gecko/gfx/gl/GLContext.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim: set ts=8 sts=4 et sw=4 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include <algorithm>
#include <stdio.h>
#include <string.h>
#include <ctype.h>

#include "GLContext.h"

#include "gfxCrashReporterUtils.h"
#include "gfxPlatform.h"
#include "gfxUtils.h"
#include "GLContextProvider.h"
#include "GLTextureImage.h"
#include "nsPrintfCString.h"
#include "nsThreadUtils.h"
#include "prenv.h"
#include "prlink.h"
#include "SurfaceStream.h"
#include "GfxTexturesReporter.h"
#include "TextureGarbageBin.h"
#include "gfx2DGlue.h"

#include "mozilla/DebugOnly.h"
#include "mozilla/Preferences.h"

#ifdef XP_MACOSX
#include <CoreServices/CoreServices.h>
#include "gfxColor.h"
#endif

#if defined(MOZ_WIDGET_COCOA)
#include "nsCocoaFeatures.h"
#endif

using namespace mozilla::gfx;

namespace mozilla {
namespace gl {

#ifdef DEBUG
unsigned GLContext::sCurrentGLContextTLS = -1;
#endif

uint32_t GLContext::sDebugMode = 0;


#define MAX_SYMBOL_LENGTH 128
#define MAX_SYMBOL_NAMES 5

// should match the order of GLExtensions, and be null-terminated.
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_ARB_depth_texture",
    "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",
    "GL_ARB_ES3_compatibility",
    "GL_OES_texture_float",
    "GL_OES_texture_float_linear",
    "GL_ARB_texture_float",
    "GL_EXT_unpack_subimage",
    "GL_OES_standard_derivatives",
    "GL_EXT_texture_filter_anisotropic",
    "GL_EXT_texture_compression_s3tc",
    "GL_EXT_texture_compression_dxt1",
    "GL_ANGLE_texture_compression_dxt3",
    "GL_ANGLE_texture_compression_dxt5",
    "GL_AMD_compressed_ATC_texture",
    "GL_IMG_texture_compression_pvrtc",
    "GL_EXT_framebuffer_blit",
    "GL_ANGLE_framebuffer_blit",
    "GL_EXT_framebuffer_multisample",
    "GL_ANGLE_framebuffer_multisample",
    "GL_OES_rgb8_rgba8",
    "GL_ARB_robustness",
    "GL_EXT_robustness",
    "GL_ARB_sync",
    "GL_OES_EGL_image",
    "GL_OES_EGL_sync",
    "GL_OES_EGL_image_external",
    "GL_EXT_packed_depth_stencil",
    "GL_OES_element_index_uint",
    "GL_OES_vertex_array_object",
    "GL_ARB_vertex_array_object",
    "GL_APPLE_vertex_array_object",
    "GL_ARB_draw_buffers",
    "GL_EXT_draw_buffers",
    "GL_EXT_gpu_shader4",
    "GL_EXT_blend_minmax",
    "GL_ARB_draw_instanced",
    "GL_EXT_draw_instanced",
    "GL_NV_draw_instanced",
    "GL_ARB_instanced_arrays",
    "GL_NV_instanced_arrays",
    "GL_ANGLE_instanced_arrays",
    "GL_EXT_occlusion_query_boolean",
    "GL_ARB_occlusion_query2",
    "GL_EXT_transform_feedback",
    "GL_NV_transform_feedback",
    "GL_ANGLE_depth_texture",
    "GL_KHR_debug",
    nullptr
};

static bool
ParseGLVersion(GLContext* gl, unsigned int* version)
{
    GLenum error = gl->fGetError();
    if (error != LOCAL_GL_NO_ERROR) {
        MOZ_ASSERT(false, "An OpenGL error has been triggered before.");
        return false;
    }

    /**
     * B2G emulator bug work around: The emulator implements OpenGL ES 2.0 on
     * OpenGL 3.2. The bug is that GetIntegerv(LOCAL_GL_{MAJOR,MINOR}_VERSION)
     * returns OpenGL 3.2 instead of generating an error.
     */
    if (!gl->IsGLES())
    {
        /**
         * OpenGL 3.1 and OpenGL ES 3.0 both introduce GL_{MAJOR,MINOR}_VERSION
         * with GetIntegerv. So we first try those constants even though we
         * might not have an OpenGL context supporting them, has this is a
         * better way than parsing GL_VERSION.
         */
        GLint majorVersion = 0;
        GLint minorVersion = 0;

        gl->fGetIntegerv(LOCAL_GL_MAJOR_VERSION, &majorVersion);
        gl->fGetIntegerv(LOCAL_GL_MINOR_VERSION, &minorVersion);

        // If it's not an OpenGL (ES) 3.0 context, we will have an error
        error = gl->fGetError();
        if (error == LOCAL_GL_NO_ERROR &&
            majorVersion > 0 &&
            minorVersion >= 0)
        {
            *version = majorVersion * 100 + minorVersion * 10;
            return true;
        }
    }

    /**
     * We were not able to use GL_{MAJOR,MINOR}_VERSION, so we parse
     * GL_VERSION.
     *
     *
     * OpenGL 2.x, 3.x, 4.x specifications:
     *  The VERSION and SHADING_LANGUAGE_VERSION strings are laid out as follows:
     *
     *    <version number><space><vendor-specific information>
     *
     *  The version number is either of the form major_number.minor_number or
     *  major_number.minor_number.release_number, where the numbers all have
     *  one or more digits.
     *
     *
     * OpenGL ES 2.0, 3.0 specifications:
     *  The VERSION string is laid out as follows:
     *
     *     "OpenGL ES N.M vendor-specific information"
     *
     *  The version number is either of the form major_number.minor_number or
     *  major_number.minor_number.release_number, where the numbers all have
     *  one or more digits.
     *
     *
     * Note:
     *  We don't care about release_number.
     */
    const char* versionString = (const char*)gl->fGetString(LOCAL_GL_VERSION);

    error = gl->fGetError();
    if (error != LOCAL_GL_NO_ERROR) {
        MOZ_ASSERT(false, "glGetString(GL_VERSION) has generated an error");
        return false;
    } else if (!versionString) {
        MOZ_ASSERT(false, "glGetString(GL_VERSION) has returned 0");
        return false;
    }

    const char kGLESVersionPrefix[] = "OpenGL ES ";
    if (strncmp(versionString, kGLESVersionPrefix, strlen(kGLESVersionPrefix)) == 0) {
        versionString += strlen(kGLESVersionPrefix);
    }

    const char* itr = versionString;
    char* end = nullptr;
    int majorVersion = (int)strtol(itr, &end, 10);

    if (!end) {
        MOZ_ASSERT(false, "Failed to parse the GL major version number.");
        return false;
    } else if (*end != '.') {
        MOZ_ASSERT(false, "Failed to parse GL's major-minor version number separator.");
        return false;
    }

    // we skip the '.' between the major and the minor version
    itr = end + 1;

    end = nullptr;

    int minorVersion = (int)strtol(itr, &end, 10);
    if (!end) {
        MOZ_ASSERT(false, "Failed to parse GL's minor version number.");
        return false;
    }

    if (majorVersion <= 0 || majorVersion >= 100) {
        MOZ_ASSERT(false, "Invalid major version.");
        return false;
    } else if (minorVersion < 0 || minorVersion >= 10) {
        MOZ_ASSERT(false, "Invalid minor version.");
        return false;
    }

    *version = (unsigned int)(majorVersion * 100 + minorVersion * 10);
    return true;
}

GLContext::GLContext(const SurfaceCaps& caps,
          GLContext* sharedContext,
          bool isOffscreen)
  : mInitialized(false),
    mIsOffscreen(isOffscreen),
    mIsGlobalSharedContext(false),
    mContextLost(false),
    mVersion(0),
    mProfile(ContextProfile::Unknown),
    mVendor(-1),
    mRenderer(-1),
    mHasRobustness(false),
#ifdef DEBUG
    mGLError(LOCAL_GL_NO_ERROR),
#endif
    mTexBlit_Buffer(0),
    mTexBlit_VertShader(0),
    mTex2DBlit_FragShader(0),
    mTex2DRectBlit_FragShader(0),
    mTex2DBlit_Program(0),
    mTex2DRectBlit_Program(0),
    mTexBlit_UseDrawNotCopy(false),
    mSharedContext(sharedContext),
    mFlipped(false),
    mBlitProgram(0),
    mBlitFramebuffer(0),
    mCaps(caps),
    mScreen(nullptr),
    mLockedSurface(nullptr),
    mMaxTextureSize(0),
    mMaxCubeMapTextureSize(0),
    mMaxTextureImageSize(0),
    mMaxRenderbufferSize(0),
    mNeedsTextureSizeChecks(false),
    mWorkAroundDriverBugs(true)
{
    mOwningThread = NS_GetCurrentThread();

    mTexBlit_UseDrawNotCopy = Preferences::GetBool("gl.blit-draw-not-copy", false);
}

GLContext::~GLContext() {
    NS_ASSERTION(IsDestroyed(), "GLContext implementation must call MarkDestroyed in destructor!");
#ifdef DEBUG
    if (mSharedContext) {
        GLContext *tip = mSharedContext;
        while (tip->mSharedContext)
            tip = tip->mSharedContext;
        tip->SharedContextDestroyed(this);
        tip->ReportOutstandingNames();
    } else {
        ReportOutstandingNames();
    }
#endif
}

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

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

    mWorkAroundDriverBugs = gfxPlatform::GetPlatform()->WorkAroundDriverBugs();

    SymLoadStruct symbols[] = {
        { (PRFuncPtr*) &mSymbols.fActiveTexture, { "ActiveTexture", "ActiveTextureARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fAttachShader, { "AttachShader", "AttachShaderARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBindAttribLocation, { "BindAttribLocation", "BindAttribLocationARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBindBuffer, { "BindBuffer", "BindBufferARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBindTexture, { "BindTexture", "BindTextureARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBlendColor, { "BlendColor", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBlendEquation, { "BlendEquation", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBlendEquationSeparate, { "BlendEquationSeparate", "BlendEquationSeparateEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBlendFunc, { "BlendFunc", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBlendFuncSeparate, { "BlendFuncSeparate", "BlendFuncSeparateEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBufferData, { "BufferData", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBufferSubData, { "BufferSubData", nullptr } },
        { (PRFuncPtr*) &mSymbols.fClear, { "Clear", nullptr } },
        { (PRFuncPtr*) &mSymbols.fClearColor, { "ClearColor", nullptr } },
        { (PRFuncPtr*) &mSymbols.fClearStencil, { "ClearStencil", nullptr } },
        { (PRFuncPtr*) &mSymbols.fColorMask, { "ColorMask", nullptr } },
        { (PRFuncPtr*) &mSymbols.fCompressedTexImage2D, {"CompressedTexImage2D", nullptr} },
        { (PRFuncPtr*) &mSymbols.fCompressedTexSubImage2D, {"CompressedTexSubImage2D", nullptr} },
        { (PRFuncPtr*) &mSymbols.fCullFace, { "CullFace", nullptr } },
        { (PRFuncPtr*) &mSymbols.fDetachShader, { "DetachShader", "DetachShaderARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fDepthFunc, { "DepthFunc", nullptr } },
        { (PRFuncPtr*) &mSymbols.fDepthMask, { "DepthMask", nullptr } },
        { (PRFuncPtr*) &mSymbols.fDisable, { "Disable", nullptr } },
        { (PRFuncPtr*) &mSymbols.fDisableVertexAttribArray, { "DisableVertexAttribArray", "DisableVertexAttribArrayARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fDrawArrays, { "DrawArrays", nullptr } },
        { (PRFuncPtr*) &mSymbols.fDrawElements, { "DrawElements", nullptr } },
        { (PRFuncPtr*) &mSymbols.fEnable, { "Enable", nullptr } },
        { (PRFuncPtr*) &mSymbols.fEnableVertexAttribArray, { "EnableVertexAttribArray", "EnableVertexAttribArrayARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fFinish, { "Finish", nullptr } },
        { (PRFuncPtr*) &mSymbols.fFlush, { "Flush", nullptr } },
        { (PRFuncPtr*) &mSymbols.fFrontFace, { "FrontFace", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetActiveAttrib, { "GetActiveAttrib", "GetActiveAttribARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetActiveUniform, { "GetActiveUniform", "GetActiveUniformARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetAttachedShaders, { "GetAttachedShaders", "GetAttachedShadersARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetAttribLocation, { "GetAttribLocation", "GetAttribLocationARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetIntegerv, { "GetIntegerv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetFloatv, { "GetFloatv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetBooleanv, { "GetBooleanv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetBufferParameteriv, { "GetBufferParameteriv", "GetBufferParameterivARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetError, { "GetError", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetProgramiv, { "GetProgramiv", "GetProgramivARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetProgramInfoLog, { "GetProgramInfoLog", "GetProgramInfoLogARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fTexParameteri, { "TexParameteri", nullptr } },
        { (PRFuncPtr*) &mSymbols.fTexParameteriv, { "TexParameteriv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fTexParameterf, { "TexParameterf", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetString, { "GetString", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetTexParameterfv, { "GetTexParameterfv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetTexParameteriv, { "GetTexParameteriv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetUniformfv, { "GetUniformfv", "GetUniformfvARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetUniformiv, { "GetUniformiv", "GetUniformivARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetUniformLocation, { "GetUniformLocation", "GetUniformLocationARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetVertexAttribfv, { "GetVertexAttribfv", "GetVertexAttribfvARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetVertexAttribiv, { "GetVertexAttribiv", "GetVertexAttribivARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetVertexAttribPointerv, { "GetVertexAttribPointerv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fHint, { "Hint", nullptr } },
        { (PRFuncPtr*) &mSymbols.fIsBuffer, { "IsBuffer", "IsBufferARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fIsEnabled, { "IsEnabled", nullptr } },
        { (PRFuncPtr*) &mSymbols.fIsProgram, { "IsProgram", "IsProgramARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fIsShader, { "IsShader", "IsShaderARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fIsTexture, { "IsTexture", "IsTextureARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fLineWidth, { "LineWidth", nullptr } },
        { (PRFuncPtr*) &mSymbols.fLinkProgram, { "LinkProgram", "LinkProgramARB", nullptr } },
        { (PRFuncPtr*) &mSymbols.fPixelStorei, { "PixelStorei", nullptr } },
        { (PRFuncPtr*) &mSymbols.fPolygonOffset, { "PolygonOffset", nullptr } },
        { (PRFuncPtr*) &mSymbols.fReadPixels, { "ReadPixels", nullptr } },
        { (PRFuncPtr*) &mSymbols.fSampleCoverage, { "SampleCoverage", nullptr } },
        { (PRFuncPtr*) &mSymbols.fScissor, { "Scissor", nullptr } },
        { (PRFuncPtr*) &mSymbols.fStencilFunc, { "StencilFunc", nullptr } },
        { (PRFuncPtr*) &mSymbols.fStencilFuncSeparate, { "StencilFuncSeparate", "StencilFuncSeparateEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fStencilMask, { "StencilMask", nullptr } },
        { (PRFuncPtr*) &mSymbols.fStencilMaskSeparate, { "StencilMaskSeparate", "StencilMaskSeparateEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fStencilOp, { "StencilOp", nullptr } },
        { (PRFuncPtr*) &mSymbols.fStencilOpSeparate, { "StencilOpSeparate", "StencilOpSeparateEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fTexImage2D, { "TexImage2D", nullptr } },
        { (PRFuncPtr*) &mSymbols.fTexSubImage2D, { "TexSubImage2D", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform1f, { "Uniform1f", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform1fv, { "Uniform1fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform1i, { "Uniform1i", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform1iv, { "Uniform1iv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform2f, { "Uniform2f", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform2fv, { "Uniform2fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform2i, { "Uniform2i", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform2iv, { "Uniform2iv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform3f, { "Uniform3f", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform3fv, { "Uniform3fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform3i, { "Uniform3i", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform3iv, { "Uniform3iv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform4f, { "Uniform4f", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform4fv, { "Uniform4fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform4i, { "Uniform4i", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniform4iv, { "Uniform4iv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniformMatrix2fv, { "UniformMatrix2fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniformMatrix3fv, { "UniformMatrix3fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUniformMatrix4fv, { "UniformMatrix4fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fUseProgram, { "UseProgram", nullptr } },
        { (PRFuncPtr*) &mSymbols.fValidateProgram, { "ValidateProgram", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttribPointer, { "VertexAttribPointer", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib1f, { "VertexAttrib1f", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib2f, { "VertexAttrib2f", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib3f, { "VertexAttrib3f", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib4f, { "VertexAttrib4f", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib1fv, { "VertexAttrib1fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib2fv, { "VertexAttrib2fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib3fv, { "VertexAttrib3fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttrib4fv, { "VertexAttrib4fv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fViewport, { "Viewport", nullptr } },
        { (PRFuncPtr*) &mSymbols.fCompileShader, { "CompileShader", nullptr } },
        { (PRFuncPtr*) &mSymbols.fCopyTexImage2D, { "CopyTexImage2D", nullptr } },
        { (PRFuncPtr*) &mSymbols.fCopyTexSubImage2D, { "CopyTexSubImage2D", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetShaderiv, { "GetShaderiv", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetShaderInfoLog, { "GetShaderInfoLog", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetShaderSource, { "GetShaderSource", nullptr } },
        { (PRFuncPtr*) &mSymbols.fShaderSource, { "ShaderSource", nullptr } },
        { (PRFuncPtr*) &mSymbols.fVertexAttribPointer, { "VertexAttribPointer", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBindFramebuffer, { "BindFramebuffer", "BindFramebufferEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fBindRenderbuffer, { "BindRenderbuffer", "BindRenderbufferEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fCheckFramebufferStatus, { "CheckFramebufferStatus", "CheckFramebufferStatusEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fFramebufferRenderbuffer, { "FramebufferRenderbuffer", "FramebufferRenderbufferEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fFramebufferTexture2D, { "FramebufferTexture2D", "FramebufferTexture2DEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGenerateMipmap, { "GenerateMipmap", "GenerateMipmapEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetFramebufferAttachmentParameteriv, { "GetFramebufferAttachmentParameteriv", "GetFramebufferAttachmentParameterivEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fGetRenderbufferParameteriv, { "GetRenderbufferParameteriv", "GetRenderbufferParameterivEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fIsFramebuffer, { "IsFramebuffer", "IsFramebufferEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fIsRenderbuffer, { "IsRenderbuffer", "IsRenderbufferEXT", nullptr } },
        { (PRFuncPtr*) &mSymbols.fRenderbufferStorage, { "RenderbufferStorage", "RenderbufferStorageEXT", nullptr } },

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

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

        { nullptr, { nullptr } },

    };

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

    if (mInitialized) {
        unsigned int version = 0;

        bool parseSuccess = ParseGLVersion(this, &version);
        printf_stderr("OpenGL version detected: %u\n", version);

        if (version >= mVersion) {
            mVersion = version;
        } else if (parseSuccess) {
            NS_WARNING("Parsed version less than expected.");
            mInitialized = false;
        }
    }

    // Load OpenGL ES 2.0 symbols, or desktop if we aren't using ES 2.
    if (mInitialized) {
        if (IsGLES2()) {
            SymLoadStruct symbols_ES2[] = {
                { (PRFuncPtr*) &mSymbols.fGetShaderPrecisionFormat, { "GetShaderPrecisionFormat", nullptr } },
                { (PRFuncPtr*) &mSymbols.fClearDepthf, { "ClearDepthf", nullptr } },
                { (PRFuncPtr*) &mSymbols.fDepthRangef, { "DepthRangef", nullptr } },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(&symbols_ES2[0], trygl, prefix)) {
                NS_ERROR("OpenGL ES 2.0 supported, but symbols could not be loaded.");
                mInitialized = false;
            }
        } else {
            SymLoadStruct symbols_desktop[] = {
                { (PRFuncPtr*) &mSymbols.fClearDepth, { "ClearDepth", nullptr } },
                { (PRFuncPtr*) &mSymbols.fDepthRange, { "DepthRange", nullptr } },
                { (PRFuncPtr*) &mSymbols.fReadBuffer, { "ReadBuffer", nullptr } },
                { (PRFuncPtr*) &mSymbols.fMapBuffer, { "MapBuffer", nullptr } },
                { (PRFuncPtr*) &mSymbols.fUnmapBuffer, { "UnmapBuffer", nullptr } },
                { (PRFuncPtr*) &mSymbols.fPointParameterf, { "PointParameterf", nullptr } },
                { (PRFuncPtr*) &mSymbols.fDrawBuffer, { "DrawBuffer", nullptr } },
                { (PRFuncPtr*) &mSymbols.fDrawBuffers, { "DrawBuffers", nullptr } },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(&symbols_desktop[0], trygl, prefix)) {
                NS_ERROR("Desktop symbols failed to load.");
                mInitialized = false;
            }
        }
    }

    const char *glVendorString = nullptr;
    const char *glRendererString = nullptr;

    if (mInitialized) {
        // The order of these strings must match up with the order of the enum
        // defined in GLContext.h for vendor IDs
        glVendorString = (const char *)fGetString(LOCAL_GL_VENDOR);
        if (!glVendorString)
            mInitialized = false;

        const char *vendorMatchStrings[VendorOther] = {
                "Intel",
                "NVIDIA",
                "ATI",
                "Qualcomm",
                "Imagination",
                "nouveau"
        };

        mVendor = VendorOther;
        for (int i = 0; i < VendorOther; ++i) {
            if (DoesStringMatch(glVendorString, vendorMatchStrings[i])) {
                mVendor = i;
                break;
            }
        }

        // The order of these strings must match up with the order of the enum
        // defined in GLContext.h for renderer IDs
        glRendererString = (const char *)fGetString(LOCAL_GL_RENDERER);
        if (!glRendererString)
            mInitialized = false;

        const char *rendererMatchStrings[RendererOther] = {
                "Adreno 200",
                "Adreno 205",
                "Adreno (TM) 205",
                "Adreno (TM) 320",
                "PowerVR SGX 530",
                "PowerVR SGX 540",
                "NVIDIA Tegra",
                "Android Emulator"
        };

        mRenderer = RendererOther;
        for (int i = 0; i < RendererOther; ++i) {
            if (DoesStringMatch(glRendererString, rendererMatchStrings[i])) {
                mRenderer = i;
                break;
            }
        }
    }


#ifdef DEBUG
    if (PR_GetEnv("MOZ_GL_DEBUG"))
        sDebugMode |= 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"))
        sDebugMode |= 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"))
        sDebugMode |= DebugAbortOnError;
#endif

    if (mInitialized) {
#ifdef DEBUG
        static bool firstRun = true;
        if (firstRun && DebugMode()) {
            const char *vendors[VendorOther] = {
                "Intel",
                "NVIDIA",
                "ATI",
                "Qualcomm"
            };

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

        InitExtensions();
        InitFeatures();

        // Disable extensions with partial or incorrect support.
        if (WorkAroundDriverBugs()) {
            if (Renderer() == RendererAdrenoTM320) {
                MarkUnsupported(GLFeature::standard_derivatives);
            }
            
#ifdef XP_MACOSX
            // The Mac Nvidia driver, for versions up to and including 10.8, don't seem
            // to properly support this.  See 814839
            // this has been fixed in Mac OS X 10.9. See 907946
            if (Vendor() == gl::GLContext::VendorNVIDIA &&
                !nsCocoaFeatures::OnMavericksOrLater())
            {
                MarkUnsupported(GLFeature::depth_texture);
            }
#endif
            // ANGLE's divisor support is busted. (see bug 916816)
            if (IsANGLE()) {
                MarkUnsupported(GLFeature::instanced_arrays);
            }
        }

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

        if (SupportsRobustness()) {
            mHasRobustness = false;

            if (IsExtensionSupported(ARB_robustness)) {
                SymLoadStruct robustnessSymbols[] = {
                    { (PRFuncPtr*) &mSymbols.fGetGraphicsResetStatus, { "GetGraphicsResetStatusARB", nullptr } },
                    { nullptr, { nullptr } },
                };

                if (!LoadSymbols(&robustnessSymbols[0], trygl, prefix)) {
                    NS_ERROR("GL supports ARB_robustness without supplying GetGraphicsResetStatusARB.");

                    mSymbols.fGetGraphicsResetStatus = nullptr;
                } else {
                    mHasRobustness = true;
                }
            }
            if (!IsExtensionSupported(ARB_robustness) &&
                IsExtensionSupported(EXT_robustness)) {
                SymLoadStruct robustnessSymbols[] = {
                    { (PRFuncPtr*) &mSymbols.fGetGraphicsResetStatus, { "GetGraphicsResetStatusEXT", nullptr } },
                    { nullptr, { nullptr } },
                };

                if (!LoadSymbols(&robustnessSymbols[0], trygl, prefix)) {
                    NS_ERROR("GL supports EXT_robustness without supplying GetGraphicsResetStatusEXT.");

                    mSymbols.fGetGraphicsResetStatus = nullptr;
                } else {
                    mHasRobustness = true;
                }
            }

            if (!mHasRobustness) {
                MarkUnsupported(GLFeature::robustness);
            }
        }

        // Check for aux symbols based on extensions
        if (IsSupported(GLFeature::framebuffer_blit))
        {
            SymLoadStruct auxSymbols[] = {
                {
                    (PRFuncPtr*) &mSymbols.fBlitFramebuffer,
                    {
                        "BlitFramebuffer",
                        "BlitFramebufferEXT",
                        "BlitFramebufferANGLE",
                        nullptr
                    }
                },
                { nullptr, { nullptr } },
            };
            if (!LoadSymbols(&auxSymbols[0], trygl, prefix)) {
                NS_ERROR("GL supports framebuffer_blit without supplying glBlitFramebuffer");

                MarkUnsupported(GLFeature::framebuffer_blit);
                mSymbols.fBlitFramebuffer = nullptr;
            }
        }

        if (IsSupported(GLFeature::framebuffer_multisample))
        {
            SymLoadStruct auxSymbols[] = {
                {
                    (PRFuncPtr*) &mSymbols.fRenderbufferStorageMultisample,
                    {
                        "RenderbufferStorageMultisample",
                        "RenderbufferStorageMultisampleEXT",
                        "RenderbufferStorageMultisampleANGLE",
                        nullptr
                    }
                },
                { nullptr, { nullptr } },
            };
            if (!LoadSymbols(&auxSymbols[0], trygl, prefix)) {
                NS_ERROR("GL supports framebuffer_multisample without supplying glRenderbufferStorageMultisample");

                MarkUnsupported(GLFeature::framebuffer_multisample);
                mSymbols.fRenderbufferStorageMultisample = nullptr;
            }
        }

        if (IsExtensionSupported(ARB_sync)) {
            SymLoadStruct syncSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fFenceSync,      { "FenceSync",      nullptr } },
                { (PRFuncPtr*) &mSymbols.fIsSync,         { "IsSync",         nullptr } },
                { (PRFuncPtr*) &mSymbols.fDeleteSync,     { "DeleteSync",     nullptr } },
                { (PRFuncPtr*) &mSymbols.fClientWaitSync, { "ClientWaitSync", nullptr } },
                { (PRFuncPtr*) &mSymbols.fWaitSync,       { "WaitSync",       nullptr } },
                { (PRFuncPtr*) &mSymbols.fGetInteger64v,  { "GetInteger64v",  nullptr } },
                { (PRFuncPtr*) &mSymbols.fGetSynciv,      { "GetSynciv",      nullptr } },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(&syncSymbols[0], trygl, prefix)) {
                NS_ERROR("GL supports ARB_sync without supplying its functions.");

                MarkExtensionUnsupported(ARB_sync);
                mSymbols.fFenceSync = nullptr;
                mSymbols.fIsSync = nullptr;
                mSymbols.fDeleteSync = nullptr;
                mSymbols.fClientWaitSync = nullptr;
                mSymbols.fWaitSync = nullptr;
                mSymbols.fGetInteger64v = nullptr;
                mSymbols.fGetSynciv = nullptr;
            }
        }

        if (IsExtensionSupported(OES_EGL_image)) {
            SymLoadStruct imageSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fEGLImageTargetTexture2D, { "EGLImageTargetTexture2DOES", nullptr } },
                { (PRFuncPtr*) &mSymbols.fEGLImageTargetRenderbufferStorage, { "EGLImageTargetRenderbufferStorageOES", nullptr } },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(&imageSymbols[0], trygl, prefix)) {
                NS_ERROR("GL supports OES_EGL_image without supplying its functions.");

                MarkExtensionUnsupported(OES_EGL_image);
                mSymbols.fEGLImageTargetTexture2D = nullptr;
                mSymbols.fEGLImageTargetRenderbufferStorage = nullptr;
            }
        }

        if (IsExtensionSupported(ARB_vertex_array_object) ||
            IsExtensionSupported(OES_vertex_array_object)) {
            SymLoadStruct vaoSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fIsVertexArray, { "IsVertexArray", "IsVertexArrayOES", nullptr } },
                { (PRFuncPtr*) &mSymbols.fGenVertexArrays, { "GenVertexArrays", "GenVertexArraysOES", nullptr } },
                { (PRFuncPtr*) &mSymbols.fBindVertexArray, { "BindVertexArray", "BindVertexArrayOES", nullptr } },
                { (PRFuncPtr*) &mSymbols.fDeleteVertexArrays, { "DeleteVertexArrays", "DeleteVertexArraysOES", nullptr } },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(&vaoSymbols[0], trygl, prefix)) {
                NS_ERROR("GL supports Vertex Array Object without supplying its functions.");

                MarkUnsupported(GLFeature::vertex_array_object);
                mSymbols.fIsVertexArray = nullptr;
                mSymbols.fGenVertexArrays = nullptr;
                mSymbols.fBindVertexArray = nullptr;
                mSymbols.fDeleteVertexArrays = nullptr;
            }
        }
        else if (IsExtensionSupported(APPLE_vertex_array_object)) {
            /*
             * separate call to LoadSymbols with APPLE_vertex_array_object to work around
             * a driver bug : the IsVertexArray symbol (without suffix) can be present but unusable.
             */
            SymLoadStruct vaoSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fIsVertexArray, { "IsVertexArrayAPPLE", nullptr } },
                { (PRFuncPtr*) &mSymbols.fGenVertexArrays, { "GenVertexArraysAPPLE", nullptr } },
                { (PRFuncPtr*) &mSymbols.fBindVertexArray, { "BindVertexArrayAPPLE", nullptr } },
                { (PRFuncPtr*) &mSymbols.fDeleteVertexArrays, { "DeleteVertexArraysAPPLE", nullptr } },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(&vaoSymbols[0], trygl, prefix)) {
                NS_ERROR("GL supports Vertex Array Object without supplying its functions.");

                MarkUnsupported(GLFeature::vertex_array_object);
                mSymbols.fIsVertexArray = nullptr;
                mSymbols.fGenVertexArrays = nullptr;
                mSymbols.fBindVertexArray = nullptr;
                mSymbols.fDeleteVertexArrays = nullptr;
            }
        }

        if (IsSupported(GLFeature::draw_instanced)) {
            SymLoadStruct drawInstancedSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fDrawArraysInstanced,
                  { "DrawArraysInstanced",
                    "DrawArraysInstancedARB",
                    "DrawArraysInstancedEXT",
                    "DrawArraysInstancedNV",
                    "DrawArraysInstancedANGLE",
                    nullptr
                  }
                },
                { (PRFuncPtr*) &mSymbols.fDrawElementsInstanced,
                  { "DrawElementsInstanced",
                    "DrawElementsInstancedARB",
                    "DrawElementsInstancedEXT",
                    "DrawElementsInstancedNV",
                    "DrawElementsInstancedANGLE",
                    nullptr
                  }
                },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(drawInstancedSymbols, trygl, prefix)) {
                NS_ERROR("GL supports instanced draws without supplying its functions.");

                MarkUnsupported(GLFeature::draw_instanced);
                mSymbols.fDrawArraysInstanced = nullptr;
                mSymbols.fDrawElementsInstanced = nullptr;
            }
        }

        if (IsSupported(GLFeature::instanced_arrays)) {
            SymLoadStruct instancedArraySymbols[] = {
                { (PRFuncPtr*) &mSymbols.fVertexAttribDivisor,
                  { "VertexAttribDivisor",
                    "VertexAttribDivisorARB",
                    "VertexAttribDivisorNV",
                    "VertexAttribDivisorANGLE",
                    nullptr
                  }
                },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(instancedArraySymbols, trygl, prefix)) {
                NS_ERROR("GL supports array instanced without supplying it function.");

                MarkUnsupported(GLFeature::instanced_arrays);
                mSymbols.fVertexAttribDivisor = nullptr;
            }
        }

        if (IsSupported(GLFeature::transform_feedback)) {
            SymLoadStruct transformFeedbackSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fBindBufferBase,
                  { "BindBufferBase",
                    "BindBufferBaseEXT",
                    "BindBufferBaseNV",
                    nullptr
                  }
                },
                { (PRFuncPtr*) &mSymbols.fBindBufferRange,
                  { "BindBufferRange",
                    "BindBufferRangeEXT",
                    "BindBufferRangeNV",
                    nullptr
                  }
                },
                { (PRFuncPtr*) &mSymbols.fBeginTransformFeedback,
                  { "BeginTransformFeedback",
                    "BeginTransformFeedbackEXT",
                    "BeginTransformFeedbackNV",
                    nullptr
                  }
                },
                { (PRFuncPtr*) &mSymbols.fEndTransformFeedback,
                  { "EndTransformFeedback",
                    "EndTransformFeedbackEXT",
                    "EndTransformFeedbackNV",
                    nullptr
                  }
                },
                { (PRFuncPtr*) &mSymbols.fTransformFeedbackVaryings,
                  { "TransformFeedbackVaryings",
                    "TransformFeedbackVaryingsEXT",
                    "TransformFeedbackVaryingsNV",
                    nullptr
                  }
                },
                { (PRFuncPtr*) &mSymbols.fGetTransformFeedbackVarying,
                  { "GetTransformFeedbackVarying",
                    "GetTransformFeedbackVaryingEXT",
                    "GetTransformFeedbackVaryingNV",
                    nullptr
                  }
                },
                { (PRFuncPtr*) &mSymbols.fGetIntegeri_v,
                  { "GetIntegeri_v",
                    "GetIntegerIndexedvEXT",
                    "GetIntegerIndexedvNV",
                    nullptr
                  }
                },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(transformFeedbackSymbols, trygl, prefix)) {
                NS_ERROR("GL supports transform feedback without supplying its functions.");

                MarkUnsupported(GLFeature::transform_feedback);
                MarkUnsupported(GLFeature::bind_buffer_offset);
                mSymbols.fBindBufferBase = nullptr;
                mSymbols.fBindBufferRange = nullptr;
                mSymbols.fBeginTransformFeedback = nullptr;
                mSymbols.fEndTransformFeedback = nullptr;
                mSymbols.fTransformFeedbackVaryings = nullptr;
                mSymbols.fGetTransformFeedbackVarying = nullptr;
                mSymbols.fGetIntegeri_v = nullptr;
            }
        }

        if (IsSupported(GLFeature::bind_buffer_offset)) {
            SymLoadStruct bindBufferOffsetSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fBindBufferOffset,
                  { "BindBufferOffset",
                    "BindBufferOffsetEXT",
                    "BindBufferOffsetNV",
                    nullptr
                  }
                },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(bindBufferOffsetSymbols, trygl, prefix)) {
                NS_ERROR("GL supports BindBufferOffset without supplying its function.");

                MarkUnsupported(GLFeature::bind_buffer_offset);
                mSymbols.fBindBufferOffset = nullptr;
            }
        }

        if (IsSupported(GLFeature::query_objects)) {
            SymLoadStruct queryObjectsSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fBeginQuery, { "BeginQuery", "BeginQueryEXT", nullptr } },
                { (PRFuncPtr*) &mSymbols.fGenQueries, { "GenQueries", "GenQueriesEXT", nullptr } },
                { (PRFuncPtr*) &mSymbols.fDeleteQueries, { "DeleteQueries", "DeleteQueriesEXT", nullptr } },
                { (PRFuncPtr*) &mSymbols.fEndQuery, { "EndQuery", "EndQueryEXT", nullptr } },
                { (PRFuncPtr*) &mSymbols.fGetQueryiv, { "GetQueryiv", "GetQueryivEXT", nullptr } },
                { (PRFuncPtr*) &mSymbols.fGetQueryObjectuiv, { "GetQueryObjectuiv", "GetQueryObjectuivEXT", nullptr } },
                { (PRFuncPtr*) &mSymbols.fIsQuery, { "IsQuery", "IsQueryEXT", nullptr } },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(queryObjectsSymbols, trygl, prefix)) {
                NS_ERROR("GL supports query objects without supplying its functions.");

                MarkUnsupported(GLFeature::query_objects);
                MarkUnsupported(GLFeature::get_query_object_iv);
                MarkUnsupported(GLFeature::occlusion_query);
                MarkUnsupported(GLFeature::occlusion_query_boolean);
                MarkUnsupported(GLFeature::occlusion_query2);
                mSymbols.fBeginQuery = nullptr;
                mSymbols.fGenQueries = nullptr;
                mSymbols.fDeleteQueries = nullptr;
                mSymbols.fEndQuery = nullptr;
                mSymbols.fGetQueryiv = nullptr;
                mSymbols.fGetQueryObjectuiv = nullptr;
                mSymbols.fIsQuery = nullptr;
            }
        }

        if (IsSupported(GLFeature::get_query_object_iv)) {
            SymLoadStruct queryObjectsSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fGetQueryObjectiv, { "GetQueryObjectiv", "GetQueryObjectivEXT", nullptr } },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(queryObjectsSymbols, trygl, prefix)) {
                NS_ERROR("GL supports query objects iv getter without supplying its function.");

                MarkUnsupported(GLFeature::get_query_object_iv);
                mSymbols.fGetQueryObjectiv = nullptr;
            }
        }

        if (IsExtensionSupported(KHR_debug)) {
            SymLoadStruct extSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fDebugMessageControl,  { "DebugMessageControl",  "DebugMessageControlKHR",  nullptr } },
                { (PRFuncPtr*) &mSymbols.fDebugMessageInsert,   { "DebugMessageInsert",   "DebugMessageInsertKHR",   nullptr } },
                { (PRFuncPtr*) &mSymbols.fDebugMessageCallback, { "DebugMessageCallback", "DebugMessageCallbackKHR", nullptr } },
                { (PRFuncPtr*) &mSymbols.fGetDebugMessageLog,   { "GetDebugMessageLog",   "GetDebugMessageLogKHR",   nullptr } },
                { (PRFuncPtr*) &mSymbols.fGetPointerv,          { "GetPointerv",          "GetPointervKHR",          nullptr } },
                { (PRFuncPtr*) &mSymbols.fPushDebugGroup,       { "PushDebugGroup",       "PushDebugGroupKHR",       nullptr } },
                { (PRFuncPtr*) &mSymbols.fPopDebugGroup,        { "PopDebugGroup",        "PopDebugGroupKHR",        nullptr } },
                { (PRFuncPtr*) &mSymbols.fObjectLabel,          { "ObjectLabel",          "ObjectLabelKHR",          nullptr } },
                { (PRFuncPtr*) &mSymbols.fGetObjectLabel,       { "GetObjectLabel",       "GetObjectLabelKHR",       nullptr } },
                { (PRFuncPtr*) &mSymbols.fObjectPtrLabel,       { "ObjectPtrLabel",       "ObjectPtrLabelKHR",       nullptr } },
                { (PRFuncPtr*) &mSymbols.fGetObjectPtrLabel,    { "GetObjectPtrLabel",    "GetObjectPtrLabelKHR",    nullptr } },
                { nullptr, { nullptr } },
            };

            if (!LoadSymbols(&extSymbols[0], trygl, prefix)) {
                NS_ERROR("GL supports KHR_debug without supplying its functions.");

                MarkExtensionUnsupported(KHR_debug);
                mSymbols.fDebugMessageControl  = nullptr;
                mSymbols.fDebugMessageInsert   = nullptr;
                mSymbols.fDebugMessageCallback = nullptr;
                mSymbols.fGetDebugMessageLog   = nullptr;
                mSymbols.fGetPointerv          = nullptr;
                mSymbols.fPushDebugGroup       = nullptr;
                mSymbols.fPopDebugGroup        = nullptr;
                mSymbols.fObjectLabel          = nullptr;
                mSymbols.fGetObjectLabel       = nullptr;
                mSymbols.fObjectPtrLabel       = nullptr;
                mSymbols.fGetObjectPtrLabel    = nullptr;
            }
        }

        // Load developer symbols, don't fail if we can't find them.
        SymLoadStruct auxSymbols[] = {
                { (PRFuncPtr*) &mSymbols.fGetTexImage, { "GetTexImage", nullptr } },
                { (PRFuncPtr*) &mSymbols.fGetTexLevelParameteriv, { "GetTexLevelParameteriv", nullptr } },
                { nullptr, { nullptr } },
        };
        bool warnOnFailures = DebugMode();
        LoadSymbols(&auxSymbols[0], trygl, prefix, warnOnFailures);
    }

    if (mInitialized) {
        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]));

        raw_fGetIntegerv(LOCAL_GL_MAX_TEXTURE_SIZE, &mMaxTextureSize);
        raw_fGetIntegerv(LOCAL_GL_MAX_CUBE_MAP_TEXTURE_SIZE, &mMaxCubeMapTextureSize);
        raw_fGetIntegerv(LOCAL_GL_MAX_RENDERBUFFER_SIZE, &mMaxRenderbufferSize);

#ifdef XP_MACOSX
        if (mWorkAroundDriverBugs) {
            if (mVendor == VendorIntel) {
                // see bug 737182 for 2D textures, bug 684882 for cube map textures.
                mMaxTextureSize        = std::min(mMaxTextureSize,        4096);
                mMaxCubeMapTextureSize = std::min(mMaxCubeMapTextureSize, 512);
                // for good measure, we align renderbuffers on what we do for 2D textures
                mMaxRenderbufferSize   = std::min(mMaxRenderbufferSize,   4096);
                mNeedsTextureSizeChecks = true;
            } else if (mVendor == VendorNVIDIA) {
                SInt32 major, minor;
                OSErr err1 = ::Gestalt(gestaltSystemVersionMajor, &major);
                OSErr err2 = ::Gestalt(gestaltSystemVersionMinor, &minor);

                if (err1 != noErr || err2 != noErr ||
                    major < 10 || (major == 10 && minor < 8)) {
                    // See bug 877949.
                    mMaxTextureSize = std::min(mMaxTextureSize, 4096);
                    mMaxRenderbufferSize = std::min(mMaxRenderbufferSize, 4096);
                }
                else {
                    // See bug 879656.  8192 fails, 8191 works.
                    mMaxTextureSize = std::min(mMaxTextureSize, 8191);
                    mMaxRenderbufferSize = std::min(mMaxRenderbufferSize, 8191);
                }
                // Part of the bug 879656, but it also doesn't hurt the 877949
                mNeedsTextureSizeChecks = true;
            }
        }
#endif
#ifdef MOZ_X11
        if (mWorkAroundDriverBugs &&
            mVendor == VendorNouveau) {
            // see bug 814716. Clamp MaxCubeMapTextureSize at 2K for Nouveau.
            mMaxCubeMapTextureSize = std::min(mMaxCubeMapTextureSize, 2048);
            mNeedsTextureSizeChecks = true;
        }
#endif

        mMaxTextureImageSize = mMaxTextureSize;

        mMaxSamples = 0;
        if (IsSupported(GLFeature::framebuffer_multisample)) {
            fGetIntegerv(LOCAL_GL_MAX_SAMPLES, (GLint*)&mMaxSamples);
        }

        // We're ready for final setup.
        fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, 0);

        if (mCaps.any)
            DetermineCaps();

        UpdatePixelFormat();
        UpdateGLFormats(mCaps);

        mTexGarbageBin = new TextureGarbageBin(this);

        MOZ_ASSERT(IsCurrent());
    }

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

    mVersionString = nsPrintfCString("%u.%u.%u", mVersion / 100, (mVersion / 10) % 10, mVersion % 10);

    return mInitialized;
}

void
GLContext::InitExtensions()
{
    MakeCurrent();
    const char* extensions = (const char*)fGetString(LOCAL_GL_EXTENSIONS);
    if (!extensions)
        return;

#ifdef DEBUG
    static bool firstRun = true;
#else
    // Non-DEBUG, so never spew.
    const bool firstRun = false;
#endif

    InitializeExtensionsBitSet(mAvailableExtensions, extensions, sExtensionNames, firstRun && DebugMode());

    if (WorkAroundDriverBugs() &&
        Vendor() == VendorQualcomm) {

        // Some Adreno drivers do not report GL_OES_EGL_sync, but they really do support it.
        MarkExtensionSupported(OES_EGL_sync);
    }

    if (WorkAroundDriverBugs() &&
        Renderer() == RendererAndroidEmulator) {
        // the Android emulator, which we use to run B2G reftests on,
        // doesn't expose the OES_rgb8_rgba8 extension, but it seems to
        // support it (tautologically, as it only runs on desktop GL).
        MarkExtensionSupported(OES_rgb8_rgba8);
    }

#ifdef DEBUG
    firstRun = false;
#endif
}


// Take texture data in a given buffer and copy it into a larger buffer,
// padding out the edge pixels for filtering if necessary
static void
CopyAndPadTextureData(const GLvoid* srcBuffer,
                      GLvoid* dstBuffer,
                      GLsizei srcWidth, GLsizei srcHeight,
                      GLsizei dstWidth, GLsizei dstHeight,
                      GLsizei stride, GLint pixelsize)
{
    unsigned char *rowDest = static_cast<unsigned char*>(dstBuffer);
    const unsigned char *source = static_cast<const unsigned char*>(srcBuffer);

    for (GLsizei h = 0; h < srcHeight; ++h) {
        memcpy(rowDest, source, srcWidth * pixelsize);
        rowDest += dstWidth * pixelsize;
        source += stride;
    }

    GLsizei padHeight = srcHeight;

    // Pad out an extra row of pixels so that edge filtering doesn't use garbage data
    if (dstHeight > srcHeight) {
        memcpy(rowDest, source - stride, srcWidth * pixelsize);
        padHeight++;
    }

    // Pad out an extra column of pixels
    if (dstWidth > srcWidth) {
        rowDest = static_cast<unsigned char*>(dstBuffer) + srcWidth * pixelsize;
        for (GLsizei h = 0; h < padHeight; ++h) {
            memcpy(rowDest, rowDest - pixelsize, pixelsize);
            rowDest += dstWidth * pixelsize;
        }
    }
}

// In both of these cases (for the Adreno at least) it is impossible
// to determine good or bad driver versions for POT texture uploads,
// so blacklist them all. Newer drivers use a different rendering
// string in the form "Adreno (TM) 200" and the drivers we've seen so
// far work fine with NPOT textures, so don't blacklist those until we
// have evidence of any problems with them.
bool
GLContext::CanUploadSubTextures()
{
    if (!mWorkAroundDriverBugs)
        return true;

    // There are certain GPUs that we don't want to use glTexSubImage2D on
    // because that function can be very slow and/or buggy
    if (Renderer() == RendererAdreno200 || Renderer() == RendererAdreno205)
        return false;

    // On PowerVR glTexSubImage does a readback, so it will be slower
    // than just doing a glTexImage2D() directly. i.e. 26ms vs 10ms
    if (Renderer() == RendererSGX540 || Renderer() == RendererSGX530)
        return false;

    return true;
}

bool GLContext::sPowerOfTwoForced = false;
bool GLContext::sPowerOfTwoPrefCached = false;

void
GLContext::PlatformStartup()
{
  CacheCanUploadNPOT();
  NS_RegisterMemoryReporter(new GfxTexturesReporter());
}

void
GLContext::CacheCanUploadNPOT()
{
    MOZ_ASSERT(NS_IsMainThread(), "Can't cache prefs off the main thread.");
    MOZ_ASSERT(!sPowerOfTwoPrefCached, "Must only call this function once!");

    sPowerOfTwoPrefCached = true;
    mozilla::Preferences::AddBoolVarCache(&sPowerOfTwoForced,
                                          "gfx.textures.poweroftwo.force-enabled");
}

bool
GLContext::CanUploadNonPowerOfTwo()
{
    MOZ_ASSERT(sPowerOfTwoPrefCached);

    if (!mWorkAroundDriverBugs)
        return true;

    // Some GPUs driver crash when uploading non power of two 565 textures.
    return sPowerOfTwoForced ? false : (Renderer() != RendererAdreno200 &&
                                        Renderer() != RendererAdreno205);
}

bool
GLContext::WantsSmallTiles()
{
    // We must use small tiles for good performance if we can't use
    // glTexSubImage2D() for some reason.
    if (!CanUploadSubTextures())
        return true;

    // We can't use small tiles on the SGX 540, because of races in texture upload.
    if (mWorkAroundDriverBugs &&
        Renderer() == RendererSGX540)
        return false;

    // Don't use small tiles otherwise. (If we implement incremental texture upload,
    // then we will want to revisit this.)
    return false;
}

// Common code for checking for both GL extensions and GLX extensions.
bool
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 == nullptr || extension == nullptr)
        return false;

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

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

already_AddRefed<TextureImage>
GLContext::CreateTextureImage(const nsIntSize& aSize,
                              TextureImage::ContentType aContentType,
                              GLenum aWrapMode,
                              TextureImage::Flags aFlags,
                              TextureImage::ImageFormat aImageFormat)
{
    return CreateBasicTextureImage(this, aSize, aContentType, aWrapMode,
                                   aFlags, aImageFormat);
}

void GLContext::ApplyFilterToBoundTexture(GraphicsFilter aFilter)
{
    ApplyFilterToBoundTexture(LOCAL_GL_TEXTURE_2D, aFilter);
}

void GLContext::ApplyFilterToBoundTexture(GLuint aTarget,
                                          GraphicsFilter aFilter)
{
    if (aFilter == GraphicsFilter::FILTER_NEAREST) {
        fTexParameteri(aTarget, LOCAL_GL_TEXTURE_MIN_FILTER, LOCAL_GL_NEAREST);
        fTexParameteri(aTarget, LOCAL_GL_TEXTURE_MAG_FILTER, LOCAL_GL_NEAREST);
    } else {
        fTexParameteri(aTarget, LOCAL_GL_TEXTURE_MIN_FILTER, LOCAL_GL_LINEAR);
        fTexParameteri(aTarget, LOCAL_GL_TEXTURE_MAG_FILTER, LOCAL_GL_LINEAR);
    }
}


void
GLContext::DetermineCaps()
{
    PixelBufferFormat format = QueryPixelFormat();

    SurfaceCaps caps;
    caps.color = !!format.red && !!format.green && !!format.blue;
    caps.bpp16 = caps.color && format.ColorBits() == 16;
    caps.alpha = !!format.alpha;
    caps.depth = !!format.depth;
    caps.stencil = !!format.stencil;
    caps.antialias = format.samples > 1;
    caps.preserve = true;

    mCaps = caps;
}

PixelBufferFormat
GLContext::QueryPixelFormat()
{
    PixelBufferFormat format;

    ScopedBindFramebuffer autoFB(this, 0);

    fGetIntegerv(LOCAL_GL_RED_BITS  , &format.red  );
    fGetIntegerv(LOCAL_GL_GREEN_BITS, &format.green);
    fGetIntegerv(LOCAL_GL_BLUE_BITS , &format.blue );
    fGetIntegerv(LOCAL_GL_ALPHA_BITS, &format.alpha);

    fGetIntegerv(LOCAL_GL_DEPTH_BITS, &format.depth);
    fGetIntegerv(LOCAL_GL_STENCIL_BITS, &format.stencil);

    fGetIntegerv(LOCAL_GL_SAMPLES, &format.samples);

    return format;
}

void
GLContext::UpdatePixelFormat()
{
    PixelBufferFormat format = QueryPixelFormat();
#ifdef DEBUG
    const SurfaceCaps& caps = Caps();
    MOZ_ASSERT(!caps.any, "Did you forget to DetermineCaps()?");

    MOZ_ASSERT(caps.color == !!format.red);
    MOZ_ASSERT(caps.color == !!format.green);
    MOZ_ASSERT(caps.color == !!format.blue);

    MOZ_ASSERT(caps.alpha == !!format.alpha);

    // These we either must have if they're requested, or
    // we can have if they're not.
    MOZ_ASSERT(caps.depth == !!format.depth || !caps.depth);
    MOZ_ASSERT(caps.stencil == !!format.stencil || !caps.stencil);

    MOZ_ASSERT(caps.antialias == (format.samples > 1));
#endif
    mPixelFormat = new PixelBufferFormat(format);
}

GLFormats
GLContext::ChooseGLFormats(const SurfaceCaps& caps) const
{
    GLFormats formats;

    // If we're on ES2 hardware and we have an explicit request for 16 bits of color or less
    // OR we don't support full 8-bit color, return a 4444 or 565 format.
    bool bpp16 = caps.bpp16;
    if (IsGLES2()) {
        if (!IsExtensionSupported(OES_rgb8_rgba8))
            bpp16 = true;
    } else {
        // RGB565 is uncommon on desktop, requiring ARB_ES2_compatibility.
        // Since it's also vanishingly useless there, let's not support it.
        bpp16 = false;
    }

    if (bpp16) {
        MOZ_ASSERT(IsGLES2());
        if (caps.alpha) {
            formats.color_texInternalFormat = LOCAL_GL_RGBA;
            formats.color_texFormat = LOCAL_GL_RGBA;
            formats.color_texType   = LOCAL_GL_UNSIGNED_SHORT_4_4_4_4;
            formats.color_rbFormat  = LOCAL_GL_RGBA4;
        } else {
            formats.color_texInternalFormat = LOCAL_GL_RGB;
            formats.color_texFormat = LOCAL_GL_RGB;
            formats.color_texType   = LOCAL_GL_UNSIGNED_SHORT_5_6_5;
            formats.color_rbFormat  = LOCAL_GL_RGB565;
        }
    } else {
        formats.color_texType = LOCAL_GL_UNSIGNED_BYTE;

        if (caps.alpha) {
            formats.color_texInternalFormat = IsGLES2() ? LOCAL_GL_RGBA : LOCAL_GL_RGBA8;
            formats.color_texFormat = LOCAL_GL_RGBA;
            formats.color_rbFormat  = LOCAL_GL_RGBA8;
        } else {
            formats.color_texInternalFormat = IsGLES2() ? LOCAL_GL_RGB : LOCAL_GL_RGB8;
            formats.color_texFormat = LOCAL_GL_RGB;
            formats.color_rbFormat  = LOCAL_GL_RGB8;
        }
    }

    uint32_t msaaLevel = Preferences::GetUint("gl.msaa-level", 2);
    GLsizei samples = msaaLevel * msaaLevel;
    samples = std::min(samples, mMaxSamples);

    // Bug 778765.
    if (WorkAroundDriverBugs() && samples == 1) {
        samples = 0;
    }
    formats.samples = samples;


    // Be clear that these are 0 if unavailable.
    formats.depthStencil = 0;
    if (!IsGLES2() || IsExtensionSupported(OES_packed_depth_stencil)) {
        formats.depthStencil = LOCAL_GL_DEPTH24_STENCIL8;
    }

    formats.depth = 0;
    if (IsGLES2()) {
        if (IsExtensionSupported(OES_depth24)) {
            formats.depth = LOCAL_GL_DEPTH_COMPONENT24;
        } else {
            formats.depth = LOCAL_GL_DEPTH_COMPONENT16;
        }
    } else {
        formats.depth = LOCAL_GL_DEPTH_COMPONENT24;
    }

    formats.stencil = LOCAL_GL_STENCIL_INDEX8;

    return formats;
}

GLuint
GLContext::CreateTextureForOffscreen(const GLFormats& formats, const gfxIntSize& size)
{
    MOZ_ASSERT(formats.color_texInternalFormat);
    MOZ_ASSERT(formats.color_texFormat);
    MOZ_ASSERT(formats.color_texType);

    return CreateTexture(formats.color_texInternalFormat,
                         formats.color_texFormat,
                         formats.color_texType,
                         size);
}

GLuint
GLContext::CreateTexture(GLenum internalFormat, GLenum format, GLenum type, const gfxIntSize& size)
{
    GLuint tex = 0;
    fGenTextures(1, &tex);
    ScopedBindTexture autoTex(this, tex);

    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);

    fTexImage2D(LOCAL_GL_TEXTURE_2D,
                0,
                internalFormat,
                size.width, size.height,
                0,
                format,
                type,
                nullptr);

    return tex;
}

static inline void
RenderbufferStorageBySamples(GLContext* gl, GLsizei samples, GLenum internalFormat, const gfxIntSize& size)
{
    if (samples) {
        gl->fRenderbufferStorageMultisample(LOCAL_GL_RENDERBUFFER,
                                            samples,
                                            internalFormat,
                                            size.width, size.height);
    } else {
        gl->fRenderbufferStorage(LOCAL_GL_RENDERBUFFER,
                                 internalFormat,
                                 size.width, size.height);
    }
}

GLuint
GLContext::CreateRenderbuffer(GLenum format, GLsizei samples, const gfxIntSize& size)
{
    GLuint rb = 0;
    fGenRenderbuffers(1, &rb);
    ScopedBindRenderbuffer autoRB(this, rb);

    RenderbufferStorageBySamples(this, samples, format, size);

    return rb;
}

void
GLContext::CreateRenderbuffersForOffscreen(const GLFormats& formats, const gfxIntSize& size,
                                           bool multisample,
                                           GLuint* colorMSRB, GLuint* depthRB, GLuint* stencilRB)
{
    GLsizei samples = multisample ? formats.samples : 0;
    if (colorMSRB) {
        MOZ_ASSERT(formats.samples > 0);
        MOZ_ASSERT(formats.color_rbFormat);

        *colorMSRB = CreateRenderbuffer(formats.color_rbFormat, samples, size);
    }

    if (depthRB &&
        stencilRB &&
        formats.depthStencil)
    {
        *depthRB = CreateRenderbuffer(formats.depthStencil, samples, size);
        *stencilRB = *depthRB;
    } else {
        if (depthRB) {
            MOZ_ASSERT(formats.depth);

            *depthRB = CreateRenderbuffer(formats.depth, samples, size);
        }

        if (stencilRB) {
            MOZ_ASSERT(formats.stencil);

            *stencilRB = CreateRenderbuffer(formats.stencil, samples, size);
        }
    }
}

bool
GLContext::IsFramebufferComplete(GLuint fb, GLenum* pStatus)
{
    MOZ_ASSERT(fb);

    ScopedBindFramebuffer autoFB(this, fb);
    MOZ_ASSERT(fIsFramebuffer(fb));

    GLenum status = fCheckFramebufferStatus(LOCAL_GL_FRAMEBUFFER);
    if (pStatus)
        *pStatus = status;

    return status == LOCAL_GL_FRAMEBUFFER_COMPLETE;
}

void
GLContext::AttachBuffersToFB(GLuint colorTex, GLuint colorRB,
                             GLuint depthRB, GLuint stencilRB,
                             GLuint fb, GLenum target)
{
    MOZ_ASSERT(fb);
    MOZ_ASSERT( !(colorTex && colorRB) );

    ScopedBindFramebuffer autoFB(this, fb);
    MOZ_ASSERT(fIsFramebuffer(fb)); // It only counts after being bound.

    if (colorTex) {
        MOZ_ASSERT(fIsTexture(colorTex));
        MOZ_ASSERT(target == LOCAL_GL_TEXTURE_2D ||
                   target == LOCAL_GL_TEXTURE_RECTANGLE_ARB);
        fFramebufferTexture2D(LOCAL_GL_FRAMEBUFFER,
                              LOCAL_GL_COLOR_ATTACHMENT0,
                              target,
                              colorTex,
                              0);
    } else if (colorRB) {
        MOZ_ASSERT(fIsRenderbuffer(colorRB));
        fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                 LOCAL_GL_COLOR_ATTACHMENT0,
                                 LOCAL_GL_RENDERBUFFER,
                                 colorRB);
    }

    if (depthRB) {
        MOZ_ASSERT(fIsRenderbuffer(depthRB));
        fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                 LOCAL_GL_DEPTH_ATTACHMENT,
                                 LOCAL_GL_RENDERBUFFER,
                                 depthRB);
    }

    if (stencilRB) {
        MOZ_ASSERT(fIsRenderbuffer(stencilRB));
        fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                 LOCAL_GL_STENCIL_ATTACHMENT,
                                 LOCAL_GL_RENDERBUFFER,
                                 stencilRB);
    }
}

bool
GLContext::AssembleOffscreenFBs(const GLuint colorMSRB,
                                const GLuint depthRB,
                                const GLuint stencilRB,
                                const GLuint texture,
                                GLuint* drawFB_out,
                                GLuint* readFB_out)
{
    if (!colorMSRB && !texture) {
        MOZ_ASSERT(!depthRB && !stencilRB);

        if (drawFB_out)
            *drawFB_out = 0;
        if (readFB_out)
            *readFB_out = 0;

        return true;
    }

    ScopedBindFramebuffer autoFB(this);

    GLuint drawFB = 0;
    GLuint readFB = 0;

    if (texture) {
        readFB = 0;
        fGenFramebuffers(1, &readFB);
        BindFB(readFB);
        fFramebufferTexture2D(LOCAL_GL_FRAMEBUFFER,
                              LOCAL_GL_COLOR_ATTACHMENT0,
                              LOCAL_GL_TEXTURE_2D,
                              texture,
                              0);
    }

    if (colorMSRB) {
        drawFB = 0;
        fGenFramebuffers(1, &drawFB);
        BindFB(drawFB);
        fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                 LOCAL_GL_COLOR_ATTACHMENT0,
                                 LOCAL_GL_RENDERBUFFER,
                                 colorMSRB);
    } else {
        drawFB = readFB;
    }
    MOZ_ASSERT(GetFB() == drawFB);

    if (depthRB) {
        fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                 LOCAL_GL_DEPTH_ATTACHMENT,
                                 LOCAL_GL_RENDERBUFFER,
                                 depthRB);
    }

    if (stencilRB) {
        fFramebufferRenderbuffer(LOCAL_GL_FRAMEBUFFER,
                                 LOCAL_GL_STENCIL_ATTACHMENT,
                                 LOCAL_GL_RENDERBUFFER,
                                 stencilRB);
    }

    // We should be all resized.  Check for framebuffer completeness.
    GLenum status;
    bool isComplete = true;

    if (!IsFramebufferComplete(drawFB, &status)) {
        NS_WARNING("DrawFBO: Incomplete");
  #ifdef DEBUG
        if (DebugMode()) {
            printf_stderr("Framebuffer status: %X\n", status);
        }
  #endif
        isComplete = false;
    }

    if (!IsFramebufferComplete(readFB, &status)) {
        NS_WARNING("ReadFBO: Incomplete");
  #ifdef DEBUG
        if (DebugMode()) {
            printf_stderr("Framebuffer status: %X\n", status);
        }
  #endif
        isComplete = false;
    }

    if (drawFB_out) {
        *drawFB_out = drawFB;
    } else if (drawFB) {
        NS_RUNTIMEABORT("drawFB created when not requested!");
    }

    if (readFB_out) {
        *readFB_out = readFB;
    } else if (readFB) {
        NS_RUNTIMEABORT("readFB created when not requested!");
    }

    return isComplete;
}



bool
GLContext::PublishFrame()
{
    MOZ_ASSERT(mScreen);

    if (!mScreen->PublishFrame(OffscreenSize()))
        return false;

    return true;
}

SharedSurface*
GLContext::RequestFrame()
{
    MOZ_ASSERT(mScreen);

    return mScreen->Stream()->SwapConsumer();
}



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, OffscreenSize().width, OffscreenSize().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::MarkDestroyed()
{
    if (IsDestroyed())
        return;

    if (MakeCurrent()) {
        DestroyScreenBuffer();

        // This is for Blit{Tex,FB}To{TexFB}.
        DeleteTexBlitProgram();

        // Likely used by OGL Layers.
        fDeleteProgram(mBlitProgram);
        mBlitProgram = 0;
        fDeleteFramebuffers(1, &mBlitFramebuffer);
        mBlitFramebuffer = 0;

        mTexGarbageBin->GLContextTeardown();
    } else {
        NS_WARNING("MakeCurrent() failed during MarkDestroyed! Skipping GL object teardown.");
    }

    mSymbols.Zero();
}

static void SwapRAndBComponents(gfxImageSurface* surf)
{
  uint8_t *row = surf->Data();

  size_t rowBytes = surf->Width()*4;
  size_t rowHole = surf->Stride() - rowBytes;

  size_t rows = surf->Height();

  while (rows) {

    const uint8_t *rowEnd = row + rowBytes;

    while (row != rowEnd) {
      row[0] ^= row[2];
      row[2] ^= row[0];
      row[0] ^= row[2];
      row += 4;
    }

    row += rowHole;
    --rows;
  }
}

static already_AddRefed<gfxImageSurface> YInvertImageSurface(gfxImageSurface* aSurf)
{
  gfxIntSize size = aSurf->GetSize();
  nsRefPtr<gfxImageSurface> temp = new gfxImageSurface(size, aSurf->Format());
  nsRefPtr<gfxContext> ctx = new gfxContext(temp);
  ctx->SetOperator(gfxContext::OPERATOR_SOURCE);
  ctx->Scale(1.0, -1.0);
  ctx->Translate(-gfxPoint(0.0, size.height));
  ctx->SetSource(aSurf);
  ctx->Paint();
  return temp.forget();
}

already_AddRefed<gfxImageSurface>
GLContext::GetTexImage(GLuint aTexture, bool aYInvert, SurfaceFormat aFormat)
{
    MakeCurrent();
    GuaranteeResolve();
    fActiveTexture(LOCAL_GL_TEXTURE0);
    fBindTexture(LOCAL_GL_TEXTURE_2D, aTexture);

    gfxIntSize size;
    fGetTexLevelParameteriv(LOCAL_GL_TEXTURE_2D, 0, LOCAL_GL_TEXTURE_WIDTH, &size.width);
    fGetTexLevelParameteriv(LOCAL_GL_TEXTURE_2D, 0, LOCAL_GL_TEXTURE_HEIGHT, &size.height);

    nsRefPtr<gfxImageSurface> surf = new gfxImageSurface(size, gfxImageFormatARGB32);
    if (!surf || surf->CairoStatus()) {
        return nullptr;
    }

    uint32_t currentPackAlignment = 0;
    fGetIntegerv(LOCAL_GL_PACK_ALIGNMENT, (GLint*)&currentPackAlignment);
    if (currentPackAlignment != 4) {
        fPixelStorei(LOCAL_GL_PACK_ALIGNMENT, 4);
    }
    fGetTexImage(LOCAL_GL_TEXTURE_2D, 0, LOCAL_GL_RGBA, LOCAL_GL_UNSIGNED_BYTE, surf->Data());
    if (currentPackAlignment != 4) {
        fPixelStorei(LOCAL_GL_PACK_ALIGNMENT, currentPackAlignment);
    }

    if (aFormat == FORMAT_R8G8B8A8 || aFormat == FORMAT_R8G8B8X8) {
      SwapRAndBComponents(surf);
    }

    if (aYInvert) {
      surf = YInvertImageSurface(surf);
    }
    return surf.forget();
}

already_AddRefed<gfxImageSurface>
GLContext::ReadTextureImage(GLuint aTexture,
                            const gfxIntSize& aSize,
                            GLenum aTextureFormat,
                            bool aYInvert)
{
    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, nullptr);
    fShaderSource(fs, 1, (const GLchar**) &fShader, nullptr);
    fCompileShader(vs);
    fCompileShader(fs);
    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, gfxImageFormatARGB32);
    if (!isurf || isurf->CairoStatus()) {
        isurf = nullptr;
        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());

    SwapRAndBComponents(isurf);

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

    if (aYInvert) {
      isurf = YInvertImageSurface(isurf);
    }

 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();
}

static bool
GetActualReadFormats(GLContext* gl, GLenum destFormat, GLenum destType,
                     GLenum& readFormat, GLenum& readType)
{
    if (destFormat == LOCAL_GL_RGBA &&
        destType == LOCAL_GL_UNSIGNED_BYTE)
    {
        readFormat = destFormat;
        readType = destType;
        return true;
    }

    bool fallback = true;
    if (gl->IsGLES2()) {
        GLenum auxFormat = 0;
        GLenum auxType = 0;

        gl->fGetIntegerv(LOCAL_GL_IMPLEMENTATION_COLOR_READ_FORMAT, (GLint*)&auxFormat);
        gl->fGetIntegerv(LOCAL_GL_IMPLEMENTATION_COLOR_READ_TYPE, (GLint*)&auxType);

        if (destFormat == auxFormat &&
            destType == auxType)
        {
            fallback = false;
        }
    } else {
        switch (destFormat) {
            case LOCAL_GL_RGB: {
                if (destType == LOCAL_GL_UNSIGNED_SHORT_5_6_5_REV)
                    fallback = false;
                break;
            }
            case LOCAL_GL_BGRA: {
                if (destType == LOCAL_GL_UNSIGNED_INT_8_8_8_8_REV)
                    fallback = false;
                break;
            }
        }
    }

    if (fallback) {
        readFormat = LOCAL_GL_RGBA;
        readType = LOCAL_GL_UNSIGNED_BYTE;
        return false;
    } else {
        readFormat = destFormat;
        readType = destType;
        return true;
    }
}

void
GLContext::ReadScreenIntoImageSurface(gfxImageSurface* dest)
{
    ScopedBindFramebuffer autoFB(this, 0);

    ReadPixelsIntoImageSurface(dest);
}

TemporaryRef<SourceSurface>
GLContext::ReadPixelsToSourceSurface(const gfx::IntSize &aSize)
{
    // XXX we should do this properly one day without using the gfxImageSurface
    RefPtr<DataSourceSurface> dataSourceSurface =
        Factory::CreateDataSourceSurface(aSize, gfx::FORMAT_B8G8R8A8);
    nsRefPtr<gfxImageSurface> surf =
        new gfxImageSurface(dataSourceSurface->GetData(),
                            gfxIntSize(aSize.width, aSize.height),
                            dataSourceSurface->Stride(),
                            gfxImageFormatARGB32);
    ReadPixelsIntoImageSurface(surf);
    dataSourceSurface->MarkDirty();

    return dataSourceSurface;
}

void
GLContext::ReadPixelsIntoImageSurface(gfxImageSurface* dest)
{
    MakeCurrent();
    MOZ_ASSERT(dest->GetSize() != gfxIntSize(0, 0));

    /* gfxImageFormatARGB32:
     * RGBA+UByte: be[RGBA], le[ABGR]
     * RGBA+UInt: le[RGBA]
     * BGRA+UInt: le[BGRA]
     * BGRA+UIntRev: le[ARGB]
     *
     * gfxImageFormatRGB16_565:
     * RGB+UShort: le[rrrrrggg,gggbbbbb]
     */
    bool hasAlpha = dest->Format() == gfxImageFormatARGB32;

    int destPixelSize;
    GLenum destFormat;
    GLenum destType;

    switch (dest->Format()) {
        case gfxImageFormatRGB24: // XRGB
        case gfxImageFormatARGB32:
            destPixelSize = 4;
            // Needs host (little) endian ARGB.
            destFormat = LOCAL_GL_BGRA;
            destType = LOCAL_GL_UNSIGNED_INT_8_8_8_8_REV;
            break;

        case gfxImageFormatRGB16_565:
            destPixelSize = 2;
            destFormat = LOCAL_GL_RGB;
            destType = LOCAL_GL_UNSIGNED_SHORT_5_6_5_REV;
            break;

        default:
            MOZ_CRASH("Bad format.");
    }
    MOZ_ASSERT(dest->Stride() == dest->Width() * destPixelSize);

    GLenum readFormat = destFormat;
    GLenum readType = destType;
    bool needsTempSurf = !GetActualReadFormats(this,
                                               destFormat, destType,
                                               readFormat, readType);

    nsAutoPtr<gfxImageSurface> tempSurf;
    gfxImageSurface* readSurf = nullptr;
    int readPixelSize = 0;
    if (needsTempSurf) {
        if (DebugMode()) {
            NS_WARNING("Needing intermediary surface for ReadPixels. This will be slow!");
        }
        ImageFormat readFormatGFX;

        switch (readFormat) {
            case LOCAL_GL_RGBA:
            case LOCAL_GL_BGRA: {
                readFormatGFX = hasAlpha ? gfxImageFormatARGB32
                                         : gfxImageFormatRGB24;
                break;
            }
            case LOCAL_GL_RGB: {
                MOZ_ASSERT(readPixelSize == 2);
                MOZ_ASSERT(readType == LOCAL_GL_UNSIGNED_SHORT_5_6_5_REV);
                readFormatGFX = gfxImageFormatRGB16_565;
                break;
            }
            default: {
                MOZ_CRASH("Bad read format.");
            }
        }

        switch (readType) {
            case LOCAL_GL_UNSIGNED_BYTE: {
                MOZ_ASSERT(readFormat == LOCAL_GL_RGBA);
                readPixelSize = 4;
                break;
            }
            case LOCAL_GL_UNSIGNED_INT_8_8_8_8_REV: {
                MOZ_ASSERT(readFormat == LOCAL_GL_BGRA);
                readPixelSize = 4;
                break;
            }
            case LOCAL_GL_UNSIGNED_SHORT_5_6_5_REV: {
                MOZ_ASSERT(readFormat == LOCAL_GL_RGB);
                readPixelSize = 2;
                break;
            }
            default: {
                MOZ_CRASH("Bad read type.");
            }
        }

        tempSurf = new gfxImageSurface(dest->GetSize(), readFormatGFX, false);
        readSurf = tempSurf;
    } else {
        readPixelSize = destPixelSize;
        readSurf = dest;
    }
    MOZ_ASSERT(readPixelSize);

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

    if (currentPackAlignment != readPixelSize)
        fPixelStorei(LOCAL_GL_PACK_ALIGNMENT, readPixelSize);

    GLsizei width = dest->Width();
    GLsizei height = dest->Height();

    readSurf->Flush();
    fReadPixels(0, 0,
                width, height,
                readFormat, readType,
                readSurf->Data());
    readSurf->MarkDirty();

    if (currentPackAlignment != readPixelSize)
        fPixelStorei(LOCAL_GL_PACK_ALIGNMENT, currentPackAlignment);

    if (readSurf != dest) {
        MOZ_ASSERT(readFormat == LOCAL_GL_RGBA);
        MOZ_ASSERT(readType == LOCAL_GL_UNSIGNED_BYTE);
        // So we just copied in RGBA in big endian, or le: 0xAABBGGRR.
        // We want 0xAARRGGBB, so swap R and B:
        dest->Flush();
        SwapRAndBComponents(readSurf);
        dest->MarkDirty();

        gfxContext ctx(dest);
        ctx.SetOperator(gfxContext::OPERATOR_SOURCE);
        ctx.SetSource(readSurf);
        ctx.Paint();
    }

    // Check if GL is giving back 1.0 alpha for
    // RGBA reads to RGBA images from no-alpha buffers.
#ifdef XP_MACOSX
    if (WorkAroundDriverBugs() &&
        mVendor == VendorNVIDIA &&
        dest->Format() == gfxImageFormatARGB32 &&
        width && height)
    {
        GLint alphaBits = 0;
        fGetIntegerv(LOCAL_GL_ALPHA_BITS, &alphaBits);
        if (!alphaBits) {
            const uint32_t alphaMask = gfxPackedPixelNoPreMultiply(0xff,0,0,0);

            dest->Flush();
            uint32_t* itr = (uint32_t*)dest->Data();
            uint32_t testPixel = *itr;
            if ((testPixel & alphaMask) != alphaMask) {
                // We need to set the alpha channel to 1.0 manually.
                uint32_t* itrEnd = itr + width*height;  // Stride is guaranteed to be width*4.

                for (; itr != itrEnd; itr++) {
                    *itr |= alphaMask;
                }
            }
            dest->MarkDirty();
        }
    }
#endif
}

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!");

    if (aSrcRect.IsEmpty() || aDstRect.IsEmpty())
        return;

    int savedFb = 0;
    fGetIntegerv(LOCAL_GL_FRAMEBUFFER_BINDING, &savedFb);

    fDisable(LOCAL_GL_SCISSOR_TEST);
    fDisable(LOCAL_GL_BLEND);

    // 2.0 means scale up by two
    float blitScaleX = float(aDstRect.width) / float(aSrcRect.width);
    float blitScaleY = float(aDstRect.height) / float(aSrcRect.height);

    // We start iterating over all destination tiles
    aDst->BeginTileIteration();
    do {
        // calculate portion of the tile that is going to be painted to
        nsIntRect dstSubRect;
        nsIntRect dstTextureRect = ThebesIntRect(aDst->GetTileRect());
        dstSubRect.IntersectRect(aDstRect, dstTextureRect);

        // this tile is not part of the destination rectangle aDstRect
        if (dstSubRect.IsEmpty())
            continue;

        // (*) transform the rect of this tile into the rectangle defined by aSrcRect...
        nsIntRect dstInSrcRect(dstSubRect);
        dstInSrcRect.MoveBy(-aDstRect.TopLeft());
        // ...which might be of different size, hence scale accordingly
        dstInSrcRect.ScaleRoundOut(1.0f / blitScaleX, 1.0f / blitScaleY);
        dstInSrcRect.MoveBy(aSrcRect.TopLeft());

        SetBlitFramebufferForDestTexture(aDst->GetTextureID());
        UseBlitProgram();

        aSrc->BeginTileIteration();
        // now iterate over all tiles in the source Image...
        do {
            // calculate portion of the source tile that is in the source rect
            nsIntRect srcSubRect;
            nsIntRect srcTextureRect = ThebesIntRect(aSrc->GetTileRect());
            srcSubRect.IntersectRect(aSrcRect, srcTextureRect);

            // this tile is not part of the source rect
            if (srcSubRect.IsEmpty()) {
                continue;
            }
            // calculate intersection of source rect with destination rect
            srcSubRect.IntersectRect(srcSubRect, dstInSrcRect);
            // this tile does not overlap the current destination tile
            if (srcSubRect.IsEmpty()) {
                continue;
            }
            // We now have the intersection of
            //     the current source tile
            // and the desired source rectangle
            // and the destination tile
            // and the desired destination rectange
            // in destination space.
            // We need to transform this back into destination space, inverting the transform from (*)
            nsIntRect srcSubInDstRect(srcSubRect);
            srcSubInDstRect.MoveBy(-aSrcRect.TopLeft());
            srcSubInDstRect.ScaleRoundOut(blitScaleX, blitScaleY);
            srcSubInDstRect.MoveBy(aDstRect.TopLeft());

            // we transform these rectangles to be relative to the current src and dst tiles, respectively
            nsIntSize srcSize = srcTextureRect.Size();
            nsIntSize dstSize = dstTextureRect.Size();
            srcSubRect.MoveBy(-srcTextureRect.x, -srcTextureRect.y);
            srcSubInDstRect.MoveBy(-dstTextureRect.x, -dstTextureRect.y);

            float dx0 = 2.0f * float(srcSubInDstRect.x) / float(dstSize.width) - 1.0f;
            float dy0 = 2.0f * float(srcSubInDstRect.y) / float(dstSize.height) - 1.0f;
            float dx1 = 2.0f * float(srcSubInDstRect.x + srcSubInDstRect.width) / float(dstSize.width) - 1.0f;
            float dy1 = 2.0f * float(srcSubInDstRect.y + srcSubInDstRect.height) / float(dstSize.height) - 1.0f;
            PushViewportRect(nsIntRect(0, 0, dstSize.width, dstSize.height));

            RectTriangles rects;

            nsIntSize realTexSize = srcSize;
            if (!CanUploadNonPowerOfTwo()) {
                realTexSize = nsIntSize(NextPowerOfTwo(srcSize.width),
                                        NextPowerOfTwo(srcSize.height));
            }

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

                for (unsigned int i = 0; i < rects.elements(); ++i) {
                    v[i].x = (v[i].x * (dx1 - dx0)) + dx0;
                    v[i].y = (v[i].y * (dy1 - dy0)) + dy0;
                }
            }

            TextureImage::ScopedBindTexture texBind(aSrc, LOCAL_GL_TEXTURE0);

            fBindBuffer(LOCAL_GL_ARRAY_BUFFER, 0);

            fVertexAttribPointer(0, 2, LOCAL_GL_FLOAT, LOCAL_GL_FALSE, 0, rects.vertexPointer());
            fVertexAttribPointer(1, 2, LOCAL_GL_FLOAT, LOCAL_GL_FALSE, 0, rects.texCoordPointer());

            fEnableVertexAttribArray(0);
            fEnableVertexAttribArray(1);

            fDrawArrays(LOCAL_GL_TRIANGLES, 0, rects.elements());

            fDisableVertexAttribArray(0);
            fDisableVertexAttribArray(1);

            PopViewportRect();
        } while (aSrc->NextTile());
    } while (aDst->NextTile());

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

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

    fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, savedFb);

    fEnable(LOCAL_GL_SCISSOR_TEST);
    fEnable(LOCAL_GL_BLEND);
}

static unsigned int
DataOffset(const nsIntPoint &aPoint, int32_t aStride, gfxImageFormat aFormat)
{
  unsigned int data = aPoint.y * aStride;
  data += aPoint.x * gfxASurface::BytePerPixelFromFormat(aFormat);
  return data;
}

GLContext::SurfaceFormat
GLContext::UploadImageDataToTexture(unsigned char* aData,
                                    int32_t aStride,
                                    gfxImageFormat aFormat,
                                    const nsIntRegion& aDstRegion,
                                    GLuint& aTexture,
                                    bool aOverwrite,
                                    bool aPixelBuffer,
                                    GLenum aTextureUnit,
                                    GLenum aTextureTarget)
{
    bool textureInited = aOverwrite ? false : true;
    MakeCurrent();
    fActiveTexture(aTextureUnit);

    if (!aTexture) {
        fGenTextures(1, &aTexture);
        fBindTexture(aTextureTarget, aTexture);
        fTexParameteri(aTextureTarget,
                       LOCAL_GL_TEXTURE_MIN_FILTER,
                       LOCAL_GL_LINEAR);
        fTexParameteri(aTextureTarget,
                       LOCAL_GL_TEXTURE_MAG_FILTER,
                       LOCAL_GL_LINEAR);
        fTexParameteri(aTextureTarget,
                       LOCAL_GL_TEXTURE_WRAP_S,
                       LOCAL_GL_CLAMP_TO_EDGE);
        fTexParameteri(aTextureTarget,
                       LOCAL_GL_TEXTURE_WRAP_T,
                       LOCAL_GL_CLAMP_TO_EDGE);
        textureInited = false;
    } else {
        fBindTexture(aTextureTarget, aTexture);
    }

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

    GLenum format;
    GLenum internalFormat;
    GLenum type;
    int32_t pixelSize = gfxASurface::BytePerPixelFromFormat(aFormat);
    SurfaceFormat surfaceFormat;

    MOZ_ASSERT(GetPreferredARGB32Format() == LOCAL_GL_BGRA ||
               GetPreferredARGB32Format() == LOCAL_GL_RGBA);
    switch (aFormat) {
        case gfxImageFormatARGB32:
            if (GetPreferredARGB32Format() == LOCAL_GL_BGRA) {
              format = LOCAL_GL_BGRA;
              surfaceFormat = FORMAT_R8G8B8A8;
              type = LOCAL_GL_UNSIGNED_INT_8_8_8_8_REV;
            } else {
              format = LOCAL_GL_RGBA;
              surfaceFormat = FORMAT_B8G8R8A8;
              type = LOCAL_GL_UNSIGNED_BYTE;
            }
            internalFormat = LOCAL_GL_RGBA;
            break;
        case gfxImageFormatRGB24:
            // Treat RGB24 surfaces as RGBA32 except for the surface
            // format used.
            if (GetPreferredARGB32Format() == LOCAL_GL_BGRA) {
              format = LOCAL_GL_BGRA;
              surfaceFormat = FORMAT_R8G8B8X8;
              type = LOCAL_GL_UNSIGNED_INT_8_8_8_8_REV;
            } else {
              format = LOCAL_GL_RGBA;
              surfaceFormat = FORMAT_B8G8R8X8;
              type = LOCAL_GL_UNSIGNED_BYTE;
            }
            internalFormat = LOCAL_GL_RGBA;
            break;
        case gfxImageFormatRGB16_565:
            internalFormat = format = LOCAL_GL_RGB;
            type = LOCAL_GL_UNSIGNED_SHORT_5_6_5;
            surfaceFormat = FORMAT_R5G6B5;
            break;
        case gfxImageFormatA8:
            internalFormat = format = LOCAL_GL_LUMINANCE;
            type = LOCAL_GL_UNSIGNED_BYTE;
            // We don't have a specific luminance shader
            surfaceFormat = FORMAT_A8;
            break;
        default:
            NS_ASSERTION(false, "Unhandled image surface format!");
            format = 0;
            type = 0;
            surfaceFormat = FORMAT_UNKNOWN;
    }

    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 =
            aData + DataOffset(iterRect->TopLeft() - topLeft, aStride, aFormat);

        NS_ASSERTION(textureInited || (iterRect->x == 0 && iterRect->y == 0),
                     "Must be uploading to the origin when we don't have an existing texture");

        if (textureInited && CanUploadSubTextures()) {
            TexSubImage2D(aTextureTarget,
                          0,
                          iterRect->x,
                          iterRect->y,
                          iterRect->width,
                          iterRect->height,
                          aStride,
                          pixelSize,
                          format,
                          type,
                          rectData);
        } else {
            TexImage2D(aTextureTarget,
                       0,
                       internalFormat,
                       iterRect->width,
                       iterRect->height,
                       aStride,
                       pixelSize,
                       0,
                       format,
                       type,
                       rectData);
        }

    }

    return surfaceFormat;
}

GLContext::SurfaceFormat
GLContext::UploadSurfaceToTexture(gfxASurface *aSurface,
                                  const nsIntRegion& aDstRegion,
                                  GLuint& aTexture,
                                  bool aOverwrite,
                                  const nsIntPoint& aSrcPoint,
                                  bool aPixelBuffer,
                                  GLenum aTextureUnit,
                                  GLenum aTextureTarget)
{

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

    if (!imageSurface ||
        (imageSurface->Format() != gfxImageFormatARGB32 &&
         imageSurface->Format() != gfxImageFormatRGB24 &&
         imageSurface->Format() != gfxImageFormatRGB16_565 &&
         imageSurface->Format() != gfxImageFormatA8)) {
        // 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),
                              gfxImageFormatARGB32);

        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(aSrcPoint, imageSurface->Stride(),
                           imageSurface->Format());
    }

    MOZ_ASSERT(imageSurface);
    imageSurface->Flush();

    return UploadImageDataToTexture(data,
                                    imageSurface->Stride(),
                                    imageSurface->Format(),
                                    aDstRegion, aTexture, aOverwrite,
                                    aPixelBuffer, aTextureUnit, aTextureTarget);
}

static gfxImageFormat
ImageFormatForSurfaceFormat(gfx::SurfaceFormat aFormat)
{
    switch (aFormat) {
        case gfx::FORMAT_B8G8R8A8:
            return gfxImageFormatARGB32;
        case gfx::FORMAT_B8G8R8X8:
            return gfxImageFormatRGB24;
        case gfx::FORMAT_R5G6B5:
            return gfxImageFormatRGB16_565;
        case gfx::FORMAT_A8:
            return gfxImageFormatA8;
        default:
            return gfxImageFormatUnknown;
    }
}

GLContext::SurfaceFormat
GLContext::UploadSurfaceToTexture(gfx::DataSourceSurface *aSurface,
                                  const nsIntRegion& aDstRegion,
                                  GLuint& aTexture,
                                  bool aOverwrite,
                                  const nsIntPoint& aSrcPoint,
                                  bool aPixelBuffer,
                                  GLenum aTextureUnit,
                                  GLenum aTextureTarget)
{
    unsigned char* data = aPixelBuffer ? nullptr : aSurface->GetData();
    int32_t stride = aSurface->Stride();
    gfxImageFormat format =
        ImageFormatForSurfaceFormat(aSurface->GetFormat());
    data += DataOffset(aSrcPoint, stride, format);
    return UploadImageDataToTexture(data, stride, format,
                                    aDstRegion, aTexture, aOverwrite,
                                    aPixelBuffer, aTextureUnit,
                                    aTextureTarget);
}

static GLint GetAddressAlignment(ptrdiff_t aAddress)
{
    if (!(aAddress & 0x7)) {
       return 8;
    } else if (!(aAddress & 0x3)) {
        return 4;
    } else if (!(aAddress & 0x1)) {
        return 2;
    } else {
        return 1;
    }
}

void
GLContext::TexImage2D(GLenum target, GLint level, GLint internalformat,
                      GLsizei width, GLsizei height, GLsizei stride,
                      GLint pixelsize, GLint border, GLenum format,
                      GLenum type, const GLvoid *pixels)
{
    if (IsGLES2()) {

        NS_ASSERTION(format == (GLenum)internalformat,
                    "format and internalformat not the same for glTexImage2D on GLES2");

        if (!CanUploadNonPowerOfTwo()
            && (stride != width * pixelsize
            || !IsPowerOfTwo(width)
            || !IsPowerOfTwo(height))) {

            // Pad out texture width and height to the next power of two
            // as we don't support/want non power of two texture uploads
            GLsizei paddedWidth = NextPowerOfTwo(width);
            GLsizei paddedHeight = NextPowerOfTwo(height);

            GLvoid* paddedPixels = new unsigned char[paddedWidth * paddedHeight * pixelsize];

            // Pad out texture data to be in a POT sized buffer for uploading to
            // a POT sized texture
            CopyAndPadTextureData(pixels, paddedPixels, width, height,
                                  paddedWidth, paddedHeight, stride, pixelsize);

            fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT,
                    std::min(GetAddressAlignment((ptrdiff_t)paddedPixels),
                            GetAddressAlignment((ptrdiff_t)paddedWidth * pixelsize)));
            fTexImage2D(target,
                        border,
                        internalformat,
                        paddedWidth,
                        paddedHeight,
                        border,
                        format,
                        type,
                        paddedPixels);
            fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 4);

            delete[] static_cast<unsigned char*>(paddedPixels);
            return;
        }

        if (stride == width * pixelsize) {
            fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT,
                    std::min(GetAddressAlignment((ptrdiff_t)pixels),
                            GetAddressAlignment((ptrdiff_t)stride)));
            fTexImage2D(target,
                        border,
                        internalformat,
                        width,
                        height,
                        border,
                        format,
                        type,
                        pixels);
            fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 4);
        } else {
            // Use GLES-specific workarounds for GL_UNPACK_ROW_LENGTH; these are
            // implemented in TexSubImage2D.
            fTexImage2D(target,
                        border,
                        internalformat,
                        width,
                        height,
                        border,
                        format,
                        type,
                        nullptr);
            TexSubImage2D(target,
                          level,
                          0,
                          0,
                          width,
                          height,
                          stride,
                          pixelsize,
                          format,
                          type,
                          pixels);
        }
    } else {
        // desktop GL (non-ES) path

        fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT,
                    std::min(GetAddressAlignment((ptrdiff_t)pixels),
                            GetAddressAlignment((ptrdiff_t)stride)));
        int rowLength = stride/pixelsize;
        fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, rowLength);
        fTexImage2D(target,
                    level,
                    internalformat,
                    width,
                    height,
                    border,
                    format,
                    type,
                    pixels);
        fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, 0);
        fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 4);
    }
}

void
GLContext::TexSubImage2D(GLenum target, GLint level,
                         GLint xoffset, GLint yoffset,
                         GLsizei width, GLsizei height, GLsizei stride,
                         GLint pixelsize, GLenum format,
                         GLenum type, const GLvoid* pixels)
{
    if (IsGLES2()) {
        if (stride == width * pixelsize) {
            fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT,
                    std::min(GetAddressAlignment((ptrdiff_t)pixels),
                            GetAddressAlignment((ptrdiff_t)stride)));
            fTexSubImage2D(target,
                          level,
                          xoffset,
                          yoffset,
                          width,
                          height,
                          format,
                          type,
                          pixels);
            fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 4);
        } else if (IsExtensionSupported(EXT_unpack_subimage)) {
            TexSubImage2DWithUnpackSubimageGLES(target, level, xoffset, yoffset,
                                                width, height, stride,
                                                pixelsize, format, type, pixels);

        } else {
            TexSubImage2DWithoutUnpackSubimage(target, level, xoffset, yoffset,
                                              width, height, stride,
                                              pixelsize, format, type, pixels);
        }
    } else {
        // desktop GL (non-ES) path
        fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT,
                    std::min(GetAddressAlignment((ptrdiff_t)pixels),
                            GetAddressAlignment((ptrdiff_t)stride)));
        int rowLength = stride/pixelsize;
        fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, rowLength);
        fTexSubImage2D(target,
                      level,
                      xoffset,
                      yoffset,
                      width,
                      height,
                      format,
                      type,
                      pixels);
        fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, 0);
        fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 4);
    }
}

void
GLContext::TexSubImage2DWithUnpackSubimageGLES(GLenum target, GLint level,
                                               GLint xoffset, GLint yoffset,
                                               GLsizei width, GLsizei height,
                                               GLsizei stride, GLint pixelsize,
                                               GLenum format, GLenum type,
                                               const GLvoid* pixels)
{
    fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT,
                 std::min(GetAddressAlignment((ptrdiff_t)pixels),
                        GetAddressAlignment((ptrdiff_t)stride)));
    // When using GL_UNPACK_ROW_LENGTH, we need to work around a Tegra
    // driver crash where the driver apparently tries to read
    // (stride - width * pixelsize) bytes past the end of the last input
    // row. We only upload the first height-1 rows using GL_UNPACK_ROW_LENGTH,
    // and then we upload the final row separately. See bug 697990.
    int rowLength = stride/pixelsize;
    fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, rowLength);
    fTexSubImage2D(target,
                    level,
                    xoffset,
                    yoffset,
                    width,
                    height-1,
                    format,
                    type,
                    pixels);
    fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, 0);
    fTexSubImage2D(target,
                    level,
                    xoffset,
                    yoffset+height-1,
                    width,
                    1,
                    format,
                    type,
                    (const unsigned char *)pixels+(height-1)*stride);
    fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 4);
}

void
GLContext::TexSubImage2DWithoutUnpackSubimage(GLenum target, GLint level,
                                              GLint xoffset, GLint yoffset,
                                              GLsizei width, GLsizei height,
                                              GLsizei stride, GLint pixelsize,
                                              GLenum format, GLenum type,
                                              const GLvoid* pixels)
{
    // Not using the whole row of texture data and GL_UNPACK_ROW_LENGTH
    // isn't supported. We make a copy of the texture data we're using,
    // such that we're using the whole row of data in the copy. This turns
    // out to be more efficient than uploading row-by-row; see bug 698197.
    unsigned char *newPixels = new unsigned char[width*height*pixelsize];
    unsigned char *rowDest = newPixels;
    const unsigned char *rowSource = (const unsigned char *)pixels;
    for (int h = 0; h < height; h++) {
            memcpy(rowDest, rowSource, width*pixelsize);
            rowDest += width*pixelsize;
            rowSource += stride;
    }

    stride = width*pixelsize;
    fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT,
                    std::min(GetAddressAlignment((ptrdiff_t)newPixels),
                            GetAddressAlignment((ptrdiff_t)stride)));
    fTexSubImage2D(target,
                    level,
                    xoffset,
                    yoffset,
                    width,
                    height,
                    format,
                    type,
                    newPixels);
    delete [] newPixels;
    fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 4);
}

void
GLContext::RectTriangles::addRect(GLfloat x0, GLfloat y0, GLfloat x1, GLfloat y1,
                                  GLfloat tx0, GLfloat ty0, GLfloat tx1, GLfloat ty1,
                                  bool flip_y /* = false */)
{
    vert_coord v;
    v.x = x0; v.y = y0;
    vertexCoords.AppendElement(v);
    v.x = x1; v.y = y0;
    vertexCoords.AppendElement(v);
    v.x = x0; v.y = y1;
    vertexCoords.AppendElement(v);

    v.x = x0; v.y = y1;
    vertexCoords.AppendElement(v);
    v.x = x1; v.y = y0;
    vertexCoords.AppendElement(v);
    v.x = x1; v.y = y1;
    vertexCoords.AppendElement(v);

    if (flip_y) {
        tex_coord t;
        t.u = tx0; t.v = ty1;
        texCoords.AppendElement(t);
        t.u = tx1; t.v = ty1;
        texCoords.AppendElement(t);
        t.u = tx0; t.v = ty0;
        texCoords.AppendElement(t);

        t.u = tx0; t.v = ty0;
        texCoords.AppendElement(t);
        t.u = tx1; t.v = ty1;
        texCoords.AppendElement(t);
        t.u = tx1; t.v = ty0;
        texCoords.AppendElement(t);
    } else {
        tex_coord t;
        t.u = tx0; t.v = ty0;
        texCoords.AppendElement(t);
        t.u = tx1; t.v = ty0;
        texCoords.AppendElement(t);
        t.u = tx0; t.v = ty1;
        texCoords.AppendElement(t);

        t.u = tx0; t.v = ty1;
        texCoords.AppendElement(t);
        t.u = tx1; t.v = ty0;
        texCoords.AppendElement(t);
        t.u = tx1; t.v = ty1;
        texCoords.AppendElement(t);
    }
}

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,
                                          bool aFlipY /* = false */)
{
    // 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],
                       aFlipY);
    } 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,
                       aFlipY);
        aRects.addRect(0.0f, ymid,
                       1.0f, 1.0f,
                       tl[0], 0.0f,
                       br[0], br[1],
                       aFlipY);
    } 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],
                       aFlipY);
        aRects.addRect(xmid, 0.0f,
                       1.0f, 1.0f,
                       0.0f, tl[1],
                       br[0], br[1],
                       aFlipY);
    } 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,
                       aFlipY);
        aRects.addRect(xmid, 0.0f,
                       1.0f, ymid,
                       0.0f, tl[1],
                       br[0], 1.0f,
                       aFlipY);
        aRects.addRect(0.0f, ymid,
                       xmid, 1.0f,
                       tl[0], 0.0f,
                       1.0f, br[1],
                       aFlipY);
        aRects.addRect(xmid, ymid,
                       1.0f, 1.0f,
                       0.0f, 0.0f,
                       br[0], br[1],
                       aFlipY);
    }
}

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, nullptr);
    fShaderSource(shaders[1], 1, (const GLchar**) &blitFSSrc, nullptr);

    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) {
            nsAutoCString 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", 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) {
        nsAutoCString 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", 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);

    GLenum result = fCheckFramebufferStatus(LOCAL_GL_FRAMEBUFFER);
    if (aTexture && (result != LOCAL_GL_FRAMEBUFFER_COMPLETE)) {
        nsAutoCString msg;
        msg.Append("Framebuffer not complete -- error 0x");
        msg.AppendInt(result, 16);
        // Note: if you are hitting this, 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_RUNTIMEABORT(msg.get());
    }
}

#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::CreatedQueries(GLContext *aOrigin, GLsizei aCount, GLuint *aNames)
{
    for (GLsizei i = 0; i < aCount; ++i) {
        mTrackedQueries.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, const 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;

        for (uint32_t i = 0; i < aArray.Length(); ++i) {
            if (aArray[i].name == name) {
                aArray.RemoveElementAt(i);
                break;
            }
        }
    }
}

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::DeletedQueries(GLContext *aOrigin, GLsizei aCount, const GLuint *aNames)
{
    RemoveNamesFromArray(aOrigin, aCount, aNames, mTrackedQueries);
}

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 (uint32_t i = 0; i < aArray.Length(); ++i) {
        if (aArray[i].origin == aContext)
            aArray[i].originDeleted = true;
    }
}

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

static void
ReportArrayContents(const char *title, const nsTArray<GLContext::NamedResource>& aArray)
{
    if (aArray.Length() == 0)
        return;

    printf_stderr("%s:\n", title);

    nsTArray<GLContext::NamedResource> copy(aArray);
    copy.Sort();

    GLContext *lastContext = nullptr;
    for (uint32_t 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()
{
    if (!DebugMode())
        return;

    printf_stderr("== GLContext %p Outstanding ==\n", this);

    ReportArrayContents("Outstanding Textures", mTrackedTextures);
    ReportArrayContents("Outstanding Buffers", mTrackedBuffers);
    ReportArrayContents("Outstanding Queries", mTrackedQueries);
    ReportArrayContents("Outstanding Programs", mTrackedPrograms);
    ReportArrayContents("Outstanding Shaders", mTrackedShaders);
    ReportArrayContents("Outstanding Framebuffers", mTrackedFramebuffers);
    ReportArrayContents("Outstanding Renderbuffers", mTrackedRenderbuffers);
}

#endif /* DEBUG */


void
GLContext::GuaranteeResolve()
{
    if (mScreen) {
        mScreen->AssureBlitted();
    }
    fFinish();
}

const gfxIntSize&
GLContext::OffscreenSize() const
{
    MOZ_ASSERT(IsOffscreen());
    return mScreen->Size();
}

bool
GLContext::CreateScreenBufferImpl(const gfxIntSize& size, const SurfaceCaps& caps)
{
    GLScreenBuffer* newScreen = GLScreenBuffer::Create(this, size, caps);
    if (!newScreen)
        return false;

    if (!newScreen->Resize(size)) {
        delete newScreen;
        return false;
    }

    DestroyScreenBuffer();

    // This will rebind to 0 (Screen) if needed when
    // it falls out of scope.
    ScopedBindFramebuffer autoFB(this);

    mScreen = newScreen;

    return true;
}

bool
GLContext::ResizeScreenBuffer(const gfxIntSize& size)
{
    if (!IsOffscreenSizeAllowed(size))
        return false;

    return mScreen->Resize(size);
}


void
GLContext::DestroyScreenBuffer()
{
    delete mScreen;
    mScreen = nullptr;
}

void
GLContext::ForceDirtyScreen()
{
    ScopedBindFramebuffer autoFB(0);

    BeforeGLDrawCall();
    // no-op; just pretend we did something
    AfterGLDrawCall();
}

void
GLContext::CleanDirtyScreen()
{
    ScopedBindFramebuffer autoFB(0);

    BeforeGLReadCall();
    // no-op; we just want to make sure the Read FBO is updated if it needs to be
    AfterGLReadCall();
}

void
GLContext::EmptyTexGarbageBin()
{
   TexGarbageBin()->EmptyGarbage();
}

bool
GLContext::IsOffscreenSizeAllowed(const gfxIntSize& aSize) const {
  int32_t biggerDimension = std::max(aSize.width, aSize.height);
  int32_t maxAllowed = std::min(mMaxRenderbufferSize, mMaxTextureSize);
  return biggerDimension <= maxAllowed;
}

bool
GLContext::IsOwningThreadCurrent()
{
  return NS_GetCurrentThread() == mOwningThread;
}

void
GLContext::DispatchToOwningThread(nsIRunnable *event)
{
    // Before dispatching, we need to ensure we're not in the middle of
    // shutting down. Dispatching runnables in the middle of shutdown
    // (that is, when the main thread is no longer get-able) can cause them
    // to leak. See Bug 741319, and Bug 744115.
    nsCOMPtr<nsIThread> mainThread;
    if (NS_SUCCEEDED(NS_GetMainThread(getter_AddRefs(mainThread)))) {
        mOwningThread->Dispatch(event, NS_DISPATCH_NORMAL);
    }
}

bool
DoesStringMatch(const char* aString, const char *aWantedString)
{
    if (!aString || !aWantedString)
        return false;

    const char *occurrence = strstr(aString, aWantedString);

    // aWanted not found
    if (!occurrence)
        return false;

    // aWantedString preceded by alpha character
    if (occurrence != aString && isalpha(*(occurrence-1)))
        return false;

    // aWantedVendor followed by alpha character
    const char *afterOccurrence = occurrence + strlen(aWantedString);
    if (isalpha(*afterOccurrence))
        return false;

    return true;
}

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