/* -*- 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
 * the Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Vladimir Vukicevic <vladimir@pobox.com>
 *   Mark Steele <mwsteele@gmail.com>
 *   Bas Schouten <bschouten@mozilla.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 <string.h>
#include <stdio.h>

#include "prlink.h"
#include "prenv.h"

#include "nsThreadUtils.h"

#include "gfxPlatform.h"
#include "GLContext.h"
#include "GLContextProvider.h"

#include "gfxCrashReporterUtils.h"

namespace mozilla {
namespace gl {

#ifdef DEBUG
// see comment near declaration in GLContext.h. Should be thread-local.
GLContext* GLContext::sCurrentGLContext = nsnull;
#endif

// define this here since it's global to GLContextProvider, not any
// specific implementation
const ContextFormat ContextFormat::BasicRGBA32Format(ContextFormat::BasicRGBA32);

#define MAX_SYMBOL_LENGTH 128
#define MAX_SYMBOL_NAMES 5

PRBool
LibrarySymbolLoader::OpenLibrary(const char *library)
{
    PRLibSpec lspec;
    lspec.type = PR_LibSpec_Pathname;
    lspec.value.pathname = library;

    mLibrary = PR_LoadLibraryWithFlags(lspec, PR_LD_LAZY | PR_LD_LOCAL);
    if (!mLibrary)
        return PR_FALSE;

    return PR_TRUE;
}

PRBool
LibrarySymbolLoader::LoadSymbols(SymLoadStruct *firstStruct, PRBool tryplatform, const char *prefix)
{
    return LoadSymbols(mLibrary, firstStruct, tryplatform ? mLookupFunc : nsnull, prefix);
}

PRFuncPtr
LibrarySymbolLoader::LookupSymbol(PRLibrary *lib,
                                  const char *sym,
                                  PlatformLookupFunction lookupFunction)
{
    PRFuncPtr res = 0;

    // try finding it in the library directly, if we have one
    if (lib) {
        res = PR_FindFunctionSymbol(lib, sym);
    }

    // then try looking it up via the lookup symbol
    if (!res && lookupFunction) {
        res = lookupFunction(sym);
    }

    // finally just try finding it in the process
    if (!res) {
        PRLibrary *leakedLibRef;
        res = PR_FindFunctionSymbolAndLibrary(sym, &leakedLibRef);
    }

    return res;
}

PRBool
LibrarySymbolLoader::LoadSymbols(PRLibrary *lib,
                                 SymLoadStruct *firstStruct,
                                 PlatformLookupFunction lookupFunction,
                                 const char *prefix)
{
    char sbuf[MAX_SYMBOL_LENGTH * 2];
    int failCount = 0;

    SymLoadStruct *ss = firstStruct;
    while (ss->symPointer) {
        *ss->symPointer = 0;

        for (int i = 0; i < MAX_SYMBOL_NAMES; i++) {
            if (ss->symNames[i] == nsnull)
                break;

            const char *s = ss->symNames[i];
            if (prefix && *prefix != 0) {
                strcpy(sbuf, prefix);
                strcat(sbuf, ss->symNames[i]);
                s = sbuf;
            }

            PRFuncPtr p = LookupSymbol(lib, s, lookupFunction);
            if (p) {
                *ss->symPointer = p;
                break;
            }
        }

        if (*ss->symPointer == 0) {
            fprintf (stderr, "Can't find symbol '%s'\n", ss->symNames[0]);
            failCount++;
        }

        ss++;
    }

    return failCount == 0 ? PR_TRUE : PR_FALSE;
}

/*
 * XXX - we should really know the ARB/EXT variants of these
 * instead of only handling the symbol if it's exposed directly.
 */

PRBool
GLContext::InitWithPrefix(const char *prefix, PRBool trygl)
{
    ScopedGfxFeatureReporter reporter("GL Context");

    if (mInitialized) {
        reporter.SetSuccessful();
        return PR_TRUE;
    }

    SymLoadStruct symbols[] = {
        { (PRFuncPtr*) &mSymbols.fActiveTexture, { "ActiveTexture", "ActiveTextureARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fAttachShader, { "AttachShader", "AttachShaderARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fBindAttribLocation, { "BindAttribLocation", "BindAttribLocationARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fBindBuffer, { "BindBuffer", "BindBufferARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fBindTexture, { "BindTexture", "BindTextureARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fBlendColor, { "BlendColor", NULL } },
        { (PRFuncPtr*) &mSymbols.fBlendEquation, { "BlendEquation", NULL } },
        { (PRFuncPtr*) &mSymbols.fBlendEquationSeparate, { "BlendEquationSeparate", "BlendEquationSeparateEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fBlendFunc, { "BlendFunc", NULL } },
        { (PRFuncPtr*) &mSymbols.fBlendFuncSeparate, { "BlendFuncSeparate", "BlendFuncSeparateEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fBufferData, { "BufferData", NULL } },
        { (PRFuncPtr*) &mSymbols.fBufferSubData, { "BufferSubData", NULL } },
        { (PRFuncPtr*) &mSymbols.fClear, { "Clear", NULL } },
        { (PRFuncPtr*) &mSymbols.fClearColor, { "ClearColor", NULL } },
        { (PRFuncPtr*) &mSymbols.fClearStencil, { "ClearStencil", NULL } },
        { (PRFuncPtr*) &mSymbols.fColorMask, { "ColorMask", NULL } },
        { (PRFuncPtr*) &mSymbols.fCullFace, { "CullFace", NULL } },
        { (PRFuncPtr*) &mSymbols.fDetachShader, { "DetachShader", "DetachShaderARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fDepthFunc, { "DepthFunc", NULL } },
        { (PRFuncPtr*) &mSymbols.fDepthMask, { "DepthMask", NULL } },
        { (PRFuncPtr*) &mSymbols.fDisable, { "Disable", NULL } },
        { (PRFuncPtr*) &mSymbols.fDisableVertexAttribArray, { "DisableVertexAttribArray", "DisableVertexAttribArrayARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fDrawArrays, { "DrawArrays", NULL } },
        { (PRFuncPtr*) &mSymbols.fDrawElements, { "DrawElements", NULL } },
        { (PRFuncPtr*) &mSymbols.fEnable, { "Enable", NULL } },
        { (PRFuncPtr*) &mSymbols.fEnableVertexAttribArray, { "EnableVertexAttribArray", "EnableVertexAttribArrayARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fFinish, { "Finish", NULL } },
        { (PRFuncPtr*) &mSymbols.fFlush, { "Flush", NULL } },
        { (PRFuncPtr*) &mSymbols.fFrontFace, { "FrontFace", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetActiveAttrib, { "GetActiveAttrib", "GetActiveAttribARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetActiveUniform, { "GetActiveUniform", "GetActiveUniformARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetAttachedShaders, { "GetAttachedShaders", "GetAttachedShadersARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetAttribLocation, { "GetAttribLocation", "GetAttribLocationARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetIntegerv, { "GetIntegerv", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetFloatv, { "GetFloatv", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetBooleanv, { "GetBooleanv", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetBufferParameteriv, { "GetBufferParameteriv", "GetBufferParameterivARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetError, { "GetError", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetProgramiv, { "GetProgramiv", "GetProgramivARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetProgramInfoLog, { "GetProgramInfoLog", "GetProgramInfoLogARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fTexParameteri, { "TexParameteri", NULL } },
        { (PRFuncPtr*) &mSymbols.fTexParameterf, { "TexParameterf", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetString, { "GetString", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetTexParameterfv, { "GetTexParameterfv", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetTexParameteriv, { "GetTexParameteriv", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetUniformfv, { "GetUniformfv", "GetUniformfvARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetUniformiv, { "GetUniformiv", "GetUniformivARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetUniformLocation, { "GetUniformLocation", "GetUniformLocationARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetVertexAttribfv, { "GetVertexAttribfv", "GetVertexAttribfvARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetVertexAttribiv, { "GetVertexAttribiv", "GetVertexAttribivARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fHint, { "Hint", NULL } },
        { (PRFuncPtr*) &mSymbols.fIsBuffer, { "IsBuffer", "IsBufferARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fIsEnabled, { "IsEnabled", NULL } },
        { (PRFuncPtr*) &mSymbols.fIsProgram, { "IsProgram", "IsProgramARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fIsShader, { "IsShader", "IsShaderARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fIsTexture, { "IsTexture", "IsTextureARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fLineWidth, { "LineWidth", NULL } },
        { (PRFuncPtr*) &mSymbols.fLinkProgram, { "LinkProgram", "LinkProgramARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fPixelStorei, { "PixelStorei", NULL } },
        { (PRFuncPtr*) &mSymbols.fPolygonOffset, { "PolygonOffset", NULL } },
        { (PRFuncPtr*) &mSymbols.fReadPixels, { "ReadPixels", NULL } },
        { (PRFuncPtr*) &mSymbols.fSampleCoverage, { "SampleCoverage", NULL } },
        { (PRFuncPtr*) &mSymbols.fScissor, { "Scissor", NULL } },
        { (PRFuncPtr*) &mSymbols.fStencilFunc, { "StencilFunc", NULL } },
        { (PRFuncPtr*) &mSymbols.fStencilFuncSeparate, { "StencilFuncSeparate", "StencilFuncSeparateEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fStencilMask, { "StencilMask", NULL } },
        { (PRFuncPtr*) &mSymbols.fStencilMaskSeparate, { "StencilMaskSeparate", "StencilMaskSeparateEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fStencilOp, { "StencilOp", NULL } },
        { (PRFuncPtr*) &mSymbols.fStencilOpSeparate, { "StencilOpSeparate", "StencilOpSeparateEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fTexImage2D, { "TexImage2D", NULL } },
        { (PRFuncPtr*) &mSymbols.fTexSubImage2D, { "TexSubImage2D", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform1f, { "Uniform1f", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform1fv, { "Uniform1fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform1i, { "Uniform1i", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform1iv, { "Uniform1iv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform2f, { "Uniform2f", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform2fv, { "Uniform2fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform2i, { "Uniform2i", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform2iv, { "Uniform2iv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform3f, { "Uniform3f", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform3fv, { "Uniform3fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform3i, { "Uniform3i", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform3iv, { "Uniform3iv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform4f, { "Uniform4f", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform4fv, { "Uniform4fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform4i, { "Uniform4i", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniform4iv, { "Uniform4iv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniformMatrix2fv, { "UniformMatrix2fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniformMatrix3fv, { "UniformMatrix3fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUniformMatrix4fv, { "UniformMatrix4fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fUseProgram, { "UseProgram", NULL } },
        { (PRFuncPtr*) &mSymbols.fValidateProgram, { "ValidateProgram", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttribPointer, { "VertexAttribPointer", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib1f, { "VertexAttrib1f", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib2f, { "VertexAttrib2f", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib3f, { "VertexAttrib3f", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib4f, { "VertexAttrib4f", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib1fv, { "VertexAttrib1fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib2fv, { "VertexAttrib2fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib3fv, { "VertexAttrib3fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib4fv, { "VertexAttrib4fv", NULL } },
        { (PRFuncPtr*) &mSymbols.fViewport, { "Viewport", NULL } },
        { (PRFuncPtr*) &mSymbols.fCompileShader, { "CompileShader", NULL } },
        { (PRFuncPtr*) &mSymbols.fCopyTexImage2D, { "CopyTexImage2D", NULL } },
        { (PRFuncPtr*) &mSymbols.fCopyTexSubImage2D, { "CopyTexSubImage2D", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetShaderiv, { "GetShaderiv", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetShaderInfoLog, { "GetShaderInfoLog", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetShaderSource, { "GetShaderSource", NULL } },
        { (PRFuncPtr*) &mSymbols.fShaderSource, { "ShaderSource", NULL } },
        { (PRFuncPtr*) &mSymbols.fVertexAttribPointer, { "VertexAttribPointer", NULL } },
        { (PRFuncPtr*) &mSymbols.fBindFramebuffer, { "BindFramebuffer", "BindFramebufferEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fBindRenderbuffer, { "BindRenderbuffer", "BindRenderbufferEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fCheckFramebufferStatus, { "CheckFramebufferStatus", "CheckFramebufferStatusEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fFramebufferRenderbuffer, { "FramebufferRenderbuffer", "FramebufferRenderbufferEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fFramebufferTexture2D, { "FramebufferTexture2D", "FramebufferTexture2DEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fGenerateMipmap, { "GenerateMipmap", "GenerateMipmapEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetFramebufferAttachmentParameteriv, { "GetFramebufferAttachmentParameteriv", "GetFramebufferAttachmentParameterivEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fGetRenderbufferParameteriv, { "GetRenderbufferParameteriv", "GetRenderbufferParameterivEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fIsFramebuffer, { "IsFramebuffer", "IsFramebufferEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fIsRenderbuffer, { "IsRenderbuffer", "IsRenderbufferEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fRenderbufferStorage, { "RenderbufferStorage", "RenderbufferStorageEXT", NULL } },

        { (PRFuncPtr*) &mSymbols.fGenBuffers, { "GenBuffers", "GenBuffersARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGenTextures, { "GenTextures", NULL } },
        { (PRFuncPtr*) &mSymbols.fCreateProgram, { "CreateProgram", "CreateProgramARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fCreateShader, { "CreateShader", "CreateShaderARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fGenFramebuffers, { "GenFramebuffers", "GenFramebuffersEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fGenRenderbuffers, { "GenRenderbuffers", "GenRenderbuffersEXT", NULL } },

        { (PRFuncPtr*) &mSymbols.fDeleteBuffers, { "DeleteBuffers", "DeleteBuffersARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fDeleteTextures, { "DeleteTextures", "DeleteTexturesARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fDeleteProgram, { "DeleteProgram", "DeleteProgramARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fDeleteShader, { "DeleteShader", "DeleteShaderARB", NULL } },
        { (PRFuncPtr*) &mSymbols.fDeleteFramebuffers, { "DeleteFramebuffers", "DeleteFramebuffersEXT", NULL } },
        { (PRFuncPtr*) &mSymbols.fDeleteRenderbuffers, { "DeleteRenderbuffers", "DeleteRenderbuffersEXT", NULL } },

        { mIsGLES2 ? (PRFuncPtr*) &mSymbols.fClearDepthf : (PRFuncPtr*) &mSymbols.fClearDepth,
          { mIsGLES2 ? "ClearDepthf" : "ClearDepth", NULL } },
        { mIsGLES2 ? (PRFuncPtr*) &mSymbols.fDepthRangef : (PRFuncPtr*) &mSymbols.fDepthRange,
          { mIsGLES2 ? "DepthRangef" : "DepthRange", NULL } },

        // XXX FIXME -- we shouldn't be using glReadBuffer!
        { mIsGLES2 ? (PRFuncPtr*) NULL : (PRFuncPtr*) &mSymbols.fReadBuffer,
          { mIsGLES2 ? NULL : "ReadBuffer", NULL } },

        { mIsGLES2 ? (PRFuncPtr*) NULL : (PRFuncPtr*) &mSymbols.fMapBuffer,
          { mIsGLES2 ? NULL : "MapBuffer", NULL } },
        { mIsGLES2 ? (PRFuncPtr*) NULL : (PRFuncPtr*) &mSymbols.fUnmapBuffer,
          { mIsGLES2 ? NULL : "UnmapBuffer", NULL } },

        { NULL, { NULL } },

    };

    mInitialized = LoadSymbols(&symbols[0], trygl, prefix);

    const char *glVendorString;

    if (mInitialized) {
        glVendorString = (const char *)fGetString(LOCAL_GL_VENDOR);
        const char *vendorMatchStrings[VendorOther] = {
                "Intel",
                "NVIDIA",
                "ATI",
                "Qualcomm"
        };
        mVendor = VendorOther;
        for (int i = 0; i < VendorOther; ++i) {
            if (DoesVendorStringMatch(glVendorString, vendorMatchStrings[i])) {
                mVendor = i;
                break;
            }
        }
    }

    if (mInitialized) {
#ifdef DEBUG
        static bool once = false;
        if (!once) {
            const char *vendors[VendorOther] = {
                "Intel",
                "NVIDIA",
                "ATI",
                "Qualcomm"
            };

            once = true;
            if (mVendor < VendorOther) {
                printf_stderr("OpenGL vendor ('%s') recognized as: %s\n",
                              glVendorString, vendors[mVendor]);
            } else {
                printf_stderr("OpenGL vendor ('%s') unrecognized\n", glVendorString);
            }
        }
#endif

        InitExtensions();

        NS_ASSERTION(!IsExtensionSupported(GLContext::ARB_pixel_buffer_object) ||
                     (mSymbols.fMapBuffer && mSymbols.fUnmapBuffer),
                     "ARB_pixel_buffer_object supported without glMapBuffer/UnmapBuffer being available!");

        GLint v[4];

        fGetIntegerv(LOCAL_GL_SCISSOR_BOX, v);
        mScissorStack.AppendElement(nsIntRect(v[0], v[1], v[2], v[3]));

        fGetIntegerv(LOCAL_GL_VIEWPORT, v);
        mViewportStack.AppendElement(nsIntRect(v[0], v[1], v[2], v[3]));

        fGetIntegerv(LOCAL_GL_MAX_TEXTURE_SIZE, &mMaxTextureSize);

        UpdateActualFormat();
    }

#ifdef DEBUG
    if (PR_GetEnv("MOZ_GL_DEBUG"))
        mDebugMode |= DebugEnabled;

    // enables extra verbose output, informing of the start and finish of every GL call.
    // useful e.g. to record information to investigate graphics system crashes/lockups
    if (PR_GetEnv("MOZ_GL_DEBUG_VERBOSE"))
        mDebugMode |= DebugTrace;

    // aborts on GL error. Can be useful to debug quicker code that is known not to generate any GL error in principle.
    if (PR_GetEnv("MOZ_GL_DEBUG_ABORT_ON_ERROR"))
        mDebugMode |= DebugAbortOnError;
#endif

    if (mInitialized)
        reporter.SetSuccessful();
    else {
        // if initialization fails, ensure all symbols are zero, to avoid hard-to-understand bugs
        mSymbols.Zero();
    }

    return mInitialized;
}

// should match the order of GLExtensions
static const char *sExtensionNames[] = {
    "GL_EXT_framebuffer_object",
    "GL_ARB_framebuffer_object",
    "GL_ARB_texture_rectangle",
    "GL_EXT_bgra",
    "GL_EXT_texture_format_BGRA8888",
    "GL_OES_depth24",
    "GL_OES_depth32",
    "GL_OES_stencil8",
    "GL_OES_texture_npot",
    "GL_OES_depth_texture",
    "GL_OES_packed_depth_stencil",
    "GL_IMG_read_format",
    "GL_EXT_read_format_bgra",
    "GL_APPLE_client_storage",
    "GL_ARB_texture_non_power_of_two",
    "GL_ARB_pixel_buffer_object",
    "GL_ARB_ES2_compatibility",
    NULL
};

void
GLContext::InitExtensions()
{
    MakeCurrent();
    const GLubyte *extensions = fGetString(LOCAL_GL_EXTENSIONS);
    char *exts = strdup((char *)extensions);

#ifdef DEBUG
    static bool once = false;
#else
    const bool once = true;
#endif

    if (!once) {
        printf_stderr("GL extensions: %s\n", exts);
    }

    char *s = exts;
    bool done = false;
    while (!done) {
        char *space = strchr(s, ' ');
        if (space) {
            *space = '\0';
        } else {
            done = true;
        }

        for (int i = 0; sExtensionNames[i]; ++i) {
            if (strcmp(s, sExtensionNames[i]) == 0) {
                if (!once) {
                    printf_stderr("Found extension %s\n", s);
                }
                mAvailableExtensions[i] = 1;
            }
        }

        s = space+1;
    }

    free(exts);

#ifdef DEBUG
    once = true;
#endif
}

PRBool
GLContext::IsExtensionSupported(const char *extension)
{
    return ListHasExtension(fGetString(LOCAL_GL_EXTENSIONS), extension);
}

// Common code for checking for both GL extensions and GLX extensions.
PRBool
GLContext::ListHasExtension(const GLubyte *extensions, const char *extension)
{
    // fix bug 612572 - we were crashing as we were calling this function with extensions==null
    if (extensions == nsnull || extension == nsnull)
        return PR_FALSE;

    const GLubyte *start;
    GLubyte *where, *terminator;

    /* Extension names should not have spaces. */
    where = (GLubyte *) strchr(extension, ' ');
    if (where || *extension == '\0')
        return PR_FALSE;

    /* 
     * It takes a bit of care to be fool-proof about parsing the
     * OpenGL extensions string. Don't be fooled by sub-strings,
     * etc. 
     */
    start = extensions;
    for (;;) {
        where = (GLubyte *) strstr((const char *) start, extension);
        if (!where) {
            break;
        }
        terminator = where + strlen(extension);
        if (where == start || *(where - 1) == ' ') {
            if (*terminator == ' ' || *terminator == '\0') {
                return PR_TRUE;
            }
        }
        start = terminator;
    }
    return PR_FALSE;
}

already_AddRefed<TextureImage>
GLContext::CreateTextureImage(const nsIntSize& aSize,
                              TextureImage::ContentType aContentType,
                              GLenum aWrapMode,
                              PRBool aUseNearestFilter)
{
    MakeCurrent();

    GLuint texture;
    fGenTextures(1, &texture);

    fActiveTexture(LOCAL_GL_TEXTURE0);
    fBindTexture(LOCAL_GL_TEXTURE_2D, texture);

    GLint texfilter = aUseNearestFilter ? LOCAL_GL_NEAREST : LOCAL_GL_LINEAR;
    fTexParameteri(LOCAL_GL_TEXTURE_2D, LOCAL_GL_TEXTURE_MIN_FILTER, texfilter);
    fTexParameteri(LOCAL_GL_TEXTURE_2D, LOCAL_GL_TEXTURE_MAG_FILTER, texfilter);
    fTexParameteri(LOCAL_GL_TEXTURE_2D, LOCAL_GL_TEXTURE_WRAP_S, aWrapMode);
    fTexParameteri(LOCAL_GL_TEXTURE_2D, LOCAL_GL_TEXTURE_WRAP_T, aWrapMode);

    return CreateBasicTextureImage(texture, aSize, aWrapMode, aContentType, this);
}

BasicTextureImage::~BasicTextureImage()
{
    GLContext *ctx = mGLContext;
    if (ctx->IsDestroyed() || !NS_IsMainThread()) {
        ctx = ctx->GetSharedContext();
    }

    // If we have a context, then we need to delete the texture;
    // if we don't have a context (either real or shared),
    // then they went away when the contex was deleted, because it
    // was the only one that had access to it.
    if (ctx && !ctx->IsDestroyed()) {
        mGLContext->MakeCurrent();
        mGLContext->fDeleteTextures(1, &mTexture);
    }
}

gfxASurface*
BasicTextureImage::BeginUpdate(nsIntRegion& aRegion)
{
    NS_ASSERTION(!mUpdateSurface, "BeginUpdate() without EndUpdate()?");

    // determine the region the client will need to repaint
    ImageFormat format =
        (GetContentType() == gfxASurface::CONTENT_COLOR) ?
        gfxASurface::ImageFormatRGB24 : gfxASurface::ImageFormatARGB32;
    if (mTextureState != Valid)
    {
        // if the texture hasn't been initialized yet, or something important
        // changed, we need to recreate our backing surface and force the
        // client to paint everything
        mUpdateRegion = nsIntRect(nsIntPoint(0, 0), mSize);
    } else {
        mUpdateRegion = aRegion;
    }

    aRegion = mUpdateRegion;

    nsIntRect rgnSize = mUpdateRegion.GetBounds();
    if (!nsIntRect(nsIntPoint(0, 0), mSize).Contains(rgnSize)) {
        NS_ERROR("update outside of image");
        return NULL;
    }

    mUpdateSurface = 
        GetSurfaceForUpdate(gfxIntSize(rgnSize.width, rgnSize.height), format);

    if (!mUpdateSurface || mUpdateSurface->CairoStatus()) {
        mUpdateSurface = NULL;
        return NULL;
    }

    mUpdateSurface->SetDeviceOffset(gfxPoint(-rgnSize.x, -rgnSize.y));

    return mUpdateSurface;
}

void
BasicTextureImage::EndUpdate()
{
    NS_ASSERTION(!!mUpdateSurface, "EndUpdate() without BeginUpdate()?");

    // FIXME: this is the slow boat.  Make me fast (with GLXPixmap?).

    // Undo the device offset that BeginUpdate set; doesn't much matter for us here,
    // but important if we ever do anything directly with the surface.
    mUpdateSurface->SetDeviceOffset(gfxPoint(0, 0));

    bool relative = FinishedSurfaceUpdate();

    mShaderType =
        mGLContext->UploadSurfaceToTexture(mUpdateSurface,
                                           mUpdateRegion,
                                           mTexture,
                                           mTextureState == Created,
                                           mUpdateOffset,
                                           relative);
    FinishedSurfaceUpload();

    mUpdateSurface = nsnull;
    mTextureState = Valid;
}

void
BasicTextureImage::BindTexture(GLenum aTextureUnit)
{
    mGLContext->fActiveTexture(aTextureUnit);
    mGLContext->fBindTexture(LOCAL_GL_TEXTURE_2D, Texture());
    mGLContext->fActiveTexture(LOCAL_GL_TEXTURE0);
}

already_AddRefed<gfxASurface>
BasicTextureImage::GetSurfaceForUpdate(const gfxIntSize& aSize, ImageFormat aFmt)
{
    return gfxPlatform::GetPlatform()->
        CreateOffscreenSurface(aSize, gfxASurface::ContentFromFormat(aFmt));
}

bool
BasicTextureImage::FinishedSurfaceUpdate()
{
    return false;
}

void
BasicTextureImage::FinishedSurfaceUpload()
{
}

bool 
BasicTextureImage::DirectUpdate(gfxASurface *aSurf, const nsIntRegion& aRegion)
{
    nsIntRect bounds = aRegion.GetBounds();
    nsIntRegion region;
    if (mTextureState != Valid) {
        bounds = nsIntRect(0, 0, mSize.width, mSize.height);
        region = nsIntRegion(bounds);
    } else {
        region = aRegion;
    }

    mShaderType =
        mGLContext->UploadSurfaceToTexture(aSurf,
                                           region,
                                           mTexture,
                                           mTextureState == Created,
                                           bounds.TopLeft(),
                                           PR_FALSE);
    mTextureState = Valid;
    return true;
}

void
BasicTextureImage::Resize(const nsIntSize& aSize)
{
    NS_ASSERTION(!mUpdateSurface, "Resize() while in update?");

    mGLContext->fBindTexture(LOCAL_GL_TEXTURE_2D, mTexture);

    mGLContext->fTexImage2D(LOCAL_GL_TEXTURE_2D,
                            0,
                            LOCAL_GL_RGBA,
                            aSize.width,
                            aSize.height,
                            0,
                            LOCAL_GL_RGBA,
                            LOCAL_GL_UNSIGNED_BYTE,
                            NULL);

    mTextureState = Allocated;
    mSize = aSize;
}

PRBool
GLContext::ResizeOffscreenFBO(const gfxIntSize& aSize)
{
    MakeCurrent();

    bool alpha = mCreationFormat.alpha > 0;
    int depth = mCreationFormat.depth;
    int stencil = mCreationFormat.stencil;

    bool firstTime = (mOffscreenFBO == 0);

    GLuint curBoundTexture = 0;
    GLuint curBoundRenderbuffer = 0;
    GLuint curBoundFramebuffer = 0;

    GLint viewport[4];

    bool useDepthStencil =
        !mIsGLES2 || IsExtensionSupported(OES_packed_depth_stencil);

    // save a few things for later restoring
    fGetIntegerv(LOCAL_GL_TEXTURE_BINDING_2D, (GLint*) &curBoundTexture);
    fGetIntegerv(LOCAL_GL_FRAMEBUFFER_BINDING, (GLint*) &curBoundFramebuffer);
    fGetIntegerv(LOCAL_GL_RENDERBUFFER_BINDING, (GLint*) &curBoundRenderbuffer);
    fGetIntegerv(LOCAL_GL_VIEWPORT, viewport);

    // the context format of what we're defining;
    // for some reason, UpdateActualFormat isn't working with a bound FBO.
    ContextFormat cf;

    // If this is the first time we're going through this, we need
    // to create the objects we'll use.  Otherwise, just bind them.
    if (firstTime) {
        fGenTextures(1, &mOffscreenTexture);
        fBindTexture(LOCAL_GL_TEXTURE_2D, mOffscreenTexture);
        fTexParameteri(LOCAL_GL_TEXTURE_2D, LOCAL_GL_TEXTURE_MIN_FILTER, LOCAL_GL_LINEAR);
        fTexParameteri(LOCAL_GL_TEXTURE_2D, LOCAL_GL_TEXTURE_MAG_FILTER, LOCAL_GL_LINEAR);

        fGenFramebuffers(1, &mOffscreenFBO);
        fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, mOffscreenFBO);

        if (depth && stencil && useDepthStencil) {
            fGenRenderbuffers(1, &mOffscreenDepthRB);
        } else {
            if (depth) {
                fGenRenderbuffers(1, &mOffscreenDepthRB);
            }

            if (stencil) {
                fGenRenderbuffers(1, &mOffscreenStencilRB);
            }
        }
    } else {
        fBindTexture(LOCAL_GL_TEXTURE_2D, mOffscreenTexture);
        fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, mOffscreenFBO);
    }

    // resize the FBO components
    if (alpha) {
        fTexImage2D(LOCAL_GL_TEXTURE_2D,
                    0,
                    LOCAL_GL_RGBA,
                    aSize.width, aSize.height,
                    0,
                    LOCAL_GL_RGBA,
                    LOCAL_GL_UNSIGNED_BYTE,
                    NULL);

        cf.red = cf.green = cf.blue = cf.alpha = 8;
    } else {
        fTexImage2D(LOCAL_GL_TEXTURE_2D,
                    0,
                    LOCAL_GL_RGB,
                    aSize.width, aSize.height,
                    0,
                    LOCAL_GL_RGB,
#ifdef XP_WIN
                    LOCAL_GL_UNSIGNED_BYTE,
#else
                    mIsGLES2 ? LOCAL_GL_UNSIGNED_SHORT_5_6_5
                             : LOCAL_GL_UNSIGNED_BYTE,
#endif
                    NULL);

#ifdef XP_WIN
        cf.red = cf.green = cf.blue = 8;
#else
        cf.red = 5;
        cf.green = 6;
        cf.blue = 5;
#endif
        cf.alpha = 0;
    }

    if (depth && stencil && useDepthStencil) {
        fBindRenderbuffer(LOCAL_GL_RENDERBUFFER, mOffscreenDepthRB);
        fRenderbufferStorage(LOCAL_GL_RENDERBUFFER,
                             LOCAL_GL_DEPTH24_STENCIL8,
                             aSize.width, aSize.height);
        cf.depth = 24;
        cf.stencil = 8;
    } else {
        if (depth) {
            GLenum depthType;
            if (mIsGLES2) {
                if (IsExtensionSupported(OES_depth32)) {
                    depthType = LOCAL_GL_DEPTH_COMPONENT32;
                } else if (IsExtensionSupported(OES_depth24)) {
                    depthType = LOCAL_GL_DEPTH_COMPONENT24;
                } else {
                    depthType = LOCAL_GL_DEPTH_COMPONENT16;
                }
            } else {
                depthType = LOCAL_GL_DEPTH_COMPONENT24;
            }

            fBindRenderbuffer(LOCAL_GL_RENDERBUFFER, mOffscreenDepthRB);
            fRenderbufferStorage(LOCAL_GL_RENDERBUFFER,
                                 mIsGLES2 ? LOCAL_GL_DEPTH_COMPONENT16
                                          : LOCAL_GL_DEPTH_COMPONENT24,
                                 aSize.width, aSize.height);
            cf.depth = mIsGLES2 ? 16 : 24;
        }

        if (stencil) {
            fBindRenderbuffer(LOCAL_GL_RENDERBUFFER, mOffscreenStencilRB);
            fRenderbufferStorage(LOCAL_GL_RENDERBUFFER,
                                 LOCAL_GL_STENCIL_INDEX8,
                                 aSize.width, aSize.height);
            cf.stencil = 8;
        }
    }

    // Now assemble the FBO, if we're creating one
    // for the first time.
    if (firstTime) {
        fFramebufferTexture2D(LOCAL_GL_FRAMEBUFFER,
                              LOCAL_GL_COLOR_ATTACHMENT0,
                              LOCAL_GL_TEXTURE_2D,
                              mOffscreenTexture,
                              0);

        if (depth && stencil && useDepthStencil) {
            fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                     LOCAL_GL_DEPTH_ATTACHMENT,
                                     LOCAL_GL_RENDERBUFFER,
                                     mOffscreenDepthRB);
            fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                     LOCAL_GL_STENCIL_ATTACHMENT,
                                     LOCAL_GL_RENDERBUFFER,
                                     mOffscreenDepthRB);
        } else {
            if (depth) {
                fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                         LOCAL_GL_DEPTH_ATTACHMENT,
                                         LOCAL_GL_RENDERBUFFER,
                                         mOffscreenDepthRB);
            }

            if (stencil) {
                fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                         LOCAL_GL_STENCIL_ATTACHMENT,
                                         LOCAL_GL_RENDERBUFFER,
                                         mOffscreenStencilRB);
            }
        }
    }

    // We should be all resized.  Check for framebuffer completeness.
    GLenum status = fCheckFramebufferStatus(LOCAL_GL_FRAMEBUFFER);
    if (status != LOCAL_GL_FRAMEBUFFER_COMPLETE) {
        NS_WARNING("Error resizing offscreen framebuffer -- framebuffer not complete");
        return PR_FALSE;
    }

    mOffscreenSize = aSize;
    mOffscreenActualSize = aSize;

    if (firstTime) {
        // UpdateActualFormat() doesn't work for some reason, with a
        // FBO bound, even though it should.
        //UpdateActualFormat();
        mActualFormat = cf;

#ifdef DEBUG
        printf_stderr("Created offscreen FBO: r: %d g: %d b: %d a: %d depth: %d stencil: %d\n",
                      mActualFormat.red, mActualFormat.green, mActualFormat.blue, mActualFormat.alpha,
                      mActualFormat.depth, mActualFormat.stencil);
#endif
    }

    // We're good, and the framebuffer is already attached, so let's
    // clear out our new framebuffer; otherwise we'll end up displaying
    // random memory.  We saved all of these things earlier so that we
    // can restore them.
    fViewport(0, 0, aSize.width, aSize.height);

    // Clear the new framebuffer with the full viewport
    ClearSafely();

    // Ok, now restore the GL state back to what it was before the resize took place.
    fBindTexture(LOCAL_GL_TEXTURE_2D, curBoundTexture);
    fBindRenderbuffer(LOCAL_GL_RENDERBUFFER, curBoundRenderbuffer);
    fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, curBoundFramebuffer);

    // -don't- restore the viewport the first time through this, since
    // the previous one isn't valid.
    if (!firstTime)
        fViewport(viewport[0], viewport[1], viewport[2], viewport[3]);

    return PR_TRUE;
}

void
GLContext::DeleteOffscreenFBO()
{
    fDeleteFramebuffers(1, &mOffscreenFBO);
    fDeleteTextures(1, &mOffscreenTexture);
    fDeleteRenderbuffers(1, &mOffscreenDepthRB);
    fDeleteRenderbuffers(1, &mOffscreenStencilRB);

    mOffscreenFBO = 0;
    mOffscreenTexture = 0;
    mOffscreenDepthRB = 0;
    mOffscreenStencilRB = 0;
}

void
GLContext::ClearSafely()
{
    // bug 659349 --- we must be very careful here: clearing a GL framebuffer is nontrivial, relies on a lot of state,
    // and in the case of the backbuffer of a WebGL context, state is exposed to scripts.
    //
    // The code here is taken from WebGLContext::ForceClearFramebufferWithDefaultValues, but I didn't find a good way of
    // sharing code with it. WebGL's code is somewhat performance-critical as it is typically called on every frame, so
    // WebGL keeps track of GL state to avoid having to query it everytime, and also tries to only do work for actually
    // present buffers (e.g. stencil buffer). Doing that here seems like premature optimization,
    // as ClearSafely() is called only when e.g. a canvas is resized, not on every animation frame.

    realGLboolean scissorTestEnabled;
    realGLboolean ditherEnabled;
    realGLboolean colorWriteMask[4];
    realGLboolean depthWriteMask;
    GLint stencilWriteMaskFront, stencilWriteMaskBack;
    GLfloat colorClearValue[4];
    GLfloat depthClearValue;
    GLint stencilClearValue;

    // save current GL state
    fGetBooleanv(LOCAL_GL_SCISSOR_TEST, &scissorTestEnabled);
    fGetBooleanv(LOCAL_GL_DITHER, &ditherEnabled);
    fGetBooleanv(LOCAL_GL_COLOR_WRITEMASK, colorWriteMask);
    fGetBooleanv(LOCAL_GL_DEPTH_WRITEMASK, &depthWriteMask);
    fGetIntegerv(LOCAL_GL_STENCIL_WRITEMASK, &stencilWriteMaskFront);
    fGetIntegerv(LOCAL_GL_STENCIL_BACK_WRITEMASK, &stencilWriteMaskBack);
    fGetFloatv(LOCAL_GL_COLOR_CLEAR_VALUE, colorClearValue);
    fGetFloatv(LOCAL_GL_DEPTH_CLEAR_VALUE, &depthClearValue);
    fGetIntegerv(LOCAL_GL_STENCIL_CLEAR_VALUE, &stencilClearValue);

    // prepare GL state for clearing
    fDisable(LOCAL_GL_SCISSOR_TEST);
    fDisable(LOCAL_GL_DITHER);
    PushViewportRect(nsIntRect(0, 0, mOffscreenSize.width, mOffscreenSize.height));

    fColorMask(1, 1, 1, 1);
    fClearColor(0.f, 0.f, 0.f, 0.f);

    fDepthMask(1);
    fClearDepth(1.0f);

    fStencilMask(0xffffffff);
    fClearStencil(0);

    // do clear
    fClear(LOCAL_GL_COLOR_BUFFER_BIT |
           LOCAL_GL_DEPTH_BUFFER_BIT |
           LOCAL_GL_STENCIL_BUFFER_BIT);

    // restore GL state after clearing
    fColorMask(colorWriteMask[0],
               colorWriteMask[1],
               colorWriteMask[2],
               colorWriteMask[3]);
    fClearColor(colorClearValue[0],
                colorClearValue[1],
                colorClearValue[2],
                colorClearValue[3]);

    fDepthMask(depthWriteMask);
    fClearDepth(depthClearValue);

    fStencilMaskSeparate(LOCAL_GL_FRONT, stencilWriteMaskFront);
    fStencilMaskSeparate(LOCAL_GL_BACK, stencilWriteMaskBack);
    fClearStencil(stencilClearValue);

    PopViewportRect();

    if (ditherEnabled)
        fEnable(LOCAL_GL_DITHER);
    else
        fDisable(LOCAL_GL_DITHER);

    if (scissorTestEnabled)
        fEnable(LOCAL_GL_SCISSOR_TEST);
    else
        fDisable(LOCAL_GL_SCISSOR_TEST);

}

void
GLContext::UpdateActualFormat()
{
    ContextFormat nf;

    fGetIntegerv(LOCAL_GL_RED_BITS, (GLint*) &nf.red);
    fGetIntegerv(LOCAL_GL_GREEN_BITS, (GLint*) &nf.green);
    fGetIntegerv(LOCAL_GL_BLUE_BITS, (GLint*) &nf.blue);
    fGetIntegerv(LOCAL_GL_ALPHA_BITS, (GLint*) &nf.alpha);
    fGetIntegerv(LOCAL_GL_DEPTH_BITS, (GLint*) &nf.depth);
    fGetIntegerv(LOCAL_GL_STENCIL_BITS, (GLint*) &nf.stencil);

    mActualFormat = nf;
}

void
GLContext::MarkDestroyed()
{
    if (IsDestroyed())
        return;

    MakeCurrent();
    DeleteOffscreenFBO();

    fDeleteProgram(mBlitProgram);
    mBlitProgram = 0;
    fDeleteFramebuffers(1, &mBlitFramebuffer);
    mBlitFramebuffer = 0;

    mSymbols.Zero();
}

already_AddRefed<gfxImageSurface>
GLContext::ReadTextureImage(GLuint aTexture,
                            const gfxIntSize& aSize,
                            GLenum aTextureFormat)
{
    MakeCurrent();

    nsRefPtr<gfxImageSurface> isurf;

    GLint oldrb, oldfb, oldprog, oldPackAlignment;
    GLint success;

    GLuint rb = 0, fb = 0;
    GLuint vs = 0, fs = 0, prog = 0;

    const char *vShader =
        "attribute vec4 aVertex;\n"
        "attribute vec2 aTexCoord;\n"
        "varying vec2 vTexCoord;\n"
        "void main() { gl_Position = aVertex; vTexCoord = aTexCoord; }";
    const char *fShader =
        "#ifdef GL_ES\n"
        "precision mediump float;\n"
        "#endif\n"
        "varying vec2 vTexCoord;\n"
        "uniform sampler2D uTexture;\n"
        "void main() { gl_FragColor = texture2D(uTexture, vTexCoord); }";

    float verts[4*4] = {
        -1.0f, -1.0f, 0.0f, 1.0f,
         1.0f, -1.0f, 0.0f, 1.0f,
        -1.0f,  1.0f, 0.0f, 1.0f,
         1.0f,  1.0f, 0.0f, 1.0f
    };

    float texcoords[2*4] = {
        0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f
    };

    fGetIntegerv(LOCAL_GL_RENDERBUFFER_BINDING, &oldrb);
    fGetIntegerv(LOCAL_GL_FRAMEBUFFER_BINDING, &oldfb);
    fGetIntegerv(LOCAL_GL_CURRENT_PROGRAM, &oldprog);
    fGetIntegerv(LOCAL_GL_PACK_ALIGNMENT, &oldPackAlignment);

    PushViewportRect(nsIntRect(0, 0, aSize.width, aSize.height));

    fGenRenderbuffers(1, &rb);
    fBindRenderbuffer(LOCAL_GL_RENDERBUFFER, rb);
    fRenderbufferStorage(LOCAL_GL_RENDERBUFFER, LOCAL_GL_RGBA,
                         aSize.width, aSize.height);

    fGenFramebuffers(1, &fb);
    fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, fb);
    fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER, LOCAL_GL_COLOR_ATTACHMENT0,
                             LOCAL_GL_RENDERBUFFER, rb);

    if (fCheckFramebufferStatus(LOCAL_GL_FRAMEBUFFER) !=
        LOCAL_GL_FRAMEBUFFER_COMPLETE)
    {
        goto cleanup;
    }

    vs = fCreateShader(LOCAL_GL_VERTEX_SHADER);
    fs = fCreateShader(LOCAL_GL_FRAGMENT_SHADER);
    fShaderSource(vs, 1, (const GLchar**) &vShader, NULL);
    fShaderSource(fs, 1, (const GLchar**) &fShader, NULL);
    prog = fCreateProgram();
    fAttachShader(prog, vs);
    fAttachShader(prog, fs);
    fBindAttribLocation(prog, 0, "aVertex");
    fBindAttribLocation(prog, 1, "aTexCoord");
    fLinkProgram(prog);

    fGetProgramiv(prog, LOCAL_GL_LINK_STATUS, &success);
    if (!success) {
        goto cleanup;
    }

    fUseProgram(prog);

    fEnableVertexAttribArray(0);
    fEnableVertexAttribArray(1);

    fVertexAttribPointer(0, 4, LOCAL_GL_FLOAT, LOCAL_GL_FALSE, 0, verts);
    fVertexAttribPointer(1, 2, LOCAL_GL_FLOAT, LOCAL_GL_FALSE, 0, texcoords);

    fActiveTexture(LOCAL_GL_TEXTURE0);
    fBindTexture(LOCAL_GL_TEXTURE_2D, aTexture);

    fUniform1i(fGetUniformLocation(prog, "uTexture"), 0);

    fDrawArrays(LOCAL_GL_TRIANGLE_STRIP, 0, 4);

    fDisableVertexAttribArray(1);
    fDisableVertexAttribArray(0);

    isurf = new gfxImageSurface(aSize, gfxASurface::ImageFormatARGB32);
    if (!isurf || isurf->CairoStatus()) {
        isurf = nsnull;
        goto cleanup;
    }

    if (oldPackAlignment != 4)
        fPixelStorei(LOCAL_GL_PACK_ALIGNMENT, 4);

    fReadPixels(0, 0, aSize.width, aSize.height,
                LOCAL_GL_RGBA, LOCAL_GL_UNSIGNED_BYTE,
                isurf->Data());

    if (oldPackAlignment != 4)
        fPixelStorei(LOCAL_GL_PACK_ALIGNMENT, oldPackAlignment);

 cleanup:
    // note that deleting 0 has no effect in any of these calls
    fDeleteRenderbuffers(1, &rb);
    fDeleteFramebuffers(1, &fb);
    fDeleteShader(vs);
    fDeleteShader(fs);
    fDeleteProgram(prog);

    fBindRenderbuffer(LOCAL_GL_RENDERBUFFER, oldrb);
    fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, oldfb);
    fUseProgram(oldprog);

    PopViewportRect();

    return isurf.forget();
}

void
GLContext::ReadPixelsIntoImageSurface(GLint aX, GLint aY,
                                      GLsizei aWidth, GLsizei aHeight,
                                      gfxImageSurface *aDest)
{
    MakeCurrent();

    if (aDest->Format() != gfxASurface::ImageFormatARGB32 &&
        aDest->Format() != gfxASurface::ImageFormatRGB24)
    {
        NS_WARNING("ReadPixelsIntoImageSurface called with invalid image format");
        return;
    }

    if (aDest->Width() != aWidth ||
        aDest->Height() != aHeight ||
        aDest->Stride() != aWidth * 4)
    {
        NS_WARNING("ReadPixelsIntoImageSurface called with wrong size or stride surface");
        return;
    }

    GLint currentPackAlignment = 0;
    fGetIntegerv(LOCAL_GL_PACK_ALIGNMENT, &currentPackAlignment);
    fPixelStorei(LOCAL_GL_PACK_ALIGNMENT, 4);

    // defaults for desktop
    GLenum format = LOCAL_GL_BGRA;
    GLenum datatype = LOCAL_GL_UNSIGNED_INT_8_8_8_8_REV;
    bool swap = false;

    if (IsGLES2()) {
        datatype = LOCAL_GL_UNSIGNED_BYTE;

        if (IsExtensionSupported(gl::GLContext::EXT_read_format_bgra) ||
            IsExtensionSupported(gl::GLContext::IMG_read_format) ||
            IsExtensionSupported(gl::GLContext::EXT_bgra))
        {
            format = LOCAL_GL_BGRA;
        } else {
            format = LOCAL_GL_RGBA;
            swap = true;
        }
    }

    fReadPixels(0, 0, aWidth, aHeight,
                format, datatype,
                aDest->Data());

    if (swap) {
        // swap B and R bytes
        for (int j = 0; j < aHeight; ++j) {
            PRUint32 *row = (PRUint32*) (aDest->Data() + aDest->Stride() * j);
            for (int i = 0; i < aWidth; ++i) {
                *row = (*row & 0xff00ff00) | ((*row & 0xff) << 16) | ((*row & 0xff0000) >> 16);
                row++;
            }
        }
    }

    fPixelStorei(LOCAL_GL_PACK_ALIGNMENT, currentPackAlignment);
}

void
GLContext::BlitTextureImage(TextureImage *aSrc, const nsIntRect& aSrcRect,
                            TextureImage *aDst, const nsIntRect& aDstRect)
{
    NS_ASSERTION(!aSrc->InUpdate(), "Source texture is in update!");
    NS_ASSERTION(!aDst->InUpdate(), "Destination texture is in update!");

    // only save/restore this stuff on Qualcomm Adreno, to work
    // around an apparent bug
    int savedFb = 0;
    if (mVendor == VendorQualcomm) {
        fGetIntegerv(LOCAL_GL_FRAMEBUFFER_BINDING, &savedFb);
    }

    fDisable(LOCAL_GL_SCISSOR_TEST);
    fDisable(LOCAL_GL_BLEND);

    SetBlitFramebufferForDestTexture(aDst->Texture());

    UseBlitProgram();

    nsIntSize srcSize = aSrc->GetSize();
    nsIntSize dstSize = aDst->GetSize();

    PushViewportRect(nsIntRect(0, 0, dstSize.width, dstSize.height));

    float dx0 = 2.0 * float(aDstRect.x) / float(dstSize.width) - 1.0;
    float dy0 = 2.0 * float(aDstRect.y) / float(dstSize.height) - 1.0;
    float dx1 = 2.0 * float(aDstRect.x + aDstRect.width) / float(dstSize.width) - 1.0;
    float dy1 = 2.0 * float(aDstRect.y + aDstRect.height) / float(dstSize.height) - 1.0;

    RectTriangles rects;
    if (aSrc->GetWrapMode() == LOCAL_GL_REPEAT) {
        rects.addRect(/* dest rectangle */
                      dx0, dy0, dx1, dy1,
                      /* tex coords */
                      aSrcRect.x / float(srcSize.width),
                      aSrcRect.y / float(srcSize.height),
                      aSrcRect.XMost() / float(srcSize.width),
                      aSrcRect.YMost() / float(srcSize.height));
    } else {
        DecomposeIntoNoRepeatTriangles(aSrcRect, srcSize, rects);

        // now put the coords into the d[xy]0 .. d[xy]1 coordinate space
        // from the 0..1 that it comes out of decompose
        GLfloat *v = rects.vertexCoords;
        for (int i = 0; i < rects.numRects * 6; ++i) {
            v[i*2] = (v[i*2] * (dx1 - dx0)) + dx0;
            v[i*2+1] = (v[i*2+1] * (dy1 - dy0)) + dy0;
        }
    }


    fActiveTexture(LOCAL_GL_TEXTURE0);
    fBindTexture(LOCAL_GL_TEXTURE_2D, aSrc->Texture());

    fBindBuffer(LOCAL_GL_ARRAY_BUFFER, 0);

    fVertexAttribPointer(0, 2, LOCAL_GL_FLOAT, LOCAL_GL_FALSE, 0, rects.vertexCoords);
    fVertexAttribPointer(1, 2, LOCAL_GL_FLOAT, LOCAL_GL_FALSE, 0, rects.texCoords);

    fEnableVertexAttribArray(0);
    fEnableVertexAttribArray(1);

    fDrawArrays(LOCAL_GL_TRIANGLES, 0, rects.numRects * 6);

    fDisableVertexAttribArray(0);
    fDisableVertexAttribArray(1);

    fVertexAttribPointer(0, 2, LOCAL_GL_FLOAT, LOCAL_GL_FALSE, 0, NULL);
    fVertexAttribPointer(1, 2, LOCAL_GL_FLOAT, LOCAL_GL_FALSE, 0, NULL);

    // unbind the previous texture from the framebuffer
    SetBlitFramebufferForDestTexture(0);

    // then put back the previous framebuffer, and don't
    // enable stencil if it wasn't enabled on entry to work
    // around Adreno 200 bug that causes us to crash if
    // we enable scissor test while the current FBO is invalid
    // (which it will be, once we assign texture 0 to the color
    // attachment)
    if (mVendor == VendorQualcomm) {
        fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, savedFb);
    }

    fEnable(LOCAL_GL_SCISSOR_TEST);
    fEnable(LOCAL_GL_BLEND);

    PopViewportRect();
}

static unsigned int 
DataOffset(gfxImageSurface *aSurf, const nsIntPoint &aPoint)
{
  unsigned int data = aPoint.y * aSurf->Stride();
  data += aPoint.x * gfxASurface::BytePerPixelFromFormat(aSurf->Format());
  return data;
}

ShaderProgramType 
GLContext::UploadSurfaceToTexture(gfxASurface *aSurface, 
                                  const nsIntRegion& aDstRegion,
                                  GLuint& aTexture,
                                  bool aOverwrite,
                                  const nsIntPoint& aSrcPoint,
                                  bool aPixelBuffer)
{
    bool textureInited = aOverwrite ? false : true;
    MakeCurrent();
    fActiveTexture(LOCAL_GL_TEXTURE0);
  
    if (!aTexture) {
        fGenTextures(1, &aTexture);
        fBindTexture(LOCAL_GL_TEXTURE_2D, aTexture);
        fTexParameteri(LOCAL_GL_TEXTURE_2D, 
                       LOCAL_GL_TEXTURE_MIN_FILTER, 
                       LOCAL_GL_LINEAR);
        fTexParameteri(LOCAL_GL_TEXTURE_2D, 
                       LOCAL_GL_TEXTURE_MAG_FILTER, 
                       LOCAL_GL_LINEAR);
        fTexParameteri(LOCAL_GL_TEXTURE_2D, 
                       LOCAL_GL_TEXTURE_WRAP_S, 
                       LOCAL_GL_CLAMP_TO_EDGE);
        fTexParameteri(LOCAL_GL_TEXTURE_2D, 
                       LOCAL_GL_TEXTURE_WRAP_T, 
                       LOCAL_GL_CLAMP_TO_EDGE);
        textureInited = false;
    } else {
        fBindTexture(LOCAL_GL_TEXTURE_2D, aTexture);
    }

    nsIntRegion paintRegion;
    if (!textureInited) {
        paintRegion = nsIntRegion(aDstRegion.GetBounds());
    } else {
        paintRegion = aDstRegion;
    }

    nsRefPtr<gfxImageSurface> imageSurface = aSurface->GetAsImageSurface();
    unsigned char* data = NULL;

    if (!imageSurface || 
        (imageSurface->Format() != gfxASurface::ImageFormatARGB32 &&
         imageSurface->Format() != gfxASurface::ImageFormatRGB24 &&
         imageSurface->Format() != gfxASurface::ImageFormatRGB16_565)) {
        // We can't get suitable pixel data for the surface, make a copy
        nsIntRect bounds = aDstRegion.GetBounds();
        imageSurface = 
          new gfxImageSurface(gfxIntSize(bounds.width, bounds.height), 
                              gfxASurface::ImageFormatARGB32);
  
        nsRefPtr<gfxContext> context = new gfxContext(imageSurface);

        context->Translate(-gfxPoint(aSrcPoint.x, aSrcPoint.y));
        context->SetSource(aSurface);
        context->Paint();
        data = imageSurface->Data();
        NS_ASSERTION(!aPixelBuffer,
                     "Must be using an image compatible surface with pixel buffers!");
    } else {
        // If a pixel buffer is bound the data pointer parameter is relative
        // to the start of the data block.
        if (!aPixelBuffer) {
              data = imageSurface->Data();
        }
        data += DataOffset(imageSurface, aSrcPoint);
    }

    GLenum format;
    GLenum internalformat;
    GLenum type;
    PRInt32 pixelSize = gfxASurface::BytePerPixelFromFormat(imageSurface->Format());
    ShaderProgramType shader;

    switch (imageSurface->Format()) {
        case gfxASurface::ImageFormatARGB32:
            format = LOCAL_GL_RGBA;
            type = LOCAL_GL_UNSIGNED_BYTE;
            shader = BGRALayerProgramType;
            break;
        case gfxASurface::ImageFormatRGB24:
            // Treat RGB24 surfaces as RGBA32 except for the shader
            // program used.
            format = LOCAL_GL_RGBA;
            type = LOCAL_GL_UNSIGNED_BYTE;
            shader = BGRXLayerProgramType;
            break;
        case gfxASurface::ImageFormatRGB16_565:
            format = LOCAL_GL_RGB;
            type = LOCAL_GL_UNSIGNED_SHORT_5_6_5;
            shader = RGBALayerProgramType;
            break;
        default:
            NS_ASSERTION(false, "Unhandled image surface format!");
            format = 0;
            type = 0;
            shader = ShaderProgramType(0);
    }

#ifndef USE_GLES2
    fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, 
                 imageSurface->Stride() / pixelSize);

    internalformat = LOCAL_GL_RGBA;
#else
    internalformat = format;
#endif

    nsIntRegionRectIterator iter(paintRegion);
    const nsIntRect *iterRect;

    // Top left point of the region's bounding rectangle.
    nsIntPoint topLeft = paintRegion.GetBounds().TopLeft();

    while ((iterRect = iter.Next())) {
        // The inital data pointer is at the top left point of the region's
        // bounding rectangle. We need to find the offset of this rect
        // within the region and adjust the data pointer accordingly.
        unsigned char *rectData = 
            data + DataOffset(imageSurface, iterRect->TopLeft() - topLeft);

#ifdef USE_GLES2
        if (imageSurface->Stride() != iterRect->width * pixelSize) {
            // Not using the whole row of texture data and GLES doesn't 
            // support GL_UNPACK_ROW_LENGTH. We need to upload each row
            // separately.
            if (!textureInited) {
                fTexImage2D(LOCAL_GL_TEXTURE_2D,
                            0,
                            internalformat,
                            iterRect->width,
                            iterRect->height,
                            0,
                            format,
                            type,
                            NULL);
            }

            for (int h = 0; h < iterRect->height; h++) {
                fTexSubImage2D(LOCAL_GL_TEXTURE_2D,
                               0,
                               iterRect->x,
                               iterRect->y+h,
                               iterRect->width,
                               1,
                               format,
                               type,
                               rectData);
                rectData += imageSurface->Stride();
            }

            continue;
        }
#endif

        if (textureInited) {
            fTexSubImage2D(LOCAL_GL_TEXTURE_2D,
                           0,
                           iterRect->x,
                           iterRect->y,
                           iterRect->width,
                           iterRect->height,
                           format,
                           type,
                           rectData);
        } else {
            fTexImage2D(LOCAL_GL_TEXTURE_2D,
                        0,
                        internalformat,
                        iterRect->width,
                        iterRect->height,
                        0,
                        format,
                        type,
                        rectData);
        }

    }

#ifndef USE_GLES2
    fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, 0);
#endif

    return shader;
}

void
GLContext::RectTriangles::addRect(GLfloat x0, GLfloat y0, GLfloat x1, GLfloat y1,
                                  GLfloat tx0, GLfloat ty0, GLfloat tx1, GLfloat ty1)
{
    NS_ASSERTION(numRects < 4, "Overflow in number of rectangles, max 4!");

    GLfloat *v = &vertexCoords[numRects*6*2];
    GLfloat *t = &texCoords[numRects*6*2];

    *v++ = x0; *v++ = y0;
    *v++ = x1; *v++ = y0;
    *v++ = x0; *v++ = y1;

    *v++ = x0; *v++ = y1;
    *v++ = x1; *v++ = y0;
    *v++ = x1; *v++ = y1;

    *t++ = tx0; *t++ = ty0;
    *t++ = tx1; *t++ = ty0;
    *t++ = tx0; *t++ = ty1;

    *t++ = tx0; *t++ = ty1;
    *t++ = tx1; *t++ = ty0;
    *t++ = tx1; *t++ = ty1;

    numRects++;
}

static GLfloat
WrapTexCoord(GLfloat v)
{
    // fmodf gives negative results for negative numbers;
    // that is, fmodf(0.75, 1.0) == 0.75, but
    // fmodf(-0.75, 1.0) == -0.75.  For the negative case,
    // the result we need is 0.25, so we add 1.0f.
    if (v < 0.0f) {
        return 1.0f + fmodf(v, 1.0f);
    }

    return fmodf(v, 1.0f);
}

void
GLContext::DecomposeIntoNoRepeatTriangles(const nsIntRect& aTexCoordRect,
                                          const nsIntSize& aTexSize,
                                          RectTriangles& aRects)
{
    // normalize this
    nsIntRect tcr(aTexCoordRect);
    while (tcr.x > aTexSize.width)
        tcr.x -= aTexSize.width;
    while (tcr.y > aTexSize.height)
        tcr.y -= aTexSize.height;

    // Compute top left and bottom right tex coordinates
    GLfloat tl[2] =
        { GLfloat(tcr.x) / GLfloat(aTexSize.width),
          GLfloat(tcr.y) / GLfloat(aTexSize.height) };
    GLfloat br[2] =
        { GLfloat(tcr.XMost()) / GLfloat(aTexSize.width),
          GLfloat(tcr.YMost()) / GLfloat(aTexSize.height) };

    // then check if we wrap in either the x or y axis; if we do,
    // then also use fmod to figure out the "true" non-wrapping
    // texture coordinates.

    bool xwrap = false, ywrap = false;
    if (tcr.x < 0 || tcr.x > aTexSize.width ||
        tcr.XMost() < 0 || tcr.XMost() > aTexSize.width)
    {
        xwrap = true;
        tl[0] = WrapTexCoord(tl[0]);
        br[0] = WrapTexCoord(br[0]);
    }

    if (tcr.y < 0 || tcr.y > aTexSize.height ||
        tcr.YMost() < 0 || tcr.YMost() > aTexSize.height)
    {
        ywrap = true;
        tl[1] = WrapTexCoord(tl[1]);
        br[1] = WrapTexCoord(br[1]);
    }

    NS_ASSERTION(tl[0] >= 0.0f && tl[0] <= 1.0f &&
                 tl[1] >= 0.0f && tl[1] <= 1.0f &&
                 br[0] >= 0.0f && br[0] <= 1.0f &&
                 br[1] >= 0.0f && br[1] <= 1.0f,
                 "Somehow generated invalid texture coordinates");

    // If xwrap is false, the texture will be sampled from tl[0]
    // .. br[0].  If xwrap is true, then it will be split into tl[0]
    // .. 1.0, and 0.0 .. br[0].  Same for the Y axis.  The
    // destination rectangle is also split appropriately, according
    // to the calculated xmid/ymid values.

    // There isn't a 1:1 mapping between tex coords and destination coords;
    // when computing midpoints, we have to take that into account.  We
    // need to map the texture coords, which are (in the wrap case):
    // |tl->1| and |0->br| to the |0->1| range of the vertex coords.  So
    // we have the length (1-tl)+(br) that needs to map into 0->1.
    // These are only valid if there is wrap involved, they won't be used
    // otherwise.
    GLfloat xlen = (1.0f - tl[0]) + br[0];
    GLfloat ylen = (1.0f - tl[1]) + br[1];

    NS_ASSERTION(!xwrap || xlen > 0.0f, "xlen isn't > 0, what's going on?");
    NS_ASSERTION(!ywrap || ylen > 0.0f, "ylen isn't > 0, what's going on?");
    NS_ASSERTION(aTexCoordRect.width <= aTexSize.width &&
                 aTexCoordRect.height <= aTexSize.height, "tex coord rect would cause tiling!");

    if (!xwrap && !ywrap) {
        aRects.addRect(0.0f, 0.0f, 1.0f, 1.0f,
                       tl[0], tl[1], br[0], br[1]);
    } else if (!xwrap && ywrap) {
        GLfloat ymid = (1.0f - tl[1]) / ylen;
        aRects.addRect(0.0f, 0.0f,
                       1.0f, ymid,
                       tl[0], tl[1],
                       br[0], 1.0f);
        aRects.addRect(0.0f, ymid,
                       1.0f, 1.0f,
                       tl[0], 0.0f,
                       br[0], br[1]);
    } else if (xwrap && !ywrap) {
        GLfloat xmid = (1.0f - tl[0]) / xlen;
        aRects.addRect(0.0f, 0.0f,
                       xmid, 1.0f,
                       tl[0], tl[1],
                       1.0f, br[1]);
        aRects.addRect(xmid, 0.0f,
                       1.0f, 1.0f,
                       0.0f, tl[1],
                       br[0], br[1]);
    } else {
        GLfloat xmid = (1.0f - tl[0]) / xlen;
        GLfloat ymid = (1.0f - tl[1]) / ylen;
        aRects.addRect(0.0f, 0.0f,
                       xmid, ymid,
                       tl[0], tl[1],
                       1.0f, 1.0f);
        aRects.addRect(xmid, 0.0f,
                       1.0f, ymid,
                       0.0f, tl[1],
                       br[0], 1.0f);
        aRects.addRect(0.0f, ymid,
                       xmid, 1.0f,
                       tl[0], 0.0f,
                       1.0f, br[1]);
        aRects.addRect(xmid, ymid,
                       1.0f, 1.0f,
                       0.0f, 0.0f,
                       br[0], br[1]);
    }
}

void
GLContext::UseBlitProgram()
{
    if (mBlitProgram) {
        fUseProgram(mBlitProgram);
        return;
    }

    mBlitProgram = fCreateProgram();

    GLuint shaders[2];
    shaders[0] = fCreateShader(LOCAL_GL_VERTEX_SHADER);
    shaders[1] = fCreateShader(LOCAL_GL_FRAGMENT_SHADER);

    const char *blitVSSrc = 
        "attribute vec2 aVertex;"
        "attribute vec2 aTexCoord;"
        "varying vec2 vTexCoord;"
        "void main() {"
        "  vTexCoord = aTexCoord;"
        "  gl_Position = vec4(aVertex, 0.0, 1.0);"
        "}";
    const char *blitFSSrc = "#ifdef GL_ES\nprecision mediump float;\n#endif\n"
        "uniform sampler2D uSrcTexture;"
        "varying vec2 vTexCoord;"
        "void main() {"
        "  gl_FragColor = texture2D(uSrcTexture, vTexCoord);"
        "}";

    fShaderSource(shaders[0], 1, (const GLchar**) &blitVSSrc, NULL);
    fShaderSource(shaders[1], 1, (const GLchar**) &blitFSSrc, NULL);

    for (int i = 0; i < 2; ++i) {
        GLint success, len = 0;

        fCompileShader(shaders[i]);
        fGetShaderiv(shaders[i], LOCAL_GL_COMPILE_STATUS, &success);
        NS_ASSERTION(success, "Shader compilation failed!");

        if (!success) {
            nsCAutoString log;
            fGetShaderiv(shaders[i], LOCAL_GL_INFO_LOG_LENGTH, (GLint*) &len);
            log.SetCapacity(len);
            fGetShaderInfoLog(shaders[i], len, (GLint*) &len, (char*) log.BeginWriting());
            log.SetLength(len);

            printf_stderr("Shader %d compilation failed:\n%s\n", nsPromiseFlatCString(log).get());
            return;
        }

        fAttachShader(mBlitProgram, shaders[i]);
        fDeleteShader(shaders[i]);
    }

    fBindAttribLocation(mBlitProgram, 0, "aVertex");
    fBindAttribLocation(mBlitProgram, 1, "aTexCoord");

    fLinkProgram(mBlitProgram);

    GLint success, len = 0;
    fGetProgramiv(mBlitProgram, LOCAL_GL_LINK_STATUS, &success);
    NS_ASSERTION(success, "Shader linking failed!");

    if (!success) {
        nsCAutoString log;
        fGetProgramiv(mBlitProgram, LOCAL_GL_INFO_LOG_LENGTH, (GLint*) &len);
        log.SetCapacity(len);
        fGetProgramInfoLog(mBlitProgram, len, (GLint*) &len, (char*) log.BeginWriting());
        log.SetLength(len);

        printf_stderr("Program linking failed:\n%s\n", nsPromiseFlatCString(log).get());
        return;
    }

    fUseProgram(mBlitProgram);
    fUniform1i(fGetUniformLocation(mBlitProgram, "uSrcTexture"), 0);
}

void
GLContext::SetBlitFramebufferForDestTexture(GLuint aTexture)
{
    if (!mBlitFramebuffer) {
        fGenFramebuffers(1, &mBlitFramebuffer);
    }

    fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, mBlitFramebuffer);
    fFramebufferTexture2D(LOCAL_GL_FRAMEBUFFER,
                          LOCAL_GL_COLOR_ATTACHMENT0,
                          LOCAL_GL_TEXTURE_2D,
                          aTexture,
                          0);

    if (aTexture) {
        GLenum status = fCheckFramebufferStatus(LOCAL_GL_FRAMEBUFFER);

        // Note: if you are hitting this assertion, it is likely that
        // your texture is not texture complete -- that is, you
        // allocated a texture name, but didn't actually define its
        // size via a call to TexImage2D.
        NS_ASSERTION(status == LOCAL_GL_FRAMEBUFFER_COMPLETE, "Framebuffer not complete!");
    }
}

#ifdef DEBUG

void
GLContext::CreatedProgram(GLContext *aOrigin, GLuint aName)
{
    mTrackedPrograms.AppendElement(NamedResource(aOrigin, aName));
}

void
GLContext::CreatedShader(GLContext *aOrigin, GLuint aName)
{
    mTrackedShaders.AppendElement(NamedResource(aOrigin, aName));
}

void
GLContext::CreatedBuffers(GLContext *aOrigin, GLsizei aCount, GLuint *aNames)
{
    for (GLsizei i = 0; i < aCount; ++i) {
        mTrackedBuffers.AppendElement(NamedResource(aOrigin, aNames[i]));
    }
}

void
GLContext::CreatedTextures(GLContext *aOrigin, GLsizei aCount, GLuint *aNames)
{
    for (GLsizei i = 0; i < aCount; ++i) {
        mTrackedTextures.AppendElement(NamedResource(aOrigin, aNames[i]));
    }
}

void
GLContext::CreatedFramebuffers(GLContext *aOrigin, GLsizei aCount, GLuint *aNames)
{
    for (GLsizei i = 0; i < aCount; ++i) {
        mTrackedFramebuffers.AppendElement(NamedResource(aOrigin, aNames[i]));
    }
}

void
GLContext::CreatedRenderbuffers(GLContext *aOrigin, GLsizei aCount, GLuint *aNames)
{
    for (GLsizei i = 0; i < aCount; ++i) {
        mTrackedRenderbuffers.AppendElement(NamedResource(aOrigin, aNames[i]));
    }
}

static void
RemoveNamesFromArray(GLContext *aOrigin, GLsizei aCount, GLuint *aNames, nsTArray<GLContext::NamedResource>& aArray)
{
    for (GLsizei j = 0; j < aCount; ++j) {
        GLuint name = aNames[j];
        // name 0 can be ignored
        if (name == 0)
            continue;

        PRBool found = PR_FALSE;
        for (PRUint32 i = 0; i < aArray.Length(); ++i) {
            if (aArray[i].name == name) {
                aArray.RemoveElementAt(i);
                found = PR_TRUE;
                break;
            }
        }
#ifdef DEBUG
        if (!found) {
            printf_stderr("GL Context %p deleting resource %d, which doesn't exist!\n", aOrigin, name);
        }
#endif
    }
}

void
GLContext::DeletedProgram(GLContext *aOrigin, GLuint aName)
{
    RemoveNamesFromArray(aOrigin, 1, &aName, mTrackedPrograms);
}

void
GLContext::DeletedShader(GLContext *aOrigin, GLuint aName)
{
    RemoveNamesFromArray(aOrigin, 1, &aName, mTrackedShaders);
}

void
GLContext::DeletedBuffers(GLContext *aOrigin, GLsizei aCount, GLuint *aNames)
{
    RemoveNamesFromArray(aOrigin, aCount, aNames, mTrackedBuffers);
}

void
GLContext::DeletedTextures(GLContext *aOrigin, GLsizei aCount, GLuint *aNames)
{
    RemoveNamesFromArray(aOrigin, aCount, aNames, mTrackedTextures);
}

void
GLContext::DeletedFramebuffers(GLContext *aOrigin, GLsizei aCount, GLuint *aNames)
{
    RemoveNamesFromArray(aOrigin, aCount, aNames, mTrackedFramebuffers);
}

void
GLContext::DeletedRenderbuffers(GLContext *aOrigin, GLsizei aCount, GLuint *aNames)
{
    RemoveNamesFromArray(aOrigin, aCount, aNames, mTrackedRenderbuffers);
}

static void
MarkContextDestroyedInArray(GLContext *aContext, nsTArray<GLContext::NamedResource>& aArray)
{
    for (PRUint32 i = 0; i < aArray.Length(); ++i) {
        if (aArray[i].origin == aContext)
            aArray[i].originDeleted = PR_TRUE;
    }
}

void
GLContext::SharedContextDestroyed(GLContext *aChild)
{
    MarkContextDestroyedInArray(aChild, mTrackedPrograms);
    MarkContextDestroyedInArray(aChild, mTrackedShaders);
    MarkContextDestroyedInArray(aChild, mTrackedTextures);
    MarkContextDestroyedInArray(aChild, mTrackedFramebuffers);
    MarkContextDestroyedInArray(aChild, mTrackedRenderbuffers);
    MarkContextDestroyedInArray(aChild, mTrackedBuffers);
}

static void
ReportArrayContents(const nsTArray<GLContext::NamedResource>& aArray)
{
    nsTArray<GLContext::NamedResource> copy(aArray);
    copy.Sort();

    GLContext *lastContext = NULL;
    for (PRUint32 i = 0; i < copy.Length(); ++i) {
        if (lastContext != copy[i].origin) {
            if (lastContext)
                printf_stderr("\n");
            printf_stderr("  [%p - %s] ", copy[i].origin, copy[i].originDeleted ? "deleted" : "live");
            lastContext = copy[i].origin;
        }
        printf_stderr("%d ", copy[i].name);
    }
    printf_stderr("\n");
}

void
GLContext::ReportOutstandingNames()
{
    printf_stderr("== GLContext %p ==\n", this);
    printf_stderr("Outstanding Textures:\n");
    ReportArrayContents(mTrackedTextures);
    printf_stderr("Outstanding Buffers:\n");
    ReportArrayContents(mTrackedBuffers);
    printf_stderr("Outstanding Programs:\n");
    ReportArrayContents(mTrackedPrograms);
    printf_stderr("Outstanding Shaders:\n");
    ReportArrayContents(mTrackedShaders);
    printf_stderr("Outstanding Framebuffers:\n");
    ReportArrayContents(mTrackedFramebuffers);
    printf_stderr("Outstanding Renderbuffers:\n");
    ReportArrayContents(mTrackedRenderbuffers);
}

#endif /* DEBUG */

} /* namespace gl */
} /* namespace mozilla */
