WebGLTexture *tex = activeBoundTextureForTarget(target);

    if (!tex)
        return ErrorInvalidOperation("texImage2D: no texture is bound to this target");

    MakeContextCurrent();

    // Handle ES2 and GL differences in floating point internal formats.  Note that
    // format == internalformat, as checked above and as required by ES.
    internalformat = InternalFormatForFormatAndType(format, type, gl->IsGLES2());

    GLenum error = LOCAL_GL_NO_ERROR;

    if (byteLength) {
        int dstFormat = GetWebGLTexelFormat(format, type);
        int actualSrcFormat = srcFormat == WebGLTexelFormat::Auto ? dstFormat : srcFormat;
        size_t srcStride = srcStrideOrZero ? srcStrideOrZero : checked_alignedRowSize.value();

        size_t dstPlainRowSize = texelSize * width;
        size_t unpackAlignment = mPixelStoreUnpackAlignment;
        size_t dstStride = ((dstPlainRowSize + unpackAlignment-1) / unpackAlignment) * unpackAlignment;

        if (actualSrcFormat == dstFormat &&
            srcPremultiplied == mPixelStorePremultiplyAlpha &&
            srcStride == dstStride &&
            !mPixelStoreFlipY)
        {
            // no conversion, no flipping, so we avoid copying anything and just pass the source pointer
            error = CheckedTexImage2D(target, level, internalformat,
                                      width, height, border, format, type, data);
        }
        else
        {
            nsAutoArrayPtr<PRUint8> convertedData(new PRUint8[bytesNeeded]);
            ConvertImage(width, height, srcStride, dstStride,
                        (PRUint8*)data, convertedData,
                        actualSrcFormat, srcPremultiplied,
                        dstFormat, mPixelStorePremultiplyAlpha, texelSize);
            error = CheckedTexImage2D(target, level, internalformat,
                                      width, height, border, format, type, convertedData);
        }
    } else {
        // We need some zero pages, because GL doesn't guarantee the
        // contents of a texture allocated with NULL data.
        // Hopefully calloc will just mmap zero pages here.
        void *tempZeroData = calloc(1, bytesNeeded);
        if (!tempZeroData)
            return ErrorOutOfMemory("texImage2D: could not allocate %d bytes (for zero fill)", bytesNeeded);

        error = CheckedTexImage2D(target, level, internalformat,
                                  width, height, border, format, type, tempZeroData);

        free(tempZeroData);
    }
    
    if (error) {
        LogMessageIfVerbose("texImage2D generated error %s", ErrorName(error));
        return NS_OK;
    }

    tex->SetImageInfo(target, level, width, height, format, type);

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::TexImage2D_array(WebGLenum target, WebGLint level, WebGLenum internalformat,
                               WebGLsizei width, WebGLsizei height, WebGLint border,
                               WebGLenum format, WebGLenum type,
                               JSObject *pixels)
{
    if (!IsContextStable())
        return NS_OK;

    return TexImage2D_base(target, level, internalformat, width, height, 0, border, format, type,
                           pixels ? JS_GetTypedArrayData(pixels) : 0,
                           pixels ? JS_GetTypedArrayByteLength(pixels) : 0,
                           pixels ? (int)JS_GetTypedArrayType(pixels) : -1,
                           WebGLTexelFormat::Auto, false);
}

NS_IMETHODIMP
WebGLContext::TexImage2D_imageData(WebGLenum target, WebGLint level, WebGLenum internalformat,
                               WebGLsizei width, WebGLsizei height, WebGLint border,
                               WebGLenum format, WebGLenum type,
                               JSObject *pixels)
{
    if (!IsContextStable())
        return NS_OK;

    return TexImage2D_base(target, level, internalformat, width, height, 4*width, border, format, type,
                           pixels ? JS_GetTypedArrayData(pixels) : 0,
                           pixels ? JS_GetTypedArrayByteLength(pixels) : 0,
                           -1,
                           WebGLTexelFormat::RGBA8, false);
}

NS_IMETHODIMP
WebGLContext::TexImage2D_dom(WebGLenum target, WebGLint level, WebGLenum internalformat,
                             WebGLenum format, GLenum type, nsIDOMElement *elt)
{
    if (!IsContextStable())
        return NS_OK;

    nsRefPtr<gfxImageSurface> isurf;

    int srcFormat;
    nsresult rv = DOMElementToImageSurface(elt, getter_AddRefs(isurf), &srcFormat);
    if (NS_FAILED(rv))
        return rv;

    PRUint32 byteLength = isurf->Stride() * isurf->Height();

    return TexImage2D_base(target, level, internalformat,
                           isurf->Width(), isurf->Height(), isurf->Stride(), 0,
                           format, type,
                           isurf->Data(), byteLength,
                           -1,
                           srcFormat, mPixelStorePremultiplyAlpha);
}

NS_IMETHODIMP
WebGLContext::TexSubImage2D(PRInt32)
{
    if (!IsContextStable())
        return NS_OK;

    return NS_ERROR_FAILURE;
}

nsresult
WebGLContext::TexSubImage2D_base(WebGLenum target, WebGLint level,
                                 WebGLint xoffset, WebGLint yoffset,
                                 WebGLsizei width, WebGLsizei height, WebGLsizei srcStrideOrZero,
                                 WebGLenum format, WebGLenum type,
                                 void *pixels, PRUint32 byteLength,
                                 int jsArrayType,
                                 int srcFormat, bool srcPremultiplied)
{
    switch (target) {
        case LOCAL_GL_TEXTURE_2D:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_X:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
        case LOCAL_GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
        case LOCAL_GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
            break;
        default:
            return ErrorInvalidEnumInfo("texSubImage2D: target", target);
    }

    WebGLsizei maxTextureSize = MaxTextureSizeForTarget(target);

    if (level < 0)
        return ErrorInvalidValue("texSubImage2D: level must be >= 0");

    if (!(maxTextureSize >> level))
        return ErrorInvalidValue("texSubImage2D: 2^level exceeds maximum texture size");

    if (width < 0 || height < 0)
        return ErrorInvalidValue("texSubImage2D: width and height must be >= 0");

    if (width > maxTextureSize || height > maxTextureSize)
        return ErrorInvalidValue("texSubImage2D: width or height exceeds maximum texture size");

    if (level >= 1) {
        if (!(is_pot_assuming_nonnegative(width) &&
              is_pot_assuming_nonnegative(height)))
            return ErrorInvalidValue("texSubImage2D: with level > 0, width and height must be powers of two");
    }

    PRUint32 texelSize = 0;
    if (!ValidateTexFormatAndType(format, type, jsArrayType, &texelSize, "texSubImage2D"))
        return NS_OK;

    if (width == 0 || height == 0)
        return NS_OK; // ES 2.0 says it has no effect, we better return right now

    CheckedUint32 checked_neededByteLength = 
        GetImageSize(height, width, texelSize, mPixelStoreUnpackAlignment);

    CheckedUint32 checked_plainRowSize = CheckedUint32(width) * texelSize;

    CheckedUint32 checked_alignedRowSize = 
        RoundedToNextMultipleOf(checked_plainRowSize.value(), mPixelStoreUnpackAlignment);

    if (!checked_neededByteLength.valid())
        return ErrorInvalidOperation("texSubImage2D: integer overflow computing the needed buffer size");

    PRUint32 bytesNeeded = checked_neededByteLength.value();
 
    if (byteLength < bytesNeeded)
        return ErrorInvalidOperation("texSubImage2D: not enough data for operation (need %d, have %d)", bytesNeeded, byteLength);

    WebGLTexture *tex = activeBoundTextureForTarget(target);

    if (!tex)
        return ErrorInvalidOperation("texSubImage2D: no texture is bound to this target");

    size_t face = WebGLTexture::FaceForTarget(target);
    
    if (!tex->HasImageInfoAt(level, face))
        return ErrorInvalidOperation("texSubImage2D: no texture image previously defined for this level and face");
    
    const WebGLTexture::ImageInfo &imageInfo = tex->ImageInfoAt(level, face);
    if (!CanvasUtils::CheckSaneSubrectSize(xoffset, yoffset, width, height, imageInfo.mWidth, imageInfo.mHeight))
        return ErrorInvalidValue("texSubImage2D: subtexture rectangle out of bounds");
    
    // Require the format and type in texSubImage2D to match that of the existing texture as created by texImage2D
    if (imageInfo.mFormat != format || imageInfo.mType != type)
        return ErrorInvalidOperation("texSubImage2D: format or type doesn't match the existing texture");

    MakeContextCurrent();

    int dstFormat = GetWebGLTexelFormat(format, type);
    int actualSrcFormat = srcFormat == WebGLTexelFormat::Auto ? dstFormat : srcFormat;
    size_t srcStride = srcStrideOrZero ? srcStrideOrZero : checked_alignedRowSize.value();

    size_t dstPlainRowSize = texelSize * width;
    // There are checks above to ensure that this won't overflow.
    size_t dstStride = RoundedToNextMultipleOf(dstPlainRowSize, mPixelStoreUnpackAlignment).value();

    if (actualSrcFormat == dstFormat &&
        srcPremultiplied == mPixelStorePremultiplyAlpha &&
        srcStride == dstStride &&
        !mPixelStoreFlipY)
    {
        // no conversion, no flipping, so we avoid copying anything and just pass the source pointer
        gl->fTexSubImage2D(target, level, xoffset, yoffset, width, height, format, type, pixels);
    }
    else
    {
        nsAutoArrayPtr<PRUint8> convertedData(new PRUint8[bytesNeeded]);
        ConvertImage(width, height, srcStride, dstStride,
                    (const PRUint8*)pixels, convertedData,
                    actualSrcFormat, srcPremultiplied,
                    dstFormat, mPixelStorePremultiplyAlpha, texelSize);

        gl->fTexSubImage2D(target, level, xoffset, yoffset, width, height, format, type, convertedData);
    }

    return NS_OK;
}

NS_IMETHODIMP
WebGLContext::TexSubImage2D_array(WebGLenum target, WebGLint level,
                                  WebGLint xoffset, WebGLint yoffset,
                                  WebGLsizei width, WebGLsizei height,
                                  WebGLenum format, WebGLenum type,
                                  JSObject *pixels)
{
    if (!IsContextStable())
        return NS_OK;

    if (!pixels)
        return ErrorInvalidValue("TexSubImage2D: pixels must not be null!");

    return TexSubImage2D_base(target, level, xoffset, yoffset,
                              width, height, 0, format, type,
                              JS_GetTypedArrayData(pixels), JS_GetTypedArrayByteLength(pixels),
                              JS_GetTypedArrayType(pixels),
                              WebGLTexelFormat::Auto, false);
}

NS_IMETHODIMP
WebGLContext::TexSubImage2D_imageData(WebGLenum target, WebGLint level,
                                      WebGLint xoffset, WebGLint yoffset,
                                      WebGLsizei width, WebGLsizei height,
                                      WebGLenum format, WebGLenum type,
                                      JSObject *pixels)
{
    if (!IsContextStable())
        return NS_OK;

    if (!pixels)
        return ErrorInvalidValue("TexSubImage2D: pixels must not be null!");

    return TexSubImage2D_base(target, level, xoffset, yoffset,
                              width, height, 4*width, format, type,
                              JS_GetTypedArrayData(pixels), JS_GetTypedArrayByteLength(pixels),
                              -1,
                              WebGLTexelFormat::RGBA8, false);
}

NS_IMETHODIMP
WebGLContext::TexSubImage2D_dom(WebGLenum target, WebGLint level,
                                WebGLint xoffset, WebGLint yoffset,
                                WebGLenum format, WebGLenum type,
                                nsIDOMElement *elt)
{
    if (!IsContextStable())
        return NS_OK;

    nsRefPtr<gfxImageSurface> isurf;

    int srcFormat;
    nsresult rv = DOMElementToImageSurface(elt, getter_AddRefs(isurf), &srcFormat);
    if (NS_FAILED(rv))
        return rv;

    PRUint32 byteLength = isurf->Stride() * isurf->Height();

    return TexSubImage2D_base(target, level,
                              xoffset, yoffset,
                              isurf->Width(), isurf->Height(), isurf->Stride(),
                              format, type,
                              isurf->Data(), byteLength,
                              -1,
                              srcFormat, mPixelStorePremultiplyAlpha);
}

bool
WebGLContext::LoseContext()
{
    if (!IsContextStable())
        return false;

    mContextLostDueToTest = true;
    ForceLoseContext();

    return true;
}

bool
WebGLContext::RestoreContext()
{
    if (IsContextStable() || !mAllowRestore) {
        return false;
    }

    ForceRestoreContext();

    return true;
}

bool
BaseTypeAndSizeFromUniformType(WebGLenum uType, WebGLenum *baseType, WebGLint *unitSize)
{
    switch (uType) {
        case LOCAL_GL_INT:
        case LOCAL_GL_INT_VEC2:
        case LOCAL_GL_INT_VEC3:
        case LOCAL_GL_INT_VEC4:
        case LOCAL_GL_SAMPLER_2D:
        case LOCAL_GL_SAMPLER_CUBE:
            *baseType = LOCAL_GL_INT;
            break;
        case LOCAL_GL_FLOAT:
        case LOCAL_GL_FLOAT_VEC2:
        case LOCAL_GL_FLOAT_VEC3:
        case LOCAL_GL_FLOAT_VEC4:
        case LOCAL_GL_FLOAT_MAT2:
        case LOCAL_GL_FLOAT_MAT3:
        case LOCAL_GL_FLOAT_MAT4:
            *baseType = LOCAL_GL_FLOAT;
            break;
        case LOCAL_GL_BOOL:
        case LOCAL_GL_BOOL_VEC2:
        case LOCAL_GL_BOOL_VEC3:
        case LOCAL_GL_BOOL_VEC4:
            *baseType = LOCAL_GL_BOOL; // pretend these are int
            break;
        default:
            return false;
    }

    switch (uType) {
        case LOCAL_GL_INT:
        case LOCAL_GL_FLOAT:
        case LOCAL_GL_BOOL:
        case LOCAL_GL_SAMPLER_2D:
        case LOCAL_GL_SAMPLER_CUBE:
            *unitSize = 1;
            break;
        case LOCAL_GL_INT_VEC2:
        case LOCAL_GL_FLOAT_VEC2:
        case LOCAL_GL_BOOL_VEC2:
            *unitSize = 2;
            break;
        case LOCAL_GL_INT_VEC3:
        case LOCAL_GL_FLOAT_VEC3:
        case LOCAL_GL_BOOL_VEC3:
            *unitSize = 3;
            break;
        case LOCAL_GL_INT_VEC4:
        case LOCAL_GL_FLOAT_VEC4:
        case LOCAL_GL_BOOL_VEC4:
            *unitSize = 4;
            break;
        case LOCAL_GL_FLOAT_MAT2:
            *unitSize = 4;
            break;
        case LOCAL_GL_FLOAT_MAT3:
            *unitSize = 9;
            break;
        case LOCAL_GL_FLOAT_MAT4:
            *unitSize = 16;
            break;
        default:
            return false;
    }

    return true;
}


int mozilla::GetWebGLTexelFormat(GLenum format, GLenum type)
{
    if (type == LOCAL_GL_UNSIGNED_BYTE) {
        switch (format) {
            case LOCAL_GL_RGBA:
                return WebGLTexelFormat::RGBA8;
            case LOCAL_GL_RGB:
                return WebGLTexelFormat::RGB8;
            case LOCAL_GL_ALPHA:
                return WebGLTexelFormat::A8;
            case LOCAL_GL_LUMINANCE:
                return WebGLTexelFormat::R8;
            case LOCAL_GL_LUMINANCE_ALPHA:
                return WebGLTexelFormat::RA8;
            default:
                NS_ASSERTION(false, "Coding mistake?! Should never reach this point.");
                return WebGLTexelFormat::Generic;
        }
    } else if (type == LOCAL_GL_FLOAT) {
        // OES_texture_float
        switch (format) {
            case LOCAL_GL_RGBA:
                return WebGLTexelFormat::RGBA32F;
            case LOCAL_GL_RGB:
                return WebGLTexelFormat::RGB32F;
            case LOCAL_GL_ALPHA:
                return WebGLTexelFormat::A32F;
            case LOCAL_GL_LUMINANCE:
                return WebGLTexelFormat::R32F;
            case LOCAL_GL_LUMINANCE_ALPHA:
                return WebGLTexelFormat::RA32F;
            default:
                NS_ASSERTION(false, "Coding mistake?! Should never reach this point.");
                return WebGLTexelFormat::Generic;
        }
    } else {
        switch (type) {
            case LOCAL_GL_UNSIGNED_SHORT_4_4_4_4:
                return WebGLTexelFormat::RGBA4444;
            case LOCAL_GL_UNSIGNED_SHORT_5_5_5_1:
                return WebGLTexelFormat::RGBA5551;
            case LOCAL_GL_UNSIGNED_SHORT_5_6_5:
                return WebGLTexelFormat::RGB565;
            default:
                NS_ASSERTION(false, "Coding mistake?! Should never reach this point.");
                return WebGLTexelFormat::Generic;
        }
    }
}

WebGLenum
InternalFormatForFormatAndType(WebGLenum format, WebGLenum type, bool isGLES2)
{
    // ES2 requires that format == internalformat; floating-point is
    // indicated purely by the type that's loaded.  For desktop GL, we
    // have to specify a floating point internal format.
    if (isGLES2)
        return format;

    switch (type) {
    case LOCAL_GL_UNSIGNED_BYTE:
    case LOCAL_GL_UNSIGNED_SHORT_4_4_4_4:
    case LOCAL_GL_UNSIGNED_SHORT_5_5_5_1:
    case LOCAL_GL_UNSIGNED_SHORT_5_6_5:
        return format;

    case LOCAL_GL_FLOAT:
        switch (format) {
        case LOCAL_GL_RGBA:
            return LOCAL_GL_RGBA32F_ARB;
        case LOCAL_GL_RGB:
            return LOCAL_GL_RGB32F_ARB;
        case LOCAL_GL_ALPHA:
            return LOCAL_GL_ALPHA32F_ARB;
        case LOCAL_GL_LUMINANCE:
            return LOCAL_GL_LUMINANCE32F_ARB;
        case LOCAL_GL_LUMINANCE_ALPHA:
            return LOCAL_GL_LUMINANCE_ALPHA32F_ARB;
        }
        break;

    default:
        break;
    }

    NS_ASSERTION(false, "Coding mistake -- bad format/type passed?");
    return 0;
}