src/gpu/gl/GrGpuGL.cpp

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */


#include "GrGpuGL.h"
#include "GrGLStencilBuffer.h"
#include "GrGLPath.h"
#include "GrTypes.h"
#include "SkTemplates.h"

static const GrGLuint GR_MAX_GLUINT = ~0U;
static const GrGLint  GR_INVAL_GLINT = ~0;

#define GL_CALL(X) GR_GL_CALL(this->glInterface(), X)
#define GL_CALL_RET(RET, X) GR_GL_CALL_RET(this->glInterface(), RET, X)

// we use a spare texture unit to avoid
// mucking with the state of any of the stages.
static const int SPARE_TEX_UNIT = GrDrawState::kNumStages;

#define SKIP_CACHE_CHECK    true

#if GR_GL_CHECK_ALLOC_WITH_GET_ERROR
    #define CLEAR_ERROR_BEFORE_ALLOC(iface)   GrGLClearErr(iface)
    #define GL_ALLOC_CALL(iface, call)        GR_GL_CALL_NOERRCHECK(iface, call)
    #define CHECK_ALLOC_ERROR(iface)          GR_GL_GET_ERROR(iface)
#else 
    #define CLEAR_ERROR_BEFORE_ALLOC(iface)
    #define GL_ALLOC_CALL(iface, call)        GR_GL_CALL(iface, call)
    #define CHECK_ALLOC_ERROR(iface)          GR_GL_NO_ERROR
#endif


///////////////////////////////////////////////////////////////////////////////

static const GrGLenum gXfermodeCoeff2Blend[] = {
    GR_GL_ZERO,
    GR_GL_ONE,
    GR_GL_SRC_COLOR,
    GR_GL_ONE_MINUS_SRC_COLOR,
    GR_GL_DST_COLOR,
    GR_GL_ONE_MINUS_DST_COLOR,
    GR_GL_SRC_ALPHA,
    GR_GL_ONE_MINUS_SRC_ALPHA,
    GR_GL_DST_ALPHA,
    GR_GL_ONE_MINUS_DST_ALPHA,
    GR_GL_CONSTANT_COLOR,
    GR_GL_ONE_MINUS_CONSTANT_COLOR,
    GR_GL_CONSTANT_ALPHA,
    GR_GL_ONE_MINUS_CONSTANT_ALPHA,

    // extended blend coeffs
    GR_GL_SRC1_COLOR,
    GR_GL_ONE_MINUS_SRC1_COLOR,
    GR_GL_SRC1_ALPHA,
    GR_GL_ONE_MINUS_SRC1_ALPHA,
};

bool GrGpuGL::BlendCoeffReferencesConstant(GrBlendCoeff coeff) {
    static const bool gCoeffReferencesBlendConst[] = {
        false,
        false,
        false,
        false,
        false,
        false,
        false,
        false,
        false,
        false,
        true,
        true,
        true,
        true,

        // extended blend coeffs
        false,
        false,
        false,
        false,
    };
    return gCoeffReferencesBlendConst[coeff];
    GR_STATIC_ASSERT(kTotalGrBlendCoeffCount ==
                     GR_ARRAY_COUNT(gCoeffReferencesBlendConst));

    GR_STATIC_ASSERT(0 == kZero_GrBlendCoeff);
    GR_STATIC_ASSERT(1 == kOne_GrBlendCoeff);
    GR_STATIC_ASSERT(2 == kSC_GrBlendCoeff);
    GR_STATIC_ASSERT(3 == kISC_GrBlendCoeff);
    GR_STATIC_ASSERT(4 == kDC_GrBlendCoeff);
    GR_STATIC_ASSERT(5 == kIDC_GrBlendCoeff);
    GR_STATIC_ASSERT(6 == kSA_GrBlendCoeff);
    GR_STATIC_ASSERT(7 == kISA_GrBlendCoeff);
    GR_STATIC_ASSERT(8 == kDA_GrBlendCoeff);
    GR_STATIC_ASSERT(9 == kIDA_GrBlendCoeff);
    GR_STATIC_ASSERT(10 == kConstC_GrBlendCoeff);
    GR_STATIC_ASSERT(11 == kIConstC_GrBlendCoeff);
    GR_STATIC_ASSERT(12 == kConstA_GrBlendCoeff);
    GR_STATIC_ASSERT(13 == kIConstA_GrBlendCoeff);

    GR_STATIC_ASSERT(14 == kS2C_GrBlendCoeff);
    GR_STATIC_ASSERT(15 == kIS2C_GrBlendCoeff);
    GR_STATIC_ASSERT(16 == kS2A_GrBlendCoeff);
    GR_STATIC_ASSERT(17 == kIS2A_GrBlendCoeff);

    // assertion for gXfermodeCoeff2Blend have to be in GrGpu scope
    GR_STATIC_ASSERT(kTotalGrBlendCoeffCount ==
                     GR_ARRAY_COUNT(gXfermodeCoeff2Blend));
}

///////////////////////////////////////////////////////////////////////////////

static bool gPrintStartupSpew;

static bool fbo_test(const GrGLInterface* gl, int w, int h) {

    GR_GL_CALL(gl, ActiveTexture(GR_GL_TEXTURE0 + SPARE_TEX_UNIT));

    GrGLuint testFBO;
    GR_GL_CALL(gl, GenFramebuffers(1, &testFBO));
    GR_GL_CALL(gl, BindFramebuffer(GR_GL_FRAMEBUFFER, testFBO));
    GrGLuint testRTTex;
    GR_GL_CALL(gl, GenTextures(1, &testRTTex));
    GR_GL_CALL(gl, BindTexture(GR_GL_TEXTURE_2D, testRTTex));
    // some implementations require texture to be mip-map complete before
    // FBO with level 0 bound as color attachment will be framebuffer complete.
    GR_GL_CALL(gl, TexParameteri(GR_GL_TEXTURE_2D,
                                 GR_GL_TEXTURE_MIN_FILTER,
                                 GR_GL_NEAREST));
    GR_GL_CALL(gl, TexImage2D(GR_GL_TEXTURE_2D, 0, GR_GL_RGBA, w, h,
                              0, GR_GL_RGBA, GR_GL_UNSIGNED_BYTE, NULL));
    GR_GL_CALL(gl, BindTexture(GR_GL_TEXTURE_2D, 0));
    GR_GL_CALL(gl, FramebufferTexture2D(GR_GL_FRAMEBUFFER,
                                        GR_GL_COLOR_ATTACHMENT0,
                                        GR_GL_TEXTURE_2D, testRTTex, 0));
    GrGLenum status;
    GR_GL_CALL_RET(gl, status, CheckFramebufferStatus(GR_GL_FRAMEBUFFER));
    GR_GL_CALL(gl, DeleteFramebuffers(1, &testFBO));
    GR_GL_CALL(gl, DeleteTextures(1, &testRTTex));

    return status == GR_GL_FRAMEBUFFER_COMPLETE;
}

GrGpuGL::GrGpuGL(const GrGLContextInfo& ctxInfo) : fGLContextInfo(ctxInfo) {

    GrAssert(ctxInfo.isInitialized());

    fillInConfigRenderableTable();

    fPrintedCaps = false;

    GrGLClearErr(fGLContextInfo.interface());

    if (gPrintStartupSpew) {
        const GrGLubyte* ext;
        GL_CALL_RET(ext, GetString(GR_GL_EXTENSIONS));
        const GrGLubyte* vendor;
        const GrGLubyte* renderer;
        const GrGLubyte* version;
        GL_CALL_RET(vendor, GetString(GR_GL_VENDOR));
        GL_CALL_RET(renderer, GetString(GR_GL_RENDERER));
        GL_CALL_RET(version, GetString(GR_GL_VERSION));
        GrPrintf("------------------------- create GrGpuGL %p --------------\n",
                 this);
        GrPrintf("------ VENDOR %s\n", vendor);
        GrPrintf("------ RENDERER %s\n", renderer);
        GrPrintf("------ VERSION %s\n",  version);
        GrPrintf("------ EXTENSIONS\n %s \n", ext);
    }

    this->initCaps();

    fProgramData = NULL;
    fProgramCache = new ProgramCache(this->glContextInfo());

    fLastSuccessfulStencilFmtIdx = 0;
    fCanPreserveUnpremulRoundtrip = kUnknown_CanPreserveUnpremulRoundtrip;
    if (false) { // avoid bit rot, suppress warning
        fbo_test(this->glInterface(), 0, 0);
    }
}

GrGpuGL::~GrGpuGL() {
    if (fProgramData && 0 != fHWProgramID) {
        // detach the current program so there is no confusion on OpenGL's part
        // that we want it to be deleted
        GrAssert(fHWProgramID == fProgramData->fProgramID);
        GL_CALL(UseProgram(0));
    }

    delete fProgramCache;
    fProgramCache = NULL;
    fProgramData = NULL;

    // This must be called by before the GrDrawTarget destructor
    this->releaseGeometry();
    // This subclass must do this before the base class destructor runs
    // since we will unref the GrGLInterface.
    this->releaseResources();
}

///////////////////////////////////////////////////////////////////////////////

void GrGpuGL::initCaps() {
    GrGLint maxTextureUnits;
    // check FS and fixed-function texture unit limits
    // we only use textures in the fragment stage currently.
    // checks are > to make sure we have a spare unit.
    const GrGLInterface* gl = this->glInterface();
    GR_GL_GetIntegerv(gl, GR_GL_MAX_TEXTURE_IMAGE_UNITS, &maxTextureUnits);
    GrAssert(maxTextureUnits > GrDrawState::kNumStages);

    GrGLint numFormats;
    GR_GL_GetIntegerv(gl, GR_GL_NUM_COMPRESSED_TEXTURE_FORMATS, &numFormats);
    SkAutoSTMalloc<10, GrGLint> formats(numFormats);
    GR_GL_GetIntegerv(gl, GR_GL_COMPRESSED_TEXTURE_FORMATS, formats);
    for (int i = 0; i < numFormats; ++i) {
        if (formats[i] == GR_GL_PALETTE8_RGBA8) {
            fCaps.f8BitPaletteSupport = true;
            break;
        }
    }

    if (kDesktop_GrGLBinding == this->glBinding()) {
        // we could also look for GL_ATI_separate_stencil extension or
        // GL_EXT_stencil_two_side but they use different function signatures
        // than GL2.0+ (and than each other).
        fCaps.fTwoSidedStencilSupport = (this->glVersion() >= GR_GL_VER(2,0));
        // supported on GL 1.4 and higher or by extension
        fCaps.fStencilWrapOpsSupport = (this->glVersion() >= GR_GL_VER(1,4)) ||
                                       this->hasExtension("GL_EXT_stencil_wrap");
    } else {
        // ES 2 has two sided stencil and stencil wrap
        fCaps.fTwoSidedStencilSupport = true;
        fCaps.fStencilWrapOpsSupport = true;
    }

    if (kDesktop_GrGLBinding == this->glBinding()) {
        fCaps.fBufferLockSupport = true; // we require VBO support and the desktop VBO
                                         // extension includes glMapBuffer.
    } else {
        fCaps.fBufferLockSupport = this->hasExtension("GL_OES_mapbuffer");
    }

    if (kDesktop_GrGLBinding == this->glBinding()) {
        if (this->glVersion() >= GR_GL_VER(2,0) || 
            this->hasExtension("GL_ARB_texture_non_power_of_two")) {
            fCaps.fNPOTTextureTileSupport = true;
        } else {
            fCaps.fNPOTTextureTileSupport = false;
        }
    } else {
        // Unextended ES2 supports NPOT textures with clamp_to_edge and non-mip filters only
        fCaps.fNPOTTextureTileSupport = this->hasExtension("GL_OES_texture_npot");
    }

    fCaps.fHWAALineSupport = (kDesktop_GrGLBinding == this->glBinding());

    GR_GL_GetIntegerv(gl, GR_GL_MAX_TEXTURE_SIZE, &fCaps.fMaxTextureSize);
    GR_GL_GetIntegerv(gl, GR_GL_MAX_RENDERBUFFER_SIZE, &fCaps.fMaxRenderTargetSize);
    // Our render targets are always created with textures as the color
    // attachment, hence this min:
    fCaps.fMaxRenderTargetSize = GrMin(fCaps.fMaxTextureSize, fCaps.fMaxRenderTargetSize);

    fCaps.fFSAASupport = GrGLCaps::kNone_MSFBOType != this->glCaps().msFBOType();

    // Enable supported shader-related caps
    if (kDesktop_GrGLBinding == this->glBinding()) {
        fCaps.fDualSourceBlendingSupport =
                            this->glVersion() >= GR_GL_VER(3,3) ||
                            this->hasExtension("GL_ARB_blend_func_extended");
        fCaps.fShaderDerivativeSupport = true;
        // we don't support GL_ARB_geometry_shader4, just GL 3.2+ GS
        fCaps.fGeometryShaderSupport = 
                                this->glVersion() >= GR_GL_VER(3,2) &&
                                this->glslGeneration() >= k150_GrGLSLGeneration;
    } else {
        fCaps.fShaderDerivativeSupport =
                            this->hasExtension("GL_OES_standard_derivatives");
    }
}

void GrGpuGL::fillInConfigRenderableTable() {

    // OpenGL < 3.0
    //  no support for render targets unless the GL_ARB_framebuffer_object 
    //  extension is supported (in which case we get ALPHA, RED, RG, RGB, 
    //  RGBA (ALPHA8, RGBA4, RGBA8) for OpenGL > 1.1). Note that we 
    //  probably don't get R8 in this case.

    // OpenGL 3.0
    //  base color renderable: ALPHA, RED, RG, RGB, and RGBA
    //  sized derivatives: ALPHA8, R8, RGBA4, RGBA8

    // >= OpenGL 3.1
    //  base color renderable: RED, RG, RGB, and RGBA
    //  sized derivatives: R8, RGBA4, RGBA8
    //  if the GL_ARB_compatibility extension is supported then we get back
    //  support for GL_ALPHA and ALPHA8

    // GL_EXT_bgra adds BGRA render targets to any version

    // ES 2.0
    //  color renderable: RGBA4, RGB5_A1, RGB565
    //  GL_EXT_texture_rg adds support for R8 as a color render target
    //  GL_OES_rgb8_rgba8 and/or GL_ARM_rgba8 adds support for RGBA8
    //  GL_EXT_texture_format_BGRA8888 and/or GL_APPLE_texture_format_BGRA8888
    //          added BGRA support

    if (kDesktop_GrGLBinding == this->glBinding()) {
        // Post 3.0 we will get R8
        // Prior to 3.0 we will get ALPHA8 (with GL_ARB_framebuffer_object)
        if (this->glVersion() >= GR_GL_VER(3,0) ||
            this->hasExtension("GL_ARB_framebuffer_object")) {
            fConfigRenderSupport[kAlpha_8_GrPixelConfig] = true;
        }
    } else {
        // On ES we can only hope for R8
        fConfigRenderSupport[kAlpha_8_GrPixelConfig] = 
                                this->glCaps().textureRedSupport();
    }

    if (kDesktop_GrGLBinding != this->glBinding()) {
        // only available in ES
        fConfigRenderSupport[kRGB_565_GrPixelConfig] = true;
    }

    // Pre 3.0, Ganesh relies on either GL_ARB_framebuffer_object or 
    // GL_EXT_framebuffer_object for FBO support. Both of these
    // allow RGBA4 render targets so this is always supported.
    fConfigRenderSupport[kRGBA_4444_GrPixelConfig] = true;

    if (this->glCaps().rgba8RenderbufferSupport()) {
        fConfigRenderSupport[kRGBA_8888_PM_GrPixelConfig] = true;
    }

    if (this->glCaps().bgraFormatSupport()) {
        fConfigRenderSupport[kBGRA_8888_PM_GrPixelConfig] = true;
    }

    // the un-premultiplied formats just inherit the premultiplied setting
    fConfigRenderSupport[kRGBA_8888_UPM_GrPixelConfig] = 
                fConfigRenderSupport[kRGBA_8888_PM_GrPixelConfig];
    fConfigRenderSupport[kBGRA_8888_UPM_GrPixelConfig] = 
                fConfigRenderSupport[kBGRA_8888_PM_GrPixelConfig];
}

bool GrGpuGL::canPreserveReadWriteUnpremulPixels() {
    if (kUnknown_CanPreserveUnpremulRoundtrip ==
        fCanPreserveUnpremulRoundtrip) {

        SkAutoTMalloc<uint32_t> data(256 * 256 * 3);
        uint32_t* srcData = data.get();
        uint32_t* firstRead = data.get() + 256 * 256;
        uint32_t* secondRead = data.get() + 2 * 256 * 256;

        for (int y = 0; y < 256; ++y) {
            for (int x = 0; x < 256; ++x) {
                uint8_t* color = reinterpret_cast<uint8_t*>(&srcData[256*y + x]);
                color[3] = y;
                color[2] = x;
                color[1] = x;
                color[0] = x;
            }
        }

        // We have broader support for read/write pixels on render targets
        // than on textures.
        GrTextureDesc dstDesc;
        dstDesc.fFlags = kRenderTarget_GrTextureFlagBit |
                         kNoStencil_GrTextureFlagBit;
        dstDesc.fWidth = 256;
        dstDesc.fHeight = 256;
        dstDesc.fConfig = kRGBA_8888_PM_GrPixelConfig;

        SkAutoTUnref<GrTexture> dstTex(this->createTexture(dstDesc, NULL, 0));
        if (!dstTex.get()) {
            return false;
        }
        GrRenderTarget* rt = dstTex.get()->asRenderTarget();
        GrAssert(NULL != rt);

        bool failed = true;
        static const UnpremulConversion gMethods[] = {
            kUpOnWrite_DownOnRead_UnpremulConversion,
            kDownOnWrite_UpOnRead_UnpremulConversion,
        };

        // pretend that we can do the roundtrip to avoid recursive calls to
        // this function
        fCanPreserveUnpremulRoundtrip = kYes_CanPreserveUnpremulRoundtrip;
        for (size_t i = 0; i < GR_ARRAY_COUNT(gMethods) && failed; ++i) {
            fUnpremulConversion = gMethods[i];
            rt->writePixels(0, 0,
                            256, 256,
                            kRGBA_8888_UPM_GrPixelConfig, srcData, 0);
            rt->readPixels(0, 0,
                           256, 256,
                           kRGBA_8888_UPM_GrPixelConfig, firstRead, 0);
            rt->writePixels(0, 0,
                            256, 256,
                            kRGBA_8888_UPM_GrPixelConfig, firstRead, 0);
            rt->readPixels(0, 0,
                           256, 256,
                           kRGBA_8888_UPM_GrPixelConfig, secondRead, 0);
            failed = false;
            for (int j = 0; j < 256 * 256; ++j) {
                if (firstRead[j] != secondRead[j]) {
                    failed = true;
                    break;
                }
            }
        }
        fCanPreserveUnpremulRoundtrip = failed ? 
                        kNo_CanPreserveUnpremulRoundtrip :
                        kYes_CanPreserveUnpremulRoundtrip;
    }

    if (kYes_CanPreserveUnpremulRoundtrip == fCanPreserveUnpremulRoundtrip) {
        return true;
    } else {
        return false;
    }
}

GrPixelConfig GrGpuGL::preferredReadPixelsConfig(GrPixelConfig config) const {
    if (GR_GL_RGBA_8888_PIXEL_OPS_SLOW && GrPixelConfigIsRGBA8888(config)) {
        return GrPixelConfigSwapRAndB(config);
    } else {
        return config;
    }
}

GrPixelConfig GrGpuGL::preferredWritePixelsConfig(GrPixelConfig config) const {
    if (GR_GL_RGBA_8888_PIXEL_OPS_SLOW && GrPixelConfigIsRGBA8888(config)) {
        return GrPixelConfigSwapRAndB(config);
    } else {
        return config;
    }
}

bool GrGpuGL::fullReadPixelsIsFasterThanPartial() const {
    return SkToBool(GR_GL_FULL_READPIXELS_FASTER_THAN_PARTIAL);
}

void GrGpuGL::onResetContext() {
    if (gPrintStartupSpew && !fPrintedCaps) {
        fPrintedCaps = true;
        this->getCaps().print();
        this->glCaps().print();
    }

    // we don't use the zb at all
    GL_CALL(Disable(GR_GL_DEPTH_TEST));
    GL_CALL(DepthMask(GR_GL_FALSE));

    fHWDrawFace = GrDrawState::kInvalid_DrawFace;
    fHWDitherEnabled = kUnknown_TriState;

    if (kDesktop_GrGLBinding == this->glBinding()) {
        // Desktop-only state that we never change
        GL_CALL(Disable(GR_GL_POINT_SMOOTH));
        GL_CALL(Disable(GR_GL_LINE_SMOOTH));
        GL_CALL(Disable(GR_GL_POLYGON_SMOOTH));
        GL_CALL(Disable(GR_GL_POLYGON_STIPPLE));
        GL_CALL(Disable(GR_GL_COLOR_LOGIC_OP));
        GL_CALL(Disable(GR_GL_COLOR_TABLE));
        GL_CALL(Disable(GR_GL_INDEX_LOGIC_OP));
        GL_CALL(Disable(GR_GL_POLYGON_OFFSET_FILL));
        // Since ES doesn't support glPointSize at all we always use the VS to
        // set the point size
        GL_CALL(Enable(GR_GL_VERTEX_PROGRAM_POINT_SIZE));

        // We should set glPolygonMode(FRONT_AND_BACK,FILL) here, too. It isn't
        // currently part of our gl interface. There are probably others as 
        // well.
    }
    fHWAAState.invalidate();
    fHWWriteToColor = kUnknown_TriState;

    // we only ever use lines in hairline mode
    GL_CALL(LineWidth(1));

    // invalid
    fHWActiveTextureUnitIdx = -1;

    fHWBlendState.invalidate();

    for (int s = 0; s < GrDrawState::kNumStages; ++s) {
        fHWBoundTextures[s] = NULL;
    }

    fHWBounds.fScissorRect.invalidate();
    // set to true to force disableScissor to make a GL call.
    fHWBounds.fScissorEnabled = true;
    this->disableScissor();

    fHWBounds.fViewportRect.invalidate();

    fHWStencilSettings.invalidate();
    // This is arbitrary. The above invalidate ensures a full setup of the
    // stencil on the next draw.
    fHWStencilClipMode = GrClipMaskManager::kRespectClip_StencilClipMode;

    // TODO: I believe this should actually go in GrGpu::onResetContext
    // rather than here
    fClipMaskManager.resetMask();

    fHWGeometryState.fIndexBuffer = NULL;
    fHWGeometryState.fVertexBuffer = NULL;
    
    fHWGeometryState.fArrayPtrsDirty = true;

    fHWBoundRenderTarget = NULL;

    // we assume these values
    if (this->glCaps().unpackRowLengthSupport()) {
        GL_CALL(PixelStorei(GR_GL_UNPACK_ROW_LENGTH, 0));
    }
    if (this->glCaps().packRowLengthSupport()) {
        GL_CALL(PixelStorei(GR_GL_PACK_ROW_LENGTH, 0));
    }
    if (this->glCaps().unpackFlipYSupport()) {
        GL_CALL(PixelStorei(GR_GL_UNPACK_FLIP_Y, GR_GL_FALSE));
    }
    if (this->glCaps().packFlipYSupport()) {
        GL_CALL(PixelStorei(GR_GL_PACK_REVERSE_ROW_ORDER, GR_GL_FALSE));
    }

    fHWGeometryState.fVertexOffset = ~0U;

    // Third party GL code may have left vertex attributes enabled. Some GL
    // implementations (osmesa) may read vetex attributes that are not required
    // by the current shader. Therefore, we have to ensure that only the
    // attributes we require for the current draw are enabled or we may cause an
    // invalid read.

    // Disable all vertex layout bits so that next flush will assume all
    // optional vertex attributes are disabled.
    fHWGeometryState.fVertexLayout = 0;

    // We always use the this attribute and assume it is always enabled.
    int posAttrIdx = GrGLProgram::PositionAttributeIdx();
    GL_CALL(EnableVertexAttribArray(posAttrIdx));
    // Disable all other vertex attributes.
    for  (int va = 0; va < this->glCaps().maxVertexAttributes(); ++va) {
        if (va != posAttrIdx) {
            GL_CALL(DisableVertexAttribArray(va));
        }
    }

    fHWProgramID = 0;
    fHWConstAttribColor = GrColor_ILLEGAL;
    fHWConstAttribCoverage = GrColor_ILLEGAL;
}

GrTexture* GrGpuGL::onCreatePlatformTexture(const GrPlatformTextureDesc& desc) {
    GrGLTexture::Desc glTexDesc;
    if (!configToGLFormats(desc.fConfig, false, NULL, NULL, NULL)) {
        return NULL;
    }

    // next line relies on PlatformTextureDesc's flags matching GrTexture's
    glTexDesc.fFlags = (GrTextureFlags) desc.fFlags;
    glTexDesc.fWidth = desc.fWidth;
    glTexDesc.fHeight = desc.fHeight;
    glTexDesc.fConfig = desc.fConfig;
    glTexDesc.fSampleCnt = desc.fSampleCnt;
    glTexDesc.fTextureID = static_cast<GrGLuint>(desc.fTextureHandle);
    glTexDesc.fOwnsID = false;
    glTexDesc.fOrientation = GrGLTexture::kBottomUp_Orientation;

    GrGLTexture* texture = NULL;
    if (desc.fFlags & kRenderTarget_GrPlatformTextureFlag) {
        GrGLRenderTarget::Desc glRTDesc;
        glRTDesc.fRTFBOID = 0;
        glRTDesc.fTexFBOID = 0;
        glRTDesc.fMSColorRenderbufferID = 0;
        glRTDesc.fOwnIDs = true;
        glRTDesc.fConfig = desc.fConfig;
        glRTDesc.fSampleCnt = desc.fSampleCnt;
        if (!this->createRenderTargetObjects(glTexDesc.fWidth,
                                             glTexDesc.fHeight,
                                             glTexDesc.fTextureID,
                                             &glRTDesc)) {
            return NULL;
        }
        texture = new GrGLTexture(this, glTexDesc, glRTDesc);
    } else {
        texture = new GrGLTexture(this, glTexDesc);
    }
    if (NULL == texture) {
        return NULL;
    }
    
    this->setSpareTextureUnit();
    return texture;
}

GrRenderTarget* GrGpuGL::onCreatePlatformRenderTarget(const GrPlatformRenderTargetDesc& desc) {
    GrGLRenderTarget::Desc glDesc;
    glDesc.fConfig = desc.fConfig;
    glDesc.fRTFBOID = static_cast<GrGLuint>(desc.fRenderTargetHandle);
    glDesc.fMSColorRenderbufferID = 0;
    glDesc.fTexFBOID = GrGLRenderTarget::kUnresolvableFBOID;
    glDesc.fSampleCnt = desc.fSampleCnt;
    glDesc.fOwnIDs = false;
    GrGLIRect viewport;
    viewport.fLeft   = 0;
    viewport.fBottom = 0;
    viewport.fWidth  = desc.fWidth;
    viewport.fHeight = desc.fHeight;
    
    GrRenderTarget* tgt = new GrGLRenderTarget(this, glDesc, viewport);
    if (desc.fStencilBits) {
        GrGLStencilBuffer::Format format;
        format.fInternalFormat = GrGLStencilBuffer::kUnknownInternalFormat;
        format.fPacked = false;
        format.fStencilBits = desc.fStencilBits;
        format.fTotalBits = desc.fStencilBits;
        GrGLStencilBuffer* sb = new GrGLStencilBuffer(this,
                                                      0,
                                                      desc.fWidth,
                                                      desc.fHeight,
                                                      desc.fSampleCnt,
                                                      format);
        tgt->setStencilBuffer(sb);
        sb->unref();
    }
    return tgt;
}

////////////////////////////////////////////////////////////////////////////////

void GrGpuGL::onWriteTexturePixels(GrTexture* texture,
                                   int left, int top, int width, int height,
                                   GrPixelConfig config, const void* buffer,
                                   size_t rowBytes) {
    if (NULL == buffer) {
        return;
    }
    GrGLTexture* glTex = static_cast<GrGLTexture*>(texture);

    this->setSpareTextureUnit();
    GL_CALL(BindTexture(GR_GL_TEXTURE_2D, glTex->textureID()));
    GrGLTexture::Desc desc;
    desc.fFlags = glTex->desc().fFlags;
    desc.fWidth = glTex->width();
    desc.fHeight = glTex->height();
    desc.fConfig = glTex->config();
    desc.fSampleCnt = glTex->desc().fSampleCnt;
    desc.fTextureID = glTex->textureID();
    desc.fOrientation = glTex->orientation();

    this->uploadTexData(desc, false,
                        left, top, width, height, 
                        config, buffer, rowBytes);
}

namespace {
bool adjust_pixel_ops_params(int surfaceWidth,
                             int surfaceHeight,
                             size_t bpp,
                             int* left, int* top, int* width, int* height,
                             const void** data,
                             size_t* rowBytes) {
    if (!*rowBytes) {
        *rowBytes = *width * bpp;
    }

    GrIRect subRect = GrIRect::MakeXYWH(*left, *top, *width, *height);
    GrIRect bounds = GrIRect::MakeWH(surfaceWidth, surfaceHeight);

    if (!subRect.intersect(bounds)) {
        return false;
    }
    *data = reinterpret_cast<const void*>(reinterpret_cast<intptr_t>(*data) +
          (subRect.fTop - *top) * *rowBytes + (subRect.fLeft - *left) * bpp);

    *left = subRect.fLeft;
    *top = subRect.fTop;
    *width = subRect.width();
    *height = subRect.height();
    return true;
}
}

bool GrGpuGL::uploadTexData(const GrGLTexture::Desc& desc,
                            bool isNewTexture,
                            int left, int top, int width, int height,
                            GrPixelConfig dataConfig,
                            const void* data,
                            size_t rowBytes) {
    GrAssert(NULL != data || isNewTexture);

    size_t bpp = GrBytesPerPixel(dataConfig);
    if (!adjust_pixel_ops_params(desc.fWidth, desc.fHeight, bpp, &left, &top,
                                 &width, &height, &data, &rowBytes)) {
        return false;
    }
    size_t trimRowBytes = width * bpp;

    // in case we need a temporary, trimmed copy of the src pixels
    SkAutoSMalloc<128 * 128> tempStorage;

    bool useTexStorage = isNewTexture &&
                         this->glCaps().texStorageSupport();
    if (useTexStorage) {
        if (kDesktop_GrGLBinding == this->glBinding()) {
            // 565 is not a sized internal format on desktop GL. So on desktop
            // with 565 we always use an unsized internal format to let the
            // system pick the best sized format to convert the 565 data to.
            // Since glTexStorage only allows sized internal formats we will
            // instead fallback to glTexImage2D.
            useTexStorage = desc.fConfig != kRGB_565_GrPixelConfig;
        } else {
            // ES doesn't allow paletted textures to be used with tex storage
            useTexStorage = desc.fConfig != kIndex_8_GrPixelConfig;
        }
    }

    GrGLenum internalFormat;
    GrGLenum externalFormat;
    GrGLenum externalType;
    // glTexStorage requires sized internal formats on both desktop and ES. ES
    // glTexImage requires an unsized format.
    if (!this->configToGLFormats(dataConfig, useTexStorage, &internalFormat,
                                 &externalFormat, &externalType)) {
        return false;
    }

    if (!isNewTexture && GR_GL_PALETTE8_RGBA8 == internalFormat) {
        // paletted textures cannot be updated
        return false;
    }

    /*
     *  check whether to allocate a temporary buffer for flipping y or
     *  because our srcData has extra bytes past each row. If so, we need
     *  to trim those off here, since GL ES may not let us specify
     *  GL_UNPACK_ROW_LENGTH.
     */
    bool restoreGLRowLength = false;
    bool swFlipY = false;
    bool glFlipY = false;
    if (NULL != data) {
        if (GrGLTexture::kBottomUp_Orientation == desc.fOrientation) {
            if (this->glCaps().unpackFlipYSupport()) {
                glFlipY = true;
            } else {
                swFlipY = true;
            }
        }
        if (this->glCaps().unpackRowLengthSupport() && !swFlipY) {
            // can't use this for flipping, only non-neg values allowed. :(
            if (rowBytes != trimRowBytes) {
                GrGLint rowLength = static_cast<GrGLint>(rowBytes / bpp);
                GL_CALL(PixelStorei(GR_GL_UNPACK_ROW_LENGTH, rowLength));
                restoreGLRowLength = true;
            }
        } else {
            if (trimRowBytes != rowBytes || swFlipY) {
                // copy data into our new storage, skipping the trailing bytes
                size_t trimSize = height * trimRowBytes;
                const char* src = (const char*)data;
                if (swFlipY) {
                    src += (height - 1) * rowBytes;
                }
                char* dst = (char*)tempStorage.reset(trimSize);
                for (int y = 0; y < height; y++) {
                    memcpy(dst, src, trimRowBytes);
                    if (swFlipY) {
                        src -= rowBytes;
                    } else {
                        src += rowBytes;
                    }
                    dst += trimRowBytes;
                }
                // now point data to our copied version
                data = tempStorage.get();
            }
        }
        if (glFlipY) {
            GL_CALL(PixelStorei(GR_GL_UNPACK_FLIP_Y, GR_GL_TRUE));
        }
        GL_CALL(PixelStorei(GR_GL_UNPACK_ALIGNMENT, static_cast<GrGLint>(bpp)));
    }
    bool succeeded = true;
    if (isNewTexture && 
        0 == left && 0 == top &&
        desc.fWidth == width && desc.fHeight == height) {
        CLEAR_ERROR_BEFORE_ALLOC(this->glInterface());
        if (useTexStorage) {
            // We never resize  or change formats of textures. We don't use
            // mipmaps currently.
            GL_ALLOC_CALL(this->glInterface(),
                          TexStorage2D(GR_GL_TEXTURE_2D,
                                       1, // levels
                                       internalFormat,
                                       desc.fWidth, desc.fHeight));
        } else {
            if (GR_GL_PALETTE8_RGBA8 == internalFormat) {
                GrGLsizei imageSize = desc.fWidth * desc.fHeight +
                                      kGrColorTableSize;
                GL_ALLOC_CALL(this->glInterface(),
                              CompressedTexImage2D(GR_GL_TEXTURE_2D,
                                                   0, // level
                                                   internalFormat,
                                                   desc.fWidth, desc.fHeight,
                                                   0, // border
                                                   imageSize,
                                                   data));
            } else {
                GL_ALLOC_CALL(this->glInterface(),
                              TexImage2D(GR_GL_TEXTURE_2D,
                                         0, // level
                                         internalFormat,
                                         desc.fWidth, desc.fHeight,
                                         0, // border
                                         externalFormat, externalType,
                                         data));
            }
        }
        GrGLenum error = CHECK_ALLOC_ERROR(this->glInterface());
        if (error != GR_GL_NO_ERROR) {
            succeeded = false;
        } else {
            // if we have data and we used TexStorage to create the texture, we
            // now upload with TexSubImage.
            if (NULL != data && useTexStorage) {
                GL_CALL(TexSubImage2D(GR_GL_TEXTURE_2D,
                                      0, // level
                                      left, top,
                                      width, height,
                                      externalFormat, externalType,
                                      data));
            }
        }
    } else {
        if (swFlipY || glFlipY) {
            top = desc.fHeight - (top + height);
        }
        GL_CALL(TexSubImage2D(GR_GL_TEXTURE_2D,
                              0, // level
                              left, top,
                              width, height,
                              externalFormat, externalType, data));
    }

    if (restoreGLRowLength) {
        GrAssert(this->glCaps().unpackRowLengthSupport());
        GL_CALL(PixelStorei(GR_GL_UNPACK_ROW_LENGTH, 0));
    }
    if (glFlipY) {
        GL_CALL(PixelStorei(GR_GL_UNPACK_FLIP_Y, GR_GL_FALSE));
    }
    return succeeded;
}

namespace {
bool renderbuffer_storage_msaa(GrGLContextInfo& ctxInfo,
                               int sampleCount,
                               GrGLenum format,
                               int width, int height) {
    CLEAR_ERROR_BEFORE_ALLOC(ctxInfo.interface());
    GrAssert(GrGLCaps::kNone_MSFBOType != ctxInfo.caps().msFBOType());
    bool created = false;
    if (GrGLCaps::kNVDesktop_CoverageAAType ==
        ctxInfo.caps().coverageAAType()) {
        const GrGLCaps::MSAACoverageMode& mode =
            ctxInfo.caps().getMSAACoverageMode(sampleCount);
        GL_ALLOC_CALL(ctxInfo.interface(),
                      RenderbufferStorageMultisampleCoverage(GR_GL_RENDERBUFFER,
                                                        mode.fCoverageSampleCnt,
                                                        mode.fColorSampleCnt,
                                                        format,
                                                        width, height));
        created = (GR_GL_NO_ERROR == CHECK_ALLOC_ERROR(ctxInfo.interface()));
    }
    if (!created) {
        // glRBMS will fail if requested samples is > max samples.
        sampleCount = GrMin(sampleCount, ctxInfo.caps().maxSampleCount());
        GL_ALLOC_CALL(ctxInfo.interface(),
                      RenderbufferStorageMultisample(GR_GL_RENDERBUFFER,
                                                     sampleCount,
                                                     format,
                                                     width, height));
        created = (GR_GL_NO_ERROR == CHECK_ALLOC_ERROR(ctxInfo.interface()));
    }
    return created;
}
}

bool GrGpuGL::createRenderTargetObjects(int width, int height,
                                        GrGLuint texID,
                                        GrGLRenderTarget::Desc* desc) {
    desc->fMSColorRenderbufferID = 0;
    desc->fRTFBOID = 0;
    desc->fTexFBOID = 0;
    desc->fOwnIDs = true;

    GrGLenum status;

    GrGLenum msColorFormat = 0; // suppress warning

    GL_CALL(GenFramebuffers(1, &desc->fTexFBOID));
    if (!desc->fTexFBOID) {
        goto FAILED;
    }
    

    // If we are using multisampling we will create two FBOS. We render
    // to one and then resolve to the texture bound to the other.
    if (desc->fSampleCnt > 0) {
        if (GrGLCaps::kNone_MSFBOType == this->glCaps().msFBOType()) {
            goto FAILED;
        }
        GL_CALL(GenFramebuffers(1, &desc->fRTFBOID));
        GL_CALL(GenRenderbuffers(1, &desc->fMSColorRenderbufferID));
        if (!desc->fRTFBOID ||
            !desc->fMSColorRenderbufferID || 
            !this->configToGLFormats(desc->fConfig,
                                     // GLES requires sized internal formats
                                     kES2_GrGLBinding == this->glBinding(),
                                     &msColorFormat, NULL, NULL)) {
            goto FAILED;
        }
    } else {
        desc->fRTFBOID = desc->fTexFBOID;
    }

    // below here we may bind the FBO
    fHWBoundRenderTarget = NULL;
    if (desc->fRTFBOID != desc->fTexFBOID) {
        GrAssert(desc->fSampleCnt > 1);
        GL_CALL(BindRenderbuffer(GR_GL_RENDERBUFFER,
                               desc->fMSColorRenderbufferID));
        if (!renderbuffer_storage_msaa(fGLContextInfo,
                                       desc->fSampleCnt,
                                       msColorFormat,
                                       width, height)) {
            goto FAILED;
        }
        GL_CALL(BindFramebuffer(GR_GL_FRAMEBUFFER, desc->fRTFBOID));
        GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER, 
                                      GR_GL_COLOR_ATTACHMENT0,
                                      GR_GL_RENDERBUFFER,
                                      desc->fMSColorRenderbufferID));
        if (!this->glCaps().isConfigVerifiedColorAttachment(desc->fConfig)) {
            GL_CALL_RET(status, CheckFramebufferStatus(GR_GL_FRAMEBUFFER));
            if (status != GR_GL_FRAMEBUFFER_COMPLETE) {
                goto FAILED;
            }
            fGLContextInfo.caps().markConfigAsValidColorAttachment(
                                                                desc->fConfig);
        }
    }
    GL_CALL(BindFramebuffer(GR_GL_FRAMEBUFFER, desc->fTexFBOID));

    GL_CALL(FramebufferTexture2D(GR_GL_FRAMEBUFFER,
                                 GR_GL_COLOR_ATTACHMENT0,
                                 GR_GL_TEXTURE_2D,
                                 texID, 0));
    if (!this->glCaps().isConfigVerifiedColorAttachment(desc->fConfig)) {
        GL_CALL_RET(status, CheckFramebufferStatus(GR_GL_FRAMEBUFFER));
        if (status != GR_GL_FRAMEBUFFER_COMPLETE) {
            goto FAILED;
        }
        fGLContextInfo.caps().markConfigAsValidColorAttachment(desc->fConfig);
    }

    return true;

FAILED:
    if (desc->fMSColorRenderbufferID) {
        GL_CALL(DeleteRenderbuffers(1, &desc->fMSColorRenderbufferID));
    }
    if (desc->fRTFBOID != desc->fTexFBOID) {
        GL_CALL(DeleteFramebuffers(1, &desc->fRTFBOID));
    }
    if (desc->fTexFBOID) {
        GL_CALL(DeleteFramebuffers(1, &desc->fTexFBOID));
    }
    return false;
}

// good to set a break-point here to know when createTexture fails
static GrTexture* return_null_texture() {
//    GrAssert(!"null texture");
    return NULL;
}

#if 0 && GR_DEBUG
static size_t as_size_t(int x) {
    return x;
}
#endif

GrTexture* GrGpuGL::onCreateTexture(const GrTextureDesc& desc,
                                    const void* srcData,
                                    size_t rowBytes) {

    GrGLTexture::Desc glTexDesc;
    GrGLRenderTarget::Desc  glRTDesc;

    // Attempt to catch un- or wrongly initialized sample counts;
    GrAssert(desc.fSampleCnt >= 0 && desc.fSampleCnt <= 64);

    glTexDesc.fFlags  = desc.fFlags;
    glTexDesc.fWidth  = desc.fWidth;
    glTexDesc.fHeight = desc.fHeight;
    glTexDesc.fConfig = desc.fConfig;
    glTexDesc.fSampleCnt = desc.fSampleCnt;
    glTexDesc.fClientCacheID = desc.fClientCacheID;

    glTexDesc.fOwnsID = true;

    glRTDesc.fMSColorRenderbufferID = 0;
    glRTDesc.fRTFBOID = 0;
    glRTDesc.fTexFBOID = 0;
    glRTDesc.fOwnIDs = true;
    glRTDesc.fConfig = glTexDesc.fConfig;

    bool renderTarget = 0 != (desc.fFlags & kRenderTarget_GrTextureFlagBit);

    const Caps& caps = this->getCaps();

    // We keep GrRenderTargets in GL's normal orientation so that they
    // can be drawn to by the outside world without the client having
    // to render upside down.
    glTexDesc.fOrientation = renderTarget ? GrGLTexture::kBottomUp_Orientation :
                                            GrGLTexture::kTopDown_Orientation;

    glRTDesc.fSampleCnt = desc.fSampleCnt;
    if (GrGLCaps::kNone_MSFBOType == this->glCaps().msFBOType() &&
        desc.fSampleCnt) {
        //GrPrintf("MSAA RT requested but not supported on this platform.");
        return return_null_texture();
    }

    if (renderTarget) {
        if (glTexDesc.fWidth > caps.fMaxRenderTargetSize ||
            glTexDesc.fHeight > caps.fMaxRenderTargetSize) {
            return return_null_texture();
        }
    }

    GL_CALL(GenTextures(1, &glTexDesc.fTextureID));
    if (renderTarget && this->glCaps().textureUsageSupport()) {
        // provides a hint about how this texture will be used
        GL_CALL(TexParameteri(GR_GL_TEXTURE_2D,
                              GR_GL_TEXTURE_USAGE,
                              GR_GL_FRAMEBUFFER_ATTACHMENT));
    }
    if (!glTexDesc.fTextureID) {
        return return_null_texture();
    }

    this->setSpareTextureUnit();
    GL_CALL(BindTexture(GR_GL_TEXTURE_2D, glTexDesc.fTextureID));

    // Some drivers like to know filter/wrap before seeing glTexImage2D. Some
    // drivers have a bug where an FBO won't be complete if it includes a
    // texture that is not mipmap complete (considering the filter in use).
    GrGLTexture::TexParams initialTexParams;
    // we only set a subset here so invalidate first
    initialTexParams.invalidate();
    initialTexParams.fFilter = GR_GL_NEAREST;
    initialTexParams.fWrapS = GR_GL_CLAMP_TO_EDGE;
    initialTexParams.fWrapT = GR_GL_CLAMP_TO_EDGE;
    GL_CALL(TexParameteri(GR_GL_TEXTURE_2D,
                          GR_GL_TEXTURE_MAG_FILTER,
                          initialTexParams.fFilter));
    GL_CALL(TexParameteri(GR_GL_TEXTURE_2D,
                          GR_GL_TEXTURE_MIN_FILTER,
                          initialTexParams.fFilter));
    GL_CALL(TexParameteri(GR_GL_TEXTURE_2D,
                          GR_GL_TEXTURE_WRAP_S,
                          initialTexParams.fWrapS));
    GL_CALL(TexParameteri(GR_GL_TEXTURE_2D,
                          GR_GL_TEXTURE_WRAP_T,
                          initialTexParams.fWrapT));
    if (!this->uploadTexData(glTexDesc, true, 0, 0,
                             glTexDesc.fWidth, glTexDesc.fHeight,
                             desc.fConfig, srcData, rowBytes)) {
        GL_CALL(DeleteTextures(1, &glTexDesc.fTextureID));
        return return_null_texture();
    }

    GrGLTexture* tex;
    if (renderTarget) {
        // unbind the texture from the texture unit before binding it to the frame buffer
        GL_CALL(BindTexture(GR_GL_TEXTURE_2D, 0));

        if (!this->createRenderTargetObjects(glTexDesc.fWidth,
                                             glTexDesc.fHeight,
                                             glTexDesc.fTextureID,
                                             &glRTDesc)) {
            GL_CALL(DeleteTextures(1, &glTexDesc.fTextureID));
            return return_null_texture();
        }
        tex = new GrGLTexture(this, glTexDesc, glRTDesc);
    } else {
        tex = new GrGLTexture(this, glTexDesc);
    }
    tex->setCachedTexParams(initialTexParams, this->getResetTimestamp());
#ifdef TRACE_TEXTURE_CREATION
    GrPrintf("--- new texture [%d] size=(%d %d) config=%d\n",
             glTexDesc.fTextureID, desc.fWidth, desc.fHeight, desc.fConfig);
#endif
    return tex;
}

namespace {

const GrGLuint kUnknownBitCount = GrGLStencilBuffer::kUnknownBitCount;

void inline get_stencil_rb_sizes(const GrGLInterface* gl,
                                 GrGLuint rb, 
                                 GrGLStencilBuffer::Format* format) {
    // we shouldn't ever know one size and not the other
    GrAssert((kUnknownBitCount == format->fStencilBits) ==
             (kUnknownBitCount == format->fTotalBits));
    if (kUnknownBitCount == format->fStencilBits) {
        GR_GL_GetRenderbufferParameteriv(gl, GR_GL_RENDERBUFFER,
                                         GR_GL_RENDERBUFFER_STENCIL_SIZE,
                                         (GrGLint*)&format->fStencilBits);
        if (format->fPacked) {
            GR_GL_GetRenderbufferParameteriv(gl, GR_GL_RENDERBUFFER,
                                             GR_GL_RENDERBUFFER_DEPTH_SIZE,
                                             (GrGLint*)&format->fTotalBits);
            format->fTotalBits += format->fStencilBits;
        } else {
            format->fTotalBits = format->fStencilBits;
        }
    }
}
}

bool GrGpuGL::createStencilBufferForRenderTarget(GrRenderTarget* rt,
                                                 int width, int height) {

    // All internally created RTs are also textures. We don't create
    // SBs for a client's standalone RT (that is RT that isnt also a texture).
    GrAssert(rt->asTexture());
    GrAssert(width >= rt->width());
    GrAssert(height >= rt->height());

    int samples = rt->numSamples();
    GrGLuint sbID;
    GL_CALL(GenRenderbuffers(1, &sbID));
    if (!sbID) {
        return false;
    }

    GrGLStencilBuffer* sb = NULL;

    int stencilFmtCnt = this->glCaps().stencilFormats().count();
    for (int i = 0; i < stencilFmtCnt; ++i) {
        GL_CALL(BindRenderbuffer(GR_GL_RENDERBUFFER, sbID));
        // we start with the last stencil format that succeeded in hopes
        // that we won't go through this loop more than once after the
        // first (painful) stencil creation.
        int sIdx = (i + fLastSuccessfulStencilFmtIdx) % stencilFmtCnt;
        const GrGLCaps::StencilFormat& sFmt =
                this->glCaps().stencilFormats()[sIdx];
        CLEAR_ERROR_BEFORE_ALLOC(this->glInterface());
        // we do this "if" so that we don't call the multisample
        // version on a GL that doesn't have an MSAA extension.
        bool created;
        if (samples > 0) {
            created = renderbuffer_storage_msaa(fGLContextInfo,
                                                samples,
                                                sFmt.fInternalFormat,
                                                width, height);
        } else {
            GL_ALLOC_CALL(this->glInterface(),
                          RenderbufferStorage(GR_GL_RENDERBUFFER,
                                              sFmt.fInternalFormat,
                                              width, height));
            created =
                (GR_GL_NO_ERROR == CHECK_ALLOC_ERROR(this->glInterface()));
        }
        if (created) {
            // After sized formats we attempt an unsized format and take
            // whatever sizes GL gives us. In that case we query for the size.
            GrGLStencilBuffer::Format format = sFmt;
            get_stencil_rb_sizes(this->glInterface(), sbID, &format);
            sb = new GrGLStencilBuffer(this, sbID, width, height, 
                                       samples, format);
            if (this->attachStencilBufferToRenderTarget(sb, rt)) {
                fLastSuccessfulStencilFmtIdx = sIdx;
                rt->setStencilBuffer(sb);
                sb->unref();
                return true;
           }
           sb->abandon(); // otherwise we lose sbID
           sb->unref();
        }
    }
    GL_CALL(DeleteRenderbuffers(1, &sbID));
    return false;
}

bool GrGpuGL::attachStencilBufferToRenderTarget(GrStencilBuffer* sb,
                                                GrRenderTarget* rt) {
    GrGLRenderTarget* glrt = (GrGLRenderTarget*) rt;

    GrGLuint fbo = glrt->renderFBOID();

    if (NULL == sb) {
        if (NULL != rt->getStencilBuffer()) {
            GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                          GR_GL_STENCIL_ATTACHMENT,
                                          GR_GL_RENDERBUFFER, 0));
            GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                          GR_GL_DEPTH_ATTACHMENT,
                                          GR_GL_RENDERBUFFER, 0));
#if GR_DEBUG
            GrGLenum status;
            GL_CALL_RET(status, CheckFramebufferStatus(GR_GL_FRAMEBUFFER));
            GrAssert(GR_GL_FRAMEBUFFER_COMPLETE == status);
#endif
        }
        return true;
    } else {
        GrGLStencilBuffer* glsb = (GrGLStencilBuffer*) sb;
        GrGLuint rb = glsb->renderbufferID();

        fHWBoundRenderTarget = NULL;
        GL_CALL(BindFramebuffer(GR_GL_FRAMEBUFFER, fbo));
        GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                      GR_GL_STENCIL_ATTACHMENT,
                                      GR_GL_RENDERBUFFER, rb));
        if (glsb->format().fPacked) {
            GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                          GR_GL_DEPTH_ATTACHMENT,
                                          GR_GL_RENDERBUFFER, rb));
        } else {
            GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                          GR_GL_DEPTH_ATTACHMENT,
                                          GR_GL_RENDERBUFFER, 0));
        }

        GrGLenum status;
        if (!this->glCaps().isColorConfigAndStencilFormatVerified(rt->config(),
                                                           glsb->format())) {
            GL_CALL_RET(status, CheckFramebufferStatus(GR_GL_FRAMEBUFFER));
            if (status != GR_GL_FRAMEBUFFER_COMPLETE) {
                GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                              GR_GL_STENCIL_ATTACHMENT,
                                              GR_GL_RENDERBUFFER, 0));
                if (glsb->format().fPacked) {
                    GL_CALL(FramebufferRenderbuffer(GR_GL_FRAMEBUFFER,
                                                  GR_GL_DEPTH_ATTACHMENT,
                                                  GR_GL_RENDERBUFFER, 0));
                }
                return false;
            } else {
                fGLContextInfo.caps().markColorConfigAndStencilFormatAsVerified(
                    rt->config(),
                    glsb->format());
            }
        }
        return true;
    }
}

////////////////////////////////////////////////////////////////////////////////

GrVertexBuffer* GrGpuGL::onCreateVertexBuffer(uint32_t size, bool dynamic) {
    GrGLuint id;
    GL_CALL(GenBuffers(1, &id));
    if (id) {
        GL_CALL(BindBuffer(GR_GL_ARRAY_BUFFER, id));
        fHWGeometryState.fArrayPtrsDirty = true;
        CLEAR_ERROR_BEFORE_ALLOC(this->glInterface());
        // make sure driver can allocate memory for this buffer
        GL_ALLOC_CALL(this->glInterface(),
                      BufferData(GR_GL_ARRAY_BUFFER,
                                 size,
                                 NULL,   // data ptr
                                 dynamic ? GR_GL_DYNAMIC_DRAW :
                                           GR_GL_STATIC_DRAW));
        if (CHECK_ALLOC_ERROR(this->glInterface()) != GR_GL_NO_ERROR) {
            GL_CALL(DeleteBuffers(1, &id));
            // deleting bound buffer does implicit bind to 0
            fHWGeometryState.fVertexBuffer = NULL;
            return NULL;
        }
        GrGLVertexBuffer* vertexBuffer = new GrGLVertexBuffer(this, id,
                                                              size, dynamic);
        fHWGeometryState.fVertexBuffer = vertexBuffer;
        return vertexBuffer;
    }
    return NULL;
}

GrIndexBuffer* GrGpuGL::onCreateIndexBuffer(uint32_t size, bool dynamic) {
    GrGLuint id;
    GL_CALL(GenBuffers(1, &id));
    if (id) {
        GL_CALL(BindBuffer(GR_GL_ELEMENT_ARRAY_BUFFER, id));
        CLEAR_ERROR_BEFORE_ALLOC(this->glInterface());
        // make sure driver can allocate memory for this buffer
        GL_ALLOC_CALL(this->glInterface(),
                      BufferData(GR_GL_ELEMENT_ARRAY_BUFFER,
                                 size,
                                 NULL,  // data ptr
                                 dynamic ? GR_GL_DYNAMIC_DRAW :
                                           GR_GL_STATIC_DRAW));
        if (CHECK_ALLOC_ERROR(this->glInterface()) != GR_GL_NO_ERROR) {
            GL_CALL(DeleteBuffers(1, &id));
            // deleting bound buffer does implicit bind to 0
            fHWGeometryState.fIndexBuffer = NULL;
            return NULL;
        }
        GrIndexBuffer* indexBuffer = new GrGLIndexBuffer(this, id,
                                                         size, dynamic);
        fHWGeometryState.fIndexBuffer = indexBuffer;
        return indexBuffer;
    }
    return NULL;
}

GrPath* GrGpuGL::onCreatePath(const SkPath& inPath) {
    GrPath* path = NULL;
    if (fCaps.fPathStencilingSupport) {
        path = new GrGLPath(this, inPath);
    }
    return path;
}

void GrGpuGL::enableScissoring(const GrIRect& rect) {
    const GrDrawState& drawState = this->getDrawState();
    const GrGLRenderTarget* rt =
        static_cast<const GrGLRenderTarget*>(drawState.getRenderTarget());

    GrAssert(NULL != rt);
    const GrGLIRect& vp = rt->getViewport();

    GrGLIRect scissor;
    scissor.setRelativeTo(vp, rect.fLeft, rect.fTop,
                          rect.width(), rect.height());
    if (scissor.contains(vp)) {
        disableScissor();
        return;
    }

    if (fHWBounds.fScissorRect != scissor) {
        scissor.pushToGLScissor(this->glInterface());
        fHWBounds.fScissorRect = scissor;
    }
    if (!fHWBounds.fScissorEnabled) {
        GL_CALL(Enable(GR_GL_SCISSOR_TEST));
        fHWBounds.fScissorEnabled = true;
    }
}

void GrGpuGL::disableScissor() {
    if (fHWBounds.fScissorEnabled) {
        GL_CALL(Disable(GR_GL_SCISSOR_TEST));
        fHWBounds.fScissorEnabled = false;
    }
}

void GrGpuGL::onClear(const GrIRect* rect, GrColor color) {
    const GrDrawState& drawState = this->getDrawState();
    const GrRenderTarget* rt = drawState.getRenderTarget();
    // parent class should never let us get here with no RT
    GrAssert(NULL != rt);

    GrIRect clippedRect;
    if (NULL != rect) {
        // flushScissor expects rect to be clipped to the target.
        clippedRect = *rect;
        GrIRect rtRect = SkIRect::MakeWH(rt->width(), rt->height());
        if (clippedRect.intersect(rtRect)) {
            rect = &clippedRect;
        } else {
            return;
        }
    }
    this->flushRenderTarget(rect);
    if (NULL != rect)
        this->enableScissoring(*rect);
    else
        this->disableScissor();

    GrGLfloat r, g, b, a;
    static const GrGLfloat scale255 = 1.f / 255.f;
    a = GrColorUnpackA(color) * scale255;
    GrGLfloat scaleRGB = scale255;
    if (GrPixelConfigIsUnpremultiplied(rt->config())) {
        scaleRGB *= a;
    }
    r = GrColorUnpackR(color) * scaleRGB;
    g = GrColorUnpackG(color) * scaleRGB;
    b = GrColorUnpackB(color) * scaleRGB;

    GL_CALL(ColorMask(GR_GL_TRUE, GR_GL_TRUE, GR_GL_TRUE, GR_GL_TRUE));
    fHWWriteToColor = kYes_TriState;
    GL_CALL(ClearColor(r, g, b, a));
    GL_CALL(Clear(GR_GL_COLOR_BUFFER_BIT));
}

void GrGpuGL::clearStencil() {
    if (NULL == this->getDrawState().getRenderTarget()) {
        return;
    }
    
    this->flushRenderTarget(&GrIRect::EmptyIRect());

    this->disableScissor();

    GL_CALL(StencilMask(0xffffffff));
    GL_CALL(ClearStencil(0));
    GL_CALL(Clear(GR_GL_STENCIL_BUFFER_BIT));
    fHWStencilSettings.invalidate();
}

void GrGpuGL::clearStencilClip(const GrIRect& rect, bool insideClip) {
    const GrDrawState& drawState = this->getDrawState();
    const GrRenderTarget* rt = drawState.getRenderTarget();
    GrAssert(NULL != rt);

    // this should only be called internally when we know we have a
    // stencil buffer.
    GrAssert(NULL != rt->getStencilBuffer());
    GrGLint stencilBitCount =  rt->getStencilBuffer()->bits();
#if 0
    GrAssert(stencilBitCount > 0);
    GrGLint clipStencilMask  = (1 << (stencilBitCount - 1));
#else
    // we could just clear the clip bit but when we go through
    // ANGLE a partial stencil mask will cause clears to be
    // turned into draws. Our contract on GrDrawTarget says that
    // changing the clip between stencil passes may or may not
    // zero the client's clip bits. So we just clear the whole thing.
    static const GrGLint clipStencilMask  = ~0;
#endif
    GrGLint value;
    if (insideClip) {
        value = (1 << (stencilBitCount - 1));
    } else {
        value = 0;
    }
    this->flushRenderTarget(&GrIRect::EmptyIRect());
    this->enableScissoring(rect);
    GL_CALL(StencilMask((uint32_t) clipStencilMask));
    GL_CALL(ClearStencil(value));
    GL_CALL(Clear(GR_GL_STENCIL_BUFFER_BIT));
    fHWStencilSettings.invalidate();
}

void GrGpuGL::onForceRenderTargetFlush() {
    this->flushRenderTarget(&GrIRect::EmptyIRect());
}

bool GrGpuGL::readPixelsWillPayForYFlip(GrRenderTarget* renderTarget,
                                        int left, int top,
                                        int width, int height,
                                        GrPixelConfig config,
                                        size_t rowBytes) const {
    // if GL can do the flip then we'll never pay for it.
    if (this->glCaps().packFlipYSupport()) {
        return false;
    }

    // If we have to do memcpy to handle non-trim rowBytes then we
    // get the flip for free. Otherwise it costs.
    if (this->glCaps().packRowLengthSupport()) {
        return true;
    }
    // If we have to do memcpys to handle rowBytes then y-flip is free
    // Note the rowBytes might be tight to the passed in data, but if data
    // gets clipped in x to the target the rowBytes will no longer be tight.
    if (left >= 0 && (left + width) < renderTarget->width()) {
           return 0 == rowBytes ||
                  GrBytesPerPixel(config) * width == rowBytes;
    } else {
        return false;
    }
}

bool GrGpuGL::onReadPixels(GrRenderTarget* target,
                           int left, int top,
                           int width, int height,
                           GrPixelConfig config,
                           void* buffer,
                           size_t rowBytes,
                           bool invertY) {
    GrGLenum format;
    GrGLenum type;
    if (!this->configToGLFormats(config, false, NULL, &format, &type)) {
        return false;
    }
    size_t bpp = GrBytesPerPixel(config);
    if (!adjust_pixel_ops_params(target->width(), target->height(), bpp,
                                 &left, &top, &width, &height,
                                 const_cast<const void**>(&buffer),
                                 &rowBytes)) {
        return false;
    }

    // resolve the render target if necessary
    GrGLRenderTarget* tgt = static_cast<GrGLRenderTarget*>(target);
    GrDrawState::AutoRenderTargetRestore artr;
    switch (tgt->getResolveType()) {
        case GrGLRenderTarget::kCantResolve_ResolveType:
            return false;
        case GrGLRenderTarget::kAutoResolves_ResolveType:
            artr.set(this->drawState(), target);
            this->flushRenderTarget(&GrIRect::EmptyIRect());
            break;
        case GrGLRenderTarget::kCanResolve_ResolveType:
            this->onResolveRenderTarget(tgt);
            // we don't track the state of the READ FBO ID.
            GL_CALL(BindFramebuffer(GR_GL_READ_FRAMEBUFFER,
                                    tgt->textureFBOID()));
            break;
        default:
            GrCrash("Unknown resolve type");
    }

    const GrGLIRect& glvp = tgt->getViewport();

    // the read rect is viewport-relative
    GrGLIRect readRect;
    readRect.setRelativeTo(glvp, left, top, width, height);
    
    size_t tightRowBytes = bpp * width;
    if (0 == rowBytes) {
        rowBytes = tightRowBytes;
    }
    size_t readDstRowBytes = tightRowBytes;
    void* readDst = buffer;
    
    // determine if GL can read using the passed rowBytes or if we need
    // a scratch buffer.
    SkAutoSMalloc<32 * sizeof(GrColor)> scratch;
    if (rowBytes != tightRowBytes) {
        if (this->glCaps().packRowLengthSupport()) {
            GrAssert(!(rowBytes % sizeof(GrColor)));
            GL_CALL(PixelStorei(GR_GL_PACK_ROW_LENGTH, rowBytes / sizeof(GrColor)));
            readDstRowBytes = rowBytes;
        } else {
            scratch.reset(tightRowBytes * height);
            readDst = scratch.get();
        }
    }
    if (!invertY && this->glCaps().packFlipYSupport()) {
        GL_CALL(PixelStorei(GR_GL_PACK_REVERSE_ROW_ORDER, 1));
    }
    GL_CALL(ReadPixels(readRect.fLeft, readRect.fBottom,
                       readRect.fWidth, readRect.fHeight,
                       format, type, readDst));
    if (readDstRowBytes != tightRowBytes) {
        GrAssert(this->glCaps().packRowLengthSupport());
        GL_CALL(PixelStorei(GR_GL_PACK_ROW_LENGTH, 0));
    }
    if (!invertY && this->glCaps().packFlipYSupport()) {
        GL_CALL(PixelStorei(GR_GL_PACK_REVERSE_ROW_ORDER, 0));
        invertY = true;
    }

    // now reverse the order of the rows, since GL's are bottom-to-top, but our
    // API presents top-to-bottom. We must preserve the padding contents. Note
    // that the above readPixels did not overwrite the padding.
    if (readDst == buffer) {
        GrAssert(rowBytes == readDstRowBytes);
        if (!invertY) {
            scratch.reset(tightRowBytes);
            void* tmpRow = scratch.get();
            // flip y in-place by rows
            const int halfY = height >> 1;
            char* top = reinterpret_cast<char*>(buffer);
            char* bottom = top + (height - 1) * rowBytes;
            for (int y = 0; y < halfY; y++) {
                memcpy(tmpRow, top, tightRowBytes);
                memcpy(top, bottom, tightRowBytes);
                memcpy(bottom, tmpRow, tightRowBytes);
                top += rowBytes;
                bottom -= rowBytes;
            }
        }
    } else {
        GrAssert(readDst != buffer);        GrAssert(rowBytes != tightRowBytes);
        // copy from readDst to buffer while flipping y
        // const int halfY = height >> 1;
        const char* src = reinterpret_cast<const char*>(readDst);
        char* dst = reinterpret_cast<char*>(buffer);
        if (!invertY) {
            dst += (height-1) * rowBytes;
        }
        for (int y = 0; y < height; y++) {
            memcpy(dst, src, tightRowBytes);
            src += readDstRowBytes;
            if (invertY) {
                dst += rowBytes;
            } else {
                dst -= rowBytes;
            }
        }
    }
    return true;
}

void GrGpuGL::flushRenderTarget(const GrIRect* bound) {

    GrGLRenderTarget* rt =
        static_cast<GrGLRenderTarget*>(this->drawState()->getRenderTarget());
    GrAssert(NULL != rt);

    if (fHWBoundRenderTarget != rt) {
        GL_CALL(BindFramebuffer(GR_GL_FRAMEBUFFER, rt->renderFBOID()));
    #if GR_DEBUG
        GrGLenum status;
        GL_CALL_RET(status, CheckFramebufferStatus(GR_GL_FRAMEBUFFER));
        if (status != GR_GL_FRAMEBUFFER_COMPLETE) {
            GrPrintf("GrGpuGL::flushRenderTarget glCheckFramebufferStatus %x\n", status);
        }
    #endif
        fHWBoundRenderTarget = rt;
        const GrGLIRect& vp = rt->getViewport();
        if (fHWBounds.fViewportRect != vp) {
            vp.pushToGLViewport(this->glInterface());
            fHWBounds.fViewportRect = vp;
        }
    }
    if (NULL == bound || !bound->isEmpty()) {
        rt->flagAsNeedingResolve(bound);
    }
}

GrGLenum gPrimitiveType2GLMode[] = {
    GR_GL_TRIANGLES,
    GR_GL_TRIANGLE_STRIP,
    GR_GL_TRIANGLE_FAN,
    GR_GL_POINTS,
    GR_GL_LINES,
    GR_GL_LINE_STRIP
};

#define SWAP_PER_DRAW 0

#if SWAP_PER_DRAW
    #if GR_MAC_BUILD
        #include <AGL/agl.h>
    #elif GR_WIN32_BUILD
        void SwapBuf() {
            DWORD procID = GetCurrentProcessId();
            HWND hwnd = GetTopWindow(GetDesktopWindow());
            while(hwnd) {
                DWORD wndProcID = 0;
                GetWindowThreadProcessId(hwnd, &wndProcID);
                if(wndProcID == procID) {
                    SwapBuffers(GetDC(hwnd));
                }
                hwnd = GetNextWindow(hwnd, GW_HWNDNEXT);
            }
         }
    #endif
#endif

void GrGpuGL::onGpuDrawIndexed(GrPrimitiveType type,
                               uint32_t startVertex,
                               uint32_t startIndex,
                               uint32_t vertexCount,
                               uint32_t indexCount) {
    GrAssert((size_t)type < GR_ARRAY_COUNT(gPrimitiveType2GLMode));

    GrGLvoid* indices = (GrGLvoid*)(sizeof(uint16_t) * startIndex);

    GrAssert(NULL != fHWGeometryState.fIndexBuffer);
    GrAssert(NULL != fHWGeometryState.fVertexBuffer);

    // our setupGeometry better have adjusted this to zero since
    // DrawElements always draws from the begining of the arrays for idx 0.
    GrAssert(0 == startVertex);

    GL_CALL(DrawElements(gPrimitiveType2GLMode[type], indexCount,
                         GR_GL_UNSIGNED_SHORT, indices));
#if SWAP_PER_DRAW
    glFlush();
    #if GR_MAC_BUILD
        aglSwapBuffers(aglGetCurrentContext());
        int set_a_break_pt_here = 9;
        aglSwapBuffers(aglGetCurrentContext());
    #elif GR_WIN32_BUILD
        SwapBuf();
        int set_a_break_pt_here = 9;
        SwapBuf();
    #endif
#endif
}

void GrGpuGL::onGpuDrawNonIndexed(GrPrimitiveType type,
                                  uint32_t startVertex,
                                  uint32_t vertexCount) {
    GrAssert((size_t)type < GR_ARRAY_COUNT(gPrimitiveType2GLMode));

    GrAssert(NULL != fHWGeometryState.fVertexBuffer);

    // our setupGeometry better have adjusted this to zero.
    // DrawElements doesn't take an offset so we always adjus the startVertex.
    GrAssert(0 == startVertex);

    // pass 0 for parameter first. We have to adjust gl*Pointer() to
    // account for startVertex in the DrawElements case. So we always
    // rely on setupGeometry to have accounted for startVertex.
    GL_CALL(DrawArrays(gPrimitiveType2GLMode[type], 0, vertexCount));
#if SWAP_PER_DRAW
    glFlush();
    #if GR_MAC_BUILD
        aglSwapBuffers(aglGetCurrentContext());
        int set_a_break_pt_here = 9;
        aglSwapBuffers(aglGetCurrentContext());
    #elif GR_WIN32_BUILD
        SwapBuf();
        int set_a_break_pt_here = 9;
        SwapBuf();
    #endif
#endif
}

void GrGpuGL::onGpuStencilPath(const GrPath&, GrPathFill) {
    GrCrash("Not implemented yet. Should not get here.");
}

void GrGpuGL::onResolveRenderTarget(GrRenderTarget* target) {

    GrGLRenderTarget* rt = static_cast<GrGLRenderTarget*>(target);

    if (rt->needsResolve()) {
        GrAssert(GrGLCaps::kNone_MSFBOType != this->glCaps().msFBOType());
        GrAssert(rt->textureFBOID() != rt->renderFBOID());
        GL_CALL(BindFramebuffer(GR_GL_READ_FRAMEBUFFER,
                                rt->renderFBOID()));
        GL_CALL(BindFramebuffer(GR_GL_DRAW_FRAMEBUFFER,
                                rt->textureFBOID()));
        // make sure we go through flushRenderTarget() since we've modified
        // the bound DRAW FBO ID.
        fHWBoundRenderTarget = NULL;
        const GrGLIRect& vp = rt->getViewport();
        const GrIRect dirtyRect = rt->getResolveRect();
        GrGLIRect r;
        r.setRelativeTo(vp, dirtyRect.fLeft, dirtyRect.fTop, 
                        dirtyRect.width(), dirtyRect.height());

        if (GrGLCaps::kAppleES_MSFBOType == this->glCaps().msFBOType()) {
            // Apple's extension uses the scissor as the blit bounds.
#if 1
            GL_CALL(Enable(GR_GL_SCISSOR_TEST));
            GL_CALL(Scissor(r.fLeft, r.fBottom,
                            r.fWidth, r.fHeight));
            GL_CALL(ResolveMultisampleFramebuffer());
            fHWBounds.fScissorRect.invalidate();
            fHWBounds.fScissorEnabled = true;
#else
            this->enableScissoring(dirtyRect);
            GL_CALL(ResolveMultisampleFramebuffer());
#endif
        } else {
            if (GrGLCaps::kDesktopARB_MSFBOType != this->glCaps().msFBOType()) {
                // this respects the scissor during the blit, so disable it.
                GrAssert(GrGLCaps::kDesktopEXT_MSFBOType ==
                         this->glCaps().msFBOType());
                this->disableScissor();
            }
            int right = r.fLeft + r.fWidth;
            int top = r.fBottom + r.fHeight;
            GL_CALL(BlitFramebuffer(r.fLeft, r.fBottom, right, top,
                                    r.fLeft, r.fBottom, right, top,
                                    GR_GL_COLOR_BUFFER_BIT, GR_GL_NEAREST));
        }
        rt->flagAsResolved();
    }
}

namespace {

GrGLenum gr_to_gl_stencil_func(GrStencilFunc basicFunc) {
    static const GrGLenum gTable[] = {
        GR_GL_ALWAYS,           // kAlways_StencilFunc
        GR_GL_NEVER,            // kNever_StencilFunc
        GR_GL_GREATER,          // kGreater_StencilFunc
        GR_GL_GEQUAL,           // kGEqual_StencilFunc
        GR_GL_LESS,             // kLess_StencilFunc
        GR_GL_LEQUAL,           // kLEqual_StencilFunc,
        GR_GL_EQUAL,            // kEqual_StencilFunc,
        GR_GL_NOTEQUAL,         // kNotEqual_StencilFunc,
    };
    GR_STATIC_ASSERT(GR_ARRAY_COUNT(gTable) == kBasicStencilFuncCount);
    GR_STATIC_ASSERT(0 == kAlways_StencilFunc);
    GR_STATIC_ASSERT(1 == kNever_StencilFunc);
    GR_STATIC_ASSERT(2 == kGreater_StencilFunc);
    GR_STATIC_ASSERT(3 == kGEqual_StencilFunc);
    GR_STATIC_ASSERT(4 == kLess_StencilFunc);
    GR_STATIC_ASSERT(5 == kLEqual_StencilFunc);
    GR_STATIC_ASSERT(6 == kEqual_StencilFunc);
    GR_STATIC_ASSERT(7 == kNotEqual_StencilFunc);
    GrAssert((unsigned) basicFunc < kBasicStencilFuncCount);

    return gTable[basicFunc];
}

GrGLenum gr_to_gl_stencil_op(GrStencilOp op) {
    static const GrGLenum gTable[] = {
        GR_GL_KEEP,        // kKeep_StencilOp
        GR_GL_REPLACE,     // kReplace_StencilOp
        GR_GL_INCR_WRAP,   // kIncWrap_StencilOp
        GR_GL_INCR,        // kIncClamp_StencilOp
        GR_GL_DECR_WRAP,   // kDecWrap_StencilOp
        GR_GL_DECR,        // kDecClamp_StencilOp
        GR_GL_ZERO,        // kZero_StencilOp
        GR_GL_INVERT,      // kInvert_StencilOp
    };
    GR_STATIC_ASSERT(GR_ARRAY_COUNT(gTable) == kStencilOpCount);
    GR_STATIC_ASSERT(0 == kKeep_StencilOp);
    GR_STATIC_ASSERT(1 == kReplace_StencilOp);
    GR_STATIC_ASSERT(2 == kIncWrap_StencilOp);
    GR_STATIC_ASSERT(3 == kIncClamp_StencilOp);
    GR_STATIC_ASSERT(4 == kDecWrap_StencilOp);
    GR_STATIC_ASSERT(5 == kDecClamp_StencilOp);
    GR_STATIC_ASSERT(6 == kZero_StencilOp);
    GR_STATIC_ASSERT(7 == kInvert_StencilOp);
    GrAssert((unsigned) op < kStencilOpCount);
    return gTable[op];
}

void set_gl_stencil(const GrGLInterface* gl,
                    GrGLenum glFace,
                    GrStencilFunc func,
                    GrStencilOp failOp,
                    GrStencilOp passOp,
                    unsigned int ref,
                    unsigned int mask,
                    unsigned int writeMask) {
    GrGLenum glFunc = gr_to_gl_stencil_func(func);
    GrGLenum glFailOp = gr_to_gl_stencil_op(failOp);
    GrGLenum glPassOp = gr_to_gl_stencil_op(passOp);

    if (GR_GL_FRONT_AND_BACK == glFace) {
        // we call the combined func just in case separate stencil is not
        // supported.
        GR_GL_CALL(gl, StencilFunc(glFunc, ref, mask));
        GR_GL_CALL(gl, StencilMask(writeMask));
        GR_GL_CALL(gl, StencilOp(glFailOp, glPassOp, glPassOp));
    } else {
        GR_GL_CALL(gl, StencilFuncSeparate(glFace, glFunc, ref, mask));
        GR_GL_CALL(gl, StencilMaskSeparate(glFace, writeMask));
        GR_GL_CALL(gl, StencilOpSeparate(glFace, glFailOp, glPassOp, glPassOp));
    }
}
}

void GrGpuGL::flushStencil() {
    const GrDrawState& drawState = this->getDrawState();

    // use stencil for clipping if clipping is enabled and the clip
    // has been written into the stencil.
    GrClipMaskManager::StencilClipMode clipMode;
    if (fClipMaskManager.isClipInStencil() &&
        drawState.isClipState()) {
        clipMode = GrClipMaskManager::kRespectClip_StencilClipMode;
        // We can't be modifying the clip and respecting it at the same time.
        GrAssert(!drawState.isStateFlagEnabled(kModifyStencilClip_StateBit));
    } else if (drawState.isStateFlagEnabled(kModifyStencilClip_StateBit)) {
        clipMode = GrClipMaskManager::kModifyClip_StencilClipMode;
    } else {
        clipMode = GrClipMaskManager::kIgnoreClip_StencilClipMode;
    }

    // The caller may not be using the stencil buffer but we may need to enable
    // it in order to respect a stencil clip.
    const GrStencilSettings* settings = &drawState.getStencil();
    if (settings->isDisabled() &&
        GrClipMaskManager::kRespectClip_StencilClipMode == clipMode) {
        settings = GetClipStencilSettings();
    }

    // TODO: dynamically attach a stencil buffer
    int stencilBits = 0;
    GrStencilBuffer* stencilBuffer = 
        drawState.getRenderTarget()->getStencilBuffer();
    if (NULL != stencilBuffer) {
        stencilBits = stencilBuffer->bits();
    }
    GrAssert(stencilBits || settings->isDisabled());

    bool updateStencilSettings = stencilBits > 0 &&
                                 ((fHWStencilSettings != *settings) ||
                                  (fHWStencilClipMode != clipMode));
    if (updateStencilSettings) {
        if (settings->isDisabled()) {
            GL_CALL(Disable(GR_GL_STENCIL_TEST));
        } else {
            GL_CALL(Enable(GR_GL_STENCIL_TEST));
    #if GR_DEBUG
            if (!this->getCaps().fStencilWrapOpsSupport) {
                GrAssert(settings->frontPassOp() != kIncWrap_StencilOp);
                GrAssert(settings->frontPassOp() != kDecWrap_StencilOp);
                GrAssert(settings->frontFailOp() != kIncWrap_StencilOp);
                GrAssert(settings->backFailOp() != kDecWrap_StencilOp);
                GrAssert(settings->backPassOp() != kIncWrap_StencilOp);
                GrAssert(settings->backPassOp() != kDecWrap_StencilOp);
                GrAssert(settings->backFailOp() != kIncWrap_StencilOp);
                GrAssert(settings->frontFailOp() != kDecWrap_StencilOp);
            }
    #endif

            unsigned int frontRef  = settings->frontFuncRef();
            unsigned int frontMask = settings->frontFuncMask();
            unsigned int frontWriteMask = settings->frontWriteMask();

            GrStencilFunc frontFunc =
                fClipMaskManager.adjustStencilParams(settings->frontFunc(),
                                                     clipMode,
                                                     stencilBits,
                                                     &frontRef,
                                                     &frontMask,
                                                     &frontWriteMask);
            if (this->getCaps().fTwoSidedStencilSupport) {
                unsigned int backRef  = settings->backFuncRef();
                unsigned int backMask = settings->backFuncMask();
                unsigned int backWriteMask = settings->backWriteMask();

                GrStencilFunc backFunc =
                    fClipMaskManager.adjustStencilParams(settings->frontFunc(),
                                                         clipMode,
                                                         stencilBits,
                                                         &backRef,
                                                         &backMask,
                                                         &backWriteMask);
                set_gl_stencil(this->glInterface(),
                               GR_GL_FRONT,
                               frontFunc,
                               settings->frontFailOp(),
                               settings->frontPassOp(),
                               frontRef,
                               frontMask,
                               frontWriteMask);
                set_gl_stencil(this->glInterface(),
                               GR_GL_BACK,
                               backFunc,
                               settings->backFailOp(),
                               settings->backPassOp(),
                               backRef,
                               backMask,
                               backWriteMask);
            } else {
                set_gl_stencil(this->glInterface(),
                               GR_GL_FRONT_AND_BACK,
                               frontFunc,
                               settings->frontFailOp(),
                               settings->frontPassOp(),
                               frontRef,
                               frontMask,
                               frontWriteMask);
            }
        }
        fHWStencilSettings = *settings;
        fHWStencilClipMode = clipMode;
    }
}

void GrGpuGL::flushAAState(bool isLines) {
    const GrRenderTarget* rt = this->getDrawState().getRenderTarget();
    if (kDesktop_GrGLBinding == this->glBinding()) {
        // ES doesn't support toggling GL_MULTISAMPLE and doesn't have
        // smooth lines.
        // we prefer smooth lines over multisampled lines
        bool smoothLines = false;

        if (isLines) {
            smoothLines = this->willUseHWAALines();
            if (smoothLines) {
                if (kYes_TriState != fHWAAState.fSmoothLineEnabled) {
                    GL_CALL(Enable(GR_GL_LINE_SMOOTH));
                    fHWAAState.fSmoothLineEnabled = kYes_TriState;
                    // must disable msaa to use line smoothing
                    if (rt->isMultisampled() &&
                        kNo_TriState != fHWAAState.fMSAAEnabled) {
                        GL_CALL(Disable(GR_GL_MULTISAMPLE));
                        fHWAAState.fMSAAEnabled = kNo_TriState;
                    }
                }
            } else {
                if (kNo_TriState != fHWAAState.fSmoothLineEnabled) {
                    GL_CALL(Disable(GR_GL_LINE_SMOOTH));
                    fHWAAState.fSmoothLineEnabled = kNo_TriState;
                }
            }
        }
        if (!smoothLines  && rt->isMultisampled()) {
            if (this->getDrawState().isHWAntialiasState()) {
                if (kYes_TriState != fHWAAState.fMSAAEnabled) {
                    GL_CALL(Enable(GR_GL_MULTISAMPLE));
                    fHWAAState.fMSAAEnabled = kYes_TriState;
                }
            } else {
                if (kNo_TriState != fHWAAState.fMSAAEnabled) {
                    GL_CALL(Disable(GR_GL_MULTISAMPLE));
                    fHWAAState.fMSAAEnabled = kNo_TriState;
                }
            }
        }
    }
}

void GrGpuGL::flushBlend(bool isLines,
                         GrBlendCoeff srcCoeff,
                         GrBlendCoeff dstCoeff) {
    if (isLines && this->willUseHWAALines()) {
        if (kYes_TriState != fHWBlendState.fEnabled) {
            GL_CALL(Enable(GR_GL_BLEND));
            fHWBlendState.fEnabled = kYes_TriState;
        }
        if (kSA_GrBlendCoeff != fHWBlendState.fSrcCoeff ||
            kISA_GrBlendCoeff != fHWBlendState.fDstCoeff) {
            GL_CALL(BlendFunc(gXfermodeCoeff2Blend[kSA_GrBlendCoeff],
                              gXfermodeCoeff2Blend[kISA_GrBlendCoeff]));
            fHWBlendState.fSrcCoeff = kSA_GrBlendCoeff;
            fHWBlendState.fDstCoeff = kISA_GrBlendCoeff;
        }
    } else {
        // any optimization to disable blending should
        // have already been applied and tweaked the coeffs
        // to (1, 0).
        bool blendOff = kOne_GrBlendCoeff == srcCoeff &&
                        kZero_GrBlendCoeff == dstCoeff;
        if (blendOff) {
            if (kNo_TriState != fHWBlendState.fEnabled) {
                GL_CALL(Disable(GR_GL_BLEND));
                fHWBlendState.fEnabled = kNo_TriState;
            }
        } else {
            if (kYes_TriState != fHWBlendState.fEnabled) {
                GL_CALL(Enable(GR_GL_BLEND));
                fHWBlendState.fEnabled = kYes_TriState;
            }
            if (fHWBlendState.fSrcCoeff != srcCoeff ||
                fHWBlendState.fDstCoeff != dstCoeff) {
                GL_CALL(BlendFunc(gXfermodeCoeff2Blend[srcCoeff],
                                  gXfermodeCoeff2Blend[dstCoeff]));
                fHWBlendState.fSrcCoeff = srcCoeff;
                fHWBlendState.fDstCoeff = dstCoeff;
            }
            GrColor blendConst = this->getDrawState().getBlendConstant();
            if ((BlendCoeffReferencesConstant(srcCoeff) ||
                 BlendCoeffReferencesConstant(dstCoeff)) &&
                (!fHWBlendState.fConstColorValid ||
                 fHWBlendState.fConstColor != blendConst)) {

                float c[] = {
                    GrColorUnpackR(blendConst) / 255.f,
                    GrColorUnpackG(blendConst) / 255.f,
                    GrColorUnpackB(blendConst) / 255.f,
                    GrColorUnpackA(blendConst) / 255.f
                };
                GL_CALL(BlendColor(c[0], c[1], c[2], c[3]));
                fHWBlendState.fConstColor = blendConst;
                fHWBlendState.fConstColorValid = true;
            }
        }
    }
}
namespace {

unsigned gr_to_gl_filter(GrSamplerState::Filter filter) {
    switch (filter) {
        case GrSamplerState::kBilinear_Filter:
            return GR_GL_LINEAR;
        case GrSamplerState::kNearest_Filter:
            return GR_GL_NEAREST;
        default:
            GrAssert(!"Unknown filter type");
            return GR_GL_LINEAR;
    }
}

// get_swizzle is only called from this .cpp so it is OK to inline it here
inline const GrGLenum* get_swizzle(GrPixelConfig config,
                                   const GrSamplerState& sampler,
                                   const GrGLCaps& glCaps) {
    if (GrPixelConfigIsAlphaOnly(config)) {
        if (glCaps.textureRedSupport()) {
            static const GrGLenum gRedSmear[] = { GR_GL_RED, GR_GL_RED,
                                                  GR_GL_RED, GR_GL_RED };
            return gRedSmear;
        } else {
            static const GrGLenum gAlphaSmear[] = { GR_GL_ALPHA, GR_GL_ALPHA,
                                                    GR_GL_ALPHA, GR_GL_ALPHA };
            return gAlphaSmear;
        }
    } else if (sampler.swapsRAndB()) {
        static const GrGLenum gRedBlueSwap[] = { GR_GL_BLUE, GR_GL_GREEN,
                                                 GR_GL_RED,  GR_GL_ALPHA };
        return gRedBlueSwap;
    } else {
        static const GrGLenum gStraight[] = { GR_GL_RED, GR_GL_GREEN,
                                              GR_GL_BLUE,  GR_GL_ALPHA };
        return gStraight;
    }
}

void set_tex_swizzle(GrGLenum swizzle[4], const GrGLInterface* gl) {
    GR_GL_CALL(gl, TexParameteriv(GR_GL_TEXTURE_2D,
                                  GR_GL_TEXTURE_SWIZZLE_RGBA,
                                  reinterpret_cast<const GrGLint*>(swizzle)));
}
}

void GrGpuGL::flushBoundTextureAndParams(int stage) {
    GrDrawState* drawState = this->drawState();

    GrGLTexture* nextTexture = 
        static_cast<GrGLTexture*>(drawState->getTexture(stage));

    // true for now, but maybe not with GrEffect.
    GrAssert(NULL != nextTexture);
    // if we created a rt/tex and rendered to it without using a
    // texture and now we're texturing from the rt it will still be
    // the last bound texture, but it needs resolving. So keep this
    // out of the "last != next" check.
    GrGLRenderTarget* texRT = 
        static_cast<GrGLRenderTarget*>(nextTexture->asRenderTarget());
    if (NULL != texRT) {
        this->onResolveRenderTarget(texRT);
    }

    if (fHWBoundTextures[stage] != nextTexture) {
        this->setTextureUnit(stage);
        GL_CALL(BindTexture(GR_GL_TEXTURE_2D, nextTexture->textureID()));
        //GrPrintf("---- bindtexture %d\n", nextTexture->textureID());
        fHWBoundTextures[stage] = nextTexture;
    }

    const GrSamplerState& sampler = drawState->getSampler(stage);
    ResetTimestamp timestamp;
    const GrGLTexture::TexParams& oldTexParams =
                            nextTexture->getCachedTexParams(&timestamp);
    bool setAll = timestamp < this->getResetTimestamp();
    GrGLTexture::TexParams newTexParams;

    newTexParams.fFilter = gr_to_gl_filter(sampler.getFilter());

    const GrGLenum* wraps =  GrGLTexture::WrapMode2GLWrap();
    newTexParams.fWrapS = wraps[sampler.getWrapX()];
    newTexParams.fWrapT = wraps[sampler.getWrapY()];
    memcpy(newTexParams.fSwizzleRGBA,
           get_swizzle(nextTexture->config(), sampler, this->glCaps()),
           sizeof(newTexParams.fSwizzleRGBA));
    if (setAll || newTexParams.fFilter != oldTexParams.fFilter) {
        this->setTextureUnit(stage);
        GL_CALL(TexParameteri(GR_GL_TEXTURE_2D,
                              GR_GL_TEXTURE_MAG_FILTER,
                              newTexParams.fFilter));
        GL_CALL(TexParameteri(GR_GL_TEXTURE_2D,
                              GR_GL_TEXTURE_MIN_FILTER,
                              newTexParams.fFilter));
    }
    if (setAll || newTexParams.fWrapS != oldTexParams.fWrapS) {
        this->setTextureUnit(stage);
        GL_CALL(TexParameteri(GR_GL_TEXTURE_2D,
                              GR_GL_TEXTURE_WRAP_S,
                              newTexParams.fWrapS));
    }
    if (setAll || newTexParams.fWrapT != oldTexParams.fWrapT) {
        this->setTextureUnit(stage);
        GL_CALL(TexParameteri(GR_GL_TEXTURE_2D,
                              GR_GL_TEXTURE_WRAP_T,
                              newTexParams.fWrapT));
    }
    if (this->glCaps().textureSwizzleSupport() &&
        (setAll || memcmp(newTexParams.fSwizzleRGBA,
                          oldTexParams.fSwizzleRGBA,
                          sizeof(newTexParams.fSwizzleRGBA)))) {
        this->setTextureUnit(stage);
        set_tex_swizzle(newTexParams.fSwizzleRGBA,
                        this->glInterface());
    }
    nextTexture->setCachedTexParams(newTexParams,
                                    this->getResetTimestamp());
}

void GrGpuGL::flushMiscFixedFunctionState() {

    const GrDrawState& drawState = this->getDrawState();

    if (drawState.isDitherState()) {
        if (kYes_TriState != fHWDitherEnabled) {
            GL_CALL(Enable(GR_GL_DITHER));
            fHWDitherEnabled = kYes_TriState;
        }
    } else {
        if (kNo_TriState != fHWDitherEnabled) {
            GL_CALL(Disable(GR_GL_DITHER));
            fHWDitherEnabled = kNo_TriState;
        }
    }

    if (drawState.isColorWriteDisabled()) {
        if (kNo_TriState != fHWWriteToColor) {
            GL_CALL(ColorMask(GR_GL_FALSE, GR_GL_FALSE,
                              GR_GL_FALSE, GR_GL_FALSE));
            fHWWriteToColor = kNo_TriState;
        }
    } else {
        if (kYes_TriState != fHWWriteToColor) {
            GL_CALL(ColorMask(GR_GL_TRUE, GR_GL_TRUE, GR_GL_TRUE, GR_GL_TRUE));
            fHWWriteToColor = kYes_TriState;
        }
    }

    if (fHWDrawFace != drawState.getDrawFace()) {
        switch (this->getDrawState().getDrawFace()) {
            case GrDrawState::kCCW_DrawFace:
                GL_CALL(Enable(GR_GL_CULL_FACE));
                GL_CALL(CullFace(GR_GL_BACK));
                break;
            case GrDrawState::kCW_DrawFace:
                GL_CALL(Enable(GR_GL_CULL_FACE));
                GL_CALL(CullFace(GR_GL_FRONT));
                break;
            case GrDrawState::kBoth_DrawFace:
                GL_CALL(Disable(GR_GL_CULL_FACE));
                break;
            default:
                GrCrash("Unknown draw face.");
        }
        fHWDrawFace = drawState.getDrawFace();
    }
}

void GrGpuGL::notifyVertexBufferBind(const GrGLVertexBuffer* buffer) {
    if (fHWGeometryState.fVertexBuffer != buffer) {
        fHWGeometryState.fArrayPtrsDirty = true;
        fHWGeometryState.fVertexBuffer = buffer;
    }
}

void GrGpuGL::notifyVertexBufferDelete(const GrGLVertexBuffer* buffer) {
    if (fHWGeometryState.fVertexBuffer == buffer) {
        // deleting bound buffer does implied bind to 0
        fHWGeometryState.fVertexBuffer = NULL;
        fHWGeometryState.fArrayPtrsDirty = true;
    }
}

void GrGpuGL::notifyIndexBufferBind(const GrGLIndexBuffer* buffer) {
    fHWGeometryState.fIndexBuffer = buffer;
}

void GrGpuGL::notifyIndexBufferDelete(const GrGLIndexBuffer* buffer) {
    if (fHWGeometryState.fIndexBuffer == buffer) {
        // deleting bound buffer does implied bind to 0
        fHWGeometryState.fIndexBuffer = NULL;
    }
}

void GrGpuGL::notifyRenderTargetDelete(GrRenderTarget* renderTarget) {
    GrAssert(NULL != renderTarget);
    GrDrawState* drawState = this->drawState();
    if (drawState->getRenderTarget() == renderTarget) {
        drawState->setRenderTarget(NULL);
    }
    if (fHWBoundRenderTarget == renderTarget) {
        fHWBoundRenderTarget = NULL;
    }
}

void GrGpuGL::notifyTextureDelete(GrGLTexture* texture) {
    for (int s = 0; s < GrDrawState::kNumStages; ++s) {
        GrDrawState* drawState = this->drawState();
        if (drawState->getTexture(s) == texture) {
            this->drawState()->setTexture(s, NULL);
        }
        if (fHWBoundTextures[s] == texture) {
            // deleting bound texture does implied bind to 0
            fHWBoundTextures[s] = NULL;
       }
    }
}

bool GrGpuGL::configToGLFormats(GrPixelConfig config,
                                bool getSizedInternalFormat,
                                GrGLenum* internalFormat,
                                GrGLenum* externalFormat,
                                GrGLenum* externalType) {
    GrGLenum dontCare;
    if (NULL == internalFormat) {
        internalFormat = &dontCare;
    }
    if (NULL == externalFormat) {
        externalFormat = &dontCare;
    }
    if (NULL == externalType) {
        externalType = &dontCare;
    }

    switch (config) {
        case kRGBA_8888_PM_GrPixelConfig:
        case kRGBA_8888_UPM_GrPixelConfig:
            *internalFormat = GR_GL_RGBA;
            *externalFormat = GR_GL_RGBA;
            if (getSizedInternalFormat) {
                *internalFormat = GR_GL_RGBA8;
            } else {
                *internalFormat = GR_GL_RGBA;
            }
            *externalType = GR_GL_UNSIGNED_BYTE;
            break;
        case kBGRA_8888_PM_GrPixelConfig:
        case kBGRA_8888_UPM_GrPixelConfig:
            if (!this->glCaps().bgraFormatSupport()) {
                return false;
            }
            if (this->glCaps().bgraIsInternalFormat()) {
                if (getSizedInternalFormat) {
                    *internalFormat = GR_GL_BGRA8;
                } else {
                    *internalFormat = GR_GL_BGRA;
                }
            } else {
                if (getSizedInternalFormat) {
                    *internalFormat = GR_GL_RGBA8;
                } else {
                    *internalFormat = GR_GL_RGBA;
                }
            }
            *externalFormat = GR_GL_BGRA;
            *externalType = GR_GL_UNSIGNED_BYTE;
            break;
        case kRGB_565_GrPixelConfig:
            *internalFormat = GR_GL_RGB;
            *externalFormat = GR_GL_RGB;
            if (getSizedInternalFormat) {
                if (this->glBinding() == kDesktop_GrGLBinding) {
                    return false;
                } else {
                    *internalFormat = GR_GL_RGB565;
                }
            } else {
                *internalFormat = GR_GL_RGB;
            }
            *externalType = GR_GL_UNSIGNED_SHORT_5_6_5;
            break;
        case kRGBA_4444_GrPixelConfig:
            *internalFormat = GR_GL_RGBA;
            *externalFormat = GR_GL_RGBA;
            if (getSizedInternalFormat) {
                *internalFormat = GR_GL_RGBA4;
            } else {
                *internalFormat = GR_GL_RGBA;
            }
            *externalType = GR_GL_UNSIGNED_SHORT_4_4_4_4;
            break;
        case kIndex_8_GrPixelConfig:
            if (this->getCaps().f8BitPaletteSupport) {
                *internalFormat = GR_GL_PALETTE8_RGBA8;
                // glCompressedTexImage doesn't take external params
                *externalFormat = GR_GL_PALETTE8_RGBA8;
                // no sized/unsized internal format distinction here
                *internalFormat = GR_GL_PALETTE8_RGBA8;
                // unused with CompressedTexImage
                *externalType = GR_GL_UNSIGNED_BYTE;
            } else {
                return false;
            }
            break;
        case kAlpha_8_GrPixelConfig:
            if (this->glCaps().textureRedSupport()) {
                *internalFormat = GR_GL_RED;
                *externalFormat = GR_GL_RED;
                if (getSizedInternalFormat) {
                    *internalFormat = GR_GL_R8;
                } else {
                    *internalFormat = GR_GL_RED;
                }
                *externalType = GR_GL_UNSIGNED_BYTE;
            } else {
                *internalFormat = GR_GL_ALPHA;
                *externalFormat = GR_GL_ALPHA;
                if (getSizedInternalFormat) {
                    *internalFormat = GR_GL_ALPHA8;
                } else {
                    *internalFormat = GR_GL_ALPHA;
                }
                *externalType = GR_GL_UNSIGNED_BYTE;
            }
            break;
        default:
            return false;
    }
    return true;
}

void GrGpuGL::setTextureUnit(int unit) {
    GrAssert(unit >= 0 && unit < GrDrawState::kNumStages);
    if (fHWActiveTextureUnitIdx != unit) {
        GL_CALL(ActiveTexture(GR_GL_TEXTURE0 + unit));
        fHWActiveTextureUnitIdx = unit;
    }
}

void GrGpuGL::setSpareTextureUnit() {
    if (fHWActiveTextureUnitIdx != (GR_GL_TEXTURE0 + SPARE_TEX_UNIT)) {
        GL_CALL(ActiveTexture(GR_GL_TEXTURE0 + SPARE_TEX_UNIT));
        fHWActiveTextureUnitIdx = SPARE_TEX_UNIT;
    }
}

void GrGpuGL::setBuffers(bool indexed,
                         int* extraVertexOffset,
                         int* extraIndexOffset) {

    GrAssert(NULL != extraVertexOffset);

    const GeometryPoolState& geoPoolState = this->getGeomPoolState();

    GrGLVertexBuffer* vbuf;
    switch (this->getGeomSrc().fVertexSrc) {
    case kBuffer_GeometrySrcType:
        *extraVertexOffset = 0;
        vbuf = (GrGLVertexBuffer*) this->getGeomSrc().fVertexBuffer;
        break;
    case kArray_GeometrySrcType:
    case kReserved_GeometrySrcType:
        this->finalizeReservedVertices();
        *extraVertexOffset = geoPoolState.fPoolStartVertex;
        vbuf = (GrGLVertexBuffer*) geoPoolState.fPoolVertexBuffer;
        break;
    default:
        vbuf = NULL; // suppress warning
        GrCrash("Unknown geometry src type!");
    }

    GrAssert(NULL != vbuf);
    GrAssert(!vbuf->isLocked());
    if (fHWGeometryState.fVertexBuffer != vbuf) {
        GL_CALL(BindBuffer(GR_GL_ARRAY_BUFFER, vbuf->bufferID()));
        fHWGeometryState.fArrayPtrsDirty = true;
        fHWGeometryState.fVertexBuffer = vbuf;
    }

    if (indexed) {
        GrAssert(NULL != extraIndexOffset);

        GrGLIndexBuffer* ibuf;
        switch (this->getGeomSrc().fIndexSrc) {
        case kBuffer_GeometrySrcType:
            *extraIndexOffset = 0;
            ibuf = (GrGLIndexBuffer*)this->getGeomSrc().fIndexBuffer;
            break;
        case kArray_GeometrySrcType:
        case kReserved_GeometrySrcType:
            this->finalizeReservedIndices();
            *extraIndexOffset = geoPoolState.fPoolStartIndex;
            ibuf = (GrGLIndexBuffer*) geoPoolState.fPoolIndexBuffer;
            break;
        default:
            ibuf = NULL; // suppress warning
            GrCrash("Unknown geometry src type!");
        }

        GrAssert(NULL != ibuf);
        GrAssert(!ibuf->isLocked());
        if (fHWGeometryState.fIndexBuffer != ibuf) {
            GL_CALL(BindBuffer(GR_GL_ELEMENT_ARRAY_BUFFER, ibuf->bufferID()));
            fHWGeometryState.fIndexBuffer = ibuf;
        }
    }
}